Regulation and control method and system suitable for production process of silver catalyst for catalyzing ethylene epoxidation

Abstract

The invention relates to the field of early warning regulation and control methods suitable for the process of producing a silver catalyst for catalyzing ethylene epoxidation, and relates to a regulation and control method and system suitable for the process of producing a silver catalyst for catalyzing ethylene epoxidation. Comprising the following steps: (1) acquiring normal working condition historical data of impregnation liquid in an impregnation section of the silver catalyst for ethylene epoxidation; (2) performing normalization preprocessing on the historical data of the normal working condition, setting upper and lower alarm thresholds according to data distribution, and obtaining a conventional data change trend; (3) monitoring real-time sampling data of the impregnation liquid on line, judging whether the real-time sampling data conforms to a conventional data change trend or not, and sending out an alarm signal if the real-time sampling data does not conform to the conventional data change trend; and (4) receiving the alarm signal, and carrying out regulation and control processing operation. According to the regulation and control method, the solution containing the precious metal salt can be fully utilized, and the production cost is reduced to the maximum extent.

Description

Technical Field

[0001] This invention relates to the field of early warning and control methods applicable to the production of silver catalysts for catalytic epoxidation of ethylene, and more specifically, to a control method and system applicable to the production of silver catalysts for catalytic epoxidation of ethylene. Background Technology

[0002] Ethylene oxide (EO), as a derivative of ethylene, is an important organic chemical product. my country is a major producer and user of EO, and downstream products such as polyester and ethylene glycol are important industrial products. Industrially, EO production typically involves the epoxidation of ethylene using a silver catalyst. The feed gas, containing ethylene and oxygen, produces ethylene oxide under specific reaction conditions, while simultaneously generating byproducts such as carbon dioxide and water. The three main performance indicators of the silver catalyst used are activity, selectivity, and stability. Differences in catalytic performance directly impact economic benefits. The activity of a silver catalyst is usually measured by the applicable space-time yield or the reaction temperature required at a given space-time yield; the higher the applicable space-time yield or the lower the reaction temperature required at a given space-time yield, the higher the activity of the silver catalyst. The selectivity of a silver catalyst refers to the ratio of the number of moles of ethylene converted to ethylene oxide to the total number of moles of ethylene reacted. Industrial production typically requires ensuring the selectivity of the catalyst during use to maximize profitability and reduce carbon emissions. For high-selectivity silver catalysts, even a 0.1% increase in selectivity is both challenging to achieve and yields significant economic benefits. Stability refers to the rate at which the activity and selectivity of a catalyst decrease under certain reaction conditions; the smaller the rate of decrease, the better the catalyst's stability. In actual reactions, due to prolonged heating and exposure to chemical atmospheres, catalysts undergo physical and chemical changes, ultimately leading to increased reaction temperature, reduced catalyst performance, or deactivation. Improving catalyst stability can extend catalyst life and increase economic efficiency. Since the production of silver catalysts is not a continuous process, proper control of relevant process parameters is essential to ensure uniform and qualified performance across different batches of catalysts. Mixing and loading these batches into the device results in better overall catalytic performance and reduces abnormal operating conditions such as temperature runaway caused by excessively high local activity.

[0003] Silver catalysts are typically prepared using the impregnation method, a crucial step in the production process. Due to the poor stability of the organic amine solvent used to dissolve silver salts and some metal salts present in the solution, oxidation, decomposition, and precipitation easily occur during storage. Because silver impregnation solutions are expensive, they are usually reused as much as possible to reduce production costs. However, used impregnation solutions often contain some α-alumina powder, and the organic impurities and inorganic precipitates generated after deterioration all affect the performance of the resulting catalyst. Therefore, how to reasonably control the stability of the relevant physical properties of the impregnation solution in the impregnation stage, keeping them within a certain fluctuation range, thereby improving the performance of the finished catalyst, is an important issue in the production of silver catalysts.

