Energy-saving acetic acid production system

Abstract

The utility model provides an energy -conserving type acetic acid production system, include: reaction unit and product rectification unit, reaction unit includes raw material methanol delivery pipeline, carbon monoxide pipeline and reactor, carbon monoxide pipeline and raw material methanol delivery pipeline connect reactor, product rectification unit includes dehydration tower and finished product tower, reactor side line export connects dehydration tower, dehydration tower bottom export connects finished product tower, and finished product tower side line export connects product pipeline, one side of reactor is provided with circulating heat exchange pipeline, and circulating heat exchange pipeline entrance connects reactor lateral wall, and export connects reactor top, be provided with circulating heat exchanger on circulating heat exchange pipeline, the both sides of finished product tower are provided with main heat exchange pipeline and auxiliary heat exchange pipeline respectively, main heat exchange pipeline entrance connects finished product tower bottom, and export connects finished product tower lateral wall, be provided with finished product reboiler on main heat exchange pipeline, this system can realize energy -conserving production acetic acid.

Description

Technical Field

[0001] This utility model relates to the field of acetic acid preparation technology, and more specifically, to an energy-saving acetic acid production system. Background Technology

[0002] Acetic acid, also known as acetic acid, is a basic organic chemical raw material. Its derivatives are widely used in key sectors of the national economy, such as pharmaceuticals, pesticides, and food. The methanol carbonylation method, which emerged in the 1960s, revolutionized acetic acid production. This technology uses methanol and carbon monoxide as raw materials and achieves a highly efficient carbonylation reaction through a rhodium-based or iridium-based catalyst system. It boasts significant advantages such as high atom economy, mild reaction conditions, and excellent product purity, and has become the mainstream technology in modern acetic acid production.

[0003] Because the crude product after the acetic acid reaction is quite complex, it typically contains acetic acid, water, iodomethane, and other byproducts. To ensure product purity, the crude product needs to be purified by distillation. These distillation purification processes consume a large amount of energy, significantly increasing production costs.

[0004] In view of the above, this utility model is hereby proposed. Utility Model Content

[0005] The purpose of this invention is to provide an energy-saving acetic acid production system that can fully utilize the waste heat from the reaction and the tail gas from the dehydration tower as a heat source for the bottom of the finished product tower. This helps improve energy utilization, achieves waste heat reuse, and reduces the amount of external steam required for the finished product tower, thus contributing to cost savings.

[0006] In order to achieve the above-mentioned objectives of this utility model, the following technical solution is adopted: This utility model provides an energy-saving acetic acid production system, comprising: a reaction unit and a product distillation unit; the reaction unit includes a raw material methanol conveying pipeline, a carbon monoxide pipeline, and a reactor; the carbon monoxide pipeline and the raw material methanol conveying pipeline are connected to the reactor; the product distillation unit includes a dehydration tower and a product tower; The reactor side outlet is connected to the dehydration tower, the bottom outlet of the dehydration tower is connected to the product tower, and the side outlet of the product tower is connected to the product pipeline. A circulating heat exchange pipeline is provided on one side of the reactor. The inlet of the circulating heat exchange pipeline is connected to the side wall of the reactor, and the outlet is connected to the top of the reactor. A circulating heat exchanger is provided on the circulating heat exchange pipeline. The steam pipeline in the circulating heat exchanger absorbs the heat of the material in the circulating heat exchange pipeline in the circulating heat exchanger. The finished product tower is equipped with a main heat exchange pipeline and an auxiliary heat exchange pipeline on both sides. The inlet of the main heat exchange pipeline is connected to the bottom of the finished product tower, and the outlet is connected to the side wall of the finished product tower. A finished product reboiler is installed on the main heat exchange pipeline. The inlet of the auxiliary heat exchange pipeline is connected to the bottom of the finished product tower, and the outlet is connected to the side wall of the finished product tower. A finished product supplementary reboiler is installed on the auxiliary heat exchange pipeline. The steam pipeline is thermally coupled to the main heat exchange pipeline through the finished product reboiler. The tail gas discharged from the tail gas outlet at the top of the dehydration tower provides a heat source for the finished product supplementary reboiler.

