Process Simulation And Optimization Of Biomass Gasification Based On Aspen Plus

Biomass gasification is a technology that converts biomass into combustible gas through high-temperature pyrolysis in a gasifier,and is a clean and efficient technology for utilizing biomass energy.Biomass gasification process is more complex,and there are numerous process factors that affect the gasification effect.It is often difficult to fully grasp the gasification characteristics of biomass and the selection of gasification process parameters through effective tests,resulting in a relatively low gasification efficiency and restricting the promotion and application of gasification technologies in corresponding fields.For the above problems,the Aspen Plus software was used to establish a fixed bed biomass gasification model.The model was utilized to study the gasification characteristics of biomass in different gasification medium,and the related parameters affecting the gasification results were optimized to obtain optimized gasification process parameters for guiding the optimization design of structure,process,control system of the biomass gasification system.The main content of this paper is as follows:⑴According to the characteristics and principles of fixed bed biomass gasification,biomass gasification reaction kinetic model was established using Aspen Plus software.FORTRAN program was prepared according to the elemental analysis method,and the yield of the pyrolysis process was calculated through the selected yield reactor（Ryield）.The pyrolysis coke was decomposed using a stoichiometric reactor（RStoic）.Then a series of multiple mixed flow reactors（RCSTR）was combined with a FORTRAN reaction kinetics program to calculate gasification and combustion process of carbon.The established gasification reaction kinetic model was used to simulate the biomass gasification process,and compared with test data to verify the accuracy of the model.The results showed that the deviation between the model simulated value and the experimental value was within a reasonable range.The content of CO₂ and CH₄ was relatively high,while the content of H₂ and CO was relatively low,which indicated the established model had a certain degree of adaptability.⑵The effect of gasification temperature,air ratio AR and gasification pressure on gasification characteristics under different gasification medium was studied using the biomass gasification model.On the basis of O₂+H₂O gasification medium,it was further discussed the effects of different biomass materials and their moisture content on the gasification results.The sensitivity analysis was performed on three gasification factors such as gasification temperature,air ratio AR and water vapor intake S/B to determine the optimal value of a single factors.The results showed that increasing gasification temperature could enhance the gasification intensity,improve the gas production calorific value,gas yield and gasification efficiency.With the increase of air ratio AR,the calorific value of gas production began to decrease gradually,and the gas yield and gasification efficiency increased slightly.The contents of CO₂ and CH₄ were on the rise with an increase in temperature,while the contents of CO and H₂ reduced gradually.The calorific value of gas production,gas yield and gasification efficiency were not significantly changed.H₂O as a gasification medium could increase the production of H₂ and promote the conversion of CO₂.When the gasification temperature was 900℃and the gasification pressure was 1atm,the air ratio AR under the O₂+H₂O,air,and O₂ gasification medium was 0.24,0.21,and 0.27 respectively,the efficiency of the process could reach a maximum of 86.08%,40.61%,and 35.29%,respectively.Under the same conditions,materials with high carbon content,low ash content and moisture content within 10%should be selected as raw materials for biomass gasification,which could effectively improve gasification efficiency.The single factor optimal value with highest gasification efficiency under O₂+H₂O gasification medium was as follows:gasification temperature 900℃,the air ratio AR0.24,and the water vapor intake S/B 2.5.⑶For optimum values of gasification temperature,air ratio AR and water vapor intake S/B,the orthogonal test was designed to optimize the three factors.Using the method of range and variance to analyze the significance of the interaction between single factors and factors on gasification efficiency,the best combination of parameters of influencing factors was obtained for optimizing the process of biomass gasification system.The results showed that the optimal combination of parameters in gasification temperature,air ratio AR and water vapor intake S/B was 900℃,0.27 and 3 respectively,which could make the biomass gasification efficiency the best.