Method and system for non-stop catalyst replacement of chemical reaction device

Abstract

The invention relates to a method and a system for non-stop catalyst replacement of a chemical reaction device. The method comprises the following steps: discharging part of materials in a chemical reaction device from a liquid-solid phase discharging pipeline, filling a first circulating pipeline and a pump cavity of a first circulating pump, and settling; a new catalyst is conveyed from the catalyst supply source to the liquid-solid phase discharging pipeline and returns to the chemical reaction device through the second circulating pipeline and the second circulating pump; after the chemical reaction device receives the new catalyst input from the second circulating pump, a second material in the new catalyst is uniformly mixed; the effective catalyst content in the second material is calculated, if the effective catalyst content in the second material is larger than or equal to a preset effective catalyst content threshold value, refund and replacement are stopped, and if the effective catalyst content in the second material is lower than the preset effective catalyst content threshold value, the settling and refund and replacement steps are repeated. According to the method and the system, the catalyst of the chemical reaction device can be recycled and replaced without stopping.

Description

Technical Field

[0001] The present invention relates to a method and system for replacing a catalyst in a chemical reaction device, and in particular to a method and system for replacing a catalyst in a chemical reaction device without stopping the device. Background Art

[0002] In the chemical production process, the catalytic reaction device is one of the core equipment, and the activity of the catalyst is directly related to the reaction efficiency and product quality. As the reaction proceeds, the activity of the catalyst will gradually be lost or deactivated, so it needs to be replaced regularly to maintain the reaction efficiency. The traditional catalyst replacement method usually requires a shutdown operation, that is, stopping the operation of the reaction device, emptying the reaction materials, and then unloading, cleaning and refilling the deactivated catalyst with fresh catalyst. However, the shutdown operation will lead to production interruption, increased energy consumption, re-inflating and pressurization, and safety hazards caused by frequent start-up and shutdown of equipment. Especially for large-scale continuous production equipment, the economic losses caused by stopping the catalyst for replacement are particularly significant.

[0003] In the existing technology, some improvement schemes attempt to optimize by reducing downtime or simplifying the operating procedures. For example, partial catalyst withdrawal can be achieved through a multi-stage reactor series design, or the catalyst online regeneration technology can be used to extend the service life. However, these methods still have limitations: the multi-stage reactor design leads to high equipment complexity and a sharp increase in investment costs; and the online regeneration technology is only applicable to specific types of catalysts, and the regeneration effect is subject to process conditions, and it cannot completely solve the problem of physical loss or permanent deactivation of the catalyst. In addition, the small number of non-stop withdrawal schemes involved in the existing technology mostly rely on complex diversion systems or reaction devices with special structures. In actual operation, problems such as incomplete catalyst withdrawal, uneven mixing of new and old catalysts, and interference with reaction stability during the withdrawal process are prone to occur.

[0004] To address the above issues, there is an urgent need to develop an efficient, stable and non-stop catalyst replacement method suitable for conventional liquid-solid phase reaction units, which can achieve accurate catalyst replacement and content control while maintaining continuous reaction operation, thereby reducing the risk of production interruption and improving the economic efficiency of unit operation. Summary of the Invention

[0005] In view of this, the present invention provides a method for non-stop catalyst replacement for a chemical reaction device, wherein a liquid-solid phase discharge pipeline of the chemical reaction device is connected to a first circulation pump through a first circulation pipeline, and is connected to a second circulation pump through a second circulation pipeline. The method comprises the following steps:

[0006] S101: discharging a portion of the first material in the chemical reaction device from the liquid-solid phase discharge pipeline, filling the first circulation pipeline and the pump cavity of the first circulation pump, and settling;

[0007] S102: delivering new catalyst from the catalyst supply source to the liquid-solid phase discharge pipeline, and returning the catalyst to the chemical reaction device via the second circulation pipeline and the second circulation pump;

[0008] S103: after the chemical reaction device receives the new catalyst input from the second circulation pump, uniformly mixing the second material in the chemical reaction device;

[0009] S104: Calculate the effective catalyst content in the second material,

[0010] If the mass percentage of the effective catalyst in the second material relative to the total amount of catalyst is greater than or equal to the maximum threshold value of the predetermined effective catalyst content, the return is stopped.

[0011] If the effective catalyst content in the second material is lower than the predetermined minimum threshold of the effective catalyst content, steps S101 to S103 are repeated.

[0012] Furthermore, in step S101, the discharged portion of the first material accounts for 30% to 50% of the total amount of the first material.

[0013] In step S102 , the amount of new catalyst delivered from the catalyst supply source to the liquid-solid phase discharge pipeline is equal to the amount of catalyst discharged in step S101 .

[0014] Furthermore, the chemical reaction device is a benzene hydrogenation reaction device.

[0015] The maximum threshold of the effective catalyst content is defined as the mass of the effective catalyst being 80% of the total mass of the catalyst; and / or the minimum threshold of the effective catalyst content is defined as the mass of the effective catalyst being 30% of the total mass of the catalyst.

[0016] According to one embodiment, the chemical reaction device is connected to the post-reaction device via a gas phase discharge pipeline, and the method further comprises, before step S101:

[0017] S100: measuring the temperature in the post-reaction device and the effective catalyst content in the chemical reaction device corresponding to the temperature.

