ABSTRACT
The word “hydrothermal gasication” (HTG) is coined in this chapter to illustrate the methods of gasication, which result in hydrogen or a mixture of gases with heavy concentration of hydrogen. Hydrothermal also implies the use of water (in some form, steam, water, or supercritical water [SCW]) and/or hydrogen in the conversion process. While natural gas, synthesis gas, and biogas largely contain methane or syngas, the processes described in this chapter largely produce gases with predominant concentration of hydrogen. Hydrogen is often produced by carrying out thermal gasication of carbonaceous materials in the presence of steam (water or SCW) and/or hydrogen. Hydrogen can also be produced by dissociation of water. For the sake of brevity, all of these processes are coined here as “hydrothermal gasication.” Hydrogen is often considered as an “ultimate fuel.” Hence, the commercial success of the processes described in this chapter can be a game changer in the energy and fuel industry. It should be noted that currently hydrogen is predominantly produced by the steam-reforming process, which is described in detail in Chapter 6.
