Title of Invention | A DIFFERENTIAL GAS COMPONENT FOR DETERMINING THE AMOUNT OF A FIRST GAS COMPONENT IN A COMBUSTION GAS |
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Abstract | The invention relates to a differential gas component probe (1) for determining the amount of a first gas component (NO2 ) in a combustion gas containing the first gas component (NO2 ) and a second gas component (NO) containing in the combustion gas including that obtainable from the first gas component (NO2 ) by reduction or oxidation, the probe (1) comprising: a first component probe (3) for taking a first sample of the gas and converting the total amount of the first gas component (NO2 ) present in the first sample to the second gas component (NO), the first component probe (3) having a first passage (7) for conveying the first sample, the wall of the first passage in contact with the first sample being made of a material that converts the first gas component (NO2 ) to the second gas component (NO) wherein the temperature of the exhaust gas including that of a heated sample transfer mechanism assist the total conversion of the first gas component (NO2 ) to the second gas component (NO); a second component probe (5) for taking a second sample of the gas, the second component probe (5) having a second passage (13) for conveying the second sample, the wall of the second passage in contact with the second sample being made of a material that is inert as regards the conversion of the first gas component (NO2 ) to the second gas component (NO); and, a measurement device suitable for measuring the second gas component (NO) in a combustion gas, wherein the measurement device when connected to the first component probe (3) , a data representing an amount of the second gas component originally present in the first sample (No - original), a converted amount of the second gas component (NO-converted) is obtained, wherein the measurement device when connected to the second component probe (5), provides a data presenting the total amount of the second gas component (NO-original) present in the second sample, and wherein a difference in the outputted data from the component probes (3,5) provides the amount of the first gas component (NO ) present in the exhaust gas. |
Full Text | FIELD OF INVENTION This invention relates to a probe for use in determining the amount of a first gas component in a gas containing the first gas component and a second gas component which is obtainable from the first gas component by reduction or oxidation. More particularly, the invention relates to a differential gas component probe for determining the amount of a first gas component in a combustion gas. The invention finds particular application in the determination of the amount of NO2 in a gas containing NO2 and NO. BACKGROUND OF INVENTION It is required to measure the NOX (nitrogen oxides) emissions produced by combustion plant to ensure that environmental standards are met. The two most important constituents of NOX are NO (nitric oxide) and NO2 is far more toxic and reactive. Currently to measure accurately NOX at low levels extractive gas analysis must be used. A probe extracts a sample of the emissions, and a transfer line conveys the sample to measurement instrumentation which measures the NO and NO2 content. It has been found that the materials of which the probe and transfer line are made alter the emission sample so that the measurement instrumentation does not give an accurate measure of NO/NO2 content. A metallic probe may convert NO2 to NO resulting in an artificially low measure of NO2. This especially occurs at high temperatures, i.e. temperatures of 500 degrees Celsius and above as found for example in a gas turbine engine exhaust. The material of the transfer line may absorb NO2, for example a transfer line made of polytetrafluoroethylene (PTFE). In contrast to NO2, NO is very stable. In conclusion, current approaches to measuring NOX tend to under -measure total NOX and especially NO2. US 4432939 ammonia gas analyzer and a sulfuric acid converter which is utilized in the ammonia gas analyzer, and, in which a sample gas is maintained at a relatively high temperature prior to entering the sulfuric acid converter to thereby prevent acidic sulfuric acid sulfates and/or ammonia sulfates from crystallizing and being deposited on the walls of the device. The ammonia gas analyzer includes gas sampling means, a gas measuring channel connected to the gas sampling means, a comparison gas channel connected parallel to the measuring gas channel with the measuring gas channel including an NH3 /NO converter for converting NH3 in a sample gas into NO and means for measuring a concentration of NH3 on the basis of variations of an amount of NO in the measuring gas channel with respect to that in the comparison gas channel. A first sulfuric acid converter has an inlet connected to the sampling means and an outlet connected to an inlet portion of the comparison gas channel for converting sulfuric acid, sulfate and sulfur trioxide in the sample gas into sulfur dioxide. A second sulfuric acid converter has an inlet connected to the outlet of the NH3 /NO converter and an outlet connected to an inlet of the measuring means. US 4822564 discloses a gas analyzer for determining the concentration of the oxides of nitrogen in a sample gas. The analyzer is particularly adapted for analyzing the exhaust from an internal combustion engine. In one embodiment, the analyzer