Device for generating ethylene glycol through reaction by using plate-type reactor in process of preparing ethylene glycol from natural gas

Abstract

The invention discloses a device for generating ethylene glycol through reaction by using a plate type reactor in preparation of ethylene glycol from natural gas. Comprising a steam pocket, an ethylene glycol synthesis reactor, a material inlet and outlet heat exchanger, a high-pressure separator I, a low-pressure flash tank I, a crude ethylene glycol water cooler, a synthesis water cooler A, a synthesis water cooler B, a steam heater II, a steam heater I, a DMO evaporation tower, a DMO feeding pump, a DMO buffer tank, a high-pressure separator II, a low-pressure flash tank II, a hydrogen recycle gas compressor and a steam pocket circulating pump, the ethylene glycol synthesis reactor adopts a plate-type reactor, and a catalyst used by the ethylene glycol synthesis reactor is a copper-based catalyst. The problems that the tubular reactor is easy to block and the catalyst is easy to coke are effectively solved, so that the product production is more stable, the yield and the heat exchange effect are improved, the energy consumption and the production cost are reduced, the price advantage of the product is enhanced, and economic benefits are brought to enterprises.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene glycol production devices, and in particular to a device for producing ethylene glycol by using a plate-type reactor in the process of producing ethylene glycol from natural gas. Background Art

[0002] Ethylene glycol (EG), also known as glycol or 1,2-ethylene glycol, has a chemical formula of C2H6O2 and is the simplest aliphatic diol. At room temperature, ethylene glycol is a colorless, odorless, sweet viscous liquid with two hydroxyl groups connected to two carbon atoms in its molecule. The molecular weight of ethylene glycol is 62.07, the melting point is -13°C, the boiling point is 197.3°C (760mmHg), and the density is 1.1135g / mL (20°C). Ethylene glycol has the characteristics of high boiling point, low freezing point and weak reducibility. It can be miscible with water in any proportion and is slightly soluble in ether. Ethylene glycol has active chemical properties and can undergo a series of reactions such as oxidation, esterification, condensation and dehydration. Ethylene glycol itself has low toxicity and will produce toxic metabolites in the human body. Even a small amount of intake will cause irreversible damage to the human central nervous system and various organs. Ethylene glycol is a widely used organic compound with many uses, such as manufacturing chemicals, automotive antifreeze, automotive brake fluid, printing and dyeing chemicals, refrigerants, solvents for synthetic resins, medicines and cosmetics, textile auxiliaries, fuels, and other applications.

[0003] There are two main production methods for ethylene glycol: petroleum route and non-petroleum route. There are three main production processes for ethylene glycol from petroleum ethylene, namely, ethylene oxide (EO) hydration, ethylene oxide intermediate synthesis of ethylene glycol, and ethylene glycol co-production of dimethyl carbonate. There are two main production processes for non-petroleum route, namely direct synthesis and indirect synthesis.

[0004] 1. Oil route production process

[0005] Ethylene oxide hydration method. Ethylene oxide hydration method is the main method for producing ethylene glycol in the world today. This method usually involves mixing ethylene oxide with water, then exchanging heat with the compound of ethylene glycol and water leaving the hydrolysis reactor, and then entering the hydrolysis reactor for hydrolysis after preheating. Due to the high water consumption and low conversion rate of the above process, direct catalytic hydration technology has begun to receive attention in recent years. Representative ones include Shell's heterogeneous catalytic hydration method and Dow's homogeneous catalytic hydration method. Dow's MeteorEG300 catalyst has also been running on a demonstration unit, with a selectivity of ethylene glycol exceeding 95%.

[0006] The process of synthesizing ethylene glycol from ethylene oxide via intermediates. Currently, the more mature process is the process of producing ethylene glycol from ethylene oxide via ethylene carbonate. The Shell OMEGA process is a process in which ethylene oxide and carbon dioxide react to form ethylene carbonate, which is then hydrolyzed under the action of a catalyst to form ethylene glycol and carbon dioxide. The selectivity of this process from EO to EG is greater than 99%, which is higher than the selectivity of traditional processes, and reduces equipment investment and energy and material consumption. It has been industrialized in ethylene glycol plants such as Lotte Daesan Company in South Korea. Asahi Kasei Company of Japan uses the reaction of ethylene oxide and carbon dioxide, and then undergoes ester exchange with methanol to produce polycarbonate (PC) and ethylene glycol. This process has been commercialized by Asahi Chemical Co., Ltd. in Taiwan, China.

[0007] The method of co-producing dimethyl carbonate with ethylene glycol. The method of co-producing dimethyl carbonate (DMC) with ethylene glycol (ester exchange method) was developed by Texaco Chemical Company in the United States in recent years. At present, there is no industrial production device for this process in China.

[0008] 2. Non-petroleum production process

[0009] The direct synthesis method is the simplest and most effective method. However, the reaction conditions of the direct method are relatively harsh, requiring high temperature and high pressure catalysts, and the catalyst rhodium is very expensive. At the same time, a large amount of by-product formate is produced. The reaction conversion rate and selectivity are relatively low, so it has not been widely promoted and applied.

