An acetic acid production system

Abstract

The utility model provides a kind of acetic acid preparation system.System includes: catalyst pipeline, methanol pipeline, carbon monoxide pipeline, first heat exchanger, second heat exchanger and sequentially communicated carbonyl reactor, evaporator, light removal tower, dehydration tower and product tower;Carbonyl reactor communicates evaporator, evaporator top outlet communicates light removal tower, light removal tower communicates dehydration tower, dehydration tower communicates product tower, and product tower side wall is connected with product pipeline;Product pipeline and methanol pipeline are coupled heat exchange by first heat exchanger;Light removal tower bottom outlet is connected with light removal tower side wall via second heat exchanger, and product tower top outlet is connected with dehydration tower via second heat exchanger;Methanol pipeline and catalyst pipeline connect carbonyl reactor;Carbonyl reactor side is provided with catalyst circulation pipe, and the inlet of catalyst circulation pipe is connected with the bottom of carbonyl reactor, and outlet is connected with the upper portion of carbonyl reactor and below liquid level.Application of the system helps to improve raw material conversion rate and product yield.

Description

Technical Field

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

[0002] Acetic acid, with the molecular formula CH3COO and a relative molecular mass of 60.05, is a colorless liquid with a pungent, acidic odor and corrosive properties. It contains the carbonyl group, a functional group characteristic of organic acids. Due to its very low freezing point, acetic acid is also known as glacial acetic acid. As a widely used and important chemical raw material, acetic acid is extensively applied in industrial production. It is primarily used to synthesize the monomer VAM for vinyl acetate, as a raw material for the synthesis of acetic anhydride, and as a solvent for the production of refined terephthalic acid. It can also be used to produce acetate esters, chloroacetic acid, and other substances. Hundreds of downstream products can be derived from it. Because acetic acid is widely used in basic organic synthesis, pharmaceuticals, pesticides, printing and dyeing, textiles, and food industries, the development of the acetic acid industry is closely related to all sectors of the national economy.

[0003] The main methods for producing acetic acid include acetaldehyde oxidation, direct olefin oxidation, and methanol carbonylation. Acetaldehyde oxidation achieves a conversion rate of 95% at atmospheric pressure and 60°C, but it is gradually being phased out due to the severe environmental pollution caused by the organomercury catalyst used. Direct olefin oxidation's competitiveness is limited by its low feedstock (butane, naphtha, etc.) conversion rate, complex product separation process, and high cost. The methanol carbonylation method for synthesizing acetic acid has advantages such as high methanol conversion rate and fewer byproducts, and is gradually becoming the mainstream method for acetic acid synthesis.

[0004] The methanol carbonylation process primarily uses methanol and CO as raw materials. Under a rhodium-iodine catalytic system, the methanol and CO are homogeneously mixed in the reactor and react to produce acetic acid. The reaction temperature and pressure are 185–190℃ and 2.9 MPa, respectively. Unreacted CO and organic vapors are discharged from the top of the reactor and then pass through a gas distributor at the bottom of the conversion vessel to react with methanol and methyl acetate in the reaction liquid, ultimately producing acetic acid. Currently, the most commonly used catalyst system is rhodium, with iodomethane as the co-catalyst and lithium iodide as the catalyst additive. However, this catalyst system easily forms trivalent rhodium precipitate, and both rhodium and iodides readily precipitate, significantly affecting catalytic efficiency. To reduce rhodium precipitation, approximately 15% water is added to the catalyst system, which needs to be removed by distillation, increasing reaction energy consumption and production costs. Simultaneously, the reaction produces byproducts such as propionic acid, CO2, and H2, reducing the final selectivity and yield. Furthermore, the process using this catalyst system is prone to water-gas reforming, resulting in low selectivity and further affecting the yield of the reaction products.

[0005] In view of the above, this utility model is hereby proposed. Utility Model Content

[0006] The primary objective of this invention is to provide an acetic acid preparation system. This system, by applying enhanced mass transfer technology and thermal coupling technology to the acetic acid production process and combining it with a specially designed carbonyl reactor, can achieve high raw material conversion rate and product yield under conditions of low moisture content in the catalyst system. This helps to reduce the cost of acetic acid production and reaction energy consumption, and meets the needs of green production.

[0007] The second objective of this invention is to provide a method for preparing acetic acid. This method, by applying the above-mentioned system, can achieve efficient production of acetic acid under low energy consumption conditions. This method is characterized by being green, energy-saving, and low-cost, and is suitable for large-scale production of acetic acid.

[0008] In order to achieve the above-mentioned objectives of this utility model, the following technical solution is adopted:

[0009] This invention provides an acetic acid preparation system, comprising: a catalyst pipeline, a methanol pipeline, a carbon monoxide pipeline, a first heat exchanger, a second heat exchanger, and a carbonyl reactor, an evaporator, a light-weight component removal tower, a dehydration tower, and a product tower connected in sequence; the carbonyl reactor is connected to the evaporator, the top outlet of the evaporator is connected to the light-weight component removal tower, the side outlet of the light-weight component removal tower is connected to the dehydration tower, the side outlet of the dehydration tower is connected to the product tower, and a product pipeline is connected to the side wall of the product tower; the product pipeline and the methanol pipeline are coupled and exchange heat through the first heat exchanger;

[0010] The bottom outlet of the light-light-removal tower is connected to the side wall of the light-light-removal tower via the second heat exchanger, and the top outlet of the finished product tower is connected to the dehydration tower via the second heat exchanger;

[0011] The methanol pipeline and the catalyst pipeline are connected to the carbonyl reactor; a catalyst circulation pipe is provided on one side of the carbonyl reactor, the inlet of the catalyst circulation pipe is connected to the bottom of the carbonyl reactor, and the outlet is connected to the upper part of the carbonyl reactor and located below the liquid level of the carbonyl reactor; a first enhanced mass transfer unit is provided inside the carbonyl reactor, the first enhanced mass transfer unit includes a first enhanced mass transferor and a second enhanced mass transferor, the bottom of the carbonyl reactor is connected to the first enhanced mass transferor via a first circulating heat exchange pipeline, and the outlet of the carbon monoxide pipeline is connected to the second enhanced mass transferor;

[0012] The first enhanced mass transfer device is located below the second enhanced mass transfer device. The outlet of the first enhanced mass transfer device faces upward, and the outlet of the second enhanced mass transfer device faces downward. The outlets of the first enhanced mass transfer device and the second enhanced mass transfer device are staggered.