comprises a sample chamber and a reference chamber. An arrangement is provided for delivering sample gas containing the lower oxide of nitrogen (NO) to the sample chamber and a quantity of ozone (O.sub.3) for reacting with this oxide of nitrogen and producing a chemiluminescence. After the chemiluminescence is completed, the sample gas is discharged to the reference chamber. A sample photodiode is disposed adjacent to the sample chamber for receiving light emitted from the sample chamber and producing a sample signal representative of the total photoemissivity of the sample gas. A reference photodiode is disposed adjacent to the reference chamber for receiving light emitted from the reference chamber and providing a reference signal representative of the dark current of the photodiodes and the background photoemissivity of the sample gas. A circuit is provided for conditioning and substracting the sample signal and the reference signal to produce an output representative of the concentration of the oxide of nitrogen in the sample gas. Dilution air is mixed with the sample gas either in the instrument with a viscous metering technique or in a sample probe, mounted in the exhaust of the engine, with a sonic metering technique. In other embodiments, a single sample photodiode is used to measure the chemiluminescent reaction and determine the oxide of nitrogen content of the sample gas. DE 10121262 (A1) discloses a volumetric flow of an analyte, comprising exhaled air, is fed to a gas sensor unit by means of a gas flow device, which can comprise various sensors for the determination of nitrogen oxides. An oxidation catalyst is used when using an NO2 sensor, which converts nitrogen monoxide to nitrogen dioxide and the gas sensor unit measures the content of nitrogen dioxide. The nitrogen monoxide content is calculated from the nitrogen dioxide content. In order to eliminate cross-sensitivity moisture and ethanol are also measured. Said device can be applied to the determination of nitrogen monoxide content of exhaled air. SUMMARY OF INVENTION Accordingly there is provided a differential gas component probe (1) for determining the amount of a first gas component (NO2) in a combustion gas containing the first gas component (NO2) and a second gas component (NO) containing in the combustion gas including that obtainable from the first gas component (NO2) by reduction or oxidation, the probe (1) comprising: a first component probe (3) for taking a first sample of the gas and converting the total amount of the first gas component (NO2) present in the first sample to the second gas component (NO), the first component probe (3) having a first passage (7) for conveying the first sample, the wall of the first passage in contact with the first sample being made of a material that converts the first gas component (NO2) to the second gas component (NO) wherein the temperature of the exhaust gas including that of a heated sample transfer mechanism assist the total conversion of the first gas component (NO2) to the second gas component (NO); a second component probe (5) for taking a second sample of the gas, the second component probe (5) having a second passage (13) for conveying the second sample, the wall of the second passage in contact with the second sample being made of a material that is inert as regards the conversion of the first gas component (NO2) to the second gas component (NO); and, a measurement device suitable for measuring the second gas component (NO) in a combustion gas, wherein the measurement device when connected to the first component probe (3), a data representing an amount of the second gas component originally present in the first sample (No - original), a converted amount of the second gas component (NO-converted) is obtained, wherein the measurement device when connected to the second component probe (5), provides a data representing the total amount of the second gas component (NO-original) present in the second sample, and wherein a difference in the outputted data from the component probes (3,5) provides the amount of the first gas component (NO2) present in the exhaust gas. Preferably: the first component probe includes a first passage for conveying the first sample, and the wall of the first passage in contact with the first sample is made of a material that converts NO2 to NO; and the second component probe includes a second passage for conveying the second sample, and the wall of the second passage in contact with the second sample is made of a material is inert as regards the conversion of NO2 to NO The first component probe may further comprise a converter for converting NO2 to NO, the converter being made of the same material as the wall of the first passage and being positioned in the first passage so that the first sample passes through the converter as it is conveyed along the first passage. The wall of the first passage is suitably made of a nickel alloy that is particularly efficient at converting NO2 to NO, and the wall of the second passage is suitably made of a ceramic material such as glass. Preferably, the first component probe comprises a first tube made of the nickel alloy, the second component probe comprises a second tube made of the ceramic material, the first and second tubes are disposed parallel and adjacent, and the first and second tubes are secured to one another such that the first tube supports the second tube. Preferably: the first tube includes a first plurality of holes at