A method and equipment for extracting salt from coal chemical wastewater

Abstract

The invention discloses a coal chemical industry wastewater salt extraction method which comprises the following steps: coal chemical industry wastewater is input into an ultrafiltration membrane assembly by a feed pump to perform pretreatment, produced water enters an ultrafiltration produced water tank, and concentrated water is recycled; the liquid stored in the ultrafiltration produced water tank is input into a nanofiltration membrane assembly by a high-pressure pump and subjected to salt separation treatment to trap divalent salts and TOC (total organic carbon) and permeate sodium chloride, the produced water mainly containing univalent sodium chloride salt enters a nanofiltration produced water tank, and the sodium chloride is separated from the divalent salts and TOC; the liquid stored in the nanofiltration produced water tank is input into a reverse osmosis membrane assembly by a high-pressure pump and subjected to concentration, thereby reducing the water quantity for subsequent treatment; and the concentrated water mainly containing sodium chloride salt is crystallized by evaporation to obtain sodium chloride industrial salt, and the produced water is recycled. The invention also discloses a coal chemical industry wastewater salt extraction facility. The method and facility effectively relieve the problem of shortage of coal chemical industry water resources, reduce the operating cost for later evaporative crystallization, and implement resource recyling.

Description

technical field [0001] The invention relates to the technical field of wastewater treatment, in particular to a method and equipment for extracting salt from coal chemical wastewater. Background technique [0002] Coal chemical industry wastewater has a large amount of discharge, complex components, and difficult treatment. According to the source composition, it can be divided into organic wastewater and saline wastewater. Among them, the concentrated brine obtained by biochemical treatment and membrane treatment of saline wastewater, the total salt content TDS (total dissolved solids) is generally ≥5000mg / L, CODcr (dichromate index) is generally 200-800mg / L, chlorine There are a lot of ions, obvious odor, high chroma, and some calcium, magnesium, sulfate, silicon and other substances that are easy to scale. [0003] In the prior art, most of the treatment methods for the concentrated brine of the coal chemical industry adopt thermal concentration process or membrane separ...

AI Technical Summary

Problems solved by technology

Both processes only reuse fresh water, and the concentrated water is evaporated and crystallized, ash washed or evaporated naturally to produce mixed salt, and mixed salt becomes a waste product that may cause potential harm to the environment

Its disadvantages are: the device is huge, energy consumption is high, and other trace miscellaneous salts are still treated as hazardous waste

The disadvantage is that although the equipment realizes zero discharge of waste water, the equipment is complex and the investment is high

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