Process using polyhalite extraction mother liquor to produce potassium sulfate

Abstract

The invention relates to a process using polyhalite extraction mother liquor to produce potassium sulfate.The process includes the steps of firstly, feeding ammonia gas into the polyhalite polyhalite extraction mother liquor to regulate pH to 10.0-12.0 so as to obtain Mg(OH)2 slurry; secondly, feeding CO2 until the pH is 7.5-8.0 to obtain carbonized mother liquor; thirdly, performing pyrolysis and solid-liquid separation to obtain MgCO3.3H2O solid salt and mother liquor after pyrolysis and separation; fourthly, adding calcium oxide slurry or calcium hydroxide slurry into the mother liquor after pyrolysis and separation, heating, stirring, and performing solid-liquid separation to obtain mother liquor after causticization separation; fifthly, performing forcible evaporation, and crystalizing to separate out potassium sulfate.The K2O content of the potassium sulfate obtained by the process reaches up to 51.9%, potassium ion yield reaches up to 91.7%, byproducts such as high-purity magnesium oxide and gypsum can be coproduced, and the process is simple in process flow, simple in needed equipment, easy in industrial production and low in cost.

Description

technical field [0001] The invention relates to a production process of potassium sulfate, in particular to a process for producing potassium sulfate by leaching mother liquor with polyhalite. Background technique [0002] Polyhalite (K 2 SO 4 · MgSO 4 2CaSO 4 2H 2 O), is an important insoluble potassium-containing salt ore, which is rich in reserves, with the largest amount in Sichuan and Hubei, and only (Sichuan) eastern (eastern) polyhalite resources are equivalent to K 2 The reserve of O is more than 20 billion tons, which is an important supplementary resource for my country's potash fertilizer industry. With the development of high-grade salt lake brine resources, available high-quality potassium-containing resources are increasingly scarce, and insoluble polyhalite potassium-containing salt ore resources are bound to become the focus of future potassium salt development and research hotspots. [0003] At present, the research on polyhalite leaching technology is...

AI Technical Summary

Problems solved by technology

For the research on extracting potassium sulfate by leaching mother liquor, most of them adopt the process of evaporation, concentration and crystallization, but the output of potassium sulfate is extremely small, and most of potassium sulfate is crystallized in the form of potassium-magnesium mixed salt, and the separation of potassium and magnesium is difficult and difficult to realize. Thorough Separation of Potassium Sulfate and Magnesium Sulfate

If it is directly sold as a potassium-magnesium fertilizer product, not only the product grade is low, but also the market sales are not ideal; Reaction raw materials, increase production costs, but also produce a large amount of constantly expanding high-potassium mother liquor that is difficult to digest, affecting the economic benefits of enterprises

[0004] Such as CN104755426A discloses a kind of method and related system of processing potassium sulfate and magnesium sulfate solution to produce potassium sulfate, is to utilize the mother liquor that contains potassium sulfate and magnesium sulfate after leaching polyhalite to mix with circulating crystal crystallization, thereby make the first concentrated solution Concentration can reduce the evaporation energy consumption of the first concentrated solution to a certain extent and increase the output of potassium sulfate, but it cannot fundamentally realize the complete separation of potassium sulfate and magnesium sulfate. Regardless of low-temperature evaporation or forced evaporation, a large amount of potassium salt It is also precipitated in the form of langbeinite or anhydrous langbeinite, which reduces the product grade and market price, and repeated evaporation crystallization and re-dissolution greatly increases energy consumption costs

CN102030487A discloses a new process of normal temperature carbonization and low-temperature pyrolysis of high-purity magnesium oxide. The combined process of carbonization and pyrolysis can realize the precipitation and separation of magnesium, but the obtained pyrolysis product magnesium carbonate is easily hydrolyzed to precipitate magnesium hydroxide with lower solubility. The particles are fine, the separation is difficult, and the mother liquor has a large amount of entrainment. If this technology is used to separate the polyhalite leaching mother liquor, the entrainment of the magnesium salt mother liquor will be large, and the yield of potassium products will be low.