LOW NOx COMBUSTION METHOD AND APPARATUS

Patent metadata

Field	Value
Publication number	US-2016018102-A1
Application number	US-201514799091-A
Country	US
Kind code	A1
Filing date	Jul 14, 2015
Priority date	Jul 15, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

A steam generator system employing a fired burner with a flue gas recirculation system with low NOx emission is disclosed. A method to retrofit fired burners for low NOx emission is also disclosed. In the system, the flue gas recirculation system is configured to include a pre-mixer, and the recirculated flue gas (RFG) is routed to the stage of the pre-mixer for mixing with a portion of the fuel stream, forming a secondary RFG fuel mixture. The secondary RFG fuel mixture is routed to the secondary stage of the burner via a plurality of injector ports. The injection of the second RFG fuel mixture results in a reduction of temperature for the NOx emission to be less than 5 ppm at 3% O 2 , dry basis.

First claim

1 . A furnace system comprising:
a structure defining a combustion chamber; sources of primary fuel, combustion air, and secondary fuel; a premix staged combustion burner having at least a port facing into the combustion chamber; a flue that conveys products of combustion (POC) from the combustion chamber; a plurality of staged fuel injectors each having a port facing into the combustion chamber; an injection apparatus configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber through the plurality of staged fuel injectors; a reactant supply and control system including means for conveying the primary fuel from the primary fuel source to the premix staged combustion burner, means for conveying the combustion air from the combustion air source to the premix staged combustion burner for mixing with the primary fuel, means for conveying the secondary fuel from the secondary fuel source to the injection apparatus, and means for conveying the flue gas from the flue to the injection apparatus for mixing with the secondary fuel.

2 . The furnace system of claim 1 , wherein at least one of the staged fuel injectors is for injection of a mixture of primary fuel and the combustion air, and at least one of the staged fuel injectors is for injection of a mixture of the secondary fuel and the POC.

3 . The furnace system of claim 1 , wherein the combustion air to the furnace system is provided to the premix staged combustion burner at a sufficient rate for the POC to have an oxygen concentration ranging from 0.4 to 3% on a wet basis.

4 . The furnace system of claim 3 , wherein the combustion air to the furnace system is provided to the premix burner at a sufficient rate for the POC to have an oxygen concentration ranging from 0.75 to 1.5% on a wet basis.

5 . The furnace system of claim 1 , wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber at a controlled volume ratio for the POC to have a NOx concentration of <5 ppm at 3% O 2 , dry basis.

6 . The furnace system of claim 5 , wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber at a controlled volume ratio for the POC to have a NOx concentration of <3 ppm on a dry gas volumetric basis corrected to 3% O 2 (<3 ppm at 3% O 2 , dry basis).

7 . The furnace system of claim 1 , wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber at a volume ratio of secondary fuel to flue gas of 1:4 to 1:20.

8 . The furnace system of claim 7 , wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber at a volume ratio of secondary fuel to flue gas of 1:5 to 1:10.

9 . The furnace system of claim 1 , wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber through 3 to 8 staged fuel injectors.

10 . The furnace system of claim 9 , wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber through 4 to 6 staged fuel injectors.

11 . The furnace system of claim 1 , wherein the primary fuel has a higher heating value of 500 to 1200 Btu/scf.

12 . The furnace system of claim 11 , wherein the primary fuel has a higher heating value range of 900 to 1180 Btu/scf.

13 . The furnace system of claim 1 , wherein the secondary fuel has a higher heating value of 500 to 1200 Btu/scf.

14 . The furnace system of claim 1 , wherein the secondary fuel has a higher heating value of 900 to 1180 Btu/scf.

15 . The furnace system of claim 1 , wherein the primary fuel and the secondary fuel have different higher heating values.

16 . The furnace system of claim 1 , wherein the primary fuel and the secondary fuel are configured to have a volumetric ratio resulting in a primary zone adiabatic flame temperature less than 2600° F. (1427° C.).

17 . The furnace system of claim 16 , wherein the primary fuel and the secondary fuel are configured to have a volumetric ratio resulting in a primary zone adiabatic flame temperature less than 2500° F. (1371° C.).

18 . A furnace system comprising:
a structure defining a combustion chamber; sources of primary fuel, combustion air, and secondary fuel, wherein the primary fuel and secondary fuel are different, and wherein the primary fuel and secondary fuel each has a higher heating value of 500 to 1200 Btu/scf, and wherein the primary fuel and the secondary fuel are configured to have a volumetric ratio resulting in a primary zone adiabatic flame temperature less than 2600° F.; a premix staged combustion burner having at least a port facing into the combustion chamber; a flue that conveys products of combustion (POC) from the combustion chamber; a plurality of staged fuel injectors each having a port facing into the combustion chamber; an injection apparatus configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber through at least 3 staged fuel injectors, wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber at a controlled volume ratio for the POC to have a NOx concentration of <5 ppm on a dry gas volumetric basis corrected to 3% O 2 ; a reactant supply and control system including means for conveying the primary fuel from the primary fuel source to the premix burner, means for conveying the combustion air from the combustion air source to the premix burner for mixing with the primary fuel, means for conveying the secondary fuel from the secondary fuel source to the injection apparatus, and means for conveying the flue gas from the flue to the injection apparatus for mixing with the secondary fuel.

19 . The furnace system of claim 18 , wherein the injection apparatus is configured to inject an unignited mixture of secondary fuel and flue gas into the combustion chamber at a volume ratio of secondary fuel to flue gas of 1:4 to 1:20.

20 . The furnace system of claim 1 , wherein the staged fuel injectors are circumferentially arranged adjacent to and around the premix staged combustion burner.

Assignees

• Chevron Usa Inc

Inventors

• Robertson Thomas F
• Nowakowski John J
• Hannum Mark C
• Storslett Stein J

Classifications

• F23D23/00

  Assemblies of two or more burners (gas burners with provision for a retention flame F23D14/26) · CPC title

• F23C9/08 Primary

  for reducing temperature in combustion chamber, e.g. for protecting walls of combustion chamber · CPC title

• F23C5/08

  Disposition of burners · CPC title

• F23K5/10

  Mixing with other fluids · CPC title

• F23C2202/20

  Premixing fluegas with fuel · CPC title