[0010] The indirect synthesis method is to first produce synthesis gas by coal gasification, then synthesize dimethyl oxalate from the synthesis gas, and then further react to synthesize ethylene glycol. The indirect synthesis method has a long process flow, complicated steps, complex equipment types, and more by-products. At present, most domestic constructions adopt this process.

[0011] In the domestic production of ethylene glycol devices, whether it is coal-to-ethylene glycol or natural gas-to-ethylene glycol, shell-and-tube reactors are used in the ethylene glycol hydrogenation synthesis reaction. Shell-and-tube reactors have the advantages of efficient mixing, temperature balance, and low energy consumption, but they also have disadvantages such as solid phase garbage clogging and poor heat transfer. Copper catalysts are used in coal-to-ethylene glycol or natural gas-to-ethylene glycol. The reaction releases a large amount of heat, and a steam drum is required to remove the heat released by the reaction. However, in the later stage, the outer wall of the reactor tube will scale, affecting the heat exchange effect. At the same time, the copper catalyst will coke at high temperature, forcing the reactor catalyst to skim or replace the catalyst, which affects the output and benefits, and is also prone to unstable product quality, bringing considerable economic losses and safety risks to the company. Summary of the invention

[0012] In order to solve one or some technical problems existing in the prior art, the purpose of the present application is to provide a device for generating ethylene glycol using a plate reactor in the natural gas to ethylene glycol reaction, which effectively solves the problems that the shell and tube reactor is easy to be blocked and the catalyst is easy to coke, makes the product production more stable, and reduces energy consumption and production costs while increasing the output and heat exchange effect, thereby enhancing the product price advantage and bringing economic benefits to the enterprise.

[0013] In order to solve the above existing technical problems, this application adopts the following technical solutions:

[0014] The invention discloses a device for generating ethylene glycol by using a plate reactor in natural gas production. The device comprises a steam drum, an ethylene glycol synthesis reactor, an inlet and outlet material heat exchanger, a high-pressure separator I, a low-pressure flash tank I, a crude ethylene glycol water cooler, a synthesis water cooler A, a synthesis water cooler B, a steam heater II, a steam heater I, a DMO evaporation tower, a DMO feed pump, a DMO buffer tank, a high-pressure separator II, a low-pressure flash tank II, a hydrogen circulating gas compressor, and a steam drum circulation pump. The ethylene glycol synthesis reactor adopts a plate reactor, and the catalyst used in the ethylene glycol synthesis reactor is a copper-based catalyst.

[0015] Fresh hydrogen from the gas workshop is mixed with the circulating gas at the outlet of the hydrogen circulating gas compressor and then enters the inlet and outlet material heat exchanger, and then enters the steam heater II for heating after heat exchange with the synthetic gas at the outlet of the ethylene glycol synthesis reactor, and then enters the DMO evaporation tower; DMO from the DMO distillation device enters the DMO buffer tank, is pressurized by the DMO feed pump, and then is sent to the upper part of the DMO evaporation tower to be fully mixed with the circulating gas, and then enters the ethylene glycol synthesis reactor for reaction to generate ethylene glycol after being heated by the steam heater I;

[0016] The hot water in the drum enters the tube side of the ethylene glycol synthesis reactor through the downcomer or the drum circulation pump, the steam-water mixture formed after the ethylene glycol synthesis reactor absorbs the reaction heat returns to the drum through the riser, and the steam after the steam-drum liquid is separated is sent to the 0.5MPa steam network;

[0017] The material at the outlet of the ethylene glycol synthesis reactor enters the inlet and outlet material heat exchanger, and after the synthesis gas is cooled, enters the high-pressure separator I for gas-liquid separation. The gas phase is cooled by the synthesis water cooler A and the synthesis water cooler B, and then enters the high-pressure separator II for gas-liquid separation.

[0018] The gas separated by the high-pressure separator II enters the hydrogen circulating gas compressor for circulation, and the gas at the outlet of the hydrogen circulating gas compressor returns to the synthesis system.

[0019] The liquid phase separated by the high-pressure separator II is depressurized and enters the low-pressure flash tank II. The liquid phase after flashing is sent to the crude methanol intermediate tank or directly sent to the ethylene glycol distillation device; the flash gas after flashing is sent to the fuel gas pipeline network or the flare;

[0020] The liquid phase of the high-pressure separator I is depressurized and enters the low-pressure flash tank I. After flashing, the liquid phase is cooled by the crude ethylene glycol water cooler and then sent to the crude ethylene glycol intermediate tank or directly sent to the ethylene glycol distillation device; the flash gas after flashing is sent to the fuel gas pipeline network or the flare.

[0021] Preferably, an inlet separator is provided between the high-pressure separator II and the hydrogen circulating gas compressor, a PSA device is provided between the hydrogen circulating gas compressor and the inlet separator, and the inlet separator is connected to the low-pressure flash tank II through a pipeline.

