CN108358808B - Method for recovering dimethylacetamide in waste oil of cyclohexanone device - Google Patents
Method for recovering dimethylacetamide in waste oil of cyclohexanone device Download PDFInfo
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- CN108358808B CN108358808B CN201810167861.7A CN201810167861A CN108358808B CN 108358808 B CN108358808 B CN 108358808B CN 201810167861 A CN201810167861 A CN 201810167861A CN 108358808 B CN108358808 B CN 108358808B
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Abstract
The invention provides a method for recovering dimethylacetamide in waste oil of a cyclohexanone device, which comprises the step of separating cyclohexane and dimethylacetamide in the waste oil of the cyclohexanone device by taking water or a mixture of water and ethanol as an entrainer and adopting a method combining azeotropic distillation and reduced pressure distillation to obtain a dimethylacetamide product with the mass concentration of more than or equal to 99.9 wt%. The method for recovering the dimethylacetamide in the waste oil of the cyclohexanone device has the advantages of simple process operation and high separation precision, not only can improve the recovery and utilization of the dimethylacetamide, but also can recover light components mainly comprising cyclohexanol for reproduction, and simultaneously reduces the waste oil discharge and the environmental pollution.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a method for recovering dimethylacetamide in waste oil of a cyclohexanone device.
Background
Dimethylacetamide is a widely used industrial raw material, and is commonly used in petroleum processing and organic synthesis industries. As an aprotic polar solvent, dimethylacetamide is a good solvent for many organic synthesis reactions. At present, dimethyl acetamide is commonly used as an extracting agent in a domestic cyclohexanone device to separate and purify cyclohexene raw materials. In the production process of cyclohexanone, various side reactions can occur, so that the extracting agent contains various impurities, and when the cyclohexene is separated and purified through extraction and rectification and the extracting agent is recycled, part of the extracting agent can enter waste oil to cause loss.
Cyclohexanol is the main component in waste oil of cyclohexanone production device, and its boiling point is 161 ℃. The boiling point of the dimethylacetamide is 166 ℃, the two have similar polarity and belong to a near-boiling-point mixture, and the dimethylacetamide product with high purity is difficult to separate by adopting common rectification.
Azeotropic distillation is a common method of separating similarly polar and near boiling systems. The screening of the entrainer is the key of the azeotropic distillation process, is related to the difficulty degree of the azeotropic distillation process, and is a fundamental way for improving the production capacity of the azeotropic distillation and reducing the energy consumption.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for recovering dimethylacetamide in waste oil of a cyclohexanone device, so as to overcome the defects of the prior art, wherein an azeotropic distillation process is adopted to separate cyclohexanol from dimethylacetamide, and then a high-purity dimethylacetamide product is obtained by vacuum distillation, such that operation cost of the cyclohexanone device can be reduced, environmental pollution caused by waste oil is reduced, and good economic benefit and environmental benefit are provided.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a method for recovering dimethylacetamide in waste oil of a cyclohexanone device comprises the step of separating cyclohexane and dimethylacetamide in the waste oil of the cyclohexanone device by taking water or a mixture of water and ethanol as an entrainer and adopting a method combining azeotropic distillation and reduced pressure distillation to obtain a dimethylacetamide product with the mass concentration of more than or equal to 99.9 wt%.
Preferably, when the entrainer is water, the method comprises the following steps:
(1) feeding waste oil raw materials containing cyclohexanol, dimethylacetamide, heavy components and trace light components into an azeotropic distillation tower, and performing azeotropic distillation by using water as an azeotropic agent;
(2) the water phase of the material at the top of the azeotropic distillation tower separated by the oil-water separator returns to the azeotropic distillation tower for recycling, and the oil phase material is returned to the cyclohexanone device; and (3) the tower bottom recombination of the azeotropic distillation tower is sent to a de-heavy tower to be separated by vacuum distillation to obtain the dimethylacetamide with the mass concentration of more than or equal to 99.9 wt%.
Preferably, the number of theoretical plates of the azeotropic distillation tower is more than or equal to 20, preferably 20-30, and the feeding position is 2-5 theoretical plates; the number of theoretical plates of the de-weighting tower is more than or equal to 35, preferably 35-45, and the feeding position is 18-25 theoretical plates.
Preferably, the azeotropic distillation tower is operated in vacuum, the operating pressure of the distillation tower is 5-20 kPaA, the reflux ratio is 10-15, the temperature of the top of the tower is 40-58 ℃, and the temperature of the bottom of the tower is 110-130 ℃.
Preferably, the de-heavy tower is operated in vacuum, the reflux ratio is 3.0-6.0, the operating pressure of the rectifying tower is 5-20 kPaA, the temperature of the top of the tower is 100-120 ℃, and the temperature of the bottom of the tower is 140-170 ℃.
Preferably, in the step (1), the mass flow ratio of the entrainer to the raw material liquid is 3.0-7.0; in the step (2), condensing the light components at the top of the azeotropic distillation tower, sending the light components into an oil-water separator, carrying out liquid-liquid delamination, returning the water phase materials to the azeotropic distillation tower for recycling, and sending the oil phase materials back to the cyclohexanone device.
