A method and apparatus for separating the products of an ethanol dehydration reaction

Abstract

The present application belongs to the technical field of ethylene preparation, and particularly relates to a method and device for separating the dehydration reaction product of ethanol. The method comprises the following steps: S1, dehydration reaction of ethanol to obtain a primary product; S2, the primary product is cooled first, enters a first product separator to perform first separation, and first liquid phase and first gas phase are obtained; S3, the first gas phase is cooled second, enters a second product separator to perform second separation, and second liquid phase and second gas phase are obtained; S4, the second liquid phase returns to the first product separator, is contacted with the gas phase therein in countercurrent, and then is mixed with the first liquid phase to obtain a mixed liquid phase, the mixed liquid phase is subjected to first rectification, and an ethanol-ethyl ether circulating stream is obtained; and the second gas phase is subjected to second rectification, and a crude ethylene product is obtained. The present application has high purity of the crude ethylene product, realizes repeated use of the intermediate generated ethyl ether and ethanol, has low energy consumption in the preparation process, and is green and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of ethylene preparation technology, specifically relating to a method and apparatus for separating ethanol dehydration reaction products. Background Technology

[0002] Ethylene is one of the most important organic chemical raw materials, mainly used to produce basic chemicals such as polyethylene (PE), ethylene glycol (EG), ethylene oxide (EO), styrene (SM), and polyvinyl chloride (PVC), and further to produce more synthetic materials and fine chemicals. Its products are widely used in various industries such as textiles, additives, construction, and automobiles, covering all aspects of people's lives, including clothing, food, housing, and transportation.

[0003] The ethylene industry is currently undergoing a significant transformation, shifting towards diversified feedstocks and high-end products. Building upon traditional steam cracking for ethylene production, breakthroughs have been achieved in non-petroleum feedstock ethylene production processes, particularly the technology for producing ethylene-containing products from ethanol dehydration. This technology uses ethanol as a raw material, reducing dependence on petroleum resources; the ethanol-to-ethylene process also produces less CO2, making it environmentally friendly.

[0004] Traditional techniques for producing ethylene-containing products from ethanol dehydration use γ-Al₂O₃ as a catalyst, with reaction temperatures ranging from 350 to 450°C. High temperatures easily cause catalyst coking and deactivation, requiring frequent catalyst regeneration and affecting continuous plant operation. By 2025, a breakthrough had been achieved in the technology of producing ethylene-containing products from ethanol dehydration. A pilot-scale plant for producing ethylene from ethanol using a low-temperature dehydration method was built and successfully started up, operating stably for 72 hours and completing calibration tests. The development of ethanol dehydration processes has presented new challenges in product separation. Intramolecular dehydration of ethanol to ethylene occurs simultaneously with intermolecular dehydration to diethyl ether; these two reactions are parallel. Temperature is a key factor affecting product distribution; high temperatures favor intramolecular dehydration to ethylene, while low temperatures favor intermolecular dehydration to diethyl ether. Therefore, the low-temperature method for producing ethylene produces products with a high diethyl ether content. Effectively separating diethyl ether from ethylene and achieving its recovery and reuse, while minimizing raw material loss, is crucial for the initial separation of products. Summary of the Invention

[0005] Therefore, this invention aims to address the aforementioned deficiencies by providing a method and apparatus for separating products from the ethanol dehydration reaction. This method efficiently separates and recovers diethyl ether and ethylene generated during the ethanol dehydration reaction. The crude ethylene product after separation has a low impurity content, and the separated diethyl ether and unreacted ethanol can be reused. Furthermore, the overall process has low energy consumption and is environmentally friendly.

[0006] Therefore, the present invention provides the following technical solution: The first aspect of this invention protects a method for separating products from an ethanol dehydration reaction, wherein the method comprises the following steps: S1, ethanol undergoes a dehydration reaction to give the initial product; S2, the initial product is cooled first and then enters the first product separator for first separation to obtain the first liquid phase and the first gas phase; S3, the first gas phase is cooled in the second cooling process and then enters the second product separator for the second separation to obtain the second liquid phase and the second gas phase; S4, the second liquid phase is returned to the first product separator, where it is countercurrently contacted with the gas phase and then mixed with the first liquid phase to obtain a mixed liquid phase. The mixed liquid phase undergoes the first distillation to obtain an ethanol-diethyl ether circulating stream. The second gas phase undergoes a second distillation to obtain crude ethylene product.

[0007] This invention provides a multi-stage separation and purification method. Specifically, the initial product obtained from the dehydration reaction of ethanol is first cooled and separated using a first cooling and first separation process. The first stage of water separation is achieved using the principle of gas-liquid phase equilibrium, enriching heavy components such as water, diethyl ether, and ethanol. The resulting first gas phase is further subjected to a second deep cooling process to achieve a second stage of water separation, effectively capturing residual water, diethyl ether, and ethanol. Subsequently, the liquid phases obtained from the two water separation processes are mixed and fed into a first distillation column for distillation purification. Ethanol and diethyl ether are efficiently enriched at the top of the column, while high-purity wastewater is discharged from the bottom. Simultaneously, the second gas phase enters a second distillation column for final purification, yielding high-purity crude ethylene at the top and the remaining diethyl ether and ethanol from the second gas phase at the bottom.

