CN109949874B - Risk grading method for safety assessment in fine chemical production process - Google Patents
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Abstract
The invention discloses a danger grading method for safety evaluation in a fine chemical production process, relates to the field of safety evaluation in an organic chemical process, and relates to a danger grading method for safety evaluation in a fine chemical production process. The method comprises the following steps: 1) acquiring parameters; 2) calculating an evaluation index; 3) dividing the risk level; based on the operating temperature obtained in the previous step; after the reaction system is cooled to lose efficacy, the highest temperature which can be reached by the synthesis reaction; initial temperature of unstable decomposition of the product; the maximum temperature which the reaction kettle can bear due to the limitation of technical conditions; and final temperature under adiabatic conditions, the magnitude of the 5 key temperatures being ordered in increments to form different types of situations, graded according to the risk index. The method can properly and accurately evaluate the thermal runaway risk of the synthesis reaction, guide the chemical enterprises to optimize process operation parameters, formulate risk reduction measures, guide the chemical enterprises to select and define the risk reduction measures, improve process safety and improve the economic benefits of the enterprises.
Description
Technical Field
The invention discloses a danger grading method for safety evaluation in a fine chemical production process, relates to the field of safety evaluation in an organic chemical process, and relates to a danger grading method for safety evaluation in a fine chemical production process.
Background
Fine chemicals have become an essential part of human society. It provides convenience and brings many dangers. In chemical enterprises, the complexity of the synthesis reaction process, the dangerousness of chemical substances and the inherent dangerousness of exothermic reactions make part of the reaction devices frequently accident. Once thermal runaway occurs in the reaction, the temperature and pressure in the reaction kettle rapidly rise, and accidents such as fire, explosion, poisoning and the like are easily caused. In order to reduce the possibility of thermal runaway and the severity of consequences, the method has the primary task of accurately evaluating the thermal runaway risk of the synthesis reaction, realizing the optimization of technological process parameters and improving the intrinsic safety level of the synthesis reaction process.
At present, for the risk of thermal runaway of exothermic reaction, Gygax proposes that thermal runaway occurs under the worst condition, namely, a cooling system completely fails and the whole reaction system is in an adiabatic state. Stoessel proposes a thermal risk assessment method based on process temperature parameters in the case of a cooling failure. The method considers the possibility of thermal runaway of the synthesis reaction, but has the defect of exaggerating the accident risk. For example, if the synthesis reaction is out of control, secondary decomposition of hydroxylamine is inevitably triggered in the temperature rising process, but the temperature does not exceed the maximum temperature which can be borne by the reaction kettle in the process of out of control of the decomposition reaction, and at the moment, evaporation cooling or emergency pressure relief can be used as a last safety barrier to reduce the accident risk. But the method is used for evaluating the danger of the production process and drawing a conclusion that the enterprise needs to redesign the process. The evaluation result exaggerates the risk of thermal runaway and brings economic loss to a certain degree to chemical enterprises. Therefore, there is an urgent need for a method that enables more accurate and reliable evaluation.
Disclosure of Invention
The invention aims to provide a method for grading the risk of safety assessment in the fine chemical production process, which is based on the situation of cooling failure, comprehensively considers all key temperature parameters occurring in the synthetic reaction process, sorts the key temperature parameters at one time according to the accident occurrence probability, and provides a more accurate and reliable method for assessing the thermal risk.
