Acetic acid preparation system and method

Abstract

The invention provides an acetic acid preparation system and method. The system comprises a catalyst pipeline, a methanol pipeline, a carbon monoxide pipeline, a first heat exchanger, a second heat exchanger, a carbonyl reactor, an evaporator, a light component removal tower, a dehydration tower and a finished product tower, a top outlet of the evaporator is communicated with a light component removal tower, the light component removal tower is communicated with a dehydration tower, the dehydration tower is communicated with a finished product tower, and the side wall of the finished product tower is connected with a product pipeline; the product pipeline and the methanol pipeline are coupled for heat exchange through the first heat exchanger; the bottom outlet of the light component removal tower is connected with the side wall of the light component removal tower through the second heat exchanger; the methanol pipeline and the catalyst pipeline are connected with the carbonyl reactor; a catalyst circulating pipe is arranged on one side of the carbonyl reactor, an inlet of the catalyst circulating pipe is connected with the bottom of the carbonyl reactor, and an outlet is connected with the upper part of the carbonyl reactor and positioned below the liquid level. By applying the system, the raw material conversion rate and the product yield can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of acetic acid preparation, and in particular, to a system and method for preparing acetic acid. Background Art

[0002] The molecular formula of acetic acid is CH3COOH, with a relative molecular mass of 60.05. It is a colorless liquid with a pungent sour smell and has corrosive properties, containing the characteristic functional group of organic acids - carbonyl. Due to its very low freezing point, acetic acid is also known as glacial acetic acid. As an important chemical raw material with wide applications, acetic acid can be widely used in the industrial production field. Acetic acid is mainly used for synthesizing the monomer VAM of vinyl acetate, the raw material for synthesizing acetic anhydride, and the solvent for producing purified terephthalic acid, etc. It can also be used for producing substances such as acetate esters and chloroacetic acid. Hundreds of downstream products can be derived from it. Since acetic acid is widely used in industries such as basic organic synthesis, medicine, pesticides, printing and dyeing, light textile, and food, the development of the acetic acid industry is closely related to various sectors of the national economy.

[0003] The main production methods of acetic acid include the acetaldehyde oxidation method, the olefin direct oxidation method, and the methanol carbonylation method. In the acetaldehyde oxidation method, the conversion rate of acetaldehyde reaches 95% at normal pressure and 60 °C. However, since the organic mercury catalyst used in this method causes serious environmental pollution, it has been gradually phased out. The olefin direct oxidation method has its competitiveness limited due to factors such as low conversion rate of its raw materials (butane, naphtha, etc.), complex product separation process, and high cost. The methanol carbonylation process for synthesizing acetic acid has advantages such as high methanol conversion rate and few by-products, and has gradually become the mainstream method for synthesizing acetic acid.

[0004] The methanol carbonylation production method mainly uses methanol and CO as raw materials. Under the rhodium-iodine catalytic system, after stirring, methanol and CO in the reactor are homogeneously mixed and then react to form acetic acid. The reaction temperature and pressure are 185 - 190 °C and 2.9 MPa respectively. The unreacted CO and organic vapor will be discharged from the top of the reactor and then reach the conversion kettle through the gas distributor at the bottom of the conversion kettle, and react with methanol and methyl acetate in the reaction liquid to finally form acetic acid. The most commonly used catalyst system is rhodium, the cocatalyst is methyl iodide, and the catalyst additive is lithium iodide. However, this catalyst system is prone to form trivalent rhodium precipitation, and both rhodium compounds and iodide compounds are prone to form precipitation, greatly affecting the catalytic efficiency. To reduce rhodium precipitation, about 15% of water is added to the catalyst system, and the water needs to be removed by distillation later, increasing the reaction energy consumption and production cost. At the same time, the reaction will produce by-products such as propionic acid, CO2, and H2, resulting in a decrease in the final selectivity and yield. At the same time, the process method using this catalyst system is prone to the water-gas reforming reaction, resulting in low selectivity and further affecting the yield of the reaction products.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The first object of the present invention is to provide an acetic acid preparation system. By applying technologies such as enhanced mass transfer technology and heat integration technology to the acetic acid production process and combining a specifically designed carbonyl reactor, a relatively high raw material conversion rate and product yield can be achieved under the condition of a relatively low water content in the catalyst system. This helps to reduce the production cost and reaction energy consumption of acetic acid and meets the requirements of green production.

[0007] The second object of the present invention is to provide an acetic acid preparation method. By applying the above-mentioned system, the high-efficiency production of acetic acid can be realized under low energy consumption conditions. This method has the characteristics of being green, energy-saving, and low-cost, and is suitable for large-scale production of acetic acid.

[0008] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted: The present invention provides an acetic acid preparation system, including: 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 de-lighting tower, a dehydration tower, and a finished product tower that are connected in sequence; the carbonyl reactor is connected to the evaporator, the top outlet of the evaporator is connected to the de-lighting tower, the side line outlet of the de-lighting tower is connected to the dehydration tower, the side line outlet of the dehydration tower is connected to the finished product tower, and a product pipeline is connected to the side wall of the finished product tower; the product pipeline and the methanol pipeline are coupled and heat-exchanged through the first heat exchanger; The bottom outlet of the de-lighting tower is connected to the side wall of the de-lighting 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 arranged 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 is located below the liquid level of the carbonyl reactor; a first enhanced mass transfer unit is arranged in the carbonyl reactor, and the first enhanced mass transfer unit includes a first enhanced mass transfer device and a second enhanced mass transfer device. The bottom of the carbonyl reactor is connected to the first enhanced mass transfer device via a first circulating heat exchange pipeline, and the outlet of the carbon monoxide pipeline is connected to the second enhanced mass transfer device; The first enhanced mass transfer device is located below the second enhanced mass transfer device, the outlet of the first enhanced mass transfer device is upward, the outlet of the second enhanced mass transfer device is downward, and the outlets of the first enhanced mass transfer device and the second enhanced mass transfer device are arranged in a staggered manner.

