System for improving yield of polyester-grade ethylene glycol

Abstract

The invention discloses a system for increasing the yield of polyester-grade ethylene glycol. The system comprises an ethylene glycol refining tower, the butanediol removal tower is positioned at the process upstream of the ethylene glycol refining tower; the dealdehyding and degreasing tank is positioned at the downstream of the ethylene glycol refining tower, and a product of the ethylene glycol refining tower reacts with a catalyst in the dealdehyding and degreasing tank to obtain a high-polyester-grade ethylene glycol product; a liquid phase hydrogenation reactor is arranged at the process downstream end of the ethylene glycol refining tower, and the liquid phase hydrogenation reactor is used for receiving a product of the ethylene glycol refining tower and carrying out hydrogenation reaction on the part of the product so as to convert trace impurities in the product into light components. The system provided by the invention can improve the product quality stability, prolong the service life of the key catalyst and improve the target product yield in a manner of adding the liquid phase hydrogenation reactor to perform hydrogenation reaction on the product.

Description

Technical Field

[0001] This invention relates to the field of ethylene glycol production technology, and more particularly to a system for increasing the yield of polyester-grade ethylene glycol. Background Technology

[0002] In the oxalate hydrogenation process, as the Cu / SiO2 catalyst operates for longer periods, its activity gradually declines and its reaction selectivity decreases towards the end of the catalyst's lifespan. This leads to a continuous increase in the amount of impurities generated in the reaction system, and a corresponding decrease in the content of the target product, ethylene glycol. At this point, the crude ethylene glycol produced after the reaction will be enriched with trace impurities, mainly including ketones, aldehydes, and organic compounds containing unsaturated bonds. These impurities directly reduce the transmittance of the product from the side stream of the ethylene glycol refining tower, severely affecting the purity of the polyester-grade ethylene glycol. Simultaneously, these impurities can undergo irreversible adsorption or chemical reactions with the dealdehyde and deesterification catalysts, significantly shortening their lifespan. Furthermore, the products from the butanediol removal tower reflux system, the ethylene glycol refining tower reflux tank, and the ethylene glycol recovery unit will carry a large amount of ethylene glycol and the aforementioned organic impurities, resulting in a reduced effective recovery rate of the target product and a significant decrease in the final yield of polyester-grade ethylene glycol.

[0003] Therefore, based on the above-mentioned technical problems, those skilled in the art urgently need to develop a system to increase the yield of polyester-grade ethylene glycol. Summary of the Invention

[0004] The purpose of this invention is to provide a system for increasing the yield of polyester-grade ethylene glycol, which can improve product quality stability, extend the service life of key catalysts, and increase the yield of target products.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a system for increasing the yield of polyester-grade ethylene glycol, the system comprising: Ethylene glycol refining tower; The butanediol removal tower located upstream of the ethylene glycol refining tower process; and The formaldehyde and ester removal tank located downstream of the ethylene glycol refining tower process is used to react the product of the ethylene glycol refining tower with the catalyst in the formaldehyde and ester removal tank to obtain high polyester grade ethylene glycol product. A liquid-phase hydrogenation reactor is installed downstream of the ethylene glycol refining tower. The product from the ethylene glycol refining tower is received through the liquid-phase hydrogenation reactor, and the product is hydrogenated to convert trace impurities in the product into light components.

[0006] Furthermore, the upper part of the ethylene glycol refining tower is connected to an air cooler and an ethylene glycol refining tower reflux tank in sequence through a first pipeline according to the process flow, and the ethylene glycol refining tower reflux tank is connected to the liquid phase hydrogenation reactor through the first reflux pipeline to transport the product of the ethylene glycol refining tower to the liquid phase hydrogenation reactor. The lower part of the ethylene glycol refining tower is connected to the dealdehyde and deesterification tank via a second pipeline.

