Combustion Characteristics Of Blends Of Straw And Wood Block In Fixed Bed

At present,the environmental problem has become a major obstacle to seriously endangering the health of human life.Biomass energy as clean energy to solve environmental pollution and energy shortages has received much attention.Biomass energy has been utilized in various ways,in which biomass and other solid fuel blending co-combustion technology has obvious advantages,but its co-combustion characteristics of the mechanism and conclusions have not yet unified.In order to provide experimental data for mixed combustion research and a wider application of biomass combustion,it is of some significance to carry out biomass mixed combustion in a layer of combustion furnace.In this paper,the behaviors of different blend ratio,characteristic length,primary air flow and its temperature on the mixed combustion of biomass was studied in a fixed bed.The structure and data sampling system of the fixed bed are introduced,and the place where the error is generated during the test is analyzed.The combustion parameters in fixed bed are calculated for the start of the test.After the completion of the test,the collected data were analyzed.Then the combustion characteristics of the ignition,devolatilization and char combustion were explained by the using macroscopic performances of the ignition time,the ignition temperature,the flame propagation velocity and the weight loss rate,and the flue gas composition during the combustion process.At last,the conversion of C and N in the fuel was observed to evaluate the combustion characteristics of each condition.The following conclusions were obtained:1)The addition of a small amount of straw in the mixed fuel can promote the ignition of the wood block,increase the burning rates of the devolatilization and char combustion,and reduce the amount of NO emissions.The degree of combustion and the conversion ratios of C and N in the fuel to the flue gas turn worse;2)The large characteristic length makes the ignition more difficult,but the burning rate,the degree of combustion and the conversion ratios of the fuel C into the flue gas increase.NO emissions and the conversion rate of N in fuel was increased first and then increased3)With the increase of the air flow rate,the behaviors of the ignition time,the ignition temperature,and the combustion reaction rate increase first and then decrease.The degree of combustion and the conversion ratios of C,N to flue gas in the fuel become larger and the release of the NO has been increasing;4)When the temperature of the primary air is raised,the co-fuel is so easy to be ignited that the rates of the volatiles combustion and the char combustion are increased,and the ratio of C and N to the flue gas in the fuel increases.The temperature of the primary air should not be too high,when the temperature exceeds 1atm of water vaporization,there will be spontaneous combustion phenomenon.