[0009] In the above technical solution, by setting the first mass transfer intensifier and the second mass transfer intensifier, carbon monoxide and the recycled materials can be dispersed and broken into the micron level, which helps to increase the gas-liquid mass transfer area, improve the reaction efficiency and conversion rate of raw materials; by staggering the outlets of the two mass transfer intensifiers, the two staggered liquid flows can be used to stir the liquid flow in the vertical direction, which helps to ensure the uniform distribution of raw materials and avoid the formation of dead zones, thereby avoiding catalyst precipitation to a certain extent and improving the utilization rate of the catalyst; in addition, since the use of two mass transfer intensifiers improves the raw material conversion rate and the catalyst utilization rate, the water content in the catalyst system can be appropriately reduced (reduced to 0.8%-1.5%), which helps to reduce the energy consumption and cost required for water separation in the subsequent process; by setting the catalyst circulation pipe, the catalyst precipitated at the bottom of the carbonyl reactor can be circulated to improve the utilization rate of the catalyst and ensure the catalytic effect; by thermally coupling the product pipeline with the methanol pipeline and using the steam at the top of the finished product tower as the heat source for the bottom of the light removal tower, the cost can be effectively saved and the comprehensive utilization of heat can be realized. In short, applying this system to acetic acid preparation can improve the raw material conversion rate and the catalyst utilization rate, improve the comprehensive heat utilization efficiency, and achieve a high raw material conversion rate and product yield under the condition of a low water content in the catalyst system, which helps to further reduce the production cost of acetic acid.

[0010] Preferably, a first filter screen is provided at the bottom of the carbonyl reactor, and one end of the first filter screen close to the catalyst circulation pipe is flush with the inlet of the catalyst circulation pipe; preferably, the first filter screen is inclined in the direction close to the catalyst circulation pipe; preferably, the first mass transfer intensifier is located horizontally on one side close to the catalyst circulation pipe, and the second mass transfer intensifier is located horizontally on the side far from the catalyst circulation pipe.

[0011] In the above solution, by setting the first filter screen, the catalyst can be blocked when it precipitates downward; at the same time, by making one end of the first filter screen close to the catalyst circulation pipe flush with the inlet of the catalyst circulation pipe, it is convenient to return the catalyst filtered by the first filter screen to the reaction liquid via the catalyst circulation pipe for continuous reaction, which helps to improve the utilization rate of the catalyst. In a further solution, by inclining the first filter screen, the catalyst on the first filter screen can be made to flow towards the inlet of the catalyst circulation pipe by the action of gravity, which helps to further improve the utilization rate of the catalyst. In an even further solution, by specifically setting the positions of the first mass transfer intensifier and the second mass transfer intensifier, the stirring flow formed between the two mass transfer intensifiers can be used to stir and push the catalyst on the first filter screen, making it move faster towards the inlet of the catalyst circulation pipe and preventing it from depositing and blocking the first filter screen.

[0012] Preferably, a stirring shaft is horizontally arranged in the carbonyl reactor, and the stirring shaft is located vertically between the first mass transfer intensifying unit and the liquid level of the carbonyl reactor; one end of the stirring shaft penetrates the side wall of the carbonyl reactor and extends deep into the catalyst circulation pipe, a paddle is arranged at the end of the stirring shaft extending into the catalyst circulation pipe, and a plurality of stirring rods are installed on the part of the stirring shaft located in the carbonyl reactor; the stirring shaft rotates driven by the reaction liquid circulating in the catalyst circulation pipe.

[0013] In the above solution, the material flow circulating in the catalyst circulation pipe can drive the rotating shaft to rotate by contacting the paddle, and then the stirring rod is used to stir the reaction liquid in the carbonyl reactor, slowing down the deposition of the catalyst and improving the distribution uniformity of microbubbles and microdroplets in the reaction liquid, which helps to further improve the reaction efficiency and the utilization rate of the catalyst.

[0014] Preferably, a plurality of layers of grids are arranged inside the carbonyl reactor, and the plurality of layers of grids are located between the liquid level in the carbonyl reactor and the first mass transfer intensifying unit; the outlet of the catalyst circulation pipe is not lower than the lowermost grid among the plurality of layers of grids and not higher than the liquid level of the carbonyl reactor; preferably, a second circulating heat exchange pipeline is further included; the inlet of the second circulating heat exchange pipeline is connected to the carbonyl reactor and is located between the lowermost grid and the uppermost grid among the plurality of layers of grids, and the outlet of the second circulating heat exchange pipeline is connected to the first mass transfer intensifier.

[0015] In the above solution, by arranging the grid, the flow rate of the reaction liquid in the upper part of the carbonyl reactor can be reduced, the reaction path of carbon monoxide can be extended, and the raw material conversion rate can be improved. By arranging the second circulating heat exchange pipeline, on the one hand, the reaction liquid can be cooled to maintain the temperature stability of the reaction system and ensure the reaction efficiency. On the other hand, the second circulating heat exchange pipeline can circulate the top reaction liquid to the first mass transfer intensifier, which can not only stir the reaction liquid in the vertical direction but also use the first mass transfer intensifier to further increase the phase boundary mass transfer area of the reaction raw materials in the reaction liquid.

