Cold Flow Experiment And Numerical Simulation Of Quadruple Fluidized Bed Gasifier

With high reaction efficiency,wide fuel applicability,and environmentally friendly performance,fluidized bed have become the mainstream of industrial reactors and occupy an important position in industrial production.This paper aims at a new type of quadruple fluidized bed gasifier(QFB)system which amalgamates dual fluidized bed(DFB)gasification and chemical looping air separation technology,and it can achieve high efficient gasification with low carbon emissions.However,only theoretical analyses were done on QFB,so the next step is study the characteristic of gas solid flow and mechanism of coupling in this system.To investigate the characteristics of QFB system,the cold flow experiment method was used.For that purpose,a visualized cold model experimental platform of QFB was built,which contains two DFB subsystems.The influence and mechanism of parameter,such as velocity in bubble fluidized bed(BFB)and fast fluidized bed(FFB)and total solid inventory(TSI),on the pressure profile and solid circulation rate were obtained in the experiment.Then,the DFB experiment was carried out in the platform.By comparing with the results of DFB,the mechanism of coupling in QFB was explored.In addition,the internal pressure equation and the exclusive pressure equation of QFB system are derived according to the pressure relationship within the system.This equation not only reveals the influence between internal subsystems,but also establishes linkages between the solid circulation rate and the external energy supply system.The connection can be used to predict the solid circulation rate and guide the selection of the energy supply system.Besides cold flow experiment,the computation fluid dynamics(CFD)software Ansys Fluent was also used to simulate the QFB experimental process.The theoretical research on the drag problem in fluidized bed simulation is carried out,and the widely used drag model is modified.After that,the simulation results of commonly used drag model(Syamlal-O'Brien,Gidaspow)and modified drag model which imported by UDF(user-defined function)were compared.The simulation results show that the modified drag model is in good agreement with the experimental results,and the ideal “core-annular” flow structure was observed and the solid phase is high in the lower zone while low in the higher zone.Through cold flow experiments and numerical simulation,the hydrodynamic characteristics of the QFB system are obtained in this study,which provides reference for the engineering application of the QFB system.