System for improving product quality and polyester grade yield of ethylene glycol prepared from synthesis gas

Abstract

The system comprises a light component removal tower, a product tower and a liquid phase hydrogenation unit which are connected in series, crude ethylene glycol and alkali liquor are input into a feed port of the light component removal tower, desalted water is input into a reflux tank of the light component removal tower, light components are extracted from the top of the light component removal tower, and the liquid phase hydrogenation unit is connected with the light component removal tower. The bottom liquid of the light component removal tower is input into a product tower, a reducing additive is also introduced into a feed port of the product tower, an outlet material flow of a reflux pump of the product tower is divided into two streams, one stream is directly refluxed, the other stream is sent to the feed port of the light component removal tower as a circulating liquid, and an ethylene glycol product is collected from a rectifying section side of the product tower and is sent to a liquid phase hydrogenation unit for hydrogenation; carrying out gas-liquid separation on the hydrogenated material flow to obtain a polyester-grade ethylene glycol product; according to the utility model, alkali liquor neutralization, water azeotropic distillation, reducing additive, liquid phase hydrogenation and ethylene glycol distillation are organically coupled, the yield of polyester grade ethylene glycol is improved to 100%, and after liquid phase hydrogenation, the ethylene glycol product collected at the side of the product tower can reach the polyester grade index, so that the inherent quality of the ethylene glycol product is improved, meanwhile, a resin adsorption method is avoided, and the production cost is reduced. The operation is simple and stable, and the operation cost is low.

Description

Technical Field

[0001] The utility model belongs to the technical field of ethylene glycol refining and is suitable for industries such as preparing ethylene glycol from synthesis gas, preparing dimethyl carbonate with by-product ethylene glycol through ethylene oxide ester exchange, and preparing ethylene oxide with by-product ethylene glycol through ethylene. Background Art

[0002] Different from the petroleum route, the traditional synthesis gas to ethylene glycol process has problems such as poor product quality and low polyester grade yield. The quality problems of ethylene glycol products are mainly reflected in the low ultraviolet transmittance and the polyester grade ethylene glycol yield of about 90%, which seriously affects the economic benefits of the enterprise.

[0003] In order to improve the quality of ethylene glycol products and polyester grade yield from synthesis gas, domestic research units have conducted in-depth research and obtained industrial application. The main technical means are to add two units: resin adsorption and liquid phase hydrogenation. Resin adsorption is mainly used to improve the quality of ethylene glycol products, increase its ultraviolet transmittance and reduce the aldehyde content. Liquid phase hydrogenation is used to remove impurities from industrial-grade ethylene glycol produced by ethylene glycol distillation to improve its ultraviolet transmittance and reduce the aldehyde content. This part of industrial-grade ethylene glycol is returned to the ethylene glycol distillation tower after improving its quality through liquid phase hydrogenation, thereby increasing the ethylene glycol polyester grade yield from 90% to 100%.

[0004] Beijing Xinggao Chemical Technology Co., Ltd. proposed "CN201811358827.4 Coal-to-ethylene glycol refining method and system", which includes: weighing a preset amount of wet resin, pre-treating the wet resin into ion exchange resin, and then filling the ion exchange resin into each process tower in the fixed bed equipment; at a preset temperature, the coal-to-ethylene glycol is filtered through each process tower at a preset liquid hourly space velocity in turn, and through the action of different resins in each process tower, the carbonyl compound impurities and aldehyde compound impurities that affect the ultraviolet transmittance in the coal-to-ethylene glycol are converted into saturated substances that do not absorb ultraviolet light, and the ester compounds and ketone compounds that affect the ultraviolet transmittance in the coal-to-ethylene glycol are reduced to saturated substances that do not absorb ultraviolet light. It achieves the dual purpose of converting aldehyde compounds in coal-to-ethylene glycol and reducing ester compounds and ketone compounds, thereby effectively improving the quality of coal-to-ethylene glycol. This method can improve the quality of ethylene glycol products, but the resin will be saturated with adsorption and need to be regenerated and replaced from time to time. There are problems of high labor intensity and high operating costs caused by frequent operations. In addition, a large amount of regeneration wastewater containing acid, alkali and ethylene glycol needs to be discharged, which has high wastewater treatment costs and great environmental pressure.

