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: EXHAUST GAS DESULFURIZATION 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 an exhaust gas desulfurization device for
desulfurizing exhaust gas discharged from a combustion 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 mixed fluid injected from the injection nozzle flows along the direction of the
injection nozzle until a predetermined jet reaching distance is reached. The mixed fluid that has reached the predetermined jet reaching distance loses momentum in the horizontal direction and flows vertically upward due to the buoyancy of the bubbles.
Citation List
Patent Literature
[0007] Patent Document 1: JP5046755B
SUMMARY Problems to be Solved
[0008] If the injection nozzle is oriented excessively downward, the mixed fluid injected
from the injection nozzle impinges on the bottom surface of the liquid reservoir and loses
momentum in the horizontal direction, so that the mixed fluid flows vertically upward before
the predetermined jet reaching distance is reached. In this case, the oxidation effective
capacity, which is a capacity of oxidation reaction promoted by the mixed fluid in the liquid
reservoir, may be decreased to be less than the oxidation effective capacity that can be
originally exerted by the mixed fluid injected from the injection nozzle. When the oxidation
effective capacity is decreased, oxidation by the mixed fluid may be insufficient, and many
unoxidized reaction products may remain in the scrubbing liquid stored in the liquid reservoir.
[0009] Therefore, in order to sufficiently perform oxidation by the mixed fluid injected
from the injection nozzle, it is necessary to determine an appropriate orientation of the

injection nozzle and arrange the injection nozzle in the appropriate orientation. However, for arranging the injection nozzle so as to be inclined downward and directed in a predetermined orientation, it is necessary to finely adjust the angle of the axis of the injection nozzle with respect to a vertical plane and a horizontal plane when attaching the injection nozzle to the absorption tower, so that the attachment work takes longer.
Although Patent Document 1 discloses a diagram in which the injection nozzle is arranged so as to be inclined downward, it discloses nothing about a specific method for attaching the injection nozzle to the absorption tower and a specific attachment structure. Further, there is no description specifically referring to the installation angle of the injection nozzle in the specification of Patent Document 1.
[0010] In view of the above circumstances, an object of at least one embodiment of the
present invention is to provide an exhaust gas desulfurization device that enables the injection nozzle to be easily attached to the absorption tower at a predetermined angle with respect to a horizontal plane in order to prevent a decrease in the oxidation effective capacity, which is a capacity of oxidation reaction promoted by the mixed fluid injected from the injection nozzle.
Solution to the Problems
[0011] (1) 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 including a liquid reservoir for storing the scrubbing liquid, at least a part of the liquid reservoir being defined by a first side wall and a second side wall facing the first side wall of the absorption tower; and a gas-liquid mixing device including a first injection nozzle with a distal end inserted in an insertion hole formed in the first side wall, the first injection nozzle being configured to inject a mixed fluid of the scrubbing liquid and a gas containing oxygen from a first discharge port of the first injection nozzle to the liquid reservoir. The first injection nozzle includes: a cylindrical portion extending along a center axis of the first discharge port

and having the first discharge port; and a first fastening portion disposed so as to protrude from an outer circumference of the cylindrical portion along a direction perpendicular to the center axis of the first discharge port. The absorption tower further includes: a cylindrical protruding portion disposed so as to protrude outward from a peripheral edge of the insertion hole formed in the first side wall along a direction inclined with respect to a horizontal plane by an angle θ, where θ is an inclination angle of the center axis of the first discharge port with respect to a horizontal plane; and a second 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 second fastening portion being configured to be fixed to the first fastening portion with a fastening device. [0012] With the above configuration (1), the first fastening portion of the first injection nozzle is fixed to the second fastening portion of the absorption tower by means of the fastening device while the distal end of the first injection nozzle including the first discharge port of the cylindrical portion is inserted in the insertion hole formed in the first side wall of the absorption tower. Here, the cylindrical portion extends along the center axis of the first 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 first 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 first discharge port when the first injection nozzle is installed. By fixing the first fastening portion extending along the direction perpendicular to the extension direction of the cylindrical portion with the second fastening portion extending along the direction perpendicular to the extension direction of the cylindrical protruding portion by means of the fastening device, the first injection nozzle can be installed at the same angle as the inclination angle θ of the center axis of the first discharge port with respect to a horizontal plane. Thus, with the above configuration, it is possible to easily attach the first injection nozzle without adjusting the installation angle of the first injection nozzle. [0013] (2) In some embodiments, in the exhaust gas desulfurization device described in

