WO2015062189A1

WO2015062189A1 - Method and apparatus for recovering caprolactam in benzene distillation residue

Info

Publication number: WO2015062189A1
Application number: PCT/CN2014/072544
Authority: WO
Inventors: 白志山; 古文全; 张�杰; 刘文君
Original assignee: 华东理工大学
Priority date: 2013-11-01
Filing date: 2014-02-26
Publication date: 2015-05-07
Also published as: CN103539738A; CN104326982B; CN104326982A

Abstract

The present invention relates to a method and apparatus for recovering caprolactam in benzene distillation residue, and provides a method for recovering caprolactam in benzene distillation residue, comprising the following steps: (a) separately feeding into a centrifugal extractor the benzene distillation residue and water obtained after distillation in a benzene distillation column; (b) causing the benzene distillation residue and water fully to mix and undergo mass transfer in the centrifugal extractor, in order to extract the caprolactam in the benzene distillation residue into the water; (c) performing liquid-liquid separation of the mixed solution of benzene distillation residue and water by means of the centrifugal extractor, in order to separate an aqueous solution rich in caprolactam and the benzene distillation residue from which the caprolactam has been removed; and (d) recycling the aqueous solution rich in caprolactam separated out in step (c), and incinerating the benzene distillation residue from which the caprolactam has been removed. The apparatus for recovering caprolactam in benzene distillation residue is also provided.

Description

Method and device for recovering caprolactam in benzene vapor residue

The invention relates to a method and a device for recycling caprolactam in a benzene vapor residue of a caprolactam production device, and more particularly, the invention relates to extracting, separating and recovering a benzene vapor residue generated in a caprolactam production process by using a centrifugal extractor. Method and apparatus. Background technique

Caprolactam (CPL) is an important organic chemical raw material, mainly used as raw material for the production of polyamide 6 engineering plastics and polyamide 6 fiber. In addition, caprolactam can also be used to produce anti-platelet drug 6-aminocaproic acid to produce laurel Ketones, etc., are widely used. Although the production of caprolactam in China has increased in recent years, it still cannot meet the needs of the development of the chemical fiber industry and the plastic products industry, and the import volume is increasing. According to customs statistics, the average annual growth rate of imports in 2000-2005 was about 15.07%. China's caprolactam dependence is so high. One of the main reasons is that the development of caprolactam industry in China is facing technical difficulties. In May 2009, the “Detailed Rules for the Adjustment and Revitalization of Petrochemical Industry” issued by the State Council proposed to increase the key technology industries such as caprolactam. Input.

The caprolactam production process is long, the number of processes is large, the equipment is large, and the circulating materials are large, resulting in large consumption of raw materials, many by-products and intermediate products, difficulty in separation, large discharge of three wastes and high content of caprolactam. The 200,000 tonne/year caprolactam production unit will produce about 200 kg/h of benzene vapor residue in the benzene steaming process, and the caprolactam content is as high as 20-50%. Now, caprolactam production companies are mostly sold to other companies at low prices, or directly incinerated. Dealing with, resulting in great waste of resources, is not conducive to improving the competitiveness of enterprises. If this part of caprolactam is recycled, it will bring good economic benefits to the company.

Therefore, there is an urgent need in the art to develop a process for recovering benzene vapor residue in production to achieve the recovery and utilization of caprolactam, greatly reducing the loss of caprolactam in production, reducing the production cost and the burden of incineration treatment, and improving production efficiency, and is suitable for caprolactam or A new method for the recovery of benzene vapor residue in similar plants. Summary of the invention

The invention provides a novel method and a device for recovering caprolactam in a benzene vapor residue, which utilizes a centrifugal extractor to extract and separate caprolactam from a benzene vapor residue in caprolactam production, thereby effectively solving the loss of caprolactam in the benzene vapor residue. , improved the production of caprolactam and reduced environmental pollution, thus solving Problems in the prior art.

In one aspect, the invention provides a method of recovering caprolactam in a benzene vapor residue, the method comprising the steps of:

(a) feeding the benzene vapor residue and water after steaming the benzene steaming tower to the centrifugal extractor;

(b) allowing the benzene vapor residue and water to be thoroughly mixed and mass-transported in a centrifugal extractor so that the caprolactam in the benzene vapor residue is extracted into the water;

(c) performing a liquid-liquid separation of the mixture of the benzene vapor residue and the water using a centrifugal extractor to separate the aqueous solution rich in caprolactam and the benzene vapor residue from which caprolactam is removed;

(d) The caprolactam-rich aqueous solution separated in the step (c) is recycled, and the caprolactam benzene vapor residue incineration treatment is removed.