[0008] The multi-stage separation and purification method of the present invention achieves the synergistic effect of phase separation and distillation technology, making the separation and recovery of ethanol dehydration reaction products more efficient, and can increase the removal rate of water in the products to more than 98%, significantly reducing the load and energy consumption of subsequent process flow.

[0009] In one alternative embodiment, the primary product comprises 35-50 wt% water, 35-50 wt% ethylene, 3-15 wt% diethyl ether, 1-10 wt% ethanol, and 0.1-3 wt% other light and heavy components.

[0010] In one optional embodiment, the temperature of the primary product is 110-130°C, and the pressure is 0.5-1 MPaG. As an example, the temperature of the primary product can be 110°C, 115°C, 120°C, 125°C, or 130°C, and the pressure can be 0.5 MPaG, 0.6 MPaG, 0.7 MPaG, 0.8 MPaG, 0.9 MPaG, or 1 MPaG, or within any range of the above values.

[0011] In this invention, MPaG refers to gauge pressure.

[0012] In one optional embodiment, the temperature of the first gas phase is 105-125°C, and the pressure is 0.497-0.997 MPaG. As an example, the temperature of the first gas phase can be 105°C, 110°C, 115°C, 120°C, or 125°C, and the pressure can be 0.497 MPaG, 0.6 MPaG, 0.75 MPaG, 0.9 MPaG, or 0.997 MPaG, or within any range of the above values.

[0013] In one optional embodiment, the temperature of the second gas phase is 50-60°C, and the pressure is 0.474-0.974 MPaG. As an example, the temperature of the second gas phase can be 50°C, 52°C, 55°C, 58°C, or 60°C, and the pressure can be 0.474 MPaG, 0.6 MPaG, 0.75 MPaG, 0.9 MPaG, or 0.974 MPaG, or within any range of the above values.

[0014] In one optional embodiment, the temperature of the mixed liquid phase is 105-125°C, and the pressure is 0.497-0.997 MPaG. As an example, the temperature of the mixed liquid phase can be 105°C, 110°C, 115°C, 120°C, or 125°C, and the pressure can be 0.497 MPaG, 0.6 MPaG, 0.75 MPaG, 0.9 MPaG, or 0.997 MPaG, or within any range of the above values.

[0015] In one alternative embodiment, the crude ethylene comprises 99-99.5 mol% ethylene and 0.5-1 mol% other light and heavy components.

[0016] In one alternative embodiment, the ethanol-ether cycle includes 80-90 wt% ethanol, 1-15 wt% ether, and 1-10 wt% water.

[0017] In an optional embodiment, the conditions for the first rectification include: the number of theoretical plates of the first rectification column is N, the feed plate position is n, both N and n are positive integers, and 0.2<n / N<0.5; the overhead operating temperature is 80-120°C, and the operating pressure is 0.02-0.3MPaG; the bottom operating temperature is 110-150°C, and the operating pressure is 0.06-0.34MPaG. As an example, the overhead operating temperature may be 80°C, 90°C, 100°C, 110°C, 120°C, and the operating pressure may be 0.02MPaG, 0.1MPaG, 0.2MPaG, 0.3MPaG; the bottom operating temperature may be 110°C, 120°C, 130°C, 140°C, 150°C, and the operating pressure may be 0.06MPaG, 0.15MPaG, 0.25MPaG, 0.34MPaG, or within a range composed of any of the above values.

[0018] In an optional embodiment, the conditions for the second rectification include: the number of theoretical plates of the second rectification column is M, the feed plate position is m, both M and m are positive integers, and 0.2<m / M<0.5; the overhead operating temperature is -15°C to -5°C, and the operating pressure is 0.452-0.952MPaG; the bottom operating temperature is 130-140°C, and the operating pressure is 0.487-0.987MPaG. As an example, the overhead operating temperature may be -15°C, -12°C, -10°C, -7°C, -5°C, and the operating pressure may be 0.452MPaG, 0.6MPaG, 0.75MPaG, 0.952MPaG; the bottom operating temperature may be 130°C, 132°C, 135°C, 138°C, 140°C, and the operating pressure may be 0.487MPaG, 0.65MPaG, 0.8MPaG, 0.987MPaG, or within a range composed of any of the above values.

[0019] In an optional embodiment, fresh ethanol is supplemented to the feed of the second rectification; the fresh ethanol can act as a high-efficiency absorbent, preferentially interacting with impurities such as diethyl ether in the feed, thereby significantly improving the separation purity and yield of the crude ethylene product at the top of the second rectification column.

[0020] In an optional embodiment, the ethanol-diethyl ether recycle stream obtained in step S4 is recycled to step S1 to re-participate in the dehydration reaction.

