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A method and apparatus for combustion in which a pressurized preheated liquid fuel is atomized and a portion thereof flash vaporized, creating a mixture of fuel vapor and liquid droplets. The mixture is mixed with primary combustion oxidant, producing a fuel/primary oxidant mixture which is then inj

A method and apparatus for combustion in which a pressurized preheated liquid fuel is atomized and a portion thereof flash vaporized, creating a mixture of fuel vapor and liquid droplets. The mixture is mixed with primary combustion oxidant, producing a fuel/primary oxidant mixture which is then injected into a primary combustion chamber in which the fuel/primary oxidant mixture is partially combusted, producing a secondary gaseous fuel containing hydrogen and carbon oxides. The secondary gaseous fuel is mixed with a secondary combustion oxidant and injected into the second combustion chamber wherein complete combustion of the secondary gaseous fuel is carried out. The resulting second stage flue gas containing very low amounts of NOx is then vented from the second combustion chamber.

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1. A method for dual-fuel combustion comprising the steps of: pressurizing a liquid fuel, wherein a means of pressurizing the liquid fuel comprises a low pressure liquid fuel inlet and a high pressure liquid fuel outlet;preheating the pressurized liquid fuel, wherein a means of preheating the pressu

1. A method for dual-fuel combustion comprising the steps of: pressurizing a liquid fuel, wherein a means of pressurizing the liquid fuel comprises a low pressure liquid fuel inlet and a high pressure liquid fuel outlet;preheating the pressurized liquid fuel, wherein a means of preheating the pressurized liquid fuel comprises at least one of an electric liquid fuel preheater, a water-liquid fuel preheater, and a steam-liquid fuel preheater; wherein said pressurized liquid fuel preheating means further comprises a water-fuel heater having a pressurized preheated liquid fuel inlet in fluid communication with said means of preheating the pressurized liquid fuel and having a pressurized preheated water inlet in fluid communication with a pressurized water preheater;atomizing the preheated liquid fuel, producing an atomized liquid fuel;flash vaporing up to about 50% of said atomized liquid fuel, producing a liquid fuel mixture comprising said atomized liquid fuel and a vaporized fuel;mixing said liquid fuel mixture with a primary combustion oxidant in a mixing chamber, producing a fuel/oxidant mixture having a primary stoichiometry less than about 1.0;introducing said fuel/oxidant mixture into a first combustion chamber in which partial combustion of said fuel/oxidant mixture occurs, producing a secondary fuel gas;cooling said secondary fuel gas, producing a cooler secondary fuel gas;mixing said cooler secondary fuel gas with a secondary combustion oxidant, producing a secondary fuel gas/oxidant mixture;introducing said secondary fuel gas/oxidant mixture into a second combustion chamber in which substantially complete combustion of said secondary fuel gas/oxidant mixture occurs, producing flue gases; andventing said flue gases from said second combustion chamber. 2. The method of claim 1, wherein in a range of about 15% to about 50% of said atomized liquid fuel is vaporized by said flash vaporizing. 3. The method of claim 1, wherein an amount of said primary combustion oxidant is selected to maintain said primary stoichiometry in a range of about 0.50 to about 0.75. 4. The method of claim 1, wherein a portion of said secondary fuel gas is internally recirculated within said first combustion chamber. 5. The method of claim 1, wherein a portion of said flue gas is internally recirculated within said second combustion chamber. 6. The method of claim 1, wherein said atomized liquid fuel comprises liquid fuel droplets, substantially all of which have a droplet size of less than or equal to about 20 μm. 7. The method of claim 1, wherein said pressurized preheated liquid fuel is mixed with pressurized preheated water, producing a liquid fuel/water mixture. 8. The method of claim 7, wherein said liquid fuel/water mixture is atomized, producing an atomized liquid fuel/water mixture and up to about 50% of said atomized liquid fuel/water mixture is flash vaporized. 9. The method of claim 7, wherein said pressurized water is preheated in a water heater disposed in at east one of said first combustion chamber and said second combustion chamber. 10. The method of claim 1, wherein said secondary fuel gas is cooled to a temperature in a range of about 1100° F. to about 1300° F. 11. The method of claim 1, wherein said pressurized preheated liquid fuel is at a temperature in a range of about 250° F. to about 550° F. 12. The method of claim 11, wherein said pressurized preheated liquid fuel is atomized using an atomizing medium selected from the group consisting of compressed air, steam, vented flue gases, and mixtures thereof. 