METHOD FOR MEASURING TEMPERATURE, MOLECULAR NUMBER DENSITY, AND/OR PRESSURE OF A GASEOUS COMPOUND FROM A THERMAL DEVICE, AND A THERMAL SYSTEM

• US 20150144297A1
• Filed: 11/26/2014
• Published: 05/28/2015
• Est. Priority Date: 11/26/2013
• Status: Active Grant

• Current Assignee: Valmet Technologies OY
• Original Assignee: Valmet Power Oy
• Inventors: TOIVONEN, Juha, AALTO, Antti, SARN, Matti, ROPPO, Juha
• Granted Patent: US 9,857,345 B2
• Time in Patent Office: Days
• US Class Current: 165/11.1
• CPC Class Codes: F23N 2225/04 pressure
• CPC Class Codes: F23N 2225/08 temperature
• CPC Class Codes: F23N 5/022 using electronic means F23N5/04 - F23N5/14 take precedence
• CPC Class Codes: F23N 5/082 using electronic means
• CPC Class Codes: F28F 27/00 Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus control arrangements in general G05
• CPC Class Codes: G01K 11/00 Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
• CPC Class Codes: G01L 11/02 by optical means
• CPC Class Codes: G01N 2021/1734 Sequential different kinds of measurements; Combining two or more methods
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G01N 21/49 within a body or fluid
• CPC Class Codes: G01N 21/51 inside a container, e.g. in an ampoule G01N21/53 takes precedence
• CPC Class Codes: G01N 2201/06113 Coherent sources; lasers
• CPC Class Codes: G01N 2201/0697 Pulsed lasers
• CPC Class Codes: G01N 33/0036 Specially adapted to detect a particular component all the other sub-groups of G01N33/0004 take precedence
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications

Abstract

A method for measuring, from a thermal device, temperature, molecular number density, and/or pressure of a gaseous compound as function of distance, the gaseous compound absorbing at least some light. The method comprises generating, for a first wavelength band and a second wavelength band, a pulse sequence comprising a light pulse or light pulses, guiding the pulse sequence into the thermal device, and measuring, as function of time, the intensity of the scattered light at the first wavelength band and at the second wavelength band. The method further comprises determining information indicative of the differential absorption between the two wavelengths bands using measured intensities and determining the temperature, the molecular number density, and/or the pressure of the gaseous compound using the information indicative of the differential absorption between the two wavelengths bands. A thermal system arranged to carry out the method.

Claims

1. A method for measuring at least two of temperature, molecular number density, and pressure of a gaseous compound as function of distance, the gaseous compound absorbing at least some light, the method comprising

selecting a first wavelength band, a second wavelength band, and a third wavelength band using information on the spectrum of the absorption coefficient of the gaseous compound and/or the temperature dependence thereof,

generating, for the first wavelength band, the second wavelength band, and the third wavelength band, a pulse sequence comprising a light pulse or light pulses, wherein the pulse sequence comprises a supercontinuum light pulse comprising light having continuously multiple wavelengths in the first wavelength band and the second wavelength band,

guiding the pulse sequence, from a location, in a first direction, into a thermal device, wherein the thermal device surrounds some gaseous mixture, the gaseous mixture comprising the gaseous compound and scattering particles, whereby

molecules of the gaseous compound absorb at least part of the light pulse or at least part of at least one of the light pulses, and

particles of the gaseous mixture scatter at least part of the light pulse or at least part of the light pulses at various moments of time at least to scattered light;

the method comprising

measuring, as function of time, the intensity of the scattered light at the first wavelength band, the second wavelength band, and the third wavelength band,

determining a first piece of information indicative of the differential absorption between the first and the second wavelengths bands using the intensity of the scattered light at the first wavelength band and the intensity of the scattered light at the second wavelength band,

determining a second piece of information indicative of the differential absorption between another pair of wavelength bands selected from the three wavelength bands using the measured intensities and

determining, as function of the distance from the location, in the first direction, using the two pieces of information indicative of the differential absorptions, at least two of the temperature, the molecular number density, and the pressure of the gaseous compound.

