Mineral Resources Potential - Geothermal Resources

202 Mineral Resources Potmtial of Ethiogia
(such as sulfur) that have environmental disadvantages. One of the
conversion methods' is known as gasification. In gasification,
crushed coal is reacted with steam and either air or pure oxygen.
The coal is converted into a complex mixture of gaseous
hydrocarbons with heat values ranging fiom 100 Btu to 1,000 Btu.
One suggestion has been to construct gasification systems within a
coal mine, making it much easier to remove the coal (in a gaseous
I form) hm its origid seam.
In the process of liquefaction, solid coal is converted to a
petroleum-like liquid that can be used as a fuel for motor vehicles
and other applications. On the one hand, both liquefaction and
gasification are attractive technologies in the United States because
of our very large coal resousccs. On the other hd, the wide
availability of raw cod means that rmew technologies have been
unable to compete ecunomically with the mtud product. During
the last century, coal oil and coal gas were important sources of
fuel for heating and lighting homes. However, with the advent of
natural gas, coal distillates quickly became unppula~, &since they
were somewhat smoky and foul-smelling.
Types of coal
As geological processes apply pressure to peai over time, it is
transformed successively into:
- Lignite also referred to as brawn coal, is the lowest rank of
coal and used almost exclusively as fuel for stearn-electric
power generation, Jet is a compact form of lignite that is
sometimes polished and has been used as an ornamental
stone since the Iron Age;
- Sub-bituminous cod whose properties range fiom those of
lignite to those of bituminous coal and are used primarily as
fuel for stearn-electric power generation;
- Bituminous coal, a dense coal, usually black, sometimes
dark brown, often with well-defined bands of bright and