Simulation Of Biomass Gasification Combustion Process And Design Of Fixed Bed Hot Air Device With Operation

The excessive consuming of fossil fuel has brought serious energy shortages and environmental pollution problems.Biomass,as the fourth largest energy source in the world,has aroused worldwide concern due to its great production,wide distribution,carbon cycle,ect.Biomass gasification and gasification combustion is an effective way to solve the problem of biomass resource utilization.Considering that the optimal condition of biomass gasification process is difficult to determine.The control of temperature and excess air coefficient in gasification and combustion process has not been studied in depth.In this study,This paper first by using Aspen Plus process simulation software for biomass gasification and gasification,to simulate the combustion process and build more factors under the optimal condition,on the basis of conducting the biomass of fixed bed gasification and combustion air heater design and experimental work,by regulating the excess air coefficient,gasification and combustion temperature,good results have been achieved.The main research conclusions are as follows:?1?Based on minimization principle of Gibbs free energy,Aspen Plus gasification model was established under the limiting partial chemical reaction equilibrium and considering incomplete carbon conversion factors.The simulation results were in good agreement with the comparison data,indicating that the model could reasonably predict the gasification process of solid fuels.?2?The influences of single factors on gasification indexes were investigated.With the increase of ER and S/B,the gasification temperature gradually increased,and the efficiency of cold gas,effective gas integral as well as the calorific value of gas gradually decreased.The highest CO content was 25.64%with ER of 0.25,and the highest H₂ content was 14.71%with ER of 0.3.Besides,with the increase of S/B ratio,both the gasification temperature and the content of CO in the effective gas decreased,but the content of H2 and CH4 continuously increased.With the increase of gasifying agent temperature,the efficiency of cold gas,the integral number of effective gas and the calorific value of gas show an increasing trend,and increase in the temperature of the gasification agent,cold gas efficiency,effective gas integral,gas calorific value is gradually rising trend,gasification agent temperature increases,the gasification temperature increased,the effective gas CO,H₂ content was increasing.When the gasification agent temperature is 700?,the production of CO,and H₂ during the gasification process can reach 21.16%,and 19.83%,respectively.Meanwhile,the CH₄ content came down.The increase of gasification pressure resulted in the increase of gasification temperature and the decrease of the efficiency of cold gas and the effective gas integral.but a slight increase of the calorific value of gas.With the increase of oxygen volume ratio,the efficiency of cold gas decreased slightly,but the effective gas integral and the calorific value of gas showed an increasing trend.The calorific value of gasification gas increased from 6.41 to 10.86MJ/Nm³.?3?The influences of multiple factors on the gasification indexes were also discussed.The air equivalent ratio?ER?had the highest influence on the calorific value,cold gas efficiency,gas production rate,and effective gas volume.Under the requirements of different gasification indexes,the order of each factor is different,and the optimal level is also different.Within the scope of this orthogonal experiment,the optimal conditions of the whole gasification process is ER of 0.2,S/B of 0.05,the gasification temperature of 700?,and the O₂ volume share is 95%.?4?Under the premise of unrestricted gasification and combustion temperature,the gasification and combustion method cannot effectively solve the emission of pollutants in the flue gases.By controlling excess air coefficient and gasification/combustion temperature,the content of NO_x and CO in the flue gas could be significantly reduced.Controlling gasification and combustion temperature or appropriately reducing excess air coefficient could make the emission of NO_x in the flue gas reach the standard without any additional treatments.Although the gasification combustion method could reduce the emission of SO_x,the SO_x amount in the flue gas still exceeded the standard and needed further treatment.?5?Design and experimental of hot air device for fixed bed of biomass has been proofed,The separation of gasification and combustion processes,adding the low temperature combustion could reduce the harm of coking in the furnace due to the low melting point of biomass ash.What's more,the NO_x and other pollutants emissions could also be reduced.After adding desulfurizer in the device,the SO₂ in the flue gases decreaseed obviously under the corresponding national emission standards,but it should be noted that the process is required to be improved to meet the Ultra-low emission standard.