Tank Reactor Temperature Control using Quantitative Feedback Theory

Temperature control of tank reactors with exothermic reactions is an acknowledgedly difficult task because of complex interacting phenomena, several nonlinearities and unstable dynamics. Traditionally, simple control functions are implemented, implying poor control performance and small operating windows. However, many advanced control schemes have been published, though in many applications they rely on too simplistic process models. Here, a control strategy using only a small number of linear controllers has successfully been applied to a rigorous reactor model, including the cooling system dynamics. The methodology is to first linearize the model in steady-state and relevant non-stationary points and let the resulting models define uncertainties in the frequency plane. Then Quantitative Feedback Theory (QFT) is used to ensure that robust feedback system specifications are fulfilled for all these uncertainties.