Separated overfire air injection for dual-chambered furnaces

摘要

A separated overfire air injection system particularly suited for use in a fossil fuel-fired steam generating power plant and more specifically to a sixpoint separated overfire air tangential firing system employed in such power plants, particularly those embodying dual-chambered furnaces. A method of operating such a fossil fuel-fired steam generating power plant equipped with the sixpoint separated overfire air injection system of the present invention is also disclosed. The separated overfire injection system in accordance with the present invention includes six SOFA windboxes strategically located about the perimeter of the dual-chambered furnace volume so as to be operative to inject separated overfire air into the furnace volume in such a manner as to engage a fireball symmetrically tangential to a circle. Furthermore, the separated overfire air injection system, when so employed, produces a mixing index that is substantially equivalent over the elevations in the furnace in which mixing of separated overfire with generated flue gases occurs, which is achieved through the use of four SOFA windboxes as done heretofore in the prior art or as in accordance with the teachings of the present invention with three SOFA windboxes per each chamber of the furnace volume.