WO2020078476A1

WO2020078476A1 - Production device and production method for synthesizing acetic acid by low-pressure carbonylation of methanol

Info

Publication number: WO2020078476A1
Application number: PCT/CN2019/112043
Authority: WO
Inventors: 刘强; 张志伟; 李志远; 鲁宜武; 赵月东; 赵洋; 王进兵; 武金锋; 史锋锋; 李涛
Original assignee: 兖矿鲁南化工有限公司; 兖矿集团有限公司
Priority date: 2018-10-19
Filing date: 2019-10-18
Publication date: 2020-04-23
Also published as: CN109134233A; CN109134233B

Abstract

Disclosed are a production device and production method for synthesizing acetic acid by low-pressure carbonylation of methanol. In the present invention, the configuration of a fluid stirring device changes the situation that a mechanical stirring shaft seal and a transmission device are easy to damage in an operation process, eliminates dynamic seal points, and greatly improves the safe and stable operation of a system. At the same time, by matching with a CO distributor, the CO gas distribution in a reactor is more uniform, the gas-liquid two-phase mixing effect is improved, the reaction rate is increased, the reaction state of the system is optimized, and the production capacity of the device is increased from 300,000 tons per year to 600,000 tons per year.

Description

Production device and production method of methanol low-pressure carbonylation to synthesize acetic acid

Technical field

The invention relates to the field of acetic acid synthesis, in particular to a production device and production method of low-pressure carbonylation of methanol to synthesize acetic acid.

Background technique

Acetic acid is an important chemical intermediate and solvent for chemical reactions. Among the currently used acetic acid synthesis processes, the most commonly used one is methanol low-pressure oxo synthesis process, which was pioneered by Monsanto in the United States in the 1970s. During the years of innovation and development, the production process has changed tremendously, and major breakthroughs have been made in device capacity, product quality, and production costs.

In terms of process technology improvement, companies are constantly seeking new solutions, as described in Beijing Zehua Chemical Engineering Co., Ltd. patent CN 101665424, which combines the functions performed by the de-lightening tower and dehydration tower in a rectification tower. It simplifies the production route of acetic acid, reduces the equipment investment of the device, and also reduces the difficulty of operation control, which can effectively reduce the energy consumption of the device and reduce production costs. Hualu Hengsheng Chemical Co., Ltd. Patent CN201525813 describes that by installing a methyl iodide circulation tower and an evaporator in front of the rectification device, the methyl iodide is circulated in the reaction system, reducing the amount of iodomethane impurities mixed in acetic acid, while saving The energy consumption required for the purification of acetic acid. At present, the technical improvement is mostly in the rectification system, and the reaction system has less changes, especially the reactor unit. The conventional mechanical stirring mode is still used for gas-liquid stirring and mixing. The reaction equipment using mechanical stirring can effectively perform liquid-liquid and gas- Liquid mixing, however, the shaft seals and bearings required for mechanical transmission are easily damaged during long-term operation, resulting in shutdown maintenance and difficult to achieve continuous, stable and safe operation.

In terms of product quality control, foreign BP, Celanese and other companies have studied the purification process of acetic acid and improved the purification process. BP's patent in China CN93108283 describes the use of a single distillation zone technology to adapt to the change of catalyst in the reaction liquid; and Celanese International's patent in China CN 101808973 a method to improve the production of acetic acid, including from light ends The tower condenses the overhead steam and separates the concentrated water vapor into a light phase and a heavy phase. The heavy phase is mainly composed of methyl iodide, and at least a portion of the light phase that is gently decanted is refluxed to the light ends column. The acetic acid content of the light end column distillate and the water content of the light end column product stream are both reduced, improving purification efficiency. Domestic Jiangsu Thorpe and other companies proposed a new removal scheme for the control of trace iodine content in the product. The patent CN101396670 describes the invention of an ion exchange resin iodine removal adsorbent and its preparation method, the adsorbent is a macroporous cross-linked ion The exchange resin is prepared by loading one or more metal ions, and has a good removal effect on trace iodide in acetic acid.

In recent years, product quality control has become an important part of the technical improvement of methanol oxo synthesis acetic acid plant.

