Particulate matter emission control from small residential boilers after biomass combustion. A review

Abstract

In this paper, lab and commercial constructions of electrostatic precipitators used for the removal of fly ash particles from small residential boilers have been reviewed. The presented solutions were evaluated in terms of removal efficiency, exploitation conditions or expected maintenance costs. Boilers used for household heating are the main sources of air contamination by particulate matter during winter seasons in many countries. The collection efficiency of such devices should be higher than 95% to comply with the ECODESIGN emission limit, and the emission level for biomass <20 mg/m3. It was shown that the collection efficiency of the lab-constructed and market-available electrostatic precipitators is too low to comply with these regulations. The difficulty with flue gas cleaning from residential boilers results from limited space in house, which determines the size of electrostatic precipitator. As a result, the available residence time of flue gases in the precipitation zone, which is one to two orders of magnitude shorter than in industrial precipitators, is too short to obtain the required emission level. Another important problem met in all of those constructions and not satisfactorily solved is the contamination of electrodes and their cleaning from tar deposit. There is an urgent need for the development of small electrostatic devices designed for exhaust gas cleaning from particles generated by small residential boilers, which could be integrated with such a boiler. The novelty of this review is a detailed analysis and comparison of parameters and performances of small electrostatic precipitators for cleaning exhaust gases from small residential boilers based on the data published in scientific research papers. An indication on the future research in this field was also provided in conclusion.