Direct And Indirect Coupling Combustion Of Coal And Biomass Characteristic Study

Biomass energy is an inevitable choice to optimize China's energy structure,alleviate the contradiction between energy supply and environmental pollution.Replacing fossil fuels with biomass in power plant boilers is of great prospectect.At present,there are two types of biomass blending methods in domestic coal-fired boilers:direct blending and post-gasification blending.In this study,we conducted a one-dimensional furnace blending thermal-state test on several common biomasses,and conducted an in-depth study on the combustion characteristics and emission characteristics of biomass pellets and biomass gas after blending.Firstly,physicochemical analysis of biomass including wood,rice,wheat,peanut shells and corn was carried out,and the combustion characteristics of biomass were preliminarily evaluated as very easy to ignite and very easy to burn out.Further,through literature review and experimental research,the grindable characteristics of biomass on a conventional coal mill were predicted,and the optimum particle size suitable for biomass blending particles was determined,and then two technical routes for biomass fuel grinding were proposed based on the research results,and the various characteristics of the two options were analyzed.Secondly,thermal tests were completed based on the thermal one-dimensional furnace,and the combustion and emission characteristics of direct coupled combustion of coal and biomass were analyzed in depth.The study on the blending position shows that the biomass burner is best fed from the reduction zone before the primary combustion wind,and the conclusions of the tests on lean coal and bituminous coal are consistent;the study on the blending ratio shows that the larger the biomass blending ratio is,the lower the NO_xemission;the study on the influence of the blending biomass type shows that what affects the NO_xdecrease is the fuel NO_xproduced in the biomass itself,and the higher the fuel NO_xis,the lower the NO_xThe higher the fuel NO_x,the lower the NO_xdecrease;the study on the effect of different coal types shows that the pattern of NO_xchange is the same after adding biomass at different locations,while the NO_xdecrease of bituminous coal is greater with the higher blending ratio,and the change of poor coal is not obvious.Finally,a thermal test was completed relying on the thermal one-dimensional furnace,and the combustion and emission characteristics of the coupled coal and biomass gas combustion were analyzed in depth.The results show that the best blending ratio of biomass gas is 10%,the best blending position of biomass gas is the reduction zone,both bituminous coal and lean coal show a certain decrease in NO_xafter blending biomass gas,and the NO_xreduction effect of biomass gas on bituminous coal is better than that of lean coal.The NO_xreduction capacity of biomass gas decreases as the load decreases.Biomass gas blending leads to a small decrease in coal burn-up.Biomass gas fed into the boiler causes the carbon content of the original main fuel fly ash to rise and the degree of combustion to decrease.Biomass gas blending leads to a small increase in furnace exit temperature.