the above (1), the first injection nozzle satisfies 10°<θ<30° where θ is an inclination angle of the center axis of the first discharge port with respect to a horizontal plane. [0014] As a result of studies by the present inventors, it was found that when the inclination angle θ of the first injection nozzle is equal to or less than 10°, there is an increased risk that the gas (bubbles) contained in the mixed fluid injected from the first injection nozzle is caught in a pump for discharging the scrubbing liquid from the liquid reservoir. Further, it was found that when the inclination angle θ of the first inj ection nozzle is equal to or more than 30°, the mixed fluid injected from the first injection nozzle impinges on the bottom surface of the liquid reservoir at an early stage, so that the reaching distance of the mixed fluid is shortened, and the oxidation effective capacity, which is a capacity of oxidation reaction promoted by the mixed fluid injected from the first injection nozzle, is decreased.
With the above configuration (2), since the inclination angle θ of the first injection nozzle satisfies 10°<θ<30°, it is possible to prevent the oxidation effective capacity from becoming smaller than the effective oxidation volume that can be exhibited originally, and it is possible to prevent the gas (bubbles) from being caught in a pump for discharging the scrubbing liquid from the liquid reservoir and deteriorating the performance of the pump. [0015] (3) In some embodiments, in the exhaust gas desulfurization device described in the above (1) or (2), the absorption tower further includes: a third side wall extending along a direction in which the first side wall and the second side wall are separated, the third side wall defining a part of the liquid reservoir; and a fourth side wall facing the third side wall and extending along a direction in which the first side wall and the second side wall are separated, the fourth side wall defining a part of the liquid reservoir. Additionally, the gas-liquid mixing device further includes: a second injection nozzle with a distal end inserted in an insertion hole formed in the third side wall, the second injection nozzle being configured to inject the mixed fluid from a second discharge port of the second injection nozzle to the liquid reservoir; and a third injection nozzle with a distal end inserted in an insertion hole formed in the fourth side wall, the third injection nozzle being configured to inject the mixed fluid from

a third discharge port of the third injection nozzle to the liquid reservoir.
[0016] With the above configuration (3), the gas-liquid mixing device further includes the
second injection nozzle with the distal end inserted in the insertion hole formed in the third
side wall, and the third injection nozzle with the distal end inserted in the insertion hole
formed in the fourth side wall. Accordingly, in an area of the liquid reservoir where the
oxidation reaction cannot be promoted by the mixed fluid injected from the first injection
nozzle, the oxidation reaction can be promoted by the mixed fluid injected from each of the
second injection nozzle and the third injection nozzle. Therefore, with the above
configuration, it is possible to reduce the area of the liquid reservoir where the oxidation reaction cannot be promoted by the mixed fluid, so that it is possible to prevent insufficient oxidation by the mixed fluid.
[0017] (4) In some embodiments, in the exhaust gas desulfurization device described in
the above (3), each of the second injection nozzle and the third injection nozzle is arranged at a height position different from the first injection nozzle.
[0018] In a top view, each of the second injection nozzle and the third injection nozzle
injects the mixed fluid along a direction intersecting the direction in which the first injection nozzle injects the mixed fluid. If each of the second injection nozzle and the third injection nozzle is arranged at the same height as the first injection nozzle, the mixed fluid injected from each of the second injection nozzle and the third injection nozzle may obstruct the flow of the mixed fluid injected from the first injection nozzle.
With the above configuration (4), since each of the second injection nozzle and the third
injection nozzle is arranged at a height position different from the first injection nozzle, it is
possible to prevent the mixed fluid injected from each of the second injection nozzle and the
third injection nozzle from obstructing the flow of the mixed fluid injected from the first
injection nozzle. Further, since the obstruction of the flow of the mixed fluid injected from
the first injection nozzle is prevented, it is possible to prevent the oxidation effective capacity
from decreasing.
[0019] (5) In some embodiments, in the exhaust gas desulfurization device described in

the above (3) or (4), each of the second injection nozzle and the third injection nozzle is
arranged at a position away from the first side wall by a predetermined distance or more.
[0020] With the above configuration (5), since each of the second injection nozzle and the
third injection nozzle is arranged at a position away from the first side wall by a predetermined distance or more, it is possible to prevent the mixed fluid injected from each of the second injection nozzle and the third injection nozzle from obstructing the flow of the mixed fluid injected from the first injection nozzle. Further, since the obstruction of the flow of the mixed fluid injected from the first injection nozzle is prevented, it is possible to prevent a decrease in oxidation effective capacity, which is a capacity of oxidation reaction promoted by the mixed fluid injected from the first injection nozzle.
[0021] (6) In some embodiments, in the exhaust gas desulfurization device described in
any one of the above (3) to (5), each of the second injection nozzle and the third injection nozzle is arranged at a position away from the second side wall by a predetermined distance or more.
[0022] With the above configuration (6), since each of the second injection nozzle and the
third injection nozzle is arranged at a position away from the second side wall by a predetermined distance or more, it is possible to prevent the mixed fluid injected from each of the second injection nozzle and the third injection nozzle from reaching a scrubbing liquid extraction port on the second side wall. Accordingly, it is possible to prevent the gas (bubbles) from being caught in a pump for discharging the scrubbing liquid from the liquid reservoir and deteriorating the performance of the pump.
Advantageous Effects
[0023] At least one embodiment of the present invention provides an exhaust gas
desulfurization device that enables the injection nozzle to be easily attached to the absorption tower at a predetermined angle with respect to a horizontal plane in order to prevent a decrease in the oxidation effective capacity, which is a capacity of oxidation reaction promoted by the mixed fluid injected from the injection nozzle.

