Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an oxygen gas analyzer and, more
particularly, to an oxygen analyzer having a probe type detector adapted
to produce a sîgnal represen~ing the difference in oxygen concentration
between the inner side ancl the outer side of a partition wall Eormed by a
solid electrolyte supported on the end of the probe type detector.
In order to describe the prior art reference is hereby made to
Figures 1 and 2 of the accompanying drawings, in which:
Figure 1 is an illustratîon of the construction of a conventional
oxygen analyzer;
lQ Figure 2 is a longitudinal section to an enlarged scale showing
the construction of the detecting section of the conventional oxygen analyzer;
Figure 3 is a sectional view illustrating the construction of a
probe type detecting sectîon of a solîd electrolyte type oxygen analyzer
constructed în accordance with the inventîon;
Figure 4A and Figure 4B are enlarged sectîonal views of portions
of the probe type detecting sectîon shown în Figure 3;
Figure 5, appearing on the same drawing sheet as Figure 3, is a
vîew similar to Figure 3 but showîng another embodiment of the invention;
Figure 6 is an enlarged view of an important part of the detecting
2~ section shown in Figure 5;
Figure 7 is a view similar to Figure 3 but to a smaller scale and
showing still another embodiment of the invention;
Figure 8A is an enlarged sectional view taken along tbe line Xl-X
of Figure 7;
Figure 8B îs a view sîmilar to Figure 8A but showing the arrange-
ment of various lead wires;
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Figure 9 is a graph illustrating the principle of operation of
the oxygen analyzer shown in Figure 7;
~ igure 10 is a fragmentary sectional view illustrating a further
embodiment of the invention; and
Figure 11 is a view sîmilar to Figure 10 but illustrating a
still further embodiment of the in~ention.
Figure 1 shows a typical known oxygen analyzer of the direct
insertion type. This oxygen analyzer has a probe 1 having an end adapted
to be inserted înto a stack or a furnace with a flange 2 of the probe
la fastened to the furnace wall 5 by means of bolts 3~ The probe 1 is provided
at its end with a solid electrolyte such as zirconia, bismuth oxide or the
like, detecting electrodes disposed across the solid electrolyte, a
temperature sensor, a heater and so forth as described in more detail below.
The oxygen analyzer also has a terminal box 4 through which the detecting
electrodes, temperature sensor and the heater are connected to external
circuits. ~he oxygen analyzer also has a signal receiving portion 7 adapted
to output a signal corresponding to the oxygen concentration. The signal
receiving portion 7 has a linearizing section for linearizing the detection
signal and a temperature adjusting section employing the heater as the
control means. The oxygen analyzer is providecl also with a pump 6 adapted
to forcibly supply air as a reference gas into the probe 1.
Thus, the conventional oxygen analyzer requires a pump for
supplying the probe 1 with a reference gas Cair2, so that the cost of the
production is raised. In addition, the reliability of operation is lowered
due to the employment of moving parts such as pump.
As an alternative, such an oxygen analyzer has been proposed as
adapted to introduce instrumentation air into the probe 1. This system,
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however, requires special piping and, therefore, is not preferred from an
economical poînt of view.
Figure 2 illustrates the construction oE the detecting section of
the conventional oxygen analyzer of the kind described. ReEerence numeral 8
designates a test-tu~e type solid electrolyte such as of zirconia, bismuth
o~ide or the like material. A barrier lA extends across the interior oE
probe 1 and the solid electrolyte 8 is securecl to and extends through the
barrier lA with its closed end located at the end of the probe 1 so as to
form a partition wall separa~ing the end portion of the probe 1 from other
portions of the same. Electrodes 9 and ln are closely secured to the inner
and outer sides of the wall of the solid electrolyte 8. A temperature sensor
11 is adapted to sense the temperature of the solid electrolyte 8 which is
adapted to be heated by a heater 12. The temperature sensor 11, heater 12
and the temperature adjusting section Cnot shown) in combination constitute a
temperature control system adapted to maintain the solid electrolyte at a
constant temperature. In operation, a signal corresponding to the difference
of oxygen concentration between the inner side and outer side of the solid
electrolyte 8 is derived from the electrodes 9 and 10 through respective
leads which are not shown. A reference numeral 13 designates a ~ilter
2Q adapted to prevent dust from attaching to the wall surface of the solid
solution 8, while a reference numeral 14 denotes a conduit passing through
barrier lA and having one end located at the closed end (outer side) of the
solid electrolyte 8 and the other end extending out of the other end of
the probe 1 so as to be able to introduce a calibration gas into the closed
end of the solid electrolyte 8.
