Reforming of Natural Fuels

The gas mixtures produced by reforming contain products such as hydrogen and carbon monoxide that can be used to generate elecfrical energy in various fuel cells, but also products that are useless or even harmful for fuel cell purposes nitrogen, carbon dioxide, sulfur compounds, and others. 

Most natural fuels contain sulfiir compounds sulfides, mercaptans, and others. These may be harmful to the activity of the catalysts, so that prior to their reforming, the fuels usually undergo a desulfurization process. 

Natural gas consists primarily of methane (CH4). Methane trapped as hydrate in marine sediments and as frozen hydrate in cold regions of the Earth should be counted in addition to the natmal gas found in independent gas fields and in coal and oil fields. Methane is a major somce for the mass production of cheap technical hydrogen. Several production methods exist, and we describe these next. 

The steam reforming (SR) of methane yields hydrogen and carbon monoxide. It is an endothermic reaction a reaction requiring an input of thermal energy (the heat of this reaction, Sreact. is negative)  

This reaction may be accompanied by the water-gas shift reaction (WGSR)  

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It must be remembered that any reforming of natural fuels will not yield pure hydrogen but a gas mixture that in addition to hydrogen contains considerable amounts of carbon monoxide and many other compounds, such as carbon dioxide, nitrogen, and sulfur compounds. Such mixtures are not fit for direct use in fuel cells, they must first be subjected to a purification by which all those contaminants are removed that could be harmful to fuel cells of a given type. Aspects of the purification of hydrogen from CO and other undesirable contaminants are discussed in Section 11.3. 

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