The invention is realized by adopting the following technical scheme:
a danger grading method for safety assessment in a fine chemical production process comprises the following steps:
1) obtaining parameters
1-1) determining an evaluation object and collecting the operation conditions of the synthesis process;
1-2) carrying out isothermal calorimetry experiment of the synthesis reaction of an evaluation object in laboratory scale to obtain data such as heat release rate, heat conversion rate, feeding rate and the like; determining the total heat of reaction of the synthesis reaction
In the unit of
(ii) a Specific heat capacity of the reaction mixture
In the unit of
(ii) a Total mass of reaction mixture in reaction vessel
In the unit of
；
Material accumulation degree in reaction kettle at any moment
In units of%;
the reaction product was analyzed using a product analyzer to determine the reaction yield
In units of%;
1-3) carrying out adiabatic calorimetry experiments on the products of the synthesis reaction of the step (1-2);
1-3-1) first determining the initial concentration of the product in units of;
1-3-2) Using the reaction data, a temperature/pressure-time curve is plotted and the initial temperature of the decomposition of the product is determined
In units of; maximum temperature that can be reached
In units of; adiabatic temperature rise
In units of;
1-3-3) drawing a temperature rise rate-temperature curve, and carrying out nonlinear fitting by using a mathematical model to obtain thermodynamic parameters including apparent activation energy
In the unit of
(ii) a Pre-factor A, reaction order n;
1-4) if the synthesis reaction system is an open system, determining the boiling point of the solvent, wherein the solvent accounts for the maximum ratio in the reaction system; and if the system is closed, determining the temperature corresponding to the maximum allowable pressure of the reaction kettle, wherein the maximum allowable pressure of the reaction kettle refers to the set pressure of a safety valve or a rupture disk.
The operation conditions in the step (1-1) include a production mode adopting batch or semi-batch operation, an operation temperature, an operation pressure, a material ratio, a solvent, a feeding sequence, a feeding speed, a stirrer rotating speed and the like.
2) Calculating an evaluation index
2-1) the operating temperature is recorded as T1 and is determined by the operating conditions of the synthesis reaction, and the initial temperature of the cooling failure condition is T1;
2-2) after the reaction system is cooled to be invalid, recording the highest temperature which can be reached by the synthesis reaction as T2;
total adiabatic temperature rise of the synthesis reaction
In units of; t2 and
is calculated by the following formula,
in the formula (I), the compound is shown in the specification,
the temperature which can be reached by the synthesis reaction is measured in units of temperature after the reaction system is cooled and loses efficacy; t2 taking
Maximum value of (d);
for a conservative assessment, in a batch reaction,
；
in the semi-batch reaction, the reaction is carried out,
；
2-3) the initial temperature of unstable decomposition of the product, noted as T3;
the initial temperature T3 of unstable decomposition of the product is desirable, and the maximum reaction rate of the product decomposition reaches the reaction initial temperature corresponding to 24 h. Determined by the following equation (3);
2-4) due to the limitation of technical conditions, the maximum temperature which can be borne by the reaction kettle is recorded as T4;
in an open system, T4 is the boiling point of the solvent; in a closed system, T4 is the temperature corresponding to the maximum allowable pressure of the reaction kettle; the maximum allowable pressure of the reaction kettle refers to the set pressure of a safety valve or a rupture disk;
2-5) Final temperature under adiabatic conditions was recorded as T5;
when the maximum temperature T2 at which the synthesis reaction can reach after failure of cooling is less than the initial temperature T3 at which the product is not stably decomposed, secondary decomposition reaction is hardly initiated, and at this time,
when the maximum temperature T2 of the synthesis reaction is greater than the initial temperature T3 of the decomposition of the product, the decomposition reaction of the product is initiated, and, at this time,
3) dividing the risk level;
the operating temperature T1 obtained on the basis of the preceding steps; cooling the reaction system to lose efficacy; the highest temperature T2 that can be reached by the synthesis reaction; the initial temperature T3 at which the product is unstably decomposed; the maximum temperature T4 that the reaction kettle can bear due to the limitation of technical conditions; and a final temperature T5 under adiabatic conditions, wherein the 5 key temperatures are ordered in an increasing order to form different types of situations and are graded according to the risk index;