In this type of oxygen analyzer, it is necessary to occasionally
renew the solid electrolyte 8 in order to maintain the desired precision of
measurement. The work required for this renewal, however, is made quite
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troublesome and -time-consuming, because the probe 1 is provided
with various small parts a-t its end as described.
Accordingly, an object of the invention is to provide a
solid electrolyte type oxygen analyzer having a cell unit which
does not have lead wires and permits an easy renewal of the solid
electrolyte in the probe type detector.
To this end, according to the invention, there is pro-
vided a solid electrolyte type oxygen analyzer having a probe type
detecting section including a solid electrolyte fixed to the end
thereof so as to form a partition wall and adapted to produce a
signal corresponding to the difference in -the oxygen concentration
between the inner side and outer side of said partition wall,
said oxygen analyzer comprising: a contact portion secured to the
inner wall surface of said probe near the end of the lat-ter
through an electrically insulating member; a test tube type solid
electrolyte inserted into and fixed to said end of said probe,
said solid electrolyte having a first electrode and a second elec-
trode which are closely secured to the outer wall surface and the
inner wall surface of the closed end wall of said solid electro-
lyte or the portion of said solid electrolyte near said end wall,a first lead closely attached to said outer wall surface of said
solid electrolyte and providing a connection between said first
electrode and said contact portion, and a second lead closely at-
tached to said inner wall surface of said solid electrolyte and
providing an electric connection between said second electrode
and the open end surface of said solid electrolyte; and a first
conductor and a second conductor connected to said contact portion
33~4~
and said open end o:E said solid electrolyte, respectively, thereby
to transmit the signals produced by said first and second elec-
trodes.
Another object of the invention is to provide a solid
electrolyte type oxygen analyzer in which, in order to facilitate
the renewal of the solid electrolyte, a cell unit consisting oE
a test tube type electrolyte and a flange integral therewith is
inserted with its closed end directed inwardly in-to the end of
the probe and a calibration gas conduit is easily separable from
the body of the oxygen analyzer.
This object of -the invention is achieved by a solid
electrolyte type oxygen analyzer comprising: a cell uni-t includ-
ing a conduit disposed in a probe such that one end of the conduit
is disposed near the end of the
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,
probe while the other end proiects toward the portion of the probe opposite
to the end, a test tube type solid electrolyte and a flange integral wi~h the
solid electrolyte, the cell unit being inserted into and secured to the probe
with the closed end of the solid electrolyte directed înwardly, a substan-
tially U-shaped plpe havlng one end inserted into the lnternal cavity of the
solid electrolyte ~hile the other end being connected to the portion of the
condult near the end of the probe, and a flange supporting the U-shaped plpe
andj~inted to the flange of the cell unit, the flange being adapted to be
fixed to the end of the probe by means of a fixing tool.
Stlll another object of the inventlon ls to provlde an oxygen
analyzer havlng a less-expensive and reliable means for introducing a
reference gas.
This object is achieved by an oxygen analyzer having a det~ction
probe having an internal cavity houslng a solid electrolyte dlsposed proximate
one end of the probe, characterized by a partîtlon plate which divides the
internal cavity of said probe in the longitudinal direction into two sections,
a communicating portion defined at a portion near said solid electrolyte and
providing a communication between said sections separated from each other by
said partition plate, and a communicating portion providing a communication
2Q between each of said sections and the atmosphere at the end portion of said
probe remote from said solid electrolyte.