[0013] In the above technical solution, by setting up a first and a second enhanced mass transfer device, carbon monoxide and recycled materials can be dispersed and broken down to the micron level. This helps to increase the gas-liquid mass transfer area and improve the reaction efficiency and conversion rate of the raw materials. By staggering the outlets of the two enhanced mass transfer devices, the two staggered liquid flows can be used to stir the liquid flow in the vertical direction. This helps to ensure uniform distribution of raw materials and avoid the formation of dead zones, thereby preventing catalyst precipitation to a certain extent and improving catalyst utilization. In addition, since the use of two enhanced mass transfer devices improves the conversion rate of raw materials and the utilization rate of catalyst, the water content in the catalyst system can be appropriately reduced (to 0.8%-1.5%). This helps to reduce the energy consumption and cost required for water separation in subsequent processes. By setting up a catalyst circulation pipe, the catalyst precipitated at the bottom of the carbonyl reactor can be circulated, improving the catalyst utilization rate and ensuring the catalytic effect. By thermally coupling the product pipeline with the methanol pipeline and using the top steam of the product tower as the heat source of the light residue removal tower, costs can be effectively saved and comprehensive utilization of heat can be achieved. In summary, applying this system to acetic acid preparation can improve raw material conversion rate and catalyst utilization rate, enhance comprehensive heat utilization efficiency, and achieve high raw material conversion rate and product yield under conditions of low moisture content in the catalyst system. This helps to further reduce the production cost of acetic acid.

[0014] Preferably, a first filter screen is provided at the bottom of the carbonyl reactor, and the end of the first filter screen near the catalyst circulation pipe is flush with the inlet of the catalyst circulation pipe; preferably, the first filter screen is inclined along the direction close to the catalyst circulation pipe; preferably, the first enhanced mass transfer device is located horizontally on the side close to the catalyst circulation pipe, and the second enhanced mass transfer device is located horizontally on the side away from the catalyst circulation pipe.

[0015] In the above scheme, by setting up a first filter screen, the catalyst can be blocked when it settles downwards. Simultaneously, by aligning the end of the first filter screen close to the inlet of the catalyst circulation pipe, it is easier to return the catalyst filtered by the first filter screen to the reaction liquid for continued reaction, which helps improve catalyst utilization. In a further scheme, by tilting the first filter screen, gravity can be used to make the catalyst on the first filter screen flow towards the inlet of the catalyst circulation pipe, which further helps improve catalyst utilization. In an even further scheme, by specifically setting the positions of the first and second enhanced mass transfer devices, the stirring flow formed between the two enhanced mass transfer devices can be used to stir and propel the catalyst on the first filter screen, causing it to move more quickly towards the inlet of the catalyst circulation pipe, preventing it from depositing and clogging the first filter screen.

[0016] Preferably, a stirring shaft is horizontally arranged inside the carbonyl reactor, and the stirring shaft is located vertically between the first enhanced mass transfer unit and the liquid surface of the carbonyl reactor; one end of the stirring shaft penetrates the side wall of the carbonyl reactor and extends into the catalyst circulation pipe, and the end of the stirring shaft extending into the catalyst circulation pipe is provided with a blade; multiple stirring rods are installed on the portion of the stirring shaft located inside the carbonyl reactor; the stirring shaft rotates under the drive of the reaction liquid circulating in the catalyst circulation pipe.

[0017] In the above scheme, the circulating material in the catalyst circulation pipe can drive the rotating shaft to rotate by contacting the impeller, and then use the stirring rod to stir the reaction liquid in the carbonyl reactor, which slows down the deposition of catalyst and improves the uniformity of the distribution of microbubbles and microdroplets in the reaction liquid. This helps to further improve the reaction efficiency and catalyst utilization.

[0018] Preferably, the carbonyl reactor is provided with multiple layers of grids, which are located between the liquid level in the carbonyl reactor and the first enhanced mass transfer unit; the outlet of the catalyst circulation pipe is not lower than the lowest grid of the multiple layers of grids and not higher than the liquid level in the carbonyl reactor; preferably, it also includes a second circulating heat exchange pipeline; the inlet of the second circulating heat exchange pipeline is connected to the carbonyl reactor and is located between the lowest and highest grids of the multiple layers of grids, and the outlet of the second circulating heat exchange pipeline is connected to the first enhanced mass transfer unit.

[0019] The above scheme, by setting up a grid, can reduce the flow rate of the reaction liquid in the upper part of the carbonyl reactor, extend the reaction path of carbon monoxide, and thus improve the feed conversion rate. By setting up a second circulating heat exchange pipeline, on the one hand, the reaction liquid can be cooled to maintain a stable temperature in the reaction system and ensure reaction efficiency. On the other hand, the second circulating heat exchange pipeline can circulate the top reaction liquid to the first enhanced mass transfer device, which can both vertically stir the reaction liquid and further increase the phase boundary mass transfer area of ​​the reactants in the reaction liquid using the first enhanced mass transfer device.

[0020] Preferably, an enhanced reactor is provided between the carbonyl reactor and the evaporator; the sidewall of the carbonyl reactor is connected to the enhanced reactor via a first discharge pipe, and the enhanced reactor is connected to the evaporator via a second discharge pipe; the catalyst pipe is connected to the enhanced reactor; the top of the enhanced reactor is connected to the carbonyl reactor.

[0021] The enhanced reactor is equipped with a second enhanced mass transfer unit; the second enhanced mass transfer unit includes a third enhanced mass transfer device and a fourth enhanced mass transfer device; the third enhanced mass transfer device and the fourth enhanced mass transfer device are located at the same horizontal height and their outlets are staggered.

