Laboratory Simulation of In-situ Leaching of Polyhalite

Deeply buried polyhalite is a kind of sulfate which contains about 28% potassium sulfate. Extraction potassium from polyhalite using in-situ leaching technology can help to resolve the problem of potassium shortage. This paper indicates a modeling study of leaching polyhalite in laboratory. Using CaCl2 as lixiviant, the effect of the concentration of lixiviant, granularity of mineral, the infiltration velocity and the length of infiltration route are studied by analyzing potassium concentration in leaching solution. The experiment results show that the granularity of mineral is one of the most influencing factors to the recovery of K+. When granularity of mineral is changed from 2-3 mm to 5-8 mm, the recovery of K+ decreased from 80.19% to 42.17%. The recovery of K+ increases with the infiltration velocity and the length of infiltration route and the concentration of K+ in lixiviating solution can be heightened to 12.1 g/L by increasing the length of infiltration route. The lixiviation process matches the metal dissolution kinetic equation. According to the experiential results, the parameters in equation are calculated. When the infiltration velocity is increased from 0.159m/h to 0.318m/h, the leaching velocity changed from 0.278h-1 to 0.673h-1 and the time of metal fully leaching to solution changed from 2.333 h to 0.951 h.