[0022] The circulating gas separated by the high-pressure separator II enters the inlet separator for gas-liquid separation. The separated liquid phase is discharged to the low-pressure flash tank II. The gas phase is compressed by the hydrogen circulating gas compressor in two stages and then mixed with the fresh hydrogen in the gas workshop and enters the inlet and outlet material heat exchanger. Most of the gas at the outlet of the hydrogen circulating gas compressor returns to the synthesis system, and a small part of the gas enters the PSA device for hydrogen purification. The purified gas returns to the inlet separator and merges with the circulating gas before entering the hydrogen circulating gas compressor. The PSA device can accurately control the hydrogen concentration in the circulation system. When the hydrogen concentration in the circulating gas becomes low, while injecting fresh hydrogen, the PSA device can purify the hydrogen in the mixed gas and recycle it to achieve a stable hydrogen content in the hydrogen circulating gas compressor. The waste can be sent to the waste gas incineration section for treatment through the PSA device, effectively avoiding the impact of direct discharge on the environment.

[0023] Preferably, the drum circulation pump is used only when the catalyst is heated for reduction, and the drum is continuously replenished with boiler water.

[0024] Preferably, the steam pressure of the steam heater II is 3.8 MPa, and the temperature of the mixed gas of fresh hydrogen and circulating hydrogen after passing through the steam heater II is 170°C-185°C.

[0025] Preferably, the temperature of the circulating gas in the DMO buffer tank after being fully mixed with DMO is 150° C.-175° C.

[0026] Preferably, the DMO from the DMO distillation device is: ≥99.5%, DMC≤1000PPm, acidity≤100PPm, moisture≤500PPm. The temperature is about: 90℃-100℃.

[0027] Preferably, the temperature of the circulating gas and DMO mixed gas heated by the steam heater I is 170°C-180°C.

[0028] Preferably, the water temperature and pressure of the drum are used to control the reaction temperature and remove the reaction heat, and the pressure of the drum is controlled at 0.65 MPa-0.98 MPa.

[0029] Preferably, the temperature of the outlet of the ethylene glycol synthesis reactor after heat exchange with the circulating synthesis gas through the inlet and outlet material heat exchanger is 70°C-90°C.

[0030] Preferably, the temperature of the gas phase in the high-pressure separator I after being cooled by the synthetic water cooler A and the synthetic water cooler B is 30°C-40°C.

[0031] Preferably, the circulation flow rate of the gas phase of the high-pressure separator II entering the inlet of the hydrogen circulation gas compressor is 550000Nm 3 / h-700000Nm 3 / h.

[0032] Preferably, the liquid phase in the high-pressure separator I is depressurized to 0.4 MPa and then sent to the low-pressure flash tank I, and the liquid phase in the high-pressure separator II is depressurized to 0.4 MPa and then sent to the low-pressure flash tank II.

[0033] Preferably, the liquid phase after flashing in the low-pressure flash tank I and the low-pressure flash tank II is sent to the ethylene glycol distillation device or the intermediate tank area by using its own pressure, and the pressure is controlled to be 0.35MPa-0.38MPa.

[0034] Preferably, the pressure of the low-pressure flash tank I and the low-pressure flash tank II is controlled by split-range, and is first sent to the fuel gas outlet, and when the opening of the regulating valve sent to the fuel gas outlet reaches 50%, it is sent to the flare outlet.

[0035] Preferably, the liquid level of the high-pressure separator I and the high-pressure separator II is 40%-50%; the liquid level of the low-pressure flash tank I and the low-pressure flash tank II is controlled at 40%-50%, the liquid level of the inlet separator is controlled at 40%-50%; and the liquid level of the steam drum is controlled at 60%-70%.

[0036] Preferably, the pressure in the synthesis circulation system formed by the inlet and outlet material heat exchanger, high-pressure separator I, synthesis water cooler A, synthesis water cooler B, high-pressure separator II, inlet separator, hydrogen circulation gas compressor, steam heater II, steam heater I, DMO evaporation tower, and ethylene glycol synthesis reactor is controlled at 2.7MPa-2.9MPa.

[0037] Preferably, the requirements for the fresh hydrogen mixed into the circulating gas at the outlet of the hydrogen circulating gas compressor are: concentration ≥ 99.9%, Cl -1≤0.01PPm, CO+CO2≤20PPm, moisture≤1000PPm, total sulfur≤0.1PPm, O2≤30PPm.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The entire device adopts a plate reactor to produce ethylene glycol. The overall structure is compact, occupies a small area, and is easy to install and move. At the same time, compared with the shell-and-tube reactor, the plate reactor increases the catalyst loading amount, improves the production capacity and output, reduces the system energy consumption and production costs, and creates objective economic benefits for the enterprise.