Preferably, when the entrainer is a mixture of water and ethanol, the following steps are included:
(1) feeding waste oil raw materials containing cyclohexanol, dimethylacetamide, heavy components and trace light components into an azeotropic distillation tower, and performing azeotropic distillation by using ethanol and water as binary azeotropic agents;
(2) the material at the top of the azeotropic distillation tower is sent to an entrainer recovery tower, an ethanol product containing a small amount of water is obtained by the separation at the top of the entrainer recovery tower, a product mainly comprising cyclohexanol and water is obtained by the separation at the bottom of the entrainer recovery tower, and the cyclohexanol product meeting the requirements is obtained by the separation of an oil-water separator and sent back to a cyclohexanone device;
(3) collecting a water phase product obtained after oil-water separation of the top product of the entrainer recovery tower and the tower kettle and returning the water phase product to the azeotropic distillation tower for recycling; and (3) sending the heavy component in the azeotropic distillation tower to a de-heavy tower for vacuum distillation and separation to obtain dimethylacetamide with the mass concentration of more than or equal to 99.9 wt%.
Preferably, the number of theoretical plates of the azeotropic distillation tower is more than or equal to 28, the number of theoretical plates of the entrainer recovery tower is more than or equal to 25, and the number of theoretical plates of the de-heavy tower is more than or equal to 35; preferably, the number of the theoretical plates of the azeotropic distillation tower is 28-36, the feeding position of the raw material is 10-18 theoretical plates, and the feeding position of the entrainer is 1-5 theoretical plates; the number of theoretical plates of the de-weighting tower is 35-45, and the feeding position is 18-25 theoretical plates; the number of theoretical plates of the entrainer recovery tower is 25-35, and the feeding position is 12-18 theoretical plates.
Preferably, the mass flow ratio of the entrainer to the raw material liquid is 1.0-5.0; the mass ratio of water to ethanol in the entrainer is 1.0-10.0; in the step (3), the water phase product is water containing a small amount of cyclohexanol.
Preferably, the azeotropic distillation tower is operated in vacuum, the operating pressure of the distillation tower is 20-40 kPaA, the reflux ratio is 1-5, the temperature of the top of the tower is 50-60 ℃, and the temperature of the bottom of the tower is 115-150 ℃; the entrainer recovery tower is operated under normal pressure, the reflux ratio is 2.0-8.0, the operating pressure of the rectifying tower is 101kPaA, the temperature of the top of the tower is 70-85 ℃, and the temperature of the bottom of the tower is 90-110 ℃; the de-heavy tower is operated in vacuum, the reflux ratio is 3.0-6.0, the operating pressure of the rectifying tower is 5-20 kPaA, the temperature of the top of the tower is 100-120 ℃, and the temperature of the bottom of the tower is 140-170 ℃; preferably, the operating pressure of the azeotropic distillation tower is 20-30 kPaA.
Compared with the prior art, the method for recovering dimethylacetamide in waste oil of the cyclohexanone device has the following advantages:
the method for recovering the dimethylacetamide in the waste oil of the cyclohexanone device utilizes azeotropic distillation and reduced pressure distillation to separate and recover the dimethylacetamide in the waste oil of the cyclohexanone device, so that a dimethylacetamide product meeting the purity requirement can be obtained, the process is simple, the dimethylacetamide in the waste oil is recovered, the cost is reduced, the pollution to the environment is reduced, and the method can be used in industrial production.
The method for recovering dimethylacetamide in the waste oil of the cyclohexanone device adopts water or ethanol and water as an entrainer for azeotropic distillation and separation of a near-boiling-point system of cyclohexanol and dimethylacetamide which are main components in the waste oil of the cyclohexanone device, so that a high-purity dimethylacetamide product is obtained, loss of dimethylacetamide is reduced, running cost of the device is reduced, and environmental pollution is reduced.
Drawings
FIG. 1 is a process flow diagram of the present invention using water as the entrainer;
FIG. 2 is a process flow diagram of the present invention using water and ethanol as the binary entrainer.
Reference numerals in fig. 1:
t1141-azeotropic distillation column; t1142-heavy component removing tower; e1141-azeotropic distillation tower kettle reboiler; e1142-azeotropic distillation tower top condenser; e1143-reboiler of heavy component removing tower kettle; e1144-heavy component removing overhead condenser; e1145-a de-weighting tower kettle cooler; v1141-azeotropic distillation tower top buffer tank; v1142-azeotropic distillation tower top oil-water separator; v1143-azeotropic distillation tower top reflux tank; v1144-heavy column top reflux drum takes off; a P1141A/B-azeotropic distillation tower kettle extraction pump; a P1142A/B-azeotropic distillation tower top extraction pump; a reflux pump at the top of the P1143A/B-azeotropic distillation tower; P1144A/B-heavy component removing tower kettle extraction pump; P1145A/B-heavy-component-removing tower top extraction pump; VP 1141A/B-vacuum pump of azeotropic distillation tower; VP 1142A/B-vacuum pump of de-heavy column.
