US3890084A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for reducing burner exhaust emissions
Assignee: John Zink Co LLC
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Filing: 1973-09-26
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Granted: 1975-06-17
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Expires: 1993-09-26
Abstract
Abstract NOx exhaust emissions from furnace or boiler burners are reduced by combusting fuel with low excess air (about 5 percent more air than the theoretically required minimum air volume). The fuel is combusted so that the maximum flame temperatures are less than the theoretically obtainable maximum temperature. This is achieved by cooling flames in the chamber through contact with combustion chamber walls and by combusting central portions of the flames in two stages. Burners in a vertically lower burner bank are initially fired with insufficient air and burners in an upper burner bank are fired with additional air to make up for the air deficiency of the lower burners. The additional air is intermixed with the uncombusted fuel from the lower burners and such fuel is burned at a later stage downstream of and spaced from the burners. The additional air supplied from the burners in the upper row is measured to provide the above stated total of 5 percent excess air for the furnace.
Inventors
- 👤 Temple S Voorheis
- 👤 Ralph R Vosper
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 06:30
CPC Classifications
F; F23; F23B; F23B5/00; F23B2700/00; F23B2700/022
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
97 words
A METHOD OF OPERATING AN EXISTING INDUSTRIAL FURNACE AT A LOW NOX EMISSION LEVEL, THE FURNACE INCLUDING AT LEAST TWO VERTICALLY SPACED BURNERS, THE METHOD COMPRISING THE STEP OF MODIFYING THE COMBUSTION PROCESS IN THE FURNACE WITH THE STEPS OF FIRING AT LEAST A PORTION OF ONE OF THE BURNERS WITH AN OFF-RATIO AIR SUPPLY, FIRING AT LEAST A PORTION OF THE OTHER BURN ERS WITH A SUFFICIENT ADDITIONAL AIR SUPPLY TO PROVIDE FOR A LOW EXCESS AIR FIRING OF ALL BURNERS, AND COMBUSTING ALL FUEL DISCHARGED BY THE BURNERS BY FIRST COMBUSTING A PORTION OF THE
Claim 2
Independent Claim
97 words
A METHOD OF OPERATING AN EXISTING INDUSTRIAL FURNACE AT A LOW NOX EMISSION LEVEL, THE FURNACE INCLUDING AT LEAST TWO VERTICALLY SPACED BURNERS, THE METHOD COMPRISING THE STEP OF MODIFYING THE COMBUSTION PROCESS IN THE FURNACE WITH THE STEPS OF FIRING AT LEAST A PORTION OF ONE OF THE BURNERS WITH AN OFF-RATIO AIR SUPPLY, FIRING AT LEAST A PORTION OF THE OTHER BURN ERS WITH A SUFFICIENT ADDITIONAL AIR SUPPLY TO PROVIDE FOR A LOW EXCESS AIR FIRING OF ALL BURNERS, AND COMBUSTING ALL FUEL DISCHARGED BY THE BURNERS BY FIRST COMBUSTING A PORTION OF THE
Claim 3
Dependent Claim
28 words
A method according to claim 1 including the step of firing at least a portion of at least one of the burners with about 5 percent excess air.
Claim 4
Independent Claim
169 words
A method of modifying an existing furnace for operating it at a low NOx emission level, the furnace having a plurality of burners arranged in at least two vertically spaced rows, each burner having a fuel discharge nozzle and an annular air supply concentrically arranged about the nozzle, the method comprising the steps of adapting at least a portion of at least one burner in the lower bank to discharge more fuel than can be completely combusted with the air supply for such burner to thereby leave a quantity of unburnt fuel, and adapting a portion of at least one burner in the upper bank proximate the adapted burner in the lower bank to discharge a volume of additional air over and above the air required by such burner for completely combusting said unburnt fuel, and adjusting the air supplied by at least said one burner in the upper bank to provide a total of no more than about 5% excess air for all fuel discharged by the burners.