[0007] In the above scheme, by coordinating the circulating heat exchange pipeline, circulating heat exchanger, finished product reboiler, finished product supplementary reboiler, finished product tower, and dehydration tower, closed-loop absorption of reaction waste heat and dehydration tower tail gas waste heat can be achieved. This waste heat recovery and utilization method not only helps to improve energy utilization efficiency and reduce heat loss, but also helps to reduce the amount of external steam introduced, save steam, and reduce product distillation costs. In addition, the crude product cooled in the circulating heat exchange pipeline is refluxed from the top of the reactor tower and exchanges heat with the tail gas at the top of the tower. This can cool methanol and other substances in the tail gas, allowing them to return to the reactor along with the reflux material to continue participating in the reaction, which helps to improve the conversion rate of raw materials.

[0008] Preferably, the outlet of the main heat exchange pipeline and the outlet of the auxiliary heat exchange pipeline are located on the same horizontal plane and face opposite directions. Since the heat sources of the two heat exchange pipelines are different, the temperature of the material after heat exchange may differ.

[0009] In the above scheme, by placing the outlets of the two heat exchange pipelines on the same horizontal plane and facing opposite directions, the two streams of material flowing in different directions can generate a stirring flow in the same plane, which helps to ensure uniform temperature in the bottom of the finished product tower and improve the distillation effect.

[0010] Preferably, the finished product tower is equipped with a stirrer, the stirrer is at the same horizontal height as the outlet of the main heat exchange pipeline and the center of the stirrer is located at the axis of the finished product tower; the outlet of the main heat exchange pipeline and the outlet of the auxiliary heat exchange pipeline are staggered in the horizontal direction and the line connecting the outlet of the main heat exchange pipeline and the outlet of the auxiliary heat exchange pipeline passes through the center of the stirrer.

[0011] In the above scheme, the two streams of material output from the two heat exchange pipelines impact the impeller of the stirrer, driving the stirrer to rotate. This allows the stirrer to agitate the material in the bottom of the column over a wide range, which helps to distribute the material after heat exchange more quickly and evenly into the bottom of the column, ensuring uniform temperature in the bottom of the column and improving the distillation effect.

[0012] Preferably, the raw material methanol conveying pipeline is thermally coupled to the product pipeline through a methanol feed heat exchanger, and the methanol in the raw material methanol conveying pipeline is fed into the reactor after exchanging heat with the product in the product pipeline.

[0013] In the above scheme, heat exchange between the raw methanol and the product is considered through a methanol feed heat exchanger. This allows the waste heat of the product to preheat the raw methanol, which can not only replace some or all of the external heat source (such as steam) required for methanol preheating, but also reduce the cooling water consumption for product cooling, achieving "two-way utilization of one unit of heat" and reducing the total energy consumption and cost of the unit. Moreover, this method can improve process efficiency and reaction stability. The temperature of the preheated methanol is close to the reaction temperature, so it does not need to absorb a large amount of heat to raise the temperature after entering the reactor. This shortens the preheating time to extend the effective reaction time and improve the conversion rate. It can also avoid local temperature fluctuations in the reactor caused by cold methanol feed, reduce side reactions such as dimethyl ether and propionic acid, and reduce the load on subsequent distillation and separation.

[0014] Preferably, a dehydration reboiler is provided on one side of the dehydration tower, with the inlet of the dehydration reboiler connected to the bottom of the dehydration tower and the outlet connected to the side wall of the dehydration tower; the steam pipeline is connected to the dehydration reboiler to provide a heat source for the dehydration reboiler.

[0015] In the above scheme, the reboiler at the bottom of the dehydration tower (i.e., the dehydration reboiler) can provide heat for the dehydration and distillation of the material inside the dehydration tower. By utilizing the waste heat of the reaction as the reboiling heat source for the dehydration reboiler, this scheme can achieve closed-loop waste heat recovery, further improve energy utilization, and at the same time reduce the amount of external steam supply, thereby reducing production costs.

