CN112871093B

CN112871093B - Reaction system for continuously removing damaged catalyst

Info

Publication number: CN112871093B
Application number: CN202110046192.XA
Authority: CN
Inventors: 薛勇勇; 乔小飞; 周兵; 刘鹏; 赵一鸣; 刘俊贤; 李金明; 杨颖�; 孙犀璨; 于丽君; 刘清贝
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2021-01-14
Filing date: 2021-01-14
Publication date: 2022-09-20
Anticipated expiration: 2041-01-14
Also published as: CN112871093A

Abstract

The invention discloses a reaction system for continuously removing damaged catalysts, which comprises an eccentric stirring reaction kettle, a Venturi ejector, a primary cyclone filter and a secondary cyclone filter, wherein a standing area is arranged above the eccentric stirring reaction kettle, a stirrer is arranged in the eccentric stirring reaction kettle, one or more liquid phase extraction ports are arranged on the standing area of the eccentric stirring reaction kettle and are connected with the Venturi ejector, overflow liquid and filtered clear liquid of the primary cyclone filter are mixed and then divided into two streams, one stream is used as a driving liquid phase of the Venturi ejector, and the other stream is mixed with the liquid phase at the outlet of the Venturi ejector and then enters the secondary cyclone filter. The invention realizes the continuous removal of damaged catalyst particles, reduces the damage amount of the catalyst caused by entering equipment such as a heat exchanger and the like, reduces the damage rate of the catalyst, improves the recovery rate of the complete catalyst and reduces the use cost of the catalyst.

Description

Reaction system for continuously removing damaged catalyst

Technical Field

The invention belongs to the field of chemical equipment and chemical raw materials, and particularly relates to a novel nitro compound hydrogenation reaction system for continuously removing a damaged catalyst.

Background

Aniline is an important chemical raw material and is mainly applied to the fields of dye, medicine, resin, rubber additive production and the like. The gas-phase catalytic hydrogenation and the liquid-phase catalytic hydrogenation of nitrobenzene are two main process routes for producing aniline, the current mainstream process in the world adopts a liquid-phase hydrogenation mode, and the reaction process of the nitrobenzene catalytic hydrogenation is as follows:

the stirred tank reactor is one of the commonly used reactors, and can be used for various reaction types such as liquid phase hydrogenation reaction and the like. In general, a catalyst is used in the reaction process, and due to the stirring, extraction, cooling and filtering processes in the reaction system, a part of the complete catalyst is damaged due to friction, collision, impact and the like, so that the crushed catalyst is inactivated, the activity of the catalyst in the reaction kettle is reduced, and the reaction conversion rate is reduced. Therefore, in order to ensure the efficient operation of the reaction process, fresh catalyst needs to be supplemented into the reaction system intermittently in operation, and part of the filtered waste catalyst is extracted, so that the purposes of replacing the catalyst and maintaining the activity of the catalyst in the reaction kettle are achieved by the method. Since a large amount of intact catalyst is mixed in the spent catalyst, catalyst replacement increases the consumption of fresh catalyst, which greatly increases the operating cost. Because the crushed catalyst has small granularity, the aggregation and blockage of equipment and pipelines are easily caused in the processes of extraction, circulation and the like, so the stability of production can be damaged, and even potential safety hazards can be brought. Because the number of the catalysts which are broken and deactivated in one operation period is increased gradually, the number of the active catalysts is reduced, and fresh catalysts are required to be added for maintaining the reaction activity, the solid content in a reaction system is high, the stirring power consumption is increased, and the operation stability and the operation elasticity of the reactor are poor. In the traditional catalyst filtering technology, a metal sintered filter element or a bag type filter is used for filtering reaction liquid, and catalyst particles can generate filter cakes on the filter element, so that the pressure drop is increased. Therefore, the breakage deactivation of the catalyst has a large influence on the reaction system.

The solution to this problem should take into account three aspects, first, reducing the amount of catalyst breakage; secondly, the separation of the broken catalyst and the complete catalyst is realized; thirdly, continuous extraction of the crushed catalyst. Patent CN102921478A proposes a method and a device for filtering and separating a catalyst in a reaction system for preparing hydrogen peroxide, which improves the non-recoverability of catalyst loss in the process of preparing hydrogen peroxide by arranging a pre-separator (in the form of a cyclone separator or a centrifugal separator) between a reactor and a filter, realizes partial recovery of the catalyst, and prolongs the service time of the filter; however, the patent does not consider the effect of the crushed catalyst on the reaction system, and does not mention the consideration of the reaction heat removal system and its interaction with the filtration system.

