CN106955500B - A method and device for purifying isopropyl acetate by three-tower heat-integrated pressure swing distillation - Google Patents

Abstract

The present invention relates to the method and devices that three towers of one kind are thermally integrated variable-pressure rectification purifying acetic acid isopropyl ester, feed stream enters normal pressure extracting tower (T1), tower bottom produces high-purity acetic acid, overhead stream enters pressurizing tower (T2) by pressurization, in the isopropyl acetate product of pressurizing tower tower bottom extraction high-purity, tower top generates isopropyl acetate and azeotropic object steam and as vacuum tower (T3) tower base stream heat source, realizes in heat exchanger (H3) and is thermally integrated completely；Enter vacuum tower (T3) after heat exchange condensation, produces high-purity isopropanol in vacuum tower tower bottom, overhead stream is recycled into pressurizing tower (T2) and is recycled.The present invention solves the problems, such as that complex system separates and recovers isopropyl acetate, and obtains the isopropyl acetate of higher degree, using technique is thermally integrated, reduces energy consumption to greatest extent, simple process, and device is reasonable.

Description

A method and device for purifying isopropyl acetate by three-tower heat-integrated pressure swing distillation

【Technical field】

The invention belongs to the separation and purification field of the chemical industry, and relates to a method and a device for purifying isopropyl acetate by three-tower heat-integrated pressure swing rectification.

【Background technique】

Isopropyl acetate is mainly used as a solvent for coatings, printing inks, etc., and is also a commonly used dehydrating agent in industry. In drug production, it is mainly used as extraction solvent for drugs, coating solvent, printing ink solvent, chemical reaction solvent, etc. -86 stipulates that the edible flavors are allowed to be used. It is mainly used to prepare the solvent of rum flavor and fruit flavor. Acetic acid can be used as an acidity regulator, acidulant, pickling agent, flavor enhancer, spice, etc. It is also a good antimicrobial agent. Isopropyl alcohol has a wide range of uses as organic raw materials and solvents. It can be used in the production of coatings, inks, extractants, aerosols, etc. It can also be used as antifreeze, detergents, additives for blending gasoline, dispersants for pigment production, and printing and dyeing industries. fixing agent, anti-fogging agent for glass and transparent plastic, etc. In industrial production, acetic acid, isopropanol and concentrated sulfuric acid are commonly used to synthesize isopropyl acetate. The synthesized isopropyl acetate product contains acetic acid and isopropanol impurities, and acetic acid and isopropanol are easy to form azeotropes and are difficult to effectively separate , therefore effectively purifying isopropyl acetate and recovering acetic acid and isopropanol not only saves energy and protects the environment, but also has great economic benefits to the enterprise.

The boiling point of isopropyl acetate is 88.52 °C, the boiling point of acetic acid is 118.01 °C, and the boiling point of isopropanol is 82.05 °C. Under normal pressure, isopropyl acetate and isopropanol are easy to form the lowest azeotrope, so special distillation methods are required to separate them. The mixture of the two, the commonly used special rectification methods include pressure swing rectification, extractive rectification, membrane permeation, rectification coupling technology, etc. Using traditional high and low pressure pressure swing rectification, the heat load QC1 of the pressure tower condenser C1 is much larger than the heat load QR2 required by the pressure reduction tower. Therefore, if the heat load QC1 of the pressure tower condenser C1 can be used to provide the heat load to the pressure reduction tower , will greatly save energy consumption. The invention can effectively purify the isopropyl acetate, solve the difficult problem that the isopropyl acetate and the isopropanol azeotrope system is difficult to separate, save energy at the same time, and realize the effective utilization of energy.

Patent (CN201510594602.9) discloses a method for separating acetonitrile-methanol-benzene ternary azeotrope by three-column pressure swing rectification, and successfully separates multi-component azeotrope, but does not adopt heat integration.

Literature (Zong Lili. Research on the separation process of methanol-acetonitrile-benzene ternary mixed system [D]. Hebei University of Technology, 2013.) reported the separation of acetonitrile-methanol-benzene azeotrope by five-column pressure swing distillation, but the energy consumption high, and the separation process is complicated.

