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

Friday, 31 July 2015: 10:40
Alsh (Scottish Exhibition and Conference Centre)
Y. Luo, W. Li, Y. Shi (Department of Thermal Engineering, Tsinghua University), X. Ye, S. Wang (Chinese Academy of Sciences), and N. Cai (Department of Thermal Engineering, Tsinghua University)
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. Theoretically, methanation reaction is possible to happen in standard condition when temperature is lower than 600oC. Tubular solid oxide electrolysis cell (TSOEC) has great potential for large-scale application due to easily sealing and high strength. Moreover, gradient distribution of temperature in flow direction is beneficial to CH4 production. In this paper, CH4 synthesis characteristics in TSOEC is studied in the temperature range of 500-650oC by combining experiment and simulation. Experiment demonstrates the addition of H2 increases the outlet molar fraction of CH4 from 0 to 2.85% at 600oC, and from 0.01% to 8.77% at 550oC. In addition, it’s found that electricity significantly promotes CH4 production, especially when H2 is added. The applied voltage of 1.5V just increases CH4 production ratio by <0.04% in the absence of H2. But when 20% H2 is fed in cathode, CH4 production ratio is improved by 3-4%. Finally, the optimal operating condition, thermal distribution and reaction active zones are simulated by a well validated thermal model. The thermal distribution can be changed by outer boundary condition. CH4production can be further improved by increasing the temperature of upstream zone and reducing that of downstream zone.

Fig.1 Methane synthesis schematic in TSOEC