In a preferred embodiment, the crude oil produced by the amidation reaction is produced by benzene extraction and water extraction, and then distilled in a benzene distillation column; the main component is 20-50% caprolactam. 20 to 50% of benzene, and 2% of benzene-soluble impurities and water-soluble impurities, based on the weight of the benzene vapor residue.

In another preferred embodiment, the caprolactam-rich aqueous solution separated in the step (c) is returned to the benzene extraction column of the caprolactam refinery unit for recycling, and the benzene vapor residue of the caprolactam is removed and sent to the waste liquid for concentration. The device is incinerated.

In another preferred embodiment, the centrifugal extractor employs single-stage extraction or multi-stage countercurrent extraction; the volumetric flow rate of water as the extractant is 10-200% by volume of the volume flow rate of the benzene vapor residue.

In another preferred embodiment, in step (a), the benzene vapor residue and water after the distillation of the benzene vapor column are fed to the centrifugal extractor from different inlets.

In another preferred embodiment, in step (b), the benzene vapor residue and water are thoroughly mixed and mass transferred between the high speed rotating inner cylinder of the centrifugal extractor and the stationary outer cylinder.

In another aspect, the present invention provides a device for recovering caprolactam in a benzene vapor residue, the device comprising: a centrifugal extractor for receiving a benzene vapor residue and water after steaming of a benzene distillation column connected thereto; The benzene vapor residue and water are thoroughly mixed and mass-transported so that the caprolactam in the benzene vapor residue is extracted into water; and the liquid mixture-liquid separation of the benzene vapor residue and the water is separated to separate the caprolactam-rich The aqueous solution and the benzene vapor residue from which caprolactam was removed.

In a preferred embodiment, the apparatus further comprises a benzene extraction column connected to the centrifugal extractor for recycling the separated caprolactam-rich aqueous solution; and a waste liquid concentrating device connected to the centrifugal extractor. The benzene vapor residue from which caprolactam has been removed is concentrated and incinerated. In another preferred embodiment, the centrifugal extractor has a motor speed of 100-3000 r/min. In another preferred embodiment, the centrifugal extractor has an operating temperature of from 50 ° C to 130 ° C.

DRAWINGS

The objects and features of the present invention will become more apparent from the detailed description of the accompanying claims

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the process of extracting and separating caprolactam from a benzene vapor residue in a centrifugal extractor according to an embodiment of the present invention.

Fig. 2 is a schematic view showing the process of extracting and separating caprolactam in a benzene vapor residue according to another embodiment of the present invention. detailed description

The inventors of the present application discovered during the long-term engineering practice and experimental research:

In the production process of caprolactam, the benzene vapor residue contains a higher content of caprolactam, and the caprolactam production enterprises mostly sell their low price to other enterprises or incinerate, resulting in great waste of resources, which is not conducive to improving the competitiveness of enterprises;

Centrifugal extraction technology is a new type of extraction and separation technology developed in recent years. It has the characteristics of compact structure, large processing capacity, stable operation, low power consumption, convenient cleaning and maintenance, etc. Since centrifugal force usually reaches several hundred times of gravity, centrifugal extraction separator It is especially suitable for the treatment of systems with small density difference between two phases, high viscosity and easy emulsification. For example, the separation of gravity phase separation requires a two-phase density difference of more than 0.1 g/cm ³ , while in a centrifugal extractor, the density difference between two phases can be as small as 0.01g/cm ³ _{; General} equipment is difficult to mix for systems with large density difference or high viscosity of two phases, and the centrifugal extractor has a powerful mixing function, which can fully mix the two-phase flow, making the two-phase flow easy. The reaction or mass transfer is carried out; and the system with small difference in specific gravity or large viscosity is easy to separate; the mixing and separation of the mixture in the centrifugal extractor is almost simultaneously performed in one apparatus, and the separation effect is particularly good. Therefore, product quality can be improved and product yield can be increased, the process can be simplified, and the production cost can be reduced; therefore, the above-mentioned caprolactam waste is utilized. The problem of heavy weight can be achieved by mixing, mass transfer and separation of the benzene vapor residue and water in a centrifugal extractor by using a water washing method, and returning the separated caprolactam-rich aqueous solution to the benzene extraction column of the caprolactam refining unit. Recycling, removing the benzene vapor residue of caprolactam into the waste liquid concentration device and incinerating;

The above separation uses a centrifugal extractor to extract and separate the benzene vapor residue in the production of caprolactam. The lactam takes into account the advantages of large flexibility, no clogging, short separation time and high efficiency of the centrifugal extractor. The caprolactam in the benzene vapor residue is separated by water washing, which improves the utilization rate and reduces the pollution. Economic and social benefits.

