Circular and comprehensive utilization method for ethylene alkali waste liquid

Abstract

The invention relates to a circular and comprehensive utilization method for ethylene alkali waste liquid. The method is characterized in that oil in waste alkali is extracted by an extractant firstly, a hydrophobic type filtering gravity oil removal tank is used for removing a oil-containing suspended substance in alkali waste liquid, hydrocarbons substances dissolved in the alkali waste liquid can be steamed by selecting an indirect steam heating stripping method, then the alkali waste liquid is evaporated and concentrated so that the Na2S concentration in the alkali liquid can reach more than 15%, and the Na2S is precipitated through cooling and crystallizing, crystals can be filtered to obtain mother liquor, the mother liquor is carried out causticizing reaction by adding quicklime, precipitated to obtain a supernatant and bottom mud, the supernatant is returned for ethylene circular and comprehensive utilization, the obtained bottom mud can be used as a raw material for cement mill. The method of the invention solves four problems of oil substances (comprising suspended substances) removal, residual alkali comprehensive disposal, sulfide treatment and dissolved organic matterdegradation in circular and comprehensive utilization of the ethylene alkali waste liquid, the ethylene alkali waste liquid treatment realizes sewage zero-discharge, saves resource and energy, and accords with circular economy idea.

Description

technical field [0001] The invention relates to a recycling and comprehensive utilization method of waste lye, in particular to a recycling and comprehensive utilization method of ethylene waste lye, which belongs to the technical field of waste lye comprehensive utilization. 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 acid gas contained in the cracked gas of the ethylene plant is mainly H 2 S, CO 2 And a small amount of RSH, HCN, etc., these acid gases must be removed to H 2 S is less than 1×10 - 6 , CO 2 less than 1×10 - 6 , cracked gas can enter the system after separation and refinement. Acid gas undergoes an irreversible chemical reaction in the alkali washing tower through countercurrent contact with about 10% fresh lye, thereby generating Na 2 CO 3 and Na 2 S, to achieve the removal of acid gas, and the excess NaOH is discharged fr...

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Problems solved by technology

[0026]Because the waste lye contains sodium sulfide, it is boiled into industrial soda sulfide for papermaking, realizing the recycling of waste. However, since the waste lye contains In addition to the active ingredients of pulping, it also contains mercaptans and oily substances, so the quality of the paper produced is poor, and the wastewater discharged from papermaking still pollutes the environment

[0027]Because ethylene waste lye mainly contains mineral oil, light hydrocarbons and other organic matter, as well as alkali sulfide, Na2CO3 and NaOH inorganic chemical substances, the problems that need to be solved for their comprehensive utilization are: the removal of oily substances (including suspended solids), the comprehensive disposal of residual alkali, the treatment of sulfides, and the degradation of dissolved organic matter. The problem is that the methods currently used in industry have some defects, and cannot solve the recycling and comprehensive utilization of ethylene waste liquid well. Therefore, it is necessary to research and develop a practical and comprehensive utilization method that can solve practical problems.

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