[0005] Shaanxi Coal Group Yulin Chemical Co., Ltd. proposed "CN202111153328.3 A coal-to-ethylene glycol distillation system and its working method", including an ethylene glycol product tower, a reflux tank, a hydrogenation reactor and a hydrogenation separator; the inlet of the reflux tank is connected to the outlet of the ethylene glycol product tower, the outlet of the reflux tank is connected to the hydrogenation reactor and the hydrogenation separator in turn, the outlet of the reflux tank and the hydrogenation separator are connected to the inlet of the ethylene glycol product tower, and the inlet of the hydrogenation reactor is connected to hydrogen; the ethylene glycol product tower is provided with a reboiler. The ethylene glycol at the outlet of the ethylene glycol product tower is sent to the hydrogenation reactor through the reflux tank to react with hydrogen. The high-quality ethylene glycol generated in the hydrogenation reactor enters the hydrogenation separator for gas-liquid separation, and is sent to the ethylene glycol product tower. Finally, polyester-grade ethylene glycol is extracted from the side line. This method extends the operation cycle of coal-to-ethylene glycol distillation by reducing the formation of coke. This patent proposes liquid-phase hydrogenation of the reflux liquid of the ethylene glycol product tower, which can increase the polyester-grade yield of the ethylene glycol product and indirectly improve the quality of the side-cut product of the ethylene glycol product tower. However, the side-cut ethylene glycol product still needs to be adsorbed by resin to increase the ultraviolet transmittance and reduce the aldehyde content so that the ethylene glycol product reaches the polyester-grade index. Summary of the invention

[0006] In order to replace the resin adsorption process system, the utility model proposes a system for improving the quality of ethylene glycol products and the polyester grade yield from synthesis gas, which uses alkali solution, water azeotropy, additives, liquid phase hydrogenation and distillation for deep coupling to improve the quality of ethylene glycol products and the polyester grade yield.

[0007] The technical solution adopted by the utility model is as follows:

[0008] A system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas comprises a light-removing tower 1, a product tower 7 and a liquid phase hydrogenation unit, wherein the light-removing tower 1 and the product tower 7 are both vacuum distillation towers; a raw material pipeline is provided in the middle of the light-removing tower 1 for supplying crude ethylene glycol 101 as a raw material to be refined; the light-removing tower 1 is used to refine the crude ethylene glycol 101 and remove light components 104 at the top of the tower; the bottom of the light-removing tower 1 is connected to a feed inlet in the middle of the product tower 7 via a light-removing tower bottom pump 6; a side sampling pipeline is provided in the distillation section of the product tower 7, and the side sampling pipeline is connected to the liquid phase hydrogenation unit.

[0009] The top of the de-lightening tower 1 is connected with a de-lightening tower condenser 2, a de-lightening tower reflux tank 3 and a de-lightening tower reflux pump 4 in sequence; wherein, the de-lightening tower reflux tank 3 is provided with a de-watered water pipeline for inputting de-watered water 103 into the de-lightening tower reflux tank 3. The de-watered water 103 is mixed with the liquid phase light component and transported by the de-lightening tower reflux pump 4, a part of which is extracted as the light component 104, and the other part is refluxed to the top of the de-lightening tower 1, and the de-watered water 103 introduced into the de-lightening tower 1 through the reflux liquid can form water azeotropic distillation with light component impurities such as aldehydes, thereby improving the separation efficiency of the light component; and significantly reducing the aldehyde content at the bottom of the de-lightening tower 1.

