Estimation of the time to maximum rate using dynamic DSC experiments

The probability of thermal risk may be described by the time to maximum rate under adiabatic conditions (TMR(ad)). In this paper a screening method based on dynamic differential scanning calorimetry (DSC) measurements was studied in order to show that, when using the TMR(ad) criterion, no process would be assessed as safe when it could, in fact, be critical. The method of investigation was based on dynamic simulation, In this, the DSC measurement equipment and five different reaction types (simple nth order, consecutive, branched and autocatalytic reactions) were described in mathematical terms and simulated using MATLAB. The reliability of the estimation was checked by comparing the simulated TMR(ad) with the estimated TMR(ad) based on dynamic DSC measurements and isothermal assessment procedures, The TMR(ad) values calculated from simulation of dynamic DSC runs were always found to lie in the range of 10-70% of those obtained by dynamic simulation of the adiabatic case. Owing to some uncertainties with regard to autocatalytic reactions, a method was developed to identify them. The application of the total method to experimental measurements showed a good correspondence to the results obtained by simulation. The estimation method is therefore a good tool for preliminary screening and may be applied at the early stages in process design to save both time and money and without loss of safety. (C) 1997 Elsevier science Ltd. All rights reserved.