[0022] The carbon monoxide pipeline is connected to the third enhanced mass transfer device, and the bottom of the enhanced reactor is connected to the fourth enhanced mass transfer device via the third circulating heat exchange pipeline.

[0023] Preferably, it further includes a fourth circulating heat exchange pipeline, the inlet of which is connected to the enhanced reactor and located below the liquid surface of the enhanced reactor, and the outlet of which is connected to the fourth enhanced mass transfer device.

[0024] In the above scheme, the enhanced reactor can further react the materials output from the carbonyl reactor, thereby improving the methanol conversion rate. By setting a third and a fourth enhanced mass transferor in the enhanced reactor, the materials can be dispersed and broken up, increasing the phase boundary mass transfer area between the raw materials and improving the conversion rate. By staggering the outlets of the third and fourth enhanced mass transferors in the horizontal direction, a stirred flow can be formed in the horizontal direction, avoiding dead zones in the reaction liquid, improving the uniformity of microbubble distribution, and helping to slow down catalyst sedimentation and improve catalyst utilization. By setting a fourth circulating heat exchange pipeline, on the one hand, the reaction liquid in the enhanced reactor can be circulated and heated to maintain the internal reaction temperature and ensure reaction efficiency; on the other hand, the reaction liquid can be stirred in the vertical direction, and the phase boundary mass transfer area of ​​the reactants in the reaction liquid can be further increased by using the fourth enhanced mass transferor.

[0025] Preferably, the enhanced mass transfer device is provided with a riser tube; the riser tube includes a tube body and a suction section, the tube body is connected above the suction section, the diameter of the suction section gradually increases from top to bottom and the bottom of the suction section faces the bottom of the enhanced mass transfer device; the top of the tube body is located below the liquid surface in the enhanced reactor;

[0026] Preferably, the enhanced mass transfer device is provided with a second filter, which is horizontally arranged and located below the inhalation section.

[0027] In the above technical solution, a riser can be used to lift the bottom reaction liquid to the top. This promotes vertical flow of the reaction liquid within the reactor, helping to prevent catalyst deposition. Simultaneously, designing the suction section to gradually increase in size from top to bottom increases the suction surface, allowing for the intake of more catalyst deposited at the bottom. This structure also causes the flow rate of the rising reaction liquid to gradually increase, and the circulating reaction liquid is sprayed out through the top of the pipe, which helps to quickly and uniformly disperse the catalyst in the recycled reaction liquid. In a further embodiment, by incorporating a second filter, the deposited catalyst can be captured and placed below the suction section. This allows the riser to better circulate the deposited catalyst back to the top reaction liquid, further improving catalyst utilization.

[0028] Preferably, the top outlet of the light component removal tower is connected to a light component cooler, the top outlet of the light component cooler is connected to a final cooler, and the bottom outlet is connected to a separator; the top outlet of the final cooler is connected to a low-pressure absorption tower, and the bottom outlet is connected to the separator; the bottom outlet of the separator is connected to the carbonyl reactor; and the bottom outlet of the low-pressure absorption tower is connected to the carbonyl reactor. The gaseous material removed from the top of the light component removal tower undergoes two stages of condensation before entering the separator. In the separator, the material separates into two phases: light (mainly acetic acid and water) and heavy (mainly iodomethane, which is a co-catalyst in the catalyst system). The uncondensed tail gas in the final cooler (including iodomethane, carbon monoxide, and carbon dioxide) is fed into the low-pressure absorption tower for further recovery of iodomethane. This design helps improve the utilization efficiency of the co-catalyst.

[0029] Preferably, the reactor further includes a high-pressure separator; the material output from the top of the carbonyl reactor is fed into the high-pressure separator after heat exchange in the evaporator, and the bottom outlet of the high-pressure separator is connected to the enhanced reactor; preferably, the top outlet 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 the carbonyl reactor. The high-pressure separator can separate the material output from the top of the carbonyl reactor. The separated liquid phase is directly returned to the enhanced reactor to continue participating in the reaction, while the gas phase is fed into the high-pressure absorption tower. In the high-pressure absorption tower, methanol carried in the gas phase is separated and returned to the carbonyl reactor to continue the reaction, thereby further improving the methanol conversion rate.

[0030] Preferably, the bottom outlet of the finished product tower is connected to the stripping tower; the top outlet of the stripping tower is connected to the finished product tower, and the bottom outlet is connected to the mixed acid pipeline. The stripping tower can separate and purify the material in the finished product tower. The vapor (mainly acetic acid) from the top of the stripping tower is returned to the finished product tower and output through the product pipeline. The bottom liquid of the stripping tower (mainly propionic acid) is discharged to the waste acid tank through the mixed acid pipeline.

[0031] It will be understood by those skilled in the art that the pneumatic enhanced mass transfer device and the hydraulic enhanced mass transfer device used in this utility model have been reflected in the inventor's prior patents, such as patents with application numbers CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660A, CN105903425A, CN205833127U and CN207581700U. The prior patent CN201610641119.6 details the specific product structure and working principle of a micron-sized bubble generator (i.e., a bubble breaker). This application document states that "the micron-sized bubble generator includes a main body and a secondary breaking component. The main body has a cavity, and an inlet communicating with the cavity is provided on the main body. The first and second ends of the cavity are both open, and the cross-sectional area of ​​the cavity decreases from the middle of the cavity towards the first and second ends. The secondary breaking component is located at at least one of the first and second ends of the cavity, with a portion of the secondary breaking component located within the cavity. A ring-shaped channel is formed between the secondary breaking component and the open through-holes at both ends of the cavity. The micron-sized bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in this application document, its specific working principle can be understood as follows: liquid enters the micron-sized bubble generator tangentially through the liquid inlet pipe, rotates at ultra-high speed, and cuts the gas, causing the gas bubbles to break into micron-sized microbubbles, thereby increasing the mass transfer area between the liquid and gas phases. Moreover, the micron-sized bubble generator in this patent is a pneumatic bubble breaker.

