WO2021026810A1 - Method for assessing risk of thermal runaway in chemical process - Google Patents

Abstract

A method for assessing the risk of thermal runaway in a chemical process, relating to the field of chemical process risk assessment. Comprising the steps: 1) collecting thermal risk data of raw materials, products, and reaction processes; 2) determining a material factor MF, the material factor MF being determined by the initial decomposition temperature T_onset and the maximum exothermic power MPD of a material; 3) determining a reaction thermal runaway risk index RI, RI being the product of the consequence severity S and probability P of a runaway reaction; and 4) calculating a thermal runaway risk index ITHI of a process and, on the basis of an ITHI thermal runaway risk classification standard, determining the thermal runaway risk level of the process. Material thermal risk is combined with reaction runaway risk to provide a method for quantitatively assessing the risk of thermal runaway in a chemical process.

Description

A method for evaluating the risk of thermal runaway in chemical process Technical field

The invention belongs to the field of risk assessment of chemical processes, and relates to a method for assessing the risk of thermal runaway in a chemical process.

Background technique

Exothermic reaction is a very common type of reaction in the chemical and pharmaceutical industry. If the energy released during the reaction is not effectively controlled, it may cause thermal runaway accidents in the process. The correct recognition of hazards is the prerequisite for controlling hazards. Therefore, pre-assessing the risk of thermal runaway in the process is an important means to understand and take corresponding measures to control hazards. How to comprehensively and accurately assess the risk of thermal runaway in the process is an important issue that needs to be resolved urgently in the chemical industry.

The current research on the risk of thermal runaway mostly focuses on the experiments and simulation studies of the thermal runaway risk of substances and reactions, but little attention has been paid to the evaluation methods of the thermal runaway risk of the process. The existing thermal runaway risk assessment methods mostly focus on the thermal risk of substances or reactions, but do not combine substances and reactions to assess the thermal runaway risk of the process, which may lead to deviations in the perception of the actual thermal runaway risk of the process.

The current methods used to assess the risk of thermal runaway are mostly only applicable to substances or reactions, and rarely combine the risk of thermal decomposition of reactive substances with the risk of runaway in the reaction stage. The risk of thermal runaway in the process of evaluating the risk of thermal runaway that combines substances and reaction processes is of great significance for improving the comprehensiveness and accuracy of the assessment results.

Summary of the invention

The purpose of the present invention is to provide a method for evaluating the risk of thermal runaway in the chemical process in response to the current demand for the risk of thermal runaway in the chemical process, combining the thermal risk of substances with the risk of reaction runaway to form a chemical process thermal runaway A quantitative risk assessment method, which comprehensively reflects the influence of substances and reactions on the risk of thermal runaway in the process.

The present invention is realized by adopting the following technical solutions:

A method for assessing the risk of thermal runaway in a chemical process. The specific steps are as follows:

1) Collect thermal hazard data of raw materials, products and reaction processes;

Obtain the thermal decomposition data of the raw materials and products involved in the process through experimental tests or consulting literature, as well as the thermal runaway risk characteristic data of the reaction process, and provide data support for subsequent evaluation;

2) Determine the material coefficient MF, which is determined by the initial decomposition temperature _{Tonset of the material} and the maximum exothermic power MPD;

3) Determine the reaction heat runaway risk index RI, which is the product of the consequence severity S and the possibility P of the runaway reaction;

4) Calculate the thermal runaway risk index ITHI of the process, and determine the thermal runaway risk of the process according to the ITHI thermal runaway risk classification standard.

Further, the method for determining the material coefficient MF in the step (2) is to test the thermal stability of all raw materials, and select the material with the worst thermal stability to determine the MF, which specifically includes the following steps:

2-1) Determine the initial decomposition temperature T _onset of the material with the worst thermal stability;

2-2) Determine the maximum heat release power MPD of the material with the worst thermal stability;

2-3) Calculate the material coefficient MF according to the following formula 1;

MF=1+I _Tonset ×I _MPD /16 formula 1;

I _Tonset represents the initial decomposition temperature coefficient, and I _MPD represents the maximum heat _release power coefficient;

The value of I _Tonset is correspondingly determined by the value range of _Tonset in Table 1; the value of I _MPD is correspondingly determined by the value range of MPD in Table 1.