Summary of the invention

In view of the above-mentioned technical problems in the prior art, the object of the present invention is to provide a production device and production method for methanol low-pressure carbonylation to synthesize acetic acid. The invention provides a fluid stirring device in the reactor to change the mechanical stirring shaft seal and transmission When the device is easily damaged during operation, the dynamic sealing point is eliminated, which greatly improves the safe and stable operation of the system. At the same time, it cooperates with the CO distributor to make the distribution of CO gas in the reactor more uniform, improves the gas-liquid two-phase mixing effect, improves the reaction rate, optimizes the system reaction state, and the capacity of the device is increased from 300,000 tons / year to 600,000 tons /year. Aiming at the product quality control after the increase in output, a aldehyde removal device and an iodine removal device are installed in the rectification system to increase the time for the product to reduce potassium permanganate fading and reduce the content of propionic acid, formic acid and iodine in the product.

In order to solve the above problems, the technical solution of the present invention is:

A production device for synthesizing acetic acid by low-pressure carbonylation of methanol includes a reaction kettle, a conversion kettle, an evaporator, a pre-washing tower, a de-lighting tower, a dehydration tower, a finished product tower and a fluid stirring device, wherein the fluid stirring device includes at least two Nozzle, pump and heat exchanger, the inlet end of the pump communicates with the middle of the reactor, the outlet end of the pump communicates with the inlet of the heat exchanger, the fixed pipe of the nozzle is fixed on the top of the reactor, the heat exchanger The outlet end communicates with the end of the fixed pipe of the spray head. The spray head is set close to the inner wall of the reaction kettle. The spray head is set 200-500 mm below the liquid level of the reaction kettle. The angle between the diameters of the two adjacent spray heads is 45 ° -90 °.

The reaction liquid in the reaction kettle flows out from the middle of the reaction kettle, and is sent to the heat exchanger for cooling under the power of the pump, and then sent to the nozzle to be sprayed out. The reaction liquid flows down the inner wall of the reaction kettle at high speed, driving the peripheral The vector of the liquid changes and turns up from the bottom of the reactor to form a double-circulation flow state with different main flow layers.

The angle between the diameters of the two adjacent nozzles is set to 45 ° -90 °, in order to ensure the generation of different double-circulation flow states, and thus to generate greater disturbance to the reaction liquid in the reactor, to ensure that the reaction liquid in the kettle is mixed Even, no dead angle, so that it can achieve a better mixing effect.

The nozzle is set 200-500mm below the liquid level of the reaction kettle, in order to ensure stronger fluid power, and drive the reaction liquid in the whole kettle to achieve better stirring effect.

The heat exchanger can reduce the temperature of the reaction liquid in the reaction kettle, remove the heat released during the system reaction in time, and ensure the continuity and stability of the system reaction.

The pipe where the spray head is located is fixed on the top of the reaction kettle. After the temperature drops, the reaction liquid flows down from a high place, which can provide a higher speed and can produce a better stirring effect.

Preferably, the number of the pumps is two, including the first pump and the second pump, and the number of the heat exchangers is two, including the first and second heat exchangers, the first pump and the second pump In parallel, the first heat exchanger and the second heat exchanger are connected in parallel. Two sets of pumps and heat exchangers are provided, which can meet the requirement of full mixing of gas-liquid two-phase of large-volume reactor.

Preferably, the end of the nozzle of the nozzle is of a reduced diameter structure. The injection speed of the circulating reaction liquid can be significantly increased, and the degree of gas-liquid mixing can be improved.

Preferably, the reactor is also provided with a CO distributor, which is installed at the bottom of the reactor, and the CO distributor is formed by connecting five layers of porous ring-shaped tubes to each other, and the first layer is ring-shaped in order from bottom to top The pipe body, the second layer ring type pipe body, the third layer ring type pipe body, the fourth layer ring type pipe body and the fifth layer ring type pipe body, these 5-layer ring type pipe bodies are of concentric structure.

The five-layer porous ring tube body of the CO distributor is distributed at different heights and is concentrically distributed. The CO can be distributed at different diameter positions at the same time, so that the CO is distributed over the entire cross section of the reactor. It is distributed at different heights to ensure the uniform distribution of CO in the vertical direction, especially when the fluid stirring is weakened, the upper reaction liquid is fully reacted, and the gas-liquid two-phase mixing reaction effect is improved.

