SPECIFICATION
Title of Invention
Gas analysis device and contamination detection method used in same
Technical 5 l Field
The present invention relates to a gas analysis device that can detect
whether or not contamination occurs in a flow path through which gas as a
measuring target flows.
10 Background Art
For example, a component such as NOX in exhaust gas emitted from
an internal combustion engine of an automobile is measured. In recent
years, in this sort of exhaust gas analysis device, analysis of adsorptive gas
such as NH3 that is a component other than NOX becomes increasingly
15 important.
Specific examples of measuring gas having adsorptivity, such as NH3,
include a scene of research and development of a urea SCR (Selective
Catalytic Reduction) system that can efficiently drive a diesel engine and
20 also suppress a production amount of NOX, and other scenes. To specifically
describe the urea SCR system, the urea SCR system is one that is configured
to, by spraying urea into high-temperature exhaust gas emitted from a diesel
engine, and as a reducing agent, supplying NH3 produced by pyrolysis of the
urea to an SCR catalyst, reduce NOX in the exhaust gas to change the NOX to
25 harmless N2 and H2O.
3
In the case where an excessive amount of urea is supplied in such a
urea SCR system, NH3 is contained in the exhaust gas to give rise to a bad
odor, or failure to meet environmental standards. For this reason, in order
to know whether or not an adequate amount of urea can be supplied in
various driving conditions, NH3 in the exhaust gas is 5 measured.
Meanwhile, differently from gas as a conventional measuring target,
such as NOX, in the case of the gas having adsorptivity, such as NH3, NH3 is
adsorbed on an inner wall or the like of a pipe before arriving at a gas
10 analyzing mechanism capable of measuring an amount of NH3, and therefore
it is difficult to measure an accurate value in real time. In particular, in the
case where due to soot and the like contained in exhaust gas, contamination
is attached on the inner wall or the like of the pipe, a response speed of the
gas measuring mechanism to such adsorptive gas is more deteriorated.
15
From the viewpoint of preventing a reduction in response speed, even
as a conventional exhaust gas analysis device, for example, as disclosed in
Patent Literature 1, there is one that is adapted to be provided with: a cell in
which nonadsorptive gas such as NO is measured; and a mechanism that
20 detects contamination in a flow path to the cell, and when contamination is
detected, appropriately perform cleaning or the like.
Specifically, this exhaust gas analysis device is one that is intended
to improve a response speed to the nonadsorptive gas such as NOX, and
25 therefore adapted to sense contamination on the basis that a large amount of
4
contamination is accumulated to narrow the flow path, and an inflow flow
rate of sample gas to the cell does not reach a specified value.
However, in the case of measuring gas having adsorptivity, even in
the case where a small amount of contamination is attached inside a 5 pipe
forming the flow path to change an area of a surface in contact with gas in
the pipe, an adsorption amount is significantly changed to give rise to a
reduction in response speed. That is, it is necessary to detect contamination
in an early stage more sensitively than the conventional contamination
10 detecting mechanism, and clean an inner surface.
Citation List
Patent Literature
15 Patent Literature 1: JP-A2002-310910
Summary of Invention
Technical Problem
20 The present invention is made in consideration of the problem as
described above, and intended to provide a gas analysis device provided with
a mechanism that can sensitively detect even a small amount of
contamination that significantly influences measurement of gas having
adsorptivity, and also a contamination detection method used for the gas
25 analysis device.
5
Solution to Problem
That is, the gas analysis device of the present invention is provided
with: a gas injecting mechanism that injects adsorptive injection gas into a
flow path through which sample gas is flowed; a gas measuring mechan5 ism
that can measure a value related to quantity of the adsorptive injection gas
flowing through the flow path; and a contamination determining part that
determines contamination in the flow path on the basis of a value related to a
measurement response speed of the gas measuring mechanism to the
10 adsorptive injection gas.
