Device and method for improving purity of ethylene glycol prepared from natural gas

Abstract

The device comprises a dealcoholization tower and an ethylene glycol product tower, and each of the dealcoholization tower and the ethylene glycol product tower comprises a rectifying tower, a tower kettle liquid delivery pump arranged on a liquid discharge pipeline at the bottom of the rectifying tower, and a vacuumizing system communicated with a gas outlet pipe at the top of the rectifying tower through a pipeline, a falling film reboiler is adopted as the reboiler, a byproduct steam waste boiler is arranged between the vacuum-pumping system and the rectifying tower, a reflux tank and a reflux pump are connected between the byproduct steam waste boiler and the tower top of the rectifying tower through pipelines, a discharge pipe is further arranged on a discharge pipe of the reflux pump, and a side-draw product pump and an intermediate tank are further arranged on one side of the rectifying tower in the ethylene glycol product tower. Through the falling film type reboiler, the residence time of crude ethylene glycol in the tower kettle of the rectifying tower is greatly shortened, the used steam grade and the use amount are reduced, the heat exchange efficiency is high, coking is not easy to occur, and used equipment is simple, so that the energy consumption is low, the investment is small, the separation effect is good, the purity of the ethylene glycol product is improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene glycol distillation, and in particular to a device and method for improving the purity of ethylene glycol produced from natural gas. Background Art

[0002] Ethylene glycol is an important chemical raw material, primarily used in the production of polyester, polyester resin, desiccant, plasticizer, surfactant, synthetic fiber, cosmetics, and explosives. It is also used as a solvent for dyes and inks, as an antifreeze agent for engines, as a gas dehydrator, and in the manufacture of resins. It is also used as a wetting agent in cellophane, fiber, leather, and adhesives. It can be used to produce synthetic resin PET, fiber-grade PET (i.e., polyester fiber), and bottle flake-grade PET for mineral water bottles. It can also be used to produce alkyd resins and glyoxal, and is also used as an antifreeze agent. Besides being used as an automotive antifreeze, it is also used for industrial cooling, generally referred to as a refrigerant. It can also be used as a condensing agent, similar to water. Therefore, the efficient conversion of natural gas into chemical raw materials such as ethylene glycol reduces dependence on coal and oil resources, contributing to an optimized energy and resource structure and is of great significance.

[0003] Currently, there are three main technical routes for producing ethylene glycol: the first is the petroleum route, which primarily involves gas-phase oxidation of ethylene over a silver catalyst to produce ethylene oxide, followed by liquid-phase non-catalytic hydration to produce ethylene glycol. This route boasts mature technology and widespread application. The second is the coal-to-ethylene glycol route, which uses coal to generate synthesis gas to produce dimethyl oxalate, which is then hydrogenated to produce ethylene glycol. The third is the natural gas-to-ethylene glycol route. With the increasing global shortage of oil resources, the coal-based ethylene glycol synthesis route has attracted widespread attention. Natural gas is used as a raw material, converting synthesis gas to produce dimethyl oxalate, which is then hydrogenated to produce ethylene glycol. Its advantages are that natural gas is cleaner than petroleum and coal, produces high-quality products, and has relatively low production costs. Considering the economic rationale and my country's energy structure, natural gas-based ethylene glycol production is most suitable for my country's current situation.

[0004] Crude ethylene glycol produced from natural gas to ethylene glycol contains dozens of components, including ethylene glycol, methanol, trace amounts of 1,2-butanediol, ethanol, water, diethylene glycol, and triethylene glycol. Removing impurities from crude ethylene glycol to produce high-quality ethylene glycol products is a current research focus. However, current natural gas to ethylene glycol distillation units suffer from the following problems due to their design and system operating conditions:

[0005] (1) During the natural gas production of ethylene glycol, some impurities with boiling points close to that of ethylene glycol are produced, such as 1,2-butanediol, glycolaldehyde, glycolic acid, etc. These impurities are difficult to completely separate through distillation. As the distillation system runs longer, the ultraviolet transmittance (UV value) of ethylene glycol gradually decreases, affecting product quality.

[0006] (2) In the distillation process of natural gas to ethylene glycol, the boiling points of the target product (ethylene glycol) and impurities (such as 1,2-butanediol, methyl glycolate, etc.) are close. Traditional distillation technology is difficult to separate them efficiently. It is necessary to control the impurities by increasing the extraction of light fractions, resulting in production losses.

[0007] (3) In the traditional distillation process, ethylene glycol has low heat exchange efficiency and long residence time in the reboiler of the tower bottom in the distillation device. Ethylene glycol is a heat-sensitive substance that is prone to polymerization at high temperatures. It is easy to condense and aggregate with the catalyst dust particles entering the system to form blocks, causing coking and scaling of the reboiler tube bundle, affecting the heat exchange efficiency of the reboiler. Summary of the Invention

[0008] In order to solve one or more technical problems existing in the prior art, one of the purposes of the present application is to provide a device and method for improving the purity of ethylene glycol produced from natural gas, wherein the residence time of crude ethylene glycol in the distillation tower kettle is greatly shortened by a falling film reboiler, the steam grade and amount used are reduced, the heat exchange efficiency is high and coking is not easy to occur, the equipment used is simple, and thus energy consumption is low, investment is small, separation effect is good, the purity of the ethylene glycol product is improved, and production costs are reduced.

[0009] The second purpose of this application is to provide a method for improving the purity of ethylene glycol produced from natural gas, which can effectively improve the purity of the produced ethylene glycol and reduce the required consumption.

[0010] In order to solve the above existing technical problems, one of the objectives of this application is achieved by adopting the following technical solutions:

[0011] A device for improving the purity of ethylene glycol produced from natural gas comprises a dealcoholization tower and an ethylene glycol product tower, both comprising a distillation tower, a bottom liquid external delivery pump provided on a bottom discharge pipe of the distillation tower, and a vacuum pumping system connected to an air outlet pipe at the top of the distillation tower via a pipeline. The reboiler is a falling film reboiler, a by-product steam waste boiler is provided between the vacuum pumping system and the distillation tower, a reflux tank and a reflux pump are connected to the top of the distillation tower via a pipeline, an external discharge pipe is further provided on the discharge pipe of the reflux pump, and a side line product pump and an intermediate tank are further provided on one side of the distillation tower in the ethylene glycol product tower.

[0012] In the actual production process, the dealcoholization tower and ethylene glycol product tower in the existing gas-to-ethylene glycol distillation device are improved. The material in the improved distillation tower is rapidly heated after heat exchange through a falling film reboiler. The pressure state in the distillation tower is maintained stable by the vacuum system. The vaporized material extracted by the vacuum system is cooled into liquid through the by-product steam waste boiler and then refluxed into the reflux tank for storage. Part of the material in the reflux tank is transported to the top of the distillation tower as reflux liquid through the reflux pump, and the other part is extracted as light components; the remaining material after distillation is discharged to the outside through the tower bottom liquid delivery pump on the bottom drainage pipe. The gaseous ethylene glycol product distilled in the distillation tower in the ethylene glycol product tower is extracted through the side line port at the top of the tower bottom and stored in the intermediate pipe. Finally, it is pumped out to the tank area for sale through the side line product pump.

