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1. WO1997049979 - APPARATUS AND METHOD FOR MEASURING GASES USING A HEATED GAS PROBE AND CLOSELY COUPLED MEASUREMENT CHAMBER

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[ EN ]

Claims

1. An apparatus for measuring concentrations of gases within a high temperature gas composition comprising:
a probe insertible into a stream of a high temperature gas composition, the probe including a tip section for receiving a sample extracted from the high
temperature gas composition and a heated extraction section extending therefrom, the tip section including a filter for removing particles from the sample; and
a heated measurement chamber coupled to the proximal end of the probe for receiving the sample from the heated extraction section, the heated
measurement chamber including a measurement device for measuring
concentrations of gases within the sample.

2. The apparatus of claim 1 wherein the filter is formed of one or more materials capable of withstanding the temperature and chemical properties of the sample extracted from the high temperature gas composition.

3. The apparatus of claim 1 wherein the heated extraction section further comprises blow-back tubing for passing pressurized gas received from a gas source to the tip section for dislodging accumulated particles from the filter.

4. The apparatus of claim 1 further comprising a condensation trap coupled to the measurement chamber for cooling the sample received therefrom.

5. The apparatus of claim 1 further comprising a pump in fluid communication with the condensation trap, the measurement chamber and the probe, the pump
providing a pressure differential for extracting the sample gas from the high
temperature gas composition and drawing the sample through the probe, through the measurement chamber and through the condensation trap.

6. The apparatus of claim 5 wherein the pump is thermally isolated from the stream of the high temperature gas composition, the probe and the measurement chamber.

7. The apparatus of claim 1 wherein the measurement device comprises an athermal optical multipass cell for receiving the extracted sample, the cell comprising
(a) first and second concave mirrors oppositely disposed along a common axis and separated by a selected distance, the first mirror defining an orifice through which an input beam of light enters the cell and is repeatedly reflected between the
mirrors before exiting the cell through the orifice as an output beam, and (b) a mounting structure for supporting the first and second concave mirrors at the selected distance.

8. The apparatus of claim 7 wherein the measurement device further comprises (a) an optical device positioned to receive the output beam exiting the cell, and (b) a detector optically coupled to the imaging device for receiving the output beam to measure concentrations of gases within the high temperature gas composition.

9. The apparatus of claim 7 wherein the first minor, the second minor and the
mounting structure have the same coefficient of thermal expansion.

10. The apparatus of claim 1 further comprising a light source spaced from the cell and generating the input beam of light enters the cell through the orifice.

11. The apparatus of claim 10 wherein the light source is a laser.

12. The apparatus of claim 10 wherein the light source, the optical imaging device and the detector are thermally isolated from the high temperature gas composition disposed in the cell.

13. An apparatus for measuring concentrations of gases within a high temperature gas composition comprising:
a probe insertible into a stream of a high temperature gas composition for receiving a sample extracted from the high temperature gas composition, the probe including (a) a tip section at a distal end of the probe and including a filter for removing particles from the extracted sample and (b) a heated extraction section extending from the tip section to a proximal end of the probe and including sample tubing for passing the extracted sample from the tip section and blow-back tubing for passing pressurized gas received from a gas source to the tip section for
dislodging accumulated particles from the filter;
a heated measurement chamber coupled to the proximal end of the probe for receiving the extracted sample from the heated extraction section, the
measurement chamber including a measurement device for measuring
concentrations of gases within the extracted sample of the high temperature gas composition; and
a pump in fluid communication with the probe and the measurement
chamber, the pump providing a pressure differential for extracting the sample gas from the high temperature gas composition and drawing the sample through the probe to the measurement chamber.

14. The apparatus of claim 13 wherein the filter is formed of one or more materials capable of withstanding the temperature and chemical properties of the sample extracted from the high temperature gas composition.

15. The apparatus of claim 13 wherein the pump is thermally isolated from the stream of the high temperature gas composition, the probe and the measurement chamber.

16. The apparatus of claim 13 wherein the measurement device comprises an athermal Herriot cell.

17. A method for measuring concentrations of gases within a high temperature gas composition comprising:
inserting a probe into a stream of a high temperature gas composition;
providing a sample extracted from the high temperature gas composition to a distal end of the probe;
filtering particulates from the sample by passing the sample through a filter disposed in the distal end of the probe;
passing the filtered sample through a heated extraction section extending from the distal end to a proximal end of the probe to a heated measurement
chamber; and measuring concentrations of gases within the sample in the measurement chamber.

18 The method of claim 17 further comprising forming the filter of one or more
materials capable of withstanding the temperature and chemical properties of the sample extracted from the high temperature gas composition.

19. The method of claim 17 further comprising passing pressurized gas received from a gas source to the distal end of the probe for dislodging accumulated particles from the filter.

20. The method of claim 17 further comprising:
passing the sample into an athermal optical multipass cell disposed in the measurement chamber, the cell comprising (a) first and second concave mirrors oppositely disposed along a common axis and separated by a selected distance, and (b) a mounting structure for supporting the mirrors at the selected distance;
directing an input beam of light into the cell through an orifice formed in the first mirror light, the input beam being repeatedly reflected between the mirrors before exiting the cell through the orifice as an output beam; and
directing the output beam onto a detector to measure concentrations of gases within the sample.

21. The method of claim 20 further comprising forming the first mirror, the second mirror and the mounting structure of materials having the same coefficient of thermal expansion.

22. The method of claim 20 further comprising providing a light source spaced from the cell and generating the input beam of light enters the cell through the orifice.

23. The method of claim 22 further comprising thermally isolating the light source, the optical imaging device and the detector from the high temperature gas composition disposed in the cell.