[0040] 2. In the ethylene glycol synthesis reaction, copper-based catalysts are used. The reaction will release a large amount of heat. If the heat exchange effect is poor, the catalyst will coke, affecting the service life of the catalyst. Therefore, the ethylene glycol synthesis reactor uses a plate reactor with a large heat transfer area, which can effectively transfer heat. This reactor can greatly slow down the coking time of the catalyst, extend the service life of the catalyst, reduce the economic losses caused by inspection and maintenance, and make product production more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a process flow chart of the present invention;

[0042] In the figure: 1. steam drum; 2. ethylene glycol synthesis reactor; 3. steam drum circulation pump; 4. inlet and outlet material heat exchanger; 5. high-pressure separator I; 6. low-pressure flash tank I; 7. crude ethylene glycol water cooler; 8. synthesis water cooler A; 9. synthesis water cooler B; 10. high-pressure separator II; 11. low-pressure flash tank II; 12. inlet separator; 13. PSA unit; 14. hydrogen circulating gas compressor; 15. DMO feed pump; 16. DMO buffer tank; 17. DMO evaporation tower; 18. steam heater I; 19. steam heater II. DETAILED DESCRIPTION

[0043] Below, the present application is further described in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0044] In the description of the present application, it should be understood that the terms "up", "down", "left", "right", etc., indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0045] The terms "first", "second", etc. in this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0046] like Figure 1 As shown, a device for generating ethylene glycol by using a plate reactor in natural gas to ethylene glycol reaction comprises a steam drum 1, an ethylene glycol synthesis reactor 2, an inlet and outlet material heat exchanger 4, a high-pressure separator I5, a low-pressure flash tank I6, a crude ethylene glycol water cooler 7, a synthetic water cooler A8, a synthetic water cooler B9, a steam heater II, a steam heater I18, a DMO evaporation tower 17, a DMO feed pump 15, a DMO buffer tank 16, a high-pressure separator II10, a low-pressure flash tank II11, a hydrogen circulating gas compressor 14, and a circulating pump 3 of the steam drum 1. The ethylene glycol synthesis reactor 2 adopts a plate reactor, and the catalyst used in the ethylene glycol synthesis reactor 2 is a copper-based catalyst.

[0047] During operation, the fresh hydrogen from the gas workshop is mixed with the circulating gas at the outlet of the hydrogen circulating gas compressor 14 and then enters the inlet and outlet material heat exchanger 4, and then enters the steam heater II for heating after heat exchange with the synthetic gas at the outlet of the ethylene glycol synthesis reactor 2, and then enters the DMO evaporation tower 17; the DMO from the DMO distillation device enters the DMO buffer tank 16, is pressurized by the DMO feed pump 15, and then is sent to the upper part of the DMO evaporation tower 17 to be fully mixed with the circulating gas, and then enters the ethylene glycol synthesis reactor 2 for reaction to generate ethylene glycol after being heated by the steam heater I 18;

[0048] The hot water in the drum 1 enters the plate core of the ethylene glycol synthesis reactor 2 through the downcomer or the circulation pump 3 of the drum 1. The steam-water mixture formed after the ethylene glycol synthesis reactor 2 absorbs the reaction heat returns to the drum 1 through the riser. The steam after the steam-liquid separation of the drum 1 is sent to the 0.5MPa steam network.

[0049] The outlet material of the ethylene glycol synthesis reactor 2 enters the inlet and outlet material heat exchanger 4, and after the synthesis gas is cooled, it enters the high-pressure separator I5 for gas-liquid separation. The gas phase is cooled by the synthesis water cooler A8 and the synthesis water cooler B9, and then enters the high-pressure separator II10 for gas-liquid separation.

[0050] The gas separated by the high-pressure separator II 10 enters the hydrogen circulating gas compressor 14 for circulation, and the gas at the outlet of the hydrogen circulating gas compressor 14 returns to the synthesis system.

[0051] The liquid phase separated by the high-pressure separator II 10 is depressurized and enters the low-pressure flash tank II 11. The liquid phase after flashing is sent to the crude methanol intermediate tank or directly sent to the ethylene glycol distillation device; the flash gas after flashing is sent to the fuel gas pipeline network or the flare;

[0052] The liquid phase of the high-pressure separator Ⅰ5 is depressurized and enters the low-pressure flash tank Ⅰ6. After flash evaporation, the liquid phase is cooled by the crude ethylene glycol water cooler 7 and then sent to the crude ethylene glycol intermediate tank or directly sent to the ethylene glycol distillation device; the flash gas after flash evaporation is sent to the fuel gas pipeline network or the flare.

[0053] At present, in the ethylene glycol devices produced domestically, whether it is coal-to-ethylene glycol or natural gas-to-ethylene glycol, shell-and-tube reactors are used in the ethylene glycol hydrogenation synthesis reaction. Although shell-and-tube reactors have the advantages of efficient mixing, temperature balance, and low energy consumption, they also have disadvantages such as solid phase garbage clogging, difficulty in cleaning, and poor heat transfer. Copper catalysts are used in coal-to-ethylene glycol or natural gas-to-ethylene glycol. The reaction releases a large amount of heat, and a steam drum 1 is required to remove the heat released by the reaction. However, in the later stage, the outer wall of the reactor shell and tube will scale, affecting the heat exchange effect. The copper catalyst will coke at high temperature, forcing the reactor catalyst to skim or replace the catalyst, which affects the output and benefits, and also brings economic losses and safety risks.

