A method for identifying and early warning of thermal runaway decomposition

Abstract

The application discloses a kind of decomposition thermal runaway early identification and early warning method, belong to the early diagnosis and control technical field of dangerous chemical safety, including the following steps: take mg level sample and carry out temperature programmed calorimetry test to obtain decomposition heat release curve, obtain initial heat release temperature;Take g level sample and carry out isothermal adiabatic calorimetry test;Online infrared analysis functional group change is used, GC / MS detects volatile composition;Reaction molecular dynamics is used to construct chemical three-dimensional molecular model, and reaction force field optimization is carried out based on the functional group, volatile information measured in experiment, obtains the mechanism of early stage of thermal runaway initiation;Identify the early molecular functional group structure change and marker molecule of thermal runaway;Develop joint early warning system;Early warning in the early stage of chemical thermal runaway, take control measures in time to handle.The application inhibits the occurrence of thermal runaway combustion and explosion accident from the root end of accident, provides accurate early prevention and control technology for the storage and transportation safety of chemical.

Description

Technical Field

[0001] This invention belongs to the field of early diagnosis and control technology for hazardous chemical safety, specifically relating to a method for early identification and early warning of decomposition thermal runaway. Background Technology

[0002] The thermal runaway hazard of hazardous chemicals is a significant factor threatening the safety of modern industry. Decomposition thermally exothermic groups are commonly found in raw materials, intermediates, and products in the contemporary fine chemical industry. Chemical groups such as nitro, peroxy, azo, and sulfonic acid groups will generate significant thermal effects during structural decomposition and recombination, triggering the continued decomposition of surrounding materials and ultimately leading to uncontrollable temperature rise and thermal explosion accidents.

[0003] For example, the cause of the fire in the 2019 Jiangsu Xiangshui "3.21" extraordinarily serious explosion accident was the decomposition of nitrated waste. Currently, the monitoring of decomposing exothermic materials mainly relies on temperature sensors and smoke detectors. By this time, combustion has already occurred and produced a significant temperature rise or a large amount of smoke. The allowable time for emergency response is short or it is difficult to effectively control the fire, which not only consumes a lot of emergency rescue resources but also causes material loss. Summary of the Invention

[0004] To overcome the problems of delayed response and difficulty in controlling temperature rise when monitoring fires using existing temperature and smoke sensors, this invention proposes a method for early identification and early warning of thermal runaway. By identifying characteristic functional groups, runaway marker molecules, or gaseous small molecules before a fire occurs and in the early stages of thermal runaway, this method can quickly diagnose thermal runaway behavior, activate early warning measures, and suppress the occurrence of thermal runaway combustion and explosion accidents from the root of the accident.

[0005] The technical solution of the present invention is as follows:

[0006] A method for early identification and early warning of decomposition thermal runaway includes the following steps:

[0007] Step 1: Take a mg-level sample and perform a programmed temperature rise calorimetry test to obtain the decomposition and exothermic curve, and determine the initial exothermic temperature;

[0008] Step 2: Take g-grade samples for isothermal adiabatic thermal testing;

[0009] Step 3: Use online infrared analysis to analyze functional group changes and GC / MS to detect volatile composition;

[0010] Step 4: Construct a three-dimensional molecular model of the chemical using reaction molecular dynamics, and optimize the reaction force field based on experimentally measured functional group and volatile matter information to obtain the initial initiation mechanism of thermal runaway;

[0011] Step 5: Identify changes in molecular functional group structure and marker molecules in the early stages of thermal runaway;

[0012] Step 6: Develop a joint early warning system for initiation temperature / characteristic functional group detection / marker molecules;

[0013] Step 7: In the early stage of chemical thermal runaway, activate the joint early warning system to trigger an alarm and take timely control measures to deal with the situation.

[0014] Furthermore, the samples include, but are not limited to, organic compounds with chemical groups such as nitro, peroxy, azo, and sulfonic acid groups.

[0015] Furthermore, in step 1, the sample volume ranges from 10 to 200 mg.

[0016] Further, the specific process of step 2 is as follows: based on the initial exothermic temperature of the mg-level sample, a temperature 20-50°C lower than the initial exothermic temperature is taken, and an isothermal adiabatic thermal experiment of the g-level sample is carried out under vacuum conditions. The test is stopped when the temperature of the measured system increases by 20%.