The inven-tion will now be described in greater detail with
reference to the accompan~ing drawings, particularly Flgures 3-11 thereof.
~ lth reference now to Flgures 3, '~A and 4B, reference numeral 15
designates a probe made of an electrically conductlve material and having a
flange 16 welded to the barrel or main body portion thereof. The probe 15 ls
secured to the wall 17 of a stack or a furnace by means of the flange 16.
4r ~
Reference numeral 18 designates a cell Imit provided at the end of the
probe 15 and consisting of a test-tube type zirconia solid e~ectrolyte 19
and a flange 20. The zirconia electrolyte 19 includes porous platinum electrode
films 21 and 22 provided on the outer wall surface and the inner wall surface,
respectively, of the closed end of the tube. A lead 23 is also provided,
this consisting of a ring-shaped portion 23a formed on the outer wall surface
of the solid electrolyte tube by baking a platinum paste and a connecting
portion 23b along the outer wall surface through which the ring-shaped
portion 23a is connected to the electrode film 21. A lead 24 is also pro-
lQ vided, this consisting of a contact surface 24a formed by baking a platinum
paste on the open end surface of the zirconia and a connecting portion 24b
fnrmed on the inner wall surface and formed by baking a platinum paste and
providing an electric connection between the contact surface 24a and the
electrode film 22.
Reference numeral 25 denotes a heater for heating the zirconia 19
electrolyte tube. This constitutes, in combination with a temperature sensor
(not shown) provided on the closed end of the zirconia tube 19 and a tem-
perature controller (not shown~, a temperature control system for maintaining
the zirconia 19 at a predetermined constant temperature. Reference numeral
2Q 26 denotes a contact ring provided with a recessed inner peripheral surface,
27 denotes a coil contact adapted to be fitted in the recess of the contact
ring 26 and consisting of a nichrome wire or a wire of a heat resistant
and anti-oxidation metal~ 28 denotes a highly insulative adhesive such as
the material known commercially as Sumiceram, for fixing the contact ring 26
to the probe 15, and 29 denotes a wire lead covered by an insulator 30 and
disposed in the probe 15 with one end thereof being connected to the contact
~rade ~1 Q ,k
3~3~3~
ring 26 while the other end is connected to an external terminal (not shown).
The coil contact 27 is held in contact with the ring-shaped portion
23a of the lead 23 wîth the zirconia tube l9 mounted in the probe 15, so
that an electric path is fornled by electrode fîlm 21, lead 239 coil contact
27, contact ring 26 and the wire lead 29. Reference numeral 31 designates a
mesh fîlter made of stainless steel, 32 denotes a flange and 33 denotes a
bolt. rChe mesh filter 31 îs pressed and secured to the open end surface of
the zirconia tube 19 by means of flange 32, so that an electric path is
formed by the electrode film 22, lead 24, mesh filter 31, flange 20,
flange 32 and the probe 15. Reference numeral 34 designates a partition
plate extendîng longitudinally of the probe 15 and adapted to divide the
internal cavity of the probe 15 other than the portion near the zirconia
tube 19 into an upper section and a lower section. Reference numeral 35
denotes a cylindrical, conductive, metallic cap portion or lid provided
adjacent the open end of the probe 15 which is remote from the zirconia tube
1~, whîle 36 denotes a wire lead connected to the metal plate cap. The
metal cap 35 is open at olle end and is so onstructed as to permit the upper
and lower sections of the internal cavity of the probe 15 to communicate with
the out~ide independently of each other. This is achieved as can be seen by
2a the cap 35 being positîoned partl~ overlapping the open end portion of probe
15, the closed end of the cap 35 being joined centrally to the end of the
partition 34. The metal cap 35 is electrically connected to the probe 15
so that the electric path including the electrode film 22 and the probe 15
is connected to the external terminal ~not shown~ through the wire lead 36.
