ICESP XI – Hangzhou, China, 2008
The International Conference on Electrostatic Precipitation (ICESP) is the official conference of the International Society for Electrostatic Precipitation (ISESP). The following is a list of papers from the XI ICESP Conference under their respective topic. Click on the title to view paper.
World-Wide Review:
Development of Chinese Electrostatic Precipitator Technology
In this paper we review the development of Chinese Electrostatic Precipitator (ESP) in the passed 20 years, introduce the recent situation of our country’s ESP technology and forecast the development prospect of ESP in China. 1B Keywords: Electrostatic Precipitator, ESP technology, technology development, technology progress
Multi-pollutants Simultaneous Removals from Flue Gas
With the stricter emission standards, more pollutants in the air need to be controlled. If the traditional mean of using a technology to treat a pollutant is adopted, there are high investment running cost and complex operation system. So the multipollutants simultaneous removal technology from flue gas is paid more and more attention in the recent ten years. The plasma technology and semi-dry flue gas cleaning technology are two very promising multi-pollutants simultaneous removal technologies. In our researches, a plasma technology of corona radical shower and a semi-dry flue gas cleaning technology using circulating suspension and multistage humidification were selected. A series of fundament and industry application works were done. In the paper, some current results are opened out to provide some reference.
Some Technical Idea Evolutions Concerned with Electrostatic Precipitators in China
Electrostatic precipitator (ESP) was applied in China more than fifty years. There are many technical idea changes along with time or idea corrections from misunderstandings in this long run. A historical review of them will not only be interesting but also can draw some inspirations from them. It is not possible to look back all the technical events. Only those have discussed thoroughly among Chinese ESP workers, such as: gas velocity in ESP, height of collecting electrodes, dust cleaning methods, selection of T/R and control modes, etc. are briefly described in this paper. Two special topics, ESP for circulating fluid bed boiler and Orimulsion® combustion are also referred with. They are different kind of problems, but have drawn divergences between Chinese engineers. So, as an assortment, described here.
Enhancement of Collection Efficiencies of Electrostatic Precipitators: Indian Experiments
With the rising oil price, coal is well positioned to make a valuable contribution to global energy security. The market share of coal in electricity generation in developing countries is around 45% at present and is expected to rise up to 47% in 2030. A significant amount of power generation in countries like China, India, USA, Russia, East Europe, South Africa and Australia is based on coal. At present India has got 61175 MW (58% of total installed power capacities) installed coal based power capacity which is expected to rise 115500 MW (53%) by the year 2012. Fly ash emitted by the coal based power plants is serious air pollutants in and around the power plant compared to SOx and NOx air pollutants in India. Electrostatic Precipitators are used to control fly ash emitting from the boilers of most the power plants in India. The coal burnt in most of the power plants in India are perhaps are among the most difficult ones in the world, which are characterized by low calorific value 3500 kcal/kg-4500 kcal/kg, and high ash contents 35%-45%. Besides, ashes have got large electrical resitivities because of low alkali and sulfur. As a result the size of ESPs in India is much larger compared to other places for similar electric out put. In order to meet the more stringent emissions standards several methods have been adopted in many old power plants with aged ESPs. These methods include: (i) enhancement of collection area of ESPs; (ii) Pulse and intermittent charging of ESP units; (iii) Flue gas conditioning by water fogging, ammonia conditioning; (iv) Dual conditioning with NH3 and SO3, and; (v) Coal ash conditioning with sodium salt. These methods have got their respective advantages and disadvantages and have met partial success. The present paper discusses some of the points for some of the selected plants.
Fundamentals and Mechanical Design:
Modeling Mercury Capture within ESPs: Continuing Development and Validation
Efforts to reduce anthropogenic mercury emissions worldwide have recently focused on a variety of sources, including mercury emitted during coal combustion. Toward that end, much research has been ongoing seeking to develop new processes for reducing coal combustion mercury emissions. Among air pollution control processes that can be applied to coal-fired boilers, electrostatic precipitators (ESPs) are by far the most common, both on a global scale and among the principle countries of India, China, and the USA that burn coal for electric power generation. A previously reported theoretical model of in-flight mercury capture within ESPs is herein validated against data from a number of full-scale tests of activated carbon injection for mercury emissions control, resulting in the first validated model of mercury capture within ESPs. By using the established particle size distribution of the activated carbon and actual or estimated values of its equilibrium mercury adsorption capacity, the incremental reduction in mercury concentration across each ESP can be predicted and compared to experimental results. Because the model does not incorporate kinetics associated with gas-phase mercury transformation or surface adsorption, the model predictions represent the mass-transfer-limited performance. Comparing field data to model results reveals many facilities performing at or near the predicted mass-transfer-limited maximum, particularly at low rates of sorbent injection. Where agreement is poor between field data and model predictions, additional chemical or physical phenomena may be responsible for reducing mercury removal efficiencies.
Reduction of Rapping Losses to Improve ESP Performance
The need to reduce emissions of particulate matter, NOx, SOx, VOC, and most recently CO2 to address Global Warming, is becoming a worldwide concern. Electrostatic Precipitators (ESPs) have been predominantly used for many years to collect particulate matter from the gas stream of power plants and industrial processes. Unfortunately when the collecting electrodes are cleaned a portion of the precipitated material typically reenters the gas stream and exits the ESP. The amount of reentrainment losses from ESPs may not be suitable to meet lower emissions limits for particulate matter in the future. Alstom Power Systems (APS) has developed a new technique to reduce the rapping losses from an ESP. This paper presents the key aspects of design and collected information from the current operating units in Guatemala and Finland. The new design is a cost effective approach to address this well-known problem for ESPs. With future development and refinement of the technology it may be possible to reduce the particulate emissions after an ESP to the Near Zero Emissions target being discussed by regulators from e.g. coal-fired power plants.
Advanced Risk Analysis for the Application of ESP-s to Clean Flammable Gas-pollutant Mixtures
There are several processes, in which risk of fire or explosion in electrostatic precipitator must be analyzed, like at certain types of biomass fired boilers, fine particle removal in pharmaceutical processes, etc. Appropriate, reliable risk analysis of such systems is vital to ensure safe operation. Application of fault tree analysis for risk calculation is a well known method, but in some cases it is difficult to identify all of the significant events and it is more difficult to determine the initial probability values for the basic events of the fault tree. When the determination of the probabilities contains uncertain information, it is necessary to evaluate the reliability of the result or to decrease uncertainty of initial probability values. This paper represents an advanced method based on fuzzy logic, that is capable to estimate the effect of uncertainty, and determine reliable input parameters for the fault tree analysis in such cases, when risk of fire or explosion in the electrostatic precipitator must be taken into consideration. The paper represents the process of the creation of fault tree, the determination of fuzzy membership functions for the input probabilities, the calculation process and the evaluation of the final result of the analysis.
ESP for Small Scale Wood Combustion
In this paper new ESP technology developed for fine particle processes are presented. The ESP is based on diffusion charging of particles using sonic jet charger. The ESP concept has been tested using a commercial 20kW wood pellet burner. The removal efficiency was measured to be 80% for submicron particles.
Control of Particulate matter (PM) emission is a key pollution issue affecting the environment and human health, especially sizes that range below 10 µm. The objective of this work is to develop a dust flow separator type electrostatic precipitator (DFS-ESP) for the effective control of fine particulate matter emission from natural gas combustion. An experiment was conducted for natural gas combustion exhaust flow rates from 2.5 Nm3/h to 9 Nm3/h, ESP applied voltage from 0 to 30 kV, and combustion gas temperature from 80 ℃ to 160 ℃. Particle measurements were conducted at upstream, downstream and middle of the DFS-ESP system. The experimental results show that particle size emitted from the natural gas combustion ranges in 17 nm -300 nm in diameter, volume density ranges approximately from 5×108 #pt/m3 to 5×109 #pt/m3 depending on the combustion conditions. The dust flow separator can concentrate 90% of fine particles in 1%-3% of the gas flow and divert it to the ESP section from the main flow channel allowing a higher efficiency for particle removal. In terms of overall particle collection efficiency, the DFS-ESP system can remove up to 95% particles based on the number density.
Electrostatic Precipitator: The Next Generation
The Electrostatic Precipitator has become known for it efficiency and reliability but there are disadvantages. Described will be Patent No 323806 which describes new developments in EP design.
Current Density and Efficiency of a Novel lab ESP for Fine Particles Collection
Understanding the current density will help to improve the ESP’s energy consumption and the collection efficiency of fine particles. In this study, corona current density and dust collection efficiency were studied with a laboratory ESP. Dust collection experiments were performed with various electrode distances from 22 mm to 330 mm, and also with a single discharge electrode. Discharge for 40 to 50 seconds with 46 kV voltage, 160 g/m3 inlet dust concentration and 700 m3/h flow rate. Ash layer thickness collected on the plate is about 4 mm on average. We observed that the total currents are greatly influenced by the plate-plate gap and electrode distance. The maximum total current was obtained in the 132 mm discharge electrode distance (about half of the plate-plate gap width). The operating voltage range of positive corona is only about half that of the negative corona. Dust layer Accumulation on the plate reduced the total collection current, and increased the spark voltage about 4 kV with 4 mm dust thickness. Increase in the discharge electrode number of the outlet field can improve fine particles collection efficiency.
Five Stages Electrostatic Precipitator Principles and Application
In order to meet the urgent demands of energy saving and pollution emission standards, Five Stages Electrostatic Precipi- tator (FS-ESP) for Electrostatic Precipitator (ESP) innovation was raised and developed, its mechanism was studied, and the optimi- zation experiments were done in industrial conditions. At the end we described FS-ESP applications for ESP innovations which have satisfactory performances and run reliably and stably in four-year operation.
Application of STAAD in ESP structure design
China is a big country which manufactures and uses the ESP. For the ESP technology, years ago we import and pattern, now we have our own technology, also, the technique better and better. As the progress of science and technology, the design technology of ESP improved ceaseless. This article introduces the steel design software—STAAD with example, the application of the STAAD optimized the ESP’s structure; reduce the consumption of metals required.
Electric Resistance of Boiler Flue Gases and Collection Efficiency of ESP
In today’s operation of ESP, various manufacturers have encountered some problems. Most ESPs smoke seriously and the concentration of dust emission fails to reach emission standards though they are normal designed, manufactured and installed with no apparent defects. Some are frequently retrofitted but less effect. To this, the thesis is mainly focused on the electrical conductivity of mixed gases in a boiler and the relationship between the electrical conductivity and the dust specific electric resistance as well as their effects on ESP efficiency. The operation of ESP will be recognized from another perspective and can be debugged more scientifically so as to achieve purposes of high-efficiency and energy saving.
Non-static Collection Process of the Electrostatic Precipitator
In order to describe non-static dust collection in electrostatic precipitator comprehensively and propose a non-static dust collection theory on it, the leading accumulation and release of the dust layer electronic charge on the collection plate was researched according to the electrostatic principle. The calculation equation of the dynamic dust collection electric-field intensity that changes with the dust layer thickness was deduced. Furthermore, the equation of the dynamic velocity of the charged particle could also be obtained. And finally, the non-static electrostatic dust collection theory was proposed. The results indicated that the particle velocity was related to many factors such as particle specific electric resistance, applied voltage and dust layer thickness during electrostatic dust collection process. The collection efficiency decreases with the increasing of the particle specific electric resistance. The collection efficiency can reach a maximum value when an optimal applied voltage is got. Multiple laboratory experiments were completed on many kinds of particles with different specific electric resistance. The experiment results obey to the theoretic results. The non-static dust collection theory could explain contradictive points between the actual electrostatic dust collection process and the traditional electrostatic dust collection theory and provided a scientific theoretical foundation for the design of the electrostatic precipitator and the decision of its operating parameters.
In order to increase the collecting efficiency of ESP and to meet requirements of saving energy and reducing emission, the new ESP design technology, according to the need of high efficient operation, is proposed under the full consideration of coal component and content, ash chemical component and content. Namely, use this technology of mixed wires and mixed same–polar distance for ESP. Through several years’ operation, the present technology by approved is good and its performance is good, reliable and stable.
A new electrostatic precipitator (ESP) for avoiding the back corona of the high resistivity dust layer is developed by fixing the barb nail discharging electrodes on the plate collecting electrodes based on the analysis of the phenomenon of the back corona of the high resistivity dust layer deposited on the grounded plate electrodes. Therefore, this ESP becomes a bipolar discharging ESP because the negative ions and the positive ions are generated simultaneously by the high voltage discharging electrodes and the grounded barb nail discharging electrodes respectively. The ionic wind is measured by a Particle Image Velocimetry (PIV) because the ionic wind plays an important role in collecting the fine dust with high Resistivity. The positive and the negative ion wind velocities in core area are about 2 m/s when the distance between the opposite electrodes is 100 mm at the voltage of 3.4 kV. In our comparison experiments, the overall efficiency of the bipolar discharging ESP for collecting the silica flour with 0.159 μm mass median diameter is higher than that of the unipolar discharging ESP at the mean electric field of 3.4 kV/cm in the room temperature and pressure. The experimental observation shows that the there is no back corona in the bipolar discharging ESP even when the very high resistivity silica flour (2.4×1014 Ω·cm) is used.
Designing ESP Systemically to Reduce Dust Emission
As the raising of relative environmental emission standards, the application of ESP is challenged now. This article focuses not only on the ESP equipment itself, but more important, on the system environment where ESP’s working. We analysis the different stages: the flue gas still not get into the ESP fields, in the fields, and passed from the fields, and discuss the details in different stages, correspondingly propose some methods and new facilities.
