| Phosphogypsum is a solid waste from process of wet phosphoric acid, which is mainly disposed with air storage. It not only occupy lots of land but also cause environmental pollution. Producing sulfuric acid and cement from phosphogypsum is an important path for its comprehensive utilization. The cyclone preheater kiln is an important gas-solid reaction unit. The function of cyclone is gas-solid separation,as well as improve the efficiency of gas-solid heat transfer and phosphogypsum decomposition rate.Then, it can collect the preheated materials and send them to the next process. So cyclone is required to transfer heat quickly, uniformly dispersed and high separation efficiency of gas-solid dispersion. By the impact of complex three-dimensional swirling turbulent flow field in cyclone, the motion characteristics of phosphogypsum in it are complex. Due to the unreasonable ratio of raw materials, system leakage, separator’s uncertain three-dimensional internal flow and other factors, cyclone congestion and other problems are likely to be caused during the actual production process. This paper uses ECT(Electrical Capacitance Tomography) to study the fluidized behavior and analyze the concentration distribution of phosphogypsum in the cyclone. Then the regression analysis is adopted to fitting the radial concentration distribution data of phosphogypsum which can provide conditions to improve cyclone structure, separation efficiency and optimize size of cyclone.Firstly, according to the on-line distribution image of two sections of the phosphogypsum under different conditions by the ECT, we found that it show high concentration on the side wall and low concentration in the middle of section. Due to the asymmetry of cyclone’s entrance, concentration distribution of phosphogypsum also showed asymmetry in section 1. Secondly, the mean concentrations over a period of time and the radial concentration distribution graph of phosphogypsum in two sections can be got by the data analysis. Along the radial direction, the concentration distribution of phosphogypsum particles has the same trend. The change of concentration is very small in the r/R<0.6. When r/R>0.6, the concentration began to change quickly. With the increase of the radius, the concentration quickly increased to the maximum value near wall. The concentration of center become dilute but dense near wall. When the wind velocity is constant, the average phosphogypsum in the section of cyclone is becoming gradually increased as the solid-gas ratio increased. When the solid-gas ratio is constant, the average phosphogypsum in the section of cyclone is becoming gradually decreased as the wind velocity increased. In the axis direction, the mean concentrations over a period of time and the radial average concentration of phosphogypsum particles of section 1are both higher than section 2. The axial particle concentration exhibits decreasing trend from section 1 to section 2. Solid-gas ratio only affects the value of phosphogypsum concentration in cyclone within a certain range without much influence on its distribution trend. But the separation efficiency will be increased with the solid-gas ratio increased. However, when solid-gas ratio increased to a certain value, the separation efficiency becoming decreased.The optimized performance of separator can be obtained when the solid-gas ratio is 2kg/m3 ~ 3kg/m3.According to the concentration distribution of phosphogypsum particles on section 1 and section 2 and the collected data, the images and results have been discussed via polynomial fitting method in MATLAB software. So we get two enpirical correlations of two cross sections’ concentration distribution whose correlation reachs 99% with actual experimental data. These can provide references to improve cyclone structure, separation efficiency and optimize size of cyclone. |
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