[0016] Preferably, a strengthening reactor is arranged between the carbonyl reactor and the evaporator; the side wall of the carbonyl reactor is connected to the strengthening reactor via a first discharge pipeline, the strengthening reactor is connected to the evaporator via a second discharge pipeline; the catalyst pipeline is connected to the strengthening reactor; the top of the strengthening reactor is connected to the carbonyl reactor; A second mass transfer intensifying unit is arranged in the strengthening reactor; the second mass transfer intensifying unit includes a third mass transfer intensifier and a fourth mass transfer intensifier; the third mass transfer intensifier and the fourth mass transfer intensifier are at the same horizontal height and the outlets of the third mass transfer intensifier and the fourth mass transfer intensifier are arranged staggeredly; The carbon monoxide pipeline is connected to the third mass transfer intensifier, and the bottom of the intensifying reactor is connected to the fourth mass transfer intensifier via a third circulation heat exchange pipeline; Preferably, a fourth circulation heat exchange pipeline is further included. The inlet of the fourth circulation heat exchange pipeline is connected to the intensifying reactor and is located below the liquid level of the intensifying reactor, and the outlet of the fourth circulation heat exchange pipeline is connected to the fourth mass transfer intensifier.

[0017] In the above solution, the intensifying reactor can further react on the materials output from the carbonyl reactor to improve the methanol conversion rate; by arranging a third mass transfer intensifier and a fourth mass transfer intensifier in the intensifying reactor, the materials can be dispersed and broken, the phase boundary mass transfer area between raw materials can be increased, and the conversion rate can be improved; by staggering the horizontal outlets of the third mass transfer intensifier and the fourth mass transfer intensifier, a stirring flow can be formed in the horizontal direction, avoiding the dead zone of the reaction liquid, improving the uniformity of the microbubble distribution, and at the same time helping to slow down the catalyst settlement and improve the catalyst utilization rate; by arranging the fourth circulation heat exchange pipeline, on the one hand, the reaction liquid in the intensifying reactor can be circulated and heat exchanged to maintain the internal reaction temperature and ensure the reaction efficiency; on the other hand, the reaction liquid can be stirred in the vertical direction, and the fourth mass transfer intensifier is used to further increase the phase boundary mass transfer area of the reaction raw materials in the reaction liquid.

[0018] Preferably, a riser is arranged in the mass transfer intensifier; the riser includes a pipe body and a suction part, the pipe body is connected above the suction part, the diameter of the suction part gradually increases from top to bottom, and the bottom of the suction part faces the bottom of the mass transfer intensifier; the top of the pipe body is located below the liquid level in the intensifying reactor; Preferably, a second filter screen is arranged in the mass transfer intensifier, and the second filter screen is horizontally arranged and located below the suction part.

[0019] In the above technical solution, the riser can be used to lift the bottom reaction liquid to the top. In this way, the reaction liquid in the intensifying reactor can be promoted to flow in the vertical direction, which helps to avoid catalyst deposition; at the same time, the suction part is arranged to gradually increase from top to bottom, which can increase the suction surface and suck more of the catalyst deposited at the bottom. Moreover, this structure makes the flow rate of the lifted reaction liquid gradually increase during the rising process, and the circulated reaction liquid is ejected through the top of the pipe body, which helps to quickly and evenly disperse the catalyst in the circulated reaction liquid into the reaction liquid. In a further solution, by arranging the second filter screen, the deposited catalyst can be trapped. Placing it below the suction part can enable the riser to better circulate the deposited catalyst back to the reaction liquid at the top, which helps to further improve the catalyst utilization rate.

[0020] Preferably, the top outlet of the light component removal column 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 column, 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 absorption column is connected to the carbonyl reactor. The gaseous material removed from the top of the light component removal column undergoes two-stage condensation and enters the separator. In the separator, the material is divided into two phases: light (mainly including acetic acid and water) and heavy (mainly including methyl iodide, and methyl iodide is a promoter in the catalyst system). The uncondensed tail gas (including methyl iodide, carbon monoxide, and carbon dioxide) in the final cooler is input into the low-pressure absorption column for further recovery of methyl iodide. This design helps to improve the utilization efficiency of the promoter.

[0021] Preferably, a high-pressure separator is further included; the material output from the top of the carbonyl reactor is heat-exchanged in the evaporator and then input into the high-pressure separator. The bottom outlet of the high-pressure separator is connected to the intensifying reactor; preferably, the top outlet of the high-pressure separator is connected to a high-pressure absorption column, and the bottom outlet of the high-pressure absorption column 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 directly flows back into the intensifying reactor to continue participating in the reaction, and the gas phase is input into the high-pressure absorption column. In the high-pressure absorption column, the methanol carried in the gas phase is separated and flows back into the carbonyl reactor to continue the reaction. Thus, the methanol conversion rate can be further improved.

[0022] Preferably, the bottom outlet of the product column is connected to a stripping column; the top outlet of the stripping column is connected to the product column, and the bottom outlet is connected to an acid mixture pipeline. The stripping column can separate and purify the material in the product column. Among them, the steam (mainly including acetic acid) coming out of the top of the stripping column returns to the product column and is output via the product pipeline. The bottom liquid of the stripping column (mainly including propionic acid) is discharged into the waste acid tank via the acid mixture pipeline.

[0023] Those skilled in the art will understand that the pneumatic enhanced mass transfer device and hydraulic enhanced mass transfer device used in the present invention have been embodied 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 describes in detail the specific product structure and working principle of the micron bubble generator (i.e., bubble breaker). The application document states that "the micron bubble generator includes a main body and a secondary crushing component, a cavity is provided in the main body, an inlet connected to the cavity is provided on the main body, and the first and second opposite ends of the cavity are open, wherein the cross-sectional area of the cavity decreases from the middle of the cavity to the first and second ends of the cavity; the secondary crushing component is provided at at least one of the first and second ends of the cavity, a portion of the secondary crushing component is provided in the cavity, and an annular channel is formed between the secondary crushing component and the through holes open at both ends of the cavity. The micron bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in the application document, it can be known that its specific working principle is: the liquid enters the micron 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-level microbubbles, thereby increasing the mass transfer area between the liquid phase and the gas phase, and the micron bubble generator in this patent is a pneumatic bubble breaker.

