SPECIFICATIONS
NAME OF THE INVENTION: Adsorbent Gas Analysis Device and Adsorbent Gas
Analysis Method
5
FIELD OF THE ART
This invention relates to an adsorbent gas analysis device for measuring a value
relating to a volume of a measurement object gas having an adsorbent characteristic.
10 BACKGROUND ART
For example, a component such as NOx in an exhaust gas emitted from an inside
combustion engine of an automobile is measured. Recently, for this kind of the exhaust gas
analysis device, importance becomes high in analyzing a gas having an adsorbent
characteristic such as NH3 as being a component other than NOx.
15 As a concrete example to measure the gas having the adsorbent characteristic such
as NH3 represented is a scene of the research and development of the urea SCR (Selective
Catalytic Reduction) system that can both drive a diesel engine at high efficiency and reduce a
volume of NOx generation. The urea SCR system will be concretely explained. Urea is
sprayed into the exhaust gas at high temperature emitted from the diesel engine and NH3 that
20 generates due to thermal decomposition of urea is supplied to the SCR catalyst as a reducing
agent so that NOx in the exhaust gas is reduced and changed to harmless N2 or H2O.
If urea is supplied excessively in the above-mentioned urea SCR system, NH3 is
contained in the exhaust gas so that bad odor is given off or it fails to meet the environmental
standard. As a result of this, NH3 is measured in the exhaust gas in order to know whether
25 urea is supplied properly under various driving conditions or not.
However, unlike the conventional measurement object gas such as NOx, in case of
the adsorbent gas such as NH3, the adsorbent gas is adsorbed onto the inside wall of the pipe
until the gas reaches the gas analysis mechanism that can measure the volume of NH3 so that
it is difficult to measure an accurate value on a real time basis.
3
If explained in more detail, for an exhaust gas analysis device 100A as shown in Fig.
7 (a) comprising a sampling pipe 2A that samples a part of an exhaust gas flowing in a gas
pipe 1A and a concentration sensor 21A that is arranged on the sampling pipe 2A and that
measures a concentration of NH3, it is necessary to flow the exhaust gas from, for example, a
muffler of an automobile to the concentration sensor 21A. At a time when the exhaust 5 t gas
initiates flowing, since NH3 is adsorbed on the inside surface of the gas pipe 1A or the
sampling pipe 2A as shown in Fig. 7 (b) as being an enlarged view of an area (R) in Fig. 7 (a),
a concentration value that is lower than the concentration value of the gas that actually flows is
output as shown by the graph in Fig. 8. A short time later, the concentration value that is
10 substantially the same as the concentration of NH3 that actually flows is measured as shown in
Fig. 7 (c) and by the graph in Fig. 8, however, in case of ceasing the exhaust gas flowing in,
since the NH3 that is adsorbed on the inside wall surface is exfoliated as shown in Fig. 7 (d),
the concentration of NH3 as shown by a graph in Fig. 8 is measured even though no exhaust
gas actually flows so that NH3 is not supposed to be detected.
15 As mentioned above, since the adsorbent gas such as NH3 is adsorbed on the inside
surface of the pipe where the exhaust gas flows, there is a time lag between the concentration
of NH3 that actually flows and the concentration indicated value of measured NH3 so that it is
not possible to measure the concentration on a real time basis. In other words, the response
speed of the exhaust gas analysis device is not sufficient concerning the adsorbent gas such as
20 NH3.
In addition, when the adsorbent gas such as NH3 is measured, a part of the area (S1)
in Fig. 7 that should be measured at a time of beginning the measurement appears as the area
(S2) in Fig. 7 at a time of just before the end of the measurement. As a result of this, there is
also a problem that a part of the information concerning the time when NH3 is emitted lacks.
25 In order to improve the response speed of an ammonia analysis device, the patent
document 1 discloses that an alkali process is provided by immersing an inside surface of the
sampling pipe in a NaOH solution so as not to adsorb NH3 on the inside surface. However,
in spite of the alkali process, if, for example, sooth in the exhaust gas attaches the inside
surface of the pipe, a part where no alkali process is provided generates and NH3 is adsorbed
4
on this part. In other words, in consideration of a continuous measurement, it is not possible
for the method disclosed in the patent document 1 to solve the problem concerning the
response delay in measuring the adsorbent gas.
PRIOR ART DOCUMEN5 T
PATENT DOCUMENT
Patent document 1: Japanese unexamined patent application publication No. 2000-155115
DISCLOSURE OF THE INVENTION
10 PROBLEMS TO BE SOLVED BY THE INVENTION
The present claimed invention intends to solve all of the problems and a main object
of this invention is to provide an adsorbent gas analysis device that makes it possible to
measure a gas having adsorbent characteristic under various conditions on a real time basis by
decreasing a response delay in measuring the gas having the adsorbent characteristic.
