Method and apparatus for improved process control in combustion applications

• US 7,217,121 B2
• Filed: 04/07/2004
• Issued: 05/15/2007
• Est. Priority Date: 06/26/2000
• Status: Expired due to Fees

• Current Assignee: Alak Chanda, Gervase I. Mackay, Jason J. Nikkari, Murray J. Thomson
• Original Assignee: Alak Chanda, Gervase I. Mackay, Jason J. Nikkari, Murray J. Thomson
• Inventors: Mackay, Gervase I., Nikkari, Jason J., Thomson, Murray J., Chanda, Alak
• Primary Examiner(s): Price; Carl D.
• Application Number:
  US10/819,227
• Publication Number:
  US 20040191712A1
• Time in Patent Office: 1,133 Days
• Field of Search: 431/2, 431/12, 431/18, 431/75, 431/76, 340/575, 356/438, 356/439, 25033901-33908, 250/338.5, 250/339.1, 753/75, 266/99
• US Class Current: 431/12
• CPC Class Codes: B08B 7/00 Cleaning by methods not provided for in a single other subclass or a single group in this subclass
• CPC Class Codes: B23K 1/0016 Brazing of electronic components
• CPC Class Codes: B23K 1/008 Soldering within a furnace B23K1/012 takes precedence
• CPC Class Codes: B23K 1/012 Soldering with the use of hot gas
• CPC Class Codes: B23K 1/206 Cleaning
• CPC Class Codes: C21C 2005/5288 Measuring or sampling devices
• CPC Class Codes: C21C 5/4673 Measuring and sampling devices
• CPC Class Codes: C21C 5/5217 equipped with burners or devices for injecting gas, i.e. oxygen, or pulverulent materials into the furnace
• CPC Class Codes: F23G 2900/55003 Sensing for exhaust gas properties, e.g. O2 content
• CPC Class Codes: F23J 2215/40 Carbon monoxide
• CPC Class Codes: F23N 5/003 using detectors sensitive to combustion gas properties F23N5/02, F23N5/18 - F23N5/26 take precedence
• CPC Class Codes: F27B 3/085 Arc furnaces
• CPC Class Codes: F27B 3/225 Oxygen blowing
• CPC Class Codes: F27B 3/28 Arrangement of controlling, monitoring, alarm or the like devices
• CPC Class Codes: G01N 2021/536 Measurement device mounted at stack
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/3577 for analysing liquids, e.g. polluted water
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 21/85 Investigating moving fluids or granular solids
• CPC Class Codes: G01N 2201/127 Calibration; base line adjustment; drift compensation
• CPC Class Codes: H05K 2203/095 : Plasma, e.g. for treating a substrate to improve adhesion with a conductor or for cleaning holes
• CPC Class Codes: H05K 3/3489 : Composition of fluxes; Methods of application thereof; Other methods of activating the contact surfaces
• CPC Class Codes: Y02P 10/20 : Recycling

Abstract

This invention relates to a method and apparatus for improved process control in combustion applications, and particularly those relating to the steelmaking industry. An apparatus is provided for process control in a combustion application comprising a laser to transmit a near-infrared laser beam through off-gas produced by the combustion application, a detector to detect the transmitted laser beam and convert the detected laser beam to an electrical signal, and a control system for providing adjustment of select inputs to the combustion application in response to the electrical signal from the detector. The method of this invention comprises transmitting a near-infrared laser beam through off-gas produced by the combustion application, detecting the transmitted laser beam, and adjusting select inputs of the combustion application in response to the detected transmitted laser beam.

Claims

1. A method for process control in a steelmaking combustion application, comprising:

a) transmitting a frequency modulated near-infrared laser beam through off-gas produced by a steelmaking combustion application, the modulation frequency of the laser beam greater than the absorption line width of targeted CO and H₂O produced by the steelmaking combustion application;

b) detecting the transmitted laser beam;

c) analyzing the detected laser beam for select CO and H₂O absorption lines;

d) determining the CO concentration from the CO and H₂O absorption lines; and

e) adjusting select inputs of the combustion application in response to the CO concentration.

2. A method according to claim 1 wherein CO concentration is determined using predetermined calibration curves.

3. A method according to claim 2 wherein the calibration curve is CO concentration as a function of CO absorption lines and temperature.

4. A method according to claim 3 wherein the H₂O absorption lines are used to determine the temperature of the off-gas.

5. A method according to claim 4 wherein the targeted H₂O has absorption lines that respond differentially to changes in temperature.

6. A method according to claim 4 wherein the temperature of the off-gas is determined from the ratio of two H₂O absorption lines.

7. A method according to claim 1 wherein the targeted CO has a profile of strong absorption lines as compared to H₂O.

8. A method according to claim 1 wherein the CO absorption line is located at 1577.96 nm, and the H₂O absorption lines are located at 1577.8 nm and 1578.1 nm.

9. A method according to claim 1 wherein the wavelength of the laser beam is in the range of about 0.7 μ

m to about 3.0 μ

m.

10. A method according to claim 1 wherein the near-infrared laser beam is transmitted by a tunable diode laser.

11. A method according to claim 10 wherein the wavelength of the laser beam is in the range of about 1.5 μ

m to about 1.7 μ

m.

12. A method according to claim 1 wherein the near-infrared laser beam is transmitted by a distributed feedback laser.

13. A method according to claim 12 wherein the wavelength of the laser beam is in the range of about 1.57 μ

m to about 1.59 μ

m.

14. A method according to claim 1 wherein the select inputs to the combustion application comprise oxygen.

15. A method according to claim 1 wherein the select inputs to the combustion application comprise fuel.

16. A method according to claim 1 wherein the select inputs to the combustion application comprise electric power.

17. A method according to claim 14 wherein the select inputs to the combustion application comprise fuel.

18. A method according to claim 14 wherein the select inputs to the combustion application comprise electric power.

19. A method according to claim 15 wherein the select inputs to the combustion application comprise electric power.

20. A method according to claim 17 wherein the select inputs to the combustion application comprise electric power.

21. A method for process control in a steelmaking combustion application, the method comprising:

a) scanning off-gas produced by a steelmaking combustion application with a laser, the step of scanning comprising;

i) targeting the off-gas with laser light corresponding to at least one CO absorption, and at least one H₂O absorption, the laser light having a modulation frequency greater than the absorption line width of the targeted CO and H₂O produced by the steelmaking combustion application; and

ii) refraining from shining laser light on the off-gas during an off-interval,

b) detecting transmitted laser light of step i),

c) analyzing the detected laser light for select CO and H₂O absorption lines;

d) measuring background radiation during the off-interval;

e) determining the CO concentration from the CO and H₂O absorption lines and from the measured background radiation; and

f) adjusting select inputs of the combustion application in response to the CO concentration.

22. The method of claim 21, wherein the step of targeting comprises:

A) transmitting laser light corresponding to CO absorption during a first time interval; and

B) transmitting laser light corresponding to H₂O absorption during a second time interval that immediately follows the first interval.

23. The method of claim 22, wherein, in the step of determining, the measured background radiation is used to account for at least one of light produced by the combustion application, dust, debris and optical misalignment of the laser.

24. The method of claim 21, wherein steps i) and ii) are repeated periodically.