ICESP VI – Budapest, Hungary, 1996

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 VI ICESP Conference under their respective topic. Click on the papers title to view the complete paper in PDF format.

Air Toxics
  • 002 – Control of Trace Elements in Combustion Flue Gas by a Corona Discharge Activated Conditioning Agent and Electrostatic Precipitator
  • 008 – Application of Wet Type Electrostatic Precipitator for Boiler Plants

    • Dust emission level is recently required to be more and more severe in advanced industrial countries. In Japan, very low emission level which would realize an almost invisiblestack, is required especially for new installation of power station near large cities. In Europe and USA, meanwhile, there are problems of bluish smoke due to SC1 mist. As the countermeasure, wet type Electrostatic Precipitator(wet type ESP) is applied in Japan. The application of wet type ESP for boiler plants is described as follows.

  • 021 – Improving Collection of Toxic Fine Particles in ESPs

    • A modern ESP performance prediction model, ESP VI 4. 0a, is used to evaluate the effect upon penetration of both the submicron and rapping reentrainment fractions from various design and upgrade approaches, submicron particles are the size range in which non volatile toxic materials, when present, mainly reside. A powerful tool is presented for predicting the reduction in particulate emissions by size fraction prior to an ESP initial design or later upgrade.

  • 027 – An Experimental Study of the Performance of an ESP Operating Downstream From a Semi-Dry Desulphurization Unit
    • Semi-dry desulphurisation processes such as spray-drying (SD), in-duct injection, or circulating fluidized bed are cost-effective retrofit technologies for low to medium capacity coal power plants. However, it is critical to the technical and economical viability of these FGD technologies that the performance of the existing and probably old ESP, operating under the new conditions, be good enough to maintain emissions levels within legal standards. This paper collects and discusses data from an SDIESP pilot plant located at the Los Barrios Power Plant (Cadiz, Spain). A series of tests with two S02 concentration levels, two flyash load levels, three Ca/S ratio levels, and three sulfur removal yields was run in a six-month experimental programme. Particle load and size distribution, ESP penetration and emissions level, electrical operating point (V-I), and power consumption were measured in order to evaluate the SD’s impact on the ESP by means of comparing these measures with those obtained at baseline conditions, i.e., bypassing the SD. The use of intermittent energization has also been analyzed as a means of reducing power consumption.
Control and Design
  • 045 – Electrostatic Precipitator Combined Pulse Charging Section with Moving Electrode Section for High Resistivity Dust
    • A combined type electrostatic precipitator which is composed of a pulse charging section and a moving electrode section was developed for the purpose of improving the collection efficiency of high resistivity dust,. The relationship between pulse waveforms and their collection efficiencies was studied by bench-scale electrostatic precipitator tests in our laboratory. In the case of higher resistivity fly ashes, the optimum points of discharge current, pulse voltage and pulse frequency were revealed. The experimental results of our field tests on coal fired boiler gas showed that the migration velocity of dust on the combined type electrostatic precipitator improved with pulse energization of the inlet field, and the electric power consumption decreased with high resistivity dust. An additional effect of the combination was that pulse energization to the inlet field of the combined type electrostatic precipitator improved the collection efficiency of the outlet field which is the moving electrode section.
  • 057 – Fundamental Characteristics and Collection Efficiency of a Model Precipit
    • Recendy, since even at traditional machine shops, the comfomble working environment is required, it is necessary to remove oil mist or fumes from operating machines. Portable or small electric precipitators are suitable for this purpose. However, the design technology of a large precipillltor is not direcdy applicable to such a small or a portable precipitator. In order to investigate the fundamental characteristics of a small precipitator, a model precipitator was constrocte<!a nd examined The experimental results of the model precipitator were compared with the theoretical. prediction of performance and revealed that the collection efficiency cannot be simply predicted from the theoretical. compullltion of particle motion.
  • 063 – Back Corona Control with Help of Advanced Microprocessor Enhances Performances
    • The Electrostatic Precipitator (ESP) is worldwide the most common dust collector to clean flue gases after coal fired boilers. A new patented concept to define back-corona has been introduced which enables the microprocessor controls to energize each ESP bus section individually, automatically and continously to optimize the voltage and current to maximize the overall collection efficiency under varying process conditions.The new concept selects current and duty cycle in intermittent energization mode, based on continous sampling and mathematical analysis of the secondary voltage from each bus section, referenced to the corona onset voltage. Maximal corona charging with minimized back-corona is achieved.Softwares for altered currents during rapping and altered rapping sequences further contribute to the drastical emission reductions presented in this paper.This paper presents the philosophy of the optimizing softwares, and reports some recent em1ss1on improvement results from operation of ESPs, mainly after PC boilers firing low-sulfur coals.
  • 071 – Field Testing of Acoustical Cleaning of Electrostatic Precipitators
    • Tests using a 20 Hz acoustic horn on a fly ash precipitator and two 125 Hz acoustic horns on a precipitator after a straw burning boiler are reported. It seems that the infrasound did not have the expected positive effect on the dust dislodgement. The higher frequency horns, however revealed an unexpected positive potential. The expectations and the experimental results are reported herein for use by others applying acoustic cleaning, for trying to confirm the results and for helping find the correct physical explanation of how the acoustic waves dislodge the dust, thus making it possible to optimize the system and the operation of acoustical cleaning.
