MCFCs with Internal Fuel Reforming

From the very outset of MCFC development, research workers were attracted by the fact that not only hydrogen but also carbon monoxide (CO) could be used as a reactant fuel (reducing agent). Carbon monoxide (as water gas, a mixture of CO and H2) is obtained readily by the steam gasification of coal  

This opens up possibilities for an indirect electrochemical utilization of huge coal reserves. 

The possibility of a direct electrochemical oxidation of carbon monoxide was soon questioned. It was suggested that hydrogen, rather than carbon monoxide. 

Sparr et al. (2006) could show that pure CO can actually be oxidized electro-chemically according to the reaction 

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In this chapter, we focus on the MCFC with internal reforming. After a brief technical introduction of this type of fuel cell, a model is presented that describes the interaction of the reforming reaction and the electrochemical oxidation reaction inside the MCFC with a set of only two ordinary differential equations (ODE) and some algebraic equations (AE). A diagram is introduced which allows the simulation results to be displayed in an easily interpretable way. Finally, the usefulness of the model and its accompanying diagram are demonstrated in several applications. 

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

Molten carbonate fuel cells (MCFC) are composed of a porous nickel-based anode, a porous nickel oxide-based cathode and molten carbonate salts as electrolyte within a porous lithium aluminate matrix. Molten carbonate fuel cells with internal reforming can be fed directly with light hydrocarbons rich gas such as... 

Solid oxide fuel cell - Similar to a MCFC, a SOFC is also a kind of high temperature fuel cell working at around 1000°C. Solid ceramic material hke yttria-stabhized zitconia is employed as the electrolyte. The internal reform reaction of fuel makes SOFC flexible to various hydrocarbon fuels without using a fuel reform system. However, the sulfur tolerance of SOFC is poor. Because of the slow start up and high operation temperature, SOFC is suitable to large-scale stationary power applications with heat cogeneration. 

Fuel Flexibility The MCFC can internally reform a wide variety of fuel sources and use carbon monoxide as a fuel, a major poison in PEFC applications. This alleviates the need for a hydrogen infrastructure with this system. 

The University of Queensland in Australia conducts general R D to support MCFC systems as part of a project to develop advanced system integration techniques and catalysts for internal reforming fuels cells. The aim is to enable a wide range of fuels to be used with MCFCs for small scale stationary applications suitable for remote areas in Australia. 

The electrolyte in this fuel cell is usually a combination of alkali carbonates, which is retained in a ceramic matrix of LiA102. The fuel cell operates at 600 to 700 " C where the alkali carbonates form a highly conductive molten salt, with carbonate ions providing ionic conduction. At the high operating temperatures in MCFCs, Ni (anode) and nickel oxide (cathode) are adequate to promote reaction. Noble metals are not required for operation, and many common hydrocarbon fuels can be reformed internally. 

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