Method for quality-divided crystallization and salt extraction from coal chemical industry high-salinity wastewater

Abstract

The invention relates to the field of resource utilization of high-salinity wastewater in coal chemical industry, in particular to a method for extracting salt from high-salinity wastewater in coal chemical industry through quality-divided crystallization, which comprises the following steps of: firstly, performing quality-divided salt separation on the high-salinity wastewater in coal chemical industry through a reduction concentration unit, and concentrating; pumping the high-salt wastewater subjected to quality separation and further concentration into a crystallization unit, respectively carrying out evaporative crystallization and cooling crystallization to extract salt, and enabling extracted salt to pass through a drying unit to obtain sodium chloride with the yield of 89%-95% and sodium sulfate with the yield of 81%-85%; according to the method, a membrane-method salt separation crystallization process and a hot-method salt separation crystallization process are combined, and according to solubility differences of different salts in the coal chemical industry high-salt wastewater at different temperatures in water and a Na < + > / / Cl <-> and SO42-H2O water-salt system phase diagram, three units of reduction concentration, crystallization and drying are designed for resource utilization of the coal chemical industry high-salt wastewater; the extracted salts pass through a drying unit to obtain sodium chloride with the yield of 89-95% and sodium sulfate with the yield of 81-85%, and the purities of the two salts both meet the national salt related standards.

Description

technical field [0001] The invention relates to the field of resource utilization of high-salt wastewater of coal chemical industry, in particular to a method for separating and crystallization of salt from high-salt wastewater of coal chemical industry. Background technique [0002] Modern coal chemical industry is my country's strategic technical reserve for energy security, and it is also an emerging industry encouraged by the state. With the transformation and upgrading of the country's utilization of coal resources, the coal chemical industry has developed rapidly. The coal chemical industry is a large water user, consuming and discharging a large amount of water resources in production. Due to the shortage of water resources and fragile ecosystems in northern my country, the discharge of coal chemical wastewater has a great impact on the water environment, easily causing soil salinization and polluting groundwater. For the discharge of coal chemical wastewater, it is...

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Problems solved by technology

[0004] So far, there is no method to extract the salts such as sodium chloride and sodium sulfate in high-salt wastewater in the form of industrial products, so as to achieve zero discharge of wastewater and near zero discharge of solid waste

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