[0007] Furthermore, the upper end of the liquid phase hydrogenation reactor is connected to the upstream hydrogenation unit via a hydrogenation pipeline to input hydrogen into the liquid phase hydrogenation reactor, and this portion of hydrogen, after being subjected to depressurization and heating treatment, is collected at the top of the liquid phase hydrogenation reactor along with the product output from the ethylene glycol refining tower.

[0008] Furthermore, the product after hydrogenation treatment in the liquid phase hydrogenation reactor is returned to the butanediol removal tower upstream of the process via the liquid phase hydrogenation reactor reflux pipeline.

[0009] Furthermore, the upper part of the butanediol removal tower is connected to a waste pot and a butanediol removal tower reflux tank in sequence through a third pipeline according to the process flow. The butanediol removal tower reflux tank returns part of the product after the light components have been removed by the butanediol removal tower to the ethylene glycol refining tower through the first reflux pipeline of the butanediol removal tower reflux tank.

[0010] Furthermore, the butanediol removal tower reflux tank returns a portion of the product to the butanediol removal tower through the second reflux pipeline for further removal of light components.

[0011] Furthermore, after the product in the liquid phase hydrogenation reactor undergoes hydrogenation reaction in the reaction bed, it passes through a gas-liquid separation section at the bottom of the reactor to separate the gas and liquid phase products after the reaction. The liquid-phase product is refluxed back to the butanediol removal tower through the reflux line of the liquid-phase hydrogenation reactor.

[0012] Furthermore, the gaseous products branch into three streams: The first branch is the gas-liquid separation section at the bottom of the liquid phase hydrogenation reactor, which transports the gaseous products to the hydrogen condenser for cooling and then returns them to the liquid phase hydrogenation reactor. The second branch is to transport the gaseous products to the hydrogen recovery system for recycling. The third branch route directly transports the gaseous products to the flare for incineration.

[0013] Furthermore, the upstream hydrogenation unit adopts the oxalate hydrogenation unit of the original system, and a hydrogen pipeline with a size of DN25 is led out from the oxalate hydrogenation unit and connected to the upper end of the liquid phase hydrogenation reactor.

[0014] Furthermore, the bottom of the butanediol removal tower is connected to the ethylene glycol refining tower via a butanediol removal tower reflux pipe.

[0015] The system for increasing the yield of polyester-grade ethylene glycol provided by the present invention, as described above, has the following beneficial effects: The system of this invention effectively improves the grade of ethylene glycol by adding a liquid-phase hydrogenation reactor. Based on a daily production of 360 tons of qualified ethylene glycol and polyester-grade ethylene glycol, a premium of 2,500 yuan per ton for the qualified grade, and an annual operating time of 8,000 hours, the annual additional benefit is approximately (360 × 88% - 360 × 82%) ÷ 24 × 8,000 × 2,500 = 18 million yuan. Compared with the initial investment, the payback period is approximately 4 months.

[0016] The system of this invention can effectively extend the service life of dealdehyde and deesterification catalysts, which not only improves product quality but also further reduces the number of times catalysts need to be replaced, thus saving production costs.

[0017] The system of the present invention can achieve the reaction through the steam condensate of the reboiler of the butanediol removal tower, thereby reducing steam consumption. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0019] Figure 1 This is a process flow diagram of a system for increasing the yield of polyester-grade ethylene glycol, as disclosed in an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Ethylene glycol refining tower; 2. Butanediol removal tower; 3. Liquid phase hydrogenation reactor; 4. Dealdehyde and deesterification tank; 101. First pipeline; 102. Second pipeline; 103. Air cooler; 104. Ethylene glycol refining tower reflux tank; 105. First reflux pipeline; 201. Third pipeline; 202. Waste boiler; 203. Butylene glycol removal tower reflux tank; 204. First reflux pipeline of the butylene glycol removal tower reflux tank; 205. Second reflux pipeline of the butylene glycol removal tower reflux tank; 206. Butylene glycol removal tower reflux pipe; 301. Hydrogenation unit; 302. Liquid phase hydrogenation reactor reflux tank line; 303. Branch line to hydrogen recovery system; 304. Branch line to flare; 305. Hydrogen condenser. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] See Figure 1 As shown; This embodiment discloses a system for increasing the yield of polyester-grade ethylene glycol. The system includes an ethylene glycol refining tower; a butanediol removal tower 2 located upstream of the ethylene glycol refining tower 1; and a formaldehyde removal and deesterification tank 4 located downstream of the ethylene glycol refining tower 1. The product of the ethylene glycol refining tower 1 reacts with the catalyst in the formaldehyde removal and deesterification tank 4 to obtain high-polyester-grade ethylene glycol. A liquid-phase hydrogenation reactor 3 is installed downstream of the ethylene glycol refining tower 1. The product of the ethylene glycol refining tower 1 is received by the liquid-phase hydrogenation reactor 3, and the product is hydrogenated to convert trace impurities in the product into light components.