Preferably, the ring radii of the fourth layer ring tube body, the third layer ring tube body, the first layer ring tube body, the second layer ring tube body and the fifth layer ring tube body are sequentially reduced. The first layer of ring tube is the CO gas distribution tube, the second, third, and fourth layer of ring tube correspond to the hemispherical bottom space, and the fifth layer of ring tube is the first four layers of ring tube. The supplement of the body on the plane and the vertical CO distribution, the five-layer porous ring tube body does not leave a dead angle in the plane area of the reactor, and it shows an overall upward trend. With the coalescence and separation of bubbles, the CO of the entire reactor space is realized. Evenly distributed.

Preferably, the inner diameter of the first-layer annular pipe body is the largest, which is a CO gas distribution pipe, and is connected with the bottom of the kettle and the central axis. While distributing CO gas, it also plays a role in supporting and strengthening the upper four-layer annular pipe body.

Preferably, the distance between the first layer ring-shaped tube body and the second layer ring-shaped tube body, the distance between the second layer ring-shaped tube body and the third layer ring-shaped tube body, the third layer ring-shaped tube body The ratio between the distance to the fourth-layer ring tube and the distance between the fourth-layer ring tube and the fifth-layer ring tube is 1: 1: 3-5: 2-3.

Preferably, the diameter of the air holes on the porous ring tube body of the CO distributor is 1-3 mm, and the space between the air holes is 3-6 mm.

Preferably, the production device further includes a delaminator, a de-alkali tower and a decanter, the inlet of the delaminator is in communication with the top of the de-lighting tower, and the light-phase outlet of the delaminator is the top inlet of the de-aldehyde tower Connected, the top outlet of the de-alder tower is connected to the inlet of the decanter through a condenser, the middle outlet of the decanter is connected to the upper part of the de-aldehyde tower, the lower outlet of the decanter is connected to the layerer, and the upper outlet of the decanter Connect with waste liquid recovery device;

The bottom outlet of the dealdehyde removal tower is connected with the delightening tower.

The “light phase” pipeline of the de-lighting tower is equipped with a de-aldehyde device. The process is as follows: the “light phase” in the delaminator enters the reflux pump of the de-light tower, and the pump outlet branches into the de-aldehyde tower. After the raw materials entering the dealdehyde removal tower are heated by the reboiler, the heat and medium are exchanged in the layers of packing from the bottom to the top of the dealdehyde removal tower. The gas-phase material containing higher reducing impurities concentrated at the top of the dealdehyde removal tower is condensed by the condenser and sent to the decanter for extraction operation. When the decanter is working, the pretreated material with higher concentration of reducing impurities is added through the top material extractant inlet, and then enters the funnel-shaped separator in the decanter barrel from the tangential inlet of the top material; The material rotates in the separator to generate centrifugal force, and the heavy components (mainly methyl iodide) are thrown toward the wall of the separator by the centrifugal force, and flow down along the wall to the outlet of the bottom of the separator, which is a low flow. Impurities of light components (mainly acetaldehyde and crotonaldehyde) are extracted by the extractant and then rise, and overflow from the top material outlet. The lower part of the decanter is the settling chamber. After the underflow falls into the settling chamber, it is fused with the extractant to carry out the second settling stratification; after the settling stratification, the heavy phase at the bottom of the decanter returns to the system through the bottom material outlet to participate in the reaction, and the middle part is mainly acetic acid The mixed material with soft water is rectified several times through the lower reflux material outlet before returning to the system. The top light component reducing impurities are discharged into the waste acid storage tank through the upper material outlet and the middle material outlet. The device can increase the time for the product to reduce potassium permanganate fading, and reduce the content of propionic acid in the product.

A production method of low-pressure carbonylation of methanol to acetic acid includes the following steps:

1) CO gas enters the reaction kettle through the CO distributor at the bottom of the reaction kettle. After mixing methanol with dilute acid and methyl iodide, it enters the reaction kettle from the bottom of the reaction kettle. The above-mentioned fluid stirring device is used to stir the materials and act as a rhodium based catalyst Under the reaction to produce acetic acid;

2) After the reaction in the reaction kettle is completed, the reaction liquid enters the conversion kettle to continue the reaction;

3) The reaction liquid in the conversion kettle is depressurized by the flash valve and enters the evaporator, the gas phase enters the pre-wash tower for washing, and the liquid phase returns to the reaction kettle to continue to participate in the reaction;

