Two-phase Flow CFD Simulations Of An Absorption Tower For Coke-oven Gas Desulfurization

In hydraulic engineering, thermal energy, and other engineering disciplines, multiphase flow is a very important phenomenon. So does in some unit operations of chemical engineering, such as reaction, absorption and so forth. Some simple flow conditions can be predicted by current empirical or semi-empirical relevant formulations, but most chemical processes cannot be, since these formulations can not show the overall flowage.This paper used a commercial code FLUENT to combine the Computational Fluid Dynamics (CFD) and the two-phase flow, in order to predict the complex flowage condition of two-phase flow in absorption tower.First, the 3-D geometric model of the desulfurizing tower constructed as an entire model to simulate single-phase and two-phase flow. Based on the convergent result of single-phase flow without packing, Euler multi-phase model and porous medium model were added to simulate single-phase flow with packing bed and two-phase flow. According to some problems showed by the flow conditions above, the structure of the riser in the upper layer and the gas-inlet in the lower layer were reformed and improved.Considering the recommendations about optimizing in former chapter, this paper divided the entire tower into two sections, namely the upper tower and the lower one, to re-establish model, and calculated the single-phase flow of semi-upper-tower without packing at four levels of the grid division scale. According to turbulence intensity, turbulence dissipation rate and other flow parameters of the former results, the grid size was determined to balance efficiency and accuracy, then the single-phase flow (no packing and with packing) and two-phase flow were calculated, too. The results show that, the division of whole tower effectively eliminated the interference between each other, and remarkably improved computation efficiency. Based on the results, the gas velocities in upper-tower were estimated, and the results show that, when the gas velocity was higher than the flooding point, the turbulence would be too strong and go against the mixing and mass transfer between two phases.There is no experimental data available to compare with the calculation of this target, so the last part of this paper validated the grid independence through comparing the single-phase and two-phase flow under two levels of grid division of lower tower with different number (268,000 and 259,000 in semi-tower). The forecast results show that, the grid determined in Chapter 5 has a good independence, so it met the accuracy requirement for calculating multi-phase flow, and there's no need to refine the mesh.