Evaluation Of DQMOM For The Micro Fluidized Bed Simulation With Nanoparticles

Fluidized bed has good heat and mass transfer characteristics,so it has been widely used in many fields.With the vigorous development of fluidization technology,the inner diameter of fluidized bed and the diameter of bed material particles are decreasing.The performance of micro fluidized bed is better than that of ordinary fluidized bed in many aspects,so it has good operability for some special research.Because of their unique properties,researchers have paid more and more attention to nanoparticles.So studying the flow characteristics of nanoparticles in the micro fluidized bed has great practical significance.Because the traditional simulation method can not track the change of particle size caused by the agglomeration of nanoparticles during fluidization,based on Euler-Euler multi-fluid model,combined with the quantity balance equation,this paper applies the direct moment integration method to solve it.Because the traditional drag force model is not suitable for calculating the flow of nanoparticles,the drag force calculation part is modified in this paper.Based on the established mathematical model,the flow of nanoparticles in the micro fluidized bed is simulated.Compared the data with experiment,the accuracy of the model is verified.The mathematical model established in this paper is used to simulate the single-component nanoparticles.The results show that the change trend of time-average concentration of different kinds of nanoparticles is roughly the same,with the main particle size distribution range of 0?5?m and mainly concentrated in 1?1.5?m.The aggregate time-average diameter decreases with the increase of bed height,and it decreases greatly at the lower bed.The increase of initial gas velocity will reduce the time for particles to reach stable fluidization;the larger the coalescence coefficient,the larger the particle size of the agglomerates.The larger the particle density,the smaller the particle size,and the more significant the concentration change.The change of the particle concentration in the bed is proportional to the particle density.The mixed nano-particles of SiO₂ and ZnO were simulated,and the ability of adding large particles to improve fluidization effect is explored.The results show that more particles with better fluidization performance can improve the fluidization performance of mixed particles.When the content of Si O₂ particles is high,the effect of improving fluidization performance with small particle size is better.When the content of Zn O particles is high,the effect of high-density particles is better.When the content of particles with good fluidization performance is high,adding a small amount of large particles can effectively improve the fluidization performance of mixed particles.