Studies On Leaching Techniques For Polyhalite

In this paper, the raw material is Polyhalite of Nongle, in Sichuan. This thesis presented the leaching mechanism and leaching behavior for leaching Polyhalite using leaching agent from the aspects of static state and dynamic state, which the lixiviant is CaCl2, and the paper introduced the fundamental kinetic theory for leaching behavior.The static leaching experiment was studied in the paper, under the condition of different granularity, temperature, concentration of lixiviant, proportions of liquid to solid, stirring and so on. It was observed that the leaching rate of desired component increases with increasing temperature, leaching time, concentration, and with decreasing liquid-to-solid ratio and particle size. The degree of effect on leached Potassium concentration in the lixiviation system is different, the experiment results show that the solid-liquid heterogeneous reaction order is one order; and the surface activation energy is lower(13.951kJ/mol) over a wide range of temperature(288K~373K). According to the numerical value that is the relation of the solid-liquid reaction with the granule's surface area, surface activation energy and temperature coefficient, leaching kinetic indicate that diffusion through the product layer is the rate controlling process during the reaction. The activation energy is determined to be lower, which is characteristic for a diffusion-controlled process. From the results of the experiment with stirring condition, the paper could establish that the process is controlled by inward diffusion. The graph from the experiment data l-2 /3-(1- )2/3~t is beeline which prove the conclusion that is precipitation CaSO4 are produced on the surface of the ore, which restrain to ore leaching.The dynamic leaching experiment was also studied. Under the condition of different granularity, concentration of leaching agent, infiltration velocity, infiltration route etc., the pole-leaching experiment results show that Polyhalite ore could be leachability. It was obtained that the leaching rate increase with increasing lixiviant's concentration that the optimum is 5%, and increasing infiltration route, and decreasing particle size, the influence on the leaching rate is complicated. When the leaching rate is to 80%, the proportions of the consuming lixiviant to quantity of the ore sample are about 10:1. From the several mostly guide line of measuring the leaching efficacy; the technology of the leaching Polyhalite using CaCl2 is feasibility.The leaching behavior has been modeled as a shrinking unreacted core (SUC). The graph from the experiment data 1-2 /3-(l- )2/3~t is beeline which prove the previous conclusion that is precipitation CaSO4 are produced on the surface of the ore, which restrain to ore leaching.