Brine refining process for removing calcium and magnesium by one step

Abstract

The invention provides a brine refining process for removing calcium and magnesium by one step, which comprises the following steps of: pumping saturated brine out of a brine tank by using a pump, dividing the saturated brine into two paths for heat exchange to preheat the brine to 45 to 60 DEG C, and causing the preheated brine to enter a reactor; adding NaOH and Na2CO3 into the reactor, wherein the NaOH and the Na2CO3 partially come from chlor-alkali production process wastewater; performing refining reaction to completely remove Mg<2+> and Ca<2+> from the brine to make 0.2 to 0.5 g / L the concentration of the NaOH and 0.3 to 0.5 g / L the concentration of the Na2CO3 in the brine, and causing the brine to automatically flow into an intermediate tank; and pumping the treated brine into an HVMTM membrane filter for filtration, adjusting a pH value to 8.5 to 10.5 by using hydrochloric acids, adding sodium sulfite to completely remove free chlorine, detecting that suspended solid (SS) content is 0.1 to 0.2 mg / l, and causing the brine to automatically flow into a refined brine tank to prepare fresh brine. The calcium and magnesium impurities are removed simultaneously so as to simplify the process; and the use of ferric chlorides is avoided so as to reduce material consumption and the emission of pollutants.

Description

technical field [0001] The invention relates to a chlor-alkali production process, in particular to a brine refining process for one-step decalcification and magnesium removal. Background technique [0002] Table salt is the main raw material of the chlor-alkali industry, and the impurities in brine are mainly suspended solids and metal ions such as Mg 2+ , Ca 2+ etc. After the impurities are sent to the ion membrane electrolysis system, it is easy to damage the ion membrane and shorten its service life, so the brine must be refined. The key to the brine refining process is the separation of the refining reaction and the refined product. The principle and process of the refining reaction are basically the same, but the process and equipment for the separation of the product are quite different. [0003] At present, more than 90% of the domestic chlor-alkali enterprises adopt the technology of Kaimembrane to refine brine, see figure 1 , the process flow is as follows: brin...

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Problems solved by technology

[0006] The characteristic of this process is that, after the pretreatment procedure, the Mg 2+ , after removing Ca 2+ , which in turn can reduce the amount of salt sludge reaching the filter especially Mg(OH) 2 However, there are obvious deficiencies in this process: the process is long, the process before entering the Kamembrane filter is cumbersome, there are many tank equipment, the floor area is large, and more inspections are required personnel

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