Table 1. Material coefficient MF value table

The specific rule is that when the initial decomposition temperature _{Tonset is} greater than 300°C, the I _Tonset coefficient is 0; when the value of _Tonset is in the interval (200°C, 300°C), the I _Tonset coefficient is 1; when the value of _Tonset is In the interval of (100℃, 200℃), the coefficient of I _Tonset is 2; when the value of _Tonset is in the interval of (50℃, 100℃], the coefficient of I _Tonset is 3; when the value of _Tonset is not greater than 50℃ (ie When the temperature is less than or equal to 50°C), the I _Tonset coefficient is 4.

When the value of the maximum heat release power MPD is less than 0.01W/ml, the I _MPD coefficient is 0; when the value of the maximum heat release power MPD is in the range of [0.01W/ml, 10W/ml), the I _MPD coefficient is 1; When the value of the maximum heat release power MPD is in the range of [10W/ml, 100W/ml), the I _MPD coefficient is 2; when the value of the maximum heat release power MPD is in the range of [100W/ml, 1000W/ml), the I _MPD coefficient is When the value of the maximum heat release power MPD is not less than 1000W/ml (that is, greater than or equal to 1000W/ml), the I _MPD coefficient is 4.

The material coefficient MF is determined by the material’s initial decomposition temperature _Tonset and the maximum exothermic power MPD, reflecting the risk of thermal decomposition of the material; among them, _Tonset refers to the temperature at which a material begins to decompose. The lower the temperature, the description The higher the possibility of thermal decomposition of the substance; MPD is an indicator reflecting the heat release and rate of heat release during the thermal decomposition of a substance. The larger the value, the more serious the consequences of the thermal decomposition of the substance.

The material coefficient MF corrects the risk of thermal runaway in the entire process, and its value range is limited to [1, 2]; if the substances involved in the reaction are thermally stable, the material coefficient MF is 1, and the material coefficient cannot be corrected. Function, the intrinsic thermal runaway risk of the process only depends on the thermal runaway risk of the reaction process; if the material coefficient is greater than 1, the thermal risk of the material will increase the thermal runaway risk of the entire process.

Further, the step (3) the specific method for determining the reaction heat runaway risk index RI includes the following steps:

3-1) Determine the severity of the consequences of loss of control S;

At the same time, the reaction heat and adiabatic temperature rise are selected as the out-of-control severity indicators for mutual verification, and the greater value of the two is used to determine the severity of the out-of-control consequences S;

The specific method is to obtain the severity coefficient S _{rx of} the target reaction and the severity coefficient S _{dec of the} secondary reaction respectively, and finally obtain the severity coefficient S of the reaction out of control. The calculation formula is as follows:

S _rx =max(I _H,rx ,I _ΔTad,rx ) formula 2;

S _dec =max(I _H,dec ,I _ΔTad,dec ) Formula 3;

S = S _rx + S _dec formula 4;

In the formula, I _H,rx represents the reaction heat coefficient of the target reaction, I _ΔTad,rx represents the adiabatic temperature rise coefficient of the target reaction, and the maximum value of the two is used to determine the severity coefficient S _{rx of the} target reaction; I _H,dec means two The reaction heat coefficient of the secondary reaction, I _ΔTad,dec represents the adiabatic temperature rise coefficient of the secondary reaction, and the maximum of the two is used to determine the severity coefficient of the secondary reaction S _dec .

Among them, the values of the severity coefficients S _rx and S _dec of the target reaction and the secondary reaction refer to Table 2; where I _H represents the heat coefficient of reaction, I _ΔTad represents the adiabatic temperature rise coefficient, and ΔT _ad represents the adiabatic temperature rise of the reaction.

Table 2. Severity S value table

The specific corresponding rules are: when the reaction heat is not greater than 100kJ/kg, the I _H coefficient takes the value 1; when the reaction heat is in the interval of (100kJ/kg, 400kJ/kg), the I _H coefficient takes the value 2. When the heat is in the range of (400kJ/kg, 800kJ/kg), the I _H coefficient takes the value 3; when the reaction heat is greater than 800 kJ/kg, the I _H coefficient takes the value 4. According to the above rules, the target reaction and the second The reaction heat of the reaction is evaluated according to Table 2, and the reaction heat coefficient I _{H,rx of the} corresponding target reaction and the reaction heat coefficient I _{H,dec of the} secondary reaction are obtained.