[0016] Preferably, the product distillation unit further includes an evaporator and a light-light product removal tower. The crude product collected from the reactor side stream is processed sequentially through the evaporator, the light-light product removal tower, the dehydration tower, and the product tower before being output through the product pipeline. An evaporator reboiler is provided in the bottom of the evaporator; a light-weight removal reboiler is provided on one side of the light-weight removal tower, with the inlet of the light-weight removal reboiler connected to the bottom of the light-weight removal tower and the outlet connected to the side wall of the light-weight removal tower; the steam pipeline connects the evaporator reboiler and the light-weight removal reboiler as a reboiling heat source.

[0017] This scheme, by setting up an evaporator and a light-weight product removal tower, can gradually separate impurities, recover resources, and enrich the target product, laying the foundation for finally obtaining high-purity acetic acid. By utilizing the waste heat from the reaction as a heat source for the evaporator-reboiler and the light-weight product removal-reboiler, a closed-loop waste heat recovery can be achieved, reducing energy waste and lowering production costs.

[0018] Preferably, the product distillation unit further includes a stripping column; the bottom outlet of the product column is connected to the stripping column, and the top outlet of the stripping column is connected to the product column; a stripping reboiler is provided on one side of the stripping column; the inlet of the stripping reboiler is connected to the bottom of the stripping column, and the outlet is connected to the side wall of the stripping column; the steam pipeline is connected to the stripping reboiler.

[0019] The above scheme, by setting up a stripping column, can deeply heat and vaporize the material discharged from the bottom of the distillation column, achieving the final separation of light and heavy components. This ensures that the purity of the heavy components (or target product) at the bottom of the column meets the standards, while also recovering the usable light components, thus avoiding resource waste. By utilizing the waste heat from the reaction as a heat source for the stripping reboiler, a closed-loop waste heat recovery can be achieved, reducing energy waste and lowering production costs.

[0020] Preferably, the tail gas outlet at the top of the reactor is connected to a high-pressure separator, the gas phase outlet at the top of the high-pressure separator is connected to a high-pressure absorption tower, and the bottom outlet of the high-pressure absorption tower is connected to a methanol absorption storage tank; the bottom outlet of the methanol absorption storage tank is connected to the reactor; the tail gas outlet at the top of the high-pressure absorption tower is connected to a high-pressure absorption tail gas cooler, and after the tail gas at the top of the high-pressure absorption tower is cooled by the high-pressure absorption tail gas cooler, the gas phase is discharged, and the liquid phase is returned to the high-pressure absorption tower. By setting up a high-pressure absorption tower, the heavy phase in the reaction tail gas can be further absorbed, which helps to further improve the raw material utilization rate.

[0021] Preferably, the bottom outlet of the methanol absorption storage tank is connected to a regeneration tower, and the bottom outlet of the regeneration tower is connected to a lean methanol tank. A regeneration reboiler is provided on one side of the regeneration tower, with its inlet connected to the bottom of the regeneration tower and its outlet connected to the side wall of the regeneration tower. By utilizing the waste heat from the reaction as a heat source for the regeneration reboiler, closed-loop waste heat recovery can be achieved, reducing energy waste and helping to further reduce production costs.

[0022] Preferably, the top tail gas outlet of the light phase removal tower is connected to a low-pressure absorption tower; the bottom outlet of the low-pressure absorption tower is connected to the methanol absorption storage tank, and the top gas phase outlet of the methanol absorption storage tank is connected to the low-pressure absorption tower. By setting up a low-pressure absorption tower, the heavy phase in the tail gas of the light phase removal tower can be further absorbed, avoiding waste, and the tail gas can be pretreated to avoid environmental pollution.

[0023] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. By coordinating the circulating heat exchange pipeline, circulating heat exchanger, finished product reboiler, finished product supplementary reboiler, finished product tower, and dehydration tower, closed-loop absorption of reaction waste heat and dehydration tower tail gas waste heat can be achieved. This waste heat recovery and utilization method not only helps to improve energy utilization and reduce heat loss, but also helps to reduce the amount of external steam introduced, save steam, and reduce product distillation costs. 2. The crude product cooled in the circulating heat exchange pipeline is refluxed from the top of the reactor tower to exchange heat with the tail gas at the top of the tower. This can cool methanol and other substances in the tail gas, allowing them to return to the reactor along with the reflux material to continue participating in the reaction. This helps to improve the conversion rate of the raw materials. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of the system according to Embodiment 1 of this utility model is shown; Figure 2 Show Figure 1 A magnified view of part A in the middle; Figure 3 Show Figure 1 A magnified view of part B in the middle section; Figure 4 A schematic diagram of the finished tower of Embodiment 1 of this utility model is shown; Figure 5 This diagram shows a cross-sectional view of the finished tower in Embodiment 1 of this utility model.