[0032] Furthermore, prior patent 201610641251.7 describes a primary bubble breaker with a circulating liquid inlet, a circulating gas inlet, and a gas-liquid mixture outlet, while a secondary bubble breaker connects the feed inlet to the gas-liquid mixture outlet. This indicates that both bubble breakers require a gas-liquid mixture to enter. Additionally, as shown in the accompanying drawings, the primary bubble breaker primarily utilizes the circulating liquid as its power source, thus classifying it as a hydraulically driven enhanced reactor. The secondary bubble breaker simultaneously introduces the gas-liquid mixture into an elliptical rotating sphere for rotation, thereby achieving bubble breakage during rotation. Therefore, the secondary bubble breaker is actually a gas-liquid linkage bubble breaker. In fact, both hydraulically driven and gas-liquid linkage bubble breakers are specific forms of bubble breakers. However, the enhanced mass transfer device used in this invention is not limited to these forms; the specific structure of the bubble breaker described in the prior patent is merely one possible form for this invention.

[0033] Furthermore, prior patent 201710766435.0 states that "the principle of the bubble breaker is to achieve mutual collision of gases by high-speed jetting"; and prior patent CN106187660 also describes the specific structure of the bubble breaker, as detailed in paragraphs

[0031] -

[0041] of the specification and the attached drawings. It elaborates on the specific working principle of the bubble breaker S-2. The top of the bubble breaker is the liquid phase inlet, and the side is the gas phase inlet. The liquid phase entering from the top provides the entrainment force, thereby achieving the effect of crushing into ultrafine bubbles. The attached drawings also show that the bubble breaker has a conical structure, with the upper diameter being larger than the lower diameter, which is also to allow the liquid phase to provide better entrainment force.

[0034] Because the bubble breaker was newly developed in the early stages of the prior patent application, it was initially named a micron bubble generator (CN201610641119.6), etc. With continuous technological improvements, it was later renamed a bubble breaker. The enhanced mass transfer device in this utility model is equivalent to the previous micron bubble generator, micro-interface generator, etc., only with different names. In summary, the enhanced mass transfer device of this utility model belongs to the prior art.

[0035] This invention also provides a method for preparing acetic acid, which uses the system of any of the above embodiments to prepare acetic acid.

[0036] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0037] 1. By setting up a first enhanced mass transfer device and a second enhanced mass transfer device, carbon monoxide and recycled materials can be dispersed and broken down to the micron level, which helps to increase the gas-liquid mass transfer area and improve the reaction efficiency and conversion rate of raw materials.

[0038] 2. By staggering the outlets of the two enhanced mass transfer devices, the two intersecting liquid flows can be used to stir the liquid flow in the vertical direction. This helps to ensure uniform distribution of raw materials and avoid the formation of dead zones, thereby preventing catalyst precipitation to a certain extent and improving catalyst utilization. In addition, since the use of two enhanced mass transfer devices improves the raw material conversion rate and catalyst utilization rate, the water content in the catalyst system can be appropriately reduced (to 0.8%-1.5%). This helps to reduce the energy consumption and cost required for water separation in subsequent processes.

[0039] 3. By setting up a catalyst circulation pipe, the catalyst precipitated at the bottom of the carbonyl reactor can be circulated, improving the catalyst utilization rate and ensuring the catalytic effect;

[0040] 4. By thermally coupling the product pipeline with the methanol pipeline and using the top steam of the product tower as the heat source for the light product removal tower bottom, costs can be effectively saved and comprehensive utilization of heat can be achieved.

[0041] 5. In summary, applying this system to acetic acid preparation can improve the raw material conversion rate and catalyst utilization rate, increase the comprehensive heat utilization efficiency, and achieve a high raw material conversion rate and product yield under the condition of low moisture content in the catalyst system, which helps to further reduce the production cost of acetic acid. Attached Figure Description

[0042] 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:

[0043] Figure 1 A schematic diagram of the acetic acid preparation system of Embodiment 1 of this utility model is shown;

[0044] Figure 2 A schematic diagram of the carbonyl reactor of Embodiment 1 of this utility model is shown;

[0045] Figure 3 A schematic diagram of the enhanced reactor of Embodiment 1 of this utility model is shown.

[0046] In the diagram: 1. Methanol pipeline; 2. Carbon monoxide pipeline; 3. Catalyst pipeline; 4. Carbonyl reactor; 401. Grid; 402. Catalyst circulation pipe; 403. Impeller; 404. Stirring shaft; 405. Stirring rod; 406. Catalyst circulation pump; 407. First enhanced mass transfer device; 408. First circulating heat exchange pipe; 409. First filter screen; 410. Second enhanced mass transfer device; 411. Second circulating heat exchange pipe; 5. Enhanced reactor; 501. Pipe body; 502. Third enhanced mass transfer device; 503. Suction section; 504. Second filter screen; 505. Fourth enhanced mass transfer device; 506. Third circulating heat exchange pipe; 507. Fourth circulating heat exchange pipe; 6. High-pressure separator; 7. Second discharge pipe; 8. First discharge pipe; 9. Evaporator; 10. Light weight removal tower; 1. Light component cooler; 12. Final cooler; 13. Separator; 14. Dehydration tower; 15. Third heat exchanger; 16. Product tower; 17. Stripping tower; 18. High-pressure absorption tower; 19. High-pressure circulation pipeline; 20. High-pressure circulation cooler; 21. First coolant pipeline; 22. Second coolant pipeline; 23. Low-pressure circulation pipeline; 24. Low-pressure circulation cooler; 25. Mixed acid pipeline; 26. Product pipeline; 27. First heat exchanger; 28. Low-pressure absorption tower; 29. ​​Second heat exchanger. Detailed Implementation

[0047] 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.

[0048] 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.

[0049] 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.

[0050] To more clearly illustrate the technical solution of this utility model, the following description is provided in the form of specific embodiments.

