JP7067137B2 - Gas scrubber - Google Patents

Description

The present invention relates to a gas scrubber. More specifically, the exhaust gas is supplied from the bottom side of the scrubber to the inside of the scrubber body, while the cleaning water is supplied from the top side of the scrubber, and the exhaust gas and the cleaning water are brought into contact with each other inside the scrubber body to remove dust. Regarding a gas-liquid contact type gas scrubber.

The gas-liquid contact type gas scrubber described above is used, for example, in an exhaust gas treatment facility of a zinc oxide ore production plant by the Waelz process. FIG. 4 is an example of such an exhaust gas treatment facility. In the exhaust gas treatment facility 10 shown in the figure, the exhaust gas containing dust discharged from the drying and heating rotary kiln (DRK) 2 which is a drying and heating furnace is the gas scrubber 1, the wet electrostatic precipitator 3, the exhaust gas fan 4, and the stack 5. Are sequentially arranged as a series of devices, and the exhaust gas to be treated is sequentially transferred through a series of exhaust gas treatment facilities 10 in which each of these devices is connected.

Here, in order to improve the cleaning efficiency of the exhaust gas in the gas-liquid contact type gas cleaning tower as described above, it is important to increase the contact opportunity between the exhaust gas and the cleaning water. For that purpose, first, it is necessary to sufficiently diffuse the washing water into the space inside the washing tower body. For this purpose, multiple shelves are provided inside the main body of the washing tower, and the washing water supplied from one place on the top of the tower sequentially passes through these shelves and falls while spreading in the horizontal direction. As described above, a washing tower (see Patent Document 1) in which a dedicated flow path for guiding the washing water is formed between the shelves, or a large number of spray nozzles for supplying the washing water are provided in the vertical and horizontal directions of the washing tower body. A cleaning tower (see Patent Document 2) and the like distributed in the water have been proposed.

In addition, as another device for increasing the chance of contact between the exhaust gas and the cleaning water, the cleaning tower body is provided with a gas flow path that guides the exhaust gas in a direction other than the ascending direction inside the cleaning tower body. A gas scrubber has also been proposed that guides the flow of exhaust gas not only in the upward direction but also in other directions, thereby increasing the chance of contact between the exhaust gas and the cleaning water (see Patent Document 2).

However, in order to introduce each of the above-mentioned gas scrubbers, complicated piping work and an increase in the size of the scrubber body are inevitable. In a general manufacturing plant that requires exhaust gas treatment, the introduction of a gas scrubber with such a huge and complicated structure is extremely difficult due to economic conditions or physical conditions related to the space of the manufacturing site. There were many.

Therefore, for example, a perforated plate is arranged in the scrubber body, and the washing water is supplied from the washing water supply means installed only on the top side of the scrubber body, and the washing water rises from the bottom side of the scrubber. Gas scrubbers, which are in contact with exhaust gas, are used in many manufacturing plants. In such a gas scrubber, usually, in order to sufficiently secure a contact opportunity between the scrubber and the exhaust gas, the scrubber is horizontally diffused and permeated inside the scrubber body. A perforated plate is installed with the intention of ensuring the contact time between the exhaust gas and the washing water near the holes.

However, in the gas cleaning tower having the above mechanism, the cleaning water supplied from the cleaning water supply means installed only on the top side of the cleaning tower body falls downward before it is sufficiently diffused in the horizontal direction. In this case, there is a problem that the contact opportunity between the exhaust gas and the washing water becomes insufficient.

Japanese Unexamined Patent Publication No. 2004-189536 Japanese Unexamined Patent Publication No. 2012-528707

The present invention is a gas cleaning tower having a structure in which exhaust gas is supplied from the bottom side of the tower, cleaning water is supplied from the top of the tower, and the water is dropped to the bottom side of the tower via a perforated plate. It is an object of the present invention to provide a gas washing tower capable of sufficiently diffusing the washing water supplied from the washing water supply means in the horizontal direction.

The inventor of the present application forms a swirling flow of washing water along the inner peripheral circle of the inner wall of the washing tower body by optimizing the injection direction of the washing water in the gas washing tower having the above structure, and is supplied from the top of the tower. We have found that the cleaning water can be uniformly dispersed on the perforated plate, and have completed the present invention.

