Methane Synthesis Characteristics of H2O/CO2 Co-Electrolysis in Tubular Solid Oxide Electrolysis Cells

Abstract

Producing methane by H2O/CO2 co-electrolysis through solid oxide electrolysis cell (SOEC) is a promising method to store unstable renewable power and reduce CO2 emission simultaneously. In this paper, CH4 synthesis characteristics in tubular SOEC (TSOEC) is studied in the temperature range of 550-650oC by combining experiment and simulation. Experiments demonstrates adding H2 increases the CH4 production ratio from 0 to 4.01% at 600oC. Besides, electricity significantly promotes CH4 production, especially when H2 is added. The voltage of 1.5 V just increases CH4 production ratio by <0.04% in the absence of H2. But when 20% H2 is fed in cathode, a voltage of 1.5 V can increase CH4 production ratio by 3-4%. Finally, chemical reactions, thermal distribution and optimal operating condition are simulated by a well validated thermal model. A reasonable thermal distribution created by operating TSOEC in counter-flow mode and lower inlet steam partial pressure can dramatically improve CH4 production.