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Advanced DIR-MCFC development


(1) DIRSEP (TM) stack design: The DIRSEP (TM) stack design is a set of specifications for a pre commercial, internal manifolding, full size MCFC stack with internal reforming. The stack is designed to function under internal and external pressure differences up to 0.3 bar, enabling its operation within a simple (no expensive pressure control equipment), low cost system. Although optimised to the SMARTER (TM) system design, for improved temperature profile and electrical performance of the stack, the stack design can be adapted to other internal manifolding MCFC systems (IR or ER). The developed stack has a lifetime over 25,000 hours. The costs for the full size stack were calculated at 1030 EUR/kWAC at a production rate of 200 MWAC/year. Further cost reduction to 530 EUR/kWAC is feasible by a limited number of rather straightforward developments. (2) Reforming Catalyst coated on Stainless Steel substrate: Conventional steam reforming catalyst is manufactured industrially in the form of particles or pellets. They cannot be used in the DIR-MCFC because of insufficient activity at the operating cell temperature and high susceptibility to poisoning by alkali, which originates from the molten carbonate electrolyte. BG has developed a particular catalyst material, which overcomes the problems associated with alkali poisoning, and has demonstrated long lifetimes in DIR-MCFC cells and stacks. Most recently, BG has investigated methods of coating such catalyst, in the form of a thin film, onto MCFC stack hardware. This will have the advantage of ease of manufacture for the MCFC developer, when compared with the use of conventional pelleted catalyst material. Several methods of catalyst deposition are currently being evaluated. A further advantage of using coated catalyst is that of cost reduction, both in the method of catalyst deposition and in the reduced amount of catalytic material that is needed for an MCFC stack. (3) SMARTER (TM) system design: The SMARTER (TM) stack concept is a generic design of a high temperature fuel cell stack that incorporates internal reforming. Although devised during the Advanced DIR-MCFC project, the concept could be applied equally to solid oxide as well as internal reforming molten carbonate fuel cell stacks. The stack concept contains two different types of cells. The anode off gas of one type of cells is recycled to the stack inlet, while the anode off gas of the other type is fed to the anode combustion. The SMARTER (TM) stack design can be applied to both co-flow and cross-flow geometry�s and gives high electrical efficiencies and improved stack temperature distributions. The SMARTER (TM) stack has been tested on a sub-scale of 0.1 m(2) within the Advanced DIR-MCFC development project. Tests have shown that the operating regime for the stack is less demanding than conventional stacks and offers good prospects for longer lifetimes, since less thermal strain is placed on the stack materials. Calculations suggest that electrical efficiency may be improved by 5 percentage points compared with more conventional designs of fuel cell stack. (4) Header Box compact system design: The Header Box compact system design is a result of the combination of the following functions: -Conduction of gases to the stacks and system components -Mechanical support of the stacks -Provisions for measuring equipment and valves -Mixing of fuel in the anode section and air in the cathode section The combination of these functions has led to a design in the shape of a flat box in the bottom of a container that encapsulates the system. Walls are implemented to separate the gases, and conduct them to / from the stacks, the hot blower, the burner and the air compressor.