[0021] In a second aspect, the present invention protects an apparatus for separating ethanol dehydration reaction products, wherein the apparatus comprises a product cooler, a first product separator, an air cooler, a second product separator, a first rectification column, and a second rectification column; Wherein the reaction unit and the first product separator are connected through a first pipeline, and a product cooler is arranged on the first pipeline; Product separator No. 1 and product separator No. 2 are connected by a second pipeline, on which an air cooler is installed; The No. 1 product separator is connected to the first distillation column; The No. 2 product separator is connected to the second distillation column; The second product separator is also connected to the first product separator via a third pipeline.

[0022] In this invention, each of the No. 1 product separator and the No. 2 product separator is independently provided with 3-10 layers of trays.

[0023] In one alternative implementation, the first top condensate reflux unit and the recovery unit are connected.

[0024] In one optional embodiment, the second distillation column reboiler and the recovery unit are connected via a fourth pipeline, on which a second distillation column reboiler pump is installed.

[0025] In one optional embodiment, the top of the first distillation column and the first top reflux condenser unit are connected via a fifth pipeline. Further, the first top reflux condenser unit includes a first distillation column top condenser, a first distillation column top reflux tank, and a first distillation column top reflux pump. The top of the first distillation column and the first distillation column top reflux tank are connected via a first branch of the fifth pipeline, on which the first distillation column top condenser is installed. The first distillation column and the first distillation column top reflux tank are connected via a second branch of the fifth pipeline, on which the first distillation column top reflux pump is installed. The section of the second branch of the fifth pipeline downstream of the first distillation column top reflux pump is connected to the section of the fourth pipeline downstream of the second distillation column bottom pump. Directly connecting these two pipeline sections allows two streams with similar compositions to be merged before entering the recovery unit, eliminating the need for a separate recovery pipeline or intermediate storage tank for the first distillation column top stream, simplifying equipment layout and piping design, and reducing engineering investment costs.

[0026] In one optional embodiment, the first distillation column reboiler and the first distillation column reboiler are connected, and the first distillation column reboiler is connected to the side line of the first distillation column reboiler.

[0027] In one optional embodiment, the top of the second distillation column and the second top reflux condenser are connected via a sixth pipeline. Further, the second top reflux condenser includes a second distillation column top condenser, a second distillation column top reflux tank, and a second distillation column top reflux pump; the top of the second distillation column and the second top reflux tank are connected via a first branch of the sixth pipeline, on which the second top condenser is installed; the second distillation column and the second top reflux tank are connected via a second branch of the sixth pipeline, on which the second branch is equipped with the second top reflux pump.

[0028] In this invention, the first and second top-of-tower condensing and reflux units enable precise control of the top-of-tower reflux, allowing for flexible adjustment of the reflux flow rate and reflux ratio based on the gas-liquid balance within the tower, thereby improving separation efficiency and facilitating recovery and recycling.

[0029] In one optional embodiment, the reboiler of the second distillation column and the reboiler of the second distillation column are connected, and the reboiler of the second distillation column is connected to the side line of the reboiler of the second distillation column.

[0030] Specifically, reaction unit 111 and the side line of product separator 2 are connected through a first pipeline. A product cooler 1 is installed on the first pipeline. Product separator 2 has 5 trays. The top of product separator 2 and the side line of product separator 4 are connected through a second pipeline. An air cooler 3 is installed on the second pipeline. The top of product separator 4 and the side line of the second distillation column 6 are connected. The bottom of product separator 4 and the side line of product separator 2 are connected through a third pipeline. Product separator 4 has 5 trays. The bottom of product separator 2 and the side line of the first distillation column 5 are connected. The top of the first distillation column 5 and the reflux tank 9 at the top of the first distillation column are connected through the first branch of the fifth pipeline. A condenser 7 at the top of the first distillation column is installed on the first branch. The gas outlet of the reflux tank 9 at the top of the first distillation column is connected to the flare, and the gas is discharged to the flare for combustion. The liquid outlet of the reflux tank 9 at the top of the first distillation column is connected to the side line at the top of the first distillation column 5 through the second branch of the fifth pipeline. A reflux pump 11 at the top of the first distillation column is installed on the second branch. The bottom of the first distillation column 5 is connected to the reboiler 13 at the bottom of the first distillation column. The reboiler 13 at the bottom of the first distillation column is also connected to the side line at the bottom of the first distillation column 5. The bottom of the first distillation column 5 is also connected to the bottom outlet pump 15 at the bottom of the first distillation column. The bottom outlet pump 15 at the bottom of the first distillation column is connected to the bottom outlet cooler 17 at the bottom of the first distillation column. The bottom outlet cooler 17 at the bottom of the first distillation column is connected to the outside of the boundary area to discharge wastewater. The top of the second distillation column 6 and the top reflux tank 10 of the second distillation column are connected through the first branch of the sixth pipeline. The first branch is equipped with the top condenser 8 of the second distillation column. The gas phase outlet of the top reflux tank 10 of the second distillation column is connected to the outside of the boundary area, to the ethylene to the product tank area or downstream unit. The liquid phase outlet of the top reflux tank 10 of the second distillation column is connected to the top side line of the second distillation column 6 through the second branch of the sixth pipeline. The top reflux pump 12 of the second distillation column is installed on the second branch. The bottom of the second distillation column 6 and the bottom reboiler 14 of the second distillation column are connected. The bottom reboiler 14 of the second distillation column is also connected to the bottom side line of the second distillation column 6. The bottom of the second distillation column 6 and the recovery unit 222 are connected through the fourth pipeline. The bottom pump 16 of the second distillation column is installed on the fourth pipeline. The second branch of the fifth pipeline, located downstream of the top reflux pump 11 of the first distillation column, is connected to the section of the fourth pipeline located downstream of the bottom pump 16 of the second distillation column. It should be understood that the reference to the specific reactors mentioned above is merely for illustrative purposes to illustrate the possible equipment forms that the present invention can take, and does not constitute a limitation on the scope of protection of the present invention.