15 MEANS TO SOLVE THE PROBLEMS
More specifically, the adsorbent gas analysis device of this invention is characterized
by comprising a gas measurement mechanism that measures a value relating to a volume of a
measurement object gas that has adsorptivity and that flows in a gas pipe, and a gas injection
mechanism that injects a predetermined volume of the adsorbent injection gas into the gas
20 pipe from a point that locates in an upstream side of a measurement point where the gas
measurement mechanism measures the measurement object gas at least while the gas
measurement mechanism is measuring the measurement object gas.
In addition, an adsorbent gas measuring method of this invention is characterized by
comprising a gas measurement step that measures a value relating to a volume of a
25 measurement object gas that has adsorptivity and that flows in a gas pipe, and a gas injection
step that injects a predetermined volume of the adsorbent injection gas into the gas pipe from a
point that locates in an upstream side of a measurement point where the measurement object
gas is measured in the gas measurement step at least while the measurement object gas is
measured.
5
In accordance with this arrangement, it is possible to make the measurement object
gas not to contact the inside wall surface directly and difficult to be adsorbed on the inside wall
surface by injecting the injection gas having adsorptivity into the gas pipe and by making the
injection gas adsorbed on the wall surface of the gas pipe at least at a time of measuring the
measurement object gas having adsorptivity5 .
Furthermore, even though contamination such as soot attaches to the inside of the
gas pipe that is coated with the injection gas, a layer where the newly injected injection gas
injected by the gas injection mechanism is adsorbed on a surface of the contamination is
immediately formed.
10 If the alkali process alone is provided for the inside of the gas pipe like a
conventional art, the effect such that the measurement object gas is prevented from being
adsorbed on the gas pipe decreases due to the newly generated contamination like soot.
However, with the above-mentioned arrangement, it is possible to prevent the measurement
object gas from adsorbing in the gas pipe because a new coating is formed on a constant basis
15 by the injection gas.
Consequently, since a new coating is formed on the inside surface of the gas pipe on
a constant basis by continuously flowing the injection gas in the gas pipe at least at a time of
measuring the measurement gas, it is possible to prevent the measurement error or the
response delay of the measurement object gas due to the adsorption of the injection gas.
20 In order to further decrease a measurement error or a response delay in measuring
the measurement object gas, it is preferable that the injection gas is a gas whose composition is
the same as that of the above-mentioned measurement object gas and that can be measured by
the gas measurement mechanism.
In accordance with this arrangement, it is possible to make inside of the gas pipe in a
25 state more than or equal to a saturation volume wherein the injection gas and the measurement
object gas can be adsorbed and to keep the equilibrium state regarding the adsorption of the
gas on the wall of the gas pipe by adjusting the injection volume of the injection gas. In other
words, even though the measurement object gas is adsorbed on the inside wall of the gas pipe,
since the same amount of the injection gas as that of the measurement object gas that is
6
adsorbed on the wall is immediately exfoliated from the wall and flows into the gas analysis
device, it is possible to prevent a fluctuation of the volume due to adsorption measured by the
gas analysis device.
As mentioned, since the equilibrium state regarding the measurement object gas and
the injection is kept in the gas pipe, it is possible to prevent the loss of the measuremen5 t
volume or the response delay that is caused by that the measurement object gas having the
adsorptivity is adsorbed and remains on the inside surface of the gas pipe. At this time, if the
volume of the injection gas injected by the gas injection mechanism is subtracted from the
volume measured and indicated by the gas measurement device, it is possible to calculate the
10 volume of the measurement object gas accurately at a time when the measurement object gas
flows in the gas pipe.
In other words about the action and the effect of the above-mentioned arrangement,
the arrangement of the adsorbent gas analysis device is not to completely prevent the
measurement object gas having the adsorptivity from being adsorbed on the inside surface of
15 the gas pipe but to conduct the measurement of the volume to be measured as the
measurement object gas alone based on the volume of the measurement object gas that
reaches the measurement point without being adsorbed on the inside surface of the gas pipe
and the volume of the measurement object gas or the injection gas that is exfoliated from the
inside surface of the gas pipe instead of the measurement object gas that is adsorbed on the
20 inside surface of the gas pipe. As a result of this, it is possible to measure the measurement
object gas accurately on a real time basis without causing the response delay regarding a value
relating to the volume of the adsorbent gas.
