Ethylene alkaline cleaning waste liquid processing method

Abstract

The present invention provides an ethylene alkaline cleaning waste liquid processing method including the following steps: (1) air floating for oil removal, to be more specific, oil matters entrained in ethylene alkaline cleaning waste liquid are removed; (2) high temperature wet oxidation treatment, to be more specific, the deoiled ethylene alkaline cleaning waste liquid is added with sodium hydroxide for reaction in alkaline conditions; (3) causticizing treatment, to be more specific, the ethylene alkaline cleaning waste liquid after the high temperature wet oxidation treatment is added with calcium oxide or calcium hydroxide for improving concentration of sodium hydroxide, and calcium carbonate is recovered; (4) evaporation and concentration, to be more specific, the ethylene alkaline cleaning waste liquid with the calcium carbonate recovered, is evaporated and concentrated, and the concentration of sodium hydroxide is further improved; and (5) alkali concentration regulating, to be more specific, the concentrated ethylene alkaline cleaning waste liquid is added with solid sodium hydroxide, precipitated sodium sulfate is recovered, and the produced high concentration sodium hydroxide solution is reused to the step (2) and / or an upstream alkaline washing tower. According to the method, COD and sulphide in the ethylene alkaline cleaning waste liquid can be effectively removed, calcium carbonate and sodium sulfate can be respectively removed, the treated sodium hydroxide solution is recycled, and ethylene alkaline cleaning waste liquid zero discharge can be achieved.

Description

technical field [0001] The invention belongs to the field of waste water treatment, and in particular relates to a treatment method for ethylene alkali washing waste liquid in chemical plants. Background technique [0002] In the process of ethylene production, alkali washing is generally used to remove CO in cracked gas. 2 、H 2 S and other acid gases. The alkaline cleaning process produces a large amount of waste liquid, which contains NaOH generated during the alkaline cleaning process in addition to the remaining NaOH. 2 S, Na 2 CO 3 and other inorganic salts. On the other hand, due to the condensation of heavy components in the cracked gas and the polymerization of diolefins and aldehydes during the alkali cleaning process, a large amount of organic matter enters the waste liquid. [0003] Ethylene alkali washing waste liquid (ethylene waste alkali liquid) is a high-concentration organic wastewater with high sulfide and salt content, making it difficult to treat. ...

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Problems solved by technology

[0007] Based on the above analysis, the current methods for treating waste lye are either inappropriate, or the treatment effect is insufficient, or the investment and operating costs are high, or the recovery quality is not high, or the waste lye after treatment needs to be discharged to sewage treatment system, or will produce high-salt wastewater and many other problems

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