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Show ADVANCED APPLICATION OF EXCESS ENTHALPY COMBUSTION TECHNOLOGY TO BOILER SYSTEMS Susumu Mochida Leading Engineer Toshiaki Hasegawa Research Manager Ryoichi Tanaka General Manager Nippon Furnace Kogyo Kaisha, Ltd. 1-53, 2-chome, Shitte, Tsurumiku, Yokohama 230, Japan ABSTRACT Excess enthalpy combustion causes flame temperature to rise, with any BTU fuel. The method uses high temperature air for combustion which is obtained from a heat-recirculation method. A practical method of excess enthalpy combustion, called High cycle Regenerative combustion System(HRS), was applied to a small water tube boiler having a steam production rate of 700 kglh. The results of field tests provided a thermal efficiency of 97% and NOx emission levels of approximately 100 ppm, corrected for 0% Oi using natural gas as the fuel. These results were with an air inlet temperature of 900 ° C using enthalpy extraction from the flue gases and modified fuel-staged combustion technique. The application of excess enthalpy flame to a conventional boiler system demonstrated an overall increase in the time averaged value of heat flux in the radiative section of the boiler. Furthermore, the results also showed that it was possible to increase the amount of heat transfer by passing part of flue gases to the convective section of the chamber. Thus, the advantage of the whole system was not only an increase in boiler efficiency, but also the improved heat transfer efficiency. The HRS boiler systems provide significant compactness. Further advantages include significant reduction in the energy usage and boiler heating-up time. The HRS can be applied to almost all types of practical power systems and in all cases significant energy savings, system cost and pollutants emission reduction occurs 1. INTRODUCTION Major savings of energy from combustion systems can be accomplished by the reduction of waste heat from the equipment. The thermal efficiency of most commercial boilers having air pre-heaters or economizers lie in the range of 85-95%. A n y further increase in efficiency necessitates the incorporation of increased size and complexity of the equipment, which translates into a higher initial cost investment and its subsequent maintenance. Enhanced heat transfer from within the system provides a significant improvement not only in the thermal efficiency but also the cost. A new high efficiency combustion technology called the High cycle Regenerative combustion System (herein called H R S ) is described here which is schematically illustrated in Figure 1. In this new technology from N F K , a controlled thermal field is used to enhance the heat transfer per unit area in the system. Development of this technology have resulted in significant down-sizing of the equipment, or an increase in productivity, while maintaining high thermal efficiency. The high performance combustion system can be recognized to provide significant conservation of natural energy resources and minimization of pollutants emission. The developed system provides significant advantages in the following six areas: 75. l Ll-8 |