Research on Vibration Period Optimization of Electrostatic Precipitator
The normal operation of the vibration equipment and the dust removing equipment of EP is an important factor to ensure EP in a safe, stable and efficient running and has a direct influence on the efficiency of EP and the working life of the related equipments. According to statistics, in electrostatic precipitators which collection efficiencies were less than 95%, it was mostly caused by the bad vibration effect. The vibration periods of each electric field were analyzed by researching the rule of ash-deposition; the influence of boiler load, fly ash coefficient, carbon content in fly ash and dust content consistency in flue gas on vibration period was analyzed by calculating with vibration period calculation formula; giving an example to show the EP at a coal-fired boiler, the vibration periods of each electric field which were calculated theoretically based on the coal and the evaporation capacity were compared with the actual vibration periods to ensure and adjust vibration periods.
Study on the Dust Removal Efficiency Formula of EP with Efficiency Enhancing and Energy-saving
Based on theoretical reaching rate, operating status quo of EP and successful study and extension of high voltage power supply facility of EP with efficiency enhancing and energy saving, the dust removal efficiency formula reflecting the characteristics of high voltage power supply, efficiency enhancing and energy saving and intelligent optimization control was studied. It was indicated that the effective reaching rate and the dust removal efficiency were in the direct ratio to the peak and the minimum of the secondary voltage under the working manner of high efficiency and energy saving and the working manner of spark setting through the formula. The basis can be provided for the optimization and the efficiency enhancing and energy saving of high voltage power supply facilities of EP by the formula.
Research and Application of the Extensive Resistivity and Efficient Electrostatic Precipitator
The normal operation of the vibration equipment and the dust removing equipment of EP is an important factor to ensure EP in a safe, stable and efficient running and has a direct influence on the efficiency of EP and the working life of the related equipments. According to statistics, in electrostatic precipitators which collection efficiencies were less than 95%, it was mostly caused by the bad vibration effect. The vibration periods of each electric field were analyzed by researching the rule of ash-deposition; the influence of boiler load, fly ash coefficient, carbon content in fly ash and dust content consistency in flue gas on vibration period was analyzed by calculating with vibration period calculation formula; giving an example to show the EP at a coal-fired boiler, the vibration periods of each electric field which were calculated theoretically based on the coal and the evaporation capacity were compared with the actual vibration periods to ensure and adjust vibration periods.
Application and Research on Technology of Longking Brand BEL Model ESP
This paper presented the main construction and technology innovation characteristics of Longking brand BEL model Electrostatic Precipitator (hereafter referred to as “BEL-ESP”) putting emphasis on the aspects of electric field plate-wire type and rapping dedusting technologies. Based on the conclusions of application and research, we have preceded practical research and industrial application improvements on the key technologies of plate-wire type, location, suspension, rapping etc, and have improved the reliability, efficiency and power-saving ability of manufacture. Meanwhile this paper pointed out that the installation quality of key points on Discharging Electrode (DE) and Collecting Electrode (CE) is important for ensuring a longterm, high efficient and stable running of ESP.
Electrode Shape and collector plate Spacing Effects on ESP Performance
ElectroStatic Precipitator (ESP) suppliers are today conducted to reduce installation cost and due to world-wide environmental emission requirements also to improve performance. Two important and critical factors when designing high performance ESP’s are discharge electrode design and collector plate spacing. Simulation and experimental results obtained in a pilot precipitator are used to investigate fundamental effects of the electrode shape for different collector plate spacing (Results – Part 1 – Simulations) and to study more “aggressive” electrodes for 300 mm and 500 mm plate spacing (Results – Part 2 – Experimental study). The ESP simulation model demonstrates, for different electrode shapes and collector plate spacing, basic characteristics of current-voltage-characteristics, current density at collecting plate, efficiency, turbulence level, strength of ionic wind, and effect of dust load. The experimental study focuses on electrode evaluation based on electrode shape and emitter orientation. An intensive study of several different electrode shapes has been carried out. ESP efficiency for wide spacing between collector plates is discussed in view of electrode shape and emitter orientation.
Resistance and Airflow Distribution of Rotary Plate
In this paper, differential pressures and airflow distributions of rotary plates have been respectively computed. The influences of these changes have been analyzed. At the end, we got the law of the influence of rotary plate on resistance and airflow distribution.
Onset Voltage of Corona in Electrostatic Filters as Influenced by Gas Flow
The onset voltage of negative corona on the discharge wire in wire-duct filters is calculated based on the criterion for the recurrence of negative corona (Trichel) pulses. The negative corona pulse corresponds to one electron avalanche followed by its successors in the ionization-zone surrounding the wire. The growth of avalanches and their successors depends on the electric field and the pressure. With gas flow in the filter, the pressure is different from the atmospheric value with a subsequent change of the onset voltage. The onset voltage is determined at different value of gas flow velocity. The obtained results are discussed in the light of gas discharge physics.
An Initial Exploration for Coulomb ESP
The coulomb ESP is fundamentally based on coulomb law which indicating the Coulomb force is inversely proportional to square of distance between two point charges. The sufficiently charged particles are all forced to dust-catching electrode by Coulomb force. Due to the velocity of wind around dust-catching electrode trends to zero, dust cleaning is on off-line mode, the secondary fly-up can be overcome. According to practical application, the inlet concentration and outlet concentration are 30 g /Nm3 and <10 mg /Nm3 respectively for a 3.5 m long electrical field. The de-dust efficiency is up to 99.95%. Coulomb ESP is a high efficiency ESP. it can either enhances dust removal efficiency of ESP and decreases its weight to 1/2. According to practical application, the inlet concentration and outlet concentration are 30g /Nm3 and <10 mg /Nm3 respectively for a 3.5 m long electrical field. The de-dust efficiency is up to 99.95 %.
Aerodynamic Effects and ESP Models:
In this work, the effect of electrohydrodynamic (EHD) secondary flow on the wire-plate type electrostatic precipitator partial collection efficiencies for submicron and ultrafine dust particles in the range from 0.01 μm to 10 μm have been calculated based on the cross-sectional averaged values of numerically obtained ion density, electric field and gas velocity and coupled together with particle surface charge models based on the modified diffusion and field particle charging rates. The results show that the particle surface charge of particles between 0.01 μm and 1 μm are not significantly influenced by EHD secondary flow, however, EHD flow do perturbing the local surface charge and local particle collection efficiency. The net effect on the partial collection efficiency is not significant for the submicron size particle range.
In this paper, results of 3-dimensional Particle Image Velocimetry (3D PIV) measurements of the flow velocity fields in a relatively wide wire-plate type ESP are presented. The ESP used in this work was an acrylic parallelepiped (10 cm × 20 cm × 100 cm) with a wire discharge electrode and two plate collecting electrodes. Air flow seeded with a cigarette smoke was blown along the ESP duct with an average velocity of 0.6 m/s. Either positive or negative DC voltage was applied to the wire electrode through a 10 MΩ resistor. The applied voltage was up to 28 kV. The 3D PIV velocity fields measurements were carried out in four parallel planes stretched along the ESP duct, perpendicularly to the wire electrode and plate electrodes. The measured flow structures show complex nature of the EHD-induced secondary flow in the ESP. The measured flow was turbulent and exhibit 3D structures caused by the side-wall effect.
Applying Numerical Simulation on Air Pollution Control Equipment
Flow management by different design of gas distribution internals are in general required for several local sections within ElectroStatic Pricipitators (ESP’s) and Fabric Filters (FF’s). Flow management in filter equipment are important for both new and retrofit equipment due to performance e.g. flow uniformity, operating costs e.g. pressure loss etc. Currently, the traditional approach of cut-and-try in the design phase, physical model testing, and field tests in the order executing phase is being replaced by Computational Fluid Dynamics (CFD) for both ESP’s and FF’s at FLSmidth Airtech. This paper discusses work from a wide range of simulation models for ESP’s and FF’s including hybrid filters (ESP + FF) and conversion of ESP to FF. Focus is placed on special designed FLSmidth Airtech CFD models for both local ESP and FF components e.g. gas distribution screens for ESP’s and modelling of bags for FF’s. Results include flow distribution, flow balance, pressure loss, thermal effects, dust prop out, and re-entrainment for several different ESP and FF installations. State of the art CFD within filter equipment are presented including simulation examples of the FLSmidth Airtech ESP electro-hydrodynamic flow model. Finally conclusions with respect to optimal performance are drawn.
CFD Simulation of Electrostatic Precipitators and Fabric Filters State of the Art and Applications
This paper clearly discloses the possibilities, which the numeric flow simulation offers in case of modelling the twophase flow in electrostatic precipitators and fabric filters with view to design new and retrofitting of old plants today. Contrary to physical flow models the CFD simulation is capable to consider high dust loads and the distribution of dust in the gas flow. This is an advantage which will lead to the displacement of the physical flow models by sophisticated CFD simulations while investigating the two phase flow in dust precipitators. This paper explains the main features of the used CFD models for the detailed simulation of these types of precipitators. Both CFD model approaches are based on an EULER-LAGRANGE formulation of the two-phase flow consisting of gas and solid particles. Also the paper points out, how important a highly detailed geometry model is for a strong simulation and reliable results. So all the ducts up- and downstream the precipitator itself including every inner part (e.g. guide vanes, dampers, etc.) are integrated in the CFD geometry model. The simulations show that today reliable CFD simulations of both precipitator types the electrostatic and the fabric filter in consideration of the phase interaction between gas and solid particles including separation are possible with high accuracy. Thus it is possible to examine special questions such as optimization of gas flow, reduction of pressure loss or the increase in separation efficiency, purposefully tailored to a precipitator, fast and economically.
Numerical Modeling of the Electro-hydrodynamics in a Hybrid Particulate Collector
The specific gas flow influenced by the electrical field in the electrostatic precipitator (ESP) is called electrohydrodynamic (EHD) flow. The hybrid particulate collector (HPC) is a hybrid of the ESP and the baghouse in a unique approach combining the best features of both. The bags are placed between two perforated collection plates. The HPC is a very compact and high efficiency system. In this paper, numerical modeling of the three-dimensional EHD flow in a hybrid particulate collector (HPC) is presented. An unstructured finite volume method (FVM) was developed to solve the Poisson’s electrical equation and the current continuity equation within the collector. The Fluent code was used to solve the fluid N-S equations and the RNG k ε − turbulent model equations with considering the electrical body force. The numerical results show that the EHD flow can produce strong recirculation in the hybrid collector. Different from the ESP, the electric field has still strong influence on the gas flow when the EHD number below one.
CFD Numerical Simulation of ESP Airflow Distribution and Application of Flue Gas Distribution
This paper GUODIAN Bengbu power plant 2×600 MW unit supporting the ESP system for flue study, details of the electrostatic precipitator tail flue contoured layout of the electrostatic precipitator, electric air impacts, as well as how to take the physical model and Mathematical Model of combining CFD numerical simulation study.
The gas flow rate distribution in pipelines and the gas flow distribution at the inlet section of the first electric field were numerically simulated with CFD. According to the simulated results, we ascertained the collocation schemes of guide vanes in pipelines and on the plate of gas flow distribution. Meanwhile, we validated simulated results with the model test. Simulated results were in accordance with the model test, and met the requirement of the electrostatic precipitator.
The current density on the collecting plates were measured of 12 kinds of common discharge electrodes matched C480 and ZT24 collecting plates. The effect of different discharge electrodes and setting manners on the experiment results was discussed with two parameters of average current density and relative standard deviation. The distributions of electric potential and electric field strength were calculated by using finite element method when V serial discharge electrodes matched ZT24 collecting plates .Combining the results of the experiments and numerical calculation, the paper analyzed the effect of electric field strength on the corona current.
Analytical study on ZT Collecting Electrode
Analytical study on ZT type collecting electrode (ZT electrode) is conducted from theoretical and practical aspects. For theoretical aspect, distribution of field strength on surface of ZT electrode is studied against that on surface of flat plate collecting electrode (plate electrode) for different type of discharge electrodes. ZT electrode is advantageous over plate electrode for less deviation in distribution of field strength on electrode surface such that ZT electrode is also to be advantageous over plate electrode for less deviation in secondary current distribution on electrode surface. Consequently, ZT electrode is advantageous over plate electrode for less rapping force required for the same collection area. For practical aspect, the influence on distribution of field strength on electrode surface due to misalignment of discharge electrode is studied for ZT electrode against plate electrode. The results indicate ZT electrode provides a robust collecting system to withstand field problems from erection and operation without compromising the collection performance in terms of evener distribution of field strength on electrode surface against plate electrode. Flow dynamic performance is also studied for ZT electrode against plate electrode. Results indicate that ZT electrode has advantage to prevent rapping re-entrainment due to the convergent-divergent or divergent-convergent configuration. In cooperation with less deviation in secondary current distribution, ZT electrode has considerable advantage over plate electrode for rapping re-entrainment.
Numerical Simulation of Influence of Baffler in Electric Field Entrance to Form Skewed Gas Flow
This article proposed that baffle plates should be added on the air current distribution boards in inlet box in order to form skewed gas flow. Air distribution was simulated and studied by Software FLUENT. The -k 2 ε equation model was taken in the Flow field simulation, and the computation was based on SIMPLE algorithm. There are five sorts of baffle plates which have different fixing angles and fixing spaces to simulate skewed gas flow. Eventually the simulative results indicated that setting baffle plates could form the skewed gas flow and the simulation accorded with the experimental data at 45 degree, space 504 mm. Comprehensively analysed, the angle of 55° was more ideal. All of these offer a basis to design, running and improving of electrostatic precipitator (ESP).
The electrostatic precipitator (ESP) numerical model developed by Author does a better job of qualitatively predicting influence of skew gas distribution in ESP upon performance. The results show that the higher efficiencies can be achieved by using some special non-uniform inlet & outlet gas distribution than that of uniform gas distribution and the re-entrainment of falling dust results in the dust load in the lower zone of a precipitator increasing compared to the upper zone as flow progresses through a precipitator. In this paper, the numerical model is applied to determine exit re-entrainment loss response to the variations in gas distributions across the full scale ESP entrance and exit. It examined how skew gas distribution affects reentrainment loss and gives a physical explana-tion for the lower re-entrainment loss or higher efficiency with controlled using some special non-uniform inlet and outlet gas distributions.