BRIEF DESCRIPTION OF DRAWINGS
[0024] 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 according to an embodiment.
FIG. 3 is a diagram for describing the arrangement state of the injection nozzle according to an embodiment.
FIG. 4 is a graph representing a relationship between the underwater depth and the distance from the discharge port of the injection nozzle to the jet reaching point.
FIG. 5 is a schematic diagram of the liquid reservoir of the absorption tower and the injection nozzle shown in FIG. 1 when viewed from the top.
FIG. 6 is a schematic diagram of the liquid reservoir of the absorption tower and the injection nozzle according to another embodiment when viewed from the top.
FIG. 7 is a diagram for describing the arrangement state of each injection nozzle shown in FIG. 6.
FIG. 8 is a schematic partial cross-sectional view of the absorption tower in the vicinity of a portion to which the injection nozzle is fixed.
DETAILED DESCRIPTION
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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 from the scrubbing liquid extraction port 262 to the spray pipe 281. 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.
[0040] 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.
[0041] 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.
[0042] 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 (e.g., 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.

[0043] 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.
[0044] 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.
[0045] FIG. 2 is a schematic cross-sectional view of the injection nozzle according to an
embodiment. As shown in FIG. 2, the injection nozzle 5 includes a first cylindrical portion 52, a contraction portion 53, and a second cylindrical portion 54.
[0046] As shown in FIG. 2, 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.
[0047] In the embodiment shown in FIG. 2, 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.
[0048] As shown in FIG. 2, 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.
[0049] In the embodiment shown in FIG. 2, the second cylindrical portion 54 has a
longitudinal 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.
[0050] As shown in FIG. 2, 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 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.
[0051] In the embodiment shown in FIG. 2, 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.
[0052] 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. The mixed fluid MF injected from the discharge port 51 to the liquid reservoir 21B flows along the extension direction of the center axis CA of the discharge port 51 until a predetermine jet reaching distance is reached, as shown in FIG. 3 described later. At this time, the width of the mixed fluid MF gradually increases as the distance from the discharge port 51 increases. The mixed fluid MF that has reached the predetermined jet reaching distance loses momentum in the horizontal direction and flows vertically upward due to the buoyancy of the bubbles.
[0053] FIG. 3 is a diagram for describing the arrangement state of the injection nozzle
according to an embodiment.
As shown in FIG. 3, the injection nozzle 5 includes a first injection nozzle 5A in which the distal end of the first cylindrical portion 52 having the discharge port 51 (first discharge port 51A) is inserted in an insertion hole 252 formed in the first side wall 25 from the outside of the first side wall 25.
[0054] As described above, the exhaust gas desulfurization device 1 according to some
embodiments includes the absorption tower 2 including the liquid reservoir 21B and the gas-liquid mixing device 4 including the first injection nozzle 5A. As shown in FIG. 3, the first injection nozzle 5A is arranged such that the center axis CA of the first discharge port 51A is

inclined downward with respect to a horizontal plane. As shown in FIG. 3, an intersection between an imaginary line IL extending from the center axis CA of the first discharge port 51A and the bottom surface 211 of the liquid reservoir 21B is defined as P.
[0055] The mixed fluid MF injected from the first discharge port 51A of the first injection
nozzle 5A to the liquid reservoir 21B flows along the imaginary line IL extending the center
axis CA of the first discharge port 51A until a predetermine jet reaching distance is reached.
[0056] If the length from the first discharge port 51A to the intersection P is longer than
the jet reaching distance, the mixed fluid MF injected from the first injection nozzle 5A may lose momentum in the horizontal direction without impinging on the wall surface of the liquid reservoir 21B.
[0057] Further, when the scrubbing liquid stored in the liquid reservoir 21B is sprayed by
the spraying device 28, if the scrubbing liquid sprayed from the injection nozzle 5 is not
sufficiently oxidized by the mixed fluid MF, the absorption efficiency of SOx from the
exhaust gas by the scrubbing liquid sprayed by the spraying device 28 may decrease.
[0058] In some embodiments, as shown in FIG. 3, the first injection nozzle 5A is arranged
such that the imaginary line IL intersects the bottom surface 211 of the liquid reservoir 21B at the intersection P. Here, if the gas G (bubbles) contained in the mixed fluid MF injected from the first injection nozzle 5A reaches the scrubbing liquid extraction port 262 opening in the second side wall 26, the gas G (bubbles) is caught in the pump (scrubbing liquid circulation pump 72) for extracting the scrubbing liquid from the liquid reservoir 21B, so that the performance of the pump may decrease. According to the above configuration, the imaginary line IL extends so as to intersect the bottom surface 211 of the liquid reservoir 21B at the intersection P. In other words, the imaginary line IL extends so as not to intersect the second side wall 26. Thus, the mixed fluid MF injected from the first injection nozzle 5A and flowing along the imaginary line IL is directed to the bottom surface 211 of the liquid reservoir 21B and loses momentum in the horizontal direction upon impingement on the bottom surface 211, so that it is possible to prevent the mixed fluid MF from reaching the scrubbing liquid extraction port 262 of the second side wall 26. Accordingly, with the above

