Abstract: A long-lasting hot water boiler. The boiler has a lower drum with a first pass fire-tube for generating combustion gases, an upper drum with a second pass fire-tube bundle for the gaseous products of combustion, and a lined fire reversing chamber for directing the gaseous products from the first pass to the second pass. The reversing chamber liner includes a saddle piece and a turnaround piece which cooperate to protect vulnerable weld joints adjacent the reversing chamber and which maintain proper positioning even after weld pins melt. The upper and lower drums are interconnected by an expansion joint which permits unequal thermal expansion of the drums, and a bypass circulation system prevents thermal shocking of the boiler.

Abstract: A swirl-type internal flame recirculation burner as used to fire asphalt plant aggregate dryers, air heaters and calcining kilns and method includes an atomizer assembly for swirling primary air in two concentric streams with the inner stream swirling more rapidly than the outer stream. Fuel oil is blast atomized in a continuous sheet into the inner stream without prefilming and then is shear atomized as the inner and outer streams violently intermix. The burning and swirling fuel and primary air mixture recirculates upstream along the burner axis. Secondary air is swirled in the same direction as the primary air and surrounds the primary air stream to promote further mixing and internal recirculation. A metal frustro-conical flame holder surrounds the burner head to stabilize and shape the recirculation flame and shield low-burn flames from tertiary air. The swirl of the secondary air is also adjusted to shape the flame. The burner may also be fired on gas or a combination of gas and oil.