[0004] Numerous reports have documented examples of production control methods used in the chemical industry to achieve desired goals. CN116661402A, by determining whether the molecular structure mapping results meet the desired molecular structure and promptly obtaining anomaly verification results, enables production control, improving management quality and technical effectiveness. CN113842857B discloses a method for preparing acylation solutions, a system and method for preparing acylation solutions that saves energy and improves preparation efficiency. Examples of control and regulation methods to improve catalyst performance in the field of silver catalysts have been published. WO2011082033A1 controls the sulfur concentration in the feed to reduce the formation of silver chloride, thereby improving the production efficiency of silver catalysts.

[0005] Although the aforementioned patent documents have achieved promising results through different optimization methods, there are still few scientifically effective control systems and methods in the field of silver catalysts, especially in the process of producing silver catalysts, particularly in the impregnation process, leaving much room for improvement and optimization. Summary of the Invention

[0006] The inventors of this invention, through comparative experimental data in the field of silver catalyst preparation, discovered that when the impregnation solution is reused multiple times, improperly stored, or stored for too long, its physical properties change significantly, and its appearance changes from clear to turbid and darker in color. Consequently, the catalytic performance of the finished catalyst prepared from impregnation solutions with significantly different physical properties also shows relatively large differences in small-scale evaluations. In production, the practice of periodically preparing fresh solutions is typically used to reduce the adverse effects of changes in the impregnation solution's physical properties. However, due to factors such as seasonal temperature variations and differences in the physical properties of different carriers, conventional empirical methods cannot scientifically and conveniently maintain stable production conditions.

[0007] Therefore, the present invention has been improved. Under the background of the above-mentioned prior art, this application provides a control method for the impregnation section in the production of silver catalyst for catalytic ethylene epoxidation. It creates a method and system for monitoring and adjusting the relevant process parameters of the impregnation solution. When the physical properties of the impregnation solution deviate from the threshold, an alarm is triggered to adjust the physical properties of the solution in a timely manner. At the same time, the solution containing precious metal salt is fully utilized, and the production cost is reduced to the greatest extent.

[0008] To achieve the objectives of this invention, a first aspect of this invention provides a method for controlling the process of producing a silver catalyst for the catalytic epoxidation of ethylene, comprising the following steps:

[0009] (1) Obtain historical data of normal operating conditions of the impregnation solution in the silver catalyst impregnation section for ethylene epoxidation;

[0010] (2) Normalize and preprocess the historical data under normal working conditions, set the upper and lower thresholds of alarms according to the data distribution, and obtain the trend of regular data changes;

[0011] (3) Monitor the real-time sampling data of the impregnation solution online and determine whether the real-time sampling data conforms to the trend of conventional data changes. If it does not conform, issue an alarm signal.

[0012] (4) Receive alarm signals and perform control and processing operations.

[0013] A second aspect of the present invention provides a control system suitable for the production of a silver catalyst for the catalytic epoxidation of ethylene, the system comprising:

[0014] The data acquisition module is used to acquire historical data on normal operating conditions of the impregnation solution in the silver catalyst impregnation section for ethylene epoxidation.

[0015] The data processing module performs normalization preprocessing on historical data under normal operating conditions, sets upper and lower alarm thresholds based on data distribution, and obtains the trend of regular data changes.

[0016] The monitoring and alarm module is used to monitor the real-time sampling data of the impregnation solution online and determine whether the real-time sampling data conforms to the normal data change trend. If it does not conform, an alarm signal is issued.

[0017] The control and processing module is used to receive alarm signals and perform adjustment and processing operations.

[0018] The control method of the present invention can make full use of solutions containing precious metal salts and also minimize production costs.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0021] Figure 1 A schematic diagram of a control method applicable to the production of a silver catalyst for the epoxidation of ethylene is shown in an embodiment of the present invention.

[0022] Figure 2 A schematic diagram of parameter monitoring results in an embodiment of the present invention is shown.