The typical nitrobenzene hydrogenation reaction system flow is as follows: under the continuous operation condition, the raw materials of nitrobenzene and hydrogen are continuously added into a stirred tank reactor; the unreacted hydrogen is compressed and then recycled to the reactor; continuously extracting reaction liquid with a certain flow from the reactor, wherein part of the reaction liquid is cooled and then returns to the reactor, and the rest part of the reaction liquid enters a subsequent separation unit after being filtered; the filtered catalyst is withdrawn from the filter intermittently and returned to the reactor or treated as spent catalyst, and fresh catalyst is replenished intermittently to the reactor. The flow chart of a typical nitrobenzene hydrogenation reaction system is shown in figure 1.

Patent CN102838510A proposes a method and a device for filtering and separating a catalyst of a reaction system for preparing cyclohexanone oxime, the method is similar to the method proposed by patent CN102921478A, and a filter system adopts a catalyst preseparator (in the form of a cyclone separator or a centrifugal separator) and a precise filter (a plate-and-frame filter, a metal sintered filter element or membrane separation equipment) to improve the production and operation period of the device and reduce energy consumption and material consumption; however, this patent does not consider the influence of the withdrawal of the crushed catalyst and the reduction of the catalyst activity on the reaction system, and changes the reaction heat removal manner from circulation cooling to jacket cooling of the outer wall of the reactor, which lowers the heat removal efficiency of the reactor.

Patent CN203494525U proposes a catalyst filtering and recycling device, which considers the problem of catalyst recycling, but does not solve the problems of catalyst breakage, catalyst blockage, catalyst activity reduction, and reaction heat transfer.

Patent CN207294648U relates to a liquid phase hydrogenation catalyst filtering, separating and recovering device, when the activity of the catalyst in the aniline reactor is reduced or partially deactivated, the device proposed in the patent can be used to separate the catalyst solid with reduced activity or deactivated, and by adding fresh catalyst, the activity of the catalyst in the reactor can be maintained to meet the production requirement; however, the patent does not consider the problem of excessive consumption of fresh catalyst.

Patent CN104771949A discloses a filtering system for slurry bed reactor, which only provides a solution to the problems of easy formation of filter cake and poor back-flushing effect when the filter element is installed inside the reactor.

Therefore, a perfect idea for solving the above problems is lacking. Therefore, a new nitrobenzene hydrogenation reaction system is needed to solve the problems of large catalyst damage, easy equipment blockage, high catalyst consumption, low catalyst activity, large filter pressure drop and the like.

Disclosure of Invention

The invention aims to provide a reaction system for continuously removing damaged catalyst, which can realize continuous removal of damaged catalyst particles, reduce the possibility of blocking heat exchanger equipment by subdividing the catalyst, reduce the consumption of fresh catalyst, improve the operation stability of the reaction system and save the cost.

In order to solve the problems, the technical scheme of the invention is as follows:

a reaction system for continuously removing damaged catalysts comprises an eccentric stirring reaction kettle, a Venturi ejector, a first-stage cyclone filter, a second-stage cyclone filter, a filter and a reaction liquid recovery tank, wherein a standing area is arranged above the eccentric stirring reaction kettle, a stirrer is arranged in the eccentric stirring reaction kettle, the eccentricity of the stirrer is 0.2-0.5, one or more liquid-phase extraction ports are arranged on the standing area of the eccentric stirring reaction kettle and connected with the Venturi ejector, overflow liquid of the first-stage cyclone filter 7 and filtered clear liquid are mixed and then divided into two streams, one stream is used as driving liquid of the Venturi ejector 6, the other stream is mixed with liquid at the outlet of the Venturi ejector 6 and then enters the second-stage cyclone filter 8, underflow liquid of the first-stage cyclone filter returns to the eccentric stirring reaction kettle 5, overflow liquid of the second-stage cyclone filter 8 returns to the eccentric stirring reaction kettle 5 after being cooled, the bottom flow enters a reaction liquid recovery tank 20 to separate out the damaged catalyst.

Preferably, the standing area is arranged above the center of the stirring reaction kettle 5, the standing area is cylindrical, and the inner diameter of the cylindrical standing area is 20% -50% of the inner diameter of the reaction kettle, preferably 20% -40%; the length-diameter ratio of the cylindrical standing area 13 is 2-8, and preferably 3-5.

