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Processing method for recycling sodium sulfate from waste alkali liquor in ethylene unit

A technology of ethylene waste lye and sodium sulfate, which is applied in the fields of neutralization, crystallization and recovery of sodium sulfate, and oxidation of ethylene waste lye, which can solve the problems of expensive precipitant, limited lye utilization, and poor precipitation quality , to achieve the effect of reducing salt content, avoiding impact and good product quality

Active Publication Date: 2012-05-16
CHINA PETROLEUM & CHEM CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Na can be obtained after secondary crystallization 2 Industrial products with an S content of 28% to 31%, containing NaOH and Na 2 CO 3 If the mother liquor is recycled to absorb the acid gas of the cracked gas, it will cause Na 2 CO 3 Accumulate in the lye and affect the operation of the device
[0009] Ethylene waste lye is deodorized by wet oxidation, diluted, and then biochemically treated. The high salt content will still have an impact on the biochemical treatment system; and the existing comprehensive utilization technology: either the amount of lye used is limited, or the waste lye is directly There is still no way out for the crystallization mother liquor, or the precipitant is expensive, and the quality of the precipitate obtained is not good

Method used

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  • Processing method for recycling sodium sulfate from waste alkali liquor in ethylene unit
  • Processing method for recycling sodium sulfate from waste alkali liquor in ethylene unit
  • Processing method for recycling sodium sulfate from waste alkali liquor in ethylene unit

Examples

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Effect test

Embodiment 1

[0048] The ethylene spent lye was oxidized in wet air at 120°C (6MPa) for 8 hours without dilution and pH adjustment, and the resulting oxidation solution was neutralized to pH 5.46 with concentrated sulfuric acid. The neutralized solution was frozen and crystallized, and the frozen mother liquor was removed. Biochemical, frozen crystallization is dried into Yuanming powder after vacuum evaporation and crystallization, and the evaporated mother liquor is returned to the neutralization unit. The sodium sulphate content of the obtained sodium sulfate is 93.76%, which meets the qualified product standard of "GB-T 6009-2003 Industrial Anhydrous Sodium Sulphate" III; L, total dissolved solids 9%.

Embodiment 2

[0050] The ethylene spent lye was subjected to wet oxygen oxidation at 150°C (4.5MPa) for 6h without dilution and pH adjustment, and the resulting oxidized solution was neutralized to pH 5.03 with concentrated sulfuric acid. The neutralized solution was frozen and crystallized, and the mother liquor was frozen. De-biochemical, frozen and crystallized by vacuum evaporation and crystallization, then dried into Yuanming powder, and the evaporated mother liquor is returned to the neutralization unit. The sodium sulfate content of the obtained sodium sulfate is 97.24%, which meets the "GB-T 6009-2003 Industrial Anhydrous Sodium Sulfate" Class II qualified product standard; the amount of the obtained frozen mother liquor is reduced to about 1 / 3 of the neutralization liquid amount, and the COD 900mg / L, total dissolved solids 7%.

Embodiment 3

[0052] The ethylene spent lye was oxidized in wet air at 160°C (6MPa) for 5 hours without dilution and pH adjustment, and the resulting oxidized solution was neutralized to pH 4.64 with concentrated sulfuric acid. Biochemical, frozen crystallization is dried into Yuanming powder after vacuum evaporation and crystallization, and the evaporated mother liquor is returned to the neutralization unit. Gained sodium sulfate sodium sulfate content is 99.05%, meets the "GB-T 6009-2003 Industrial Anhydrous Sodium Sulfate" Class II qualified product standard (because the color turns yellow); the amount of frozen mother liquor of gained is reduced to about 1% of the amount of neutralizing liquid / 3, COD 450mg / L, total dissolved solids 6%.

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Abstract

The invention discloses a processing method for recycling sodium sulfate from waste alkali liquor in an ethylene unit, wherein the method comprises the following steps: (1), performing wet oxidation on waste alkali liquor with air or oxygen under wet oxidation conditions to obtain oxidation liquid; (2), neutralizing the oxidation liquid to obtain neutralized liquid; (3), crystallizing out sodium sulfate decahydrate from the neutralized liquid by a freezing crystallization method; (4), performing biochemical treatment on frozen mother liquor; (5), performing vaccum evaporation to dry the sodium sulfate decahydrate to obtain anhydrous sodium sulfate products, and returning evaporation mother liquor to the neutralizing unit. The method solves the technical problem that waste alkali liquor of ethylene after being processed by deodorization, dilution and biochemical treatment still contains high-salt which can cause an impact to the biochemical treatment system. The method can be applied in fields like petrochemical, chemical engineering, environment protection, comprehensive utilization of the resources and light industries.

Description

technical field [0001] The present invention relates to the technology that reclaims sodium sulfate from ethylene plant waste lye, more specifically relates to the technology of the wet oxidation treatment of waste lye and the technology that separates sodium sulfate from waste liquid, i.e. the oxidation of ethylene plant waste lye, Neutralize and crystallize to recover sodium sulfate. Background technique [0002] The acid gases in the ethylene cracking gas mainly include hydrogen sulfide, carbon dioxide, organic sulfur, etc. To remove the acid gases, the alkaline solution is used to contact and wash the cracking gas in countercurrent, and the waste liquid produced is called ethylene spent alkali. In addition to Na in waste lye 2 S, Na 2 CO 3 , NaOH and a small amount of Na 2 SO 3 、Na 2 S 2 o 3 In addition, it also contains organic sulfur compounds such as mercaptans, so it has an unpleasant odor. [0003] The methods for treating waste ethylene lye include direct ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01D5/16C01D5/18C02F9/14
Inventor 高凤霞程学文张宾侯秀华莫馗
Owner CHINA PETROLEUM & CHEM CORP
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