[0054] In order to solve the above problems, the process flow is as follows: fresh hydrogen is mixed with the circulating gas at the outlet of the hydrogen circulating gas compressor 14, and then enters the inlet and outlet material heat exchanger 4, and then enters the steam heater II for heating after heat exchange with the synthesis gas at the outlet of the ethylene glycol synthesis reactor 2, and then enters the DMO evaporation tower 17. The DMO from the DMO distillation device enters the DMO buffer tank 16, and is pressurized by the DMO feed pump 15 and sent to the upper part of the DMO evaporation tower 17, where it is fully mixed with the circulating gas, and then enters the ethylene glycol synthesis reactor 2 after heating by the steam heater I 18, and reacts to generate ethylene glycol under the action of the copper catalyst. The material at the reactor outlet enters the inlet and outlet material heat exchanger 4 and enters the high-pressure separator Ⅰ5 for gas-liquid separation after being cooled by the synthesis gas. The gas phase enters the high-pressure separator Ⅱ10 for gas-liquid separation after being cooled by the synthesis water cooler. The separated gas enters the hydrogen circulating gas compressor 14 for circulation. The gas at the outlet of the circulating gas compressor returns to the synthesis system. The liquid phase of the high-pressure separator Ⅰ5 enters the low-pressure flash tank Ⅰ6. After flashing, the liquid phase is cooled by the crude ethylene glycol water cooler 7 and sent to the crude ethylene glycol intermediate tank or directly to the ethylene glycol distillation device. The liquid phase of the high-pressure separator Ⅱ10 is decompressed and enters the low-pressure flash tank Ⅱ11. After flashing, the liquid phase is sent to the crude methanol intermediate tank or directly to the ethylene glycol distillation device. The flash gas of the low-pressure flash tank is sent to the fuel gas pipeline network or flare. The hot water in the drum 1 enters the reactor plate core through the downcomer or the drum 1 circulation pump 3, absorbs the reaction heat to form a steam-water mixture, and returns to the drum 1 through the riser. The steam after gas-liquid separation is sent to the steam pipe network; in order to maintain the stability of the liquid level of the drum 1, it is necessary to continuously add boiler water to the drum 1. The circulating gas from the high-pressure separator Ⅱ10 enters the hydrogen circulating gas compressor 14 inlet separator 12 for gas-liquid separation. The separated liquid phase is discharged to the low-pressure flash tank Ⅱ11. The gas phase is compressed by the hydrogen circulating gas compressor 14 in two stages and then mixed with fresh hydrogen to enter the inlet and outlet material heat exchanger 4. The present invention uses a new type of reactor, using an ethylene glycol synthesis reactor 2, and utilizing the compact structure of the plate reactor, small footprint, easy installation and movement. At the same time, the plate reactor increases the catalyst loading amount, improves the production capacity and output, reduces the system energy consumption and production cost compared with the shell and tube reactor, and creates objective economic benefits for the enterprise. The plate reactor has a large heat transfer area and can effectively transfer heat. In the ethylene glycol synthesis reaction, copper catalysts are used. The reaction will release a lot of heat. If the heat exchange effect is poor, the catalyst may coke and affect the service life of the catalyst. Therefore, this reactor can greatly slow down the coking time of the catalyst, delay the service life of the catalyst, and reduce the economic losses caused by inspection and maintenance of the enterprise. This plate reactor is used for the first time in the ethylene glycol industry. While increasing production and increasing benefits, it also provides a research direction for the ethylene glycol industry to reduce energy consumption and increase production capacity.

[0055] As a further improvement, an inlet separator 12 is provided between the high-pressure separator II 10 and the hydrogen circulating gas compressor 14, a PSA device 13 is provided between the hydrogen circulating gas compressor 14 and the inlet separator 12, and the inlet separator 12 is connected to the low-pressure flash tank II 11 through a pipeline.

[0056] The circulating gas separated by the high-pressure separator II 10 enters the inlet separator 12 for gas-liquid separation, and the separated liquid phase is discharged to the low-pressure flash tank II 11. The gas phase is compressed in two stages by the hydrogen circulating gas compressor 14 and mixed with the fresh hydrogen in the gas workshop before entering the inlet and outlet material heat exchanger 4. Most of the gas at the outlet of the hydrogen circulating gas compressor 14 returns to the synthesis system, and a small part of the gas enters the PSA device 13 for hydrogen purification. The purified gas returns to the inlet separator 12 and merges with the circulating gas before entering the hydrogen circulating gas compressor 14. The PSA device 13 can accurately control the hydrogen concentration in the circulation system. When the hydrogen concentration in the circulating gas becomes low, while injecting fresh hydrogen, the PSA device 13 can purify the hydrogen in the mixed gas and recycle it to achieve the stability of the hydrogen content in the hydrogen circulating gas compressor 14. The waste gas can be sent to the waste gas incineration section for treatment through the PSA device 13, effectively avoiding the impact of direct discharge on the environment.