  • 080 – Self Exploring ESP Rapping Optimization System
    • The complexity of ESP processes states among others in ambiguity of physical parameters interrelation. That diversity may be formally described using fuzzy sets theory methods. In paper [ 1] it has been presented a control method for ESP operation by fuzzy logic rulers organised as expert system. This method operates on fuzzy sets named High, Low, Small, Large, Medium, membership functions most of which have complicated shape. In the below consideration a slightly another method for fuzzy control of ESP operation is presented. Applied fuzzy sets have the following membership functions: triangular, rectangular and trapezoidal. The ·fuzzy relation sup min [ … ] on fuzzy numbers representing 11authenticity” of some measurement data is applied for control signal determination. The control problem is analysed for interrelation efficiency and pause interval of collection electrodes rapping. An extension of this methods for another ESP parameters is simple.
  • 100 – Rigid Discharge Electrode and Wide Spacing Electrostatic Precipitators in Poland
    • The first rigid electrode (RDE) and wide spacing electrostatic precipitator (WS ESP) of indigenous design was manufactured and commissioned in Poland in June 1993. Up to the end of 1995 there have been commissioned more than 25 installations with RDE & WS ESPs on power units with capacity up to 200 MW as well as on small district heating units with a gas flow rate of 120 000 m3/h (Nil>>” After correction of some problems – especially in the high voltage isulation and supply systems – nearly all of the ESPs operate with the designed efficiency and much below the guaranteed emission levels. This paper describes some of the encountered problems having a negative influence on ESP performance and reliability as well as its solutions. Some general observations and remarks have been drawn out investigating the performance of RDE & WS ESPs which are presented below.
Modeling
  • 107 – An Efficient Pseudo-Transient Solution Method for Monopolar Corona with Charge Advection and Diffusion
  • 113 – Precipitation Modeling by Calculating Particle Tracks in Simulated Flow Fields
    • The work introduces into the method of tracking particles in simulated flow fields. It is demonstrated, how a commercial tool for flow field simulations can be used to model particle collection in ESPs. The simulated particle trajectories agree better with experimental observations than the Deutschian assumption of ideal mixing in precipitator ducts. For an 200 mm duct with given operating conditions and a given particle size distrFig. 2ibution the local mass fluxes of collected particles have been simulated. The curve of collected mass complies with industrial experiences of high collection at the beginning of the ESP and a rapid decrease further downstream. For a lab-scale precipitator the grade efficiency was simulated with different particle tracking models and compared to other models and experiments.
  • 124 – Removal of Submicrometer Dust Particles by a Charged Spherical Collector
    • A numerical model for determining 3D trajectories of charged dust particles in the vicinity of a falling down, oppositely charged spherical co11ector (a droplet) is presented. A new definition of the collection efficiency is also proposed. The model is applied to determine the limiting collision trajectories for dust particles, the precipitation space and collection efficiency for a single charged spherical collector.
  • 130 – A Model of the Non-Stationary Charge Flow in an Electrostatic Precipitator
    • In this paper, the authors present a numerical model based on the combination of finite element and finite volume techniques for the self consistent coupling of Poisson’s equation and the non-stationary current continuity equation. The numerical methods are based on high-resolution schemes developed in computational fluid dynamics. They represent a new approach in electrical engineering and especially in electrostatics. The continuity equation ( conservation of charge) is solved in non-stationary form by means of a second order finite volume scheme for arbitrary non regular grids. Time integration is performed either by a very robust explicit approach or by an implicit method where large time steps may be chosen without restriction by the CFL condition. The finite volume mesh is obtained from the topological dual of the triangulation used for the finite element computation of Poisson’s equation. The presented method permits modeling of the propagation of charge pulses in precipitators with pulsed energization.
  • 154 – A Finite Element Method for Modeling 3D Field and Current Distributions in Electrostatic Precipitators with Electrodes of Any Shape
  • 166 – Three-Dimensional Corona Current Distribution in Complex ESP Configurations
    • A simple physical corona model is presented that makes use of the effective ionization coefficient of the medium to define a local ignition criterion for the formation of active corona regions at the high voltage electrode. Detailed predictions about the current density distribution in a specially shaped duct with a set of unequally spaced helical corona electrodes are compared with current density distributions measured at the collecting plates.
  • 172 – Advance of Field Calculation Method in Electrostatic Precipitators with Non-Cylindrical Corona Electrodes
    • The digital simulation of unipolar corona discharge is considered. Distribution of the initial field strength on the surface of corona electrode with variable radius is investigated. The modification of the method of corona discharge field calculation is presented by the authors. Computation results for electrostatic precipitator and electrogasdynamic generator nozzle are shown.
  • 184 – Modeling of the Velocity Field in Electrostatic Precipitators
    • The presented method contributes to the solution of problems concerning uniformity of gas distribution in a retrofitted horizontal electrostatic precipitator. In this approach gas flow is described by means of a physical model which uses air to simulate transport phenomena. Results are presented graphically.
  • 190 – Motion of Macroscopic Particles in Electric Field
