A decalcification process for old bittern in high calcium salt fields

Abstract

A decalcification technique of high-calcium old brine in a salt field includes the following steps: (1), dissolving mirabilite; (2), evenly mixing mirabilite mother liquid obtained in the step (1) with the high-calcium old brine in the salt field according to a molar ratio of Ca2+ to SO42- being 1: (1-1.2) for 1-24 hours to obtain slurry; (3), filtering; (4) washing and drying; (5), returning the decalcified old brine obtained in the step (3) to the sodium chloride salt field and continuing to evaporate the old brine. The decalcification technique has the advantages that sodium sulfate resources of a salt lake or nearby places are fully used for reacting with calcium sources in the high-calcium old brine to achieve decalcification of the old brine; technological process is simple and cost is low; the technique can be implemented directly in resource locations, circular brine mixing of high-concentration magnesium chloride brine after decalcification of the high-calcium old brine can be achieved, gypsum products can be produced, sodium sulfate minerals can be digested and local environment problems of the salt lake can be relieved.

Description

technical field [0001] The invention relates to a decalcification process for old brine from salt fields, in particular to a decalcification process for high-calcium chloride-type salt lake brine. Background technique [0002] my country is a country with many salt lakes. There are thousands of large and small salt lakes in the inland areas, mainly distributed in the Qinghai-Tibet Plateau and Xinjiang. The larger ones are Chaerhan and Lop Nur, which are chloride type and sulfate type respectively. salt lake. The proven reserves of various types of salt in the Chaerhan Salt Lake alone amount to more than 60 billion tons, and the mining value of the entire salt lake exceeds tens of trillions of yuan. [0003] In the current development process of chloride-type salt lakes, in order to speed up the evaporation progress of sodium chloride stage, shorten the drying time of salt fields, and improve the production efficiency of salt lakes, the old brine in salt fields and the origin...

AI Technical Summary

Problems solved by technology

However, for some chloride-type brines in Qinghai Salt Lake, the calcium content is relatively high, and its concentration will continue to increase due to the cyclic accumulation of calcium. If the traditional brine blending process is not used to treat high-calcium old brine, this may affect the brine The extraction of potassium chloride has a certain impact, and it may also cause calcium salt to be brought into the potassium mixed salt mine to affect the flotation process and reduce product quality. However, the production of potassium chloride from high-calcium carnallite is also a problem faced by many enterprises in the Qinghai Salt Lake area. Therefore, it is necessary to chemically treat the high-calcium old brine

[0004] At present, most of the research on the decalcification process adopts ion exchange and precipitation processes, etc., such as CN203741143U discloses a method for the deep purification of calcium and magnesium ions by a resin adsorption device, and CN103641264A discloses a sewage treatment field that converts secondary The method of passing the effluent into a reactor filled with mixed ion exchange resins to simultaneously remove multivalent cations such as calcium, barium, and iron, and negatively charged small molecular soluble organic matter. Both of the above two methods use the principle of ion exchange to replace calcium and magnesium ions synchronously In order to achieve the purpose of removal, but it is only suitable for the deep purification of low-concentration calcium-magnesium-containing water quality with the concentration of calcium and magnesium ions lower than 100mg / L, and the adsorption capacity of exchange resins suitable for specific ions is limited. If the concentration is too high, on the one hand it will Increasing the amount of adsorbent will increase the production cost. At the same time, the adsorption and regeneration effect will be greatly affected. The brine solution with complex composition will also cause varying degrees of damage to the chemical and mechanical properties of the ion exchange resin.

CN103864249A discloses a process of adding sodium carbonate to remove calcium and magnesium ions in salt lake brine, which also precipitates calcium and magnesium synchronously; but the above processes all have the defect that calcium and magnesium cannot be separated and effectively utilized

CN103508472A discloses a method for enriching lithium and removing calcium from oilfield water by using the evaporation-freezing principle. In essence, according to the phase diagram theory, since the chemical properties of calcium and magnesium are very similar, the concentrated calcium chloride type oilfield water obtained by evaporation is located exactly in the The calcium sulfate saturated phase region of the low-temperature phase diagram, so the purpose of freezing and decalcification can be achieved by freezing; CN103523801A discloses a method for jointly extracting potassium, boron, and lithium from chloride-type potassium-containing underground brine, and also uses Glauber’s salt to remove calcium. Calcium is removed from the mother liquor before boron and potassium analysis to eliminate the influence of calcium on the subsequent lithium extraction process, but the precipitated calcium sulfate will co-precipitate and crystallize with NaCl salt in the sodium chloride salt field. Due to the large amount of sodium chloride precipitated, the industrial value is low This results in higher harvesting costs, and it is difficult to separate, recover and utilize the precipitated calcium sulfate in the form of products

However, there are few reports on the process of using the by-product gypsum from the old brine in Yantian