When the reaction adiabatic temperature rise ΔT _{ad is} not greater than 50°C, the I _ΔTad coefficient takes the value 1; when the reaction adiabatic temperature rise ΔT _{ad is} in the (50°C, 200°C) interval, the I _ΔTad coefficient takes the value 2; when the reaction is adiabatic When the temperature rise ΔT _{ad is} in the interval of (200℃,400℃), the I _ΔTad coefficient takes the value 3; when the reaction adiabatic temperature rise ΔT _{ad is} greater than 400℃, the I _ΔTad coefficient takes the value 4. According to the above rules, the target The adiabatic temperature rise of the reaction and the secondary reaction is evaluated according to Table 2, and the corresponding adiabatic temperature rise coefficient I _ΔTad,rx of the target reaction and the adiabatic temperature rise coefficient I _{ΔTad,dec of the} secondary reaction are _obtained.

The severity of the consequences of out-of-control reaction is determined by the severity of the target reaction and the out-of-control of the secondary reaction; using the reaction heat criterion and adiabatic temperature rise criterion for the same process may result in different coefficient levels. In order to obtain a conservative estimation result, both are selected in the present invention The heat of reaction and adiabatic temperature rise are used as indicators of the severity of the runaway to verify each other, and the larger value of the two is used to determine S. When testing the exothermic data of the secondary decomposition reaction in the experiment, try to use the reaction system mixture containing the product to test, which can better reflect the risk of thermal runaway in the actual process.

3-2) Determine the possibility P of the reaction out of control;

The possibility of reaction out of control is determined by the maximum reaction rate arrival time TMR _ad and the criticality classes of the out-of-control scenario; TMR _ad represents the time required for the secondary decomposition reaction to occur and is an indicator of the time dimension. The larger the value, the greater the occurrence. The longer the time required for the secondary reaction, the more sufficient time the operator has to take emergency measures to control the reaction, and the lower the possibility of a secondary reaction eventually; the risk level of out-of-control scenarios is inferred from the temperature scale. The criterion for the possibility of loss of control.

Taking the process operating temperature T _P , the maximum temperature of the synthesis reaction MTSR, the maximum reaction rate arrival time TMR _ad as 24 hours, the corresponding temperature T _D24 and the maximum temperature MTT for technical reasons, the relative magnitude relationship of these four temperatures divides the out-of-control scenarios into Category 5, the risk of out-of-control scenarios describes the conditions under which out-of-control occurs. The higher the level, the higher the possibility of secondary reactions.

The possibility of reaction out of control P is the sum of the maximum reaction rate arrival time coefficient I _TMR and the risk level coefficient I _CC . The calculation formula is as shown in the following formula 5. The greater the possibility P of an out of control reaction, the higher the possibility of an out of control reaction.

P=I _TMR +I _CC Formula 5.

The following Table 3 is a value table for the possibility of reaction out of control P. In this table, determine the value range of the maximum reaction rate arrival time TMR _ad from Table 3, and obtain the corresponding maximum reaction rate arrival time coefficient I _TMR ; Table 3 determines the value range of the relationship between the risk of out-of-control scenarios, and obtains the corresponding risk level coefficient I _CC ; thereby calculating the possibility of reaction out of control P.

Table 3. Possibility P value table

The specific rule is that when the maximum reaction rate arrival time TMR _ad value is greater than 50h, the maximum reaction rate arrival time coefficient I _TMR is 1; when the maximum reaction rate arrival time TMR _ad value is in the (24h, 50h) interval, the maximum The reaction rate arrival time coefficient I _TMR is 2; when the maximum reaction rate arrival time TMR _ad value is in the (8h, 24h) interval, the maximum reaction rate arrival time coefficient I _TMR is 3; when the maximum reaction rate arrival time TMR _ad value In the interval (1h, 8h), the maximum reaction rate arrival time coefficient I _TMR is 4; when the maximum reaction rate arrival time TMR _ad is not greater than 1h (that is, less than or equal to 1h), the maximum reaction rate arrival time coefficient I _TMR is 5; Among them, h means hour.

When Tp<MTSR<MTT<T _D24 , the risk level coefficient I _CC is 1; when Tp<MTSR<T _D24 <MTT, the risk level coefficient I _CC is 2; when Tp<MTT<MTSR<T _D24 , the risk level The grade coefficient I _CC is 3; when Tp<MTT<T _D24 <MTSR, the risk grade coefficient I _CC is 4; when Tp<T _D24 <MTSR<MTT, the risk grade coefficient I _CC is 5.

