Process and apparatus for control of NOx in catalytic combustion systems

• US 6,595,003 B2
• Filed: 08/31/2001
• Issued: 07/22/2003
• Est. Priority Date: 08/31/2000
• Status: Expired due to Fees

• Current Assignee: Kawasaki Jukogyo Kabushiki Kaisha
• Original Assignee: Catalytica Energy Systems, Inc. (Renegy Holdings, Inc.)
• Inventors: Dalla Betta, Ralph A., Nickolas, Sarento G., McCarty, Jon G., Caron, Timothy J., Spencer, Mark J., Corr, Robert A. II
• Primary Examiner(s): FREAY, CHARLES GRANT
• Application Number:
  US09/944,094
• Publication Number:
  US 20020056276A1
• Time in Patent Office: 690 Days
• Field of Search: 607/75, 607/77, 60/393, 60/395.3, 60/395.5, 607/23
• US Class Current: 60/777
• CPC Class Codes: F01K 21/047 having at least one combustion gas turbine
• CPC Class Codes: F23C 13/00 Apparatus in which combustion takes place in the presence of catalytic material in a fluidised bed of catalytic particles F23C10/01; radiant gas burners using catalysis for flameless combustion F23D14/18
• CPC Class Codes: F23D 14/68 Treating the combustion air or gas, e.g. by filtering, or moistening
• CPC Class Codes: F23L 2900/07008 Injection of water into the combustion chamber
• CPC Class Codes: F23L 2900/07009 Injection of steam into the combustion chamber
• CPC Class Codes: F23L 7/002 Supplying water
• CPC Class Codes: F23R 3/40 characterised by the use of catalytic means

Abstract

Methods and apparatus for control of NO_x in catalytic combustion systems, and more particularly to control of thermal or/and prompt NO_x produced during combustion of liquid or gaseous fuels in the combustor sections of catalytic combustor-type gas turbines, by controlled injection of water in liquid or vapor form at selected locations, orientations, amounts, rates, temperatures, phases, forms and manners in the compressor and combustor sections of gas turbines. The ratio of thermal NO_x ppm reduction to water addition, in weight %, is on the order of 4-20, with % NO_x reduction on the order of up to about 50-80% and NO_x of below 2 ppm. Liquid water, steam or superheated steam can be used to reduce NO_x in combustion systems operating at reaction zone temperatures above 900° C., preferably 1400° C. to 1700° C. The amount of water added is sufficient to provide a concentration of water in the range of from about 0.1% to about 20% by weight of the total air and fuel mixture flowing into the post catalyst reaction zone. Water is introduced simultaneously or sequentially in a plurality of locations, at selected rates, amounts, temperatures, forms, and purity, preferably in accord with a suitable control algorithm.

Claims

1. In a method of operating a catalytic combustion system wherein fuel is introduced into and are mixed with process air flowing through a combustor or/and compressor, upstream of a catalyst module in said combustor to form a fuel/air mixture, a portion of the fuel in said fuel/air mixture is combusted in said catalyst module, and a portion of the fuel is combusted in a post catalyst reaction zone downstream of said catalyst module to provide a hot gases stream of a preselected output temperature value, the improvement comprising the step of introducing water from an external source into at least one of said process air, said fuel and said fuel/air mixture in an amount sufficient to reduce NO_x produced in said post catalyst reaction zone.

2. Method as in claim 1 wherein said water is introduced in a phase selected from liquid water, steam, and mixtures thereof.

3. Method as in claim 2 wherein the fuel concentration in said fuel/air mixture is adjusted to compensate for the added mass of water and to maintain the gases output temperature at substantially a preselected value.

4. Method as in claim 3 wherein the water added provides a concentration of water in the range of from about 0.1% to about 20% by weight of the total mass of air and fuel.

5. Method as in claim 4 wherein the amount of water added is in the range of from about 1% to about 5% by weight of the total mass of air and fuel.

6. Method as in claim 2 wherein said introduced water is added simultaneously or sequentially in a plurality of locations along the path of the gases flow through said combustion system.

7. Method as in claim 6 wherein said water introduction locations include at least one of:

adjacent the gases inlet to the catalyst module;

in the catalyst module;

at the exit of the catalyst module;

upstream of a homogeneous combustion zone in said post catalyst reaction zone;

in said post catalyst reaction zone;

adjacent the introduction of catalyst fuel;

intermixed in said fuel; and

in association with additional fuel introduced downstream of said catalyst module and upstream of a homogeneous combustion zone, and combination of said locations.

8. Method as in claim 2 in which said catalytic combustion system is disposed in a combustion section of a gas turbine, said combustor section includes a pre-burner section upstream of said catalytic combustion system, a compressor section is disposed upstream of said combustor section, and the output hot gas stream feeds said turbine, wherein said water is introduced selectively in at least one location along the path of gases flow into and through said compressor section and said combustor section, and when water is introduced in a plurality of locations said introduction may be simultaneous or sequential in accord with operating conditions, including selected level of NO_x reduction.

9. Method as in claim 8 wherein water is introduced in at least one mode selected from mixed in said fuel, separately from said fuel or combinations of said modes of introduction.

10. Method as in claim 8 wherein water is introduced in said preburner section in amounts sufficient to reduce NO_x produced in said preburner.

11. Method as in claim 8 wherein water is introduced upstream in said preburner section in amounts sufficient to reduce NO_x produced in said preburner section.

12. Method as in claim 11 wherein water is introduced upstream in at least one location selected from said compressor inlet, interstage in said compressor, and combinations thereof.

13. Method as in claim 1 which includes the steps of measuring NO_x level in at least one of the combustor section gases, combustor section outlet gases, and where the combustor section feeds a turbine, the turbine outlet gases;

and controlling the introduction of water to limit the NO_x to a preselected value range.

14. Method as in claim 13 wherein said control step includes a feedback loop comprising substantially continuous measurement of the NO_x level and adjustment of water introduction responsive thereto.

15. Method as in claim 1 in which includes the steps of determining the adiabatic combustion temperature adjacent the outlet of said combustor section;

and introducing said water in accord with a schedule of water injection rate to adiabatic combustion temperature needed to reduce NO_x to a preselected target level.

16. Method as in claim 15 wherein said schedule is derived from consideration of NO_x produced vs temperature in said combustor section and NO_x reduction vs water injection.

17. Method as in claim 16 wherein said NO_x value produced at said combustor section temperature is an estimated value of NO_x produced in both said post catalyst reaction zone and in said preburner section.

18. Method as in claim 17 wherein NO_x produced in said preburner is controlled by introduction of water in at least one location of:

upstream of said preburner section;

in said preburner section; and

combinations of said locations.

19. Method as in claim 18 which includes the steps of recovering waste heat from said combustion to convert water to high pressure steam for introduction in at least one of said compressor, said preburner section, and said combustor section.

20. Apparatus for reduction of NO_x produced in a combustor section of a gas turbine downstream of a compressor section, which combustor section includes a catalytic combustion system, comprising:

a) at least one water source;

b) at least one manifold connecting said water source to at least one of said combustion section and said compressor section for introduction of water into the process gasses flowing into and through said compressor section and into and through said combustor section, at selected one or more locations along the flow path of said gases; and

c) at least one controller that controls the introduction of water in amounts sufficient to reduce NO_x otherwise produced in said combustor section in accord with a target NO_x value range.