4) After the vapor phase of the evaporator is washed by the pre-washing tower, it enters the rectification and separation of the de-lighting tower, and the light components are separated at the top of the de-lighting tower. The main components are methyl iodide, methyl acetate, water, etc., and return to the synthesis system to continue participating in the reaction; The crude acetic acid produced at the bottom of the lightening tower is dried in the dehydration tower and purified in the finished tower to produce refined acetic acid;

The gas phase at the top of the delightening tower is condensed by the heat exchanger and enters the delaminator. Due to the difference in density, the light phase and the heavy phase are separated in the delaminator. The light phase enters the dealdehyde tower. The gas-phase material containing higher reducing impurities is condensed by the condenser and then sent to the decanter for extraction and centrifugation. The mixture of acetic acid and water in the middle part is returned to the dealdehyde tower, and the heavy phase at the bottom is returned to the layerer.

Preferably, in step 1), the fluid flow rate provided by each pump of the fluid stirring device is 350-420 m ³ / h.

Preferably, in step 1), the fluid velocity of each nozzle is 10-25m / s.

Preferably, in step 4), the acetic acid produced from the finished product tower is cooled to 100 ° C, and then enters the adsorption tower. The pressure in the adsorption tower is 0.2-0.5Mpa, and the temperature is 40-138 ° C. Formic acid in acetic acid, the acetic acid from the adsorption tower enters the ion exchange tower, the pressure of the ion exchange tower is 0.2-0.5Mpa, the temperature is 80-100 ℃, after the adsorption of polystyrene ion exchange resin, the acetic acid is removed The iodine in the mixture is purified acetic acid. The acetic acid from the ion exchange tower is cooled by a heat exchanger, the temperature is reduced to 30-50 ° C, and then enters the storage tank for storage. After being removed by the deiodination device, the formic acid impurity content in acetic acid can be reduced to below 30PPm, and the iodine content to below 10PPb.

The beneficial effects of the present invention are:

1) The CO distributor and fluid stirring device of the present invention utilize the circulation of the mother liquor of the reaction kettle to improve the distribution of CO gas and circulating mother liquor. The small holes of the distributor disperse the large CO bubbles into small bubbles and become more uniform, realizing the reaction kettle The full mixing of the gas and liquid phases greatly improves the reaction rate, and ensures the CO partial pressure, which is beneficial to the stability of the catalyst. The production capacity of the device is increased from 300,000 tons / year to 600,000 tons / year. At the same time, the application of this technology not only eliminates the hidden dangers caused by mechanical stirring, but also achieves continuous, stable and safe operation, and saves the investment, operation and maintenance costs.

2) The above-mentioned dealdehyde removal device can effectively remove the reducing impurities in the acetic acid refining process, can improve the shrinkage time of potassium permanganate in the quality standard of the finished product, and reduce the content of the most important impurity propionic acid in the finished product.

3) The present invention adds a deiodination device, which can reduce the formic acid impurity content in acetic acid to below 30PPm and the iodine content to below 10PPb. The refined acetic acid product produced through this refining process meets the needs of downstream high-end products and can be used for the production of vinyl acetate and other high-end customers.

BRIEF DESCRIPTION

The drawings of the description forming part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions of this application are used to explain this application, and do not constitute an undue limitation on this application.

1 is a schematic diagram of the connection structure of the improved methanol low-pressure carbonylation synthesis acetic acid production system of the present invention;

2 is a schematic diagram of the connection structure of the fluid stirring system of the present invention;

3 is a schematic structural view of a top view of the fluid stirring tube of the present invention;

Figure 4 Schematic diagram of the front view of the fluid mixing tube;

5 is a schematic structural view of the front view of the CO distributor of the present invention;

6 is a schematic structural view of a top view of a CO distributor of the present invention;

7 is a flowchart of a fine deiodination device of the present invention;

Fig. 8 is a flow chart of the dealdehyde device of the present invention.

Among them: 1, high-pressure absorption tower, 2, low-pressure absorption tower, 3, reaction kettle, 4, reforming kettle, 5, evaporator, 6, pre-wash tower, 7, delighting tower, 8, delaminator, 9, dehydration Tower, 10, finished product tower, 11, deiodination device, 12, stripping tower, 13, dealkane tower, 14, dealdehyde tower, 15, first spray head, 16, second spray head, 17, first heat exchanger , 18, the second heat exchanger, 19, the first pump, 20, the second pump, 21, the central fixed shaft, 22, the fifth layer ring tube, 23, the fourth layer ring tube, 24, the first Three-layer ring tube, 25, second layer ring tube, 26, CO nozzle, 27, first layer ring tube, 28, first cooler, 29, adsorption tower, 30, ion exchange tower , 31, second cooler, 32, decanter.

detailed description

It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanations of the present application. Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

It should be noted that the terminology used herein is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates There are features, steps, operations, devices, components, and / or combinations thereof.

