Numerical Simulation Of Hydrocracking Trickle-bed Reactor

Trickle-bed reactor was one of the most widely used three-phase fixed-bed reactor, especially in the area of petroleum refinery and petrochemical engineering, such as the hydro-desulfurization, hydrocracking and hydrotreating process of petroleum fraction,lube oil hydrotreating process,α-styrene hydrogenization, etc. Most of the recent research about trickle-bed reactor focused on the hydrodynamic in such kind of reactors, including the flow and mixing of gas-liquid two phase flow in catalyst bed, efficiently wetting of catalysts, the mass transfer of gas-liquid and liquid-solid. Some mathematical models were proposed to describe the behavior in trickle bed. In this paper, the method of computational fluid dynamics (CFD) and the computational software FLUENT was used to simulate the flow behavior in a bench scale hydrocracking trickle-bed reactor. The simulating results were validated through comparing with the results reported on correlative literature and experiment data. Good agreement between numerical simulation results and published work illuminated the effectiveness of the model.The selection of the gas-liquid-solid momentum interaction model, the effects that the partition of mesh and the porosity in catalyst bed made to the flow field information were mainly investigated in this paper. Three-dimension simulation was preformed. The fluid -fluid interfacial force model gave most accurate simulation result in all investigated models. Because the influence of pressure on the gas-liquid drag force was taken into consideration in this model, the simulating resul??itted well with the literature publication; Both of the accurate results and the calculating efficiency were considered to establish the sound partition of mesh; Since the ratio of the reactor diameter to the particle size(D/dP) was larger than 18, it's advisable that the bed porosity was set as a constant 0.384.So the model for fluid flow was set up.Based on the fluid flowing model, the hydrocracking reaction kinetics model and experiment data from literature were used to simulate the hydro cracking reaction, the reaction kinetics model was programmed with Runge-Kutta method as user defined function (UDF) to calculate in species equation. The simulating results were compared with the experimental data, the results show that there were errors between the experimental and simulating data for the reaction conversion and products yield, but it's reasonable for it was caused by the inbeing of reaction kinetics model. By analyzing the results synthetically, the method and model setting we used were sound, thus it can supply the method for complicated reaction research.Considering of the simulating results above, the whole simulation frame for fluid flow and reaction calculating in the trickle-bed reactor was set up successfully. It may guide the research for the design of trickle-bed reactor of hydrocracking and the study of the reaction result.