Model-based Control of an Additively Manufactured Reactor for Catalytic Methanation of Biogenic Syngas

Fossil natural gas is a key energy source but should be replaced by green synthetic natural gas in the context of the climate crisis. One possibility to generate synthetic natural gas is the methanation of synthesis gas from biomass gasification. Currently, the operation of such process chains is hardly economically feasible, which is why the investigated novel methanation reactor has been designed. Another key issue are fluctuating synthesis gas volume flows and composition caused by inhomogeneous feedstock properties. To address this issue, the heat pipe pressure of the methanation reactor as a key process quantity should be controlled. To design the control concepts, a physically motivated grey box model of the process based on dynamic energy balances is derived. Validation of the model using experimental data revealed a satisfactory fit in the context of control engineering, after an optimization-based parameter identification has been conducted. Then, a classical PI controller and a PI controller supported by a feed forward control law based on the proposed dynamic model are designed to control the heat pipe pressure. Both control concepts appeared to be well suited during experimental validation. The PI controller could deliver faster set point changes, while the feed forward control law could compensate certain disturbances better, leading to a reduced control error compared to the classical PI controller.