[0023] Specifically, this embodiment discloses a system for increasing the yield of polyester-grade ethylene glycol. The system adds a liquid-phase hydrogenation reactor 3 downstream of the ethylene glycol refining tower 1 process. The product from the ethylene glycol refining tower 1 is refluxed to the liquid-phase hydrogenation reactor 3 for hydrogenation to convert trace impurities in the product into lighter components, thereby increasing the overall yield of polyester-grade ethylene glycol in the process system. Simultaneously, the product from the ethylene glycol refining tower 1 can be directly pressurized and transported to the liquid-phase hydrogenation reactor 3 via a reflux pump without needing to enter a cooler. The product temperature of 120°C meets the process requirements of the liquid-phase hydrogenation reactor 3.

[0024] Preferably, in this embodiment, the upper part of the ethylene glycol refining tower 1 is connected to an air cooler 103 and an ethylene glycol refining tower reflux tank 104 in sequence through a first pipeline 101 according to the process flow, and the ethylene glycol refining tower reflux tank 104 is connected to the liquid phase hydrogenation reactor 3 through a first reflux pipeline 105 to transport the product of the ethylene glycol refining tower 1 to the liquid phase hydrogenation reactor 3; secondly, in this embodiment, the lower part of the ethylene glycol refining tower 1 is connected to a dealdehyde and deesterification tank 4 through a second pipeline 102.

[0025]

[0026] Table 1 above shows the composition and UV transmittance of the reflux liquid from the ethylene glycol refining tower in the system.

[0027] First, based on the process of adding a liquid-phase hydrogenation reactor 3 to the system, two pipelines are set at the top of the ethylene glycol refining tower 1. The product in the first pipeline 101 enters the liquid-phase hydrogenation reactor 3 through the first reflux pipeline 105 of the ethylene glycol refining tower reflux tank 104. This part of the product enters the liquid-phase hydrogenation reactor 3 for hydrogenation treatment to remove trace impurities. At the same time, when it is detected that the product in the ethylene glycol refining tower 1 meets the process requirements, this part of the product can be directly transported to the downstream dealdehyde and deesterification tank 4 through the second pipeline 102 of this embodiment for catalytic reaction to obtain the final product.

[0028] Preferably, in this embodiment, the upper end of the liquid phase hydrogenation reactor 3 is connected to the upstream hydrogenation unit 301 via a hydrogenation pipeline to input hydrogen into the liquid phase hydrogenation reactor 3, and this portion of hydrogen, after being subjected to pressure reduction and heating treatment, is collected at the top of the liquid phase hydrogenation reactor 3 along with the product output from the ethylene glycol refining tower 1.

[0029] The product after hydrogenation treatment in the liquid phase hydrogenation reactor 3 is returned to the butanediol removal tower 2 upstream of the process via the liquid phase hydrogenation reactor reflux pipeline 302.

[0030] Preferably, in this embodiment, the upstream hydrogenation unit 301 adopts the oxalate hydrogenation unit of the original system, and a hydrogen pipeline with a size of DN25 is led out from the oxalate hydrogenation unit and connected to the upper end of the liquid phase hydrogenation reactor 3.

