阅读说明：本技术 一种烷基酚生产废水中的苯酚回收方法 (Method for recovering phenol in alkylphenol production wastewater ) 是由 余晶云 卢双 李兆忠 吴声晓 沈鸿基 邓冠亮 孙土贵 于 2021-07-20 设计创作，主要内容包括：本发明公开了一种烷基酚生产废水中的苯酚回收方法,将含酚废水和二氯甲烷同时通入萃取塔进行萃取分离,所述二氯甲烷自萃取塔塔顶流入并与下方进入的含酚废水进行逆向接触萃取含酚废水中的苯酚；萃取所得的苯酚-二氯甲烷溶液从萃取塔底部抽出并送入溶剂回收塔,进行苯酚和二氯甲烷分离；水溶液则从萃取塔顶抽出,送入脱水塔与共沸剂进行共沸精馏,以回收水溶液中残留的苯酚。本发明可以极大地回收苯酚,减少苯酚损耗,回收过程更为安全。(The invention discloses a method for recovering phenol in waste water from alkylphenol production, which comprises the steps of simultaneously introducing phenol-containing waste water and dichloromethane into an extraction tower for extraction and separation, wherein the dichloromethane flows from the top of the extraction tower and reversely contacts the phenol-containing waste water entering from the lower part of the extraction tower to extract phenol in the phenol-containing waste water; extracting the phenol-dichloromethane solution obtained by extraction from the bottom of the extraction tower, and sending the phenol-dichloromethane solution into a solvent recovery tower for separating phenol from dichloromethane; the aqueous solution is extracted from the top of the extraction tower and sent to a dehydration tower to carry out azeotropic distillation with the entrainer so as to recover the residual phenol in the aqueous solution. The invention can greatly recover phenol, reduce phenol loss and ensure safer recovery process.)

1. A phenol recovery method in waste water of alkylphenol production is characterized in that phenol-containing waste water and dichloromethane are simultaneously introduced into an extraction tower for extraction and separation, and the dichloromethane flows in from the top of the extraction tower and reversely contacts the phenol-containing waste water entering from the lower part to extract phenol in the phenol-containing waste water; extracting the phenol-dichloromethane solution obtained by extraction from the bottom of the extraction tower, and sending the phenol-dichloromethane solution into a solvent recovery tower for separating phenol from dichloromethane; the aqueous solution is extracted from the top of the extraction tower and sent to a dehydration tower to carry out azeotropic distillation with the entrainer so as to recover the residual phenol in the aqueous solution.

2. The method for recovering phenol from waste water of alkylphenol production as recited in claim 1, wherein the phenol-dichloromethane solution is distilled in a solvent recovery column, the dichloromethane is distilled from the top of the solvent recovery column, condensed and returned to a dichloromethane tank for reuse, and the phenol is extracted from the bottom of the solvent recovery column and sent to a storage tank for storage.

3. The method for recovering phenol from waste water from the production of alkylphenol as claimed in claim 1, wherein the water-entrainer solution in azeotropic distillation is distilled from the top of the dehydration column into the layering tank, and the layering is carried out by standing, water is discharged from the bottom of the tank, and the entrainer can be recycled.

4. The process according to claim 1, 2 or 3, wherein the azeotropic agent is dodecane.

5. The method for recovering phenol from waste water from the production of alkylphenol as claimed in claim 1 or 2, wherein the volume ratio of the phenol-containing waste water to methylene chloride is 1: 3-6.

6. The method for recovering phenol from waste water from the production of alkylphenol as claimed in claim 5, wherein the volume ratio of the phenol-containing waste water to methylene chloride is 1: 3.5-4.5.

7. The method for recovering phenol from waste water of alkylphenol production as set forth in claim 1, wherein the extraction conditions are: the temperature is 20-30 ℃, and the pressure is normal pressure.

8. The method for recovering phenol from waste water from the production of alkylphenol as claimed in claim 1, wherein the solvent recovery conditions are as follows: the temperature is 45-70 ℃, and the pressure is normal pressure.

9. The method for recovering phenol from waste water from the production of alkylphenol as claimed in claim 1, wherein the azeotropic distillation conditions are as follows: the temperature is 90-120 ℃, and the pressure is normal pressure.

Technical Field

The invention relates to wastewater treatment, in particular to a method for recovering phenol in alkylphenol production wastewater.

Background

The alkylphenol is produced by the reaction of phenol and olefin. However, because the raw material phenol contains a certain amount of water, during the distillation and dehydration process of the raw material, an azeotrope is formed between the phenol and the water, so that a large amount of phenol and water are distilled out from the top of the tower during the distillation and dehydration process, and the waste water contains a large amount of phenol, which not only causes a large amount of phenol loss, but also easily causes environmental pollution because the phenol in the waste water poisons bacteria in a sewage treatment biochemical system. Therefore, the treatment of phenol-containing wastewater is always a difficult problem in the production of alkylphenol and in the sewage treatment.

