Simulation On Air-Liquid Flow In The Seed Precipitation Process Of Alumina Prodionuct

The seeded precipitation is a complex crystallization and mass transfer process and is one of the key steps in the Bayer process for the production of alumina. It has great influence on alumina product's outputs and quality and also has indirect effect on other procedures. Owing to the difference of the bauxite with foreign one, China has its own precipitation process. The study of the mechanics and dynamics of the precipitation with Chinese character is significant.In this paper, multi-fluid model of multi-phase flow in the seed precipitation process was built based on the detailed study of the precipitation process, equipment and theories for multi-phase fluid dynamics, computational fluid dynamics and transmission. The numerical simulation system of multi-phase flow in the precipitation process was developed based on the commercial software CFX4.3. The air-liquid two-phase flow of the seed precipitation process in two air-agitated tanks with different structures was numerical simulated in three dimensions. The results showed that the flow field had a direct effect on the solution mixing and sediment in air-agitated tanks, and the flow field in the tank using horn riser tube was better than that of in the tank using straight riser tube since the solution circulation was increased by using horn tube and disturbance was enhanced by lifting the secondary windpipe.Scalar transport model in the precipitation process was built and coupled with multi-fluid model, the numerical simulation program of solution diffusion and precipitation time was developed in this paper. The results illustrated that there was obviously short-circuiting in the tank using straight riser tube, and precipitation time is less comparing with the tank using horn tube.Experimental apparatus for water model was design and the solution diffusion and precipitation time experiments were carried out in it. Experimental data showed that there was short-circuiting in the tank without baffle plate. And the experiment results agreed well with simulation situation, which proved that the numerical simulation program was credible.