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Show Another difficulty that was solved while working on the pulsation problem was online fuel Ch~~9~ over. In order t? maintain smokeless operation during change over from gas to oil the ato~lzlnthe steam shall be Introduced through the oil gun prior to oil. This steam was adversely affecting stability of gas combustion of QLN burner, even with the burner pilots brought on.. With the modification made to the gas injection pattern and to the gas train both low and high fire change over can be reliably and safely accomplished. TRADE OFFS BEiWEEN DIFFERENT PERFORMANCE PARAMETERS Extensive tests and field data on QLN burner operations reviled relations between the system operating parameters, furnace geometry and performance parameters of the bumer. Fu~ace size and its tightness are of the greatest importance to the level of NOx, CO and excess air t~at can be achieved in the application. It was also found, that higher gas pressure of up to 25 pSlg at the burner, and higher differential air pressure of up to 10" water column, if properly utilized in the burner design, are beneficial for lower NOx and CO. Good air distribution by the wind box is important for both NOx and CO reduction. There is also strong tradeoff between NOx and CO. By adjusting the burner firing regime and making the flame narrower CO emissions typically can be reduced. At the same time NOx emissions go up. In practical applications, however, available gas pressure, air pressure, furnace geometry and furnace condition are often fixed and a typical task for a burner company is to offer the most effective· combustion device that meets the required emission standards and limitations to the system. This task is difficult, as even identical boilers differ with respect to the available gas pressure, condition of the boiler, requirements to NOx and CO. Retrofit jobs sometimes impose additional limitations to stay within the size existing wind boxes or to reuse the existing fans. In order to utilize properly all the available resources the design of the burner shall be properly tailored to the parameters and requirements of each application. To make this tailoring process easier special computer programs were developed that for each case compute expected performance and design parameters. CONCLUSION A unique class of fuel staged combustion low NOx burners was developed for a wide range of industrial applications. When firing gaseous fuels the burner shows NOx emissions that were achievable in the past only with high amounts of FGR. There was a large distance from the original successful prototype to a commercial product that might be safely used by the industry. Special attention was given to the compatibility of the burner with simple combustion controls. Some difficulties reviled itself when the scale and variety of applications had increased. The burner appeared to be very adaptable to different fuels, air preheat, FGR. Development of various modifications and important improvements to the design continued over the period of two years. At the same time the burner proved itself in the industry with over 100 of installations. 9 |