[0018] According to another embodiment, when steps S101 to S103 are repeated, one of the first circulation line and the first circulation pump or the second circulation line and the second circulation pump is optionally used in step S101, and the other one is used in step S102.

[0019] Furthermore, in step S102, the new catalyst is heated by a heat exchange device after passing through the second circulation pump and before returning to the chemical reaction device.

[0020] The method further comprises:

[0021] S105: Discharge the first material portion settled in step S101 to a returned material storage device.

[0022] During the implementation of the method, one or more of the following parameters are controlled:

[0023] The temperature range in the chemical reaction device is controlled to be 185°C to 200°C;

[0024] The temperature range in the post-reaction device is controlled to be 185°C to 230°C;

[0025] The drum pressure of the heat exchange device is ≥600KPa;

[0026] The system hydrogen pressure in the method is ≥2.4 MPa; and

[0027] The amount of the first material in the chemical reaction device is maintained at a liquid level of 60% to 80%.

[0028] According to another aspect of the present invention, a system for replacing a catalyst in a chemical reaction device without shutting down the device is provided, comprising:

[0029] The chemical reaction device and the liquid-solid phase discharge pipeline located at the bottom of the chemical reaction device;

[0030] a catalyst supply source in communication with the liquid-solid phase discharge pipeline;

[0031] a first circulation pump connected to the liquid-solid phase discharge pipeline via a first circulation pipeline;

[0032] a second circulation pump connected to the liquid-solid phase discharge pipeline via a second circulation pipeline;

[0033] The first circulation pump and the second circulation pump are connected to the returned material storage device through the sediment discharge pipeline, and are connected to the heat exchange device through the pumping pipeline;

[0034] Wherein, one of the first circulation pump and the second circulation pump is operated to pump materials, and the other is stationary to settle materials.

[0035] According to one embodiment, the system further includes a gas phase discharge pipeline located at the top of the chemical reaction device, and a post-reaction device connected to the chemical reaction device through the gas phase discharge pipeline.

[0036] According to another embodiment, the post-reaction device is connected to the cooling device and the separation device in sequence along the material flow direction.

[0037] The system further comprises a steam generating device for supplying steam to the heat exchange device.

[0038] According to one embodiment, the heat exchange device is communicated with the chemical reaction device, and is used to return the material heated by the heat exchange device to the chemical reaction device.

[0039] The method and system of the present invention can combine catalyst replacement and dynamic load adjustment, maintain the design load and normal production process conditions for continued operation, increase product output, and reduce steam consumption and sewage discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic diagram of a catalyst withdrawal system according to the present invention;

[0041] Figure 2 The figure is a flow chart of the method for replacing catalyst without stopping the vehicle according to the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods, but is not limited to the following embodiments. Those skilled in the art can propose other embodiments within the framework of the technical solution of the present invention, but these embodiments are all included in the protection scope of the present invention.

[0043] In the later stages of a liquid-phase benzene hydrogenation system to produce cyclohexane, catalyst deactivation gradually occurs, leading to rising postreactor temperatures and a continuous decrease in feed load. This necessitates shutting down the system to remove all deactivated catalyst and refilling with fresh catalyst to resume production. This downtime reduces cyclohexane production, while system cleaning increases wastewater discharge. Restarting and raising temperatures further increases steam consumption. Therefore, there is a need in the art for a cost-effective system and method for replacing deactivated catalyst generated in liquid-phase benzene hydrogenation units.

[0044] Catalyst return system

[0045] See also Figure 1 The catalyst withdrawal system according to the present invention may mainly include a chemical reaction device (also called a main reaction device) 1, a post-reaction device part and a catalyst withdrawal part.

[0046] The above-mentioned chemical reaction device can be, for example, a liquid benzene hydrogenation reaction device, which can accommodate a reaction raw material comprising liquid benzene and hydrogen, and a catalyst. During the liquid benzene hydrogenation reaction process, the catalyst in the liquid benzene hydrogenation reaction device can be a nickel catalyst, typically a liquid nickel catalyst, preferably an organic complex nickel catalyst suspended in an organic solvent, such as a citric acid nickel catalyst suspended in propylene glycol. Further, at this time, the nickel content in the nickel catalyst is typically 1.5%. The liquid nickel catalyst will become a powdery fine particle solid due to the influence of benzene containing water during the reaction process, thereby settling during the later catalyst withdrawal process. Further, the fresh catalyst supplemented during the catalyst withdrawal process is also the above-mentioned liquid nickel catalyst.

[0047] The chemical reaction device 1 may be equipped with a first temperature monitoring element (not shown) for real-time monitoring of the first temperature within the chemical reaction device 1. Preferably, the monitored first temperature value is further transmitted to a control center. According to one embodiment, the first temperature monitoring element may be a thermocouple or a temperature sensor, preferably an infrared temperature sensor. Within the chemical reaction device, the reaction temperature may be controlled to be between 185°C and 200°C, for example, 190°C or 195°C.

