Arge Dfc A European Approach To Mcfc Commercialization

Peter Kraus, Gerhard Huppmann MTU Friedrichshafen GmbH D-81663 München

Dr. Andreas Heiming Ruhrgas AG Halterner Str. 125 D-46284 Dorsten

Dr. Kim Aasberg-Petersen Haldor Topsoe A/S Nymollevej 55 DK-2800 Lyngby

The largest European program for the commercialization of the molten carbonate fuel cell technology is carried out by the European Direct Fuel Cell Consortium (ARGE DFC). The consortium consists of the following companies:

• MTU Friedrichshafen GmbH (Germany), within the DaimlerBenz Group responsible for off-road propulsion and decentralized energy systems.

• Haldor Topsoe A/S (Denmark), a plant engineering company and specialist for catalytic processes

• Elkraft A.m.b.A. (Denmark), one of the countries two utility companies

• Ruhrgas AG (Germany), the largest German gas company

• RWE AG (Germany), the largest German electrical utility company

MTU acts as a consortium leader. The company shares a license and technology exchange agreement with Energy Research Corporation of Danbury, Connecticut.

Three Phases of Development

Established in 1990. the ARGE DFC has set up a comprehensive 10 year program to bring the MCFC from a laboratory technology to a marketable power plant. The overall program volume will be approx. 100 Million S to be spent between the years 1990 and 2000. The program is divided into three phases. The first phase (1990-6/1994) can be entitled basic technology development. The second period (7/1994-12/1994) is a product development phase. The upcoming third phase (1998-2000) will see field testing of a number of pilot plants leading gradually into commercialization by the turn of the century.

Achievements of Phase I

In the beginning of our program the work of the ARGE DFC focused on cell technology. Based on the cooperation with ERC we concentrated on finding solutions for material and corrosion problems that limit MCFC life. Improvements In this field were usually tested in small scale 7 x 7" single cells and ministacks. Experience with larger stacks was obtained by the operation of a 3 kW 2x3' Internal reforming stack in our laboratories in Ottobrunn and a 7 kW 2x3' Internal reforming stack at the ARGE's test facility operated by Elkraft in Kyndby, Denmark.

The most Important result of our Phase I cell technology work is the development of stabilization methods for nickel oxide cathodes that reduce the NiO dissolution in the electrolyte by a factor of approx. 4. bringing about cathode lifetimes well beyond 40.000 hours.

In parallel to the cell development, the MCFC technology was qualified for the application with coal gas and other syn-gases in a comprehensive experimental program.

The ARGE's work in MCFC system design came to a turning point in 1992 when we realized that conventional system designs do not hold the promise for competitive power plants. As a rule of thumb tbe fuel cell stack contributes only one third to the cost of the overall system. In a standard configuration the cost of conventional components would keep the system too expensive, even if the cost of the fuel cell stack itself could be reduced to zero (1).

Optimization by Simplification and Integration - the Hot Module Concept In essence we have found that

• system designs for small to medium scale MCFC power plants have to be as simple as by all means possible. System costs are greatly influenced by this simplification.

• System costs remain prohibitively high even for simplified systems, if these designs are built in a conventional plant engineering manner. Only a high degree of mechanical, thermal, and pneumatic integration promises sufficiently low system cost.

• Intelligent mechanical and pneumatic integration can solve critical fuel cell problems completely, e.g., differential cell pressure.

These findings have led us to the invention of an innovative design approach characterized by the term Hot Module (Fig. 1). A Hot Module combines all the components of an MCFC system operating at similar temperatures and pressures into a common thermally insulated vessel. A typical configuration contains the MCFC stack, a catalytic burner for the anode tail gas and a cathode recycle loop including mixing-in of fresh air and anode exhaust. The cell stack is resting in a horizontal position on the fuel-in manifold, thus providing excellent gas sealing by gravity forces. On the top of the stack the gases exiting from the anodes are mixed into the cathode recycle loop together with fresh air supplied from the outside. The mixture is transported through a bed of combustion catalyst located on top of the mixing area and blown back to the cathode input by the cathode recycle blowers on the top end of the vessel. No gas piping or sealed cathode manifolds are necessary. For start-up, an electrical or gas fired heater is arranged along the cathode input of the stack.

The Hot Module is complemented by a fuel processing system of a similar high degree of mechanical integration. All heat exchangers necessary for preheating of the fuel gas and evaporation of the reforming water are integrated into a common duct supplied with the cathode exit of the Hot Module. The reactors for the desulphurization and preconversion of higher hydrocarbons in the fuel gas are skid mounted alongside this duct to form a compact unit finding its place at one end of the cylindrical stack module. The other end of the stack module is taken by an electrical and electronics compartment containing the control electronics and a state-of-the-an efficient liquid cooled IGBT inverter. The whole arrangement is truck transportable and intended to be installed within buildings as well as in the open.

ARGE DFC Product Development Targets

In the current second phase of our program the ARGE DFC concentrates on the development, qualification and demonstration of a Hot Module power plant with one fuel cell stack of 280 k\V. In parallel. R&D work in cell technology is proceeding towards longer lifetimes. Our target is to qualify the cell components for lifetimes up to 40.000 hours. The cell technology work is complemented by a manufacturing technology program for full scale cell components.

Hot Module Power Plant Qualification

In 1995 a first full scale mockup of an integrated fuel cell module was built and tested at room temperature. It consists of all the components of a Hot Module, the cells being substituted by dummy plates of identical dimensions and flow resistance. This Cold Dummy was used for mechanical and flow tests and proved the feasibility of the mechanical and pneumatic integration concept. In this year a Hot Dummy of the fuel cell module has been tested to prove the mechanical and pneumatic behavior at full operating temperatures of 650°C.

Construction of the first real fuel cell module with the same design starts in the last quarter of 1996. It will go into operation as a complete "system in spring 1997 at the Ruhrgas facilities located in Dorsten at the northern end of the Ruhr area. After extensive testing and optimization the plant will be ready for demonstration towards the end of 1997.

Things to Come

After successful test of the Hot Module system demonstrator the ARGE DFC plans to sell a number of precommercial Field Test Units into key applications in industrial and commercial cogeneration. This third phase of the ARGE's program is intended to generate operational experience on the side of the supplier and confidence into this new technology on the side of the customer, paving the way into commercial application of our innovative product concept.

Acknowledgments

The development of the MCFC technology towards market application is performed jointly by the ARGE DFC. cf. Introduction. Programs underlying this report have been funded by the German Federal Minister for Education and Research, as well as by the European Community. The responsibility for the contents of the publication is with the authors.

1. P. Kraus, "Systems' optimization: achieving the balance," J. of Power Sources. Vol. 49 (1994), No. 1-3, pp. 53-60,

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