Fine-Particles and Their Agglomeration:
Research Progress of the Control Technology of the PM10 from Combustion Sources
The particulate and combustion engineering (PACE) group is a vigorous research team dedicated to the study and application of the control technology of the PM10 from combustion sources in the Tsinghua University in china. Most of our recent work has been on the filtration and clean of the charged particles. First, different filters were tested systematically in various filtration conditions, including charging the particles as pretreatment. It was found that charged particles slowed the clogging and made increase rate of pressure drop larger than in neutralized cases and the penetration varied a lot. Second, direct observation of particle deposit on a single fiber was conducted to investigate the mechanism of the described phenomena. It was found that when the particles were charged, straight chains or chains with branches on which particles were evenly distributed were formed. Moreover, the discrete element method (DEM) based on JKR theory of adhesive elastic contacts, was used for three-dimensional simulations. A dimensionless adhesion parameter is defined and shown to have a dominant effect on the predicted particle deposition rate. Third, a continuous filtration bench was set up according to VDI 3926 to investigate the differences of cake detachment stresses between charged particle filtration and common filtration. The cake cleaning is carried out under a slowly increased reverse flow, when the overall pressure drop and cake detached is recorded. Primary results show that with the same filter, charged particle cake is harder to remove.
Enhanced Fine Particle and Mercury Emission Control Using the Indigo Agglomerator
Fine particles are a major health issue as they remain suspended in the atmosphere for extended periods, are able to penetrate deep into the human lung and contain significant concentrations of heavy metals, such as Arsenic. They are also a significant component of the smog that limits the visibility in many cities and even in some national parks plus scientists believe they have an effect on global weather patterns. The Indigo Agglomerator enhances fine particle collection by attaching the fine particles to the larger particles. These large agglomerated particles are easily collected in existing control devices, such as Electrostatic Precipitator (ESP), fabric filters, scrubbers and cyclones. This paper concentrated on PM2.5 particles, that is particles less than 2.5 μm in diameter, including data that was collected on particles down to 50 nm in diameter. It was found that the reduction in fine particle emission from an Electrostatic Precipitator provided by installing an Indigo Agglomerator increases with reducing particle size from a factor of 5 at 2 μm to a factor of 10 at 100 nm. Reductions of this magnitude will have a significant effect on the impact of fine particles on both visibility and health. It will also result in a reduction in heavy metal emissions.Recent regulations in the US require Mercury emission control on coal fired power stations. Mercury is considered a major health hazard because it concentrates in the food chain and, in particular, may result in very high concentrations in some fish. The Indigo Agglomerator enhances Mercury collection by increasing the interaction between the Mercury, in the form of elemental or ionic molecules contained in the gas stream, and the adsorbent, either injected Activated Carbon or using the LOI from the combustion process. Initial tests have shown a factor of four enhancement of the Mercury removal when an Indigo Agglomerator is installed in front of an Electrostatic Precipitator. This is in compliance with the long term EPA requirements in the US.
Emission Reductions at a Chinese Power Station
Growing attention is being placed on the adverse health effects of fine particulates, with the haze and smog through Hong Kong and Mainland China becoming a major concern for local authorities. With a large proportion of these emissions originating from the smoke stacks of power stations and other large industrial process’s, a cost effective solution to this pollution is to install an Indigo Agglomerator. Through electrostatic and fluidic methods the Indigo Agglomerator has been proven to be extremely effective at reducing opacity by 50%–80% and mass emissions by up to 50%. An Indigo Agglomerator was installed at a Chinese Power Station during an outage in December 2007. The 300 MW boiler has 2 side by side Electro-Static Precipitators (ESP’s) with the Indigo Agglomerator installed prior to one of the ESP’s. The Indigo Agglomerator and Power Station have been operating since January the 1st with a limited number of outages for inspections of the Agglomerator and ESP.Particle size testing was performed by Indigo Technologies at the inlet and outlet of the Agglomerator as well as the inlet and outlet of the ESP’s. A historical analysis of ESP emissions was also performed, comparing before and after Agglomerator emissions against each other. These tests show significant reductions in particles less than 5 micron across the Agglomerator and consequently across the ESP giving rise to large reductions in emissions and opacity.
The Indigo Agglomerator is installed directly upstream of the ESP in a rebuilt section of the existing inlet ducting. The Agglomerator can be installed in either vertical or horizontal flow configurations, with limited space and lifting access giving a flexibility of installation options and virtual zero additional footprint requirements.
On-line Measurement of Hazardous Fine Particles for the Future APC Technology
At FLSmidth Airtech we have long experience, and good knowledge, on how to design APC equipment such as ESP’s, FF’s and Hybrid filters. We know how to choose the optimum equipment and how to apply the optimum control strategy. To meet the demand for better performance, lower emissions at lower costs, R&D is considered an important activity at FLSmidth Airtech. Among other tests and investigations we use an Electrical Low Pressure Impactor, ELPI, in R&D to measure time resolved number particle size distributions between 0.007 and 10 µm. The instrument has been used on both ESP’s and FF’s to establish the performance, and it is also used on R&D projects. The instrument has proven to be robust and useful in real plant situations at severe conditions, and provide very useful information. There are several issues to understand when using the instrument, as described in this paper.
In this work we have combined the Electrical Low Pressure Impactor ELPI (Dekati Ltd., Finland) with an FPS-4000, Fine Particle Sampler also made by Dekati Ltd. to measure combustion aerosol particle concentration, size distribution and sizeclassified electrical charge in power plant environment.
We show how the FPS is used to take the sample from power plant stack before and after the ESP, we show how the sample is diluted, conditioned and temperature decreased in a controlled way and how the ELPI is then used to determine the particle size distribution, concentration and charge levels in different size classes. We discuss about the effects of sampling and dilution for the particle charge levels and losses.
We present the construction and operation principle of each part of the system and how different parts are calibrated for accuracy and for particle losses. We show how the system has been applied for demanding power plant environment and finally present measurement results from pulverized coal power plant showing ELPI measurement results compared to gravimetric impactor measurement showing good agreement between different methods.
The monte carlo method was used to simulate chemical agglomeration of sub-micron particle which based on the flocculation model of the water processing, the influence of different agglomeration solution volume on sub-micron particle agglomeration was investigated. Simulation results show that the growth of particle mean diameter and the decrease of particle number are fast at the initial stage of agglomeration, and the speed of them increase with agglomeration solution volume increasing. After achieving stability, as a whole, the particle mean diameter is almost in proportion to agglomeration solution volume. At the last stage of agglomeration, particle number follows a similar bimodal distribution, which is varying with different agglomeration solution volumes. When agglomeration solution volume is 2 ml/min, the peak value of diameter is the biggest.
Enrichment of typical toxic trace elements As on PM2.5 was investigated through bench scale experiments. Results showed that the vaporization of arsenic in pyrite was easier than in arsenate form. Along with increasing temperature from 1100℃ to 1400℃, arsenic content in PM2.5 increased from 0.09 mg/Nm3 to 0.35 mg/Nm3. Then, a novel Electrostatic precipitators (ESPs) combined with chemical agglomeration technique was developed to control the emission of PM2.5 and toxic trace elements. PM2.5 enriched toxic trace elements are agglomerated by some new chemical agents injected as an aqueous solution upstream of ESPs and come into being conglomerations which can be captured by ESPs easily. Systematic experiments of PM2.5 agglomeration showed that chemical agglomeration was a useful method to promote growing up process of submicron particles, XTG was the most effective agglomerant. Resistivity tests revealed that agglomerants could make fly ash resistivity two orders lower at certain concentration, would improve the performance of ESPs with resistivity related performance problems.
How to improve ESP collection efficiency for PM2.5 is getting a matter of environmental concern. in this paper, a process capable of capturing PM2.5 efficiently was proposed, which utilizes a pulsed corona discharge combined with dc agglomeration. a laboratory-scale wire-plate electrode configuration was established. the particle electrostatic charging and number concentration distribution of PM2.5 have been measured by an electric low pressure impactor (elpi) at real time with the size range from 0.007 μm to 10 μm. the particle charging and collection efficiency characteristics of PM2.5 were quantitatively investigated under different applied pulse peak voltage. the results show that for a certain given operating condition, PM2.5 collection efficiency increases with the increasing pulse peak voltage. dc voltage agglomeration is used to achieve a number reduction exceeding 90% on the submicron fraction of particles. this research may provide a new technology for efficient removal of PM2.5 from flue gas in coal-fired power plant.
Based on the kinetic equation of particles and the method used in Williams’ research on acoustic coagulation (Aerosol Science, 1991), an approximate expression is proposed for the coagulation coefficient of bipolar-charged particles with the effect of an alternating-current (AC) electric field. When the external electric field is high enough, the proposed solution agrees well with the previous numerical results of Koizumi et al (Journal of Electrostatics, 2000).
The experiments carried out in this study have focused on improving nano-particle collection efficiency and suppressing particle re-entrainment at the same time in an ACESP with hole-punched electrode. a trapezoidal ac high voltage was applied to a collector. the collection efficiencies as a function of particle diameter were studied on three ESP cases, which were the universal DCESP, DCESP with hole-punched electrode and ACESP with hole-punched electrode. as a result, ACESP with hole-punched electrode was successfully developed.
Electrical Operation and Power Sources:
Precipitator Performance Improvements and Energy Savings Based on IGBT Inverter Technology
Energy efficiency and energy saving become more important for many technical applications due to the higher cost of energy and environmental impact (e.g. CO2 emissions). Dust emissions need to be maintained below the emissions limits regardless of the operation mode or fuel type of the process.
Basically, precipitator performance improvements can be achieved by applying higher electrical power to a precipitator. The limitation of a conventional SCR based high voltage power supply is the 50/60 Hz voltage ripple, which leads to flashovers during the peak voltage, while the average voltage is comparably low. High frequency IGBT inverter technology can deliver a DC voltage with a higher average value resulting in significantly higher power. Additionally, the current can be interrupted at any time for faster reaction to flashovers. High space charge density is avoided and therefore shorter wait time for deionisation is required resulting in higher average power. In case of high resistivity dust short superimposed pulses can be applied for increased charge density generation at the spray electrodes.
Existing plants can be upgraded easily by just replacing the control cubicle, while the TR set can be kept in use in many installations. For optimum performance the TR set can be replaced by a high frequency (500 Hz / 10 kHz) type. An advantage of this concept particularly can be found in existing plants, because the cable installation between the cubicle and TR set can be still up to 120 m.
Grid current waveforms of IGBT inverters are different from SCRs. The reactive power demand is much lower due to the diode bridge at the input stage and the voltage link capacitor. The load current is symmetrical for the three phases. The harmonics of the grid current are typical for a standard diode rectifier. This is very common due to the fact that IGBT inverters are used for electrical drives frequently. The low demand of reactive power limits the apparent power to a value very close to the active power. Therefore supply transformers which are rated for the apparent power demand of the connected load can be reused, even if higher electrical power for the precipitator is required. For future requests the input rectifier can be equipped with an IGBT based power factor control to limit the harmonic distortion.
Active Power savings (real savings) can be achieved by a computer based energy management system which calculates the required power for each zone of the precipitator. Due to the high dust load the inlet fields of a precipitator generally require more power than the middle fields or outlet fields. Practical tests have shown that the total power consumption of a precipitator can be decreased significantly, depending on the operation mode and the process conditions X 0X . Lowering the power of a precipitator results in a higher sensitivity to any process changes, particularly during collection electrode rapping when dust from the plates is being released. To avoid dust emission peaks the high voltage and current control has to be synchronized with the rapping interval of the entire field. Increasing the current during rapping has been proven to keep the emissions low, even during rapping.
The achievable power savings depend on the operating conditions of the precipitator, and they usually vary during operation. The system shown in this paper is designed to keep the emissions within the required range with highest priority. Anytime the emissions range can be reached with lower power, the system will drop down the power as low as possible. In coal fired power stations it has been shown that usually 30%-60% of the electrical energy within a period of operation can be saved. This results in a reduction of CO2 gas emissions in a coal fired power station due to the resulting electrical usage savings. The power consumed in the precipitators has to be generated additionally in the generation plant.
Performance Enhancements Achieved with High Frequency Switch Mode Power Supplies
The PowerPlus can provide kVdc outputs that range from fast IE (low to fractional ON and OFF times) to nearly pure DC as well as numerous operational modes in between these two limits. This provides maximum flexibility in obtaining optimum ash collection from various fossil fuels.
With its high power factor, the PowerPlus unit provides much more kW into the ESP while requiring less kVA from the source when compared to conventional units.
The reduced size and weight and less dielectric fluid of the PowerPlus allows for easier installation and service, less fire and environmental hazard, less field wiring costs, and lower total installed costs.
The PowerPlus represents the future of power supply technology for ESP’s, and will soon be the standard solution for powering ESP fields. Any user considering New ESP’s or upgrades to ESP’s should be fully well aware of PowerPlus technology and its potential for enhancing ESP performance
High Frequency Power Supply Operation on Hot-Side ESP
In recent years Switch Mode Power Supplies (SMPS) have been introduced into the utility ESP market. This paper summarizes EPRI and Southern Company funded Switch Mode Power Supply testing on Alabama Power’s Plant Barry Unit 4 Hot-Side ESP. For this test program, eight Switch Mode Power Supplies were installed parallel to the existing four T/R sets.
During the test program, the ESP was operated for a time using each power supply type and emission measurements were taken. Included are ESP Outlet Loading and Size Distribution Results as well as EPA Method 5 mass emission results. Additionally, the paper includes an analysis of the ESP electrical characteristics during the operation of both types of power supplies as well as any possible conclusions.
