JPH09141048A - Wet flue gas desulfurizing method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the drift of inside gas flow and to reduce the cost necessary for a supporting steel frame by providing a gas straightening part in a post flow zone behind a gas flow direction change part. SOLUTION: A flue gas 1 containing a sulfur oxide is introduced to an absorbing tower 2 of a flue gas desulfurizing device. A partition plate 18 is provided in a vertical direction in the absorbing tower 2 with a space provided between the ceiling of the tower 2 and the partition plate 18 so as to cause U-turn of the flue gas in the upper side of the absorbing tower 2. The flue gas 1 is brought into contact with fine absorbing solution drops sprayed from a spray nozzle 4 in a gas ascending flow part 19, is passed through the U-turn part in the upper part of the absorbing tower 2 to make U-turn, is brought into contact again with the fire drops sprayed from the nozzle 4 in a descending flow part 21 and is discharged from an outlet duct 24 in the side part of the absorbing tower 2. Further, the gas straightening plate 22 is provided in the gas descending flow part 21 to reduce the gas drift generated in the U-turn part 20 of the upper part of the absorbing tower 2. Thus, the desulfurization performance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet exhaust gas desulfurization method and apparatus, and more particularly to a wet exhaust gas desulfurization method and apparatus suitable for removing sulfur oxides in exhaust gas. Is an ascending flow, and an absorption tower with a structure in which the exhaust gas makes a U-turn in the upper part of the tower and descends to the absorption tower outlet, prevents uneven flow of the internal gas flow, and reduces the cost required for the supporting steel frame. TECHNICAL FIELD The present invention relates to an exhaust gas desulfurization method and apparatus.

[0002]

2. Description of the Related Art In order to prevent air pollution, a wet limestone-gypsum desulfurization device has been widely put into practical use as a device for removing sulfur oxides in exhaust gas. A conventional technique of this wet limestone-gypsum desulfurization device is shown in FIG. Exhaust gas 1 containing sulfur oxides and soot generated from a thermal power plant, etc.
It is led to. In the absorption tower 2, at least two or more spray headers 3 each having a plurality of spray nozzles 4 are installed, and the absorption liquid sprayed as fine droplets from the spray nozzle 4 is contacted with the exhaust gas 1 rising in the absorption tower. By doing so, the sulfur oxides in the exhaust gas are chemically removed on the surface of the absorbing droplet, and the soot dust is physically removed by collision with the droplet. The minute droplets accompanying the exhaust gas flow are removed by the mist eliminator 5 installed at the upper part of the uppermost spray header 3, and the purified exhaust gas 6 is installed on the downstream side of the absorption tower if necessary and reheated. It is heated by the equipment and discharged from the chimney. Most of the droplets sprayed from the nozzle 4 absorb the sulfur oxide and then fall into the absorption tower circulation tank 7 provided at the lower part of the absorption tower.

Sulfur oxide (SO ₂ ) absorbed in the absorbing liquid
Reacts with limestone (CaCO ₃ ) contained in the absorption liquid,
Further, the gypsum (CaSO ₄ .2H ₂ O) is oxidized by the air 8 supplied to the absorption tower circulation tank 7. This series of reactions is represented by the following formula. SO ₂ + 2H ₂ O
+ CaCO ₃ +1/2 O ₂ → CaSO ₄・ 2H ₂ O + CO
_{2 Further} , the removed dust falls into the absorption tower circulation tank 7 together with the absorbing liquid.

On the other hand, limestone 9 which is an absorbent is stored as limestone slurry in a limestone supply facility 10 and is supplied from a limestone slurry pump 11 to an absorption tower circulation tank 7. Further, in order to recover the gypsum produced in the absorption tower, a part of the absorption liquid in the absorption tower circulation tank 7 is extracted and sent to the gypsum dewatering facility 13 by the pump 12 to obtain the gypsum contained in the absorption liquid. And soot and dust are collected as solids 14. A part of the dehydrated liquid of gypsum and dust is discharged to the outside of the system through the drain line 15 in order to prevent impurities from concentrating in the system, and the remaining liquid is used as makeup water for limestone slurry production in the limestone supply facility 10. The rest is sent to the absorption tower through the dehydration liquid return line 16.

