FORM 2
THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)

1. Title of the invention: GAS-LIQUID MIXING DEVICE AND EXHAUST GAS
DESULFURIZATION DEVICE INCLUDING GAS-LIQUID MIXING DEVICE
2. Applicant(s)
NAME NATIONALITY ADDRESS
MITSUBISHI POWER, LTD. Japanese 3-1, Minatomirai 3-Chome, Nishi-ku, Yokohama-shi, Kanagawa 2208401, Japan
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICAL FIELD
[0001] The present disclosure relates to a gas-liquid mixing device for injecting a
scrubbing liquid and a gas containing oxygen to a liquid reservoir for storing the scrubbing liquid in an absorption tower configured to bring the scrubbing liquid into contact with an exhaust gas discharged from a combustion device, and an exhaust gas desulfurization device including the gas-liquid mixing device.
BACKGROUND
[0002] For example, exhaust gas discharged from a combustion engine such as a boiler
contains air pollutants such as SOx (sulfur oxide). As a method for reducing SOx contained in exhaust gas, there may be mentioned a wet desulfurization method in which substances such as SO2 are absorbed and removed by an absorption liquid such as an alkaline aqueous solution or an absorption slurry.
[0003] Some exhaust gas desulfurization devices used in the wet desulfurization method
are provided with an absorption tower including a gas-liquid contact part configured to bring exhaust gas and scrubbing liquid into contact by spraying the scrubbing liquid to the exhaust gas flowing in the absorption tower, and a liquid reservoir, disposed below the gas-liquid contact part, for storing the scrubbing liquid which has been sprayed (for example, see Patent Document 1). When the exhaust gas comes into contact with the scrubbing liquid, SO2 contained in the exhaust gas is absorbed in the scrubbing liquid. The scrubbing liquid that has absorbed SO2 is stored in the liquid reservoir.
[0004] Since the scrubbing liquid stored in the liquid reservoir contains reaction products
such as sulfites produced from SO2 absorbed from the exhaust gas, in order to remove the reaction products, the reaction products may be oxidized by spreading a gas containing oxygen such as air through the scrubbing liquid stored in the liquid reservoir.

[0005] Patent Document 1 discloses a gas-liquid mixing apparatus including an injection
nozzle configured to inject a mixed fluid of scrubbing liquid and the gas containing oxygen
from a discharge port to the liquid reservoir. The injection nozzle has a contraction portion
in the middle of a flow passage for the scrubbing liquid, and the contraction portion contracts
the flow of the scrubbing liquid flowing through the flow passage to generate a negative
pressure region. The suction force generated in the negative pressure region sucks a gas
supplied via a branch pipe to a portion of the flow passage on the downstream side of the
contraction portion. Further, the injection nozzle shears and atomizes the gas sucked by the
scrubbing liquid flowing in the flow passage of the scrubbing liquid to generate a mixed fluid
(scrubbing liquid containing fine bubbles), and injects the mixed fluid from the discharge port.
[0006] The injection nozzle includes a main pipe through which the scrubbing liquid
(including the mixed fluid) and a branch pipe (gas introduction pipe) for introducing the gas into the main pipe. In order to efficiently shear and atomize the gas, the branch pipe is arranged such that the axis of the branch pipe extends along a direction perpendicular to the axis of the main pipe so that the gas is introduced into the main pipe along a direction perpendicular to the flow direction of the scrubbing liquid. The gas-liquid mixing device includes, in addition to the injection nozzle, a scrubbing liquid introduction line and a gas introduction line. The scrubbing liquid introduction line includes a scrubbing liquid introduction pipe connected to the main pipe, and the scrubbing liquid is introduced into the main pipe through a scrubbing liquid introduction port formed in the main pipe. The gas introduction line includes a gas introduction pipe connected to the branch pipe, and the gas is introduced into the branch pipe through a gas introduction port formed in the branch pipe.
Citation List
Patent Literature
[0007] Patent Document 1: JP5046755B
SUMMARY

Problems to be Solved
[0008] The injection nozzle is subjected to vibration and thermal contraction along the
axial direction of the main pipe from the scrubbing liquid introduction pipe and other components of the scrubbing liquid introduction line. Further, the injection nozzle is subjected to vibration and thermal contraction along the direction perpendicular to the axial direction of the main pipe from the gas introduction pipe and other components of the gas introduction line. In other words, the injection nozzle is subject to superimposed vibration and thermal contraction from two mutually perpendicular directions, which may cause wear and damage to the injection nozzle.
[0009] In view of the above, an object of at least one embodiment of the present invention
is to provide a gas-liquid mixing device whereby it is possible to prevent wear and damage to the injection nozzle due to the transmission of vibration and thermal contraction to the injection nozzle from both the scrubbing liquid introduction line and the gas introduction line.
Solution to the Problems
[0010] (1) A gas-liquid mixing device according to at least one embodiment of the present
invention comprises an injection nozzle configured to inject a scrubbing liquid and a gas containing oxygen to a liquid reservoir for storing the scrubbing liquid in an absorption tower configured to bring the scrubbing liquid into gas-liquid contact with an exhaust gas discharged from a combustion device. The injection nozzle includes: a first cylindrical portion internally defining a first flow passage and having a scrubbing liquid introduction port for introducing the scrubbing liquid into the first flow passage, a gas introduction port for introducing the gas into the first flow passage along a direction perpendicular to a flow direction of the scrubbing liquid introduced from the scrubbing liquid introduction port and flowing through the first flow passage, and a discharge port for discharging a mixed fluid of the scrubbing liquid introduced from the scrubbing liquid introduction port and the gas introduced from the gas introduction port; a contraction portion disposed, in the flow direction of the scrubbing liquid, upstream of a merging portion at which the scrubbing liquid

