Abstract: A tangentially-fired, pulverized coal burning furnace (10) having overfire air (OFA) introduced into the upper portion of the furnace. The fuel and air are introduced (36, 38) into the furnace at the burner level tangentially of an imaginary circle, so that the resultant fireball moves upwardly within the furnace with a rotational spin. The OFA is introduced (40, 42) tangentially of an imaginary circle, in the reverse rotational direction to that of the fireball, so that the exhaust gases flowing from the furnace to the rear gas pass (16) flows in a straight line, with little or no spin. The OFA is made up of a mixture of low pressure air and high pressure air of sufficient volume and pressure to nullify the spin of the fireball.

Abstract: A water-wall, coal-fired furnace has a Coutant transition section extending down from the lower end to the water wall to the surface of water impounded in the lower ash hopper. The surface of the water is provided with a reflecting material which will permit the passage of solid residue from the coal firing into the water while reflecting incident radiant heat back up into the generating section of the furnace.

Abstract: A bottom supported steam generator for burning solid fuel with a vertical tube bank connecting an upper steam drum with a lower water drum. Horizontal economizer tubes are interspersed between the vertical tubes of the steam generating bank.

Abstract: A process heater which is fired by an ash containing fuel, generally coal, has a housing which includes a front radiant section and a rear convection section. The radiant section is provided with vertically extending process tubes against the walls thereof, arranged in a single row, and horizontal process tubes arranged in a single row across the roof. The horizontal and vertical tubes contain longitudinal fins over the length thereof, with adjacent fins being in contact with each other to provide a fin tube wall which prevents a build-up of ash behind the tubes. The bottom of the radiant section is downwardly and inwardly sloped and terminates in an ash collecting hopper. The process tubes extend along the downwardly and inwardly sloped portion to provide cooling which prevents ash melting whereby ash enters the hopper in solid form for removal. The vertical and horizontal process tubes are interconnected to provide for at least two passes of process fluid through the radiant section.