GB2113833A - Gas analysis apparatus and method of operation - Google Patents
Gas analysis apparatus and method of operation Download PDFInfo
- Publication number
- GB2113833A GB2113833A GB08201750A GB8201750A GB2113833A GB 2113833 A GB2113833 A GB 2113833A GB 08201750 A GB08201750 A GB 08201750A GB 8201750 A GB8201750 A GB 8201750A GB 2113833 A GB2113833 A GB 2113833A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gas
- infra red
- radiation
- filter cells
- red radiation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000004868 gas analysis Methods 0.000 title claims abstract description 14
- 238000000034 method Methods 0.000 title claims description 9
- 230000005855 radiation Effects 0.000 claims abstract description 56
- 239000007789 gas Substances 0.000 claims description 56
- 238000010521 absorption reaction Methods 0.000 claims description 9
- 238000004458 analytical method Methods 0.000 claims description 7
- 238000011835 investigation Methods 0.000 claims description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 11
- 229910002091 carbon monoxide Inorganic materials 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 230000003287 optical effect Effects 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000004291 sulphur dioxide Substances 0.000 description 1
- 235000010269 sulphur dioxide Nutrition 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
- G01N21/3518—Devices using gas filter correlation techniques; Devices using gas pressure modulation techniques
Abstract
Infra red gas analysis apparatus, comprises a source, a rotatable wheel (2) carrying a reference cell (9) and two filter cells (10, 11), a gas analysis chamber and infra red detecting means. Cell (9) contains a reference gas which does not absorb infra red radiation, and cells (10, 11) contain gas which offers different levels of absorbtion to the infra red radiation. The gas analysis chamber is filled with the gas sample to be analysed, and the detecting means detects the intensity of the radiation at three levels, namely: after the radiation has passed through cell (9) and the gas sample, after the radiation has passed through cell (10) and the gas sample, and after the radiation has passed through cell (11) and the gas sample. From these three levels, a measure of concentration of gas sample is derived compensated for effects due to temperature variation in the filter cells (10, 11). <IMAGE>
Description
SPECIFICATION
Gas analysis apparatus and method of
operation
This invention relates to infra red gas analysis
apparatus and to a method of operating such
apparatus.
Heteroatomic gases or vapours (i.e. those having
molecules of two or more dissimilar atoms) absorb
radiation in the infra red region of the spectrum at wavelengths characteristic of each gas or vapour
and by an amount dependent on the concentratior
of the gas or vapour. Examples of heteroatomic
gases or vapours which can be analysed by infra
red absorption methods include carbon monoxide, carbon dioxide, sulphur dioxide, the oxides of
nitrogen, organic gases and water vapour.
Homoatomic gases (i.e. those having the same
atoms in their molecules) do not absorb infra red
radiation. A sample gas under investigation may
therefore be analysed by irradiation first with infra
red radiation which has previously been passed
through a homoatomic gas such as nitrogen, and
secondly with infra red radiation which has
previously been passed through a filter cell containing a sample of the gas being analysed. The
resulting energy levels of the infra red radiation emerging from the sample are detected, and the
difference between these two energy levels is
used to derive a measure of the concentration of the sample gas under investigation.
A known infra red analysis apparatus relying on this technique has a reference cell filled with
nitrogen and a single filter cell filled with gas such as carbon monoxide corresponding to that being analysed. A major disadvantage of such gas analysis apparatus is that variation in temperature causes the absorption properties of the gas in the filter cell to vary, giving rise to temperatureinduced drift which adversely affects the accuracy of the resulting concentration reading. An object of the invention is to provide gas analysis apparatus and a method of operation, wherein compensation is provided for temperature-induced drift.
According to the invention infra red gas analysis apparatus comprises a source of infra red radiation, a reference cell containing a reference gas which does not absorb infra red radiation or does not absorb infra red radiation at the pertinent wavelength, two filter cells containing gas or gases which offer different levels of absorption to the infra red radiation, a gas sample chamber for accommodating a gas to be analysed, the reference cell and the two filter cells being brought individually and sequentially into the path of the infra red radiation, and detecting means for detecting the intensity of radiation at three levels, namely: after the radiation has passed through the reference cell and the gas sample, and after the radiation has passed through the first filter cell and the gas sample, and after the radiation has passed through the second filter cell and the sample.Since variations in temperature will affect the absorption characteristics of both filter cells by proportionate amounts, the detecting means is able to derive a signal representative of the concentration of the gas sample in the chamber, regardless of changes in the absorption characteristics of the two filter cells resulting from temperature variation.
The reference cell and the two filter cells may be mounted on a common member which is conveniently positioned between the source of infra red radiation and the gas sample chamber.
Normally, the gas sample chamber will have inlet and outlet connections enabling a flow of gas under investigation to be passed through the chamber, enabling the detecting means to'provide a continuous read out of gas concentration.
The common member may be rotatable in order to bring the reference cell and the two filter cells sequentially and individually into the path of the infra red radiation, and in the preferred embodiment to be described, the common member is in the form of a wheel of disc rotatable about its central axis and having a reference cell and two filter cells arranged at equi-angularly spaced positions.
