Method for risk assessment of continuous flow processes in chemical processes

Abstract

This invention discloses a risk assessment method for continuous flow chemical processes, comprising: establishing a chemical process safety information data list based on the chemical process to be assessed; identifying whether the chemical process has risks; determining the critical temperature range corresponding to the risks if risks are determined, and conducting risk assessment, including: obtaining the reaction temperature distribution in the continuous flow reactor under the assessed process conditions; assessing the severity and probability of process risks based on the reaction temperature distribution, critical temperature range, and maximum reaction temperature; and assessing the overall process risk based on the severity and probability of process risks. This method enables the quantification of risks in continuous flow processes under different process conditions, solving the problem of a lack of risk quantification methods in the development and application of continuous flow chemical processes.

Description

Technical Field

[0001] This invention relates to the field of risk assessment technology for chemical processes, specifically a method for risk assessment of continuous flow chemical processes. Background Technology

[0002] In recent years, continuous flow reactors, with their low liquid holdup and high efficiency in mass and heat transfer, have become a key technology for enhancing the safety of high-risk processes in the fine chemical industry. Compared to traditional batch synthesis, continuous flow reactors significantly reduce the online liquid holdup of hazardous chemicals and substantially improve heat exchange efficiency, thereby reducing the overall risk of the process. However, continuous flow chemical processes are not inherently safe; process risks still exist. For example, in continuous flow processes, increased reaction rates may lead to the release of large amounts of heat in localized areas within a short period, creating hot spots and causing overheating. Therefore, effective assessment methods are still needed for continuous flow processes to identify risk variations under different process conditions and at different scales within the same continuous flow process.

[0003] Existing chemical process risk assessment methods are mostly applicable to traditional batch and semi-batch batch processes. They cannot quantitatively compare the risk levels of continuous flow chemical processes under different process conditions at the same scale, nor can they characterize the risk changes of continuous flow processes at different scales. For example, there is a Chinese patent with publication number CN110414868B entitled: A method for assessing the risk of thermal runaway in chemical processes.

[0004] Therefore, how to quantify the risks in continuous flow processes is an urgent problem to be solved for the optimization and industrial application of continuous flow processes. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a risk assessment method for continuous flow processes in chemical engineering, which can quantify the risks in continuous flow processes under various conditions.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] This invention is a risk assessment method for continuous flow processes in chemical engineering, comprising:

[0008] Based on the chemical process to be evaluated, establish a list of chemical process safety information data.

[0009] Based on the chemical process safety information data list, identify whether there are risks in the chemical process;

[0010] If a risk is determined to exist, the critical temperature range corresponding to the risk is identified, and a risk assessment is conducted, including:

[0011] Obtain the reaction temperature distribution in the continuous flow reactor under the evaluated process conditions;

[0012] Based on the reaction temperature distribution, critical temperature range, and maximum reaction temperature, assess the severity and likelihood of process risks.

[0013] The process risk is assessed based on the severity and likelihood of the process risk.

[0014] A further improvement of the present invention is that the chemical process safety information data list includes material risk characteristic information, reaction risk characteristic information, and process condition characteristic information.

[0015] A further improvement of the present invention is that the risks in the chemical process include combustion and explosion risks and thermal runaway risks. If it is determined that both combustion and explosion risks and thermal runaway risks exist at the same time, the risk that is more likely to be triggered is determined based on the relationship between the lowest boiling point of the combustible substance and the lowest initial decomposition temperature of the substance in the reaction system. The risk assessment is carried out on the risk that is more likely to be triggered, and the corresponding critical temperature range is determined.

[0016] A further improvement of the present invention is that the process for determining the critical temperature range of combustion and explosion risk includes: using the lowest boiling point of the combustible substance in the reaction system as the characteristic temperature of combustion and explosion hazard to determine the upper limit T of the critical temperature range. U,crit The lower limit T of the critical temperature range is determined by extrapolating from the lowest boiling point towards lower temperatures. L,crit The lower limit of the critical temperature range T L,crit It is below the lowest boiling point of the flammable substance and above the flash point of the corresponding flammable substance.

[0017] A further improvement of this invention is that the process for determining the critical temperature range for thermal runaway risk includes: selecting the substance with the lowest initial decomposition temperature in the reaction system, and obtaining the temperature TD corresponding to the time to reach the maximum reaction rate in 24 hours based on the decomposition kinetic parameters of the substance with the lowest initial decomposition temperature. 24 The time to reach the maximum reaction rate is the temperature TD corresponding to the reaction residence time. res Determine the temperature TD 24 The lower limit temperature T of the critical temperature range L,crit Temperature TD res T is the upper limit of the critical temperature range. U,crit .