    • In this paper the conditions which are suitable for separation of macroscopic particles in ac high voltage electric field are analysed. Motion equations of particles creating space charge are solved according to statement of power effects affecting in the transport area. In this case we suppose that particles enter into the electric field with initial velocity v0 . Dust particles are charged in surroundings of electrode system with small radius of curvature. Coronary electrode has the shape of sharp cone and it is made of metal needle covered with dielectric. Collector electrode is made of metal. Occurence of monopolar charge in surroundings of combined coronary electrode is discussed in this paper and it is given the physical analysis of this phenomena. In the conclusion of this paper the results obtained by separation of selected dust are introduced. Theoretical considerations are supported by experiment.
Operation and Upgrade
Physics
  • 275 – The Spectra of the Corona in an Electrostatic Precipitator
    • An optical detection system to measure the spectra of the corona in an electrostatic precipitator has been constructed. The corona light is focussed by a lens on to the input slit of a spectrograph. The output of the spectrograph is detected by a CCD unit connected to a PC for experimental run control and data processing. Preliminary results have shown that the detection system has allowed the spectra to be measured with a high signal-to-noise ratio and resolution. The ionic species present in the corona and the abundance of the individual ionic species are being identified from the measured spectra.
  • 293 – Studies on Electrostatic Precipitation at Temperatures around Acid Dewpoint
    • Electrostatic Precipitators(ESP) for coal-fired boilers are generally operated at a temperature above acid dewpoint. Recently, an alternative technique has been developed from the view point of high efficiency, in which the ESP is operated below acid dewpoint temperature. Because of the formation of sulfuric acid mist, the collecting performance of the ESP is improved. This formation is mainly due to condensation of sulfuric acid vapor, created by the reaction between H2O and sulfur trioxide (SO3 )vapor, in the stack gases. In this paper we describe an experimental study of the collecting performance of an ESP at temperatures around acid dewpoint, and the behavior of condensed SO3. The results may be summarized as follows: (l)The collecting performance of the ESP is improved by the effect of condensed SO3. (2)Condensed SO3 exists as sulfuric acid mist on the surface of dust particles. (3)At a temperature below ·acid dewpoint, it is possible to remove SO3 and dust particles from the stack gas with high efficiency .
  • 299 – Relations between Coal/Fly Ash Properties and Cohesive Forces in Electrostatically Precipitated Ash Layers
    • The main results of a research programme directed to the investigation of fly ash cohesiveness and adherence to ESP plates and their relation with coal and ash properties are presented.A total of 58 coal and fly ash samples coming from 6 pc boilers have been extensively characterized by means of standard and non-standard analyses to identify physical, chemical, morphological, mineralogical, and ESP performance related characteristics, like resistivity and dust layer adherence to the collecting plates. A measuring method of cohesive forces on electrostatically precipitated fly ash and a test apparatus have been developed. The ash cohesion under approximate real conditions in industrial ESPs has been measured. Correlations between the cohesive force and the coal/fly ash characteristics have been established, and also the relation with ash resistivity.
  • 306 – Electrostatically Enhanced Core Separator System
    • The Electrostatically Enhanced Core Separator (EECS) system employs the same design principles as the mechanical Core Separator system plus an electrostatic separation enhancing technique. The EECS system (patent pending) contains a special type of separator, the EECS element; a conventional solids collector and means for flow recirculation. In the EECS system solids separation and collection are accomplished in two different components.The EECS element acts as a separator, not as a collector so panicles are not collected on its walls. This eliminates or at least mitigates the problems associated with reentrainment (due to high or low dust resistivity), sweepage (due to gas flow below the precipitator plates and over the hoppers}, sneakage (due to gas flow both above and below the precipitator plates}, and rapping reentrainment (due to the mixing of gas and broken dust layers). If the EECS separation efficiency is high enough, particles cannot leave the system with the process stream. They recirculate until they are extracted by the collector. As a result, the separation efficiency of the EECS element detennines the efficiency of the system, even if the collector efficiency is relatively low.
  • 312 – Recent Experience in Controlling Fine Particles in ESP
    • The future will require much more stringent control of fine particulate emissions. Conventional particulate collectors such as electrostatic precipitators and fabric filters will be pushed to their limits to meet the new requirements. The need for the development of novel methods or enhancements for improved fine particulate control will become obvious. This paper discusses the difficulties in capturing the fine particles and presents several potential means for ultimately accomplishing the goal of high-efficiency fine particulate control.
  • 325 – Local Deposition of Particles in a Laboratory-Scale Electrostatic Precipitator with Barbed Discharge Electrodes
    • The precipitation of particles in an electrostatic precipitator (ESP) results in striking dust patterns at the collecting electrodes, strongly depending on forces of the electrohydrodynamic (EHD) field in the duct. Due to precipitator geometry, electrical operation status, and process parameters, areas of high and low dust density are visible. Since latest results show a direct correlation of precipitator efficiency with the shape and size of those patterns, a better knowledge of local dust layer properties is necessary in order to improve the performance of electrostatic precipitators, e.g. by electrode optimization.For this paper experimental investigations were carried out with a laboratory scale electrostatic precipitator. In order to analyze the different characteristics of the collected dust at compressed and light dust layer regions, particle size distributions and dust layer porosity were determined with the help of a scanning_ electron microscope (SEM). Moreover, high accuracy weight measurements were executed to reveal preferred dust deposition along the collecting electrodes.