[0013] The specific operation is as follows: when the material enters the delivery, the material first enters the dealcoholization tower for dealcoholization, and the dealcoholized material is then transported to the ethylene glycol product tower through the tower bottom liquid external delivery pump for ethylene glycol distillation collection and waste liquid discharge. The operation process is as follows:

[0014] After the material enters the dealcoholization tower, the crude ethylene glycol is separated in the dealcoholization distillation tower. The top gas phase is the vapor (~139°C) of diols lighter than ethylene glycol (such as 2,3-butanediol, 1,2-propylene glycol, and 1,2-butanediol). After condensation in the dealcoholization by-product steam waste boiler, the liquid phase enters the reflux tank. The non-condensable gas is extracted through the vacuum system in the dealcoholization tower to maintain the vacuum degree of the dealcoholization tower. After the condensate in the reflux tank is pressurized by a reflux pump, most of it returns to the dealcoholization distillation tower as reflux, and a small amount is extracted and sent to the EG concentration tower for separation; the discharge from the dealcoholization distillation tower bottom is pumped into the distillation tower in the ethylene glycol product tower by the dealcoholization tower bottom liquid external delivery pump. Part of the by-product steam from the dealcoholization by-product steam waste boiler is sent to the waste heat steam reboiler of the methanol recovery tower, and part is sent to the steam compressor.

[0015] After entering the ethylene glycol product tower, crude ethylene glycol is separated in the ethylene glycol distillation tower. The overhead vapor is condensed in the byproduct steam waste boiler, and the liquid phase enters the ethylene glycol product reflux tank. Non-condensable gases are extracted through the ethylene glycol product tower's vacuum system to maintain vacuum within the ethylene glycol distillation tower. The reflux tank is pressurized by a reflux pump, with most of the product returning to the ethylene glycol distillation tower as reflux. The remaining overhead product is sent via an external discharge pipe to an industrial-grade ethylene glycol cooler, cooled, and then forwarded to the liquid-phase hydrogenation unit. Polyester-grade ethylene glycol, a side stream from the ethylene glycol distillation tower, is pumped to a polyester-grade ethylene glycol intermediate tank via a side stream pump and then delivered to a tank farm for sale. The ethylene glycol distillation tower bottom discharge is pumped to the ethylene glycol recovery tower by a bottom liquid transfer pump. The byproduct steam from the ethylene glycol product tower's byproduct steam waste boiler is fed to the waste heat steam reboiler in the methanol recovery tower. Heat exchange and condensation are carried out between the vacuum system and the distillation tower through the by-product steam waste boiler. The by-product steam can be reused through the by-product steam waste boiler, thereby achieving heat exchange through the by-product steam while saving economic benefits and being more energy-efficient. Secondly, the reboiler used in the traditional distillation process has low heat exchange efficiency and long residence time. Ethylene glycol is a heat-sensitive substance that is prone to polymerization reactions at high temperatures. It is easy to condense and aggregate with catalyst dust particles entering the system, causing coking and scaling of the reboiler tube bundle, affecting the heat exchange efficiency of the reboiler. Therefore, the distillation tower adopts a falling film reboiler for heat exchange, which can greatly shorten the time that the material stays in the distillation tower kettle, thereby controlling the amount of ethylene glycol polymerization reaction at high temperature, making it difficult for the reboiler tube bundle to produce coking and scaling, and making the heat exchange efficiency of the reboiler more stable; at the same time, impurities such as 1,2-butanediol, glycolaldehyde, and glycolic acid with a boiling point close to that of ethylene glycol can be more effectively separated by distillation, and the situation in which the ultraviolet transmittance (UV value) of ethylene glycol gradually decreases due to a long residence time will not occur, thereby improving the quality and output of the product. It effectively solves the defects of the reboiler used in the traditional distillation process. Through the present invention, the current ethylene glycol with a purity of about 99.91% can be increased to more than 99.95% and extracted for sale, increasing the yield of the ethylene glycol product to more than 98%, reducing the use of steam, saving energy consumption, creating objective economic benefits, and reducing production costs. The steam grade and usage are reduced, the heat exchange efficiency is high, it is not easy to coke, steam is saved, and the equipment used is simple, so the energy consumption is low, the investment is small, and the separation effect is good. While separating other materials from crude ethylene glycol, the generation of by-products is reduced, the product quality of ethylene glycol is improved, the production cost of ethylene glycol is reduced, the competitiveness of the enterprise is improved, the sales price is greatly increased, and the price advantage of the product ethylene glycol is enhanced.

[0016] Preferably, a circulation pump is provided between the distillation tower and the reboiler.

[0017] Since the materials in the distillation tower are circulated and heated through the reboiler in the prior art, the material flow cannot be improved, which also leads to low overall heat exchange efficiency and a long residence time of the materials in the distillation tower. Although the use of a falling film reboiler can effectively improve this, due to the insufficient heat exchange efficiency, the reboiler tube bundle will still produce coking and scaling problems after long-term operation, resulting in a decrease in the heat exchange efficiency of the heat exchanger. Therefore, in order to further reduce the residence time of the material in the distillation tower and improve the long-term heat exchange stability of the heat exchanger, after replacing the reboiler, a circulation pump was added between the reboiler and the distillation tower. The circulation pump can further enhance the circulation efficiency of the tower bottom material when the reboiler exchanges heat with the material in the distillation tower, thereby improving the heat exchange efficiency. At the same time, it reduces the residence time of the material, prevents material scaling and ethylene glycol polymerization reaction, makes the reboiler tube bundle less likely to produce coking and scaling, and makes the heat exchange efficiency of the reboiler more stable. It has high heat exchange efficiency, is not easy to coke, saves steam, further reduces the amount of steam used after long-term operation, saves energy consumption, can create objective economic benefits, and uses simple equipment.

[0018] Preferably, the vacuum system includes a buffer tank and a vacuum pump system. After the extracted gas phase passes through the buffer tank for gas-liquid separation, the liquid phase flows into the reflux tank of the distillation tower, and the gas phase is discharged through the vacuum pump system.

[0019] If the liquid phase material carried in the non-condensable steam at the top of the tower is not effectively separated, the material will be brought into the vacuum pump system. The light component material entering the vacuum pump system will dilute the vacuum pump working fluid material, thereby affecting the vacuum pump suction capacity, affecting the distillation tower pressure and various process indicators of the distillation tower system, and subsequently directly affecting the product quality. Therefore, before the gas phase extracted from the distillation tower enters the vacuum pump system, it is first separated from the liquid phase material carried in the non-condensable steam at the top of the tower through a buffer tank. After the extracted gas phase is separated into gas and liquid in the buffer tank, the liquid phase flows into the reflux tank of the distillation tower, and the gas phase is discharged through the vacuum pump system. This can effectively prevent the liquid phase material carried in the non-condensable steam from being brought into the vacuum pump system.

