Hydrogen from solid fuels

A combination of pyrolysis and gasification is applied to produce hydrogen from solid fuels. In the past, a variety of methods has been used to gasify solid fuels, to... 

The National Technical University of Athens (NTUA) works on hydrogen production from waste gases, production of hydrogen from solid fuels, water-gas-shift reaction catalysts, membrane separation, gasification of solid fuels, simulation of advanced power systems based on fuel cells, and hydrogen production and infrastructure. 

To conclude, the generation of pure hydrogen from solid biomass is only reasonable if transportation fuel should be produced. But it is not reasonable to produce pure hydrogen from biomass for stationary heat and electricity generation. 

Coal and Coal-Tar Hydrogenation. If paraffinic and olefinic liquids are extracted from solid fuel substances, the hydrogen content of the residual material is reduced even further, and the residues become more refractory. The yields of liquids so derivable are generally low, even when a significant fraction of the hydrogen is extractable. Thus production of fuel liquids from nonliquid fuel substances such as coal and coal tars may be enhanced only by the introduction of additional hydrogen in a synthesis process. The principal differences in the processes are from the modes in which hydrogen is introduced and the catalysts used. 

Mixed Protonic-Electronic Conducting Membrane for Hydrogen Production from Solid Fuels... 

Solid fuels, unlike gases and liquids, are entirely characterized by their composition. For example, coal can be characterized by its carbon, hydrogen, oxygen, sulfur, and nitrogen content. The water and mineral content of coal are also important means of differentiating coals from various sources. 

Heat from all the hot exhaust gas streams is used for steam generation to drive the steam turbine. Thus, the final products from the GE fuel-flexible process are pure hydrogen from the first reactor, C02 from the second reactor, and heat for electricity production from the third reactor. A portion of the solids in the chemical loops needs to be purged to avoid ash accumulation and maintain solid reactivity (Rizeq et al., 2002). The overall energy conversion efficiency for the GE fuel-flexible process is estimated to be 60% (Rizeq et al., 2003). 

For natural-gas-fuelled CHP plants, the same line of argumentation holds as for the stationary use of hydrogen from biomass. It is more reasonable to use natural gas directly than to convert it to hydrogen first and then to heat and electricity. High electrical efficiencies can be reached in the stationary sector by feeding natural gas to molten-carbonate fuel cells (MCFC) and solid-oxide fuel cells (SOFC). Molten-carbonate fuel cells have the added advantage of using C02 for the electrolyte (see also Chapter 13). 

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