In the absorption tower, the absorption liquid in the tank 7 is sent to the spray header 3 by the circulation pump 17 and sprayed from the spray nozzle 4 described above. The amount of the absorption liquid circulated and sprayed is the amount of exhaust gas and the sulfur in exhaust gas. It is determined by the oxide concentration and the required desulfurization rate. On the other hand, spray header 1
Since the flow rate per stage is determined by the capacity of the spray nozzle used and the spray nozzle mounting interval, a plurality of spray headers are usually installed. The absorbing liquid sprayed from the spray nozzle 4 becomes fine droplets and comes into contact with the exhaust gas, and the sulfur oxides in the exhaust gas are absorbed and removed.

Further, the exhaust gas is introduced from an absorption tower inlet duct provided on the upper side of the absorption tower circulation tank, becomes an upward flow in the absorption tower, and comes into countercurrent contact with the absorbing liquid being sprayed, and then the absorption tower. The water is discharged from the absorption tower outlet duct provided in the upper part to the outside of the absorption tower in the horizontal direction. Since minute liquid droplets are entrained in the gas at the outlet of the absorption tower, it causes deposition and scaling in the duct, which causes problems such as trip of gas ventilator due to increase of pressure loss. Mist eliminator 5 is installed. After the scattered mist is removed by the mist eliminator, the processing gas is guided to the reheating facility, heated, and discharged from the chimney. Since the mist eliminator needs to be installed adjacent to the outlet of the absorption tower, it is supported by the steel frame from the ground, and the mist eliminator outlet duct is also supported by the steel frame from the ground. Since the tower height is usually 20 to 30 m, these supporting steel frames cause an increase in desulfurization equipment cost.

On the other hand, by making a U-turn in the upper part of the absorption tower shown in FIG. 9 and extracting the processing gas 6 from the absorption tower outlet duct provided on the side of the absorption tower, the mist eliminator and the absorption tower outlet duct are separated. An invention has been proposed to reduce the supporting steel frame. This invention is an upflow from the absorption tower inlet to the absorption tower upper part, a downflow from the absorption tower upper part to the absorption tower outlet, each has a spray part, and considers efficient contact between the absorbing liquid and the exhaust gas. It was done.
However, in the present invention, since the U-turn is made in the upper part of the absorption tower, the gas is liable to drift in the absorption tower, and the contact efficiency between the absorbing liquid and the exhaust gas is not necessarily good.

[0008]

The above-mentioned prior art has a problem that the desulfurization performance is deteriorated because the gas-liquid contact is not performed uniformly due to the uneven flow of the exhaust gas flow. The object of the present invention is to make a U-turn in the upper part of the absorption tower to extract the processing gas from the absorption tower outlet duct provided on the side of the absorption tower.
Even when the support steel frames of the mist eliminator and the absorption tower outlet duct are reduced, it is possible to obtain a higher desulfurization performance by efficiently contacting the absorbing liquid with the exhaust gas by reducing the exhaust gas drift in the absorption tower as much as possible. It is to provide a wet exhaust gas desulfurization method and apparatus.

[0009]

The invention claimed in this application to achieve the above object is as follows. (1) An uppermost gas flow direction conversion section in an absorption tower that is surrounded by a side wall and a ceiling wall that covers an upper end of the side wall, and an absorption tower connected to the gas flow direction conversion section except for the gas flow direction conversion section A partition plate that divides the inner lower region into an exhaust gas rising region and an exhaust gas falling region, an absorption tower gas inlet duct provided on the absorption tower side wall in the lower part of the exhaust gas rising region, and an absorption tower side wall in the lower part of the exhaust gas falling region Absorption tower gas outlet duct, a plurality of spray stages provided in the exhaust gas ascending region and descending region in the absorption tower for spraying the sulfur oxide absorbing liquid to the exhaust gas, and absorption for circulating and supplying the absorbing liquid to these spray stages In a wet exhaust gas desulfurization device provided with a liquid circulation tank and a circulation pump, a wet exhaust gas desulfurization device is characterized in that a gas rectification unit is provided in a downstream region from the gas flow direction conversion unit. (2) The wet exhaust gas desulfurization apparatus according to the above (1), wherein a gas straightening plate is provided in the exhaust gas descending region.

