Future fuels for internal-combustion engines will be derived increasingly from solids such as coal. An alternative to processing coal into liquid fuels is the direct use of solid coal by reciprocating, internal -combustion engines. Specific applications which would be especially suitable for solid fueled engines consist of stationary power plants, marine propulsion systems, and railroad locomotives. Agricultural, construction and mining equipment are examples of other possible applications. The objectives of this study were to review past research on the development of solid coal fueled engines and, from this review, to identify major technical problems and current research needs. The objectives also included comparing the energy usage of several fuels. This comparison indicated a possible 25% energy advantage by directly using solid coal fuels as opposed to using synfuels.
The literature review indicated that operation of solid reciprocating engine has been attempted for nearly a hundred years. Problems which have been encountered continuously have involved the fuel delivery system, solid-particle combustion, and engine component wear. Recent investigations (1979-1982) using coal/oil, carbon-black/oil, and coal/water slurries in a variety of reciprocating engines have yielded encouraging results. The use of coal/water slurries is an attractive approach to using solid coal in engines, since fuel handling problems are simpler than using dry-powder fuels, and the slurry is petroleum independent.