introduced from the scrubbing liquid introduction port merges with the gas introduced from
the gas introduction port; and a second cylindrical portion internally defining a second flow
passage communicating with the gas introduction port and having a second gas introduction
port for introducing the gas into the second flow passage along a direction perpendicular to
the flow direction of the scrubbing liquid. The gas-liquid mixing device further includes an
expansion joint including a body portion internally defining an introduction flow passage for
feeding the scrubbing liquid or the gas and configured to be expandable along at least a
direction of extension of the introduction flow passage. The expansion joint is disposed on
at least one of a scrubbing liquid introduction line for feeding the scrubbing liquid to the first
flow passage through the scrubbing liquid introduction port or a gas introduction line for
feeding the gas to the second flow passage through the second gas introduction port.
[0011] According to the above configuration (1), the gas-liquid mixing device includes
the expansion joint disposed on at least one of the scrubbing liquid introduction line or the gas
introduction line, and the injection nozzle. The expansion joint includes the body portion
internally defining the introduction flow passage for feeding the scrubbing liquid or the gas
and configured to be expandable along at least the extension direction of the introduction flow
passage. In such a gas-liquid mixing device, the expansion joint absorbs vibration and
thermal contraction and thus prevents the transmission of vibration and thermal contraction
from at least one of the scrubbing liquid introduction line or the gas introduction line to the
injection nozzle. Since the injection nozzle is prevented from being subjected to
superimposed vibration and thermal contraction from two mutually perpendicular directions, it is possible to reduce wear and damage to the injection nozzle.
[0012] (2) In some embodiments, in the gas-liquid mixing device described in the above
(1), the expansion joint is disposed on both of the scrubbing liquid introduction line and the gas introduction line.
[0013] According to the above configuration (2), the expansion joint is disposed on both
of the scrubbing liquid introduction line and the gas introduction line. This prevents the transmission of vibration and thermal contraction from both of the scrubbing liquid

introduction line and the gas introduction line to the injection nozzle. With the above configuration, it is possible to more reliably prevent the injection nozzle from being subjected to superimposed vibration and thermal contraction from two mutually perpendicular directions, compared with the case where the expansion joint is disposed on at least one of the scrubbing liquid introduction line or the gas introduction line.
[0014] (3) In some embodiments, in the gas-liquid mixing device described in the above
(1) or (2), the injection nozzle further includes a scrubbing-liquid-introduction-side fastening portion disposed so as to protrude from an outer circumference of the first cylindrical portion on an upstream side of the merging portion in the flow direction of the scrubbing liquid. Additionally, a first expansion joint which is the expansion joint disposed on the scrubbing liquid introduction line further includes a downstream fastening portion disposed so as to protrude from an outer circumference of the body portion along a direction intersecting a direction of extension of a center axis of the first expansion joint, and the downstream fastening portion is configured to be fixed to the scrubbing-liquid-introduction-side fastening portion by means of a first fastening device while the contraction portion is interposed between the first expansion joint and the first cylindrical portion.
[0015] According to the above configuration (3), the downstream fastening portion of the
first expansion joint is fixed to the scrubbing-liquid-introduction-side fastening portion of the injection nozzle by means of the first fastening device while the contraction portion is interposed between the first expansion joint and the first cylindrical portion.
[0016] (4) An exhaust gas desulfurization device according to at least one embodiment of
the present invention for desulfurizing an exhaust gas discharged from a combustion device comprises: an absorption tower configured to bring a scrubbing liquid into gas-liquid contact with the exhaust gas introduced into the absorption tower, the absorption tower internally defining a liquid reservoir for storing the scrubbing liquid; and the gas-liquid mixing device described in any one of the above (1) to (3).
[0017] According to the above configuration (4), the absorption tower is configured to
bring the scrubbing liquid into gas-liquid contact with the exhaust gas introduced into the

absorption tower, and internally defines the liquid reservoir for storing the scrubbing liquid. The gas-liquid mixing device can cause sufficient oxidation reaction for the scrubbing liquid stored in the liquid reservoir of the absorption tower by the mixed fluid discharged from the discharge port of the inj ection nozzle to the liquid reservoir of the absorption tower. Further, according to the above configuration, since the injection nozzle is prevented from being subjected to superimposed vibration and thermal contraction from two mutually perpendicular directions, it is possible to reduce wear and damage to the injection nozzle. [0018] (5) In some embodiments, in the exhaust gas desulfurization device described in the above (4), the first cylindrical portion extends along a center axis of the discharge port. The injection nozzle further includes a discharge-port-side fastening portion disposed so as to protrude from an outer circumference of the first cylindrical portion on a downstream side of the merging portion in the flow direction of the scrubbing liquid along a direction perpendicular to the center axis of the discharge port. The absorption tower further includes: a side wall defining at least a part of the liquid reservoir and having an insertion hole in which a distal end of the first cylindrical portion including the discharge port is inserted; a cylindrical protruding portion disposed so as to protrude outward of the side wall from a peripheral edge of the insertion hole of the side wall along a direction inclined with respect to a horizontal plane by an angle equal to θ, where θ is an inclination angle of the center axis of the discharge port with respect to a horizontal plane; and an injection nozzle fastening portion disposed so as to protrude from a distal end of the cylindrical protruding portion along a direction perpendicular to a direction of extension of the cylindrical protruding portion, the injection nozzle fastening portion being configured to be fixed to the discharge-port-side fastening portion by means of a second fastening device.
[0019] According to the above configuration (5), the discharge-port-side fastening portion of the gas-liquid mixing device is fixed to the injection nozzle fastening portion of the absorption tower by means of the second fastening device while the distal end of the first cylindrical portion including the discharge port is inserted in the insertion hole formed in the side wall of the absorption tower. Since the inj ection nozzle is fixed to the absorption tower,

even if vibration and thermal contraction are transmitted to the injection nozzle from both the scrubbing liquid introduction line and the gas introduction line, it is possible to prevent the deterioration of oxidation reaction of the scrubbing liquid by the mixed fluid injected from the injection nozzle due to shifting the position or angle of the discharge port of the injection nozzle.
[0020] Further, according to the above configuration, the first cylindrical portion extends
along the center axis of the discharge port. The cylindrical protruding portion of the absorption tower extends along a direction inclined with respect to a horizontal plane by the same angle as the inclination angle θ of the center axis of the discharge port with respect to a horizontal plane. In other words, the cylindrical protruding portion of the absorption tower extends along the same direction as the center axis of the discharge port when the first cylindrical portion is installed. By fixing the discharge-port-side fastening portion extending along the direction perpendicular to the extension direction of the first cylindrical portion with the injection nozzle fastening portion extending along the direction perpendicular to the extension direction of the cylindrical protruding portion by means of the second fastening device, the first cylindrical portion can be installed at the same angle as the inclination angle θ of the center axis of the discharge port with respect to a horizontal plane. Thus, with the above configuration, it is possible to easily attach the first cylindrical portion without adjusting the installation angle of the first cylindrical portion.
Advantageous Effects
[0021] At least one embodiment of the present invention provides a gas-liquid mixing
device whereby it is possible to prevent wear and damage to the injection nozzle due to the transmission of vibration and thermal contraction to the injection nozzle from both the scrubbing liquid introduction line and the gas introduction line.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is a schematic cross-sectional view of an exhaust gas desulfurization device