3-3) After the severity S of the reaction out of control determined in step (3-1) and the possibility P determined in step (3-2), the thermal runaway risk index RI of the chemical process is determined by formula 6;

RI=S×P Formula 6;

Further, step (4) calculates the thermal runaway risk index ITHI of the process, and determines the thermal runaway risk of the process according to the ITHI thermal runaway risk classification standard. The specific method includes the following steps:

4-1) As shown in formula 7, the ITHI value is obtained by multiplying the substance coefficient MF and the reaction out of control risk index RI;

ITHI=MF×RI Formula 7;

4-2) According to ITHI thermal runaway risk classification standard, classify and analyze the thermal runaway risk of the process.

The ITHI thermal runaway risk classification standards in step (4-2) are as follows:

Table 4. ITHI thermal runaway risk classification standards

range	grade	Risk
<16	I	Very low
[16,32)	II	Lower
[32,48)	III	medium
[48,64)	IV	Higher
>64	V	Very high

The meaning of Table 4 above is that when the thermal runaway risk index ITHI (hereinafter referred to as ITHI) value of the process is less than 16, it belongs to the first danger level and the risk is very low; when the ITHI value is in the interval of [16,32), It belongs to the second hazard level and the degree of risk is low; when the ITHI value is in the interval of [32,48), it belongs to the third hazard level and the degree of danger is medium; when the ITHI value is in the interval of [48,64), it belongs to the IV The danger level is high; when the ITHI value is not less than 64, it belongs to the V danger level and the danger level is very high.

Advantages of the invention:

The present invention separately establishes the thermal runaway risk coefficient of the raw materials and the thermal runaway risk coefficient of the reaction process, and combines the two to evaluate the thermal runaway risk of the process, thereby improving the comprehensiveness and accuracy of the evaluation results; In terms of evaluation, the thermal runaway hazards of different processes are more distinguished, and the recognition of the thermal runaway hazard assessment results is improved, which is conducive to the realization of process optimization and intrinsic safety. The assessment method is simple and easy to understand. The data required for the assessment is in It can be obtained through experiments in the early stage and has strong operability, so it can be used for the risk assessment of thermal runaway in the initial stage of design.

Description of the drawings

The present invention will be further described below in conjunction with the drawings:

Fig. 1 is a flowchart of a method for evaluating the risk of thermal runaway in a chemical process according to the present invention.

detailed description

The method of the present invention will be described in detail below with reference to FIG. 1 and specific embodiments.

Referring to Figure 1, the method of the present invention includes the following steps:

Step 1. Collect thermal hazard data of raw materials, products and reaction process;

Obtain data on the thermal decomposition of raw materials and products involved in the process through experimental tests or consulting literature, as well as data on the thermal runaway hazard characteristics of the reaction process, and provide data support for subsequent evaluation;

Step 2. Determine the material factor MF;

The material coefficient MF is determined by the initial decomposition temperature (T _onset ) of the material and the maximum exothermic power (MPD), which reflects the risk of thermal decomposition of the material. _Tonset refers to the temperature at which a substance begins to decompose. The lower the temperature, the higher the possibility of thermal decomposition of the substance. MPD is an indicator reflecting the heat release and rate of heat release during the thermal decomposition of a substance. The larger the value, the more serious the consequences of the thermal decomposition of the substance. MF can correct the risk of thermal runaway in the whole process, and its value range is limited to [1,2]. If the substances involved in the reaction are all thermally stable, the material coefficient MF is 1, and the material coefficient has no corrective effect. The intrinsic thermal runaway risk of the process only depends on the thermal runaway risk of the reaction process. If the material coefficient is greater than 1, the thermal risk of the material will increase the risk of thermal runaway in the entire process. In the actual evaluation process, the thermal stability of all raw materials needs to be tested, and the material with the worst thermal stability is selected to determine the MF. The calculation formula is as follows:

MF=1+I _Tonset ×I _MPD /16 (1)

Determine the material factor MF by following Table 1:

Table 1. Material coefficient MF value table

Step 3. Determine the risk index RI for out-of-control reaction;

The reaction out-of-control risk index is the product of the consequence severity (S) and the probability (P) of the out-of-control reaction, and S and P are determined in sequence according to steps 3-1 and 3-2;