configuration, it is possible to prevent the gas G from being caught in the pump (scrubbing liquid circulation pump 72) for extracting the scrubbing liquid from the liquid reservoir 21B and deteriorating the performance of the pump.
[0059] In some embodiments, as shown in FIG. 3, the absorption tower 2 further includes a bubble suppression member 29 disposed in the liquid reservoir 21B (interior space 21). As shown in FIG. 3, the bubble suppression member 29 extends in the direction perpendicular to the first direction and is placed at a position between the second side wall 26 and a center line CL, which represents the center of the distance between the first discharge port 51A and the second side wall 26, so as to be away from the second side wall 26 toward the first side wall 25. The bubble suppression member 29 is formed in a plate shape with a plurality of through holes and prevents the bubbles from flowing from the first side wall 25 to the second side wall 26. In the illustrated embodiment, assuming that the distance from the first discharge port 51A to the bubble suppression member 29 in the first direction is L1, the distance L1 satisfies 0.7L≤L1≤0.9L.
[0060] With the above configuration, the bubble suppression member 29 disposed away from the second side wall 26 to the first side wall 25 prevents the gas G (bubbles) contained in the mixed fluid MF injected from first injection nozzle 5A from reaching the scrubbing liquid extraction port 262 opening in the second side wall 26.
[0061 ] FIG. 4 is a graph representing a relationship between the underwater depth and the horizontal distance from the discharge port of the injection nozzle to the jet reaching point. Here, as shown in FIG. 3, the underwater depth Z means a height from the bottom surface 211 of the liquid reservoir 21B to the discharge port 51 of the injection nozzle 5. The jet reaching point is the intersection P between the imaginary line IL extending from the center axis CA of the first discharge port 51A and a plane including the bottom surface 211 of the liquid reservoir 21B. Further, the horizontal distance from the discharge port 51 of the injection nozzle 5 to the jet reaching point (intersection P) is defined as I, and the installation angle of the injection nozzle 5, i.e., the inclination angle of the center axis CA of the discharge port 51 with respect to a horizontal plane is defined as θ.

[0062] In a typical absorption tower 2, the length L from the discharge port 51 to the second side wall 26 is between 8 m and 20 m. For this reason, in FIG. 4, thick solid lines are drawn for reference at 4m and 10m, which are half of the upper and lower limits of the length L.
[0063] As shown in FIG. 4, when the inclination angle θ of the injection nozzle 5 is equal to or less than 10°, the horizontal distance I becomes longer. When the horizontal distance I is too long, there is an increased risk that the gas G (bubbles) contained in the mixed fluid MF injected from the injection nozzle 5 passes through the scrubbing liquid extraction port 262 that opens in the side wall (second side wall 26) facing the discharge port 51 of the injection nozzle 5, and gets caught in the pump (scrubbing liquid circulation pump 72) for extracting the scrubbing liquid from the liquid reservoir 21B.
[0064] When the inclination angle θ of the inj ection nozzle 5 is equal to or more than 30°, the horizontal distance I becomes shorter. When the horizontal distance I is too short, there is an increased risk that the mixed fluid MF injected from the injection nozzle 5 impinges on the bottom surface 211 of the liquid reservoir 21B at an early stage.
[0065] In some embodiments, the first injection nozzle 5A satisfies 10°<θ<30° where θ is the inclination angle of the center axis CA of the first discharge port 51A with respect to a horizontal plane.
[0066] As a result of studies by the present inventors, it was found that when the inclination angle θ of the first injection nozzle 5A is equal to or less than 10°, there is an increased risk that the gas G (bubbles) contained in the mixed fluid MF injected from the first injection nozzle 5A is caught in the pump (scrubbing liquid circulation pump 72) for extracting the scrubbing liquid from the liquid reservoir 21B. Further, it was found that when the inclination angle θ of the first injection nozzle 5A is equal to or more than 30°, the mixed fluid MF injected from the first injection nozzle 5A impinges on the bottom surface 211 of the liquid reservoir 21B at an early stage, so that the reaching distance of the mixed fluid MF is shortened, and the oxidation effective capacity, which is a capacity of oxidation reaction promoted by the mixed fluid MF injected from the first injection nozzle 5A, is

decreased.
[0067] With the above configuration, since the inclination angle θ of the first injection
nozzle 5A satisfies 10°<θ<30°, it is possible to prevent the oxidation effective capacity from becoming smaller than the effective oxidation volume that can be exhibited originally, and it is possible to prevent the gas G (bubbles) from being caught in the pump (scrubbing liquid circulation pump 72) for extracting the scrubbing liquid from the liquid reservoir 21B and deteriorating the performance of the pump.
[0068] FIG. 5 is a schematic diagram of the liquid reservoir of the absorption tower and
the injection nozzle shown in FIG. 1 when viewed from the top. In some embodiments, as shown in FIG. 5, the absorption tower 2 further includes a third side wall 30 and a fourth side wall 31. In other words, the shape of the interior space 21 of the absorption tower body 22 in a plane is rectangular defined by the first side wall 25, the second side wall 26, the third side wall 30, and the fourth side wall 31. Each of the third side wall 30 and the fourth side wall 31 extends along a direction (first direction) in which the first side wall 25 and the second side wall 26 are separated in a top view, and defines a part of the interior space 21 including the liquid reservoir 21B. The fourth side wall 31 faces the third side wall 30 in a top view and is located at a distance from the third side wall in the second direction, which is a direction perpendicular to the first direction.
[0069] A plurality of the first injection nozzles 5A are attached to the first side wall 25 of
the absorption tower body 22. The first injection nozzles 5A are spaced from each other in the second direction. The area where the oxidation reaction of the scrubbing liquid is promoted by the mixed fluid MF injected from the plurality of first injection nozzles 5A is referred to as a first oxidation effective area EA1 (oxidation effective area). The first oxidation effective area EA1 is an area having the maximum length LE1 in the first direction and the maximum width WE1 in the second direction when the liquid reservoir 21B is viewed from the top.
[0070] The maximum length LE1 in the first direction is about the same length as the jet
reaching distance of the mixed fluid MF injected from the first injection nozzle 5A, and may

