The Molten Carbonate Fuel Cell MCFC

The PAFC is, however, suitable for stationary power generation, but faces several direct fuel cell competitors. One is the molten carbonate fuel cell (MCFC), which operates at "650°C and uses an electrolyte made from molten potassium and lithium carbonate salts. Fligh-teinperature operation is ideal for stationary applications because the waste heat can enable co-generation it also allows fossil fuels to be reformed directly within the cells, and this reduces system size and complexity. Systems providing up to 2 MW have been demonstrated. 

In order to describe the geometrical and structural properties of several anode electrodes of the molten carbonate fuel cell (MCFC), a fractal analysis has been applied. Four kinds of the anode electrodes, such as Ni, Ni-Cr (lOwt.%), Ni-NiaAl (7wt.%), Ni-Cr (5wt.%)-NijAl(5wt.%) were prepared [1,2] and their fractal dimensions were evaluated by nitrogen adsorption (fractal FHH equation) and mercury porosimetry. These methods of fractal analysis and the resulting values are discussed and compared with other characteristic methods and the performances as anode of MCFC. 

Just as the aqueous, alkaline fuel cell can be adopted to C02 separation and concentration, the molten carbonate fuel cell (MCFC) can function in this application as well. Recall that the MCFC cathode operates with the net reaction... 

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

The most important fuel cells that are in use nowadays are the polymer electrolyte membrane fuel ceU (PEMFC), the molten carbonate fuel cell (MCFC), and the solid oxide fuel cell (SOFC). In a PEMFC, the electrolyte is a polymer membrane that conducts protons, in an MCFC the electrolyte is a carbonate melt in which oxygen is conducted in the form of carbonate ions, CO , and in an SOFC the electrolyte is a solid oxide that conducts oxygen ions, While a PEMFC can be operated at low temperatures of about 80 °C, an MCFC works at intermediate temperatures of about 650 °C, and an SOFC needs relatively high temperatures of 800-1000 °C (see next sections). 

Similar efforts in solid-state electrochemistry for SOFC development focus on the exploration of new perovskites not only for the ORR but also for the anodic oxidation of hydrocarbons [182]. In this area, the discovery that Cu-based anodes present a viable alternative to the classical Ni-YSZ cermet anodes is particularly noteworthy [166, 183, 184], owing to the significant enhancement of performance by avoiding coke deposition. Similar important advances have occurred in the molten carbonate fuel cell (MCFC) area [9]. 

Legergren, C. Lundblad, A. Bergman, B. Synthesis and performance of LiCo02 cathodes for the molten carbonate fuel cell (MCFC). J. Electrochem. Soc. 1994, 141 (11), 2959-2966. 

In the molten carbonate fuel cell (MCFC) a mixture of potassium and lithium carbonate is used as an electrolyte. It is thus possible to reach a far higher temperature, about 650°C, than in the three types already mentioned. 

The molten carbonate fuel cell (MCFC) plant is a high-temperature fuel cell power generation... 

The molten carbonate fuel cell, MCFC, and the solid oxide fuel cell, SOFC, are high temperature fuel cells, due to their temperatures of operation of arotmd 650 °C, respectively, 800-900 °C. Both can be considered as alkaline fuel cells. 

A number of fuel cells, currently in the development stage, may soon compete with fossil fuel electricity production. Several companies have developed fuel cell power plants that generate up to several megawatts of power. The most promising of these is called the molten carbonate fuel cell (MCFC), which uses potassium carbonate as the electron transfer medium and methane gas as the fuel. In an initial process called reforming, the methane gas reacts with water to form carbon dioxide and hydrogen gas ... 

Another fuel cell design is the molten carbonate fuel cell (MCFC) (Yuh, 1995), which operates in the temperature range 620-660°C with an efficiency of >50%. FuelCell Energy, Inc. (Danbury, CT) produces MCEC units. These units are designed as back-up generators for intermittent use. The operational lifetimes of fuel cell systems need to be extended. In order to do so, it is necessary to limit component corrosion. 

Despite operating at temperatures of up to 1000°C, the SOFC always stays in the solid state. This is not true for the molten carbonate fuel cell (MCFC), which has the interesting feature that it needs the carbon dioxide in the air to work. The high temperature means that a good reaction rate is achieved by using a comparatively inexpensive catalyst - nickel. The nickel also forms the electrical basis of the electrode. Like the SOFC it can use gases such as methane and coal gas (H2 and CO) directly, without an external reformer. However, this simplicity is somewhat offset by the nature of the electrolyte, a hot and corrosive mixture of lithium, potassium, and sodium carbonates. 

The molten carbonate fuel cell (MCFC) operates at high temperature, which is about 600-700 °C. It consists of two porous conductive electrodes in contact with an electrolyte of molten carbonate. This type of cell allows the internal reform. The main advantage of the MCFC is its high efficiency (50-60%) without external reformer and metal catalyst, due to the high operating temperature (Farooque Maru, 2001). This cell is intolerant to sulfur and its launching is slow, these are its main disadvantages. 

As it can be seen, low-temperature and high-temperature fuel cells can be distinguished. Low-temperature fuel cells are the Alkaline Fuel Cell (AFC), the Polymer Electrolyte Fuel Cell (PEMFC), and the Phosphoric Acid Fuel Cell (PAFC). The high-temperature fuel cells operate in the temperatures region from 500 to 1000 °C two different types have been developed the Molten Carbonate Fuel Cell (MCFC) and the Solid Oxide Fuel Cell (SOFC). They have the ability of using methane as fuel and thus present high inherent generation efficiency (45-60 % for common fuels such as natural gas, 90 % with heat recovery [3]). 

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