JP2001157819A - Absorption and desulfurizer provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorption tower of a desulfurizer wherein a ductwork of the absorption tower and that of a gas inlet side duct of the tower and that of a gas outlet side duct of the tower are simplified, while desulfurization performances are maintained at the same level as a conventional technics, and the levels of frames supporting constituent apparatus are made lower. SOLUTION: In an absorption tower of a desulfurization device to absorb and remove sulfur oxides of a combustion exhaust gas, the interior of the tower is divided into an upstream side which is connected to the gas inlet of the inner wall to form a rising flow of gas and a downstream side which is connected to the gas outlet provided in the inner wall of the tower to form a downward flow of gas, while a partition plate 23 is provided in the top zone of the tower to connect the upstream side and the downstream side. A gas/liquid contact devices 25a, 25b are provided on the upstream side and the downstream side, respectively, and further a portion of the horizontal projected area of the gas inlet and a portion of the horizontal projected area of the gas outlet are disposed so that both portions of the areas are on the same level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention simplifies a ductwork around an absorption tower of a desulfurization apparatus for removing sulfur oxides from combustion exhaust gas discharged from a thermal power generation boiler which performs a large-capacity gas treatment. Regarding the configuration.

[0002]

2. Description of the Related Art A general flue gas treatment system for a boiler for thermal power generation comprises a combination of elemental devices for denitration, dust removal, desulfurization, and gas cooling / heating. When it comes to the exhaust gas throughput of a coal-fired power plant with the largest capacity, it is necessary to process a large amount of gas of about 3 million cubic meters per unit time.

[0003] The duct for connecting the component equipment and the gas to be treated is complicated and greatly affects the construction cost. Also, considering the ductwork around the absorption tower, the heat exchanger for reheating the processing gas at the outlet of the absorption tower is as large as 1500 tons, and the base of the earthquake-resistant structure that supports this is considerably strong.

[0004]

SUMMARY OF THE INVENTION Denitration, dedusting, desulfurization, gas cooling and cooling of a comprehensive flue gas treatment system for a thermal power plant
Simplifying the ductwork that connects the gas inlet of the absorption tower of the desulfurization unit, the gas outlet of the electric precipitator, the outlet of the absorber and the inlet of the heat exchanger for heating, among the heating element devices, It is necessary to adopt the structure of the absorption tower and the duct so that the frame supporting the component devices has a structure with the height level reduced as much as possible.

[0005] An object of the present invention is to simplify the respective duct works of an absorption tower, a duct on an absorption tower gas inlet side, and a duct on an absorption tower gas outlet side of a desulfurization apparatus, while maintaining desulfurization performance equivalent to that of the prior art. And to provide a structure in which the height level of the gantry supporting the element devices is reduced.

[0006]

The above object of the present invention is attained by the following constitution. (1) In an absorption tower of a desulfurization apparatus for absorbing and removing sulfur oxides in the exhaust gas by introducing the combustion exhaust gas and bringing the exhaust gas into contact with an absorbing solution containing lime slurry, a gas inlet portion provided on an absorption tower side wall is used for the inside of the tower. A gas flow path on the upstream side that forms an upward flow of the gas introduced into the gas flow path and a gas flow path on the downstream side that forms a downward flow of gas toward the gas outlet provided on the side wall of the absorption tower; A partition plate that forms a gas flow path connecting the upstream side and the downstream side is installed, and a gas-liquid contact device is provided in the upstream side and downstream side gas flow paths. An absorption tower of a desulfurization device in which a part of a projected sectional area and a part of a horizontal projected sectional area of a gas outlet are arranged at the same height level.

