Modeling of Micro-Tubular Solid Oxide H2O/CO2 co-Electrolysis Cell for Syngas Production

In this paper, a one dimensional chemical equilibrium co-electrolysis model is established to reveal the high temperature H2O/CO2 co-electrolysis process in a micro-tubular cell. The model has been roughly validated by the experimental data, systematically demonstrating the effects of current density, cell length, operating temperature and inlet gas flow rate on the products composition as well as the syngas quality. It is indicated that increasing both the electrolysis current and cell length will lead to an improved conversion rate of H2O and CO2 as well as an increased yield of H-2 and CO. High-quality syngas with 100% CO2 and steam conversion rate as well as ideal H-2/CO ratio of 2 is achieved when the 15-cm cell is exposed to a 50-sccm cathode gas stream consisting of 56.67% H2O+33.33%CO2+10% H-2 at 800 degrees C and 1.0 Acm(-2). It is also found that the operating temperature, which is strongly associated with the equilibrium of reverse water gas shift reaction, plays an important role in the as-products properties. A constant H-2/CO ratio of 2 is achieved at 817.5 degrees C. Besides, reducing the inlet gas flow rate is beneficial to increase the conversion rate of H2O and CO2, but decrease the syngas production rate.