[0031] The technical solution of this invention has the following advantages: 1. This invention provides a method for separating products from an ethanol dehydration reaction, comprising the following steps: S1, ethanol undergoes a dehydration reaction to obtain a primary product; S2, the primary product is cooled first and then enters a first product separator for first separation to obtain a first liquid phase and a first gas phase; S3, the first gas phase is cooled second and then enters a second product separator for second separation to obtain a second liquid phase and a second gas phase; S4, the second liquid phase is returned to the first product separator, where it is countercurrently contacted with the gas phase and then mixed with the first liquid phase to obtain a mixed liquid phase, which is then subjected to a first distillation to obtain an ethanol-diethyl ether circulating stream; the second gas phase is subjected to a second distillation to obtain crude ethylene product; In the present invention, the primary product undergoes first cooling and first separation to obtain a first liquid phase (mainly water, diethyl ether and ethanol) and a first gas phase (mainly ethylene, diethyl ether, ethanol and water), realizing first-stage water separation; the first gas phase undergoes second cooling and second separation to obtain a second liquid phase (mainly water, diethyl ether, ethanol, and a small amount of ethylene) and a second gas phase (mainly ethylene, diethyl ether, ethanol, and a small amount of water), realizing second-stage water separation; the second liquid phase is returned to the No.1 product separator to be in countercurrent contact with the gas phase therein, which can fully remove the ethylene components entrained in the second liquid phase, the second liquid phase and the first liquid phase are mixed to obtain a mixed liquid phase, which contains almost no ethylene, reducing ethylene loss from the source; the mixed liquid phase is subjected to first rectification, an ethanol stream (mainly diethyl ether and ethanol) is separated at the top of the column, and wastewater is separated at the bottom of the column, realizing third-stage water separation; the second gas phase is subjected to second rectification, a crude ethylene product is separated at the top of the column, and diethyl ether and ethanol are separated at the bottom of the column, realizing preliminary separation of ethanol dehydration reaction products. The crude ethylene prepared by the present invention has high purity and clean product, and the product performance has a high degree of consistency among different production batches, which can be used as a raw material for downstream deep processing or sold as a product; the water removal rate is high, which can achieve more than 98% removal of water in the product, significantly reduce the load of the subsequent rectification system and the risk of equipment corrosion, and provide a separation basis for further purification of ethylene; no additional reagents are added in the separation process, no secondary pollutants are generated, the wastewater can be discharged up to the standard or utilized as resources, light components are collected and treated in an orderly manner, the whole process is clean, environmentally friendly, safe and controllable, which meets the development requirements of modern chemical processes for green, low-carbon, safe and efficient production.

[0032] 2. Fresh ethanol is supplemented to the feed of the second rectification in the present invention, and the ethanol stream is used as a washing medium, which can efficiently absorb and remove diethyl ether impurities in the crude ethylene gas, greatly improve the diethyl ether recovery rate, and further increase the purity of the crude ethylene product at the same time; fresh ethanol can be used as a high-efficiency absorbent, which preferentially interacts with impurities such as diethyl ether in the feed, thereby significantly improving the separation purity and yield of the crude ethylene product at the top of the second rectification column; at the same time, it can inhibit the formation of hydrates caused by the low condensation temperature at the top of the column.

[0033] 3. The number of theoretical plates of the second rectification column adopted in the present invention is M, the feed plate position is m, both M and m are positive integers, and 0.2 < m / M < 0.5, the feed position is biased to the upper part of the column, and the entire lower section is a stripping section; the present invention is provided with a stripping section, which can efficiently realize the separation of ethylene, ensure that the stream extracted from the bottom of the column contains no ethylene, and reduce the ethylene loss rate.

[0034] 4. The ethanol-diethyl ether recycle stream obtained in step S4 of the present invention is returned to step S1 to re-participate in the dehydration reaction, which can reduce raw material consumption, reduce waste discharge, lower operating costs, and realize resource recycling.

[0035] 5. The second liquid phase obtained in step S4 of this invention is returned to the No. 1 product separator and comes into countercurrent contact with the gas phase therein to separate the ethylene from the second liquid phase. Then the second liquid phase is mixed with the first liquid phase to obtain a mixed liquid phase, which is then sent to the first distillation to reduce ethylene loss and the separation difficulty of the first distillation.