Reference numerals in fig. 2:
t1141-azeotropic distillation column; t1142-entrainer recovery column; t1143-heavy component removing tower; e1141-azeotropic distillation tower kettle reboiler; e1142-azeotropic distillation tower top condenser; e1143-reboiler of the entrainer recovery tower kettle; e1144-entrainer recovery tower kettle cooler; e1145-entrainer recovery overhead condenser; e1146-reboiler of heavy component removing tower kettle; e1147-a product cooler of the de-weighting tower kettle; e1148-a de-heavy tower top condenser; v1141-azeotropic distillation tower top buffer tank; v1142-entrainer recovery tower top buffer tank; v1143-oil-water separator in the entrainer recovery tower kettle; v1144-azeotropic distillation tower top reflux tank; v1145-heavy column top reflux drum; a P1141A/B-azeotropic distillation tower kettle extraction pump; a P1142A/B-azeotropic distillation tower top extraction pump; a P1143A/B-entrainer recovery tower kettle extraction pump; a P1144A/B-entrainer recovery tower top extraction pump; a reflux pump at the bottom of the P1145A/B-azeotropic distillation tower; P1146A/B-heavy component removing tower kettle extraction pump; P1147A/B-heavy-component-removing tower top extraction pump; VP 1141A/B-vacuum pump of azeotropic distillation tower; VP 1142A/B-vacuum pump of de-heavy column.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
All numerical designations such as pH, temperature, time, concentration, including ranges, are approximations. It is to be understood, although not always explicitly stated that all numerical designations are preceded by the term "about". It is also to be understood that, although not always explicitly recited, the reagents described herein are merely exemplary and equivalents thereof are known in the art.
The present invention will be described in detail with reference to the following examples and accompanying drawings.
The operating pressures described herein are absolute pressures.
A method for recovering dimethylacetamide in waste oil of a cyclohexanone device comprises the step of separating cyclohexane and dimethylacetamide in the waste oil of the cyclohexanone device by taking water or a mixture of water and ethanol as an entrainer and adopting a method combining azeotropic distillation and reduced pressure distillation to obtain a dimethylacetamide product with the mass concentration of more than or equal to 99.9 wt%.
1. When the entrainer is water, the method comprises the following steps:
(1) feeding waste oil raw materials containing cyclohexanol, dimethylacetamide, heavy components and trace light components into an azeotropic distillation tower, and performing azeotropic distillation by using water as an azeotropic agent;
(2) extracting cyclohexanol and azeotropic agent water in the waste oil in an azeotrope form and trace light components from the top of the azeotropic distillation tower, separating by an oil-water separator, returning a water phase part to the azeotropic distillation tower for recycling, and sending an organic phase (namely an oil phase) mainly containing cyclohexanol to a cyclohexanone device for reproduction; and (3) delivering the dimethylacetamide and heavy components in the waste oil from the tower bottom of the azeotropic distillation tower to a de-heavy tower, and carrying out vacuum distillation and separation to obtain a dimethylacetamide product with high purity (the mass concentration is more than or equal to 99.9 wt%).
The azeotropic agent adopts water, and the boiling point of the formed azeotrope is obviously reduced due to the azeotrope formed by the water and cyclohexanol in the waste oil, and the formed azeotrope is distilled out from the top of the tower in the form of azeotrope in the rectification process.
The number of theoretical plates of the azeotropic distillation tower is 20-30, and the feeding position is 2-5 theoretical plates; the number of theoretical plates of the de-weighting tower is 35-45, and the feeding position is 18-25 theoretical plates.
The azeotropic distillation tower is operated in vacuum, the operating pressure of the distillation tower is 5-20 kPaA, the reflux ratio is 10-15, the temperature of the top of the tower is 40-58 ℃, and the temperature of the bottom of the tower is 110-130 ℃. Under the condition, a cyclohexanol (containing 9.3 wt%) product with the mass concentration of 90% and water (containing 1.8 wt%) with the mass concentration of 97.5% can be obtained after the tower top of the azeotropic distillation tower passes through an oil-water separator. And returning the separated water to the azeotropic distillation tower for recycling.
The de-heavy tower is operated in vacuum, the reflux ratio is 3.0-6.0, the operating pressure of the rectifying tower is 5-20 kPaA, the temperature of the top of the tower is 100-120 ℃, and the temperature of the bottom of the tower is 140-170 ℃. Under the condition, a dimethylacetamide product with the mass concentration of 99.9 percent can be obtained at the top of the tower.
In the step (1), the mass flow ratio of the entrainer to the raw material liquid is 3.0-7.0; in the step (2), condensing the light components at the top of the azeotropic distillation tower, sending the light components into an oil-water separator, carrying out liquid-liquid delamination, returning the water phase materials to the azeotropic distillation tower for recycling, and sending the oil phase materials back to the cyclohexanone device.
