Hydrogen molten carbonate fuel cells

Hydrogen use as a fuel in fuel cell appHcations is expected to increase. Fuel cells (qv) are devices which convert the chemical energy of a fuel and oxidant directiy into d-c electrical energy on a continuous basis, potentially approaching 100% efficiency. Large-scale (11 MW) phosphoric acid fuel cells have been commercially available since 1985 (276). Molten carbonate fuel cells (MCFCs) ate expected to be commercially available in the mid-1990s (277). 

Cavallaro, S. Freni, S., Ethanol steam reforming in a molten carbonate fuel cell. A preliminary kinetic investigation. International Journal of Hydrogen Energy 1996, 21, 465-469. 

For natural-gas-fuelled CHP plants, the same line of argumentation holds as for the stationary use of hydrogen from biomass. It is more reasonable to use natural gas directly than to convert it to hydrogen first and then to heat and electricity. High electrical efficiencies can be reached in the stationary sector by feeding natural gas to molten-carbonate fuel cells (MCFC) and solid-oxide fuel cells (SOFC). Molten-carbonate fuel cells have the added advantage of using C02 for the electrolyte (see also Chapter 13). 

Hydrogen natural gas mixtures (NaturalHy, EU 6th FP project) (TUBITAK-MRC and ICDAS). 500 kW Molten Carbonate Fuel-Cell Plant (international project) (TUBITAK-MRC). 

In the molten carbonate fuel cell, methane is used as the fuel. This cell runs at high temperatures and uses a molten mixture of lithium and potassium carbonates as electrolyte. In most such cells, the methane is reformed into hydrogen and carbon monoxide before reacting in the cell ... 

Molten carbonate fuel cells Micro-electro-mechanical systems Microreactor Technology for Hydrogen and Electricity Micro-structured membranes for CO Clean-up Membrane reactor... 

Molten carbonate fuel cell (MCFC) 650 Calcium carbonate Hydrogen, methane 45-60 1 up to 100 MW power plants, 5-500 kW heating power station... 

Molten carbonate fuel cells use a mixture of carbonates that are liquid at operating temperature—600°C to 650°C. MCFC, like SOFC, operates at a higher temperature than the PEMFC does it does not require a fuel reformer and it can be operated with a hydrogen-rich fuel. The MCFC s liquid electrolyte means more handling issues. It does not have the ability to be pressurized. The MCFC could serve a niche market of data centers and hospitals. FuelCell Energy has recently made a commercial offering of MCFCs. These fuel cells will probably not have the same market penetration potential as SOFCs and thus would likely have little or no impact as a transition strategy for H2 use. 

Other fuels were also tried in the early stages of fuel cell development. Coal, the major fuel at that time, was considered as a candidate. Attempts to replace hydrogen with coal resulted in the invention of alkaline fuel cells (AFCs) and molten carbonate fuel cells (MCFCs). Mond used reformate gas from coal, which contained abundant hydrogen, as the fuel, with the intention of scaling up Grove s fuel cell to produce electric power. However, impurities poisoned the catalyst and made Mond s design impractical. 

Lim and Winnick [110] examined removal of H2S from a simulated hot coal-gas stream fed to the cathode while elemental sulfur gas was evolved at the anode. This process was performed in a cell that was similar in construction to a molten carbonate fuel cell (Fig. 23). The electrolyte was a mixture of Na2S and Li2S retained in a porous inert matrix material (MgO). The cathodic reaction involved the two-electron reduction of hydrogen sulfide to hydrogen (information on the equilibrium potential for H2S reduction can be obtained from [111] ... 

However, at the present fuel cells, for example PAFC (Phosforic acid fuel cell) or MCFC (Molten carbonate fuel cell), the residual fuel is finally burned by the already N2-diluted e2(hausted gas for the heat supply in order to convert the fuel to hydrogen and CO. On the other hand, SOFC (Solid oxide fuel cell) could more easily separate the CO2 recycling gas Much more research and development should be necessary for the recovery of CO2 in the fuel cell system. 

Fig. 12 Methane reforming reaction at the anode of a molten carbonate fuel cell. The reaction between fuel and water takes place in the outer part of the anode, the produced hydrogen reacts at the interface anode-electrolyte.

Giorgi, L. Carewska, M. Scaccia, S. Simonetti, E. Giacometti, E. Tulli, R. Development of molten carbonate fuel cell using novel cathode material. Int. J. Hydrogen Energy 1996, 21 (6), 491-496. 

Bohme, O. Leidich, F.U. Salge, H.J. Wendt, H. Development of materials and production technologies for molten carbonate fuel cells. Int. J. Hydrogen Energy 1994, 19 (4), 349-355. 

Parmaliana, A. Frusteri, F. Tsiakaras, P. Giordano, N. Out of the cell performance of reforming catalysts for direct molten carbonate fuel cells (DMCFC). In Advances in Hydrogen Energy 5, 6th World Hydrogen Energy Conference, 1986 Vol. 3, 1252-1258. 

Cavallaro, S. Mondello, N. Freni, S. Hydrogen produced from ethanol for internal reforming molten carbonate fuel cell. J. Power Sources 2001, 102 (1-2), 198-204. 

Fuel cells can be used to generate electricity, heat, and hydrogen. FuelCell Energy uses this technique in its molten carbonate fuel cell. Some solid oxide fuel cell (SOFC) companies are developing similar products. 

Lithium aluminates are also important in the development of molten carbonate fuel cells (MCFC) [82, 83], In these fuel cells, a molten carbonate salt mixture is used as an electrolyte. These fuel cells operate through an anode reaction, which is a reaction between carbonate ions and hydrogen. A cathode reaction combines oxygen, C02, and electrons from the cathode to produce carbonate ions, which enter the electrolyte. These cells operate at temperatures of 650°C and the electrolyte, which is usually lithium and potassium carbonate, is suspended in an inert matrix, which is usually a lithium aluminate. 

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