[0025] In the diagram: 1. Reactor; 2. Circulating heat exchange pipeline; 3. Circulating heat exchanger; 4. Reactor tail gas cooler; 5. High-pressure separator; 6. Carbon monoxide pipeline; 7. Evaporator; 8. Evaporator-reboiler; 9. Light weight removal tower; 10. Light weight removal primary cooler; 11. Acetic acid collection tank; 12. Light weight removal reboiler; 13. Separator; 14. Raw material methanol conveying pipeline; 15. Light weight removal final cooler; 16. Dehydration tower; 17. Dehydration reboiler; 18. Dehydration cooler; 19. Dehydration reflux tank; 20. Product tower; 21. Product replenishment reboiler; 22. Product reboiler. 23. Finished product tail gas cooler; 24. Finished product reflux tank; 25. Stripping tower; 26. Stripping reboiler; 27. Methanol feed heat exchanger; 28. Product cooler; 29. ​​High-pressure absorption tail gas cooler; 30. High-pressure absorption tower; 31. Low-pressure absorption tower; 32. High-pressure absorption methanol cooler; 33. Methanol absorption storage tank; 34. Regeneration tower; 35. Regeneration tail gas cooler; 36. Lean liquor cooler; 37. Regeneration reboiler; 38. Methanol lean liquor tank; 39. Product pipeline; 40. Auxiliary heat exchange pipeline; 41. Main heat exchange pipeline; 42. Agitator. Detailed Implementation

[0026] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this utility model, not all embodiments, and are only used to illustrate this utility model, and should not be regarded as limiting the scope of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0027] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0029] To more clearly illustrate the technical solution of this utility model, the following description is provided in the form of specific embodiments.

[0030] Example 1 See also Figure 1-5This embodiment provides an energy-saving acetic acid production system, which includes a reaction unit and a product distillation unit. The reaction unit includes a raw material methanol conveying pipeline 14, a carbon monoxide pipeline 6, and a reactor 1. The carbon monoxide pipeline 6 and the raw material methanol conveying pipeline 14 are connected to the reactor 1. The product distillation unit includes a dehydration tower 16 and a product tower 20. The side outlet of the reactor 1 is connected to the dehydration tower 16, the bottom outlet of the dehydration tower 16 is connected to the product tower 20, and the side outlet of the product tower 20 is connected to the product pipeline 39. A circulating heat exchange pipeline 2 is provided on one side of the reactor 1. The inlet of the circulating heat exchange pipeline 2 is connected to the side wall of the reactor 1, and the outlet is connected to the top of the reactor 1. A circulating heat exchanger is provided on the circulating heat exchange pipeline 2. 3; The steam pipeline in the circulating heat exchanger 3 absorbs heat from the material in the circulating heat exchange pipeline 2 in the circulating heat exchanger 3; The main heat exchange pipeline 41 and the auxiliary heat exchange pipeline 40 are respectively set on both sides of the finished product tower 20; The inlet of the main heat exchange pipeline 41 is connected to the bottom of the finished product tower 20, and the outlet is connected to the side wall of the finished product tower 20. The finished product reboiler 22 is set on the main heat exchange pipeline 41; The inlet of the auxiliary heat exchange pipeline 40 is connected to the bottom of the finished product tower 20, and the outlet is connected to the side wall of the finished product tower 20. The finished product supplement reboiler 21 is set on the auxiliary heat exchange pipeline 40; The steam pipeline is thermally coupled to the main heat exchange pipeline 41 through the finished product reboiler 22, and the tail gas discharged from the tail gas outlet at the top of the dehydration tower 16 provides a heat source for the finished product supplement reboiler 21.

[0031] It is understandable that pumps and valves can be installed on pipelines as needed to facilitate material flow and control, which will not be elaborated upon here.

