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Method for recycling sodium sulfate from waste alkali liquor of ethylene unit

A technology of waste ethylene lye and sodium sulfate, which is applied in the directions of alkali metal sulfite/sulfite, chemical instruments and methods, alkali metal compounds, etc. Operation and other issues to achieve the effect of reducing salt content, avoiding shocks, and reducing emissions

Active Publication Date: 2013-08-14
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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  • Method for recycling sodium sulfate from waste alkali liquor of ethylene unit
  • Method for recycling sodium sulfate from waste alkali liquor of ethylene unit
  • Method for recycling sodium sulfate from waste alkali liquor of ethylene unit

Examples

Experimental program
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Effect test

Embodiment 1

[0051] 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, and the neutralized solution was crystallized by vacuum evaporation. Dried into Yuanming powder, part of the mother liquor is evaporated to freeze and crystallize, the freeze crystal is returned to the neutralization unit, and the frozen mother liquor is removed for biochemical treatment. Part of the evaporated mother liquor is returned to the neutralization unit to reduce the content of sodium carbonate and increase the yield of qualified products. The sodium sulfate content of the obtained sodium sulfate is 97.05%, 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 / 20 of the neutralization liquid amount, and the COD is 2800mg / L, total dissol...

Embodiment 2

[0054] The ethylene spent lye was oxidized in wet air at 180°C (6MPa) for 5 hours without dilution and pH adjustment, and the resulting oxidized solution was neutralized to pH 4.01 with concentrated sulfuric acid, and the neutralized solution was crystallized by vacuum evaporation. Dried into Yuanming powder, part of the mother liquor is evaporated to freeze and crystallize, the freeze crystal is returned to the neutralization unit, and the frozen mother liquor is removed for biochemical treatment. Part of the evaporated mother liquor is returned to the neutralization unit to reduce the content of sodium carbonate and increase the yield of qualified products. The sodium sulfate content of the obtained sodium sulfate is 97.12%, which meets the standard of "GB-T 6009-2003 Industrial Anhydrous Sodium Sulfate" Class II qualified products; L, total dissolved solids 6%.

Embodiment 3

[0056] The ethylene spent lye was subjected to wet oxygen oxidation at 210°C (6MPa) for 2 hours without dilution and pH adjustment, and the resulting oxidized solution was neutralized to pH 4.70 with concentrated sulfuric acid, and the neutralized solution was crystallized by vacuum evaporation. Dried into Yuanming powder, part of the mother liquor is evaporated to freeze and crystallize, the freeze crystal is returned to the neutralization unit, and the frozen mother liquor is removed for biochemical treatment. Part of the evaporated mother liquor is returned to the neutralization unit to reduce the content of sodium carbonate and increase the yield of qualified products. The sodium sulfate content of the obtained sodium sulfate is 97.13%, which meets the standard of "GB-T 6009-2003 Industrial Anhydrous Sodium Sulfate" Class II qualified products; L, total dissolved solids 6%.

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Abstract

The invention relates to a method for recycling sodium sulfate from a waste alkali liquor of an ethylene unit, specifically to a technology of wet oxidation treatment of the waste alkali liquor of ethylene and separation of sodium sulfate from a waste liquid. The method comprises the steps of: (1) under wet oxidizing condition, performing wet oxidation to the waste alkali liquor of ethylene by air or oxygen to obtain an oxidized liquid; (2) neutralizing the oxidized liquid to obtain a neutralization liquid; (3) crystallizing water-entrained anhydrous sodium sulfate from the neutralization liquid; (4) returning a part of evaporative mother liquor to a neutralizing unit and performing de-biochemical treatment for frozen mother liquor after freezing the other part of evaporative mother liquor to recycle sodium sulfate decahydrate, wherein the recycled sodium sulfate decahydrate returns to the neutralizing unit; and (5) drying the water-entrained sodium sulfate decahydrate to obtain anhydrous sodium sulfate product. The method solves the technical problem that high content of salt still impacts the biochemical system after deodorization of waste alkali liquor of ethylene through wet oxidation and biochemical treatment after dilution and can be used in the fields of petrochemical and chemical industries, environment protection, comprehensive utilization of resources and light industry and the like.

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 Patents(China)
IPC IPC(8): C01D5/00C02F9/14
Inventor 高凤霞程学文张宾莫馗杜蓓
Owner CHINA PETROLEUM & CHEM CORP
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