[0024] In addition, the prior patent 201610641251.7 records that the primary bubble breaker has a circulating liquid inlet, a circulating gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker connects the feed port with the gas-liquid mixture outlet, indicating that the bubble breaker requires a gas-liquid mixture to enter. In addition, it can be seen from the following figures that the primary bubble breaker mainly uses circulating liquid as power, so in fact the primary bubble breaker belongs to a hydraulic enhanced reactor, and the secondary bubble breaker simultaneously passes the gas-liquid mixture into an elliptical rotating ball for rotation, thereby achieving bubble breakage during the rotation process, so the secondary bubble breaker actually belongs to a gas-liquid linkage bubble breaker. In fact, whether it is a hydraulic bubble breaker or a gas-liquid linkage bubble breaker, it is a specific form of bubble breaker. However, the enhanced mass transfer device adopted by the present invention is not limited to the above-mentioned forms. The specific structure of the bubble breaker recorded in the prior patent is only one of the forms that can be adopted by the present invention.

[0025] In addition, it is recorded in the prior patent 201710766435.0 that "the principle of the bubble breaker is to achieve gas collision through high-speed jet flow"; moreover, the prior patent CN106187660 also has relevant records on the specific structure of the bubble breaker. Specifically, see paragraphs

[0031] -

[0041] in the specification and the attached drawings. It elaborates in detail 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 entrainment power, thereby achieving the effect of being crushed into ultra-fine bubbles. It can also be seen from the attached drawings that the bubble breaker has a conical structure, and the diameter of the upper part is larger than that of the lower part, which is also to enable the liquid phase to better provide entrainment power.

[0026] In the initial stage of the prior patent application, since the bubble breaker was just developed, it was initially named a microbubble generator (CN201610641119.6), etc. With continuous technological improvement, it was later renamed the bubble breaker. Now, the mass transfer intensifier in the present invention is equivalent to the previous microbubble generator, microinterface generator, etc., only with different names. In summary, the mass transfer intensifier of the present invention itself belongs to the prior art.

[0027] The present invention also provides a method for preparing acetic acid, which uses the system of any of the above embodiments to prepare acetic acid.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By setting the first mass transfer intensifier and the second mass transfer intensifier, carbon monoxide and the recycled materials can be dispersed and broken 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; 2. By staggeredly arranging the outlets of the two mass transfer intensifiers, the two intersecting liquid flows can be used to stir the liquid flow in the vertical direction, which helps to ensure the uniform distribution of raw materials and avoid the formation of dead zones, thereby avoiding catalyst precipitation to a certain extent and improving the utilization rate of the catalyst; in addition, since the use of the two mass transfer intensifiers improves the raw material conversion rate and catalyst utilization rate, the water content in the catalyst system can be appropriately reduced (reduced to 0.8%-1.5%), which helps to reduce the energy consumption and cost required for water separation in the subsequent process; 3. By setting the catalyst circulation pipe, the catalyst precipitated at the bottom of the carbonylation reactor can be circulated to improve the utilization rate of the catalyst and ensure the catalytic effect; 4. By thermally coupling the product pipeline with the methanol pipeline and using the steam at the top of the finished product tower as the heat source for the bottom of the de-lighting tower, the cost can be effectively saved and the comprehensive utilization of heat can be realized; 5. In summary, applying this system to acetic acid production can improve the raw material conversion rate and catalyst utilization rate, enhance the comprehensive heat utilization efficiency, and achieve a high raw material conversion rate and product yield under the condition of a relatively low water content in the catalyst system, which helps to further reduce the production cost of acetic acid. Description of the Drawings

[0029] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings: Figure 1 A schematic diagram of the acetic acid production system according to Embodiment 1 of the present invention is shown; Figure 2 A schematic diagram of the carbonyl reactor according to Embodiment 1 of the present invention is shown; Figure 3 A schematic diagram of the intensifying reactor according to Embodiment 1 of the present invention is shown.

[0030] In the figure: 1, methanol pipeline; 2, carbon monoxide pipeline; 3, catalyst pipeline; 4, carbonyl reactor; 401, grid; 402, catalyst circulation pipe; 403, paddle; 404, stirring shaft; 405, stirring rod; 406, catalyst circulation pump; 407, first mass transfer intensifier; 408, first circulating heat exchange pipeline; 409, first filter screen; 410, second mass transfer intensifier; 411, second circulating heat exchange pipeline; 5, intensifying reactor; 501, pipe body; 502, third mass transfer intensifier; 503, suction part; 504, second filter screen; 505, fourth mass transfer intensifier; 506, third circulating heat exchange pipeline; 507, fourth circulating heat exchange pipeline; 6, high-pressure separator; 7, second discharge pipeline; 8, first discharge pipeline; 9, evaporator; 10, light component removal tower; 11, light component cooler; 12, final cooler; 13, stratifier; 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 Embodiments

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0032] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In order to more clearly illustrate the technical solution in the present invention, it will be described below in the form of specific embodiments.

[0035] Embodiment 1 With reference to Figures 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 carbonylation reactor 4, an evaporator 9, a light component removal tower 10, a dehydration tower 14, and a finished product tower 16 that are connected in sequence. In this embodiment, the catalyst pipeline 3 is used to transport a catalyst composition, and the catalyst composition includes a rhodium catalyst, a promoter methyl iodide, a catalyst promoter lithium propionate, and water. Among them, the water content is in the range of 0.8% - 1.5%.