Industrial Applications of Three-phase T/R for Upgrading ESP Performance
This paper reports one of our recent ESP upgrading activities. It was performed with a 600 MW coal fired boiler equipped with a four-channels and four-fields ESP. The dust collection efficiency was around 98.69% and the emission was in the range of 200 mg/m3–300 mg/m3. The upgrading include replacing the four traditional single-phase T/Rs used for inlet fields with four three-phase ones. The new HV system has been in operation for over one year. Dust emission keeps to be below 200 mg/m3 with more than 400 kW energy saving.
Industrial Applications of a New AVC for Upgrading ESP to Save Energy and Improve Efficiency
This paper reports one demonstration investigation on one new automatic voltage controller (AVC) named ZH2005 to improve dust collection efficiency and save energy consumption. Experiments were performed with a 200 MW coal-fired boiler owned by Huaneng Beijing Cogeneration Co., Ltd. Energization methods, such as simple-pulsing, spark-rate control, intermittent energization and ZH2005 method, were adopted for evaluation of both dust emission and energy consumption. After almost oneyear utilization, we conclude that the ZH2005 can keep outlet dust emission to be below 20mg/Nm3 and/or a total dust reduction of about 120T per year with an energy-saving of about 70% or 1260 MWh.
Highly efficient switch-mode 100 KV, 100 KW power supply for ESP applications
For nearly a century, electrostatic precipitators (ESP) were driven by line-frequency transformer-rectifier sets. The last decade has been marked by steady penetration of high-frequency HV power supplies (HVPS) that offer considerable benefits for the industry. This paper describes a novel concept and physical demonstration of an ultra-high efficiency, small size and low cost HVPS specifically designed for ESP and similar markets. Key technology includes a modular HV converter with energy dosing inverters, which operate at about 50 kHz and have demonstrated an efficiency of 97.5% in a wide range of operating conditions. The inverters’ output voltages are phase-shifted, which yields an exceptionally low ripple of 1% and a slew rate of 3 kV/μs combined with low stored energy. Modular construction allows easy tailoring of HVPS for specific needs. Owing to high efficiency, small size is achieved without turning to liquid cooling. Controls provide standard operating features and advanced digital processing capabilities, along with easiness of accommodating application-specific requirements.
HVPS design and testing are detailed. Experimental current and voltage waveforms indicate virtually lossless switching for widely-varying load in the full range of the line input voltages, and fair agreement with simulations. Calorimetric measureme nt of losses indicates to a >98.5% efficiency of the HV section. The overall efficiency is 95% at full load and greater than 90% at 20% load, with power factor typically greater than 93%.
The Crystal Ball Gazing with Electrostatic Precipitators: V-I Curves Analysis.
Have you dreamed about knowing what happens inside an electrostatic precipitator (ESP) without opening it? Well, the main defects can be revealed using voltage – current curves. When the unit is operating, it is impossible to intervene in the electrofilter. Many parameters can be used to demonstrate an increase in dust emission levels which might result in a malfunctioning of the ESP itself or of other components of the unit. When the external elements of the electrostatic precipitator have been eliminated, attention can be focused on the Electrostatic precipitator itself. If a diagnosis can be performed “in state” before shutting down the unit, valuable gains can be made in time and efficiency during the maintenance operation. V-I curves constitute an invaluable aid, indeed, they are the signature of the ESP itself and are more precise than the maximum recorded voltage and current points. The voltage-current curves were obtained in experimental pilot conditions and in an industrial situation to demonstrate the four main defects most commonly encountered in ESP:
- the fouling of the emissive wires;
- the misalignment of plates and wires;
- insulators problems;
- the presence of back-corona.
In parallel, a modelling of the physical phenomena corresponding to these defects confirmed the modification of the curve. So, it is possible to predict the defects by analysing the V-I curves. To facilitate the V-I curves analysis of a significant size ESP, software was created in order to give:
- a display by field and file, the V-I curves;
- a comparison of different sets of data to follow the evolution of the curves;
- a defect mapping (clogging, misalignment or insulators problem, back-corona).
Subsequent validation on different ESP of the EDF fleet confirmed the power and the reliability of the software.
Modern high speed microprocessors, advanced display technologies and recently developed circuit protection components have allowed a new generation of ESP controls to be developed. This paper reviews the advances made and how they impact users. Specifics of the designs will be shown and described along with real-world examples of their application. A discussion of the rational behind features such a “Closed Door” troubleshooting, and multi-language support will be discussed. Closed Door troubleshooting is critical to minimize the risk of Arc-Flash injuries. Multi-Language support is becoming a requirement to ensure that the controls are setup and used properly wherever they are installed. Both of these requirements put demands on the electronics and display technologies which drive the choice of components and support circuitry. A description of the design trade-offs made during the development process will be included. Field experience with the new design, reliability statistics and plans for future development will complete the presentation.
Another Concept of Three Phase High Frequency High Voltage Supply
Get your electrostatic precipitator boosted with “GNP 800”.
Development and Application Features of High Power High Frequency Power Supply for ESP
This article briefly introduce the current development progress status of high power high frequency power supply for esp of fujian longking, illustrating comparatively its application characteristics and putting emphasis upon discussing its application features in former electric fields with specific cases. Furthermore, it makes a study of the application of high frequency power supply in large-scale coal burnt unit and makes an outlook of the application heading in other fields.
The Application Strategy of Three-phase HV Power Supply for Special Working Condition
Breaking through below 50mg/Nm3 emission, has become an important issue that the ESP technology must resolve. This paper elaborates the whole solution of three-phase H&L voltage integrated control, and it’s successful applications in different industries, to share with every expert on meeting. The promotion and application of this whole solution technology will enable the majority ESP in-service satisfying the new emission standard. It provides powerful technical support to realize the target of energy saving and emission reduction in “The Eleventh Five-Year Plan”.
This paper discusses the development and application of the technology of compounded type power control rapping, introduces the two basic parts of the technology: high and low voltage related mode power-off rapping and enhanced type timing power-off rapping, and analyzes the effect of the technology of compounded type power control rapping in the aspect of reducing the outlet flue dust emission concentration with the project rebuilding instances.
Study on Efficiency Enhancing and Energy Saving of High Voltage Power Supply of EP
It was analyzed that theoretical and practical watt consumption needed in flue gas cleaning in electrostatic precipitator in this paper to find that they were quite different from each other. Actually, the operating electrical energy consumption of EP should be classified as effective, minus effective, ineffective and natural energy consumption. The effective electrical energy is very little, but the proportion of the others is big. The proportion of effective electrical energy can be enhanced and the others can be reduced via techno-measure. Based on the White’s theory about EP power supply, the operating status quo of EP and the successful study and extension of high voltage power supply facility of EP with efficiency enhancing and energy saving, the working manner of electrostatic precipitator power supply should be transferred from the single spark setting of high current, high power and high consumption to the scientific track of high efficiency and energy saving in coal-fired power plants in China.
The paper analyses the main issues and the key technologies which need to be solved of the electrostatic precipitator (ESP) energy saving control. On the basis of analyzing many ESP on-site operation data and the voltage-current curves, we developed a new type energy saving control system by combining a lot of ESP performance tests comparison and technologists’ experiences. The new system is a closed-loop control system with multi-parameter feedback, and it has the functions of analyzing the ESP’s working conditions accurately and adopting the optimal control by using the latest analysis software of the working conditions characteristics. The paper also introduces the field applications of this system.
Based on analysis on the physical nature of dust precipitation using optimal electric spark rate and some problems relating to dust removing effects, high consumption of electric power and steel material, this article brings forward the query on its sustainable development. Finally this article points out that dust precipitation using direct current supply with extra wide polar distance is the solution to these problems.
ESP has been applied widely in environmental protection. In this paper, the measure methods and tested setup of the collecting plate current density on ESP were introduced. In pulse engergization and direct current power supplies, distribution of collecting plate current density in vertical and parallel direction of corona discharge line on ESP are contrastively measured. It is concluded that distribution of collecting plate current density on ESP with pulse engergization was more uniform than that with direct current power supply in experiments, and it is advantageous to improve dust performance of ESP.
Energy-saving and efficiency enhancing are more and more important to the electrostatic precipitator (EP). This article introduces the structure of hardware platform and the connotative meaning of combination of high voltage (H.V) control and low voltage (L.V) control, presents the schematic diagram of multi-processors system structure and explains the advantages of hardware platform. The article also analyzes the power consumption during the EP’s running process and introduces the two key technologies of achieving energy-saving and efficiency enhancing effect: one is using pulse power supply to reduce the noneffective and adversely effective electric power, lower the power consumption and improve the efficiency; the other is achieving dynamic optimization control by the method of analyzing the critical electricity parameters, it make the equipment run in the optimal state of energy-saving and efficiency enhancing. As is proved in practice, the equipment can lower the EP’s working power consumption obviously, reduce the dust emitting and eliminate or weaken the back corona. This equipment has important actual meaning and high popularizing value.
Research on High Frequency Switched HV Power Supplies for ESP
High voltage switching power supplies have found wide applications in many fields, and great progress in ESP also has been made in recent years. In this paper many concepts on designing a high frequency switched HV power supply have been presented, the paper also briefly describes a newly developed 32 kW high frequency switched HV power supply for ESP.
Design of Switch Mode Power Supply for ESP
In this paper we describe the design of Switch Mode Power Supply for Electrostatics Precipitator. The Supply can work at any point in the square area of 80kv-1000mA. It has several Working Modes, such as Spark-Rate, Pulse, Approach Back Corona etc.
Research and Application of Automatic Control Technology of Back Corona
High voltage switching power supplies have found wide applications in many fields, and great progress in ESP also has been made in recent years. In this paper many concepts on designing a high frequency switched HV power supply have been presented, the paper also briefly describes a newly developed 32 kW high frequency switched HV power supply for ESP.
The Research on Three-phase Medium-frequency DC High-voltage Power
This paper analyzes the primary problems of SCR power and high-frequency and high-voltage power (SMPS), which apply to electrostatic precipitator(ESP), raises a original three-phase medium-frequency DC high-voltage power applied to ESP, and introduces the background of the research, the principle of working, the structure of the device, the output of simulation and the laboratorial trials of this original power supply.
Investigation of Current Density Distribution Model for Barb-plate ESP
In order to satisfy Gaussian electric flux theorem, current distribution at the plane of barb-plate electrostatic precipitator (ESP) must follow a certain specified distribution function. It is proved that, in this paper, the current distribution at the plane of barb-plate ESP is t-distribution with 4 degree of freedom by variable analysis on Warburg’s Law. According to the characteristics of the current distribution, a more applicable calculation formula is derived by using the total current at the plate electrode. The values predicted by our t-distribution model are in sound agreement with the experimental data presented by other researchers.
SLC500 Programmerable Logic Controller Hot Standby Two-node Cluster
This paper describe the hardware configuration and communication test of SLC500 Programmerable Logic Controller Hot Standby Two-node Cluster
Evaluation of HV Power Source for ESP
Since the formal application of industrial ESP, our country has got great breakthrough in technology and wide application of it. As an important part of ESPs, High-voltage power source has gone through procedures as simulative control single-phase power source, constant-current power source, pulsed power source, three-phase HV power source, high frequency switch power source and HV contravene DC power source. For single field, one type of power source was used in the past. A few ESP manufactures begin to apply various types of HV power source on the same ESP in recent years. This article will analyze the advantages and drawbacks of HV power sources of ESP, give theoretic analysis and research for comprehensive use of various HV power source on the same ESPs.
V-I characteristic Principle of Electrostatic Precipitator
Based on the systematic analysis of the V-I characteristic of 384 group typical experimented electrodes-arrangements with the same 480 C plate collection electrode but various discharge electrode type, width of the cross channel, wire-wire spacing and design of the tri-electrode, this paper puts forward that V-I characteristic curve of common wire-plate type electrostatic precipitator can be expressed as I=aVb model and provide the corresponding value of a, b. The results indicate that R-square is less than 0.5%.
Enhanced Fine Particle Collection by the Application of SMPS Energization
Over the past decade or so the health problems associated with the inhalation of submicron particles from industrial processes has taken prominence and has lead to the stricter legislation of emissions such as the US PM2.5 approach. Generally most forms of control equipment readily handle and collect particles greater than 1 micron diameter, however, those less than 1 micron diameter are very much more difficult to collect.
In the case of electrostatic precipitation, which involves both particle charging and migration under the influence of an electric field, the larger particles, generally greater than 1 micron are charged by collision with the ions and electrons present in the inter electrode area. It will be shown that the charge on these particles is proportional to the radius squared and its migration velocity proportional to the voltage squared, both reducing with particle size. The very small particles however, are charged by a diffusion processes and migrate under the influence of Brownian Motion which increases as the particle size decreases. The result of this is that a typical particle size/efficiency curve indicates a significant penetration window in the 0.8 to 0.2 micron diameter, which coincides with the change from collision to diffusion charging of the particles.
Because of this penetration window, should an existing precipitator operating under optimum electrical conditions, not comply with fine particle emission requirements, the conventional enhancement scenario would be to increase the precipitators plate area, a very expensive solution, since the charging and precipitation operating conditions have been already optimised. It will be shown, however, that the replacement of the conventional mains energization system by an SMPS approach in an existing ESP will enhance the collection efficiency of particles in the penetration window as a result of the increase in both operating field voltages and currents.
An application was applied to a 2 field ESP, dealing predominately with sub micron fume. This was initially assessed using PALCPE™ (Proactive Approach to Low Cost Precipitator Enhancement), which indicated a significant reduction in the fine particle emissions was achievable by operation under SMPS Operation. An SMPS unit was subsequently fitted to the outlet field of this precipitator and the operating data will be examined in detail. With the outlet field under a mains rectification energization system the overall emission was -25 mg/Nm3, which after installation of the SMPS unit reduced to less than 15 mg/Nm3.