[0017] Further, the specific process of step 3 is as follows: An online infrared analyzer is connected inside the adiabatic heating device to collect the infrared absorption spectrum curve of nitrate during the initial thermal decomposition of chemicals in real time. The peak position and peak height information are recorded as a function of time / temperature through a peak search program. The peak position is then retrieved and compared with the stored position in the peak position database and converted into information on the change of functional groups with time / temperature in real time. At the same time, the gas valve is controlled by the program to pass 2 ml of volatile gas to the gas chromatograph / mass spectrometer every 5-20 minutes for volatile gas component analysis to identify the change of volatile gas composition with time / temperature.

[0018] Further, the specific process of step 4 is as follows: construct a three-dimensional molecular model of the chemical based on the spatial density and pressure conditions of the adiabatic test sample, and perform NVE ensemble simulation based on molecular dynamics of the reaction force field and accelerated Monte Carlo simulation under near-real initial isothermal temperature conditions; find the inflection point of system temperature rise based on the temperature and internal energy changes during the simulation calculation, and then search for the changes in the functional group structure of chemical molecules before the temperature rise inflection point, and find the volatile small molecule components. If it matches the experimental measurement, it is recorded and statistically analyzed. If it does not match the experimental measurement, the force field parameters are changed and the simulation calculation is continued.

[0019] Further, the specific process of step 5 is as follows: based on the results of online analysis and simulation analysis of the sample, obtain the changes in the functional group structure and products of the sample before runaway, and calculate the energy and heat changes of the reaction steps before runaway based on quantum chemistry. Identify the functional group structure of the key intermediates and marker molecules that trigger thermal runaway through the energy-heat evolution of the reaction steps before runaway.

[0020] Furthermore, the specific process of step 6 is as follows: based on the changes in the molecular functional group structure and the identification of marker molecules in the early stage of thermal runaway of chemicals, an infrared spectrometer, a gas analyzer, and a temperature monitor are installed in the chemical storage tank to develop a joint early warning system for initiating temperature / characteristic functional group detection / marker molecules.

[0021] Furthermore, in step 6, the joint early warning system comprises four parts: a host computer, an infrared spectrometer, a gas analyzer, and a temperature monitor. The infrared spectrometer is used to detect characteristic functional groups in the early stages of runaway, the gas analyzer is used to detect runaway marker molecules, and the temperature monitor detects the temperature at which runaway is triggered. The infrared spectrometer, gas analyzer, and temperature monitor are connected to the host computer in parallel. The infrared spectrometer, gas analyzer, and temperature monitor transmit data to the host computer, which then provides early warning for the early stages of runaway.

[0022] Furthermore, in step 7, the control measures include adopting air cooling and inert gas protection methods.

[0023] The beneficial technical effects of this invention are as follows:

[0024] This invention can identify and monitor early-stage characteristic functional groups, runaway marker molecules, or gaseous small molecule features, enabling rapid identification of thermal runaway in the early stages of exothermic chemical decomposition. This allows for the initiation of effective early warning measures, suppressing the early development of thermal runaway accidents. By preventing thermal runaway combustion and explosion accidents at their root, this invention provides precise early prevention and control technology for the safe storage and transportation of chemicals. This invention offers precise and efficient early fire warning technology, greatly avoiding economic losses and casualties caused by the development of accidents, and has broad application prospects in chemical safety, accident emergency response, and other fields. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method for early identification and early warning of decomposition thermal runaway according to the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0027] This invention relates to a method for early identification and early warning of decomposition thermal runaway. This method combines thermal analysis calorimetry, molecular characterization, reaction molecular dynamics, and quantum chemistry to identify changes in gaseous small molecules and organic functional groups in the early stage of runaway at the microscopic molecular level. It can quickly diagnose runaway behavior in the early stage of thermal effect or before the temperature rises, and initiate early warning measures to suppress the occurrence of thermal runaway combustion and explosion accidents from the root of the accident.