(3) In the above (1) or (2),
A wet exhaust gas desulfurization device, characterized in that a gas straightening plate is provided in the cleaning region of the cleaning water spray nozzle provided at the top of the exhaust gas descending region. (4) The wet method according to the above (1), (2) or (3), characterized in that a perforated plate having holes with a diameter of 20 to 50 mm is horizontally provided in the gas descending region as a rectifying section or a rectifying plate. Exhaust gas desulfurization equipment. (5) The exhaust gas containing sulfur oxides is introduced into the absorption tower through an absorption tower inlet duct provided on the side wall of the absorption tower, and the sulfur oxide absorption liquid is sprayed from a plurality of spray stages provided with a large number of spray nozzles to spray the inside of the absorption tower. It makes gas-liquid contact with rising exhaust gas, changes the gas flow direction in the upper part of the absorption tower, and introduces it into the descending flow section partitioned by the ascending flow section and partition plate, where it is used from multiple spray stages with multiple spray nozzles. In the wet exhaust gas desulfurization method in which the absorption gas is sprayed and brought into gas-liquid contact with the descending exhaust gas, and then the treated gas is discharged from the absorption tower outlet duct provided on the side wall of the absorption tower, which is caused by the exhaust gas direction change at the upper part of the absorption tower. A wet exhaust gas desulfurization method, characterized in that the flow is rectified by a rectifying means and the rectifying means is washed by a cleaning liquid spray.

(6) An upright absorption tower having a side wall, a ceiling wall for sealing the upper end of the side wall, and a bottom wall provided at the lower end of the side wall, and having an upright absorption tower having a quadrangular cross section, and a gas flow direction conversion section in the uppermost region of the absorption tower. A partition plate for partitioning the lower region of the absorption tower following the gas flow direction changing section into an exhaust gas rising flow region and an exhaust gas falling flow region, and an absorption tower gas inlet duct provided on the absorption tower front side wall below the exhaust gas rising flow region, An absorption tower gas outlet duct provided on the absorption tower rear side wall in the lower part of the exhaust gas downward flow region, and a plurality of spray stages for spraying the sulfur oxide absorption liquid to the exhaust gas, which are provided in the exhaust gas upstream flow region and the downward flow region inside the absorption tower, In a wet exhaust gas desulfurization device provided with an absorption liquid circulation tank provided at the bottom of the absorption tower, and a circulation pump for supplying the absorption liquid in the circulation tank to the spray stage, almost the upper end surface of the partition plate at the exhaust gas descending flow region inlet Within the same horizontal plane A plurality of straightening vanes having a predetermined height in the vertical direction are provided at predetermined intervals so as to be substantially parallel to the partition plate, and the side wall of the absorption tower from the top of the ceiling wall of the gas flow converter to the gas descending flow region. A wet exhaust gas desulfurization apparatus, wherein a ceiling wall portion connected to an upper end is configured to be inclined substantially linearly. (7) In claim 6, an inclination angle θ formed by the ceiling wall portion connecting from the ceiling wall top portion to the absorption tower rear side wall upper end with a horizontal plane,
The relationship between the straightening plate height H and the straightening plate distance P is expressed by the following equation.