be regarded as the same length as the jet reaching distance. The maximum width WE1 in the second direction is variable depending on the number of first injection nozzles 5A attached to the first side wall 25. In the illustrated embodiment, the maximum width WE1 in the second direction is the same length as the length W from the third side wall 30 to the fourth side wall 31.
[0071] FIG. 6 is a schematic diagram of the liquid reservoir of the absorption tower and
the injection nozzle according to another embodiment when viewed from the top. As shown in FIG. 6, when the length L0 from the first side wall 25 to the second side wall 26 is longer than the maximum length LE1 of the first oxidation effective area EA1, an oxidation ineffective area IA, where the oxidation reaction is not promoted by the mixed fluid MF injected from the first injection nozzle 5A, is formed on the second side wall 26 side of the first oxidation effective area EA1. As the oxidation ineffective area IA is increased, the oxidation in the liquid reservoir 21B may become insufficient.
[0072] In some embodiments, the injection nozzle 5 further includes at least one second
injection nozzle 5B in which the distal end of the first cylindrical portion 52 having the discharge port 51 (second discharge port 51B) is inserted in an insertion hole 301 formed in the third side wall 30, and at least one third injection nozzle 5C in which the distal end of the first cylindrical portion 52 having the discharge port 51 (third discharge port 51C) is inserted in an insertion hole 311 formed in the fourth side wall 31.
[0073] The second injection nozzle 5B is configured to inject the mixed fluid MF into the
liquid reservoir 21B from the second discharge port 51B located in the liquid reservoir 21B.
The second injection nozzle 5B is oriented so that the injected mixed fluid MF flows along
the second direction toward the fourth side wall 31. The third injection nozzle 5C is
configured to inject the mixed fluid MF from the third discharge port 51C located in the liquid
reservoir 21B into the liquid reservoir 21B. The third injection nozzle 5C is oriented so that
the injected mixed fluid MF flows along the second direction toward the third side wall 30.
[0074] In the illustrated embodiment, a plurality of the second injection nozzles 5B are
attached to the third side wall 30 on the first side wall 25 side of the bubble suppression

member 29 in the first direction. The second injection nozzles 5B are spaced from each other in the first direction. Further, a plurality of the third injection nozzles 5C are attached to the fourth side wall 31 on the first side wall 25 side of the bubble suppression member 29 in the first direction. The third injection nozzles 5C are spaced from each other in the first direction.
[0075] The area where the oxidation reaction of the scrubbing liquid is promoted by the
mixed fluid MF injected from the plurality of second injection nozzles 5B is referred to as a
second oxidation effective area EA2 (oxidation effective area). The second oxidation
effective area EA2 is an area having the maximum length WE2 in the second direction and the
maximum width LE2 in the first direction when the liquid reservoir 21B is viewed from the
top. The area where the oxidation reaction of the scrubbing liquid is promoted by the mixed
fluid MF injected from the plurality of third injection nozzles 5C is referred to as a third
oxidation effective area EA3 (oxidation effective area). The third oxidation effective area
EA3 is an area having the maximum length WE3 in the second direction and the maximum
width LE3 in the first direction when the liquid reservoir 21B is viewed from the top.
[0076] Each of the maximum length WE2 of the second oxidation effective area EA2 and
the maximum length WE3 of the third oxidation effective area EA3 is about the same length as the jet reaching distance of the mixed fluid MF injected from each of the second injection nozzle 5B and the third injection nozzle 5C, and may be regarded as the same length as the jet reaching distance. Each of the maximum width LE2 of the second oxidation effective area EA2 and the maximum width LE3 of the third oxidation effective area EA3 is variable depending on the number of injection nozzles 5 attached to the side wall (third side wall 30, fourth side wall 31), and the sum of the maximum width LE2 or LE3 and the maximum length LE1 of the first oxidation effective area EA1 is less than the distance LA from the first discharge port 51A to the bubble suppression member 29 in the first direction. Accordingly, the mixed fluid MF does not reach the second side wall 26.
[0077] According to the above configuration, the injection nozzle 5 of the gas-liquid
mixing device 4 further includes the second injection nozzle 5B and the third injection nozzle