the classification is as follows,
3-1) level 1 hazard situations, including 2 cases;
first, T1< T2< T4< T3< T5; under the condition, after the synthesis reaction is out of control, the temperature does not reach the maximum temperature T4 which can be borne by the reaction kettle, the decomposition of products is not caused, and the maximum temperature T4 which can be borne by the reaction kettle can be reached only after the reaction materials stay for a long time under the condition of heat accumulation;
second, T1< T2< T3< T5< T4; under the condition, after the synthesis reaction is out of control, the product decomposition cannot be initiated, if the reaction materials stay in a heat accumulation state for a long time, the secondary decomposition reaction can be initiated, but the final temperature T5 of the reaction under the adiabatic condition cannot reach the maximum temperature T4 which can be borne by the reaction kettle, and the evaporative cooling or the emergency release can play the role of an additional safety barrier;
3-2) grade 2 risk profile, T1< T2< T3< T4< T5; after the synthesis reaction is out of control, the temperature cannot reach the maximum temperature T4 which can be borne by the reaction kettle, the decomposition of products cannot be initiated, if the reaction materials stay in a heat accumulation state for a long time, the secondary decomposition reaction is initiated, and the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle. If the synthesis reaction is at a high exotherm at T4, a hazard may be triggered;
3-3) level 3 hazard situations, including 2 cases;
first, T1< T4< T2< T3< T5; after the synthesis reaction is out of control, the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle, but the product decomposition is not initiated. The safety of the reaction process depends on the exothermic rate of the synthesis reaction at T4;
second, T1< T3< T2< T5< T4; after the synthesis reaction is out of control, the system initiates a secondary decomposition reaction of the product, but the final temperature T5 under the adiabatic condition does not reach the maximum temperature T4 which can be borne by the reaction kettle, and evaporative cooling or emergency pressure relief can be used as a final safety barrier.
3-4) class 4 risk profile, T1< T4< T3< T2< T5; after the synthesis reaction is out of control, the temperature reaches the technical limit, and the product decomposition is triggered by theoretical analysis; the safety of the reaction process depends on the sum of the heat release rates of the synthesis reaction and the secondary decomposition reaction when the maximum temperature T4 can be borne by the reaction kettle;
3-5) grade 5 risk profile, T1< T3< T2< T4< T5; after the synthesis reaction is out of control, the system can initiate the decomposition of products, the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle in the process of the secondary decomposition reaction out of control, and at the moment, the evaporation cooling or the emergency pressure relief cannot play the role of a safety barrier.
The invention provides a more reliable and accurate method for identifying and evaluating the thermal runaway risk of the synthesis reaction, can properly and accurately evaluate the thermal runaway risk of the synthesis reaction, and is beneficial to guiding chemical enterprises to optimize process operation parameters, formulating risk reduction measures, guiding the chemical enterprises to select and define enough risk reduction measures, improving process safety and improving economic benefits of the enterprises.
Drawings
The invention will be further explained with reference to the drawings, in which:
FIG. 1 is a schematic diagram of a hazard map hierarchy established by the method of the present invention;
FIG. 2 is a graph of temperature and heat release rate for a TBPA synthesis reaction in accordance with an example of the present invention;
FIG. 3 is a graph of temperature and pressure for a TBPA decomposition reaction in accordance with an embodiment of the present invention;
FIG. 4 is a graph of the rate of rise curve and a kinetic fit for a TBPA decomposition reaction in accordance with an embodiment of the present invention;
FIG. 5 shows the final temperature achievable for the TBPA synthesis reaction after a cooling failure according to an embodiment of the present invention
Curve line.
Detailed Description
The invention will be further described with reference to the accompanying drawings and specific embodiments.
In fig. 1, the numbers on the X-axis represent the risk level;
the vertical axis represents temperature, where labeled:
t1 denotes operating temperature;
t2 represents the highest temperature that the synthesis reaction can reach after the reaction system fails to cool;
t3 denotes the initial temperature of unstable decomposition of the product;
t4 represents the maximum temperature that the reaction kettle can bear due to the limitation of technical conditions;
t5 represents the final temperature under adiabatic conditions.