[0023] Figure 3 A schematic diagram of a control system applicable to the production of a silver catalyst for the epoxidation of ethylene is shown in an embodiment of the present invention. Detailed Implementation

[0024] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] To achieve the objectives of this invention, a first aspect of this invention provides a method for controlling the process of producing a silver catalyst for the catalytic epoxidation of ethylene, comprising the following steps:

[0026] (1) Obtain historical data of normal operating conditions of the impregnation solution in the silver catalyst impregnation section for ethylene epoxidation;

[0027] (2) Normalize and preprocess the historical data under normal working conditions, set the upper and lower thresholds of alarms according to the data distribution, and obtain the trend of regular data changes;

[0028] (3) Monitor the real-time sampling data of the impregnation solution online and determine whether the real-time sampling data conforms to the trend of conventional data changes. If it does not conform, issue an alarm signal.

[0029] (4) Receive alarm signals and perform control and processing operations.

[0030] According to the present invention, preferably, in step (1), the historical data of normal operating conditions includes the absorption value x of the diluent of the impregnation liquid to light of a specific wavelength, the content y of insoluble solid particles in the impregnation liquid, and the kinematic viscosity z of the impregnation liquid.

[0031] In step (2), the normalization preprocessing is the Z-score normalization method, and the formula is as follows:

[0032]

[0033] Where μ represents the mean of the corresponding sample data and σ represents the standard deviation of the corresponding sample data.

[0034] According to the present invention, preferably, step (2) includes setting the upper limit of the alarm threshold x for x, y, and z.阈值上限 y 阈值上限 、z 阈值上限 The lower limit of the alarm threshold for x, y, and z. 阈值下限 y 阈值下限 、z 阈值下限 ;

[0035] Where, x 阈值上限 y 阈值上限 、z 阈值上限 The lower confidence limit of the 90% confidence interval for the maximum values ​​of x, y, and z, where x 阈值下限 y 阈值下限 and z 阈值下限 It is the minimum value of x, y, and z.

[0036] According to the present invention, preferably, in step (4), when the alarm signal is that the real-time data deviates from the trend of normal data change, but does not exceed the upper and lower thresholds of the alarm, the processing operation includes: shortening the sampling time interval.

[0037] In this invention, to improve production quality, the upper limit of the process alarm threshold is taken as the lower limit of the 90% confidence interval of the maximum values ​​of x, y, and z at each time point. The minimum value of x, y, and z of the freshly prepared impregnation solution is used as the lower threshold. When the impregnation solution is too clear below the monitoring lower limit, an on-site inspection should be conducted to check whether there is an equipment malfunction or a missing part of the material. The data change trend is plotted based on the boundary values ​​of x, y, and z at each time point. When the real-time data changes deviate from the historical data change trend, attention should be paid to reasonably shortening the sampling time interval to determine whether the real-time process data meets the requirements. When any parameter of x, y, or z exceeds the threshold, an alarm is triggered, and corresponding actions are taken.

[0038] According to the present invention, preferably, in step (4), when the alarm signal is x 实时 >x 阈值上限 At that time, the processing operation includes: stopping production and preparing (x) 实时 / x 阈值下限 Mix a new impregnation solution of 1.5 times its original volume with the original impregnation solution.

[0039] According to the present invention, preferably, in step (4), when the alarm signal is y 实时 >y 阈值上限 The processing operations include: stopping production, filtering out large-diameter solid particles, and preparing a new impregnation solution with a volume exceeding that of the original impregnation solution and mixing it with the original impregnation solution.

[0040] According to the present invention, preferably, in step (4), when the alarm signal is z 实时 >z 阈值上限The processing operation includes: checking whether the temperature of the impregnation solution is normal; if the temperature is not within the normal operating range, restoring it to the normal temperature range and continuing observation; if the temperature is within the normal operating range, preparing (z) 实时 / z 阈值下限 Mix a new impregnation solution of 1.5 times its original volume with the original impregnation solution.