rn the detecting section of the oxygen analyzer, the end of the
probe 15 is held in the stream of the hot flue gas to be analyzed. Typically
3~
the gas temperature is about 200 to 50QC. The flue gas comes into the
zirconia through the filter 31 by diffusion and convection to continuously
contact the inner surface of the zirconia 19. The gas contacting the outer
wall surface of the zirconia 19, i.e. the air in the probe 15, has been
heated to a high temperature of about 700 to 800 C by the heat derived from
the measurement gas and the heat produced by the heater 25. A natural
convection current of air is thereby formed to include, as shown in Figure 3,
the atmosphere, lower section of the internal cavity of the probe 15, end of
the probe lS Cnear the zîrconia 19~, upper section of the internal cavity
lQ of the probe 15 and the atmosphere. Therefore, the reference gas side of the
zirconia 19 is always held in contact with fresh air, so that it is possible
to obtain stably a detection signal between the two electrode films 21 and
22. The signal is then derived through the wire leads 29 and 30. Figure 3
shows the probe 15 held in a horizontal position but it should be stated
that sufficient convection of air is maintained even if the probe 15 is
inclined with the end thereof directed downwardly until the probe 15 comes to
take a substantially vertical position with the cap 35 at the bottom.
As has been described above, the cell unit 18 is secured to the
end of the probe 15 by means of a flange 32 and bolts 33, and the electric
connection between the electrode fîlms 21,22 and the external terminals is
made through the leads 23,24, coil contact 27 and the mesh filter 31. It
is, therefore, possible to easily mount and demount the cell ~Init 18.
Thus, according to the invention, there is provided a solid
eLectrolyte type oxygen analyzer having a cell unit which does not have
lead wires so that the renewal of the solid e:Lectrolyte can be made easily
to reduce the maintenance cost.
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ReEerring now to Figures 5 and ~, reEerence numeral 37 denotes a
probe having a flange 38 welded thereto and mounted on a flue or a furnace wall
39 by means of the flange 38. Reference numeral 40 denotes a cell unit con-
sisting of a ~est-tube type zirconia solid electrolyte 41 and a flange 42 and
adapted to be mounted on the end of the probe 37, while 43 designates a
heater for heating the zirconia 41. Although not shown, porous electrode
films of platinum are formed on both surfaces of the end (bottom of the test
tube2 of the zirconia 41 as in the first described embodiment. A signal
corresponding to the difference in the oxygen concentration between the two
chambers separated by the wall of the zirconia 41, i.e. between the inner
side and the outer side of the probe 37, is taken out of the probe by means
of the electrode films as before. ~ temperature sensor (not shown) pro-
vided at th~ end of the zirconia 41 constitutes, în combination with a
temperature controller Cnot shown~ and a heater 43, a temperature control
system which serves to maintain the zirconia at a predetermined constant
temperature.
Reference numeral 44 denotes a conduit consisting of a straight
portion 44a and a U-shaped portion 44b, 45 denotes a mesh filter provided
at the open end of the zîrconia 41 and 46 denotes a flange. The flange 46
2Q supports the U-shaped portion 44b of the conduit 44 through the bracket 47
CFigure 6) and is adapted to be secured to thP probe 37 by means of bolts 48
thereby to fix the cell unit 40 to the end of the probe 37.
In this state, the open end of the U-shaped portion 44b of the
conduit 44 is positioned in the hollow cavity of the zirconia 41, while the
other end of the U-shaped portion is connected to one end of the straight
portion 44a of the conduit 44. Reference numeral 49 denotes a partition
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plate which divides the internal cavity of the probe 37 other than the V:iCillity
of the zirconia into an upper section and a lower section. A cylindrical
lid 50 is constructed and positioned as in the first embodiment to permi-t
the upper and lower sections of the internal cavity of the probe 37 to
communicate with the atmosphere independently of each other.
