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ICESP X CONFERENCE PAPER ABSTRACTS 9C SERIES

Held in Cairns, Australia
June 25 - 29, 2006

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 9C Series papers from the X ICESP Conference.  

9C1
FABRIC FILTER RETROFITS
AN ELECTROSTATIC PRECIPITATOR UPGRADE TECHNOLOGY
FRANCOIS STEYN, LEON BAIDJURAK AND ROD HANSEN

Abstract

Increasingly more stringent emission limits have required many electricity-generating Utilities to upgrade existing electrostatic precipitators (ESPís). Design efficiencies of 2 and 3 field ESPís built in the 1960Ďs and 1970ís ranged from 96% to 98% and were adequate then. One of their primary functions was to reduce ash erosion of the induced draught fans. 

Retrofitting pulse jet fabric filters into these small casings have provided a cost effective solution to Eskom. These fabric filters require a small ďfootprintĒ and emissions of less than 50 mg/Sm3 are sustainable and not as dependant on coal quality and up-stream conditions as is the case with ESPís. This is an important consideration for Eskom because legislation requires load losses or unit shutdown prior to contravening emission limits. A total of 7 700 MW of Eskomís plant have been or are presently being converted to fabric filters at 5 power stations on 31 boilers.

This paper provides an overview of one of these projects presently in progress at Camden power station on 6 x 200MW boilers. These fabric filters have a unique 4 cell design allowing for on- load maintenance, bag changes and operating flexibility. Lessons learnt from previous projects and improvement in fabric material and construction through research will ensure that these advanced fabric filters are successful.

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9C2 
RETROFITTING FABRIC FILTER PLANTS INTO SMALL
ELECTROSTATIC PRECIPITATOR CASINGS
HENDRE D GROBBELAAR

Abstract

Electrostatic precipitators (ESP) built in the 20th century were suitable for the emission requirements of the time, but as environmental legislation and awareness increased, the performance of these precipitators were sometimes no longer compliant with increasingly stringent legislative requirements. Often these precipitators were two or three-field devices and it is difficult to improve the performance of such small-footprint plants to current requirements.

A viable option for improving the efficiency of these emission control devices is to retrofit pulse jet fabric filters into the old and small ESP casings. Such a project has recently been completed at Hendrina power station, South Africa.

The plant was originally equipped with ESPís for gas cleaning, but these were recently replaced with fabric filter plants (FFP), retrofitted into the two and three field ESP casings. The project was executed in three phases, starting in 1994. It was completed in 2004.

This paper will describe the original performance of the ESPís, the performance of the FFPís, the factors influencing the decision to improve the plant, and what criteria the new / refurbished plant had to meet.

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9C3 
SELECTION CRITERIA OF PPS AND PPS/PI BLENDS FOR USE IN
POWER STATION APPLICATIONS
MICHAEL CLAYTON

Abstract

The use of PPS in CFBs is not new, in fact the since the introduction of the original fibre Ryton ģ introduced by Phillips Co many thousands of filter bags have been installed and operated satisfactorily. Todayís challenges are however substantially more demanding than they were 20 or even 10 years ago. Power Station Managers are not happy with bag lifetimes of two or three years as was the case on many of the earlier installations, the quest today is for lifetimes to meet with Power Station GOís. This can mean bag lifetimes of > 48000hrs. This for a textile can be a huge demand, it is achievable but in turn Power Station Managers must also understand the factors which can affect the fabrics lifetime. These factors take three basic forms, chemical, thermal and physical. The PPS fibre performance is the first issue and this is examined relative to the flue gas analysis and the operating temperatures inside the bag filter. Once established that the PPS fibre can withstand the chemical/thermal conditions then the construction of the needlefelt is taken into consideration. To achieve long lifetimes it is necessary to design a high efficiency needlefelt which would require less cleaning cycles than a normal PPS felt offers. These designs can take two basic forms. Firstly by applying a PTFE coating and secondly by blending PI fibres into the surface structure of the needlefelt.

Today we have the possibility to compare the standard PPS filter bag with the more sophisticated designs using a filter test rig according to VDI/DIN 3926. The rig allows us to compare the filtration performance of different fabrics under defined conditions.

The conclusion of the testing allows us to have more confidence in the selection of the correct filter media. We must however combine the gas data and the ash data to be able to make the correct selection. Laboratory tests can of course only be used as indicators the experience gathered in from actual applications is and always will be the most effective criteria for fabric selection. Our experience in the field is extensive and from a wide reference list we highlight two interesting installations.

Gutsche introduced the first PTFE coated fabrics and the first blended fabrics in the mid 80s, the PTFE coated PPS has been successfully installed in many earlier stations such as Rooiwal and Kelvin Power Stations in South Africa, the first blends also being installed at Arnot Power Station in South Africa and Hohot Power Station in China.

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