[0057] Further improvement is that the steam pressure of the steam heater II is 3.8MPa, and the temperature of the mixed gas of fresh hydrogen and circulating hydrogen after passing through the steam heater II is 170℃-185℃; the temperature of the circulating gas in the DMO buffer tank 16 after being fully mixed with DMO is 150℃-175℃.

[0058] After fresh hydrogen and circulating hydrogen pass through steam heater II, they need to be heated to 175°C-185°C. The temperature of the circulating gas after being fully mixed with DMO is 150°C-175°C. In order to make all DMO gasified and enter the ethylene glycol synthesis reactor 2 with the circulating gas, it is necessary to add 3.8MPa steam to the steam heater II, heat the circulating gas, and use the temperature of the circulating gas to make all the DMO entering the upper part of the DMO evaporation tower 17 gasified. The temperature after the circulating gas and DMO are mixed is controlled by controlling the amount of steam entering the steam heater II. The temperature is controlled to be lower than 150°C to become liquid and enter the bottom of the DMO evaporation tower 17. Too much will cause the system pressure difference to be too high, causing the compressor to trip. If the temperature is too high, on the one hand, it will cause steam waste, and on the other hand, it will cause DMO sintering, affecting the reaction and product quality. Therefore, the temperature is generally between 150°C-175°C.

[0059] Further improvement is that the DMO from the DMO distillation device is: ≥99.5%, DMC≤1000PPm, acidity≤100PPm, moisture≤500PPm. The temperature is about: 90℃-100℃; the temperature of the circulating gas and DMO mixed gas heated by the steam heater I18 is 170℃-180℃.

[0060] The inlet temperature of the ethylene glycol synthesis reactor 2 will directly affect the reactor bed temperature, and this temperature plays a great role in the activity of the catalyst. Therefore, the control of this temperature must be stable. The control of the inlet synthesis gas temperature of the ethylene glycol synthesis reactor 2 is achieved by controlling the steam amount of the steam heater Ⅰ18151-E-1002 while ensuring the stability of the gas phase temperature of the DMO evaporation tower 17. Therefore, the circulating gas is controlled to be fully mixed with DMO and then heated by the steam heater Ⅰ18 to a temperature of 170℃-180℃.

[0061] A further improvement is that the reaction temperature is controlled by utilizing the water temperature and pressure of the steam drum 1 to remove the reaction heat, and the pressure of the steam drum 1 is controlled at 0.65MPa-0.98MPa; one side of the steam drum 1 is also connected to a water supply pipeline connected to boiler water, and the circulation pump 3 of the steam drum 1 is only used when the catalyst is heated and reduced, and the steam drum 1 is continuously replenished with boiler water.

[0062] The ethylene glycol synthesis reactor 2 is an exothermic reaction, so the heat released by the reaction needs to be removed. In order to control and remove the heat released by the reaction in the ethylene glycol synthesis reactor 2, a drum 1 is set up, and the water temperature and pressure of the drum 1 are used to control the reaction temperature and remove the reaction heat. The pressure of the drum 1 is controlled at 0.65MPa-0.98MPa. The hot water in the drum 1 enters the reactor plate core through the downcomer or the drum 1 circulation pump 3 (the drum 1 circulation pump 3 is only used when the catalyst is heated and reduced), and after absorbing the reaction heat, a steam-water mixture is formed and returned to the drum 1 through the riser. The steam after steam-liquid separation is sent to the 0.5MPa steam network; in order to maintain the stability of the liquid level of the drum 1, boiler water needs to be continuously added to the drum 1. By controlling the pressure of the drum 1, the water temperature is controlled, so as to control the bed temperature of the reactor. If the pressure of the drum 1 is too low, the reaction is incomplete, which may cause DMO to not be fully reacted and converted. If the pressure of the drum 1 is too high, on the one hand, there are too many reaction by-products, which will affect the product quality. On the other hand, if the pressure of the drum 1 is too high, the catalyst will be coked. Therefore, the pressure of drum 1 is controlled at 0.65MPa-0.98MPa based on the system load and the sampling and analysis data of high-pressure separation unit 1.

[0063] A further improvement is that the temperature of the outlet of the ethylene glycol synthesis reactor 2 after heat exchange with the circulating synthesis gas through the inlet and outlet material heat exchanger 4 is 70℃-90℃; the temperature of the gas phase of the high-pressure separator Ⅰ5 after cooling through the synthesis water cooler A8 and the synthesis water cooler B9 is 30℃-40℃.

[0064] A further improvement is that the circulation flow rate of the gas phase from the high-pressure separator II 10 entering the inlet of the hydrogen circulation gas compressor 14 is 550,000 Nm3 / h-700,000 Nm3 / h.

[0065] Since the ethylene glycol synthesis reactor 2 is an exothermic reaction, the heat released by the reaction needs to be removed. However, when the circulation flow rate is lower than 550,000 Nm3 / h, the heat of the ethylene glycol synthesis reactor 2 may not be removed in time, resulting in coking, unqualified product quality, and even equipment damage. When the circulation flow rate is higher than 700,000 Nm3 / h, the copper-based catalyst does not react fully, resulting in unqualified product quality, and may also easily cause catalyst crushing. Therefore, the circulation flow rate of the gas phase entering the inlet of the hydrogen circulating gas compressor 14 is between 550,000 Nm3 / h-700,000 Nm3 / h.