[0036] 6. This invention provides an apparatus for separating products from an ethanol dehydration reaction. The apparatus includes a product cooler, a first product separator, an air cooler, a second product separator, a first distillation column, and a second distillation column. The reaction unit and the first product separator are connected via a first pipeline, on which a product cooler is installed. The first and second product separators are connected via a second pipeline, on which an air cooler is installed. The first product separator is connected to the first distillation column. The second product separator is connected to the second distillation column. The second product separator is also connected to the first product separator via a third pipeline. The apparatus used in this invention mainly includes a product cooler, two-stage product separators, an air cooler, and first and second distillation columns. It has a small number of core components, a compact structure, and a simple and efficient process flow. The apparatus layout is reasonable, and the connections between units are smooth, effectively reducing energy consumption while achieving high-efficiency separation. In traditional designs, the separated liquid phase often needs to be collected in an intermediate tank and then pumped back to the reaction unit. This invention directly connects the second product separator to the first product separator via a dedicated third pipeline. Utilizing the operating pressure within the second product separator, it achieves gravity-flow or differential pressure transport of the liquid phase, eliminating the need for additional collection tanks and transfer pumps. This design simplifies the number of devices and reduces investment costs. Simultaneously, this connection allows diethyl ether to re-equilibrate within the reactor and partially convert to ethylene (diethyl ether can be dehydrated to ethylene at high temperatures), while unreacted ethanol can participate in the dehydration reaction again, achieving resource recycling and reducing energy consumption. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the apparatus used in Example 1 to separate the products of the ethanol dehydration reaction; Figure 2 This is a schematic diagram of the apparatus used to separate the products of the ethanol dehydration reaction in Comparative Example 1. Explanation of reference numerals in the attached figures: 1. Product cooler; 2. First product separator; 3. Air cooler; 4. Second product separator; 5. First distillation column; 6. Second distillation column; 7. First distillation column overhead condenser; 8. Second distillation column overhead condenser; 9. First distillation column overhead reflux tank; 10. Second distillation column overhead reflux tank; 11. First distillation column overhead reflux pump; 12. Second distillation column overhead reflux pump; 13. First distillation column reboiler; 14. Second distillation column reboiler; 15. First distillation column reboiler pump; 16. Second distillation column reboiler pump; 17. First distillation column reboiler cooler; 111. Reaction unit; 222. Recovery unit; 333. Reaction unit'; 21. Quenching column; 22. Stripping distillation column; 23. Condenser'; 24. Gas-liquid separator. Detailed Implementation