[0010] The top of the product tower 7 is connected in sequence with a product tower condenser 8, a product tower reflux tank 9 and a product tower reflux pump 10; the outlet stream of the product tower reflux pump 10 is divided into two streams, one of which is sent back to the top of the product tower 7 as reflux liquid, and the rest is sent back to the feed port of the light removal tower 1 as circulating liquid 107 (industrial grade ethylene glycol). This circulation process can effectively prevent the accumulation of light components at the top of the product tower 7, thereby ensuring the purity of the side-cut ethylene glycol product 108, and the ethylene glycol in the circulating liquid can enter the product tower 7 again for refining after being treated in the light removal tower 1, thereby achieving a 100% yield of polyester-grade ethylene glycol products.

[0011] Alkali solution 102 is also introduced into the feed inlet of the light-removal tower 1, and reducing additive 106 is also introduced into the feed inlet of the product tower 7.

[0012] The side sampling pipeline includes a side sampling product cooler 11 connected to the distillation section of the product tower 7, and its output end is connected to the side sampling product buffer tank 12. The outlet of the side sampling product buffer tank 12 is connected to the material inlet of the liquid phase hydrogenation unit through the side sampling product pump 13.

[0013] Hydrogen 110 is also introduced into the material inlet of the liquid phase hydrogenation unit.

[0014] The liquid phase hydrogenation unit comprises a liquid phase hydrogenation reactor 16 and a flash tank 17 connected in series; the liquid phase hydrogenation reactor 16 is preferably a trickle bed reactor, which comprises a catalyst bed and a gas-liquid separation chamber located below the catalyst bed, and the upper and lower parts of the gas-liquid separation chamber are connected to the flash tank 17 through a purge gas pipe with a purge gas control valve and an ethylene glycol pipe with an ethylene glycol control valve, respectively. In the reactor, hydrogen 110 is a continuous phase, and liquid is a dispersed phase. The gas and liquid phases are separated in the gas-liquid separation chamber at the bottom of the reactor, and the separated gas phase enters the flash tank 17 through the purge gas pipe. The operating pressure of the reactor is controlled by hydrogen feed, and the hydrogen concentration in the reactor is adjusted by the purge gas control valve.

[0015] The catalyst used in the liquid phase hydrogenation reactor 16 is preferably an intrinsically safe supported nickel catalyst, and Raney nickel catalyst is not used.

[0016] The top of the flash tank 17 is connected to a purge gas cooler 18 to condense and recover part of the vaporized ethylene glycol.

[0017] A product pump 19 is provided at the bottom of the flash tank 17 , and an outlet of the product pump 19 is connected to a product cooler 20 for producing a cooled ethylene glycol product (polyester grade) 112 .

[0018] A light-removal tower reboiler 5 is provided at the bottom of the light-removal tower 1 ; a product tower reboiler 14 and a product tower kettle pump 15 are provided at the bottom of the product tower 7 , and the product tower kettle pump 15 is used to discharge the ethylene glycol heavy component 109 .

[0019] The utility model also provides a method for improving the quality of ethylene glycol products prepared from synthesis gas and the polyester grade yield, using an alkali solution, water azeotropy, additives and a system for deep coupling of liquid phase hydrogenation and distillation to purify ethylene glycol, and the specific steps are as follows:

[0020] (1) Crude ethylene glycol 101 from upstream enters light-removal tower 1, and alkali solution 102 is added to the feed of light-removal tower 1; in light-removal tower 1, low-boiling point components including 1,2-butanediol are separated from ethylene glycol, and the top of the tower is a mixture of low-boiling point components including 1,2-butanediol, aldehydes, and ethylene glycol, i.e., light component 104, and the bottom of the tower is mainly ethylene glycol, which is then refined in product tower 7.

[0021] (2) In the light removal tower 1, since the feed crude ethylene glycol 101 contains impurities such as aldehydes, and since vacuum distillation is used for separation, air will leak into the light removal tower 1, causing the alcohols to be oxidized into aldehydes. In order to reduce the aldehyde content at the bottom of the light removal tower 1, a water azeotropic distillation method is used, and desalted water 103 is added to the reflux tank 3 of the light removal tower. The aldehydes that azeotropize with water are enriched at the top of the tower and are discharged from the system along with part of the light components 104, thereby improving the quality of ethylene glycol obtained at the bottom of the light removal tower 1.

