Explosions in Chemical Processes
An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. Explosions in a chemical plant need to be avoided at all costs. There are two primary causes of explosions during a chemical process:
- The material is energetically unstable, and has explosive properties. A comprehensive safety study of the process will identify whether materials are sensitive to shock, friction, heat, etc., and may dictate special procedures for safe handling.
- The process could lead to uncontrolled heat or gas generation, resulting in an escape of flammable vapor, or an over-pressurization of the reactor leading to rupture and loss of contents, which may be flammable.
In order to avoid the risk of uncontrolled heat generation, it is imperative that the process is studied using a Reaction Calorimeter in order to determine the Heat of Reaction (enthalpy) and the rate of heat release, so that a process can be designed that minimizes risk of loss of control.
Accumulation and Heat Evolution
Accumulation typically refers to material being dosed during a semi-batch reaction which does not react right away. The concentration of this material builds up/accumulates and poses a hazard if the reaction then begins to run at a faster rate, or if there is a cooling failure. Accumulation can be measured using a Reaction Calorimeter to determine the rate at which heat is produced, and how that compares to the rate of addition. It is also possible to use in situ analysis to directly measure the concentration of the unreacted reagent.
Gas Evolution and Pressure Increase
Risk of Explosion
When a process is being studied for safety, it is essential to confirm whether gas is being produced, and under what circumstances. In some cases, such as decarboxylation releasing CO2, this is an obvious and expected part of the process. In other cases, such as at the onset of runaway during nitration, gas production may be due to an unexpected side-reaction or decomposition. Unexpected gas evolution can quickly lead to over-pressurization of the equipment, with risk of loss of containment or even rupture the plant, with catastrophic consequences.
Measurement of gas evolution is a crucial part of process safety investigations at the laboratory scale, and the Reaction Calorimeter can easily be equipped with a meter or sensor system to quantitatively detect the time and rate of gas evolution so that suitable provision may be made at scale.
Evaporation and Reflux
When a liquid evaporates, it requires a significant amount of energy to change from the liquid phase to the vapor phase. This is known as the latent heat of evaporation. This phenomenon is often used during large-scale chemical manufacturing in order to help remove heat from the system, and thereby reduce the costs and increase the safety of the process. It is thus common practice to operate at least part of a batch process under conditions of reflux, in order to maximize the rate of reaction while maintaining a safe and efficient process. Operation of a Reaction Calorimeter under reflux conditions requires special attention to capture the heat that is taken away in the reflux condenser, and to ensure that the complete energy balance of the process is maintained even under reflux conditions.
Risk of Thermal Accumulation in Chemical Process
This paper assesses the following questions about thermal accumulation through practical case studies from both the lab and plant:
- Why and when does thermal accumulation occur?
- Is thermal accumulation important to consider, and how big is it?
- What is the impact of an incorrect calculation of thermal accumulation?
Autocatalysis and Associated Risks
Autocatalytic reactions have a tendency to begin very slowly, and then suddenly increase in rate due to the formation of catalytic compounds or intermediates. This can be extremely dangerous at large scale, since it may mean the rapid production of large amounts of heat that the cooling system is unable to remove. It is critically important to know in advance if a system exhibits autocatalytic behavior, so that the process can be properly designed. The Reaction Calorimeter allows direct measurement of the rate of heat production, and in situ analysis can give further information about the rate at which the reaction takes place.
Initiation and Chemical Reaction
Initiation is the point at which the chemical reaction begins, and it is not necessarily when the reagents are mixed. In some cases, initiation only occurs after a certain time period has elapsed (during autocatalysis), when an inhibiting material has been consumed, or when a certain temperature has been reached (during a non-isothermal reaction or a decomposition). The existence of an initiation period does not necessarily mean that the reaction is dangerous, but it is vitally important that the parameters of the event (time, duration, etc.) are well-understood in order to avoid hazardous conditions. For example, Grignard reactions typically undergo a delayed initiation, and it is important not to add too much halide to the reactor before initiation has been confirmed. Otherwise, there is a high risk of accumulation and runaway.