[0039] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0040] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0041] Example 1 This embodiment provides an apparatus and method for separating the products of ethanol dehydration reaction; A schematic diagram of the device is shown below. Figure 1 As shown in the figure, the reaction unit 111 and the side line of the first product separator 2 are connected through the first pipeline. The first pipeline is equipped with a product cooler 1. The first product separator 2 has 5 trays. The top of the first product separator 2 and the side line of the second product separator 4 are connected through the second pipeline. The second pipeline is equipped with an air cooler 3. The top of the second product separator 4 and the side line of the second distillation column 6 are connected. The second product separator 4 has 5 trays. The bottom of the second product separator 4 is connected to the side line of the first product separator 2 through the third pipeline. The bottom of the first product separator 2 and the side line of the first distillation column 5 are connected. The top of the first distillation column 5 and the reflux tank 9 at the top of the first distillation column are connected through the first branch of the fifth pipeline. A condenser 7 at the top of the first distillation column is installed on the first branch. The gas outlet of the reflux tank 9 at the top of the first distillation column is connected to the flare, and the gas is discharged to the flare for combustion. The liquid outlet of the reflux tank 9 at the top of the first distillation column is connected to the side line at the top of the first distillation column 5 through the second branch of the fifth pipeline. A reflux pump 11 at the top of the first distillation column is installed on the second branch. The bottom of the first distillation column 5 is connected to the reboiler 13 at the bottom of the first distillation column. The reboiler 13 at the bottom of the first distillation column is also connected to the side line at the bottom of the first distillation column 5. The bottom of the first distillation column 5 is also connected to the bottom outlet pump 15 at the bottom of the first distillation column. The bottom outlet pump 15 at the bottom of the first distillation column is connected to the bottom outlet cooler 17 at the bottom of the first distillation column. The bottom outlet cooler 17 at the bottom of the first distillation column is connected to the outside of the boundary area to discharge wastewater. The top of the second distillation column 6 and the top reflux tank 10 of the second distillation column are connected through the first branch of the sixth pipeline. The first branch is equipped with the top condenser 8 of the second distillation column. The gas phase outlet of the top reflux tank 10 of the second distillation column is connected to the outside of the boundary area, to the ethylene to the product tank area or downstream unit. The liquid phase outlet of the top reflux tank 10 of the second distillation column is connected to the top side line of the second distillation column 6 through the second branch of the sixth pipeline. The top reflux pump 12 of the second distillation column is installed on the second branch. The bottom of the second distillation column 6 and the bottom reboiler 14 of the second distillation column are connected. The bottom reboiler 14 of the second distillation column is also connected to the bottom side line of the second distillation column 6. The bottom of the second distillation column 6 and the recovery unit 222 are connected through the fourth pipeline. The bottom pump 16 of the second distillation column is installed on the fourth pipeline. The second branch of the fifth pipeline, located downstream of the top reflux pump 11 of the first distillation column, is connected to the section of the fourth pipeline located downstream of the bottom pump 16 of the second distillation column. The primary product obtained from the dehydration of fresh ethanol with a processing capacity of 1000 tons / year includes 42.88 wt% water, 43.49 wt% ethylene, 9.48 wt% diethyl ether, 3.77 wt% ethanol, and 0.38 wt% other light and heavy components; the flow rate is 288 kg / h, the temperature is 126℃, and the pressure is 0.788 MPaG. The method includes the following steps: After being cooled by product cooler 1, the product enters product separator 2 from the bottom for gas-liquid separation, yielding a first gas phase and a first liquid phase. The first gas phase, with a flow rate of 199.3 kg / h, a temperature of 121.1℃, and a pressure of 0.785 MPaG, enters air cooler 3 from the top of product separator 2 for further cooling. After cooling, it enters product separator 4 from the bottom for another gas-liquid separation, yielding a second liquid phase and a second gas phase. The second gas phase, with a flow rate of 160.0 kg / h, a temperature of 55.0℃, and a pressure of 0.762 MPaG, flows out from the top of product separator 4 and enters the second distillation column 6 through the 13th theoretical plate. The second distillation column 6 has the following number of theoretical plates: The first distillation column has 28 theoretical plates. The top operating temperature is -8℃, the top operating pressure is 0.745 MPaG, the bottom operating temperature is 139.5℃, and the bottom operating pressure is 0.780 MPaG. The second liquid phase returns to the first product separator by gravity to mix with the first liquid phase, resulting in a mixed liquid phase. The flow rate is 128.0 kg / h, the temperature is 121.1℃, and the pressure is 0.785 MPaG. The mixed liquid phase flows out from the bottom of the first product separator 2 and enters the first distillation column 5 through the 14th theoretical plate. The first distillation column 5 has 29 theoretical plates, a top operating temperature of 84.9℃, a top operating pressure of 0.03 MPaG, a bottom operating temperature of 114.4℃, and a bottom operating pressure of 0.065 MPaG. The top of the first distillation column 5 produces a gaseous stream (48.7 kg / h) containing light components such as diethyl ether and ethanol. This stream is condensed by the top condenser 7 (inlet temperature 84.9℃, outlet temperature 81.2℃) and collected in the top reflux tank 9. A liquid stream (42.0 kg / h) flows out from the liquid outlet of the top reflux tank 9. Part of this liquid stream returns to the first distillation column 5 via the first theoretical plate, while the other part is used as a recycle stream. A portion of the bottom stream (74.4 kg / h) is heated by the reboiler 13 (inlet temperature 114.4℃, outlet temperature 114.5℃) and returned to the bottom stream. A portion of the bottom stream (121.3 kg / h) is pumped out by the bottom pump 15 and cooled by the bottom cooler 17, resulting in wastewater. 157.4 kg / h of fresh ethanol was added to the side stream of the second distillation column. Crude ethylene vapor stream (126.0 kg / h) was collected from the top of the second distillation column 6. After condensation in the second distillation column top condenser 8 (inlet temperature -8℃, outlet temperature -15.1℃), it was collected in the second distillation column top reflux tank 10. 125.8 kg / h of vapor ethylene was collected as product from the top of the second distillation column top reflux tank 10, yielding crude ethylene product (based on crude ethylene, including 1.39 ppm water, 99.49 mol% ethylene, and 0.51 mol% other light and heavy components). 0.1 kg / h of liquid phase was collected from the top of the second distillation column... The liquid phase outlet of the reflux tank 10 at the top of the second distillation column flows back to the second distillation column 6 via the first theoretical plate. Part of the bottom stream (438.9 kg / h) is heated by the reboiler 14 at the bottom of the second distillation column (inlet temperature 139.5℃, outlet temperature 140.8℃) and returned to the bottom stream. Part of the bottom stream (191.5 kg / h) is pumped out by the bottom pump 16 of the second distillation column and mixed with the circulating stream collected from the first distillation reflux tank to obtain an ethanol-diethyl ether circulating stream (based on the ethanol-diethyl ether circulating stream, it includes 84.69 wt% ethanol, 13.77 wt% diethyl ether, and 1.15 wt% water).