[0041] According to the present invention, preferably, in step (4), when the alarm signal is x 实时 y 实时 and z 实时 When at least one of the following is below the lower limit of the alarm threshold, the processing operation includes: stopping production, performing a comprehensive component analysis of the impregnation solution, and deciding, based on the results, to either re-formulate the impregnation solution or adjust the physical properties of the original impregnation solution by supplementing components.

[0042] In this invention, when the real-time detection data of the x, y, and z values ​​of the impregnation solution fall below the threshold range, production is stopped, and a comprehensive component analysis of the impregnation solution is performed to investigate whether the problem is caused by detection error or preparation error. Based on the results, a decision is made to either re-prepare the impregnation solution or adjust its properties by adding components. In general, by addressing the cause of the alarm and mixing fresh and old solutions, the main parameters of the impregnation solution during the impregnation process are maintained within a relatively constant range throughout the overall production of each batch of catalyst, reducing changes in catalyst performance caused by variations in the impregnation solution's properties.

[0043] According to the present invention, preferably, in step (3), if no alarm signal is issued, the original operation cycle is followed and the impregnation liquid is used normally for catalyst production.

[0044] A second aspect of the present invention provides a control system suitable for the production of a silver catalyst for the catalytic epoxidation of ethylene, the system comprising:

[0045] The data acquisition module is used to acquire normal operating condition data of the impregnation solution in the silver catalyst impregnation section for ethylene epoxidation.

[0046] The data processing module performs normalization preprocessing on normal operating data, establishes a data model, sets upper and lower alarm thresholds based on data distribution, and obtains the trend of regular data changes.

[0047] The monitoring and alarm module is used to monitor whether the real-time sampled data conforms to the normal data change trend, and to issue an alarm when it does not.

[0048] The control and processing module is used to receive alarm signals and perform adjustment and processing operations.

[0049] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0050] The present invention will be further described in conjunction with the following embodiments and accompanying drawings, but the scope of the present invention is not limited to the following embodiments.

[0051] The catalyst prepared in this invention is evaluated using a microtubular reactor (microreactor). The microreactor evaluation device uses a stainless steel reaction tube with an inner diameter of 4 mm, which is placed in a copper or aluminum heating jacket. Silver catalyst particles are crushed and sieved to a size between 12 and 18 mesh, and 0.5–1 g of these particles are packed into the reactor and compacted. Inert packing material is placed at the bottom of the reactor to ensure the catalyst bed is located within the constant temperature zone of the heating jacket.

[0052] The standard evaluation conditions for catalytic activity and selectivity used in this invention are as follows:

[0053] Composition of inlet gases (mol%): Ethylene, 30.0±5.0; Oxygen, 7.0±1.0; Carbon dioxide, <3.0; Dichloroethane, 0.1~10.0 ppm; Nitrogen, balance. Reaction pressure: 1.5~3.0 MPa; Space velocity: 2000~8000 h⁻¹ -1 The concentration of ethylene oxide in the reactor outlet tail gas is 1.0–3.0%.

[0054] The reactor was gradually heated from room temperature. Once the reaction stabilized under operating conditions, the composition of the gas at the reactor inlet and outlet was continuously measured. After correcting for volume shrinkage, the selectivity (S) was calculated using the following formula:

[0055]

[0056] Where ΔEO is the concentration difference of ethylene oxide in the reactor outlet gas and the reactor inlet gas, and ΔCO2 is the concentration difference of carbon dioxide in the reactor outlet gas and the reactor inlet gas.

[0057] Example 1

[0058] like Figure 3 As shown, the control system of this embodiment, applicable to the production of silver catalysts for catalytic ethylene epoxidation, includes:

[0059] The data acquisition module is used to acquire historical data on normal operating conditions of the impregnation solution in the silver catalyst impregnation section for ethylene epoxidation.

[0060] The data processing module performs normalization preprocessing on historical data under normal operating conditions, sets upper and lower alarm thresholds based on data distribution, and obtains the trend of regular data changes.

