Modelling of Gradual Internal Reforming Process Over Ni‐YSZ SOFC Anode With a Catalytic Layer Kelly Girona, 1 Sébastien Sailler, 2,3 Patrick Gélin, 1 Nicolas Bailly, 2,3 Samuel Georges 2,3 and Yann Bultel 2,3 * 1. IRCELYON, Université Lyon 1, CNRS, UMR 5256, Institut de recherches sur la catalyse et l'environnement de Lyon, 2 avenue Albert Einstein F‐69626, Villeurbanne, France 2. Univ. Grenoble Alpes, LEPMI, 38000, Grenoble, France 3. CNRS, LEPMI, 38000, Grenoble, France Methane appears to be a fuel of great interest for solid oxide fuel cell (SOFC) systems because it can be directly converted into hydrogen by Internal Reforming within the SOFC anode. To cope with carbon formation, a new SOFC cell configuration combining a catalyst layer with a classical anode was developed. The rate of the CH 4 consumption in the catalyst layer (Ir‐CGO) was determined experimentally for small values of steam to carbon ratios. This paper proposes a modelling and a simulation, using the CFD‐Ace software package, of the behaviour of a SOFC operated in Gradual Internal Reforming (GIR) conditions. This model of SOFC takes into account the kinetics of the steam reforming reaction in the catalyst layer in order to assess the influence of the steam to carbon ratio and the cell polarization. Because the risk of carbon formation is greater under GIR operation, a detailed thermodynamic analysis was carried out. Thermodynamic equilibrium calculations allowed us to predict the conditions of carbon formation occurrence. Keywords: SOFC, modelling, Gradual Internal Reforming, carbon deposition INTRODUCTION S olid oxide fuel cells (SOFCs) are promising candidates for power generation while preserving the environment. Nowadays most of the SOFC developers adopt a fuel containing a significant part of hydrogen. However their high operating temperature (973–1273 K) allows a real flexibility towards the fuel. In particular,biogas that contains methane, can be used. Namely, the Direct Internal Reforming (DIR) within the SOFC anode allows the conversion of hydrocarbons into hydrogen without reformer by supplying to the anode enough steam to complete the catalytic conversion of the hydrocarbon. [1] Various fuels like natural gas, ethane, butane, toluene or alcohols have been tested and the results have shown the feasibility of this concept on the classical Ni‐YSZ cermet [2–4] or on other anode materials. [5–9] Numerous investigations on SOFCs operating under DIR of methane have been reported, [10–17] with methane remaining the most interesting fuel for SOFC systems. In this process, steam is used as reforming agent. The steam to carbon ratio must be higher than 1 in order to prevent the risk of carbon formation which reduces considerably the performance and durability of the cells. However, an important quantity of steam in the system may lead to thermomechanical damages; the fast endothermic conversion leads to local cooling at the entrance and steam management represents a serious problem. Moreover, steam is produced in situ by electrochemical oxidation of hydrogen. To address these problems, Gradual Internal Reforming (GIR) has been put forward. [18] GIR, like DIR, is based on local coupling between the steam reforming of the fuel, which occurs on a catalyst (Nickel), and the electrochemical oxidation of hydrogen at the electrode’s triple‐phase. GIR also enables the hydrogen required by the electrochemical reaction to be generated in situ. However, unlike DIR, which requires large amounts of steam, this process requires very small quantities of steam at the fuel inlet. In fact, the steam used by the reforming reaction is generated by the electrochemical reaction. However, in GIR mode, carbon forma- tion becomes a serious problem because of the low S/C ratio. However, the risk of cell degradation is increased in Ni‐based anodes since Ni is a good catalyst for hydrocarbons reforming reactions but also for carbon deposition reactions. To cope with carbon formation, Zhan and Barnett [19] introduced the concept of inert or catalytic layer added onto the anode and acting as either physical barrier or catalytic active membrane. Good performances were obtained using these concepts for dry (CO 2 ) reforming of iso‐ octane and for partial oxidation of methane using methane–air mixtures by several groups, [20,21] which emphasizes the essential role of heterogeneous catalysis in the operation of such fuel cells with hydrocarbons. Zhu et al. [22] show that a porous chemically inert barrier layer can extend the range of coke‐free operation on Ni–YSZ anode structures, even with pure methane as the fuel. Similarly, Klein et al. [23] proposed a new cell configuration combining a catalyst layer with the conventional cermet Ni‐YSZ anode. The catalyst layer requires specific catalytic properties: (i) high catalytic activity towards methane steam reforming at the operating temperature (1073 K), and (ii) high resistance against the thermodynamically favoured formation of carbon deposits because of high CH 4 /H 2 O molar ratios at the anode (near to 10/1). Thus, according to the cell configuration, the greater part of the reforming reaction occurs in the catalytic layer and therefore most hydrocarbon species are converted before the fuel has reached the *Author to whom correspondence may be addressed. E‐mail address: Yann.Bultel@lepmi.grenoble-inp.fr Can. J. Chem. Eng. 93:285–296, 2015 © 2014 Canadian Society for Chemical Engineering DOI 10.1002/cjce.22113 Published online 17 December 2014 in Wiley Online Library (wileyonlinelibrary.com). VOLUME 93, FEBRUARY 2015 THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING 285