[0042] Comparative Example 1 This comparative example provides an apparatus and method for separating products from the ethanol dehydration reaction; A schematic diagram of the device is shown below. Figure 2 As shown in the figure, reaction unit '333 is connected to the side line of quench tower 21. Crude ethylene product is discharged from the top of quench tower 21. The bottom of quench tower 21 is connected to the side line of stripping distillation tower 22. Washing water is introduced into the side line of the top of quench tower 21. The top of stripping distillation tower 22 is connected to condenser '23. Condenser '23 is connected to the side line of gas-liquid separator 24. The top of gas-liquid separator 24 extends to the outside of the boundary area and discharges waste gas. The pipelines extending from the bottom of gas-liquid separator 24 are connected to the side line of stripping distillation tower 22 and the outside of the boundary area respectively. The connection to the outside of the boundary area is for discharging ethanol-diethyl ether circulating stream. The bottom of stripping distillation tower 22 is connected to the outside of the boundary area and discharges lean organic wastewater. The primary product obtained from the dehydration of fresh ethanol with a processing capacity of 1000 tons / year includes 42.88 wt% water, 43.49 wt% ethylene, 9.48 wt% diethyl ether, 3.77 wt% ethanol, and 0.38 wt% other light and heavy components; the flow rate is 288 kg / h, the temperature is 126℃, and the pressure is 0.788 MPaG. The initial product from reaction unit '333 enters the quench tower 21 through the fourth theoretical plate and comes into countercurrent contact with the washing water entering from the top of the quench tower. While being cooled, the impurities of the initial product are absorbed by the washing water. The quench tower has four theoretical plates, the top operating temperature is 44.7℃, the top operating pressure is 0.75MPaG, the bottom operating temperature is 94℃, and the bottom operating pressure is 0.76MPaG. The first gas phase is obtained at the top of the quench tower, and the first liquid phase is obtained at the bottom of the tower. The first gas phase is crude ethylene product (based on crude ethylene, including 1.07 mol% water, 90.98 mol% ethylene, and 7.95 mol% other light and heavy components, with a flow rate of 153.4 kg / h, a temperature of 44.7℃, and a pressure of 0.75 MPaG). The first liquid phase is organic wastewater containing impurities such as ethylene, ethanol, and diethyl ether, with a flow rate of 134.6 kg / h, a temperature of 94℃, and a pressure of 0.76 MPaG. The first liquid phase enters the stripping distillation column 22 from the 14th theoretical plate. The stripping distillation column has 29 theoretical plates, a top operating temperature of 82.7℃, a top operating pressure of 0.03 MPaG, a bottom operating temperature of 114.4℃, and a bottom operating pressure of 0.065 MPaG. The stripping distillation column contains a gaseous stream of light components such as ethylene, diethyl ether, and ethanol at the top. This stream is condensed in condenser '23', which has an inlet temperature of 82.7℃ and an outlet temperature of 40.6℃. After condensation, the stream enters a gas-liquid separator 24 for gas-liquid separation. A second gaseous stream is obtained at the top of the separator. This second gaseous stream contains ethylene, carbon dioxide, water, acetaldehyde, diethyl ether, and ethanol, with a flow rate of 0.04 kg / h, a temperature of 40.6℃, and a pressure of 0.03 MPaG. This second gaseous stream is discharged as waste gas. The liquid phase is discharged from the bottom of the gas-liquid separator 24, part of which is refluxed into the stripping distillation column 22 through the first theoretical plate, and part is collected as the second liquid phase (flow rate of 13 kg / h). The second liquid phase has a temperature of 42℃ and a pressure of 1.7 MPaG, and is used as the ethanol-diethyl ether circulating stream. The bottom of the stripping distillation column 22 yields the third liquid phase, which is lean organic wastewater (containing trace amounts of organic matter), with a flow rate of 121.5 kg / h, a temperature of 114.5℃, and a pressure of 0.065 MPaG.

[0043] Test case The test method for water removal rate is as follows: Water removal rate = [Water flow rate in wastewater / (Water flow rate in crude ethylene product + Water flow rate in ethanol-ether circulating stream + Water flow rate in wastewater + Water flow rate in exhaust gas - Water flow rate in fresh ethanol)] × 100%; Test method for diethyl ether recovery rate: Diethyl ether recovery rate = [Ether flow rate in ethanol-diethyl ether circulating stream / (Ether flow rate in ethanol-diethyl ether circulating stream + Ether flow rate in wastewater + Ether flow rate in exhaust gas + Ether flow rate in crude ethylene product)] × 100%; The purity of crude ethylene was tested by gas chromatography, following the test methods in GB / T7715-2014 "Ethylene for Industrial Use" to determine the ethylene purity. Directly read the required circulating water and electricity consumption within 72 hours; The test results are shown in Table 1; Table 1

[0044] Comparing Example 1 and Comparative Example 1, it can be seen that the water removal rate of Example 1 is basically the same as that of Comparative Example 1, the purity of crude ethylene and the recovery rate of diethyl ether are greatly improved, the amount of circulating water used is significantly reduced, and the overall separation effect and economy are better.