Also, the contamination detection method of the present invention is
a contamination detection method for a flow path through which sample gas
is flowed in a gas analysis device, and provided with: a gas injecting step of
15 injecting adsorptive injection gas into the flow path; a gas measuring step of
measuring a value related to quantity of the adsorptive injection gas flowing
through the flow path; and a contamination determining step of determining
contamination in the flow path on the basis of a value related to a
measurement response speed to the adsorptive injection gas in the gas
20 measuring step. Note that “determining contamination” is a concept
including not only determining whether the contamination such as soot is
present but also determining a level of the contamination. Also, the value
related to the measurement response speed to the adsorptive injection gas is
a concept including, for example, not only a response speed or a response
25 time, but calculating a response speed on the basis of a concentration value
6
of the injection gas, which is measured within a predetermined period of
time.
If so, the contamination determining part is configured to determine
contamination on the basis of the value related to the measurement respon5 se
speed of the gas measuring mechanism to the adsorptive injection gas that is
flowed through the flow path, and the measurement response speed to the
adsorptive injection gas is changed even in the case where a small amount of
contamination is present, so that the presence or absence of contamination
10 can be sensed more sensitively than before.
Accordingly, the flow path can be cleaned at an appropriate frequency
even in the presence of a small amount of contamination in adsorptive gas
measurement that is easily influenced by contamination, and therefore, for
15 example, within a predetermined reference range of measurement response
speed, gas having adsorptivity can be measured.
Specific aspects that make it possible for the contamination
determining part to sense even a small amount of contamination to, in
20 particular, favorably keep a response speed in adsorptive gas measurement
include an aspect in which: the flow path is formed in a gas pipe through
which the sample gas is flowed, and in a sampling pipe for sampling part of
the sample gas; and the gas measuring mechanism is provided in the
sampling pipe, and the contamination determining part is configured to
25 determine contamination on an inner surface of the sampling pipe on the
7
basis of the value related to the measurement response speed.
In order to make it possible to sense the presence or absence of
contamination throughout a measurement system to favorably keep a
response speed for a long period of time in adsorptive gas measurement, 5 ement, it is
only necessary that the gas injecting mechanism is configured to inject the
adsorptive injection gas into the gas pipe.
In order to make it possible to accurately detect even a small amount
10 of contamination in spite of a simple configuration, it is only necessary that
the contamination determining part is configured to determine that, in the
case where a response time necessary for at least a predetermined amount of
adsorptive injection gas to be measured by the gas measuring mechanism
after the adsorptive injection gas has been injected by the gas injecting
15 mechanism is equal to or more than a predetermined time, the
contamination is present in the flow path.
Advantageous Effects of Invention
As described, the present invention is configured to sense the
20 presence of absence of contamination with use of a reduction in response
speed, which is caused by the adsorption of the adsorptive injection gas on an
inner surface, and can therefore accurately detect even a small amount of
contamination. Accordingly, the flow path can be appropriately cleaned to
favorably keep a response speed in adsorptive gas measurement that is
25 influenced even by a small amount of contamination.
8
Brief Description of Drawings
[Fig. 1]
Fig. 1 is a schematic diagram illustrating a configuration of an
exhaust gas analysis device according to one embodiment of the pres5 ent
invention.
[Fig. 2]
Fig. 2 is a schematic graph illustrating a concentration change and a
response speed at the time of determining contamination in the same
10 embodiment.
[Fig. 3]
Fig. 3 is a schematic diagram that enlarges a region indicated by an
imaginary line in the schematic diagram of Fig. 1 and illustrates adsorption
and peeling states of NH3 on an inner surface.
15 [Fig. 4]
Fig. 4 is a graph illustrating a difference in response at the time of
measuring NH3 concentration between the same embodiment and a
conventional technique.
[Fig. 5]
20 Fig. 5 is a graph illustrating a difference in response at the time of
measuring minute NH3 concentration between the same embodiment and a
conventional technique.
[Fig. 6]
Fig. 6 is a graph illustrating results of verifying a relationship among
25 an injection gas amount, a rise time, and a fall time in the same embodiment.
9
Reference Signs List
100: Exhaust gas analysis device (gas analysis device)
11: Flow path
21: Gas 5 s measuring mechanism
3: Gas injecting mechanism
Description of Embodiments
10 One embodiment of the present invention is described with reference
to drawings.
