Numerical Simulation And Experimental Study On Distribution Characteristics Of Phosphogypsum In Cyclone

Phosphogypsum is a solid waste produced in the process of wet process phosphoric acid production.It will cause serious environmental pollution and take up a lot of land.The technology of producing acid and producing cement by phosphogypsum is an effective way to make use of phosphogypsum.However,the traditional process is affected by the low heat and mass transfer efficiency and the high energy consumption.Phosphogypsum kiln cyclone preheating and decomposition process for producing sulfuric acid and cement can significantly improve the heat transfer and mass transfer efficiency,thereby significantly reducing the energy consumption of the process.The cyclone is high temperature exhaust using rotary kiln out of phosphogysum by preheating and precalcining,but also bear the task of gas-solid separation.The concentration distribution of phosphogypsum particles in cyclone will directly affect the heat transfer efficiency,and the size and operating conditions of cyclone can affect the concentration distribution and separation efficiency of phosphogypsum particles in cyclone.Therefore,the research on the measuring of phosphogypsum in the concentration distribution in the cyclone in the cold state experiment,numerical simulation is carried out by Fluent software,the optimization of cyclone structure size and operating conditions,and compare with experimental results.First of all,using double layer capacitance tomography system measurement in cold experimental equipment.The online measurement of upper and lower entrance section of cyclone and cone at the junction of phosphogypsum particle concentration distribution in cyclone section.Effects of velocity,solid-gas ratio and outlet diameter on concentration distribution and separation efficiency of phosphogypsum were investigated,the effect of gas-solid contact area and concentration of SO₂ is analyzed.The results show that phosphogypsum particles in the cyclone separator assumes the circular distribution.The particle concentration in the center area and near the wall is low,high separately.The particle concentration in the upper section of the straight tube is larger than that of the lower section.With velocity increasing,the radial particle concentration decreases,andthe separation efficiency increases firstly and then decreases.It's conducive to improving the gas-solid contact area and heat transfer,not conducive to increase of SO₂ concentration in the decomposition of phosphogypsum.The radial particle concentration increased,as well as separation efficiency with solid-gas ratio increasing.It's reducing the gas-solid contact area and unfavorable for heat transfer,but in the decomposition process of phosphogypsum,it's conducive to enhance the SO₂ concentration.When the outlet diameter of the cyclone separator increased,the radial particle concentration decreased and then increased,the separation efficiency increased too.However,with the further increase of the solid-gas ratio,there will be different situation,different solid-gas ratio has diverse suitable outlet diameter.Numerical simulation and optimization of gas-solid two phase flow by using FLUNT to study the concentration distribution of phosphogypsum in cyclone.This research takes of Reynolds stress and the Euler—Euler model to optimize the parameters of the separation efficiency and heat transfer efficiency.The results show that compared with the experimental results,the calculated results agree with experimental results.On the basis of experiment,increasing velocity,it has little effect on the separation efficiency and gas-solid contact area.With the increase of solid-gas ratio,the separation efficiency is obviously increased,the particle concentration increases.Although the gas solid contact area will be reduced,but the decomposition process of phosphogypsum SO₂ concentration will increase The optimization results are as follows: the outlet diameter of cyclone is 50 mm,the velocity is 17 m/s,the solid-gas ratio is 2.25 kg/m³,the separation efficiency is 94.2 %.