Patent ID: 7694637
Filing Date: 2010-04-13
Classification: F23C,F23G,F23L

Abstract:
1. A method of introducing primary air in two or more portions at a lowest air zone into a furnace firing black liquor from a kraft recovery process, the furnace firing black liquor from a soda process, the furnace firing black liquor from a sodium-based sulphite process, or the furnace firing black liquor from a closed-cycle CTMP process, said method comprising: a) introducing a portion of the primary air in a jet pattern created by a number of first principal jets from along a first active side of a principal-jet plane and said pattern also being created by a number of second principal jets from along a second active side of the said principal-jet plane opposite to the first side, the plane being bounded, respectively, by a first active wall and a second active wall opposite to the first active wall of the interior of the furnace and by a third inactive wall and a fourth inactive wall, of the interior of the furnace, the said plane being essentially flat, or, a first side of the said plane being curved to form a shallow arch, or both the first and second sides of the said plane being curved to form a shallow arch; b) directing the said principal jets in a fully-opposed or partly-opposed juxtaposition relative to the principal-jet plane; c) introducing a portion of the primary air as third and fourth pairs of scavenging jets or pairs of sets of scavenging jets located in the principal-jet plane, each scavenging jet or set of scavenging jets being at opposite ends of the active walls, or at opposite ends of the inactive walls, or at opposite ends of the active walls and between each principal jet, or at opposite ends of the inactive walls and between each principal jet, such that the scavenging jets are of similar size or of different sizes and d) where the portions of the primary air which are introduced as principal jets and scavenging jets are together less than the total quantity of primary air, introducing the remainder of the primary air, as fifth and sixth central jets or sets of central jets or groups of central jets, located on the inactive walls, in the principal-jet plane, or located in a second plane above the principal-jet plane, such that the central jets are of similar size or of different sizes and such that the vertical centrelines of all the ports from which the central jets issue are close to the centre of each inactive wall or are between the two sets of scavenging jets on each inactive wall; e) having an average momentum flux of the principal jets approximately double, or more than double, the average momentum flux of the scavenging jets, where the momentum flux is defined hereinafter as the product of the jet's initial velocity and its mass flow; f) having an average momentum flux of the central jets less than the average momentum flux of the principal jets and different from the average momentum flux of the scavenging jets; g) directing the scavenging jets and central jets in a fully-opposed or partly-opposed or steeply-sloping-downwards juxtaposition relative to the principal-jet plane or the plane above the principal-jet plane, as applicable.