Why Thermal Process Safety?
On August 4, 2020, a warehouse containing ammonium nitrate exploded in the port of Beirut. The explosion destroyed large parts of the harbor. In total, more than 200 people were killed and around 7,000 were injured [1]. Thermal safety relates not only to production, but also to the storage and transport of chemicals.
Control of Reaction Hazards in the Pharmaceutical, Chemical, Food and Agricultural Industries
Seveso 1976, Bhopal 1984 – Two very large-scale chemical accidents caused by uncontrolled ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermic chemical reactions known as thermal runaways.
Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).Thermal runaway (sometimes called thermal explosion) refers to overheating due to a self-reinforcing/self-accelerating ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermic process. The rate of heat production is greater than the rate of heat dissipation, causing the temperature (and consequently the pressure) in a reaction vessel to rise continuously. The consequences of Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).thermal runaway reactions are potential fires and/or explosions that can release toxic gases and endanger human life.
The release of methyl isocyanate from a Union Carbide plant producing pesticides on 3 December 1984 in India is sometimes even referred to as the "most devastating chemical disaster in history". [3] Thousands of people died as a result of this accident.
The Seveso accident occurred on July 10, 1976, at the Icmesa chemical plant in Meda, near Milan, Italy, and led to the massive release of the dioxin TCDD (chemical name: 2,3,7,8-tetrachlorodibenzodioxin) [4]. It gave its name to the European regulation 2012/18/EU “on the control of major-accident hazards involving dangerous substances” known as the Seveso III Directive.
Fortunately, such serious accidents are very rare, but minor incidents do occur from time to time. For example, around 25% of incidents in the French chemical industry between 1974 and 2014 can be attributed to Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).thermal runaway reactions [5]. In China, Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).thermal runaway reactions were responsible for 271 incidents between 1984 and 2019 [6]. In the USA, 167 incidents related to Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).thermal runaway reactions occurred between 1985 and 2001 [7].
Recently, Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).thermal runaway reactions in lithium-ion batteries, which are used in electric cars, e-bikes and e-scooters, have been making headlines. In July 2023, a fire broke out on a car transporter with 3000 vehicles near the Dutch coast.
What is thermal process safety?
The objective of thermal process safety is to allow chemical reactions to take place in a controlled manner and to prevent Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).thermal runaway.
Risk Analysis as an Important Issue
In order to achieve the above-mentioned objective, the risks of a chemical reaction or the chemicals used must be systematically determined and assessed and appropriate measures derived to minimize the hazards. This takes place in a detailed risk analysis which is carried out in instances such as:
- When introducing a new synthesis process (scale-up)
- When changing/optimizing an existing process with regard to
- Amount and type of reagents
- Amount and type of solvents
- Addition sequence
- Process conditions
- When relocating the production site
- from one reactor to another
- from one plant to another or
- from one country to another
From development to production, material quantities increase from mg to kg or even tons. In the same way, the dangers of handling flammable solvents and energetic substances/reactions also increase.
What can happen if a reaction gets out of control, e.g., due to failure of a cooling system:
In order to identify, quantify and understand the potential hazards, risks and dangers to the working environment, various techniques and models can be used.
Safety First! – Determination of Key Parameters
The European Federation of Chemical Engineering (EFCE) defines the term “risk” as a measure of the potential for damage and harm to the environment or people in terms of probability and severity. This relationship is often expressed in the form of the following equation:
Risk = Severity x Probability [8]
To determine the inherent weaknesses of a process, incident scenarios are described and analyzed with regard to the expected severity and probability of occurrence. The result can be a risk matrix.
Example of the criteria for a risk assessment (according to [9]):
Severity: The higher the temperature, the higher the pressure, the higher the expected damage
Probability: The shorter the time remaining to restore a safe situation, the greater the probability of a Thermal runawayA thermal runaway is the situation where a chemical reactor is out of control with respect to temperature and/or pressure production caused by the chemical reaction itself. Simulation of a thermal runaway is usually carried out using a calorimeter device according to accelerated rate calorimetry (ARC).thermal runaway reaction.