Furthermore, even though contamination such as soot attaches to the inside of the
gas pipe, since the layer that adsorbs the injection gas is formed on a surface of the
25 contamination so that the equilibrium is substantially kept. It is possible to prevent the
response delay due to adsorption of the injection gas.
As a concrete example of the injection volume of the injection gas not to produce
the response delay as much as possible, it is represented that the above-mentioned
predetermined volume is set as equal to or more than a volume wherein an adsorption volume
7
of the measurement object gas and the injection gas that is adsorbed on an inside surface of the
gas pipe is substantially equilibrium to an exfoliated volume of the measurement object gas
and the injection gas that is exfoliated from the inside surface of the gas pipe.
When calculating a volume of the measurement object gas that flows in the gas pipe,
in order to make it possible to calculate a generally accurate value easily without conductin5 g
an operation of subtracting the volume of the injection gas, it is preferable that the
predetermined volume is set so as to make the value relating to the volume of the injection gas
indicated by the gas measurement mechanism equal to or less than an allowable difference.
10 EFFECT OF THE INVENTION
As mentioned, in accordance with the adsorbent gas analysis device of this
invention, since the measurement object gas having adsorptivity is measured while injecting
the adsorbent injection gas in the gas pipe by means of the gas injection mechanism, it is
possible to immediately form a coating with a new injection gas even though there is
15 contamination such as soot so that the measurement object gas is difficult to be adsorbed
oiiiiuu8n the inside surface of the gas pipe on a constant basis. As a result of this, it is
possible to prevent the measurement error or the response delay of the measurement object
gas.
20 BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a pattern diagram showing a configuration of an exhaust gas analysis
device in accordance with one embodiment of this invention.
Fig. 2 is a pattern graph showing a concentration change and a response speed at a
time of judging contamination in this embodiment.
25 Fig. 3 is a pattern diagram showing an enlarged view of an area indicated by an
imaginary line in the pattern diagram in Fig. 1 and showing adsorbed and exfoliated states of
NH3 on the inside surface.
Fig. 4 is a graph showing a difference of a response at a time of measuring a
concentration of NH3 between this embodiment and a conventional art.
8
Fig. 5 is a graph showing a difference of a response at a time of measuring a small
value of a concentration of NH3 between this embodiment and a conventional art.
Fig. 6 is a graph showing a verified result of a relationship between a volume of an
injection gas, a rise time and a fall time in this embodiment.
Fig. 7 is a pattern diagram showing a configuration of a conventional exhaust ga5 s
analysis device and a change of the adsorbed state of NH3 in an area indicated by an
imaginary line.
Fig. 8 is a pattern diagram showing a response characteristic in measuring a
concentration of NH3 by the conventional exhaust gas analysis device.
10
EXPLANATION OF CODES
100 … exhaust gas analysis device (adsorbent gas analysis device)
1 … gas pipe
21 … gas measurement mechanism
15 3 … gas injection mechanism
BEST MODES OF EMBODYING THE INVENTION
One embodiment of this invention will be explained with reference to drawings.
An adsorbent gas analysis device of this embodiment is, so called, an exhaust gas
20 analysis device 100 and is used for measuring a concentration of NH3 contained in an exhaust
gas emitted from a diesel engine on which urea the SCR (Selective Catalytic Reduction)
system is loaded.
More concretely, the adsorbent gas analysis device 100 comprises, as shown in Fig.
1, a gas pipe 1 where an exhaust gas as being a sample gas flows, a sampling pipe 2 that
25 samples a part of the exhaust gas from inside of the gas pipe 1, a gas measurement mechanism
21 that has a measurement point (M) in the sampling pipe 2 and that measures the
concentration of NH3 contained in the exhaust gas, a gas injection mechanism 3 that injects a
gas whose composition is the same as that of a measurement object gas having adsorptivity
into inside of the gas pipe 1, and a control mechanism 4 that controls each members. In
9
other words, a flow channel 11 where the exhaust gas flow is formed by the gas pipe 1 and the
sampling pipe 2. An area (R) surrounded by an imaginary line in Fig. 1 indicates a part
enlarged in Fig. 3, to be described later.
Each member will be explained.
The gas pipe 1 is, for example, a stainless pipe whose shape is a general cylinde5 r
mounted on a muffler of an automobile, not shown in drawings, and a surface finish such as
an electrolytic grinding is provided on an inside surface that makes a contact with the exhaust
gas so as not to attach NOx or soot. In addition, almost all of the exhaust gas introduced into
the gas pipe 1 is discharged from an opening locating in the downstream side to the outside as
10 it is.