Preferably, the eccentricity ratio of the stirrer of the eccentric stirring reaction kettle 5 is 0.2-0.45;

when the inner diameter of the cylindrical standing area is less than 20 percent of the inner diameter of the reaction kettle, because the gas phase is extracted from the top of the cylindrical standing area, when the inner diameter of the cylindrical standing area is too small, the influence caused by the disturbance of rising bubbles in the reaction liquid is greatly increased, the stability of the liquid phase in the standing area is damaged, and the effect of the particle size layering of the catalyst in the standing area is poor; when the inner diameter of the cylindrical standing area is more than 50%, the eccentricity set by the eccentric stirrer is too large, and when the eccentricity of the eccentric stirrer exceeds 0.5, the stirring effect begins to be poor, so that the phenomenon of uneven stirring can occur; the internal diameter of the cylindrical standing zone is therefore 20% to 50%, preferably 20% to 40%, of the internal diameter of the stirred tank. The length-diameter ratio of the cylindrical standing area is not suitable to be too large, because the content of the broken catalyst is gradually reduced along with the rising of the height, the content of the broken catalyst in a liquid phase at the height is extremely low, and the too large length-diameter ratio increases a reaction dead zone and reduces the reaction conversion rate; when the length-diameter ratio is too small, the catalyst particle size layering effect in the standing zone cannot be achieved.

Preferably, 1-4 extraction ports, preferably 1-3 extraction ports are longitudinally arranged on the side surface of the cylindrical standing area 13, the distance between the extraction ports is 10% -20% of the total length of the cylindrical standing area, and each extraction port is provided with a valve for controlling opening and closing.

In the invention, the side surface of the cylindrical standing area 13 is longitudinally provided with a mining outlet, and each mining outlet is required to be provided with a valve for controlling the opening and the closing. The number of the extraction outlets is not suitable to be set too small, the suspension condition is changed because the particle size of the crushed catalyst is not a fixed value, and the operation flexibility of the reaction system with few extraction outlets is reduced; too many extraction ports are not suitable, equipment investment is increased due to the excessive extraction ports, the distance between the extraction ports is too small, redundancy exists in design, and operation complexity is increased.

In some preferred embodiments of the present invention, the distance between the stirring blade on the side of the stirrer close to the reaction kettle and the inner side wall surface of the reaction kettle is 2% to 10%, preferably 4% to 8%, of the inner diameter of the reaction kettle; the distance between the stirring blade and the inner side wall surface of the reaction kettle is not too far, the fluid stirring effect near the wall surface with too far distance is poor, and the reaction conversion rate is influenced; the distance from the inner side wall surface of the reaction kettle is too close, which influences the arrangement of the baffle. The agitator sets up 1 ~ 3 of stirring rake, preferred 1 ~ 2. Too few stirring paddles have poor distribution effect of the catalyst in the reaction kettle, and too much stirring energy consumption is too high.

The distance between the stirring blade at the bottommost part and the bottom of the reaction kettle is 1-10%, preferably 2-5% of the height of the main body part (not containing the cylindrical standing zone (13)) of the eccentric stirring reaction kettle. The stirring blade pitch is too far away from the bottom of the reaction kettle, the catalyst is easy to deposit at the bottom of the reaction kettle, the distance from the bottom is too close, and the stirring effect at the center of the reaction kettle is poor.

In the reaction system, reaction raw materials are respectively sent into an eccentric stirring reaction kettle 5 by a raw material feeding pump. Unreacted recycle hydrogen is extracted from the cylindrical standing zone 13, mixed with fresh hydrogen, pressurized by a recycle hydrogen compressor 4 and returned to the eccentric stirring reaction kettle 5. Fresh catalyst can be supplemented into the reaction kettle, and the adding amount of the fresh catalyst is determined by the amount of the extracted broken catalyst and the activity condition of the catalyst. Baffle 11 is arranged on the inner wall surface of the eccentric stirring reaction kettle 5.

The eccentric stirring reaction kettle adopted by the invention can enhance the stirring effect, so that the catalyst is suspended more uniformly in the reaction kettle, the amount of the catalyst settled at the bottom of the reaction kettle is reduced, the entrainment of the catalyst in the circulating reaction liquid is reduced, and the eccentric stirring energy consumption is lower under the same stirring effect. Through setting up eccentric stirring, can set up cylindrical district that stews in reation kettle top, damaged catalyst can be accumulated in reation kettle top because the granule is little, light in weight, can be in succession, timely the damaged catalyst of adopting through this setting, has realized the continuous extraction of catalyst, has practiced thrift time and cost. The baffle 11 arranged in the reaction kettle can form a flow field circulating up and down in the reaction kettle, and the stirring effect is enhanced.