2. The method of claim 1, comprising

selecting a wavelength band such that the molecular absorptance or the expected molecular absorptance for the wavelength band is at least 1%;

optionally selecting another wavelength band such that the molecular absorptance or the expected molecular absorptance for the other wavelength band is at most 99%.

3. The method of claim 1, comprising

selecting the first wavelength band such that the total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound has a first value,

selecting the second wavelength band such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound has a second value, wherein

the first value is different from the second value;

preferably (i) at a temperature, the smallest total attenuation factor is less than 10<sup>−

23</sup> cm² or (ii) at a temperature, the ratio of the greatest total attenuation factor to the smallest total attenuation factor is at least 2, and

determining the molecular number density of the gaseous compound as function of the distance from the location in the first direction.

4. The method of claim 1, comprising

selecting the first wavelength band such that the total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound depends on temperature in a first way,

selecting the second wavelength band such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound depends on temperature in a second way, wherein

the first way is different from the second way;

preferably at least one total attenuation factor has an absolute temperature dependence of at least 100 ppm/K, and

determining the temperature of the gaseous compound as function of the distance from the location in the first direction.

5. The method of claim 1, wherein

the gaseous compound comprises at least one of steam (H₂O), oxygen (O₂), carbon dioxide (CO₂), carbon monoxide (CO), ammonia (NH₃), nitrogen oxide (NO_X), and sulfur oxide (SO_X);

preferably the gaseous compound comprises steam (H₂O) or carbon dioxide (CO₂).

6. The method of claim 1, wherein

the temperature of the gaseous compound is at least 400°

C.; and

optionally the temperature of the gaseous compound is at most 1200°

C.

7. The method of claim 1, wherein

the first wavelength band or the second wavelength band comprises wavelengths from the range 750 nm to 2000 nm and/or

the linear size of the space is at most 50 m and/or

the duration of a light pulse of the pulse sequence is at most 10 ns, optionally at least 1 ps;

the sampling rate at which the intensities of the scattered light is detected is at least 100 MHz; and

the pulse response of a detector arrangement used for the measuring of the intensity is less than 5 ns, optionally less than 1 ns and/or

the energy of a light pulse of the pulse sequence is at least 0.01 μ

J, optionally at most 1 J.

8. The method of claim 1, comprising

generating, for a first wavelength band and a second wavelength band, a further pulse sequence comprising a light pulse or light pulses,

guiding, from the location, the further pulse sequence into the thermal device in a second direction, wherein the second direction forms an angle with the first direction, whereby

molecules of the gaseous compound absorb at least part of the light pulse or at least part of the light pulses of the further pulse sequence, and

particles of the gaseous mixture scatter at least part of the light pulse or at least part of the light pulses of the further pulse sequence at various moments of time at least to a scattered further light;

the method comprising

measuring, as function of time, the intensity of the scattered further light at the first wavelength band,

measuring, as function of time, the intensity of the scattered further light at the second wavelength band,

determining information indicative of the differential absorption between the two wavelengths bands using the intensities of the scattered further light, and

determining the temperature, pressure, and/or the molecular number density of the gaseous compound as function of the distance from the location in the second direction using the information indicative of the differential absorption between the two wavelengths bands for the scattered further light.

9. The method of claim 8, comprising

generating multiple pulse sequences,

guiding, from the location, the multiple pulse sequences in to the thermal device in different directions;

at least one pulse sequence to a direction, and

determining the temperature, pressure, and/or the molecular number density of the gaseous compound as function of the distance from the location in the different directions, optionally using statistical means, thereby obtaining a two-dimensional or a three-dimensional profile of the temperature, pressure, and/or the molecular number density.