[0036] The carbonyl reactor 4 is connected to the evaporator 9. The top outlet of the evaporator 9 is connected to the light component removal tower 10. The side line outlet of the light component removal tower 10 is connected to the dehydration tower 14. The side line outlet of the dehydration tower 14 is connected to the finished product tower 16. A product pipeline 26 is connected to the side wall of the finished product tower 16; the product pipeline 26 and the methanol pipeline 1 are coupled for heat exchange through the first heat exchanger 27; the bottom outlet of the light component removal tower 10 is connected to the side wall of the light component removal tower 10 via the second heat exchanger 29, and the top outlet of the finished product tower 16 is connected to the dehydration tower 14 via the second heat exchanger 29. The bottom outlet of the finished product tower 16 is connected to the stripping tower 17; the top outlet of the stripping tower 17 is connected to the finished product tower 16, and the bottom outlet is connected to the mixed acid pipeline 25. In this embodiment, it is considered to use the steam at the top of the finished product tower 16 as the heat source for the bottom of the light component removal tower 10. Calculated based on an annual acetic acid output of 200,000 tons, the steam temperature at the top of the finished product tower 16 is 135.8 °C, and the heat load is 36.972×106 KJ / h. The temperature of the bottom liquid in the kettle of the light component removal tower 10 is 133.6 °C, and the heat load is 3.376×106 KJ / h. The steam temperature and heat load at the top of the finished product tower 16 are both greater than those at the bottom of the light component removal tower 10. Therefore, heat transfer can be achieved between the steam at the top of the finished product tower 16 and the bottom liquid in the kettle of the light component removal tower 10. This way of heat exchange and comprehensive utilization can meet the requirements of modern industry for greening and is applicable to the large-scale preparation of acetic acid.

[0037] As Figure 1 shown, an intensifying reactor 5 is arranged between the carbonyl reactor 4 and the evaporator 9; the side wall of the carbonyl reactor 4 is connected to the intensifying reactor 5 via the first discharge pipeline 8, and the intensifying reactor 5 is connected to the evaporator 9 via the second discharge pipeline 7; the catalyst pipeline 3 is connected to the intensifying reactor 5; the top of the intensifying reactor 5 is connected to the carbonyl reactor 4.

[0038] Continuing to refer to 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.

[0039] Continuing to refer to Figure 1 , the system of this embodiment further includes a high-pressure separator 6; the material output from the top of the carbonyl reactor 4 is input into the high-pressure separator 6 after heat exchange in the evaporator 9. 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.

[0040] In this embodiment, a heat exchanger is provided inside the evaporator 9. The product in the carbonyl reactor 4 enters the intensifying reactor 5 through the first discharge pipeline 8 for further reaction. After the overhead discharge of the carbonyl reactor 4 exchanges heat in the heat exchanger inside the evaporator 9, it is input into the high-pressure separator 6 for separation. The separated liquid phase part returns to the intensifying reactor 5 to continue participating in the reaction, and the gas phase part is input into the high-pressure absorption tower 18 for separation. One side of the high-pressure absorption tower 18 is connected with a first coolant pipeline 21, and this first coolant pipeline 21 is used to input 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 through the first coolant pipeline 21, flows from top to bottom, absorbs main organic components such as methyl iodide, and is sent back to the carbonyl reactor 4 from the bottom of the high-pressure absorption tower 18 to continue participating in the reaction. The tail gas inside 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 through a high-pressure circulation pipeline 19, and a high-pressure circulation cooler 20 is arranged on the high-pressure circulation pipeline 19.

[0041] The gas (including part of carbon monoxide) at the top of the intensifying reactor 5 is input into the carbonyl reactor 4, and the product in the intensifying reactor 5 enters the evaporator 9 through the second discharge pipeline 7. The liquid phase components obtained by flashing in the evaporator 9 return to the carbonyl reactor 4 through the bottom outlet to continue the reaction, and the gas phase components enter the light component removal tower 10 through the top outlet to remove the light components in the gas phase components, then go to the dehydration tower 14 for drying, and then go to the product tower 16 for rectification. The rectified acetic acid product is taken out from the side line three-layer trays of the product tower 16 through the product pipeline 26, and after heat exchange with the methanol in the methanol pipeline 1 through the first heat exchanger 27, it is output. The product outlet on the side wall of the light component removal tower 10 is connected to the dehydration tower 14, and part of the product output from the bottom is input into the carbonyl reactor 4 to continue participating in the reaction, and part returns to the light component removal tower 10 after heat exchange with the second heat exchanger 29.

[0042] The gas phase (mainly acetic acid, water, methyl iodide) separated at the top of the light component removal tower 10 enters the light component cooler 11 for cooling, the condensate enters the separator 13, the uncondensed gas phase enters the final cooler 12, and is further condensed with condensed water. The uncondensed tail gas enters the low-pressure absorption tower 28 to further recover methyl iodide, and the condensate of the final cooler 12 enters the separator 13. The heavy components in the separator 13 are sent back to the carbonyl reactor 4 to continue the reaction.

[0043] The gas phase at the top of the dehydration tower 14 enters the third heat exchanger 15 for heat exchange and cooling. Part of the condensate returns to the dehydration tower 14, and part is directly sent out. The uncondensed gas phase components are then input into the low-pressure absorption tower 28 to further recover methyl iodide.