In operation, the end portion of the probe 37 is held in the
stream of hot (having a temperature of about 200 to 500 C) flue gas to be
analyzed and the gas comes into the zirconia 41 through the filter 46 by
diffusion and convection, thereby to make continuous contact with the inner
wall surface of the zirconia 41. On the other hand, the gas contacting the
outer wall surface of the zirconia 41, i.e. the air inside the probe 37, is
heated to a high temperature of 700 to 850C by the heat from the flue gas
- to be measured and the heat produced by the heater 43. In consequence, a
natural convection current of air is formed to include, as shown in Figure 5,
the atmosphere, lower section of the internal cavity of the probe 37, end of
the probe 37 (near zirconia 41~, upper section of the internal cavity of the
probe 37 and the atmosphere.
Therefore, the reference gas side of the zirconia 41 is always
kept in contact with fresh air, so ~hat a stable signal is derived from the
2Q electrodes. In the measuring operation stated above, the conduit 44 is
normally kept closed so that the gas in the conduit 44 never flows. The
presence of the conduit 44, therefore, does not adversely affect at all the
state of flow and composition oE the measured gas flowing into the zirconia
37. It is, however, possible to improve the response by making use of the
conduit 44. Namely, the introduction of the measured gas into the zirconia 37
is accelerated to promote the substitution of the gas, by connecting one end of
the conduit 44 to the SUCtiOII port of an ejector or the like.
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An explanation will be made as to the calibrating operation and
cleaning opera~ion. The calibration is conducted by introducing, through the
conduit 44, a calibration gas having a pressure somewhat higher than the
pressure of the gas being analyzed into the zirconia 37. Since the calibra-
tiOII gas has a pressure higher than the gas being analyzed, the substitution
of two gases in the zirconia 37 can be made in quite a smooth manner to permit
an accurate substitution of two gases.
By using a cleaning gas, e.g. instrumentation air in place of
the calibration gas, it is possible to remove the dust attaching to the
filter 46 and the zirconia 37 by blow-back.
For renewing the zirconia 37, the bolts 48 are loosened to sep-
arate the straight portion 44a and the U-shaped portion 44b of the conduit
44 from each other, and the cell unit 40 is withdrawn from the end of the
probe 37. It is, therefore, possible to renew the zirconia 37 in quite an
easy manner.
As has been described, in the solid electrolyte type oxygen analyzer
of the invention, the cell unit consisting of a test-tube type solid electro-
lyte and a flange integral therewith is inserted into and fixed to the end
of the probe with the closed end of the solid electrolyte directed inwardly.
~Q In addition, the conduit for introducing the calibration gas can be separated
at a portion thereof near the end of the probe. It will be seen that the
described arrangement of the oxygen analyzer remarkably facilitates the
protective maintenance work for renewing the solid electrolyte.
Figure 7 shows an oxygen analyzer constructed in accordance with
still another embodiment of the invention which achieves the aforesaid third
object of the invention. ~he oxygen analyzer of this embodiment includes a
~ ~l8q,~ fl
probe 51 having a flange 57 welcled to the barrel thereof and provided with
through holes 55 and 56 Eormed in the side wall near the portion 51b thereof
opposite to the end, a test-tube type zirconia solid electrolyte 52 mounted
on the end of the probe 51, a heater 53 for heating the end (bottom of the
test-tube~ of the zirconia 52, a partition plate 54 adapted to divide the
internal cavity of the zirconîa 52 into two sections 51d and 51e while
leaving a communicating portion 51c in the vicinity of the end of the zir-
conia 52 as shown in Figure 8A, a cylindrical lid 59 adapted to close only
the end Slb of the probe 51, detect-ing electrodes formed on both surfaces of
1~ the end wall of the zirconia 52, temperature sensor (not shown) for sensing
the temperature of the end portion of the zirconia 52, a heater 53, a
terminal box 60 for connecting the electrodes, temperature sensor and the
heater to external circuits, a linearizing portion (not shown~ for linearizing
the detection signal deri~ed through the terminal box 60 and adapted to
deliver the linearized signal as its output, and a signal receiving portion
(not shown~ consisting of the temperature sensor as the detection end and
the heater 53 as the operation end. The probe 51 is adapted to be fixed to
the stack or the furnace wall 61 by means of bolts 58 with the end 51a
inserted into the flue thereby to measure the oxygen concentration in the
~Q measurement gas.