A gas analysis device of the present embodiment is a so-called
exhaust gas analysis device 100, and is one that is used to measure the
concentration of NH3 contained in exhaust gas emitted from a diesel engine
15 mounted with a urea SCR system.
More specifically, as illustrated in Fig. 1, the gas analysis device 100
is one that is provided with: a gas pipe 1 through which the exhaust gas as
sample gas flows; a sampling pipe 2 for sampling part of the exhaust gas
20 from inside the gas pipe 1; a gas measuring mechanism 21 that has a
measuring point M in the sampling pipe 2 to measure the concentration of
the NH3 contained in the exhaust gas; a gas injecting mechanism 3 that
injects gas having the same component as a measuring target gas having
absorptivity in the gas pipe 1; and a control mechanism 4 that controls the
25 respective parts. In other words, the gas pipe 1 and the sampling pipe 2
10
form a flow path 11 through which the exhaust gas flows. In addition, a
region R surrounded by an imaginary line in Fig. 1 is one that indicates an
after-mentioned part enlarged in Fig. 3.
The respective parts are described5 .
The gas pipe 1 is a substantially cylindrically shaped, for example,
stainless steel pipe attached to an unillustrated muffler of an automobile,
and an inner surface thereof in contact with the exhaust gas is
10 surface-treated such as being electrolytically polished so as to prevent NOX,
soot, and the like from being easily attached. Also, the gas pipe 1 is adapted
such that most of the exhaust gas introduced into the gas pipe 1 is directly
led outside from an opening on a downstream side.
15 The sampling pipe 2 is a substantially thin cylindrically shaped
stainless steel pipe bent in an L-shape, and one end thereof is adapted to be
radially thrust to a central part of the gas pipe 1 and also opened inside the
gas pipe 1 to be able to sample the part of the exhaust gas. The sampling
pipe 2 is, sequentially from an upstream side, provided with an on/off valve
20 23, a suction pump 22, and the gas measuring mechanism 21. In the case of
measuring the concentration of NH3 gas in the exhaust gas, the on/off valve
is opened, and also the exhaust gas is sucked by the suction pump 22 so as to
flow into the sampling pipe 2 at a predetermined flow rate. In addition, an
inner surface of the sampling pipe 2 is also surface-treated by electrolytic
25 polishing or the like as with the gas pipe 1.
11
The gas measuring mechanism 21 is one that can simultaneously
measure concentrations of various components such as NOX, CO, CO2, and
carbon hydrides in addition to NH3 contained in the exhaust gas by FTIR
(Fourier Transform Infrared Spectroscopy), and configured to update an5 d
output the concentrations of the respective components measured at cyclic
intervals of, for example, 1 second. That is, concentration indicated values
of the various components contained in the exhaust gas can be updated in
substantially real time. In addition, the measuring point M of the gas
10 measuring mechanism 21 in the present embodiment corresponds to a place
where the gas measuring mechanism 21 is provided in the sampling pipe 2.
The gas injecting mechanism 3 is one that, as injection gas, injects
NH3 having adsorptivity among the measuring target components into the
15 gas pipe 1, and is provided with: a gas injecting pipe 34 of which one end is
connected to an injection gas source 31 where NH3 are accumulated, and the
other end is opened in the gas pipe 1; an on/off valve 33 that is provided in
the gas pipe 1; and a flow rate control valve 32. The gas injecting
mechanism 3 is adapted to keep supplying a predetermined amount of NH3
20 into the gas pipe 1 at least while the concentration of NH3 in the exhaust gas
is being measured by the gas measuring mechanism 21. Further, the gas
injecting mechanism 3 is also used for introducing zero gas and span gas for
NH3 to thereby perform calibration before measurement.
25 To describe in detail a position where the gas injecting pipe 34 is
12
opened in the gas pipe 1, the position where the injection gas is introduced is
set upstream of the measuring point M of the gas measuring mechanism 21.
