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Show AFRC90-PAPER # 28 PREMIXED RADIANT BURNERS: IMPROVED PROCESS PERFORMANCE WITH ULTRA-LOW NOx EMISSIONS S~~f" A. C. Minden, D. G. Perkins, and J. M. Kennedy Alzeta Corporation Santa Clara, California 95054-1008 ABSTRACT In the past decade, users and manufacturers of industrial combustion systems have been attempting to reduce NOx emissions generated by these systems to meet ever more stringent regulations. These efforts have led to some improvements in the understanding and application of traditional flame burners with the introduction of staged combustion burners and flue gas recirculation. These approaches are based on stretching existing technology to achieve incrementally better emISsIons characteristics, but have not made any comparable improvements in the underlying thermal performance limitations of these burners. Premixed radiant burners represent a new approach to industrial combustion which combines inherently low NOx emissions with significantly improved thermal performance. Beginning in 1983 with the retrofit of a muItitank asphalt heating system, Alzeta Corporation has introduced Pyrocore® and Pyromat TH radiant burners to a variety of industrial applications, demonstrating their enhanced performance. Since then, the range of industrial applications which have seen widespread use of these burners include: frred process heaters, immersion tube heaters, frretube boilers, industrial air heaters, incinerators, and directfrred paper dryers. The benefits which users of these systems have obtained include: low NOx emissions, increased system thermal efficiency, improved heat flux uniformity and responsiveness, and increased capacity on existing system retrofits. This paper describes the burners, their application histories, and the performance benefits achieved by these many applications. 1 INTRODUCTION Pyrocore and Pyromat burners belong to the class of combustion devices known generically as infrared, or radiant, burners. A radiant burner is distinguished from a conventional flame burner by its hot, incandescent surface which transfers a significant fraction of the burner's heat input as radiant energy directly off the burner's surface to the process load. Pyrocore and Pyromat burners are a subtype of infrared burner which are constructed of a micro-porous matrix of small diameter fibers through which premixed gaseous fuel and air are forced. When this fuel/air mixture is ignited, the combustion reactions stabilize on the outer surface of the burner causing it to glow flamelessly and uniformly. Figure 1 shows the basic energy exchange modes occurring on the surface of a radiant burner. While the outer surfaces glow k AOI"NT HC"T f lUX Figure 1: Energy Exchange Mechanisms for Porous Radiant Burners |