[0022] (3) Additive 106 is added from the feed pipeline of product tower 7. Reducing additive 106 helps to further reduce the aldehyde content in ethylene glycol in product tower 7 and improve the ultraviolet transmittance. A part of the condensate at the top of product tower 7 is returned to the light removal tower 1 as circulating liquid (industrial grade ethylene glycol) to achieve the purpose of 100% ethylene glycol polyester grade yield. High-purity ethylene glycol is removed from the liquid phase hydrogenation unit on the side of the rectification section of product tower 7, and ethylene glycol heavy components 109 are extracted from the bottom of product tower 7.

[0023] (4) The hydrogen 110 and the side-produced ethylene glycol product 108 are mixed and then sent to a liquid phase hydrogenation reactor 16. The liquid phase hydrogenation reactor 16 has a built-in hydrogenation catalyst. The liquid phase hydrogenation reactor 16 is a trickle bed reactor. The gas is a continuous phase, the liquid is a dispersed phase, and the gas, liquid, and solid react in three phases. Gas-liquid separation is performed at the bottom of the liquid phase hydrogenation reactor 16, and the purge gas and the hydrogenated liquid are sent to a flash tank 17.

[0024] (5) Low-pressure flash evaporation is performed in the flash tank 17, and the purge gas and the polyester-grade ethylene glycol after hydrogenation are separated. The purge gas 111 is recovered by the purge gas cooler 18, and the rest is sent to the external system. The ethylene glycol product 112 obtained after hydrogenation is cooled by the product pump 19 and the product cooler 20 and then sent to the tank area.

[0025] The light-removal tower 1 and the product tower 7 are both operated under reduced pressure.

[0026] The alkali solution 102 is NaOH alkali solution, preferably 32wt% NaOH. The amount of the alkali solution 102 added is determined according to the acid value of the bottom of the lightness removal tower 1 to control the acid value at 0-2mg / kg.

[0027] The amount of desalted water 103 added to the light-removal tower reflux tank 3 is determined according to the water content in the light component 104, so as to control the water content in the light component 104 to be between 5wt% and 20wt%.

[0028] The additive 106 is preferably added in an amount of 0 to 200 ppm.

[0029] Compared with the prior art, the utility model has the following beneficial effects: the yield of polyester-grade ethylene glycol is increased to 100% by adopting a process of deep coupling of alkali solution, water co-boiling, additives, liquid-phase hydrogenation and distillation; after liquid-phase hydrogenation, the ethylene glycol product collected from the product tower side reaches the polyester-grade index, thereby improving the intrinsic quality of the ethylene glycol product; the resin adsorption method is no longer used, the technology is more advanced, the operation is simple and stable, the operating cost is low, and it is more environmentally friendly, which is of great significance to the upgrading and transformation of ethylene glycol production technologies such as coal, coke oven gas or calcium carbide tail gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The schematic diagram of a system for improving the product quality and polyester grade yield of ethylene glycol produced from synthesis gas.

[0031] In the figure: 1 is a light removal tower, 2 is a light removal tower condenser, 3 is a light removal tower reflux tank, 4 is a light removal tower reflux pump, 5 is a light removal tower reboiler, 6 is a light removal tower kettle pump, 7 is a product tower, 8 is a product tower condenser, 9 is a product tower reflux tank, 10 is a product tower reflux pump, 11 is a side-cut product cooler, 12 is a side-cut product buffer tank, 13 is a side-cut product pump, 14 is a product tower reboiler, 15 is a product tower kettle pump, 16 is a liquid phase Hydrogenation reactor, 17 is a flash tank, 18 is a purge gas cooler, 19 is a product pump, 20 is a product cooler, 101 is crude ethylene glycol, 102 is alkali solution, 103 is desalted water, 104 is a light component, 105 is a product tower feed, 106 is an additive, 107 is a circulating liquid, 108 is a side-cut ethylene glycol product, 109 is an ethylene glycol heavy component, 110 is hydrogen, 111 is a purge gas, and 112 is an ethylene glycol product.