Referring to the attached figure 1, the method for grading the risk of the safety assessment in the fine chemical production process comprises the following steps:
1) obtaining parameters
1-1) determining an evaluation object and collecting the operation conditions of the synthesis process;
1-2) carrying out isothermal calorimetry experiment of the synthesis reaction of an evaluation object in laboratory scale to obtain data such as heat release rate, heat conversion rate, feeding rate and the like; determining the total heat of reaction of the synthesis reaction
(ii) a Specific heat capacity of the reaction mixture
(ii) a Total mass of reaction mixture in reaction vessel
；
Material accumulation degree in reaction kettle at any moment
；
The reaction product was analyzed using a product analyzer to determine the reaction yield
；
1-3) carrying out adiabatic calorimetry experiments on the products of the synthesis reaction of the step (1-2);
1-3-1) first determining the initial concentration of the product;
1-3-2) Using the reaction data, a temperature/pressure-time curve is plotted and the initial temperature of the decomposition of the product is determined
Maximum temperature that can be reached
Adiabatic temperature rise
；
1-3-3) drawing a temperature rise rate-temperature curve, and carrying out nonlinear fitting by using a mathematical model to obtain thermodynamic parameters including apparent activation energy
(ii) a Pre-factor A, reaction order n;
1-4) if the reaction system is an open system, determining the boiling point of the solvent, wherein the ratio of the solvent in the reaction system is the largest; and if the system is closed, determining the temperature corresponding to the maximum allowable pressure of the reaction kettle, wherein the maximum allowable pressure of the reaction kettle refers to the set pressure of a safety valve or a rupture disk.
2) Calculating an evaluation index
2-1) the operating temperature is recorded as T1 and is determined by the operating conditions of the synthesis reaction, and the initial temperature of the cooling failure condition is T1;
2-2) after the reaction system is cooled to be invalid, recording the highest temperature which can be reached by the synthesis reaction as T2;
total adiabatic temperature rise of the synthesis reaction
(ii) a T2 and
is calculated by the following formula,
in the formula (I), the compound is shown in the specification,
the temperature which can be reached by the synthesis reaction is measured in units of temperature after the reaction system is cooled and loses efficacy; t2 taking
Maximum value of (d);
for a conservative assessment, in a batch reaction,
；
in the semi-batch reaction, the reaction is carried out,
；
2-3) the initial temperature of unstable decomposition of the product, noted as T3;
the initial temperature T3 of unstable decomposition of the product is desirable, the maximum reaction rate arrival time of the decomposition of the product is 24h, and the corresponding reaction initial temperature is determined by the following equation (3);
2-4) due to the limitation of technical conditions, the maximum temperature which can be borne by the reaction kettle is recorded as T4;
in an open system, T4 is the boiling point of the solvent; in a closed system, T4 is the temperature corresponding to the maximum allowable pressure of the reaction kettle; the maximum allowable pressure of the reaction kettle refers to the set pressure of a safety valve or a rupture disk;
2-5) Final temperature under adiabatic conditions was recorded as T5;
when the maximum temperature T2 at which the synthesis reaction can reach after failure of cooling is less than the initial temperature T3 at which the product is not stably decomposed, secondary decomposition reaction is hardly initiated, and at this time,
when the maximum temperature T2 of the synthesis reaction is greater than the initial temperature T3 of the decomposition of the product, the decomposition reaction of the product is initiated, and, at this time,
3) dividing the risk level;
the operating temperature T1 obtained on the basis of the preceding steps; cooling the reaction system to lose efficacy; the highest temperature T2 that can be reached by the synthesis reaction; the initial temperature T3 at which the product is unstably decomposed; the maximum temperature T4 that the reaction kettle can bear due to the limitation of technical conditions; and a final temperature T5 under adiabatic conditions, wherein the 5 key temperatures are ordered in an increasing order to form different types of situations and are graded according to the risk index;
