CFD-PBM Simulation Of Bubble Column Reactors

Bubble column reactor is a gas-liquid-solid reaction equipment,which is of simple structure,good heat and mass transfer performance.It is widely applied in the Fischer-Tropsch synthesis,residue hydrodesulfurization and other industrial processes.Computational fluid dynamics(CFD)simulation is an important method of fluid equipment design.We can not only get the whole flow field information comprehensively,but also greatly reduce the time and labor costs.In this paper,the CFD-PBM method for gas-liquid-solid bubble column is used.The bubble-induced turbulence(BIT),corrector of coalescence rate,drag models,coalescence and breakage models are the topics we studied.The results show that the coalescence and breakage rates can increase when considering bubble-induced turbulence,but breakage rate increases much more.As a result,bubble size decreases finally.The drag model mainly affects the distribution of gas holdup,while it has little influence on the bubble size distribution(BSD).Reasonable drag model combined with coalescence and breakage models can improve the simulation results of gas holdup near the wall.The selection of the critical Weber number in Lehr breakage model greatly influences the simulation.Concave parabolic daughter PDF can give a better simulation results.The results of Laakkonen breakage model are similar to that of Luo & Svendsen.Its calculation cost is low because of a simple expression for the daughter PDF.The liquid-solid drag model is an important factor for prediction of solid holdup.It is difficult to obtain the reasonable results of BSD and gas holdup when only changing the physical properties of slurry.Finally,we develop the LBM simulation for different reactor geometries,e.g.,porous distributor,cylindrical bubble column and loop reactor.