2. When the entrainer is a mixture of water and ethanol, the method comprises the following steps:
(1) feeding waste oil raw materials containing cyclohexanol, dimethylacetamide, heavy components and trace light components into an azeotropic distillation tower, and performing azeotropic distillation by using ethanol and water as binary azeotropic agents;
(2) cyclohexanol and azeotropic agent 'ethanol + water' in waste oil are extracted from the top of the azeotropic distillation tower in an azeotrope form together with trace light components, and are sent to an azeotropic agent recovery tower, and an ethanol product containing a small amount of water is obtained by separation from the top of the azeotropic agent recovery tower; separating the azeotropic agent recovery tower kettle to obtain a product mainly containing cyclohexanol and water, separating the product by an oil-water separator to obtain a cyclohexanol product meeting the requirement, and sending the cyclohexanol product back to the cyclohexanone device;
(3) collecting a water phase product obtained after oil-water separation of the top product of the entrainer recovery tower and the tower kettle and returning the water phase product to the azeotropic distillation tower for recycling; and (3) sending the heavy component in the azeotropic distillation tower to a de-heavy tower for vacuum distillation and separation to obtain dimethylacetamide with the mass concentration of more than or equal to 99.9 wt%.
The binary azeotropic agent 'ethanol + water' and cyclohexanol in waste oil form azeotrope, so that the boiling point of the formed azeotrope is obviously reduced, and the formed azeotrope is distilled out from the top of the tower in the form of azeotrope in the rectification process.
The number of theoretical plates of the azeotropic distillation tower is 28-36, the feeding position of the raw material is 10-18 theoretical plates, and the feeding position of the entrainer is 1-5 theoretical plates; the number of theoretical plates of the de-weighting tower is 35-45, and the feeding position is 18-25 theoretical plates; the number of theoretical plates of the entrainer recovery tower is 25-35, and the feeding position is 12-18 theoretical plates.
The mass flow ratio of the entrainer to the raw material liquid is 1.0-5.0; the mass ratio of water to ethanol in the entrainer is 1.0-10.0; in the step (3), the water phase product is water containing a small amount of cyclohexanol.
The azeotropic distillation tower is operated in vacuum, the operating pressure of the distillation tower is 20-40 kPaA, the reflux ratio is 1-5, the temperature of the top of the tower is 50-60 ℃, and the temperature of the bottom of the tower is 115-150 ℃. Under the condition, the content of the dimethylacetamide + heavy components in the product at the bottom of the azeotropic distillation tower is more than or equal to 99.97 wt%.
The entrainer recovery tower is operated under normal pressure, the reflux ratio is 2.0-8.0, the operating pressure of the rectifying tower is 101kPaA, the temperature of the top of the tower is 70-85 ℃, and the temperature of the bottom of the tower is 90-110 ℃. Under the condition, ethanol (93.45 wt%) and water (6.54 wt%) products are obtained by separating the top of the entrainer recovery tower, and oil phase products with the mass fraction of cyclohexanol (containing water) being more than or equal to 91 wt% are obtained by separating products at the bottom of the tower through an oil-water separator. And (3) returning the water-phase product obtained after the azeotropic agent recovery tower top product and the tower bottom oil phase separator are separated to the azeotropic distillation tower for recycling.
The de-heavy tower is operated in vacuum, the reflux ratio is 3.0-6.0, the operating pressure of the rectifying tower is 5-20 kPaA, the temperature of the top of the tower is 100-120 ℃, and the temperature of the bottom of the tower is 140-170 ℃; preferably, the operating pressure of the azeotropic distillation tower is 20-30 kPaA.
The product at the bottom of the entrainer recovery tower is condensed and then sent into an oil-water separator, after liquid-liquid delamination, the water phase material is water containing a small amount of cyclohexanol, and the water phase material and the product (ethanol and a small amount of water) at the top of the entrainer recovery tower are returned to the azeotropic distillation tower for recycling; the oil phase material of the oil-water separator is cyclohexanol meeting the quality requirement, and is sent to a cyclohexanone device by a pump.
The process of the present invention in which water, water + ethanol are used as the entrainer is further described, specifically as follows:
as shown in fig. 1, when water is used as the entrainer:
the process for recovering dimethylacetamide in waste oil of cyclohexanone device by azeotropic distillation comprises the following steps:
feeding waste oil containing dimethylacetamide and cyclohexanol into the upper part of an azeotropic distillation tower T1141, adding entrainer water from the upper part of the tower, heating the azeotropic distillation tower at an operating pressure of 5-20 KPaA, heating an azeotropic tower kettle reboiler E1141 by steam, condensing a tower top gas phase by an azeotropic distillation tower top condenser E1142, feeding the tower top gas phase into an azeotropic distillation tower top buffer tank V1141, feeding a condensate into an oil-water separator V1142 by an azeotropic distillation tower top extraction pump P1142A/B, feeding a separated water phase into an azeotropic distillation tower top reflux tank V1143, feeding the separated water phase back to the azeotropic distillation tower T1141 for recycling by an azeotropic distillation tower top reflux pump P1143A/B, and feeding the separated oil phase into a cyclohexanone device for regeneration. The dimethylacetamide and the recombinant components at the bottom of the azeotropic distillation tower T1141 are sent to a de-heavy tower T1142 for continuous separation through an extraction pump P1141A/B at the bottom of the azeotropic distillation tower. The operating pressure of the heavy component removal tower is 5-20 KPaA, a tower kettle reboiler E1143 is heated by steam, gas phase at the top of the tower is condensed by an azeotropic distillation tower kettle reboiler E1144 and then enters a heavy component removal tower reflux tank V1144, and condensate partially reflows to a heavy component removal tower T1142 by a heavy component removal tower top extraction pump P1145A/B. The rest is taken out as a dimethylacetamide product. Heavy components are obtained from the kettle of the de-heavy tower T1142 and are sent to a collection system through a recovery pump P1144A/B of the de-heavy tower kettle.
