Model-based design of a segmented reactor for the flexible operation of the methanation of CO2

Abstract

As the share of renewable energies is growing, chemical plants need to adapt to the current energy availability. This is highly relevant for power-to-gas plants, where large amounts of electricity are used for hydrogen and subsequent synthetic natural gas production. A high plant flexibility allows adjusting the plant load according to the availability of feed streams. This raises the question how the methanation process can meet the high flexibility of the upstream electrolytic hydrogen production. As a possible solution, we propose a segmented, adiabatic fixed-bed reactor for the enhancement of the load range for CO2 methanation. A 1D pseudo-homogenous model is presented to investigate the reactor regarding its main thermal effects. Our findings prove the feasibility of the concept and illustrate its main features: a larger operating window and shorter start-up times compared to a conventional unit. Furthermore, unlimited standby at high temperature levels is possible, if at least one segment is actively operated.