Investigation On Pyrolysis And Gasification Characteristics Of Biomass And On Fouling And Slagging Law Of Residual Ashes

The utilization of biomass energy includes pyrolysis,gasification and combustion.Among them,biomass gasification technology that converts biomass energy into combustible gas has received extensive attention.However,in the process of biomass gasification,there are usually problems such as tar blockage and adhesion,ash agglomeration and slagging,and alkali metal corrosion equipment,which severely restrict the efficient utilization and development of biomass energy.In view of this,this paper selects the common,easily available and typical biomass straw fuel in rural areas:corn stalks are used as the raw material for biomass gasification experiments to study the gas production law of corn stalks under different pyrolysis and gasification conditions and their residual ash contamination Slagging evolution law,by analyzing its microstructure evolution,ash element composition,mineral crystal phase structure and melting and sintering characteristics,reveals the fouling and slagging mechanism of residual ash during biomass pyrolysis and gasification,which is the development of biomass energy Use to provide a theoretical basis to avoid melting and slagging of ash.Firstly,using a tube furnace with a controllable atmosphere and a gas composition analyzer,the effect of different pyrolysis temperatures in N2 atmosphere on the gas production law of corn stalk pyrolysis was studied;at the same time,the O2 content was studied by changing the composition of the atmosphere in the tube furnace.The effect of different oxygen concentration and temperature in the atmosphere on the gasification of corn stalks and different temperature and residence time in the atmosphere containing CO2 on the gas production law of corn stalk pyrolysis.The experimental results show that under N2 pyrolysis conditions,low temperature is conducive to the production of CH4,high temperature is conducive to the production of H2,and the addition of O2 promotes the production of CO2 in the process of biomass pyrolysis.The influence of temperature on biomass pyrolysis and gasification is greater than that of oxygen volume fraction;in the CO2 atmosphere,no obvious pyrolysis reaction occurs when corn stover is lower than 600℃,while at 700～800℃,The CO2 atmosphere obviously promotes the production of CO gas;and at 800℃,under the experimental conditions of incomplete reaction of the corn stover in this study,the longer the residence time of the pyrolysis reaction,the larger the gas production of CO.Secondly,this study systematically analyzed the fouling and slagging characteristics of residual ash after pyrolysis and gasification of corn stalks,and explored the pyrolysis ash quality,crystal phase composition and microstructure evolution law of corn stalks at different temperatures in N2 atmosphere;At the same time,the quality of ash produced during the pyrolysis and gasification of corn stover,the crystalline phase composition and microstructure evolution of corn stalks under different oxygen concentrations,different reaction temperatures,and different reaction temperatures and different residence times in an oxygen-containing atmosphere were studied.The results showed that the higher the pyrolysis or gasification temperature,the lower the quality of residual ash produced during the pyrolysis or gasification of corn stover.In N2 atmosphere,the main mineral crystal phases of corn stover are KCl and SiO2.Comparing the microscopic morphology of corn stalk ash at different temperatures,it can be found that when the pyrolysis or gasification temperature is lower than 800℃,the KCl mineral crystal phase mainly exists on the surface of corn stalk ash in a massive structure,and when the temperature rises.At 800℃,the KCl crystal phase mainly exists in the molten state.In a gasification atmosphere with a temperature of 600℃,as the oxygen concentration increases,the ash generated by corn stover fuel will hinder the contact of organic matter in the straw fuel with oxygen,thereby inhibiting the further progress of the gasification reaction;when the temperature rises at 800℃,the content of KCl crystals in the ash is significantly reduced.In a pyrolysis atmosphere containing CO2,when the temperature is lower than 800℃,the mineral crystal phase of the residual ash is similar to that of the N2 atmosphere,which is also mainly KCl and SiO2.When the temperature rises to 800℃,the residual ash content Inorganic salts melt and slag,resulting in low melting point salts such as CaMgSi203 and KAlSi3O8.Finally,in order to further reveal the mechanism of ash fouling and slagging,this study used a microcomputer ash fusion temperature tester to determine the melting characteristics of corn stalk ash under different atmospheres and different pyrolysis or gasification temperatures;the deformation was studied by scanning electron microscopy The microstructure evolution law of corn stalk ash under temperature(DT)and softening temperature(ST),and the ash contamination and slagging judgment index is used to judge and predict its contamination and slagging degree.The results show that the higher the pyrolysis or gasification reaction temperature during the experiment,the higher the melting characteristic temperature of corn stalk ash;and the corn stalk ash mainly exists in the form of strip structure at the deformation temperature,while the corn stalk ash is more at the softening temperature It exists in the form of small spheres in the molten state,which indicates that the softening temperature is more conducive to judging the degree of contamination and slagging of the biomass.