Challenges in Start-up Control of a Heat Exchange Reactor With Exothermic Reactions; A Hybrid Approach

Abstract

This chapter investigates the control of a continuous heat exchange reactor is from a hybrid perspective with focus on the start-up phase and the transition to the optimal operating point. The temperature sensitive exothermic reaction leads to the possibility of multiple steady states and in combination with safety constraints forms an interesting challenge for a safe and efficient start-up. A series of MPC controllers are developed with a switching logic that transfers the process from initial rest to continuous optimal operation mode. The control procedure is verified in simulations with a full nonlinear model of the Open Plate Reactor. For industrial production of temperature sensitive exothermic reactions, safe and efficient start-up control is important. Normally the reactor operates in a continuous mode around an optimal operating point. However, there are several different control modes associated with the production. This chapter focuses on the start-up mode, the continuous operation mode, and the transition in between. It shows that it may be necessary to switch between several controllers with different optimization criteria to allow a safe and efficient start-up and thereafter optimal production. The chemical reactor and the exothermic reaction form a highly nonlinear process and for some operating conditions also an unstable process. It is therefore essential that the reactor be started in a safe and accurate fashion.