Numerical Simulation And Experimental Study Of Solid-liquid Two-phase Flow In Horizontal Biaxial Stirred Tank

The horizontal biaxial stirred tank for mixing high viscosity fluid is widely used inpetroleum, chemical, rubber and pharmaceutical industry, especially inpolymerization productions and distillation of the raffinate. However, the design andindustrial application of the equipment mainly depends on experience now, withoutsystematic theory guidance. The performance of mixing is also difficult to predict.There it is very necessary to research the hydrodynamic characteristics of the novelstirrer.In this paper, the3D model of the horizontal biaxial stirred tank was established.The solid-liquid two phase flow was simulated with unstructured mesh, Eulerianmultiphase flow model, Realizable k-ε turbulence model, dynamic mesh method andtransient simulation technology. The details of pressure distribution, velocitydistribution, turbulent kinetic energy distribution and power consumption werepredicted to explore the influences of operating condition and stirring medium.The results show that there are gradients of pressure, velocity and turbulent kineticenergy in the horizontal biaxial stirred tank. And they are affected strongly by theimpeller rotating speed and fluid viscosity. The higher the rotating speed, the greaterthe fluid viscosity, the velocity distribution and turbulent kinetic energy distributionare more homogeneous. The addition of solid particle makes the velocity andturbulence kinetic energy reduced and the attenuation amplitude increases with theparticle concentration. When the volume fraction of solid are2.5%,5%and10%, theliquid velocity decreases by10%,15%and17.5%compared with single liquid phaseflow. The turbulent kinetic energy is also reduced by8.3%,11.1%and19.4%. Theeffects of various diameter particles on the liquid velocity are different while they arethe same on the turbulent kinetic energy. The liquid velocity is reduced by15%whilethe change of the turbulent kinetic energy is within5%, when the particle size, addinginto the high viscosity fluid, ranges from50μm to1000μm. The stirring powerchanges periodically over time, and is proportional to the square of the rotating speed,and increases linearly with the viscosity of stirring medium. The power number (Np)is decreased with the increase of the Reynolds number (Re) in log-log coordinate. Andthere is a linear relationship between Npand Re when Re is less than100.Finally, the mixing time of the stirred tank under different conditions was measured by the tracer method. The law of how the mixing time change is obtained. Thepresence of solid particles increases the liquid mixing time. The mixing time increasesfrom180s to557s after adding particles (the volume fraction is10%). What is more,the smaller the particle size, the longer the mixing time is.