Hydrogen from coal carbonization

In conventional production of hydrogen from coal, as described earlier, coal is converted to hydrogen and carbon monoxide (CO) through the water-carbon reaction as shown in reactions 3.9 through 3.11. CO is then converted to hydrogen and carbon dioxide by the water-gas shift reaction as shown in reaction 3.12. 

However, biomass plants appear earlier than coal and more biomass plants are built, because they are smaller and can become central supplies at smaller market penetration. It is important to note that the delivered cost of hydrogen from coal, biomass and natural gas central plants are typically quite close (within 0.5/kg). Thus, the choice of a feedstock may be determined by other factors, such as state policies favouring renewables and the availability of carbon-sequestration sites. 

Both the production of hydrogen from coal and the production of oil from unconventional resources (oil sands, oil shale, CTL, GTL) result in high C02 emissions and substantially increase the carbon footprint of fuel supply, unless the C02 is captured and stored. While the capture of C02 at a central point source is equally possible for unconventionals and centralised hydrogen production, in the case of hydrogen, a C02-free fuel results, unlike in the case of liquid hydrocarbon fuels. This is all the more important, as around 80% of the WTW C02 emissions result from the fuel use in the vehicles. If CCS were applied to hydrogen production from biomass, a net C02 removal from the atmosphere would even be achievable. 

Thermodynamics provide a useful guide to possible gaseous products from coal carbonization at high temperatures. This paper describes published and original work on the high temperature equilibria between carbon, hydrogen, and nitrogen. 

A key rationale for moving to a hydrogen economy is to minimize carbon emissions. Producing hydrogen from coal actually could result in increased carbon dioxide emissions, unless carbon capture and sequestration is an integral part of these plants. 

The production of mixtures of carbon monoxide and hydrogen from coal or coke was the basis for town gas manufacture from well before the turn of the century, and the processes were adapted to provide appropriate feeds for ammonia and methanol synthesis in Germany and elsewhere. 

Parsley, D., Ciora, R. J., Jr., Flowers, D. L., Laukaitaus, J., Chen, A., Liu, P. K. T., et al. (2014). Field evaluation of carbon molecular sieve membranes for the separation and purification of hydrogen from coal- and biomass-derived syngas. Journal of Membrane Science, 450, 81-92. 

Synthetic oil is feasible and can be produced from coal or natural gas via synthesis gas (a mixture of carbon monoxide and hydrogen obtained from incomplete combustion of coal or natural gas). However, these are themselves nonrenewable resources. Coal conversion was used in Germany during World War II by hydrogenation or. 

In Germany, large-scale production of synthetic fuels from coal began in 1910 and necessitated the conversion of coal to carbon monoxide and hydrogen. 

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