Salt separation and purification recovery method for salt-containing wastewater

Abstract

The invention discloses a salt separation and purification recovery method for salt-containing wastewater. The method comprises the following steps: performing advanced oxidation treatment on pretreated salt-containing wastewater so as to obtain salt-containing wastewater in which organic matters are removed; desalting and purifying the salt-containing wastewater in which organic matters are removed so as to obtain desalted produced water and desalted concentrated water, performing secondary softening treatment on the desalted concentrated water so as to obtain softened concentrated water; performing deep concentration on the softened concentrated water so as to obtain deeply concentrated produced water and deeply-concentrated concentrated water; performing freezing crystallization on the deeply-concentrated concentrated water so as to obtain sodium sulfate crystals and freezing crystallized concentrated water; performing freezing crystallization on the freezing crystallized concentrated water for at least one time so as to obtain freezing crystallized produced water and freezing crystallized concentrated water; and evaporating or drying the freezing crystallized concentrated water, thereby obtaining the sodium chloride crystal. The traditional evaporative crystallization process is replaced with the freezing crystallization, the process is implemented under low temperature and normal pressure, the equipment is difficultly corroded, the operation is safe and reliable, the energy consumption is effectively reduced, the pipeline is difficultly blocked, and the investment and operating cost can be reduced.

Description

technical field [0001] The invention relates to a salt separation and purification recovery method of saline waste water. Background technique [0002] Coal chemical industry uses coal as raw material and converts coal into gas, liquid and solid products through chemical processing. However, because the coal chemical industry needs to consume and by-produce a large amount of water, the problems of water resource recycling and environmental protection are becoming increasingly prominent. Coal chemical wastewater mainly includes coking wastewater, coal gasification wastewater, coal direct / indirect liquefaction wastewater, and wastewater generated during the preparation of synthesis gas conversion catalysts. The huge water consumption and wastewater discharge are a prominent factor restricting the development of the coal chemical industry. , and one of the important issues involved is the safe treatment of high-salt wastewater. [0003] Usually coal chemical industry wastewat...

AI Technical Summary

Problems solved by technology

Evaporation crystallization is mainly to use heat source to heat water into steam and separate concentrated brine mother liquor. Although multi-effect evaporation or mechanical steam recompression utilizes steam waste heat to reduce energy consumption, the energy consumption of evaporation crystallization due to the thermal limitation of water vapor phase change is still relatively high. high

The second is that evaporation and crystallization lead to corrosion and scaling of equipment and pipelines

Due to high-temperature heating, the corrosiveness of the concentrated brine increases, and as the evaporation proceeds, the concentration of the mother liquor of the concentrated brine continues to increase, which further enhances the corrosiveness. Therefore, corrosion-resistant materials must be used in the material selection of evaporation crystallization equipment, which also increases equipment Investment cost; and evaporator fouling also leads to increased heat transfer resistance of equipment and increased unit steam consumption, thereby increasing the operating cost of evaporation and crystallization technology

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