spaced positions along its length, the first component probe taking the first sample by way of the first plurality holes; and the second tube includes a second plurality of holes at spaced positions along its length, the second component probe taking the second sample by way of the second plurality of holes. The first and second pluralities of holes are suitably formed in the same sides of the first and second tubes and at corresponding positions along the lengths of the tubes. According to a second aspect of the present invention there is provided a method of measuring the amount of a first gas component in a gas containing the first gas component and a second gas component obtainable from the first gas component by reduction or oxidation, the method comprising: taking a first sample of the gas, converting the first gas component present in the first sample to the second gas component, and measuring the total amount of the second gas component present in the first sample following the conversion; taking a second sample of the gas, and measuring the total amount of the second gas component present in the second sample; and subtracting the total amount of the second gas component present in the second sample from the total amount of the second gas component present in the first sample to determine the amount of first gas component present in the gas. The first gas component may be NO2 and the second gas component NO. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig 1 illustrates a probe in accordance with the present invention; Fig 2 is an end view of the probe of Fig 1, viewing the probe from the right in Fig 1; Fig 3 is a cross-section on the line Ill-Ill in Fig 2; and Fig 4 is a cross-section on the line IV-IV in Fig 1. Referring to the drawings, the probe 1 comprises a first component probe 3 and a second component probe 5. Component probe 3 comprises a tube 7 made of a nickel alloy that is particularly efficient at converting NO2 to NO. Component probe 3 further comprises an NO2 to NO converter 9 comprising shavings of the same nickel alloy as tube 7 held between perforated plates 11, again of the said nickel alloy. Component probe 5 comprises a ceramic tube 13, e.g. a glass tube. Tubes 7, 13 are disposed parallel and adjacent. Towards one end the tubes are held by a mounting plate 15. Approximately three fifths of the way along the tubes from this one end the tubes are secured to one another by means of a clamp 17. Clamp 17 comprises two halves 19 secured together by means of a nut 21, bolt 23 and washer 25. By securing tubes 7,13 together as aforesaid the stronger nickel alloy component probe 3 supports the weaker ceramic component probe 5. Formed in the same side of tubes 7, 13 and at corresponding positions along the length of the tubes are holes 27. Probe 1 is intended to be mounted so as to extend across the exhaust gas flow of a gas turbine engine so that holes 27 face into the gas flow. For this purpose mounting plate 15 includes fixings 29. By so mounting the probe efficient sampling takes place across the breadth of the exhaust gas flow. Sampling across the breadth of the flow accurately characterises the flow. In use of probe 1 a heated switching arrangement, e.g. a heated solenoid valve made of inert materials, is connected to the probe to periodically switch between component probes 3, 5. A heated sample transfer line including a heated sample pump is connected to the common outlet from the heated switching arrangement to transfer samples to measurement instrumentation suitable for measuring NO. Sample integrity is maintained within the measurement instrumentation by the use of heated components. When component probe 3 is connected to the measurement instrumentation the sample pump sucks in exhaust gas from the gas turbine engine exhaust by way of holes 27 in nickel alloy tube 7. The gas travels along tube 7 and through converter 9. The nickel alloy of the tube 7 and converter 9 operates to convert all the NO2 present in the exhaust gas to NO. It is to be noted that this conversion is assisted by the temperature of the exhaust gas. The original NO present in the exhaust gas, NO-original, together with the NO that was obtained by converting the NO2, NO-converted, is then measured by the measurement instrumentation. This provides a measurement reading NO-total equals NO-original plus NO-converted. When component probe 5 is connected to the measurement instrumentation exhaust gas is sucked in via holes 27 in ceramic tube 13. Since ceramic is inert as regards the conversion of NO2 to NO, no NO2 will be converted to NO in component probe 5. Thus, in the case of component probe 5, the measurement instrumentation will measure only the original NO present in the exhaust gas, NO-original. The difference between the measurements readings of component probes 3, 5 is a measure of the amount of NO2 present in the exhaust gas as there is a direct relationship between the amount of NO2 present and NO- converted. The component probe 5 measurement, NO-original, is subtracted from the component probe 3 measurement, NO-original plus NO-converted, to provide NO-converted. In the prior art the conversion by the probe of NO2 to NO is a problem as it results in an artificially low measure of NO2. In the above described probe in accordance with the present invention, in component probe 3, this property is turned to advantage, and utilised to convert all NO2 present to NO. In the prior art the absorption of NO2 by