[0012]

## EQU2 ## A wet exhaust gas desulfurization apparatus characterized in that it satisfies H ≥ Ptan θ.

[0013]

FIG. 1 shows a first embodiment of the present invention. The exhaust gas 1 containing sulfur oxides is guided to the absorption tower 2 of the exhaust gas desulfurization device. In the absorption tower 2, a partition plate 18 is installed vertically in the upper part of the absorption tower with a space between the absorption tower 2 and the tower ceiling wall so that exhaust gas can make a U-turn. The exhaust gas guided from the absorption tower inlet duct 23 comes into contact with the fine absorption droplets sprayed from the spray nozzle 4 in the gas upflow section 19, and then passes through the U-turn section 20 at the upper part of the absorption tower to make a U-turn. In the descending flow section 21, the fine droplets sprayed from the spray nozzle 4 come into contact again and are discharged from the absorption tower outlet duct 24 provided on the side of the absorption tower 2. In addition,
A gas straightening plate 22 is provided in the gas descending flow section to reduce the gas drift generated in the U-turn section 20 above the absorption tower.

The gas rectifying plate 22 is installed above the absorbing liquid spray stage, and a washing water pipe 25 is installed above the gas rectifying plate 22. The spray nozzle attached to the washing water pipe 25 is installed. Since the top surface of the gas straightening plate is always washed with makeup water or absorption liquid sprayed from
There is no problem of clogging of solid deposits. As a result, the gas straightening plate is less likely to cause clogging or scaling of fixed objects,
A perforated plate having a hole diameter of about 20 to 50 mm is desirable.

Further, as shown in FIG. 2, the installation position of the gas rectifying plate is also effective if the cleaning water pipe 25 is omitted and the gas rectifying plate is installed below the uppermost spray stage. The direction in which the absorbing liquid is sprayed from the spray nozzle is not particularly limited, and the effect of the present invention does not change even if the absorbing liquid is sprayed downward or upward. FIG. 3 shows the results of a comparative test regarding the degree of gas drift that occurs after passing through the U-turn section 20 above the absorption tower, with and without the gas straightening plate installed in the gas downflow section. When the gas flow straightening plate is not installed in the gas downflow portion, the gas uneven flow degree is large, and when the gas flow straightening plate is installed in the gas downflow portion, the gas flow unevenness degree is reduced. Further, the relationship between the degree of gas drift and the desulfurization performance is shown in FIG. The smaller the degree of gas drift, the higher the desulfurization performance can be. Therefore, the desulfurization performance is improved when the flow straightening plate is installed in the gas downflow part, as compared with the case where the flow straightening plate is not installed.

The second embodiment of the present invention is shown in FIG.
It is shown in (C). Note that FIG. 5B is BB of FIG.
FIG. 5C is a partially enlarged explanatory view of FIG. 5A, which is a cross-sectional view taken along the line. In this embodiment, in the square type absorption tower 2,
A gas rectifying plate 22 is arranged above the gas downflow section 21 so that its upper surface is substantially level with the partition plate 18 and in parallel with the partition plate 18. Further, the ceiling wall section 26 of the gas downflow section 21 is arranged.
A is provided with a linear inclination in the gas flow direction from the top of the absorption tower to almost the same height as the upper surface of the partition plate.

With the above-mentioned structure, the absorption tower U
The exhaust gas flow on the gas downflow section side of the turn section 20 flows substantially parallel to the slope of the gas downflow section ceiling wall 26a. Since the gas straightening plate is arranged so that the exhaust gas inflow surface thereof is substantially the same as the upper surface of the partition plate 18, the exhaust gas flows into the gas straightening plate portion before breaking the parallel state. Since the exhaust gas flowing into the gas straightening plate is a parallel flow, the amount of exhaust gas flowing into each gas straightening plate becomes almost equal, and the flow direction of the exhaust gas is adjusted by each gas straightening plate, and the gas downflow part Flows evenly toward the uppermost spray part of. Therefore, since the gas drift due to the U-turn part of the absorption tower can be mitigated, the contact between the absorbing liquid and the exhaust gas in the spray part is made uniform, and the desulfurization performance does not deteriorate.

In this embodiment, the relational expression between the height H of the straightening vanes and the pitch P of the straightening vanes was calculated by the following equation as a result of the exhaust gas flow test.