[0028] This invention applies to chemicals that decompose and release heat, including but not limited to organic compounds with chemical groups such as nitro, peroxy, azo, and sulfonic acid groups. The decomposition and heat release curves of chemicals are tested using microcalorimetry. The gaseous products are connected to a gas chromatography / mass spectrometry (GC / MS) analyzer to detect gaseous components before or in the early stages of heat release. A Fourier transform infrared (FTIR) spectrometer is connected within the calorimeter to analyze the functional group structural changes of the chemicals before decomposition and heat release. Simultaneously, a three-dimensional molecular model of the chemical is constructed, and molecular dynamics calculations are performed using a reaction force field to simulate the molecular structural evolution during the thermal decomposition process. Combined with data from thermal analysis-FTIR-GC / MS measurements, the molecular structures of gaseous molecules and key biomarkers in the early stages of runaway are identified. Based on this early runaway molecular identification, an effective early warning system for thermal runaway is developed to suppress its occurrence.

[0029] This invention combines thermal analysis calorimetry, molecular characterization, reaction molecular dynamics, and quantum chemistry to analyze and obtain the early initiation mechanism of thermal runaway in organic matter decomposition at the microscopic molecular level. It identifies and monitors early-stage runaway characteristic functional groups, runaway marker molecules, or gaseous small molecule characteristics. This allows for rapid diagnosis of runaway behavior at the initial stage of thermal effects or before temperature rise, initiating early warning measures and preventing thermal runaway fires and explosions at their root. Specific implementation details are attached. Figure 1 As shown, 1. A mg-level sample was subjected to programmed temperature ramp calorimetry to obtain the decomposition exothermic temperature; 2. A g-level sample was subjected to isothermal adiabatic calorimetry; 3. Online infrared spectroscopy was used to analyze functional group changes, and GC / MS was used to detect the volatile composition; 4. A three-dimensional molecular model of the chemical was constructed using reaction molecular dynamics, and the reaction force field was optimized based on experimentally measured functional group and volatile information to obtain the initial initiation mechanism of thermal runaway; 5. The structural changes of molecular functional groups and marker molecules in the early stage of thermal runaway were identified; 6. A joint early warning system for initiation temperature / characteristic functional group detection / marker molecules was developed; 7. Control measures such as air cooling and inert gas protection were adopted.

[0030] The specific operational steps for achieving early identification and early warning of decomposition thermal runaway are as follows:

[0031] Step 1: First, take a mg-level sample and perform a programmed temperature rise calorimetry test to obtain the decomposition and exothermic curve, and then determine the initial exothermic temperature.

[0032] Step 2: Measure the initial exothermic temperature based on the mg-level sample. Take a temperature 20-50°C lower than the initial exothermic temperature and conduct a g-level isothermal adiabatic thermal experiment under vacuum conditions. Stop the test when the system temperature rises by 20%.

[0033] Step 3: Connect an online infrared analyzer to the adiabatic heating device to collect the infrared absorption spectrum curve of the sample during the initial thermal decomposition of the chemical in real time. Record the changes in peak position and peak height over time / temperature using a peak search program, and compare the results with the peak position database to convert the data into information on functional group changes over time / temperature. Simultaneously, control the gas valve to pass 2 ml of volatile gas to a gas chromatograph / mass spectrometer every 5-20 minutes for volatile gas component analysis, identifying changes in volatile gas composition over time / temperature.

[0034] Step 4: Construct a three-dimensional molecular model of the chemical based on the spatial density and pressure conditions of the adiabatic test sample. Perform NVE (equal number of molecules, equal volume, equal energy) ensemble simulations based on molecular dynamics and accelerated Monte Carlo simulations under near-real initial isothermal conditions using the reaction force field. Identify the temperature inflection point during the simulation based on temperature and internal energy changes. Then, search for changes in the functional group structure of the chemical molecules before the temperature inflection point and identify the volatile small molecule components. If the results match experimental measurements, record and statistically analyze them; otherwise, change the force field parameters and continue the simulation.

[0035] Step 5: Based on the results of online and simulated analysis of the sample, obtain the changes in the functional group structure and products of the sample before runaway, and calculate the energy and heat changes of the reaction steps before runaway based on quantum chemistry. Identify the functional group structure of key intermediates and marker molecules that trigger thermal runaway by the energy-heat evolution of the reaction steps before runaway.

[0036] Step 6: Based on the structural changes of molecular functional groups and the identification of marker molecules in the early stage of thermal runaway of chemicals, develop a joint early warning system for initiating temperature / characteristic functional group detection / marker molecules by setting up infrared spectrometers, gas analyzers, temperature monitors, etc. in chemical storage tanks.