[0031] In this embodiment, the hydrogen from the oxalate hydrogenation unit of the system is used to draw out a DN25 hydrogen pipeline as the gas source for the liquid phase hydrogenation reactor 3. After depressurization and heating, the hydrogen is transported to the liquid phase hydrogenation reactor 3 to provide the necessary conditions for the hydrogenation reaction.

[0032] Simultaneously, the liquid-phase hydrogenation reaction converts double-bond impurities into ethylene glycol. This converted ethylene glycol then re-enters the distillation system to improve product purity, thus reducing the yield of originally qualified ethylene glycol and increasing the yield of polyester-grade ethylene glycol. Furthermore, the liquid-phase hydrogenation process does not require high temperatures; the reaction can be achieved at only 100°C. Therefore, the system's heating element can utilize 1.0 MPa steam condenser, significantly reducing steam consumption costs.

[0033] Preferably, in this embodiment, the upper part of the butanediol removal tower 2 is connected to the waste pot 202 and the butanediol removal tower reflux tank 203 in sequence through the third pipeline 201 according to the process flow. The butanediol removal tower reflux tank 203 refluxes part of the product after the light components are removed from the butanediol removal tower 2 back to the ethylene glycol refining tower 1 through the first reflux pipeline 204 of the butanediol removal tower reflux tank.

[0034] To further improve the processing effect, in this embodiment, the butanediol removal tower reflux tank 203 returns part of the product to the butanediol removal tower 2 through the second reflux pipeline 205 and performs light component removal treatment again.

[0035] The bottom of the butanediol removal tower 2 is connected to the ethylene glycol refining tower 1 via the butanediol removal tower reflux pipe 206.

[0036]

[0037] Table 2 above shows the composition and UV transmittance of the reflux liquid from the butanediol removal tower in the system.

[0038] Preferably, in this embodiment, after the product undergoes hydrogenation reaction in the reaction bed, it passes through a gas-liquid separation section at the bottom of the reactor to separate the gas and liquid phase products. The liquid product is refluxed to the butanediol removal tower 2 through the reflux pipeline of the liquid phase hydrogenation reactor 3.

[0039] The gaseous products are divided into three branches: The first branch is the gas-liquid separation section at the bottom of the liquid phase hydrogenation reactor 3, which transports the gaseous products to the hydrogen condenser 305 for cooling and then returns them to the liquid phase hydrogenation reactor 3. The second branch is to transport the gaseous products to the hydrogen recovery system for recycling. The third branch route directly transports the gaseous products to the flare for incineration.

[0040] The system for increasing the yield of polyester-grade ethylene glycol provided by the present invention, as described above, has the following beneficial effects: The system of this invention effectively improves the grade of ethylene glycol by adding a liquid-phase hydrogenation reactor 3. Based on a daily production of 360 tons of qualified ethylene glycol and polyester-grade ethylene glycol, a premium of 2,500 yuan per ton for the qualified grade, and an annual operating time of 8,000 hours, the annual additional benefit is approximately (360 × 88% - 360 × 82%) ÷ 24 × 8,000 × 2,500 = 18 million yuan. Compared with the initial investment, the investment payback period is approximately 4 months.

[0041] The system of this invention can effectively extend the service life of dealdehyde and deesterification catalysts, which not only improves product quality but also further reduces the number of times catalysts need to be replaced, thus saving production costs.

[0042] The system of the present invention can achieve the reaction through the steam condensate of the reboiler of the butanediol removal tower, thereby reducing steam consumption.

[0043] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A system for increasing the yield of polyester-grade ethylene glycol, characterized in that, The system includes: Ethylene glycol refining tower (1); The butanediol removal tower (2) is located upstream of the ethylene glycol refining tower (1) process; and The formaldehyde and ester removal tank (4) located downstream of the ethylene glycol refining tower (2) process, after the product of the ethylene glycol refining tower (1) reacts with the catalyst in the formaldehyde and ester removal tank (4), a high polyester grade ethylene glycol product is obtained. A liquid-phase hydrogenation reactor (3) is installed downstream of the ethylene glycol refining tower (1). The product of the ethylene glycol refining tower (1) is received by the liquid-phase hydrogenation reactor (3), and the product is hydrogenated to convert trace impurities in the product into light components.