[0020] Preferably, a product cooler is provided between the distillation tower and the intermediate tank, and the temperature of the cooled gaseous ethylene glycol product is 40±2° C. The gaseous ethylene glycol product flows into the intermediate tank after passing through the product cooler.

[0021] Since the extracted material is around 140 degrees Celsius, cooling it naturally or in an intermediate tank can easily cause excessive internal pressure. This high temperature can also affect pump operation and make it difficult to maintain the temperature of the sold material at room temperature, making storage and transportation unsafe. Therefore, it is necessary to cool the gas-fired ethylene glycol product to around 40 degrees Celsius in a product cooler before injecting it into the intermediate tank. This ensures normal operation of the pump while facilitating room temperature control of the sold material, making storage and transportation safer.

[0022] Preferably, a steam condensate tank is provided on the outlet pipeline of the reboiler.

[0023] After the reboiler is heated by steam, part of the steam after heat exchange will condense into steam condensate when it flows out. If this part of the steam condensate is not filtered, the steam condensate will flow back and cause unstable steam condensate level control. Therefore, a steam condensate tank is provided on the outlet pipeline to collect the steam condensate after the steam passes through the reboiler for heat exchange; it can ensure the stable steam condensate level control to ensure the stable heat exchange efficiency of the reboiler; at the same time, it also prevents the steam volume from being too large, and the steam from being excessive after the reboiler heat exchange, causing steam to flow into the condensate pipe network, causing water hammer vibration of the condensate pipe network, and damaging the steam condensate pipe line.

[0024] Preferably, a circulating water condenser is provided between the by-product steam waste boiler and the vacuum pumping system, and the circulating water condenser is connected to the reflux tank.

[0025] During the actual operation, it was found that when the three distillation towers were subjected to heat exchange and condensation, the by-product steam waste boiler could only heat and condense 95% of the top gas phase. Therefore, in order to improve the heat exchange and condensation efficiency of the top gas phase, a circulating water condenser was set up. The uncondensed gas phase in the by-product steam waste boiler entered the circulating water condenser for re-condensation, and the condensed liquid flowed into the reflux tank. The non-condensable gas phase that could not be cooled was extracted by the vacuum system, which could further condense the uncondensed gas phase at the top of the tower, thereby achieving better heat exchange and condensation effects.

[0026] Preferably, a cryogenic cooler is provided between the circulating water condenser and the vacuum pumping system, and the cryogenic cooler is connected to the reflux tank.

[0027] The top gas phase can basically cool 99% of the top gas phase through the by-product steam waste boiler and the circulating water condenser. However, there is still a trace amount of non-condensable gas at the top of the tower, which is a substance that cannot be cooled under normal temperature medium cooling, such as methyl acetate, ethylene glycol methyl ether, methyl glycolate, etc. Therefore, a deep freezer is added again between the circulating water condenser and the vacuum pumping system. The deep freezer can condense the gas phase that cannot be condensed in the circulating water condenser for a third time, and the condensed liquid flows into the reflux tank. The non-condensable gas phase that cannot be cooled by the deep freezer is extracted by the vacuum pumping system, thereby ensuring the condensation effect of the gas phase extracted from the top of the tower.

[0028] A method for improving the purity of ethylene glycol produced from natural gas, the method comprising:

[0029] S1. Crude methanol and crude ethylene glycol from the ethylene glycol synthesis section or the ethylene glycol intermediate tank area enter different positions of the methanol recovery tower. After separation in the methanol recovery tower, the overhead gas phase is condensed, and a small amount of produced liquid is sent to the methanol separation tower for separation; the methanol recovery tower produces refined methanol product from the side line, and the bottom liquid is sent to the dehydration tower;

[0030] S2, after the crude ethylene glycol entering the dehydration tower is separated, the top gas phase is condensed, and a small amount of produced liquid is sent to the methanol separation tower for separation; the bottom liquid in the dehydration tower is then sent to the dealcoholization tower;

[0031] S3, after the materials separated by the methanol recovery tower and the dehydration tower enter the methanol separation tower, methanol is separated by the methanol separation tower, and the remaining materials are transported to the ethanol product again, and after ethanol separation, the waste liquid is discharged externally;

[0032] S4. After the material enters the dealcoholization tower, the crude ethylene glycol in the dealcoholization distillation tower is injected into the falling film reboiler through a circulating pump for heat exchange, and then recirculated into the dealcoholization distillation tower for separation. After the crude ethylene glycol is separated, the top gas phase is a glycol vapor that is lighter than ethylene glycol. After condensation through the dealcoholization by-product steam waste boiler, circulating water condenser, and cryogenic freezer, the liquid phase enters the reflux tank, and the non-condensable gas is extracted through the vacuum system in the dealcoholization tower to maintain the vacuum degree of the dealcoholization tower. After the condensate out of the reflux tank is pressurized by the reflux pump, most of it returns to the dealcoholization distillation tower as reflux, and a small amount is extracted and sent to the EG concentration tower for separation; the discharge from the dealcoholization distillation tower bottom is pumped into the ethylene glycol product tower by the dealcoholization tower bottom liquid external delivery pump;

[0033] S5. After the material enters the ethylene glycol product tower, the crude ethylene glycol in the ethylene glycol distillation tower is injected into the falling film reboiler through a circulation pump for heat exchange, and then recirculated into the ethylene glycol distillation tower for separation. After the crude ethylene glycol is separated, the top gas phase is glycol vapor that is lighter than ethylene glycol. After condensation in the ethylene glycol by-product steam waste boiler, circulating water condenser, and cryogenic refrigerator, the liquid phase enters the reflux tank, and the non-condensable gas is extracted through the vacuum system in the ethylene glycol product tower to maintain the vacuum degree of the ethylene glycol product tower. After the condensate in the reflux tank is pressurized by a reflux pump, most of it returns to the ethylene glycol distillation tower as reflux, and a small amount is extracted and sent to the liquid phase hydrogenation unit; the polyester-grade ethylene glycol product in the ethylene glycol distillation tower is extracted through the ethylene glycol distillation tower side line, pumped to the product cooler for cooling, and then sent to the polyester-grade ethylene glycol product intermediate tank, and finally sent to the tank area for sale by the polyester-grade ethylene glycol delivery pump. The discharge from the ethylene glycol distillation tower bottom liquid is pumped into the ethylene glycol recovery tower by the tower bottom liquid delivery pump;

[0034] S6. After the materials entering the EG concentration tower are separated, the non-condensable gas at the top of the tower is extracted and sent to the ethylene glycol finished product tank area or area 48 for incineration, and the materials in the EG concentration tower kettle are sent to the liquid phase hydrogenation unit or the dealcoholization tower;

[0035] S7, After the crude ethylene glycol in the ethylene glycol recovery tower is separated, the non-condensable gas at the top of the tower is sent to the liquid phase hydrogenation unit; the kettle liquid is sent to the tank area or area 48 for incineration;

[0036] S8. The materials in the liquid phase hydrogenation unit are refluxed into the ethylene glycol product tower or dealcoholization tower after hydrogenation.

