Fuel cell contaminants fossil fuels

Similar to SO, NO, are also important fuel cell contaminants. NO, derive from several sources [104-106]. The primary sources are motor vehicles, electrical utilities, and other industrial, commercial, and residential sources that burn fuels. Other NO, arise from human activities that include biomass burning, waste disposal, solvent use, and fertilizer use. NO, are formed when fuel is burned at high temperatures, as in a combustion process. Fossil... 

Biofuels being feedstocks result in a high yield of permanent gas (i.e., /6, CO, CO2, CH4, etc), volatiles, char, and condensible hydrocarbons i.e., tar, due to their higher hydrogen/carbon. and oxygen/caibon ratios than older fossil fuels. However, if the tar is allowed to condense or polymerise when the produced fuel gas is cooled down considerable problems with equipment contamination can result. Power generation requires high levels of gas clean up especially in gas turbines and fuel cell systems. 

Electrolysis also lends itself to operation under higher pressures, which in turn aids process efficiency. Importantly, electrolysis produces very pure hydrogen gas. Fossil-fuel-derived hydrogen is usually somewhat contaminated—potentially problematic for its use in fuel cells. It can be cleaned up, but that adds more steps and therefore increases cost. 

A further factor has to be considered, namely, the purity of the hydrogen. As a fuel for internal combustion engines, purity is not a prime consideration and hydrogen from almost any source will be suitable, provided that sulfur is removed. With low-temperature types of fuel cell, however, purity is a critical parameter since the electrocatalysts are subject to poisoning by many contaminants, several of which are found in fossil fuels see Section 6.3, Chapter 6. In this regard, hydrogen produced by the electrolysis of water is much purer and may prove to be the preferred source for this application, despite its higher cost. 

At the fuel cell cathode side, the prominent contaminants are NO (NO and NO2) and SO (SO2 and SO3). These mainly arise from electricity generation and fossil fuel combustions. NO, adsorb weakly on the Pt catalyst surface, and the contamination mechanism is mainly via the formation of NHJ, which... 

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