System and process for fluorine-circulation magnesium removal of sulfate solution

Abstract

The invention discloses a system and process for fluorine-circulation magnesium removal of sulfate solution. The process includes: step one, magnesium removal, to be more specific, adding a fluoride serving as a magnesium removal agent into magnesium-containing sulfate solution, filtering a reaction product, and performing liquid-solid separation, wherein filter residue is magnesium fluoride; steptwo, defluorination, to be more specific, adding a calcium-containing fluorine removal agent into zinc sulfate solution subjected to magnesium removal, filtering a reaction product, and performing liquid-solid separation, wherein filter residue is calcium fluoride; step three, magnesium fluoride conversion, to be more specific, subjecting sulfuric acid and magnesium fluoride generated in the stepone to co-heating reaction in a reaction tank, absorbing hydrogen fluoride by water to obtain hydrofluoric acid, cooling the solution to crystallize, separating out magnesium sulfate crystal, neutralizing obtained hydrofluoric acid by a metal oxide to obtain fluoride solution, and returning the fluoride solution obtained in reaction to the step one to serve as the magnesium removal agent. Therefore, the process realizes fluorine recycling, so that treatment cost is sharply reduced.

Description

technical field [0001] The invention relates to the technical field of metallurgy, in particular to a sulfate solution fluorine cycle demagnesization process and system. Background technique [0002] In the metallurgical and chemical production where sulfate is the medium, magnesium often accumulates in the solution, some as high as 50g / l, which greatly increases the energy consumption of electrolysis and electrowinning, and the whole industry of hydrometallurgy alone consumes more electricity every year 800 million kwh, the accumulation of magnesium will also block the pipeline, corrode the electrolytic plate, and pollute the environment. The accumulation of magnesium into the sulfate crystal product will also seriously affect the quality of the product. The removal of magnesium in sulfate medium is a recognized problem in the industry. Regarding the problem of magnesium removal, enterprises and researchers have studied the following solutions: [0003] ①Precipitation zinc...

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Problems solved by technology

[0003] ①Precipitation zinc removal method: that is, the priority zinc removal method, SZP method, for example, extract part of the high magnesium solution from the wet zinc smelting system, neutralize the free acid with lime milk, and then use lime milk to neutralize the free acid And zinc ions are precipitated to generate basic zinc sulfate and returned to the system, while magnesium ions are left in the solution and discharged into the wastewater treatment system for further treatment, realizing the open circuit of magnesium, but this method produces a large amount of gypsum slag containing heavy metals, which is difficult to handle, and the zinc Severe loss, high cost, rarely used by factories

[0004] ② Magnesium fluoride salt precipitation: Add sodium fluoride to magnesium-containing zinc sulfate solution, fluorine and magnesium will form insoluble magnesium fluoride precipitation, after filtration, the magnesium content in the solution can be reduced to below 1g / l, but the solution remains The fluorine in the fluoride is as high as 1000mg / l, far greater than the production requirement of 50mg / l, and needs to be treated; the price of sodium fluoride is high, which makes the treatment cost very high; and the produced magnesium fluoride contains a large amount of heavy metals, which cannot be processed or stored for a long time; sodium fluoride The harm of ions entering the solution to the conventional method of zinc smelting process is similar to that of magnesium ions; with the tightening of environmental protection regulations, this method cannot be applied

[0005] ③ Saturated crystallization method: Evaporate and concentrate high-magnesium manganese sulfate or zinc sulfate solution, use the difference in solubility of magnesium sulfate, manganese sulfate, and zinc sulfate in water at different temperatures, repeatedly concentrate and crystallize, and separate magnesium, but due to magnesium sulfate, sulfuric acid The mixed crystals of manganese and zinc sulfate are serious during crystallization, and the actually obtained magnesium sulfate crystal contains more zinc than magnesium, and the concentrated crystallization process consumes a large amount of steam, making this method impracticable

[0006] ④ High-temperature and high-pressure precipitation method: Using a high-pressure reactor at 200°C and 5MPa, part of the magnesium sulfate in the solution precipitates, and part of the magnesium ions can be removed after liquid-solid separation. However, the reaction is completed in high-temperature and high-pressure equipment. The conditions are harsh and the equipment requires High, high energy consumption, currently unavailable

[0007] ⑤ Other methods: There are still some methods such as solvent extraction, zinc concentrate pickling, strong acid neutralization, etc., which cannot be applied on a large scale in actual production due to factors such as cost, equipment, and operability.

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