[0061] The monitoring and alarm module is used to monitor the real-time sampling data of the impregnation solution online and determine whether the real-time sampling data conforms to the normal data change trend. If it does not conform, an alarm signal is issued.

[0062] The control and processing module is used to receive alarm signals and perform adjustment and processing operations.

[0063] Example 2

[0064] This embodiment uses the control system described in Example 1, suitable for the production of silver catalysts for catalytic ethylene epoxidation. The specific process is as follows: Figure 1 As shown, it includes the following steps:

[0065] (1) Obtain historical real-time data on the absorption value x of the diluent of the impregnation solution to a specific wavelength of light, the content y of insoluble solid particles in the impregnation, and the kinematic viscosity z of the impregnation solution during the impregnation process under the existing normal production operation conditions, and manually screen out invalid data points caused by measurement accuracy and other reasons.

[0066] (2) Normal operating condition historical data are preprocessed by normalization. The following formula is used to perform Z-score normalization on each historical data of the impregnation liquid during the impregnation production process:

[0067]

[0068] Where μ represents the mean of the corresponding sample data and σ represents the standard deviation of the sample data, alarm upper and lower thresholds are set according to the data distribution. The upper limit is taken from the lower confidence limit of the 90% confidence interval of the maximum values ​​of x, y, and z at each time node under normal production conditions in historical data. The minimum values ​​of x, y, and z of the newly prepared impregnation solution are used as the lower threshold. The data change trend is plotted according to the boundary values ​​of x, y, and z at each time node to obtain the predicted data change trend.

[0069] (3) When the online real-time sampling data matches the predicted data trend, the impregnation solution can be used normally for catalyst production. If the data exceeds the set threshold range, an early warning will be issued and appropriate action will be taken. This can effectively reduce product quality fluctuations caused by impregnation solution storage and repeated use. (Appendix) Figure 2 This is a diagram illustrating how, when a parameter fluctuates and exceeds a threshold, it is processed to return to the threshold range and achieve normal production standards.

[0070] (4) Different handling methods are used for different abnormal changes in different parameters, when x 实时 >x 阈值上限 When this occurs, production using the impregnation solution must be stopped, and a new impregnation solution with a volume equal to (x real-time / x lower threshold) times its volume should be prepared and mixed with it, based on real-time data of x. When y 实时 >y 阈值上限 When this occurs, production must be stopped using the impregnation solution. First, large-diameter solid particles must be removed by filtering the solution, and then a new impregnation solution of equal volume should be prepared and mixed with it. When z 实时 >z 阈值上限During operation, the temperature of the impregnation solution is checked to ensure it is within the normal range. If the temperature is too low, it is restored to the normal range and observation continues. If the temperature is within the normal operating range, a new impregnation solution with a volume equal to (z real-time / z lower threshold) is prepared and mixed with it. When one or more real-time detection data of x, y, and z values ​​are below the threshold range, production is stopped, and a comprehensive component analysis of the impregnation solution is performed. Based on the results, a decision is made to either re-prepare the impregnation solution or adjust its properties by adding components.

[0071] The table below lists the catalytic performance of the catalyst produced daily using the method of this invention and the catalyst produced daily without the method of this invention, and compares them, as shown in Table 1.

[0072] Table 1

[0073]

[0074] Based on the performance comparison in Table 1, the mean difference, average value, and variance of reaction temperature and selectivity were calculated, as shown in Table 2:

[0075] Table 2

[0076]

[0077] As can be seen from Table 2, after adopting the method of the present invention, the reaction temperature representing catalyst activity and the mean difference and variance representing catalyst selectivity are significantly reduced, the overall performance is more uniform, and the comprehensive performance is better.