according to an embodiment.
FIG. 2 is a schematic cross-sectional view of an injection nozzle for describing a function of the injection nozzle according to an embodiment.
FIG. 3 is a schematic cross-sectional view of an injection nozzle according to an embodiment.
FIG. 4 is a schematic diagram of an absorption tower in the vicinity of a portion to which the injection nozzle is fixed, for describing a first expansion joint and a second expansion joint.
FIG. 5 is a schematic partial cross-sectional view of the absorption tower in the vicinity of the portion to which the injection nozzle is fixed.
DETAILED DESCRIPTION
[0023] Embodiments of the present invention will now be described in detail with
reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions, and the like of components described in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present invention.
For instance, an expression of relative or absolute arrangement such as “in a direction”, “along a direction”, “parallel”, “orthogonal”, “centered”, “concentric” and “coaxial” shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function.
For instance, an expression of an equal state such as “same” “equal” and “uniform” shall not be construed as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or a difference that can still achieve the same function.
Further, for instance, an expression of a shape such as a rectangular shape or a cylindrical shape shall not be construed as only the geometrically strict shape, but also

includes a shape with unevenness or chamfered corners within the range in which the same effect can be achieved.
On the other hand, an expression such as “comprise”, “include”, “have”, “contain” and “constitute” are not intended to be exclusive of other components.
The same features can be indicated by the same reference numerals and not described in detail.
[0024] FIG. 1 is a schematic cross-sectional view of an exhaust gas desulfurization device
according to an embodiment. The exhaust gas desulfurization device is a device for
desulfurizing exhaust gas discharged from a combustion device. Examples of the
combustion device include an engine such as a diesel engine, a gas turbine engine, or a steam turbine engine, and a boiler. As shown in FIG. 1, the exhaust gas desulfurization device 1 includes an absorption tower 2 and a gas-liquid mixing device 4.
[0025] The absorption tower 2 is configured to bring a scrubbing liquid into gas-liquid
contact with an exhaust gas introduced into the absorption tower 2. In the illustrated embodiment, as shown in FIG. 1, the absorption tower 2 internally defines a gas-liquid contact part 21A configured to bring the exhaust gas and the scrubbing liquid into gas-liquid contact by spraying the scrubbing liquid to the exhaust gas introduced into the gas-liquid contact part 21A, and a liquid reservoir 21B, disposed below the gas-liquid contact part, for receiving the scrubbing liquid that has absorbed SOx in the exhaust gas by the gas-liquid contact part 21A. Examples of the scrubbing liquid include liquids including an alkaline agent and seawater. Examples of the alkaline agent include CaCO3, NaOH, Ca(OH)2, NaHCO3, and Na2CO3, and an alkali reduced in volume to increase concentration may be used.
[0026] More specifically, as shown in FIG. 1, the absorption tower 2 includes an
absorption tower body 22 having an interior space 21 including the gas-liquid contact part 21A and the liquid reservoir 21B, an exhaust gas introduction unit 23 for introducing the exhaust gas into the absorption tower body 22, and an exhaust gas discharge unit 24 for discharging the exhaust gas from the absorption tower body 22. As shown in FIG. 1, the

direction in which the absorption tower body 22 and the exhaust gas introduction unit 23 are adjacent is defined as a first direction; the side adjacent to the exhaust gas introduction unit 23 in the first direction is defined as a first side; and the side adjacent to the exhaust gas discharge unit 24 in the first direction is defined as a second side.
[0027] As shown in FIG. 1, a first side wall 25 of the absorption tower body 22 on the
first side in the first direction has an exhaust gas introduction port 251 communicating with the interior space 21 (lower interior space 21C). A second side wall 26 of the absorption tower body 22 on the second side in the first direction has an exhaust gas discharge port 261 communicating with the interior space 21 (upper interior space 21C) at a position higher than the exhaust gas introduction port 251. Each of the first side wall 25 and the second side wall 26 extends along a second direction perpendicular to the first direction in a top view, and defines at least a part of the interior space 21 including the liquid reservoir 21B.
[0028] The exhaust gas introduced from a combustion device (not shown) to the exhaust
gas introduction unit 23 passes through the exhaust gas introduction unit 23 and then is introduced into the interior space 21 (lower interior space 21C) through the exhaust gas introduction port 251. The exhaust gas introduced into the interior space 21 flows in the lower interior space 21C from the first side wall 25 on the first side to the second side wall 26 on the second side and then rises in the interior space 21. The exhaust gas that has risen to the upper interior space 21D flows from the first side wall 25 to the second side wall 26 and then is discharged to the exhaust gas discharge unit 24 through the exhaust gas discharge port 261.
[0029] As shown in FIG. 1, the gas-liquid contact part 21A disposed above the lower
interior space 21C and below the upper interior space 21D of the absorption tower body 22 has a spraying device 28 for spraying the scrubbing liquid to the interior space 21. The spraying device 28 is configured to spray the scrubbing liquid to the exhaust gas passing through the gas-liquid contact part 21A to bring the exhaust gas and the scrubbing liquid into gas-liquid contact in order to absorb and remove SOx (including SO2) contained in the exhaust gas.

[0030] As shown in FIG. 1, the spraying device 28 includes a spray pipe 281 extending
along the first direction in the interior space 21 of the absorption tower body 22 and a plurality of spray nozzles 282 disposed on the spray pipe 281. The spray nozzle 282 is configured to spray the scrubbing liquid to the downstream side in the flow direction of the exhaust gas, i.e., to the upper side in the vertical direction. In the illustrated embodiment, the spray nozzle 282 is adapted to inject a pillar of the scrubbing liquid. That is, the illustrated absorption tower 2 is a double contact flow absorber.
[0031] The absorption tower 2 is not limited to a double contact flow absorber as long as
it is configured to bring the scrubbing liquid into gas-liquid contact with the exhaust gas
introduced into the absorption tower 2. For example, the absorption tower 2 may be a grid
absorber including a packed layer packed with a packing material for promoting gas-liquid
contact, or may be a spray absorber including a spray nozzle 282 configured to radially spray
the scrubbing liquid. Further, the spray pipe 281 may extend along the direction
perpendicular to the first direction in a top view. Further, the spray nozzle 282 may be
configured to spray the scrubbing liquid to the lower side in the vertical direction.
[0032] The exhaust gas having passed through the gas-liquid contact part 21A contain a
large amount of moisture. On the downstream side of the gas-liquid contact part 21A in the exhaust gas flow direction, a mist eliminator 27 is disposed. The mist eliminator 27 is configured to remove moisture from the exhaust gas passing through the mist eliminator 27. The exhaust gas having passed through the mist eliminator 27 is discharged to the outside of the absorption tower 2.
[0033] In the illustrated embodiment, the mist eliminator 27 is arranged in the exhaust gas
discharge unit 24 and extends along the vertical direction so as to separate the upstream side
and the downstream side in the exhaust gas flow direction in the exhaust gas discharge unit 24.
However, the mist eliminator 27 may be arranged in the upper interior space 21D and extend
along the horizontal direction. Further, the mist eliminator 27 may have a multi-stage
structure.
[0034] The liquid reservoir 21B is configured to store the scrubbing liquid that has been

sprayed to the exhaust gas introduced into the interior space 21. In the illustrated
embodiment, the liquid reservoir 21B is disposed below the lower interior space 21C such that the liquid surface is positioned below the exhaust gas introduction port 251. The scrubbing liquid stored in the liquid reservoir 21B contains reaction products produced from SOx absorbed from the exhaust gas. Examples of the reaction products include sulfites produced by the absorption of SO2 in the scrubbing liquid.
[0035] As shown in FIG. 1, the second side wall 26 has a scrubbing liquid extraction port
262 near the bottom surface 211 of the liquid reservoir 21B in the vertical direction to extract the scrubbing liquid stored in the liquid reservoir 21B to the outside. The scrubbing liquid extraction port 262 communicates with the liquid reservoir 21B.
[0036] In the illustrated embodiment, as shown in FIG. 1, the exhaust gas desulfurization
device 1 further includes a scrubbing liquid circulation line 7 configured to feed the scrubbing liquid stored in the liquid reservoir 21B to the spraying device 28, and a scrubbing liquid supply line 8 configured to supply the scrubbing liquid from the outside of the absorption tower 2 to the liquid reservoir 21B.
[0037] The scrubbing liquid circulation line 7 includes at least one pipe 71 connecting the
scrubbing liquid extraction port 262 and the spray pipe 281, and a scrubbing liquid circulation
pump 72 disposed in the middle of the scrubbing liquid circulation line 7 for feeding the
scrubbing liquid to the spray pipe 281 through the scrubbing liquid extraction port 262. In
other words, at least part of the scrubbing liquid sprayed from the spraying device 28 and
stored in the liquid reservoir 21B is pumped by the scrubbing liquid circulation pump 72,
passes through the scrubbing liquid circulation line 7, and is fed to the spraying device 28.
[0038] The scrubbing liquid supply line 8 includes a scrubbing liquid storage tank 81
disposed outside the absorption tower 2, and at least one pipe 82 connecting the scrubbing
liquid storage tank 81 and the liquid reservoir 21B. The scrubbing liquid is fed from the
scrubbing liquid storage tank 81 to the liquid reservoir 21B through the scrubbing liquid
supply line 8.
[0039] As shown in FIG. 1, the gas-liquid mixing device 4 includes an injection nozzle 5

configured to inject a mixed fluid MF of the scrubbing liquid and the gas containing oxygen such as air to the liquid reservoir 21B of the absorption tower 2, a scrubbing liquid introduction line 41 configured to feed the scrubbing liquid to the injection nozzle 5, and a gas introduction line 42 configured to feed the gas containing oxygen to the injection nozzle 5. The gas-liquid mixing device 4 injects the mixed fluid MF from the injection nozzle 5 to the liquid reservoir 21B to distribute the mixed fluid MF to the scrubbing liquid stored in the liquid reservoir 21B, so that the reaction products are oxidized by the mixed fluid MF to form oxidation products. Examples of the oxidation products include gypsum.
[0040] In the illustrated embodiment, as shown in FIG. 1, the exhaust gas desulfurization
device 1 further includes a scrubbing liquid discharge line 9 configured to discharge the scrubbing liquid containing oxidation products (gypsum) stored in the liquid reservoir 21B. In the embodiment shown in FIG. 1, the scrubbing liquid discharge line 9 is configured to discharge the scrubbing liquid via the scrubbing liquid circulation line 7 connected to the liquid reservoir 21B. More specifically, the scrubbing liquid discharge line 9 branches off from a branch portion 73 of the scrubbing liquid circulation line 7 and is connected to a device 91 disposed outside the absorption tower 2 so that the scrubbing liquid containing oxidation products is transferred from the branch portion 73 of the scrubbing liquid circulation line 7 to the device 91. Examples of the device 91 include a dehydrator (separator) for dehydrating the scrubbing liquid containing oxidation products and a storage tank for temporarily storing the scrubbing liquid.
[0041] In the embodiment shown in FIG. 1, the scrubbing liquid introduction line 41
branches off from the scrubbing liquid circulation line 7 at a branch portion 44 located
downstream of the branch portion 73 in the flow direction of the scrubbing liquid. The
scrubbing liquid circulation pump 72 is configured to feed part of the scrubbing liquid from
the scrubbing liquid extraction port 262 to the injection nozzle 5 via the branch portion 44.
[0042] In the illustrated embodiment, the gas introduction line 42 is connected at one end
to the injection nozzle 5 and opens at the other end to the atmosphere at a position higher than the liquid surface of the liquid reservoir 21B.

[0043] FIG. 2 is a schematic cross-sectional view of an injection nozzle for describing a
function of the injection nozzle according to an embodiment. FIG. 3 is a schematic cross-sectional view of the injection nozzle according to an embodiment. As shown in FIGs. 2 and 3, the injection nozzle 5 includes a first cylindrical portion 52, a contraction portion 53, and a second cylindrical portion 54.
[0044] As shown in FIGs. 2 and 3, the first cylindrical portion 52 is formed in a
cylindrical shape that internally defines a first flow passage 55. The first cylindrical portion 52 has a scrubbing liquid introduction port 56 for introducing the scrubbing liquid to the first flow passage 55, a gas introduction port 57 for introducing the gas to the first flow passage 55 along the direction perpendicular to the flow direction of the scrubbing liquid introduced from the scrubbing liquid introduction port 56 and flowing through the first flow passage 55, and a discharge port 51 described above. The discharge port 51 is provided to discharge the mixed fluid MF of the scrubbing liquid introduced from the scrubbing liquid introduction port 56 and the gas introduced from the gas introduction port 57.
[0045] In the embodiment shown in FIGs. 2 and 3, the first cylindrical portion 52 has a
longitudinal direction along the direction of extension of the center axis CA of the discharge port 51. The scrubbing liquid introduction port 56 opens at one end of the first cylindrical portion 52 in the longitudinal direction, and the discharge port 51 opens at the other end of the first cylindrical portion 52 in the longitudinal direction. The gas introduction port 57 opens in the outer circumferential surface of the first cylindrical portion 52. The scrubbing liquid introduced from the scrubbing liquid introduction line 41 to the first flow passage 55 via the scrubbing liquid introduction port 56 flows through the first flow passage 55 along the extension direction of the center axis CA from the scrubbing liquid introduction port 56 to the discharge port 51.
[0046] As shown in FIGs. 2 and 3, the second cylindrical portion 54 internally defines a
second flow passage 58 communicating with the gas introduction port 57 and extends along the direction in which the gas is introduced through the gas introduction port 57 (direction perpendicular to the flow direction of the scrubbing liquid). The second cylindrical portion