(1) A cylindrical scrubber body, a scrubber injection means installed on the top side of the scrubber body, a perforated plate horizontally arranged inside the scrubber body, and the scrubber A gas scrubber having a gas supply port formed on the bottom side of the main body and a gas discharge port formed on the top side of the scrubber body, and the perforated plate has a large number of permeation. The holes are formed over substantially the entire surface, and the scrubber injection means can form a swirling flow of the scrubber along the inner peripheral circle of the inner wall of the scrubber body in the direction of the scrubber injection. The horizontal direction is such that the scrubber spraying means on the inner circumference is rotated at a predetermined angle from the tangential direction passing through the installed point toward the center of the inner circle with the one point as the starting point. The gas scrubber.

(2) The gas scrubber according to (1), wherein a plurality of the washing water injection means are arranged.

(3) A set consisting of two cleaning water injection means arranged at opposite positions 180 ° inverted from each other on the inner peripheral circle of the inner wall, and injecting cleaning water in the same rotation direction with each other. The gas cleaning tower according to (2), which has a cleaning water injection unit.

(4) The gas cleaning tower according to any one of (1) to (3), wherein the cleaning water injection means is composed of an injection port and a scattering plate.
(5) A plurality of the perforated plates are horizontally arranged inside the scrubber body along the vertical direction, and the opening diameters of the transmission holes in each of the perforated plates are substantially the same, and the inside of the scrubber body. The gas scrubber according to any one of (1) to (4), wherein the opening diameter of the transmission hole of the perforated plate arranged at the uppermost stage is smaller than that of the other perforated plate.

(6) An exhaust gas treatment facility provided with the gas scrubber according to any one of (1) to (5).

According to the present invention, in a gas cleaning tower having a structure in which exhaust gas is supplied from the bottom side of the tower, cleaning water is supplied from the top of the tower, and the water is dropped to the bottom side of the tower via a perforated plate, the cleaning water is supplied to the top side of the main body of the cleaning tower. It is possible to provide a gas cleaning tower capable of sufficiently diffusing the cleaning water supplied from the installed cleaning water supply means in the horizontal direction.

It is a schematic perspective view of the gas scrubber of this invention, and is the drawing which provides the explanation of the operation | action | effect of this invention. It is a top view of each of a plurality of perforated plates provided in the gas scrubber of the present invention. It is a schematic plan view of the cleaning water injection means that can be provided in the gas cleaning tower of the present invention. It is a schematic diagram which shows the structural example of the exhaust gas treatment equipment which comprises the gas scrubber of this invention.

<Manufacturing process of zinc oxide ore>
INDUSTRIAL APPLICABILITY The present invention can be preferably applied to the exhaust gas treatment of the exhaust gas discharged from the dry heating rotary kiln (DRK) in the production plant where the "production process of zinc oxide ore by the Waelz method" is performed. The "production process of zinc oxide ore by the Waelz process" is a process in which each of the following "reduction roasting process", "wet process", and "dry heating process" is sequentially performed. However, the present invention is not limited to such an embodiment. The present invention is widely applied to a gas scrubber having a structure in which cleaning water is supplied from the top of the tower and lowered to the bottom of the tower via a perforated plate, and exhaust gas treatment equipment and exhaust gas treatment methods using the same. Can be done.

[Reduction roasting process]
In the reduction roasting step, reduction roasting treatment of zinc-containing ore such as steel dust is performed. The reduction roasting process is usually carried out using a reduction roasting rotary kiln (RRK). The metallic zinc that has been reduced and roasted in the RRK and volatilized is reoxidized in the furnace to become powdery zinc oxide. The powdery zinc oxide is introduced into the dust collector together with the exhaust gas from the RRK, is captured, and is recovered as crude zinc oxide dust.

[Wet process]
In the wet step, the above crude zinc oxide dust is repulped with a treatment liquid to form a crude zinc oxide slurry, and impurities such as cadmium, chlorine and fluorine are distributed in the treatment liquid. Then, the crude zinc oxide slurry that has undergone the above treatment is dehydrated and supplied as a crude zinc oxide cake to the drying and heating step of the next step.