[0018] A further improvement of the present invention is that the assessment of the severity of process risk includes:

[0019] Based on process operating temperature T p and the upper limit of the critical temperature range T U,critDetermine the process-sensitive temperature T s :

[0020] ;

[0021] in, This refers to the temperature sensitivity coefficient.

[0022] Based on the reaction temperature distribution, identify the reaction temperature T in the continuous flow reactor. r Temperature T above the process sensitivity temperature s axial distance of the channel And calculate the overtemperature volume under the evaluated process conditions:

[0023] ;

[0024] Among them, S r The cross-sectional area of ​​the continuous flow reactor channel. The volume is above the temperature limit;

[0025] The overheat volume is converted into the potential hazard energy E, and then transformed into a characterization of severity. The damage radius is given by the expression for calculating the damage radius:

[0026] ;

[0027] in, The damage radius.

[0028] A further improvement of the present invention is that the assessment of the possibility of process risk includes:

[0029] In determining the critical temperature range [T] L,crit T U,crit After that, the lower limit of the critical temperature T is set. L,crit and the upper limit of critical temperature T U,crit Substitute into the sigmoid function:

[0030] ;

[0031] in, Due to the possibility of process risks, The maximum reaction temperature is given by k, which controls the slope of the central region of the sigmoid function.

[0032] Let the critical temperature limit T be... L,crit At that time, the possibility of process risks At the upper limit of the critical temperature T U,crit At that time, the possibility of process risks , The slope k is calculated, and the probability function corresponding to the critical temperature range is established.

[0033] The highest reaction temperature T obtained based on the reaction temperature distribution r,max Substituting this into the probability function yields the probability of the risk occurring under the evaluated process conditions.

[0034] A further improvement of this invention lies in: assessing process risk based on the severity and probability of the process risk, expressed as:

[0035]

[0036] in, For process risks, The severity of the process risk, This is to account for the potential for process risks.

[0037] The beneficial effects of this invention are: it enables the quantification and comparison of risks in continuous flow processes under different process conditions and at different scales, thus solving the problem of a lack of risk quantification methods in the development and application of continuous flow chemical processes. The assessment method of this invention is simple and universally applicable to risk assessment of continuous flow chemical processes. Attached Figure Description

[0038] Figure 1 This is a flowchart of the risk assessment process in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the reaction temperature distribution in a continuous flow reactor at different scales under a process operating temperature of 35°C in an embodiment of the present invention.

[0040] Figure 3 This is a schematic diagram of the reaction temperature distribution in a continuous flow reactor at different scales under a process operating temperature of 40°C in an embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram of the reaction temperature distribution in a continuous flow reactor at different scales under a process operating temperature of 45°C in an embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram of the reaction temperature distribution in a continuous flow reactor at different scales under a process operating temperature of 50°C in an embodiment of the present invention.

[0043] Figure 6 This is a schematic diagram showing the reaction temperature distribution in a continuous flow reactor at different scales under a process operating temperature of 30°C in an embodiment of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Example 1:

[0046] like Figure 1 As shown, the risk assessment method for continuous flow chemical processes in this embodiment includes the following steps:

[0047] S1, Identify the chemical process to be evaluated and establish a chemical process safety information data list, including material risk characteristic information, reaction risk characteristic information, and process condition characteristic information, among which:

[0048] Material risk characteristic information includes the chemical substances involved in the process, the physical information of the chemical substances, combustion and explosion risk characteristic parameters, and thermal runaway risk characteristic parameters. The chemical substances include reactants, solvents, catalysts, intermediate products, products, and by-products. The physical information of the chemical substances includes CAS number, structural formula, molar mass, density, and specific heat. The combustion and explosion risk characteristic parameters include flash point, boiling point, heat of combustion, and explosion limits. The thermal runaway risk characteristic parameters include initial decomposition temperature, heat of decomposition, and decomposition kinetic parameters.

[0049] Reaction risk characteristics include reaction pathways, reaction enthalpy, and reaction kinetics information involved in the process. Reaction pathways include main reactions and side reactions.

[0050] The process condition characteristics information includes process operating temperature, reaction pressure, catalyst dosage, feed molar ratio, reaction residence time, channel material of the continuous flow reactor, reactor volume, channel length, and channel hydraulic diameter.

[0051] This embodiment establishes a process safety information data list for continuous flow chemical processes under different scales and process operating temperature conditions, as shown in Tables 1.1, 1.2, and 1.3. In this embodiment, the scale refers to the hydraulic diameter of the channel.