The azeotropic distillation process comprises main equipment such as an azeotropic distillation tower T1141, an oil-water separator V1142 and the like.
Example 1
A process flow for recovering dimethylacetamide in waste oil of cyclohexanone device is shown in figure 1. Azeotropic distillation column T1141 has 21 theoretical plates. Water is used as an entrainer, the entrainer is added from a 1 st theoretical plate (the number of plates is from top to bottom), the adding amount is 5000kg/hr, waste oil containing dimethylacetamide, cyclohexanol, a small amount of light components and heavy components is added from a 3 rd plate on the upper part of the tower, the total flow is 1000kg/hr, and the mass fractions of the dimethylacetamide and the cyclohexanol are 17 wt% and 35 wt%. The operating pressure of the azeotropic distillation tower is 15kPaA, the reflux ratio at the top of the tower is 13, the temperature at the top of the tower is 54 ℃, the temperature at the bottom of the tower is 126 ℃, and the material flow at the top of the tower passes through an oil-water separator to obtain a cyclohexanol (containing water) product with the mass fraction of 90.5 wt% and water with the mass fraction of 97.5 wt%. The separated water is sent back to the azeotropic distillation tower for recycling, and the cyclohexanol (containing water) product can be dried to remove water to obtain a product with the mass fraction of more than or equal to 99.0 wt%. The mixture of the dimethylacetamide and the heavy components in the tower bottom is sent into a de-heavy tower T1142, the operation pressure at the tower top is 15kPaA, the reflux ratio at the tower top is 4, the temperature at the tower top is 106 ℃, the temperature at the tower bottom is 161 ℃, and a dimethylacetamide product with the mass fraction of 99.9 wt% is obtained at the tower top.
Example 2
A process flow for recovering dimethylacetamide in waste oil of cyclohexanone device is shown in figure 1. Azeotropic distillation column T1141 has 21 theoretical plates. Water is used as an entrainer, the entrainer is added from a 1 st theoretical plate (the number of plates is from top to bottom), the adding amount is 6000kg/hr, waste oil containing dimethylacetamide, cyclohexanol, a small amount of light components and heavy components is added from a 3 rd plate on the upper part of the tower, the total flow is 1000kg/hr, and the mass fractions of the dimethylacetamide and the cyclohexanol are 17 wt% and 35 wt%. The operating pressure of the azeotropic distillation tower is 10kPaA, the reflux ratio at the top of the tower is 15, the temperature at the top of the tower is 46 ℃, the temperature at the bottom of the tower is 115 ℃, and the material flow at the top of the tower passes through an oil-water separator to obtain a cyclohexanol (containing water) product with the mass fraction of 91.0 wt% and water with the mass fraction of 97.5 wt%. The separated water is sent back to the azeotropic distillation tower for recycling, and the cyclohexanol (containing water) product can be dried to remove water to obtain a product with the mass fraction of more than or equal to 99.5 wt%. The mixture of the dimethylacetamide and the heavy components in the tower bottom is sent into a de-heavy tower T1142, the operation pressure at the tower top is 10kPaA, the reflux ratio at the tower top is 4, the temperature at the tower top is 95 ℃, the temperature at the tower bottom is 149 ℃, and a dimethylacetamide product with the mass fraction of 99.9 wt% is obtained at the tower top.
Example 3
A process flow for recovering dimethylacetamide in waste oil of cyclohexanone device is shown in figure 1. Azeotropic distillation column T1141 has 21 theoretical plates. Water is used as an entrainer, the entrainer is added from a 1 st theoretical plate (the number of plates is from top to bottom), the adding amount is 4000kg/hr, waste oil containing dimethylacetamide, cyclohexanol, a small amount of light components and heavy components is added from a 3 rd plate on the upper part of the tower, the total flow is 1000kg/hr, and the mass fractions of the dimethylacetamide and the cyclohexanol are 17 wt% and 35 wt%. The operating pressure of the azeotropic distillation tower is 10kPaA, the reflux ratio at the top of the tower is 10, the temperature at the top of the tower is 45 ℃, the temperature at the bottom of the tower is 115 ℃, and the material flow at the top of the tower passes through an oil-water separator to obtain a cyclohexanol (containing water) product with the mass fraction of 90.0 wt% and water with the mass fraction of 97.5 wt%. The separated water is sent back to the azeotropic distillation tower for recycling, and the cyclohexanol (containing water) product can be dried to remove water to obtain a product with the mass fraction of more than or equal to 98.5 wt%. The mixture of the dimethylacetamide and the heavy components in the tower bottom is sent into a de-heavy tower T1142, the operation pressure at the tower top is 10kPaA, the reflux ratio at the tower top is 4, the temperature at the tower top is 95 ℃, the temperature at the tower bottom is 149 ℃, and a dimethylacetamide product with the mass fraction of 99.9 wt% is obtained at the tower top.