[0044] One side of the low-pressure absorption tower 28 is connected with a second coolant pipeline 22, and the second coolant pipeline 22 is used to input 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 from top to bottom, absorbs the main organic components such as methyl iodide, and is sent back to the carbonyl reactor 4 from the bottom of the low-pressure absorption tower 28 to continue participating in the reaction. The tail gas in 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, and a low-pressure circulation cooler 24 is arranged on the low-pressure circulation pipeline 23.

[0045] The bottom outlet and the side wall outlet of the dehydration tower 14 are both connected to the finished product tower 16. The gas phase at the top of the finished product tower 16 is input into the dehydration tower 14 after heat exchange with the bottom circulating material of the light component removal tower 10 via the second heat exchanger 29, and the bottom product is sent to the stripping tower 17 for further rectification. The gas phase at the top of the stripping tower after rectification returns to the finished product tower 16 for re-rectification, and the mixed acid produced at the bottom of the tower is output from the mixed acid outlet. The main component of the mixed acid is propionic acid.

[0046] Refer to Figure 1 、 Figure 2 As shown in, the methanol pipeline 1 and the catalyst pipeline 3 are connected to the carbonyl reactor 4; a catalyst circulation pipe 402 is arranged on one side of the carbonyl reactor 4. The inlet of the catalyst circulation pipe 402 is connected to the bottom of the carbonyl reactor 4, and the outlet is connected to the upper part of the carbonyl reactor 4 and is located below the liquid level of the carbonyl reactor 4; a catalyst circulation pump 406 is arranged on the catalyst circulation pipe 402 to provide power for the liquid flow therein. A first enhanced mass transfer unit is arranged in the carbonyl reactor 4, and the first enhanced mass transfer unit includes a first enhanced mass transfer device 407 and a second enhanced mass transfer device 410. The bottom of the carbonyl reactor 4 is connected to the first enhanced mass transfer device 407 via a first circulation heat exchange pipeline 408, and the outlet of the carbon monoxide pipeline 2 is connected to the second enhanced mass transfer device 410; the first enhanced mass transfer device 407 is located below the second enhanced mass transfer device 410. The outlet of the first enhanced mass transfer device 407 is upward, and the outlet of the second enhanced mass transfer device 410 is downward. The outlets of the first enhanced mass transfer device 407 and the second enhanced mass transfer device 410 are arranged staggeredly. In this embodiment, the solvent in the carbonyl reactor 4 accounts for 2 / 3 - 4 / 5 of the volume of the carbonyl reactor 4.

[0047] A first filter screen 409 is arranged at the bottom of the carbonyl reactor 4. One end of the first filter screen 409 close to the catalyst circulation pipe 402 is flush with the inlet of the catalyst circulation pipe 402; wherein, the first filter screen 409 is arranged obliquely along the direction close to the catalyst circulation pipe 402; the first enhanced mass transfer device 407 is horizontally located on one side close to the catalyst circulation pipe 402, and the second enhanced mass transfer device 410 is horizontally located on one side far from the catalyst circulation pipe 402.

[0048] As Figure 2As shown, a stirring shaft 404 is horizontally arranged in the carbonyl reactor 4. The stirring shaft 404 is vertically located between the first enhanced mass transfer unit and the liquid level of the carbonyl reactor 4. One end of the stirring shaft 404 penetrates the side wall of the carbonyl reactor 4 and extends deep into the catalyst circulation pipe 402. A paddle 403 is arranged at the end of the stirring shaft 404 that extends into the catalyst circulation pipe 402. A plurality of stirring rods 405 are installed on the part of the stirring shaft 404 located inside the carbonyl reactor 4. The stirring shaft 404 rotates driven by the reaction liquid circulating in the catalyst circulation pipe 402.

[0049] Continue to refer to Figure 2 , a plurality of layers of grids 401 are arranged inside the carbonyl reactor 4. The plurality of layers of grids 401 are located between the liquid level in the carbonyl reactor 4 and the first enhanced mass transfer unit. The outlet of the catalyst circulation pipe 402 is not lower than the lowermost grid 401 of the plurality of layers of grids 401 and not higher than the liquid level of the carbonyl reactor 4. The system of this embodiment further includes a second circulation heat exchange pipeline 411. The inlet of the second circulation heat exchange pipeline 411 is connected to the carbonyl reactor 4 and is located between the lowermost grid 401 and the uppermost grid 401 of the plurality of layers of grids 401. The outlet of the second circulation heat exchange pipeline 411 is connected to the first enhanced mass transfer device 407.

[0050] As Figure 3 shown, a second enhanced mass transfer unit is arranged in the enhanced reactor 5. The second enhanced mass transfer unit includes a third enhanced mass transfer device 502 and a fourth enhanced mass transfer device 505. The third enhanced mass transfer device 502 and the fourth enhanced mass transfer device 505 are at the same horizontal height and the outlets of the third enhanced mass transfer device 502 and the fourth enhanced mass transfer device 505 are staggered. The carbon monoxide pipeline 2 is connected to the third enhanced mass transfer device 502. The bottom of the enhanced reactor 5 is connected to the fourth enhanced mass transfer device 505 via a third circulation heat exchange pipeline 506. The system in this embodiment further includes a fourth circulation heat exchange pipeline 507. The inlet of the fourth circulation heat exchange pipeline 507 is connected to the enhanced reactor 5 and is located below the liquid level of the enhanced reactor 5. The outlet of the fourth circulation heat exchange pipeline 507 is connected to the fourth enhanced mass transfer device 505. In this embodiment, circulation heat exchangers are arranged on each circulation heat exchange pipeline to facilitate maintaining the temperature inside the reactor.