[0037] The joint early warning system consists of four parts: a host computer, an infrared spectrometer, a gas analyzer, and a temperature monitor. The infrared spectrometer is used to detect characteristic functional groups in the early stages of runaway, the gas analyzer is used to detect runaway marker molecules, and the temperature monitor is used to detect the temperature at which runaway is triggered. The infrared spectrometer, gas analyzer, and temperature monitor are connected to the host computer in parallel. The infrared spectrometer, gas analyzer, and temperature monitor transmit data to the host computer, which then provides early warnings for the early stages of runaway.

[0038] Step 7: In the early stage of chemical thermal runaway, activate the joint early warning system to take timely control measures such as air cooling and inert gas protection to prevent the development of fire accidents and large-scale loss of raw materials.

[0039] This invention analyzes the early initiation mechanism of organic matter decomposition and heat release at the microscopic molecular level. By identifying characteristic functional groups, runaway marker molecules, or gaseous small molecule characteristics before a fire occurs and in the early stage of thermal runaway reaction, it can diagnose early thermal runaway behavior in advance, activate advanced warning measures, and suppress the occurrence of thermal runaway combustion and explosion accidents from the root of the accident, providing accurate and efficient early warning technology for fires.

[0040] Example 1

[0041] The specific process of identifying and providing early warning of the early stage of thermal runaway of nitro-containing organic compounds (nitrates) is as follows, wherein nitro-containing organic compounds include, but are not limited to, polynitroalkanes, aromatic organic compounds, and mixtures of various nitro groups.

[0042] Step 1: First, take 10-100mg of nitrate sample and perform programmed temperature rise calorimetry test to obtain the decomposition exothermic curve, and obtain the initial exothermic temperature: 250~350℃;

[0043] Step 2: Based on the initial exothermic temperature measured by mg-level nitrate, take a temperature 20-50°C lower than the initial exothermic temperature and conduct an isothermal adiabatic thermal experiment on 10-30g samples under vacuum conditions. Stop the test when the temperature of the measurement system rises by 20%.

[0044] Step 3: Connect an online infrared analyzer to the adiabatic heating device to collect the infrared absorption spectrum curves of nitrates during the initial thermal decomposition of chemicals in real time. Record the changes in peak position and peak height over time / temperature using a peak search program, and compare these data with the peak position database to convert them into information on functional group changes over time / temperature. Simultaneously, control the gas valve to pass 2 ml of volatile gas to a gas chromatograph / mass spectrometer every 5-20 minutes for volatile gas component analysis, identifying changes in volatile gas composition over time / temperature.

[0045] Step 4: Construct a three-dimensional molecular model of the chemical based on the spatial density and pressure conditions of the nitrate in the adiabatic test experiment. Perform an ensemble simulation (NVE, equal molecular number, equal volume, equal energy) based on molecular dynamics of the reaction force field and accelerated Monte Carlo simulation under near-real initial isothermal conditions. Based on the temperature and internal energy changes during the simulation, identify the measurement point where the system temperature increases by 10%. Then, search for changes in the functional group structure of the nitrate molecules before the 10% temperature increase point and identify the volatile small molecule components. If the results match experimental measurements, record and statistically analyze them; if they do not match experimental measurements, change the force field parameters and continue the simulation.

[0046] Step 5: Based on the online analysis and simulation analysis results of the nitrate sample, obtain the functional group structure and product changes of the sample before runaway, and calculate the energy and heat changes of the reaction steps before runaway based on quantum chemistry. Identify the key intermediate functional group structure (C=O bond), marker molecules (NO, NOH) and corresponding initiation temperature of thermal runaway by the energy-heat evolution of the reaction steps before runaway.

[0047] Step 6: Based on the structural changes of molecular functional groups and the identification of marker molecules in the early stage of thermal runaway of chemicals, develop a combined early warning system for initiating temperature / characteristic functional group detection / marker molecules by setting up infrared spectrometers to detect C=O functional groups, NO, NOH spectrometers, and temperature monitoring instruments (200-300℃) in chemical storage tanks.

[0048] Step 7: In the early stage of thermal runaway of nitrate, activate the alarm of the joint early warning system and take timely control measures such as air cooling and inert gas protection to prevent the development of fire accident and large loss of raw materials.

