Lattice Boltzmann Study On The Effect Of Particle Movements On Mass Transfer Process

The matching of transfer and reaction process is the key to high-efficiency and green conversion in chemical process.In heterogeneous catalytic reactions,the overall rate of reaction is always limited by the mass transfers of reactants diffusion within particle and reactants between the particle’s surface and the bulk fluid.Equipment such as the fluidized bed is usually adopted to enhance the mass transfer rate of catalysts in industries.In essence,it is the movement of particles that enhance the mass transfer rate.Previous experiments mostly focused on the relation between macroscopic states of particles and mass transfer rates,and from which we can’t establish the relation between the particle movement and the mass transfer rate.In this paper,the lattice Boltzmann method coupled with mass transfer is used to investigate mass transfers between a 2D spherical particle with constant surface concentration and external bulk fluid.The effect of particle movement on the mass transfer rate is studied at microscopic level.First,the influence of the rotating particle on the mass transfer rate in the tube with uniform inflow was studied.By investigating the mass transfer process of rotating particle with different rotating speed,Reynolds number,and Schmidt number,it was found that the mass transfer rate decreased slightly with the rotating speed increased and increased with the Reynolds number and Schmidt number increased.The effect of the harmonically vibrating particle under the same conditions on mass transfer was studied secondly.By exploring the mass transfer process of the vibrating particle with different vibration directions,amplitude,frequency,and other factors,it was found that the lock-in effect due to the vibrating particle would increase the mass transfer rate remarkably,but the increment became small without the lock-in effect.The lock-in effect was related to the Reynolds number,amplitude,frequency,and vibration direction.It would occur at a lower frequency when the Reynolds number and amplitude became larger and the particle vibrated transversely.This work established the quantitative relation between particle movements and interphase mass transfer rate and obtained the key factors of mass transfer.The results described the effect of particle movement on mass transfer process from the microscopic aspects and the underlying mechanism of enhancing the mass transfer process,providing a theoretical guidance of strengthening the mass transfer process and eliminating the negative effects of mass transfer on heterogeneous catalytic reactions.