54 has a second gas introduction port 59 for introducing the gas to the second flow passage 58.
[0047] In the embodiment shown in FIGs. 2 and 3, the second cylindrical portion 54 has a
longitudinal direction along the extension direction of the center axis CA2 of the gas introduction port 57, i.e., along the direction perpendicular to the extension direction of the center axis CA of the discharge port 51. One end of the second cylindrical portion 54 is integrally connected to the outer circumference of the first cylindrical portion 52. In other words, the first cylindrical portion 52 and the second cylindrical portion 54 are formed integrally with each other. The second gas introduction port 59 opens at the other end of the second cylindrical portion 54 in the longitudinal direction. The gas introduced from the gas introduction line 42 to the second flow passage 58 via the second gas introduction port 59 passes through the second flow passage 58 and then enters the first flow passage 55 via the gas introduction port 57. The gas introduced into the first flow passage 55 merges with the scrubbing liquid at a merging portion 60.
[0048] As shown in FIGs. 2 and 3, the contraction portion 53 is disposed upstream of the
merging portion 60 in the flow direction of the scrubbing liquid. The contraction portion 53, through which the scrubbing liquid flows, has a contraction formation port 61 with a sharply reduced cross-sectional area as compared with the upstream and downstream sides in the flow direction of the scrubbing liquid. The contraction portion 53 contracts the flow of the scrubbing liquid by the contraction formation port 61 to generate a negative pressure region 62 (see FIG. 2) on the downstream side of the contraction portion 53 in the flow direction of the scrubbing liquid. The injection nozzle 5 sucks the gas from the gas introduction port 57 by the suction force generated in the negative pressure region 62. When the amount of gas fed to the first flow passage 55 is insufficient only by the suction force, a pump (not shown) for feeding the gas to the first flow passage 55 may be provided on the gas introduction line 42 to increase the amount of the gas fed to the first flow passage 55 by the pump.
[0049] In the embodiment shown in FIGs. 2 and 3, the contraction portion 53 may be
formed separately from the first cylindrical portion 52. In another embodiment, the contraction portion 53 may be formed integrally with the first cylindrical portion 52. For

example, the contraction portion 53 may be disposed so as to protrude from the inner
circumferential surface of the first cylindrical portion 52 defining the first flow passage 55.
[0050] The injection nozzle 5 shears and atomizes the gas introduced into the first flow
passage 55 by the scrubbing liquid flowing through the first flow passage 55 to generate the
mixed fluid MF (scrubbing liquid containing fine bubbles). Further, the injection nozzle 5
injects the mixed fluid MF produced in the injection nozzle 5 from the discharge port 51.
[0051] FIG. 4 is a schematic diagram of the absorption tower in the vicinity of the portion
to which the injection nozzle is fixed, for describing a first expansion joint and a second expansion joint.
[0052] In some embodiments, as shown in FIGs. 2 and 3, the gas-liquid mixing device 4
includes the injection nozzle 5 having the first cylindrical portion 52, the contraction portion 53, and the second cylindrical portion 54. In addition, the gas-liquid mixing device 4 further includes an expansion joint 45 disposed on at least one of the scrubbing liquid introduction line 41 or the gas introduction line 42, as shown in FIG. 4.
[0053] As shown in FIG. 4, the expansion joint 45 includes a body portion 451 internally
defining an introduction flow passage 455 for feeding the scrubbing liquid or the gas and configured to be expandable along at least the extension direction of the introduction flow passage 455.
[0054] In the illustrated embodiment, as shown in FIG. 4, the introduction flow passage
455 and the body portion 451 of the expansion joint 45 extend along the extension direction of the axis CE1, CE2. Further, the expansion joint 45 includes a downstream fastening portion 453 disposed so as to protrude from the outer circumference of one end (downstream end) of the body portion 451 in the extension direction along the direction perpendicular to the extension direction of the body portion 451, and an upstream fastening portion 454 disposed so as to protrude from the outer circumference of the other end (upstream end) of the body portion 451 in the extension direction along the direction perpendicular to the extension direction of the body portion 451. The expansion joint 45 has a bellows 452 with elasticity and bendability in the middle of the body portion 451 The expansion joint 45 with the

bellows 452 on the body portion 451 is expandable along the extension direction of the introduction flow passage 455 and along the direction perpendicular to the extension direction of the introduction flow passage 455.
[0055] According to the above configuration, the gas-liquid mixing device 4 includes the
expansion joint 45 disposed on at least one of the scrubbing liquid introduction line 41 or the gas introduction line 42, and the injection nozzle 5. The expansion joint 45 includes the body portion 451 internally defining the introduction flow passage 455 for feeding the scrubbing liquid or the gas and configured to be expandable along at least the extension direction of the introduction flow passage 455. In such a gas-liquid mixing device 4, the expansion joint 45 absorbs vibration and thermal contraction and thus prevents the transmission of vibration and thermal contraction from at least one of the scrubbing liquid introduction line 41 or the gas introduction line 42 to the injection nozzle 5. Since the injection nozzle 5 is prevented from being subjected to superimposed vibration and thermal contraction from two mutually perpendicular directions (extension direction of center axis CA and extension direction of center axis CA2), it is possible to reduce wear and damage to the injection nozzle 5.
Further, with the above configuration, by removing the expansion joint 45 from the scrubbing liquid introduction line 41, the contraction portion 53 can be inspected without removing the pipe upstream of the expansion joint 45 in the scrubbing liquid introduction line 41, thus making it possible to perform the inspection work quickly.
[0056] In some embodiments, as shown in FIG. 4, the expansion joint 45 is disposed on
both of the scrubbing liquid introduction line 41 and the gas introduction line 42. In other words, the expansion joint 45 includes a first expansion joint 45A disposed on the scrubbing liquid introduction line 41 and a second expansion joint 45B disposed on the gas introduction line. In this case, since the expansion joint 45 is disposed on both of the scrubbing liquid introduction line 41 and the gas introduction line 42, it is possible to prevent the transmission of vibration and thermal contraction from both of the scrubbing liquid introduction line 41 and the gas introduction line 42 to the injection nozzle 5. With the above configuration, it is

