Simulation Of The Residence Time Distribution In KYF-0.2 Flotation Cell

In flotation process, the performance of flotation cells have great influence on the flotation index and efficiency, while the residence time distribution (RTD) is one of the most significant show of the flotation performance. But the mutiphase flow of solid-luqiud-gas in the flotation cell is too complex that it is very hard to get a true solution of RTD with mathematical calculation. And data getting by experiment is often uncomprehensive and will cost a lot of money and time. This article uses the basic mutiphase flow theory and computational fluid dynamics (CFD) to make a simulation of the residence time distribution in KYF-0.2 flotation cell. It also analysis the effect of the operating parameters, such as impeller speed, pulp density, mass flow and some others, on RTD and the form of short circuit and dead zone in flotation cells. The main research contents are as follows:1) Simplify the real physical process and make realistic assumption, build the flow model in KYF-0.2 flotation cell with Euler-Euler multifluid model, k-ε turbulence model, Wen Yu drag model and some other parameters;2) Make simulations of single-phase flow and solid-luqid flow in flotation cell and get the residence time distribution. Analyze and study the flow discipline of solid phase and liquid phase in the flotation machine;3) Buidl a mathmatic model to fit the RTD curve and make reasonable analysis and explnnation of the possible existing short circuit and dead zone;4) Study the effect of impeller speed on the residence time distribution.The result shows that in single phase flow, the increase of impeller speed will not increase the residence time obviously, as there is already a complete flow field with a impeller speed of 200rpm. But in two phase flow, it will increase the the average residence time from 102s to 164s, and the short circuit and dead zone improve significantly;5) Study the effect of mass flow on the residence time distribution. The result shows that when the mass flow fall by half, the average residence time in fall from 0.89 to 0.85 which may beacause of a newly formed dead zone in the upper circulation. But in two phase, the average residence time of solid increase from 0.64 to 0.78 with a better dead zone and short circuit;6) Study the effect of pulp density and particle size on the residence time distribution. The result shows that, when the pulp density increase from 12% to 18%, the average residence time fall from 164s to 153s, and when the particle size increase from 0.074mm to 0.15mm, the average residence fall seriouly from 164s to 118s with a large mount of dead zone.7) Make simulations of solid-luqid-gas flow in flotation cell and get the residence time distribution of gas. The result shows that most of the bubbles have similar residence time which is about 2s。And the existence ofbubbls make some effect on the RTD of solid, while the Simulation shows it reduce the mean time which is not so conform to Reality. The reason may be such as the not perfect Flotation cell model, the reduction of rotor shaft power caused by high gas holdup, or the simulation timescale. The real reason still need to be discussed and tested by experiment.