Dynamic Operation of Two-stage CO₂ Methanation Reactor

A study conducted by Shogo Sayama et al. was published in the Renewable Energy.

Considerable attention has been paid to CO₂ methanation, in which industrial CO₂ is converted into CH₄ using H₂. The hydrogen is produced by a water electrolyzer using solar photovoltaic and wind electricity. Because solar and wind outputs intrinsically fluctuate over time, the H₂ production rate varies accordingly; however, CH₄ production cannot fully follow these fluctuations. A buffer tank is installed between the electrolyzer and the CO₂ methanation unit, which mitigates the variation of H₂ provision rate to the CO₂ methanation unit. The tank size varies depending on the time required for start-up and adjusting the CH₄ production rate in the CO₂ methanation unit.
To this end, this study suggested a fast start-up method of the CO₂ methanation unit, combusting H₂ for heating methanation catalysts rapidly. This method lighted off the methanation reaction in as less as 4 minutes while the conventional method by electrical heater required 26 minutes. Also, it was shown that a detailed catalyst temperature control can prevent the unexpected reaction termination during adjusting the CH₄ production rate. These achievements can contribute to the realization of a zero-CO₂-emission society.

Title: Dynamic Operation of Two-stage CO₂ Methanation Reactor: Start-up by H₂ Combustion and Load Change by Independent Control of Heat-carrier Flow Rate
Authors: Sayama, S., Yamamoto, S.
Journal Name: Renewable Energy
Published: February 1, 2025
https://doi.org/10.1016/j.renene.2025.122548