[0032] To facilitate the addition of catalyst, a catalyst pipeline can be installed. This pipeline can be directly connected to reactor 1 or indirectly connected to reactor 1 through other pipelines, which will not be elaborated here.

[0033] To prevent residual trace acidic impurities (especially halide impurities) in the tower from corroding equipment, contaminating products, or affecting subsequent processes, the side wall of the finished product tower 20 can also be connected to a potassium hydroxide pipeline for inputting potassium hydroxide, which will not be elaborated here.

[0034] See also Figure 1 , 3 The top tail gas outlet of the finished product tower 20 is connected to the finished product tail gas cooler 23. The outlet of the finished product tail gas cooler 23 is connected to the finished product reflux tank 24. The bottom outlet of the finished product reflux tank 24 is connected to both the finished product tower 20 and the dehydration tower 16. The tail gas at the top of the finished product tower 20 is cooled by the finished product tail gas cooler 23 and then enters the finished product reflux tank. Part of the material in the finished product reflux tank enters the finished product tower 20 for further distillation, and the other part enters the dehydration tower 16 for further processing.

[0035] See also Figure 4 , 5The outlets of the main heat exchanger pipe 41 and the auxiliary heat exchanger pipe 40 are located on the same horizontal plane and face opposite directions. An agitator 42 is installed inside the product tower 20. The agitator 42 is at the same horizontal height as the outlet of the main heat exchanger pipe 41, and its center is located at the axis of the product tower 20. The outlets of the main heat exchanger pipe 41 and the auxiliary heat exchanger pipe 40 are staggered horizontally, and the line connecting their outlets passes through the center of the agitator 42. The material output from both the main heat exchanger pipe 41 and the auxiliary heat exchanger pipe 40 impacts the blades of the agitator 42, thereby driving the agitator 42 to rotate and thus agitate the material in the tower bottom.

[0036] In this embodiment, the raw material methanol conveying pipeline 14 is thermally coupled to the product pipeline 39 via a methanol feed heat exchanger 27. The methanol in the raw material methanol conveying pipeline 14 exchanges heat with the product in the product pipeline 39 before being fed into reactor 1. The product in the product pipeline 39 is then cooled by the product cooler 28 after passing through the methanol feed heat exchanger 27 before being output.

[0037] Continue reading Figure 1 , 2 A dehydration reboiler 17 is installed on one side of the dehydration tower 16. The inlet of the dehydration reboiler 17 is connected to the bottom of the dehydration tower 16, and the outlet is connected to the side wall of the dehydration tower 16. A steam pipeline is connected to the dehydration reboiler 17 to provide a heat source for the dehydration reboiler 17. The product distillation unit also includes an evaporator 7 and a light-light product removal tower 9. The crude product collected from the side of the reactor 1 is processed sequentially through the evaporator 7, the light-light product removal tower 9, the dehydration tower 16, and the product tower 20, and then output through the product pipeline 39. An evaporation reboiler 8 is installed in the bottom of the evaporator 7. A light-light product removal reboiler 12 is installed on one side of the light-light product removal tower 9. The inlet of the light-light product removal reboiler 12 is connected to the bottom of the light-light product removal tower 9, and the outlet is connected to the side wall of the light-light product removal tower 9. A steam pipeline is connected to the evaporation reboiler 8 and the light-light product removal reboiler 12 to serve as a reboiling heat source.

[0038] In this embodiment, an acetic acid collection tank 11 is provided between the light-light removal tower 9 and the dehydration tower 16. The outlet of the side wall of the light-light removal tower 9 is connected to the top inlet of the acetic acid collection tank 11, and the bottom outlet of the acetic acid collection tank 11 is connected to the dehydration tower 16.

[0039] In this embodiment, the product distillation unit further includes a stripping column 25; the bottom outlet of the product column 20 is connected to the stripping column 25, the top outlet of the stripping column 25 is connected to the product column 20, and acetic acid is discharged from the bottom outlet; a stripping reboiler 26 is provided on one side of the stripping column 25; the inlet of the stripping reboiler 26 is connected to the bottom of the stripping column 25, and the outlet is connected to the side wall of the stripping column 25; a steam line is connected to the stripping reboiler 26. The stripping reboiler 26 may also be connected to a supplementary steam line to meet the operating requirements of the stripping reboiler 26.

