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ICESP IX CONFERENCE PAPER ABSTRACTS A 16-20 SERIES

Held in Kruger Gate, Mpumalanga, South Africa
May
May 17 - 21, 2004

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 the Abstracts for the A 16-20 Series papers from the IX ICESP Conference.  

A16  ORCHIDEE: Efficiency Optimisation of Coal Ash Collection in Electrostatic Precipitators
Véronique Arrondel, Jean Salvi
Ivo Gallimberti, Gianluca Bacchiega

Abstract
In a coal thermal power plant, one of the industrial solutions for collecting the fly ashes produced  during  the combustion  process,  is  the  electrostatic  precipitation.  However,  electrostatic precipitation is a process affected by many parameters, in particular the physical and chemical nature of  the  ash,  the  flow  rate  and  composition  of  the  flue  gas.  In  addition,  the  operation  and  the maintenance of an electrostatic precipitator may prove to be difficult on account of the great number of physical processes concerned.

To satisfy current regulations, the efficiency of the electrostatic precipitator must always be greater than 99.5%. To sustain these high performances requires good control of the impact of various malfunctions on the level of emissions. For that, two distinct approaches can be described. The first, influenced by the problems the ESP manufacturers, describes the process as a whole and requires a substantial experimental database. The second, influenced by research in universities, accurately describes the physical phenomena.

With the ORCHIDEE software, an intermediate approach is proposed, based on physical modelling  of  the  collection  process.  This  approach  enables  to  estimate  the  efficiency  of  an electrostatic  precipitator  without  using  an  experimental  database,  and  to  be  independent  on manufacturer's empirical data. The operator is then able to have a better real time understanding of the problems, and to react efficiently. By introducing properly all input data, ORCHIDEE makes it possible:

¾   to  evaluate  the  impact  of  combustion  parameters  on  dust  emission  rapidly       (too  much  air inleakages, flue gas temperature too high in the electrostatic precipitator).
¾   to test the hypotheses of blending types of coal to avoid back-corona.
¾   to evaluate the impact of unfavourable distribution of the flue gas in the electrostatic precipitator. ¾   to simulate electrical malfunctions: a field or section out of service.

The Maintenance Department can optimise its actions. The Technical Department can make a better  assessment  of  slow  drift  in  operation.  The  Engineering  Department  can  better  appreciate actions for renovation, as the ORCHIDEE physical model makes possible to verify the effect of changes in internal components (height, plate-to-plate distance, and type of wires), changes in the electrical power supplies, the addition of a new field, for both existing units to be retrofitted, and for new units that to be designed.

ORCHIDEE is a tool to assist operation and maintenance of electrostatic filters, that is unique for its high scientific content and its user-friendly interface: it has shown to fulfil the expectations of its users.


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A17  Improvements of An European Type Electrostatic Precipitator With Chinese Design Experiences   
Huang Mei

Abstract
In the beginning of  1980’s, China imported precipitator technology from a European country. Several hundreds of such type precipitators have been manufactured and operated in Chinese cement and other industries. Some drawbacks of detailed design lead  to  abnormal  operations.  Improvements  by  using  of  Chinese  experiences  are described.


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A18  PRACTICAL EXPERIENCE AND RESULTS OF ESP OPERATION COLLECTING HIGH RESISTIVITY FLY ASH WITH HIGH DUST LOAD. 
Abduazim A. Rustambayev, Alexander Koptev and Kjell Porle

Abstract
The article describes results gained during an ESP replacement programme at Aksu power plant in Kazakhstan, carried by the power plant and under the pressure from the State, in order to improve environmental situation in the region.

The task was to both meet reduced emission requirements when collecting a high resistivity fly ash  from  Ekibastus  coal  in  combination  with  the  use  of  the  same  foundation  and  support structures. The coal has low sulphur (<0.6%) and high ash content (> 40%) resulting in an ESP inlet load of  60 g/Nm3 and higher. Intensive back-corona was expected to develop inside the ESP.  The  fly  ash  is  highly  abrasive.  The  combination  of  these  factors  required  special precautions during project implementation.

Combination of modern ESP technology with the use of spiral discharge electrodes and state-of-
the-art microprocessor controllers resulted in successful project implementation with much lower than required emission level. 

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A19  How to Eliminate ESP Insulator Thermal Break Down and Insulation Aging
Long Tao, Xu Jian, Zhou Baoshan

Abstract
High voltage electric field combining with high temperature may lead to ESP insulator failure. Particulates having a relatively lower breakdown voltage strength stick on the  insulator  surface  can  induce  corona  discharge  and  local  temperature  rise thereby  speed  insulator  aging.  Select  insulator  material  with  higher  Te (the temperature when the resistivity lowers to 1MΩ·cm) and optimize design to even the field around insulator can effectively protect insulator from heat breakdown and aging.


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A20 ESP emission reductions with advanced electrode rapping together with novel energising methods
Christer Mauritzson, Martin Kirsten, Hans Jacobsson, Anders Karlsson

Abstract
To help keep the collecting plates clean, Power Down Rapping (PDR) and Power Off Rapping (POR) have been used for many years.

In this paper it is shown, that the simple TR interaction available with PDR and POR can be made in more elaborate ways, and that this greatly reduces the ESP emission compared to the old strategies.Increased rapping losses that may cause major emission peaks when conventional PDR or POR is used can, in many cases, be managed with the more advanced rapping regimes discussed in this paper.

For the ESP entry fields, excessive dust build-up on the collecting plates may increase the voltage that is required to start the corona. The increased voltage increases the risk for spark-over limitation at a
[too] low current.

This and other disturbances have been successfully addressed with more intricate novel rapping strategies combined with new ways of using PDR, what we call Power Control Rapping (PCR).

Compared with ESPs that use conventional rapping the novel methods have in several ESP plants reduced the emission with 30 % for low to medium resistivity dusts. For dusts characterised by a high resistivity this novel method is even more successful, and emission reductions of more than 50 % have been obtained at several plants.

Combining advanced rapping and a more smooth HVDC supply - also referred to as Switched Mode Power Supply (SMPS) technology - even higher emission reductions have been obtained in a number of ESPs, especially when operating with low to medium resistivity dust.

It seems possible that the above mentioned emission reductions can be obtained for all ESPs, provided the dust is, for whatever reason, difficult to dislodge from the collecting plates.


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