Patent ID: 7207280

Claim:
A furnace of a recovery boiler comprising: a front wall, a rear wall and side walls to the furnace, at least one black liquor spraying device disposed at or above a black liquor spray horizontal elevation on at least one of said walls, wherein said black liquor spray horizontal elevation is substantially devoid of air ports; a plurality of primary air ports on at least one of said walls; a first horizontal elevation of secondary air ports arranged on opposite walls of said furnace and a second horizontal elevation of secondary air ports on said opposite walls, wherein substantially all secondary air enters the furnace through said ports in the first and second horizontal elevations and said first and second horizontal elevations of secondary air ports are vertically lower on said walls than the black liquor horizontal spray elevation and are vertically above the primary air ports; the secondary air ports in each of said first and second horizontal elevations on said opposite walls are such that the air ports for each horizontal elevation project a pattern of air jets into the furnace from said opposite walls; wherein the primary air ports includes an upper horizontal elevation of the primary air ports each have a vertical centerline that is offset horizontally from a vertical centerline of the secondary air ports in the first horizontal elevation of air ports.