[0052] Table 1.1 List of Material Risk Characteristics in Example 1

[0053]

[0054] Table 1.2 List of reaction risk characteristics in Example 1

[0055]

[0056] Table 1.3 List of process condition characteristics in Example 1

[0057]

[0058] S2, based on the chemical process safety information data list, identify whether there is a risk of combustion or explosion or thermal runaway in the chemical process. If it is determined that there is no such risk, proceed to S7, and the risk assessment ends. If it is determined that there is a risk of combustion or explosion or thermal runaway, proceed to S3, and determine the critical temperature range [T] corresponding to the risk. L,crit T U,crit ].

[0059] If both combustion / explosion risk and thermal runaway risk are identified simultaneously, the risk more likely to be triggered is determined based on the relationship between the lowest boiling point of the combustible substance and the lowest initial decomposition temperature of the substance in the reaction system. If the combustion / explosion risk is more likely to be triggered, the upper limit T of the critical temperature range is determined by using the lowest boiling point of the combustible substance in the reaction system as the characteristic temperature of the combustion / explosion hazard. U,crit The lower limit T of the critical temperature range is determined by extrapolating from the lowest boiling point towards lower temperatures. L,crit The lower limit of the critical temperature range T L,crit The temperature should be below the lowest boiling point of the flammable substance but above its flash point. If thermal runaway is more likely to be triggered, then the initial decomposition temperature T in the reaction system should be selected. onset For the substance with the lowest reaction rate, the temperature TD corresponding to the time to reach the maximum reaction rate after 24 hours is obtained based on the decomposition kinetic parameters of that substance. 24 The time to reach the maximum reaction rate is the residence time t. res The corresponding temperature TD res Confirmed. Temperature TD confirmed. 24 The lower limit of the critical temperature range, T L,crit Temperature TD res T is the upper limit of the critical temperature range. U,crit。 When evaluating processes with different reaction residence times, temperature TD res The upper limit of the critical temperature range T varies with the reaction residence time. U,crit Corresponding changes should also be made.

[0060] According to the process safety information data lists in Tables 1.1, 1.2, and 1.3, the continuous flow process in this embodiment is exothermic and involves flammable and thermally decomposable chemicals. This continuous flow process presents both combustion / explosion and thermal runaway risks. However, the substance with the lowest initial decomposition temperature in the reaction system is the feedstock hydrogen peroxide, with an initial decomposition temperature of 40.9°C. The substance with the lowest boiling point in the reaction system is the solvent acetonitrile, with a boiling point of 81°C-82°C. Therefore, the thermal runaway risk of this continuous flow process is more easily triggered and is identified as a risk to be assessed. The TD corresponding to the thermal decomposition of hydrogen peroxide...24 =12.8°C. According to Table 1.3, the reaction residence time t res For 900s, the corresponding TD res =47.5°C. Therefore, the critical temperature range is [12.8, 47.5].

[0061] S3. Obtain the reaction temperature distribution along the axial direction of the continuous flow reactor channel under the evaluated process conditions. This can be achieved through continuous flow reaction calorimetry or reaction kinetic calculations. Based on the reaction kinetics in Table 1.2, calculate the axial distribution of the reaction temperature in the process. Figures 2 to 5 As shown.

[0062] This embodiment focuses on adjusting the process operating temperature T. p The following example demonstrates the risk assessment process for a continuous flow process.

[0063] S4, Assess the severity of process risks. S: Based on T p and T U,crit Determine the process-sensitive temperature T s By combining the reaction temperature distribution obtained from S3, the reaction temperature T in the continuous flow reactor can be identified. r Temperature T above the process sensitivity temperature s axial distance of the channel The supertemperature volume under the evaluated process conditions is obtained by multiplying it by the cross-sectional area of ​​the continuous flow reactor channel. The overheated volume is converted into potential hazardous energy E, and then into a damage radius D. r With damage radius D r Characterize the severity S of process risk.