[0037] Preferably, the falling film reboiler of the dealcoholization distillation tower adopts 0.7MPag saturated steam for heating; part of the by-product steam of the dealcoholization by-product steam waste boiler is sent to the waste heat steam reboiler of the methanol recovery tower, and part is sent to the steam compressor.

[0038] At present, the reboiler is conventionally heated with 1.7MPa steam, and the flow rate is controlled at around 45T / h. The steam pressure level is fixed, and the flow rate is adjusted according to the temperature required by the distillation tower process indicators. As a result, the production cost is higher after using conventional pressure. After reducing the steam pressure to 0.7MPa, it is only necessary to increase the steam volume per hour to between 52 and 55T to meet the requirements, and the production cost can also be effectively reduced.

[0039] Preferably, the top temperature of the distillation tower of the dealcoholization tower is 133-134° C., the bottom temperature is 152-154° C., and the top pressure is 10-11 KPa.A.

[0040] The top temperature of the distillation tower used in the existing process is generally around 135-138°C, the bottom temperature is 155-158°C, and the tower pressure is around 13KPa, which results in a relatively high amount of steam consumed by the reboiler during the heating process. Excessive temperature can easily cause scaling of the bottom material, thereby affecting the heat exchange effect of the reboiler and product quality. Therefore, the temperature of the distillation tower of the dealcoholization tower is appropriately lowered, wherein the top temperature is 133-136°C, and the bottom temperature is 152-154°C, which is about 2°C lower than the existing process temperature. By lowering the temperature, the problem of the high amount of steam consumed by the reboiler during the heating process is solved, and the scaling of the material in the bottom of the distillation tower is reduced, which is better for the heat exchange effect of the reboiler and product quality control. At the same time, the existing distillation tower pressure is generally 13~14KPa. The pressure control is too high, which can easily affect the separation of light and heavy components of the material in the actual production process, thereby affecting the product quality. Therefore, the top pressure of the distillation tower is reduced to about 10~11KPa. By reducing the pressure, the light and heavy components of the material can be separated more thoroughly, thereby ensuring product quality.

[0041] Preferably, the top temperature of the distillation tower in the ethylene glycol product tower is 133-134° C., the bottom temperature is 149-151° C., and the top pressure is 10-12 KPa.A.

[0042] In the existing process, the distillation tower used in the ethylene glycol product column typically has a top temperature of around 135-136°C, a bottom temperature of 153-154°C, and a tower pressure of around 11 kPa. This results in high steam consumption in the reboiler during heating. Excessive temperatures can easily cause scaling in the bottom of the tower, impacting the reboiler's heat exchange efficiency and product quality. Therefore, the distillation tower temperature was appropriately lowered to 133-134°C and 149-151°C, approximately 2°C lower than the existing process. This temperature reduction not only addresses the high steam consumption during reboiler heating, but also reduces scaling in the bottom of the distillation tower, improving reboiler heat exchange efficiency and product quality. Meanwhile, the internal pressure remains around 11 kPa, enabling a more thorough separation of the light and heavy components of the material, thereby ensuring product quality.

[0043] Preferably, the ratio of the reflux flow rate L of the distillation tower top returning to the tower to the top product flow rate D is R=L / D, the reflux ratio R of the dealcoholization tower is about 40, and the reflux ratio of the ethylene glycol product tower is about 1.4.

[0044] Among them, the ratio of the reflux liquid flow rate L returned from the top of the distillation tower to the top product flow rate D is R=L / D, the reflux ratio R of the dealcoholization tower is about 40, and the reflux ratio of the ethylene glycol product tower is about 1.4. Through precise control and optimization of various process indicators of the distillation tower; parameters such as temperature, pressure, and reflux ratio, impurities and ethylene glycol are separated as much as possible, the extraction of light fractions is reduced, and the product yield is improved.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The structural design of the falling film reboiler allows the liquid to flow in a film-like manner within the heating tube, greatly increasing the contact area between the liquid and the heating tube wall. Compared with traditional kettle-type reboilers, this can significantly improve heat transfer efficiency. In the distillation process of natural gas to ethylene glycol, the mixed liquid in the tower kettle can be heated faster and more evenly, promoting the vaporization of substances such as ethylene glycol and improving the distillation separation effect.

[0047] (2) The liquid flows in the form of a thin film, with a shorter residence time in the heating tube and a more stable flow state, making local overheating less likely to occur. This reduces the polymerization and carbonization of materials such as ethylene glycol on the heating surface, thereby reducing the possibility of scaling. Reducing scaling not only maintains the efficient heat transfer performance of the reboiler, but also extends the operating cycle of the equipment and reduces maintenance costs.

[0048] (3) For heat-sensitive ethylene glycol, the falling film reboiler can effectively control the heating temperature and time, preventing the material from being in a high-temperature environment for a long time, thereby reducing the degradation and deterioration of the material. In the process of natural gas to ethylene glycol, it can better ensure the product quality of ethylene glycol and improve the purity and yield of the product.

[0049] (4) The falling film reboiler can flexibly adapt to different production loads and process requirements by adjusting parameters such as feed rate and heating medium flow rate. In the production process of the natural gas to ethylene glycol unit, whether it is during the startup and shutdown phases of the unit or when the production load changes, the falling film reboiler can respond quickly and operate stably to ensure the smooth progress of the distillation process.

[0050] (5) Due to its efficient heat transfer performance, the falling film reboiler can achieve the same vaporization effect at a lower heating medium temperature. Compared with other types of reboilers, it can reduce the consumption of heating medium, thereby saving energy. At the same time, it reduces energy losses caused by problems such as scaling and material degradation, further improving energy utilization efficiency and reducing production costs.

[0051] (6) The structure of the falling film reboiler is relatively compact and does not require a large vapor-liquid separation space like a kettle reboiler. Therefore, in a natural gas to ethylene glycol unit, it can save a lot of space, make the layout of the unit more reasonable, and facilitate the overall planning and construction of the plant.

[0052] (7) The liquid in the falling film reboiler is evenly distributed and flows stably, making it less likely to experience flooding or tower flushing due to uneven boiling of the liquid. This improves the stability and safety of the distillation tower operation. Furthermore, by reducing material degradation and scaling, the risk of equipment failure and leakage is also reduced, ensuring the safe operation of the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a process flow chart of the dealcoholization tower in the present invention;

[0054] Figure 2 1 is a process flow chart of the ethylene glycol product tower in the present invention;

[0055] Figure 3 It is a process flow chart of the entire distillation device in the present invention;

[0056] In the figure: 1. Reboiler; 2. Steam condensate tank; 3. Reflux pump; 4. External discharge pipe; 5. Reflux tank; 6. Cryogenic chiller; 7. Circulating water condenser; 8. By-product steam waste boiler; 9. Vacuum pumping system; 91. Buffer tank; 92. Vacuum pump system; 10. Distillation tower; 11. Bottom liquid delivery pump; 12. Circulating pump; 13. Product cooler; 14. Intermediate tank; 15. Side-line product pump. DETAILED DESCRIPTION

[0057] 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 new embodiments.