(2) An absorption tower for absorbing and removing sulfur oxides in the exhaust gas by bringing the combustion exhaust gas into contact with an absorption liquid containing lime slurry, and a circulation for storing the absorption liquid provided at a lower portion of the absorption tower. A desulfurization apparatus including a tank, an absorption liquid circulation flow path for supplying a part of the absorption liquid in the circulation tank to the gas-liquid contact portion of the absorption tower, and a gas flow path for the processing gas discharged from the absorption tower. After forming a rising flow of gas introduced into the tower from the gas inlet provided on the side wall of the absorption tower, and forming a downward flow of gas toward the gas flow path on the upstream side and the gas outlet provided on the side wall of the absorption tower. Partitioning the gas flow path on the upstream side, and installing a partition plate forming a gas flow path connecting the upstream side and the downstream side on the ceiling,
A gas-liquid contact device is installed in the gas flow path on the upstream and downstream sides, and a part of the horizontal projected cross-sectional area of the gas inlet and a part of the horizontal projected cross-sectional area of the gas outlet are the same height level. And an apparatus for post-processing the processing gas in the gas flow path of the processing gas discharged from the absorption tower, and a gas inlet and a gas outlet of the absorption tower, A desulfurization unit arranged on each side wall of the absorption tower so that the gas flow path connecting the absorption tower is the shortest.

[0008] In the integrated flue gas treatment system of a thermal power generation system, a gas to be treated such as a combustion gas is cooled to about 100 ° C, and then introduced into an electric dust collector to remove dust. The gas after dedusting is introduced into the absorption tower of the desulfurization device, and the gas is adiabatically cooled at the same time as desulfurization by direct contact with the absorbent,
It is cooled to about 50 ° C.

[0009] The processing gas from the outlet of the absorption tower is introduced into a mist eliminator for removing mist. Further, the outlet gas from the mist eliminator is introduced into a reheating heat exchanger to prevent white smoke from the chimney, and is heated to about 100 ° C.

In order to simplify the ductwork connecting the outlet of the electrostatic precipitator to the absorber and the ductwork connecting the outlet of the absorber and the heat exchanger for reheating, the structure of the absorber is devised. It is necessary.

[0011] The weight of the heat exchanger for gas heating installed at the exit of the absorption tower of the current maximum capacity coal-fired power boiler is about 1500 tons, and the base of the earthquake-resistant structure that supports it is strong. Is required.

If it is possible to adopt a configuration of the absorption tower that makes the height level of the heat exchanger for heating the gas at the outlet of the absorption tower as low as possible, a frame at the gas inlet and gas outlet, a frame at the heat exchanger, a duct, etc. The work can be simplified and the construction cost can be reduced.

To reduce the height level of the heat exchanger for heating the gas at the outlet of the absorption tower, it is possible to install the duct at a lower level as compared with the prior art, but the duct piping is longer. Become.

Therefore, in the present invention, a gas inlet and a gas outlet are provided at a low height position on the side wall of the absorption tower, and the flow direction of the exhaust gas introduced from the gas inlet is changed from an upward flow to a downward flow in the absorption tower. After the conversion, the gas was taken out from the gas outlet and introduced into the heat exchanger, so that the height level at which the heat exchanger was installed was reduced, and the ductwork was simplified.

In order to divert (return) the gas flow in the absorption tower, the gas flow region is divided into two by a partition plate.
The process gas was withdrawn from a lower height level.

Dividing the interior of the absorption tower into two by a partition plate means that the flow rate of the exhaust gas is 2 if the cross-sectional area of the exhaust gas channel is the same as that of the conventional method.
Becomes high as times, but this time, SO ₂ absorption rate of the absorbing liquid drops sprayed from the spray in the case of adopting a spray method as the gas-liquid contact apparatus, ventilation losses, necessary to clarify the influence of the scattered mist amount There is.

With respect to the SO ₂ absorption rate of the droplet sprayed in the high gas flow velocity field, the mass transfer speed of the single droplet and the droplet sprayed from the spray nozzle was evaluated. The mass transfer speed of the droplet is affected by the film mass transfer speed on the gas side and the liquid side existing around the droplet. The rate of material movement of the film on the gas side of the droplet is affected by the film thickness, but can be increased because the film thickness can be reduced as the gas flow rate increases.

Further, since a part of the energy received by the droplets flying at a high speed assists the internal circulation flow and promotes the renewal of the film at the interface, the material transfer speed at the film surface at the interface of the droplets can be increased. .