[0051] Example 1

[0052] See also Figure 1-3 This embodiment provides an acetic acid preparation system, including: a catalyst pipeline 3, a methanol pipeline 1, a carbon monoxide pipeline 2, a first heat exchanger 27, a second heat exchanger 29, and a carbonyl reactor 4, an evaporator 9, a light precipitator removal tower 10, a dehydration tower 14, and a product tower 16 connected in sequence. In this embodiment, the catalyst pipeline 3 is used to transport a catalyst composition, which includes a rhodium catalyst, a co-catalyst iodomethane, a catalyst promoter lithium propionate, and water. The water content is in the range of 0.8%-1.5%.

[0053] The carbonyl reactor 4 is connected to the evaporator 9. The top outlet of the evaporator 9 is connected to the light-weight residue removal tower 10. The side outlet of the light-weight residue removal tower 10 is connected to the dehydration tower 14. The side outlet of the dehydration tower 14 is connected to the product tower 16. The side wall of the product tower 16 is connected to the product pipeline 26. The product pipeline 26 and the methanol pipeline 1 are coupled and exchange heat through the first heat exchanger 27. The bottom outlet of the light-weight residue removal tower 10 is connected to the side wall of the light-weight residue removal tower 10 via the second heat exchanger 29. The top outlet of the product tower 16 is connected to the dehydration tower 14 via the second heat exchanger 29. The bottom outlet of the product tower 16 is connected to the stripping tower 17. The top outlet of the stripping tower 17 is connected to the product tower 16, and the bottom outlet is connected to the mixed acid pipeline 25. In this embodiment, the top steam of the product tower 16 is considered as the heat source for the bottom of the light-weight residue removal tower 10. Based on an annual acetic acid production of 200,000 tons, the top steam temperature of product tower 16 is 135.8 ℃, with a heat load of 36.972 × 10⁶ KJ / h, while the bottom liquid temperature of light-light product stripping tower 10 is 133.6 ℃, with a heat load of 3.376 × 10⁶ KJ / h. Both the top steam temperature and heat load of product tower 16 are higher than those of the bottom liquid of light-light product stripping tower 10. Therefore, heat transfer can be achieved between the top steam of product tower 16 and the bottom liquid of light-light product stripping tower 10. This method of heat exchange and comprehensive utilization can meet the green requirements of modern industry and is suitable for large-scale acetic acid production.

[0054] like Figure 1 As shown, an enhanced reactor 5 is provided between the carbonyl reactor 4 and the evaporator 9; the side wall of the carbonyl reactor 4 is connected to the enhanced reactor 5 via the first discharge pipe 8, and the enhanced reactor 5 is connected to the evaporator 9 via the second discharge pipe 7; the catalyst pipe 3 is connected to the enhanced reactor 5; the top of the enhanced reactor 5 is connected to the carbonyl reactor 4.

[0055] Continue reading Figure 1 The top outlet of the light component removal tower 10 is connected to the light component cooler 11, the top outlet of the light component cooler 11 is connected to the final cooler 12, and the bottom outlet is connected to the separator 13; the top outlet of the final cooler 12 is connected to the low-pressure absorption tower 28, and the bottom outlet is connected to the separator 13; the bottom outlet of the separator 13 is connected to the carbonyl reactor 4; the bottom outlet of the low-pressure absorption tower 28 is connected to the carbonyl reactor 4.

[0056] Continue reading Figure 1 The system in this embodiment also includes a high-pressure separator 6; the material output from the top of the carbonyl reactor 4 is heat-exchanged in the evaporator 9 and then input into the high-pressure separator 6, and the bottom outlet of the high-pressure separator 6 is connected to the carbonyl reactor 4. The top outlet of the high-pressure separator 6 is connected to the high-pressure absorption tower 18, and the bottom outlet of the high-pressure absorption tower 18 is connected to the carbonyl reactor 4.

[0057] In this embodiment, a heat exchanger is installed inside the evaporator 9. The product from the carbonyl reactor 4 enters the enhanced reactor 5 via the first discharge pipe 8 to continue the reaction. The top discharge from the carbonyl reactor 4 is heated in the heat exchanger inside the evaporator 9 and then fed into the high-pressure separator 6 for separation. The separated liquid phase is returned to the enhanced reactor 5 to continue the reaction, while the gas phase is fed into the high-pressure absorption tower 18 for separation. A first cooling liquid pipe 21 is connected to one side of the high-pressure absorption tower 18, which is used to feed low-temperature methanol into the high-pressure absorption tower 18. The low-temperature methanol enters from the top of the high-pressure absorption tower 18 via the first cooling liquid pipe 21, flows from top to bottom, absorbs the main organic components such as iodomethane, and is sent back to the carbonyl reactor 4 from the bottom of the high-pressure absorption tower 18 to continue the reaction. The tail gas in the high-pressure absorption tower 18 is discharged from the top and can be sent to the flare system for incineration. The bottom of the high-pressure absorption tower 18 is connected to the side wall via a high-pressure circulation pipe 19, on which a high-pressure circulation cooler 20 is installed.

[0058] The gas from the top of the enhanced reactor 5 (including some carbon monoxide) is fed into the carbonyl reactor 4. The product from the enhanced reactor 5 is fed into the evaporator 9 via the second discharge pipe 7. The liquid phase obtained by flash evaporation in the evaporator 9 is returned to the carbonyl reactor 4 via the bottom outlet to continue the reaction. The gaseous phase enters the light component removal tower 10 via the top outlet to remove the light components from the gaseous phase, and then goes to the dehydration tower 14 for drying, and then to the product tower 16 for rectification. The acetic acid product after rectification is collected from the three trays of the product tower 16 via the product pipe 26, and after heat exchange in the first heat exchanger 27, it is heat-exchanged with methanol in the methanol pipe 1 before being output. The product outlet on the side wall of the light component removal tower 10 is connected to the dehydration tower 14. Part of the product output from the bottom is fed into the carbonyl reactor 4 to continue the reaction, and part is returned to the light component removal tower 10 after heat exchange in the second heat exchanger 29.