[0051] Continue to refer to Figure 3 , a riser is arranged inside the enhanced mass transfer device. The riser includes a pipe body 501 and a suction part 503. The pipe body 501 is connected above the suction part 503. The diameter of the suction part 503 gradually increases from top to bottom and the bottom of the suction part 503 faces the bottom of the enhanced mass transfer device. The top of the pipe body 501 is located below the liquid level inside the enhanced reactor 5. A second filter screen 504 is arranged inside the enhanced mass transfer device. The second filter screen 504 is horizontally arranged and is located below the suction part 503. To facilitate the riser in lifting the reaction liquid inside the enhanced mass transfer device, a pump can be arranged on the riser.

[0052] It can be understood that in this embodiment, for the convenience of the flow of the medium in each pipeline and pipeline control, a pump body, a valve, etc. can be provided on the pipeline, which will not be elaborated.

[0053] This embodiment also provides a method for preparing acetic acid, which uses the above system to prepare acetic acid. During the preparation process, the pressures in the carbonylation reaction tower and the enhanced reaction tower are both 2.6 - 3.2 MPa, and the reaction temperatures are both 150 - 200 °C. The pressure of the acetic acid vapor at the top of the evaporator is 0.1 - 0.3 Mpa, and the temperature is 110 - 150 °C. The pressure of the finished acetic acid taken out at the outlet of the finished product tower is 0.1 - 0.3 Mpa, and the temperature is 120 - 180 °C.

[0054] Example 2 The difference between this embodiment and Example 1 is that the first enhanced mass transfer device is located horizontally on one side away from the catalyst circulation pipe, and the second enhanced mass transfer device is located horizontally on one side close to the catalyst circulation pipe.

[0055] Example 3 The difference between this embodiment and Example 1 is that the outlets of the third enhanced mass transfer device and the fourth enhanced mass transfer device in the enhanced reactor are arranged opposite to each other.

[0056] Example 4 The difference between this embodiment and Example 1 is that the riser is not provided.

[0057] Comparative Example 1 The difference between this embodiment and Example 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.

[0058] Comparative Example 2 The difference between this embodiment and Example 1 is that the inlet of the catalyst circulation pipe is connected to the upper part of the carbonylation reactor, and the outlet is connected to the bottom of the carbonylation reactor.

[0059] Experimental Example The systems of Examples 1 - 4 and Comparative Examples 1 - 2 were respectively used to prepare acetic acid under the same reaction conditions (catalyst concentration is 900 ppm, the reaction temperatures in the carbonylation reactor and the enhanced reactor are both 170 °C, and the water content is 1%), and the methanol conversion rate and acetic acid yield were statistically analyzed based on the reaction products output from the enhanced reactor in each system. The statistical results are shown in Table 1.

[0060] Table 1 Statistical Results

[0061] According to the data shown in the above table, the technical solution of this application can achieve better methanol conversion rate and acetic acid yield on the premise of lower water content of the catalyst. Among them, the system of Example 1 achieves the best effect, with the methanol conversion rate reaching 96.10% and the acetic acid yield reaching 92.32%. Compared with the traditional acetic acid preparation technology, the methanol conversion rate is increased by more than 10%. And this solution reacts under the condition of 170 °C, and saves the reaction energy consumption through heat coupling in the subsequent process. At the same time, since the water content of the catalyst is greatly reduced, the energy consumption required for separating water in the subsequent dehydration tower can be effectively reduced.

[0062] By comparing Example 1 and Example 2, it can be found that both the methanol conversion rate and the acetic acid yield in Example 1 are better than those in Example 2. This may be because the stirring directions of the two mass transfer intensifiers in Example 2 are opposite to the circulation direction of the catalyst circulation pipe, which hinders the circulation of the catalyst by the catalyst circulation pipe to a certain extent. At the same time, the stirring effects of the two mass transfer intensifiers on the microbubbles and the catalyst are offset by the catalyst circulation pipe to a certain extent, reducing the dispersion effect.

[0063] By comparing Example 1 and Example 3, it can be found that both the methanol conversion rate and the acetic acid yield in Example 1 are better than those in Example 3. This may be because in Example 3, the outlets of the third mass transfer intensifier and the fourth mass transfer intensifier are arranged oppositely, and the two opposing liquid flows cause a dead zone in the reaction liquid, accelerating the precipitation of the rhodium catalyst and affecting the uniform distribution of the microbubbles.

[0064] By comparing Example 1 and Example 4, it can be found that both the methanol conversion rate and the acetic acid yield in Example 1 are better than those in Example 4. This may be because the riser in the intensifying reactor in Example 1 can stir the reaction liquid in the intensifying reactor up and down. This stirring method cooperates with the horizontal stirring caused by the two mass transfer intensifiers, achieving a better stirring effect, enabling the microbubbles and the catalyst to be evenly distributed, increasing the interfacial mass transfer area of the raw materials and the catalytic effect of the catalyst, and thus increasing the methanol conversion rate and the acetic acid yield.

[0065] By comparing Example 1 and Comparative Example 1, it can be found that both the methanol conversion rate and the acetic acid yield in Example 1 are better than those in Comparative Example 1. This may be because in Example 4, the outlets of the first mass transfer intensifier and the second mass transfer intensifier are arranged oppositely, and the two opposing liquid flows cause a dead zone in the reaction liquid, accelerating the precipitation of the rhodium catalyst and affecting the uniform distribution of the microbubbles.

[0066] By comparing Example 1 and Comparative Example 2, it can be found that both the methanol conversion rate and the acetic acid yield in Example 1 are 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.

