Case Study on Tubular Reactor Hot-Spot Temperature Control for Throughput Maximization

Abstract

Auctioneering hot-spot temperature control of a highly exothermic cooled tubular reactor (constant coolant temperature) for cumene production via the irreversible gas-phase alkylation of benzene with propylene (A + B → C) is studied. Specifically, three control configurations are quantitatively evaluated for tightness of hot-spot temperature control and maximum achievable process throughput with reactor cooling duty as the bottleneck constraint. The configurations manipulate respectively the reactor cooling duty (CS1), the reactor inlet temperature (CS2), and the fresh propylene feed (CS3) for regulating the hot-spot temperature. Plantwide dynamic simulation results show that tightest hot-spot temperature control is achieved by the direct manipulation of the reactor cooling duty (CS1). Use of reactor inlet temperature as the manipulation handle (CS2) is not recommended due to large deviations in the reactor temperature profile for a throughput increase. Manipulating the fresh propylene feed rate (limiting reactant) as in CS3 provides loose but acceptable hot-spot temperature control. CS3 is most preferred for throughput maximization as the reactor is operated at the bottleneck constraint of maximum heat removal capacity. For the sample case study, the maximum achievable throughput increases by more than 7% by use of CS3 (over CS1).