[0059] The gas phase separated at the top of the light component removal tower 10 (mainly acetic acid, water, and iodomethane) enters the light component cooler 11 for cooling. The condensate then enters the separator 13, while the uncondensed gas phase enters the final cooler 12 for further condensation with cooling water. The uncondensed tail gas enters the low-pressure absorption tower 28 for further recovery of iodomethane. The condensate from the final cooler 12 enters the separator 13. The heavy components in the separator 13 are sent back to the carbonyl reactor 4 for continued reaction.

[0060] The vapor phase at the top of the dehydration tower 14 enters the third heat exchanger 15 for heat exchange and cooling. Part of the condensate is returned to the dehydration tower 14, and part is sent directly out. The uncondensed vapor phase components are fed into the low-pressure absorption tower 28 for further recovery of iodomethane.

[0061] A second coolant pipeline 22 is connected to one side of the low-pressure absorption tower 28, which is used to feed low-temperature methanol into the low-pressure absorption tower 28. The low-temperature methanol enters from the top of the low-pressure absorption tower 28 via the second coolant pipeline 22, flows downwards, absorbs major organic components such as iodomethane, and is then returned from the bottom of the low-pressure absorption tower 28 to the carbonyl reactor 4 to continue participating in the reaction. The tail gas inside the low-pressure absorption tower 28 is discharged from the top and can be sent to the flare system for incineration. The bottom of the low-pressure absorption tower 28 is connected to the side wall via a low-pressure circulation pipeline 23, on which a low-pressure circulation cooler 24 is installed.

[0062] The bottom outlet and side wall outlet of the dehydration tower 14 are both connected to the product tower 16. The vapor phase at the top of the product tower 16 exchanges heat with the circulating material at the bottom of the light residue removal tower 10 via the second heat exchanger 29 and then enters the dehydration tower 14. The liquid collected at the bottom goes to the stripping tower 17 for further rectification. After rectification, the vapor phase at the top of the tower returns to the product tower 16 for further rectification. The mixed acid produced in the bottom of the tower is output from the mixed acid outlet. The mixed acid is mainly composed of propionic acid.

[0063] See also Figure 1 , Figure 2 Methanol pipeline 1 and catalyst pipeline 3 are connected to carbonyl reactor 4. A catalyst circulation pipe 402 is provided on one side of carbonyl reactor 4. The inlet of catalyst circulation pipe 402 is connected to the bottom of carbonyl reactor 4, and the outlet is connected to the upper part of carbonyl reactor 4 and located below the liquid level of carbonyl reactor 4. A catalyst circulation pump 406 is provided on catalyst circulation pipe 402 to provide power for the liquid flow inside. A first enhanced mass transfer unit is provided inside carbonyl reactor 4. The first enhanced mass transfer unit includes a first enhanced mass transferor 407 and a second enhanced mass transferor 410. The bottom of carbonyl reactor 4 is connected to the first enhanced mass transferor 407 via a first circulating heat exchange pipeline 408, and the outlet of carbon monoxide pipeline 2 is connected to the second enhanced mass transferor 410. The first enhanced mass transferor 407 is located below the second enhanced mass transferor 410. The outlet of the first enhanced mass transferor 407 is upward, and the outlet of the second enhanced mass transferor 410 is downward. The outlets of the first enhanced mass transferor 407 and the second enhanced mass transferor 410 are staggered. In this embodiment, the solvent in the carbonyl reactor 4 occupies 2 / 3 to 4 / 5 of the volume of the carbonyl reactor 4.

[0064] A first filter screen 409 is provided at the bottom of the carbonyl reactor 4. The end of the first filter screen 409 near the catalyst circulation pipe 402 is flush with the inlet of the catalyst circulation pipe 402. The first filter screen 409 is inclined along the direction close to the catalyst circulation pipe 402. The first enhanced mass transfer device 407 is located horizontally on the side close to the catalyst circulation pipe 402, and the second enhanced mass transfer device 410 is located horizontally on the side away from the catalyst circulation pipe 402.

[0065] like Figure 2As shown, a stirring shaft 404 is horizontally arranged inside the carbonyl reactor 4. The stirring shaft 404 is located vertically between the first enhanced mass transfer unit and the liquid surface of the carbonyl reactor 4. One end of the stirring shaft 404 penetrates the side wall of the carbonyl reactor 4 and extends into the catalyst circulation pipe 402. A blade 403 is provided at the end of the stirring shaft 404 that extends into the catalyst circulation pipe 402. Multiple stirring rods 405 are installed on the part of the stirring shaft 404 located inside the carbonyl reactor 4. The stirring shaft 404 rotates under the drive of the reaction liquid circulating in the catalyst circulation pipe 402.

[0066] Continue reading Figure 2 The carbonyl reactor 4 is equipped with multiple layers of grids 401, which are located between the liquid surface inside the carbonyl reactor 4 and the first enhanced mass transfer unit. The outlet of the catalyst circulation pipe 402 is not lower than the bottommost grid 401 of the multiple layers of grids 401, and not higher than the liquid surface of the carbonyl reactor 4. The system of this embodiment also includes a second circulating heat exchange pipe 411. The inlet of the second circulating heat exchange pipe 411 is connected to the carbonyl reactor 4 and is located between the bottommost grid 401 and the topmost grid 401 of the multiple layers of grids 401. The outlet of the second circulating heat exchange pipe 411 is connected to the first enhanced mass transfer unit 407.

[0067] like Figure 3 As shown, a second enhanced mass transfer unit is installed inside the enhanced reactor 5; the second enhanced mass transfer unit includes a third enhanced mass transferor 502 and a fourth enhanced mass transferor 505; the third enhanced mass transferor 502 and the fourth enhanced mass transferor 505 are located at the same horizontal level and their outlets are staggered; a carbon monoxide pipeline 2 is connected to the third enhanced mass transferor 502, and the bottom of the enhanced reactor 5 is connected to the fourth enhanced mass transferor 505 via a third circulating heat exchange pipeline 506; the system in this embodiment also includes a fourth circulating heat exchange pipeline 507, the inlet of which is connected to the enhanced reactor 5 and located below the liquid surface of the enhanced reactor 5, and the outlet of the fourth circulating heat exchange pipeline 507 is connected to the fourth enhanced mass transferor 505. In this embodiment, circulating heat exchangers are installed on each circulating heat exchange pipeline to maintain the temperature inside the reactor.

