Method for pretreating coal chemical industry production waste water and recycling resources of waste water

Abstract

The invention discloses a method for pretreating coal chemical industry production waste water and recycling resources of the waste water. According to the technical scheme, the method comprises the following steps of: (1) performing rectification, deacidification and deamination, namely feeding the coal chemical industry waste water into a rectification, deacidification and deamination tower, transferring ammonia and carbon dioxide in the waste water from a liquid phase to a gas phase, and respectively recycling 15 to 20 percent of ammonia water and ammonium bicarbonate; and (2) performing complexing extraction and recycling phenolic substances, namely adjusting the pH of the rectified residual solution in a kettle to be less than 3 by acid, adding a prepared oil phase according to a certain proportion, performing complexing extraction, after extraction is balanced, obtaining a load oil phase and pretreated waste water, performing reverse extraction on the load oil phase by sodium hydroxide solution serving as an extraction agent to obtain a concentrated sodium phenolate solution and a regenerated oil phase, acidifying the sodium phenolate to obtain crude phenol, and recycling the regenerated oil phase. Compared with the prior art, the method has the advantages that the technical flow is simple; the equipment investment is small, the energy consumption is low, the efficiency is high, and the phenol recycling rate is high; harmlessness and reclamation of the waste water are realized; and the method is obvious in economical and environmental benefits.

Description

technical field [0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for pretreatment of coal chemical production wastewater and resource recovery thereof. Background technique [0002] Coal chemical industry is the foundation and one of the main pillars of China's chemical industry. Coal chemical industry wastewater is high-concentration organic wastewater produced in the process of coal coke, gas purification and coking product recovery. The sources of coal chemical wastewater mainly include gasification wastewater, coal liquefaction wastewater, and coal dry distillation wastewater (coking wastewater or semi-coke wastewater). Coal chemical industry wastewater contains a large amount of toxic and harmful substances such as phenols, alkanes, aromatic hydrocarbons, heterocycles and ammonia nitrogen. The treatment of coal chemical wastewater is not only a bottleneck restricting the development of my country's coal chem...

AI Technical Summary

Problems solved by technology

This method cannot recycle resources, and the processing cost is high

[0006] The following problems exist in the above methods: 1) The deacidification process is unreasonable, so that acid gases such as ionic carbon dioxide and hydrogen sulfide dissolved in wastewater cannot be economically and effectively converted into free states, and the residual amount of acid gases is too high

The separation of ammonia and phenol is not complete, resulting in high phenol content and acid gas content in ammonia products. The deamination section and solvent recovery section need to be carried out under higher temperature and pressure, which makes the preparation of by-products more difficult; 2) When the ammonia content in the wastewater is high, the operation of the deammonization tower is unstable. In some processes, a complex tower with side line extraction is used to strip ammonia. The tower pressure is unstable, and the ammonia content in the purified water fluctuates; 3) Since the problem of volatile phenols affecting the quality of ammonia cannot be effectively solved, some processes adopt the process of extraction first and then deamination, so the pH of the extraction is relatively high

When pH>8, phenol mainly exists in ionic state in water and the hydrophilicity is greatly improved, which greatly reduces the efficiency of extraction and removal of phenols; 4) The extraction agent used is highly water-soluble and azeotropic with water, which cannot be achieved by rectification. Completely recycle it; 5) The biochemical feasibility of pretreated wastewater is poor, and the treated effluent cannot meet the discharge standard; 6) The enhanced pretreatment system has many structures and complex operations, and the dephenolization unit uses chemical-assisted physical methods; 7) Energy consumption Large, high investment cost

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