The Prediction Of Polyhalite Dissolving Balance And The Experimental Stimulation Of Column Leaching In The Process Of Dissolving Exploitation

The solubility potash resource reserves that our country already ascertains are difficult to meet the need of future agriculture to the potash fertilizer. It is of great significance to exploit the prolific resources of polyhalite.In this paper, the dissolving balance constant K_sp of polyhalite is calculated based on the Pitzer theory, the HW formula and the balanced liquid phase compositions of the polyhalite dissolving in water at 298K, 323K and 348K. The K_sp of polyhalite increases with the increasing of temperature and the pressure. It increases from 6.7496E-15 to 5.8807E-13, when the temperature increases from 298K to 348K and the pressure increases from 1bar to 100 bar. The average activity coefficients of simgle salt, K₂SO₄, MgSO₄ and CaSO₄ are calculated. The K_sp of polyhalite, which roughly calculated by the average activity coefficient of simgle salts, increases from 1.3371E-16 to 1.8450E-13, when the temperature increases from 298K to 348K and the pressure increases from 1 bar to 100 bar. Comparing the estimating result with the calculating K_sp of polyhalite from HW formula, they are comparatively approached.In the experiment, the raw material is polyhalite of Nongle, in Sichuan. The leaching agent is CaCl₂ solution. Through Simulating the unidirectional diffusional leaching progress in the laboratory, it is examined the influence of the particle size, the concentration of leaching agent, the infiltration velocity and the path length of the leaching progress on the leaching progress of K⁺. The infiltration experiment indicates that decreasing the particle size, increasing the infiltration velocity and increasing the path length of the leaching progress are beneficial to accelerating infusion speed. When increasing the concentration of CaCl₂ solution, the infusion speed is accelerating along with the formation of calcium sulfate.It is according with the B. C.Голубев-Г. Н.Крцчевmodel that exploitation of polyhalite using CaCl₂ solution as the leaching agent. The concentration of K⁺ is a exponential function of the ratio of the infiltration velocity and the path length of the leaching progress. The infiltration velocity coefficient can be calculated by the slope of the straight line. The leaching velocity coefficient increases with the increasing of the infiltration velocity. When the infiltration velocity increases from 0.159 m/h to 0.318 m/h, the leaching velocity coefficient increases from0.03132 h^-1 to 0.04383 h^-1. The result is according with the experimental data.X-ray diffraction pattern of the leaching refuse shows that it has the typical gypsum characteristics. It indicates that the transfer of polyhalite in CaCl₂ solution is complete. The scanning electron microscopy analysis shows that the leaching refuse is crumble. It means that there isn't a stratum compactum on the ore.