More specifically, the position is located upstream of a place where the
sampling pipe 2 is opened in the gas pipe 1, and the other end of the gas
injection pipe 34 is opened near an opening on a side where the gas 5 pipe 1 is
attached to the muffler. That is, the present embodiment is configured such
that, substantially throughout the flow path 11 from the side where the
exhaust gas is introduced to the measuring point M, the NH3 gas can be
dispersed by the gas injecting mechanism 3. Further, in other words, in the
10 pipe located upstream of the measuring point M, the injecting position for
the injection gas is set such that an area of an inner surface in contact with
both of NH3 in the exhaust gas, which is the measuring target gas, and the
injection gas is larger than an area of an inner surface in contact with only
NH3 in the exhaust gas. For example, the injecting position is set such that
15 even in the case where adsorption takes place on the inner surface in contact
with only the NH3 in the exhaust gas, only an amount equal to or less than a
measurement limit of the gas measuring mechanism 21 is adsorbed.
The control mechanism 4 is a so-called computer provided with an
20 input/output interface, memory, CPU, A/D and D/A converters, and the like,
and configured to execute a program stored in the memory to thereby
perform control or the like of various valves, and fulfill a function as at least
a contamination determining part 41.
25 The contamination determining part 41 is configured to, on the basis
13
of a value related to a measurement response speed of the gas measuring
mechanism 21 to the adsorptive gas, determine the presence or absence of
contamination in the flow path 11. Specifically, the contamination
determining part 41 is one that determines that in the case where the
adsorptive gas of which concentration or a flow rate is known 5 is introduced
into the gas pipe 1 and the sampling pipe 2 by the gas injecting mechanism 3,
and the value related to the measurement response speed calculated from a
measured value outputted from the gas measuring mechanism 21 at the time
is lower than a predetermined specified value, at least an allowable amount
10 of contamination such as soot is attached on the inner surface in contact with
the flow path 11 through which the exhaust gas as the sample gas flows.
In the present embodiment, the contamination determining part 41
determines the contamination on the basis of a response time necessary to
15 transit from a state where no measurement is made as the value related to
the measurement response speed to a state where the value related to the
measurement response speed is stabilized at a predetermined value, and is
configured to determine that, in the case where the response time exceeds a
predetermined specified time, at least the allowable amount of
20 contamination is attached on the inner surface of the gas pipe 1 or sampling
pipe 2.
A series of operations at the time of measuring the NH3 gas, and the
like, in the exhaust gas analysis device 100 configured as described are
25 described.
14
First, operation performed by the contamination determining part 41
to sense contamination in the flow path 11 through which the exhaust gas
flows is described.
5
Before the gas measuring mechanism 21 starts to measure the NH3
in the exhaust gas, an output value from the gas measuring mechanism 21 is
calibrated with the zero gas and span gas injected by the gas injecting
mechanism 3. In addition, the present embodiment is adapted such that
10 while contamination is being sensed, the sample gas such as the exhaust gas
is not introduced into the gas pipe 1.
The contamination determining part 41 measures a response time tn
that is a time necessary for the concentration of the NH3 gas, which is
15 measured by the gas measuring mechanism 21, to be stabilized after the
span gas of which NH3 concentration is set to concentration near a full scale
of the gas measuring mechanism 21 has been injected into the gas pipe 1.
As illustrated here in Fig. 2, it turns out that the response time tn in
20 the presence of contamination is longer than a response time t0 in an initial
state where no contamination is present. This is because in the case where
contamination such as soot is attached inside the gas pipe 1 or sampling pipe
2, a surface area is increased correspondingly, and therefore a more amount
of adsorptive gas such as NH3 is adsorbed. Accordingly, even in the case
25 where the span gas is injected from the gas injecting mechanism 3, as an
15
amount of contamination is increased, an amount of NH3 gas to be trapped
increases, and therefore it takes time for an indicated value to reach the
concentration set for the span gas. That is, the contamination determining
part 41 senses the contamination with use of responsiveness of the gas
measuring mechanism 21, which is deteriorated by the adsorption 5 rption of the
adsorptive gas to the contamination. According to the contamination
determining part 41 configured as described, the contamination is sensed on
the basis of the adsorptivity of the NH3 that is adsorptive gas, and therefore
contamination that cannot be easily sensed on the basis of a parameter such
10 as a flow rate or another parameter, and particularly adversely influences
adsorptive gas measurement can be quickly sensed. The present
embodiment is configured to, in the case where contamination is sensed, for
example, automatically clean up the gas pipe 1 or sampling pipe 2 to be able
to improve a response speed of the gas measuring mechanism 21 in the NH3
15 measurement, and prevent a situation such as situation where inaccurate
calibration is performed in a state where the span gas is still adsorbed to
contamination, and subsequent measurement is continued in a state of
including a large error.