Claim 5
Independent Claim
169 words
A method of modifying an existing furnace for operating it at a low NOx emission level, the furnace having a plurality of burners arranged in at least two vertically spaced rows, each burner having a fuel discharge nozzle and an annular air supply concentrically arranged about the nozzle, the method comprising the steps of adapting at least a portion of at least one burner in the lower bank to discharge more fuel than can be completely combusted with the air supply for such burner to thereby leave a quantity of unburnt fuel, and adapting a portion of at least one burner in the upper bank proximate the adapted burner in the lower bank to discharge a volume of additional air over and above the air required by such burner for completely combusting said unburnt fuel, and adjusting the air supplied by at least said one burner in the upper bank to provide a total of no more than about 5% excess air for all fuel discharged by the burners.
Claim 6
Independent Claim
158 words
A method for combusting fuel discharged into a combustion chamber from at least one lower nozzle and at least one upper nozzle disposed above the lower nozzle, the method comprising the steps of discharging fuel from each nozzle in a generally circular pattern, discharging combustion air concentrically with respect to the discharged fuel from each nozzle for admixture and combustion with the fuel, limiting the air-to-fuel ratio in at least a section of the lower nozzle adjoining the upper nozzle to less than the stoichiometric ratio, injecting additional air in excess of the stoichiometric ratio over a section of the upper nozzle adjoining the lower nozzle, and combusting some of the fuel discharged from the section of the lower nozzle with additional air from the section of the upper nozzle at a point spaced from and downstream of the nozzles to effect a complete fuel combustion at a relatively low temperature to thereby reduce the emission of NOx.
Claim 7
Independent Claim
158 words
A method for combusting fuel discharged into a combustion chamber from at least one lower nozzle and at least one upper nozzle disposed above the lower nozzle, the method comprising the steps of discharging fuel from each nozzle in a generally circular pattern, discharging combustion air concentrically with respect to the discharged fuel from each nozzle for admixture and combustion with the fuel, limiting the air-to-fuel ratio in at least a section of the lower nozzle adjoining the upper nozzle to less than the stoichiometric ratio, injecting additional air in excess of the stoichiometric ratio over a section of the upper nozzle adjoining the lower nozzle, and combusting some of the fuel discharged from the section of the lower nozzle with additional air from the section of the upper nozzle at a point spaced from and downstream of the nozzles to effect a complete fuel combustion at a relatively low temperature to thereby reduce the emission of NOx.
Claim 8
Dependent Claim
56 words
A method according to claim 4 including outer nozzles disposed on each side of each of the upper nozzle and the lower nozzle, and including the step of discharging from the outer nozzles a quantity of fuel and a quantity of air to effect a low excess air combustion of fuel discharged by the outer nozzles.
Claim 9
Dependent Claim
36 words
A method according to claim 5 wherein the steps of discharging air comprise the step of discharging approximately 5 percent more air than the air required to effect a theoretically complete combustion of all discharged fuel.
Claim 10
Dependent Claim
46 words
A method according to claim 4 wherein the step of discharging air at the section of the lower nozzle comprises the step of discharging approximately 10 percent less air than the air required to effect a theoretically complete combustion of the fuel discharged by such section.
Claim 11
Dependent Claim
64 words
A method according to claim 7 wherein the step of discharging additional air from the section of the upper nozzle comprises the step of discharging from the upper nozzle a quantity of additional air sufficient to supply approximately 5 percent more air in the chamber than theoretically required to effect a complete combustion of all fuel discharged from the section of the lower nozzle.
Claim 12
Independent Claim
190 words
A method for reducing the level of NOx emissions in exhaust gases of a furnace comprising the steps of discharging fuel and combustion air into a combustion chamber of the furnace from an upper and a lower bank of burners, providing a total air volume discharged into the chamber of no more than about 5 percent in excess of the theoretically required air volume to effect a complete combustion of the fuel, and maintaining the maximum gas temperature within the chamber at less than the theoretically attainable maximum gas temperature by discharging less air than the theoretically required minimum amount of air from at least portions of central burners in the lower bank facing the upper bank, and discharging additional air from central burners in the upper bank over and above the air volume required to effect a complete combustion of fuel discharged by such burners, the additional air being discharged over a portion of the central burners in the upper bank adjoining the lower bank to effect an interfacing of fuel-rich mixture discharged at the lower bank and air-rich mixture discharged at the upper bank downstream of the burners.
