Study On Pneumatic Conveying And High Temperature Thermal Storage Gasification Of Biomass Microparticles

Under a rapid development of renewable energy worldwide,the long-term planning of renewable energy in China has given the strategic position of biomass energy.Biomass is defined as a renewable,clean energy source because of its own characteristics,and has broadly application foreground,obtaining high-calorific value and low-cost biomass gas for industrial alternative energy is an important goal of biomass energy,that is efficient production of high-quality biomass gas,but there are still many technical bottlenecks to achieve this goal.The stable transportation of biomass feedstock is the precondition for ensuring the gasification effect,the operating parameters of biomass gasification determine the quality of gasification,the gasification equipment is the carrier of biomass gasification,and its performance greatly affects the gasification effect and gasification efficiency,and its structural design plays an important role.Based on application of biomass microparticles in biomass gasification,the pneumatic conveying characteristics of biomass microparticles,the gasification characteristics of biomass microparticles,the design of heat storage tube gasification system and other key theoretical and technical issues were studied.The main work and conclusions include:The method with superheated steam as carrier gas in pneumatic conveying is proposed.After analyzing the feasibility of replacing the superheated steam as carrier gas,based on the principle of gas-solid two-phase stratified flow,the correlation analysis of important macroscopic physical parameters expressed during the pneumatic conveying of sawdust was carried out,and the influences of Froude number(Fr)on the friction coefficient(λ_s,λ_z),the change of sawdust quality(W)with time(T)and the change of flow rate of carrier gas volume(Q)with the mass flow rate(w)of sawdust were analyzed.For different solid-gas ratiosμin the test,as the Fr increases,the friction coefficientλ_sdecreases,but the influence of Fr onλ_sis greater thanμ.As Fr increases,μdecreases.In the case of small error,the fitting formula can be used as an empirical formula for the pneumatic conveying of sawdust microparticles under certain conditions.5 m/s can be used as a reasonable conveying velocity for sawdust microparticles in pneumatic conveying.Under the same pressure drop conditions,the influences of initial pressure and superficial gas velocity on solid mass flow rate(w)and solid-gas ratio(μ)were further analyzed,and the prediction method of pressure drop was proposed.Some conclusions have been drawn:as the initial pressure increases,the solid mass flow increases,but the change of initial pressure has less effect on the solid mass flow.High pressure is beneficial to increase the solid-gas ratio.In order to improve the quality of biomass syngas,sawdust microparticles are chosen as biomass gasification feedstock,a single-tube down-gasifier is designed.Gasification experiment with steam as gasification agent was in research.By changing the operating parameters such as the gasification temperature,the particles size and the dose of gasifying agent,the optimal operating conditions of sawdust gasification were obtained by comparing the experimental data with the simulated data.For the gasification of sawdust,80 mesh(180μm)is the suitable particle size,850°C can be used as the preferred gasification temperature,and the steam to biomass mass ratio(S/B)1.4 is the best ratio.Based on the existing biomass gasification research,selecting sawdust powder and rice husk powder as biomass feedstock,choosing heat storage tube gasifier as the main gasification equipment,and selecting air as gasifying agent,the gasification effect of sawdust powder and rice husk powder were compared by means of air gasification.In the test of sawdust powder gasification,the suitable operating conditions of gasification are:T=950℃,the mass ratio of air to biomass(A/B)=1.5,equivalent ratio(ER)=0.202.In the test of rice husk powder gasification,suitable operating conditions of gasification are:T=900℃,the mass ratio of air to biomass(A/B)=2.5,equivalent ratio(ER)=0.393.The results showed that sawdust powder are more suitable for air gasification than rice husk powder.Proposing the design concept of the heat storage gasifier,and designing a heat storage gasifier that consists of a feed chamber,a gasification chamber and a combustion chamber.Each piece is separately designed and produced,and then connected by flanges to form a complete gasifier.After connecting the two gasifiers by installing the control equipment,the two gasifiers independently perform the two processes of heating and gasification,the heat storage gasifier and other equipment constitute a complete gasification system,gasification experiments with steam have been performed,getting better results.