THE THREE T'S OF COMBUSTION

Many advances have been made since. One of the most important was the introduction of the Cyclone Furnace in the 1940's. This is a horizontal, water-cooled cylinder entered by the coal jet and several air streams which improve mixing while also preventing the formation of slag on the fire tubes. ("Fire tubes" carry the fire through the surrounding water; "water tubes" carry the water through the surrounding fire.)

This type of furnace enables lower-grade coal to be burned, makes the furnace smaller, reduces the fly ash, and saves costs in fuel preparation, since it is now sufficient only to crush the coal instead of completely pulverizing it.

Such innovations are forced on power plants by economic demands, such as the increasing scarcity of high-grade coal in easily accessible and mineable seams. In another instance, when coal-fired plants carried the (ever present) base load, initial ignition of the pulverized coal by oil or gas was not often needed, and the same two fuels also stabilized coal burning at times of very low demand. But as coal-fired plants began yielding their role of base-power plants to nuclear plants, initial ignition and low-load stabilization became more frequent as coal-fired plants were cycled in to supply additional demand. At the same time oil and gas became expensive, all of which put the pressure on new inventions such as direct ignition of pulverized coal (DIPC) by ultra-high energy electric arcs. They are now widely used, saving the more costly fuels.

[More: Steam, Its Generation and Use, Babcock & Wilcox (161 E.42^nd St., New York, NY 10017)), 1975; Combustion Fossil Power Systems, Combustion Engrg. (100 Prospect Rd., Windsor, CT 06095), 1981.