Both filter cells will normally contain the component gas to be analysed. The filter cells may be identical in shape and size, in which case the gas in the filter cells will be at different pressures.
Alternatively, the gas in the two filter cells may be at the same pressure, but in this case it is necessary to make the two filter cells of different sizes so that the path lengths of the infra red radiation through the two filter cells are different.
It will be appreciated that any combination of differing pressures in the filter cells or differing sizes between the filter cells is possible, providing that the infra red radiation passes through different numbers of molecules of the gas in one filter cell as compared with the other filter cell.
This can also be achieved by arranging for the radiation to follow a path of the desired length within each filter cell, e.g. by optical means using reflection of the radiation. The filter cells may intercommunicate if at the same pressure. Where the filter cells are separate, their fillings may be different.
According to another aspect of the invention a method of compensating for temperature-induced drift in gas concentration readings obtained by infra-red analysis, comprises using a reference cell containing a reference gas which does not absorb infra red radiation or does not absorb infra red radiation at the pertinent wavelength, and two filter cells containing gas or gases offering different levels of absorption to the infra red radiation, and individually and sequentially bringing the reference cell and the two filter cells into the path of the infra red radiation passing through the gas to be analysed, detecting the resulting three levels of radiation and deriving therefrom a measure of concentration of the gas sample with compensation for temperature variation of the filter cells.
Infra red gas analysis apparatus forming a preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of the apparatus,
Figure 2 is an elevation of a filter wheel of the apparatus, and
Figure 3 is a graph illustrating infra red energy levels detected by detecting means of the apparatus.
Referring to Figures 1 and 2, the infra red gas analysis apparatus comprises a source 1 of infra red radiation, a disc-like filter wheel 2 rotatable about an axis 3, an optical interference filter 4, (which is optional), a gas analysis or sample chamber 5 and infra red detecting means 6. The gas sample chamber 5 has inlet and outlet connection 7 and 8 to enable a sample gas being investigated (carbon monoxide in the present example) to be passed through the chamber 5.
The infra red detecting means 6 s aligned with the passage of infra red radiation through the apparatus, as illustrated in Figure 1.
The filter wheel 2 is best shown in Figure 2. The filter wheel is rotatable about its central axis 3 and has three symmetrically arranged cells, namely a reference cell 9 containing nitrogen, a first filter cell 10 containing carbon monoxide at a first pressure, and a second filter cell 11 also containing carbon monoxide but at a different pressure from that of the first filer cell 10. The wheel 2 is arranged so that the reference cell 9 and the two filter cells 10, 11 are brought individually and sequentially into the path of the infra red radiation as the latter passes from the infra red source 1 to the optical interference filter 4.Hence, the detecting means 6 detect infra red energy at three different levels respectively corresponding to the three cells 9, 10 and 11 of the filter wheel 2 being aligned with the direction of passage of infra red radiation through the apparatus. The detecting means 6 converts these three energy levels into respective analogue electrical signals.
Figure 3 shows by way of example a graphical
representation of the three electrical signal levels V9, Vr0, V11 representative of the three energy
levels detected by the detecting means 6. V9 is
representative of the energy level detected by the detecting means 6 after the infra red radiation has passed serially through the reference cell 9, the filter 4 and the carbon monoxide in the analysis
chamber 5;V10 is representative of the energy
level detected by the detecting means 6 after the
infra red radiation has passed serially through the filter cell 10, the filter 4 and the carbon monoxide in the analysis chamber 5; and V11 is representative
of the energy level detected by the detecting
means 6 after the infra red radiation has passed
serially through the filter cell 11, the filter 4 and
the carbon monoxide in the analysis chamber 5.
These three signal levels are referenced to a datum voltage VN which corresponds to zero infra red absorption and which is derived (in an initial calibration) by detecting the level of infra red radiation falling upon the detecting means 6 after passing through the reference cell 9 and through nitrogen in the chamber 5. The detecting means 6 provides an indication of the concentration of the carbon monoxide passing through the chamber 5 by obtaining the quotient of the two signals marked as VA and VB in Figure 3. These signals are always of differing amplitude because the two filter cells 10, 11 contain carbon
monoxide at differing pressures. When the filter wheel 2 is subjected to temperature variations, the two signals VA/ VB vary in proportion to their
respective amplitudes so that the quotient of these signals remains insensitive to temperature
variations. The detecting means 6 has electrical or
electronic circuitry which, from the quotient of the signals VA/ VB provides a direct read out of the concentration of carbon monoxide in the gas sample chamber 5.
Although the previous description refers to the
provision of two filter cells, there may be three or
more filter cells in the filter wheel, if desired.
Claims (10)
1. Infra red gas analysis apparatus comprising a source of infra red radiation, a reference cell containing a reference gas which does not absorb infra red radiation or does not absorb infra red radiation at the pertinent wavelength, two filter cells containing gas or gases which offer different levels of absorption to the infra red radiation, a gas sample chamber for accommodating a gas to be analysed, the reference cell and the two filter cells being brought individually and sequentially into the path of the infra red radiation, and detecting means for detecting the intensity of radiation at three levels, namely: after the radiation has passed through the reference cell and the gas sample, after the radiation has passed through the first filter cell and the gas sample, and after the radiation has passed through the second filter cell and the sample.