[0066] At the same time, the circulating hydrogen-ester ratio in the entire cycle is calculated based on the ratio of the molar amount of hydrogen in the circulating gas to the molar amount of dimethyl oxalate. If the hydrogen-ester ratio is too low, the catalyst bed temperature may rise, which may cause catalyst sintering in severe cases; if the hydrogen-ester ratio is too high, the catalyst bed temperature may drop, the synthesis loop pressure rises, and in severe cases, the catalyst bed temperature may cross the temperature. Therefore, the molar amount of hydrogen and the molar amount of dimethyl oxalate in the entire circulation system are controlled between 60 and 80, and the circulation flow rate is controlled. In the initial stage, the catalyst has good activity and more over-hydrogenation reactions. At this time, low load and high hydrogen-ester ratio operation should be adopted. When adjusting the circulating hydrogen-ester ratio, both the circulation amount of the hydrogen circulating gas compressor 14 and the addition amount of dimethyl oxalate (DMO) can be adjusted, but both cannot be adjusted at the same time. When the circulating hydrogen-ester ratio is too high, the circulating volume of the hydrogen circulating gas compressor 14 can be reduced to reduce the circulating hydrogen-ester ratio; when the circulating hydrogen-ester ratio is too low, the circulating volume of the hydrogen circulating gas compressor 14 can be increased to increase the circulating hydrogen-ester ratio.

[0067] A further improvement is that the liquid phase of the high-pressure separator I5 is depressurized to 0.4MPa and then sent to the low-pressure flash tank I6, and the liquid phase of the high-pressure separator II10 is depressurized to 0.4MPa and then sent to the low-pressure flash tank II11; the liquid phase after flashing in the low-pressure flash tank I6 and the low-pressure flash tank II11 is sent to the ethylene glycol distillation device or the intermediate tank area using its own pressure, and the pressure is controlled to be 0.35MPa-0.38MPa.

[0068] After separation by high-pressure separator Ⅰ5, some inert gases such as hydrogen and nitrogen are dissolved in the crude ethylene glycol material. In order to prevent these gases from entering the distillation section and affecting production, it must be flashed under reduced pressure in low-pressure flash tank Ⅰ6 to separate the gases dissolved in the crude ethylene glycol material and discharge them. In order to ensure that the crude ethylene glycol in low-pressure flash tank Ⅰ6 can be transported to the distillation section or the intermediate tank area, and to minimize the loss of methanol in low-pressure flash tank Ⅰ6, the pressure of low-pressure flash tank Ⅰ6 must be maintained at 0.35MPa-0.38MPa. After separation by high-pressure separator Ⅱ10, some gases are dissolved in the crude methanol material. In order to prevent these gases from entering the distillation section and affecting production, it must be flashed under reduced pressure in low-pressure flash tank Ⅱ11 to separate the gases dissolved in the crude methanol material and discharge them. These gases are mainly hydrogen and nitrogen. In order to ensure that the crude methanol in the low-pressure flash tank Ⅱ11 can be transported to the distillation section or the intermediate tank area and to minimize the methanol loss in the low-pressure flash tank Ⅱ11, the pressure of the low-pressure flash tank Ⅱ11 should be maintained at 0.35MPa-0.38MPa.

[0069] As a further improvement, the pressure of the low-pressure flash tank I6 and the low-pressure flash tank II11 are controlled by split-range, and are first sent to the fuel gas official website. When the regulating valve opening of the fuel gas official website reaches 50%, they are sent to the flare official website.

[0070] The pressure of low-pressure flash tank Ⅰ6 and low-pressure flash tank Ⅱ11 is controlled by split range, and is first sent to the fuel gas official website. When the regulating valve opening of the fuel gas official website reaches 50%, it is sent to the flare official website. Most of the gas phases discharged from low-pressure flash tank Ⅰ6 and low-pressure flash tank Ⅱ11 are hydrogen and nitrogen, which are sent to the fuel official website for combustion. The heat released will form steam as a by-product, increasing the economic benefits of the enterprise, reducing costs, saving energy and reducing consumption, and being green and environmentally friendly. In order to prevent equipment overpressure and the fuel gas pipeline network from not meeting the acceptance conditions, it is set to be sent to the flare official website.

[0071] Further improvement is that the liquid level of the high-pressure separator I5 and the high-pressure separator II10 is 40%-50%; the liquid level of the low-pressure flash tank I6 and the low-pressure flash tank II11 is controlled at 40%-50%, the liquid level of the inlet separator 12 is controlled at 40%-50%; the liquid level of the steam drum 1 is controlled at 60%-70%.

[0072] The liquid level of high-pressure separators Ⅰ5 and Ⅱ is set at 40%-50%. Firstly, it is to prevent the low liquid level from causing high pressure to jump to low pressure, damaging the low-pressure flash tank Ⅰ6 and Ⅱ equipment and pipelines, and causing safety accidents; secondly, if the liquid level is too high, the liquid will be brought into the compressor, causing damage to the compressor.