A cylindrical standing area is arranged on the central axis above the eccentric stirring reaction kettle 5, and the cylindrical standing area is used for layering large complete catalyst particles and small broken catalyst particles; the principle is that because the diameter of cylindrical region of stewing is far less than the diameter of stirred tank, so the fluid flow that causes because of the stirring in the stirred tank is less to the disturbance in the region of stewing, consequently the region of stewing is comparatively stable, broken catalyst particle in the stirred tank floats up to cylindrical region of stewing along with the stirring, and comparatively complete large granule catalyst is difficult to float up to cylindrical region of stewing because of the action of gravity, and the suspension participates in the reaction in the stirred tank. The side surface of the standing area is provided with a plurality of liquid phase extraction ports, each extraction port is longitudinally arranged and is respectively provided with a valve, and the extraction ports arranged at different positions can select different extraction positions according to the floating position of the crushed catalyst and the content of the crushed catalyst in the standing area, so that the operation flexibility is improved.

Reaction liquid with damaged catalyst in the standing area is sucked by the Venturi ejector 6, the driving liquid phase is a strand of liquid phase formed by mixing overflow liquid from the primary cyclone filter 7 and filtered clear liquid, and the liquid phase at the outlet of the Venturi ejector 6 is mixed with residual overflow liquid and filtered clear liquid of the primary cyclone filter 7 and then enters the secondary cyclone filter 8; the venturi ejector 6 is employed for the reason that: firstly, sucking reaction liquid carrying broken catalyst by using a Venturi tube; secondly, the high-speed turbulent liquid injection in the Venturi tube can avoid blockage caused by deposition of broken catalyst particles in the pipeline in the suction process; thirdly, since the extraction position and the suction volume may need to be frequently adjusted during the operation, the service life of the equipment may be shortened if the centrifugal pump is used for frequent adjustment, and the venturi ejector is used to avoid the problem, so that the operation of the system has stronger flexibility.

The reaction liquid extracted from the bottom of the eccentric stirring reaction kettle 5 is pressurized by a reaction liquid circulating pump 3 and then enters a primary cyclone filter 7, and the function of the cyclone filter is to separate out large-particle catalysts carried in the reaction liquid; the underflow liquid containing large catalyst particles returns to the reaction kettle 5 from the bottom of the primary cyclone filter 7, and the catalyst is redistributed in the reactor under the stirring action; the suction amount of the entrained crushed catalyst reaction liquid is controlled by the flow control valve 16 to drive the liquid phase flow to be adjusted. The large-particle catalyst in the circulating reaction liquid can be recovered by adopting a primary cyclone filter; moreover, the method adopts the first-stage cyclone filter, so that the continuous operation can be realized, the back flushing is not needed, the treatment capacity is larger, a filter cake is not formed, the pressure drop is smaller, the operation procedures are reduced, and the operation cost is reduced. The first-stage cyclone filter is provided with a bottom flow extraction line, and when the activity of the catalyst in the reactor becomes low, part of the catalyst can be extracted and fresh catalyst can be supplemented to maintain the activity of the catalyst in the reactor.

The liquid phase at the outlet of the Venturi ejector 6 is mixed with the overflow liquid and the filtered clear liquid of the primary cyclone filter 7 and then enters the secondary cyclone filter 8, and the effect of the secondary cyclone filter is to filter the inactivated broken catalyst and extract the catalyst from the reaction system.

Preferably, the overflow liquid outlet pipeline of the second-stage cyclone filter is also connected with a filter 12, and the overflow liquid is cooled by a cooler after being filtered by the filter 12 and returns to the eccentric stirring reaction kettle. Since there is a possibility that the catalyst powder having a small particle diameter may be entrained from the overflow liquid of the second-stage cyclone filter 8, the filter 12 is provided to filter the overflow liquid, thereby preventing the cooler from being clogged with the catalyst powder that has not been filtered by the second-stage cyclone filter.

The filter 12 is a filter with a metal sintered mesh.

The overflow liquid at the top of the secondary cyclone filter 8 enters a filter 12, a bypass is arranged to adjust the flow passing through the filter 12, and the filter is controlled to be opened and closed by gate valves at two sides; when the filter 12 is in normal use, the flow into the filter 12 is regulated by the filter bypass control valve 18; when the filter 12 is cut to change cartridges, the bypass control valve is fully open and the filter 12 is closed by gate valves on both sides. The purpose of the two-stage cyclone filter is to remove the broken catalyst in the reaction solution. In the first-stage cyclone filter 7, the relatively complete large-particle catalyst returns to the reaction kettle along with the underflow, and the crushed catalyst is light in weight and is entrained out of the first-stage cyclone filter along with the overflow liquid, so that the majority of the crushed catalyst entering the second-stage cyclone filter 8 is the crushed catalyst with a small particle size, and the crushed catalyst flows into the reaction liquid recovery tank 20 along with the underflow of the second-stage cyclone filter 8.