13. The method of claim 1, wherein a gaseous fuel is mixed with said liquid fuel mixture and said primary combustion oxidant in said mixing chamber. 14. An apparatus for dual-fuel combustion comprising: a pressurized liquid fuel preheating means for preheating a pressurized liquid fuel, said pressurized liquid fuel preheating means having a pressurized liquid fuel inlet, and a pressurized preheated liquid fuel outlet, said pressurized preheated liquid fuel outlet in fluid communication with a liquid fuel atomizer, wherein said pressurized liquid fuel preheating means comprises an electric liquid fuel preheater, wherein said pressurized liquid fuel preheating means further comprises a water-fuel heater having a pressurized preheated liquid fuel inlet in fluid communication with said electric liquid fuel preheater and having a pressurized preheated water inlet in fluid communication with a pressurized water preheater:said liquid fuel atomizer having a liquid fuel inlet and an atomized liquid fuel outlet;flash vaporization means for flash vaporizing a portion of an atomized liquid fuel;a mixing chamber having an atomized liquid fuel inlet in fluid communication with said atomized liquid fuel outlet, a primary combustion oxidant inlet, and a combustible mixture outlet;a first combustion chamber having at least one combustible mixture inlet in fluid communication with said combustible mixture outlet and having a first stage combustion products outlet; anda second combustion chamber having at least one first stage combustion products inlet in fluid communication with said first stage combustion products outlet, a secondary combustion oxidant inlet, and a second stage combustion products outlet. 15. The apparatus of claim 14 further comprising a cooling chamber having a heated first stage combustion products inlet in fluid communication with said first stage combustion products outlet and having a cooler first stage combustion products outlet in fluid communication with said first stage combustion products inlet. 16. The apparatus of claim 14, wherein said apparatus is a fuel-fired boiler. 17. The apparatus of claim 16, wherein the pressurized water preheater disposed within one of said first combustion chamber and said second combustion chamber. 18. The apparatus in accordance with claim 14, wherein said mixing chamber has a gaseous fuel inlet. 19. The apparatus of claim 14 further comprising combustion products recirculation means for internally recirculating combustion products disposed in at least one of said first combustion chamber and said second combustion chamber. 20. An apparatus for dual-fuel combustion comprising: a liquid fuel pressurizing means having low pressure liquid fuel inlet and high pressure liquid fuel outlet;a pressurized liquid fuel preheating means for preheating the pressurized liquid fuel, said pressurized liquid fuel preheating means having a pressurized liquid fuel inlet, and a pressurized preheated liquid fuel outlet, said pressurized preheated liquid fuel outlet in fluid communication with a liquid fuel atomizer, wherein said pressurized liquid fuel preheating means comprises a steam-fuel preheater having a pressurized liquid fuel inlet, a steam inlet in fluid communication with a steam source, heat exchange means for transferring heat from steam to said pressurized liquid fuel, a steam preheated liquid fuel outlet, and a condensate outlet;said liquid fuel atomizer having a liquid fuel inlet and an atomized liquid fuel outlet;flash vaporization means for flash vaporizing a portion of an atomized liquid fuel;a mixing chamber having an atomized liquid fuel inlet in fluid communication with said atomized liquid fuel outlet, a primary combustion oxidant inlet, and a combustible mixture outlet;a first combustion chamber having at least one combustible mixture inlet in fluid communication with said combustible mixture outlet and having a first stage combustion products outlet; anda second combustion chamber having at least one first stage combustion products inlet in fluid communication with said first stage combustion products outlet, a secondary combustion oxidant inlet, and a second stage combustion products outlet. 21. The apparatus of claim 20, wherein said pressurized liquid fuel preheating means further comprises a pressurized water preheater disposed within one of said first combustion chamber and said second combustion chamber having a condensate inlet in fluid communication with said condensate outlet and having a pressurized preheated water outlet, a water-liquid fuel preheater having a steam preheated liquid fuel inlet in fluid communication with said steam preheated liquid fuel outlet, a pressurized preheated water inlet in fluid communication with said pressurized preheated water outlet, and a pressurized water-preheated liquid fuel outlet, and an electric fuel heater having a water-preheated liquid fuel inlet in fluid communication with said pressurized water-preheated liquid fuel outlet and having an electric preheated liquid fuel outlet in fluid communication with said liquid fuel atomizer.