possible to more reliably prevent the injection nozzle 5 from being subjected to superimposed vibration and thermal contraction from two mutually perpendicular directions, compared with the case where the expansion joint 45 is disposed on at least one of the scrubbing liquid introduction line 41 or the gas introduction line 42. Further, by removing the first expansion joint 45A from the scrubbing liquid introduction line 41 and the second expansion joint 45B from the gas introduction line 42, it is possible to quickly remove the injection nozzle 5 from the absorption tower 2.
[0057] FIG. 5 is a schematic partial cross-sectional view of the absorption tower in the
vicinity of the portion to which the injection nozzle is fixed. Hereinafter, the method of attaching the injection nozzle 5 will be described based on FIG. 5.
[0058] First, the distal end of the first cylindrical portion 52 having the discharge port 51
of the injection nozzle 5 is inserted into the insertion hole 252 formed through the first side wall 25.
[0059] As shown in FIG. 5, the injection nozzle 5 includes a discharge-port-side fastening
portion 63. The first cylindrical portion 52 extends along the center axis CA of the discharge port 51, and the discharge port 51 is formed at one end of the first cylindrical portion 52 in the extension direction. The discharge-port-side fastening portion 63 is disposed so as to protrude from the outer circumference of the first cylindrical portion 52 along the direction perpendicular to the center axis CA of the discharge port 51. The discharge-port-side fastening portion 63 is disposed around the outer circumference of the first cylindrical portion 52 on the downstream side of the connection portion with the second cylindrical portion 54 and the merging portion 60 in the flow direction of the scrubbing liquid.
[0060] As shown in FIG. 5, the absorption tower 2 further includes the cylindrical
protruding portion 29 and an injection nozzle fastening portion 30. As shown in FIG. 5, the cylindrical protruding portion 29 is disposed so as to protrude from the peripheral edge of the insertion hole 252 of the first side wall 25 along a direction inclined with respect to a horizontal plane by the inclination angle θ which is the inclination angle of the center axis CA of the discharge port 51 with respect to a horizontal plane. The injection nozzle fastening

portion 30 is disposed so as to protrude from the distal end of the cylindrical protruding portion 29 along the direction perpendicular to the extension direction of the cylindrical protruding portion 29.
[0061] Then, the injection nozzle 5 is fixed to the first side wall 25. The discharge-port-
side fastening portion 63 of the injection nozzle 5 is fixed to the injection nozzle fastening portion 30 of the absorption tower 2 by means of a fastening device 66 (66A). In the illustrated embodiment, the fastening device 66A (second fastening device) includes a bolt 67 (67A) and a nut 68 (68A).
[0062] The bolt 67 (67A) has a shaft portion 671 with a threaded portion formed on at
least part of the outer circumferential surface, and a head portion 672 formed at the base of the shaft portion 671 with a larger diameter than the shaft portion 671. The discharge-port-side fastening portion 63 and the injection nozzle fastening portion 30 have through holes 631 and 301 in which the shaft portion 671 of the bolt 67A can be inserted along the extension direction of the cylindrical protruding portion 29. The shaft portion 671 of the bolt 67A is inserted into the through holes 631 and 301 formed in the discharge-port-side fastening portion 63 and the injection nozzle fastening portion 30 from one side in the extension direction of the cylindrical protruding portion 29, and the distal end of the shaft portion 671 inserted on the other side in the extension direction of the cylindrical protruding portion 29 is screwed into the nut 68A to fix the injection nozzle 5 to the first side wall 25.
[0063] After the injection nozzle 5 is fixed to the first side wall 25, the gas introduction
line 42 is connected to the injection nozzle 5. In the illustrated embodiment, as shown in FIG. 5, the injection nozzle 5 further includes a gas-introduction-side fastening portion 64 disposed so as to protrude from the outer circumference of the end portion of the second cylindrical portion 54 at which the second gas introduction port 59 is formed. As shown in FIG. 4, the gas introduction line 42 includes a gas introduction pipe 47 connected to the upstream side of the second cylindrical portion 54, the second expansion joint 45B connected to the upstream side of the gas introduction pipe 47, and a second gas introduction pipe 49 connected to the upstream side of the second expansion joint 45B.

[0064] As shown in FIG. 4, the gas introduction pipe 47 includes a gas downstream
fastening portion 48 (see FIG. 5) disposed so as to protrude from the outer circumference of the downstream end portion having an opening communicating with the second gas introduction port 59, and a gas upstream fastening portion 472 disposed so as to protrude from the outer circumference of the upstream end portion. The second gas introduction pipe 49 includes a second gas downstream fastening portion 491 disposed so as to protrude from the outer circumference of the downstream end portion.
[0065] The gas downstream fastening portion 48 of the gas introduction pipe 47 is fixed
to the gas-introduction-side fastening portion 64 of the injection nozzle 5 by means of a fastening device 66 (66B). In the illustrated embodiment, the fastening device 66B includes a bolt 67B having the same configuration as the bolt 67A and a nut 68B having the same configuration as the nut 68A. The distal end of the shaft portion 671 of the bolt 67B inserted into through holes 641 and 481 formed in the gas-introduction-side fastening portion 64 and the gas downstream fastening portion 48 is screwed into the nut 68B to fix the second cylindrical portion 54 of the injection nozzle 5 to the gas introduction pipe 47.
[0066] As shown in FIG. 4, the downstream fastening portion 453 (453B) of the second
expansion joint 45B is fixed to the gas upstream fastening portion 472 of the gas introduction pipe 47 by means of a fastening device 66 (66E), and the upstream fastening portion 454 (454B) of the second expansion joint 45B is fixed to the second gas downstream fastening portion 491 of the second gas introduction pipe 49 by means of a fastening device 66 (66F). In the illustrated embodiment, the fastening devices 66E, 66F include a bolt and a nut, as with the fastening device 66B.
[0067] After the injection nozzle 5 is fixed to the first side wall 25, the scrubbing liquid
introduction line 41 is connected to the injection nozzle 5. The connection between the scrubbing liquid introduction line 41 and the injection nozzle 5 may be made at the same time as the connection between the gas introduction line 42 and the injection nozzle 5, or may be made before or after the connection between the gas introduction line 42 and the injection nozzle 5.

