Method for extracting high-purity sodium sulfate and sodium chloride products from high-salt content wastewater in coal chemical industry

Abstract

The invention provides a method for extracting high-purity sodium sulfate and sodium chloride products from high-salt content wastewater in the coal chemical industry. The method comprises the following steps: firstly, pretreating the high-salt content wastewater in the coal chemical industry to reduce the hardness thereof and primarily concentrate the wastewater till the TDS content is about 30000mg/L, and primarily separating sodium sulfate and sodium chloride from the high-salt content wastewater in the coal chemical industry by a nanofiltration process to obtain nanofiltration concentrated water with the sodium sulfate as a main component and a nanofiltration produced water with the sodium chloride as a main component; secondly, removing a part of organic matters from the nanofiltration concentrated water to reduce the COD by an electrolytic oxidizing technology, and performing a hot crystallization technology and a freezing crystallizing technology to obtain a pure sodium sulfate product and a small amount of sodium chloride product; treating the nanofiltration produced water by a membrane concentration technology and a hot crystallizing technology to obtain a pure sodium chloride product. In the whole technical process, on the basis of achieving zero discharge of the wastewater, reuse of all water and maximized recycle of the salts in the wastewater are achieved, so that the economic efficiency is improved and the environment pollution is avoided.

Description

technical field [0001] The patent of the invention belongs to the technical field of "zero discharge" of coal chemical industry, specifically a method for extracting high-purity sodium sulfate and sodium chloride from high-salt wastewater of coal chemical industry. Background technique [0002] The coal chemical process is an industry that converts coal into gas, liquid and solid products or semi-products, and then further processes them into chemical and energy products. At the same time, my country's actual energy is characterized by lack of oil and gas, relatively abundant coal resources, and relatively low coal prices. Therefore, the coal chemical industry has huge market demand and development opportunities in China. The new coal chemical industry will play an important role in the sustainable process of China's energy. It is of great significance for China to reduce environmental pollution caused by coal burning, reduce dependence on imported oil, and develop the domes...

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Problems solved by technology

If these waste salts are not properly treated, they will have a great impact on the surrounding environment of the factory area; if they are sent to the hazardous waste disposal center, it will seriously affect the economic benefits of the factory

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