Simulation Study On Biomass Pyrolysis And Gasification Process Under Flue Gas Atmosphere

Biomass is an ideal renewable energy resource.As a main technology of utilizing biomass energy,biomass pyrolysis and gasification can realize the goal of high efficiency and environment friendly.Based on the preliminary study,a new biomass treatment concept called loop process of pyrolysis under flue gas atmosphere combined with combustion of low calorific value gas has been proposed in this paper.The loop system is of major interest in context of climate change mitigation and simplifying equipment,which is of great research meaning.Firstly,Two models of biomass pyrolysis and gasification process were built for the loop device based on Aspen Plus,which are respectively the thermodynamic equilibrium model and the reaction kinetics model.According to the consistence analysis between the experimental results and numerical simulation values,the reaction kinetics model is more in line with the experimental process therefore it is more reasonable.Secondly,the effects of influence factors on the gasification process of biomass(corn straw)were investigated.The results indicate that: compared with the nitrogen as the gasification agent,when the flue gas acts as the gasification agent,the output of combustible gas is found to increase and a improvement in gas heating value and carbon conversion efficiency is achieved.High temperature and pressure favor Syngas heating value and carbon conversion efficiency.Compared with the co-current flow,performance in the countercurrent flow is better.A longer solid phase retention time increases the carbon conversion efficiency slightly,but degrades the gas heating value.Then,optimized conditions were simulated using Aspen Plus and validated by the experiment.The results indicate that employing the oxygen-rich air as the replacement of compressed air increases the syngas heating value.Decreasing ratio of flue gas to bimass improves the proportion of combustible gas in the pyrolysis gas and increases the lower heating value(LHV),but the growth trend is slowing down.The LHV of syngas is up to 3.95 MJ under a condition of flue gas to bimass ratio of 2.232,which is slightly lower than the simulation results.Finally,The energy balance analysis was conducted in this paper.When the extracted medium temperature flue gas accounts for 21.69% of the total flue gas,the loop device can achieve energy balance automatically,which provides theoretical basis for the loop system.