The production of substitute (or synthetic) natural gas (SNG) by methanation of CO2 with hydrogen is energy intensive and also requires a purification step to remove the byproduct water and remaining reactants. To address these issues, researchers at The Swiss Federal Laboratories for Materials Science and Technology (Empa; Dübendorf, Switzerland; www.empa.ch) have developed a new, optimized reactor concept for methanation.
The new concept uses a process called sorption-enhanced methanation. H2 and CO2 are fed to a fixed-bed reactor containing nickel-impregnated porous zeolite pellets as catalyst. As the reaction proceeds, byproduct water is continuously adsorbed by the zeolite, which shifts the reaction equilibrium toward the products. At the outlet of the reactor, only CH4 remains, which can be used without further purification. The water is then removed from the zeolite by flushing the reactor with H2, and another batch can begin.
“This process is more flexible and stable than previous processes, but it also has some potential for energy savings because we can run it at a lower pressure and do without hydrogen separation and recirculation,” explains project leader Florian Kiefer. “However, a precise assessment of the energy efficiency will only be possible once the demonstrator is in full operation,” he says. An industrial-scale process would require at least two reactors alternating in parallel.
Kiefer and his team spent around three years developing this reactor concept, in collaboration with industrial partners, as part of project MEGA within Empa’s “move” demonstrator for the mobility of the future. A patent has been filed.