Literature (Zhu Z, Xu D, Liu X, et al.Separation of acetonitrile/methanol/benzene ternary azeotrope via triple column pressure-swing distillation[J].Separation&Purification Technology,2016,169:66-77.) reported three towers The method for separating the acetonitrile-methanol-benzene ternary azeotrope by pressure swing rectification realizes the effective separation of the azeotrope without adopting the heat integration process.

Literature (Wu Y C, Huang H P, Chien I L.Investigation of the Energy-SavingDesign of an Industrial 1,4-Dioxane Dehydration Process with Light FeedImpurity[J].Industrial&Engineering Chemistry Research,2014,53(40):15667-15685. ) reported the separation of triethylamine, water and 1,4-dioxane by three-tower pressure swing distillation, the use of enrichment towers to discharge triethylamine gas, and the use of low-pressure double towers to separate water and 1,4-dioxane Six rings, but without thermal integration.

The present invention adopts the method of first normal pressure rectification, then pressurized rectification, and finally vacuum rectification, and utilizes the vapor from the top of the pressure tower (T2) to provide heat to the reboiler of the reduced pressure tower (T3). Specifically, utilize atmospheric tower (T1) to obtain high-purity acetic acid product, in pressurized tower (T2), utilize isopropyl acetate and isopropanol system along with pressure change, the characteristic that azeotropic composition shifts, Isopropyl acetate and isopropanol azeotrope enter the pressurized tower (T2) rectification, and the isopropyl acetate product is extracted at the bottom of the tower, from the top distillate steam of the pressurized tower (T2) and the pressure reduction tower (T3 ) bottom stream isopropanol carries out heat exchange, gas is completely liquefied through heat exchange, a part is refluxed in pressurized tower (T2), a part is entered in decompression tower (T3) by pipeline 9, and high-purity isopropyl alcohol A part of the alcohol liquid is completely vaporized into the decompression tower (T3) through heat exchange, and a part is directly extracted through pipeline 15 without heat exchange. Among them, a part is circulated by the high pressure pump P2 through the pipeline 16 into the pressurizing tower (T2) for re-rectification. The invention utilizes isopropyl acetate and n-propanol to form the lowest azeotrope, and the heat load of the condenser at the top of the pressurized tower is far greater than the heat load of the reboiler at the bottom of the decompression tower, so as to realize the high pressure reduction tower. Fully thermally integrated process reduces energy consumption.

[Content of the invention]

[Technical problem to be solved]

The purpose of this invention is to provide a kind of method of three-tower heat-integrated pressure swing distillation purifying isopropyl acetate.

Another object of the present invention is to provide a method and device for purifying isopropyl acetate using the three-column heat-integrated pressure swing distillation of the device Uses in isopropyl acetate.

[Technical solutions]

The present invention is achieved through the following technical solutions.

1, the method and the device of three-tower heat-integrated pressure swing rectification purifying isopropyl acetate, it is characterized in that the device for purifying isopropyl acetate mainly comprises the following parts:

Atmospheric pressure column (T1), pressure column (T2), decompression column (T3), condenser (C1), condenser (C3), reboiler (R1), reboiler (R2), heat exchanger (H3), pressurizing pump (P1), pressurizing pump (P2); wherein the pressurizing pump (P1) is connected to the feed port of the pressurizing tower (T2), and the reboiler (R1) is connected to the atmospheric tower (T1) At the bottom of the tower, the reboiler (R2) is connected to the pressurized tower (T2), and the condenser (C1) and the condenser (C3) are connected to the top of the atmospheric tower (T1) and the decompression tower (T3) in turn, and pressurized The pump (P2) is connected with the pressurizing tower (T2), the gas phase outlet stream of the pressurizing tower (T2) is connected with the hot stream inlet of the heat exchanger (H3), and the hot stream outlet of the heat exchanger (H3) is pressurized by the pump (P3). ) is connected at the top of the pressure tower (T2), the bottom of the pressure reduction tower (T3) is connected with the cold flow inlet of the heat exchanger (H3), and the cold flow outlet of the heat exchanger (H3) is connected with the pressure reduction tower (T3);

The method mainly includes the following steps:

(1) crude product isopropyl acetate is entered into the atmospheric tower (T1), and the outlet of the atmospheric tower (T1) at the bottom of the tower distills liquid-phase acetic acid, and a part of it enters into the reboiler (R1), through the reboiler (R1) enters the atmospheric column (T1) after reboiling, and another part of the stream is directly extracted as the acetic acid product, and the overhead distillate of the atmospheric column (T1) enters the pressurized column (T2) through the pressure pump (P1) )middle;

