Quantitative Comparison of Temperature Control of Reactors with Jacket Cooling or Internal Cooling Coils

Abstract

This paper presents a quantitative comparison of the effectiveness of two alternative heat-removal schemes in the control of continuous stirred tank reactors (CSTRs). The chemistry features an exothermic irreversible reaction A → B, and different design levels of conversion are explored. Two mechanisms for removing the heat of reaction are studied: (1) a cooling jacket surrounding the vessel or (2) an internal cooling coil. Controllability is shown to become more difficult as the design conversion decreases. Results demonstrate that internal coil cooling provides better dynamic controllability than jacket cooling in terms of being able to handle larger disturbances. A generic “reactor controllability index” (RCI) is proposed that can be used to assess the dynamic robustness of any CSTR. The RCI is the dimensionless ratio of the temperature difference between the reactor and jacket (or the log-mean temperature difference for coil cooling) and the maximum available temperature difference (reactor temperatu...