As shown in FIG. 1, a production device for synthesizing acetic acid by low-pressure carbonylation of methanol includes a high-pressure absorption tower 1, a low-pressure absorption tower 2, a reaction kettle 3, a conversion kettle 4, an evaporator 5, a pre-wash tower 6, and a delighting tower 7 , Dehydration tower 9, finished product tower 10 and fluid stirring device. The process flow is as follows: CO gas with a gauge pressure of 3.2 MPa enters the reactor 3 through the bottom of the reactor 3, and the CO is divided into small bubbles of uniform size by the CO distributor, methanol (including absorbed methanol) and the dilute acid from the rectification system After mixing with methyl iodide, the reaction kettle 3 enters the reaction kettle 3 from the bottom of the reaction kettle. The various materials react under the action of the rhodium-based catalyst to produce acetic acid. The reaction liquid enters the conversion kettle 4 from the middle of the reaction kettle 3 to continue the reaction, increase the conversion depth, and convert The reaction liquid in kettle 4 is depressurized by a pressure reducing valve and then enters evaporator 5. The gas phase in conversion kettle 4 passes into high-pressure absorption tower 1 and uses methanol as an absorbent to absorb methyl iodide and acetic acid vapor in the tail gas. The gas phase enters the pre-washing tower 6 for washing, recovers components such as HI and catalyst, and the liquid phase in the evaporator 5 returns to the reaction kettle 3 to continue participating in the reaction. After the flash vapor phase of the evaporator 5 is washed by the pre-washing tower 6, it enters the de-lighting tower 7 for preliminary separation operation. The gas phase at the top of the de-lighting tower 7 is condensed by a heat exchanger, and the condensate is divided into "light phase" and "according to the density. Heavy phase "and layering in the layerer 8, the" light phase "is mainly methyl acetate and water, the" heavy phase "is mainly methyl iodide, and the two are recycled to the reactor 3 under the action of a power pump to continue Participate in the reaction. The non-condensable gas enters the low-pressure absorption tower 2 and uses methanol as an absorbent to absorb methyl iodide and acetic acid vapor in the tail gas, and then returns to the reaction kettle 3 to continue to participate in the reaction. After the crude acetic acid produced at the bottom of the delighting tower 7 is dried by the dehydration tower 9 and purified by the finished tower 10, refined acetic acid with a content of up to 99.85% is produced.

As shown in Fig. 2, Fig. 3 and Fig. 4, the fluid stirring device includes at least two spray heads, a pump and a heat exchanger, the inlet end of the pump communicates with the middle of the reactor 3, and the outlet end of the pump communicates with the heat exchanger The inlet end of the reactor is connected, the fixed pipe of the spray head is fixed on the top of the reaction kettle 3, the outlet end of the heat exchanger communicates with the end of the fixed pipe of the spray head, the spray head is arranged near the inner wall of the reaction kettle 3, and the spray head is set at the liquid level of the reaction kettle Below 200-500mm, the angle between the diameters of the two adjacent nozzles is set to 45 ° -90 °, preferably 90 °.

As a specific embodiment, the number of the pumps is two, including the first pump 19 and the second pump 20, and the number of heat exchangers is two, including the first heat exchanger 17 and the second heat exchanger 18. The first pump 19 and the second pump 20 are connected in parallel, and the first heat exchanger 17 and the second heat exchanger 18 are connected in parallel. Two sets of pumps and heat exchangers are provided, which can meet the requirement of full mixing of gas-liquid two-phase of large-volume reactor.

As shown in FIG. 4, the end of the nozzle of the nozzle is provided with a reduced diameter structure. The injection speed of the circulating reaction liquid can be significantly increased, and the degree of gas-liquid mixing can be improved.

As shown in FIG. 5 and FIG. 6, as a preferred embodiment, a CO distributor is further provided in the reaction kettle 3, and the CO distributor is installed on the bottom of the reaction kettle 3 through a central fixed shaft 21, and the CO distributor is composed of 5 The multi-layer porous ring tube body is connected to each other, from bottom to top are the first layer ring tube body 27, the second layer ring tube body 25, the third layer ring tube body 24, the fourth layer ring tube The body 23 and the fifth layer annular pipe body 22 are concentric structures.