[0040] See also Figure 1 , 3The tail gas outlet at the top of reactor 1 is connected to high-pressure separator 5. The tail gas from the top of reactor 1 is cooled by tail gas cooler 4 before entering high-pressure separator 5 for separation. The gas phase outlet at the top of high-pressure separator 5 is connected to high-pressure absorption tower 30. The bottom outlet of high-pressure absorption tower 30 is connected to methanol absorption storage tank 33. The bottom outlet of methanol absorption storage tank 33 is connected to reactor 1. The tail gas outlet at the top of high-pressure absorption tower 30 is connected to high-pressure absorption tail gas cooler 29. After being cooled by high-pressure absorption tail gas cooler 29, the gas phase of the tail gas from the top of high-pressure absorption tower 30 is discharged, and the liquid phase is returned to high-pressure absorption tower 30. After being cooled by high-pressure absorption tail gas cooler 29, the liquid phase of the tail gas from the top of high-pressure absorption tower 30 is returned, and the gas phase is sent to the flare system for incineration.

[0041] like Figure 3 As shown, the bottom outlet of the methanol absorption storage tank 33 is connected to the regeneration tower 34, and the bottom outlet of the regeneration tower 34 is connected to the methanol lean liquid tank 38. A regeneration reboiler 37 is installed on one side of the regeneration tower 34, with its inlet connected to the bottom of the regeneration tower 34 and its outlet connected to the side wall of the regeneration tower 34. The tail gas from the top of the regeneration tower 34 is treated by the regeneration tail gas cooler 35, and the gas phase is sent to the light component removal final cooler 15, while part of the liquid phase is returned to the regeneration tower 34, and the other part is sent to the reactor 1 to continue participating in the reaction. The material at the bottom of the regeneration tower 34 is cooled by the lean liquid cooler 36 and then sent to the methanol lean liquid tank 38. The methanol in the methanol lean liquid tank 38 can be recycled back to the reactor 1 to continue participating in the reaction.

[0042] The top tail gas outlet of the light gas removal tower 9 is connected to the low-pressure absorption tower 31; the bottom outlet of the low-pressure absorption tower 31 is connected to the methanol absorption storage tank 33, and the top gas phase outlet of the methanol absorption storage tank 33 is connected to the low-pressure absorption tower 31. The tail gas at the top of the low-pressure absorption tower 31 is sent to the flare system for incineration. Part of the material at the bottom of the methanol absorption storage tank 33 is sent to the regeneration tower 34 for treatment, and the other part is sent to the reactor 1 to continue participating in the reaction.

[0043] To facilitate the absorption of methanol in the gas phase by the high-pressure absorption tower 30 and the low-pressure absorption tower 31, in this embodiment, low-temperature methanol can be introduced into the two absorption towers through pipelines. Furthermore, a high-pressure methanol absorption cooler 32 can be installed on the pipeline used to introduce methanol into the low-pressure absorption tower 31, which will not be elaborated further.

[0044] In this embodiment, the top tail gas outlet of the light-duty carbon removal tower 9 is connected to the light-duty carbon removal pre-cooler 10, the top gas phase outlet of the light-duty carbon removal pre-cooler 10 is connected to the light-duty carbon removal final cooler 15, the bottom liquid phase outlet of the light-duty carbon removal pre-cooler 10 is connected to the separator 13, the middle outlet of the separator 13 is connected to the light-duty carbon removal tower 9, and the bottom outlet is connected to the reactor 1; the top gas phase outlet of the light-duty carbon removal final cooler 15 is connected to the low-pressure absorption tower 31, and the bottom liquid phase outlet is connected to the separator 13. The top tail gas outlet of the dehydration tower 16 is connected to the dehydration cooler 18, the outlet of the dehydration cooler 18 is connected to the dehydration reflux tank 19, and the bottom outlet of the dehydration reflux tank 19 is connected to the dehydration tower 16. The side wall of the separator 13 can also be connected to a demineralized water supply pipeline for replenishing demineralized water into the separator 13, which will not be described in detail.