The sampling pipe 2 is of a stainless pipe whose shape is an L-shaped general
cylinder, and one end of the sampling pipe 2 thrusts a center part of the gas pipe 1 in a radial
direction and opens inside of the gas pipe 1 so as to make it possible to sample a part of the
exhaust gas. An open/close valve 23, a suction pump 22 and a gas measurement mechanism
15 21 are arranged on the sampling pipe 2 in this order from the upstream. In case of measuring
a concentration of the NH3 gas in the exhaust gas, the open/close valve 23 is open and a
predetermined flow rate of the exhaust gas is sucked so as to be introduced into inside of the
sampling pipe 2 by the sucking pump 22. Similar to the gas pipe 1, a surface finish such as
an electrolytic grinding is provided for the sampling pipe 2 on an inside surface that makes a
20 contact with the exhaust gas so as not to attach NOx or soot.
The gas measurement mechanism 21 can measure a concentration of various
components such as NOx, CO, CO2, hydrocarbons or the like in addition to NH3 contained in
the exhaust gas at once by means of, for example, FTIR (Fourier Transform Infrared
Spectroscopy), and updates and outputs the concentration of each component measured in, for
25 example, one second cycle. In other words, it is possible to update an indicating value of the
concentration of various components contained in the exhaust gas generally on a real-time
basis. The measurement point (M) of the gas measurement mechanism 21 in accordance
with this embodiment corresponds to a place where the gas measurement mechanism 21 is
arranged on the sampling pipe 2.
10
The gas injection mechanism 3 is to inject the adsorbent NH3 gas among
components as being the measurement object into the gas pipe 1 as the injection gas, and
comprises a gas injection pipe 34 whose one end is connected with an injection gas source 31
where NH3 is stored and whose other end opens inside of the gas pipe 1, an open/close valve
33 arranged on the gas pipe 1 and a flow rate control valve 32. The gas injection mechanis5 m
3 is so configured to keep supplying the predetermined volume of NH3 to inside of the gas
pipe 1 at least while the concentration of NH3 in the exhaust gas is measured by the gas
measurement mechanism 21. In addition, the gas injection mechanism 3 is also used in case
of conducting a correction prior to the measurement by introducing a zero gas and a span gas
10 of NH3.
The position where the gas injection pipe 34 opens in the inside of the gas pipe 1
will be described in detail. The position where the injection gas is introduced is set at a
position that is the upstream side of the measurement point (M) of the gas measurement
mechanism 21. More specifically, one end of the gas injection pipe 34 opens at a position
15 that locates in the upstream side of a place where the sampling pipe 2 opens inside of the gas
pipe 1 and that is near an opening on a side where the gas pipe 1 is mounted on a muffler.
More specifically, the gas injection pipe 34 is so configured that NH3 gas can be sprayed over
almost all area from the point where the exhaust gas is introduced to the measurement point
(M). In other words, the position where the injection gas is injected is so set that an area
20 where both NH3 in the exhaust gas as being the measurement object gas and the injection gas
contact the inside surface of the pipe locating in the upstream side of the measurement
position (M) is sufficiently larger than an area with which only NH3 in the exhaust gas
contacts. For example, it is so set that only a volume that is equal to or less than a
measurement limit of the gas measurement mechanism 21 is adsorbed even though
25 adsorption generates in the inside surface with which only NH3 in the exhaust gas contacts.
The control mechanism 4 is, so called, a computer comprising an input/output
interface, a memory, a CPU, an A/D converter and a D/A converter or the like, and produces
functions as controlling various valves or at least as a contamination judging part 41 by
executing programs stored in the memory.
11
The contamination judging part 41 judges whether there is contamination or no not
in the flow channel 11 based on a value relating to a response speed in case that the gas
measurement mechanism 21 detects the adsorbent gas. Concretely, an adsorbent gas
(injection gas) whose concentration or flow rate is known is introduced into the gas pipe 1 and
the sampling pipe 2 by means of the gas injection mechanism 3. In case that the valu5 e
relating to the response speed calculated from a measurement value output by the gas
measurement mechanism 21 is made worse than a previously determined specified value, it is
judged that contamination such as soot attaches by a volume equal to or more than an
allowable volume by the inside surface that contacts with the flow channel 11 where the
10 exhaust gas as being the sample gas flows.
In this embodiment, the contamination judging part 41 judges the contamination
based on a response time taken from a time when no value is detected as a value relating to the
response speed to a time when the value is stabilized at a predetermined value. In case that
the response time exceeds the previously determined specified time, the contamination
15 judging part 41 judges that contamination attaches to the inside surface of the gas pipe 1 or the
sampling pipe 2 by a volume equal to or more than the allowable volume.