[0019]

## EQU00003 ## It was confirmed that a high rectification effect can be obtained by configuring as specified by H.gtoreq.Ptan.theta .. Here, θ: the absorption tower ceiling part which is arranged so as to be linear from the top of the ceiling part in the upper part of the absorption tower in the gas flow direction to the wall surface side of the absorption tower which is almost level with the upper surface of the partition plate is It is an angle.

A third embodiment of the present invention is shown in FIG. In this embodiment, a gas straightening plate is installed below the lowermost spray section of the gas downflow section in the absorption tower. The effect of this embodiment is that by installing the gas rectifying plate below the lowermost spray section of the gas downflow section in the absorption tower, the absorbing liquid is sprayed downward from the spray nozzle installed in the lowermost spray section. In this case, there is an effect that the amount scattered to the absorption tower outlet duct can be reduced. When the gas straightening plate is not installed below the lowermost spray portion, there is a certain spread angle (for example, 80 to 1).
(00 degree) Since the absorbing liquid is sprayed downward from the spray nozzle, the amount of the absorbing liquid sprayed from the spray nozzle is scattered to the absorption tower outlet duct, but the gas straightening is performed below the lowermost spray part of the gas downflow part. By installing a plate,
The momentum sprayed from the spray nozzle is relaxed by the gas straightening plate and falls vertically, so that the amount of the absorbing liquid scattered to the outlet tower duct can be reduced.

A fourth embodiment of the present invention is shown in FIG. In this embodiment, the gas rectifying plate 22 is installed in the spray part of the gas upflow part in the absorption tower, and the gas rectifying plate is installed in the spray part of the gas downflow part. The effect of this embodiment is that, in addition to the effect of the embodiment shown in FIG. 2, when the exhaust gas is introduced from the absorption tower inlet duct installed on the side of the absorption tower in the gas upflow section to become an upflow. This has the effect of reducing the occurrence of gas drift, which can further improve the desulfurization performance.

[0022]

EFFECTS OF THE INVENTION According to the present invention, the height of the absorption tower can be reduced by making a U-turn in the upper part of the absorption tower and making gas-liquid contact with the absorption liquid even in the gas downflow part. Since the inlet duct and the outlet duct can be provided relatively below the tower, the weight of the steel frame supporting them can be reduced. In addition, with such a configuration, it is possible to reduce the gas drift in the tower that occurs, and thus it is effective in improving the desulfurization performance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a modification of the first embodiment of the present invention.

FIG. 3 is an explanatory view showing the effect of the current plate in the present invention.

FIG. 4 is a diagram showing a relationship between a drift in the absorption tower and a desulfurization rate.

FIG. 5 is an explanatory diagram of a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a third embodiment of the present invention.

FIG. 7 is an explanatory diagram of a fourth embodiment of the present invention.

FIG. 8

FIG. 9 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1 ... Exhaust gas, 2 ... Absorption tower, 3 ... Spray header, 4 ... Spray nozzle, 5 ... Mist eliminator, 6 ... Purified gas, 7
... Absorption tower circulation tank, 8 ... Air, 9 ... Limestone, 10 ... Limestone supply equipment, 11 ... Limestone slurry pump, 12 ... Extraction pump, 13 ... Gypsum dewatering equipment, 14 ... Solid matter (gypsum, gypsum,
Dust), 15 ... drain line, 16 ... dehydration liquid return line,
17 ... Circulation pump, 18 ... Partition plate, 19 ... Gas upflow section, 20 ... Gas U-turn section, 21 ... Gas downflow section, 22
... Gas straightening plate, 23 ... Absorption tower inlet duct, 24 ... Absorption tower outlet duct, 25 ... Wash water pipe, 26 ... Ceiling wall, 26a
... downflow part ceiling wall, 27 ... absorption tower front side wall, 28 ... absorption tower rear side wall.

