Chemical process safety is concerned with ensuring that the energy released by the reaction can be safely removed from the reactor without the risk of thermal runaway or explosion. Simple at the laboratory scale, it becomes progressively more difficult throughout scale-up, due to the changing ratio of heat removal capacity to reactor volume. Thus, an exothermic process which runs safely in the laboratory may be spectacularly unsafe to run at plant scale. It is critical to fully understand the risks inherent in moving to the larger scale before manufacturing begins. The use of reaction calorimetry is an essential part of process development studies, providing detailed information about the rate of heat production. This allows researchers to optimize the temperature and dosing profiles to maximize the safety of the process at all times, and reduce to a minimum the risks involved.
Comprehensive Heat Analysis
A reaction calorimeter is used to study a chemical process at laboratory scale in order to characterize the true rate of heat production, and understand how it may be influenced by process parameters such as temperature, mixing, and reagent concentration. By mapping the full reaction space, the safest process conditions can be identified. Researchers then can adapt the process to ensure it only operates within the boundaries that minimize risk. Reaction Calorimetry also allows researchers to safely explore conditions that may lead to a process upset, and determine the consequences of out-of-limits operation.
Understand the Risks of Chemical Processes
Reaction Calorimetry Applications
The hazard potential and risk of chemical processes are related to reactivity of chemicals involved and the process design itself. The appropriate design of a process is essential to keep the reaction under control at any given time. Striving for an intrinsically safe process is thus the goal of process development
Considering an exothermal reaction, the worst case scenario is a total failure of cooling. If this occurs, risks include adiabatic temperature rise driven by the synthesis reaction and accumulated energy, potential process emergency if the boiling point is reached, and thermal decomposition leading to secondary reactions and explosion.
In the semi-batch reaction to the left, the reactant is added during a temperature ramp. The overlapping effects (temperature ramp, reactant addition, and the reaction itself) require an accurate determination of the heat flow across the reactor wall, the heat accumulation, and the energy needed to adjust the temperature of the added reactant. This places high demands on the measuring system in terms of accuracy and data evaluation. Caution should be exercised when choosing a calorimeter to be sure it can provide these values, especially under non-isothermal conditions.
Reactions can liberate a significant amount of energy, and if this is not removed from the system, the temperature can increase up to the point where a thermal decomposition occurs. This can lead to a thermal runaway and explosion. Before any process is operated at scale, it is essential to study the relative stability of the materials and understand the risk of exothermic decomposition. Micro-calorimetry tools, such as differential scanning calorimetry (DSC), can quickly and easily provide an early indication of thermal instability. A series of isothermal experiments of a reaction mixture are shown thermal measuring the behavior at different temperatures. The heat evolution signals are use to calculate the adiabatic runaway potential and timeframe under which it would occur.
METTLER TOLEDO Reaction Calorimeters have been used in Chemical Process Safety laboratories for more than 30 years. Our Publications Library contains a range of presentations, case studies and examples provided by our customers from across the chemical, pharmaceutical and polymer industries.
METTLER TOLEDO manufactures a range of reaction calorimeter systems for use at any stage of chemical process development. EasyMax HFCal is ideal for use in early-stage development, and provides critical thermal data from a 100 mL scale reaction. OptiMax HFCal operates at the 1 L scale, and is ideal for use in process development and scale-up laboratories. RC1mx is the gold standard for the process safety laboratory, where it has been the reference system for more than 30 years.
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