Carbon heat management

Heat management is of crucial importance for ethylene oxide synthesis (see original citahons in [4]). The reachon enthalpy of the total oxidation to carbon dioxide (AH = -1327 kj/mol) is more than 10 times larger than that of the partial oxidahon (AH = -105 kJ/mol), which induces locally very hot temperatures (hot spots) with corresponding negative consequences on the reaction course. 

The temperature of operation of polymer electrolyte membrane fuel cells tends to get higher, because certain advantages are faced, such as improved tolerance of carbon monoxide, the improved ease of water and heat management, and increased energy efficiency. However, several commonly used polymeric membranes cannot withstand the high temperatures. Therefore, there is a need to look for alternative materials. 

Zalc and Loffler also proposed the application of plate heat-exchanger technology for the preferential oxidation of carbon monoxide to improve the heat-management of the highly exothermic process [378]. 

High-temperature proton exchange membrane fuel cells (HT-PEM fuel cells), which use modified perfluorosulfonic acid (PFSA) polymers [1—3] or acid-base polymers as membranes [4—8], usually operate at temperatures from 90 to 200 °C with low or no humidity. The development of HT-PEM fuel cells has been pursued worldwide to solve some of the problems associated with current low-temperature PEM fuel cells (LT-PEM fuel cells, usually operated at <90 °C) these include sluggish electrode kinetics, low tolerance for contaminants (e.g. carbon monoxide (CO)), and complicated water and heat management [4,5]. However, operating a PEM fuel cell at >90 °C also accelerates degradation of the fuel cell components, especially the membranes and electrocatalysts [8]. 

The business manager is frugal so he asks, Why not burn the coal directly and save the cost ot manufacturing the water gas The mechanical engineer is practical so he asks, How much heat will the boiler receive if I use coal instead of water gas The chemical engineer goes to the laboratory to find the answers by measuring the heat released per mole of carbon burned in reaction (4). The laboratory result shows that reaction (4) releases 94.0 kcal/mole ... 

A virtually defunct form of chemical treatment program employed in older design, low heat-flux boilers, whereby the risk of BW scale formation is managed by means of a controlled reserve of carbonate ions. 

Due to the operating requirements of PEM stack technology, shift reactors and a carbon monoxide removal step are required to produce reformate of sufficient quality. Similarly, the stack operating temperature and its humidity requirements require a water management system as well as radiators for heat rejection. Some developers are developing pressurized systems to the benefit from higher reactant partial pressures on both anode and cathode. Fuel processing for PEM APU systems is identical to that needed in residential power or propulsion applications. 

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