The underflow liquid of the secondary cyclone filter 8 automatically flows into the reaction liquid recovery tank 20, and the reaction liquid recovery tank 20 is arranged to recover the reaction liquid in the underflow liquid of the secondary cyclone filter 8. Because the underflow liquid is a liquid phase with high catalyst particle concentration, a large amount of reaction liquid still exists and needs to be recycled. The reaction liquid recovery tank 20 is divided into two horizontal areas by a partition plate, namely an underflow liquid standing area and a clear liquid area, the underflow liquid enters the bottom 20 of the underflow liquid standing area through a pipeline, catalyst particles are settled and accumulated in the area, clear liquid on the upper layer of the liquid phase overflows to the clear liquid area, and liquid in the clear liquid area is pressurized and returned to the reaction kettle 5 through a reaction liquid recovery pump 21. And extracting a concentrated liquid phase containing the broken catalyst from the bottom of the underflow liquid standing area.

The outlet filtrate of the filter 12 is combined with the filtrate of the second-stage cyclone filter 8 and then enters the reaction system cooler 9. The reaction system cooler is used for removing reaction heat to maintain the heat balance of the reaction system. The cooler is bypassed and the flow through the cooler is controlled by a cooler bypass control valve 19. The liquid phase at the outlet of the cooler is mixed with the liquid phase at the bypass and then divided into two streams, one stream is extracted to a subsequent refining and separating unit, and the other stream is returned to the reaction kettle 5.

The key parameters and the parameter selection principle of the invention are as follows:

in the invention, a cylindrical standing area 13 is arranged above the center of a stirring reaction kettle 5;

in the present invention, the residence time of the reaction liquid recovery tank 20 is 10min to 1h, preferably 10min to 30 min. The reaction liquid recovery tank 20 has too long retention time, the volume of the reaction recovery tank is increased, the equipment investment is increased, a large amount of reaction liquid stays in the reaction liquid recovery tank, the crushed catalyst still has a certain catalytic action, and the retention time is too long, so that the generation of side reaction products is increased; the retention time is too short, the settling time of the broken catalyst is insufficient, the separation effect of the broken catalyst and the reaction liquid is poor, and part of the broken catalyst is pumped back into the reaction kettle, so that the energy consumption is increased.

The invention relates to three-stage filtration, wherein a first-stage cyclone filter 7 filters catalyst particles with the particle size of more than or equal to 10 mu m, a second-stage cyclone filter 8 filters catalyst particles with the particle size of less than 10 mu m, and a filter 12 filters catalyst particles with the particle size of less than 5 mu m. As the particle size of the broken catalyst particles is less than 10 mu m, the first-stage cyclone filter filters the catalyst particles with the particle size of more than or equal to 10 mu m. If the filter particle size is too large, a part of the whole catalyst will be lost, increasing the consumption of fresh catalyst, and if the filter particle size is too small, a part of the crushed catalyst will not be removed from the reaction system.

The invention has the positive effects that:

(1) the complete catalyst is separated from the broken catalyst, so that the broken catalyst particles are continuously removed, the breakage of the catalyst caused by entering equipment such as a heat exchanger is reduced, the damage rate of the catalyst is reduced, and the replacement cost of the catalyst is reduced;

(2) the broken catalyst and the catalyst powder with extremely small particle size are removed before the circulating reaction liquid enters the cooler, so that the possibility of blocking equipment such as a heat exchanger by the catalyst powder is greatly reduced, and the stable operation time of a reaction system is prolonged;

(3) the complete catalyst and the broken catalyst are separated by the first-stage cyclone filter and the second-stage cyclone filter, so that the recovery rate of the complete catalyst is improved, the amount of the fresh catalyst to be supplemented is reduced, the consumption of the fresh catalyst is reduced, the unit consumption of the catalyst can be reduced by 70%, and the use cost of the catalyst is saved.

(4) Higher catalyst activity can be maintained in the reaction kettle, and the reaction kettle adopts eccentric stirring, so that the stirring shaft work is further reduced by 30%;

(5) avoiding larger pressure drop caused by filter cakes, saving pump power consumption and reducing pump power consumption by about 20 percent

(6) The operation stability and the operation flexibility of the reaction system are increased.

Drawings

FIG. 1 shows a novel reaction system for hydrogenation of nitro compound of example 1 of the present invention.

FIG. 2 is a schematic diagram of a nitrobenzene hydrogenation reaction system of a comparative example.

