Transient Flow Rate Ramps for Methanation of Carbon Dioxide in an Adiabatic Fixed-Bed Recycle Reactor

Abstract

The power-to-gas (PtG) process, enabling the long-term indirect storage of electrical energy, includes the water electrolysis for hydrogen production and the subsequent hydrogenation of carbon dioxide in a methanation reactor. The dynamic operation of methanation reactors is favored to limit upstream storage capacities, but not fully understood thus far. Therefore, this contribution investigates the dynamic operation of a fixed-bed recycle reactor during flow rate ramps with a variation of the ramp time. Load ramps of the volumetric flow rate lead to global maxima during the transition; for the methane content if the flow rate is decreased, and for the gas temperature if the flow rate is increased. Furthermore, the adaptation of the product recirculation during flow rate ramps is discussed at the end. The recycle ratio turns out to provide an additional degree of freedom for stabilizing the reactor behavior under fluctuating feed conditions.