Based on the above findings, the present invention has been completed.

The technical idea of the present invention is as follows:

Generally, the system is difficult to mix for a system with a large difference in density between two phases or a large viscosity, and the centrifugal extractor has a powerful mixing function, so that the two-phase stream can be thoroughly mixed, so that the two-phase stream can be easily reacted or mass-transferred; For systems with small specific gravity difference or high viscosity, separation is easy. The mixing and separation of the mixture in the centrifugal extractor is almost simultaneously performed in one equipment, and the separation effect is particularly good, thus improving product quality and The product yield is increased, the process is simplified, and the production cost is reduced. The invention fully considers the advantages of large flexibility, no clogging, short separation time and high efficiency of the centrifugal extractor, and the extraction and separation of caprolactam in the benzene vapor residue by a centrifugal extractor is performed. The loss of caprolactam is reduced.

In a first aspect of the invention, there is provided a method of recovering caprolactam in a benzene vapor residue, the method comprising the steps of:

(a) the benzene vapor residue discharged from the benzene distillation column enters the inlet of one end of the centrifugal extractor, and the water enters the inlet of the other end of the centrifugal extractor;

(b) mixing the benzene vapor residue with water in a centrifugal extractor and mass transfer, so that the caprolactam in the benzene vapor residue enters the water;

(c) a mixture of the benzene vapor residue and water is subjected to liquid-liquid separation in a centrifugal extractor to form an aqueous solution rich in caprolactam and a benzene vapor residue from which caprolactam is removed;

(d) The benzene vapor residue from which caprolactam has been removed is sent to a waste liquid concentration device for incineration treatment, and the aqueous solution rich in caprolactam is returned to the benzene extraction column of the caprolactam refinery unit for recycling.

In the present invention, the crude oil produced by the amidation reaction of the benzene vapor residue is produced by benzene extraction and water extraction and then steaming in a benzene distillation tower, and the main component thereof is: about 20 to 50% of caprolactam. About 20 to 50% of benzene and about 2% of benzene-soluble impurities and water-soluble impurities, based on the weight of the benzene vapor residue.

In the present invention, caprolactam in the benzene vapor residue is recovered by a water washing method.

In the present invention, the volume flow rate of water as an extractant is 10-200 volumes of the volume flow rate of the benzene vapor residue.

In a second aspect of the invention, there is provided a device for recovering caprolactam in a benzene vapor residue, the device comprising: a centrifugal extracting machine for receiving the benzene vapor residue and water after steaming of the benzene distillation tower connected thereto; fully mixing and massing the benzene vapor residue and water to make caprolactam in the benzene vapor residue Extracted into water; and liquid-liquid separation of the mixture of benzene vapor residue and water, separating the aqueous solution rich in caprolactam and the benzene vapor residue from caprolactam.

In the present invention, the centrifugal extractor comprises a motor, a stationary outer cylinder, a high-speed rotating inner cylinder, an inlet for supplying benzene vapor residue, an inlet for supplying water, and one for The outlet of the benzene vapor residue from which caprolactam is removed is discharged, and an outlet for discharging the aqueous solution containing caprolactam is discharged.

In the present invention, there is no particular limitation on the centrifugal extractor to be used, and those skilled in the art can determine whether the centrifugal extractor adopts single or multiple stages according to the actual separation effect, in order to achieve the desired effect.

In the present invention, the centrifugal extractor is an apparatus which integrates mixing and separation and separates by centrifugal force. The structural characteristics and principles of the centrifugal extractor can be found in Chinese patents ZL 96250989.2, ZL 200720103434.X, etc.

In the present invention, the working speed of the centrifugal extractor is not particularly limited in principle, and those skilled in the art can make flexible selections according to actual needs according to actual production needs, generally at 100-3000 r/min, preferably 700-3000 rpm. The scope.

In the present invention, the operating temperature of the centrifugal extractor is not particularly limited in principle, and those skilled in the art can make flexible selections according to actual needs according to actual production needs, generally at 50 ° C to 130 ° C, preferably 60. °C ~ 70 ° C range.

The structure and method of the device of the present invention will be described in detail below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the process of extracting and separating caprolactam from a benzene vapor residue in a centrifugal extractor according to an embodiment of the present invention. As shown in Fig. 1, the benzene vapor residue from the benzene steaming tower 2 flows by gravity into the inlet of the centrifugal extractor 1, and the water (water washing water) enters the other inlet of the centrifugal extractor 1, and the benzene vapor residue and water enter. After centrifuging the extractor 1, the mixture is thoroughly mixed and mass-transferd, and the caprolactam in the benzene vapor residue is introduced into the water. The benzene and the oil-soluble impurities are sent to the waste liquid concentration device for incineration treatment as a waste liquid; the aqueous solution rich in caprolactam is returned to the caprolactam refining process. The benzene extraction column of the unit is reused as a raw material, and the benzene from the benzene distillation column 2 is returned to the benzene extraction column of the caprolactam refining unit, and is reused as a raw material.