[0045] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for separating products from an ethanol dehydration reaction, characterized in that, Said method comprises the following steps: In S1, ethanol is subjected to a dehydration reaction to obtain a primary product, the primary product has a temperature of 110-130°C and a pressure of 0.5-1MPaG, and based on the primary product, the primary product comprises 35-50 wt% of water, 35-50 wt% of ethylene, 3-15 wt% of diethyl ether, 1-10 wt% of ethanol, and 0.1-3 wt% of other light and heavy components; In S2, the primary product is subjected to first cooling and then enters a first product separator for first separation, so as to obtain a first liquid phase and a first gas phase, and the first gas phase has a temperature of 105-125°C and a pressure of 0.497-0.997MPaG; In S3, the first gas phase is subjected to second cooling and then enters a second product separator for second separation, so as to obtain a second liquid phase and a second gas phase, the second gas phase has a temperature of 50-60°C, and the second gas phase has a pressure of 0.474-0.974MPaG; In S4, the second liquid phase is returned to the first product separator, is in countercurrent contact with the gas phase therein and then mixed with the first liquid phase to obtain a mixed liquid phase, the mixed liquid phase has a temperature of 105-125°C and a pressure of 0.497-0.997MPaG, the mixed liquid phase is subjected to first rectification to obtain an ethanol-diethyl ether recycle stream, and based on the ethanol-diethyl ether recycle stream, the ethanol-diethyl ether recycle stream comprises 80-90 wt% of ethanol, 1-15 wt% of diethyl ether, and 1-10 wt% of water; The second gas phase is subjected to second rectification to obtain a crude ethylene product, and based on the crude ethylene, the crude ethylene comprises 99-99.5 mol% of ethylene and 0.5-1 mol% of other light and heavy components.

2. The method according to claim 1, characterized in that, The conditions for the first rectification include: the number of theoretical plates of the first rectification column is N, the position of the feed plate is n, N and n are both positive integers, and 0.2<n / N<0.5; the top operating temperature is 80-120°C, and the operating pressure is 0.02-0.3MPaG; the bottom operating temperature is 110-150°C, and the operating pressure is 0.06-0.34MPaG; and / or, the conditions for the second rectification include: the number of theoretical plates of the second rectification column is M, the position of the feed plate is m, M and m are both positive integers, and 0.2<m / M<0.5; the top operating temperature is from -15°C to -5°C, and the operating pressure is 0.452-0.952MPaG; the bottom operating temperature is 130-140°C, and the operating pressure is 0.487-0.987MPaG.

3. The method according to claim 1, characterized in that, Fresh ethanol is supplemented into the feed of the second rectification; and / or, the ethanol-diethyl ether recycle stream obtained in step S4 is recycled to step S1 to participate in the dehydration reaction again.

4. An apparatus for separating products from the dehydration reaction of ethanol, characterized in that, Said apparatus comprises a product cooler, a first product separator, an air cooler, a second product separator, a first rectification column, and a second rectification column; wherein the reaction unit and the first product separator are connected through a first pipeline, and the product cooler is arranged on the first pipeline; The first product separator and the second product separator are connected through a second pipeline, and the air cooler is arranged on the second pipeline; The first product separator is connected with the first rectification column; The second product separator is connected with the second rectification column; Said second product separator is further connected with the first product separator through a third pipeline; The apparatus further includes a first overhead reflux condenser unit, a second overhead reflux condenser unit, a recovery unit, a first distillation column reboiler, a second distillation column reboiler, and a second distillation column reboiler pump. The top of the first distillation column and the first top reflux condenser are connected by a fifth pipeline. The first top reflux condenser is connected to the recovery unit. The bottom of the first distillation column is connected to the reboiler of the first distillation column. The reboiler of the first distillation column is connected to the side line of the bottom of the first distillation column. The top of the second distillation column and the second top condensation reflux unit are connected by a sixth pipeline, and the bottom of the second distillation column and the recovery unit are connected by a fourth pipeline. A bottom pump of the second distillation column is installed on the fourth pipeline. The reboiler of the second distillation column is connected to the reboiler of the second distillation column, and the reboiler of the second distillation column is connected to the side line of the reboiler of the second distillation column.

5. The apparatus according to claim 4, characterized in that, The first overhead condenser and reflux unit includes an overhead condenser of the first distillation column, an overhead reflux tank of the first distillation column, and an overhead reflux pump of the first distillation column. The top of the first distillation column and the reflux tank at the top of the first distillation column are connected by the first branch of the fifth pipeline, and the condenser at the top of the first distillation column is installed on the first branch. The first distillation column and the first distillation column top reflux tank are connected by the second branch of the fifth pipeline, and the first distillation column top reflux pump is installed on the second branch.

6. The apparatus according to claim 4, characterized in that, The second overhead condenser and reflux unit includes a second distillation column overhead condenser, a second distillation column overhead reflux tank, and a second distillation column overhead reflux pump; The top of the second distillation column and the reflux tank at the top of the second distillation column are connected through the first branch of the sixth pipeline, and the condenser at the top of the second distillation column is installed on the first branch. The second distillation column and the second distillation column top reflux tank are connected through the second branch of the sixth pipeline, and the second branch is equipped with the second distillation column top reflux pump.

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