[0032] In the figure, CWS is circulating cooling water supply, CWR is circulating cooling water return, and LS is low-pressure steam. DETAILED DESCRIPTION

[0033] Example 1

[0034] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with the embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0035] According to the previous article and Figure 1 The system for improving the product quality and polyester grade yield of ethylene glycol produced from synthesis gas is shown, taking the 150,000 tons / year natural gas to ethylene glycol project of Xinjiang Production and Construction Corps Tianying Petrochemical Co., Ltd. as an example.

[0036] (1) Crude ethylene glycol 101 from upstream enters lightness removal tower 1 for refining, and alkali solution 102 is added to lightness removal tower feed 101. In lightness removal tower 1, low boiling point components containing 1,2-butanediol are separated from ethylene glycol, and the top of the tower is a mixture of low boiling point components containing 1,2-butanediol and ethylene glycol, and the bottom of the tower is mainly ethylene glycol, which is refined in product tower 7. Lightness removal tower 1 adopts negative pressure operation, and the operating pressure is 10kPaA.

[0037] (2) Desalted water 103 is added to the reflux tank 3 of the light-removal tower. The desalted water 103 enters the light-removal tower 1 along with the reflux liquid to form a water azeotrope with the aldehydes, thereby enriching the aldehydes at the top of the tower and being discharged from the system along with the light components 104, thereby improving the quality of ethylene glycol at the bottom of the light-removal tower 1.

[0038] (3) Additive 106 is added from the feed pipeline of product tower 7, and part of the industrial-grade ethylene glycol is taken from the top of product tower 7 as circulating liquid 107 to be fed back to light-removal tower 1 to achieve a 100% yield of ethylene glycol polyester grade. High-purity ethylene glycol is taken from the side of the rectification section of product tower 7 for liquid phase hydrogenation, and ethylene glycol heavy components 109 are taken from the bottom of product tower 7. Product tower 7 is operated under negative pressure, and the operating pressure is 10 kPaA.

[0039] (4) The hydrogen 110 and the side-produced ethylene glycol product 108 are mixed and sent to the liquid phase hydrogenation reactor 16. The liquid phase hydrogenation reactor 16 has a built-in hydrogenation catalyst. The reactor is a trickle bed reactor. The gas is a continuous phase, the liquid is a dispersed phase, and the gas, liquid, and solid react in three phases. The gas and liquid are separated at the bottom of the liquid phase hydrogenation reactor, and the vented gas and the hydrogenated liquid are sent to the flash tank 17. The operating conditions of the liquid phase hydrogenation reactor 16 are: 0.6 MPaG, 130°C.

[0040] (5) Low-pressure flash evaporation is performed in the flash tank 17, and the purge gas and the hydrogenated polyester-grade ethylene glycol are separated. The purge gas 111 is recovered by the purge gas cooler 18, and the rest is sent to the external system. The hydrogenated ethylene glycol product 112 is cooled by the product pump 19 and the product cooler 20 and then sent to the tank area.

[0041] Among them, the feed rate of crude ethylene glycol 101 is 20t / h, the addition rate of 32wt% alkali solution 102 is 15kg / h, the addition rate of desalted water 103 is 300kg / h, the addition rate of additive 106 is 20kg / h, the flow rate of side-collected ethylene glycol product 108 is 19t / h, and the flow rate of hydrogen 110 is 38Nm 3 / h.

[0042] Table 1 shows the data of the side-collected ethylene glycol product before and after liquid phase hydrogenation in Example 1. It can be seen from the table that after liquid phase hydrogenation, the aldehyde content and UV of ethylene glycol meet the national standard polyester grade requirements, aldehyde content ≤ 8ppm, 220nm UV transmittance ≥ 75%, 275nm UV transmittance ≥ 92%. Ethylene glycol after liquid phase hydrogenation no longer needs to be adsorbed with resin to improve quality, and the system operation stability is better.