2 is a schematic view showing a process of extracting and separating caprolactam in a benzene vapor residue according to another embodiment of the present invention. As shown in Fig. 2, the crude oil enters the benzene extraction column 4 through the upper inlet of the benzene extraction column 4, and the benzene is pumped into the benzene extraction column 4 through the lower inlet of the benzene extraction column 4 through the pump 3; after extraction in the benzene extraction column 4, benzene The caprolactam and the oil-soluble impurities are discharged through the upper outlet of the benzene extraction column 4, and enter the water extraction column 5 through the lower inlet of the water extraction column 5, and the raffinate It is discharged through the lower outlet of the benzene extraction column 4; the washing water is washed into the water extraction column 5 through the upper inlet of the water extraction column 5 for water washing; the caprolactam-rich benzene and the oil-soluble impurities are discharged through the upper outlet of the water extraction column 5, and are distilled by benzene. The inlet of the column 2 enters the benzene distillation column 2, and the water and caprolactam are discharged through the lower outlet of the water extraction column 5; the benzene vapor residue from the lower outlet of the benzene distillation column 2 flows by gravity into the centrifugal extraction machine 1 At the inlet, the washing water enters the other inlet of the centrifugal extractor 1, and the benzene vapor residue and water enter the centrifugal extractor 1 to be thoroughly mixed and mass-transferd, so that the caprolactam in the benzene vapor residue enters the water, and the benzene and the oil-soluble impurities act as The waste liquid is sent to a waste liquid concentrating device for incineration treatment; the aqueous solution rich in caprolactam is returned to the benzene extraction column 4 of the caprolactam refinery unit, and reused as a raw material (recycling of water and caprolactam), and benzene from the benzene steaming tower 2 is also used. The benzene extraction column 4 returned to the caprolactam refining unit is reused as a raw material. The main advantages of the invention are:

(i) The present invention uses a centrifugal extractor to extract and separate caprolactam from the benzene vapor residue in caprolactam production, which overcomes the problem that it is difficult to recycle caprolactam in the benzene vapor residue by the existing separation technique, and reduces the load of incineration treatment. , saving energy consumption;

(ii) The device of the present invention has a simple structure, is easy to implement, is easy to operate, and is suitable for long-cycle operation;

(iii) The device of the present invention has a small investment, a small size, and a small footprint. Example

The invention is further illustrated by the following specific examples. However, it is to be understood that the examples are not intended to limit the scope of the invention. The test methods for which specific conditions are not specified in the following examples are usually carried out according to conventional conditions or according to the conditions recommended by the manufacturer. All percentages and parts are by weight unless otherwise indicated. Example L

In a 200t/year benzene vapor residue recovery device, according to the separation process of the amidation reaction liquid shown in FIG. 1, the caprolactam in the benzene vapor residue is separated and recovered by the method of the present invention, thereby achieving high efficiency and high efficiency. Accuracy, low energy consumption, the purpose of recovering caprolactam in the benzene vapor residue, the economic benefit of caprolactam recovery is greatly improved, and environmental problems are solved. The specific operation process and effects are as follows:

Material properties

(1) Benzene vapor residue: The material is a mixture of an organic phase and an inorganic phase, and the content of caprolactam is about 40%. The rated flow rate is 2t/h, the temperature is 60-80 ° C, and the average is about 70 ° C.

(2) Washing water: The flow rate is 20% by volume of the benzene vapor residue, 0.4t/h, and the temperature is 50-60°C, and the average is about 57°C.

2. The motor speed of the centrifugal extractor is 900r/min.

3. Method for determination of content: Meteorological chromatography was used.

4. Application effect

(1) Adding water washing water 0.4t/h, the content of caprolactam in the benzene vapor residue after separation is less than 5%, and the caprolactam content in water is not less than 50%.

(2) Recycling 76 tons of caprolactam per year reduces the loss of caprolactam and avoids environmental pollution, thereby improving economic and social benefits.