      Whereas the dust mass varies only insignificantly for short-time particle collection ( e.g. 1 minute), the dust mass in high-density regions is much larger after having collected a dust layer for a longer period (e.g. 45 minutes). This phenomenon is due to a permanent dust layer erosion by forces of the gas flow. Moreover, a totally different structure of the dust layer can be observed directly opposite and between the discharge electrodes. Porosity investigations underline the observations and prove significantly lower porosity in dust layer areas directly opposite the coronating barbs. The different particle size distributions of dust at high- and low-density regions of the dust layer show that fine particles were preferably deposited in high-density regions.

      Since the dust layer patterns strongly depend on design and arrangement of the discharge electrodes, the results show potential for an improvement of the ESP-geometry. Further, the porosity investigations explain observations of local b3;ck corona occurrence at the dust layer.

  • 335 – Improved Discharge Electrode Design Yields Favorable EHD-Field with Low Dust Layer Erosion in Electrostatic Precipitator
    • The performance of electrostatic precipitators strongly depends on design and geometry parameters of the discharge electrode system. Since the geometry of the electrode system determines the electric field and corona intensity, design and distance of the coronating electrodes must be carefully adapted to the properties of the dust-laden gas. Only few results exist on the correlation between geometry parameters and fine dust precipitation efficiency. In industrial applications type and distance of the corona ting electrodes are often chosen heuristically.This paper presents the results of experimental investigations with a plate-type laboratory- scale ESP. A special frame construction allowed gradually increasing the distance of the coronating electrodes over -a wide range. Fractional efficiency measurements were conducted for a various geometric and electric settings under constant gas conditions. Depending on the settings, dust patterns of different size occured at the collecting electrode, showing areas of high- and low-density dust. Video recordings prove that fine dust strongly reentrains from areas of low density dust. Freeze frames, taken out of the video, visualize the reentraining process of collected dust agglomerates. The fractional efficiency curves show optimum ESP performance for coronating electrode distances in the range of the half gap width or smaller. Further, a dust pattern analysis demonstrates that ESP performance can be optimized through geometric and electric settings, which yield small areas of low-density dust at the collecting electrode.

      The investigations demonstrate that a suitable design and arrangement of the electrodes results in an EHD field, which makes small areas of low density dust appear at the collecting.electrodes and, therefore, leads to low dust layer erosion.

  • 343 – Fractional Efficiency Investigations under Back Corona Conditions Considering the Local Occurrence of Back Corona at the Dust Layer of Electrostatic Precipitators
    • High dust resistivities in combination with a collected dust layer are responsible for the occurrence of back corona, which is the cause for a dramatic decrease in the efficiency of an electrostatic precipitator (ESP). So far, a lot of research has been done in order to understand the theoretical background of this phenomenon. Also, technical solutions were developed to reduce the adverse effects on the precipitator performance, such as conditioning or pulse power supplies. However, only few investigations keep attention on the local back corona behaviour at the collecting plates, which depends on dust layer thickness and density, on their part strongly influenced by forces of the electro hydrodynamic (EHD) field.The present paper deals with observations of local back corona occurrence in a laboratory scale electrostatic precipitator and with the influence of back corona on fractional efficiencies under various geometric and electric operation settings. Upon collection of an appropriate dust layer, back corona was artificially generated by increasing the voltage beyond back corona onset. The growing intensity and spatial expansion of back corona glow-points at the collecting electrode were obtained for slowly increased voltage on a series of impressive pictures.

      These experimental investigations underline the existence of different back corona types as already shown in literature. Back corona mainly occured at certain regions of the ESP inlet due to specific conditions of dust layer thickness and porosity. The majority of back corona glow-points appeared in high porosity areas of the dust layer. The fractional efficiency measurements under identical conditions confirm earlier investigations with a laboratory scale tubular precipitator, which proved that back corona affects submicron particles much stronger than particles in the IO μm-range. Further measurements with different distances of the discharge electrodes show higher efficiencies for certain geometric adjustments. This result is due to the minimization of back corona areas at the collecting electrode.

  • 353 – Studies of Dust Layer Formation on Electrostatic Precipitator Electrodes at Alternating Polarity Power Supply (Apps)
  • 359 – The Study of Agglomeration and Collection Efficiency in Electrostatic Precipitators
  • 365 – Investigations into the Local Mass Flux of Dust to be Precipitated at the Collecting Electrode
    • The paper is dealing with the presentations of collecting efficiencies of electrostatic precipitators. Whereas the total separation efficiency and effective migration rates respectively bear some problems in interpretation and discussion an observation of the flux of locally precipitated dust should lead to more clarity and an improved insight of precipitation because it is only based on physical terms.The paper presents model calculations accounting for the size-dependent local particle transport. The local mass flux was calculated for varying median particle size and width of the particle size distribution. One interesting result is the influence of the classification along the duct, due to the size dependence of the particle migration velocity, on the local mass flux. It causes an increasing curvature resulting in a higher flux at the entrance of the precipitator, and a higher flux at the outlet for increasing width of the particle size distribution. Furthermore one can show that higher fluid velocities cause a shift of the classification towards the back part of the precipitator. Furthermore an integration over the precipitator length yields the total mass flux and therefore the total separation efficiency may be calculated. From this quantity effective migration rates weff according to the modelequations of Deutsch and Matts-Ohnfeldt can be recalculated. The so-called ‘applied Deutsch-equation’ yields a w eff which is very sensitive to the classification effect whereas the empirical formula by Matts and Ohnfeldt yields a weff which is less sensitive in acertain range.

      Preliminary experimental investigations of the local precipitated dust show the influence of an evolving particle concentration profile at the entrance of the duct.