Two ESP Power Supply Patent Technologies
Two ESP power supply technologies introduced in this paper use “amplitude modulation & phase shift” as key technique, overcome most of the weakens on the basis of all the advantages of SCR phase shift and voltage regulation technique, improve the performance and collection efficiency of ESP in the bad condition, as well as has energy saving effect.
“SCR amplitude modulation & phase shift high voltage (HV) power supply patent technology” which updated form the SCR phase shift and voltage regulation technique, totally perverse existing ESP power supply system, can accomplish technical upgrading without stopping production.
“Integrated SCR amplitude modulation & phase shift high / low voltage power supply patent technology” has accomplished the integration of ESP high/low voltage power supply system with two patents of “amplitude modulation & phase shift” and “3 W industrial control machine”, and decrease its size of hardware by 4/5 than existing SCR phase shift and voltage regulation system.
Flue Gas Conditioning and Back Corona:
Particulate and Mercury Emissions Control by Non-traditional Conditioners
Despite significant progress made in reducing the installed costs of bag houses, Electrostatic Precipitators (ESP) remain the most accepted device all over the world. Similarly advances in the design and electronics have been made in ESP. Still ESPs continue to become limited, on occasions, for multiple reasons. This limitation is widely overcome by conditioning the fly ash prior to its collection in the ESP. In many cases traditional conditioning with SO3 or SO3 & ammonia is a good choice, (particularly in the USA where expenses on capital costs are more acceptable than operating costs.) However, non-traditional conditioners are especially favorable where the conditioning is needed only on an intermittent basis both in and out of USA. Nontraditional conditioners bring extra value when other components can be incorporated into them for multi pollutant control. In the area of mercury control, particularly in the USA, use of non-traditional conditioners outweighs the value of traditional conditioners when activated carbon injection (ACI) is selected as the method of choice. Contrary to the experience with traditional conditioning, laboratory and small scale field tests have clearly shown that the mercury removal capacity of injected carbon is not adversely affected when non-traditional conditioners are used. Switching the traditional with non-traditional conditioning can bring significant cost advantage to mercury control by ACI. This paper discusses some of the novel conditioners which alone or in conjunction with others are useful in opacity and multi pollutant control.
Flue gas conditioning (FGC) systems offer an effective option for control of Particulate Matter (PM) emissions and enhances the performance of the Electrostatic Precipitators (EPs) when using coal of different properties. The increasing environmental awareness and the mandate of the Environmental Protection Agencies (EPA) in various countries to thermal power stations using coal-fired boilers for lowering Suspended Particulate Matter (SPM) emissions has increased the urgency for reviewing options and alternatives. As compared to ESP retrofits or bag filters, the FGC systems in conjunction with existing EP offer cost effective and flexible alternatives for controlling SPM emission levels. The paper describes recent advances in FGC technologies. Chemithon’s FGC technologies are in use at more than 170 thermal power plants world wide. The presentation reviews the flue gas conditioning technology as well as few case studies for high ash and low sulfur coal and highlights the economic advantages of a cost effective technology option.
Modeling of Back Corona in Pulse Energized “Multizone” Precipitators
Most of the electrostatic precipitators have at least two zones in which different supply parameters, rapping programs can be used. Lot of ESP models are handling the electrostatic precipitator as one block whit the same energization. However, separated operation of zones is useful to improve collection efficiency. In this paper authors represent an improved numerical ESP model that is capable to handle multiple zones with different properties. The represented modeling process is focused on different energization modes and the formation of back corona.
As a case study, application of the model is presented in case of such a situation, when aluminum-oxide dust must be separated from the gas-powder mixture. Determination of electrical and physical properties of the aluminum-oxide dust is involved in the paper as well as results of laboratory measurements predicting the performance of precipitation. Measurement results are compared with calculation results and the performance of the existing industrial electrostatic precipitator for different supply modes to select the best one among them.
Some Investigations on Fly Ash Resistivity Generated in Indian Power Plants
The design and operation of Electrostatic Precipitator depends on the properties of the coal burned and fly ash generated in the boilers of the power plant. The properties of the coal used in different power plants cross the India vary widely, but most of the times the sulfur contents are low in the coals. As a result the resistivity of the fly ash is in general, very high and it leads to develop back corona at the collecting electrodes even at comparatively low current densities flowing through the different fields of ESP. All this results in detorieting the Collection efficiency of ESP and large size of ESP is required to meet the emission standard for similar level of power generation elsewhere. Knowledge of electrical resistivity is essential for sizing of ESP and to determine a strategy to improve its performance. A special facility has been developed at IIT Delhi to investigate the variation of resistivity at different temperature and moisture levels under simulated conditions those exiting in side an ESP. A series of experiments have been conducted on the fly ash samples obtained from different power plants in India. Empirical relations developed by Bickelhaupt, which are based on chemical composition of fly ash for calculating the electrical resistivity, are used to calculate as theoretical value for given experimental conditions. New empirical relations based on experimental results and operating conditions have been developed to provide better agreements.
Enhancing ESP Efficiency for High Resistive Fly Ash by Reducing Flue Gas Temperature
The resistivity of fly ash after coal-fired boilers varies with the flue gas temperature. the normal esp operating temperature of around 150 ℃ is typically near the maximum resistivity of the ash. for low sulphur coals the resistivity will sharply decrease if the flue gas temperature at the esp inlet is reduced to about 100 ℃ or less. this will mean that a significantly smaller esp can be built for a given efficiency. already in the early 1970’s esps were built at the liddell power station in australia purposely designed to operate at low temperature to reduce the fly ash resistivity. the full-scale design at liddell was based on pilot testing at other locations in order to verify the low temperature approach. despite successful implementation at liddell the experiences did not result in much follow-up of low temperature esp operation. the concept was revived in japan in the 1990’s, resulting in several installations working at temperatures below 100 ℃ these units have a considerably reduced esp size, and the energy recovered upstream the esp is used to re-heat the flue gas after the desulphurisation system. the low temperature esp operation is now well proven and a viable alternative when burning low sulphur coals.
The Technical and Economical Analysis on the Application of FGC in Large Scale Coal-fired Units
In this paper we describe that large scale coal-fired units are designed basing on the working condition of burning several coals because of the internal coal resources status in China at present. It differs a lot for ESP to collect the dust when using different coals. Taking the dedusting technology of ESPs equipped with FGC system of Guangdong Pinghai Power Station 2×1000 MW units as an example, after adopting combined dedusting technology, the ESP can be designed basing on the easily dedusting coal, which reduces the overall investment of dedusting system. FGC system is completely separated from ESPs, which has the advantage of flexible operation. Furthermore, compared with other dedusting technologies, it keeps the characteristic of low pressure loss, high reliability, low cost of running and maintenance, which has competitive advantages in technology and economy.
Upgrading of Existing Electrostatic Precipitator:
Advanced Methods of Upgrading Electrostatic Precipitators
Many electrostatic precipitators (esp) around the world have been operating for several decades. more stringent emission requirements and more challenging conditions due to fuel switching and other process changes result in a need for improved dust collecting efficiency. often, it is sufficient to improve the performance of the existing esp system by utilizing appropriate upgrading technologies. another reason to invest in esp upgrade technology is to reduce operating costs. For the existing ESP upgrade applications, some technologies may be better suited than others for reasons of layout and cost, process integration, age and design of that plant and the emission levels to be achieved. The most appropriate solution can be selected after detailed inspection and assessment of the present electrical, mechanical and gas distribution status as well as process conditions. Initially the ESP needs to be restored to mechanical and electrical operating conditions. The Upgrade solutions include full range of options for; Control System Upgrade, Extension of Field, Flue gas Conditioning.
The paper will first present environmental drivers facing ESP operators. Secondly, The various ESP technological upgrades will be reviewed, including a discussion on the advantages and disadvantages of the selected upgrade methodology.
Challenges for Reduction in Emission in Old Electrostatic Precipitators at Lower Cost
Industrial plants are one of the major users of Electrostatic Precipitators (ESPs) for particulate emission control. These are primarily Cement, Metallurgy, Pulp & Paper and Aluminum industries. The paper generally speaks about the challenges that we face with the old Industrial Precipitators to cope with stringent emission norms in spite of Physical dimensional and plant layout Restrictions. The Precipitators in such Industrial applications are used not only for emission control but also to recover the dust either to recycle or to use as end product. In such conditions, ESPs really face challenges in front of Fabric Filters in spite of quite a few Operation and Maintenance advantages. Today’s technology has advanced very fast, particularly in the area of High Frequency Power Supplies and really shows extremely promising results beginning usually at 30% emission reduction, but commonly much better than this – in spite of all the constraints. Present market scenario for such Industrial plants may sometimes not even allow a proper shut-down period to replace/rectify defective Mechanical components or to realign critical ESP internals or to carry out a reasonable Gas Distribution and sneakage Tests. For obvious reason, thrust is more and more towards Electronics and Controls to overcome problems in other areas as a substantial portion of the work can be carried out without a shutdown. In this paper we discuss and compare the emission performance enhancement of two Industrial ESPs plants in Australia.
Least Cost to Maximise Dust Collection in Electrostatic Precipitators
Electrostatic Precipitators (ESPs) are widely used to contain the particle emission from industrial plants, with coal-fired boilers as the largest user. Human health requires reduced particle emission. This paper lines up the most commonly used means to reduce the particle emission, and compares their relative cost. A deeper analysis focuses on relatively low-cost means to improve the ESP collection efficiency by energising and operating the ESP in new ways. This technology development has recently, at an accelerating pace, occurred during the last 5-7 years, and is still ongoing. Achieved emission reductions are really large, seldom smaller than 30%, and usually larger. New ESP operation–beginning by changing the way in which collecting plates are cleaned (but usually not changing mechanical components)–necessarily must be combined with co-ordinated operation of both conventional TRs and high-frequency energisers. This is today an emission-predictable means for which emission guarantees can usually be given on a plant-specific basis. This paper provides recent examples, both from USA and Europe.
ESP Renovation in Da Wukou Power Plant, Ningxia
This article introduces the renovation scheme of 4#, 3# boiler ESP in Da Wukou Power Plant, Ningxia. Under the limited space condition, the outlet concentration is not over 300 mg/Nm3, the de-dusting efficiency≥ 99.5 %, which offers good experience for the renovation of the similar equipment in China.
Hybrid ESP & FF Precipitation:
Cost Effectively increasing the Filtration Area in Fabric Filters for Large Power Plants
The market demand for very low outlet particulate emissions from power plants is resulting in the choice of fabric filters (FFs) over electrostatic precipitators (ESPs) in many projects. For the same flue gas volume flow, the higher the required removal efficiency, the choice between ESP or FF tends to favor the FF, due to its lower capital cost. As a result of the increasing demand for FFs, suppliers need to meet the market requirements by providing properly designed, efficient, cost effective FF designs. Many of the projects requesting FFs today are for coal fired boilers. As the size of the boiler increases, the larger the amount of flue gas that needs to be cleaned, and the larger the size of the FF. Increasing the filtration area in each compartment of a FF to meet this need is not a simple process of scale-up. Maintaining low outlet emissions, the same or lower FF pressure losses, and equal or longer bag life are all key factors. As the filtration area in each filter compartment increases, the amount of flue gas and dust entering the compartment increases, and the risk of performance, pressure drop and bag life problems increases if the compartment arrangement is not designed properly. Alstom Power Systems (APS) is currently completing an extensive effort of increasing the amount of filter area that can be installed in each compartment of a FF. This paper presents the key aspects of design to address gas and dust distribution, and pressure drop issues, as well as the pulse cleaning system design and capacity. APS is actively working in the research laboratory as well as in new FF installations to demonstrate the success of the new design.
Long-term COHPAC Baghouse Performance at Alabama Power CompanyS E. C. Gaston Units 2&3
Following a successful pilot-scale baghouse testing program and after reviewing the performance of Luminant’s COHPAC (EPRI’s patented Compact Hybrid Particulate Collector technology) baghouse installation at its Big Brown Station, Alabama Power Company (APCO) decided to install a COHPAC baghouse on Unit 3 at its E. C. Gaston Steam Plant located near Wilsonville, Alabama in late 1996. A second COHPAC baghouse was installed at Gaston Unit 2 in 1999. These baghouse systems were designed with the low pressure/high volume pulse-jet cleaning technology (Hamon Research-Cottrell) that orients the bags in concentric rings and uses rotating pulse manifold arms. Performance of these systems at Plant Gaston Unit 3 and Unit 2 has been excellent during the past eleven and a half and nine years, respectively. Original 3.0 and 2.7 denier Ryton felted fabrics have given way to higher permeability 7.0 denier PPS felt bags in both units. Overall flange-to-flange and tubesheet pressure drop performance has improved without compromising particulate collection efficiency. Recent filter drag values of 0.5 in. H2O/ft/min on Unit 3 and 0.3 in. H2O/ft/min on Unit 2 have been experienced at air-to-cloth values of 8.0 ft/min. Average pulsing frequencies have ranged from 0.2 pulses per bag per hour for recently installed 7.0 denier PPS felted bags up to 0.7 pulses per bag per hour for older 2.7 denier Ryton felt bags. COHPAC baghouse installation has successfully reduced stack opacity. Comparing the average of the last eleven years of operation (1997 – 2007) to the average of the two years prior to COHPAC baghouse installation on Unit 3 (1995 – 1996), the average opacity has been reduced 50% and the number of hours per month that the average opacity has exceeded 20% has been reduced 95%. Similar results have been experienced on Unit 2. Except for early bag failure episodes on each unit caused by bag-to-bag abrasion, bag life has been very good. The original 3.0 denier Ryton felted bags in the rear modules of the Unit 3 baghouse remained in service for five years accumulating over 39,500 hours of exposure to flue gas with few bag failures. Front module bags in Unit 3, however, had much shorter bag lives because of a higher incidence of bag failures. Average service lives for the 3.0 and 2.7 denier filter bags were similar to those of the follow-on 7.0 denier PPS felted fabrics, typically two to three years, 19,000 to 27,000 hours of exposure to flue gas. Evaluation of the performance of various test bags has been ongoing for several years. Early tests compared the performance of 6.0 denier and 7.0 denier PPS felts with traditional 2.7 denier felts. 7.0 denier felted fabrics performed very well. More recently, various dual-density felts have been tested. Results after 20,000 hours of flue gas exposure indicate that the Dual Density Torcon – 9058 felt is the best of the four test fabrics. The test program is continuing. COHPAC baghouse performance for Alabama Power Company has exceeded expectations and continues to provide an excellent air pollution control benefit.