[0064] Determine the process-sensitive temperature T s The expression is:

[0065] ;

[0066] in, This is the temperature sensitivity coefficient, with a value range of [0,1]. The magnitude of this value determines the sensitive temperature T of the process. s With process operating temperature T p deviation, The value is determined by the assessors based on the stringency of the process temperature control requirements. The smaller the value, the more sensitive the process temperature T is. s The closer to the process operating temperature T p This indicates that the lower the temperature that the process can be raised to, the more stringent the temperature control requirements of the process. The larger the value, the more sensitive the process temperature T is. s With process operating temperature T p The greater the difference, the higher the temperature that the process can tolerate, meaning the lower the temperature control requirements of the process. In this embodiment, different process operating temperatures T... p The corresponding process-sensitive temperature T s As shown in Table 2:

[0067] Table 2: Operating Temperature T for Different Processes p The corresponding process-sensitive temperature T s

[0068]

[0069] Under the evaluated process conditions, the formula for calculating the overtemperature volume is:

[0070] ;

[0071] Among them, S r The cross-sectional area of ​​the continuous flow reactor channel. The volume is above the temperature limit.

[0072] For combustion and explosion risks, the potential hazardous energy E is calculated as follows:

[0073] ;

[0074] The potential danger energy E for thermal runaway risk is calculated as follows:

[0075] ;

[0076] The formula for calculating the damage radius is as follows:

[0077] ;

[0078] Among them, D r The damage radius, It is the fluid density within the channels of a continuous flow reactor. It is the heat of decomposition of matter. It is the heat of combustion.

[0079] The severity S in this embodiment is shown in Table 3:

[0080] Table 3: Operating temperatures T at different scales and processes in continuous flow processes p Severity of process risk S

[0081]

[0082] S5, Assess the likelihood of process risk P: based on the critical temperature range [T] determined in step S2. L,crit , T U,crit ], set the upper limit of the critical temperature T U,crit and the critical temperature limit T L,crit Substitute into the sigmoid function:

[0083] ;

[0084] Here, k controls the slope of the central region of the sigmoid function. The larger the value, the steeper the curve in the central region, and the faster the sigmoid function value increases. Conversely, the flatter the curve in the central region, the slower the increase.

[0085] Let the critical temperature limit T be... L,crit At that time, the possibility of process risks At the upper limit of the critical temperature T U,crit At that time, the possibility of process risks , The slope k is calculated, and the probability function corresponding to the critical temperature range is established.

[0086] The critical temperature range in this embodiment is [12.8, 47.5]. Substituting this into the sigmoid function, we get k = 0.1697.

[0087] The highest reaction temperature T of the continuous flow process is obtained based on the reaction temperature distribution. r,max Substituting this into the probability function yields the probability of the risk occurring under the evaluated process conditions.

[0088] .

[0089] The potential process risks in this embodiment are shown in Table 4:

[0090] Table 4: Probability of process risk P under different scales and process conditions in continuous flow processes

[0091]

[0092] S6. Assess the process risk R by multiplying the severity S of the process risk by the probability P of the process risk. The results obtained in this embodiment are shown in Table 5.

[0093] Table 5: Risk R of Continuous Flow Process under Different Scales and Process Conditions

[0094]

[0095] S7, Process risk assessment completed.

[0096] Example 2:

[0097] The method steps in this embodiment are the same as in Embodiment 1. In S1, the process safety information data lists established in this embodiment for continuous flow chemical processes at different scales are shown in Tables 6.1, 6.2, and 6.3:

[0098] Table 6.1: List of Material Risk Characteristics in Example 2

[0099]

[0100] Table 6.2 List of reaction risk characteristics in Example 2

[0101]

[0102] Table 6.3 List of process condition characteristics in Example 2

[0103]

[0104] According to Tables 6.1, 6.2, and 6.3, the continuous flow process in this embodiment is exothermic, involves flammable substances, but does not involve substances prone to thermal decomposition, making it susceptible to combustion and explosion risks. Therefore, combustion and explosion risk is identified as an assessed risk. Table 6.1 shows that the substance with the lowest boiling point in the reaction system is the solvent dichloroethane. Critical temperature upper limit T U,crit The corresponding boiling point of dichloroethane is 83.5℃, the flash point of dichloroethane is 17℃, and the lower limit of the critical temperature T is... L,crit The value is below the boiling point and above the flash point. Let T... L,crit If the value is 53.5℃, then the critical temperature range of this continuous flow process is [53.5, 83.5].

[0105] The axial distribution of the reaction temperature in this process was obtained from the apparent reaction kinetic equations in Table 6.2. Figure 6 As shown.

[0106] In this embodiment, the process operating temperature T p The process-sensitive temperature T corresponding to 30℃ s As shown in Table 7:

[0107] Table 7: Process operating temperature T p The process-sensitive temperature T corresponding to 30℃ s

[0108]

[0109] The severity S of process risk at different scales in the continuous flow process calculated in this embodiment is shown in Table 8:

[0110] Table 8: Severity of Process Risk S at Different Scales in Continuous Flow Processes

[0111]

[0112] The critical temperature range determined in this embodiment is [53.5, 83.5]. Substituting the lower critical temperature limit of 53.5 and the upper critical temperature limit of 83.5 into the sigmoid function yields k = 0.1963. The probability P of process risk is:

[0113] .