Step 3-1: Determine the severity S of the consequences of losing control;

The severity of the consequences of a reaction out of control is determined by the severity of the target reaction and the second reaction out of control. Using the reaction heat criterion and adiabatic temperature rise criterion for the same process may result in different coefficient levels. In order to obtain a conservative estimation result, the present invention simultaneously selects reaction heat and adiabatic temperature rise as indicators of the out-of-control severity for mutual verification, and the two The larger value determines S. When testing the exothermic data of the secondary decomposition reaction in the experiment, try to use the reaction system mixture containing the product to test, which can better reflect the risk of thermal runaway in the actual process. The severity coefficients S _rx and S _{dec of} the target reaction and the secondary reaction are obtained respectively, and the severity coefficient S of the reaction out of control is finally obtained. The value of the severity coefficients S _rx and S _dec of the target reaction and the secondary reaction is referred to Table 2. The calculation formula is as follows:

S _rx =max(I _H,rx ,I _ΔTad,rx ) (2)

S _dec ＝max(I _H,dec ,I _ΔTad,dec ) (3)

S=S _rx +S _dec (4)

Table 2. Severity S value table

Step 3-2. Determine the possibility P of the reaction out of control;

The possibility of reaction out of control is determined by the time to reach the maximum reaction rate (TMR _ad ) and the criticality classes of the out-of-control scenario. TMR _ad characterizes the time required for the secondary decomposition reaction and is an indicator of the time dimension. The larger the value, the longer the time required for the secondary reaction to occur, and the operator has more time to take emergency measures. Control the reaction, the lower the possibility of a secondary reaction eventually. The risk level of out-of-control scenarios is a criterion for inferring the possibility of out-of-control from the temperature scale. Based on the process operating temperature ( _TP ), the maximum temperature of the synthesis reaction (MTSR), the temperature corresponding to 24 hours of TMR _ad (T _D24 ), and the maximum temperature (MTT) for technical reasons, the relative magnitude of the four temperature relationships will be divided into out-of-control scenarios. There are five categories. The risk level of out-of-control scenarios describes the conditions under which out-of-control occurs. The higher the level, the higher the possibility of secondary reactions. The possibility of out-of-control reaction P is the sum of the maximum reaction rate arrival time coefficient and the out-of-control risk level coefficient. The greater the P, the higher the possibility of an out-of-control reaction.

The calculation formula for the possibility of reaction out of control P is as follows:

P=I _TMR +I _CC (5)

Table 3 below is the value table of possibility P. In this table, determine the value range of the maximum reaction rate arrival time TMR _ad from Table 3, and obtain the corresponding maximum reaction rate arrival time coefficient I _TMR ; determine it from Table 3 The value range of the relationship between the risk of out-of-control scenarios belongs to, and the corresponding risk level coefficient I _CC is obtained; thus, the possibility of reaction out of control P is calculated.

Table 3. Possibility P value table

Step 3-3. After determining the severity S and the possibility P of the reaction out of control, the thermal runaway risk index RI of the chemical process is determined by the following formula.

RI=S×P (6)

Step 4. Calculate the thermal runaway risk index ITHI of the process, and determine the thermal runaway risk of the process according to the ITHI thermal runaway risk classification standard.

Step 4-1: Multiply the substance coefficient MF and the reaction out of control risk index RI to obtain the ITHI value;

ITHI=MF×RI (7)

Step 4-2. According to ITHI thermal runaway risk classification standard, classify and analyze the thermal runaway risk of the process. The ITHI thermal runaway risk classification standards are as follows:

Table 4. ITHI thermal runaway risk classification standards

range	grade	Risk
<16	I	Very low
[16,32)	II	Lower
[32,48)	III	medium
[48,64)	IV	Higher
≥64	V	Very high

The present invention will be further elaborated below in conjunction with examples.

The raw material for the reaction of cyclohexanone peroxidation is 210g cyclohexanone, 60g of a mixed solution of hydrogen peroxide and nitric acid with a concentration of ≥30%, the reaction condition is a temperature of 12°C, a stirring blade speed of 250r/min, and the product is cyclohexanone peroxide; The reaction formula is as follows:

2C ₆ H ₁₀ O+2H ₂ O ₂ →C ₁₂ H ₂₂ O ₅ +H ₂ O.