At present, the method for recovering phenol from waste water comprises the following steps: chemical precipitation method. Adding chemical agent to make the phenols in the waste water produce insoluble precipitate, separating and recovering, for example, the phenol-containing waste water and formaldehyde are reacted and condensed into phenolic resin. (II) ion exchange method. The best effect is to remove phenol by ion exchanger and adsorb and regenerate phenol by weak base anion exchange resin. ③ biological methods. The phenol-containing wastewater is treated by an activated sludge method, a biological filter method, an oxidation pond method and the like to reach dozens to hundreds of milligrams of phenol per liter, and then enters a common industrial wastewater station for purification treatment.

Disclosure of Invention

The invention aims to provide a method for recovering phenol in waste water in alkylphenol production.

In order to achieve the purpose, the invention provides the following technical scheme: a phenol recovery method in waste water of alkylphenol production, pass phenol-containing waste water and dichloromethane into the extraction column at the same time and extract and separate, said dichloromethane flows into and carries on the phenol-containing waste water that the reverse contact draws phenol in the phenol-containing waste water with the entering below from the top of the extraction column; extracting the phenol-dichloromethane solution obtained by extraction from the bottom of the extraction tower, and sending the phenol-dichloromethane solution into a solvent recovery tower for separating phenol from dichloromethane; the aqueous solution is extracted from the top of the extraction tower and sent to a dehydration tower to carry out azeotropic distillation with the entrainer so as to recover the residual phenol in the aqueous solution.

According to the similar compatibility principle, phenol can be dissolved in dichloromethane at normal temperature and normal pressure, and dichloromethane is difficult to be compatible with water. In the invention, dichloromethane is used as an extracting agent to extract phenol in the phenol-containing wastewater, most of phenol is separated from the phenol-containing wastewater, and the extracted phenol-dichloromethane solution enters a solvent recovery tower to separate phenol from dichloromethane; under normal pressure, the boiling point of the dichloromethane is 39.8 ℃ which is much lower than that of the phenol, thus being beneficial to distillation and recovery, leading the dichloromethane and the phenol to be completely separated and obtaining the phenol with higher purity. And the extracted water solution, namely raffinate, which contains a small amount of phenol and dichloromethane, enters a dehydration tower to be subjected to azeotropic distillation with an entrainer, and the residual phenol in the water solution is further recovered, so that the phenol in the phenol-containing wastewater is recovered to the maximum extent.

In the invention, the phenol-dichloromethane solution enters the solvent recovery tower for distillation, because dichloromethane has low boiling point and is easy to evaporate and vaporize, the phenol is distilled from the top of the solvent recovery tower, condensed and returned to the dichloromethane tank for reuse, and the phenol has high boiling point and is difficult to evaporate and vaporize, exists in the solvent recovery tower in a liquid state, and can be pumped out from the bottom of the solvent recovery tower and sent to a storage tank for storage.

The volume ratio of the phenol-containing wastewater to the dichloromethane is 1: 3-6.

The volume ratio of the phenol-containing wastewater to the dichloromethane is 1: 3.5-4.5.

The extraction conditions are as follows: the temperature is 20-30 ℃, and the pressure is normal pressure.

The solvent recovery conditions are as follows: the temperature is 45-70 ℃, and the pressure is normal pressure.

The invention selects the dodecane as the azeotropic agent, and because the azeotropic point of the dodecane-water azeotrope is lower than that of the phenol-water azeotrope, water and phenol are difficult to form an azeotrope, so that the dodecane and water form an azeotrope during azeotropic distillation, thereby separating water and phenol and realizing phenol recovery. And the dodecane is harmless to human bodies, has a flash point as high as 215-217 ℃, is not easy to catch fire, and improves the production safety.

In the invention, the volume ratio of the extracted aqueous solution to the dodecane is 1: 2.5-4; preferably 1:3.

The azeotropic distillation conditions are as follows: the temperature is 90-120 ℃, and the pressure is normal pressure.

Further, the water-entrainer solution in the azeotropic distillation is distilled out from the top of the dehydration tower and enters a layering tank, standing and layering are carried out, water is discharged from the bottom of the tank, and the entrainer can be recycled.

Compared with the prior art, the invention has the following beneficial effects:

1. the phenol recovery method provided by the invention uses dichloromethane as an extracting agent, and simultaneously introduces the dichloromethane and the phenol-containing wastewater into the extraction tower, and the dichloromethane flows in from the top of the extraction tower and reversely extracts phenol from the phenol-containing wastewater entering from the lower part of the extraction tower, and is separated from water. Extracting the lower layer of phenol and dichloromethane solution from the bottom of the extraction tower, introducing the extracted lower layer of phenol and dichloromethane solution into a solvent recovery tower, and recovering dichloromethane to obtain clean phenol; and the aqueous solution on the upper layer enters a dehydration tower for azeotropic rectification, and the residual phenol in the water is further recovered, so that the phenol in the phenol-containing wastewater is recovered to the maximum extent. The practical application of the inventor shows that the recovery rate of phenol is as high as 99.5%.