[0045] The tail gas from the top of the light-weight gas removal tower 9 is cooled by the primary cooler 10. The liquid phase enters the separator 13, a portion of the gas phase enters the final cooler 15 for cooling, and the remaining portion enters the dehydration cooler 18. The gas phase obtained from the final cooler 15 enters the low-pressure absorption tower 31, while the liquid phase enters the separator 13. The material in the middle of the separator 13 enters the light-weight gas removal tower 9, while the heavy phase separated at the bottom flows to the reactor 1 to continue participating in the reaction. The tail gas from the top of the dehydration tower 16 is cooled by the dehydration cooler 18 and enters the dehydration reflux tank 19. The material at the bottom of the dehydration reflux tank 19 is returned to the dehydration tower 16.

[0046] In this embodiment, methanol, carbon monoxide, and catalyst / co-catalyst are introduced into the reactor (2.8 MPa, 188 °C) in a certain proportion for reaction; a portion of the reaction liquid is heated in a circulating heat exchanger to generate steam at ~175 °C (0.9 MPa) to heat the reboilers of the light component removal tower, dehydration tower, product tower, stripping tower, and regeneration tower; another portion of the reaction liquid undergoes flash evaporation in an evaporator, with the gas phase (acetic acid, water, iodomethane, etc.) entering the light component removal tower for further separation, and the liquid phase (acetic acid, water, catalyst, etc.) returning to the reactor to continue participating in the reaction; iodomethane and C are separated in the upper part of the light component removal tower. After the removal of light components such as O, crude acetic acid (acetic acid, water, etc.) is collected from the side stream of the tower and enters the dehydration tower (0.26MPa, 140℃). The bottom of the tower (acetic acid, catalyst, etc.) is returned to the reactor through the evaporator. The top steam (0.26MPa, 140℃) in the dehydration tower is thermally coupled with the circulating liquid in the bottom of the product tower (0.03MPa, 127℃). The acetic acid in the lower part (containing trace impurities such as propionic acid) enters the product tower (0.03MPa, 127℃) for further removal. The acetic acid (containing trace light components) collected from the top of the product tower is returned to the dehydration tower for separation. The product acetic acid (>99.9 wt.%) is collected from the tower body and used to preheat the raw material methanol. The bottom liquid of the tower enters the stripping tower (to further separate acetic acid and propionic acid). The high-pressure absorption tower and the low-pressure absorption tower are used for tail gas absorption and recovery of iodomethane, which is returned to the reaction system.

[0047] Testing revealed that the system in this embodiment requires 1.7 kcal of heat for heating the reboiler of the light component removal column, 7.72 kcal for the reboiler of the dehydration column, 6.7 kcal for the reboiler of the product column, and 0.01 kcal for the reboiler of the stripping column, totaling 16.1 kcal. The reactor heat can be recovered to obtain 8.99 kcal, and the waste heat from the top steam of the dehydration column can provide 5.52 kcal, generating a total waste heat of 14.51 kcal. Therefore, by utilizing this heat in the various reboilers, this solution can reduce energy loss by approximately 89.96% and save approximately 90% of the steam consumption of the original equipment, thereby significantly reducing production costs.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. An energy-saving acetic acid production system, characterized in that, include: The reaction unit includes a methanol feedstock pipeline, a carbon monoxide pipeline, and a reactor; the carbon monoxide pipeline and the methanol feedstock pipeline are connected to the reactor; the product distillation unit includes a dehydration tower and a product tower. The reactor side outlet is connected to the dehydration tower, the bottom outlet of the dehydration tower is connected to the product tower, and the side outlet of the product tower is connected to the product pipeline. A circulating heat exchange pipeline is provided on one side of the reactor. The inlet of the circulating heat exchange pipeline is connected to the side wall of the reactor, and the outlet is connected to the top of the reactor. A circulating heat exchanger is provided on the circulating heat exchange pipeline. The steam pipeline in the circulating heat exchanger absorbs the heat of the material in the circulating heat exchange pipeline in the circulating heat exchanger. The finished product tower is equipped with a main heat exchange pipeline and an auxiliary heat exchange pipeline on both sides. The inlet of the main heat exchange pipeline is connected to the bottom of the finished product tower, and the outlet is connected to the side wall of the finished product tower. A finished product reboiler is installed on the main heat exchange pipeline. The inlet of the auxiliary heat exchange pipeline is connected to the bottom of the finished product tower, and the outlet is connected to the side wall of the finished product tower. A finished product supplementary reboiler is installed on the auxiliary heat exchange pipeline. The steam pipeline is thermally coupled to the main heat exchange pipeline through the finished product reboiler. The tail gas discharged from the tail gas outlet at the top of the dehydration tower provides a heat source for the finished product supplementary reboiler.

