Improvements in reaction calorimetry techniques, data quality and hazard assessment procedures are key elements to improve process safety decisions. Reaction calorimetry techniques have improved over the past thirty years with the advent of the real time calorimetry RTCal™ and iC Safety™ software – which extends the data available from the RC1e reaction calorimeter and provides a critical information link between reaction calorimetry data and its place in the overall safety assessment strategy.Reaction calorimetry is an essential part of the process information required to develop and understand chemical processes and is an intrinsic part of the process development procedure. Chilworth Technology Ltd,
Chilworth conducted a series of experiments on a solution polymerization of a high molecular weight acrylate monomer in toulene using AZDN as initiator. The reaction was performed by adding the initiator solution into the reactor containing the solvent/monomer mixture at 80°C. The polymerization was likely to result in a significant viscosity change (U change). The experiment results confirmed this (Figure 3 and Table 1). For the conventional calorimetric data, the uncorrected U value was proportional to Vv resulting in an extreme underestimate of the overall heat flow and heat of reaction. However, RTCal™ provided an accurate measurement of heat flow in real time eliminating the need for additional data work.
Chilworth Technology Ltd found numerous benefits of integrating RTCal™ into their experimental workflows including improved reaction accuracy, elimination of the need for calibrations, real time heat flow measurement for feedback experiment control and many others.
Reaction calorimetry, specifically its application in process safety studies, provides important data to describe the overall risk of the process but it cannot be used in isolation. Criticality classes are used to classify the relative thermal risk of a process (Figure 4). The Criticality Classes are based on thermal effects and described by four key temperatures, the process temperature Tr, the “maximum Temperature of the Synthesis reaction” (MTSR), the “Maximum Technical Temperature” (MTT), and the onset of the secondary reaction (Tdec or TD24). However, the aspect of generation must be considered in the overall safety assessment too and can be used to define the relative risk of a reaction and to make decisions regarding safety measures and procedures.
In addition to RC1e and RTCal™, Chilworth also invested in iC Safety™ software for its experiments to convert basic RC1e data into usable information for safety assessment. Figure 5 provides an example relating to the methanol/acetic anhydride reaction (stoichiometric and acid catalyzed) at 20°C. (Insert figure 5).
The software is a valuable addition, says Chilworth, which automates the process of deriving information from data for safety application of RC1 data. The most valuable information relates to the maximum reaction power output, MTSR and extent of accumulation/conversion during the process.