the classification is as follows,
3-1) level 1 hazard situations, including 2 cases;
first, T1< T2< T4< T3< T5; under the condition, after the synthesis reaction is out of control, the temperature does not reach the maximum temperature T4 which can be borne by the reaction kettle, the decomposition of products is not caused, and the temperature can reach T4 only after the reaction materials stay for a long time under the condition of heat accumulation;
second, T1< T2< T3< T5< T4; under the condition, after the synthesis reaction is out of control, the product decomposition cannot be initiated, if the reaction materials stay in a heat accumulation state for a long time, the secondary decomposition reaction can be initiated, but the final temperature T5 of the reaction under the adiabatic condition cannot reach the maximum temperature T4 which can be borne by the reaction kettle, and the evaporative cooling or the emergency release can play the role of an additional safety barrier;
3-2) grade 2 risk profile, T1< T2< T3< T4< T5; after the synthesis reaction is out of control, the temperature cannot reach the maximum temperature T4 which can be borne by the reaction kettle, the decomposition of products cannot be initiated, if the reaction materials stay in a heat accumulation state for a long time, the secondary decomposition reaction is initiated, and the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle. If the synthesis reaction is at a high exotherm at T4, a hazard may be triggered;
3-3) level 3 hazard situations, including 2 cases;
first, T1< T4< T2< T3< T5; after the synthesis reaction is out of control, the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle, but the product decomposition is not initiated. The safety of the reaction process depends on the exothermic rate of the synthesis reaction at T4;
second, T1< T3< T2< T5< T4; after the synthesis reaction is out of control, the system initiates a secondary decomposition reaction of the product, but the final temperature T5 under the adiabatic condition does not reach the maximum temperature T4 which can be borne by the reaction kettle, and evaporative cooling or emergency pressure relief can be used as a final safety barrier.
3-4) class 4 risk profile, T1< T4< T3< T2< T5; after the synthesis reaction is out of control, the temperature reaches the technical limit, and the product decomposition is triggered by theoretical analysis; the safety of the reaction process depends on the sum of the heat release rates of the synthesis reaction and the secondary decomposition reaction at T4;
3-5) grade 5 risk profile, T1< T3< T2< T4< T5; after the synthesis reaction is out of control, the system can initiate the decomposition of products, the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle in the process of the secondary decomposition reaction out of control, and at the moment, the evaporation cooling or the emergency pressure relief cannot play the role of a safety barrier.
Example (b):
1. obtaining parameters
1-1) determining an evaluation object as the process safety evaluation of the tert-butyl peroxyacetate (TBPA) synthesis process under the alkaline reaction condition.
In the actual process, tert-butyl hydroperoxide (TBHP) is firstly reacted with sodium hydroxide to form an organic salt solution of tert-butyl hydroperoxide, then acetic anhydride (Ac 2O) is added, and a stirrer is started to react with the organic salt to form TBPA. The reaction temperature was controlled with frozen brine during the reaction, and was 20 ℃. The process is operated in a semi-batch mode, and the reaction equation is as follows:
1-2) carrying out a TBPA synthesis isothermal calorimetry experiment;
the experimental instrument used was a reaction calorimeter;
the experimental procedure was as follows:
1-2-1) the reaction calorimeter temperature control mode was set to isothermal mode, the reaction temperature was set to 20 ℃, the stirring rate was set to 150rpm/min, and the feed rate was set to 4.5 g/min.
1-2-2) of the reaction
The TBPA synthesis reaction under alkaline condition is carried out in two steps, wherein 953.4g of tert-butyl hydroperoxide/sodium hydroxide salt solution is added into a reaction kettle in the first step, and 222.7g of acetic anhydride is added dropwise for reaction at a programmed feeding rate in the second step. The mass of the reaction mixture amounted to 1176.1 g. The exothermic characteristics of the second main reaction were investigated.