[0049] Example 2

[0050] Nitrophenols, including but not limited to polynitrophenol, nitrocellulose, and mixtures of various nitrophenols.

[0051] First, take 10-100 mg of nitrophenolate sample and perform programmed temperature rise calorimetry to obtain the decomposition exothermic curve, and find the initial exothermic temperature: 230-300℃.

[0052] Based on the initial exothermic temperature measured by mg-level nitrophenolate, a temperature 20–50°C lower than the initial exothermic temperature was used, and an isothermal adiabatic thermal experiment was conducted on 10–30g samples under vacuum conditions. The test was stopped when the temperature of the measurement system increased by 20%.

[0053] An online infrared analyzer is connected within the adiabatic heating device to collect the infrared absorption spectrum curves of nitrophenolates during the initial thermal decomposition of chemicals in real time. A peak search program records the changes in peak position and peak height over time and temperature, and retrieves and compares these data with a peak position database, converting them in real time into information on functional group changes over time and temperature. Simultaneously, a program-controlled gas valve introduces 2 ml of volatile gas every 5-20 minutes into a gas chromatograph / mass spectrometer for volatile gas component analysis, identifying changes in volatile gas composition over time and temperature.

[0054] A three-dimensional molecular model of the chemical was constructed based on the spatial density and pressure conditions of the nitrophenolate in an adiabatic test. Molecular dynamics and accelerated Monte Carlo simulations were then performed using near-real initial isothermal conditions, employing NVE (equal molecular number, equal volume, equal energy) ensemble simulations. The simulation was conducted to identify the measurement point where the system temperature increased by 10% based on the temperature and internal energy changes. The changes in the functional group structure of the nitrophenolate molecule before this 10% temperature increase were then investigated, and the volatile small molecule components were identified. If the results matched experimental measurements, they were recorded and statistically analyzed; otherwise, the force field parameters were adjusted, and the simulation was continued.

[0055] Based on the results of online and simulated analysis of the samples, the changes in functional group structure and products of the samples before runaway were obtained. Based on quantum chemical calculations, the energy and heat changes of the reaction steps before runaway were calculated. By analyzing the energy-heat evolution of the reaction steps before runaway, the key intermediate functional group structure (C=O bond), marker molecule (NOH), and corresponding initiation temperature of thermal runaway were identified.

[0056] Based on the structural changes of molecular functional groups and the identification of marker molecules in the early stages of thermal runaway of chemicals, a combined early warning system for initiating temperature / characteristic functional group detection / marker molecules is developed in chemical storage tanks by installing infrared spectrometers to detect C=O functional groups, NOH spectrometers, and temperature monitors (180-350℃).

[0057] In the early stages of thermal runaway of nitrophenolates, the joint early warning system is activated to take timely control measures such as air cooling and inert gas protection to prevent the development of fire accidents and the loss of large amounts of raw materials.

[0058] Example 3

[0059] The specific process of identifying and providing early warning of the early stage of thermal runaway of nitrosulfonates (including but not limited to nitrobenzenesulfonic acid, nitrobenzene disulfonic acid, and mixtures of various nitrosulfonic acids and their salts) is as follows.

[0060] Step 1: First, take 10-100mg of nitrosulfonate sample and perform programmed temperature rise calorimetry to obtain the decomposition exothermic curve, and obtain the initial exothermic temperature: 180~250℃;

[0061] Step 2: Based on the initial exothermic temperature measured by mg-level nitrosulfonate, take a temperature 20-50°C lower than the initial exothermic temperature and conduct an isothermal adiabatic thermal experiment on 10-30g samples under vacuum conditions. Stop the test when the temperature of the measurement system increases by 20%.

[0062] Step 3: An online infrared analyzer is connected to the adiabatic heating device to collect the infrared absorption spectrum curves of nitrosulfonates during the initial thermal decomposition of chemicals in real time. A peak position and peak height information is recorded as a function of time / temperature using a peak search program. This data is then retrieved and compared using a peak position database, and converted into information on functional group changes over time / temperature in real time. Simultaneously, a program controls a gas valve to introduce 2 ml of volatile gas every 5-20 minutes into a gas chromatograph / mass spectrometer for volatile gas component analysis, identifying changes in volatile gas composition over time / temperature.

