Abstract: A method for reducing nitrogen oxides of a recovery boiler, and a recovery boiler, where the furnace of the recovery boiler is supplied with primary air from primary air nozzles, black liquor from liquor nozzles, secondary air from secondary air nozzles above the primary air nozzles but still below the liquor nozzles, tertiary air from tertiary air nozzles above the liquor nozzles, and quaternary air from quaternary air nozzles above the tertiary air nozzles. Black liquor is supplied to the furnace from first liquor nozzles and second liquor nozzles, which liquor nozzles are arranged substantially on the same level with respect to the height of the furnace, and the droplet size of liquor fed from the second liquor nozzles is substantially smaller than the droplet size of liquor fed from the first liquor nozzles.

Abstract: A method for processing flue gas scrubber material flows. The flue gas is scrubbed with a calcium-based absorbent containing washing fluid for absorbing sulphur oxides from the flue gases, and the formed gypsum slurry is directed from the flue gas scrubber to the separator. At the separating point of the separator, gypsum is separated from the washing fluid and the gypsum and washing fluid are taken out of the separator as separate material flows. From the flue gas scrubber the washing fluid is directed to a tank located before the separating point of the separator or after the separating point of the separator, in which tank foam is separated from the washing fluid as its own phase and taken out of the tank.

Abstract: A fluidized bed boiler, which comprises at least a furnace defined by walls, a grate and a roof, as well as a bed ash cooler. In addition, the fluidized bed boiler comprises at least a primarily vertical partition wall between the grate and the roof, and at least one of the walls of the bed ash cooler is formed of a part of the partition wall.

Abstract: A fluidized bed boiler comprises a furnace whose lower part is equipped with a grate comprising means for supplying fluidizing air into the furnace. The furnace also comprises at least one heat transfer surface extending across the furnace and comprising elongated heat transfer tubes on top of each other. The heat transfer surface is supported on the grate from underneath, substantially over its whole length, in the section extending across the furnace.