[0058] In the description of this application, it should be understood that the terms "up", "down", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on this application.

[0059] The terms "first," "second," and the like in this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0060] like Figures 1 to 3As shown, the methanol recovery tower: crude methanol and crude ethylene glycol from the ethylene glycol synthesis section or ethylene glycol intermediate tank 14 enter the methanol recovery tower (tower 1) at different locations. After separation in the methanol recovery tower, the overhead gas phase (51.8°C) consists of dimethyl ether, methyl formate, methanol, and trace amounts of ethanol. After condensation through the methanol recovery tower primary cooling A / B, the methanol recovery tower secondary cooling, and the methanol recovery tower deep cooling, the condensate enters the methanol recovery tower reflux tank 5. Non-condensable gases are extracted by the methanol recovery tower vacuum system to maintain the required vacuum level. The material leaving the reflux tank 5 is pressurized by the methanol recovery tower reflux pump 3. Most of it returns to the methanol recovery tower as reflux, while a small amount is mixed with the dehydration tower overhead produced liquid and sent to the methanol separation tower (tower 8) for separation. The refined methanol product produced from the methanol recovery tower side line is cooled in the refined methanol cooler and sent to the refined methanol intermediate tank 14. It is then sent to the tank farm via the refined methanol transfer pump. The bottom liquid is pumped into the dehydration tower (tower 2) via the dehydration tower feed pump. There are 5 methanol recovery tower reboilers 1 in total. The methanol recovery tower waste heat steam reboiler 1 (A / B) uses 0.5MPag low-pressure steam in the pipeline network as the heat source during startup, and uses the by-product steam of the dealcoholization tower waste boiler A / B / C / D as the heat source during normal operation. The methanol recovery tower waste heat steam reboiler 1 (C / D) uses the by-product steam of the ethylene glycol product tower waste boiler A / B as the heat source during normal operation. The methanol recovery tower bottom reboiler 1 (E) uses 1.7MPag low-pressure steam in the pipeline network as the heat source.

[0061] In the dehydration tower (Tower 2), crude ethylene glycol from the methanol recovery tower is separated, and the overhead gas phase is a vapor (~53.6°C) containing light components such as C2-C5 alcohols, methyl glycolate, and dimethyl oxalate. After condensation in the dehydration tower condenser and dehydration tower cryocooler 6, the liquid phase enters the dehydration tower reflux tank 5. Non-condensable gases are extracted through the dehydration tower vacuum system to maintain the dehydration tower vacuum. The material leaving the reflux tank 5 is pressurized by the dehydration tower reflux pump 3 and most of it returns to Tower 2 as reflux. A small amount of produced liquid is mixed with the overhead product from the methanol recovery tower and sent to the methanol separation tower (Tower 8) for separation. The tower bottom is heated by 1.7MPag saturated steam from the dehydration tower reboiler 1; the dehydration tower bottom discharge is pressurized by the dealcoholization tower feed pump and sent to the dealcoholization tower (3A / B). In the dealcoholization tower (3A / B), after the crude ethylene glycol from tower 2 is separated, the top gas phase is the vapor (~139°C) of diols lighter than ethylene glycol (such as 2,3-butanediol, 1,2-propylene glycol, 1,2-butanediol).

[0062] After condensation in the de-alcoholization tower waste pot (A / B / C / D), the de-alcoholization tower condenser (A / B), and the de-alcoholization tower cryocooler 6(A / B), the liquid phase enters the de-alcoholization tower reflux tank 5(A / B). Non-condensable gases are extracted via the de-alcoholization tower vacuum system (A / B / C / D) to maintain the de-alcoholization tower vacuum. The material exiting reflux tank 5A / B is pressurized by the de-alcoholization tower reflux pump 3(A / B / C / D). Most of it returns to tower 3A / B as reflux, while a small amount is extracted and sent to the EG concentration tower (tower 10) for separation. The tower bottom uses a falling film reboiler 1A / B, with circulation established by circulating pumps 12A / B / C / D / E / F. 0.7 MPa saturated steam is supplied by the de-alcoholization tower reboiler 1(A / B). The de-alcoholization tower bottom discharge is pumped into the ethylene glycol product tower (tower 4) by the ethylene glycol product tower feed pump (A / B / C / D). Part of the by-product steam from the waste boiler of the dealcoholization tower (A / B / C / D) is sent to the waste heat steam reboiler 1 (A / B) of the methanol recovery tower, and part is sent to the steam compressor.

[0063] In the ethylene glycol product tower (tower 4), the crude ethylene glycol from towers A / B in tower 3 is separated, and the overhead vapor is condensed through the ethylene glycol product tower waste boiler (A / B), the ethylene glycol product tower secondary cooler, and the ethylene glycol product tower cryogenic freezer 6. The liquid phase enters the ethylene glycol product tower reflux tank 5; the non-condensable gas is extracted through the ethylene glycol product tower vacuum system to maintain the vacuum degree of the ethylene glycol product tower. The material leaving the reflux tank 5 is pressurized by the ethylene glycol product tower reflux pump 3, and most of it returns to tower 4 as reflux. The remaining overhead product is mixed with ethylene glycol from the top of the ethylene glycol recovery tower (tower 5) and sent to the industrial-grade ethylene glycol cooler. After cooling, it is sent to the liquid-phase hydrogenation unit. The polyester-grade ethylene glycol product extracted from the ethylene glycol product tower side line is cooled in the polyester-grade ethylene glycol product cooler 13 and sent to the polyester-grade ethylene glycol product intermediate tank 14. It is then sent to the tank farm via the polyester-grade ethylene glycol transfer pump. The tower kettle uses a falling-film reboiler 1, with circulation established by circulating pumps 12A / B / C. 0.7 MPa saturated steam is supplied by the ethylene glycol product tower reboiler 1. The ethylene glycol product tower kettle discharge is pumped into the ethylene glycol recovery tower (tower 5) by the ethylene glycol recovery tower feed pump. Byproduct steam from the ethylene glycol product tower waste boiler (A / B) is fed into the methanol recovery tower waste heat steam reboiler 1 (C / D).

[0064] In the glycol recovery tower (tower 5), crude glycol from tower 4 is separated, and the overhead vapor is condensed in the glycol recovery tower condenser and glycol recovery tower cryocooler 6. The liquid phase then enters the glycol product tower reflux tank 5. Non-condensable gases are extracted via the glycol product tower vacuum system to maintain the glycol recovery tower's vacuum level. The liquid exiting reflux tank 5 is pressurized by the glycol recovery tower reflux pump 3, with most returning to tower 5 as reflux. The remainder is cooled in an industrial-grade glycol cooler and then sent to the liquid-phase hydrogenation unit. The tower kettle is heated by 1.7 MPa saturated steam from the glycol recovery tower reboiler 1. The kettle liquid is pumped to the tank area or area 48 for incineration via the heavy component output pump.