As shown in fig. 2, when "water + ethanol" is used as the binary entrainer:
the process for recovering dimethylacetamide in waste oil of cyclohexanone device by azeotropic distillation comprises the following steps:
waste oil containing dimethylacetamide and cyclohexanol is sent to the middle of an azeotropic distillation tower T1141, entrainer ethanol and water are added from the upper part of the tower, the operating pressure of the azeotropic distillation tower is 20-30 KPaA, an azeotropic distillation tower kettle reboiler E1141 is heated by steam, gas phase at the top of the tower is condensed by an azeotropic distillation tower top condenser E1142 and then enters an azeotropic distillation tower top buffer tank V1141, and condensate is sent to an entrainer recovery tower T1142 by an azeotropic distillation tower top extraction pump P1142A/B. Separating by an entrainer recovery tower, condensing a product at the top of the tower by an entrainer recovery tower top condenser E1145, sending the product to an entrainer recovery tower top buffer tank V1142, refluxing a part of the product to the entrainer recovery tower T1142 by an entrainer recovery tower top extraction pump P1144A/B, and sending a part of the product to an azeotropic distillation tower reflux tank V1144 for recycling; and the tower bottom product is cooled by an entrainer recovery tower bottom cooler E1144 and then is sent to an oil-water separator V1143, the separated water phase product is sent to a reflux tank V1144 of the azeotropic distillation tower for recycling, and the oil phase product is sent to a cyclohexanone device. The dimethylacetamide and the recombinant components at the bottom of the azeotropic distillation tower T1141 are sent to a de-heavy tower T1143 for continuous separation through an extraction pump P1141A/B at the bottom of the azeotropic distillation tower. The operating pressure of the de-heavy tower is 5-20 KPaA, a de-heavy tower kettle reboiler E1146 is heated by steam, a gas phase at the top of the tower is condensed by a de-heavy tower top condenser E1148 and then enters a de-heavy tower reflux tank V1145, and a condensate partially reflows to a de-heavy tower T1143 by a de-heavy tower top extraction pump P1147A/B. The rest is taken out as a dimethylacetamide product. Heavy components are obtained from the heavy component removal tower kettle and are sent to a collection system through a heavy component removal tower kettle extraction pump P1146A/B.
The azeotropic distillation process comprises main equipment such as an azeotropic distillation tower T1141, an entrainer recovery tower T1142, an oil-water separator V1143 and the like.
Example 4
A process flow for recovering dimethylacetamide from waste oil of cyclohexanone device is shown in figure 2. Azeotropic distillation column T1141 has 30 theoretical plates. Ethanol and water are used as binary entrainers, the mass ratio of water to ethanol is 4:1, the binary entrainers are added from a theoretical plate 1 (the number of plates is from top to bottom), the adding amount is 1500kg/hr, waste oil containing dimethylacetamide, cyclohexanol, heavy components and trace light components is added from a plate 16 in the middle of the tower, the total flow is 500kg/hr, and the mass fractions of dimethylacetamide and cyclohexanol are 20 wt% and 35 wt%. The operating pressure of the azeotropic distillation tower is 25kPaA, the reflux ratio at the top of the tower is 4, the temperature at the top of the tower is 56 ℃, the temperature at the bottom of the tower is 138 ℃, and the product at the top of the tower is condensed and then sent to an entrainer recovery tower T1142. The operating pressure of the entrainer recovery tower is 101kPaA, the reflux ratio at the top of the tower is 4, the temperature at the top of the tower is 78 ℃, the temperature at the bottom of the tower is 98 ℃, the number of theoretical plates is 30, and the 15 th theoretical plate is arranged at the feeding position. Separating the top of an entrainer recovery tower T1142 to obtain a mixture of ethanol (93.45 wt%) and water (6.54 wt%), refluxing a part of the mixture to the top of the T1142 tower through a pump P1144, and extracting a part of the mixture to a reflux tank of a V1144 azeotropic distillation tower for recycling; separating the product in the T1142 tower kettle by an oil-water separator to obtain an oil phase product (91 wt% of cyclohexanol + 9.3 wt% of water), sending the oil phase product to a cyclohexanone device, and sending the water phase product (97 wt% of water + 2.9 wt% of cyclohexanol) to a reflux tank of a V1144 azeotropic distillation tower for recycling.