(3) Reduce the incineration load and effectively save energy. Example 2:

In a 200t/year benzene vapor residue recovery device, according to the separation process of the amidation reaction liquid shown in Fig. 1, the caprolactam in the benzene vapor residue is separated and recovered by the method of the invention, thereby achieving high efficiency and high precision. The low energy consumption completes the recovery of caprolactam in the benzene vapor residue, which greatly improves the economic benefit of caprolactam recovery and solves environmental problems. The specific operation process and effects are as follows:

Material properties

(1) Benzene vapor residue: The material is a mixture of an organic phase and an inorganic phase, and the content of caprolactam is about 40%. The rated flow rate is 2t/h, the temperature is 60-80 °C, and the average is about 70 °C.

(2) Washing water: The flow rate is 50% by volume of the benzene vapor residue, which is 1.0 t/h, and the temperature is 50-60 ° C, and the average is about 57 ° C.

2. The motor speed of the centrifugal extractor is 900r/min.

3. Method for determination of content: Meteorological chromatography was used.

4. Application effect

(1) Add 1.0 t/h of water washing water, and the content of caprolactam in the benzene vapor residue after separation is less than 3%, and the caprolactam content in water is not less than 45%.

(2) Recycling 77.6 tons of caprolactam annually reduces the loss of caprolactam and avoids environmental pollution, thereby improving economic and social benefits.

(3) Reduce the incineration load and effectively save energy. Example 3:

Material properties

(2) Washing water: The flow rate is 100% by volume of the benzene vapor residue, which is 2.0 t/h, and the temperature is 50-60 ° C, and the average is about 57 ° C.

2. The motor speed of the centrifugal extractor is 900r/min.

3. Method for determination of content: Meteorological chromatography was used.

4. Application effect

(1) Adding water wash water 2.0t/h, the content of caprolactam in the benzene vapor residue after separation is less than 1.5%, and the caprolactam content in water is not less than 40%.

(2) Recycling 78.8 tons of caprolactam per year reduces the loss of caprolactam and avoids environmental pollution, thereby improving economic and social benefits.

(3) Reduce the incineration load and effectively save energy. All documents mentioned in the present application are hereby incorporated by reference in their entirety in their entireties in the the the the the the the the the In addition, it is to be understood that various modifications and changes may be made by those skilled in the art in the form of the appended claims.

Claims

Rights request

A method for recovering caprolactam in a benzene vapor residue, the method comprising the steps of:

(b) thorough mixing and mass transfer of the benzene vapor residue and water in a centrifugal extractor to extract caprolactam from the benzene vapor residue into water;

The method according to claim 1, wherein the crude oil produced by the amidation reaction is produced by benzene extraction and water extraction, and then steamed in a benzene steaming tower; the main component is 20 to 50% of caprolactam, 20 to 50% of benzene, and 2% of benzene-soluble impurities and water-soluble impurities, based on the weight of the benzene vapor residue.

3. The method according to claim 1, wherein the caprolactam-rich aqueous solution separated in the step (c) is returned to the benzene extraction column of the caprolactam refining unit for recycling, and the caprolactam benzene vapor residue is removed. It is sent to the waste liquid concentration device and incinerated.

4. The method according to claim 1, wherein the centrifugal extractor adopts single-stage extraction or multi-stage countercurrent extraction; and the volume flow rate of water as the extractant is 10-200 volumes of the volume flow rate of the benzene vapor residue. %.

The method according to claim 1, wherein in the step (a), the benzene vapor residue and water after the distillation of the benzene distillation column are separately fed into the centrifugal extractor from different inlets.

6. The method according to claim 1, wherein in step (b), the benzene vapor residue and water are sufficiently mixed and transferred between the high-speed rotating inner cylinder and the stationary outer cylinder of the centrifugal extractor. quality.

7. A device for recovering caprolactam in a benzene vapor residue, the device comprising:

The centrifugal extracting machine (1) is configured to receive the benzene steaming tower and the water after the steaming of the benzene steaming tower (2) connected thereto; to fully mix and mass transfer the benzene steaming liquid and water to steam the benzene The caprolactam in the raffinate is extracted into water; and the liquid mixture of the benzene vapor residue and the water is subjected to liquid-liquid separation, and the caprolactam-rich aqueous solution and the caprolactam-removed benzene vapor residue are separated.

8. The apparatus according to claim 7, further comprising a benzene extraction column (4) connected to the centrifugal extractor (1) for recycling the separated caprolactam-rich aqueous solution; as well as A waste liquid concentrating device connected to the centrifugal extractor (1) for concentrating the benzene vapor residue from which caprolactam has been removed and incinerating.

9. Apparatus according to claim 7, characterized in that the centrifugal extractor (1) has a motor speed of 100-3000 r/min.

10. Apparatus according to claim 7, wherein the operating temperature of the centrifugal extractor (1) is

50 ° C ~ 130 ° C.