Experimental Study And Numerical Simulation Of Gas-Liquid Distributors Used In Upward Slightly Expanded Bed Reactor

The slightly expanded bed reactor is a new one used in residue hydrotreating, feedstock upflow through the gas-liquid distributor then the catalytic layer which is slightly expanded. Gas-liquid maldistribution can induce the coke, hot point, temperature runway, so it’s significant to improve the design and optimization of gas-liquid distributors used in upward reactor.In this paper, it mainly used CFD numerical simulation and experimental validation to design and study two kinds of gas-liquid distributors used in upward slightly expanded reactor. Firstly we simulated the gas-liquid distribution characteristics of single tube scale used in upward gas-liquid distributors using VOF model, including the hydrodynamic characteristic, flow pattern, gas bubble distribution, gas bubble rising velocity and pressure drop, compared the characteristics of two kinds of distributors with the changing of gas-liquid superficial velocity. Then using Euler model and porous media model to simulate the gas-liquid-solid three phases hydrodynamics in reactor bed scale, including the gas holdup, gas velocity and the pressure drop etc, compared the accuracy and applicability of this two kinds of CFD models. Mealtime we also constructed the experimental setup to determine the gas velocity of gas-liquid distributor, expansion ratio and pressure drop, in case of validation with the CFD simulation results. The main conclusions are as follows.1、We studied the axial and radial gas velocity change of gas-liquid distributor. With the axial rising, the gas velocity decreasing; in the radial direction, when H=0.01m, the gas velocity is distribution, while H=0.10m、H=0.20m and H=0.28m, the gas velocity became decreasing while the radial increased. It shows that the gas-liquid distributor can improve the flow initial distribution.2、The VOF model can simulate the gas-liquid interface and gas-liquid distributors dynamic flow characteristics, this model can guide the design of distributors.3、On the single tube scale of gas-lqiuid distributors, With increasing gas and liquid superficial velocities, the gas bubble rising velocity increases; with an increase in gas superficial velocity or decrease in liquid superficial velocity, the gas bubble size and average gas holdup increase; the pressure drop increases with increased liquid superficial velocity or decreased gas superficial velocity.4、Compared with the change of liquid velocity, the gas-liquid distributor is more sensitive to the change of gas superficial velocity.5、Compared with the operating load and gas distribution of these two kinds of gas-liquid distributors, the distributor II with rain cap is more stabilization.6、Compared about the accuracy and precision of Euler model and porous media model and validation with the experimental study, the Euler model is more accurate when using the appropriate drag models.