[0048] The chemical reaction device 1 may also be equipped with a liquid level monitoring element (not shown) for real-time monitoring of the liquid level within the chemical reaction device 1. Preferably, the monitored liquid level value is further transmitted to a control center. According to one embodiment, the liquid level monitoring element may be a liquid level gauge or a liquid level sensor. To ensure the safety of the production process, the liquid level within the chemical reaction device is typically controlled to be 60% to 80% of the maximum liquid level of the chemical reaction device, for example, 65%, 70%, or 75%.

[0049] The chemical reaction device 1 may also be equipped with a first pressure monitoring element (not shown) for real-time monitoring of the pressure within the chemical reaction device 1. Preferably, the monitored pressure value is further transmitted to a control center. The first pressure monitoring element may be, for example, a pressure gauge or a pressure sensor. According to one embodiment, the pressure (e.g., hydrogen pressure) within the catalyst withdrawal system according to the present invention is maintained above 2.4 MPa.

[0050] The post-reaction unit section may include a post-reaction unit 10, a cooling unit 11, a separation unit 12, and a product storage tank 13, connected to the chemical reaction unit (i.e., the main reaction unit) 1, according to the material flow direction. The post-reaction unit 10 is typically connected via a gas phase discharge line located at the top of the chemical reaction unit 1, and is used to receive products discharged from the chemical reaction unit 1, unreacted raw materials (e.g., benzene and hydrogen), and trace amounts of water vapor. Therefore, the post-reaction unit 10 is pre-loaded with a solid catalyst, such as alumina balls-4A molecular sieve-solid catalyst-4A molecular sieve-alumina balls. If the effective catalyst content in the chemical reaction unit 1 decreases and the degree of reaction progress decreases, the benzene and hydrogen delivered to the post-reaction unit 10 will increase, and the temperature in the post-reaction unit 10 will increase. Therefore, a relationship can be established between the temperature in the post-reaction unit 10 and the effective catalyst content in the chemical reaction unit 1. By monitoring the temperature in the post-reaction unit 10, the effective catalyst content in the chemical reaction unit 1 can be determined, and then the catalyst needs to be replaced. The temperature in the post-reaction device 10 is generally controlled at 185°C to 230°C, preferably 190°C to 220°C, for example, 200°C or 210°C. The cooling device 11 may be a condenser, in which the product (e.g., cyclohexane) and a trace amount of water vapor generated after the reaction in the post-reaction device 10 are condensed into a liquid state, and the unreacted raw material (e.g., hydrogen) is cooled to a lower temperature and transported to the separation device 12. In the separation device 12, the cooled raw material gas (e.g., hydrogen) is returned to the pipe network from the top, the liquid material is separated into oil and water (e.g., the oil phase is cyclohexane and the aqueous phase is water), the separated oil phase product (e.g., cyclohexane) is transported from the bottom to the product storage tank 13, and the aqueous phase material (e.g., water) is transported from the bottom to the drainage line.

[0051] Furthermore, the post-reaction device 10 may be equipped with a second temperature monitoring element (not shown) for real-time monitoring of the temperature within the post-reaction device 10. Preferably, the monitored second temperature value is further transmitted to the control center. According to one embodiment, the temperature monitoring element may be a thermocouple or a temperature sensor, preferably an infrared temperature sensor.

[0052] The catalyst replacement part may include the following components:

[0053] The liquid-solid phase discharge pipeline located at the bottom of the chemical reaction device 1 is used to discharge the liquid and solid phase materials in the chemical reaction device 1. The liquid and solid phase materials may include some liquid materials (such as raw material liquid benzene, product cyclohexane and a trace amount of water) and possible solid materials. The solid material may be, for example, a solid catalyst precipitated from a catalyst in a liquid phase (such as a suspension) as the reaction proceeds;

[0054] A catalyst supply source (not shown) in communication with the liquid-solid phase discharge pipeline is used to supply new catalyst to the catalyst withdrawal system. Furthermore, a valve may be provided between the catalyst supply source and the liquid-solid phase discharge pipeline to control the start and stop of the new catalyst supply;

[0055] A first circulation pump 3 connected to the liquid-solid phase discharge pipeline via a first circulation pipeline (i.e., circulation pipeline A). Preferably, a first valve 7 and a second valve 8 are provided on the feed pipeline upstream of the first circulation pump 3 and the discharge pipeline downstream of the first circulation pump 3, respectively;

[0056] A second circulation pump 4 connected to the liquid-solid phase discharge pipeline via a second circulation pipeline (i.e., B circulation pipeline). Preferably, a third valve 6 and a fourth valve 9 are provided on the feed pipeline upstream of the second circulation pump 4 and the discharge pipeline downstream of the second circulation pump 4, respectively;

[0057] A returned material storage device 5 connected to the first circulation pump 3 and the second circulation pump 4 through a returned material pipeline;

[0058] A heat exchange device 2 is connected to the first circulation pump 3 and the second circulation pump 4 through a pumping pipeline, and a discharge pipeline of the heat exchange device 2 is connected to the chemical reaction device 1; and

[0059] Steam generator 14 is used to supply steam to heat exchanger 2. A sixth valve 15 may be provided between steam generator 14 and heat exchanger 2. Steam generator 14 heats boiler water into steam, which is used to heat new catalyst received by heat exchanger 2 to replenish catalyst for chemical reaction unit 1. The low-pressure steam, which has been cooled after heat exchange, is then recycled into the pipeline network.

