Experimental Research On Alkali Release From Biomass Combustion

With the fossil fuel resource decreasing and the serious pollution caused by fossil fuel combustion, the biomass energy attracts more and more attention. China is an agricultural country. The amount of agriculture residue is great, and the distribution is extensive. The utilization of biomass is important to release the pressure from energy resource shortage and pollution. Biomass combustion in thermal power plants is an effective way of using biomass energy in China. The fluidized bed is better than the grate furnace as a combustor since its diversity of fuel kinds, high efficiency of combustion and lower temperature of operation. Biomass combustion in fluidized bed is a promising technology. While commonly the high content of alkali minerals always brings agglomeration, corrosion and deposition on the heating surfaces in fluidized bed, and becomes the main reason which limits the utilization of straw in large scale. Consequently, to better understand the alkali behaviors during the combustion of agricultural residue, and seize the law of alkali separation and transformation is of great importance to solve the alkali problems.This article pays some attention on the behavior characteristic of alkali in biomass combustion process. Combined with the project, research on melting characteristic was done with the mixture of lignin and coal ash. The result shows that the content of alkali and the ratio of its content to other elements in ash are the main reasons influencing the melting point. Based on the tubular furnace, the influence between the alkali and other relative elements in biomass combustion and the influence from addition were researched, showing that Al and Si have great influence to potassium and chlorine separating from biomass.Several kinds of biomass were combusted in laboratory-scale fluidized bed, and research on fluidization characteristic was done, including furnace temperature, fluidization velocity, ratio to coal and addition. The law of alkali separation and deposition was summarized. The result shows that: agglomeration is more serious when the furnace temperature rises; defluidization time is longer when wind rate increases; the alkali problem is reduced if biomass is co-combusted with coal, and if increases coal proportion, agglomeration appears later; additions influence the alkali content separated from biomass very much, and add Fe₂O₃ to biomass fuel is an...