[Drying and heating process]
In the drying and heating step, the above-mentioned crude zinc oxide cake is charged into a drying and heating rotary kiln (DRK) 2 and baked. By this step, zinc oxide ore (burnt ore) having a further reduced concentration of cadmium or the like can be obtained. The charged material such as the crude zinc oxide cake charged in the DRK is granulated, dried, heated and baked in a rotary kiln having a total length of about 30 m, but the charged material is scattered in the process of granulation and drying. Dust, oxides, halides, etc. volatilized in the process of heating and firing become dust. The dust concentration of the exhaust gas discharged from the DRK (hereinafter, also referred to as “DRK exhaust gas”) is usually about 30 to 40 g / Nm ³ .

<Gas scrubber>
Hereinafter, the gas scrubber 1 capable of constituting the exhaust gas treatment equipment 10 will be described. As shown in FIG. 1, in the gas cleaning tower 1, cleaning water injection means 13A and 13B are installed on the tower top side of the circular tower-shaped cleaning tower main body 11. Then, inside the circular tower-shaped scrubber main body 11, three perforated plates 12A, 12B, and 12C are horizontally arranged at different positions along the vertical direction. Further, the gas supply port 14 to the inside of the scrubber main body 11 is formed on the bottom side of the scrubber main body 11, and the gas discharge port 15 is formed on the tower top side of the scrubber main body 11.

The number of perforated plates in the gas scrubber of the present invention is not necessarily limited to three as shown in FIG. As long as the other requirements of the present invention are satisfied, the gas scrubber of the present invention may have one perforated plate. However, the number of perforated plates is preferably two or more, and any plurality of perforated plates can be installed. However, in order to facilitate understanding of the action and effect of the plurality of perforated plates in the present invention, the gas scrubber 1 having three perforated plates 12A, 12B, 12C is exemplified as a preferred embodiment of the present invention. While doing so, the details of the present invention will be described.

In the gas cleaning tower of the present invention, a cleaning water injection means in which the injection direction of the cleaning water w is optimized is installed on the top side of the main body of the cleaning tower. As shown in FIG. 3, the injection direction of the wash water w of the wash water injection means is 1 from the tangential direction passing through one point on the inner peripheral circle of the inner wall of the wash tower main body 11 where the wash water injection means is installed. It may be a horizontal direction that is rotated toward the center of the inner peripheral circle starting from a point, and may be a direction in which the cleaning water w can be directly hit on the inner wall of the cleaning tower main body 11 near the cleaning water injection means 13. ..

The number of cleaning water injection means 13 installed is not particularly limited, but as will be described in detail later, in order to efficiently diffuse the cleaning water in the horizontal direction with the minimum cleaning water supply means, the gas cleaning shown in FIG. 1 is performed. It is preferable that a pair of cleaning water injection means 13A and 13B are installed at positions facing each other on the inner peripheral circle of the inner wall of the cleaning tower main body 11 as in the tower 1.

In the gas scrubber 1 having the above-mentioned configuration as a basic configuration, as shown in FIG. 1, the exhaust gas g introduced into the inside of the scrubber main body 11 from the gas supply port 14 has the inside of the scrubber main body 11 at the top of the tower. It will rise toward you. Then, the cleaning water w supplied from the cleaning water injection means 13 to the inside of the cleaning tower main body 11 descends inside the cleaning tower main body 11 while being diffused horizontally on each of the perforated plates 12. In this process, the exhaust gas g and the cleaning water w come into contact with each other inside the cleaning tower main body 11, and the dust in the exhaust gas g is removed by the cleaning water w.

[Scrubber body]
The scrubber main body 11 is composed of a circular tower-shaped hollow structure. In detail, the shape may be at least a hollow cylindrical shape as the main portion serving as an ascending path of the exhaust gas g. Regarding the material that forms the hollow structure in the shape of a circular tower, the strength and durability required for each manufacturing plant where the gas scrubber 1 is actually installed, and the type of exhaust gas to be treated Various materials having the required corrosion resistance and the like can be appropriately selected. Generally, the scrubber main body 11 is formed of various metal materials such as rolled steel for general structure (SS steel) and stainless steel. Further, if the chemical properties of the gas to be treated and the conditions of the treatment temperature are suitable, it can also be formed of fiber reinforced plastic (FRP). Further, the inner surface of the metal scrubber main body 11 is subjected to various lining treatments such as rubber lining, FRP lining, fluororesin lining, etc., depending on the chemical properties of the gas to be treated and the conditions of the treatment temperature. Is preferable.

