Importance

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Abstract

A new and improved burner for pulverized coal comprises a tubular nozzle for containing a primary, flowing stream of coal/air mixture having an outlet for discharging the stream into a combustion zone of a furnace. A venturi is mounted in the nozzle having a convergent section, a throat, and divergent flow section adjacent the outlet. The convergent section concentrates the pulverized coal toward a central portion of the flowing stream in the throat of the venturi. A conical flow spreader is mounted in the divergent section and includes a hollow, open outer end. The spreader cone and the divergent flow section of the venturi form an annular, expanding, flow pattern of coal/air mixture for discharge into the combustion zone and a plurality of swirl vanes between the spreader cone and wall of the divergent section impart swirl to stabilize an annular discharge of the primary coal/air stream from the nozzle to form a high temperature reducing zone wherein a portion of the hot combustion products are recirculated back toward the open end of the flow spreader so that volatiles in the coal are driven off rapidly and burned in a fuel-rich, reducing atmosphere, minimizing the formation of NO.sub.x . A stream of secondary air is introduced by vanes to swirl around the primary coal/air stream discharged from the outlet forming a long stable flame pattern providing a relatively slow combustion rate.

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First Claim