Although not shown in Figure 7, the wiring to the detecting
electrodes, temperatllre sensor and the heater 53 is effected by making use
of the partition plate 54 as the substrate, as shown in Figure 8B. Namely,
the heater lead ~ire 62 and the electrode leads 63 are placed on the
partition plate 54 and are pressed down and fixed by means of a leaf spring
65. ~t the same time, a temperature sensor lead 64 is fixed to the leaf
spring 65 by spot welding.
The oxygen analyzer of this embocliment operates as fol:Lows:
In the measuring state, the end 5]a of the probe 51 i9 held in
the stream of -the gas to be measured which has a temperature of about 200 to
500 C and one wall surface of the zirconia 52 is held in continuous contact
with this stream oE gas. The space inside the probe 51 communiGates with
the atmosphere through the through holes 55 and 56 and, therefore, is always
filled with fresh air. Therefore, the detection electrodes provided on both
surEaces of the wall of the zirconia produce a detection signal in accordance
with the Nenlst's equation using the air as the reference gas. The detection
signal i8 delivered to the signal receiving portion which conducts a pre-
determined arithmetic operation to provide a signal corresponding to the
oxygen concentration of the measured gas. The air in the probe 51 is heated
to a high temperature of about 700C by the heat derived from the measured
gas and the heat produced by the heater 53, so that a natural convection
current of air is formed to include the atmosphere, through hole, 55, section
51e, communicating portion 51c, section 51d, through hole 56 and the atmos~
phere, as shown in Figure 7. In consequence, the other wall surface of the
zirconia 52 îs maintained in contact with fresh air serving as the reference
gas, so that the oxygen analyzer provides a stable output signal.
2a The present inventor has conducted the following test to confirm
the presence of the convection current of air.
Atmospheric air was introduced into the area where the gas
to be analyzed normally flows so that both sides of the wall of the zirconia
52 were subjected to atmospheric air. The space inside the probe 51 was
maintained at a high temperature of about 700C. Then, N2 gas containing
about 1% of 2 gas was supplied for 2 to 3 seconds to the area X2 in the
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vic:inity of the through hole 55. Figure 9 :i9 a graph showing the change of the
detectlon signal. The time To represents the time length over which the 1%
2 gas was blown. As will be understood from Figure q~ the change in the 2
gas concentration appearing at the area X2 is transmitted to the end of the
zirconia 52 in about 8 seconds. Since the volume of section 51e in the
probe 51 used in the experiment was about 150 ml, the flow rate of air
moved by the convection can roughly be calculated to be about 1125 ml/min.
The embodiments heretofore described are not exclusive. For
instance, it is possible to employ the communication means as shown in
Figures 10 and 11. Namely, in the embodiment shown in Figure 10, the probe
51 is provided with a discharge sleeve 56' connected to the through hole 56
so that the convection in the probe 51 is promoted by the chimney-like action
of the discharge sleeve 56'. In contrast, in the embodiment shown in
Figure 11, the probe 1 is devoid of the through holes 55 and 56 shown in
Figure 7 but, instead, the convection current is formed through the gap
between the cylindrical lid 59 and the adjacent end portion 51b of the probe.
As has been described, in the oxygen analy~er of the inven~ion,
the internal cavity of the probe is divided into t~o sections by a partition
plate and the air is introduced into the cavity divided into two sections,
to eliminate the necessity for a pump for supplying the air or piping for
introducing instrumentation air, thereby reducing the co~t of production
while remarkably improving the reliability of operation.
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