Study On The Pollutant Emission Characteristics Of Biomass Combustion

As a renewable energy source, biomass and its utilization are gaining an increasing important role worldwide due to the gradual reduction of fossil fuel. Biomass direct combustion, as a utilization mode of biomass energy, has gained more and more widely based on mature experience during development of fossil fuel power plants. The pulverized combustion, grate combustion and fluidized bed combustion are the most common combustion technologies in biomass direct combustion, sulfur oxides and so on during biomass direct combustion could cause serious harm to the natural environment. Considering the advantages of fluidized bed combustion, this paper studies on the pollutant, such as sulfur oxides and so on, emission characteristics of biomass fluidized bed combustion.At first, the sulfur transformations in biomass combustion were experimentally investigated, and the experimental result indicates that the sulfur transformations are mainly related to temperature, formation of sulfur, ash components. Sulfur release is mainly related to temperature and formation of sulfur during devolatilization; the microcosmic reaction mechanism of sulfur transformations during char burnout were studied by the X-ray diffraction and scanning electron microscopy, and found that sulfur release is mainly related to temperature and ash components.Then, self-desulfurization characteristics of biomass have been experimentally investigated. The adsorption mechanism of SO2 by biomass char in the temperature range of 700-900℃was studied by the X-ray photoelectron spectroscopy, effective SO2 adsorption capacity of the biomass char has been found, the organic sulfur formed from the combination of SO2 and biomass char is predominance during the adsorption, this reaction will be weakened with increasing the temperature; and the transformations of sulfur adsorbed by biomass char during char burnout were experimentally investigated, found that the retention of sulfur adsorbed by biomass char was reduced when temperature exceeded 800℃.At last, sulfur oxides emission characteristics of biomass fluidized bed combustion were studied by 20KWthCFB combustor and 1MWCFB combustor based on the above mechanism analysis, and found that fluidized bed combustion provides a good reaction environment for self-desulfurization of biomass so that high sulfur retention was achieved in biomass fluidized bed combustion; nitrogen oxides emission characteristics of biomass fluidized bed combustion were also studied by adjusting the operating conditions in 1MWCFB combustor.