1) Obtain the thermal decomposition data of the raw materials and products involved in the cyclohexanone peroxidation process, as well as the thermal runaway risk characteristic data of the reaction process through experimental tests or consulting literature.

2) Determine the material factor MF of the cyclohexanone peroxidation process. Obtain the thermal decomposition data of the reaction raw material cyclohexanone and hydrogen peroxide solution through experiments and literature, as shown in the following table for the material coefficient MF value table of cyclohexanone peroxide process. The thermal hazard of hydrogen peroxide solution is higher than that of cyclohexanone, so the material coefficient is determined by the thermal decomposition data of hydrogen peroxide solution. Finally, the MF is determined to be 1.75 according to formula (1) in step 2.

Cyclohexanone peroxidation process material coefficient MF value table

3) Determine the RI

Substituting the thermal hazard parameters of the cyclohexanone peroxidation reaction in turn, the severity S and the probability P of the out-of-control are 5 and 8, respectively, as shown in the following table.

Cyclohexanone peroxidation process out of control severity S

The possibility of out-of-control cyclohexanone peroxidation process P

According to formula (6) in step 3-3, the risk coefficient of cyclohexanone peroxidation out of control is RI=S×P=40.

4) Finally, according to formula (7), ITHI=MF×RI=70 is obtained. According to the ITHI thermal runaway risk classification standard in step 4-2, it is considered that the thermal runaway risk of cyclohexanone peroxidation process is extremely high. Accepted.

The invention proposes a method for evaluating the risk of thermal runaway in a chemical process, which is composed of a material coefficient (MF) and a reaction runaway risk index (RI). The material coefficient MF is determined by the initial decomposition temperature of the material and the maximum power density. The reaction out-of-control risk index RI is determined by the possibility and severity of out-of-control. The time to reach the maximum reaction rate under adiabatic conditions and the out-of-control risk level are used to determine the possibility of out-of-control in the process. The severity of the runaway reaction is determined by the adiabatic temperature rise of the target reaction and the secondary reaction. Finally, use pre-defined hazard levels to grade and analyze the ITHI assessment results. The present invention combines the thermal runaway risk of substances and reactions to evaluate the thermal runaway risk of the technological process, thereby improving the comprehensiveness and accuracy of the evaluation result. In addition, the evaluation from the two aspects of material and reaction makes the risk of thermal runaway of different processes more distinguishable, improves the recognition of the evaluation results of thermal runaway risk, and is conducive to the realization of process optimization and intrinsic safety. In addition, the present invention is simple and easy to understand, the data required for evaluation can be obtained through experiments in the early stage, and the operability is strong. Therefore, it can be used for the evaluation of the risk of thermal runaway in the initial stage of design, and provides a reference basis for process optimization and hazard identification.

Claims (8)

1. A method for evaluating the risk of thermal runaway in a chemical process is characterized by comprising the following steps:

   1) Collect thermal hazard data of raw materials, products and reaction processes;

   Obtain the thermal decomposition data of the raw materials and products involved in the process through experimental tests or consulting literature, as well as the thermal runaway risk characteristic data of the reaction process, and provide data support for subsequent evaluation;

   2) Determine the material coefficient MF, which is determined by the initial decomposition temperature _{Tonset of the material} and the maximum exothermic power MPD;

   3) Determine the reaction heat runaway risk index RI, which is the product of the consequence severity S and the possibility P of the runaway reaction;

   4) Calculate the thermal runaway risk index ITHI of the process, and determine the thermal runaway risk of the process according to the ITHI thermal runaway risk classification standard.
2. The method for evaluating the risk of thermal runaway in a chemical process according to claim 1, wherein the method for determining the material coefficient MF in step (2) is to test the thermal stability of all raw materials, and select the worst thermal stability To determine the MF of the substance, it includes the following steps:

   2-1) Determine the initial decomposition temperature T _onset of the material with the worst thermal stability;

   2-2) Determine the maximum heat release power MPD of the material with the worst thermal stability;

   2-3) Calculate the material coefficient MF according to the following formula 1;

   MF=1+I _Tonset ×I _MPD /16 formula 1;

   Among them, I _Tonset represents the initial decomposition temperature coefficient, and I _MPD represents the maximum heat _release power coefficient.
3. The method for evaluating the risk of thermal runaway in a chemical process according to claim 2, wherein the rules for determining the initial decomposition temperature coefficient I _Tonset and the maximum heat _release power coefficient I _MPD are as follows:

