Process for preparing potassic-magnesian fertilizer by using polyhalite

Abstract

The invention provides a process for preparing a potassic-magnesian fertilizer by using the polyhalite. The process comprises the steps of (1) grinding ores: grinding the polyhalite till 85wt% of the polyhalite are over 100 meshes in size; (2) washing: washing with water to remove the sodium chloride in the polyhalite; (3) roasting: roasting washed minerals at a high temperature; (4) leaching: leaching to extract potassium and magnesium in the polyhalite; (5) solid-liquid separation: subjecting the ore pulp obtained through the leaching step to solid-liquid separation so as to obtain a mother liquor containing potassium sulfate and magnesium sulfate; (6) evaporation: evaporating and crystallizing the mother liquor to obtain a potassium-magnesium fertilizer product. The process is simple, wide in source of raw materials and low in cost, wherein the sodium chloride in the polyhalite can be effectively removed. Meanwhile, the leaching rate of K+ is high and the water consumption of leaching is reduced. The concentration of K+ in the leaching mother liquor is high, and the energy consumption of the subsequent evaporation and crystallization step is reduced. The potassium-magnesium fertilizer product obtained after the evaporation step meets the requirements of first-class products specified in GB / T20937-2007.

Description

technical field [0001] The invention relates to a process for preparing potassium-magnesium fertilizer with potassium-containing minerals, in particular to a process for preparing potassium-magnesium fertilizer with insoluble polyhalite. Background technique [0002] Polyhalite (K 2 SO 4 · MgSO 4 2CaSO 4 2H 2 O), is a kind of insoluble potassium ore, which is light gray or dark gray, widely distributed in sulfate-type potassium ore, and its theoretical potassium content (K 2 O) reaches 15.6%, which is an important potash resource. The polyhalite resources in the world are very rich, and the geological ages of its production are mainly concentrated in the Permian, Triassic and Tertiary. In terms of geological plane distribution, they are relatively concentrated in the ring belt of 25°-50° north latitude . With the continuous development of high-quality potassium-containing brine resources and the scarcity of soluble solid potassium ore resources, it is necessary to loo...

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Problems solved by technology

[0004] Some literatures have reported the method of preparing potassium fertilizer from polyhalite, but there are K + The leaching rate and utilization rate are low, the process is complicated, etc., and the polyhalite used does not contain sodium chloride or has a low sodium chloride content, and polyhalite ore is mostly associated with rock salt. In some areas, polyhalite The content of sodium chloride is relatively high, in order to ensure the purity of the product, it is also necessary to solve the problem of removing impurities of sodium chloride