Study of the Use of Bag Filters in Hot Gas Filtration Applications: Pilot Plant Experiences
A complete experimental campaign has been carried out in a hot gas filtration test facility so as to test different types of bag filters. The facility is designed to operate under a wide range of conditions, thus providing an excellent tool for the investigation of hot gas filtration applications for the conventional and advanced electrical power generation industry such as IGCC, PFBC or fuel cell technologies.
Relevant parameters for the characterization and optimization of the performance of the filters have been studied for a variety of operation conditions such as filtration velocity, particle concentration, pressure and temperature among others. Pressure drop across the filter, cleaning pulse interval, baseline pressure drop, filtration efficiency and durability of the filter have been investigated for each type considered and dependences on parameters have been established. On top of that, optimal operating conditions and cleaning strategies were determined.
The tests results show that bag filters are a suitable alternative for the hot gas particle removal due to the better performance and the high efficiency observed, which makes them suitable for industrial applications operating under high temperature and high pressure conditions considered within the study (200 ℃-370 ℃ and up to 7.5 barg).
Additionally, a technology based on combined dry removal of particles and SO2 in a single step by using a high temperature filter unit and solid sorbent injection for large coal combustion power plants is proposed to be studied in this paper.
The R&D and Application of Electrostatic-fabric Organic Integrated Precipitator in China
In recent years, the Chinese government vigorously promotes the “energy -saving and emission reduction” policy and the conventional ESP and fabric filter technologies applicable in all different industries face some new challenges. FE type Electrostatic-Fabric Organic Integrated Precipitator (EFOIP for short) is a new type of dust removal technology successfully developed by Longking, which has been applied in a number of projects in China. Practice shows that the technology has the following characteristics such as significant energy saving, stable, reliable, low-emission and so on. It is an ideal next generation dust removal device.
Research on Performance of Electrostatic-bag Precipitator with Comparative Industrial Tests
The industrial tests made a comparison of three key factors under different filtration velocities, which comprised the outlet emission H concentrationH of dust, grade collection efficiency of PM10 and the rising rate of pressure drop .Meanwhile, the paper provided the reasonable scope of filtration velocity of EBP through the tests, which was helpful for the design and application of large-scale EBP.
A Discussion on the ESP-FF Hybrid Precipitator
This article introduced several concerned questions when people choose the ESP-FF hybrid precipitator and compared the performance characteristics and applicability of integral and detachable ESP-FF hybrid precipitator.
Collection of High Concentration of Desulfurized Dust with ESP & FF
The application experience for electric static precipitator (ESP) or fabric filter (FF) fitted in 200 MW dry/semi-dry FGD system is introduced. The flexibility, invest and maintenance cost for these two kinds dust collector are generally compared when they are collecting high concentration desulphurization dust. The suggestion of how to choose desulphurization and dust collecting technics for the environmental protection are provided.
Application of ESP and Fabric Filter in Power Plants in China
Electrostatic precipitators have been used in power plants of China for decades. As the dust emission limit becomes stricter than before, fabric filters come into using in power plants. This paper presents two examples of electrostatic precipitator and fabric filter and analyze their technique economy.
Application of Electrostatic Fabric Hybrid Particulate Collector
This paper introduced several examples of electrostatic fabric hybrid particulate collector (EFPC), and discussed their advantages and shortcomings. In addition, the suitable application conditions for the use of EFHDC are presented.
Application of ControlLogix in Remote Monitoring System of ESP-FF Hybrid Precipitator
Remote monitoring system in JHARSUGUDA 6×600 MW independent power station in India includes three parts, which are program controls of high voltage ESP, low voltage ESP and fabric filter. The technology applied in this system has reached international advanced levels. RSView monitoring software from Rockwell Automation Power Systems Ltd. and programmable logic controller of ControlLogix series are selected in this system Remote monitoring system provides perfect communication mode and network, and use redundant configuration of double- machine and double-net to ensure the system reliable. This paper introduces the system in detail.
Numerical simUlation on a Hybrid Electrostatic-bag Precipitator
The electrostatic-bag precipitator which has an ability to meet the ever stricter air quality directive will be the choice of future particle collectors. In this paper, a numerical model was proposed to simulate the electrostatic-bag precipitator with actual size. This numerical investigation was mainly focused on the influence of opening ratio of distributor plates on gas flow distribution. The simulation results revealed that the impact velocity on front bags was higher with larger opening ratio. And the flow rate distribution in both electrostatic precipitator and bags was uneven, which should be solved in the optimum design of hybrid electrostatic-bag precipitator.
Wet Electrostatic Precipitation:
Evaluation of Corrosion-Resistant Alloys for Wet Electrostatic Precipitator
We found suitable corrosion-resistant alloys for a wet electrostatic precipitator (WESP) equipped with an intermittent washing function used in power plants that use fuel with a high sulfur content. Using seven types of corrosion-resistant alloys selected in advance, tests were run to compare the four forms of corrosion that occur within the WESP. N06022 or N10276 produced better results when pH was lower than 0.5. In the 0.5 pH to 1.0 pH range, S32053 was found to be the ideal material from the viewpoint of both corrosion resistance and cost. By capitalizing on our wealth of design technologies and know-ledge of materials, we can provide optimum systems for the corrosive environment within the WESP.
Wet ESP for the Collection of Sub-micron Particles, Mists, and Air Toxics
New regulations are restricting particulate, acid gas and organic emissions to extremely low levels. Wet tubular electrostatic precipitators, with their ability to generate strong electrical fields in a wet, cooled atmosphere have demonstrated particulate emissions less than 0.0003 gr/dscf, with toxic organic, heavy metals and acid mist collection exceeding 99%. Designing parameters, field test data and operating data from installations on these processes are discussed in the paper
Industrial Applications for Coal-fired Boilers:
A Discussion about Strategy of Flue Gas Dust Removal for Indian Coal Fired Boiler
This paper analyses the effect of characteristics of Indian coal and ash on various modes of dust removal, using the Indian BALCO power plant as an example, and discusses the strategy of flue gas dust removal for Indian coal fired boiler. A new technique of Electrostatic-Fabric Organic Integrated Precipitator (hereafter referred to as EFOIP) developed by Fujian Longking Co., Ltd. is also introduced in this paper.
Assessment of Hot ESPs as Particulate Collector for Oxy-coal Combustion and CO2 Capture
Considerable effort is spent on development of technologies for CO2 capture and storage (CCS) to stabilise atmospheric levels of greenhouse gases. Oxy-coal combustion is one promising technical option for the CO2 capture from coal-fired power generation. A 30 MWth pilot oxy-coal fired power plant has been built by Vattenfall at Schwarze Pumpe in Germany to demonstrate the CCS technology. Lignite and bituminous coals will be tested for the oxy-coal combustion and CO2 capture. The flue gas cleaning system comprises electrostatic precipitator (ESP), scrubber and condenser. The ESP-often referred to as a cold ESP when it is placed downstream an air preheater in a conventional air fired plant-operates at a temperature below 200 ℃. Conceptual studies are in progress for a full-scale demonstration plant and an attractive option is to have the ESP operating around 350 ℃ to improve the overall thermal efficiency of the oxy-coal concept. Such an ESP is frequently referred to as a hot ESP and is placed upstream the air preheater.
This paper will review the oxy-coal combustion and CO2 capture and discuss the advantages with an ESP operating at a high temperature. It will also review the existing experience with hot ESPs built in the 1960’s and 1970’s mainly in USA. Most of these plants were later converted to cold ESPs operating at a temperature of around 150 ℃. The main reason for these conversions was the so-called sodium depletion in the fly ash that caused the ESP performance to deteriorate below acceptable levels. The sodium depletion resulted in high resistivity ash and back-corona conditions. The poor performance prevented any further installations of hot ESPs.
When discussing the feasibility of hot ESPs for oxy-coal combustion consideration is paid to the fact that numerous conventional cold ESPs today reach low emissions in spite of high resistivity ash.
Recent Application and Running Cost of Moving Electrode Type Electrostatic Precipitator
Advantages of a moving electrode type electro-static precipitator (ESP) and the present supply record are described briefly. The latest gas treatment system for a coal fire power station consists of a moving electrode type ESP, a DeSOx system and a wet ESP in Japan. The gas temperature of the moving electrode type ESP is 80 deg-90 deg. Celsius. This system can reduce outlet dust concentration to less than 1 mg/m3N and outlet sulfuric acid mist to less than 0.1 ppm. The running cost of a moving electrode type ESP was studied using actual operation results. Maintenance and repair cost of a moving electrode type ESP accounts for 10%-12% of the running cost. That is almost the same as the maintenance and repair cost of a fixed electrode type ESP. The total cost of the moving electrode type ESP including facility and running cost is cost effective compared to a fixed electrode type ESP.
Dedusting unit is necessary in the circulating fluidized bed flue gas desulfurization (CFB-FGD) system, a semi-dry FGD technique which is widely used in air pollution control projects. The dedusting unit is located after the FGD absorber, to collect the desulfurization absorbent for recycle, and also to ensure to satisfy the dust emission standards. Electrostatic precipitator (ESP) is most popularly used in large-scale semi-dry FGD system. But the ESP operating conditions in FGD system are much different from those in general use, with high dust concentration, high humidity and high specific resistivity. According to the ESP operating cases in the semi-dry FGD projects, the effect factors on ESP performance are studied in this paper, such as dust specific resistivity, dust concentration, gas humidity, dust cleaning mode and power supply. The measures to improve the collection performance are also studied in this paper, from the stage of design, installation and operation.
Analysis and Countermeasures for Fly-ash Feature from Zhungeer Coal with Electrostatic Precipitation
Zhungeer coal for ESP is a extremely difficult one with low sulfur content (0.43%), low inherent moisture (≯2%), high ash (31.7%), over-high aluminum (Al2O3: 51.72%), middle-high silicon (SiO2: 40.63%), low iron (Fe2O3: 1.38%), low sodium (Na2O: 0.02%)，and low potassium (K2O: 0.43%) etc. This kind of coal can, after firing in boiler, result in difficult dust conditions with the light specific gravity, fine particles and high resistivity, but it belongs to “green coal” due to low sulfur content and has a great number of reserves, and for the future, many power stations will still use it. The present paper, through the analysis of physical and chemical for this coal and contrasting the practice experiences used for industries, proposes requirement of design electrotype and other eligible corresponding measures.
High Dust Concentration ESP for Coal-fired Boiler of 300 MW Generator
In the dry Flue Gas Desulphurization(FGD) system, ESP plays an important role; one of its outstanding characteristics is that it can treat with high dust concentration flue gas. Compared with conventional ESP equipped for coal-fired boilers, the successful application of this kind of ESP is a great breakthrough. This article described the main characteristics of this kind of ESP such as different electrodes, distribution in the inlet plenum and fields, internal design, pre-collection etc.
ESP Application on Combustion of High-sulfur Heavy Crude Oil
The specialties of the flue gas and dust produced by combusting the Orimulsion oil are shown here. The research is carried out for the technology that the electrostatic precipitator (ESP) collects the multiple dust after dry ammonia desulphurization through the execution of Zhanjiang power project. The reasonable proposal is also supported here.
Regarding the Selection, Operation and Maintenance of Booster Fan
According to the WFGD project in TangShan Thermal Power Plant 2×300 MW units and the experiences in other WFGD project, the article discussed the selection, disposal, installation, running and maintenance of the booster fan in WFGD.
The Application Practices of the Double-zone ESP in Coal-fired power Plant
Through intensifying respectively functions of the charge zone and the dust collection zone of the electric fields, double-zone ESP is able to avoid back corona and to collect dust negatively charged and dust positively charged at the same time consequently to increase dust removal efficiency. Through the application effects of the mating four sets of double-zone ESPs and 4 sets of traditional horizontal type ESPs for the 4×300 MW unit in some power plant, it is proven that the double-zone ESP possesses higher dust removal efficiency and is able to increase dust migration velocity and to save floor space, steel consumption and power consumption, as compared with the conventional ESP.
Industrial Applications for Steel Industries:
Successful Application of Longking Bf-ESP Technology in Brazil GA Steel Plant
The successful application of Longking BF model Electrostatic Precipitator (hereafter referred to as “BF-ESP”) technology in Brazil GA Steel Plant fully illuminates the possibility of lower emission in metallurgy industry and structural security of enduring the working condition of high negative pressure at sinter main ESP. It is a successful application example of strategic cooperation between Longking and Chinese famous metallurgy design institute. This paper mainly dissertates the technical characteristics and technical guarantee measures of BF-ESP applied.
By analysising on process of sintering machine and flue gas characteristics in electrostatic precipitator (ESP) before sintering machine, this article introduces several issues that should be paid more attention in the application of ESP before sintering machine and gives some solutions for these issues in order to meet the emission standard and requirements of sintering process. Finally the flue gas is purified and our environment is protected.
