Single-effect four-body MVR (mechanical vapor recompression) saline wastewater separation device and separation method thereof

Abstract

The invention discloses a single-effect four-body MVR (mechanical vapor recompression) saline wastewater separation device, comprising a pre-concentration evaporator, a salt evaporation crystallizer, a nitrate evaporation crystallizer, an incidental salt evaporation crystallizer and a steam compressor, wherein secondary steam outlets of the pre-concentration evaporator, the salt evaporation crystallizer, the nitrate evaporation crystallizer and the incidental salt evaporation crystallizer are connected to an inlet of the same steam compressor, and inlet steam temperature of the steam compressor is 80-100 DEG C. The invention also discloses a saline wastewater separation method using the device. The device has zero emission of saline wastewater, can isolate and recycle high-purity salt and anhydrous nitrate from the wastewater, and has low investment cost and operational energy consumption.

Description

technical field [0001] The invention belongs to the field of chemical wastewater treatment, and in particular relates to a one-effect four-body MVR mixed-salt wastewater separation device and a separation method. Background technique [0002] Some enterprises in the fields of salt chemical industry, coal chemical industry, hydrometallurgy, and pharmaceuticals will produce a large amount of high-concentration mixed-salt wastewater containing sodium chloride, sodium sulfate, and other salts. For the desalination treatment of this kind of wastewater, there are usually the following treatment technologies: One is to obtain mixed salt by direct evaporation and crystallization. This technology is simple in process, but its economic value is not high. The second is the multi-effect vacuum evaporation process of salt and nitrate co-production. This technology uses the solubility relationship between sodium chloride and sodium sulfate to obtain salt (sodium chloride) at high temperat...

AI Technical Summary

Problems solved by technology

For the desalination treatment of this kind of wastewater, there are usually the following treatment technologies: One is to obtain mixed salt by direct evaporation and crystallization. This technology is simple in process, but its economic value is not high.

The second is the multi-effect vacuum evaporation process of salt and nitrate co-production. This technology uses the solubility relationship between sodium chloride and sodium sulfate to obtain salt (sodium chloride) at high temperature and nitrate (sodium sulfate) at low temperature, so that higher purity salt can be obtained products and nitrate products, but the final effect steam is condensed, resulting in a great waste of energy

However, this process requires at least two high-temperature and low-temperature steam compressors, and the volume flow rate of the low-temperature steam compressor is very large, both in terms of equipment investment and operating energy consumption.

The fourth is the frozen nitric acid extraction process, that is, the freezing method is used to crystallize sodium sulfate and separate it from sodium chloride. This process has a low freezing temperature and requires a large circulation of low-temperature mother liquor, and the system consumes a lot of energy.

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