Anode exhaust gas

It is usual practice in an MCFC system that the CO2 generated at the anode be routed to the cathode where it is consumed. This will require some scheme that will either 1) transfer the CO2 from the anode exit gas to the cathode inlet gas ("CO2 transfer device"), 2) produce CO2 by combustion of the anode exhaust gas, which is mixed directly with the cathode inlet gas, or 3) supply CO2 from an alternate source. 

SOFC cathode air stream co2 + h2o Combustion of remaining fuel in SOFC anode exhaust gas... 

Anode exhaust gas SOFC containing unconverted fuel h2o + co2 h2 Combustion of SOFC anode off-gas with cathode air stream (SOFC-GT concept). Recycling of fuel or for PEM, and so on. 

The anode exhaust gas is mixed with air, and the nonoxidized components are totally oxidized in a catalytic combustion chamber. Because air is fed in excess, the exhaust gas from the burner still contains a significant amount of oxygen. This gas is then fed to the cathode channel where the electrochemical reduction of oxygen takes place. There, new carbonate ions are produced from carbon dioxide and oxygen according to the backward direction of the following cathode reaction ... 

An evaluation of a fuel cell operated with an anode exhaust gas recycle. 

In the open literature, one can find the proposal to recycle part of the anode exhaust gas back towards the anode inlet [5, 6], as shown in Fig. 2.3. Especially for pure DIR systems, this has certain advantages If fresh feed gas is fed into the anode channel, only low hydrogen contents will be present at the inlet, and consequently the electrode will not be used in this region. This can be amended by recycling a part of the exhaust, which still contains some hydrogen, back to the inlet Define the recycle flow via a recycle ratio, R, according to ... 

Nuvera will design, build, test, and deliver a 15 kilowatt electrical (kWe ) direct current (DC) fuel cell power module that will be specifically designed for stationary power operation using ethanol as a primary fuel. Two PEM fuel cell stacks in parallel will produce 250 amps and 60 volts at rated power. The power module will consist of a fuel processor, carbon monoxide (CO) clean-up, fuel cell, air, fuel, water, and anode exhaust gas management subsystems. A state-of-the-art control system will interface with the power system controller and will control the fuel cell power module under start-up, steady-state, transient, and shutdown operation. Temperature, pressure, and flow sensors will be incorporated in the power module to monitor and control the key system variables under these various operating modes. The power module subsystem will be tested at Nuvera and subsequently be delivered to the Williams Bio-Energy Pekin, Illinois site. 

Developed a prototype CFD model including all the key elements of auto-thermal reforming (ATR) Developed a model that accounts for fuel atomization and vaporization, partial oxidation, steam gasification, and anode exhaust gas combustion... 

Effect of hydrogen sulfide on fuel cell performance and the results of anode exhaust gas analysis. (From Imamura, D., Hashimasa, Y 2007. ECS Transactions 11 853-62. With permission.)... 

It can be noticed that while carbon dioxide is produced at the anode side, it is also consumed at the cathode side. At the cathode side, the inlet oxygen or air gas stream includes a mixture with carbon dioxide, which can be supplied by either recovering carbon dioxide from the anode exhaust gas stream and recirculating it back to the cathode side or just drying and mixing the anode exhaust with the cathode inlet gas stream. 

The first way is to burn the anode exhaust gas with excess air in a combustion chamber and then mix it with cathode inlet gas. Another way is to separate the carbon dioxide from the other components in the anode exhaust by separation methods such as pressure swing absorption techniques or selective membranes. 

To avoid carbon formation in the SOFC stack, a minimum steam-to-carbon molar ratio of 2.5-3.0 is needed [7]. This ratio is maintained by controlling the amount of recirculation of H20-rich anode exhaust gas. 

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