FGD and SCR for Coal-fired Power Plants:
Development of New Gas Cleaning System with Salt Solution Spray
For heavy oil fired boiler plants, the NH3 injection Dry-ESP system has been applied to remove SO3 since 1970’s in Japan. This system has very high performance for SO3 removal by the chemical reaction of NH3 and SO3. However, it generates a lot of by-product, ammonium sulfate and sulfite as solid industrial waste, which needs much cost for the system operation. Furthermore, ammonium sulfate and sulfite, due to very sticky dust, is apt to cause ash clogging in ESP hoppers and ash handling system. Now we have developed a new gas cleaning system for SO3 removal by means of spraying SALT SOLUTION (ex. Na, Mg, K, Ca) to flue gas, which incorporates the new technology onto the conventional wet-FGD. This technology reusing the wetFGD waste water has high performance of SO3 removal, by that the sprayed SALT SOLUTION physically and chemically adsorbs SO3 and the adsorbed solids are collected by the wet-FGD circulation water.
Numerical Investigation of the Entire Boiler System with SCR De-NOx Reactor
The numerical investigation of a 300 MW boiler with SCR de-NOX equipment is carried out with advanced methods. The simulation includes furnace, economizer, super-heater, re-heater, air pre-heater, SCR De-NOx equipment, ESP, induced draft fan. A reasonable agreement has been attained when compared with the designed statistics, which proves the reliability of this simulation and implicates its utility value. As a result, an analysis tool is available to study the temperature and pressure characters of the whole boiler system, in a feasible and economic manner.
Research on Complex Multi-pollutants Control Technology in a Large-scale Coal-fired Power Plant
The combined Selective-Catalyst-Reduction and Multi-Circulating-Fluid-Bed (SCR-MCFB) technology was investigated on a 300 MW boiler in a coal-fired power plant. The influence of this combined technology on the efficiency of dust collection, desulphurization, and denitrification, especially the interaction and the match of each system, was studied in order to improve the performance of the flue gas cleaning systems. Meanwhile, the ability on removing mercury of this combined system was studied with Ontario-Hydro (OH) method. The experimental results showed that the combined SCR-MCFB technology can remove not only SO2, NOx and dust but also mercury in the flue gas with high efficiency.
New Concept of CFB Boiler with FGD
This paper introduces the technology characteristic of CFB Boiler with CFB-FGD on the basis of the summary of desulfurization principle in CFB boiler. The technology can overcome disadvantage of high sulfur of desulfurization in the boiler and thus pledge strict requirement of environment protection.
Dry FGD Technology Research and Application in Steel Sintering
Based on wet and dry flue desulfurization technology (FGD), and after digesting the import of technology, we developed LJS-steel sintered two-stage reaction of sintering flue gas pollutants removal process. this process is successful applied in Fujian SanMing 180 m2 sintering machine, desulfurization efficiency more than 93%, while total removal of SO3, HCl, HF acidic gases. The project obviously improve the atmospheric environment around steel plants.
Design and Application of Inlet nozzle of Dry Desulphurization ESP
The gas distribution of ESP is effected by the design of inlet nozzle. In this paper, based on the gas character of CFB-FGD dry desulphurization, the design of inlet nozzle and gas distribution of ESP after desulphurization were analyzed, which can guide the detailed design of inlet nozzle with high concentration.
Taking a wet limestone-gypsum Flue Gas Desulphurization (FGD) operation data for example, the absorbent preparation system is compared based on different limestone supply way in 3 proposals: purchasing limestone powder outside, dry mill and wet mill. For dry mill vertical and horizontal type are further compared. This paper has given the operation feature of mill and main configuration comparison of 3 proposals, analyzed the initial investment and operation cost difference based on fixed assets, power consumption, main maintenance cost and price of absorbent. The advantages and disadvantages of 3 proposals are given based on comparison, also dry mill is considered more suitable for long distance absorbent preparation. The paper provides advices for the choice of FGD absorbent preparation system.
Economic Analysis of Wet Flue Gas Desulphurization Project Operation
After the flue gas desulphurization (FGD) of the #6 unit of Jiujiang Power Plant, the cost of electricity production is increased. This paper list the operation cost of FGD system and draw a conclusion that optimizing system design and operation management, and decreasing electrical consumption are critical to reducing the cost.
Discussion on the Mechanism of Semi-dry Desulphurization
This paper discussed on the mechanism of four type of semi-dry desulphurization technics (Circulating, Fluid bed, LIFAC -limestone injection into Furnace and Activation of Calcium Oxide and Spray semi-dry desulphurization), and introduced several engineering examples of these desulphurization technics. In addition, the reaction time, operation temperature, ratio of calcium to sulfur, suitable conditions for coal and future application are also discussed.
Analysis on Chimney Inner Wall Anti-corrosion in GGH Eliminated Wet Desulfurization System
This paper discusses on the physicochemical mechanism of chimney corrosion in wet desulfurization. Gas temperature, internal pressure and structure defects of chimney are pointed out to be the main factors. According to these factors, various methods about treating chimney anti-corrosion at home and abroad are also indicated. Moreover, we propose an anti-corrosion plan which based on comparing anti-corrosion mechanism, H construction methods H and H construction periodH s of anti-corrosion methods.
Simultaneous Removal of SO2 and NO2 by Wet Scrubbing Using Limestone Slurry
The simultaneous removal of SO2/NO2 by limestone slurry was studied in a gas-liquid bubbling reactor. Experiments were carried out to find the effect of various operating parameters such as inlet concentration of SO2 and NO2, reaction temperature, O2 content in the flue gas and additive on the SO2 and NO2 removal efficiencies. SO2 removal efficiency decreased with inlet NO2 concentration, reaction temperature and O2 content in the flue gas. Inlet SO2 concentration had a favorable effect on NO2 absorption while reaction temperature and O2 content in the flue gas had an inhibition effect on it. And additives such as MgSO4 and Na2SO4 could promote the removal of SO2 and NO2.
Study on Mid-temperature SCR DeNOx Catalyst under High SO2 and CaO
This article introduce the performance of vanadium-titanium Middling temperature SCR DeNOx catalyst, considering the factor NH3/NOx, SO2 concentration, GHSV, O2 concentration, H2O concentration changes in high SO2 and high CaO.
Research and Application of Numerical Calculation Methods in SCR DeNOx Reactor & Duct Design
SCR reactor& duct design is the key part for a SCR DeNOx project to insure the best gas flow and the most reasonable structure. In this paper, gas CFD simulation and structure FEA simulation are used for SCR reactor& duct design based on CAE technology. According to this analysis result, position, dimension and joint of all structure components will be ascertained. These were applied in DeNOx project for Fujian Huadian Kemen Power Plant 2×600 MW units (stage II).
This paper takes the example of the retrofit of 2×100 MW units of Yushe Power Plant in Shanxi Province, and summarizes the applications of circulation fluid bed flue gas desulphurization (CFB-FGD) adopted “two boilers one line” in the retrofit of existing power plants.
Design and Application of the Dry-FGD Process in Sanming Steel No.2 Sintering Plant
In this paper, it summarizes the characteristics of sinter flue gas, and study the application of dry-type-FGD (flue gas desulphurization) process for Sanming Steel Co., Ltd. No.2 sinter plant flue gas treatment. This project has become a successful example for sinter flue gas desulphurization in steel industry.
The Fouling Characteristics and Comparative Analysis of Cleaning Technology of SCR
The paper mainly discussed the related issues of fouling and blowing problem of power plant de-nitrification systems. The fouling mechanism and the harm of fouling problem in SCR were pointed out. Then the paper compared the characteristics of the acoustic soot blower and steam soot blower. The advantage of acoustic soot blower was also analyzed here. At last, the paper concluded the future research direction.
Non-Thermal Plasmas:
AC/DC Power Modulation for Corona Plasma Generation
Gas cleaning techniques using non-thermal plasma are slowly introduced into industry nowadays. Here we present a novel power modulator for the efficient generation of large volume corona plasma. No expensive high-voltage components are required. Switching is done at an intermediate voltage level of 1 kV with standard thyristors. Detailed investigations on the modulator and a wire-plate corona reactor will be presented. In a systematic way, modulator parameters have been varied. Also reactor parameters, as the number of electrodes and the electrode-plate distance have been varied systematically. The yield of Oradicals was determined from the measured ozone concentrations at the exhaust of the reactor.
Development of the PPCP Technology in IEPE
The development of the PPCP technology in the IEPE has been introduced in this paper, including process technologies, pulsed powers, plasma reactor, activated vapor and ammonia, additional catalyzer, by-product catcher, match between the pulsed power and the reactor, and so on. According the experimental results, the feasibilities of the industrial application has been proved and there is a plan on building an industrial demonstration set.
Non-thermal Plasma Processing for Dilute VOCs Decomposition Combined with the Catalyst
Atmospheric pressure non-thermal plasma process combined with the new catalyst for volatile organic compounds, especially dilute tricholorethylene (TCE) in synthesized dry air is discussed. TCE decomposition efficiency is very good and more than 95% of TCE is easily decomposed at SED (specific energy density) of 18 Joule/litter which is practical value. However, more discharge energy is necessary to the full oxidization, which means that almost carbon included in TCE can be oxidized to carbon oxide (CO and CO2) named as the carbon balance. For better carbon balance, SED of the electric discharge is more than 90 J/L which is pretty large. We would like to find more efficient catalyst for that purpose. The decomposition mechanisms by the non-thermal plasma should be clear and the new catalyst which decomposes the ozone and TCE simultaneously will be developed. Byproduct analysis suggested that nonthermal plasma direct process generates DCAC byproducts from TCE but the catalyst process do not generates any DCAC and the generation of only TCAA is detected indicating the atomic oxygen radical can oxidize TCE to TCAA only. The new catalyst is inserted in the plasma reactor where the diameter of the discharge electrode is thin and the catalyst can be filled in that space between the electrode and the tube wall. The electric field effect and radical life time effects are examined also.
NOx removal from a smoke tube boiler flue gas was investigated using a commercial ozonizer for indirect NO oxidation and a Na2SO3 chemical scrubber. The flue gas flow rate was in the range of 410 Nm3/h-1480 Nm3/h, the gas temperature of 185 ℃-325 ℃, and NOx concentration of around 40 ppm in city gas firing. Operational and performance data were obtained. The NOx removal efficiency was clearly dependent on the ORP, and increased inversely as the oxidation reduction potential (ORP) in the liquid decreased. To keep the specified NOx removal performance, it is essential to maintain the ORP properly by controlling additional Na2SO3 and NaOH solution injection. NOx emission of less than 4 ppm was attained at 410 Nm3/h for a 300 minutes system continuous operation by maintaining ORP of -30 mV and pH of more than 7.8.
Experimental Investigation on Styrene Emission with a 1000m3 /h Plasma System
This paper reports experimental investigations on plasma-induced styrene emission abatement in air at room temperature (24±2℃) and pressure. Tests were performed with a 1000 m3/h plasma system under DC corona discharge. It is observed that styrene destruction in DC glow discharge is negligible in contrast to streamer corona. When relative humidity (RH) is in the range of 30%-80%, the energy consumption for styrene decomposition rises with RH value. The energy coefficient β value becomes larger with increasing either RH or the initial styrene concentration for RH in 30%-80% and the concentrations within 90 ppm-1000 ppm, respectively. With regards to those dependence sensitivity, the lower the concentration, the more sensitive to the RH value. Under optimal condition (100 ppm initial concentration, 35 %RH), the β value is 18.73 J/L.
Streamer Corona Plasmas and NO Removal
This paper reports experimental studies on the discharge modes with AC/DC and DC power sources and different electrode configurations. Very uniform streamer coronas can be generated by using AC/DC source. The energy cost for NO oxidation in air is about 30 eV/NO.
Influence of Ratio of NO/NO2 on NOx Removal Using DBD with Urea Solution
Air pollution due to the exhaust gas from motorcars causes serious environmental problems, so it is necessary to remove NOx from the exhaust gas. In this study, NOx removal by dielectric barrier discharge (DBD) with an urea solution without any catalyst at room temperature has been investigated. The NOx removal rate and NOx removal efficiency has been measured with and without adding an urea solution. Furthermore, the influence of the ratio of NO and NO2 on the amount of removed NOx by DBD with the urea solution in actual apparatus has been measured experimentally. The ratio of NO and NO2 of an initial mimic exhaust gas was adjusted by DBD treatment. From the results of measurement, it has been found that NOx removal by DBD with an urea solution is effective and the optimum concentration of the urea solution is 23% in the present study. And it was estimated that the optimum ratio of NO and NO2 is about 6 to 1 for NOx removal with an urea solution.
TNT removal by the combination of high voltage pulsed discharge plasma and different catalysts with various concentration was investigated. In the case of 9.8 kV peak pulsed voltage and 120Hz pulsed frequency, the degradation rate of 30 mg/L TNT solution with pH value of 6.8 reached 66.1% after 60 min treatment. It was showed that Fe2+ had a remarkable catalytic effect on degradation of TNT. When the concentration of Fe2+ was 0.15 mmol/L, it promoted the TNT degradation, and 84.0% removal was obtained. However, addition of H2O2 into TNT solution inhibited the TNT removal, especially at the initial reaction. After 120min treatment, the degradation efficiency of 100mg/L TNT was 87%, and COD reduced 80%. The results indicated that TNT could be efficiently removed by high voltage pulsed discharge plasma.
Plasma-catalytic Removal of Formaldehyde in Atmospheric Pressure Gas Streams
Formaldehyde is a major indoor air pollutant and it is able to cause serious health disorders in residents. Major conventional techniques in removing formaldehyde from gas streams include absorption, adsorption, catalytic and photo-catalytic oxidation processes. Low efficiency, high energy consumption and harmful byproducts are major problems in these methods. This work combined dielectric barrier discharge (DBD) plasmas with Ag/CeO2 catalysts, and achieved lower energy consumption (-90 eV/molecule of HCHO), higher GHVS (16500 h-1), high oxidative conversion into CO2 (86%) and high removal efficiency (99%) to remove formaldehyde in gas streams at atmospheric pressure, when a feed gas mixture of 276 ppm HCHO, 21.0% O2, 1.0% H2O in N2 was used. Experimental results indicate that the plasma-generated short-lived gas phase radicals, such as O, OH and HO2, play important roles in the catalytic redox circles of Ag/CeO2 to oxidize HCHO and CO to CO2.
