Screening Adiabatic Calorimetry: Simulating Phi=1 In Glass Test Cells By Increasing The Concentration

When a runaway reaction occurs in a large vessel in a chemical plant, the thermal inertia of the system will be very low ( phi() close to unity). To mimic this behavior in an adiabatic reaction calorimeter, it is advisable to perform the measurements in a test cell with a factor close to unity as well. From a practical point of view, this is not always easy to realize. In this paper, we describe a possible way of simulating the behavior at) 1 in test cells with higher thermal inertia. This approach consists of leaving out an amount of solvent which matches exactly the thermal mass of the measuring cell. By doing so, the total adiabatic temperature rise will be reproduced correctly. Changing the concentration, however, will alter the reaction kinetics as well. This will lead to an overestimation of the maximum selfheat rate and an underestimation of the time to maximum rate. Hence, the error which is introduced is on the safe side of reality and, therefore, acceptable for screening purposes. The influence of different experimental parameters on the reliability of the result is discussed. The validity of this approach is demonstrated with a couple of examples.