indirectly by a secondary fluid other than the combustion products

Full Title

Combustion apparatus characterised by arrangements for air supply (inlets for fluidisation air F23C10/20; baffles or shields with air supply passages F23M9/04) > Disposition of air supply not passing through burner (to obtain a cyclonic tapering flame when burning pulverulent fuel F23C5/32) > for heating the incoming air (arrangements of regenerators and recuperators F23L15/00) > indirectly by a secondary fluid other than the combustion products