At a time of measuring the NH3 gas, a continuous operation of the exhaust gas
analysis device 100 having the above-mentioned arrangement will be explained.
First, the operation of the contamination judging part 41 for detecting the
20 contamination in the flow channel 11 where the exhaust gas flows will be explained.
Correction of an output value of the gas measurement mechanism 21 is conducted
by the zero gas and the span gas injected by the gas injection mechanism 3 prior to initiation of
the measurement of the NH3 in the exhaust gas by the gas measurement mechanism 21. The
sample gas such as the exhaust gas is not introduced into inside of the gas pipe 1 while the
25 contamination is detected.
The contamination judging part 41 measures the response time (tn) as being a time
period that is taken from a time when the span gas in which NH3 concentration is set around a
full scale of the gas measurement mechanism 21 is injected into the gas pipe 1 to a time when
the concentration change of the NH3 gas measured by the gas measurement mechanism 21is
12
stabilized.
As shown by a graph in Fig. 2, the response time (tn) in case that there is
contamination is turned out to be longer than the response time (t0) in an initial state with no
contamination. This indicates that when contamination such as soot attaches to the inside of
the gas pipe 1 or the sampling pipe 2, a surface area of the inside of the gas pipe 1 or th5 e
sampling pipe 2 increases accordingly so that much more volume of the adsorbent gas such as
NH3 is adsorbed. As a result of this, even though the span gas is injected from the gas
injection mechanism 3, if the contamination increases, a volume of the trapped NH3 gas
increases so that it takes time for the indicating value to reach the concentration set for the span
10 gas. In other words, the contamination judging part 41 detects the contamination by the use
of a matter that the responsiveness of the gas measurement mechanism 21 is aggravated
because the adsorbent gas is adsorbed on the contamination. In accordance with the
contamination judging part 41 having the above-mentioned arrangement, since the
contamination is detected based on the adsorbent characteristics of the NH3 gas as being the
15 adsorbent gas, it becomes possible to immediately detect the contamination that is difficult to
detect depending on the flow rate or other parameter and that exerts a bad influence especially
on the measurement of the adsorbent gas. In case that the contamination is detected, the gas
pipe 1 or the sampling pipe 2 is automatically cleaned up so that it is possible to improve the
response speed of the gas measurement mechanism 21 in measuring the NH3 gas or to prevent
20 a situation that the measurement is continued while the measurement includes a big error after
an incorrect correction is conducted in a state that the span gas is adsorbed on the
contamination.
Next, an operation of each part in measuring the concentration of the NH3 gas in the
exhaust gas after completion of the correction will be explained. The NH3 gas whose
25 concentration is different from that of the span gas can be supplied to the gas pipe 1 and the
sampling pipe 2 as the injection gas by switching the injection gas source 31 to the other gas
source after completion of the correction. In this case, the concentration of the NH3 gas as
the injection gas is so set to be a value that is, for example, equal to or less than a half in the
measurable range of the gas measurement mechanism 21 so as not to saturate the
13
concentration indicated value in the gas measurement mechanism 21 even though the NH3
gas derived from the exhaust gas is furthermore added.
The gas injection mechanism 3 initiates injection of the NH3 gas as being the
injection gas to the gas pipe 1 from a state before the exhaust gas flows into the gas pipe 1, in
other words, before an automobile starts an engine. In this case, a suction pump 22 arrang5 ed
on the sampling pipe 2 also initiates driving, and the injection gas flows also in the sampling
pipe 2. As shown in Fig. 3 (a), the exhaust gas is introduced after the volume of NH3 reaches
a saturation volume wherein the NH3 is adsorbed on the inside surface of the gas pipe 1 and
the sampling pipe 2. For example, the exhaust gas may be introduced when a predetermined
10 time period has passed after the gas injection mechanism 3 initiates injection of the NH3, or
introduction of the exhaust gas may be initiated in case that the gas concentration measured by
the gas measurement mechanism 21 is substantially stabilized at the gas concentration injected
by the gas injection mechanism 3.
As shown in Fig. 3 (b), the above-mentioned predetermined volume as being the
15 volume of the injection gas injected by the gas injection mechanism 3 is set at a volume that is
equal to or more than a volume where an adsorbent volume of the adsorbent gas and the
injection gas that are adsorbed on the inside surface of the gas pipe 1 is in equilibrium with an
exfoliated volume of the measurement object gas and the injection gas that exfoliate from the
inside surface of the gas pipe 1.