Presentation: Understand Scale-up Risks
Learn how reaction calorimetry helps scientists to quickly screen conditions and safely scale-up - without the need for large testing volumes. Examples presented include:
- Detecting Heat Release While Changing Temperature
- Understanding the Effect of Heat Accumulation
- Screening For Scalability Issues at Small Scale
- Eliminating Risk of Runaway Reactions
Deflagration and Explosion
Deflagration occurs when a solid material, such as a reactor vessel or storage container, undergoes a self-sustaining decomposition reaction that liberates significant quantities of energy (heat). Deflagration is essentially burning, but can occur in the absence of oxygen from the atmosphere. Deflagration differs from detonation, primarily in respect of the speed of the reaction, with a detonation occurring at supersonic velocity, and deflagration at sub-sonic velocity. During a chemical process, deflagration needs to be avoided at all costs. Chemical process safety studies should always include an assessment of the susceptibility of the material to deflagration (and explosion), as well as an understanding of what temperatures could be reached during the process, especially in cases of process upset or cooling failure.
Reaction Calorimeters
Avoid Explosion Risks in Reactions
The heating and cooling system of the RC1 Reaction Calorimeter is based on circulating heat transfer fluid with a high velocity and a large amount of pre-cooled oil. While the high velocity ensures fast response to temperature changes, the reservoir with the pre-cooled oil guarantees instantaneous cooling in case of a large exotherm or emergency. Along with the algorithms that ensure the highest precision of calculation, the thermostat is designed to quickly respond to changing conditions in the reactor in order to maintain the desired temperature accurately.
The temperature control system of the EasyMax and OptiMax Reaction Calorimeter uses the concept of electrical heating and Peltier-based solid-state cooling technology. Both heating and cooling are extremely fast due to the compact thermostat design, and enable the system to achieve temperatures well below 0 °C without the use of a cryostat. As a result of the design, the space requirements are minimal.
Applications
Design Robust and Sustainable Chemical Processes For Faster Transfer To Pilot Plant and Production
Design Robust and Sustainable Chemical Processes For Faster Transfer To Pilot Plant and Production
How Heat Transport in Agitated Vessels Affects Process Scale-up
Scaling-up a chemical process from lab to manufacturing gives useful results only with accurate heat transfer coefficients. Measuring the jacket and reactor temperature (during the release of a well-defined amount of heat) allows researchers to accurately compute the thermal resistance which is used to model the heat transfer and make critical predictions for reactors at larger scale. Reaction calorimetry is essential to determine parameters that impact the heat transfer and the heat transfer coefficients to develop models to maximize the bandwidth of a manufacturing plant.
Mixing in a Chemical Reactor and the Effect on Reaction Kinetics and Scale-up
Mixing is the reduction or elimination of inhomogeneity of phases that are either miscible or immiscible. Process scale-up and optimization require that the impact of mixing on the reaction rate be quantified. Automated, controlled experiments can be run in parallel in a laboratory reactor system to establish a mass transfer correlation, and provide a means to quickly adjust the gas/ liquid interface area and reactor volume. This achieves the desired conditions required for the scale-up or scale-down of a process.
Study Chemical Reaction Rates and Measure Kinetics Inline
In situ chemical reaction kinetics studies provide an improved understanding of reaction mechanism and pathway by providing concentration dependences of reacting components in real-time. Continuous data over the course of a reaction allows for the calculation of rate laws with fewer experiments due to the comprehensive nature of the data. Reaction Progression Kinetics Analysis (RPKA) uses in situ data under synthetically relevant concentrations and captures information throughout the whole experiment ensuring that the complete reaction behavior can be accurately described.
Understand and Control Exothermic Events
Grignard reactions are one of the most important reaction classes in organic chemistry. Grignard reactions are useful for forming carbon-carbon bonds. Grignard reactions form alcohols from ketones and aldehydes, as well as react with other chemicals to form a myriad of useful compounds. Grignard reactions are performed using a Grignard reagent, which is typically a alkyl-, aryl- or vinyl- organomagnesium halide compound. To ensure optimization and safety of Grignard reactions in research, development and production, in situ monitoring and understanding reaction heat flow is important.
Safe Reaction Monitoring at Elevated Temperature and Pressure
Hydrogenation reactions are used in the manufacturing of both bulk and fine chemicals for reducing multiple bonds to single bonds. Catalysts are typically used to promote these reactions and reaction temperature, pressure, substrate loading, catalyst loading, and agitation rate all effect hydrogen gas uptake and overall reaction performance. Thorough understanding of this energetic reaction is important and PAT technology in support of HPLC analysis ensure safe, optimized and well-characterized chemistry.