[0063] Step 4: Construct a three-dimensional molecular model of the chemical based on the spatial density and pressure conditions of the nitrosulfonate in the adiabatic test experiment. Perform an NVE (equal number of molecules, equal volume, equal energy) ensemble simulation based on molecular dynamics of the reaction force field and accelerated Monte Carlo simulation under near-real initial isothermal conditions. Based on the temperature and internal energy changes during the simulation, find the measurement point where the system temperature increases by 10%. Then, search for changes in the functional group structure of the nitrosulfonate molecule before the 10% temperature increase point and identify the volatile small molecule components. If the results match experimental measurements, record and statistically analyze them; if they do not match experimental measurements, change the force field parameters and continue the simulation.

[0064] Step 5: Based on the results of online and simulated analysis of the sample, obtain the changes in the functional group structure and products of the sample before runaway, and calculate the energy and heat changes of the reaction steps before runaway based on quantum chemistry. Identify the functional group structure (C=O bond), marker molecules (SO2, NOH), and corresponding initiation temperature of the key intermediates that trigger thermal runaway by the energy-heat evolution of the reaction steps before runaway.

[0065] Step 6: Based on the structural changes of molecular functional groups and the identification of marker molecules in the early stage of thermal runaway of chemicals, develop a combined early warning system for initiating temperature / characteristic functional group detection / marker molecules by setting up infrared spectrometers to detect C=O functional groups, SO2, NOH spectrometers, and temperature monitoring instruments (150-200℃) in chemical storage tanks.

[0066] Step 7: In the early stage of thermal runaway of nitrosulfonates, the joint early warning system is activated to alarm and timely control measures such as air cooling and inert gas protection are taken to prevent the development of fire accidents and large-scale loss of raw materials.

[0067] Example 4

[0068] Organic compounds containing peroxides (organic peroxides) include, but are not limited to, hydroperoxides (ROOH), dialkyl peroxides (ROOR), diacyl peroxides (RCOOOOCR), peroxyesters (RCOOOR), peroxycarbonates (ROCOOOOCOR), and ketone peroxides [RC(OOH)]. The specific process for early identification and warning of thermal runaway in the decomposition of organic compounds containing peroxides is as follows.

[0069] Step 1: First, take 10-200mg of organic peroxide sample and perform programmed temperature rise calorimetry to obtain the decomposition exothermic curve, and obtain the initial exothermic temperature: 50-90℃;

[0070] Step 2: Based on the initial exothermic temperature measured from the mg-level organic peroxide sample, take a temperature 20-50°C lower than the initial exothermic temperature and conduct an isothermal adiabatic thermal experiment on 30-50g samples under vacuum conditions. Stop the test when the temperature of the measurement system rises by 20%.

[0071] Step 3: An online infrared analyzer is connected to the adiabatic heating device to collect the infrared absorption spectrum curve of the sample during the initial thermal decomposition of the chemical in real time. A peak position and peak height information is recorded as a function of time / temperature using a peak search program. This data is then retrieved and compared using a peak position database, and converted into information on the change of functional groups over time / temperature. Simultaneously, a gas valve is controlled by a program to introduce 2 ml of volatile gas into a gas chromatograph / mass spectrometer every 5-20 minutes for volatile gas component analysis, identifying changes in volatile gas composition over time / temperature.

[0072] Step 4: Construct a three-dimensional molecular model of the chemical based on the spatial density and pressure conditions of the organic peroxide sample in the adiabatic test experiment. Perform an ensemble simulation (NVE, equal molecular number, equal volume, equal energy) based on molecular dynamics and accelerated Monte Carlo simulation under near-real initial isothermal conditions using the reaction force field. Based on the temperature and internal energy changes during the simulation, identify the measurement point where the system temperature increases by 20%. Then, search for changes in the functional group structure of the chemical molecules before the 20% temperature increase point and identify the volatile small molecule components. If the results match experimental measurements, record and statistically analyze them; if they do not match experimental measurements, change the force field parameters and continue the simulation.

[0073] Step 5: Based on the results of online and simulated analysis of the sample, obtain the changes in the functional group structure and products of the sample before runaway, and calculate the energy and heat changes of the reaction steps before runaway based on quantum chemistry. Identify the key intermediate functional group structure (C=O bond), marker molecules (CH4, O2), and corresponding initiation temperature of thermal runaway by the energy-heat evolution of the reaction steps before runaway.