[0060] The steam generator 14 may also be equipped with a second pressure monitoring element (not shown) for real-time monitoring of the pressure within the steam generator 14. Preferably, the monitored pressure value is further transmitted to a control center. The pressure monitoring element may be, for example, a pressure gauge or a pressure sensor. According to one embodiment, the pressure (e.g., hydrogen pressure) within the catalyst decomposition system according to the present invention is maintained above 2.4 MPa.

[0061] According to one embodiment, the drum pressure in the steam generating device 14 may be above 600 KPa.

[0062] One of the first and second circulating pumps 3 and 4 is in operation to pump material (e.g., fresh catalyst), while the other is stationary to settle material (e.g., material discharged from the bottom of a chemical reaction unit, typically including catalyst, product, and unreacted raw materials). The two can be used alternately. According to one embodiment, the aforementioned circulating pipelines A and B, together with the pump cavities of the corresponding circulating pumps, form a catalyst settling area. Preferably, the circulating pipelines can be DN500 diameter pipelines.

[0063] According to one embodiment, the A circulation line is used as a settling line. In this case, the third valve 6 of the B circulation line is closed, the first valve (i.e., the inlet gate valve) 7 of the A circulation line is opened, and the second valve (i.e., the outlet gate valve) 8 is closed. This allows the materials in the chemical reaction unit 1 (e.g., including catalyst, unreacted raw materials, and a small amount of water) to be discharged from the liquid-solid phase discharge line, pass through the first valve 7, and reach the first circulation pump 3, filling the pump chambers of the A circulation line and the first circulation pump 3 and settling therein. After a certain settling time, for example, 2 to 3 hours, the settled materials in the pump chambers of the A circulation line and the first circulation pump 3 (primarily catalyst in this case) are discharged from the material return line to the returned material storage device 5. Preferably, a fifth valve 16 is provided on the return line for opening or closing according to the timing of the material return.

[0064] Meanwhile, the B circulation line serves as a pipeline for replacing new catalyst. After the discharge material from chemical reaction unit 1 fills the A circulation line, the first valve 7 and the fifth valve 16 are closed, and the new catalyst supply (not shown) and the third valve 6 and the fourth valve 9 are opened. The new catalyst is then pumped through the B circulation line to the heat exchanger 2. The new catalyst is heated in the inner cavity of the heat exchanger 2 by the water vapor in the jacket of the heat exchanger 2, and then transported to the chemical reaction unit 1. The new catalyst is opposite to the flow direction of the water vapor, thereby increasing the heat exchange time and ensuring that the new catalyst is fully heated.

[0065] Furthermore, the catalyst withdrawal system according to the present invention may also include a control center (not shown) for communicating with the temperature sensors and pressure sensors of various components in the system (e.g., the chemical reaction unit, the post-reaction unit, and / or the steam generation unit), and comparing the received temperature and pressure values ​​with pre-set thresholds, thereby controlling the start or stop of corresponding material transportation, such as the feeding of raw liquid benzene and the input of hydrogen, the discharge of materials from the chemical reaction unit, the transportation of new catalyst, etc. According to a specific embodiment, the control center receives a temperature value T1 transmitted by a temperature sensor in the post-reaction unit 10, and pre-sets the maximum temperature threshold in the post-reaction unit 10 as T0 in the control center. The control center compares T1 with T0, and if T1 is greater than T0, the catalyst withdrawal process is initiated.

[0066] Catalyst return method

[0067] In the present invention, the chemical reaction unit can be a reaction unit for preparing cyclohexane by hydrogenation of liquid benzene. The materials in the chemical reaction unit can generally include liquid benzene (containing trace water), hydrogen and a liquid-phase nickel catalyst (a suspension of an organic nickel complex). As the reaction in the chemical reaction unit proceeds, the gaseous materials in the chemical reaction unit are discharged from its top to the after-reaction unit, and the activity of the catalyst decreases. The gaseous materials discharged at this time generally can include product cyclohexane, unreacted benzene and hydrogen, and a trace amount of water vapor. The gaseous materials discharged are transported to the after-reaction unit, and under the action of a pre-loaded catalyst (usually a solid catalyst) in the after-reaction unit, the unreacted benzene is reacted completely. The product mixture after the complete reaction is now separated into an oil-liquid mixture to obtain a cyclohexane product.

[0068] The method of the present invention uses a combination of a sedimentation method and a withdrawal method to withdraw all or part of the deactivated catalyst once or multiple times and add new catalyst without stopping the liquid phase benzene hydrogenation unit, so that the benzene hydrogenation unit maintains the designed feed load and normal production process conditions and continues to operate, thereby increasing the output of the product cyclohexane and reducing steam consumption and sewage discharge.

[0069] Furthermore, the inventors have found that the greater the feed load in the chemical reaction device, the faster the effective catalyst content therein decreases, and as the effective catalyst content decreases, the degree of reaction completion in the chemical reaction device decreases, and the temperature in the post-reaction device gradually increases. According to the method of the present invention, by establishing a relationship between the temperature in the post-reaction device and the feed load and effective catalyst content in the chemical reaction device, it is possible to determine the effective catalyst content in the chemical reaction device by monitoring the temperature in the post-reaction device, and then determine the start and end timing of catalyst replacement.