The five-layer porous ring tubes of the CO distributor are distributed at different heights and are distributed concentrically. The CO can be distributed at different diameters at the same time, which facilitates the distribution of CO across the entire cross section of the reactor. It is distributed at different heights to ensure the uniform distribution of CO in the vertical direction, especially when the fluid stirring is weakened, the upper reaction liquid is fully reacted, and the gas-liquid two-phase mixing reaction effect is improved.

As shown in FIG. 5, the fourth layer ring tube 23, the third layer ring tube 24, the first layer ring tube 27, the second layer ring tube 25 and the fifth layer ring tube 22 The radius of the ring body decreases in turn. The ring radii of the fourth layer ring tube body, the third layer ring tube body, the first layer ring tube body, the second layer ring tube body and the fifth layer ring tube body decrease in sequence. The first layer of ring tube is the CO gas distribution tube, the second, third, and fourth layer of ring tube correspond to the hemispherical bottom space, and the fifth layer of ring tube is the first four layers of ring tube. The supplement of the body on the plane and the vertical CO distribution, the five-layer porous ring tube body does not leave a dead angle in the plane area of the reactor, and it shows an overall upward trend. With the coalescence and separation of bubbles, the CO of the entire reactor space is realized. Evenly distributed. The inner diameter of the first-layer annular pipe body 27 is the largest, which is the CO gas distribution pipe, which is connected to the bottom and the central axis of the kettle and distributes the CO gas while also supporting the upper 4-layer annular pipe body The role of reinforcement. The distance between the first layer ring tube and the second layer ring tube, the distance between the second layer ring tube and the third layer ring tube, the third layer ring tube and the fourth The ratio of the distance between the layered ring tube body and the distance between the fourth layered ring tube body and the fifth layered ring tube body is 1: 1: 3-5: 2-3.

The diameter of the air holes on the porous ring tube body is 1-3 mm, and the space between the air holes is 3-6 mm.

The fluid stirring device is set in two sets, and the fluid flow control of a single set is 350-420m ³ / h to meet the requirement of full-scale mixing of gas and liquid in a large-volume reactor. Each set consists of a power pump, heat exchanger, fluid stirring tube and The structure of the nozzle is as follows: the reaction liquid flows out through the middle and enters the two sets of power pumps in two ways, the power pump outlet is connected to the heat exchanger, and the reaction liquid is cooled by the heat exchanger, and then enters the reaction from the top of the reactor The kettle continues to participate in the reaction. There are fluid stirring tubes inside the reactor. The angle between the two fluid stirring tubes and the center plane of the kettle is 90 °. The root of each fluid stirring tube is reduced in diameter to control the fluid flow rate of 10-25m / s. Fluid stirring effect, the nozzle of the fluid stirring tube should be between 200-500mm below the liquid level of the reactor. During operation, the reaction liquid enters into the reaction kettle from the top of the reaction kettle, flows down at high speed along the wall of the kettle, drives the surrounding liquid to change the vector, and flips up from the bottom of the reaction kettle, forming a number of different main flow layers. Double circulating flow state.

The CO distributor and fluid agitation device changed the condition that the mechanical agitation shaft seal and the transmission device were easily damaged during operation, and eliminated the dynamic sealing point, which greatly improved the safe and stable operation of the system. At the same time, the CO gas distribution was more uniform and the gas was improved. The liquid-liquid two-phase mixing effect improves the reaction rate and optimizes the reaction state of the system. The production capacity of the device is increased from 300,000 tons / year to 600,000 tons / year.

As shown in FIG. 8, the production device further includes a dealdehyde removal step. The dealdehyde removal step includes a delaminator 8, a dealdehyde remover 14 and a decanter 32. The inlet of the delaminator 8 and the top of the delightizer 7 Connected, the light phase outlet of the delaminator 8 is communicated with the top inlet of the deamination tower 14, the top outlet of the deamination tower 14 is connected to the inlet of the decanter 32 through the condenser, and the middle outlet of the decanter 32 is connected to the dealdehyde tower 14 is connected to the upper part, the lower outlet of the decanter 32 is connected to the delaminator 8, the upper outlet of the decanter 32 is connected to the waste liquid recovery device, and the bottom outlet of the dealdehyde removal tower 14 is connected to the delighting tower 7.