  • 375 – Investigations on Particle Dynamics in a Plate Type Electrostatic Precipitator Using Double-Pulse Holography
    • The separation of particles from gases within electrostatic precipitators is mainly depending on the flow conditions. The flow field is governed by the mutual interaction of the electric field with the gas ions and the turbulent channel flow. Especially for wire-plate electrostatic precipitators this causes secondary flows, well known as the ‘ionic wind’. The influence of the ionic wind on the precipitation of particles has been discussed widely in the past.Double-pulse holography was applied to investigate the particle motion within a laboratory scaled plate-type electrostatic precipitator with round wires as discharge electrodes. This experimental method allows to determine size, location and velocity of all particles within a specified volume at one distinct moment. Subsequently frequency distributions as well as spatial distributions of the particle collective within the precipitation zone are evaluated.

      A quantitative analysis of the migration velocities in the near-wall region and a comparison with theoretical migration velocities, leads to the conclusion that the ionic wind has an order of magnitude about some 10 emfs.

  • 382 – Experiments on Simultaneous Variation of Plate Spacing and Duct Length
  • 388 – Conduction and Charging Phenomena in a Fluidised Bed of Solid Insulating Particles
  • 394 – Fact: a Non-Traditional Fly Ash Conditioning Technology
  • 400 – Measurement of Discharge Electrode Emission Characteristics in the Laboratory
  • 406 – Particle Flow Field in a Commercial Design ESP during Intermittent Energization
    • Spatially and temporally resolved particle velocity has been measured by means of Laser-Doppler-Velocimetry (LDV) in a laboratory ESP of commercial design operating with Intermittent Energization (IE). Rigid Discharge Electrodes (RDEs) and helical wires were used as Discharge Electrodes (DEs) and the Collecting Electrodes (CEs) were of the G-shape type. The electrode spacing was 300 mm. The negative high voltage was run in a mode with charging ratios of 1: 1 and 1: 19. The average current density was 0.4 mA/m2 for the 1: 1 tests and 19 times lower for the 1: 19 tests. Submicron polystyrene particles were added to the air flow at the ESP inlet.The LDV -measurements consisted of three particle velocity components and the whole flow fields were mapped by traversing in three directions. The time base of the velocity registrations was synchronised to the high voltage supply pulses, which made it possible to track the time history of the particle velocities.

      The results show marked spatial gradients in both mean particle velocity and turbulence level, especially where the corona is located. Those gradients are steeper for the RDEs than for the helical wires. The 1: 19 tests reveal also the transient behaviour of the particle transport in the ESP.

      The aerodynamically generated overall (and time averaged) turbulence level is significant compared to the electrically generated turbulence. This is especially true close to the CEs due to the flow separation at the G-shaped stiffeners.

  • 417 – FGC as a Means for Cost-Effective ESPs for Low Sulfur Coals
    • The fly ash generated from many low sulfur coals results in large Electrostatic Precipitators (ESPs) in order to achieve acceptable particulate emission levels. When the fly ash has a high content of Si and Al and a low content of primarily Na and S, backcorona is formed on the collecting plates due to the high resistivity nature of the ash cake. Flue Gas Conditioning (FGC) is a proven, cost-effective method to lower resistivity. Then a smaller ESP can achieve the same collecting efficiency and emission as a larger one without FGC. A proper control of back-corona with modem microprocessors will minimize the sulfur consumption and at the same time avoid overdosing of the conditioning agent. The economics favor the smaller ESP with FGC over the larger ESP.This paper discusses the technical, capital and operating cost advantages of the smaller ESP with FGC over the larger ESP. It also briefly discuss alternative techniques for back-corona prevention.
  • 427 – Flue Gas SO3 Conditioning for Improvement of Particle Collection in ESP
  • 432 – Results of IES Utilities, Burlington Station SO3 Conditioning
    • Burlington Station’s (200 Mw) electrostatic precipitator operation, originally designed for high sulfur flyash, would not allow the plant to achieve desired load when burning US low sulfur western fuels due to the high resistivity of the fly ash. Unit load was derated 90 Mw or more to avoid exceeding emission limits.The ESP sizing makes collection of fly ash difficult at best. Originally designed for a forced draft unit (See Table 1, ESP Data Before Conversion), the ESP was virtually unchanged after conversion to balanced draft (See Table 2, ESP Data After Conversion). With such ESP conditions as SCA= 5.4; 1529280 m2/Am3/hour@ 158°C and face velocity of 2.5 m/sec, the ESP could not successfully collect the particulate With Unit loads of 70 to 80 Mw, the opacity was near the 40% limits. In balanced draft, maximum Unit load was 180 Mw.
  • 438 – Impact of Ash Characteristics on Precipitator Performance
    • For new boilers firing fossil fuels, the emission standard for particulates are often in the 20- 50 mg/m 3 NTP range. Future standards are expected to be stricter, most likely below 5 mg/m 3 NTP.An integrated knowledge base of the fuel, boiler operation, the fly ash properties and the precipitation process is needed to properly design an electrostatic precipitator (ESP) to achieve a prescribed degree of cleaning. This paper describes a study with several coals of how the fly ash properties vary for different coals and combustion conditions and the relationship of the ash characteristics to precipitability.

      Detailed measurements of the fly ash characteristics from two coals were conducted in a 500 and a 630 MWe field unit. These data were used to calibrate and validate an ash generation methodology using a drop-tube reactor. Further tests were carried out for 7 coals in the drop-tube reactor. Ash characteristics, in the size range smaller than about 5 μm, were correlated to migration velocities determined from field data Particularly noteworthy, was the positive correlation between the ash surface area and precipitability and the strong dependence of the both the fine (0.5-4 μm) and ultra-fine(< 0.5 μm) ash loading on combustion temperature.