[0070] Specifically, see Figure 2 The method for non-stop catalyst replacement for a chemical reaction device of the present invention includes the following steps, wherein the liquid-solid phase discharge pipeline of the chemical reaction device is connected to the first circulation pump through the first circulation pipeline, and is connected to the second circulation pump through the second circulation pipeline.

[0071] S101: A portion of the first material in the chemical reaction unit is discharged from the liquid-solid phase discharge pipeline, filling the first circulation pipeline and the pump cavity of the first circulation pump, and then settling. In this step S101, the amount of catalyst discharged from the first material portion of the chemical reaction unit accounts for 30% to 50% of the total amount of catalyst in the first material. For example, if the total amount of the first material in the chemical reaction unit is 60 tons and the catalyst content is 10%, or 6 tons, then the first material discharged each time is 18 tons to 30 tons, and the amount of catalyst discharged should be 1.8 tons to 3 tons. The settling time can be 2 to 3 hours. Generally, the discharged catalyst usually contains deactivated catalyst.

[0072] S102: New catalyst is transported from the catalyst supply source to the liquid-solid phase discharge pipeline and returned to the chemical reaction device via the second circulation pipeline and the second circulation pump. The amount of new catalyst replenished is equal to the amount of catalyst discharged in step S101.

[0073] S103: After the chemical reaction device receives the new catalyst input from the second circulation pump, the second material in the chemical reaction device is mixed evenly.

[0074] S104: Calculate the effective catalyst content in the second material. If the effective catalyst content in the second material is greater than or equal to a predetermined effective catalyst content threshold, the return process ceases. If the effective catalyst content in the second material is less than the effective catalyst content threshold, steps S101 to S103 are repeated. Herein, the effective catalyst content in the chemical reaction unit is defined as the percentage of the mass of the effective catalyst in the chemical reaction unit relative to the mass of the total catalyst in the chemical reaction unit.

[0075] The initial material in a chemical reaction unit is generally referred to as the first material, and the material in the chemical reaction unit after one or more catalyst replacements is referred to as the second material. The effective catalyst content in the chemical reaction unit is calculated using the following formulas (I) and (II):

[0076] M0×a%=C0 (I)

[0077] [C0×(1-b%)×A0+C1×100%] / C0=A1 (II)

[0078] Wherein, M0 is the total mass of the first material, where the first material is the sum of non-gaseous raw materials, for example, a mixture of liquid raw materials (such as liquid benzene) and liquid catalyst fed into the chemical reaction device;

[0079] a% is the mass percentage of the catalyst in the first material;

[0080] C0 is the total mass of the catalyst in the first material;

[0081] b% is the mass percentage of the discharged first material portion to the total amount of the first material;

[0082] A0 is the effective catalyst content (%) in the first material, that is, the mass percentage of the effective catalyst in the first material to the total amount of catalyst;

[0083] C1 is the mass of new catalyst added; and

[0084] A1 is the effective catalyst content (%) in the second material, that is, the mass percentage of the effective catalyst in the second material to the total amount of catalyst. In this case, the second material refers to the material in the chemical reaction device after one or more catalyst replacements.

[0085] In the chemical reaction apparatus of the present invention, the effective catalyst content should be maintained at above 30%, preferably above 70%. If the effective catalyst content is below 30%, the catalyst in the chemical reaction apparatus needs to be replaced. To ensure the normal progress of the reaction in the chemical reaction apparatus, the effective catalyst content should not be less than 30%. When the effective catalyst content reaches above 80%, catalyst replacement can be stopped.

[0086] In step S101, the mass percentage b% of the first material portion discharged from the chemical reaction device in a single discharge to the total amount of the first material may be 20% to 50%, preferably 25% to 45%, for example 30% or 35%.

[0087] Furthermore, in step S102, the amount of new catalyst delivered from the catalyst supply source to the liquid-solid phase discharge pipeline is equal to the amount of catalyst discharged from the chemical reaction device in step S101, thereby ensuring that the total amount of catalyst in the chemical reaction device remains unchanged after each catalyst replacement process.

[0088] In the method of the present invention, when steps S101 to S103 are repeated, one of the first circulation line and the first circulation pump or the second circulation line and the second circulation pump is optionally used in step S101, and the other one is used in step S102.