the material of the transfer line is a problem. In the above described probe in accordance with the present invention, in the case of component probe 3, all the NO2 is converted to NO and hence there is no NO2 to be absorbed by the transfer line, and, in the case of component probe 5, any absorption of NO2 by the transfer line is of no consequence as the purpose of probe 5 is measurement of the original NO only. The above described probe in accordance with the present invention is for use in the exhaust of a gas turbine engine, and utilises the high temperatures present in such an exhaust to assist in the conversion in component probe 3 of all the NO2 to NO. In the case where the probe is used to measure the amount of NO2 in a gas not at such high temperatures, then an additional heater would be desirable to ensure conversion of all the NO2 to NO in component probe 3. It is to be appreciated that in the limiting case the probe described above in accordance with the present invention may be utilised to measure the amount of NO2 in a gas not containing NO, i.e. where no NO is present in the gas only NO2. In this case the component probe 5 measurement, NO- original, would be zero, and the component probe 3 measurement, NO- original plus NO-converted, would equal NO-converted, i.e. the measure of the NO2 present in the gas. The present invention has been described above in the context of determining the amount of NO2 in a gas containing NO2 and NO. It is to be realised that the invention may also be used to determine the amount of a gas component other than NO2 (the gas component measured) where the gas contains the gas component measured and a further gas component which is obtainable from the gas component measured by reduction. For example, the invention might be used to determine the amount of S03 (sulphur trioxide) in a gas containing S03 and S02 (sulphur dioxide). The present invention has been described above in the context of determining the amount of a first gas component in a gas containing the first gas component and a second gas component obtainable from the first gas component by reduction. It is to be realised that the invention may be also be used to determine the amount of a first gas component in a gas containing the first gas component and a second gas component obtainable from the first gas component by oxidation, the reverse of reduction. Of course in this case the catalyst would be chosen for the purpose of converting the second gas component to the first gas component by oxidation. An example of this use of the invention is determination of the amount of CO (carbon monoxide) in a gas containing CO and CO2 (carbon dioxide). WE CLAIM 1. A differential gas component probe (1) for determining the amount of a first gas component (NO2) in a combustion gas containing the first gas component (NO2) and a second gas component (NO) containing in the combustion gas including that obtainable from the first gas component (NO2) by reduction or oxidation, the probe (1) comprising: a first component probe (3) for taking a first sample of the gas and converting the total amount of the first gas component (NO2) present in the first sample to the second gas component (NO), the first component probe (3) having a first tube (7) for conveying the first sample, the wall of the first tube in contact with the first sample being made of a material that converts the first gas component (NO2) to the second gas component (NO) wherein the temperature of the exhaust gas including that of a heated sample transfer mechanism assist the total conversion of the first gas component (NO2) to the second gas component (NO); a second component probe (5) for taking a second sample of the gas, the second component probe (5) having a second tube (13) for conveying the second sample, the wall of the second passage in contact with the second sample being made of a material that is inert as regards the conversion of the first gas component (NO2) to the second gas component (NO); and, a measurement device suitable for measuring the second gas component (NO) in a combustion gas, wherein the measurement device when connected to the first component probe (3), a data representing an amount of the second gas component originally present in the first sample (No - original), a converted amount of the second gas component (NO-converted) is obtained, wherein the measurement device when connected to the second component probe (5), provides a data representing the total amount of the second gas component (NO-original) present in the second sample, and wherein a difference in the outputted data from the component probes (3,5) provides the amount of the first gas component (NO2) present in the exhaust gas. 2. The probe as claimed in claim 1, wherein the sample transfer mechanism comprises: a heated solenoid valve connected to the probe (1) to periodically switch between the first component probe (3) and the second component probe (5); and a heated sample transfer line including a heated sample pump connected between the sample measurement device and the common outlet from the heated solenoid valve for transfer of samples to the measurement device. 3. The probe as claimed in claim 1, wherein the first component probe (3) comprises a converter (9) for converting the first gas component (NO2) to the second gas component (NO), the converter (9) being made of material identical to that of said wall of the first tube (7), and wherein the converter (9) is positioned in the first tube (7) so that the first sample passes through the converter (9) as it is conveyed along the first tube (7). 