Abstract: A boiler (10) made up of three separate sections consisting of (1) a bottom supported fluidized bed (12); (2) a top supported upper furnace portion (14); and (3) a vertical boiler section (24) in fluid communication with the furnace outlet. Seals (34, 36) are located between each of the three sections, so they can expand thermally relative to each other while preventing the surrounding atmosphere from exposure to the hot combustion gases. The seals consist of fluid cooled (48, 70) troughs (38, 60) containing sand (40, 62), with fluid cooled (48, 70) plates (42, 64) extending down into the sand.

Abstract: A steam generating unit using gas recirculation (28) for steam temperature control, where the recirculated gases are introduced (38) into the furnace (12) through the bottom opening (34) through which the ash is discharged. Dampers (40) are positioned in the gas recirculation duct (28) for controlling flow therethrough.

Abstract: An apparatus and method for maintaining the heat input to a pulverized coal-fired steam generator when firing a lower grade coal than for which the pulverizers were designed. A dense phase pulverized coal stream consisting essentially of a mixture of pulverized coal and air having an air-to-coal weight ratio below approximately 1.0 is injected into main pulverized coal stream, thereby providing the necessary supplemental fuel for maintaining the heat input at that full load level.

Abstract: A slide gate damper arrangement which works well in large ducts, which are conveying hot, dust laden gases, and which duct has an obstruction extending down through the middle of it, such as a concentric pipe. The slide gate arrangement comprises a pair of gates which traverse the large duct from opposite sides thereof, seating in the middle of the duct. The leading edges of the two gates have a configuration such that they match and seal around the inner pipe.