立式搅拌釜中固-液混合特性模拟研究

Simulation of solid⁃liquid mixing characteristics in vertical stirred tank

研究固-液混合特性对生产效率、能耗等指标的优化具有重要意义,实际生产中立式搅拌釜应用较多,本文采用CFD方法和DEM方法从颗粒密度、粒径、搅拌速度和初始液面高度等4个方面对立式搅拌釜的颗粒混合特性进行了数值模拟研究,并且从速度场、湍动能分布和颗粒混合度3个维度来评判颗粒的混合特性。结果表明,在这些影响因素中,颗粒密度和搅拌速度对混合特性的影响最大,特别是当颗粒密度为1200 kg/m3时,相对标准差值达到0.5左右,说明混合程度较好;搅拌速度越大,混合性能越好;颗粒粒径对混合性能的影响较小,但粒径越小,越容易悬浮,粒径增大,混合程度降低;初始液面高度的改变导致固含率的改变,但是对固液混合性能基本不产生影响。

The study of solid⁃liquid mixing characteristics is of great significance to the optimization of production efficiency,energy consumption and other indicators,and the vertical mixing kettle is more often used in actual production.In this paper,we use the CFD method and the DEM method to carry out numerical simulation research on the particle mixing characteristics of the vertical mixing kettle in terms of the particle density,particle size,mixing speed and the initial liquid level height,etc.,and evaluate the particle mixing characteristics in terms of three dimensions,namely the velocity field,turbulent kinetic energy distribution and the degree of mixing of the particles.The mixing characteristics of particles were judged from three dimensions:velocity field,turbulence energy distribution and particle mixing degree.The results show that,among these factors,the particle density and stirring speed have the greatest influence on the mixing characteristics,especially when the particle density is 1200 kg/m3,the relative standard deviation value reaches about 0.5,which indicates that the mixing degree is better;the larger the stirring speed is,the better the mixing performance is;the particle size has less influence on the mixing performance,but the smaller the particle size is,the more easy it is to be suspended,and the increase of the particle size decreases the mixing degree;the change of initial liquid surface height leads to the change of solid content rate,but it has no effect on the solid⁃liquid mixing performance.