CGM Simulation And Experimental Study On Reaction Kinetics Of Catalytic Biomass Gasification In Fluidized Bed

Due to the shortage and high pollution rate of fossil energy,biomass is an ideal alternative energy source because of its clean and sustainable development properties.Fluidized bed reactors are widely used in biomass gasification due to their excellent performance along with their high and stable conversion efficiency and feedstock flexibility.However,experimental measurements of fluidized bed gasification do possess certain limitations due to harsh operational conditions,high cost,as well as limited optical access.Meanwhile,CFD?Computational Fluid Dynamics?simulations can be used to reveal the details of hydrodynamic behavior and distribution of solid and gaseous species inside a fluidized bed which could not be obtained from experimental measurement.A comprehensive coarse grain model?CGM?is applied to the simulation of biomass steam gasification in bubbling fluidized bed reactor.The influence of modified red mud extract and Fe?NO₃? solution on gas releasing kinetics during sawdust pyrolysis and in-situ coke gasification were investigated in a micro-fluidized bed dynamic analysis system.Additionally,reactions kinetics were deduced based on a universal integral method.Then,the CGM and reactions kinetics of catalytic gasification were evaluated.The main research contents are reflected in the following section1.CFD-CGM is used to simulate biomass steam gasification in a bubbling fluidized bed.The CGM was evaluated through comparing the hydrodynamic behavior and heat transfer prediction with the results observed from the discrete element method?DEM?and experimental data.The CGM is also applied to study the effects of different operating temperatures and steam/biomass?S/B?ratios on the gasification process and product gas composition.The predicted concentration of different product gases aligns well with the experimental data.2.The influence of modified red mud extract and Fe?NO₃? solution on gas releasing kinetics during sawdust pyrolysis and in-situ coke gasification were investigated in a micro-fluidized bed dynamic analysis system.Reactions kinetics were deduced based on a universal integral method.Then,a comprehensive catalytic gasification kinetics model was established.The results indicated that the apparent activation energies of catalytic pyrolysis and in-situ coke gasification decreased in the presence of two kind of catalysts.3.The CFD-CGM model and catalyst gasification kinetic model established in this work were used to simulate gas releasing kinetics during sawdust pyrolysis and in-situ coke gasification in the micro-fluidized bed dynamic analysis system.Compared with experimental data,the relative error did not exceed 9%.The catalyst gasification kinetic model established in this work was show provide reliable predictions.4.The CFD-CGM model was used to simulate the catalyst steam gasification in the fluidized bed which was fed continuously.The effects of the catalysts on gasification in different operating temperatures and steam/biomass?S/B?ratios were then investigated.The results indicate that with the effect of the catalysts,the contents of H₂ and CO increased,CO₂ decreased,CH₄ is insensitive to catalysts.Because of the combine action of Fe and other element?Al?Ca?Na?in modified red mud extract,its catalytic effect is better than compared with the Fe?NO₃? solution.5.The CFD-CGM model and the gasification kinetic model from literatures were used in fluidized bed biomass gasification with CaO sorption.The reliability of the model was firstly evaluated in the simulation of the CO₂ capture process.Then,the catalytic biomass gasification process in different temperatures and equivalence ratios were numerically investigated.The results reflected that CaO sorption enhanced the production of H₂,CO is inhibited,and that CH₄ is insensitive to catalysts.