[0074] Step 6: Based on the structural changes of molecular functional groups and the identification of marker molecules in the early stage of thermal runaway of chemicals, develop a combined early warning system for initiating temperature / characteristic functional group detection / marker molecules by setting up infrared spectrometers to detect C=O functional groups, CH4 and O2 gas analyzers, and temperature monitors (30-50℃) in chemical storage tanks.

[0075] Step 7: In the early stage of thermal runaway of organic peroxides, the joint early warning system is activated to alarm and timely control measures such as air cooling and inert gas protection are taken to prevent the development of fire accidents and large-scale loss of raw materials.

[0076] Example 5

[0077] Organic compounds containing azo groups (azo compounds), including but not limited to 2,2'-azodialkanes, 2,2'-azodiaromatics, 2,2'-azodiisoalkylnitriles, and 2,2'-azodiisoalkane hydrochlorides, etc. The specific process for early identification and warning of the decomposition thermal runaway of organic compounds containing azo groups is as follows.

[0078] Step 1: First, take 10-200mg of azo compound sample and perform programmed temperature rise calorimetry to obtain the decomposition exothermic curve, and obtain the initial exothermic temperature: 70-100℃.

[0079] Step 2: Based on the initial exothermic temperature measured by the mg-level azo compound sample, take a temperature 20-50°C lower than the initial exothermic temperature and conduct an isothermal adiabatic thermal experiment on 30-50g samples under vacuum conditions. Stop the test when the temperature of the measurement system rises by 20%.

[0080] Step 3: An online infrared analyzer is connected to the adiabatic heating device to collect the infrared absorption spectrum curve of the sample during the initial thermal decomposition of the chemical in real time. A peak position and peak height information is recorded as a function of time / temperature using a peak search program. This data is then retrieved and compared using a peak position database, and converted into information on the change of functional groups over time / temperature. Simultaneously, a gas valve is controlled by a program to introduce 2 ml of volatile gas into a gas chromatograph / mass spectrometer every 5-20 minutes for volatile gas component analysis, identifying changes in volatile gas composition over time / temperature.

[0081] Step 4: Construct a three-dimensional molecular model of the chemical based on the spatial density and pressure conditions of the azo compound sample in the adiabatic test experiment. Perform an ensemble simulation (NVE, equal molecular number, equal volume, equal energy) based on molecular dynamics and accelerated Monte Carlo simulation under near-real initial isothermal conditions using the reaction force field. Based on the temperature and internal energy changes during the simulation, identify the measurement point where the system temperature increases by 20%. Then, search for changes in the functional group structure of the chemical molecules before the 20% temperature increase point and identify the volatile small molecule components. If the results match experimental measurements, record and statistically analyze them; otherwise, change the force field parameters and continue the simulation.

[0082] Step 5: Based on the results of online and simulated analysis of the sample, obtain the changes in the functional group structure and products of the sample before runaway, and calculate the energy and heat changes of the reaction steps before runaway based on quantum chemistry. Identify the key intermediate functional group structure (CC≡N bond), marker molecule (N2), and corresponding initiation temperature of thermal runaway by the energy-heat evolution of the reaction steps before runaway.

[0083] Step 6: Based on the structural changes of molecular functional groups and the identification of marker molecules in the early stage of thermal runaway of chemicals, develop a combined early warning system for initiating temperature / characteristic functional group detection / marker molecules by installing an infrared spectrometer for detecting CC≡N functional groups, an N2 gas analyzer, and a temperature monitor (40-70℃) in the chemical storage tank.

[0084] Step 7: In the early stage of thermal runaway of azo compounds, the joint early warning system is activated to take alarms and timely control measures such as air cooling and inert gas protection to prevent the development of fire accidents and large-scale loss of raw materials.