[0065] In the EG concentrator (tower 10), after separation of the mixed diols from towers 3 A / B, the overhead gas phase consists of mixed alcohol ester vapor (such as 2,3-butanediol, 1,2-propylene glycol, 1,2-butanediol, ethylene glycol, methyl glycolate, etc.) (~119.2°C). After condensation in the EG concentrator condenser and EG concentrator cryocooler 6, the liquid phase enters the EG concentrator reflux tank 5. Non-condensable gases are extracted via the EG concentrator vacuum system (to maintain the EG concentrator vacuum level). The material exiting reflux tank 5 is pressurized by the EG concentrator reflux pump 3, with the majority returning to tower 10 as reflux. A small amount is extracted and sent to the ethylene glycol product tank area or incineration in area 48. The tower bottom is heated by 1.7 MPa saturated steam from the EG concentrator reboiler 1. The EG concentrator bottom discharge is pumped by the EG concentrator extraction pump to the liquid-phase hydrogenation section or dealcoholization tower 3 A / B.

[0066] In the methanol separation tower (8), after the mixed monohydric alcohols from the methanol recovery tower and dehydration tower (2) are separated, the overhead vapor is condensed in the methanol separation tower condenser, and the liquid phase enters the methanol separation tower reflux tank 5. The liquid exiting reflux tank 5 is pressurized by the methanol separation tower reflux pump 3, and most of it returns to tower 8 as reflux. The remainder is extracted as the overhead product and sent to the methanol separation cooler for cooling before being sent to the tank farm. The tower kettle uses the overhead process gas from the ethanol product tower (9) and is heated by the methanol separation tower reboiler 1. The kettle liquid is sent to the ethanol product tower (9) via the ethanol product tower feed pump.

[0067] In the ethanol product tower (tower 9), crude ethanol from tower 8 is separated and then condensed in the methanol separation tower reboiler 1 via thermal coupling. The liquid then enters the ethanol product tower reflux tank 5. The liquid exiting reflux tank 5 is pressurized by the ethanol product tower reflux pump 3, with most of it returning to tower 9 as reflux. The remainder is extracted as overhead product and sent to the ethanol product cooler 13 for cooling before being transferred to the tank farm. The tower kettle is heated by 0.5 MPa saturated steam from the ethanol product tower reboiler 1. The kettle liquid is pumped to wastewater treatment via a wastewater transfer pump.

[0068] Since the tail gas from the methanol recovery tower (methanol recovery tower) and each vacuum pump contains methanol and the like, it cannot be discharged directly into the air. Therefore, the corresponding tail gas needs to be sent to the vacuum pump tail gas washing tower (6 tower) for treatment. Fresh water is used to wash the methanol, methyl formate, etc. The treated gas can be discharged directly into the atmosphere, and the methanol-containing wastewater in the tower bottom is sent to the sewage treatment section for treatment by the vacuum pump tail gas washing sewage delivery pump.

[0069] In the entire distillation section, the heat of reboiler 1 is mainly provided by 1.7MPa(G) steam, 0.7MPa(G) steam and 0.5MPa(G) steam. The heat of the overhead process gas of the ethylene glycol product tower and the overhead process gas of the dealcoholization tower is recovered in the ethylene glycol product tower waste pot (A / B) and the dealcoholization tower waste pot (A / B / C / D) to generate 70KPaG low-pressure steam. This low-pressure steam is removed from A / B and C / D as the heat source of the methanol recovery tower and then cooled by the condensate cooler. It enters the condensate tank and is sent to the condensate network through the condensate pump. The condenser has two cooling media: circulating water and ethylene glycol refrigerant.

[0070] Currently, the bottom of the distillation tower 10 in an ethylene glycol distillation plant uses a thermosyphon reboiler 1. This natural circulation system heats and partially vaporizes the liquid at the bottom of the distillation tower 10. The inlet line of the reboiler 1 is filled with liquid, while the outlet line contains a vapor-liquid mixture. The higher the vaporization rate of the reboiler 1, the lower the density of the material in the outlet line, and the greater the density difference between the two. This density difference between the inlet and outlet lines is exploited to continuously "siphon" the liquid at the bottom of the tower into the reboiler 1. The heated and vaporized vapor-liquid mixture automatically returns to the tower, allowing for continuous circulation without the need for a pump. The outlet vaporization rate of the thermosyphon reboiler 1 is generally between 5% and 40%, and the pressure drop in the outlet line generally does not exceed 30% of the total pressure drop. The flow rate in the heating pipe is generally controlled between 0.5 and 1.5 m / s, the flow rate in the inlet pipe is generally controlled between 0.6 and 2 m / s, and the flow rate in the outlet pipe is generally controlled between 0.3 and 1 m / s. When the outlet vaporization volume remains unchanged, the vaporization rate decreases, the circulation volume in the reboiler 1 tube will increase, the heat transfer coefficient in the tube increases, the area of the reboiler 1 decreases, and the heat flux of the reboiler 1 increases, but generally does not exceed 70% of the maximum heat flux. The present invention uses a falling film reboiler 1 for the distillation tower 10 in the dealcoholization tower and the ethylene glycol product tower. The falling film reboiler 1 is a method of using gravity to make the liquid flow in a thin film on the heating tube wall and transfer heat. The material is evenly distributed to each heating tube through a distributor. Under the action of gravity, the material flows downward along the tube wall to form a thin film. At the same time, it is heated by steam or heat carrier outside the tube, causing part of the material to vaporize and generate steam. The generated steam enters the distillation tower 10 together with the liquid to achieve separation and purification of the gas-liquid two-phase. The flow state and method of the falling film reboiler 1 improve the heat transfer efficiency of the falling film reboiler 1. The falling film reboiler 1 utilizes low-grade steam, consumes minimal steam, and has high heat transfer efficiency. Its simple structure and easy maintenance also reduce equipment failure rates and repair costs. Its compact structure and small footprint also conserve land resources, reducing energy consumption and production costs. It also reduces material residence time in the distillation column 10, improving separation efficiency and increasing the purity of the ethylene glycol product. Compared to traditional equipment, the falling film reboiler 1 reduces energy consumption by over 30%, offering significant energy-saving potential. Its simple design results in low energy consumption and minimal investment, while also providing excellent separation efficiency, improving ethylene glycol product purity, and offering energy-saving, high-efficiency, and reduced production costs, enhancing product pricing.