4. The probe as claimed in claim 1 or claim 3, wherein said wall of the first tube (7) is made of a nickel alloy that is particularly efficient at converting the first gas component (NO2) to the second gas component (NO), and wherein said wall of the second passage is made of a ceramic material such as glass. 5. The probe as claimed in claim 4, wherein said first tube (7) comprises nickel alloy, said second tube (13) comprises a ceramic material and wherein said first and second tubes (7,13) are disposed parallel and adjacent, and said first and second tubes (7,13) are secured to one another such that the first tube (7) supports the second tube (13). 6. The probe as claimed in claim 5, wherein the first tube (7) comprises a first plurality of holes (27) at spaced positions along its length, the first component probe (3) taking the first sample by way of the first plurality (27) holes; and the second tube (13) comprises a second plurality of holes (27) at spaced positions along its length, the second component probe (5) taking the second sample by way of the second plurality of holes (27). 7. The probe as claimed in claim 6, wherein the first and second pluralities of holes (27,27) are formed in the same sides of the first and second tubes (7,13) and at corresponding positions along the lengths of the tubes (7,13). 8. The probe as claimed in any one of claims 2 to 7, wherein it is enabled to determining the amount of NO2 present in the exhaust gas produced by a gas turbine engine. The invention relates to a differential gas component probe (1) for determining the amount of a first gas component (NO2 ) in a combustion gas containing the first gas component (NO2 ) and a second gas component (NO) containing in the combustion gas including that obtainable from the first gas component (NO2 ) by reduction or oxidation, the probe (1) comprising: a first component probe (3) for taking a first sample of the gas and converting the total amount of the first gas component (NO2 ) present in the first sample to the second gas component (NO), the first component probe (3) having a first passage (7) for conveying the first sample, the wall of the first passage in contact with the first sample being made of a material that converts the first gas component (NO2 ) to the second gas component (NO) wherein the temperature of the exhaust gas including that of a heated sample transfer mechanism assist the total conversion of the first gas component (NO2 ) to the second gas component (NO); a second component probe (5) for taking a second sample of the gas, the second component probe (5) having a second passage (13) for conveying the second sample, the wall of the second passage in contact with the second sample being made of a material that is inert as regards the conversion of the first gas component (NO2 ) to the second gas component (NO); and, a measurement device suitable for measuring the second gas component (NO) in a combustion gas, wherein the measurement device when connected to the first component probe (3) , a data representing an amount of the second gas component originally present in the first sample (No - original), a converted amount of the second gas component (NO-converted) is obtained, wherein the measurement device when connected to the second component probe (5), provides a data presenting the total amount of the second gas component (NO-original) present in the second sample, and wherein a difference in the outputted data from the component probes (3,5) provides the amount of the first gas component (NO ) present in the exhaust gas. |
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01171-kolnp-2007-correspondence others 1.1.pdf
01171-kolnp-2007-correspondence others 1.2.pdf
01171-kolnp-2007-correspondence others.pdf
01171-kolnp-2007-description complete.pdf
01171-kolnp-2007-international exm report.pdf
01171-kolnp-2007-international publication.pdf
01171-kolnp-2007-international search report.pdf
01171-kolnp-2007-pct request.pdf
01171-kolnp-2007-priority document.pdf
1171-KOLNP-2007-CANCELLED DOCOMENT.pdf
1171-KOLNP-2007-CLAIMS 1.1.pdf
1171-KOLNP-2007-CORRESPONDENCE 1.3.pdf
1171-kolnp-2007-correspondence.pdf
1171-KOLNP-2007-DESCRIPTION COMPLETE.pdf
1171-kolnp-2007-examination report.pdf
1171-kolnp-2007-granted-abstract.pdf
1171-kolnp-2007-granted-claims.pdf
1171-kolnp-2007-granted-description (complete).pdf
1171-kolnp-2007-granted-drawings.pdf
1171-kolnp-2007-granted-form 1.pdf
1171-kolnp-2007-granted-form 2.pdf
1171-kolnp-2007-granted-specification.pdf
1171-kolnp-2007-reply to examination report-1.1.pdf
1171-KOLNP-2007-REPLY TO EXAMINATION REPORT.pdf
Patent Number | 250103 | ||||||||
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Indian Patent Application Number | 1171/KOLNP/2007 | ||||||||
PG Journal Number | 49/2011 | ||||||||
Publication Date | 09-Dec-2011 | ||||||||
Grant Date | 07-Dec-2011 | ||||||||
Date of Filing | 04-Apr-2007 | ||||||||
Name of Patentee | SIEMENS AKTIENGESELLSCHAFT | ||||||||
Applicant Address | WITTELSBACHERPLATZ 2, 80333 MUNCHEN | ||||||||
Inventors:
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PCT International Classification Number | G01N 1/22 | ||||||||
PCT International Application Number | PCT/EP2005/056292 | ||||||||
PCT International Filing date | 2005-11-29 | ||||||||
PCT Conventions:
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