Title of Invention

A DIFFERENTIAL GAS COMPONENT FOR DETERMINING THE AMOUNT OF A FIRST GAS COMPONENT IN A COMBUSTION GAS

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.

Documents:

01171-kolnp-2007-abstract.pdf

01171-kolnp-2007-claims.pdf

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-drawings.pdf

01171-kolnp-2007-form 1.pdf

01171-kolnp-2007-form 18.pdf

01171-kolnp-2007-form 2.pdf

01171-kolnp-2007-form 3.pdf

01171-kolnp-2007-form 5.pdf

01171-kolnp-2007-gpa.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-ABSTRACT.pdf

1171-KOLNP-2007-CANCELLED DOCOMENT.pdf

1171-KOLNP-2007-CLAIMS 1.1.pdf

1171-KOLNP-2007-CLAIMS.pdf

1171-KOLNP-2007-CORRESPONDENCE 1.3.pdf

1171-kolnp-2007-correspondence.pdf

1171-KOLNP-2007-DESCRIPTION COMPLETE.pdf

1171-KOLNP-2007-DRAWINGS.pdf

1171-kolnp-2007-examination report.pdf

1171-KOLNP-2007-FORM 1.pdf

1171-kolnp-2007-form 18.pdf

1171-KOLNP-2007-FORM 2.pdf

1171-kolnp-2007-form 3.pdf

1171-kolnp-2007-form 5.pdf

1171-KOLNP-2007-FORM-27.pdf

1171-kolnp-2007-gpa.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

abstract-01171-kolnp-2007.jpg


Patent Number 250103
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:
# Inventor's Name Inventor's Address
1 PEARCE, ROBERT EDMUND LISSINGTON ROAD, LINCOLN WICKENBY LINCOLNSHIRE LN3 5AB
PCT International Classification Number G01N 1/22
PCT International Application Number PCT/EP2005/056292
PCT International Filing date 2005-11-29
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 0426656.5 2004-12-04 U.K.