(2) isopropyl acetate-isopropanol steam at the top of the pressurized tower (T2) is used as the heat source of the decompression tower (T3), and the heat source is utilized to realize heat integration in the heat exchanger (H3), from the pressurized tower (T2) the isopropyl acetate-isopropanol steam at the top of the tower and the vacuum tower (T3) bottom stream isopropanol carry out heat exchange, and the isopropyl acetate-isopropanol azeotrope gas is completely liquefied through heat exchange, A part of the stream flows back into the pressure column (T2), the other part enters the pressure reduction column (T3), and a part of the isopropanol liquid in the bottom stream of the pressure reduction column (T3) is fully vaporized into the pressure reduction column (T3) through heat exchange. T3), a part is directly extracted from the bottom of the decompression tower (T3) without heat exchange;

(3) The stream at the top of the decompression column (T3) enters the decompression column (T3) through the condenser (C3), and the other part is re-entered into the pressure column (T2) by the pump (P2) as a circulating stream for re-rectification.

According to another preferred embodiment of the present invention, it is characterized in that: it is characterized in that the number of theoretical plates of the atmospheric column (T1) is 50-60, the position of the material plate is the 20-30th, and the pressure column (T2) The number of theoretical plates is 25 to 35, the position of the feed plate is the 16th, the position of the circulating flow feed plate is the 16th, the number of theoretical plates of the decompression tower (T3) is 45 to 55, and the position of the feed plate is Blocks 31 to 38. According to another preferred embodiment of the present invention, it is characterized in that: it is characterized in that: the reflux ratio of the atmospheric column (T1) is 0.4-0.6, and the reflux ratio of the pressure column (T3) is 1.6-1.9 The reflux ratio of the decompression column (T3) The ratio is 1.6 to 1.9.

According to another preferred embodiment of the present invention, it is characterized in that: it is characterized in that: the temperature at the top of the atmospheric tower (T1) is 70.35-85.72 °C, the temperature at the bottom of the atmospheric tower (T1) is 107.93-117.47 °C, and the pressure column (T2) the temperature at the bottom of the tower is 152.42～172.64°C, and the temperature at the top of the decompression tower (T3) is -10.41～-5.41°C.

According to another preferred embodiment of the present invention, it is characterized in that: it is characterized in that: the mass fraction of crude isopropyl acetate is 60%-75%.

According to another preferred embodiment of the present invention, it is characterized in that: the purity of the purified isopropyl acetate is greater than 99.90%, the recovery rate is 99.90%-99.95%, the purity of acetic acid is greater than 99.90%, the recovery rate of acetic acid It is 99.90%～99.98%, the purity of isopropanol is more than 99.90%, and the recovery rate of isopropanol is 99.90%～99.97%.

In the present invention, the method for heat-integrated purification of crude product isopropyl acetate by pressure swing rectification is specifically described as follows:

The isopropyl acetate-acetic acid-isopropanol mixture enters the atmospheric column (T1) through pipeline 1, and in the atmospheric column, the feed stream enters the column bottom reboiler R1, and the reboiler is fed with steam for heating , a part is extracted through pipeline 5, and a part is returned to the tower, the top stream enters the pressurized tower (T2) for rectification, and the bottom stream vaporizes and rises to the pressurized tower (T2) and rises to the top of the tower , the top steam is extracted from the pipeline 6 as the heat source of the decompression tower (T3), and complete heat integration is realized in the heat exchanger H3. Heat, the gas is completely liquefied through heat exchange, part of it is returned to the pressurizing tower (T2) from the pipeline 11, and a part enters the decompression tower (T3) from the pipeline 12, and the gas rising in the pressurizing tower (T2) Carry out multi-stage mass transfer and heat transfer with the descending liquid, and another part of the stream that descends to the bottom of the tower is extracted through pipeline 7, enters the stream in the decompression tower (T3), enters the bottom of the tower, passes through the heat exchanger H3, A part is directly extracted through pipeline 15, a part is reboiled into the pressure reducing tower (T3) and the top of the tower is condensed by a condenser, a part of the condensed stream is refluxed into the pressure reducing tower (T3), and a part is circulated by the pump P2 through pipeline 16 Enter the pressurized tower (T2) for re-rectification.

The operating pressure of the atmospheric tower (T1) adopted in the present invention is 1 atm (absolute pressure), the operating pressure of the pressurizing tower (T2) is 8 atm (absolute pressure), and the operating pressure of the decompression tower (T3) is 0.01 atm (absolute pressure); The number of theoretical plates in the atmospheric tower (T1) is 50 to 55, and the position of the feed plate is the 20th to 30th. The number of theoretical plates in the pressurized column (T2) is 25 to 35, and the position of the feed plate is the 16th. , the position of the feed plate of the circulating stream is the 16th, the theoretical plate number of the vacuum tower (T3) is 45 to 50, the position of the feed plate is the 31st to 38th; the reflux ratio of the atmospheric tower (T1) is 0.41 to 1.5 , the reflux ratio of the pressure tower (T2) is 0.5 to 1.5, the reflux ratio of the decompression tower (T3) is 2.85 to 3.8; the temperature at the top of the atmospheric tower (T1) is 70.35 to 85.72°C, and the bottom of the atmospheric tower (T1) The temperature is 107.93～117.47, the temperature at the bottom of the pressure tower (T2) is 152.42～172.64°C, and the temperature at the top of the decompression tower (T3) is -10.41～-5.41°C.

The purified isopropyl acetate of the invention has a purity of more than 99.90%, a recovery rate of 99.90% to 99.95%, a purity of acetic acid of more than 99.90%, a recovery rate of acetic acid of 99.90% to 99.98%, and a purity of isopropyl alcohol of more than 99.90%. The recovery rate of isopropanol was 99.90% to 99.97%.

[Beneficial effect]

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

(1) The isopropyl acetate product was successfully purified, and two high-purity products, acetic acid and isopropanol, were obtained.

(2) Compared with the traditional pressure swing rectification process, the equipment investment cost of the present invention is low.

(3) Compared with the traditional pressure swing rectification process, the present invention has low operating cost and high heat utilization rate.

(4) Compared with the extractive distillation process, the present invention does not introduce other component impurities, and the product purity is high.

【Description of drawings】

Accompanying drawing 1 is the structure schematic diagram of heat-integrated three-column pressure swing distillation to purify isopropyl acetate.

In the figure, T1 atmospheric column; T2 pressure column; T3 pressure reduction column; C1, C3 condenser; R1, R3 reboiler; H3 heat exchanger; D2 liquid storage tank; P1, P2 pressure pump; digital representation All logistics pipelines.

【Detailed ways】

Below in conjunction with embodiment, the present invention is further described, but the present invention is not limited to embodiment.

Example 1:

The feed temperature was 25° C., the flow rate was 1000 kmol/h, and the pressure was 1 atm (absolute pressure). The feed contained 60% isopropyl acetate, 5% acetic acid, and 35% isopropanol. The number of theoretical plates of the atmospheric column is 50, the number of fresh material feed plates is 20, the number of theoretical plates of the pressurized column is 25, the number of theoretical plates of the fresh material flow is 16, and the number of circulating material plates is 16; the number of theoretical plates of the decompression column is 45, The feed plate is 31. The reflux ratio of the atmospheric column is 0.41, the temperature at the top of the column is 70.35 °C, and the temperature at the bottom of the column is 107.93 °C; the operating pressure of the pressurized column is 8 atm (absolute pressure), the reflux ratio is 0.5, the temperature at the top of the column is 135.75 °C, and the temperature at the bottom of the column is 152.42 °C; The operating pressure of the decompression column is 0.01 atm (absolute pressure), the reflux ratio is 2.85, the temperature at the top of the column is -10.41°C, and the temperature at the bottom of the column is 47.58°C. After separation, isopropyl acetate is obtained with a purity of 99.95% and a yield of 99.90%, acetic acid with a purity of 99.97% and a yield of 99.90%, and isopropanol with a purity of 99.8% and a yield of 99.0%.