[0089] According to one embodiment, the method of the present invention further includes, before step S101, establishing a corresponding relationship between the temperature in the post-reaction device and the effective catalyst content in the chemical reaction device:

[0090] The initial conditions of the chemical reaction device are set as follows: initial feed load L(t0) = L max =100%, the effective catalyst content in the initial material (i.e., the first material) A(t0)=A0=100%;

[0091] Measure the temperature T(t0), T(t1), ..., T(t n ), that is, input time series temperature data, wherein n is an integer from 0 to 100, preferably an integer from 1 to 100, wherein the time step of the test Δt=t i -t i-1 =0.5~1.5h, preferably Δt=1h, i is an integer from 1 to 100;

[0092] Determine the time t according to formula (III) iWhen the temperature in the post-reaction device is T(t i ) corresponds to the feed load L(t i ):

[0093] L(t i )=L max -α·(T(t i )-T0)(III)

[0094] Among them, L max is the maximum feed load allowed by the chemical reaction device, that is, L max =100%, α is the adjustment coefficient of the feed load, α=2% / °C, T0 is the initial steady-state temperature of the post-reaction device, that is, the temperature in the post-reaction device at time t0, for example, T0=185°C, i is an integer from 1 to 100; in the system of the present invention, the temperature in the chemical reaction device can be 185°C to 200°C, and the temperature control range in the post-reaction device is preferably set to 185°C to 230°C;

[0095] Based on the temperature A(t i-1 ) and the feed load L(t i-1 ), determine the effective catalyst content change rate D in the chemical reaction device according to formula (IV) A (t i ):

[0096] D A (t i )=-k·L(t i-1 )·A(t i-1 )(IV)

[0097] Wherein, k is the rate constant of reduction of effective catalyst content in the chemical reaction device, preferably, k = 0.1h -1 ,

[0098] According to formula (V), t is predicted i The effective catalyst content A(t i ):

[0099] A(t i )=A(t i-1 )+Δt·D A (t i )(V).

[0100] Thus, the time series A(t i ) and L(t i ). When predicting A(t i ) is lower than the minimum threshold value of the predetermined effective catalyst content (such as 30%), the catalyst replacement process is started, that is, S101; when the predicted A(ti ) is higher than a predetermined maximum threshold value of effective catalyst content (such as 80%), the catalyst replacement process is stopped.

[0101] In the above formulas (III) and (IV), the larger α is, the more sensitive the feed load is to the temperature change in the post-reaction device, and the slower the catalyst activity in the chemical reaction device decays; the larger k is, the faster the catalyst activity in the chemical reaction device decays, and the feed load needs to be adjusted more frequently to maintain the set temperature range in the chemical reaction device, i.e., 185°C to 200°C.

[0102] During the implementation of the above method, one or more of the following parameters are controlled:

[0103] The temperature range in the chemical reaction device is controlled at 185℃~200℃;

[0104] The temperature range in the post-reaction device is controlled to be 185°C to 230°C;

[0105] The drum pressure of the heat exchange device is ≥600KPa;

[0106] The system hydrogen pressure in the above method is ≥ 2.4 MPa; and

[0107] The liquid level in the chemical reaction device is maintained at 60% to 80% of the amount of the first material.

[0108] According to another aspect of the present invention, a method for controlling the catalyst retirement process described above may be provided, comprising the following steps:

[0109] The temperature range in the chemical reaction unit is set to 185° C. to 200° C., the temperature range in the post-reaction unit is set to 185° C. to 230° C., the initial feed load value of the chemical reaction unit is 100%, and the effective catalyst content in the chemical reaction unit can be controlled in the range of 30% to 80%, for example, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%;

[0110] Real-time measurement of the actual temperature in the post-reaction device and prediction of the effective catalyst content in the chemical reaction device based on the actual temperature;

[0111] The predicted effective catalyst content is compared with the control range of the effective catalyst content. When the predicted effective catalyst content is less than 30%, the catalyst withdrawal process is started. When the predicted effective catalyst content is greater than or equal to 80%, the catalyst withdrawal process is stopped.

[0112] On the other hand, when the temperature in the post-reaction device is higher than 230° C., the feeding load of the chemical reaction device is increased, and when the temperature in the post-reaction device is lower than 185° C., the feeding load of the chemical reaction device is reduced.

[0113] The method and system of the present application can monitor the working conditions of the main reaction device, the secondary reaction device and the catalyst replacement device in the chemical reaction system in real time, and replace the catalyst of the chemical reaction device without stopping the device according to the temperature change of the post-reaction device, while maintaining the design load and the normal process conditions by dynamic load adjustment, thereby increasing the product yield, reducing the steam consumption and the discharge of sewage.

[0114] The advantages and various effects of the present application will be more clearly presented by the following specific embodiments and examples. It should be understood by those skilled in the art that the specific embodiments and examples are used to illustrate the present application, but not to limit the present application.

[0115] Example 1

[0116] The total amount of materials in the benzene hydrogenation production line (reactor and circulating pipeline) is 60 tons, and the catalyst content is 10%, i.e. 6 tons; the diameter of the settling pipeline in the A / B area is DN500mm, and the length is 12 meters, and the total volume of the pipeline and pump cavity settling is about 2.35 cubic meters; the settling time is 2 hours, and the total amount of deactivated catalyst withdrawn at a time is about 3 tons.

[0117] 1. Addition and replacement amount of new catalyst:

[0118] (1) The amount of catalyst in the system is 6 tons at one time, and the effective catalyst content is 30%;

[0119] Then: the amount of effective catalyst in the system is: 6x30%=1.8 tons.

[0120] The amount of deactivated catalyst withdrawn is 3 tons, and 3 tons of fresh catalyst is added;

[0121] Then the amount of effective catalyst in the system is (6-3)x30%+3x100%=3.9 tons;

[0122] Then the effective catalyst content in the system is 3.9 / 6x100%=65%;

[0123] (2) The total amount of catalyst in the system is 6 tons at two times, and the effective catalyst content is 65%;

[0124] Then: the amount of effective catalyst in the system is: 6x65%=3.9 tons.

