Numerical Simulation And Structure Optimization Of Quench Box For Fixed-bed Hydroprocessing Reactor

Nowadays,the world's crude oil is increasingly heavier and worse in quality.The improvement of the hydroprocessing technology is extremely important in the refining industry,as a result of the increased demand for light fuel oil and stricter environmental regulations.The hydrogenation reaction is an exothermic reaction,causing a temperature rise across the reactor.The control of the temperature rise in the reactor directly affects the performance of the catalyst and the quality of the product.Fixed-bed reactors with various catalyst beds are frequently employed in industrial hydroprocessing.The quench box is positioned in the interbed space in the reactor to control and adjust the temperature rise.Accordingly,the development and design of the quench box are particularly important.Hence,the quench box is studied in this paper and the main contents are as follows.Based on quench box cold model experimental research in the literature.A numerical simulation studied on the quench box is carried out applying Euler-Euler multiphase flow model and the RNG k-? turbulence model,with the Computational Fluid Dynamics software ANSYS Fluent.The results show that the simulation results are in good agreement with the experimental results in the literature.Hence,the accuracy of the mathematic model for quench box are verified.In this paper,the UOC type quench box is simulated and optimized.The basic configuration of the UOC type quench box is simulated by using k-? two-equation model to analyse the distribution of internal flow field,pressure,concentration and temperature,in order to research performance of the basic structure.Afterwards,the main structural parameters are optimized,including the space of the contraction channel and sieve baffle,the length of sieve baffle and the height of built-in baffles.The performance of different structure quench box is investigated based on pressure drop and temperature nonuniformity.The simulation results show that,compared with the basic configuration,the temperature nonuniformity and pressure drop of improved configuration decrease by 36.78% and 21 Pa respectively.This study also simulate and optimize the UFQ type quench box.Firstly,the basic structure size of the UFQ quench box is determined by combining the Froude number and the mechanical energy balance of the UFQ quench box.Then it is similarly simulated by using k-? two-equation model to analyse the distribution of internal flow field,pressure,concentration and temperature.Afterwards,the main structural parameters are optimized,containing the number and angle of swirling vanes,the number and angle of nozzle,the height of mixing box and the height of redistribution plate.The performance of different structure quench box is investigated by pressure drop and temperature nonuniformity.The simulation results show that,compared with the basic configuration,the temperature nonuniformity is decreased by 59.81% and the pressure drop is reduced by 18 Pa.