20 Next, operation and the like of each of the parts at the time of
measuring the concentration of the NH3 gas in the exhaust gas after the end
of the calibration are described. In addition, the present embodiment is
adapted to be able to, after the end of the calibration, supply NH3 as injection
gas to the gas pipe 1 and the sampling pipe 2 at concentration different from
25 that of the span gas by switching the injection gas source 31 to another
16
source. In doing so, the present embodiment is adapted to set the
concentration of the NH3 as the injection gas to a value such as a value equal
to or less than a half in a measurable range of the gas measuring mechanism
21, and even in the case where the exhaust gas-derived NH3 is further added,
prevent a concentration indicated value from being saturated 5 in the gas
measuring mechanism 21.
The gas injecting mechanism 3 starts to inject the NH3 as the
injection gas into the gas pipe 1 before the exhaust gas flows into the gas
10 pipe 1, i.e., in a state before the automobile starts the engine. In doing so,
the present embodiment is adapted to such that the suction pump 22
provided in the sampling pipe 2 also starts driving and thereby the injection
gas flows into the sampling pipe 2 as well. Then, as illustrated in Fig. 3(a),
after a saturation amount up to which NH3 is adsorbed on the inner surfaces
15 of the gas pipe 1 and sampling pipe 2 has been reached, the exhaust gas is
introduced. For example, after a predetermined time has passed since the
gas injecting mechanism 3 started to inject NH3, the exhaust gas may be
introduced, or in the case where gas concentration measured by the gas
measuring mechanism 21 is substantially stabilized at the concentration of
20 the gas injected by the gas injecting mechanism 3, the introduction of the
exhaust gas may be started.
The predetermined amount that is an amount of the injection gas
injected from the gas injecting mechanism 3 is set to at least the same
25 amount as an amount at which, as illustrated in Fig. 3(b), a total adsorption
17
amount of the adsorbing gas and the injection gas adsorbed on the inner
surface of the gas pipe 1 and a total peeling amount of the measuring target
gas and the injection gas peeled off from the inner surface of the gas pipe 1
are substantially equilibrated.
5
A change in gas concentration measured by the gas measuring
mechanism 21 during a period from the start to stop of the engine as
described is described by comparing a measurement result by a conventional
exhaust gas analysis device and a measurement result by the exhaust gas
10 analysis device 100 of the present embodiment with each other.
As illustrated in graphs of Fig. 4, in the case of using the
conventional exhaust gas analysis device, an NH3 concentration indicated
value does not indicate an actual concentration value immediately after the
15 start of the engine, and a delay in response occurs due to the adsorption of
NH3 on the inner surfaces of the pipes. After a while, the NH3
concentration indicated value is stabilized at the actual concentration value;
however, even though after the engine stop, the exhaust gas does not flow in,
NH3 peeled off from the inner surfaces is detected, and the concentration
20 indicated value gradually decreases.
On the other hand, according to the exhaust gas analysis device 100
of the present embodiment, the NH3 gas is started to be flowed as the
injection gas at a constant concentration value into the gas pipe 1 and the
25 sampling pipe 2 before the start of measurement, and therefore before the
18
introduction of the exhaust gas, the NH3 concentration indicated value is
brought into a state raised by a predetermined concentration indicated value.
