Direct internal-reforming fuel cell

Developers of internal reforming fuel cells have generally adopted one of two approaches, and these are usually referred to as direct (DIR) and indirect (HR) internal reforming. They are illustrated schematically in Figure 8.4. In some cases, a combination of both approaches has been taken. A thermodynamic analysis and comparison of the two approaches to internal reforming in the MCFC has been completed by Freni and Maggio... 

Aguiar P., Adjiman C.S., Brandon N.P. (2005) Anode-supported intermediate-temperature direct internal reforming solid oxide fuel cell II Model-based dynamic performance and control. Journal of Power Sources 147, 136-147. 

Fig. 2.1. Working principle of the Molten Carbonate Fuel Cell (MCFC) with direct internal reforming (DIR).

In this chapter, three applications of this model are demonstrated. The comparison of different reforming concepts reveals the advantages of direct internal reforming (DIR) in the anode channel of the fuel cell. Moreover, with the help of the proposed model, the benefit of fuel cell cascades can be demonstrated and they can be compared to single cells. Results indicate that a considerable power increase can be expected, but the additional hardware required might offset any benefit in the case of smaller systems. The third application demonstrates that anode gas recycle can be simulated with this model, but it also reveals its limitations, as temperature effects are not considered. 

In the direct internal reforming MCFC (DIR-MCFC) system, the direct reformation of fuel at the anode can give fuel saving of 20%, resulting in 12 /o improvement in fuel cell electrical efficiency. The schematic representation of the HR and DIR concepts is shown in Fig. 4. 

Gonjyo, Y. Matsumura, M. Tanaka, T. Performance of direct internal reforming molten carbonate fuel cells. Proceedings of the 26 ... 

Reforming fossil fuels will make sense only if the hydrogen is used directly, as in fuel cell engines. For internal combustion engines, it is always more efficient to use the fossil fuel directly without passing it through a reformer first. 

Nakagawa N, Sagara H and Kato K (2001) Catalytic activity of Ni-YSZ-Ce02 Anode for the steam reforming in a direct internal-reforming solid oxide fuel cell. J Power Sources 92 88—95. 

In contrast to stationary applications, portable applications require frequent start and stop procedures. Therefore for SOFC, a robust cell design and adapted electrode-electrolyte assemblies are an important issue. Frequent thermal cycles between room temperature and an operation temperature of about 600-800 °C pose challenges to the layered system consisting of solid anode, ceranfic electrolyte and solid cathode with respect to thermal and mechanical stability. For several years, different approaches to developing tubular nficro SOFC have been undertaken but did not lead to a commercial product yet. As SOFC can be operated with pure hydrogen, reformate and hydrocarbons as fuel as well - the latter option means direct internal reforming at the anode catalyst — various investigations focused on reduced operation temperature and a parallel conversion of fuels [21]. 

Though the focus of this thesis is on direct internal reforming, the existing applications use some extend of pre-reformed fuel. Therefore, a systematic study to understand the influence of non-reformed and pre-reformed fuels on cell efficiency is carried out. It is well known that direct internal reforming can result in reduced cost and increased overall efficiency of the system. However, it is quite convincing from Fig. 7.19 that, the efficiency of the fuel cell is higher for pre-reformed fuel. Both efficiency and power density increases with extent of pre-reforming for both adiabatic and isothermal case (Fig. 7.20). 

Aguiar P, Adjiman CS, Brandon (2004) Anode-suppoited intermediate-temperature direct internal reforming solid oxide fuel cell I. Model-based steady-state performance. J Power Sources 138 120-136. 

Heldebrecht, P. and Sundmacher, K. (2005) Dynamic model of a cross-flow molten carbonate fuel cell with direct internal reforming. J. Electrochem. Soc., 152 (11), A2217-A2228. 

In direct internal reforming (DIR) the reforming reaction is carried out on the fuel cell anode itself (or as close to it as possible) in this way hydrogen produced by reforming is immediately consumed by the electrochemical cell reaction allowing to shift the equilibrium of the reforming and WGS reactions to the right as product is consumed by the electrochemical reaction [13, 95, 133-135]. The DIR approach is best carried out at low pressures with catalyst inside the anode compartment close to the anode of the ceU. 

Zhang J, Zhang X, Liu W, Liu H, Qiu J, Yeung KL (2014) A new alkaU-resistant Ni/A1203-MSU-1 core-shell catalyst for methane steam reforming in a direct internal reforming molten carbonate fuel cell. J Power Sources 246 74—83... 

Lanzini A, Leone P (2010) Experimental investigation of direct internal reforming of biogas in solid oxide fuel cells. Int J Hydrogen Energy 35 2463-2476... 

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