20 The change of the gas concentration measured by the gas measurement mechanism
21 during a period from initiation of the engine to halt of the engine will be explained with
comparing a measurement result obtained by a conventional exhaust gas analysis device and a
measurement result obtained by the exhaust gas analysis device 100 of this embodiment.
As shown by a graph in Fig. 4, in case that the conventional exhaust gas analysis
25 device is used, it is not immediately after the start of the engine that an actual concentration
value is indicated and but response delay generates because the NH3 is adsorbed on the inside
surface of the pipe. After a while, the concentration value is stabilized at the actual
concentration value. However, after halt of the engine, although no exhaust gas flows, the
NH3 that is exfoliated from the inside surface of the pipe is detected so that the concentration
14
indicated value gradually drops.
Meanwhile, in accordance with the exhaust gas analysis device 100 of this
embodiment, since the NH3 gas as being the injection gas flows at a constant concentration
value in the gas pipe 1 and the sampling pipe 2 from before initiation of the measurement, the
concentration value increases by the predetermined concentration indicated value from a tim5 e
before the exhaust gas is introduced. Then, since the adsorption and the exfoliation of the
NH3 on and from the inside surface of the pipe is substantially in the equilibrium state as
shown in Fig. 3 (b), even though the NH3 derived from the exhaust gas is adsorbed on the
inside surface of the pipe, substantially the same volume of NH3 is exfoliated from the inside
10 surface of the pipe. Accordingly, since almost no response delay generates due to adsorption
of NH3, it is possible for the concentration indicated value output by the gas measurement
mechanism 21 to reproduce the concentration change derived from the actual exhaust gas on a
substantially real time basis.
Next, not a case that a large volume of the NH3 derived from the exhaust gas flows
15 in but a case that NH3 is output only by a subtle volume when, for example, the engine is coldstarted
will be explained while comparing the measurement result of the conventional exhaust
gas analysis device and the measurement result of the exhaust gas analysis device 10 of this
embodiment.
As shown by a graph in Fig. 5 (a), in case that a subtle volume of the NH3 flows in
20 the exhaust gas analysis device 100 immediately after the initiation of the measurement, in
case of the conventional device, all of the NH3 is adsorbed on the inside surface of the gas pipe
1 and the sampling pipe 2 so that it is not possible for the gas measurement mechanism 21
even to detect the NH3. Even though the predetermined time period has passed after the
engine is started, the measurement value that is smaller than the actual NH3 concentration is
25 output or an event such as a response waveform does not coincide occurs, and then a
measurement value and the actual value of the NH3 concentration coincide each other and the
measurement value is stabilized. In addition, after the engine is halted, no NH3 must be
detected, however, the NH3 that has been adsorbed on the inside surface of the gas pipe 1 and
the sampling pipe 2 detaches one after another so that the concentration indicated value drops
15
gradually and it is not possible to reproduce the actual waveforms. In other words, not only
it is not possible to conduct a real time measurement but also there is a defect that the
measurement value lacks information concerning time.
Meanwhile, in accordance with this embodiment, since the adsorbed volume of the
NH3 on the inside surface of the gas pipe 1 and the sampling pipe 2 is set to be saturated 5 d by
introducing the injection gas prior to initiation of the engine, no NH3 is adsorbed on the inside
surface of the gas pipe 1 and the sampling pipe 2 even though a subtle volume of the NH3
derived from the exhaust gas exists after initiation of the engine. Or even though the NH3 is
adsorbed, the NH3 is exfoliated from the inside surface of the gas pipe 1 and the sampling pipe
10 2 by the same volume as that of the adsorbed NH3. As a result of this, as shown in Fig. 5 (b),
even though a subtle volume of the NH3 derived from the exhaust gas exists immediately after
the initiation of the measurement, it is possible to detect and measure the concentration of the
NH3 accurately. In other words, in accordance with the conventional device, it is likely to
falsely judge that no NH3 is discharged. However, with this arrangement, it is possible to
15 measure the NH3 accurately on a real time basis without loosing information concerning the
time period while the NH3 is discharged even thought the discharged volume is subtle. As a
result of this, it is possible to obtain knowledge that has not been obtained by the conventional
device, thereby enabling to further contribute to development of urea SCR (Selective Catalytic
Reduction).