2. The invention selects the dichloromethane as the extracting agent, has low boiling point and larger difference with the boiling point of the phenol, is not possible under the common use condition, can carry out distillation recovery under the condition of lower temperature, has simple equipment in the recovery link and lower energy consumption.

3. The invention selects the dodecane as the entrainer, water and phenol are difficult to form an azeotrope in a dodecane system, but the dodecane and water are easy to form the azeotrope, so that extracted water is taken out azeotropically, and water and phenol are separated.

4. The invention selects the dodecyl alkane as the entrainer, the flash point of the dodecyl alkane is 71 ℃, and the dodecyl alkane is safer in the azeotropic distillation process.

5. The selected dodecane and the dichloromethane are low-toxicity solvents, so that the harm to the health of operators is reduced as much as possible.

Drawings

FIG. 1 is a phenol recovery system in waste water from alkylphenol production of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following specific embodiments and the accompanying drawings.

Example one

FIG. 1 shows a phenol recovery system used in the embodiment of the present invention. As shown in the drawing, an extraction column 1, a solvent recovery column 2 and a dehydration column 3 are provided from left to right. The dichloromethane tank 4 is connected with a feed inlet at the upper part of the extraction tower 1 through a pipeline and a material pump 6. The water outlet at the top of the extraction tower 1 is connected with the feed inlet at the middle part of the dehydration tower 3, and the discharge outlet at the bottom is connected with the solvent recovery tower 2 through a material pump 7 and a pipeline. An air outlet at the top of the solvent recovery tower 2 is connected with the dichloromethane tank 4 through a pipeline and a condenser 8, and the vaporized dichloromethane is condensed and then returned to the dichloromethane tank 4 for storage so as to be recycled. A discharge port at the bottom of the solvent recovery tower 2 is connected with a phenol storage tank through a material pump 10 and a pipeline, and the recovered phenol is conveyed to the phenol storage tank for storage. The gas outlet at the top of the dehydration tower 3 is connected with the layering tank 5 through a pipeline and a condenser 9, the dehydrated water and the entrainer are kept stand and separated in the layering tank 5, the entrainer on the upper layer can be returned to the dehydration tower 3 for recycling, and the water is purified and discharged.

Specifically, the phenol-containing wastewater and dichloromethane are simultaneously introduced into an extraction tower for extraction and separation, and the dichloromethane flows from the top of the extraction tower 1 and reversely contacts with the phenol-containing wastewater entering from the lower part of the extraction tower 1 to extract phenol in the phenol-containing wastewater and separate the phenol from the water. Since the density of dichloromethane is greater than that of water, the phenol-dichloromethane solution obtained by extraction is the lower solution, and the aqueous solution is the upper solution. The lower phenol-dichloromethane solution, i.e., the extract, is withdrawn from the bottom of the extraction column and sent to the solvent recovery column 2, where phenol and dichloromethane are separated by distillation. Because the boiling point of the dichloromethane is low, the dichloromethane is easy to evaporate and vaporize, the dichloromethane is distilled from the top of the solvent recovery tower, condensed and returned to the dichloromethane tank for reuse, and the phenol has high boiling point, is not easy to evaporate and vaporize, exists in the solvent recovery tower in a liquid state, and can be pumped out from the bottom of the solvent recovery tower 2 and sent to the phenol storage tank for storage. The upper aqueous solution, namely raffinate, is extracted from the top of the extraction tower 1 and sent into a dehydration tower 3 to be subjected to azeotropic rectification with an entrainer, namely, dodecane, so that the dodecane and water form an azeotrope, the azeotrope is discharged from the top of the tower, and the azeotrope is condensed and then enters a layering tank to be stood for layering. And the residual phenol in the aqueous solution is discharged from the bottom of the dehydration tower 3 and is conveyed to a phenol storage tank for storage. After the extraction and azeotropic distillation treatment, the recovery of phenol is over 99.5 percent, and the content of phenol in the discharged water is lower than 300 ppm.

In this example, the volume ratio of the phenol-containing wastewater to dichloromethane was 1: 4. The extraction conditions were: the temperature is 20-30 ℃, and the pressure is normal pressure. The conditions for solvent recovery were: the temperature is 40-70 ℃, and the pressure is normal pressure. The volume ratio of the extracted aqueous solution to the dodecane was 1:3. The azeotropic distillation conditions are as follows: the temperature is 90-120 ℃, and the pressure is normal pressure.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The above-described embodiments of the present invention are to be considered in all respects as illustrative and not restrictive. Any minor modifications, equivalent changes and modifications to the above embodiments in accordance with the essential technology of the present invention are within the scope of the technical solution of the present invention.