US auto industry researchers are examining powdered coal as a possible substitute for liquid motor fuel refined from high-priced OPEC oil or synthesized from coal.
General Motors Corporation has developed experimental engines that have been fitted into a Cadillac El Dordado and an Oldsmobile Delta 88. The turbine power plants burn coal that has been crushed into a powder finer than confectioners sugar.
The finely ground fuel is stored in a tank located in the engine compartment above the right-front wheel. A metering fuel pump, aided by an engine-driven air compressor, transports the powder in a steady stream from the tank to the engine. Mechanical vibrators in the tank assure the smooth flow of powdered coal to the engine.
The combustion system consists of a burner, a fuel injection nozzle, and ignition system. A liquid fuel pilot light ignites the powder as it enters the burner.
Technician at GM and Ford who have worked with methanol derived from coal say the methanol burns cleaner than powdered coal and could more easily be used to run automobiles. But GM says the combustion of powdered coal offers the maximum utilization of the energy in coal. Both mechanically cleaned and solvent-refined powdered coal retain more than 80 percent of the energy initially present in the mined coal. This compares with about 55 percent for the liquid fuels derived from coal.
Says Richard Stettler, project manager of the coal fired turbine project at GM, "Right now the powdered coal is not clean enough. We need to get the ash contents down, so we're moving toward a solvent- refined project which dissolves the coal and filters out the ash. It also takes out some of the sulfur."
He expects that standards for powdered coal will be similar to those of gasoline when research on the coal cleaning process is completed over the next several years.
Dr. Douglass B. Keller Jr., chairman of the board of Otisca Industries Ltd., a coal refining company in Syracuse, N.Y., says several oil and coal cleaning and refining companies are working on methods to attain powdered coal with less than a half percent of ash.
GM technicians say that before the coal-fueled engine is ready for widespread installation in passenger automobiles, the following challenges must be met:
* Mechanical areas, such as storage, transfer, pumping, and injection in the engine, need further development.
* Further effort is needed to bring particulate emissions and smoke to acceptable levels.
* Coal products contain relatively large amounts of nitrogen. As a result, further effort will be required minimize the effects of nitrogen in coal.
Dr. Keller estimates that powdered coal could be produced at $2 per million Btus. Currently, crude oil costs between $6 to $7 per million Btus. Gas at the pump price of $10.30 per gallon costs $10.30 per million Btus.