Modeling of SOFC running on partially pre-reformed gas mixture

Abstract

A two dimensional model is developed to study the transport and reaction processes in solid oxide fuel cells (SOFCs) fueled by partially pre-reformed gas mixture, considering the direct internal reforming (DIR) of methane and water gas shift (WGS) reaction in the porous anode of SOFC.Electrochemical oxidations of H 2 and CO fuels are both considered. The model consists of an electrochemical, a chemical model, and a computational fluid dynamics (CFD) model. Two chemical models are compared to examine their effects on SOFC modeling results. Different from the previous studies on hydrogen fueled SOFC, higher gas velocity is found to slightly decrease the performance of SOFC running on pre-reformed gas mixture, due to suppressed gas composition variation at a higher gas velocity. The current density distribution along the gas channels at an inlet temperature of 1173K is quite different from that at 1073K, as DIR reaction is facilitated at a higher temperature. It is also found that neglecting the electrochemical oxidation of CO can considerably underestimate the total current density of SOFC running on pre-reformed hydrocarbon fuels. An alternative method is proposed to numerically determine the open-circuit potential of SOFC running on hydrocarbon fuels. Electrochemical reactions are observed at open-circuit potentials.

SOFC modeling considering hydrogen and carbon monoxide as electrochemical reactants

“…The electrochemical oxidation of methane (eqns (7)- (8)) is neglected, because the electrochemical oxidation rate of methane is neglible, compared to the ones for hydrogen and carbon monoxide [9,27]. Note that this electrochemical 13 approach also includes the gas-phase partial pressures, which are frequently neglected within the open literature and also in our previous models [3,37,44].…”

“…Also Ni [27] assumes the exchange current density for hydrogen electrochemical reaction to be 2.5 times that for the CO electrochemical oxidation. These assumptions can be compared to the result from Matsuzaki and Yasuda in [47], where it was concluded that the electrochemical oxidation rate of H 2 at the interface in a porous…”

Comparison of humidified hydrogen and partly pre-reformed natural gas as fuel for solid oxide fuel cells applying computational fluid dynamics

“…Solid oxide fuel cells (SOFCs) offer the possibility of environmentally friendly production of electricity by high efficiency, low emissions of pollutants and several options of fuels [1][2].…”

“…1). If hydrogen is used as fuel, the active species involved in the electrochemical reactions are oxygen and hydrogen, as shown in eqns (1)- (2). H 2 forms a molecule of H 2 O during this oxidation reaction and releases electrons [9][10].…”

Economic analysis of a solid oxide fuel cell cogeneration/trigeneration system for hotels in Hong Kong

“…Due to their distinct features, extensive efforts have been made to develop efficient and reliable SOFCs systems capable of using various alternative fuels (i.e. conventional natural gas and renewable biofuel) for a variety of applications [6][7][8]. In order to improve the long-term stability of SOFC and decrease the cost of SOFC system, there is a trend to lower the operating temperature of SOFC [9].…”