Reaction calorimeter
A reaction calorimeter is a calorimeter that measures the amount of energy released (exothermic) or absorbed (endothermic) by a chemical reaction. These measurements provide a more accurate picture of such reactions.
When considering scaling up a reaction to large scale from lab scale, it is important to understand how much heat is released. At a small scale heat released may not cause a concern, however when scaling up, that heat can build up and be extremely dangerous.
Crystallizing a reaction product from solution is a highly cost effective purification technique. It is therefore valuable to be able to measure how effectively crystallization is taking place in order to be able to optimize it. The heat absorbed by the process can be a useful measure.
The energy being released by any process in the form of heat is directly proportional to the rate of reaction and hence reaction calorimetry (as a time resolved measurement technique) can be used to study kinetics.
The use of reaction calorimetry in process development has been historically limited due to the cost implications of these devices however calorimetry is a fast and easy way to fully understand the reactions which are conducted as part of a chemical process.
Heat flow calorimetry measures the heat flowing across the reactor wall and quantifying this in relation to the other energy flows within the reactor.
where
Heat flow calorimetry allows the user to measure heat whilst the process temperature remains under control. While the driving force Tr − Tj is measured with a relatively high resolution, the overall heat transfer coefficient U or the calibration factor UA respectively, is determined by means of calibration before and after the reaction takes place. The calibration factor UA (or the overall heat transfer coefficient U) are affected by the product composition, process temperature, agitation rate, viscosity, and the liquid level. Good accuracy can be achieved with experienced staff who know the limitations and how to get the best results from an instrument.
Calorimetry in real time is a calorimetry technique based on heat flux sensors that are located on the wall of the reactor vessels. The sensors measure heat across the reactor wall directly and thus, the measurement is independent of temperature, the properties or the behavior of the reaction mass. Heat flow as well as heat transfer information are obtained immediately without any calibrations during the experiment.
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