Study On Formation Mechanism Of H₂,CO And NO Pollutants In Biomass Gasification

Biomass gasification technology provides an efficient way to use clean energy.The influence mechanism of gasification conditions on syngas is still unclear.Therefore,it is necessary to explore the reaction mechanism in gasification process to improve gasification utilization efficiency and reduce pollutant emissions.In this paper,a compound model is used to model the gasification process.In the pyrolysis stage,a three-component model on the pyrolysis stage is established with the pyrolysis properties of cellulose,hemicellulose and lignin,and a finite-rate kinetic model is established on the redox stage for study on reaction mechanism of each component in pine gasification.It was found that the reaction path of H₂ includes direct reaction of light hydrocarbons and CH₃-CH₃O-CH₂O-H₂,while that of CO is CH₃-CH₃O-CH₂O-CHO-CO under the condition of air gasification at 1207K with equivalent ratio of 0.35.Under the condition of air gasification at 900-1300K with equivalent ratio of 0.35,increasing temperature increases the efficiency of direct reaction of light hydrocarbons to H₂,and decreases the conversion of group reaction chain.R3?O+H₂=H+OH?and R84?OH+H₂=H+H₂O?are more sensitive to temperature,so high temperature increases the consumption rates of H₂ and CO.Under the condition of air gasification at 1207K with equivalent ratio of 0.15-0.35,the conversion efficiency of CH₄ to H₂ is the highest at 0.25 because of the effect of Equivalent Ratio on R53?H+CH₄=CH₃+H₂?,while the direct conversion of other light hydrocarbons to H₂ decreases with the increase of Equivalent Ratio,and the effect of group reaction on H₂ yield increases.Compared with the air atmosphere,the process of gasification in H₂O/N₂ atmosphere greatly improves the H₂/CO ratio and reduces the reaction pathways of H₂ and CO.The formation mechanism of nitrogen pollutants in biomass gasification at 1207K and0.35 equivalence ratio was studied.The main nitrogen pollutants in the syngas are NH₃,NO and HCN.NH₃ is mainly produced by NO and HCN.The reaction pathway of NO is N₂-N-NO,and some HCN and NH₃ are formed simultaneously.HCN depends partly on the conversion of NO and partly on the generation of N₂.Temperature increases the group activity and the reaction rate,and increases the total yield of nitrogen pollutants.The conversion of NO to NH₃ and HCN was higher than that of N₂ to NO,which resulted in the decrease of NO yield and the increase of NH₃ and HCN.