[Perforated plate]
The perforated plate 12 (12A, 12B, 12C) is a disk-shaped member installed in such a manner that the outer periphery thereof is fitted to the inner peripheral circle of the inner wall of the scrubber main body 11, and as shown in FIG. 2, this member. A large number of transmission holes 121 (121A, 121B, 121C) penetrating the above are formed over substantially the entire surface. When a plurality of perforated plates are arranged along the vertical direction, in each perforated plate (for example, the perforated plate 12A), the opening diameter (diameter) of the transmission hole 121 (for example, the transmission hole 121A) is set in all the holes. It is preferable that they are substantially the same. Further, it is preferable that the opening pitch (distance between the centers of the circles) of the transmission holes 121 in each perforated plate is substantially the same in all the holes.

Regarding the opening diameter of the transmission hole 121 of each perforated plate 12, the opening diameter of the transmission hole 121C of the perforated plate 12C arranged at the lowest stage inside the cleaning tower main body 11, that is, closest to the bottom of the column in the vertical direction, is set. It is preferable that the size is at least larger than the uppermost transmission hole 121A and equal to or larger than the opening diameter of the transmission hole of all the other perforated plates.

Regarding the opening diameter of the transmission hole 121 of the perforated plate 12, when two perforated plates 12 are installed vertically along the inside of the cleaning tower main body 11 (when the perforated plate 12B does not exist: not shown). ), It is preferable that the opening diameter of the transmission hole 121C of the perforated plate 12C arranged near the bottom of the column in the vertical direction is larger than the opening diameter of the transmission hole 121A of the perforated plate 12A arranged from the top of the column. ..

Further, as shown in FIG. 1, when three or more porous plates are arranged inside the scrubber main body 11 along the vertical direction, the lowermost porous plate is better than the uppermost porous plate. In addition to satisfying the above-mentioned condition that the opening diameter of the transmission hole is large, the opening diameter of any of the perforated plates is the same as the opening diameter of the other perforated plates arranged immediately under each perforated plate. It is preferable that the opening diameter is the same or less.

Specifically, for example, as shown in FIG. 1, in the gas scrubber 1 in which the three perforated plates 12A, 12B, and 12C are arranged, the opening diameter of the lowermost transmission hole 121C is at least the uppermost stage. It is preferably larger than the opening diameter of the transmission hole 121A, and more preferably equal to or larger than the opening diameter of the transmission hole 121B in the middle stage, and more preferably larger than the same opening diameter. The opening diameter of the transmission hole 121B in the middle stage is preferably the same as or larger than the opening diameter of the transmission hole 121A in the upper stage, and more preferably larger than the opening diameter.

In the gas scrubber 1 provided with the three perforated plates 12A, 12B, and 12C, the permeation holes 121C of the lowermost perforated plate 12C, which are in contact with each other in the state where the exhaust gas dust concentration is the highest, are most likely to cause clogging. By making the opening diameter of the transmission hole 121C relatively larger than the opening diameter of the other transmission holes, the occurrence of clogging of the perforated plate 12C is relatively suppressed, and the dust load on each perforated plate is reduced. By dispersing it, the frequency of shutdowns for cleaning clogging can be reduced as compared with the conventional case.

On the other hand, since the through hole 121A of the perforated plate 12A arranged at the uppermost stage inside the cleaning tower main body 11 is relatively unlikely to be clogged, the cleaning water sprinkled on the surface of the perforated plate at the uppermost stage is relatively unlikely to occur. In order to maintain the residence time sufficiently long and sufficiently diffuse the washing water in the horizontal direction, the opening diameter of the transmission hole of the perforated plate is preferably as small as possible unless other inconveniences occur. As a result, a large amount of cleaning liquid can be uniformly dispersed on the perforated plate, and the cleaning efficiency of exhaust gas can be further improved.