20 Furthermore, actual measurement results of a rise time and a fall time at a time of
measuring the NH3 by the exhaust gas analysis device 100 of this embodiment will be
explained with reference to Fig. 6. In this actual measurement, the NH3 whose volume is
known is introduced in a step input state from an inlet port side of the gas pipe 1 while the
NH3 as being the predetermined volume of the injection gas is flown by means of the gas
25 injection mechanism 3, and the response speed of the gas measurement mechanism 21 is
evaluated. As shown in Fig. 6 (a), measurements were conducted for each case respectively;
(1) the NH3 is introduced into the gas pipe 1 without injecting NH3 from the gas injection
mechanism 3, (2) 13 ppm of the NH3 is continuously injected from the gas injection
mechanism 3 and the NH3 is further introduced into the gas pipe 1, and (3) 23 ppm of the NH3
16
is continuously injected from the gas injection mechanism 3 and the NH3 is further introduced
into the gas pipe 1.
As is clear from the enlarged view at a time of rising in Fig. 6 (b) and the enlarged
view at a time of falling in Fig. 6 (c), the rise time and the fall time in the experimental
conditions (1), (2) and (3) were 26s, 6s, and 2s respectively. In other words, it turns out 5 that
the near the NH3 approaches the saturation volume by increasing the volume of the injection
gas, the shorter the rise time and the fall time tend to be. In addition, it was proved that the
responsiveness regarding the NH3 measurement of the gas measurement mechanism 21 was
improved by measuring the NH3 in the exhaust gas while NH3 was continuously flowing
10 from the gas injection mechanism 3 at a time of measuring the exhaust gas similar to the
exhaust gas analysis device of this embodiment.
Other embodiment will be explained.
In the above-mentioned embodiment, the gas analysis device of this invention is
explained as an example of the exhaust gas analysis device, however, the gas analysis device
15 may measure other gas as the sample gas. In addition, the NH3 is represented as the
measurement object gas having the adsorbent characteristic, however, it may be other gas
having the adsorbent characteristic such as HCl or hydrocarbon (HC) or the like. As an
example of the hydrocarbon (HC) represented are aromatic hydrocarbons such as toluene,
alcohol such as methanol or ethanol, and high boiling HC or the like. Furthermore, as an
20 example of a gas whose adsorbent characteristic is high represented are the gas having polarity
such as NO2, SO2, and H2O.
Not only the predetermined volume is set to be a volume that can keep the
equilibrium state of the adsorption and the exfoliation but also the predetermined volume may
be so set that a volume regarding an injection gas volume indicated by the gas measurement
25 mechanism becomes less than or equal to an allowable difference. The allowable difference
indicates a volume of an error that is allowable for a full-scale that can be measured by, for
example, a certain measurement device, and is concretely indicated by a numerical value of
about several % of the full-scale. In other words, since the concentration indicated value
derived from the injection gas falls within the error of the measurement value of the
17
concentration allowed by the gas measurement mechanism while keeping the equilibrium
state, it is possible to know a sufficiently accurate value without nearly narrowing a
measurement range and without conducting an operation to deduct the concentration value
derived from the injection gas from a value obtained for knowing the concentration value
derived from the exhaust 5 gas.
The above-mentioned contamination judging part detects whether there is
contamination or not based on the response time as being the value relating to the response
speed of the adsorbent gas, however, the value may be the other relating value such as a rate of
variability in case of changing from a certain measurement value indicated by the gas
10 measurement mechanism to the other measurement value. In other words, the
contamination judging part may conduct judgment based on the concentration value
measured within a predetermined period of time. In the above-mentioned embodiment, the
concentration to be actually measured by injecting the span gas by means of the gas injection
mechanism is set to be stepwise, however, the measurement value may be in other shape such
15 as a rectangular wave, a sine wave or a pulse. For example, in case that a pulse-shaped
change is measured by the gas measurement mechanism, whether there is contamination or
not may be judged based on a time period taken from a time when the adsorbent gas is
injected by the gas injection mechanism to a time when the gas is actually detected by the gas
measurement mechanism. In addition, a portion from which the adsorbent injection gas is
20 injected by the gas injection mechanism may be anywhere as long as it locates in the upstream
side of the measurement point of the gas measurement mechanism, and the adsorbent
injection gas may be injected, for example, in the sampling pipe. In addition, the
contamination judging part not only detects whether there is contamination or not but also
may judge a degree of contamination based on the measurement value.
