Abstract: An apparatus for use in the pulp industry for recovering heat in the spent liquor recovery boiler, whereby the boiler walls are formed of water-cooled tubes connected to the water/steam circulation system of the boiler. Supply of air into the lower section of the furnace is effected symmetrically through air ports which are disposed at equal distances from the center of the furnace. The lower section of the furnace is preferably cylindrical and connected to a separate cooling medium circulation system.

Abstract: Waste liquor from cellulose pulp processes is used in a recovery boiler to recover energy and chemicals. The recovery boiler includes a furnace section in which heat and exhaust gases are generated, and heat recovery surfaces downstream of the furnace section in a path of exhaust gas movement. Waste liquor is injected into the furnace section of the recovery boiler at a first location, and the exhaust gases produced are divided into at least first and second streams. The first stream is passed into association with the heat recovery surfaces of the recovery boiler and then discharged, while the second stream is withdrawn from the recovery boiler at a second location between the first location and the heat recovery surfaces. The withdrawn second stream is positively cooled exteriorly of the recovery boiler preferably utilizing a circulating bed cooler.

Abstract: A method and apparatus for use in the pulp industry for recovering heat in the spent liquor recovery boiler, whereby the boiler walls are formed of water-cooled tubes connected to the water/steam circulation system of the boiler. The lower section of the boiler is defined by water tubes connected to a separate water circulation system of a forced type. Thus, heat is preferably recovered in the lower section of the boiler by a separate water circulation system having a lower pressure than in the water/steam circulation system of the boiler.