5C. Accordingly, in an area (oxidation ineffective area IA) of the liquid reservoir 21B where the oxidation reaction cannot be promoted by the mixed fluid MF injected from the first injection nozzle 5A, the oxidation reaction can be promoted by the mixed fluid MF injected from each of the second injection nozzle 5B and the third injection nozzle 5C. In other words, since the second oxidation effective area EA2 and the third oxidation effective area EA3 are formed in the oxidation ineffective area IA, the area where the oxidation reaction cannot be promoted by the mixed fluid MF can be reduced. Therefore, with the above configuration, it is possible to reduce the area of the liquid reservoir 21B where the oxidation reaction cannot be promoted by the mixed fluid MF, so that it is possible to prevent insufficient oxidation by the mixed fluid MF.
[0078] In some embodiments, as shown in FIG. 6, each of the second injection nozzle 5B
and the third injection nozzle 5C is arranged at a position away from the first side wall 25 by a predetermined distance L2 or more. The predetermined distance L2 is longer than the maximum length LE1 of the first oxidation effective area EA1. In this case, since each of the second injection nozzle 5B and the third injection nozzle 5C is arranged at a position away from the first side wall 25 by the predetermined distance L2 or more, it is possible to prevent the mixed fluid MF injected from each of the second injection nozzle 5B and the third injection nozzle 5C from obstructing the flow of the mixed fluid MF injected from the first injection nozzle 5A. Further, since the obstruction of the flow of the mixed fluid MF injected from the first injection nozzle 5A is prevented, it is possible to prevent a decrease in oxidation effective capacity, which is a capacity of oxidation reaction promoted by the mixed fluid MF injected from the first injection nozzle 5A.
[0079] In some embodiments, as shown in FIG. 6, each of the second injection nozzle 5B
and the third injection nozzle 5C is arranged at a position away from the second side wall 26 by a predetermined distance L3 or more. The predetermined distance L3 is longer than the length from the second side wall 26 to the bubble suppression member 29. In this case, since each of the second injection nozzle 5B and the third injection nozzle 5C is arranged at a position away from the second side wall 26 by the predetermined distance L3 or more, it is

possible to prevent the mixed fluid MF injected from each of the second injection nozzle 5B and the third injection nozzle 5C from reaching the scrubbing liquid extraction port 262 on the second side wall 26. Accordingly, with the above configuration, it is possible to prevent the gas G (bubbles) from being caught in the pump (scrubbing liquid circulation pump 72) for extracting the scrubbing liquid from the liquid reservoir 21B and deteriorating the performance of the pump.
[0080] FIG. 7 is a diagram for describing the arrangement state of each injection nozzle
shown in FIG. 6.
In some embodiments, as shown in FIG. 7, each of the second injection nozzle 5B and the third injection nozzle 5C is arranged at a height position different from the first injection nozzle 5A. In the illustrated embodiment, each of the second injection nozzle 5B and the third injection nozzle 5C is arranged at a position lower than the first injection nozzle 5A. In other words, each of the underwater depth Z2 of the second injection nozzle 5B and the underwater depth Z3 of the third injection nozzle 5C is smaller than the underwater depth Z1 of the first injection nozzle 5A. In this case, each of the inclination angle θ2 of the second injection nozzle 5B and the inclination angle θ3 of the third injection nozzle 5C may be smaller than the inclination angle θ1 of the first injection nozzle 5A.
[0081] In a top view, each of the second injection nozzle 5B and the third injection nozzle
5C injects the mixed fluid MF along the second direction intersecting the first direction in which the first injection nozzle 5A injects the mixed fluid MF. If each of the second injection nozzle 5B and the third injection nozzle 5C is arranged at the same height as the first injection nozzle 5A, the mixed fluid MF injected from each of the second injection nozzle 5B and the third injection nozzle 5C may obstruct the flow of the mixed fluid MF injected from the first injection nozzle 5A.
[0082] With the above configuration, since each of the second injection nozzle 5B and the
third injection nozzle 5C is arranged at a height position different from the first injection nozzle 5A, it is possible to prevent the mixed fluid MF injected from each of the second injection nozzle 5B and the third injection nozzle 5C from obstructing the flow of the mixed

fluid MF injected from the first injection nozzle 5A. Further, since the obstruction of the flow of the mixed fluid MF injected from the first injection nozzle 5A is prevented, it is possible to prevent the oxidation effective capacity from decreasing.
[0083] In the embodiment shown in FIG. 7, each of the second injection nozzle 5B and the third injection nozzle 5C is arranged at a position lower than the first injection nozzle 5A, but in another embodiment, each of the second injection nozzle 5B and the third injection nozzle 5C may be arranged at a position higher than the first injection nozzle 5A. In other words, each of the underwater depth Z2 of the second injection nozzle 5B and the underwater depth Z3 of the third injection nozzle 5C may be greater than the underwater depth Z1 of the first injection nozzle 5A. In this case, each of the inclination angle θ2 of the second injection nozzle 5B and the inclination angle θ3 of the third injection nozzle 5C may be greater than the inclination angle θ1 of the first injection nozzle 5A.
[0084] FIG. 8 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. 8. Although the method of attaching the first injection nozzle 5A will be described as an example, the method of attaching the second injection nozzle 5B or the third injection nozzle 5C is similar to the method of attaching the first injection nozzle 5A.
[0085] First, the distal end of the first cylindrical portion 52 having the discharge port 51 (first discharge port 51A) of the first injection nozzle 5A is inserted into the insertion hole 252 formed through the first side wall 25.
[0086] As shown in FIG. 8, the first injection nozzle 5A includes the first cylindrical portion 52 and a discharge-port-side fastening portion 63 (first fastening portion). The first cylindrical portion 52 extends along the center axis CA of the first discharge port 51A, and the first discharge port 51A is formed at one end of the first cylindrical portion 52 in the extension direction. The discharge-port-side fastening portion 63 is disposed around the outer circumference on the downstream side of the connection portion with the second cylindrical portion 54 and the merging portion 60 and on the upstream side of the first discharge port 51A

