Calorimetric Techniques For Reflux Analysis And Scale Up For The Design And Operation Of Batch Reactors

The possibility for thermal runaway in batch chemical synthesis is reduced by thorough analysis of the proposed chemical reaction or process modification. The investigation, in many cases, will initially take place in the laboratory. Only when measurements have proved satisfactorily that the process is “safe", are investigations started on the pilot plant scale. A new bench scale instrument for thermal hazard analysis has been designed and built which enables the power release from chemical reactions which self heat into the reflux regime to be monitored. Several chemical reactions have been carried out at reflux for a range of different thermometric scenarios. The results and calorimetric technique are discussed in detail. Ultimately, control of an exothermic batch chemical reaction depends upon the reactors ability to control the heat release. By understanding how large scale heat transfer characteristics change during the course of a chemical reaction, from bench scale studies it is possible to predict, with greater certainty, whether or not the process is safe once scaled up. A Mettler RC1 heat flow calorimeter, at South Bank Polytechnic and a fully instrumented pilot plant reactor at the Boots Company plc in Nottingham have been used for heat transfer studies. It has been possible to investigate empirical correlations for the inside film heat transfer coefficient, and its prediction ona large scale, from small scale studies. A novel technique is presented for measuring inside film heat transfer coefficients on a large scale. From a knowledge of heat transfer on the pilot plant scale it has been possible to use the pilot plant reactor for basic calorimetric studies. The advantages and disadvantages of heat balance and heat flow calorimetry on a large scale are evaluated. Finally calorimetric investigation of two industrial reactions, on the pilot plant scale and on the bench scale, is presented.