Phosphogypsum Carbon Thermal Decomposition Of Performance And Technology Research

The mainly composition of Phosphogypsum is CaSO4·2H2O,and Phosphogypsum is the solid waste of wet phosphoric acid production process,also contain many harmful impurities heating to human health and biological growth,such as calcium fluoride, acid insoluble matter, Fe-Al compounds, organic matter and so on.The mainly treatment of phosphogypsum is piled on the ground or discharged into the sea.the stock of phosphogypsum in the world has as many as 1 billion tons,but less than 15 percent of phosphogypsum has been utilized,which has caused serious pollution to errestrial and marine and human existence environment. At present, the resourcelization of phosphogypsum is one of the most popular studies in he world,and also it is one of the difficulty issues to many experts.At first, phosphogypsum decomposed at high temperature with different parameters, and the decomposition of phosphogypsum under various conditions have been studied in this paper.Then, different kinds of the raw meal are prepared with phosphogypsum as the main raw material,after the raw meal calcinated at the high temperature, analyze the chemical properties of the products,and discuss the feasibility of preparing cement clinker with phosphogypsum in this paper.In this paper, samples of phosphogypsum are heated in the resistance furnace, microwave and static reduction furnace respectively firstly,then the decomposition properties of phosphogypsum are studied under the the three parameters:heating temperature, decomposition time and the amount of coal mixed.Through the difference of SO3 content in the samples before and after decomposition, thermal gravimetric and XRD analysis of the samples, the following conclusions are concluded:The three different kinds of heating way show:phosphogypsum samples heated in the resistance furnace is high energy consumption;the Microwave is low energy consumption, short time, and high decomposition efficiency, but the output is smaller; Static reduction furnace can maximize the decomposition rate of phosphogypsum in a relatively short time, and the waste heat can be further used for power generation or other purposes.The decomposition temperature of Phosphogypsum is high. CaSO4 in the phosphogypsum starts to decompose at 900℃, when the temperature is between 1100-1200℃, the decomposition rate is the greatest, in order to make the phosphogypsum decomposed completely the temperature must reaches 1300℃above. The deoxidation the atmosphere can improve the decomposition efficiency, phosphogypsum decomposed in a shorter time and more completely by adding carbon material. In this study,coal is doped to providing deoxidation atmosphere for phosphogypsum decomposing, when the rate of coal is 20-25%, the decomposition rate is the maximum. Phosphogypsum as the main raw materials is used to prepare cement clinker in this paper. Different raw meals are calcined in muffle furnace and static reduction furnace respectively, whether the raw meal is calcined in a good condition can measured by the f-CaO and SO3 contented in the clinker.The experimental results show that phosphogypsum can be used to prepare cement clinker, the reaction atmosphere and raw meal components are the key factors of the progress.Appropriate amount of Carbon can improve the decomposition efficiency of phosphogypsum, and also promote the formation of clinker minerals. The raw meal components have a greate impact on the decomposition of phosphogypsum.The raw meal can be calcined into clinker in a shorter time in static reduction furnace, and the quantity of f-CaO and SO3 is lower, no adhesive basically, particle clear,and the clinker colour near the cement clinker that prepared from limestone. The XRD test show that there are still a large number of CaSO4 in the clinker becaue the temperature is below 1300℃in the muffle furnace, and basically there is little of clinker mineral. while the raw meal calcined in the the static reduction furnace, the products contains large amounts of clinker minerals in the transition phase, XRD also showed the presence of clinker minerals. Because phosphogypsum contains a lot of SiO2 and a small amount of other impurities, the reaction is complex during the decomposition process,and reduce the melting point of materials,which make clinker minerals difficult to generate. Temperature and atmosphere control are of great important, appropriate atmosphere and temperature will be able to avoid the phenomenon of bonding and ring formation.