[0071] Example 1:

[0072] Example 1 operating parameters:

[0073] equipment Hourly steam level / volume Tower top / bottom temperature Tower top pressure Ethylene glycol concentration Reboiler 0.7MPa / 52T 133℃ / 152℃ 10KPa.A 99.95％

[0074] The crude material enters the middle of the ethylene glycol product distillation tower, and the material is sent to the top of the falling film reboiler through the tower bottom circulation pump in the distillation tower. The falling film reboiler uses 0.7MPa steam to control the temperature at 52T / h for heating. After the distillation tower bottom temperature is 152℃, part of the vaporization occurs. The gas phase rises to the top of the distillation tower and enters the by-product steam waste boiler for heat exchange and then condensed through the circulating water condenser and the cryogenic cooler. The condensed liquid flows into the reflux tank of the distillation tower, and part of the material in the reflux tank is sent to the distillation tower through the reflux pump at the top of the distillation tower. The top of the tower is used as reflux liquid, and the other part is extracted as light components and then enters the liquid phase hydrogenation system; the temperature of the top of the distillation tower is controlled at 133°C, and the bottom liquid in the distillation tower is sent to the ethylene glycol recovery tower through the distillation tower bottom liquid external pump. The ethylene glycol product is extracted from the side sampling port of the distillation tower, and is cooled to 40°C in the side product extraction cooler. The cooled liquid flows into the side sampling intermediate tank. After sampling and analysis, the ethylene glycol concentration is 99.95%. The side product is pumped out to the tank area for sale, and the pressure at the top of the distillation tower is controlled at 10KPa.A by a vacuum pump.

[0075] Example 2:

[0076] Example 2 operating parameters:

[0077] equipment Hourly steam level / volume Tower top / bottom temperature Tower top pressure Ethylene glycol concentration Reboiler 0.7MPa / 53T 134℃ / 153℃ 11KPa.A 99.93％

[0078] The crude material enters the middle of the ethylene glycol product distillation tower, and the material is sent to the top of the falling film reboiler through the tower bottom circulation pump in the distillation tower. The falling film reboiler uses 0.7MPa steam to control the temperature at 53T / h for heating. After the distillation tower bottom temperature is 153℃, part of the vaporization occurs. The gas phase rises to the top of the distillation tower and enters the by-product steam waste boiler for heat exchange and then condensed through the circulating water condenser and the cryogenic cooler. The condensed liquid flows into the reflux tank of the distillation tower, and part of the material in the reflux tank is sent to the distillation tower through the reflux pump at the top of the distillation tower. The top of the tower is used as reflux liquid, and the other part is extracted as light components and then enters the liquid phase hydrogenation system; the temperature of the top of the distillation tower is controlled at 134°C, and the bottom liquid in the distillation tower is sent to the ethylene glycol recovery tower through the distillation tower bottom liquid external pump. The ethylene glycol product is extracted from the side sampling port of the distillation tower, and is cooled to 40°C in the side product extraction cooler. The cooled liquid flows into the side sampling intermediate tank. After sampling and analysis, the ethylene glycol concentration is 99.93%. The side product is pumped out to the tank area for sale, and the pressure at the top of the distillation tower is controlled at 11KPa.A by a vacuum pump.

[0079] Example 3:

[0080] Example 3 operating parameters:

[0081] equipment Hourly steam level / volume Tower top / bottom temperature Tower top pressure Ethylene glycol concentration Reboiler 0.7MPa / 54T 135℃ / 155℃ 12KPa.A 99.92％

[0082] The crude material enters the middle of the ethylene glycol product distillation tower, and the material is sent to the top of the falling film reboiler through the tower bottom circulation pump in the distillation tower. The falling film reboiler uses 0.7MPa steam to control the temperature at 54T / h for heating. After the distillation tower bottom temperature is 155℃, part of the vaporization occurs. The gas phase rises to the top of the distillation tower and enters the by-product steam waste boiler for heat exchange and then condensed through the circulating water condenser and the cryogenic cooler. The condensed liquid flows into the reflux tank of the distillation tower, and part of the material in the reflux tank is sent to the distillation tower through the reflux pump at the top of the distillation tower. The top of the tower is used as reflux liquid, and the other part is extracted as light components and then enters the liquid phase hydrogenation system; the temperature of the top of the distillation tower is controlled at 135°C, and the bottom liquid in the distillation tower is sent to the ethylene glycol recovery tower through the distillation tower bottom liquid external pump. The ethylene glycol product is extracted from the side sampling port of the distillation tower, and is cooled to 40°C in the side product extraction cooler. The cooled liquid flows into the side sampling intermediate tank. After sampling and analysis, the ethylene glycol concentration is 99.92%. The side product is pumped out to the tank area for sale, and the pressure at the top of the distillation tower is controlled at 12KPa.A by a vacuum pump.

[0083] Example 4:

[0084] Example 4 operating parameters:

[0085] equipment Hourly steam level / volume Tower top / bottom temperature Tower top pressure Ethylene glycol concentration Reboiler 0.7MPa / 55T 136℃ / 156℃ 13KPa.A 99.91％

[0086] The crude material enters the middle of the distillation tower, and the material is sent to the top of the falling film reboiler through the tower kettle circulation pump in the distillation tower. The falling film reboiler uses 0.7MPa steam to control the temperature at 55T / h for heating. After the distillation tower kettle temperature is 156℃, part of the vaporization occurs. The gas phase rises to the top of the distillation tower and enters the by-product steam waste boiler for heat exchange and then condensed through the circulating water condenser and the cryogenic cooler. The condensed liquid flows into the reflux tank of the distillation tower. Part of the material in the reflux tank is sent to the distillation tower through the reflux pump at the top of the distillation tower. The top of the tower is used as reflux liquid, and the other part is extracted as light components and then enters the liquid phase hydrogenation system; the temperature of the top of the distillation tower is controlled at 136°C, and the bottom liquid in the distillation tower is sent to the ethylene glycol recovery tower through the distillation tower bottom liquid external pump. The ethylene glycol product is extracted from the side sampling port of the distillation tower, and is cooled to 40°C in the side product extraction cooler. The cooled liquid flows into the side sampling intermediate tank. After sampling and analysis, the ethylene glycol concentration is 99.91%. The side product is pumped out to the tank area for sale, and the top pressure of the distillation tower is controlled at 13KPa.A by a vacuum pump.

[0087] The operating parameters of Comparative Examples 1 to 4 are as follows:

[0088]

[0089]

[0090] Comparative Examples 1 to 4 are the ethylene glycol concentrations after distillation using a thermosiphon reboiler in the prior art.

[0091] It can be seen from the above Examples 1 to 4 and Comparative Examples 1 to 4 that, compared with the prior art, the hourly steam level / volume is smaller, and production can be achieved with only 0.7 MPa, with lower energy consumption, and without affecting the concentration of ethylene glycol output. In particular, when the top pressure and temperature are reduced, the less high-temperature esterification reaction occurs, the higher the ethylene glycol concentration is, and the lowering of temperature will inevitably lead to a reduction in energy consumption, which requires less investment for the enterprise, better achieves the goals of energy saving, high efficiency and reduced production costs, and enhances the price advantage of the product.

[0092] The above-mentioned embodiments are only preferred embodiments of the present application and cannot be used to limit the scope of protection of the present application. Any non-substantial changes and replacements made by technicians in this field based on the present application shall fall within the scope of protection required by the present application.

