Biomass Co-firing --New Challenge for Electrostatic Precipitators--
A. Jaworek1 3, M. Jędrusik2, A. Świerczok2, T. Czech3, A. T. Sobczyk3, and M. Lackowski3
1 Institute of Physics, Pomeranian Academy in S?upsk, Poland
2 Institute of Heat Engineering and Fluid Mechanics, Wroc?aw University of Technology, Poland
3 Institute of Fluid Flow Machinery, Polish Academy of Sciences, Poland
Abstract
Power plants are the most important sources of atmospheric pollutants. It refers equally well to conventional, coal-fired, and to biomass co-firing plants. The composition of flue gas from biomass co-firing differs from that emitted by coal fired boilers. Particularly, there are an increased number of particles in submicron size range and the number of particles larger than 100 µm, and increased emission of CO and tar leaving the boiler. These new after-burning products can decrease the overall collection efficiency of electrostatic precipitator (ESP), increase emission of submicron particles, and cause degradation of the construction elements of precipitator. The construction elements are degraded due, for example, to chlorine or sulfur corrosion of metal elements, or their contamination with tar. Tar present in flue gases after biomass burning can, after longer time, be deposited onto HV insulators, changing their electrical properties, leading to increasing leakage current or even to the surface breakdown. It was reported in the literature that increased amount of CO in flue gases, or increased amount of unburned coal could result in fires in ESP. The long-term effects of biomass cofiring on the electrostatic precipitator are, however, not known. Although there are an increasing number of publications on troubles encountered in boilers co-firing biomass, there is still low number of papers on experimental results regarding the changes in performances of ESPs cleaning flue gases from biomass burning. These new problems arising in electrostatic precipitators result from the fact that the precipitators were designed for cleaning flue gases from coal burning boilers. Different chemical composition of biomass results in different chemical composition and physical properties of flue gases and fly ash to be removed.
The positive and negative effects of biomass co-firing on the operation of electrostatic precipitators are discussed in the paper. The paper indicates future directions in the investigation of operational properties of electrostatic precipitators cleaning flue gases after co-firing biomass with coal or firing various kinds of biomass in boilers. It is concluded that further research should be aimed at investigating the collection efficiency of electrostatic precipitator, maintenance of the precipitators, emission of submicron particles, heavy metals and tar as well as contamination and degradation of electrodes and insulators due to increased amount of tar, chlorine and sulfur compounds. The goal of this paper is to turn an attention of scientists and engineers to these specific problems.
Keywords - Electrostatic precipitator, biomass, co-firing, gas cleaning
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