[0068] Continue reading Figure 3 The enhanced mass transfer device includes a riser tube. The riser tube comprises a tube body 501 and a suction section 503. The tube body 501 is connected above the suction section 503. The diameter of the suction section 503 gradually increases from top to bottom, and the bottom of the suction section 503 faces the bottom of the enhanced mass transfer device. The top of the tube body 501 is located below the liquid surface within the enhanced reactor 5. A second filter screen 504 is installed inside the enhanced mass transfer device. The second filter screen 504 is horizontally positioned below the suction section 503. To facilitate the riser tube's lifting of the reaction liquid within the enhanced mass transfer device, a pump can be installed on the riser tube.

[0069] It is understood that, in this embodiment, pumps, valves, etc., can be installed on the pipelines to facilitate the flow of the medium in each pipeline and to control the pipelines, which will not be elaborated here.

[0070] This embodiment also provides a method for preparing acetic acid using the system described above. During the preparation process, the pressure inside both the carbonyl reaction tower and the enhanced reaction tower is 2.6-3.2 MPa, and the reaction temperature is 150-200℃. The acetic acid vapor pressure at the top of the evaporator is 0.1-0.3 MPa, and the temperature is 110-150℃. The finished acetic acid exiting the product tower has a pressure of 0.1-0.3 MPa and a temperature of 120-180℃.

[0071] Example 2

[0072] The difference between this embodiment and Embodiment 1 is that the first enhanced mass transfer device is located horizontally on the side away from the catalyst circulation pipe, while the second enhanced mass transfer device is located horizontally on the side closer to the catalyst circulation pipe.

[0073] Example 3

[0074] The difference between this embodiment and Embodiment 1 is that the outlets of the third and fourth enhanced mass transfer devices are arranged opposite each other in the enhanced reactor.

[0075] Example 4

[0076] The difference between this embodiment and Embodiment 1 is that no riser is provided.

[0077] Comparative Example 1

[0078] The difference between this embodiment and Embodiment 1 is that the outlets of the first enhanced mass transfer device and the second enhanced mass transfer device are arranged opposite to each other.

[0079] Comparative Example 2

[0080] The difference between this embodiment and Embodiment 1 is that the inlet of the catalyst circulation pipe is connected to the upper part of the carbonyl reactor, and the outlet is connected to the bottom of the carbonyl reactor.

[0081] Experimental Example

[0082] Acetic acid was prepared using the systems of Examples 1-4 and Comparative Examples 1-2 under the same reaction conditions (catalyst concentration of 900 ppm, reaction temperature of 170°C in both the carbonyl reactor and the enhanced reactor, and moisture content of 1%). The methanol conversion rate and acetic acid yield were calculated based on the reaction products output from the enhanced reactor in each system. The statistical results are shown in Table 1.

[0083] Table 1 Statistical Results

[0084]

[0085] Based on the data shown in the table above, the technical solution of this application can achieve better methanol conversion and acetic acid yield with lower catalyst water content. The system in Example 1 achieves the best results, with a methanol conversion of 96.10% and an acetic acid yield of 92.32%. Compared with traditional acetic acid preparation technology, the methanol conversion is increased by more than 10%. Furthermore, this solution conducts the reaction at 170°C and saves reaction energy consumption through thermal coupling in subsequent processes. Simultaneously, due to the significantly reduced catalyst water content, the energy consumption required for water separation in the subsequent dehydration tower can be effectively reduced.

[0086] Comparing Examples 1 and 2, it can be found that the methanol conversion rate and acetic acid yield in Example 1 are both better than those in Example 2. This may be because the stirring action of the two enhanced mass transfer devices in Example 2 is opposite to the circulation direction of the catalyst circulation pipe, which to some extent hinders the circulation of the catalyst by the catalyst circulation pipe. At the same time, the stirring action of the two enhanced mass transfer devices on the microbubbles and catalyst is partially offset by the catalyst circulation pipe, reducing the dispersion effect.

[0087] Comparing Examples 1 and 3, it can be found that the methanol conversion rate and acetic acid yield in Example 1 are both better than those in Example 3. This may be because the outlets of the third and fourth enhanced mass transfer devices in Example 3 are set opposite each other, and the opposing liquid flows create a dead zone in the reaction liquid, which accelerates the precipitation of the rhodium catalyst and affects the uniform distribution of microbubbles.

[0088] Comparing Examples 1 and 4, it can be found that the methanol conversion rate and acetic acid yield in Example 1 are both better than those in Example 4. This may be because the riser in the enhanced reactor in Example 1 can stir the reaction liquid in the enhanced reactor vertically. This stirring method, combined with the horizontal stirring caused by the two enhanced mass transfer devices, achieves a better stirring effect, allowing microbubbles and catalyst to be evenly distributed, increasing the mass transfer area at the feed phase interface and the catalytic effect of the catalyst, thereby improving the methanol conversion rate and acetic acid yield.

[0089] Comparing Example 1 and Comparative Example 1, it can be found that the methanol conversion rate and acetic acid yield in Example 1 are both better than those in Comparative Example 1. This may be because the outlets of the first enhanced mass transfer device and the second enhanced mass transfer device in Example 4 are set opposite to each other, and the two opposing liquid flows create a dead zone in the reaction liquid, which accelerates the precipitation of the rhodium catalyst and affects the uniform distribution of microbubbles.

[0090] Comparing Example 1 and Comparative Example 2, it can be found that the methanol conversion rate and acetic acid yield in Example 1 are both better than those in Comparative Example 2. This may be because the method of circulating the bottom reaction liquid to the top in Example 1 can further extend the residence time of the rhodium catalyst in the reaction liquid, thereby further improving the catalytic effect.

