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Show i/r »n M M . w COM. u~± Figure 2 applications from package boilers to multiburner field erected boilers. The Variflame is based on TODD's low excess air venturi burner. The Variflame has tertiary air for air staging and a special arrangement of the gas injection for fuel staging. TODD's A E R O S DM model was used to correct windbox air flow problems. The result is very consistent N O x performance. It is a very versatile burner that can be used in many different applications. A side view of the burner is shown in Figure 2. The burner produces a good, short, high turbulence flame. It was situated six feet above the bed; high enough to allow the overfire air system help burnout the coal that has been lifted off the bed yet low enough to allow cold light of the boiler and the coal bed as coal is added. The combustion control for the cofiring burner is a single loop controller that operates both electric drives for the fan damper and the gas control valve. The gas burner control is tied into the main boiler control. For cold light off the burner is operated in hand by the boiler operator. Full automatic control is designed into the system to allow gas cofiring at a constant rate. COLD LIGHT RESULTS After installation, the first cold light went very well. During the summer of 98, a second cold start was required after the summer shutdown; during this startup, extensive measurements were made to document boiler and cofiring burner operation. During the summer of 98 startup the boiler warmed up in about twelve hours, coal was added to the bed at 5 0 % load. A small opacity spike up to 1 5 % was recorded as the coal was added to the bed at 5 0 % load. The unit was brought up to full load and the coal was increased as the gas was decreased. During the cold start period, the NOx. o2, IV98 AJFRC SYMPOSIM MAUI 4 |