ΔTad stands for the temperature rise under AdiabaticAdiabatic describes a system or measurement mode without any heat exchange with the surroundings. This mode can be realized using a calorimeter device according to the method of accelerating rate calorimetry (ARC). The main purpose of such a device is to study scenarios and thermal runaway reactions. A short description of the adiabatic mode is “no heat in – no heat out”.adiabatic conditions and is a measure of the consequences of a runaway reaction; TMRad stands for the time-to-maximum-rate under AdiabaticAdiabatic describes a system or measurement mode without any heat exchange with the surroundings. This mode can be realized using a calorimeter device according to the method of accelerating rate calorimetry (ARC). The main purpose of such a device is to study scenarios and thermal runaway reactions. A short description of the adiabatic mode is “no heat in – no heat out”.adiabatic conditions.
What are AdiabaticAdiabatic describes a system or measurement mode without any heat exchange with the surroundings. This mode can be realized using a calorimeter device according to the method of accelerating rate calorimetry (ARC). The main purpose of such a device is to study scenarios
and thermal runaway reactions. A short description of the adiabatic mode is “no heat in – no heat out”.adiabatic conditions?
AdiabaticAdiabatic describes a system or measurement mode without any heat exchange with the surroundings. This mode can be realized using a calorimeter device according to the method of accelerating rate calorimetry (ARC). The main purpose of such a device is to study scenarios
and thermal runaway reactions. A short description of the adiabatic mode is “no heat in – no heat out”.Adiabatic means: No heat exchange between a system and its environment. If heat cannot discharge during an ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermic reaction, this is a Worst-Case ScenarioRelated to a chemical reactor, a worst-case scenario is the situation where temperature and/or pressure production caused by the reaction runs out of control.worst-case scenario. All the energy released by the reaction increases the temperature of the system.
What is TMR?
The time-to-maximum rate is the time between the start of a runaway reaction and the point of maximum reaction rate. In other words, the time it takes for a thermal explosion to develop.
According to the Van't Hoff rule, the reaction rate doubles with a temperature increase of 10 K [8].
TMR is a time specification, whereas TMR24h (or TD24, D = Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. decomposition) is a temperature: the temperature at which TMR is 24 hours. Sometimes, however, other times are also used as a basis for calculation, e.g., 8 hours as a measure for one layer.
Example of a flow chart for assessment of chemical hazards (according to [10]):
Methods of thermal analysis (dynamic differential calorimetry, thermogravimetric analysis, AdiabaticAdiabatic describes a system or measurement mode without any heat exchange with the surroundings. This mode can be realized using a calorimeter device according to the method of accelerating rate calorimetry (ARC). The main purpose of such a device is to study scenarios
and thermal runaway reactions. A short description of the adiabatic mode is “no heat in – no heat out”.adiabatic calorimetry) serve for the assessment of Thermal StabilityA material is thermally stable if it does not decompose under the influence of temperature. One way to determine the thermal stability of a substance is to use a TGA (thermogravimetric analyzer). thermal stability.
NETZSCH – Your Complete Solution Provider
NETZSCH Analyzing & Testing is your complete provider for solutions in the field of thermal safety. We offer analysis instruments along with the appropriate software for prediction and simulation:
For studies of thermal risk assessment, Differential Scanning Calorimetry (DSC) is the most commonly used method. Also included are Accelerating Rate Calorimetry (ARC®) (see flow chart). The Multiple Module Calorimeter (MMC)A multiple mode calorimeter device consisting of a base unit and exchangeable modules. One module is prepared for accelerating rate calorimetry (ARC), the ARC-Module. A second one is used for scanning tests (Scanning Module) and a third one is related to battery testing for coin cells (Coin Cell Module).MMC Multiple Module Calorimeter holds a special position since it can be used for both screening procedures (Scanning-Module) and Accelerating Rate Calorimetry (ARC)The method describing isothermal and adiabatic test procedures used to detect thermally exothermic decomposition reactions.ARC® tests (Accelerating Rate Calorimetry (ARC)The method describing isothermal and adiabatic test procedures used to detect thermally exothermic decomposition reactions.ARC® Module).
