Kotler V.R., Open JSC “VTI”

A method of Over fire air is called two-staged combustion, because in the furnace two combustion zones are formed: the first – feeding through the burner all the fuel with oxygen deficiency (α < 1), and the second zone, in which the rest air is supplied, required for reburning of incomplete combustion products from the first zone. Even in cases when additional air is fed at two or three levels throughout the furnace height, this method is to be called as two-staged combustion. Its effectiveness is determined by the presence of zones with reducing medium (before supply of additional air), a degree of air deficiency in this zone and time of residence of combustion products in the same zone (i.e., duration of reducing reactions).