Claim 13
Independent Claim
190 words
A method for reducing the level of NOx emissions in exhaust gases of a furnace comprising the steps of discharging fuel and combustion air into a combustion chamber of the furnace from an upper and a lower bank of burners, providing a total air volume discharged into the chamber of no more than about 5 percent in excess of the theoretically required air volume to effect a complete combustion of the fuel, and maintaining the maximum gas temperature within the chamber at less than the theoretically attainable maximum gas temperature by discharging less air than the theoretically required minimum amount of air from at least portions of central burners in the lower bank facing the upper bank, and discharging additional air from central burners in the upper bank over and above the air volume required to effect a complete combustion of fuel discharged by such burners, the additional air being discharged over a portion of the central burners in the upper bank adjoining the lower bank to effect an interfacing of fuel-rich mixture discharged at the lower bank and air-rich mixture discharged at the upper bank downstream of the burners.
Claim 14
Dependent Claim
51 words
A method according to claim 9 wwherein the step of discharging additional air comprises the step of discharging sufficient additional air to provide an overall excess combustion air for the central burners of about 5 percent above the theoretical minimum to effect a complete combustion of fuel discharged by such burners.
Claim 15
Independent Claim
171 words
A method for reducing NOx in exhaust gases from furnaces, boilers and the like comprising the steps of arranging a plurality of burners in at least two vertically spaced burner banks, providing an overall air supply to the burners of no more than about 5 percent above the required theoretical minimum air volume for effecting a complete combustion of fuel discharged from the burners, mixing approximately 5 percent excess combustion air with fuel discharged by at least portions of burners defining sides of the burner banks, discharging from at least a portion of at least one of the burners in the lower bank insufficient air to effect a complete combustion of the fuel discharged by such burner, supplying sufficient additional air from at least one of the burners in the upper bank to combust all uncombusted fuel discharged by at least one burner in the lower bank, mixing such additional air with the uncombusted fuel, and combusting the uncombusted fuel with the additional air at a location spaced from the burners.
Claim 16
Independent Claim
171 words
A method for reducing NOx in exhaust gases from furnaces, boilers and the like comprising the steps of arranging a plurality of burners in at least two vertically spaced burner banks, providing an overall air supply to the burners of no more than about 5 percent above the required theoretical minimum air volume for effecting a complete combustion of fuel discharged from the burners, mixing approximately 5 percent excess combustion air with fuel discharged by at least portions of burners defining sides of the burner banks, discharging from at least a portion of at least one of the burners in the lower bank insufficient air to effect a complete combustion of the fuel discharged by such burner, supplying sufficient additional air from at least one of the burners in the upper bank to combust all uncombusted fuel discharged by at least one burner in the lower bank, mixing such additional air with the uncombusted fuel, and combusting the uncombusted fuel with the additional air at a location spaced from the burners.
Claim 17
Dependent Claim
58 words
A method according to claim 11 wherein there are provided two burners in each bank, and wherein the step of discharging insufficient air from the burners in the lower bank and additional air from the burners of the upper bank comprises the step of discharging such air from burner portions facing the other burner in the same bank.
Claim 18
Dependent Claim
48 words
A method according to claim 12 wherein the step of discharging approximately 5 percent excess air from the side burners comprises the step of discharging the 5 percent excess air from portions of the burners in the banks facing away from the other burner in the same bank.
Claim 19
Dependent Claim
49 words
A method according to claim 11 wherein the burners discharge fuel and air in a generally conical pattern, and wherein the step of discharging the adDitional air comprises the step of discharging such additional air over a downwardly facing section of at least one burner in the upper bank.
Claim 20
Dependent Claim
60 words
A method according to claim 14 wherein the step of discharging fuel and insufficient air from the burners in the lower bank comprises the step of substantially evenly discharging fuel and insufficient air from at least one burner in the lower bank in a generally conical pattern, and including the further step of intermixing the additional air with non-combusted fuel.
Claim 21
Dependent Claim
26 words
A method according to claim 15 including the step of discharging approximately 5 percent excess air from remaining sections of the burners in the upper bank.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |