阅读说明：本技术 带有侧线采出的热集成萃取精馏分离乙酸乙酯-乙醇的节能工艺 (Energy-saving process for separating ethyl acetate-ethanol by heat integration extraction rectification with side extraction ) 是由 申威峰 石涛 于 2019-10-28 设计创作，主要内容包括：本发明公开了一种带有侧线采出的热集成萃取精馏分离乙酸乙酯-乙醇的节能工艺,属于化工行业的分离提纯领域。该过程中待分离的乙酸乙酯和乙醇共沸混合物从17～27块塔板进入侧线萃取精馏塔,二甲基亚砜作为萃取剂从第3～5块板进入侧线萃取精馏塔,乙酸乙酯产品由塔顶采出,塔底采出部分萃取剂,同时从侧线萃取精馏塔的第28～35块板采出部分物流进入溶剂回收精馏塔。该溶剂回收精馏塔的塔顶采出乙醇,塔底采出的萃取剂循环至进料换热器,并将新鲜进料的温度提高至72℃。而循环萃取剂经冷却器降温后,进入侧线萃取精馏塔。该工艺的产品质量分数和回收率均保持在99.9％以上,通过与传统萃取精馏对比,该方法具有能耗低,设备投资少,分离后产品纯度高等优点。(The invention discloses an energy-saving process for separating ethyl acetate-ethanol by heat integration extraction rectification with side extraction, belonging to the field of separation and purification in the chemical industry. In the process, an azeotropic mixture of ethyl acetate and ethanol to be separated enters a side-stream extraction rectifying tower from 17-27 tower plates, dimethyl sulfoxide serving as an extracting agent enters the side-stream extraction rectifying tower from 3 rd-5 th plates, an ethyl acetate product is extracted from the top of the side-stream extraction rectifying tower, part of the extracting agent is extracted from the bottom of the side-stream extraction rectifying tower, and meanwhile, part of material flow extracted from 28 th-35 th plates of the side-stream extraction rectifying tower enters a solvent recovery rectifying tower. Ethanol is extracted from the top of the solvent recovery rectifying tower, an extracting agent extracted from the bottom of the tower is circulated to a feeding heat exchanger, and the temperature of fresh feeding is increased to 72 ℃. And the circulating extractant is cooled by a cooler and then enters a side-line extraction rectifying tower. The product quality fraction and recovery rate of the process are both kept above 99.9%, and compared with the traditional extraction and rectification, the method has the advantages of low energy consumption, less equipment investment, high purity of the separated product and the like.)

1. The energy-saving process for separating ethyl acetate-ethanol by heat integration extraction rectification with side line extraction is characterized in that an extraction rectification method and a device used by the process comprise the following parts: the system comprises a cooler 1, a feeding heat exchanger 2, a side line extraction rectifying tower 3, a condenser 4, a reflux tank 5, a reboiler 6, a tower bottom material flow conveying pump 7, a side line material flow conveying pump 8, a solvent recovery rectifying tower 9, a condenser 10, a reflux tank 11, a reboiler 12 and a tower bottom material flow conveying pump 13; wherein the condenser 4 and the condenser 10 are respectively connected with the top of the side-line extraction rectifying tower and the top of the solvent recovery rectifying tower, the reboiler 6 and the reboiler 12 are respectively connected with the bottom of the side-line extraction rectifying tower and the bottom of the solvent recovery rectifying tower;

an energy-saving process for separating ethyl acetate-ethanol by adopting heat integration extraction rectification with side line extraction comprises the following steps:

(1) the raw material ethyl acetate-ethanol mixture enters a side-stream extraction rectifying tower 3 through a feeding heat exchanger 2, meanwhile, a circulating extracting agent is cooled through a cooler 1 and then enters the side-stream extraction rectifying tower 3, a gas-phase material flow at the top of the extraction rectifying tower 3 enters a reflux tank 5 through a condenser 4, a part of the gas-phase material flow flows back to the top of the side-stream extraction rectifying tower 3, and a part of the gas-phase material flow is extracted as an ethyl acetate product material flow; part of material flow at the bottom of the extraction rectifying tower 3 enters a reboiler 6, the material flow is vaporized and then returns to the bottom of the side-line extraction rectifying tower 3, and the other part of extractant at the bottom of the tower enters the heat exchanger 2 through a delivery pump 7; the material extracted from the side line of the extraction and rectification tower 3 enters a solvent recovery tower 9 through a delivery pump 8;

(2) gas-phase materials at the top of the solvent recovery tower 9 enter a reflux tank 11 through a condenser 10, a part of materials reflux to the top of the solvent recovery tower 9, and a part of materials are extracted as ethanol products; the material at the bottom of the tower returns to the solvent recovery tower 9 after being vaporized by a reboiler 12, and the other part of the material as a circulating extracting agent enters the heat exchanger 2 through a delivery pump 12 for heat exchange.

2. The energy-saving process for separating ethyl acetate-ethanol by heat integration extraction rectification with side draw according to claim 1, which is characterized in that the operating pressure of the side draw extraction rectification tower 3 is 0.5atm absolute pressure, the number of theoretical plates of the side draw extraction rectification tower 3 is 34-40 plates, the feeding position is 17-27 blocks, the feeding position of a circulating stream is 3-5 blocks, the side draw position is 28-35 blocks, the reflux ratio of the side draw extraction rectification tower is 1.2-2.5, and the mass ratio of the side draw material to the ethyl acetate-ethanol mixture is 0.8-1.1; the operation pressure of the solvent recovery tower 9 is absolute pressure 0.5atm, the number of theoretical plates is 11-13, the feeding position is 5-7, the reflux ratio is 0.07-0.13, and the ratio of the total amount of the circulating extracting agent to the mass of the ethyl acetate-ethanol mixture is 1.01-1.34; the feeding temperature of the mixture to be separated is increased to 60-74 ℃ by the feeding heat exchanger, the top temperature of the side-line extraction rectifying tower is 57-61 ℃, the bottom temperature of the side-line extraction rectifying tower is 167-170 ℃, the top temperature of the solvent recovery rectifying tower 9 is 57-61 ℃, and the bottom temperature of the solvent recovery rectifying tower is 167-170 ℃.

3. The method as claimed in claim 1, wherein the mass fraction of ethyl acetate obtained from the top of the side-draw extractive distillation column 3 is greater than 99.92%, the recovery rate of ethyl acetate is greater than 99.95%, the mass fraction of ethanol obtained from the top of the solvent recovery distillation column 9 is greater than 99.92%, and the recovery rate of ethanol is greater than 99.90%.

Technical Field

The invention relates to an energy-saving process for separating ethyl acetate-ethanol by heat integration extraction rectification with side line extraction, belonging to the field of separation and purification in chemical industrial production.

Background

Ethyl acetate is one of the most widely used fatty acid esters, is a fast-drying solvent, has excellent dissolving capacity, and is an excellent industrial solvent and an important organic chemical raw material. The ethyl acetate can be used in the production process of acetate fiber, ethyl fiber, chlorinated rubber, vinyl resin, acetate fiber resin and synthetic rubber, and can also be used in liquid nitrocellulose ink for copying machines; can be used as solvent of binder and diluent of spray paint, and can be used as cleaning agent in textile industry; used as a flavor extractant of special modified alcohol in food industry. At present, the direct esterification method is a main process route for industrially producing ethyl acetate in China. Acetic acid and ethanol are used as raw materials, esterification reaction is carried out under the catalysis of sulfuric acid to obtain ethyl acetate, and then dehydration and rectification are carried out to obtain a finished product. The yield of the product is improved by adding excess ethanol, which forms a minimum azeotrope with ethyl acetate at normal pressure.

The special distillation methods studied and developed in academia and industry at present are commonly used for separating the azeotrope-like mixtures, and include pressure swing distillation, extractive distillation, azeotropic distillation, membrane distillation and the like. The patent (CN103951544A) discloses a method for separating azeotrope of ethyl acetate and ethanol by differential pressure distillation, however, the method only relates to purification separation containing high-purity ethyl acetate, and does not relate to separation of ester-alcohol mixture with other concentration content. Patent (CN103467286A) discloses a method for separating ethyl acetate-ethanol by extractive distillation, which uses ionic liquid or a composite solvent composed of ionic liquid and organic solvent as an extractant. The process is difficult to be applied industrially because the process uses expensive ionic liquid as an extracting agent. The patent (CN110041167A) discloses a process method for separating ethyl acetate-ethanol-water by extractive distillation, and the process of the three-tower extractive distillation scheme does not apply side line extraction and has high energy consumption and equipment investment cost. The patent (CN109534998A) discloses an energy-saving process for separating ethyl acetate-ethanol, which adopts a method of pressure swing distillation combined with side line extraction. The process adopts side extraction, reduces energy consumption compared with the traditional pressure swing rectification scheme, but has more tower plates and increased pressure in the pressure swing rectification process, thus leading to high equipment investment cost.

In the traditional extractive distillation process flow, a stream of material flow extracted from the side line of the extractive distillation tower is added and enters the solvent recovery distillation tower, and a part of extractant is also extracted from the bottom of the side line extractive distillation tower, so that the energy consumption of a reboiler can be greatly reduced.

Disclosure of Invention

The technical problem to be solved is as follows:

the invention solves the problem that the ethyl acetate-ethanol mixture is difficult to separate due to the existence of azeotropy, and provides an energy-saving process for separating ethyl acetate-ethanol by heat integration extraction rectification with side extraction. Compared with the traditional extractive distillation scheme, the process has the advantages of saving equipment investment and reducing energy consumption of a reboiler.

