Calculation of the maximum temperature in stirred tank reactors in case of a breakdown of cooling

• Published in: Chemical engineering science 1988, Vol.43 (8), p.2147-2152
• Main Authors: Hugo, P., Steinbach, J., Stoessel, F.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical engineering; CSTR; Exact sciences and technology; Reactors; safe operation conditions; Semi-Batch-Reactor (SBR)
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/0009-2509(88)87096-9

Safety is an important aim of chemical reactor design. If the reactor is equipped with a cooling device, the temperature rise at a cooling breakdown must be predictable. In the present paper this problem is discussed for continuous stirred tank reactors (CSTR) and semi-batch reactors (SBR). At breakdown of cooling, runaway of the reactor temperature occurs. The maximum temperature T m reached under adiabatic conditions, depends on the process conditions at the time of breakdown. The process temperature T s must be selected in such a way that in case of a cooling breakdown the maximum temperature T m is low compared to a temperature at which decomposition is critically active. For highly exothermic reactions it will be shown by theoretical considerations that, depending on the reaction number B, an optimal process temperature T s exists, for which the temperature T m has its lowest value. For a second order reaction if B exceeds 5.83 in the CSTR and 2 in the SBR the plot of T m versus T s will present a minimum. So a larger number of reactions will be concerned by this optimisation problem for the SBR than for the CSTR. General relationships will be derived to calculate the maximum temperature T m from T s and other operating conditions. It will be shown further how the operating conditions can be changed to get a sufficiently low runaway of temperature.