In the figure: 1. a nitrobenzene feed pump; 2. a water feed pump; 3. a reaction liquid circulating pump; 4. a recycle hydrogen compressor; 5. an eccentric stirring reaction kettle; 6. a venturi ejector; 7. a first-stage cyclone filter; 8. a second stage cyclone filter; 9. a reaction system cooler; 10. a stirrer; 11. a baffle plate; 12 a filter; 13 a cylindrical resting zone; 14. a venturi ejector suction inlet valve; 15. an inlet valve of a reaction liquid circulating pump; 16. a flow control valve; 17. a catalyst intermittent production pipe valve; 18. a filter bypass control valve; 19. a cooler bypass control valve; 20. a reaction liquid recovery tank; 21. a reaction liquid recovery pump, 22. a stirred tank reactor.

Detailed Description

The technical solution of the present invention is illustrated by the following specific examples, which show specific implementation and specific operation procedures, but the scope of the present invention is not limited to the following examples.

Example 1

Referring to FIG. 1, the eccentric stirring reaction vessel 5 used in the example of the present invention has a volume of 48m ³ (not containing reaction standing area), the inner diameter is 3m, the upper end of the eccentric stirring reaction kettle is provided with a cylindrical standing area, the inner diameter is 0.9m, the height is 3.6m, the length-diameter ratio is 4, the side surface is longitudinally provided with 3 extraction ports, and the interval of each extraction port is 0.5 m. Set up eccentric agitator in the stirred tank, the eccentricity is 0.4, and the agitator sets up 2 stirring rakes, and the stirring rake of lower extreme is 0.05m from the reactor bottom, and stirring vane is 0.2m apart from the cauldron inside wall nearest distance. 4 baffles are symmetrically arranged on the inner side wall of the kettle, and the width of each baffle is 0.125 m. The particle size of the catalyst is 0.1-50 μm.

In the embodiment of the invention, a nitrobenzene catalytic hydrogenation reaction is taken as an example to introduce the reaction system of the application.

Pressurizing nitrobenzene by a nitrobenzene feed pump 1, and then feeding the nitrobenzene into an eccentric stirred tank reactor 5 at the flow rate of 20000 kg/h; water is pressurized by a water feeding pump 2 and then is sent into an eccentric stirred tank reaction kettle 5, and the water flow is 21423 kg/h; pressurizing the circulating hydrogen to 2.2MPa by a circulating hydrogen compressor, and then sending the circulating hydrogen into an eccentric stirring reaction kettle 5, wherein the flow rate of the circulating hydrogen is 157.14kg/h, and the flow rate of fresh hydrogen is 1012 kg/h; the eccentric stirring reaction kettle adopts a Pt/Pd catalyst loaded with activated carbon, and the mass concentration of the catalyst in the reaction kettle is 2.3%. Nitrobenzene and hydrogen react in a stirred tank reactor at a pressure of 1.7MPa and a temperature of 220 ℃ to produce aniline and water. The agitator power consumption during operation was 1.5 kw.

155574kg/h of reaction liquid is extracted from the bottom of the eccentric stirring reaction kettle 5 and enters the first-stage cyclone filter 7 after being pressurized by the reaction liquid circulating pump 3, 3308kg/h of bottom flow liquid returns to the eccentric stirring kettle 5, and 165kg/h of catalyst is carried in the bottom flow. The overflow liquid and the filtrate are mixed together for 152266kg/h and divided into two parts, one part is 3067kg/h and used as the driving liquid phase of the Venturi ejector 6, the other part is 149199kg/h, and the mixed liquid is combined with 3089kg/h of liquid at the inlet of the Venturi ejector for 152288kg/h and enters the secondary cyclone filter 8. The venturi ejector 6 sucks 22kg/h of the reaction liquid with the crushed catalyst, and the reaction liquid is sucked from the venturi ejector suction inlet valve 14 (in the present embodiment, the uppermost suction inlet valve is opened, and the other valves are closed). Two stage cyclone filter<10 μm crushed catalyst particles, 17kg/h underflow entrained crushed catalyst into the reaction liquid recovery tank, entrained about 300ppm<152169kg/h of overflow of 5 μm catalyst powder was introduced into the filter 12, and 102kg/h of the clear solution was filtered. The filter was back flushed every 5 months. Fresh catalyst was replenished at 0.2 kg/h. The filter was a 1 μm metal sintered mesh. 152169kg/h of filtrate at the outlet of the filter 12 is mixed with clear filtrate of the second-stage cyclone filter, and 152271kg/h of liquid enters a reaction system cooler. The reaction liquid is cooled to 40 ℃ and then divided into two parts, one part is taken as a reaction product and enters 42433kg/h into a subsequent separation and refining unit, and the other part is 112905kg/h of reaction liquid and returns to the reaction stirring kettle 5. The bottom flow of the second-stage cyclone filter 8 is 17kg/h and enters a reaction liquid recovery tank 20, and the volume of the recovery tank is 0.03m ³ 2.3kg/h of liquid phase carrying 8% of crushed catalyst is extracted from the bottom of the reaction liquid standing zone in the reaction liquid recovery tank 20, and 14.7kg/h of reaction liquid is extracted from the clear liquid zone and pumped back to the reaction kettle 5 by a pump reaction liquid recovery pump 21. The pressure drop of the mixture passing through the primary cyclone filter is 70kpa, and the pressure drop of the mixture passing through the secondary cyclone filter is two stagesThe rotational flow filter is 40kpa, the pressure drop of the filter is 120kpa, the total pressure drop is 0.230MPa, and the power of the reaction liquid circulating pump is 140 kw. The novel reaction system stably runs for 10 months without the blockage phenomenon of a cooler.

