Modeling and simulation of CO methanation process for renewable electricity storage

In this paper, a new approach of converting renewable electricity into methane via syngas (a mixture of CO and H2) and CO methanation is presented. Surplus of electricity is used to electrolyze H2O and CO2 to H2 and CO by using a SOEC (Solid Oxide Electrolysis Cell). Syngas produced is then converted into methane. When high consumption peaks appear, methane is used to produce electricity. The main conversion step in this process is CO methanation. A modeling of catalytic fixed bed methanation reactor and a design of methanation unit composed of multistage adiabatic reactors are carried out using Aspen plus™ software. The model was validated by comparing the simulated results of gas composition (CH4, CO, CO2 and H2) with industrial data. In addition, the effects of recycle ratio on adiabatic reactor stages, outlet temperature, and H2 and CO conversions are carefully investigated. It is found that for storing 10 MW of renewable electricity, methanation unit is composed of three adiabatic reactors with recycle loop and intermediate cooling at 553 K and 1.5 MPa. The methanation unit generates 3778.6 kg/h of steam at 523.2 K and 1 MPa (13.67 MW).