The change curves of the jacket temperature (Tj), the reaction kettle temperature (Tr), the heat release rate (qr) and the corresponding feeding curve in the TBPA synthesis reaction process under the alkaline condition are shown in a figure 2. The total reaction heat of the synthesis reaction can be obtained by integrating the qr-t curve
. The specific heat capacity of the reaction mixture was experimentally measured,
。
and (3) analyzing the components of the synthesized product by using a product analyzer, wherein the oil phase and the water phase of the product are layered under an alkaline condition, and the components of the product in the oil phase mainly comprise tert-butyl hydroperoxide (TBHP), di-tert-butyl hydroperoxide (DTBP) and tert-butyl peroxyacetate (TBPA). The yield of TBPA under alkaline conditions was found to be 71% by calculation.
1-3) carrying out a TBPA adiabatic decomposition calorimetric experiment;
the experimental instrument adopts an adiabatic calorimeter;
the experimental procedure is that 0.8g of TBPA sample is loaded into a pressure-resistant test ball, and the initial concentration is determined
. The initial temperature was set to 70 deg.C, the end temperature was set to 250 deg.C, the heating temperature was stepped at 5 deg.C, and the waiting time was set to 10 min. And (3) adopting a heating-waiting-searching (H-W-S) mode, and if the self-heating rate of the equipment is automatically detected to reach an initial set value of 0.02 ℃/min, considering that the TBPA starts to decompose and release heat, and enabling the system to enter an adiabatic state. The temperature (T), pressure (P), rate of temperature rise (dT/dT) are automatically recorded as a function of time (T), see fig. 3 and 4.
The initial decomposition temperature of the TBPA sample can be known
Final temperature of
Adiabatic temperature rise of decomposition reaction
. Using mathematical models
The dT/dT-t curve is subjected to nonlinear fitting, so that the reaction order n =0.61 and the apparent activation energy can be obtained
(ii) a Factor of premodial finger
。
1-4) the basic synthesis of TBPA is carried out at atmospheric pressure, the boiling point of the solvent water being 100 ℃.
2. Calculating an evaluation index
1) An operating temperature T1, wherein T1=20 ℃;
2) the highest temperature T2 that the synthesis reaction can reach after the reaction system is cooled and loses efficacy:
the total heat of reaction of the synthesis reaction
Specific heat capacity of reaction mixture
The total adiabatic temperature rise of the synthesis reaction was calculated by substituting the mass M =1176.1g of the reaction mixture and the yield Y =71% into equation (1)
Correcting the warp yield;
TBPA synthesis is a semi-batch process, and by utilizing isothermal calorimetry experimental data of TBPA synthesis, curves of feeding rate and heat conversion rate and accumulation degree can be drawn
Feed rate-heat conversion. The operating temperature T1 and the total adiabatic temperature rise
And degree of accumulation
By substituting the value of (2) into equation (2), the final temperature achievable in the reaction system after cooling failure can be obtained
The time-dependent curve is shown in FIG. 5.
And determining the highest temperature T2=62.5 ℃ which can be reached by the synthesis reaction after the reaction system is cooled and failed.
3) The initial temperature T3 at which the product is unstably decomposed;
data obtained in the TBPA adiabatic decomposition calorimetric experiment, including the initial concentration of TBPA
(ii) a Final temperature of decomposition reaction
Adiabatic temperature rise of reaction
(ii) a Number of reaction stages n =0.61, apparent activation energy
(ii) a Factor of premodial finger
(ii) a Substituting into the following equation (3),
the equation was solved to give an initial temperature of unstable decomposition of the product T3=60.3 ℃.
4) The maximum temperature T4 that the reaction kettle can bear due to the limitation of technical conditions;
since the basic TBPA synthesis process is carried out at atmospheric pressure, the boiling point of the solvent water is taken to be the maximum temperature that the reaction kettle can withstand, so T4=100 ℃.
5) Final temperature under adiabatic conditions T5;
from the above calculation, it is found that the secondary decomposition of TBPA is necessarily triggered in the TBPA synthesis reaction. The operating temperature T1=20 ℃ of the basic synthesis of TBPA; adiabatic temperature rise measured in isothermal calorimetry experiment of TBPA synthesis
No yield correction; adiabatic temperature rise measured in TBPA adiabatic decomposition calorimetric experiment
. Substituting the above values into equation (5) gives the final temperature T5=96.5 ℃ under adiabatic conditions.