In this research, the relationship between discharge electrode geometry and ozone generation in Electrostatic precipitator (ESP) has been experimentally investigated. The experimental ESP was two-stage-type which composed of a precharger, followed by the collecting section. The precharger consists of high voltage electrodes and grounded electrodes. The high voltage electrode was saw-tooth type and the grounded electrodes was plate type. The collecting electrode section had a parallel-plates configuration. The electric field distribution of saw-tooth electrode neighborhood was calculated. The relationship between the ozone generation and electric field distribution of the saw-tooth neighborhood was investigated. The geometry of the saw-tooth electrode changed a tip angle and the number of saw-tooth. The relationship between the saw-tooth electrode geometry and ozone generation was also investigated.
Study of Carbon Monoxide Oxidation by Discharge
In semi-closed space such as highway tunnel, diesel exhaust particles (DEP) and carbon monoxide are high concentration. DEP is removed by the electrostatic precipitator (ESP), and carbon monoxide is diffused by the ventilation fan in ventilation tower. Recently, underground tunnel type expressways have been constructed in under area. It is necessary to raise the ventilative tower because many people live in this area. The ventilation tower lowers when the carbon monoxide can be removed even a little. Therefore, the decrease technology of the carbon monoxide is requested. In this work, the conversion of carbon monoxide to carbon dioxide by dielectric barrier discharge (DBD) and corona discharge has been experimentally investigated.
The experimental results are as follows. A carbon monoxide conversion in a wet condition was higher than that in a dry condition. Two-stage wire corona discharge reactor is 20% at 3.5 W carbon monoxide conversion more than one-stages. It was 50% at 3.5 W carbon mon-oxide conversion at by for DBD.
Application of a Dielectric Barrier Discharge Reactor for Diesel PM Removal
An uneven DBD reactor driven by a pulse power supply for diesel particulate matter (PM) removal has been characterized using a diesel engine. The relations between energy injection, PM removal, space velocity and pressure loss are given.
Catalyst Size Impact on Non-thermal Plasma Catalyst Assisted DeNOx Reactors
Non-thermal plasma assisted catalytic reaction is an effective way to remove NOx from automobile exhaust. Dielectric barrier discharge is used to generate non-thermal plasma in a packed bed of solid catalyst particles acting as dielectric in this study. The size of the catalyst particle affects gas-solid phase chemical reactions. At the same time, the geometry of the particles affects the space factor of the packing and the characteristics of the dielectric barrier discharge, such as power. The NOx removal efficiency is also affected. The results of this study show that the diameter of the catalyst particle affects NOx removal efficiency. A minimum peak value of discharge power can be found at a specific particle diameter for a given reactor and power supply. NOx removal efficiency increased with the size of the catalyst to a peak before decreasing on a similar pattern. Therefore an optimum pellet size can be found that that gives maximum removal efficiency. In a catalyst packed bed reactor assisted by dielectric barrier discharge it is important to choose the optimum diameter of catalyst particle.
The Study on Series of Copper Catalyst in the Reactor of Dielectric Barrier Discharge to Remove NOx
Dielectric barrier discharge assisted catalyst can effectively remove NOx, catalyst plays an important role in the process of reaction. The series of copper catalyst carried by active carbon, ratio of removal NOx, main productions and catalyst character before and after used have been studied in the reactor of dielectric barrier discharge. The experiment results show that non-thermal plasma can not only activate reagents to bring activated particles and radicals, but also have catalyst activated to improve adsorption and catalytic character. The main production of the chemical reaction is copper nitrate and deposited in activated carbon surface. The NOx has been reduced by carbon element of activated carbon to come into bring nitrogen under the non-thermal plasma effected condition.
VOC Removal Using Adsorption and Surface Discharge
The decomposition of toluene using a combination of adsorption and nonthermal plasma was investigated. On this research, the molecular sieve was used as the adsorbent and concentrated toluene was decomposed by the surface discharge. The molecular sieve was used to adsorb toluene and desorbed using thermal heat. Toluene was concentrated from 400 ppm to 9,000 ppm, while the gas flow rate was reduced to 1/25 times. The high concentration of toluene was decomposed by the surface discharge. The uniqueness of this system is the combination of concentration treatment by adsorption and plasma treatment, which is able to achieve compact and economical system.
A Novel Concept of Remediation of Polluted Streams Using High Energy Density glow Discharge (HEDGe)
Effluent gases containing various pollutants are generated from many sources. Non-thermal plasmas, including pulsed nanosecond corona (PC), were suggested for simultaneous removal of particulates and gaseous pollutants. PC demonstrated high removal efficiency, also in pilot-scale installations, but the cost of pulsed power supplies remains prohibitively high for most applications. With the purpose of reducing capital costs, DC flow-stabilized coronas had been proposed. Known devices employ linear flow and thus the residence time is very short. Spellman High Voltage Electronics Corp. has patented an approach to creating a flow-stabilized discharge in large volumes required by industrial applications. The main idea is providing a fast velocity gas flow in the vicinity of the ionizing electrodes that may be similar to those used in commercial ESPs, using rotational mechanism rather than longitudinal flow. Several designs are envisaged and discussed depending on the application, whereas either HV electrodes or grounded electrodes or both are rotated relative to each other in the same or opposite directions. Expected results and challenges are presented.
Gaseous Elemental Mercury Oxidation by Non-thermal Plasma
The effects of the discharge tooth wheel number and the concentrations of CO2, NO and SO2 in the simulated flue gas on elemental mercury oxidation by non-thermal plasma were investigated by using a link tooth wheel-cylinder reactor energized by a negative high voltage DC power supply. The results indicated that a significant amount of elemental mercury was oxidized by non-thermal plasma. And the total mercury concentration of reactor outlet decreased as the discharge voltage increased. When the number of the discharge tooth wheel increased, more elemental mercury could be oxidized and more energy was injected into the plasma reactor. The spark voltage enhanced with the increase of CO2 concentration and the discharge voltage corresponding to the same elemental mercury oxidation rate also increased. The presence of SO2 resulted in a significant decrease of outlet total mercury concentration. NO restrained the oxidation of elemental mercury and the removal of mercury.
A Multiple-switch Technology for High-power Pulse Discharging
This article presents our recent research on a new multiple-switch pulsed power technology. With this technique, multiple spark-gap switches can be synchronized automatically, like in Marx generator. However, in contrast to a Marx, Pulsed power can be produced either at a high voltage or with a large current, or it can be used to drive multiple independent loads simultaneously. It is promising for the development of an efficient large pulsed power supply with an increased lifetime. Through use of this technique, an efficient ten-switch prototype system has been successfully developed. Experimental results show that 10 spark-gap switches can be synchronized within about 10 ns. The system has been successfully demonstrated at repetition rates up to 300 pps (Pulses Per Second). Pulses with a rise-time of about 11 ns, a pulse width of about 55 ns, an energy of 9 J-24 J per pulse, a peak power of 300 MW-810 MW, a peak voltage of 40-77 kV, and a peak current of 6 kA-11 kA have been achieved with an energy conversion efficiency of 93%-98%.
Humidity and Oxygen Effects on Dimethyl Sulfide Decomposition by a Plasma Corona Reactor
The influence of humidity and oxygen on decomposition of dimethyl sulfide (DMS) was investigated experimentally by a wire-cylinder pulse corona reactor at room temperature. The DMS decomposition efficiency was investigated using varying oxygen concentration (0.6%-21.0%), humidity (0%-1.0%) and different balance gas (air, N2, Ar). DMS conversion in Ar is more efficient than that in N2 and air at a fixed peak voltage. In addition, it is found that 5% oxygen is the optimum concentration in decomposition of DMS, due to higher conversion of DMS and relatively fewer yields of by products, such as O3, NOx and SO2. The highest DMS removal efficiency was achieved with the gas stream containing 0.3% H2O in air.
The Mechanism of Naphthalene Decomposition in Corona Radical Shower System by DC Discharge
Polycyclic aromatic hydrocarbons (PAHs) from coal-fired boilers and waste incinerators are regarded as some toxic and difficult decomposition pollutants. In this paper, it was studied how the applied voltage, the initial concentration and the catalyst affected the naphthalene decomposition characteristics using a corona discharge radical shower system. The emission spectrum of OH (A2Σ → X2Π) was detected to understand the decomposition mechanism of naphthalene better. In addition, the decomposition by-products and the decomposition process were also analyzed initially. The results show that the increasing applied voltage and humidity is helpful to the naphthalene decomposition because of the increasing OH radicals. High initial concentration of naphthalene can heighten the decomposition amounts and the catalyst can improve the naphthalene decomposition. The main decomposed by-product is CO2 and H2O. However, there are also little CO and small-molecule organic compounds to be found because of the incompletely oxidative reactions.
Surface Modification of Polestar Fabrics by Non- thermal Plasma for Improving Hydrophilic Properties
Polyester fabrics are exposed to glow discharge plasma and the physical and chemical properties of the fabrics were studied. From the vertical dragging analysis, hydrophilic properties of fabrics are improved after the plasma treatment. Group concentration and atomic concentration of the fabric was studied from an X-ray photoelectron spectroscopy and it is seen that the polar groups are increased after plasma treatment. These increasing polar groups are used for improvement of hydrophilic properties of fabrics. Surface analysis was studied using scanning electron microscope.
Predictive Model of Nonequiliburium Plasma Decontamination Efficiency for Gaseous Pollutant
The conception of energy conversion factor (Ef) and the predictive model of decontamination efficiency are put forward, respectively, by analyzing the quantitative relation of discharge power, molecular structure of pollutant (dissociation energy of chemical bond) and decontamination efficiency. The Ef of chemical bonds, such as S-H, C-S, C-Cl and C-H, are obtained by experimental data of H2S and 2-chloroethyl ethyl sulfide (2-CEES) with the same pulsed corona plasma equipment. And then, the predictive model is used to estimate the decontamination efficiency of ethanethiol and 2-CEES by scale-up pulsed corona plasma equipment. As a result, the predictive values are close to experimental data. The model can be used to estimate whether the decontamination efficiency of redesigned plasma equipment attains the expectant target in the engineering design of nonequilibrium plasma equipment, therefore, it has an important application value in engineering design.
Applied Electrostatics:
Application Study of Electrostatic Precipitation with Earthed Atomizing Discharges
The comparative researches on both positive- and negative-direct current earthed atomizing corona discharges were carried out, and the influence of water flux on corona discharges was also studied. The experimental results showed that the capture efficiency of negative electrostatic precipitation with earthed atomizing discharges is higher than that of the positive one with earthed atomizing discharges. The reason is probably that the ionization region of positive-earthed atomizing discharges was expanded and more aerosol particles passed through the ionization region, which tended to neutralize the charges on the aerosol particles. In contrast, the expanding ionization region was not existent in the negative-earthed atomizing discharges. In addition, under the condition that the wire discharge electrode is 70 mm in length and 1 mm in diameter, the mean diameter of spraying droplets was larger than 80μm when the water flux was more than 3320 μL/min, while it was smaller than 80μm when the water flux was less than 2280 μL/min.
Integrated Clarification Technology for De-dusting, Desulfurization and Odor Elimination
Based on the truth that traditional ESP is unable to capture the fine dust of low specific resistance efficiently, the paper introduced a self-determination developed technology known as “an oily fine soot dust removal equipment”. This technology, also known as the “preposed-spraying-screen static electrical soot remover”, has awarded the invention patent certificate issued by the National Patent Bureau. With this new technology, ESP can capture fine dust of low specific resistance efficiently (such as soot and black carbon), therefore breakthrough the specific resistance lower limit law for traditional ESP. Besides, the lower limit range of specific resistance for ESP’s high efficiency dust capture is largely expanded; and high efficiency desulfurization can be approached simultaneously, thereby largely expanded the technological field of the combination of ESP and desulfurization equipment. With the adoption of using simplified agent plus water spray as deashing method, the new technology has overcome the problem of secondary dust emission during the vibration deashing in traditional ESP and oily soil. As “Preposed- Spraying-Screen Static Electrical Soot Remover” has reformed the traditional ESP from the above three aspects, the traditional ESP technology is glowed up with strong vitality.
In this paper the charging technique used in PMM (Pulsed Magnetron Modulator) of ICT (Industrial Computerized Tomography) system is introduced. This charging technique is based on the high frequency series resonant inverter technology, which is applied in many kinds of power supplies or modulators. For high spatial resolution and high density resolution in ICT, the required precision of output voltage between pulses of PMM is more than 99.9%. Based on the requirement of output parameters of PMM (shown in Table 1), a two-stage series resonant charging technique is adopted. First stage is fast-charging stage which lasts 2ms, and the PFN (Pulse Forming Line) could be charged to 97% of rating voltage in the end of the stage. Second stage is slow-charging stage which lasts 0.6ms and ensures the voltage of PFN varies less than 0.1% between pulses.
CDM test system and verification method of ESDA and JEDEC standards have been studied. There are several different items. They can be categorized into 5 major items, which are charging system, discharging system, verification module, waveform verification, and classification level. Regarding waveform verifications at each stress level, ESDA system provides higher peak current whereas lower rise time and lower full width at half maximum, compared to JEDEC system. It implies that ESDA standard provides higher inductance in a discharge system and higher discharge energy, which make it more severe system. The current continuously increases with the stress level. The linear relationship of stress conditions by these standards can be obviously observed. The electrical failure yield of each standard system is then predicted by a stress condition of the other system.