[0068] As shown in FIG. 5, the injection nozzle 5 further includes a scrubbing-liquid-introduction-side fastening portion 65 disposed so as to protrude from the outer circumference of the end portion of the first cylindrical portion 52 at which the scrubbing liquid introduction port 56 is formed. As shown in FIG. 4, the scrubbing liquid introduction line 41 includes the first expansion joint 45A connected to the upstream side of the first cylindrical portion 52, and a scrubbing liquid introduction pipe 46 connected to the upstream side of the first expansion joint 45A. The scrubbing liquid introduction pipe 46 includes a scrubbing liquid downstream fastening portion 461 disposed so as to protrude from the outer circumference of the downstream end portion.
[0069] As shown in FIG. 5, the downstream fastening portion 453 (453A) of the first expansion joint 45A is fixed to the scrubbing-liquid-introduction-side fastening portion 65 of the injection nozzle 5 by means of a fastening device 66C (first fastening device). In the illustrated embodiment, the fastening device 66C includes a bolt 67C having the same configuration as the bolt 67A and a nut 68C having the same configuration as the nut 68A. The distal end of the shaft portion 671 of the bolt 67C inserted in the through holes 651 and 456 formed in the scrubbing-liquid-introduction-side fastening portion 65 and the downstream fastening portion 453 (453A) is screwed into the nut 68C to fix the first expansion joint 45A to the first cylindrical portion 52 of the injection nozzle 5 while the contraction portion 53 is interposed between the first cylindrical portion 52 and the first expansion joint 45A. [0070] As shown in FIG. 4, the upstream fastening portion 454 (454A) of the first expansion joint 45A is fixed to the scrubbing liquid downstream fastening portion 461 of the scrubbing liquid introduction pipe 46 by means of a fastening device 66 (66D). In the illustrated embodiment, the fastening device 66D includes a bolt and a nut, as with the fastening device 66C.
[0071] In the illustrated embodiment, as shown in FIG. 4, when θ is the inclination angle of the center axis CA of the discharge port 51 with respect to a horizontal plane, and θ1 is the inclination angle of the axis CE1 of the first expansion joint 45A with respect to a horizontal plane, the inclination angle θ1 is within the range of θ±5°. In other words, the axis CE1 of

the first expansion joint 45A extends along the direction parallel to the center axis CA of the discharge port 51. In this case, the resistance for feeding the scrubbing liquid from the first expansion joint 45 A to the first cylindrical portion 52 can be reduced. In other embodiments, θ1 may be out of the range of θ±5°.
Further, in the illustrated embodiment, as shown in FIG. 4, the second expansion joint 45B is disposed above the first expansion joint 45A.
[0072] As described above, in some embodiments, as shown in FIG. 5, the injection nozzle 5 includes a scrubbing-liquid-introduction-side fastening portion 65 disposed so as to protrude from the outer circumference of the end portion of the first cylindrical portion 52 at which the scrubbing liquid introduction port 56 is formed on the upstream side of the connection portion with the second cylindrical portion 54 and the merging portion 60 in the flow direction of the scrubbing liquid. The first expansion joint 45A includes the downstream fastening portion 453A disposed so as to protrude from the outer circumference of the end portion of the body portion 451 along a direction intersecting the extension direction of the axis CE1 of the first expansion joint 45A. The downstream fastening portion 453A is fixed to the downstream fastening portion 453A by means of the fastening device 66C (first fastening device) while the contraction portion 53 is interposed between the first expansion joint 45A and the first cylindrical portion 52.
[0073] According to the above configuration, the downstream fastening portion 453A of the first expansion joint 45A is fixed to the scrubbing-liquid-introduction-side fastening portion 65 of the injection nozzle 5 by means of the fastening device 66C (first fastening device) while the contraction portion 53 is interposed between the first expansion joint 45A and the first cylindrical portion 52. Since the first expansion joint 45A is directly fixed to the injection nozzle 5, it can effectively absorb vibration and thermal contraction from the scrubbing liquid introduction line 41.
[0074] In some embodiments, the exhaust gas desulfurization device 1 includes the absorption tower 2 and the gas-liquid mixing device 4 described above. According to the above configuration, the absorption tower 2 is configured to bring the scrubbing liquid into

gas-liquid contact with the exhaust gas introduced into the absorption tower 2, and internally
defines the liquid reservoir 21B for storing the scrubbing liquid. The gas-liquid mixing
device 4 can cause sufficient oxidation reaction for the scrubbing liquid stored in the liquid
reservoir 21B of the absorption tower 2 by the mixed fluid MF discharged from the discharge
port 51 of the injection nozzle 5 to the liquid reservoir 21B of the absorption tower 2.
Further, according to the above configuration, since the injection nozzle 5 is prevented from
being subjected to superimposed vibration and thermal contraction from two mutually
perpendicular directions, it is possible to reduce wear and damage to the injection nozzle 5.
[0075] In some embodiments, the injection nozzle 5 (gas-liquid mixing device 4) includes
the first cylindrical portion 52 and the discharge-port-side fastening portion 63. Additionally, the absorption tower 2 includes the cylindrical protruding portion 29 and the injection nozzle fastening portion 30.
[0076] According to the above configuration, the discharge-port-side fastening portion 63
of the injection nozzle 5 (gas-liquid mixing device 4) is fixed to the injection nozzle fastening portion 30 of the absorption tower 2 by means of the fastening device 66A (second fastening device) while the distal end of the first cylindrical portion 52 including the discharge port 51 is inserted in the insertion hole 252 formed in the side wall (e.g., first side wall 25) of the absorption tower 2. Since the injection nozzle 5 is fixed to the absorption tower 2, even if vibration and thermal contraction are transmitted to the injection nozzle 5 from both the scrubbing liquid introduction line 41 and the gas introduction line 42, it is possible to prevent the deterioration of oxidation reaction of the scrubbing liquid by the mixed fluid MF injected from the injection nozzle 5 due to shifting the position or angle of the discharge port 51 of the injection nozzle 5.
[0077] Further, according to the above configuration, the first cylindrical portion 52
extends along the center axis CA of the discharge port 51. The cylindrical protruding portion 29 of the absorption tower 2 extends along a direction inclined with respect to a horizontal plane by the same angle as the inclination angle θ of the center axis CA of the discharge port 51 with respect to a horizontal plane. In other words, the cylindrical

protruding portion 29 of the absorption tower 2 extends along the same direction as the center axis CA of the discharge port 51 when the first cylindrical portion 52 is installed. By fixing the discharge-port-side fastening portion 63 extending along the direction perpendicular to the extension direction of the first cylindrical portion 52 with the injection nozzle fastening portion 30 extending along the direction perpendicular to the extension direction of the cylindrical protruding portion 29 by means of the fastening device 66A, the first cylindrical portion 52 can be installed at the same angle as the inclination angle θ of the center axis CA of the discharge port 51 with respect to a horizontal plane. Thus, with the above configuration, it is possible to easily attach the first cylindrical portion 52 without adjusting the installation angle of the first cylindrical portion 52.
[0078] The present invention is not limited to the embodiments described above, but
includes modifications to the embodiments described above, and embodiments composed of combinations of those embodiments.
[0079] For example, in the above-described embodiments, the exhaust gas discharge unit
24 is disposed on the opposite side of the absorption tower body 22 from the exhaust gas introduction unit 23 in the first direction, but it may be disposed on the same side as the exhaust gas introduction unit 23. Further, the exhaust gas discharge unit 24 may adjoin the absorption tower body 22 in the second direction perpendicular to the first direction in a top view.
Reference Signs List [0080]
1 Exhaust gas desulfurization device
2 Absorption tower 21 Interior space 211 Bottom surface
21A Gas-liquid contact part
21B Liquid reservoir