The standard test protocol for Accelerating Rate Calorimetry (ARC)The method describing isothermal and adiabatic test procedures used to detect thermally exothermic decomposition reactions.ARC® measurements is called Heat-Wait-Search (HWS)Heat-Wait-Search is a measurement mode used in calorimeter devices according to accelerating rate calorimetry (ARC).Heat-Wait-Search [11]. The sample is heated in steps and checked for self-heating in a corresponding waiting phase (see diagram). If a certain self-heating threshold value (usually 0.02 K/min) is exceeded, the measuring system switches to tracking mode and measures the occurring temperature increase.
Schematic diagram of a Heat-Wait-Search (HWS)Heat-Wait-Search is a measurement mode used in calorimeter devices according to accelerating rate calorimetry (ARC).heat-wait-search experiment [12]
In accordance with ASTM E1981 [11], the amount of heat released can be determined from the temperature increase observed, ΔTobs, by multiplying it with the Thermal inertiaThe thermal inertia is equivalent to the PHI-factor. Both describe the ratio of mass and specific heat capacity of a sample or sample mixture compared to that of the vessel or sample container.thermal inertia (or the Phi factor), ΔTad, and by multiplying the product, in turn, with the heat capacity of the sample container.
TMR24h or TD24 can be calculated on the basis of various kinetic models.
By means of the new Termica Neo software, the thermal behavior of chemicals in large volumes (reactors, silos, etc.) can be simulated.
Webinars:
References:
Literature:
[1] https://en.wikipedia.org/wiki/2020_Beirut_explosion
[2] K. Hungerbühler, Risk Analysis of Chemical Processes and Products, lecture, FS 2017
https://ethz.ch/content/dam/ethz/special-interest/chab/icb/set-dam/documents/downloads/risk-analysis17/2017-05-16-Part5.pdf
[3] Article in the GEO magazine (German language) from Jan. 13, 2023; https://www.geo.de/wissen/weltgeschichte/katastrophe-von-bhopal-1984--das-schwerste-chemieunglueck-aller-zeiten-32733526.html
[4] https://de.wikipedia.org/wiki/Sevesounglück
[5] A. Dakkoune, L. Vernières-Hassimi, S. Leveneur, D. Lefebvre and L. Estel; Analysis of Thermal Runaway Events in French Chemical Industry, HAL Id: hal-02314230,
https://normandie-univ.hal.science/hal-02314230
[6] H. Zhang, M. Bai, X. Wang, J. Gai, Chi-Min Shu, N. Roy, Yi Liu, Thermal Runaway Incidents – a Serious Cause of Concern: An Analysis of Runaway Incidents in China, Process Saf Environ Prot, Vol. 155, 2021, p 277 – 286
[7] Improving Reactive Hazard Management; Hazard Investigation Report; United States Chemical Safety Board, 2002. https://www.hsdl.org/?view&did=234839
[8] F. Stoessel, Thermal Safety of Chemical Processes, Wiley-VCH, 2008
[9] F. Stoessel, EPSC Award Lecture, Leverkusen, 6. Oktober 2020
https://epsc.be/About+Us/EPSC+Award/_/Award_2020_Presentation.pdf
[10] P. Sharrat, S. Shaik, Institute of Chemical & Engineering Sciences, lecture within the Chemical Reaction Safety Workshop, Technical Process Safety Seminar, Singapore, August 19, 2019
https://www.icheme.org/media/12371/w1-icheme-tpsseminar-chemrxnsafetywrkshp-aug2019.pdf
[11] ASTM E1981 - 22, Standard Guide for Assessing Thermal StabilityA material is thermally stable if it does not decompose under the influence of temperature. One way to determine the thermal stability of a substance is to use a TGA (thermogravimetric analyzer). Thermal Stability of Materials by Methods of Accelerating Rate Calorimetry (ARC)The method describing isothermal and adiabatic test procedures used to detect thermally exothermic decomposition reactions.Accelerating Rate Calorimetry
[12] NETZSCH Onset 26, 2023