According to the process method and device for purifying isopropyl acetate by heat-integrated three-column pressure swing rectification provided by the present invention, the steam from the top distillate of the pressure column is used to supply heat to the decompression column, which can be compared with the traditional pressure swing rectification operation. Compared with the energy consumption, the cooling water consumption of the condenser of the pressurization tower and the steam consumption of the reboiler of the decompression tower are saved. Calculated based on the separation of 1000kmol/h of materials, to achieve the same purity and yield, the consumption of cooling water is saved by 50%, and the consumption of steam 50% reduction. Table 1 Rectification system process operation parameters

Example 2:

The feed temperature was 25° C., the flow rate was 1000 kmol/h, and the pressure was 1 atm (absolute pressure). The feed contained 65% isopropyl acetate, 10% acetic acid, and 25% isopropanol. The number of theoretical plates in the atmospheric column is 55, the number of theoretical plates in the fresh stream is 23, the number of theoretical plates in the pressurized column is 30, the number of theoretical plates in the fresh stream is 16, and the number of plates in the circulating stream is 16; the number of theoretical plates in the decompression column is 48, The feed plate is 33. The reflux ratio of the atmospheric column is 0.44, the temperature at the top of the column is 79.75 °C, and the temperature at the bottom of the column is 110.43 °C; the operating pressure of the pressurized column is 8 atm (absolute pressure), the reflux ratio is 0.8, the temperature at the top of the column is 140.46 °C, and the temperature at the bottom of the column is 160.34 °C; The operating pressure of the decompression column is 0.01 atm (absolute pressure), the reflux ratio is 3.05, the temperature at the top of the column is -5.47°C, and the temperature at the bottom of the column is 52.58°C. After separation, isopropyl acetate is obtained with a purity of 99.92% and a yield of 99.90%, acetic acid with a purity of 99.97% and a yield of 99.90%, and isopropanol with a purity of 99.98% and a yield of 99.0%.

Example 3:

The feed temperature was 25° C., the flow rate was 1000 kmol/h, and the pressure was 1 atm (absolute pressure). The feed contained 70% isopropyl acetate, 10% acetic acid, and 20% isopropanol. The number of theoretical plates in the atmospheric column is 60, the number of theoretical plates in the fresh stream is 25, the number of theoretical plates in the pressurized column is 35, the number of plates in the fresh stream is 16, and the number of plates in the circulating stream is 16; the number of theoretical plates in the decompression column is 50, The feed plate is 38. The reflux ratio of the atmospheric column is 0.49, the temperature at the top of the column is 80.75 °C, and the temperature at the bottom of the column is 115.53 °C; the operating pressure of the pressurized column is 8 atm (absolute pressure), the reflux ratio is 1, the temperature at the top of the column is 145.76 °C, and the temperature at the bottom of the column is 168.64 °C; The operating pressure of the decompression column is 0.01 atm (absolute pressure), the reflux ratio is 3.3, the temperature at the top of the column is -10.35°C, and the temperature at the bottom of the column is 54.6°C. After separation, isopropyl acetate is obtained with a purity of 99.94% and a yield of 99.95%, acetic acid with a purity of 99.95% and a yield of 99.90%, and isopropanol with a purity of 99.97% and a yield of 99.3%.

Example 4:

The feed temperature was 25° C., the flow rate was 1000 kmol/h, and the pressure was 1 atm (absolute pressure). The feed contained 75% isopropyl acetate, 15% acetic acid, and 10% isopropanol. The number of theoretical plates of the atmospheric column is 55, the number of theoretical plates of the fresh stream is 23, the number of theoretical plates of the pressurized column is 30, the number of the theoretical plates of the fresh stream is 16, and the number of the feeding plates of the circulating stream is 16; the number of theoretical plates of the decompression column is 55, The feed plate is 35. The reflux ratio of the atmospheric column is 0.5, the temperature at the top of the column is 85.72 °C, and the temperature at the bottom of the column is 117.47 °C; the operating pressure of the pressurized column is 8 atm (absolute pressure), the reflux ratio is 1.5, the temperature at the top of the column is 125.76 °C, and the temperature at the bottom of the column is 172.64 °C; The operating pressure of the decompression column is 0.01 atm (absolute pressure), the reflux ratio is 3.8, the temperature at the top of the column is -10.35°C, and the temperature at the bottom of the column is 57.87°C. After separation, isopropyl acetate is obtained with a purity of 99.94% and a yield of 99.95%, acetic acid with a purity of 99.98% and a yield of 99.97%, and isopropanol with a purity of 99.96% and a yield of 99.7%.

