LOW NOx FUEL INJECTION FOR AN INDURATING FURNACE
AssigneeFives North American Combustion, Inc.
InventorsBruce E. Cain, Thomas F. Robertson, John J. Nowakowski
Life of this patent
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Abstract
An indurating furnace has a heating station and an air passage leading to the heating station. A draft of preheated recirculation air is driven through the passage toward the heating station, and is mixed with fuel gas to form a combustible mixture of preheated recirculation air and fuel gas that ignites in the passage. This is accomplished by injecting the fuel gas into the passage in a stream that does not form a combustible mixture with the preheated recirculation air before entering the passage.
Claims35
A method comprising:
- conveying pelletized material through an indurating furnace having a heating station and a passage configured to direct a draft of preheated recirculation air to the heating station;
- driving a draft of preheated recirculation air at an elevated temperature through the passage toward the heating station;
- and
- mixing the draft of preheated recirculation air with fuel gas having an auto-ignition temperature below the elevated temperature, and thereby forming a combustible mixture of preheated recirculation air and fuel gas that ignites in the passage, by injecting fuel gas into the passage in a stream that does not form a combustible mixture before entering the passage.
A method comprising:
- conveying pelletized material through an indurating furnace having a heating station and a passage configured to convey a draft of preheated recirculation air to the heating station;
- driving a draft of preheated recirculation air at an elevated temperature through the passage toward the heating station;
- and
- mixing the draft of preheated recirculation air with fuel gas having an auto-ignition temperature below the elevated temperature, and thereby forming a combustible mixture of preheated recirculation air and fuel gas that ignites in the passage, by injecting fuel gas into the passage in multiple streams, each of which does not form a combustible mixture before entering the passage.
An apparatus comprising:
- an indurating furnace structure including a heating station;
- a conveyor configured to convey pelletized material through the heating station;
- a passage configured to direct a draft of preheated recirculation air at an elevated temperature toward the heating station;
- a source of fuel gas having an auto-ignition temperature below the elevated temperature;
- and
- a system configured to inject fuel gas from the source into the passage in a stream that does not form a combustible mixture before entering the passage, whereby the fuel gas and preheated recirculation air in the passage can form a combustible mixture that ignites in the passage.
An apparatus as defined in claim 28 wherein the system is configured to limit the stream to an amount of fuel that obtains a peak reaction temperature in the passage of not greater than 2800 degrees F.
An apparatus comprising:
- an indurating furnace structure including a heating station;
- a conveyor configured to convey pelletized material through the heating station;
- a passage configured to direct a draft of preheated recirculation air at an elevated temperature toward the heating station;
- a source of fuel gas having an auto-ignition temperature below the elevated temperature;
- and
- a system configured to inject fuel gas from the source into the passage in multiple streams, each of which does not form a combustible mixture before entering the passage, whereby the fuel gas and preheated recirculation air in the passage can form a combustible mixture that ignites in the passage.
Dependencies are inferred from the claim text.