[0125] The amount of deactivated catalyst withdrawn from the system is 3 tons, and 3 tons of fresh catalyst is added;

[0126] Then the amount of effective catalyst in the system is (6-3)x65%+3x100%=4.95 tons;

[0127] The effective catalyst content in the system is 4.95 / 6×100%=82.5%.

[0128] Example 2

[0129] The total material volume of the benzene hydrogenation single production line (reactor and circulation pipeline) is 60 tons, and the catalyst content is 10%, i.e. 6 tons; the diameter of the sedimentation pipelines in the A / B areas is DN500mm and the length is 12 meters. The total sedimentation volume of the pipelines and pump chambers is approximately 2.35 cubic meters; the sedimentation time is 2 hours, and the total amount of deactivated catalyst withdrawn in a single time is approximately 3 tons.

[0130] (1) The initial feed load of the chemical reaction unit is set to 100%, the feed load adjustment coefficient is α = 2% / °C, the initial steady-state temperature T0 of the post-reaction unit is set to 185°C, the effective catalyst content A0 in the initial material (i.e., the first material) is set to 100%, and the effective catalyst content in the chemical reaction unit is set to be within the range of 30% to 80%. These initial parameters are input into the control center;

[0131] (2) After 1 hour, the temperature T1 in the post-reaction device is measured to be 190°C. The control center calculates the feed load of the chemical reaction device at this time: L1 = L max -α·(T(t1)-T0)=100%-2%×(190-185)=90%, and

[0132] Calculate the effective catalyst content change rate D in the chemical reaction device A (t1)=-k·L(t0)·A(t0)=-0.1×100%×100%=-0.1h -1 ,

[0133] Calculate A(t1)=A(t0)+Δt·D A (t0)=100%+1×(-0.1)=90%,

[0134] The control center compares the calculated A(t1) value with the predetermined minimum threshold of 30% of the effective catalyst content. If 90%>30%, there is no need to return the catalyst.

[0135] (3) After 2 hours, the temperature T2 in the post-reaction device is measured to be 200°C. The feed load of the chemical reaction device at this time is calculated as: L2 = L max -α·(T(t2)-T(t0))=100%-2%×(200-185)=70%,

[0136] Calculate the effective catalyst content change rate D in the chemical reaction device A (t2)=-k·L(t1)·A(t1)=-0.1×90%×70%=-0.063h -1 ,

[0137] Calculate A(t2) = A(t1) + Δt·D A (t1) = 90% + 1 × (-0.063) = 83.7% > 30%, then there is no need to replace the catalyst;

[0138] (4) After 3 hours, the temperature T3 in the post-reaction device is measured to be 210°C. The feed load of the chemical reaction device at this time is calculated as: L3 = L max -α·(T(t3)-T(t0))=100%-2%×(210-185)=50%,

[0139] Calculate the effective catalyst content change rate D in the chemical reaction device A (t3)=-k·L(t2)·A(t2)=-0.1×70%×83.7%=-0.05859h -1 ,

[0140] Calculate A(t3)=A(t2)+Δt·D A (t2) = 83.7% + 1 × (-0.05859) = 77.8% > 30%, then there is no need to replace the catalyst;

[0141] (5) After 4 hours, the temperature T4 in the post-reaction device is measured to be 220°C. The feed load of the chemical reaction device at this time is calculated as: L4 = L max -α·(T(t4)-T(t0))=100%-2%×(220-185)=30%,

[0142] Calculate the effective catalyst content change rate D in the chemical reaction device A (t4)=-k·L(t3)·A(t3)=-0.1×30%×77.8%=-0.02334h -1 ,

[0143] Calculate A(t4)=A(t3)+Δt·D A (t3) = 30% + 1 × (-0.02334) = 27.7% < 30%, then start the catalyst replacement;

[0144] (6) 50% (30 tons) of the first material in the chemical reaction unit is withdrawn, i.e., 3 tons of catalyst is withdrawn, and 3 tons of new catalyst is added. At this time, the effective catalyst content of the second material in the chemical reaction unit after the new catalyst is added is (3×27.7%+3×100%) / 6×100%=63.85%;

[0145] (7) 50% (30 tons) of the second material in the chemical reaction device is withdrawn, that is, 3 tons of catalyst is withdrawn, and 3 tons of new catalyst is added. At this time, the effective catalyst content of the second material in the chemical reaction device after adding the new catalyst is (3×63.85%+3×100%) / 6×100%=81.93%. If the effective catalyst content is higher than the predetermined maximum threshold value of 80% of the effective catalyst content, the catalyst withdrawal is stopped.