Comparative example

As shown in figure 2, nitrobenzene is pressurized by a nitrobenzene feed pump and then sent into a stirred tank reactor, and the flow rate is 20000 kg/h; pressurizing water by a water feeding pump, and then feeding the water into a stirred tank reactor, wherein the water flow is 21423 kg/h; pressurizing the circulating hydrogen to 2.2MPa by a circulating hydrogen compressor, and then sending the circulating hydrogen into a stirring reaction kettle, wherein the flow rate of the circulating hydrogen is 157.14kg/h, and the flow rate of the fresh hydrogen is 1012 kg/h; the stirring reaction kettle adopts a Pt/Pd catalyst loaded with activated carbon, and the mass concentration of the catalyst in the reaction kettle is 3.1 percent (mass fraction). Nitrobenzene and hydrogen react in a stirred tank reactor at a pressure of 1.7MPa and a temperature of 220 ℃ to produce aniline and water. The grain diameter of the catalyst in the reaction kettle is 0.1-50 μm.

152272kg/h of reaction liquid is extracted from the bottom of the stirring kettle, pressurized by a reaction liquid circulating pump and then sent into a cooler, and then the reaction liquid enters a filter after being cooled to 40 ℃. The filter backflushes once every 5min, 0.6kg of catalyst is extracted as waste catalyst every one hour, the rest catalyst returns to the reaction kettle and is supplemented with 0.6kg of fresh catalyst, and the filter filters catalyst particles with the particle size of more than 1 mu m. The filtrate extracted from the filter is divided into two parts, one part is taken as a reaction product, 42435kg/h of liquid phase is extracted to enter a subsequent refining separation unit, the other part is 109836kg/h and returns to the reaction kettle, and the pressure drop of the filter is 0.3 Mpa. The stirring power was 2.2kw and the pump power consumption was 179 kw. The reaction system needs to stop and clean the catalyst powder in the cooler every 6 months, and if the catalyst powder is not cleaned in time, the cooler can be blocked.

By comparing the examples with the comparative examples, it can be found that: in the examples, 3200kg/a of catalyst was consumed less than that in comparative example, 0.7kw of stirring power was consumed less, 39kw of power of a reaction liquid circulation pump was consumed less, and total pressure drop by a filter was reduced by 0.07 Mpa.

Since the broken catalyst powder accumulated in the stirred tank reactor in the comparative example and the catalyst powder had been deactivated, the catalyst content in the stirred tank reactor in the comparative example was required to be larger than that of the eccentric stirred tank in example 1 to achieve a catalyst concentration of 3.1% (mass fraction) under the same conversion rate.

Claims

1. The reaction system for continuously removing the damaged catalyst is characterized by comprising an eccentric stirring reaction kettle (5), a Venturi ejector (6), a first-stage cyclone filter (7), a second-stage cyclone filter (8) and a reaction liquid recovery tank (20), wherein a standing area (13) is arranged above the eccentric stirring reaction kettle (5), a stirrer is arranged in the eccentric stirring reaction kettle (5), the eccentricity of the stirrer is 0.2-0.5, one or more liquid-phase extraction ports are arranged on the standing area of the eccentric stirring reaction kettle, the liquid-phase extraction ports are connected with the Venturi ejector (6), overflow liquid and filtered clear liquid of the first-stage cyclone filter (7) are divided into two streams after being mixed, one stream is used as a driving liquid phase of the Venturi ejector (6), the other stream is mixed with the liquid phase at the outlet of the Venturi ejector (6) and then enters the second-stage cyclone filter (8), and bottom liquid of the first-stage cyclone filter (7) returns to the eccentric stirring reaction kettle (5), the overflow liquid of the second-stage cyclone filter (8) is cooled and then returns to the eccentric stirring reaction kettle (5), and the bottom flow liquid enters a reaction liquid recovery tank (20) to separate out damaged catalyst;

the standing area is cylindrical, and the inner diameter of the cylindrical standing area is 20-50% of the inner diameter of the reaction kettle;

the reaction liquid extracted from the bottom of the eccentric stirring reaction kettle (5) is pressurized by a reaction liquid circulating pump (3) and then enters a primary cyclone filter (7).

