A novel approach to methane production: integration of solar hydrogen and Chemical Looping Gasification

In this work, an innovative process layout for methane production is proposed and numerically investigated with the aim to promote the chemical storage of renewable energy via the integration between hydrogen production by water electrolysis and chemical looping gasification. The core of the proposed layout is a chemical looping fixed bed gasification system, fed with different mixtures of biomass and Plastic Solid Waste (PSW) and using Fe2O3 as oxygen carrier, and a methanation unit. This latter consists of a series of adiabatic fixed bed reactors with inter-cooling, water condensation at the exit of each reactor, and product recycle. The performance of the methanation system was evaluated by considering that the syngas stream coming from the gasifier system reacts, after purification and mixing with a pure hydrogen stream coming from an electrolysis cells array (EC), over Ni/Al2O3 catalyst. The number of ECs to be stacked in the hydrogen production unit was evaluated by considering that a constant H2 production able to reach 7:1:1 H2:CO:CO2 molar ratio at the inlet of the methanation unit should be attained. Moreover, by considering that only energy from renewable sources (such as photovoltaic panels or wind turbines) was used in the system, the capability of the proposed process to be used as an energy storage system was assessed.