  • 452 – Physical Simulation of the Particle Migration in ESP Part II Application Results
    • In order to simulate the operating conditions of electrostatic precipitators and to improve the physical knowledge of internal processes, a new numerical model of ESP has been developed and a series of laboratory tests have been performed. For purpose of model validation, in this paper some of the simulation results, for different ESP energization voltages and operating conditions, are presented and compared with experimentals observations.
  • 460 – The Evolution of Back Corona Conditions in an ESP
    • Experiments with fly ash resistivities of 1012 Ocm and 1015 ncm have been performed in a laboratory ESP with a plate spacing and electrode shapes similar to commercial units. Both DC and intermittent energization were applied. The spatial and temporal evolution of back corona conditions could be observed in detail by a fast current detection at each individual collecting plate. An increase in filter current at the first plate pair indicated the back corona onset after the start of an experiment with initially clean plates. Subsequently the back corona onset could be observed at the second and third plate pair as a result of the developing high resistivity dust layers. The corresponding decrease in filter efficiency was monitored and compared for different resistivities and dust layer thicknesses. The recorded correlation of electrical data and particle measurements permit a deeper insight how back corona evolves and affects ESP Performance.
Plasma Catalysis
  • 479 – Non-Thermal Plasma Processing for Air Cleaning
    • Atmospheric pressure discharge Non-Thermal Plasma processing of air contaminated by dilute Volatile Organic Compounds (VOCs) or flue gas with NO and NOz was experimentally tested. As VOCs, 100 – 1,000 ppm trichlorofluoroethylene, trichlene and others were decomposed by the Non-Thermal Plasma processing. If discharge power is sufficient, most of contaminants are decomposed more than 99% in any case. The decomposition mechanism is not yet clear but various decomposition byproduct analyses in air, oxygen or nitrogen were observed by using GC or GC-MS. Mixing effects of plasma processed pure air and contaminated air were also tested. In the case of NOx reduction from the flue gas, the plasma is not so effective to reduce the NOx. At some condition, the plasma oxide NO to NOz, but that all. Total amount of NOx increased when the discharge power was large and residual oxygen concentration was large enough. When the flue gas was plasma processed with hydrocarbon additives and the processed gas was exposed to catalyst at room temperature, NOx concentration was much decreased.
  • 485 – Decomposition of Methylmercaptan by Non Thermal Plasma
    • It is well known that the non-thermal plasma technologies are having a considerable potential in decomposing air pollutants, such as NOx, SOx, ozone layer depleting gases, VOC-s and others. It is also well known that in certain paper pulp making technologies, especially in processes based on straw, a rather high concentration of Methylmercaptan is generated, which is a hazardous pollutant for human health. It can be especially dangerous for children even at low or trace concentration if it inhaled regularly. To investigate the effect of non-thermal plasma on the Methylmercaptan electrostatic precipitator having a fast rising pulse energisation has been used. A pulse with variable rise and width were used. The rise was varied between 20 and 500 nsec, the width was between 70 and 1500 nsec. The pulse peak voltage was changeable up to -40 kV. The repetition frequency was between 10Hz and 1 kHz. The initial concentration of the Methylmercaptan was around 1%V. The carrier gases were nitrogen, helium and argon. In some experiments oxygen was also added to the mixture up to 22% on volume base. The flow rate was varied from 1 l/rnin to 10 l/rnin. The concentration of the Methylmercaptan was measured by using gaschromatography. The result of the investigation was that about 90% removal could be achieved. The change in the rise time did not effect the removal efficiency, but the length of the pulse was an important factor in that. The shorter pulse resulted higher efficiency.
  • 490 – Removal of the Ozone Layer Depleting Gases Using Non-Thermal Plasma Technology
    • It is well known that the ozone layer is seriously attacted by certain gases emitted by both the nature, and with increasing importance, by the human activity. It is also known that the nonthermal plasma technology is a powerful tool to abate hazardous pollutants in flue and exhaust gases. It has been proved in the literature by Masuda, Oda and others that with surface discharge type ozonizers the ozone layer depleting gases can be eliminated or abated. In this investigation the freons and carbon tetracloride were treated with surface and volume discharge. For the surface discharge type reactor a cylindrical type ozoniser was used with internal diameter of 10, 20 and 30mm and with active electrode length of 0.6, 1 and 5m. The applied voltage was varied between 5 and 12 kV peak-to-peak sinusoidal. The frequency was changed in the interwal of 0.05-10 kHz. Pulse energized cylindrical electrostatic precipitator was used as a volume discharge type reactor. The diameter of the discharge electrode wire was 0.2 mm, the internal diameter of the round electrode cylinder was 45 mm. The applied voltage was between 5 kV and 40 kV peak. The repetition frequency was varied in the 10-500 Hz interval. The width of the pulse could be changed from 50 nsec to 1500 nsec. The rise was variable in the 20-500 nsee interval. The input gases were freon 12 and 22 in pure or mixed with dry and moist air. The concentration was varied between 1000 ppm and 100 %. The chemical analyses were made by gas-chromatography. The results show that the abatement and decomposition of freons can be achieved. At lower concentrations the decomposition is more difficult.