Further, the NH3 concentration indicated value is in a state where the
adsorption of NH3 on the inner surfaces and the peeling off of the NH3 from
the inner surfaces are equilibrated as illustrated in Fig. 3(b), 5 , and therefore
even if the exhaust gas-derived NH3 is adsorbed on the inner surfaces,
substantially the same amount of NH3 is peeled off from the inner surfaces
instead. Accordingly, the response delay due to the adsorption hardly
occurs, and therefore the concentration indicated value outputted by the gas
10 measuring mechanism 21 can reproduce an actual concentration change
derived from the exhaust gas in substantially real time.
Next, not the case where a large amount of exhaust gas-derived NH3
flows in as described above, but the case where NH3 is outputted only by a
15 minute amount in the case where, for example, the engine is cold started, or
in another case is described by comparing a measurement result by the
conventional exhaust gas analysis device and that by the exhaust gas
analysis device 100 of the present embodiment with each other.
20 As illustrated in graphs of Fig. 5(a), in the case where a minute
amount of NH3 flows into the exhaust gas analysis device 100 immediately
after the start of measurement, in the conventional case, the NH3 is entirely
adsorbed on the inner surfaces of the gas pipe 1 and sampling pipe 2, and
therefore the gas measuring mechanism 21 cannot even detect the NH3.
25 Further, even after a predetermined time has passed since the engine start,
19
phenomena such as outputting a smaller value than actual NH3
concentration and inconformity in response waveform occur, and then an
actual value and a measured value coincide with each other to lead to
stabilization. Also, after the engine stop, NH3 is supposed to be undetected;
however, NH3 adsorbed to the gas pipe 1 and sampling pipe 2 is gradua5 lly
peeled off, and therefore a concentration indicated value is gradually reduced
to make it impossible to reproduce an actual waveform. In other words, the
conventional case is disadvantageous in that, in addition to being unable to
perform measurement in real time, information on time is missing in a
10 measured value obtained by the measurement.
On the other hand, the present embodiment is adapted to start
injecting the injection gas before the engine start to saturate an NH3
adsorption amount on the inner surfaces, and therefore even in the case
15 where there is a minute amount of exhaust gas-derived NH3 after the engine
start, the NH3 is not adsorbed on any of the inner surfaces, or even in the
case where the NH3 is adsorbed, substantially the same amount of NH3 is
peeled off from the inner surfaces. Accordingly, as illustrated in Fig. 5(b),
even in the case where there is a minute amount of exhaust gas-derived NH3
20 immediately after the start of measurement, NH3 can be accurately detected
to measure the concentration of the NH3. That is, in the conventional case,
an erroneous determination that NH3 is not emitted in the first place tends
to be made; however, even a minute amount of NH3 can be accurately
measured in real time without losing information on emission time. For
25 this reason, knowledge that has not been obtained in the past can be
20
obtained from exhaust gas measurement to further contribute to
development of the urea SCR system.
Further, with reference to Fig. 6, results of actually measuring a rise
time and fall time at the time of measuring NH3 in the exhaust gas 5 analysis
device 100 of the present embodiment are described. In the actual
measurement, a response speed in the gas measuring mechanism 21 was
evaluated under the conditions that a known amount of NH3 was introduced
from an inlet side of the gas pipe 1 in a step input manner with a
10 predetermined amount of NH3 as the injection gas being flowed from the gas
injecting mechanism 3. As illustrated in Fig. 6(a), measurements were
made respectively for the cases of (1) without injecting NH3 from the gas
injecting mechanism 3, introducing NH3 into the gas pipe 1, (2) keeping
injecting 13 ppm NH3 from the gas injecting mechanism 3 as well as
15 introducing NH3 into the gas pipe 1, and (3) keeping injecting 23 ppm NH3
from the gas injecting mechanism 3 as well as introducing NH3 into the gas
pipe 1.
