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  Fuelcell: Molten Carbonate Fuel Cells (MCFC)

Introduction l

Direct Methanol l

Alkaline l

Proton Exchange Memb. l

Solid Oxide l

Molten Carbonate l

Phosphoric Acid l



MCFCs are so named because the electrolyte used is a molten alkali carbonate mixture, retained in a matrix. They are fuelled with hydrogen and operate at a temperature of about 650°C, meaning that useful heat is produced.

In this type of cell, the cathode is supplied with carbon dioxide, which reacts with the oxygen and electrons to form carbonate ions, which carry the ionic current through the electrolyte.

At the anode side these ions are consumed in the oxidation of hydrogen, which also forms water vapour and carbon dioxide to be transferred back to the cathode. There are two ways of doing this: either by burning the anode exhaust with excess air and removing the water vapour before mixing it with the cathode inlet gas; or by separating the CO 2 from the exhaust gas

The fuel consumed in an MCFC is usually natural gas, though this must be reformed in some way to create a hydrogen-rich gas to feed to the stack. An MCFC produces heat and water vapour at the anode, which can be used for the steam reformation of methane. This means that it is inherently more efficient than a cell requiring external fuel processing. Again, the MCFC can use carbon monoxide at the anode as a fuel.

The MCFC is seen by many as an ideal source for large scale power generation. One reason for this is the necessity for large amounts of ancillary equipment, which would render a small operation uneconomic. There is also no requirement for expensive catalysts as in low temperature fuel cells, and a third reason is the fact that the heat generated can be used for internal reformation of methane, a bottoming cycle and for fuel processing and cogeneration. This increases the CHP efficiency of the fuel cell system.

For further information contact David Hart (email: firstname.lastname@e4tech.com) from E4tech


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