Phosphogypsum Reduction In The Circulating Fluidized Bed Decomposition Of The Experimental Study And Numerical Simulation

Phosphogypsum is a kind of gypsum that occurs as a by-product and is obtained from phosphate rock during the production of phosphoric acid in fertilizer plants. In view of the problem of phosphogypsum of 30 million tons per year in China, s industry with low utilization and high pile—up. Phosphogypsum causes water and air pollution due to the presence of noxious vapor containing heavy metals, sulphates, fluorosilicates, hydrogen fluorides. Many environmental problems arise throughout the entire chain, one of which is the production of phosphoric acid, which is particularly well-known for the discharge of waste phosphogypsum into surface water and the release of the highly polluting substances. There are various ways to treat phosphogypsums for utilisation in industry. The treatment methods can roughly be divided into three different types, namely, chemical, physical, and thermal methods of treatment. Sometimes a specific process employs a combination of these different approaches to treat the phosphogypsum and convert it into a suitable product for use in industry. This article in view of the current exist major problems in the decomposition of Phosphogypsum to product cement and sulfuric acid techniques, proposed the new technologies of that using high-sulfur coal to replace coke to restore the system decomposition of phosphogypsum to product sulfate and cement in circulating fluidized bed reactor.This dissertation is composed of three main parts:I Study on the reaction condition and influencing factors of phosphogypsum deoxidization and decomposition.In this study, Raise deoxidization and decomposition Phosphogypsum using high sulfur coal on the high temperature. In the experiment with the advance of reaction temperature, the resolution ratio and desulfurization degree of the phosphorus gypsum elevates, the resolution ratio of phosphorus gypsum achieved 97% and reaction time gradually decrease. And in the situation of increasing reducing atmosphere, the reaction time can reduce. Reducing atmosphere stronger, the resolution ratio of phosphorusgypsum higher, otherwise, the desulfurization degree of phosphorusgypsum is lower, we can conclude that the decomposition of phosphorusgypsum is more advantageous under the weak reducible atmosphere.II Circulation fluid bed technical process and parameter computationCarried out a detailed introduction flow of the simulation experiments using circulating fluidized bed plant; calculated the parameters of the Phosphogypsum material particles' critical fluidization velocity and terminal velocity; At the same time, analyzed the gas distributor of test-bed fluidized bed plate, solid circulating rate; introduced the characteristics of fast bed; carried on the handling bed's flow pattern transformation of turbulent bed to fast bed, as well as fast bed to the dense-phase pneumatic conveying bed and carries on the computation to the transformation speed.III Circulating fluidized bed riser cold numerical simulationUtilized large-scale fluid engineering calculation commercial software Fluent to conduct the numerical simulation research to the laboratory bench, before the union use fluid simulation, has processed software gambit to carry on the grid division, used was mad that the solid two phase current Euler model and the standard k-e rapids model, haved overcome formerly as a result of the geometry modelling difficulty and the model selection not, when the question caused the analogue result not ideal limitation. The simulation uses the unsteady state, the separation formula solution, causes with actual compared to close. Explained simulation results of the gas velocity follow bed height distribution of phosphogypsum particle, volume fraction distribution of materials, material particles trace. When the distribution of plate holes gas imports gas velocity increases near the gas distributor plate near the gas velocity has also the increase; With the flow of the wind speed increases Riser material particle volume fraction is relatively decreased; when the gas velocity increases, the phosphogypsum material particles in circulating fluidized bed in the residence time is also relatively reduced; When the gas velocity for 65m/s when the trace has to retract and return, but also between the lines cross and Francis, which is proof of the stochastic fluid flow, complexity and unpredictable nature. Analyzed the results of the stress distribution of bad results, under different flow of wind turbulence kinetic energy dissipation rate to. When the flow of the wind speed increases, the stress along the bed height decreases bad; when the flow of the wind speed decreases, the stress along the bed height increased bad. With the wind speed increases the basic turbulent kinetic energy is decreasing, but also reduced lower turbulent kinetic energy, turbulent kinetic energy increases on paragraph. At the same time, as the wind speed increased turbulent dissipation rate was increased the basic trend, but lower turbulent dissipation rate decreases, the upper turbulent dissipation rate has been increased.