Control of temperature wave trains in periodically forced networks of catalytic reactors for methanol synthesis

We study the stabilisation of traveling temperature wave trains in periodically forced networks of catalytic reactors where methanol synthesis takes place. Temperature wave train solutions reproduce the inter-stage cooling effect of multistage fixed bed reactors and are therefore particularly attractive in terms of methanol conversion. However, these solutions are generally stable within narrow operating windows and always coexist with solutions characterised by lower methanol conversion. We implement a feedback control strategy with the switching time as a manipulated variable to ensure the stability of temperature wave trains. The reaction front velocity is estimated during each cycle based on temperature measurements. This allows the switching time to be computed so that the reaction front does not cross a prescribed set-point position. Indications on how to place temperature sensors and to select the set-point and controller parameters are provided. Numerical simulations demonstrating the ability of the implemented control law to prevent the transition to undesired solutions in the presence of disturbances both in the operating regime and during start-up are reported.