Highly reactive chemistry is a terminology used to describe chemical reactions that are particularly challenging to handle and develop due to the potentially hazardous and/or energetic nature of the reactants, intermediates and products that are present during synthesis. These chemistries often involve highly exothermic reactions which require specialized equipment or extreme operating conditions (such as low temperature) to ensure adequate control. Ensuring safe operating conditions, minimizing human exposure, and gaining the maximum amount of information from each experiment are key factors in successfully designing and scaling-up highly reactive chemistries.
Particularly challenging is the fact that sampling the reactor contents during the reaction is often impractical or impossible under the desired operating conditions. In addition, as highly reactive materials are often unstable, the accuracy of any possible offline analysis is often limited.
Handling of reagents can be minimized through the use of synthesis workstations, a new generation of technology, that are designed to provide high quality synthetic conditions (such as control over temperature and pH), a degree of automation of methods, and importantly greatly reduce the amount of material that comes into contact with the operator.
The sampling challenge can be addressed through the use of in situ reaction monitoring technology such as ReactIR™. This technology allows scientists to design and develop better and safer processes through the delivery of information regarding the behavior of reaction species such as starting materials, intermediates and products, allowing them to gain a greater understanding of the reaction being studied.
Improve Safety, Reduce Cycle Time, Increase Quality and Yield
Continuous flow chemistry opens options with exothermic synthetic steps that are not possible in batch reactors, and new developments in flow reactor design provide alternatives for reactions that are mixing limited in batch reactors. This can often result in better product quality and higher yield. When coupled with Process Analytical Technology (PAT), flow chemistry allows for rapid analysis, optimization, and scale-up of a chemical reaction.
Comprehensive Understanding of Kinetics to Develop Synthetic Polymer Chemistry
Measuring and understanding polymerization reactions, mechanisms, kinetics, reactivity ratios, and activation energies lead researchers to employ in situ infrared spectroscopy as a routine technique to gain comprehensive, information-rich data that is used to advance research in a shorter time frame.
Optimize Crystal Size, Yield and Purity
Optimization and scale-up of crystallization and precipitation to produce a product that consistently meets purity, yield, form and particle size specifications can be one of the biggest challenges of process development.
Risks of Explosions in Chemical Process and How to Avoid Hazards in the Plant
Scientists and engineers eliminate risks of explosions in a chemical plant with a comprehensive safety study. The safety study is applied to develop a process that eliminates uncontrolled heat or gas generation, flammable vapor release, or an over-pressurization of the reactor leading to rupture and loss of contents, which may be flammable. In order to avoid the risk of uncontrolled heat generation, reaction calorimetry determines the heat of reaction and the rate of heat release, so that a process can be designed that minimizes the risk of loss of control.
Develop a Safe Chemical Process
Essential measurements and calculations are necessary to model runaway scenarios and establish the ideal reaction procedure. Measuring, calculating, and understanding the parameters are essential to assess and avoid risk in a chemical process. This allows scientists to make predictions about the temperature profiles, maximum operating temperature, and dosing.
Assess the Risk of Chemical Processes
The heat of reaction, or reaction enthalpy, is an essential parameter to safely and successfully scale-up chemical processes. The heat of reaction is the energy that is released or absorbed when chemicals are transformed in a chemical reaction.
Design Robust and Sustainable Chemical Processes For Faster Transfer To Pilot Plant and Production
Scaling-up a chemical process from lab to manufacturing gives useful results only with accurate heat transfer coefficients. Measuring the jacket and reactor temperature (during the release of a well-defined amount of heat) allows researchers to accurately compute the thermal resistance which is used to model the heat transfer and make critical predictions for reactors at larger scale. Reaction calorimetry is essential to determine parameters that impact the heat transfer and the heat transfer coefficients to develop models to maximize the bandwidth of a manufacturing plant.
Mixing is the reduction or elimination of inhomogeneity of phases that are either miscible or immiscible. Process scale-up and optimization require that the impact of mixing on the reaction rate be quantified. Automated, controlled experiments can be run in parallel in a laboratory reactor system to establish a mass transfer correlation, and provide a means to quickly adjust the gas/ liquid interface area and reactor volume. This achieves the desired conditions required for the scale-up or scale-down of a process.
In situ chemical reaction kinetics studies provide an improved understanding of reaction mechanism and pathway by providing concentration dependences of reacting components in real-time. Continuous data over the course of a reaction allows for the calculation of rate laws with fewer experiments due to the comprehensive nature of the data. Reaction Progression Kinetics Analysis (RPKA) uses in situ data under synthetically relevant concentrations and captures information throughout the whole experiment ensuring that the complete reaction behavior can be accurately described.