   When the initial decomposition temperature _{Tonset is} greater than 300°C, the I _Tonset coefficient is 0;

   When the value of _Tonset is in the interval of (200℃, 300℃), the coefficient of I _Tonset is 1;

   When the value of _Tonset is in the interval of (100°C, 200°C), the I _Tonset coefficient is 2;

   When the value of _Tonset is in the interval of (50°C, 100°C), the I _Tonset coefficient is 3;

   When the value of _Tonset is not greater than 50°C, that is, less than or equal to 50°C, the I _Tonset coefficient is 4;

   When the value of the maximum heat release power MPD is less than 0.01W/ml, the I _MPD coefficient is 0;

   When the value of the maximum heat release power MPD is in the range of [0.01W/ml, 10W/ml), the I _MPD coefficient is 1;

   When the maximum heat release power MPD value is in the range of [10W/ml, 100W/ml), the I _MPD coefficient is 2;

   When the value of the maximum heat release power MPD is in the range of [100W/ml, 1000W/ml), the I _MPD coefficient is 3;

   When the value of the maximum heat release power MPD is not less than 1000W/ml (that is, greater than or equal to 1000W/ml), the I _MPD coefficient is 4.
4. The method for assessing the risk of thermal runaway in a chemical process according to claim 1, wherein the step (3) determines the specific method for the risk index RI of thermal runaway of reaction, comprising the following steps:

   3-1) Determine the severity of the consequences of loss of control S;

   At the same time, the reaction heat and adiabatic temperature rise are selected as the out-of-control severity indicators for mutual verification, and the greater value of the two is used to determine the severity of the out-of-control consequences S;

   3-2) Determine the possibility P of the reaction out of control;

   The reaction out-of-control possibility P is the sum of the maximum reaction rate arrival time coefficient I _TMR and the risk level coefficient I _CC , calculated as the following formula 5; the greater the reaction out-of-control possibility P, the higher the possibility of an out-of-control reaction;

   P = I _TMR + I _CC formula 5;

   3-3) After the severity S of the reaction out of control determined in step (3-1) and the possibility P determined in step (3-2), the thermal runaway risk index RI of the chemical process is determined by formula 6;

   RI=S×P Formula 6.
5. The method for evaluating the risk of thermal runaway in a chemical process according to claim 4, characterized in that, in the step (3-1), the specific method for determining the severity S of the runaway consequences is to obtain the severity of the target reaction respectively. The degree coefficient S _rx and the severity coefficient of the secondary reaction S _dec , finally get the severity coefficient S of the reaction out of control. The calculation formula is as follows:

   S _rx =max(I _H,rx ,I _ΔTad,rx ) formula 2;

   S _dec =max(I _H,dec ,I _ΔTad,dec ) Formula 3;

   S = S _rx + S _dec formula 4;

   In the formula, I _H,rx represents the reaction heat coefficient of the target reaction, I _ΔTad,rx represents the adiabatic temperature rise coefficient of the target reaction, and the maximum value of the two is used to determine the severity coefficient S _{rx of the} target reaction; I _H,dec means two The reaction heat coefficient of the secondary reaction, I _ΔTad,dec represents the adiabatic temperature rise coefficient of the secondary reaction, and the maximum of the two is used to determine the severity coefficient of the secondary reaction S _dec ;

   The specific value rules for the severity coefficient of the target reaction S _rx and the severity coefficient of the secondary reaction S _dec are as follows:

   When the reaction heat is not more than 100kJ/kg, the I _H coefficient is set to 1;

   When the reaction heat is in the range of (100kJ/kg, 400kJ/kg), the I _H coefficient is set to 2;

   When the reaction heat is in the range of (400kJ/kg, 800kJ/kg), the I _H coefficient is set to 3;

   When the reaction heat is greater than 800kJ/kg, the I _H coefficient is set to 4;

   According to the above rules, the reaction heats of the target reaction and the secondary reaction are evaluated respectively, and the corresponding reaction heat coefficients I _H,rx of the target reaction and the reaction heat coefficients I _{H,dec of the} secondary reaction are obtained;

   When the adiabatic temperature rise ΔT _{ad of the} reaction is not greater than 50°C, the I _ΔTad coefficient takes the value 1;

   When the adiabatic temperature rise ΔT _{ad of the} reaction is in the interval of (50℃,200℃), the I _ΔTad coefficient takes the value 2;

