Method for purifying waste solvent

Patent metadata

Field	Value
Publication number	US-11465906-B2
Application number	US-201816496061-A
Country	US
Kind code	B2
Filing date	Nov 12, 2018
Priority date	Nov 13, 2017
Publication date	Oct 11, 2022
Grant date	Oct 11, 2022

Abstract

Provided is a method for purifying a waste solvent by removing carbon dioxide contained in a waste solvent derived from supercritical waste liquid generated after supercritical drying by a decompression process, and removing ammonia by a multi-stage distillation process to obtain a solvent of high purity, which can be reused in producing silica aerogel or a silica aerogel blanket.

First claim

The invention claimed is:

1. A method for purifying a waste solvent, the method comprising:
decompressing a waste solvent containing ammonia and carbon dioxide, wherein the decompressing is performed at a temperature of 30-50° C. and a pressure of 100-200 mbar to remove carbon dioxide;
introducing the decompressed waste solvent into a distillation column; and
distilling the introduced decompressed waste solvent to yield a purified waste solvent, wherein the distillation is performed by a multi-stage distillation method.

2. The method of claim 1 , wherein an amount of ammonia contained in the decompressed waste solvent introduced into the distillation column is 400-1000 ppm, and an amount of ammonia contained in the purified waste solvent is 50 ppm or less.

3. The method of claim 1 , wherein an amount of ammonia contained in the purified waste solvent is 30 ppm or less.

4. The method of claim 1 , wherein the waste solvent is derived from supercritical waste liquid generated after a supercritical drying process.

5. The method of claim 1 , wherein a pH of the waste solvent after the decompression is 9.0-10.0.

6. The method of claim 1 , wherein the distillation is performed by a multi-stage distillation method involving 20-30 stages.

7. The method of claim 1 , wherein a ratio of a discharge rate by weight of steam discharged from the distillation column with respect to an inflow rate by weight of the waste solvent introduced into the distillation column is 0.01-0.07.

8. The method of claim 1 , wherein a reboiler output based on the inflow rate of 1 kg/hr of the waste solvent introduced into the distillation column is 200-700 W.

9. The method of claim 1 , wherein the distilling has a reflux ratio of 3-10.

10. The method of claim 1 , wherein a recovery rate of the purified solvent is 93% or greater.

11. The method of claim 1 , wherein no salt is formed in a cooling column during the distilling.

Assignees

• Lg Chemical Ltd

Inventors

• Choi Seung Won
• Jang Sung Keun
• Joo Eun Jung
• Lee Young Ho

Classifications

• B01D3/4205 Primary

  Reflux ratio control splitter · CPC title

• C01B33/1585 Primary

  Dehydration into aerogels · CPC title

• C07C29/80 Primary

  by distillation · CPC title

• C07C31/08

  Ethanol · CPC title

• B01D3/143

  by two or more of a fractionation, separation or rectification step · CPC title