Salt-containing organic wastewater recycling and zero discharge process

Abstract

The invention discloses a salt-containing organic wastewater recycling and zero discharge process, which comprises the following steps: adjusting and decarbonizing organic salt-containing waste liquid, feeding the organic salt-containing waste liquid into a coagulative precipitation tank, and feeding effluent into a multi-medium filter; mixing the effluent and subsequent separation mother liquor in an intermediate water tank, carrying out primary catalytic oxidation, entering a weak acid cation bed, removing impurities, and carrying out ultrafiltration; enabling water after ultrafiltration to enter a first-stage nanofiltration device to be subjected to quality-divided concentration; enabling that the concentrated water sequentially enters a secondary catalytic oxidation device and a sand filter tank to remove organic matters and residual impurities, and is conveyed to a concentrated water nanofiltration device and a sodium sulfate evaporative crystallization device; mixing the produced water, performing high-pressure reverse osmosis, sequentially feeding the water into a secondary coagulative precipitation tank and a sand filter tank to remove impurities in water, and feeding the water into a sodium chloride evaporative crystallization device; and producing sodium chloride and sodium sulfate in the purity higher than 98%. The mother liquor separated by evaporative crystallization flows back to a pre-process system, and the evaporation condensate is conveyed to a recycling water tank, so that the treatment and disposal of the mother liquor and a series of pollution problems are avoided, huge hazardous waste disposal cost is reduced, and the environmental pollution is reduced while the cost is reduced.

Description

technical field [0001] The invention is applicable to the field of resource recovery of salt-containing organic wastewater in the coal chemical industry, and specifically discloses a process for resource recovery and zero discharge of salt-containing organic wastewater. Background technique [0002] The coal chemical industry is a high-energy-consuming industry, which produces a large amount of saline organic wastewater every year. If it is directly discharged into the environment, it will cause serious damage to the ecological environment. With the improvement of discharge standards, enterprises have begun to treat high-salt wastewater. The core process of traditional zero-discharge treatment of high-salt wastewater is the combined process of membrane concentration and evaporation crystallization. The by-product crystalline salts appear in mixed forms, containing various ions, and the degree of resource utilization It is not high, and can only be landfilled as hazardous was...

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Problems solved by technology

[0002] The coal chemical industry is a high-energy-consuming industry, which produces a large amount of saline organic wastewater every year. If it is directly discharged into the environment, it will cause serious damage to the ecological environment. With the improvement of discharge standards, enterprises have begun to treat high-salt wastewater. The core process of traditional zero-discharge treatment of high-salt wastewater is the combined process of membrane concentration and evaporation crystallization. The by-product crystalline salts appear in mixed forms, containing various ions, and the degree of resource utilization It is not high, and can only be landfilled as hazardous waste in the end, and the cost per ton of salt treatment is as high as 5,000 yuan; the crystallization of mixed salt is currently the bottleneck problem that hinders the realization of zero discharge of high-salt wastewater. It is very important to explore feasible by-product recycling processes. The salt separation process is one of the important ways

[0003] Chinese patent CN 109809592 A discloses a salt separation method for coking wastewater nanofiltration concentrate. After pretreatment and concentration, the coking wastewater enters a high-pressure nanofiltration salt separation system, and the nanofiltration concentration rich in high-concentration sulfate Sodium sulfate crystalline salt is produced through MVR evaporative crystallization and freezing crystallization units; the nanofiltration product water containing higher concentration of chloride salt is produced through sodium chloride crystallizer. Process scheme The output of miscellaneous salt (hazardous waste) in the traditional process scheme failed to meet the by-product salt in the "Sodium Sulfate by-product Industry of Coal Chemical Industry" and "Sodium Chloride By-Product Industry of Coal Chemical Industry" issued by the China Coal Processing and Utilization Association in 2019 Physical and chemical indicators

[0004] For coal chemical industry salt-containing organic wastewater, the conventional zero discharge process adopts the core process of pretreatment + double membrane method (nanofiltration + reverse osmosis) + evaporation crystallization, which can remove colloids, suspended solids and calcium and magnesium ions in wastewater, while Most of the pollutants are not removed. During the process of membrane concentration and separation, not only the fouling of organic matter will lead to frequent cleaning of the membrane and shorten the service life of the membrane, but also cause the physical and chemical index TOC of the evaporated and crystallized product salt to exceed the standard, which can only be processed in the form of hazardous waste in the end. treatment, resulting in a waste of the entire zero-discharge treatment cost, and it is urgent to develop a zero-discharge process for COD that is refractory to degradation in high-salt water, to achieve high value-added recycling of resources, to produce non-hazardous waste and miscellaneous salts, and to have low treatment costs

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