Claims (7)

[Claims] 1. An uppermost gas flow direction changing section in an absorption tower which is surrounded by a side wall and a ceiling wall which covers an upper end of the side wall and which is connected to the gas flow direction changing section except for the gas flow direction changing section. A partition plate for partitioning the lower area of the absorption tower into an exhaust gas rising area and an exhaust gas falling area, an absorption tower gas inlet duct provided on the absorption tower side wall in the lower part of the exhaust gas rising area, and an absorption tower side wall in the lower part of the exhaust gas falling area. An absorption tower gas outlet duct, a plurality of spray stages provided in the exhaust tower ascending region and descending region in the absorption tower for spraying the sulfur oxide absorbing liquid onto the exhaust gas, and for supplying the circulating liquid to the spray stages. In the wet exhaust gas desulfurization device provided with the absorption liquid circulation tank and the circulation pump of
A wet exhaust gas desulfurization apparatus, characterized in that a gas rectifying unit is provided in a downstream region of the gas flow direction changing unit. 2. The wet exhaust gas desulfurization device according to claim 1, wherein a gas straightening plate is provided in the exhaust gas descending region. 3. The wet exhaust gas desulfurization device according to claim 1, wherein a gas straightening plate is provided in the cleaning region of the cleaning water spray nozzle provided at the uppermost part of the exhaust gas descending region. 4. The wet exhaust gas desulfurization device according to claim 1, 2 or 3, wherein a perforated plate having holes with a diameter of 20 to 50 mm is horizontally provided in a gas descending region as a rectifying section or a rectifying plate. . 5. The absorption tower in which the sulfur oxide-containing exhaust gas is introduced into the absorption tower through an absorption tower inlet duct provided on the side wall of the absorption tower, and the sulfur oxide absorption liquid is sprayed from a plurality of spray stages provided with a plurality of spray nozzles. Gas-liquid contact with the rising exhaust gas,
Exhaust gas that changes the gas flow direction at the upper part of the absorption tower and introduces it into the descending flow part partitioned by the ascending flow part and partition plate, where the absorbing liquid is sprayed from multiple spray stages provided with multiple spray nozzles and descends. In the wet exhaust gas desulfurization method in which the treated gas is discharged from the absorption tower outlet duct provided on the side wall of the absorption tower after the gas-liquid contact with A wet exhaust gas desulfurization method characterized in that the rectifying means is washed with a cleaning liquid spray. 6. An upright absorption tower having a side wall, a ceiling wall for sealing the upper end of the side wall and a bottom wall provided at the lower end of the side wall, and an upright absorption tower having a quadrangular cross section, and a gas flow direction changing section in the uppermost region of the absorption tower, A partition plate for partitioning the lower region of the absorption tower following the gas flow direction changing section into an exhaust gas rising flow region and an exhaust gas falling flow region, an absorption tower gas inlet duct provided on the side wall of the absorption tower front part below the exhaust gas rising flow region, and exhaust gas An absorption tower gas outlet duct provided on the side wall at the rear of the absorption tower in the lower part of the descending flow area, and a plurality of spray stages for spraying the sulfur oxide absorption liquid on the exhaust gas provided in the exhaust gas ascending and descending flow areas in the absorption tower, and absorbing In a wet exhaust gas desulfurization device provided with an absorption liquid circulation tank provided at the bottom of the tower and a circulation pump for supplying the absorption liquid in the circulation tank to the spray stage, the exhaust gas descending flow zone inlet is almost the same as the upper end surface of the partition plate. Vertical in horizontal plane A plurality of straightening vanes having a predetermined height in the direction are provided at predetermined intervals so as to be substantially parallel to the partition plate, and the upper end of the absorption tower rear side wall in the gas downflow region from the top of the ceiling wall of the gas flow converter The wet exhaust gas desulfurization device, wherein the ceiling wall portion connected to the above is configured to be inclined substantially linearly. 7. The relationship between the inclination angle θ formed by the ceiling wall portion connecting from the top of the ceiling wall to the upper end of the rear wall of the absorption tower with the horizontal plane, the height H of the straightening vanes, and the spacing P of the straightening vanes according to the following equation: ## EQU1 ## A wet exhaust gas desulfurization apparatus characterized by being configured to satisfy H ≥ Ptan θ.