[0067] In summary, the system of the present invention can achieve better methanol conversion rate and acetic acid yield under the condition of lower water content of the catalyst, which can effectively reduce the production energy consumption and cost of acetic acid. Moreover, the system of the present invention makes full use of waste heat by means of heat coupling, thereby contributing to improving the energy utilization efficiency. This system can be used for the green production of acetic acid.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An acetic acid preparation system, characterized in that, Including: A catalyst pipeline, a methanol pipeline, a carbon monoxide pipeline, a first heat exchanger, a second heat exchanger, and a carbonylation reactor, an evaporator, a light component removal tower, a dehydration tower, and a finished product tower connected in sequence; the carbonylation reactor is connected to the evaporator, the top outlet of the evaporator is connected to the light component removal tower, the side line outlet of the light component removal tower is connected to the dehydration tower, the side line outlet of the dehydration tower is connected to the finished product tower, and a product pipeline is connected to the side wall of the finished product tower; the product pipeline and the methanol pipeline are coupled for heat exchange through the first heat exchanger. The bottom outlet of the light component removal tower is connected to the side wall of the light component 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 carbonylation reactor; a catalyst circulation pipe is arranged on one side of the carbonylation reactor, the inlet of the catalyst circulation pipe is connected to the bottom of the carbonylation reactor, and the outlet is connected to the upper part of the carbonylation reactor and is below the liquid level of the carbonylation reactor; a first mass transfer intensification unit is arranged in the carbonylation reactor, and the first mass transfer intensification unit includes a first mass transfer intensifier and a second mass transfer intensifier. The bottom of the carbonylation reactor is connected to the first mass transfer intensifier via a first circulating heat exchange pipeline, and the outlet of the carbon monoxide pipeline is connected to the second mass transfer intensifier. The first mass transfer intensifier is located below the second mass transfer intensifier, the outlet of the first mass transfer intensifier is upward, the outlet of the second mass transfer intensifier is downward, and the outlets of the first mass transfer intensifier and the second mass transfer intensifier are arranged staggeredly.

2. The acetic acid preparation system according to claim 1, wherein A first filter screen is arranged at the bottom of the carbonylation reactor, and one end of the first filter screen close to the catalyst circulation pipe is flush with the inlet of the catalyst circulation pipe. Preferably, the first filter screen is arranged obliquely along the direction close to the catalyst circulation pipe. Preferably, the first mass transfer intensifier is horizontally located on one side close to the catalyst circulation pipe, and the second mass transfer intensifier is horizontally located on one side far from the catalyst circulation pipe.

3. The acetic acid preparation system according to claim 1, characterized in that, A stirring shaft is horizontally arranged in the carbonylation reactor, and the stirring shaft is vertically located between the first mass transfer intensification unit and the liquid surface of the carbonylation reactor; one end of the stirring shaft penetrates the side wall of the carbonylation reactor and extends deep into the catalyst circulation pipe, a paddle is arranged at the end of the stirring shaft extending deep into the catalyst circulation pipe, and a plurality of stirring rods are installed on the part of the stirring shaft located in the carbonylation reactor; the stirring shaft rotates driven by the reaction liquid circulating in the catalyst circulation pipe.

4. The acetic acid preparation system according to claim 2, wherein A plurality of layers of grids are arranged inside the carbonylation reactor, and the plurality of layers of grids are located between the liquid surface in the carbonylation reactor and the first mass transfer intensification unit; the outlet of the catalyst circulation pipe is not lower than the lowermost grid of the plurality of layers of grids and not higher than the liquid surface of the carbonylation reactor. Preferably, a second circulating heat exchange pipeline is further included; the inlet of the second circulating heat exchange pipeline is connected to the carbonylation reactor and is between the lowermost grid and the uppermost grid of the plurality of layers of grids, and the outlet of the second circulating heat exchange pipeline is connected to the first mass transfer intensifier.

5. The acetic acid preparation system according to claim 1, wherein A strengthening reactor is arranged between the carbonyl reactor and the evaporator; the side wall of the carbonyl reactor is communicated with the strengthening reactor through a first discharge pipeline, and the strengthening reactor is communicated with the evaporator through a second discharge pipeline; the catalyst pipeline is connected to the strengthening reactor; the top of the strengthening reactor is connected to the carbonyl reactor; A second strengthening mass transfer unit is arranged in the strengthening reactor; the second strengthening mass transfer unit includes a third strengthening mass transfer device and a fourth strengthening mass transfer device; the third strengthening mass transfer device and the fourth strengthening mass transfer device are at the same horizontal height and the outlets of the third strengthening mass transfer device and the fourth strengthening mass transfer device are arranged staggeredly; The carbon monoxide pipeline is connected to the third strengthening mass transfer device, and the bottom of the strengthening reactor is connected to the fourth strengthening mass transfer device through a third circulating heat exchange pipeline; Preferably, a fourth circulating heat exchange pipeline is further included, the inlet of the fourth circulating heat exchange pipeline is connected to the strengthening reactor and is below the liquid level of the strengthening reactor, and the outlet of the fourth circulating heat exchange pipeline is connected to the fourth strengthening mass transfer device.

6. The acetic acid preparation system according to claim 5, wherein, A riser is arranged in the strengthening mass transfer device; the riser includes a pipe body and a suction part, the pipe body is connected above the suction part, the diameter of the suction part gradually increases from top to bottom and the bottom of the suction part faces the bottom of the strengthening mass transfer device; the top of the pipe body is below the liquid level in the strengthening reactor; Preferably, a second filter screen is arranged in the strengthening mass transfer device, the second filter screen is horizontally arranged and is below the suction part.

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 absorption tower is connected to the carbonyl reactor.

8. The acetic acid preparation system according to any one of claims 1-6, characterized in that, A high-pressure separator is further included; 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; 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.

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

10. A method for preparing acetic acid, characterized in that, Use the system according to any one of claims 1-9 to prepare acetic acid.

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