21C Lower interior space
21D Upper interior space
22 Absorption tower body
23 Exhaust gas introduction unit
24 Exhaust gas discharge unit
25 First side wall

251 Exhaust gas introduction port
252 Insertion hole
26 Second side wall
261 Exhaust gas discharge port
262 Extraction port

27 Mist eliminator
28 Spraying device

281 Spray pipe
282 Spray nozzle
29 Cylindrical protruding portion
30 Injection nozzle fastening portion
301 Through hole
4 Gas-liquid mixing device
41 Scrubbing liquid introduction line
42 Gas introduction line
44 Branch portion
45 Expansion joint
45A First expansion joint
45B Second expansion joint
451 Body portion
452 Bellows
453, 453A, 453B Downstream fastening portion

454, 454A, 454B Upstream fastening portion
455 Introduction flow passage
456 Through hole
46 Scrubbing liquid introduction pipe
461 Scrubbing liquid downstream fastening portion
47 Gas introduction pipe
472 Gas upstream fastening portion
48 Gas downstream fastening portion
481 Through hole
49 Second gas introduction pipe
491 Second gas downstream fastening portion
5 Injection nozzle
51 Discharge port
52 First cylindrical portion
53 Contraction portion
54 Second cylindrical portion
55 First flow passage
56 Scrubbing liquid introduction port
57 Gas introduction port
58 Second flow passage
59 Second gas introduction port
60 Merging portion
61 Contraction formation port
62 Negative pressure region

63 Discharge-port-side fastening portion 631 Through hole
64 Gas-introduction-side fastening portion 641 Through hole

65 Scrubbing-liquid-introduction-side fastening portion
651 Through hole
66, 66A to 66F Fastening device
671 Shaft portion
672 Head portion 67A, 67B, 67C Bolt 68A, 68B, 68C Nut
7 Scrubbing liquid circulation line
71 Pipe
72 Scrubbing liquid circulation pump
73 Branch portion
8 Scrubbing liquid supply line
81 Scrubbing liquid storage tank
82 Pipe
9 Scrubbing liquid discharge line
91 Device
CA Center axis of discharge port
CA2 Center axis of gas introduction port
CE1 Axis of first expansion joint
CE2 Axis of second expansion joint
G Gas
MF Mixed fluid

I/We Claim:
1. A gas-liquid mixing device, comprising an injection nozzle configured to inject a
scrubbing liquid and a gas containing oxygen to a liquid reservoir for storing the scrubbing liquid in an absorption tower configured to bring the scrubbing liquid into gas-liquid contact with an exhaust gas discharged from a combustion device, wherein the injection nozzle includes:
a first cylindrical portion internally defining a first flow passage and having a scrubbing liquid introduction port for introducing the scrubbing liquid into the first flow passage, a gas introduction port for introducing the gas into the first flow passage along a direction perpendicular to a flow direction of the scrubbing liquid introduced from the scrubbing liquid introduction port and flowing through the first flow passage, and a discharge port for discharging a mixed fluid of the scrubbing liquid introduced from the scrubbing liquid introduction port and the gas introduced from the gas introduction port;
a contraction portion disposed, in the flow direction of the scrubbing liquid, upstream of a merging portion at which the scrubbing liquid introduced from the scrubbing liquid introduction port merges with the gas introduced from the gas introduction port; and
a second cylindrical portion internally defining a second flow passage communicating with the gas introduction port, the second cylindrical portion having a second gas introduction port for introducing the gas into the second flow passage along a direction perpendicular to the flow direction of the scrubbing liquid, and
wherein the gas-liquid mixing device further includes an expansion joint including a body portion internally defining an introduction flow passage for feeding the scrubbing liquid or the gas and configured to be expandable along at least a direction of extension of the introduction flow passage, the expansion joint being disposed on at least one of a scrubbing liquid introduction line for feeding the scrubbing liquid to the first flow passage through the scrubbing liquid introduction port or a gas introduction line for feeding the gas to the second flow passage through the second gas introduction port.

2. The gas-liquid mixing device according to claim 1,
wherein the expansion joint is disposed on both of the scrubbing liquid introduction line and the gas introduction line.
3. The gas-liquid mixing device according to claim 1 or 2,
wherein the injection nozzle further includes a scrubbing-liquid-introduction-side fastening portion disposed so as to protrude from an outer circumference of the first cylindrical portion on an upstream side of the merging portion in the flow direction of the scrubbing liquid, and
wherein a first expansion joint which is the expansion joint disposed on the scrubbing liquid introduction line further includes a downstream fastening portion disposed so as to protrude from an outer circumference of the body portion along a direction intersecting a direction of extension of a center axis of the first expansion joint, and the downstream fastening portion is configured to be fixed to the scrubbing-liquid-introduction-side fastening portion by means of a first fastening device while the contraction portion is interposed between the first expansion joint and the first cylindrical portion.
4. An exhaust gas desulfurization device for desulfurizing an exhaust gas discharged from
a combustion device, the exhaust gas desulfurization device comprising:
an absorption tower configured to bring a scrubbing liquid into gas-liquid contact with the exhaust gas introduced into the absorption tower, the absorption tower internally defining a liquid reservoir for storing the scrubbing liquid; and
the gas-liquid mixing device according to any one of claims 1 to 3.
5. The exhaust gas desulfurization device according to claim 4,
wherein the first cylindrical portion extends along a center axis of the discharge port, wherein the injection nozzle further includes a discharge-port-side fastening portion

disposed so as to protrude from an outer circumference of the first cylindrical portion on a downstream side of the merging portion in the flow direction of the scrubbing liquid along a direction perpendicular to the center axis of the discharge port, and wherein the absorption tower further includes:
a side wall defining at least a part of the liquid reservoir and having an insertion hole in which a distal end of the first cylindrical portion including the discharge port is inserted;
a cylindrical protruding portion disposed so as to protrude outward of the side wall from a peripheral edge of the insertion hole of the side wall along a direction inclined with respect to a horizontal plane by an angle equal to θ, where θ is an inclination angle of the center axis of the discharge port with respect to a horizontal plane; and
an injection nozzle fastening portion disposed so as to protrude from a distal end of the cylindrical protruding portion along a direction perpendicular to a direction of extension of the cylindrical protruding portion, the injection nozzle fastening portion being configured to be fixed to the discharge-port-side fastening portion by means of a second fastening device.