초록 ▼

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 emis

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.

대표청구항 ▼

[ What is claimed is:] [9.] A process for controlling the carbon monoxide and nitrogen oxides emissions from a boiler comprising the steps of:passing a mixture of recirculated flue gas and combustion air through a combustion air fan and into a burner;increasing the speed of the fan at increasing fir

[ What is claimed is:] [9.] A process for controlling the carbon monoxide and nitrogen oxides emissions from a boiler comprising the steps of:passing a mixture of recirculated flue gas and combustion air through a combustion air fan and into a burner;increasing the speed of the fan at increasing firing level to prevent pulsations of said burner while allowing the boiler to operate with reduced fan speeds and reduced power consumption..Iaddend..Iadd.10. The process according to claim 9 further comprising the steps of:passing said 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..Iaddend..Iadd.11. The process according to claim 10 wherein said cone blocks at least 40 percent of the flow cross section of said cylindrical member to force the majority of said combustion air mixture to flow in close proximity to said perforations and to create turbulence within said mixture to improve mixing and combustion bility..Iaddend..Iadd.12. The process according to claim 11 wherein a majority of said fuel is injected downstream of said cone to prevent ignited fuel products form overheating said cone..Iaddend..Iadd.13. The process according to claim 12 wherein said 40 percent blockage created by said cone comprises the surface of said cone which is substantially nonperforated and is at least 98 percent solid area to prevent said combustion air mixture from bypassing said annulus so that as much combustion air as possible mixes with and oxidizes said fuel..Iaddend..Iadd.14. The process according to claim 10 wherein said recirculated flue gas is induced into the inlet of said combustion air fan for supplying said mixture to said annulus..Iaddend..Iadd.15. The process according to claim 14 wherein said combustion air fan is operated by a variable speed drive..Iaddend.