The process is as follows: the "light phase" in the delaminator enters the reflux pump of the de-lighting tower, and the pump outlet branches into the de-aldehyde tower. After the raw materials entering the dealdehyde removal tower are heated by the reboiler, the heat and medium are exchanged in the layers of packing from the bottom to the top of the dealdehyde removal tower. The gas-phase material containing higher reducing impurities concentrated at the top of the dealdehyde removal tower is condensed by the condenser and sent to the decanter for extraction operation. When the decanter is working, the pretreated material with higher concentration of reducing impurities is added through the top material extractant inlet, and then enters the funnel-shaped separator in the decanter barrel from the tangential inlet of the top material; The material rotates in the separator to generate centrifugal force, and the heavy components (mainly methyl iodide) are thrown toward the wall of the separator by the centrifugal force, and flow down along the wall to the outlet of the bottom of the separator, which is low flow. Impurities of light components (mainly acetaldehyde and crotonaldehyde) are extracted by the extractant and then rise, and overflow from the top material outlet. The lower part of the decanter is the settling chamber. After the underflow falls into the settling chamber, it is fused with the extractant to carry out the second settling stratification; after the settling stratification, the heavy phase at the bottom of the decanter returns to the system through the bottom material outlet to participate in the reaction. The mixed material with soft water is rectified several times through the lower reflux material outlet before returning to the system. The top light component reducing impurities are discharged into the waste acid storage tank through the upper material outlet and the middle material outlet. The device can increase the time for the product to reduce potassium permanganate fading, and reduce the content of propionic acid in the product.

As shown in FIG. 7, the finished product tower is provided with a deiodination device in the finished product extraction pipeline, including a first cooler 28, an adsorption tower 29, an ion exchange tower 30, and a second cooler 31 connected in sequence. The first cooling The device 28 is connected to the acetic acid outlet of the finished column 10.

The process is as follows: after the acetic acid produced from the finished product tower 10 is cooled to 100 ° C through the first cooler 28, it enters the adsorption tower 29, the pressure in the adsorption tower 29 is 0.2-0.5Mpa, the temperature is 40-138 ° C, and the internal setting The silver-loaded oxidant adsorbent layer removes the formic acid in acetic acid through the adsorption of the silver-loaded oxidant. The acetic acid from the adsorption tower 29 enters the ion exchange tower 30. The pressure of the ion exchange tower 30 is 0.2-0.5Mpa and the temperature is 80- At 100 ° C, a polystyrene type ion exchange resin layer is provided inside. Acetic acid is adsorbed by the polystyrene type ion exchange resin to remove iodine from acetic acid to obtain refined acetic acid. The acetic acid from the ion exchange tower 30 undergoes a second exchange The heater 31 is cooled, the temperature drops to 30-50 ° C, and then enters the storage tank for storage. After being removed by the deiodination device, the formic acid impurity content in acetic acid can be reduced to less than 30PPm, and the iodine content can be reduced to less than 10PPb.

The above are only the preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of this application shall be included in the protection scope of this application.

Claims

A production device for synthesizing acetic acid by methanol low-pressure carbonylation, characterized in that it comprises a reaction kettle, a conversion kettle, an evaporator, a pre-washing tower, a lightening tower, a dehydration tower, a finished product tower and a fluid stirring device, wherein the fluid is stirred The device includes at least two nozzles, a pump and a heat exchanger. The inlet end of the pump communicates with the middle of the reactor, the outlet end of the pump communicates with the inlet of the heat exchanger, and the fixed pipe of the nozzle is fixed on the top of the reactor. The outlet of the heat exchanger communicates with the end of the fixed pipe of the spray head. The spray head is located near the inner wall of the reaction kettle. The spray head is set 200-500 mm below the liquid level of the reaction kettle. The angle between the diameters of the two adjacent spray heads is 45 ° -90 °, the nozzle end of the nozzle is of a reduced diameter structure. During operation, the reaction liquid enters the reactor from the top of the reactor, and flows down along the wall at a high speed, causing the surrounding liquid to change the vector, and from the reactor The lower part is turned up, forming multiple double circulating flow states with different main flow layers;