And (3) feeding the mixture of the dimethylacetamide and the heavy components in the bottom of the azeotropic distillation tower into a de-heavy tower T1143, wherein the operation pressure at the top of the tower is 15kPaA, the reflux ratio at the top of the tower is 4, the temperature at the top of the tower is 106 ℃, the temperature at the bottom of the tower is 161 ℃, and the dimethylacetamide product with the mass fraction of 99.9 wt% is obtained at the top of the tower.
Example 5
A process flow for recovering dimethylacetamide from waste oil of cyclohexanone device is shown in figure 2. Azeotropic distillation column T1141 has 30 theoretical plates. Ethanol and water are used as binary entrainers, the mass ratio of water to ethanol is 9:1, the binary entrainers are added from a 2 nd theoretical plate (the number of plates is from top to bottom), the adding amount is 2000kg/hr, waste oil containing dimethylacetamide, cyclohexanol, heavy components and trace light components is added from a 16 th plate in the middle of the tower, the total flow is 500kg/hr, and the mass fractions of dimethylacetamide and cyclohexanol are 20 wt% and 35 wt%. The operating pressure of the azeotropic distillation tower is 30kPaA, the reflux ratio at the top of the tower is 2, the temperature at the top of the tower is 62 ℃, the temperature at the bottom of the tower is 144 ℃, and the product at the top of the tower is condensed and then sent to an entrainer recovery tower T1142. The operating pressure of the entrainer recovery tower is 101kPaA, the reflux ratio at the top of the tower is 6, the temperature at the top of the tower is 78 ℃, the temperature at the bottom of the tower is 98 ℃, the number of theoretical plates is 30, and the 18 th theoretical plate is arranged at the feeding position. Separating the top of the entrainer recovery tower T1142 to obtain a mixture of ethanol (90.9 wt%) and water (9.09 wt%), refluxing a part of the mixture to the top of the T1142 tower through a pump P1144, and extracting a part of the mixture to be sent to a reflux tank of a V1144 azeotropic distillation tower for recycling; and separating the product in the T1142 tower kettle by an oil-water separator to obtain an oil phase product (90.7 wt% of cyclohexanol + 9.26 wt% of water), sending the oil phase product to a cyclohexanone device, and sending the water phase product (97 wt% of water + 2.98 wt% of cyclohexanol) to a reflux tank of a V1144 azeotropic distillation tower for recycling.
And (3) feeding the mixture of the dimethylacetamide and the heavy components in the bottom of the azeotropic distillation tower into a de-heavy tower T1143, wherein the operation pressure at the top of the tower is 15kPaA, the reflux ratio at the top of the tower is 4, the temperature at the top of the tower is 106 ℃, the temperature at the bottom of the tower is 161 ℃, and the dimethylacetamide product with the mass fraction of 99.9 wt% is obtained at the top of the tower.
Example 6
A process flow for recovering dimethylacetamide from waste oil of cyclohexanone device is shown in figure 2. Azeotropic distillation column T1141 has 30 theoretical plates. Ethanol and water are used as binary entrainers, the mass ratio of water to ethanol is 4:1, the binary entrainers are added from a theoretical plate 3 (the number of plates is from top to bottom), the adding amount is 1500kg/hr, waste oil containing dimethylacetamide, cyclohexanol, heavy components and trace light components is added from a plate 15 in the middle of the tower, the total flow is 500kg/hr, and the mass fractions of dimethylacetamide and cyclohexanol are 30 wt% and 50 wt%. The operating pressure of the azeotropic distillation tower is 20kPaA, the reflux ratio at the top of the tower is 4, the temperature at the top of the tower is 52 ℃, the temperature at the bottom of the tower is 120 ℃, and the product at the top of the tower is condensed and then sent to an entrainer recovery tower T1142. The operating pressure of the entrainer recovery tower is 101kPaA, the reflux ratio at the top of the tower is 4, the temperature at the top of the tower is 78 ℃, the temperature at the bottom of the tower is 97 ℃, the number of theoretical plates is 30, and the 16 th theoretical plate is arranged at the feeding position. Separating the top of an entrainer recovery tower T1142 to obtain a mixture of ethanol (93.57 wt%) and water (6.42 wt%), refluxing a part of the mixture to the top of the T1142 tower through a pump P1144, and extracting a part of the mixture to a reflux tank of a V1144 azeotropic distillation tower for recycling; and separating the product in the T1142 tower bottom by an oil-water separator to obtain an oil phase product (90.7 wt% of cyclohexanol + 9.26 wt% of water), sending the oil phase product to a cyclohexanone device, and sending the water phase product (96.96 wt% of water + 2.98 wt% of cyclohexanol) to a reflux tank of a V1144 azeotropic distillation tower for recycling.
And (3) feeding the mixture of the dimethylacetamide and the heavy components in the bottom of the azeotropic distillation tower into a de-heavy tower T1143, wherein the operation pressure at the top of the tower is 15kPaA, the reflux ratio at the top of the tower is 4, the temperature at the top of the tower is 106 ℃, the temperature at the bottom of the tower is 161 ℃, and the dimethylacetamide product with the mass fraction of 99.9 wt% is obtained at the top of the tower.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (11)
1. A method for recovering dimethylacetamide in waste oil of a cyclohexanone device is characterized by comprising the following steps: comprises the step of separating cyclohexane and dimethylacetamide in cyclohexanone device waste oil by taking water or a mixture of water and ethanol as an entrainer and adopting a method of combining azeotropic distillation and reduced pressure distillation to obtain a dimethylacetamide product with the mass concentration of more than or equal to 99.9 wt%.
2. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 1, characterized in that: when the entrainer is water, the method comprises the following steps:
(1) feeding waste oil raw materials containing cyclohexanol, dimethylacetamide, heavy components and trace light components into an azeotropic distillation tower, and performing azeotropic distillation by using water as an azeotropic agent;
(2) the water phase of the material at the top of the azeotropic distillation tower separated by the oil-water separator returns to the azeotropic distillation tower for recycling, and the oil phase material is returned to the cyclohexanone device; and (3) the tower bottom recombination of the azeotropic distillation tower is sent to a de-heavy tower to be separated by vacuum distillation to obtain the dimethylacetamide with the mass concentration of more than or equal to 99.9 wt%.
3. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 2, characterized in that: the number of theoretical plates of the azeotropic distillation tower is 20-30, and the feeding position is 2-5 theoretical plates; the number of theoretical plates of the de-weighting tower is 35-45, and the feeding position is 18-25 theoretical plates.
4. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 2, characterized in that: the azeotropic distillation tower is operated in vacuum, the operating pressure of the distillation tower is 5-20 kPaA, the reflux ratio is 10-15, the temperature of the top of the tower is 40-58 ℃, and the temperature of the bottom of the tower is 110-130 ℃.
5. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 2, characterized in that: the de-heavy tower is operated in vacuum, the reflux ratio is 3.0-6.0, the operating pressure of the rectifying tower is 5-20 kPaA, the temperature of the top of the tower is 100-120 ℃, and the temperature of the bottom of the tower is 140-170 ℃.
6. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 2, characterized in that: in the step (1), the mass flow ratio of the entrainer to the raw material liquid is 3.0-7.0; in the step (2), condensing the light components at the top of the azeotropic distillation tower, sending the light components into an oil-water separator, carrying out liquid-liquid delamination, returning the water phase materials to the azeotropic distillation tower for recycling, and sending the oil phase materials back to the cyclohexanone device.
7. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 1, characterized in that: when the entrainer is a mixture of water and ethanol, the method comprises the following steps:
(1) feeding waste oil raw materials containing cyclohexanol, dimethylacetamide, heavy components and trace light components into an azeotropic distillation tower, and performing azeotropic distillation by using ethanol and water as binary azeotropic agents;
(2) the material at the top of the azeotropic distillation tower is sent to an entrainer recovery tower, an ethanol product containing a small amount of water is obtained by the separation at the top of the entrainer recovery tower, a product mainly comprising cyclohexanol and water is obtained by the separation at the bottom of the entrainer recovery tower, and the cyclohexanol product meeting the requirements is obtained by the separation of an oil-water separator and sent back to a cyclohexanone device;
(3) collecting a water phase product obtained after oil-water separation of the top product of the entrainer recovery tower and the tower kettle and returning the water phase product to the azeotropic distillation tower for recycling; and (3) sending the heavy component in the azeotropic distillation tower to a de-heavy tower for vacuum distillation and separation to obtain dimethylacetamide with the mass concentration of more than or equal to 99.9 wt%.
8. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 7, characterized in that: the number of theoretical plates of the azeotropic distillation tower is 28-36, the feeding position of the raw material is 10-18 theoretical plates, and the feeding position of the entrainer is 1-5 theoretical plates; the number of theoretical plates of the de-weighting tower is 35-45, and the feeding position is 18-25 theoretical plates; the number of theoretical plates of the entrainer recovery tower is 25-35, and the feeding position is 12-18 theoretical plates.
9. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 7, characterized in that: the mass flow ratio of the entrainer to the raw material liquid is 1.0-5.0; the mass ratio of water to ethanol in the entrainer is 1.0-10.0; in the step (3), the water phase product is water containing a small amount of cyclohexanol.
10. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 7, characterized in that: the azeotropic distillation tower is operated in vacuum, the operating pressure of the distillation tower is 20-40 kPaA, the reflux ratio is 1-5, the temperature of the top of the tower is 50-60 ℃, and the temperature of a tower kettle is 115-150 ℃; the entrainer recovery tower is operated under normal pressure, the reflux ratio is 2.0-8.0, the operating pressure of the rectifying tower is 101kPaA, the temperature of the top of the tower is 70-85 ℃, and the temperature of the bottom of the tower is 90-110 ℃; the de-heavy tower is operated in vacuum, the reflux ratio is 3.0-6.0, the operating pressure of the rectifying tower is 5-20 kPaA, the temperature of the top of the tower is 100-120 ℃, and the temperature of the bottom of the tower is 140-170 ℃.
11. The method for recovering dimethylacetamide in waste oil of a cyclohexanone device according to claim 7, characterized in that: the operating pressure of the azeotropic distillation tower is 20-30 kPaA.
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