Low nox burner process for boilers
OwnerRobert P. Benz, William G. Brown, IIinventors
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Abstract
Process is described for reducing emissions of nitrogen oxides and carbon monoxide from fuel gas fired boilers by using a computer to closely control the flow rate of combustion air and by installing a duct to allow flue gas to recirculate into the air intake of the boiler. In most cases strict emission standards can be met without making any other mechanical modifications to the boiler. A computer controller maps burner characteristics and controls both a variable speed drive and the damper on the combustion air fan, and a damper on recirculated flue gas to meet emission requirements over the various firing rates while maintaining a stable flame free of pulsations. In some burners a simple cone structure placed in the burner provides additional flame stability.
Claims8
A process for controlling carbon monoxide and nitrogen oxides emissions from a boiler comprising:
- passing a mixture of recirculated flue gas and combustion air through a fan and a damper into a burner;
- increasing the speed of the fan at increasing firing level while varying the opening of the damper to prevent pulsations of said burner while allowing the boiler to operate with reduced fan speeds and reduced power consumption.
A process for controlling carbon monoxide and nitrogen oxides emissions from a boiler comprising:
- passing a mixture of recirculated flue gas and combustion air through a fan into a burner;
- increasing the speed of the fan at increasing firing level;
- mapping out and digitally storing those firing levels resulting in burner instability;
- while operating said boiler at said digitally stored unstable firing levels, substantially reducing the fraction of recirculated flue gas so that NOx emissions increase at least 20 percent above average NOx emissions at firing levels outside said digitally stored unstable levels;
- minimizing the time of operating said boiler at said unstable firing levels by increasing of decreasing the firing level to levels outside said firing levels so that net average NOx emissions from the boiler are within compliance limits.
A process for controlling carbon monoxide and nitrogen oxides emissions from a boiler comprising:
- passing a mixture of recirculated flue gas and combustion air in an axial direction through an annulus created by a cone placed coaxially within a cylindrical member;
- injecting gaseous fuel into said mixture through perforations in a ring on the exterior of said annulus;
- igniting the gaseous fuel mixture downstream of said cone.
Dependencies are inferred from the claim text.