  • 495 – Optimizing Pulse Corona Characteristics for Removal of SO2 by Pulse Corona from Simulated Flue Gas
    • This paper researched the optimization of pulse corona characteristics for removal of ~ by pulse corona from simulated flue gas of 4-16NmJ/h.The discharge circuit of generator was investigated. Moreover.some compositions of gas being processed were regulated.By measuring pulse waveforms and analyzing chemical compositions of byproducts, energy yield and removal efficiency were discussed in detail.The optimization in this system has been realized successfully. At the same time, a succinct criterion about whether the energy yield is high or low has been provided. Finally ,the energy yield is raised effectively. With an initial concentration of 1500-2000 ppm of SOz, a gas temperature of 50-65 °c and a stoichiometric ratio of anunonia to ~ between 0.8 -1 ~ the results show that up to 65%-85% of S~ is removed at a power consumption rate of 4WhlNmJ .
  • 505 Decomposition of Hydrocarbons by Back Corona Discharges
    • Back-corona discharge has been successfully applied for decomposition of hydrocarbons. Back-corona discharge is generated in a needle-to-plate reactor, with a corona-counter electrode covered with a perforated mica plate. The results of laboratory experiments show that the back-corona discharge can be more efficient in decomposition of hydrocarbons than positive de streamer corona discharges.
  • 517 No removal by Pulsed Corona Discharge in ESP with Irrigated Plate
  • 523 Removal of Toulene from Air Stream by a Pulse Corona Plasma Reactor
    • Non-thermal plasma technologies offer an innovative approach to the problem of decomposing various volatile organic compounds (YOCs). We focussed on pulse corona discharge plasma reactors to study the decomposition/destruction efficiency for toluene at 80 to 2200 ppm level in dry air. The effects of gas flow rate, concentration and reactor operating conditionson the decomposition and analysis of reactant conversion for toluene were investigated. The experimental results show that destruction efficiencies oftoluene nonmonotonically depend on applied dc charging voltage, and decrease with increasing gas flow rate, no significant 03, Nox’ N20 and CO are observed from air as discharge by-products, and CO2 and H20 are observed to be the final products of toluene destructions.
  • 535 The Reduction of NOx and SOx from Flue Gas Using Sub microsecond Pulsed Energization
    • Experimental and theoretical studies have been carried out by CSIRO on the effects of submicrosecond positive voltage pulses on the reduction of sulphur and nitrogen oxides in the flue gas from two different Australian coals. The experiments showed that, at suitable residence times, the pulsed system removed about 40% of the sulphur oxides (SOx) but more than 90% of the nitrogen oxides (NOx)’ It was also shown that water vapour was essential for the removal of SOx but not for NOx. . The theoretical study showed that the removal of SOxwas mainly due to OH radicals from water vapour producing H2S04, whilst NOxwas reduced by N atoms.
  • 544 Reduction of Chemical Pollutants in the Exhaust as of the Municipal Waste Incinerator by PPCP (Pulse Corona Induced Plasma Chemical Process)
    • Our research aims at reduction of dioxin and other chemical pollutants such as nitrogen oxide in the exhaust gas of the Municipal solid waste incinerator by Pulse Corona Induced Plasma Chemical Process named PPCP. The test facility is constructed at the working incineration plant (300 t/dx 2) and operated since 1993. This research is promoted by the government organization named New Energy and Industrial Technology Development organization (NEDO) and its entrusted agency named Engineering Advancement Association (ENAA). Under them Takuma Co., LTD. and Masuda Research Inc. are studying this project.
  • 550 Removal of NOx in a DC Corona Discharge Used in Wet Precipitators
    • The object of this investigation was the influence of H20 on N02 decomposition and production ofNO and N20 in a mixture ofN2:02:C02:N02 subjected to a direct current (de) corona discharge. The dc corona discharge was generated in a needle-to-plate reactor. 35 positively polarised needles were used as one electrode. The other was a stainless steel plate covered with water film, similarly as the collecting electrode in wet precipitators. The time-averaged discharge current was varied from 0 to 7 rnA. It was found that the presence of H20 increases the decomposition of N02 and decreases the production of NO. As a result the concentration of NO” decreases. The highest N02 and NO” reduction was observed for discharge current of 4 rnA.
  • 555 Pulse Corona Discharge Investigations and Concept of Combined Effluents Cleaning from Dust and Oxides
  • 562 NOx Removal Characteristics of Corona Radical Shower System
    • The effects of flue gas flow rate and seed gas on the corona discharge current- voltage characteristics and NOx removal characteristics are experimentally investigated for a Corona Radical Shower System. The corona discharge current-voltage characteristics have two operating modes which have a significant influence on NOx removal characteristics, where the threshold gas residence time of the treatment gas in active corona discharge region is about 8. Maximum NOx reduction rate observed under the non-monotonic corona discharge current -voltage characteristics is higher than that for the monotonic corona discharge current-voltage characteristics. The leak ammonia in exhaust gas can be significantly lowered by optimizing the ammonia concentration in additional gas. Maximum NOx removal rate reaches 100% for UNH3IUNO is greater than 1.5.
  • 568 Effect of Non-Thermal Plasma on Carbon Dioxide