10. The method of claim 1, comprising

selecting the first wavelength band such that the total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound has a first value, and such that such that the total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound depends on temperature in a first way,

selecting the second wavelength band such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound has a second value, and such that such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound depends on temperature in a second way

selecting the third wavelength band such that the total attenuation factor for the pulse sequence, the third wavelength band, and the gaseous compound has a third value, and such that such that the total attenuation factor for the pulse sequence, the third wavelength band, and the gaseous compound depends on temperature in a third way, wherein

the first way is different from the second way, and

the second value is different from the third value, the method comprising

determining the temperature and the molecular number density of the gaseous compound as function of the distance from the location in the first direction.

11. The method of claim 1, comprising

selecting a further wavelength band using information on the spectrum of the absorption coefficient of a further gaseous compound,

generating the pulse sequence also for the further wavelength band,

measuring, as function of time, the intensity of the scattered light at the further wavelength band,

determining information indicative of the differential absorption between at least two pairs of wavelengths bands selected from the at least four wavelength bands using the measured intensities, and

determining the temperature, the molecular number density, and/or the pressure of the further gaseous compound as function of the distance from the location in the first direction using the information indicative of the differential absorption between the further wavelength band and another wavelength band.

12. A method for controlling a thermal process, the method comprising

determining the temperature, the molecular number density, and/or the pressure of the gaseous compound as function of the distance from the location in the first direction according to the method of the claim 1,

providing information indicative of the temperature, the molecular number density, and/or the pressure, and

controlling the thermal process using the information indicative of the temperature, the molecular number density, and/or the pressure.

13. A thermal system comprising

a thermal device comprising at least a member limiting a space, the member having an optical inlet, wherein, in use, the space is arranged to contain some gaseous mixture comprising some gaseous compound and scattering particles, the gaseous molecules of the compound absorbing at least some light at least at a first wavelength band, a second wavelength band, or a third wavelength band and the scattering particles scattering at least some light at least at a first wavelength band, a second wavelength band, or a third wavelength band;

the system comprising

a light pulse source arrangement arranged to generate, for the first wavelength band, the second wavelength band, and the third wavelength band, a pulse sequence comprising a supercontinuum light pulse or light pulses, wherein the light pulse source arrangement comprises a supercontinuum light pulse source,

means for guiding, from a location, to a first direction, the pulse sequence into the space through the optical inlet, whereby molecules of the gaseous compound absorb at least part of at least one of the light pulses and the particles of the gaseous mixture scatter at least part of the light pulse or at least part of the light pulses to scattered light,

a detector arrangement arranged to measure, as function of time, the intensity of the scattered light at the first wavelength band, at the second wavelength band, and at the third wavelength band, and

a processing unit configured to determine at least two of the temperature, the molecular number density, and the pressure of the gaseous compound as function of the distance from the location in the first direction using the measurement results of the detector by determining information indicative of the differential absorption between two pairs of the wavelength bands using the information provided by the detector arrangement.

14. The thermal system of claim 13, wherein

the member or another member limiting the space of the thermal device comprises heat exchange pipes to recover heat from the member by convection and/or

the linear size of the space is from 2 m to 50 m.

15. The thermal system of claim 13, wherein the detector arrangement comprises

a beam splitter arranged to divide at least a part of the scattered light to a first part comprising light corresponding to the first wavelength band and to a second part comprising light corresponding to the second wavelength band.

16. The thermal system of claim 13, comprising

a reflector configured to guide the pulse sequence to the gaseous mixture, wherein

at least an angle of the reflector is arranged changeable, whereby the direction in to which the pulse sequence is guided is arranged changeable.

17. The thermal system of the claim 13, comprising

a controller, wherein

the processing unit is arranged to provide information indicative of the temperature, pressure, and/or the molecular number density of the gaseous compound, and

means for providing the information indicative of the temperature, the molecular number density, and/or the pressure to the controller, wherein

the controller is arranged to control a flow into or out of the thermal device using the information provided by the processing unit.