2. The system according to claim 1, characterized in that, The outlet of the main heat exchange pipeline and the outlet of the auxiliary heat exchange pipeline are located on the same horizontal plane and their outlets face opposite directions.

3. The system according to claim 2, characterized in that, The finished product tower is equipped with a stirrer, which is located at the same horizontal level as the outlet of the main heat exchange pipeline and the center of the stirrer is located at the axis of the finished product tower; the outlet of the main heat exchange pipeline and the outlet of the auxiliary heat exchange pipeline are staggered in the horizontal direction and the line connecting the outlet of the main heat exchange pipeline and the outlet of the auxiliary heat exchange pipeline passes through the center of the stirrer.

4. The system according to claim 1, characterized in that, The raw material methanol delivery pipeline is thermally coupled to the product pipeline through a methanol feed heat exchanger. The methanol in the raw material methanol delivery pipeline exchanges heat with the product in the product pipeline before being fed into the reactor.

5. The system according to claim 1, characterized in that, A dehydration reboiler is provided on one side of the dehydration tower. The inlet of the dehydration reboiler is connected to the bottom of the dehydration tower, and the outlet is connected to the side wall of the dehydration tower. The steam pipeline is connected to the dehydration reboiler to provide a heat source for the dehydration reboiler.

6. The system according to any one of claims 1-5, characterized in that, The product distillation unit also includes an evaporator and a light-light product removal tower. The crude product collected from the reactor side stream is processed sequentially through the evaporator, the light-light product removal tower, the dehydration tower, and the product tower before being output through the product pipeline. An evaporator reboiler is provided in the bottom of the evaporator; a light-weight removal reboiler is provided on one side of the light-weight removal tower, with the inlet of the light-weight removal reboiler connected to the bottom of the light-weight removal tower and the outlet connected to the side wall of the light-weight removal tower; the steam pipeline connects the evaporator reboiler and the light-weight removal reboiler as a reboiling heat source.

7. The system according to any one of claims 1-5, characterized in that, The product distillation unit further includes a stripping column; the bottom outlet of the product column is connected to the stripping column, and the top outlet of the stripping column is connected to the product column. A stripping reboiler is provided on one side of the stripping column; the inlet of the stripping reboiler is connected to the bottom of the stripping column, and the outlet is connected to the side wall of the stripping column; the steam pipeline is connected to the stripping reboiler.

8. The system according to claim 6, characterized in that, The tail gas outlet at the top of the reactor is connected to a high-pressure separator, the gas phase outlet at the top of the high-pressure separator is connected to a high-pressure absorption tower, and the bottom outlet of the high-pressure absorption tower is connected to an absorption methanol storage tank. The bottom outlet of the absorption methanol storage tank is connected to the reactor. The tail gas outlet at the top of the high-pressure absorption tower is connected to a high-pressure absorption tail gas cooler. After the tail gas at the top of the high-pressure absorption tower is cooled by the high-pressure absorption tail gas cooler, the gas phase is discharged and the liquid phase is returned to the high-pressure absorption tower.

9. The system according to claim 8, characterized in that, The bottom outlet of the methanol absorption storage tank is connected to a regeneration tower, and the bottom outlet of the regeneration tower is connected to a methanol lean solution tank. A regeneration reboiler is provided on one side of the regeneration tower. The inlet of the regeneration reboiler is connected to the bottom of the regeneration tower, and the outlet is connected to the side wall of the regeneration tower.

10. The system according to claim 8, characterized in that, The tail gas outlet at the top of the light gas removal tower is connected to the low-pressure absorption tower; the bottom outlet of the low-pressure absorption tower is connected to the methanol absorption storage tank, and the gas phase outlet at the top of the methanol absorption storage tank is connected to the low-pressure absorption tower.

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