    • It is well known that the increasing concentration of carbon dioxide can result a serious disturbance in the heat balance of Earth. It is also known that this gas can be decomposed by electric discharge, however it does not seem energetically feasible. The high possibility of corona discharges along the high voltage transmission lines can decompose this gas and in the presence of nitrogen and oxygen other chemicals can be produced. To investigate the decomposition of carbon dioxide by non-thermal plasma surface discharge, volume discharge were used. As surface discharge type reactor, a cylindrical type ozonizer was used with internal diameter of 10, 20 and 30 mm and with active electrode length of 0,6 1 and 5 m. The applied voltage was varied between 5 and 12 kV peak-to-peak sinusoidal. The frequency was changed in the interval of 0,5-12 kHz. As volume discharge reactor, a pulse energized cylindrical electrostatic precipitator was used. The diameter of the wire was 0,2 mm, the diameter of the cylinder was varied between 5 and 15 em. The applied voltage was between -5 kV and -60 kV peak. The repetition frequency was varied in the 10-500 Hz interval. The width of the pulse could be changed from 50 nsec to 1500 nsec. The rise was variable in the 20-500 nsec interval. The input gas was pure carbon dioxide mixed with nitrogen or with air. The concentration was varied between 100 % and 1000 ppm. The chemical analysis was made by carbon dioxide analyzer, infrared spectroscopy and gaschromatography. The results show that the carbon dioxide can be decomposed in the reactors. In pulse plasma in the presence of nitrogen and no oxygen, dinitrogen oxide can be generated which is also a greenhouse gas. The processes which take place in the presence of high voltage if carbon dioxide and nitrogen oxides are non-stochiometric and resulting different byproducts.
  • 574 Removal of NO from Flue and Exhaust Gases Using Non-Thermal Plasma Technology
    • It is well known that non-thermal plasma technology is a powerful tool to abate hazardous pollutants in flue and exhaust gases. The most common representation for that technology is an electrostatic precipitator energized by fast rising pulse. The length of the pulse is usually shorter than 1000 nsec, and the rise is faster than a few hundred nsec. In order to investigate the effect of the pulse energisation on the removal characteristics and efficiency cylindrical and rectangular precipitators were made with central wires. The diameter of the wire was 0.2 mm, the diameter of the cylinder was varied between 5 and 15 cm. The distance of the sides of the rectangular was 10 cm. The applied voltage was between -5 kV and -80 kV peak. The repetition frequency was varied in the 101500Hz interval. The width of the pulse could be changed from 50 nsec to 1500 nsec. The rise was variable in the 20-500 nsec interval. The input gas was pure NO mixed with nitrogen or argon or helium. The concentration was varied between 100% and 1%. The chemical analysis was made by FTIR, conventional IR analyzer equipment. The result shows that the abatement of NO, even at 100% concentration can be achieved, and that various kinds of nitrogen oxides can be produced even at pure NO. The removal efficiency was independent on the rise time in the 70-500 nsec interval, but increased by decreasing rise time below.
  • 580 The use of Pulsed Corona Technology to Destroy VOCs, Dioxins and Furans at a Municipal Solid Waste Incinerator
Power Supply
  • 587 Application of Pulse Power for Gas Cleaning Direct-Coupled Pulse Energization in ESP and Pulse Corona Induced Plasma Chemical Process
    • Pulse power has been used for collecting high-resistivity dusts and also decompose gaseous pollutants in the field of gas cleaning. The difference in both applications are energy input of pulse power into corona discharge. In the case of pulse energization of ESP (collection of dusts), pulse power is only used to produce ions in the restrict region of the corona electrode. On the other hand, in the case of decomposition of gaseous pollutants, the reaction field is needed to be filled with plasma oriented radicals. As a result, pulse power is converted to streamers elongated in the entire reaction field.
  • 596 Design of a Low Cost Pulsed Power Supply for Electrostatic Precipitators Using Magnetic Switching Technique
    • Although the benefits ofpulsed energization of Electrostatic Precipitators (ESPs) for high resistivity applications are well known, limits on the electrical side do not allow a design oflow cost devices with short pulse widths and a long life time. The pulse width ofcommercial pulsedpower sets and the repetition rate are limited by the turn-off time of the used power thyristors. The thyristors are loaded with a pulse current of very high derivative and an amplitude many times higher than the average value. . In order to overcome these problems a novel pulsed power supply was developed and designed It includes a magnetic switch in addition to modem high voltage solid-state switching technology. The new power supply allows rise times of2-3 f.JS and total pulse widths below 10 us, a repetition rate of more than 400 Hz and a pulse amplitude of more than 100 kV superimposed on a DC voltage. The design is based on an energy saving concept recovering the energy not being utilized in the ESP. First operating tests with a capacitive load are presented and discussed Low first costs, a small number ofhigh voltage components and short pulse widths with the potential to further enhancement of the ESP performance at high resistivity dust favour the new concept.
  • 602 Pulsed Energization Application to Cleaning of Flue Gases
  • 608 The New Scope for EPPS Under the High Voltage Vacuum Switching Tubes – EBV Usage
    • The characteristics of the high voltage switching tubes-electron beam valve (EBV) are described. The high hold-off voltage (up to 200kV), specific VA-characteristics form and small switching on/off time allow to use this EBV in power supplies for electrostatic precipitators with great efficiency. Due to the EBV one can construct special type, for example, alternative polarity power supplies (L.7)d essentially improve the characteristics of conventional unipolar power supplies. The pulse power supply design concept is considered also.
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ICESP Conference in Kyoto, Japan