25 Furthermore, in case that the response time of the non-adsorbent gas is obtained and
the obtained response time of the non-adsorbent gas is substantially equal to the response time
of the adsorbent gas, it may judge that maintenance of the suction pump is required or there is
leakage. And in case that only the response time of the adsorbent gas is long, it may judge that
there is contamination in the flow channel where the measurement object gas flows. For
18
example, in case that there is contamination, while the response time of the adsorbent gas is
aggravated and longer due to a change of the inside surface area of the pipe, the response time
of the non-adsorbent gas is not affected so much even though the surface area changes and the
response time hardly changes. Meanwhile, in case that the suction pump is defective, it takes
time for both the adsorbent gas and the non-adsorbent gas to reach the gas measuremen5 t
mechanism so that the response time becomes long for both of them. As mentioned, it
becomes possible to judge a cause of the two different response delays strictly by comparing
the response time of the adsorbent gas and the response time of the non-adsorbent gas. In
case of this arrangement, it is preferable that the gas measurement device can measure a gas
10 composed of multiple components simultaneously, and CO, CO2, NO, N2O or the like is
represented as a concrete example of the non-adsorbent gas.
In addition, the contamination judging part is not limited to a part that is used for
only the exhaust gas analysis device, and may be used for other gas analysis device.
Furthermore, the above-mentioned gas measurement mechanism can measure a gas
15 of multiple components by means of the FTIR, however, may be able to measure the
adsorbent gas alone. Concretely, similar to the NDIR or the laser measurement, the gas
measurement mechanism may be able to measure the adsorbent gas alone such as NH3. In
addition, the value measured by the gas measurement mechanism is not limited to the
concentration, and may be a value relating to a volume such as a flow rate, a volume or the
20 like of the adsorbent gas. Furthermore, the measurement point of the gas measurement
mechanism is not limited to inside of the sampling pipe, and may be inside of the gas pipe.
In short, it may be acceptable as long as the injection gas injected by the gas injection
mechanism flows together with the measurement object gas from the upstream of the
measurement point.
25 In addition, the gas measurement mechanism is arranged in the downstream of the
suction pump in the above-mentioned embodiment, however, it may be arranged in the
upstream of the suction pump. Also in this case like, so called, a decompression flow, it is
possible to obtain the same effect regarding the contamination detection or the measurement
of the measurement object gas having the adsorbent characteristic as the above-mentioned
19
effect.
It is a matter of course that the present claimed invention may be variously
combined or modified without departing from the spirit of the invention
POSSIBLE APPLICATIONS IN INDUSTR5 Y
As mentioned, in accordance with the adsorbent gas analysis device of this
invention, since it is so configured that the measurement object gas having the adsorbent
characteristic is measured while injecting the injection gas having the adsorbent characteristic
in the gas pipe by means of the gas injection mechanism, it is possible to provide a new
10 coating of the injection gas immediately after being contaminated by soot or the like so that
the measurement object gas is hard to adsorb on the inside surface of the gas pipe on a
constant basis. As a result of this, it is possible to prevent the measurement error and the
response delay of the measurement object gas. In other words, it is possible to preferably
apply this invention to the exhaust gas analysis device whose measurement object is, for
15 example, the adsorbent gas.
20
We Claim:-
1. An adsorbent gas analysis device (100) comprising
a gas measurement mechanism (21) that measures a value relating to a volume of a
measurement object gas that has adsorptivity and that flows in a gas pipe (1), and
a gas injection mechanism (3) that injects a predetermined volume of the adsorben5 t
injection gas into the gas pipe (1) from a point that locates in an upstream side of a
measurement point where the gas measurement mechanism (21) measures the measurement
object gas at least while the gas measurement mechanism (21) is measuring the measurement
object gas.
10
2. The adsorbent gas analysis device (100) as claimed in claim 1, wherein
the injection gas is a gas whose composition is the same as that of the abovementioned
measurement object gas and that can be measured by the gas measurement
mechanism (21).
15
3. The adsorbent gas analysis device (100) as claimed in claim 1, wherein
the above-mentioned predetermined volume is set as equal to or more than a
volume wherein an adsorption volume of the measurement object gas and the injection gas
that is adsorbed on an inside surface of the gas pipe (1) is substantially equilibrium to an
20 exfoliated volume of the measurement object gas and the injection gas that is exfoliated from
the inside surface of the gas pipe (1).
4. The adsorbent gas analysis device (100) as claimed in claim 1, wherein
the predetermined volume is set so as to make the value relating to the volume of the
25 injection gas indicated by the gas measurement mechanism (21) equal to or less than an
allowable difference.
5. An adsorbent gas measuring method comprising
a gas measurement step that measures a value relating to a volume of a
21
measurement object gas that has adsorptivity and that flows in a gas pipe (1), and
a gas injection step that injects a predetermined volume of the adsorbent injection
gas into the gas pipe (1) from a point that locates in an upstream side of a measurement point
where the measurement object gas is measured in the gas measurement step at least while the
measurement object gas is measured