in the flow direction of the scrubbing liquid. 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 first discharge port 51A.
[0087] As shown in FIG. 8, the absorption tower 2 includes the cylindrical protruding
portion 32 and an injection nozzle fastening portion 33 (second fastening portion). As shown in FIG. 8, the cylindrical protruding portion 32 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 angle θ which is the inclination angle of the center axis CA of the first discharge port 51A with respect to a horizontal plane. The injection nozzle fastening portion 33 is disposed so as to protrude from the distal end of the cylindrical protruding portion 32 along the direction perpendicular to the extension direction of the cylindrical protruding portion 32.
[0088] Then, the first injection nozzle 5A is fixed to the first side wall 25. The
discharge-port-side fastening portion 63 of the first injection nozzle 5A is fixed to the injection nozzle fastening portion 33 of the absorption tower 2 by means of a fastening device 66 (66A). In the illustrated embodiment, the fastening device 66A includes a bolt 67 (67A) and a nut 68 (68A).
[0089] 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 33 have through holes 631 and 331 in which the shaft portion 671 of the bolt 67A can be inserted along the extension direction of the cylindrical protruding portion 32. The shaft portion 671 of the bolt 67A is inserted into the through holes 631 and 331 formed in the discharge-port-side fastening portion 63 and the injection nozzle fastening portion 33 from one side in the extension direction of the cylindrical protruding portion 32, and the distal end of the shaft portion 671 inserted on the other side in the extension direction of the cylindrical protruding portion 32 is screwed into the nut 68A to fix the first injection nozzle 5A to the first side wall 25.

[0090] After the first injection nozzle 5A is fixed to the first side wall 25, the gas
introduction line 42 is connected to the first injection nozzle 5A. In the illustrated embodiment, as shown in FIG. 8, the first injection nozzle 5A 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. The gas introduction line 42 includes a gas introduction pipe 47 extending along the extension direction of the second cylindrical portion 54. The gas introduction pipe 47 includes a gas downstream fastening portion 48 disposed so as to protrude from the outer circumference of the end portion having an opening communicating with the second gas introduction port 59. The gas downstream fastening portion 48 of the gas introduction pipe 47 is fixed to the gas-introduction-side fastening portion 64 of the first injection nozzle 5A by means of a fastening device 66 (66B).
[0091] 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 first injection nozzle 5A to the gas introduction pipe 47.
[0092] After the first injection nozzle 5A is fixed to the first side wall 25, the scrubbing
liquid introduction line 41 is connected to the first injection nozzle 5A. The connection between the scrubbing liquid introduction line 41 and the first injection nozzle 5A may be made at the same time as the connection between the gas introduction line 42 and the first injection nozzle 5A, or may be made before or after the connection between the gas introduction line 42 and the first injection nozzle 5A.
[0093] As shown in FIG. 3, the first injection nozzle 5A 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. The scrubbing liquid introduction line 41 includes a

scrubbing liquid introduction pipe 45 extending along the extension direction of the first cylindrical portion 52. The scrubbing liquid introduction pipe 45 includes a scrubbing liquid downstream fastening portion 46 disposed so as to protrude from the outer circumference of the end portion having an opening 451 communicating with the scrubbing liquid introduction port 56 via the contraction portion 53, as shown in FIG. 3. As shown in FIG. 8, the scrubbing liquid downstream fastening portion 46 of the scrubbing liquid introduction pipe 45 is fixed to the scrubbing-liquid-introduction-side fastening portion 65 of the first injection nozzle 5A by means of a fastening device 66C.
[0094] 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 into through holes 651 and 461 formed in the scrubbing-liquid-introduction-side fastening portion 65 and the scrubbing liquid downstream fastening portion 46 is screwed into the nut 68C to fix the first cylindrical portion 52 of the first injection nozzle 5A to the scrubbing liquid introduction pipe 45.
[0095] As described above, in some embodiments, the first injection nozzle 5A includes
the first cylindrical portion 52 and the discharge-port-side fastening portion 63 (first fastening portion). Additionally, the absorption tower 2 includes the cylindrical protruding portion 32 and the injection nozzle fastening portion 33 (second fastening portion).
[0096] With the above configuration, the discharge-port-side fastening portion 63 of the
first injection nozzle 5A is fixed to the injection nozzle fastening portion 33 of the absorption tower 2 by means of the fastening device 66 (66A) while the distal end of the first injection nozzle 5A including the first discharge port 51A of the first cylindrical portion 52 is inserted in the insertion hole 252 formed in the first side wall 25 of the absorption tower 2. Here, the first cylindrical portion 52 extends along the center axis CA of the first discharge port 51A. The cylindrical protruding portion 32 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 first discharge port 51A with respect to a horizontal plane. In other

