Chemical and Morphological Properties of Particulate Matter Generated from Coal-fired Circulating Fluidized Bed Boiler

The particulate matter generated from coal-fired boilers is one of the most important reasons for air pollution. This paper has made a comprehensive research on the particulate matter generated from the circulating fluidized bed boiler. The samples of PM₁₀ were collected from the entrance and the exit of the electrostatic precipitator by the FA-3 aerosol sampler, and the analysis of particle size, morphology and chemical composition were conducted. The results show that, PM₁₀ of the entrance and the exit both present the bimodal distribution, the peak of the large-size is about 8.0μm~9.0μm, the small size is at about 3.5μm~4.5μm. The chemical composition of different particles was observed by the energy spectrum. Different formation mechanisms were analyzed based on the composition. The sub-micron particles were enriched with gasified elements. It is shown that they are mainly formed by minerals gasification-condensation mechanism. But these particles only took about 2.2%~4.5% mass percentage of PM₁₀. However, the main composition of micron particle were Si, Al, Fe and so on. There were Si, Al, Ca, Fe, S, Na, Ti, Mg elements at the small peak, while Si, Mg, Ti, Ca, K elements at the large peak. It is shown that there are two kinds of micron particles. The particle at the small peak is generated by the coal combustion, and the other is formed by both the limestone and the coal combustion.