Grignard reactions are one of the most important reaction classes in organic chemistry. Grignard reactions are useful for forming carbon-carbon bonds. Grignard reactions form alcohols from ketones and aldehydes, as well as react with other chemicals to form a myriad of useful compounds. Grignard reactions are performed using a Grignard reagent, which is typically a alkyl-, aryl- or vinyl- organomagnesium halide compound. To ensure optimization and safety of Grignard reactions in research, development and production, in situ monitoring and understanding reaction heat flow is important.
Hydrogenation reactions are used in the manufacturing of both bulk and fine chemicals for reducing multiple bonds to single bonds. Catalysts are typically used to promote these reactions and reaction temperature, pressure, substrate loading, catalyst loading, and agitation rate all effect hydrogen gas uptake and overall reaction performance. Thorough understanding of this energetic reaction is important and PAT technology in support of HPLC analysis ensure safe, optimized and well-characterized chemistry.
Highly reactive chemistry is a terminology used to describe chemical reactions that are particularly challenging to handle and develop due to the potentially hazardous and/or energetic nature of the reactants, intermediates and products that are present during synthesis. These chemistries often involve highly exothermic reactions which require specialized equipment or extreme operating conditions (such as low temperature) to ensure adequate control. Ensuring safe operating conditions, minimizing human exposure, and gaining the maximum amount of information from each experiment are key factors in successfully designing and scaling-up highly reactive chemistries.
Particularly challenging is the fact that sampling the reactor contents during the reaction is often impractical or impossible under the desired operating conditions. In addition, as highly reactive materials are often unstable, the accuracy of any possible offline analysis is often limited.
Handling of reagents can be minimized through the use of synthesis workstations, a new generation of technology, that are designed to provide high quality synthetic conditions (such as control over temperature and pH), a degree of automation of methods, and importantly greatly reduce the amount of material that comes into contact with the operator.
The sampling challenge can be addressed through the use of in situ reaction monitoring technology such as ReactIR™. This technology allows scientists to design and develop better and safer processes through the delivery of information regarding the behavior of reaction species such as starting materials, intermediates and products, allowing them to gain a greater understanding of the reaction being studied.
Continuous flow chemistry opens options with exothermic synthetic steps that are not possible in batch reactors, and new developments in flow reactor design provide alternatives for reactions that are mixing limited in batch reactors. This can often result in better product quality and higher yield. When coupled with Process Analytical Technology (PAT), flow chemistry allows for rapid analysis, optimization, and scale-up of a chemical reaction.
Measuring and understanding polymerization reactions, mechanisms, kinetics, reactivity ratios, and activation energies lead researchers to employ in situ infrared spectroscopy as a routine technique to gain comprehensive, information-rich data that is used to advance research in a shorter time frame.
Optimization and scale-up of crystallization and precipitation to produce a product that consistently meets purity, yield, form and particle size specifications can be one of the biggest challenges of process development.
Scientists and engineers eliminate risks of explosions in a chemical plant with a comprehensive safety study. The safety study is applied to develop a process that eliminates uncontrolled heat or gas generation, flammable vapor release, or an over-pressurization of the reactor leading to rupture and loss of contents, which may be flammable. In order to avoid the risk of uncontrolled heat generation, reaction calorimetry determines the heat of reaction and the rate of heat release, so that a process can be designed that minimizes the risk of loss of control.
Essential measurements and calculations are necessary to model runaway scenarios and establish the ideal reaction procedure. Measuring, calculating, and understanding the parameters are essential to assess and avoid risk in a chemical process. This allows scientists to make predictions about the temperature profiles, maximum operating temperature, and dosing.
The heat of reaction, or reaction enthalpy, is an essential parameter to safely and successfully scale-up chemical processes. The heat of reaction is the energy that is released or absorbed when chemicals are transformed in a chemical reaction.
Publications
Know-how
The series of safety resources offers application-specific knowledge.
Resources to help gain insight into every reaction
Resources to help design processes for manufacturability early in the process
Guide to Process Safety discusses challenges to consider when designing a safe process including thermal hazard analysis in chemical production, runaw...
In chemical process scale-up, understanding temperature change and the associated heat that is accumulated by the reaction are critical to process saf...
On-Demand Webinars
As chemical reactions are scaled from lab to manufacturing, potential safety issues of non-scalable conditions need to be identified early in developm...
This webinar discusses how to perform safe scale-up of chemical processes and includes a close examination of thermal risks and hazards.
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