The number of through holes 121A, 121B, 121C in each of the perforated plates 12A, 12B, and 12C is not particularly limited. However, as described above, the perforated plate 12A arranged at the uppermost stage has a smaller opening diameter than the other perforated plates, while the number of holes is larger than that of the other perforated plates, and the other perforated plates. It is preferable to form the transmission holes more densely than the plate. As a result, the horizontal diffusion of the washing water is sufficiently promoted, and the amount of the washing water w falling onto the middle-stage porous plate 12B arranged immediately below the perforated plate 12B is more evenly dispersed on the entire surface of the perforated plate. be able to.

Further, in each perforated plate, the area ratio of the through-hole portion to the total surface area (including the through-hole portion) of the perforated plate, that is, the aperture ratio is not particularly limited. For example, in the case of treating DRK exhaust gas having a dust concentration of about 30 to 40 g / Nm ³ , the effect of the present invention can be enjoyed in a good manner by setting the aperture ratio within the range of about 10% to 40%. can do. However, it is preferable that the opening ratio of the uppermost perforated plate 12A is smaller than that of at least the lowermost perforated plate 12C in order to secure sufficient time to hold the washing water.

As described above, as a design example of a perforated plate for making a gas cleaning tower capable of enjoying the effect of the present invention in a good manner, three perforated plates 12A are sequentially arranged from the tower top side of the cleaning tower main body 11. , 12B, 12C are juxtaposed, the opening diameter of the perforated plate 12A on the top side of the tower is 20 mm, the aperture ratio is 16%, and the opening diameter of the perforated plates 12B, 12C on the middle stage and the bottom side of the tower is 30 mm. An example in which the ratio is 28% is given as a preferable specific example.

When three or more perforated plates are juxtaposed in the vertical direction, the opening diameter of the transmission hole of each perforated plate gradually decreases from the uppermost perforated plate to the lowermost perforated plate for each stage. It is more preferable to have a plumb bob structure. As a result, while maintaining good dust removal efficiency from the exhaust gas of the gas scrubber, the time until the perforated plate is clogged, that is, the time until the operation is interrupted to clean the perforated plate is extended. , The operating efficiency of the exhaust gas treatment equipment can be further improved.

[Washing water injection means]
As shown in FIG. 3, the cleaning water injection means 13 indicates the injection direction of the cleaning water w from the cleaning water injection means 13 at one point where the cleaning water injection means on the inner peripheral circle of the inner wall of the cleaning tower main body 11 is installed. From the tangential direction passing through the water, the horizontal direction is defined as being rotated at a predetermined angle toward the center of the inner peripheral circle starting from that one point. Further, as the cleaning water injection means 13, various water sprinkling instruments having a function of supplying cleaning water w from the top side of the tower to the inside of the cleaning tower main body 11 such as a conventionally known general injection nozzle can be appropriately adopted. can.

As shown in FIG. 3, the injection direction of the above-mentioned cleaning water w in the cleaning water injection means 13 is a direction in which the cleaning water w can be directly hit along the inner wall of the cleaning tower main body 11 in the vicinity of the cleaning water injection means 13. It is a substantially essential requirement for the injection direction to be able to inject the washing water w toward (da, db). More specifically, when the washing tower body having an inner diameter (diameter) of 2.6 m is taken as an example, the washing water spraying means on the inner peripheral circle of the inner wall of the washing tower body is used. When the tangential direction passing through one installed point is 0 ° and the center direction of the inner peripheral circle is 90 ° starting from that one point, the temperature is approximately 20 ° to 40 °. By injecting the washing water w in this direction, the washing water is spirally diffused toward the center on the perforated plate while swirling along the circumferential direction of the perforated plate on the uppermost perforated plate 12A. It is possible to form a swirling flow of wash water.

In order to direct the injection direction of the cleaning water from the cleaning water injection means 13 in the above direction, for example, the injection port of the injection means such as an injection nozzle may be installed in advance in that direction. For example, FIG. As shown in the above, when the injection ports 131 (131A, 131B) are installed as the cleaning water injection means 13 toward the central axis of the cylinder of the cleaning tower main body, the water flow is in the vicinity of these injection ports 131A, 131B. By installing the scattering plates 132A and 132B that regulate the water in each of the above directions (da, db), a jet stream of washing water in such a direction (da, db) may be formed. Further, according to the configuration in which the water flow direction and the spread are controlled by the scattering plate as described above without using the injection port as a shower-shaped nozzle, the above-mentioned structure is simple and easy to install. The angle of the injection direction can be adjusted appropriately. It is also advantageous in that clogging of the shower-like nozzle due to dust in the exhaust gas can be avoided.