[0091] In summary, the system of this invention can achieve optimal methanol conversion and acetic acid yield under conditions of low catalyst water content, which can effectively reduce the energy consumption and cost of acetic acid production. Furthermore, the system utilizes heat coupling to fully leverage waste heat, thereby contributing to improved energy utilization efficiency. This system can be used for the green production of acetic acid.

[0092] 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 acetic acid preparation system, characterized in that, include: The system includes a catalyst pipeline, a methanol pipeline, a carbon monoxide pipeline, a first heat exchanger, a second heat exchanger, and a carbonyl reactor, an evaporator, a light component removal tower, a dehydration tower, and a product tower connected in sequence. The carbonyl reactor is connected to the evaporator, the top outlet of the evaporator is connected to the light component removal tower, the side outlet of the light component removal tower is connected to the dehydration tower, the side outlet of the dehydration tower is connected to the product tower, and a product pipeline is connected to the side wall of the product tower. The product pipeline and the methanol pipeline are coupled and exchange heat through the first heat exchanger. The bottom outlet of the light-light-removal tower is connected to the side wall of the light-light-removal tower via the second heat exchanger, and the top outlet of the finished product tower is connected to the dehydration tower via the second heat exchanger; The methanol pipeline and the catalyst pipeline are connected to the carbonyl reactor; a catalyst circulation pipe is provided on one side of the carbonyl reactor, the inlet of the catalyst circulation pipe is connected to the bottom of the carbonyl reactor, and the outlet is connected to the upper part of the carbonyl reactor and located below the liquid level of the carbonyl reactor; a first enhanced mass transfer unit is provided inside the carbonyl reactor, the first enhanced mass transfer unit includes a first enhanced mass transferor and a second enhanced mass transferor, the bottom of the carbonyl reactor is connected to the first enhanced mass transferor via a first circulating heat exchange pipeline, and the outlet of the carbon monoxide pipeline is connected to the second enhanced mass transferor; The first enhanced mass transfer device is located below the second enhanced mass transfer device. The outlet of the first enhanced mass transfer device faces upward, and the outlet of the second enhanced mass transfer device faces downward. The outlets of the first enhanced mass transfer device and the second enhanced mass transfer device are staggered.

2. The acetic acid preparation system according to claim 1, characterized in that, The bottom of the carbonyl reactor is provided with a first filter screen, and the end of the first filter screen near the catalyst circulation pipe is flush with the inlet of the catalyst circulation pipe.

3. The acetic acid preparation system according to claim 1, characterized in that, A stirring shaft is horizontally arranged inside the carbonyl reactor. The stirring shaft is located vertically between the first enhanced mass transfer unit and the liquid surface of the carbonyl reactor. One end of the stirring shaft penetrates the side wall of the carbonyl reactor and extends into the catalyst circulation pipe. A blade is provided at the end of the stirring shaft that extends into the catalyst circulation pipe. Multiple stirring rods are installed on the portion of the stirring shaft located inside the carbonyl reactor. The stirring shaft rotates under the influence of the reaction liquid circulating in the catalyst circulation pipe.

4. The acetic acid preparation system according to claim 2, characterized in that, The carbonyl reactor is equipped with multiple layers of grids, which are located between the liquid level in the carbonyl reactor and the first enhanced mass transfer unit; the outlet of the catalyst circulation pipe is not lower than the lowest grid of the multiple layers of grids, and not higher than the liquid level in the carbonyl reactor.

5. The acetic acid preparation system according to claim 1, characterized in that, An enhanced reactor is disposed between the carbonyl reactor and the evaporator; the sidewall of the carbonyl reactor is connected to the enhanced reactor via a first discharge pipe, and the enhanced reactor is connected to the evaporator via a second discharge pipe; the catalyst pipeline is connected to the enhanced reactor; the top of the enhanced reactor is connected to the carbonyl reactor. The enhanced reactor is equipped with a second enhanced mass transfer unit; the second enhanced mass transfer unit includes a third enhanced mass transfer device and a fourth enhanced mass transfer device; the third enhanced mass transfer device and the fourth enhanced mass transfer device are located at the same horizontal height and their outlets are staggered. The carbon monoxide pipeline is connected to the third enhanced mass transfer device, and the bottom of the enhanced reactor is connected to the fourth enhanced mass transfer device via the third circulating heat exchange pipeline.

6. The acetic acid preparation system according to claim 5, characterized in that, The enhanced mass transfer device is equipped with a riser tube; the riser tube includes a tube body and a suction section, the tube body is connected above the suction section, the diameter of the suction section gradually increases from top to bottom and the bottom of the suction section faces the bottom of the enhanced mass transfer device; the top of the tube body is located below the liquid surface in the enhanced reactor.

7. The acetic acid preparation system according to any one of claims 1-6, characterized in that, The top outlet of the light component removal tower is connected to a light component cooler, the top outlet of the light component cooler is connected to a final cooler, and the bottom outlet is connected to a separator; the top outlet of the final cooler is connected to a low-pressure absorption tower, and the bottom outlet is connected to the separator. The bottom outlet of the separator is connected to the carbonyl reactor; the bottom outlet of the low-pressure absorber is connected to the carbonyl reactor.

8. The acetic acid preparation system according to any one of claims 1-6, characterized in that, It also includes a high-pressure separator; the material output from the top of the carbonyl reactor is heat-exchanged in the evaporator and then input into the high-pressure separator, and the bottom outlet of the high-pressure separator is connected to the carbonyl reactor.

9. The acetic acid preparation system according to claim 8, characterized in that, The top outlet of the high-pressure separator is connected to the high-pressure absorption tower, and the bottom outlet of the high-pressure absorption tower is connected to the carbonyl reactor.

10. The acetic acid preparation system according to any one of claims 1-6, characterized in that, The bottom outlet of the finished product tower is connected to the stripping tower; the top outlet of the stripping tower is connected to the finished product tower, and the bottom outlet is connected to the mixed acid pipeline.

Images