Typical cyclone burner. Source: Dept. of Energy.
A cyclone burner is a furnace in which finely ground fuel, in the form of low-grade, pulverized coal, is blown in spirals in the combustion chamber to maximize combustion efficiency. Cyclone burners are typically used in industrial steam-generating boilers. They were first introduced by Babcock & Wilcox in 1942 as a means of utilizing coal grades that weren't suitable for conventional furnaces.
A cyclone burner has three main parts: a burner area at the back end, which ignites the coal by using oil or gas; a barrel area where the coal and air are mixed in a swirling action and ignited by the oil or gas fired burners and a re-entrant throat where the fire from the ignited coal is forced into the furnace area of the boiler.