2. The reaction system according to claim 1, wherein the rest zone (13) is arranged centrally above the stirred tank reactor (5).

3. The reaction system of claim 1, wherein the inner diameter of the cylindrical standing zone is 20-40% of the inner diameter of the reaction kettle; the length-diameter ratio of the cylindrical standing area is 2-8.

4. The reaction system of claim 3, wherein the aspect ratio of the cylindrical standing section is 3 to 5.

5. The reaction system of claim 1, wherein 1-4 extraction ports are longitudinally arranged on the side surface of the cylindrical standing zone (13), the distance between the extraction ports is 10% -20% of the total length of the cylindrical standing zone, and each extraction port is provided with a valve for controlling opening and closing.

6. The reaction system of claim 5, wherein 1-3 extraction ports are longitudinally arranged on the side surface of the cylindrical standing zone (13).

7. The reaction system of claim 1, wherein the distance between the stirring blade on the side of the stirrer close to the reaction kettle and the inner side wall surface of the reaction kettle is 2-10% of the inner diameter of the reaction kettle; 1-3 stirring paddles are arranged on the stirrer;

the distance between the stirring blade at the bottommost part and the bottom of the reaction kettle is 1-10% of the height of the main body part of the eccentric stirring reaction kettle.

8. The reaction system of claim 7, wherein the distance between the stirring blade on the side of the stirrer close to the reaction kettle and the inner side wall surface of the reaction kettle is 4-8% of the inner diameter of the reaction kettle; 1-2 stirring paddles are arranged on the stirrer;

the distance between the stirring blade at the bottommost part and the bottom of the reaction kettle is 2-5% of the height of the main body part of the eccentric stirring reaction kettle.

9. The reaction system of claim 1, wherein a baffle 11 is arranged on the inner wall surface of the eccentric stirring reaction kettle (5).

10. The reaction system of claim 1, wherein the eccentricity ratio of the stirrer of the eccentric stirring reaction kettle (5) is 0.2-0.45.

11. The reaction system of claim 1, wherein the reaction liquid with the damaged catalyst in the standing zone (13) is sucked by the venturi ejector (6), the driving liquid phase is a liquid phase obtained by mixing overflow liquid from the primary cyclone filter (7) with clear filtrate, and the liquid phase at the outlet of the venturi ejector (6) is mixed with the residual overflow liquid and clear filtrate of the primary cyclone filter (7) and then enters the secondary cyclone filter (8);

the underflow liquid containing large catalyst particles returns to the reaction kettle (5) from the bottom of the primary cyclone filter (7), and the catalyst is redistributed in the reactor under the action of stirring.

12. The reaction system of claim 1, wherein the liquid phase at the outlet of the venturi ejector (6) is mixed with the overflow liquid and the filtered clear liquid of the primary cyclone filter (7) and then enters the secondary cyclone filter (8) to filter the deactivated broken catalyst.

13. The reaction system of claim 1, wherein the overflow liquid outlet pipeline of the secondary cyclone filter is further connected with a filter (12), and the overflow liquid outlet pipeline is cooled by a cooler after being filtered by the filter (12) and returns to the eccentric stirring reaction kettle.

14. A reaction system according to claim 13, wherein the filter (12) is a filter with a metal sintered mesh.

15. The reaction system of claim 1, wherein the underflow of the secondary cyclone filter (8) enters the reaction liquid recovery tank (20) from the flow.

16. The reaction system according to claim 1, wherein the reaction liquid recovery tank (20) comprises an underflow liquid standing zone and a clear liquid zone, and liquid in the clear liquid zone is pressurized and returned to the reaction kettle (5) through a reaction liquid recovery pump (21); and extracting the concentrated liquid phase containing the broken catalyst from the bottom of the underflow liquid standing zone.

17. The reaction system according to claim 1, wherein the residence time of the reaction liquid recovery tank (20) is 10min to 1 h.

18. The reaction system according to claim 17, wherein the residence time of the reaction liquid recovery tank (20) is 10 to 30 min.

19. The reaction system of claim 1, wherein the outlet filtrate of the filter (12) is combined with the filtrate of the second-stage cyclone filter (8) and then enters the reaction system cooler (9), one is taken out and sent to a subsequent refining separation unit, and the other is returned to the eccentric stirring reaction kettle (5).