TG-FTIR Experimental Study And Simulation Of Reaction Process On Pyrolysis Of Biomass

In recent years,as biomass energy gradually becomes an important part of the energy composition of countries,there are more and more researches on biomass pyrolysis and combustion,the study of its combustion mechanism is also deepening,including the proposed chemical reaction model and dynamic simulation,also made a lot of important results.However,in the previous study,most studies have studied the effect of reaction conditions on the product by experimental methods,for the reaction mechanism and the kinetic study,there are only the calculation of the apparent kinetic parameters,or in the inert atmosphere to establish a chemical reaction model,for the oxygen involved in the pyrolysis and combustion process research is not complete.Therefore,in order to reflect the effect of oxygen on combustion,it is necessary to establish a combustion kinetic model related to oxygen concentration.In this paper,the four kinds of biomass pyrolysis and combustion were systematically studied and simulated.The TG-FTIR experiment was carried out at different heating rate and oxygen concentration.The effect of heating rate and oxygen concentration on the combustion process was analyzed.A two-step reaction was proposed based on the thermogravimetric experiment.The multi-component biomass combustion kinetics model and the lattice Boltzmann method were used to simulate the heat and mass transfer in the combustion of biomass particles.Firstly,TG-FTIR experiment was used to study the effect of heating rate and oxygen concentration on the combustion.The results showed that the pyrolysis of biomass was a complicated process.First,moisture is precipitated at low temperatures,then a series of depolymerization reaction,to produce small molecular gas components and some organic molecules,as temperature continues to rise,the macromolecules degrade to produce CO and other gases.Heating rate has contributed to the rate of reaction but has no effect on the gas phase composition and apparent activation energy,the effect of oxygen concentration on the activation energy is the trend of decreasing first and then increasing,and the increase of oxygen concentration reduces the amount of reducing gas in the volatile matter.Secondly,a two-step reaction model of multi-component biomass combustion was established and the kinetic simulation of biomass combustion was carried out.The kinetic parameters were fitted and simulated,the simulation results are about 2%of the mass residuals compared to the experimental results.The results showed that the activation energy of cellulose is 89.44?110.7 kJ/mol,hemicellulose is 52.21?59.90kJ/mol,lignin is 34.14?38.85 kJ/mol,the coke is 11.45-24.05 kJ/mol,the mass change of each component and the generation of coke are also simulated.Finally,the lattice Boltzmann method was used to simulate the heat and mass transfer process in the pyrolysis of biomass particles,the changes of temperature and the effect of the particle size on the heat transfer process were studied.The results were compared with those calculated by the difference method in the literature,and the consistency was obtained.The change of porosity and the effect of Dumcole number on the porosity were studied.It is also proved that the lattice Boltzmann method can be used to simulate the combustion of biomass particles.