Experimental study of the processes of reducing the formation of sulfur oxides during the co-combustion of particles of metalignitous coal and wood processing waste

This paper presents results of experimental research on thermal decomposition processes of a rather common D grade steam coal (metalignitous coal) and wood. The research aims to substantiate the previously formulated hypothesis on the mechanism of sulfur oxide sequestration in the combustion products of such mixtures. The elemental composition of the reference coal and wood biomass (pine sawdust) and the ash remaining after complete thermal decomposition of the studied mixtures was analyzed. The obtained results, along with results of the X-ray phase analysis of the ash composition, showed an increase in the proportion of calcium and aluminum sulfates in solid pyrolysis products. The performed experiments substantiate that the use wood as an additive for mixed metalignitous coal fuels reduces sulfur oxide yield during their combustion in power boilers in large-scale and small-scale power generation systems. It was established that pyrolysis of two-component fuels based on the D grade coal mixed with dispersed wood biomass contributes to reducing sulfur oxide concentration in gaseous products of their thermal decomposition. This effect can be attributed to formation of calcium and aluminum sulfates in the mixed fuel ash. They are formed as a result of reactions between the coal and wood pyrolysis products that occur if the content of wood components in the mixture is from 10% to 50%.