Analysis Of Multi-Component Particle Flow Characteristics Based On Direct Quadrature Method Of Moments

Gas-solid fluidized bed has high combustion efficiency and heat and mass transfer.It is widely used in the chemical,petroleum,drying,and pharmaceutical industries due to its simple structure and ease of control.With the development of research on particle flow characteristics,the type of particles in the fluidized bed gradually transits from Geldart B particles to Geldart C particles and nanoparticles.Some studies have shown that a certain amount of auxiliary particles were added to Geldart C particles and nanoparticles,which could effectively improve the particle fluidization effect.Therefore,It is important for industrial production to study the flow characteristics of multi-component particles after adding auxiliary particles.In this paper,based on the Euler-Euler method and particle kinetic theory,the effect of viscous force on the parameters of particle fluidization process is considered.The viscous particle drag model is applied to the multi-component particle fluidization process,and the drag coefficient is modified for nanoparticles.The microscopic changes of aggregation and breakage of viscous particles under the interaction of gasparticle phase and particle-particle phase is considered.In order to intuitively describe the changes of particle number and aggregation diameter in the simulation process,direct quadrature method of moments is used to realize the coupling of Euler-Euler method and population balance equation,in order to accurately predict the changes of flow parameters in the fluidization process of multi-component particles and obtain the relevant distribution law.Based the mathematical model established in this paper,the flow characteristics of multi-component particles after adding auxiliary particles in Geldart C particles are studied.The simulated results and the experimental findings agree fairly well.The variation rules of bed pressure drop,bed expansion ratio,particle aggregation diameter,particle aggregation concentration,moments,granular temperature and other parameters under different ratios were obtained.Particle concentration contour and velocity vector contour at different times were also obtained,and the instantaneous time cloud map and the variation rules of various parameters were analyzed and summarized.The results show that the fluidization characteristics of Geldart C particles can be significantly improved by adding auxiliary particles.The bed pressure drop and bed expansion ratio are increased,which the contact area between gas and particles is increased,and the non-uniform distribution the bed particle is reduced.When the auxiliary particles with a mass fraction of 13.04 % are added,the value of moment and the granular temperature increase.The concentration distribution of particle aggregation in the bed is relatively uniform.Based on the model established in this paper,the flow characteristics of multicomponent particles after adding auxiliary particles into nanoparticles are studied,and the simulation results are in good agreement with the experimental results.The improvement of fluidization characteristics of nanoparticles by different mass fractions of auxiliary particles was simulated,and the variation rules of bed pressure drop,bed expansion height,particle agglomeration diameter,particle moment and other parameters were obtained.The results show that adding different mass fractions of auxiliary particles can significantly improve the agglomeration phenomenon of nanoparticles and reduce the agglomeration diameter in the bed.With the mass percentage of auxiliary particles increases,the decreasing range of particle agglomeration diameter steadily shrinks.