Modeling And Optimization Of Shell Entrained-flow Pulverized Coal Gasification Processes

Recently,researchers pay more attention in Shell entrained-flow coal gasification processes because of its wide adaptability and high coal conversion.However,there are some problems during operation,such as unexpected shutdown due to the fluctuation of the flowrate in the pulverized coal transport pipe,nozzles burn-out by local overheating,or the blockage of the gas pipeline with the entrained fly-ash in the syngas.It is of great significance to investigate the distribution of key variables in the gasifier to solve the above problems.For this purpose,the following work is carried out:A systematic model of an industrial Shell coal gasification processes is established.The gasification core zone is described with a three-dimensional CFD model and the heat exchange and treatment zone for raw syngas is demonstrated by a mathematical model.The model is verified by comparing the simulation results with the industrial datum.In addition,the simulation results of the gasification core zone are systematically analyzed and the results show that an obvious vortex is formed in the center of the gasifier by collision of the injected feedstock via the nozzles.Because of the intensified gas-solid mixing and heat transfer with the role of the vortex,the position and shape of the vortex has a serious influence on the performance of the gasifier.Furthermore,three kinds of abnormal operating condition are simulated to analyze the difference of the vortex in the gasifier and Case 1(the flowrate of one nozzle is 0,and that of the other nozzles keeps invariant)performs relatively better.The effects of the bias angle of nozzle,the ratio of oxygen with coal,and the ratio of carrier gas with coal on the performance of the gasifier are investigated.According to the simulation results,the optimal bias angle,the oxygen-coal ratio,and the carrier gas-coal ratio are 5.0°,0.9,and 0.35 respectively.Finally,the effect of angle of upper shrinkage on the amount of the entrained fly-ash is considered by the simulation results.For this gasifier,it is beneficial to reduce the amount of entrained fly-ash for the angle as 115.5°.