Furnaces – Utilizing powdered fuel
Patent
1982-09-13
1985-06-04
Favors, Edward G.
Furnaces
Utilizing powdered fuel
239587, 239591, 239600, F23D 100
Patent
active
045207399
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to burner nozzle tips adapted for use in pulverized-coal fired furnaces and, more particularly, to a nozzle tip for pulverized coal-fired burner having a replaceable cast insert of highly abrasion resistant material and a replaceable end cap of temperature resistant material.
One common method of firing coal in conventional coal-fired steam generating boiler furnaces is known as tangential firing. In this method pulverized coal is introduced into the furnace in a primary air stream through burners, frequently termed fuel-air admission assemblies, located in the corner windboxes of the furnace. The pulverized coal-air streams discharging from these burners are aimed tangentially to an imaginary circle in the middle of the furnace to create a massive flame therein termed a fireball.
Upon leaving the furnace proper, the combustion products formed in the fireball pass through a boiler section typically housing a superheater, a reheater, and other various heat absorption surfaces to cool the combustion products and generate superheated steam. By changing the position of the fireball formed in the furnace upon convergence of the fuel-air streams emanating from the burners, control of the temperature of the steam leaving the superheater or reheater is achieved. By tilting the burner nozzle tips in unison the fireball can be physically raised or lowered within the furnace so as to increase or decrease the heat absorption of the furnace waterwalls thereby raising or lowering the temperature of the combustion products leaving the furnace proper and passing over the superheater and reheater surface. As the temperature of the combustion products entering the boiler section changes, the temperature of the steam generated in the heat absorption surface disposed therein changes proportionately. Such a method of steam temperature control is shown in U.S. Pat. No. 2,363,875 to Kreisinger et al.
A typical coal-air admission assembly or burner employed heretofore on tangentially-fired furnaces comprises a coal delivery pipe, often termed a coal nozzle, through which pulverized coal entrained in a primary air stream is delivered to the furnace, an air conduit surrounding the coal delivery pipe through which additional air is delivered to the furnace, and a nozzle tip pivotally mounted to the coal delivery pipe so as to be tiltable in a vertical plane whereby the pulverized coal-air stream being delivered to the furnace through the coal delivery pipe and the additional air passing through the air conduit can be selectively directed into the furnace as dictated by steam temperature requirements.
A typical prior art burner nozzle tip, such as that shown in U.S. Pat. No. 2,895,435 to Bogot et al, was formed of a steel open-ended inner shell defining a flow passage through which the pulverized coal-air stream from the coal delivery pipe is delivered into the furnace and a steel open-ended outer shell spaced from and surrounding the inner shell so as to define therebetween an annular duct through which the air leaving the air conduit is directed into the furnace. Additionally, one or more steel or stainless steel baffles, termed splitter plates, are typically disposed within the inner shell of the nozzle tip and aligned parallel to the longitudinal axis thereof, to impart additional directional force to the coal-air stream discharging through the inner shell and to insure a uniform distribution of the coal-air stream particularly when the nozzle is tilted away from the horizontal for steam temperature control.
A major problem heretofore encountered in using such nozzle tips has been the rapid wear of the steel or stainless steel splitter plates due to extreme erosion caused by the impingement of coal particles entrained in the high velocity air stream passing from the coal delivery pipe. As these splitter plates wear away, they lose their ability to adequately direct the pulverized-coal air stream into the furnace, thus detracting from the effectiveness of the tip. Addition
REFERENCES:
patent: 2895435 (1959-07-01), Bogot et al.
patent: 4274343 (1981-06-01), Kokkinos
patent: 4304196 (1981-12-01), Chadshay et al.
Chadshay Roman
Erlacher Richard F.
McCartney Michael S.
Combustion Engineering Inc.
Favors Edward G.
Habelt William W.
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