Simulation And Study Of Fly-ash Deposition Characteristics In Shell Gasifier

Recently,Shell entrained-flow coal gasification processes are used widely because of its strong adaptability,high mole fraction of CO and H2 in the product,and low energy consumption.However,a small amount of ash is easily entrained and adhered to the surface of the heat exchanger.It will reduce the heat transfer efficiency of the syngas cooler or shut down the process due to the blockage of gas pipelines.It is of great significance to investigate on how to reduce fly-ash entrainment to solve the above problems.For this purpose,the following work is carried out:The improved model for the Shell gasifier is provided by considering the capture/reflection of fly-ash particles on the gasification furnace wall.The capture/reflection of particles is treated as boundary condition and integrated in the improved model by User Defined Function(UDF).The model is validated by comparing the simulation results with the industrial data.In addition,the influence of the swirl intensity of the flow field in the gasifier on the motion trajectory and capture of the fly-ash particles is analyzed.Furthermore,the relationship between the structure and installation parameters of the nozzle and the swirl intensity of the flow field is investigated.Then a dimensionless number Rn/Rw for judgement the swirl intensity is summarized on the basis of the simulation results.Finally,the effect of other factors(including angle of upper end closure,operating pressure,flowrate of coal and gas-coal ratio)on fly-ash deposition is considered by the simulation results.The results show that the operating pressure and flowrate of coal is positively correlated with swirl intensity and fly-ash particle capture ratio,while the gas-coal ratio is opposite.In particular,the fly-ash capture ratio increases as the angle of upper end closure decreases to 115°.