[0085] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for early identification and early warning of decomposition thermal runaway, characterized in that, Includes the following steps: Step 1: Take a mg-level sample and perform a programmed temperature rise calorimetry test to obtain the decomposition and exothermic curve, and determine the initial exothermic temperature; Step 2: Take g-grade samples for isothermal adiabatic thermal testing; Step 3: Use online infrared analysis to analyze functional group changes and GC / MS to detect volatile composition; Step 4: Construct a three-dimensional molecular model of the chemical using reaction molecular dynamics, and optimize the reaction force field based on experimentally measured functional group and volatile matter information to obtain the initial initiation mechanism of thermal runaway; The specific process of step 4 is as follows: a three-dimensional molecular model of the chemical is constructed based on the spatial density and pressure conditions of the sample in the adiabatic test experiment. Based on the molecular dynamics of the reaction force field and accelerated Monte Carlo simulation, an NVE ensemble simulation is performed under near-real initial isothermal temperature conditions. The temperature and internal energy changes during the simulation calculation are used to find the inflection point of the system temperature increase. Then, the changes in the functional group structure of the chemical molecules before the temperature increase inflection point are searched, and the small molecule components of volatiles are found. If they are consistent with the experimental measurements, they are recorded and statistically analyzed. If they are inconsistent with the experimental measurements, the force field parameters are changed and the simulation calculation is continued. Step 5: Identify changes in molecular functional group structure and marker molecules in the early stages of thermal runaway; Step 6: Develop a joint early warning system for initiation temperature / characteristic functional group detection / marker molecules; In step 6, the joint early warning system comprises four parts: a host computer, an infrared spectrometer, a gas analyzer, and a temperature monitor. The infrared spectrometer is used to detect characteristic functional groups in the early stages of runaway, the gas analyzer is used to detect runaway marker molecules, and the temperature monitor detects the temperature at which runaway is triggered. The infrared spectrometer, gas analyzer, and temperature monitor are connected to the host computer in parallel. The infrared spectrometer, gas analyzer, and temperature monitor transmit data to the host computer, which then provides early warning for the early stages of runaway. Step 7: In the early stage of chemical thermal runaway, activate the joint early warning system to trigger an alarm and take timely control measures to deal with the situation.

2. The method for early identification and early warning of decomposition thermal runaway according to claim 1, characterized in that, The samples include, but are not limited to, organic compounds with chemical groups such as nitro, peroxy, azo, and sulfonic acid groups.

3. The method for early identification and early warning of decomposition thermal runaway according to claim 1, characterized in that, In step 1, the sample volume range is 10-200 mg.

4. The method for early identification and early warning of decomposition thermal runaway according to claim 1, characterized in that, The specific process of step 2 is as follows: based on the initial exothermic temperature of the mg-level sample, a temperature 20-50°C lower than the initial exothermic temperature is taken, and an isothermal adiabatic thermal experiment of the g-level sample is carried out under vacuum conditions. The test is stopped when the temperature of the measured system increases by 20%.

5. The method for early identification and early warning of decomposition thermal runaway according to claim 2, characterized in that, The specific process of step 3 is as follows: An online infrared analyzer is connected inside the adiabatic heating device to collect the infrared absorption spectrum curves of nitro chemical group organic compounds in real time during the initial thermal decomposition of chemicals. The peak position and peak height information are recorded as a function of time / temperature through a peak search program. The peak position is then retrieved and compared with the stored position in the peak position database and converted into information on the change of functional groups with time / temperature in real time. At the same time, the gas valve is controlled by the program to pass 2 ml of volatile gas to the gas chromatograph / mass spectrometer every 5-20 minutes for volatile gas component analysis to identify the change of volatile gas composition with time / temperature.

6. The method for early identification and early warning of decomposition thermal runaway according to claim 1, characterized in that, The specific process of step 5 is as follows: based on the results of online analysis and simulation analysis of the sample, obtain the changes in the functional group structure and products of the sample before runaway, and calculate the energy and heat changes of the reaction steps before runaway based on quantum chemistry. Identify the functional group structure of the key intermediates and marker molecules that trigger thermal runaway through the energy-heat evolution of the reaction steps before runaway.

7. The method for early identification and early warning of decomposition thermal runaway according to claim 1, characterized in that, The specific process of step 6 is as follows: Based on the changes in the functional group structure of molecules in the early stage of thermal runaway of chemicals and the identification of marker molecules, an infrared spectrometer, a gas analyzer, and a temperature monitor are installed in the chemical storage tank to develop a joint early warning system for initiating temperature / characteristic functional group detection / marker molecules.

8. The method for early identification and early warning of decomposition thermal runaway according to claim 1, characterized in that, In step 7, the control measures include adopting air cooling and inert gas protection methods.

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