Combustion system with precombustor for recycled flue gas

Patent metadata

Field	Value
Publication number	US-9243799-B2
Application number	US-56681909-A
Country	US
Kind code	B2
Filing date	Sep 25, 2009
Priority date	Sep 26, 2008
Publication date	Jan 26, 2016
Grant date	Jan 26, 2016

Abstract

A precombustor system to be used in conjunction with an oxy-fuel burner employing recycled flue gas is disclosed. A method of introducing streams into the precombustor to achieve desired improvements in flame properties is also disclosed.

First claim

The invention claimed is:

1. An oxy/fuel combustion system comprising:
a burner having a longitudinal axis;
a furnace; and
a precombustor comprising a passage extending through the precombustor, said passage adapted to receive reaction products from the burner wherein the longitudinal axis of the burner is coincident with the passage, and wherein the burner comprises at least two annular fluid apertures surrounding a central aperture so that fluid exiting the at least two surrounding fluid apertures surrounds fluid exiting the central aperture and wherein one of the apertures contains oxygen, one contains fuel, and one contains RFG;
wherein the precombustor comprises a first end adjacent to an end of the burner emitting reaction products and a second end adjacent to the furnace;
wherein RFG is supplied to the combustion system via a first RFG stream that flows through the precombustor and a second RFG stream that flows outside the precombustor to the furnace;
wherein oxygen is supplied to the combustion system via a first oxygen stream that flows through the precombustor and a second oxygen stream that flows outside the precombustor to the furnace;
wherein the combustion system further comprises a flow control system wherein the flow rates of the first and second RFG streams are varied in response to a predetermined parameter; and
wherein the oxygen is an oxidizer having an oxygen concentration greater than about 30 mol %.

2. The combustion system of claim 1 wherein the central aperture comprises at least one fuel comprising a member selected from the group consisting of natural gas, hydrogen, refinery off gas, refinery fuel gas, blast furnace gas, propane, fuel oils, anthracite, bituminous, sub-bituminous, and lignite coals, tar, bitumen, petroleum coke, paper mill sludge solids and sewage sludge solids, wood, peat, and grass.

3. The combustion system of claim 1 wherein the RFG aperture surrounds the oxygen aperture.

4. The combustion system of claim 1 wherein the dimensions of the burner are sufficient to achieve a flow velocity ratio R1=Velocity oxygen/velocity RFG between about 0.3 and about 3.0.

5. The combustion system of claim 1 wherein the second end of the precombustor comprises a converging opening.

6. The combustion system of claim 1 wherein the second end of the precombustor comprises a diverging opening.

7. The combustion system of claim 1 further comprising a flow control system wherein recycled flue gas is combined with at least one of oxygen and fuel prior to entering the oxy/fuel burner.

8. The combustion system of claim 1 further comprising a flow control system wherein the flow rate of oxygen is varied in response to a predetermined parameter.

9. The combustion system of claim 1 wherein the first RFG stream is introduced adjacent to the burner and flows through a passage within the precombustor.

10. The combustion system of claim 1 wherein the first oxygen stream is introduced adjacent to the burner and flows through a passage within the precombustor.

11. The combustion system of claim 1 wherein at least three distinct fluid mixtures are conveyed through the passages.

12. The combustion system of claim 1 wherein the predetermined parameter comprises one or more of burner firing rate, furnace temperature, fuel quality, flue gas temperature, flame intensity, flame length, and flame stability.

13. The combustion system of claim 1 wherein the fluid exiting each aperture is of different composition.

14. A method for combusting a fuel comprising:
providing a combustion system comprising an oxy/fuel burner comprising a longitudinal axis, a furnace, and a precombustor comprising a passage extending through the precombustor, said passage adapted to receive streams from the oxy/fuel burner wherein the longitudinal axis is coincident with the passage, and wherein the burner comprises at least two concentric fluid apertures surrounding a central aperture for fuel so that fluid exiting the at least two surrounding fluid apertures surrounds fuel exiting the central aperture and wherein one of said at least two surrounding apertures contains oxygen and one contains RFG;
providing RFG to the combustion system via a first RFG stream that flows through the precombustor and a second RFG stream that flows outside the precombustor to the furnace;
providing oxygen to the combustion system via a first oxygen stream that flows through the precombustor and a second oxygen stream that flows outside the precombustor to the furnace;
passing the first oxygen stream, fuel, and the first RFG stream through their respective conduits in the oxy/fuel burner; and
passing the streams through the precombustor; wherein the flow rate of at least one of the first oxygen stream and the first RFG stream is varied in response to an external measurement;
wherein the oxygen is an oxidizer having an oxygen concentration greater than about 30 mol %.

15. The method of claim 14 wherein the external measurement comprises at least one member selected from the group consisting of firing rate, sensors viewing the flame, sensors measuring the precombustor temperature, heat flux sensors in the furnace, emissions measurements and furnace gas/process fluid temperatures.

16. The method of claim 14 wherein a flame is formed and the flow rate of the first RFG stream is varied in a manner sufficient to maintain a substantially constant flame length.

17. The method of claim 14 wherein the first oxygen stream and first RFG stream flow rates are varied in a manner sufficient to maintain a predetermined level of NOx emissions.

18. The method of claim 14 where said passing the first oxygen stream, fuel, and the first RFG stream through their respective conduits in the oxy/fuel burner comprises passing at least three distinct fluid mixtures through the oxy/fuel burner.

Assignees

• D Agostini Mark Daniel
• Hendershot Reed Jacob
• Slavejkov Aleksandar Georgi
• He Xiaoyi
• Air Prod & Chem

Inventors

• D Agostini Mark Daniel
• Hendershot Reed Jacob
• Slavejkov Aleksandar Georgi
• He Xiaoyi

Classifications

• F23C2202/10

  Premixing fluegas with fuel and combustion air · CPC title

• Y02E20/344

  Cross-Sectional Technologies · mapped topic

• F23C6/04

  in series connection (consuming smoke or fumes in separate combustion apparatus F23G7/06) · CPC title

• F23L2900/07006

  Control of the oxygen supply · CPC title

• F23C2202/50

  Control of recirculation rate · CPC title