words, the cylindrical protruding portion 32 of the absorption tower 2 extends along the same direction as the center axis CA of the first discharge port 51A when the first injection nozzle 5A 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 33 extending along the direction perpendicular to the extension direction of the cylindrical protruding portion 32 by means of the fastening device 66 (66A), the first injection nozzle 5A can be installed at the same angle as the inclination angle θ of the center axis CA of the first discharge port 51A with respect to a horizontal plane. Thus, with the above configuration, it is possible to easily attach the first injection nozzle 5A without adjusting the installation angle of the first injection nozzle 5A.
Further, by releasing the fixation between the discharge-port-side fastening portion 63 and the injection nozzle fastening portion 33 with the fastening device 66 (66A), the first injection nozzle 5A can be quickly detached from the insertion hole 252 of the absorption tower 2, so that the first injection nozzle 5 A can be easily inspected, repaired, or replaced. [0097] 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.
[0098] 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 [0099]
1 Exhaust gas desulfurization device
2 Absorption tower

21 Interior space
21A Gas-liquid contact part
21B Liquid reservoir
21C Lower interior space
21D Upper interior space
211 Bottom surface
22 Absorption tower body
221 Bottom surface
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 Scrubbing liquid extraction port

27 Mist eliminator
28 Spraying device

281 Spray pipe
282 Spray nozzle
29 Bubble suppression member
30 Third side wall 301 Insertion hole
31 Fourth side wall 311 Insertion hole
32 Cylindrical protruding portion
33 Injection nozzle fastening portion (Second fastening portion)
331 Through hole

4 Gas-liquid mixing device
41 Scrubbing liquid introduction line
42 Gas introduction line

44 Branch portion
45 Scrubbing liquid introduction pipe
46 Scrubbing liquid downstream fastening portion
47 Gas introduction pipe
48 Gas downstream fastening portion
481 Through hole
5 Injection nozzle
5A First injection nozzle
5B Second injection nozzle
5C Third injection nozzles
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 (First fastening portion)
631 Through hole
64 Gas-introduction-side fastening portion

641 Through hole
65 Scrubbing-liquid-introduction-side fastening portion
66, 66A to 66C Fastening device
671 Shaft portion
672 Head portion 67A to 67C Bolt 68A to 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
CL Center line
EA1 First oxidation effective area
EA2 Second oxidation effective area
EA3 Third oxidation effective area
G Gas
I Horizontal distance
IA Oxidation ineffective area
IL Imaginary line
MF Mixed fluid
P Intersection

I/We Claim:
1. 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 including a liquid reservoir for storing the scrubbing liquid, at least a part of the liquid reservoir being defined by a first side wall and a second side wall facing the first side wall of the absorption tower; and
a gas-liquid mixing device including a first injection nozzle with a distal end inserted in an insertion hole formed in the first side wall, the first injection nozzle being configured to inject a mixed fluid of the scrubbing liquid and a gas containing oxygen from a first discharge port of the first injection nozzle to the liquid reservoir,
wherein the first injection nozzle includes:
a cylindrical portion extending along a center axis of the first discharge port and having the first discharge port; and
a first fastening portion disposed so as to protrude from an outer circumference of the cylindrical portion along a direction perpendicular to the center axis of the first discharge port, and
wherein the absorption tower further includes:
a cylindrical protruding portion disposed so as to protrude outward from a peripheral edge of the insertion hole formed in the first side wall along a direction inclined with respect to a horizontal plane by an angle θ, where θ is an inclination angle of the center axis of the first discharge port with respect to a horizontal plane; and
a second 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 second fastening portion being configured to be fixed to the first fastening portion with a fastening device.

2. The exhaust gas desulfurization device according to claim 1,
wherein the first injection nozzle satisfies 10°<θ<30° where θ is an inclination angle of the center axis of the first discharge port with respect to a horizontal plane.
3. The exhaust gas desulfurization device according to claim 1 or 2,
wherein the absorption tower further includes:
a third side wall extending along a direction in which the first side wall and the second side wall are separated, the third side wall defining a part of the liquid reservoir; and
a fourth side wall facing the third side wall and extending along a direction in which the first side wall and the second side wall are separated, the fourth side wall defining a part of the liquid reservoir,
wherein the gas-liquid mixing device further includes:
a second injection nozzle with a distal end inserted in an insertion hole formed in the third side wall, the second injection nozzle being configured to inject the mixed fluid from a second discharge port of the second injection nozzle to the liquid reservoir; and
a third injection nozzle with a distal end inserted in an insertion hole formed in the fourth side wall, the third injection nozzle being configured to inject the mixed fluid from a third discharge port of the third injection nozzle to the liquid reservoir.
4. The exhaust gas desulfurization device according to claim 3,
wherein each of the second injection nozzle and the third injection nozzle is arranged at a height position different from the first injection nozzle.
5. The exhaust gas desulfurization device according to claim 3 or 4,
wherein each of the second injection nozzle and the third injection nozzle is arranged at a position away from the first side wall by a predetermined distance or more.

6. The exhaust gas desulfurization device according to any one of claims 3 to 5,
wherein each of the second injection nozzle and the third injection nozzle is arranged at a position away from the second side wall by a predetermined distance or more.