[0078] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0079] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for controlling the production of silver catalysts for the epoxidation of ethylene, characterized in that, The steps include: (1) Obtain historical data of normal operating conditions of the impregnation solution in the silver catalyst impregnation section for ethylene epoxidation; (2) Normalize and preprocess the historical data under normal working conditions, set the upper and lower thresholds of alarms according to the data distribution, and obtain the trend of regular data changes; (3) Monitor the real-time sampling data of the impregnation solution online and determine whether the real-time sampling data conforms to the trend of conventional data changes. If it does not conform, issue an alarm signal. (4) Receive alarm signals and perform control and processing operations.

2. The control method according to claim 1, wherein, In step (1), the historical data of normal operating conditions includes the absorption value x of the diluent of the impregnation liquid to light of a specific wavelength, the content y of insoluble solid particles in the impregnation liquid, and the kinematic viscosity z of the impregnation liquid.

3. The control method according to claim 2, wherein, In step (2), the normalization preprocessing is the Z-score normalization method, and the formula is as follows: Where μ represents the mean of the corresponding sample data and σ represents the standard deviation of the corresponding sample data.

4. The control method according to claim 3, wherein, Step (2) includes setting the upper limit of the alarm threshold x for x, y, and z. 阈值上限 y 阈值上限 、z 阈值上限 The lower limit of the alarm threshold for x, y, and z. 阈值下限 y 阈值下限 、z 阈值下限 ; Where, x 阈值上限 y 阈值上限 、z 阈值上限 The lower confidence limit of the 90% confidence interval for the maximum values ​​of x, y, and z, where x 阈值下限 y 阈值下限 and z 阈值下限 It is the minimum value of x, y, and z.

5. The control method according to claim 4, wherein, In step (4), when the alarm signal is that the real-time data deviates from the trend of normal data change, but does not exceed the upper or lower alarm threshold, the processing operation includes: shortening the sampling time interval.

6. The control method according to claim 4, wherein, In step (4), when the alarm signal is x 实时 >x 阈值上限 At that time, the processing operation includes: stopping production and preparing (x) 实时 / x 阈值下限 Mix a new impregnation solution of 1.5 times its original volume with the original impregnation solution.

7. The control method according to claim 4, wherein, In step (4), when the alarm signal is y 实时 >y 阈值上限 The processing operation includes: stopping production, filtering out large-diameter solid particles, and preparing a new impregnation solution with a volume exceeding that of the original impregnation solution and mixing it with the original impregnation solution.

8. The control method according to claim 4, wherein, In step (4), when the alarm signal is z 实时 >z 阈值上限 The processing operation includes: checking whether the temperature of the impregnation solution is normal; if the temperature is not within the normal operating range, restoring it to the normal temperature range and continuing observation; if the temperature is within the normal operating range, preparing (z) 实时 / z 阈值下限 Mix a new impregnation solution of 1.5 times its original volume with the original impregnation solution.

9. The control method according to claim 4, wherein, In step (4), when the alarm signal is x 实时 y 实时 and z 实时 When at least one of the following is below the lower limit of the alarm threshold, the processing operation includes: stopping production, performing a comprehensive component analysis of the impregnation solution, and deciding, based on the results, to either re-formulate the impregnation solution or adjust the physical properties of the original impregnation solution by supplementing components.

10. The control method according to claim 1, wherein, In step (3), if no alarm signal is issued, the original operating cycle shall be followed and the impregnation liquid shall be used normally for catalyst production.

11. A control system suitable for the production of a silver catalyst for the epoxidation of ethylene, characterized in that, The system includes: The data acquisition module is used to acquire historical data on normal operating conditions of the impregnation solution in the silver catalyst impregnation section for ethylene epoxidation. The data processing module performs normalization preprocessing on historical data under normal operating conditions, sets upper and lower alarm thresholds based on data distribution, and obtains the trend of regular data changes. The monitoring and alarm module is used to monitor the real-time sampling data of the impregnation solution online and determine whether the real-time sampling data conforms to the normal data change trend. If it does not conform, an alarm signal is issued. The control and processing module is used to receive alarm signals and perform adjustment and processing operations.

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