Technical scheme

In the traditional extraction and rectification process flow, a material flow extracted from the side line of the extraction and rectification tower is added and enters a solvent recovery and rectification tower, and meanwhile, a mixture to be separated is heated by utilizing a circulating extracting agent for heat integration. The operation can greatly reduce the energy consumption of the reboilers of the two towers, and simultaneously can save the equipment cost compared with the side pressure swing rectification process. The specific embodiment of the invention is as follows:

(1) heating a raw material ethyl acetate-ethanol mixture through a raw material preheater 2 and then feeding the heated raw material ethyl acetate-ethanol mixture into a side-line extraction rectifying tower 3, feeding part of the material at the bottom of the side-line extraction rectifying tower 3 into a reboiler 6, vaporizing part of the material and then feeding the vaporized material back to the bottom of the side-line extraction rectifying tower 3, finally refluxing the other part of the material at the bottom of the tower serving as a circulating extracting agent into the side-line extraction rectifying tower 3 through a conveying pump 6, condensing the steam at the top of the side-line extraction rectifying tower 3 through a condenser 4 and then feeding the condensed steam into a reflux tank 5, refluxing part of the material to the top of the side-line extraction rectifying tower 3;

(2) a side stream is extracted from the side extraction rectifying tower 3 through a delivery pump 8 and enters a solvent recovery rectifying tower 9;

(3) a part of materials at the bottom of the solvent recovery rectifying tower 9 enter a reboiler 12, the other part of materials serving as a recovered circulating solvent are refluxed through a delivery pump 13 and finally refluxed into the side extraction rectifying tower 3, the steam at the top of the tower is condensed through a condenser 10 and then enters a reflux tank 11, and a part of materials are refluxed to the top of the solvent recovery tower 9; the other part is directly extracted as an ethanol product;

(4) and after mixing the circulating extractants at the bottoms of the rectifying towers 3 and 9, exchanging heat with the feed mixture through the heat exchanger 2, mixing the heat-exchanged material with the supplemented extractants, cooling the mixture through the cooler 1, and finally enabling the circulating extractants to reach the top of the side-line extraction rectifying tower 3.

The energy-saving process for separating ethyl acetate-ethanol in the heat integration continuous process with the side line extractive distillation is characterized in that the number of theoretical plates of a side line extractive distillation tower 3 is 34-40, the feeding position is 17-27, the feeding position of a circulating material flow is 3-5, the side line extraction position is 28-35, the reflux ratio of the side line extractive distillation tower is 1.2-2.5, and the mass ratio of the side line extraction material to the feeding of an ethyl acetate-ethanol mixture is 0.8-1.1; the operation pressure of the solvent recovery tower 9 is absolute pressure 0.5atm, the number of theoretical plates is 11-13, the feeding position is 5-7, the reflux ratio is 0.07-0.13, and the ratio of the total amount of the circulating extracting agent to the mass of the ethyl acetate-ethanol mixture is 1.01-1.34; the feeding temperature of the mixture to be separated is increased to 60-74 ℃ by the feeding heat exchanger, the top temperature of the side-line extraction rectifying tower is 57-61 ℃, the bottom temperature of the side-line extraction rectifying tower is 167-170 ℃, the top temperature of the solvent recovery rectifying tower 9 is 57-61 ℃, and the bottom temperature of the solvent recovery rectifying tower is 167-170 ℃.

The energy-saving process for separating ethyl acetate-ethanol in the heat integration continuous process with the side line extractive distillation is characterized in that the mass fraction of ethyl acetate obtained from the top of the side line extractive distillation column 3 is more than 99.92%, the recovery rate of ethyl acetate is more than 99.95%, the mass fraction of ethanol obtained from the top of the solvent recovery distillation column 9 is more than 99.92%, and the recovery rate of ethanol is more than 99.90%.

Advantageous effects

Compared with the prior art, the invention mainly has the following gain effects: the invention utilizes the characteristic that the relative volatility of ethyl acetate and ethanol can be obviously changed by the extractant dimethyl sulfoxide, adopts the heat integration scheme with side line extraction rectification to separate the ethyl acetate-ethanol mixture, solves the problem of changing the separation and purification of the azeotropic mixture, and has the advantages of energy saving, consumption reduction and equipment investment cost reduction compared with the traditional extraction rectification process.

Drawings

FIG. 1 is a schematic diagram of an energy-saving process for separating ethyl acetate-ethanol in a heat integration process with a side-draw extractive distillation column.

In the figure: 1-a cooler; 2-a heat exchanger; 3-a side-draw extractive distillation column; 4, 10-condenser; 5, 11-reflux tank; 6, 12-reboiler; 9-a solvent recovery rectifying tower; 7, 8, 13-material transfer pump.

Detailed Description

The present invention is further described below with reference to the drawings and the following detailed description, but the present invention is not limited to the drawings and the following detailed description.