| The chemical processing methods of phosphoric acid and phosphorus fertilizer produced by using phosphorus rock can be divided into two big classes: acidulating with inorganic acid and high temperature disposing. In the producing of phosphoric acid and phosphorus fertilizer, the main method is to acidulate phosphorus rock by using sulphuric acid. A great deal of questions exist for a long time while the acid acidulates phosphorus rock, for example: in the production process of the phosphoric acid, the unstable or tiny crystal of calcium sulfate not only make it difficult to filter and wash, but also easily lump in the course of filtering or washing, so that the operating can not be going on normally; While producing the products containing phosphorus, such as calcium superphosphate, heavy calcium superphosphate and carbamide compound fertilizer etc, it will produce highly saturated solution of calcium sulfate in the interface layer between the phosphorus rock particle and the solution, thus lead to produce a large amount of tiny crystals of calcium sulfate. These crystals can deposit on the particle surface of phosphorus rock. The formed solid membrane shall wrap up reactive particles, increase the diffusion obstruction of phosphoric acid to phosphorus rock surface, affect the continual decompose of the phosphorus rock, slow down the speed of resolving of the phosphorus rock, even discontinue the dissolving course. There are many studies about improving calcium sulfate crystallization both at home and abroad, most of which qualitatively describe the impact of the additives and impurities on crystallization. It is rarely researched on the crystallization course and the crystallization kinetics under the function of additives. This subject is put forward on this basis, which study the crystallization mechanism and the crystallization kinetics under the function of additives from two angles of qualitative analysis and quantitative analysis. And it probes into the influences of various kinds of factors on crystallization in order to improve the physical property of the products, choose suitable process conditions and design rational reactor.The course of acidulating phosphorus rock is an extremely complicated reaction course with the crystallization in industrial production. Because of the existence of impurities in the phosphorus rock, there are also other compositions besides calcium sulfate in the crystallization. And different responses have different environments of the crystallization. In order to avoid the influences of these factors and makesystematic study of the calcium sulfate crystallization course, this subject simulates crystallization environment in the industrial production by adopting the raw materials of calcium carbonate, sulphuric acid and phosphoric acid and the improved MSMPR crystallizer. Under the imitating environment, the influences of many factors on crystallization course of calcium sulfate are discussed including crystallization temperature, the average staying time, dissociative sulphuric acid density and active & porous agents(APA), etc. And the macro-dynamics model of the crystallization of dehydrate calcium sulphate is set up by utilizing mathematics method:G = 3.83 X 105 exp(-1126.89/T) Cs1.25 -1.70This thesis has studied the impact of APA on crystallization from two aspects, which are the joining and consumption of APA. Further, the half experience mathematics model of crystallization course is set up at the base of the function of APA.G'= 5.658 .CA0.131.GThe result shows that the impact of APA on crystallization course is most remarkable in four main factors. It can make increase crystal growth speed, change the form of crystals wholly and improve crystallization quality obviously. The impact on crystallization course takes second place in the average time of staying; in turn, dissociative sulphuric acid density, crystallization temperature.The Crystallization dynamics is a part of the basic theoretical researches during the course of discomposing phosphorus rock with...
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