It is clear from an enlarged view of a rising period in Fig. 6(b) and an
20 enlarged view of a falling period in Fig. 6(c), rise and fall times under the
experimental conditions (1), (2), and (3) were respectively 26 seconds, 6
seconds, and 2 seconds. That is, it turns out that as an amount of injection
gas is increased to bring NH3 closer to the saturation amount up to which
NH3 is adsorbed on the inner surfaces, the rise and fall times tend to be
25 shorter. Also, it is verified that as with the exhaust gas analysis device of
21
the present embodiment, by measuring NH3 in the exhaust gas with keeping
flowing NH3 from the gas injecting mechanism 3, NH3 measurement
responsiveness of the gas measuring mechanism 21 can be improved.
Other embodiments are describe5 d.
In the above-described embodiment, the exhaust gas analysis device
is taken as an example to describe the gas analysis device of the present
invention; however, the gas analysis device may be one that measures
10 another gas as the sample gas. Also, as the measuring target gas having
adsorptivity, NH3 is taken as an example; however, another adsorptive gas
such as HCl or a hydrocarbon (HC) is also possible. Examples of the
hydrocarbon include aromatic hydrocarbons such as toluene, alcohols such as
methanol and ethanol, high-boiling HCs, and the like. Further, examples of
15 gas having high adsorptivity include polar gases such as NO2, SO2, and H2O.
The predetermined amount may be set not only to the amount at
which the equilibrium state between the adsorption and the peeling off can
be retained, but such that a value related to quantity of the injection gas,
20 which is indicated by the gas measuring mechanism, is equal to or less than
an allowable difference. Note that the allowable difference is one that, for
example, represents a preliminarily allowable error amount with respect to a
full scale measurable by some measuring instrument, and is specifically
represented by a numerical value such as approximately a few % of the full
25 scale. That is, by making an injection gas-derived concentration indicated
22
value equal to or less than an error of a concentration measured value, which
is allowed by the gas measuring mechanism, while keeping the equilibrium
state, a sufficiently accurate value can be known with little narrowing a
measurement range and even without performing an operation such as
subtracting an injection gas-derived concentration value from a value that 5 at is
obtained in order to know an exhaust gas-derived concentration value.
The contamination determining part is configured to sense the
presence or absence of contamination on the basis of the response time that
10 is a value related to the measurement response speed to the absorptive gas;
however, another related value such as a change rate at the time of changing
from some measured value indicated by the gas measuring mechanism to
another measured value may be used. That is, the contamination
determining part may be one that makes a determination on the basis of a
15 concentration value measured within a predetermined period of time. In
the above-described embodiment, the span gas is injected by the gas injecting
mechanism, and concentration to be actually measured is formed in a step
shape; however, a measured value may be variously changed in a manner
such as a rectangular wave, sine wave, or pulse-shaped manner. For
20 example, in the case where the gas measuring mechanism is adapted to
measure a pulse-shaped change, the contamination determining part may
determine the presence or absence of contamination on the basis of a period
of time necessary for the adsorptive gas to be actually detected by the gas
measuring mechanism after the adsorptive gas has been injected by the gas
25 injecting mechanism. Also, a place where the adsorptive injection gas is
23
injected by the gas injecting mechanism is anywhere as long as the place is
located in the flow path through which the sample gas flows, and upstream
of the measuring point M of the gas measuring mechanism, and for example,
the present invention may be adapted to inject the adsorptive injection gas
into the sampling pipe. Further, the contamination determining part ma5 y
be one that not only senses the presence or absence of contamination but
determines a level of the contamination on the basis of a measured value.
Further, the contamination determining part may be configured to
10 determine that, in the case where a response time to nonadsorptive gas is
obtained, and the response time to the adsorptive gas and the response time
to the nonadsorptive gas are substantially the same, maintenance of the
suction pump is necessary, or leakage occurs, and in the case where only the
response time to the adsorptive gas is longer, contamination is present in the
15 flow path through which the measuring target gas flows. For example, in
the case where contamination is present, the response time to the adsorptive
gas is deteriorated and increased due to a change in surface area inside the
pipes, whereas even in the case where the surface area is changed, the
nonadsorptive gas is not significantly influenced, and the response time is
20 little changed. On the other hand, in the case where the suction pump has a
trouble, the response times to both of the adsorptive gas and the
nonadsorptive gas are longer because it takes longer times for both of the
gases to arrive at the gas measuring mechanism. As described, by
comparing the response times to the adsorptive and nonadsorptive gases
25 with each other, the contamination determining part can exactly determine
24
causes for two different response delays. In the case of employing such a
configuration, the gas measurement device is preferably one that can
simultaneously measure multi-component gas, and specific examples of the
nonadsorptive gas include CO, CO2, NO, N2O, and the like.