The reactor is also provided with a CO distributor, which is installed at the bottom of the reactor. The CO distributor is formed by interconnecting 5 layers of porous ring tubes, and the first layer of ring tubes is in order from bottom to top. The second layer ring tube body, the third layer ring tube body, the fourth layer ring tube body and the fifth layer ring tube body, these 5-layer ring tube bodies are concentric structures;

The ring radii of the fourth layer ring tube body, the third layer ring tube body, the first layer ring tube body, the second layer ring tube body and the fifth layer ring tube body are successively reduced;

The inner diameter of the first-layer ring tube is the largest, which is the CO gas distribution tube, and is connected to the bottom of the kettle and the central axis;

The distance between the first layer ring tube and the second layer ring tube, the distance between the second layer ring tube and the third layer ring tube, the third layer ring tube and the fourth The ratio of the distance between the layered ring tube body and the distance between the fourth layered ring tube body and the fifth layered ring tube body is 1: 1: 3-5: 2-3.
The production device according to claim 1, wherein the number of the pumps is two, including the first pump and the second pump, and the number of the heat exchangers is two, including the first heat exchanger and the second In the heat exchanger, the first pump and the second pump are connected in parallel, and the first heat exchanger and the second heat exchanger are connected in parallel.
The production device according to claim 1, wherein the diameter of the air holes on the porous ring tube body of the CO distributor is 1-3 mm, and the air hole spacing is 3-6 mm.
The production device according to claim 1, characterized in that the production device further comprises a delaminator, a de-aldehyde tower and a decanter, the inlet of the delaminator is connected to the top of the de-lighting tower, the delaminator The light phase outlet is connected to the top inlet of the dealdehyde tower. The top outlet of the dealdehyde tower is connected to the inlet of the decanter through a condenser. The middle outlet of the decanter is connected to the upper part of the dealdehyde tower. The layerer is connected, and the upper outlet of the decanter is connected to the waste liquid recovery device;

The bottom outlet of the dealdehyde removal tower is connected with the delightening tower.
A production method of a production device for synthesizing acetic acid using low-pressure carbonylation of methanol according to any one of claims 1 to 4, characterized in that it includes the following steps:

1) CO gas enters the reaction kettle through the CO distributor at the bottom of the reaction kettle. After mixing methanol with dilute acid and methyl iodide, it enters the reaction kettle from the bottom of the reaction kettle. The material is stirred by a fluid stirring device under the action of a rhodium-based catalyst. Reacts to produce acetic acid;

2) After the reaction in the reaction kettle is completed, the reaction liquid enters the conversion kettle to continue the reaction;

3) The reaction liquid in the conversion kettle is depressurized by the flash valve and enters the evaporator, the gas phase enters the pre-wash tower for washing, and the liquid phase returns to the reaction kettle to continue to participate in the reaction;

4) After the gas phase of the evaporator is washed by the pre-washing tower, it enters the rectification and separation of the de-lighting tower, and the light components are separated at the top of the de-lighting tower; the crude acetic acid produced at the bottom of the de-lighting tower is dried by the dehydration tower and purified by the finished tower. Refined acetic acid;

The gas phase at the top of the delightening tower is condensed by the heat exchanger and enters the delaminator. Due to the difference in density, the light phase and the heavy phase are separated in the delaminator. The light phase enters the dealdehyde tower. The gas-phase material containing higher reducing impurities is condensed by the condenser and then sent to the decanter for extraction and centrifugation. The mixture of acetic acid and water in the middle part is returned to the dealdehyde tower, and the heavy phase at the bottom is returned to the layerer.
The production method according to claim 5, characterized in that: in step 1), the fluid flow rate provided by each pump of the fluid stirring device is 350-420m 3 / h; the fluid flow rate of each nozzle is 10-25m / s.
The production method according to claim 5, characterized in that in step 4), the acetic acid produced from the finished tower is cooled to 100 ° C and enters the adsorption tower, the pressure in the adsorption tower is 0.2-0.5Mpa, and the temperature is 40 -138 ℃, the formic acid in the acetic acid is stripped off by the adsorption of the silver-loaded oxidant. The acetic acid from the adsorption tower enters the ion exchange tower. The pressure of the ion exchange tower is 0.2-0.5Mpa, and the temperature is 80-100 ℃. The adsorption of ethylene ion exchange resin removes the iodine in acetic acid to obtain refined acetic acid. The acetic acid from the ion exchange tower is cooled by a heat exchanger, the temperature is reduced to 30-50 ℃, and then enters the storage tank for storage.