[0043] Table 1 Data before and after liquid phase hydrogenation of side-recovered ethylene glycol product in Example 1

[0044]

[0045] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A system for improving the quality of ethylene glycol products prepared from synthesis gas and the polyester grade yield, comprising a lightness removal tower (1), a product tower (7) and a liquid phase hydrogenation unit, wherein the lightness removal tower (1) and the product tower (7) are both vacuum distillation towers; a raw material pipeline is provided in the middle of the lightness removal tower (1) for supplying crude ethylene glycol (101) as a raw material to be refined; the lightness removal tower (1) is used to refine the crude ethylene glycol (101) and remove light components (104) at the top of the tower; the bottom of the lightness removal tower (1) is connected to a feed inlet in the middle of the product tower (7) via a lightness removal tower bottom pump (6); and the system is characterized in that: The distillation section of the product tower (7) is provided with a side sampling pipeline, the side sampling pipeline is connected to the liquid phase hydrogenation unit, and the side sampling material is subjected to liquid phase hydrogenation to obtain an ethylene glycol product (112); an alkali solution (102) is introduced at the feed inlet of the light removal tower (1), and desalted water (103) is introduced at the top; and a reducing additive (106) is introduced at the feed inlet of the product tower (7).

2. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas according to claim 1, characterized in that: The top of the lightness removal tower (1) is connected in sequence to a lightness removal tower condenser (2), a lightness removal tower reflux tank (3) and a lightness removal tower reflux pump (4); wherein the lightness removal tower reflux tank (3) is provided with a desalted water pipeline for inputting desalted water (103) into the lightness removal tower reflux tank (3); the desalted water (103) is mixed with the liquid phase light component and then transported through the lightness removal tower reflux pump (4); a part of the desalted water is extracted as the light component (104), and the other part is refluxed to the top of the lightness removal tower (1).

3. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas as claimed in claim 2, characterized in that: The top of the product tower (7) is connected in sequence to a product tower condenser (8), a product tower reflux tank (9) and a product tower reflux pump (10); the outlet flow of the product tower reflux pump (10) is divided into two streams, one of which is sent back to the top of the product tower (7) as reflux liquid, and the rest is sent back to the feed inlet of the light removal tower (1) as circulating liquid (107).

4. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas as claimed in claim 3, characterized in that: The side sampling pipeline comprises a side sampling product cooler (11) connected to the distillation section of the product tower (7), the output end of which is connected to the side sampling product buffer tank (12), and the outlet of the side sampling product buffer tank (12) is connected to the material inlet of the liquid phase hydrogenation unit through the side sampling product pump (13); hydrogen (110) is also introduced into the material inlet of the liquid phase hydrogenation unit.

5. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas as claimed in claim 4, characterized in that: The liquid phase hydrogenation unit comprises a liquid phase hydrogenation reactor (16) and a flash tank (17) connected in series.

6. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas as claimed in claim 5, characterized in that: The liquid phase hydrogenation reactor (16) is a trickle bed reactor, which includes a catalyst bed and a gas-liquid separation chamber located below the catalyst bed. The upper part and the bottom part of the gas-liquid separation chamber are respectively connected to the flash tank (17) via a purge gas pipe with a purge gas control valve and an ethylene glycol pipe with an ethylene glycol control valve.

7. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas as claimed in claim 6, characterized in that: The catalyst used in the liquid phase hydrogenation reactor (16) is an intrinsically safe supported nickel catalyst, and no Raney nickel catalyst is used.

8. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas according to claim 7, characterized in that: The top of the flash tank (17) is connected to a purge gas cooler (18) to condense and recover part of the vaporized ethylene glycol; the bottom of the flash tank (17) is provided with a product pump (19), and the outlet of the product pump (19) is connected to a product cooler (20) for extracting a cooled ethylene glycol product (112).

9. The system for improving the product quality and polyester grade yield of ethylene glycol prepared from synthesis gas as claimed in claim 8, characterized in that: A light-removal tower reboiler (5) is provided at the bottom of the light-removal tower (1); a product tower reboiler (14) and a product tower kettle pump (15) are provided at the bottom of the product tower (7), and the product tower kettle pump (15) is used to discharge the ethylene glycol heavy component (109).

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