3. Rating the risk
In the alkaline synthesis of TBPA, the above 5 critical temperature settings are shown in Table 1.
TABLE 15 Critical temperatures in the basic synthesis of TBPA
The risk rating for the TBPA synthesis process is 3 due to T1< T3< T2< T5< T4.
In view of the evaluation results, the enterprises are recommended to adopt technical measures of designing a distillation device, adopting a standby cooling system, dumping reaction materials or quenching and the like.
The method comprehensively considers the difficulty of thermal runaway occurrence based on 5 key temperature parameters appearing in the reaction process, evaluates and grades the thermal risk of the synthesis reaction, and has more accurate and proper evaluation result. The method can guide enterprises to carry out process safety design and management, make corresponding safety protection measures and prevent thermal runaway and thermal explosion. On the premise of ensuring safe production, the economic benefit is maximized, which has great significance for the development of enterprises. Thereby ensuring that the safety investment of the enterprise is optimized.
Claims (2)
1. A danger grading method for safety assessment in a fine chemical production process is characterized by comprising the following steps:
1) obtaining parameters
1-1) determining an evaluation object, and collecting the operating conditions of the tert-butyl peroxyacetate TBPA synthesis process;
1-2) carrying out isothermal calorimetry experiment of the synthesis reaction of an evaluation object in laboratory scale to obtain heat release rate, heat conversion rate and charging rate; determining the total heat of reaction of the synthesis reaction
In the unit of
(ii) a Specific heat capacity of the reaction mixture
In the unit of
(ii) a Total mass of reaction mixture in reaction vessel
In the unit of
；
Material accumulation degree in reaction kettle at any moment
In units of%;
the reaction product was analyzed using a product analyzer to determine the reaction yield
In units of%;
1-3) carrying out adiabatic calorimetry experiments on the products of the synthesis reaction of the step (1-2);
1-3-1) first the initial concentration of the product is determined
In the unit of
；
1-3-2) Using the reaction data, a temperature/pressure-time curve is plotted and the initial temperature of the decomposition of the product is determined
Unit ofIs that; maximum temperature that can be reached
In units of; adiabatic temperature rise
In units of;
1-3-3) drawing a temperature rise rate-temperature curve, and carrying out nonlinear fitting by using a mathematical model to obtain thermodynamic parameters including apparent activation energy
In the unit of
(ii) a Pre-factor A, reaction order n;
1-4) if the synthesis reaction system is an open system, determining the boiling point of the solvent, wherein the solvent accounts for the maximum ratio in the reaction system; if the system is closed, determining the temperature corresponding to the maximum allowable pressure of the reaction kettle, wherein the maximum allowable pressure of the reaction kettle refers to the set pressure of a safety valve or a rupture disk;
2) calculating an evaluation index
2-1) the operating temperature is recorded as T1 and is determined by the operating conditions of the synthesis reaction, and the initial temperature of the cooling failure condition is T1;
2-2) after the reaction system is cooled to be invalid, recording the highest temperature which can be reached by the synthesis reaction as T2;
total adiabatic temperature rise of the synthesis reaction
In units of; t2 and
is calculated by the following formula,
in the formula (I), the compound is shown in the specification,
the temperature which can be reached by the synthesis reaction is measured in units of temperature after the reaction system is cooled and loses efficacy; t2 taking
Maximum value of (d);
for a conservative assessment, in a batch reaction,
；
in the semi-batch reaction, the reaction is carried out,
；
2-3) the initial temperature of unstable decomposition of the product, noted as T3;
the initial temperature T3 of unstable decomposition of the product is selected, and the maximum reaction rate of the product decomposition reaches the reaction initial temperature corresponding to 24 h;
determined by the following equation (3);
2-4) due to the limitation of technical conditions, the maximum temperature which can be borne by the reaction kettle is recorded as T4;
in an open system, T4 is the boiling point of the solvent; in a closed system, T4 is the temperature corresponding to the maximum allowable pressure of the reaction kettle; the maximum allowable pressure of the reaction kettle refers to the set pressure of a safety valve or a rupture disk;
