Coal

A number of processes have been developed by which solid coal can be converted to a liquid or gaseous form for use as a fuel. Conversion has a number of advantages. In a liquid or gaseous form, the fuel may be easier to transport, and the conversion process removes a number of impurities from the original coal (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 from 100 Btu to 1000 Btu. One suggestion has been to construct gasification systems within a coal mine, making it much easier to remove the coal (in a gaseous form) from its original 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 resources. On the other hand, the wide availability of raw coal means that new technologies have been unable to compete economically with the natural 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 unpopular, since they were somewhat smoky and foul smelling.