2. Apparatus according to Claim 1, wherein the reference cell and the two filter cells are mounted on a common member.
3. Apparatus according to Claim 2, wherein the common member is positioned between the source of infra red radiation and the gas sample chamber.
4. Apparatus according to Claim 2 or 3, wherein the common member is rotatable in order to bring the reference cell and the two filter cells sequentially and individually into the path of the infra red radiation.
5. Apparatus according to Claim 4, wherein the common member is in the form of a wheel or disc rotatable about its central axis and having the reference cell and the two filter cells arranged at equi-angularly spaced positions.
6. Apparatus according to any of the preceding claims, wherein the filter cells are identical in shape and size, the gas in the filter cells being at different pressures.
7. Apparatus according to any of Claims 1 to 5, wherein the two filter cells are at the same pressure, the two filter cells being of different sizes so that the path lengths of the infra red radiation through the two filter cells are different.
8. A method of compensating for tempertureinduced drift in gas concentration readings obtained by infra-red analysis, comprising using a reference cell containing a reference gas which does not absorb infra red radiation or does not absorb infra red radiation at the pertinent wavelength, and two filter cells containing gas or gases offering different levels of absorption to the infra red radiation, and individually and sequentially bringing the reference cell and the two filter cells into the path of the infra red
radiation passing through the gas to be analysed, detecting the resulting three levels of radiation
and deriving therefrom a measure of
concentration of the gas sample with compensation for temperature variation of the filter cells.
9. Apparatus according to any of the preceding claims, wherein the gas sample chamber has inlet and outlet connections enabling a flow of gas under investigation to be passed through the chamber, enabling the detecting means to provide a continuous read out of gas concentration.
10. Infra red gas analysis apparatus
constructed and arranged substantially as herein
particularly described with reference to the
accompanying drawings.
1 A method of compensating for
temperature-induced drift in gas concentration
readings obtained by infra red analysis,
substantially as herein particularly described with
reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08201750A GB2113833B (en) | 1982-01-22 | 1982-01-22 | Gas analysis apparatus and method of operation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08201750A GB2113833B (en) | 1982-01-22 | 1982-01-22 | Gas analysis apparatus and method of operation |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2113833A true GB2113833A (en) | 1983-08-10 |
| GB2113833B GB2113833B (en) | 1985-02-06 |
Family
ID=10527788
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08201750A Expired GB2113833B (en) | 1982-01-22 | 1982-01-22 | Gas analysis apparatus and method of operation |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2113833B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5900635A (en) * | 1995-09-29 | 1999-05-04 | Instrumentarium Oy | Correction of collision broadening in non-dispersive absorption measurement of gases |
| EP1790971A1 (en) * | 2005-11-23 | 2007-05-30 | Servomex Group Ltd | Method for cross interference correction for correlation spectroscopy |
| CN102507461A (en) * | 2011-11-02 | 2012-06-20 | 南京智达分析仪器有限公司 | Negative-filtering type two-component infrared gas analyzer |
| CN104237126A (en) * | 2014-09-09 | 2014-12-24 | 中国科学院电工研究所 | Photoacoustic spectrometry detection device adopting axial multilayer filter plate structure |
| EP3561487B1 (en) * | 2018-04-25 | 2023-01-18 | ABB Schweiz AG | Measuring device for analysis of a composition of a combustible gas with a filter chamber arranged in front of a detector |
-
1982
- 1982-01-22 GB GB08201750A patent/GB2113833B/en not_active Expired
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5900635A (en) * | 1995-09-29 | 1999-05-04 | Instrumentarium Oy | Correction of collision broadening in non-dispersive absorption measurement of gases |
| EP1790971A1 (en) * | 2005-11-23 | 2007-05-30 | Servomex Group Ltd | Method for cross interference correction for correlation spectroscopy |
| US7751051B2 (en) | 2005-11-23 | 2010-07-06 | Servomex Group Limited | Method for cross interference correction for correlation spectroscopy |
| CN1971247B (en) * | 2005-11-23 | 2011-06-29 | 仕富梅集团公司 | Method for cross interference correction for correlation spectroscopy |
| CN102507461A (en) * | 2011-11-02 | 2012-06-20 | 南京智达分析仪器有限公司 | Negative-filtering type two-component infrared gas analyzer |
| CN104237126A (en) * | 2014-09-09 | 2014-12-24 | 中国科学院电工研究所 | Photoacoustic spectrometry detection device adopting axial multilayer filter plate structure |
| EP3561487B1 (en) * | 2018-04-25 | 2023-01-18 | ABB Schweiz AG | Measuring device for analysis of a composition of a combustible gas with a filter chamber arranged in front of a detector |
| US11796456B2 (en) | 2018-04-25 | 2023-10-24 | Abb Schweiz Ag | Measuring device for analyzing the composition of a fuel gas, having a filter chamber arranged upstream of a detector |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2113833B (en) | 1985-02-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20000122 |