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粒子谱演变过程的数值模拟应用于粉体材料的制备过程,对于认识粒子的生成规律、优化生产条件、辅助设计制备设备具有一定的帮助作用。本文在分析制备过程特点的基础上,建立了粒子形成过程的控制方程,并利用Fluent软件对流体流动的控制方程、粒子谱演变方程及粒子的体积浓度方程构成的方程组进行了求解。模拟结果表明,氧化铋粒子的成核与凝并过程都发生在很短的时间内,较小的空间范围内,因此,所得粒子的大小受流体下游冷却系统的影响较小。在这个制备系统中,氧化铋粒子的数值浓度较低,易生成粒度较小的粒子。在反应舟区流体的径向速度较大,在炉子出口处,热迁移速度较大,氧化铋有可能在这2个地方向反应器壁沉积,造成产品产率降低。数值模拟不同制备温度下氧化铋粒度大小与实验结果基本一致。
The numerical simulation of particle spectrum evolution is applied to the preparation of powder materials, which is helpful to understand the rules of particle generation, optimize the production conditions and assist in the design and preparation of equipment. Based on the analysis of the characteristics of the preparation process, this paper established the governing equation of the particle formation process, and solved the equations of fluid flow control equation, particle spectrum evolution equation and particle volume concentration equation using Fluent software. The simulation results show that the nucleation and condensation of bismuth oxide particles occur in a short time and a small space, so the size of the resulting particles is less affected by the cooling system downstream of the fluid. In this preparation system, the bismuth oxide particles have low numerical concentration and tend to produce particles with smaller particle size. The radial velocity of the fluid in the reaction boat is larger. At the exit of the furnace, the heat transfer rate is relatively high, and the bismuth oxide may deposit on the reactor wall in the two places, resulting in the decrease of the product yield. The particle size of bismuth oxide at different preparation temperature is in good agreement with the experimental results.