Further, the cleaning water injection means 13 are installed as cleaning water injection means 13A and 13B at opposite positions on the inner peripheral circle of the inner wall of the cleaning tower main body 11 which are inverted by 180 °, respectively, and they are the same as each other. It is preferable that it is installed as a set of washing water injection units capable of injecting washing water in the direction of rotation. By using the cleaning water injection unit having such a configuration as the cleaning water injection means, the swirling flow of the cleaning water described above can be easily formed uniformly over the entire perforated plate.

(Action effect of gas scrubber)
In the gas cleaning tower 1 according to the present invention described above, the cleaning water injection means 13 on the inner peripheral circle of the inner wall of the cleaning tower main body 11 is installed so that the injection direction of the cleaning water w by the cleaning water injection means 13 is set. From the tangential direction passing through one point, the horizontal direction is rotated at a predetermined angle toward the center of the inner peripheral circle starting from that one point, and is on the inner wall of the scrubber main body 11 near the cleaning water injection means 13. It is optimized in the direction in which the wash water w can be directly hit along the line. As a result, the washing water swirls and diffuses uniformly on the surface of the uppermost porous plate 12A. Then, the washing water diffused over the entire surface of the perforated plate 12A over a sufficient period of time uniformly drops on the entire surface of the perforated plate 12B immediately below the perforated plate 12C and further on the entire surface of the perforated plate 12C. On the other hand, the exhaust gas introduced from the bottom side of the scrubber main body 11 is given a sufficient contact opportunity with the washing water that descends while being sufficiently diffused in the horizontal direction in the above embodiment, so that the exhaust gas is contained in the exhaust gas with a good removal rate. Dust can be removed.

1 Gas scrubber 11 Scrubber body 12 (12A, 12B, 12C) Perforated plate 121 (121A, 121B, 121C) Through hole 13 (13A, 13B) Cleaning water injection means 131 (131A, 131B) Injection port 132 (132A, 132A, 132B) Scrubber 14 Gas supply port 15 Gas discharge port 2 Drying and heating rotary kiln (DRK)
3 Wet electrostatic precipitator 4 Exhaust gas fan 5 Stack 10 Exhaust gas treatment equipment g Exhaust gas w Washing water

Claims (5)

Cylindrical scrubber body and
The cleaning water injection means installed on the top side of the cleaning tower body and
The perforated plate horizontally arranged inside the scrubber body and
The gas supply port formed on the bottom side of the scrubber body and
The gas discharge port formed on the top side of the scrubber body and
It is a gas scrubber with
The perforated plate has a large number of through holes formed over substantially the entire surface.
The washing water injection means is composed of an injection port and a scattering plate.
The injection port is installed toward the central axis of the cylinder of the scrubber body.
The scattering plate causes the water flow ejected from the injection port on the inner peripheral circle of the inner wall so that the swirling flow of the washing water along the inner peripheral circle of the inner wall of the washing tower body can be formed. The wash water injection means is installed at a position and orientation that can be regulated in the horizontal direction by rotating at a predetermined angle toward the center of the inner peripheral circle from the tangential direction passing through the one point where the one point is installed. ing,
Gas scrubber. The gas cleaning tower according to claim 1, wherein a plurality of the cleaning water injection means are arranged. A set of cleaning water that comprises two cleaning water injection means arranged at opposite positions that are 180 ° inverted from each other on the inner peripheral circle of the inner wall and injects cleaning water in the same rotation direction with each other. The gas cleaning tower according to claim 2, which has an injection unit. A plurality of the perforated plates are horizontally arranged inside the scrubber body along the vertical direction.
The opening diameters of the transmission holes in each perforated plate are substantially the same,
The opening diameter of the permeation hole of the perforated plate arranged at the uppermost stage in the scrubber body is smaller than the permeation hole of the other perforated plate.
The gas scrubber according to any one of claims 1 to 3 . An exhaust gas treatment facility provided with the gas scrubber according to any one of claims 1 to 4 .

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