Claims (3)

1. a method for purifying isopropyl acetate by three-tower heat-integrated pressure swing distillation, is characterized in that the device for purifying isopropyl acetate mainly comprises the following parts: Atmospheric pressure column T1, pressure column T2, pressure reduction column T3, condenser C1, condenser C3, reboiler R1, reboiler R2, heat exchanger H3, pressure pump P1, pressure pump P2; The pressure pump P1 is connected to the feed port of the pressurized tower T2, the reboiler R1 is connected to the bottom of the atmospheric tower T1, the reboiler R2 is connected to the bottom of the pressurized tower T2, and the condenser C1 and the condenser C3 are connected to the atmospheric pressure in turn. Tower T1 and decompression tower T3 tower top, pressurizing pump P2 is connected with pressurizing tower T2, pressurizing tower T2 gas phase outlet stream is connected with the hot stream inlet of heat exchanger H3, and the hot stream outlet of heat exchanger H3 is pressurized The pump P3 is connected to the top of the pressurizing tower T2, the bottom of the decompression tower T3 is connected to the cold stream inlet of the heat exchanger H3, and the cold stream outlet of the heat exchanger H3 is connected to the decompression tower T3; The method mainly includes the following steps: (1) The crude product isopropyl acetate is sent to the atmospheric tower T1, and a part of the bottom distillate of the atmospheric tower T1 enters the reboiler R1, and then enters the atmospheric tower after reboiler R1 T1, another part of the stream is directly extracted as an acetic acid product, and the overhead distillate of the atmospheric tower T1 enters the pressurized tower T2 through the pressurized pump P1; (2) The isopropyl acetate-isopropanol vapor at the top of the pressurized tower T2 is used as the heat source of the decompression tower T3, and the heat source is used to realize heat integration in the heat exchanger H3, and the isopropyl acetate from the top of the pressurized tower T2 is used. Propyl ester-isopropanol steam and vacuum tower T3 bottom stream isopropanol carry out heat exchange, isopropyl acetate-isopropanol azeotrope gas is completely liquefied through heat exchange, and a part of stream is refluxed in pressurized tower T2 , the other part enters into the decompression tower T3, and part of the isopropanol liquid at the bottom of the decompression tower T3 is vaporized into the decompression tower T3 through heat exchange, and a part is directly extracted from the bottom of the decompression tower T3 without heat exchange. ; (3) the overhead stream of the decompression tower T3 enters the decompression tower T3 through the condenser C3 part, and the other part enters the compression tower T2 as a circulating stream by the pressure pump P2 for reuse; The number of theoretical plates in the atmospheric column T1 is 50 to 60, the position of the feed plate is the 20th to 30th, the number of theoretical plates in the pressurized column T2 is 25 to 35, the position of the feed plate is the 16th, and the circulation flow The position of the feeding plate is the 16th, the number of theoretical plates of the decompression tower T3 is 45-55, and the position of the feeding plate is the 31st-38th; The reflux ratio of the atmospheric tower T1 is 0.41 to 1.5, the reflux ratio of the pressurized tower T2 is 0.5 to 1.5, and the reflux ratio of the decompression tower T3 is 2.85 to 3.8; The operating pressure of the atmospheric tower T1 is absolute pressure 1atm, the temperature at the top of the tower is 70.35-85.72°C, and the temperature at the bottom of the tower is 107.93-117.47°C; The operating pressure of the pressure tower T3 is an absolute pressure of 0.01 atm, and the temperature at the top of the tower is -10.41 to -5.41°C. 2. the method for a kind of three-tower heat-integrated pressure swing distillation to purify isopropyl acetate as claimed in claim 1, it is characterized in that: the massfraction of isopropyl acetate in crude product isopropyl acetate is 60%～75% . 3. the method for purifying isopropyl acetate by three-tower heat-integrated pressure swing distillation as claimed in claim 1, it is characterized in that: the purity of isopropyl acetate after purification is greater than 99.90%, and the rate of recovery is 99.90%～99.95% %, the purity of acetic acid is greater than 99.90%, the recovery rate of acetic acid is 99.90%-99.98%, the purity of isopropyl alcohol is greater than 99.90%, and the recovery rate of isopropyl alcohol is 99.90%-99.97%.