[0073] A further improvement is that the pressure in the synthesis circulation system formed by the inlet and outlet material heat exchanger 4, the high-pressure separator I5, the synthesis water cooler A8, the synthesis water cooler B9, the high-pressure separator II10, the inlet separator 12, the hydrogen circulation gas compressor 14, the steam heater II, the steam heater I18, the DMO evaporation tower 17, and the ethylene glycol synthesis reactor 2 is controlled at 2.7MPa-2.9MPa.

[0074] Since the process of hydrogenation reaction to generate EG is a volume reduction process, the conversion rate of DMO and the selectivity of EG increase slightly, and the selectivity of MG decreases slightly as the pressure increases. Therefore, the pressure control value should be selected in the system control, and the pressure 151PI1022 should be controlled at 2.7MPa~2.9MPa.

[0075] Further improvement is that the requirements for fresh hydrogen mixed into the circulating gas at the outlet of the hydrogen circulating gas compressor 14 are: concentration ≥ 99.9%, Cl -1 ≤0.01PPm, CO+CO2≤20PPm, moisture≤1000PPm, total sulfur≤0.1PPm, O2≤30PPm; it can effectively prevent H2O, O2, S, Cl- and carbonyl compounds in the materials from having adverse effects on catalyst activity, catalyst life and selectivity.

[0076] The above-mentioned implementation modes are only preferred implementation modes of the present application and cannot be used to limit the scope of protection of the present application. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present application shall fall within the scope of protection required by the present application.

Claims

1. A device for producing ethylene glycol by using a plate reactor in natural gas to ethylene glycol, characterized in that: The invention comprises a steam drum (1), an ethylene glycol synthesis reactor (2), an inlet and outlet material heat exchanger (4), a high-pressure separator I (5), a low-pressure flash tank I (6), a crude ethylene glycol water cooler (7), a synthesis water cooler A (8), a synthesis water cooler B (9), a steam heater II (19), a steam heater I (18), a DMO evaporation tower (17), a DMO feed pump (15), a DMO buffer tank (16), a high-pressure separator II (10), a low-pressure flash tank II (11), a hydrogen circulating gas compressor (14), and a steam drum circulating pump (3). The ethylene glycol synthesis reactor (2) adopts a plate reactor, and the catalyst used in the ethylene glycol synthesis reactor (2) is a copper-based catalyst.

2. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: An inlet separator (12) is provided between the high-pressure separator II (10) and the hydrogen circulating gas compressor (14), a PSA device (13) is provided between the hydrogen circulating gas compressor (14) and the inlet separator (12), and the inlet separator (12) is connected to the low-pressure flash tank II (11) through a pipeline.

3. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: The steam pressure of the steam heater II (19) is 3.8 MPa, and the temperature of the mixed gas of fresh hydrogen and circulating hydrogen after passing through the steam heater II (19) is 170°C-185°C.

4. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: The temperature of the circulating gas in the DMO buffer tank (16) after being fully mixed with DMO is 150°C-175°C.

5. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 4, characterized in that: The DMO from the DMO distillation unit is: ≥99.5%, DMC≤1000PPm, acidity≤100PPm, moisture≤500PPm. The temperature is about: 90℃-100℃.

6. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: The water temperature and pressure of the steam drum (1) are used to control the reaction temperature and remove the reaction heat. The pressure of the steam drum (1) is controlled at 0.65 MPa-0.98 MPa.

7. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: The circulation flow rate of the gas phase of the high-pressure separator II (10) entering the inlet of the hydrogen circulation gas compressor (14) is 550,000 Nm3 / h-700,000 Nm3 / h.

8. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: The liquid levels of the high-pressure separator I (5) and the high-pressure separator II (10) are 40%-50%; the liquid levels of the low-pressure flash tank I (6) and the low-pressure flash tank II (11) are controlled at 40%-50%, the liquid level of the inlet separator (12) is controlled at 40%-50%; and the liquid level of the steam drum (1) is controlled at 60%-70%.

9. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: The pressure in the synthesis circulation system formed by the inlet and outlet material heat exchanger (4), the high-pressure separator I (5), the synthesis water cooler A (8), the synthesis water cooler B (9), the high-pressure separator II (10), the inlet separator (12), the hydrogen circulation gas compressor (14), the steam heater II (19), the steam heater I (18), the DMO evaporation tower (17), and the ethylene glycol synthesis reactor (2) is controlled at 2.7 MPa-2.9 MPa.

10. The device for producing ethylene glycol by using a plate-type reactor in natural gas production according to claim 1, characterized in that: The requirements for the fresh hydrogen mixed into the circulating gas at the outlet of the hydrogen circulating gas compressor (14) are: concentration ≥99.9%, Cl-1 ≤0.01PPm, CO+CO2 ≤20PPm, moisture ≤1000PPm, total sulfur ≤0.1PPm, O2 ≤30PPm.

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