Claims

1. A method for replacing catalysts without stopping a chemical reaction device, wherein the liquid-solid phase discharge pipeline of the chemical reaction device is connected to a first circulation pump through a first circulation pipeline and is connected to a second circulation pump through a second circulation pipeline, characterized in that: The following steps are involved: S101: discharging a portion of the first material in the chemical reaction device from the liquid-solid phase discharge pipeline, filling the first circulation pipeline and the pump cavity of the first circulation pump, and settling; S102: delivering new catalyst from the catalyst supply source to the liquid-solid phase discharge pipeline, and returning the catalyst to the chemical reaction device via the second circulation pipeline and the second circulation pump; S103: after the chemical reaction device receives the new catalyst input from the second circulation pump, uniformly mixing the second material in the chemical reaction device; S104: Calculate the effective catalyst content in the second material, If the mass percentage of the effective catalyst in the second material relative to the total amount of catalyst is greater than or equal to the maximum threshold value of the predetermined effective catalyst content, the return is stopped. If the effective catalyst content in the second material is lower than the predetermined minimum threshold of the effective catalyst content, steps S101 to S103 are repeated.

2. The method according to claim 1, wherein In step S101 , the discharged portion of the first material accounts for 30% to 50% of the total amount of the first material.

3. The method according to claim 2, wherein: In step S102 , the amount of new catalyst delivered from the catalyst supply source to the liquid-solid phase discharge pipeline is equal to the amount of catalyst discharged in step S101 .

4. The method according to claim 1, wherein The chemical reaction device is a benzene hydrogenation reaction device.

5. The method according to claim 1, wherein The maximum threshold value of the effective catalyst content is defined as the mass of the effective catalyst being 80% of the total mass of the catalyst; and / or The minimum threshold value of the effective catalyst content is defined as the mass of the effective catalyst being 30% of the total mass of the catalyst.

6. The method according to claim 1, wherein The chemical reaction device is connected to the post-reaction device via a gas phase discharge pipeline. The method further comprises, before step S101: S100: measuring the temperature in the post-reaction device, establishing a correspondence between the temperature in the post-reaction device and the effective catalyst content in the chemical reaction device, and predicting the effective catalyst content in the chemical reaction device corresponding to the temperature in the reaction device.

7. The method according to claim 6, step S100 comprising: The initial conditions of the chemical reaction device are set as follows: initial feed load L(t0) = L max =100%, the effective catalyst content in the first material A(t0)=A0=100%; The temperature T(t0), T(t1), ..., T(t n ), where n is an integer from 0 to 100, and the time step of the test Δt=t i -t i-1 =0.5~1.5h; Determine the time t according to formula (III) i When the temperature T(t i ) corresponds to the feed load L(t i ): L(t i )=L max -α·(T(t i )-T0)(III) Among them, L max is the maximum feed load allowed for the chemical reaction unit, L max =100%, α is the adjustment coefficient of the feed load, α=2% / ℃, T0 is the temperature in the post-reaction device at time t0, T(t i ) is the time t i The temperature in the post-reaction device; Based on the temperature A(t i-1 ) and the feed load L(t i-1 ), determine the effective catalyst content change rate D in the chemical reaction device according to formula (IV) A (t i ): D A (t i )=-k·L(t i-1 )·A(t i-1 )(IV) Where k is the rate constant of reduction of effective catalyst content in chemical reaction device, k = 0.1h -1 , According to formula (V), t is predicted i The effective catalyst content A(t i ): A(t i )=A(t i-1 )+Δt·D A (t i )(V); When predicting A(t i ) is lower than the minimum threshold of the effective catalyst content, step S101 is started. When the predicted A(t i ) when the effective catalyst content exceeds a predetermined maximum threshold, the catalyst replacement process is stopped; Here, i is an integer from 1 to 100.

8. The method according to claim 1, when steps S101 to S103 are repeated, in step S101, one of the first circulation line and the first circulation pump, or the second circulation line and the second circulation pump is optionally used, and in step S102, the other one is used.

9. The method according to claim 1, wherein in step S102, the new catalyst is heated by a heat exchange device after passing through the second circulation pump and before returning to the chemical reaction device.

10. The method according to claim 1, further comprising: S105: Discharge the first material portion settled in step S101 to a returned material storage device.

11. A system for replacing catalysts in a chemical reaction device without stopping the device, characterized in that: include: The chemical reaction device and the liquid-solid phase discharge pipeline located at the bottom of the chemical reaction device; a catalyst supply source in communication with the liquid-solid phase discharge pipeline; a first circulation pump connected to the liquid-solid phase discharge pipeline via a first circulation pipeline; a second circulation pump connected to the liquid-solid phase discharge pipeline via a second circulation pipeline; The first circulation pump and the second circulation pump are connected to the returned material storage device through the sediment discharge pipeline, and are connected to the heat exchange device through the pumping pipeline; Wherein, one of the first circulation pump and the second circulation pump is operated to pump materials, and the other is stationary to settle materials. 12 . The system according to claim 11 , further comprising a gas phase discharge pipeline located at the top of the chemical reaction device, and a post-reaction device connected to the chemical reaction device through the gas phase discharge pipeline.

13. The system according to claim 12, wherein: The post-reaction device is connected to the cooling device and the separation device in sequence along the material flow direction.

14. The system according to claim 11, further comprising a steam generating device for supplying steam to the heat exchange device.

15. The system according to claim 11, wherein The heat exchange device is communicated with the chemical reaction device and is used to return the material heated by the heat exchange device to the chemical reaction device.

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