   When the reaction adiabatic temperature rise ΔT _{ad is} in the interval of (200℃,400℃), the I _ΔTad coefficient takes the value 3;

   When the adiabatic temperature rise of the reaction ΔT _{ad is} greater than 400°C, the I _ΔTad coefficient takes the value 4; according to the above rules, the adiabatic temperature rise of the target reaction and the secondary reaction are evaluated separately to obtain the corresponding adiabatic temperature rise coefficient I of the target reaction _ΔTad,rx and the adiabatic temperature rise coefficient of the secondary reaction I _ΔTad,dec .
6. The method for assessing the risk of thermal runaway in a chemical process according to claim 4, characterized in that, in the step (3-2), the possibility of reaction runaway is determined from the maximum reaction rate reaching time TMR _ad and the risk level of the runaway scenario Confirm; TMR _ad characterizes the time required for the secondary decomposition reaction and is an indicator of the time dimension. The larger the value, the longer the time required for the secondary reaction to occur, and the operator has more time to take emergency response Disposal measures control the reaction, the lower the possibility of a secondary reaction will eventually be triggered; the risk level of out-of-control scenarios is the criterion for inferring the possibility of out-of-control from the temperature scale;

   Taking the process operating temperature T _P , the maximum temperature of the synthesis reaction MTSR, the maximum reaction rate arrival time TMR _ad as 24 hours, the corresponding temperature T _D24 and the maximum temperature MTT for technical reasons, the relative magnitude relationship of these four temperatures divides the out-of-control scenarios into Category 5: The risk of out-of-control scenarios describes the conditions under which out-of-control occurs. The higher the level, the higher the possibility of secondary reactions;

   The value rules for the maximum response rate arrival time coefficient I _TMR include:

   When the value of the maximum reaction rate arrival time TMR _ad is greater than 50h, the maximum reaction rate arrival time coefficient I _TMR is 1;

   When the maximum response rate arrival time TMR _ad is in the (24h, 50h) interval, the maximum response rate arrival time coefficient I _TMR is 2;

   When the maximum reaction rate arrival time TMR _ad is in the interval (8h, 24h), the maximum reaction rate arrival time coefficient I _TMR is 3;

   When the maximum reaction rate arrival time TMR _ad is in the (1h, 8h) interval, the maximum reaction rate arrival time coefficient I _TMR is 4;

   When the value of the maximum reaction rate arrival time TMR _ad is not greater than 1h, that is, less than or equal to 1h, the maximum reaction rate arrival time coefficient I _TMR is 5;

   The value rules for the risk level coefficient I _CC include:

   When Tp<MTSR<MTT<T _D24 , the risk level coefficient I _CC is 1; when Tp<MTSR<T _D24 <MTT, the risk level coefficient I _CC is 2; when Tp<MTT<MTSR<T _D24 , the risk level The grade coefficient I _CC is 3; when Tp<MTT<T _D24 <MTSR, the risk grade coefficient I _CC is 4; when Tp<T _D24 <MTSR<MTT, the risk grade coefficient I _CC is 5.
7. The method for evaluating the risk of thermal runaway in a chemical process according to claim 1, wherein the step (4) calculates the thermal runaway risk index ITHI of the process, and determines the process according to the ITHI thermal runaway risk classification standard The specific method for the risk of thermal runaway includes the following steps:

   4-1) As shown in formula 7, the ITHI value is obtained by multiplying the substance coefficient MF and the reaction out of control risk index RI;

   ITHI=MF×RI Formula 7;

   4-2) According to ITHI's thermal runaway risk grading standard, classify and analyze the thermal runaway risk of the process.
8. The method for assessing the risk of thermal runaway in a chemical process according to claim 1, characterized in that the ITHI thermal runaway risk classification standard in step (4-2) is as follows: When the thermal runaway risk index of the process is ITHI When the value is less than 16, it belongs to the first hazard level and the degree of danger is very low; when the ITHI value is in the interval of [16,32), it belongs to the second hazard level, and the degree of danger is low; when the ITHI value is in [32,48) In the interval, it belongs to the third hazard level and the degree of danger is medium; when the ITHI value is in the interval of [48,64), it belongs to the IV hazard level and the degree of danger is high; when the ITHI value is not less than 64, it belongs to the V hazard level , The risk is high.

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