Claims

1. A device for improving the purity of ethylene glycol produced from natural gas, comprising a dealcoholization tower and an ethylene glycol production tower, characterized in that: The dealcoholization tower and the ethylene glycol product tower both comprise a distillation tower (10), a bottom liquid external delivery pump (11) provided on a bottom discharge pipe of the distillation tower (10), and a vacuum pumping system (9) connected to an air outlet pipe at the top of the distillation tower (10) through a pipe. The reboiler (1) adopts a falling film reboiler (1). A by-product steam waste boiler (8) is provided between the vacuum pumping system (9) and the distillation tower (10). A reflux tank (5) and a reflux pump (3) are connected to the top of the distillation tower (10) through a pipe. An external discharge pipe (4) is further provided on the discharge pipe of the reflux pump (3). A side line product pump (15) and an intermediate tank (14) are further provided on one side of the distillation tower (10) in the ethylene glycol product tower.

2. The device for improving the purity of ethylene glycol from natural gas according to claim 1, characterized in that: A circulation pump (12) is provided between the distillation tower (10) and the reboiler (1).

3. The device for improving the purity of ethylene glycol from natural gas according to claim 2, characterized in that: The vacuum pumping system (9) includes a buffer tank (91) and a vacuum pump system (92). After the extracted gas phase is separated into gas and liquid by the buffer tank (91), the liquid phase flows into the reflux tank of the distillation tower (10), and the gas phase is discharged through the vacuum pump system (92).

4. The device for improving the purity of ethylene glycol from natural gas according to claim 1, characterized in that: A product cooler (13) is provided between the distillation tower (10) and the intermediate tank (14). The temperature of the cooled gaseous ethylene glycol product is 40±2° C. The gaseous ethylene glycol product flows into the intermediate tank (14) after passing through the product cooler (13).

5. The device for improving the purity of ethylene glycol from natural gas according to claim 2, characterized in that: A steam condensate tank (2) is provided on the gas outlet pipeline of the reboiler (1).

6. The device for improving the purity of ethylene glycol from natural gas according to claim 2, characterized in that: A circulating water condenser (7) is provided between the by-product steam waste boiler (8) and the vacuum pumping system (9), and the circulating water condenser (7) is communicated with the reflux tank (5).

7. The device for improving the purity of ethylene glycol from natural gas according to claim 6, characterized in that: A cryogenic cooler (6) is further provided between the circulating water condenser (7) and the vacuum pumping system (9), and the cryogenic cooler (6) is in communication with the reflux tank (5).

8. A method for improving the purity of ethylene glycol produced from natural gas, characterized by: The device according to any one of claims 1 to 7, wherein the method comprises: S1, crude methanol and crude ethylene glycol from the ethylene glycol synthesis section or the ethylene glycol intermediate tank (14) enter different positions of the methanol recovery tower, and after separation in the methanol recovery tower, the top gas phase is condensed, and a small amount of produced liquid is sent to the methanol separation tower for separation; the methanol recovery tower produces refined methanol product from the side line, and the bottom liquid is sent to the dehydration tower; S2, after the crude ethylene glycol entering the dehydration tower is separated, the top gas phase is condensed, and a small amount of produced liquid is sent to the methanol separation tower for separation; the bottom liquid in the dehydration tower is then sent to the dealcoholization tower; S3, after the materials separated by the methanol recovery tower and the dehydration tower enter the methanol separation tower, methanol is separated by the methanol separation tower, and the remaining materials are transported to the ethanol product again, and after ethanol separation, the waste liquid is discharged externally; S4, after the material enters the dealcoholization tower, the crude ethylene glycol in the dealcoholization distillation tower (10) is injected into the falling film reboiler (1) through the circulation pump (12) for heat exchange, and then recirculated into the dealcoholization distillation tower (10) for separation. After the crude ethylene glycol is separated, the top gas phase is a glycol vapor lighter than ethylene glycol. After condensation through the dealcoholization by-product steam waste pot (8), the circulating water condenser (7), and the deep freezer (6), the liquid phase enters the reflux tank (5). The non-condensable gas is extracted through the vacuum system (9) in the dealcoholization tower to maintain the vacuum degree of the dealcoholization tower. After the condensate out of the reflux tank (5) is pressurized by the reflux pump (3), most of it returns to the dealcoholization distillation tower (10) as reflux, and a small amount of it is extracted and sent to the EG concentration tower for separation; the discharge from the bottom of the dealcoholization distillation tower (10) is pumped into the ethylene glycol product tower by the dealcoholization tower bottom liquid external delivery pump (11); S5. After the material enters the ethylene glycol product tower, the crude ethylene glycol in the ethylene glycol distillation tower (10) is injected into the falling film reboiler (1) through the circulation pump (12) for heat exchange, and then recirculated into the ethylene glycol distillation tower (10) for separation. After the crude ethylene glycol is separated, the top gas phase is glycol vapor lighter than ethylene glycol. After condensation through the ethylene glycol by-product steam waste boiler (8), the circulating water condenser (7), and the deep freezer (6), the liquid phase enters the reflux tank (5). The non-condensable gas is extracted through the vacuum system (9) in the ethylene glycol product tower to maintain the vacuum degree of the ethylene glycol product tower, and then exits the reflux tank ( After the condensate of 5) is pressurized by the reflux pump (3), most of it returns to the ethylene glycol distillation tower (10) as reflux, and a small amount is extracted and sent to the liquid phase hydrogenation unit; the polyester grade ethylene glycol product in the ethylene glycol distillation tower (10) is extracted through the side line of the ethylene glycol distillation tower (10), sent to the product cooler (13) for cooling through the side line extracted product pump (15), and then sent to the polyester grade ethylene glycol product intermediate tank (14), and finally sent to the tank area for sale through the polyester grade ethylene glycol delivery pump, and the discharge from the bottom of the ethylene glycol distillation tower (10) is pumped into the ethylene glycol recovery tower by the bottom liquid delivery pump (11); S6. After the materials entering the EG concentration tower are separated, the non-condensable gas at the top of the tower is extracted and sent to the ethylene glycol finished product tank area or area 48 for incineration, and the materials in the EG concentration tower kettle are sent to the liquid phase hydrogenation unit or the dealcoholization tower; S7, After the crude ethylene glycol in the ethylene glycol recovery tower is separated, the non-condensable gas at the top of the tower is sent to the liquid phase hydrogenation unit; the kettle liquid is sent to the tank area or area 48 for incineration; S8. The materials in the liquid phase hydrogenation unit are refluxed into the ethylene glycol product tower or dealcoholization tower after hydrogenation.

9. The method for improving the purity of ethylene glycol produced from natural gas according to claim 8, characterized in that: The top temperature of the distillation tower (10) of the dealcoholization tower is 133-134°C, the bottom temperature is 152-154°C, and the top pressure is 10-11 KPa.A.

10. The method for improving the purity of ethylene glycol produced from natural gas according to claim 8, characterized in that: The top temperature of the distillation tower (10) in the ethylene glycol product tower is 133-134° C., the bottom temperature is 149-151° C., and the top pressure is 10-12 KPa.A.

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