2. The system for increasing the yield of polyester-grade ethylene glycol according to claim 1, characterized in that, The upper part of the ethylene glycol refining tower (1) is connected to an air cooler (103) and an ethylene glycol refining tower reflux tank (104) in sequence through a first pipeline (101) according to the process flow. The ethylene glycol refining tower reflux tank (104) is connected to the liquid phase hydrogenation reactor (3) through a first reflux pipeline (105) to transport the product of the ethylene glycol refining tower (1) to the liquid phase hydrogenation reactor (3). The lower part of the ethylene glycol refining tower (1) is connected to the dealdehyde and deesterification tank (4) via a second pipeline (102).

3. The system for increasing the yield of polyester-grade ethylene glycol according to claim 2, characterized in that, The upper end of the liquid phase hydrogenation reactor (3) is connected to the upstream hydrogenation unit (301) via a hydrogenation pipeline to input hydrogen into the liquid phase hydrogenation reactor (3). After being subjected to pressure reduction and heating treatment, this portion of hydrogen is collected at the top of the liquid phase hydrogenation reactor (3) along with the product output from the ethylene glycol refining tower (1).

4. A system for increasing the yield of polyester-grade ethylene glycol according to claim 2 or 3, characterized in that, The product after hydrogenation treatment in the liquid phase hydrogenation reactor (3) is returned to the butanediol removal tower (2) upstream of the process via the liquid phase hydrogenation reactor reflux pipeline (302).

5. The system for increasing the yield of polyester-grade ethylene glycol according to claim 4, characterized in that, The upper part of the butadiene glycol removal tower (2) is connected to the waste pot (202) and the butadiene glycol removal tower reflux tank (203) in sequence through the third pipeline (201) according to the process flow. The butadiene glycol removal tower reflux tank (203) refluxes part of the product after the light components are removed by the butadiene glycol removal tower (2) back to the ethylene glycol refining tower (1) through the first reflux pipeline (204) of the butadiene glycol removal tower reflux tank.

6. The system for increasing the yield of polyester-grade ethylene glycol according to claim 5, characterized in that, The butanediol reflux tank (203) refluxes part of the product back to the butanediol tower (2) through the second reflux pipeline (204) and performs light component removal treatment again.

7. The system for increasing the yield of polyester-grade ethylene glycol according to claim 4, characterized in that, The product in the liquid phase hydrogenation reactor (3) undergoes hydrogenation reaction in the reaction bed and then passes through the gas-liquid separation section at the bottom of the reactor to separate the gas and liquid phase products after the reaction. The liquid product is refluxed to the butanediol removal tower (2) through the reflux line (302) of the liquid phase hydrogenation reactor.

8. The system for increasing the yield of polyester-grade ethylene glycol according to claim 7, characterized in that, The gaseous products are divided into three branches: The first branch is the gas-liquid separation section at the bottom of the liquid phase hydrogenation reactor (3) after the gas phase product is transported to the hydrogen condenser (305) for cooling and then returned to the gas-liquid separation section. The second branch is to transport the gaseous products to the hydrogen recovery system for recycling. The third branch route directly transports the gaseous products to the flare for incineration.

9. The system for increasing the yield of polyester-grade ethylene glycol according to claim 3, characterized in that, The upstream hydrogenation unit (301) adopts the oxalate hydrogenation unit of the original system, and a hydrogen pipeline with a size of DN25 is led out from the oxalate hydrogenation unit and connected to the upper end of the liquid phase hydrogenation reactor (3).

10. The system for increasing the yield of polyester-grade ethylene glycol according to claim 5, characterized in that, The bottom of the butadiene glycol removal tower (2) is connected to the ethylene glycol refining tower (1) via the butadiene glycol removal tower reflux pipe (205).

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