5
Also, the contamination determining part is not one used only for the
exhaust gas analysis device but may be one used for another gas analysis
device.
10 In addition, the gas measuring mechanism is one that can measure
multi-component gas by the FTIR, but may be one that can measure only
another adsorptive gas. Specifically, the gas measuring mechanism may be
one that can measure only adsorptive gas such as NH3 as with NDIR or laser
measurement. Also, a value measured by the gas measuring mechanism is
15 not limited to concentration, but may be a value related to quantity of
adsorptive gas, such as a flow rate or volume. In addition, the measuring
point of the gas measuring mechanism is not in the sampling pipe but may
be provided in the gas pipe. In short, it is only necessary that the present
invention is adapted such that the injection gas injected from the gas
20 injecting mechanism flows together with the measuring target gas from
upstream of the measuring point.
Also, the gas measuring mechanism is placed downstream of the
suction pump in the above-described embodiment; however, for example, the
25 gas measuring mechanism may be placed upstream of the suction pump.
25
Even in the case of employing a so-called reduced pressure flow configuration
as described, the same effects on contamination sensing and measurement of
measuring target gas having adsorptivity as those described above can be
obtained.
5
Besides, it should be appreciated that unless contrary to the scope of
the present invention, various combinations and modifications of the
embodiments may be made.
Industrial Applicability
10
As described, the present invention is configured to sense the
presence or absence of contamination with use of a reduction in response
speed, which is caused by the adsorption of the adsorptive injection gas on
the inner surfaces, and can therefore accurately detect even a small amount
15 of contamination. Accordingly, the flow path can be appropriately cleaned
to preferably keep a response speed in adsorptive gas measurement that is
influenced even by a small amount of contamination. From these, applying
the present invention enables an accurate exhaust gas analysis device to be
provided.
20
26
We Claim:-
1. A gas analysis device (100) comprising:
a gas injecting mechanism (3) that injects adsorptive injection gas
into a flow path (11) through which sample gas is flowed;
a gas measuring mechanism (21) that can measure a value 5 lue related to
quantity of the adsorptive gas flowing through the flow path (11); and
a contamination determining part that determines contamination in
the flow path (11) on a basis of a value related to a measurement response
speed of the gas measuring mechanism (21) to the adsorptive gas.
10
2. The gas analysis device (100) as claimed in claim 1, wherein:
the flow path (11) is formed in a gas pipe through which the sample
gas is flowed, and in a sampling pipe for sampling part of the sample gas;
and the gas measuring mechanism (21) is provided in the sampling pipe, and
15 the contamination determining part is configured to determine
contamination on an inner surface of the sampling pipe on a basis of the
value related to the measurement response speed.
3. The gas analysis device (100) as claimed in claim 2, wherein
20 the gas injecting mechanism (3) is configured to inject the adsorptive
injection gas into the gas pipe.
4. The gas analysis device (100) as claimed in claim 1, wherein
the contamination determining part is configured to determine that,
25 in a case where a measurement response time necessary for at least a
27
predetermined amount of adsorptive gas to be measured by the gas
measuring mechanism (21) after the adsorptive injection gas has been
injected by the gas injecting mechanism (3) is equal to or more than a
predetermined time, the contamination is present in the flow path.
5
5. A contamination detection method for a flow path (11) through
which sample gas is flowed in a gas analysis device, the contamination
detection method comprising:
a gas injecting step of injecting adsorptive injection gas into the flow
10 path (11);
a gas measuring step of measuring a value related to quantity of the
adsorptive gas flowing through the flow path (11); and
a contamination determining step of determining contamination in
the flow path (11) on a basis of a value related to a measurement response
15 speed to the adsorptive gas in the gas measuring step.