[0114] Table 9 shows the probability P of process risk at different scales in continuous flow processes:

[0115] Table 9: Probability of process risk P at different scales in continuous flow processes

[0116]

[0117] Table 10 shows the process risk R of the continuous flow process at different scales obtained in this embodiment:

[0118] Table 10: Process Risk R of Continuous Flow Process at Different Scales

[0119]

[0120] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0121] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A risk assessment method for continuous flow processes in chemical engineering, characterized in that, include: Based on the chemical process to be evaluated, establish a list of chemical process safety information data. Based on the chemical process safety information data list, identify whether there are risks in the chemical process; If a risk is determined to exist, the critical temperature range corresponding to the risk is identified, and a risk assessment is conducted, including: Obtain the reaction temperature distribution in the continuous flow reactor under the evaluated process conditions; Based on the reaction temperature distribution, critical temperature range, and maximum reaction temperature, assess the severity and likelihood of process risks. Assess process risks based on the severity and likelihood of the risks. Risks in chemical processes include combustion and explosion risks and thermal runaway risks. If it is determined that both combustion and explosion risks and thermal runaway risks exist simultaneously, the risk that is more likely to be triggered is determined based on the relationship between the lowest boiling point of the combustible substance and the lowest initial decomposition temperature of the substance in the reaction system. The risk assessment is carried out on the risk that is more likely to be triggered, and the corresponding critical temperature range is determined. The process for determining the critical temperature range for combustion and explosion risks includes: using the lowest boiling point of the combustible substance in the reaction system as the characteristic temperature of combustion and explosion hazard to determine the upper limit T of the critical temperature range. U,crit The lower limit T of the critical temperature range is determined by extrapolating from the lowest boiling point towards lower temperatures. L,crit The lower limit of the critical temperature range T L,crit It is below the lowest boiling point of the flammable substance and above the flash point of the corresponding flammable substance. The process for determining the critical temperature range for thermal runaway risk includes: selecting the substance with the lowest initial decomposition temperature in the reaction system; and, based on the decomposition kinetic parameters of the substance with the lowest initial decomposition temperature, obtaining the temperature TD corresponding to the time to reach the maximum reaction rate in 24 hours. 24 The time to reach the maximum reaction rate is the temperature TD corresponding to the reaction residence time. res Determine the temperature TD 24 The lower limit of the critical temperature range, T L,crit Temperature TD res T is the upper limit of the critical temperature range. U,crit ; The severity assessment of process risks includes: Based on process operating temperature T p and the upper limit of the critical temperature range T U,crit Determine the process-sensitive temperature T s : in, Temperature sensitivity coefficient; Based on the reaction temperature distribution, identify the reaction temperature T in the continuous flow reactor. r Temperature T above the process sensitivity temperature s axial distance of the channel And calculate the overtemperature volume under the evaluated process conditions: Among them, S r The cross-sectional area of ​​the continuous flow reactor channel. The volume is above the temperature limit; The overtemperature volume is converted into potential hazardous energy E, and then into a damage radius that characterizes the severity S of the process risk. The expression for calculating the damage radius is as follows: in, The damage radius; The assessment of the potential process risks includes: In determining the critical temperature range [T] L,crit T U,crit After that, the lower limit of the critical temperature T is set. L,crit and the upper limit of critical temperature T U,crit Substitute into the sigmoid function: in, Due to the possibility of process risks, The maximum reaction temperature is given by k, which controls the slope of the central region of the sigmoid function. Let the lower limit T be at the critical temperature. L,crit At that time, the possibility of process risks At the upper limit of the critical temperature T U,crit At that time, the possibility of process risks The slope was calculated. Establish the probability function corresponding to the critical temperature range; The highest reaction temperature T obtained based on the reaction temperature distribution r,max Substituting this into the probability function yields the probability of the risk occurring under the evaluated process conditions.

2. The risk assessment method for continuous flow chemical processes according to claim 1, characterized in that, The chemical process safety information data list includes information on the characteristics of material risks, the characteristics of reaction risks, and the characteristics of process conditions.

3. The risk assessment method for continuous flow chemical processes according to claim 1, characterized in that, Based on the severity and probability of process risks, process risks are assessed using the following expression: in, For process risks, The severity of the process risk, This is to account for the potential for process risks.

Images