2-5) Final temperature under adiabatic conditions was recorded as T5;
when the maximum temperature T2 at which the synthesis reaction can reach after failure of cooling is less than the initial temperature T3 at which the product is not stably decomposed, secondary decomposition reaction is hardly initiated, and at this time,
when the maximum temperature T2 of the synthesis reaction is greater than the initial temperature T3 of the decomposition of the product, the decomposition reaction of the product is initiated, and, at this time,
3) dividing the risk level;
the operating temperature T1 obtained on the basis of the preceding steps; after the reaction system is cooled and failed, the highest temperature T2 which can be reached by the synthesis reaction; the initial temperature T3 at which the product is unstably decomposed; the maximum temperature T4 that the reaction kettle can bear due to the limitation of technical conditions; and a final temperature T5 under adiabatic conditions, wherein the 5 key temperatures are ordered in an increasing order to form different types of situations and are graded according to the risk index;
the classification is as follows:
3-1) level 1 hazard situations, including 2 cases;
first, T1< T2< T4< T3< T5; under the condition, after the synthesis reaction is out of control, the temperature does not reach the maximum temperature T4 which can be borne by the reaction kettle, the decomposition of products is not caused, and the maximum temperature T4 which can be borne by the reaction kettle can be reached only after the reaction materials stay for a long time under the condition of heat accumulation;
second, T1< T2< T3< T5< T4; under the condition, after the synthesis reaction is out of control, the product decomposition cannot be initiated, if the reaction materials stay in a heat accumulation state for a long time, the secondary decomposition reaction can be initiated, but the final temperature T5 of the reaction under the adiabatic condition cannot reach the maximum temperature T4 which can be borne by the reaction kettle, and the evaporative cooling or the emergency release can play the role of an additional safety barrier;
3-2) grade 2 risk profile, T1< T2< T3< T4< T5; after the synthesis reaction is out of control, the temperature cannot reach the maximum temperature T4 which can be borne by the reaction kettle, the decomposition of products cannot be caused, if the reaction materials stay in a heat accumulation state for a long time, the secondary decomposition reaction is caused, and the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle; if the synthesis reaction is at a high exotherm at T4, a hazard may be triggered;
3-3) level 3 hazard situations, including 2 cases;
first, T1< T4< T2< T3< T5; after the synthesis reaction is out of control, the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle, but the decomposition of products is not initiated; the safety of the reaction process depends on the exothermic rate of the synthesis reaction at T4;
second, T1< T3< T2< T5< T4; after the synthesis reaction is out of control, the system initiates a secondary decomposition reaction of the product, but the final temperature T5 under the adiabatic condition does not reach the maximum temperature T4 which can be borne by the reaction kettle, and evaporative cooling or emergency pressure relief can be used as a final safety barrier;
3-4) class 4 risk profile, T1< T4< T3< T2< T5; after the synthesis reaction is out of control, the temperature reaches the technical limit, and the product decomposition is triggered by theoretical analysis; the safety of the reaction process depends on the sum of the heat release rates of the synthesis reaction and the secondary decomposition reaction when the maximum temperature T4 can be borne by the reaction kettle;
3-5) grade 5 risk profile, T1< T3< T2< T4< T5; after the synthesis reaction is out of control, the system can initiate the decomposition of products, the temperature reaches the maximum temperature T4 which can be borne by the reaction kettle in the process of the secondary decomposition reaction out of control, and at the moment, the evaporation cooling or the emergency pressure relief cannot play the role of a safety barrier.
2. The method for grading the risk of safety evaluation in the fine chemical production process according to claim 1, wherein the operation conditions in step (1-1) include a production mode using batch or semi-batch operation, an operation temperature, an operation pressure, a material ratio, a solvent, a feeding sequence and a feeding rate, and a stirrer rotation speed.
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