On the other hand, the ventilation loss increases with an increase in the gas flow rate of the exhaust gas. However, since the mass transfer rate can be increased by increasing the gas flow rate of the exhaust gas, the amount of absorbing liquid per unit processing gas amount can be reduced. Even if the gas velocity is increased, the ventilation loss does not become extremely high. When the exhaust gas has a high gas flow rate, the amount of scattered mist tends to increase. In order to collect the flying mist, inertial collection by a collision plate is effective. Structurally, in order to reduce the ventilation loss of gas flow, a method using a mist eliminator that arranges a plurality of flat plates in the gas flow direction at a certain gap and collides gas with the flat plate to collect scattered mist is often used. You.

A plurality of mist eliminator units are installed in the gas flow direction to collect scattered mist.
When the gas flow rate increases, the collection efficiency of the mist eliminator can be increased. Therefore, even if the amount of scattered mist increases, mist can be collected with high efficiency by the trough structure of the mist eliminator.

In the absorption tower of the present invention, a spray-type gas-liquid contact device for spraying the absorbing liquid against the exhaust gas flow may be used as the gas-liquid contact device provided in the gas flow paths on the upstream and downstream sides. it can.

The spraying method of the absorbing liquid of the gas-liquid contacting device is a countercurrent spraying method in which the upstream side has a direction opposite to the gas flow direction, and the downstream side has a cocurrent flow in the same direction as the gas flow direction. It is possible to adopt a spray system, or conversely, a co-current spray system on the upstream side and a counter-current spray system on the downstream side.

Further, the spraying method of the absorbing liquid of the gas-liquid contacting device may be all cocurrent spraying or all countercurrent spraying in the gas flow direction on the upstream and downstream sides.

In order to prevent the inner wall of the ceiling of the absorption tower from drying up, a spraying device for spraying part of the absorbing liquid from the gas-liquid contact portion toward the inner wall of the ceiling is provided, or the inner wall of the ceiling is cooled. The apparatus may be arranged to cool the inner wall surface of the ceiling of the absorption tower and condense the water in the gas in the absorption tower on the inner wall of the ceiling of the absorption tower to prevent dry-up.

[0025]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows a typical integrated flue gas treatment system of a thermal power boiler. The combustion exhaust gas 2 from the thermal power boiler 1 is introduced into the denitration device 5 after heat recovery by the air preheater 3. The denitrified combustion exhaust gas 6 is cooled to about 100 ° C. in a gas / gas heat exchanger 7, the cooling gas flow 8 is introduced into an electric precipitator 9, and after dedusting, the pressure is increased by a desulfurization fan 11, and the absorption tower 13 of the desulfurization device is removed. Will be introduced.

The processing gas 14 in the absorption tower 13 is introduced into a heat exchanger 15 for heating, and the processing gas 14 processed in the absorption tower 13 is reheated, and after being pressurized by a desulfurization fan 17, the chimney 1
9 to the atmosphere.

FIG. 1 shows the structure of an absorption tower according to an embodiment of the present invention.
(FIG. 1A is a side sectional view of the absorption tower, and FIG.
(A) as viewed from the line AA). The flue gas 12 at the outlet of the electric precipitator 9 (FIG. 2) is introduced into the absorber main body 24. The partition plate 23 is provided in the absorption tower main body 24, and the partition plate 23 is a plate-shaped member extending from the liquid in the circulation tank 21 to a position above the gas-liquid contact portion 25.

The tower structure in which the partition plate 23 is installed in the absorption tower main body 24 is adopted because the size of the absorption tower main body 24 is reduced and the height level of the gas inlet and the gas outlet is the same, thereby simplifying the ductwork. It is to make it.

As shown in FIG. 1 (a), a partition plate 23 used in a vertical direction in the main body 24 of the absorption tower divides a gas-liquid contact region in a gas flow passage into gas-liquid contact portions 25a and 25b. Divide and divide. The combustion exhaust gas introduced into the absorption tower main body 24 rises along the partition plate 23, comes into gas-liquid contact with the absorption liquid 26 supplied from the circulation tank 21 at the gas-liquid contact portion 25a, and is cooled simultaneously with desulfurization.

The combustion exhaust gas rising in the gas-liquid contact portion 25a reaches the upper part of the absorption tower main body 24, reverses the flow on the opposite side of the partition plate 23, and is introduced into the gas-liquid contact portion 25b. The gas flow flowing through the gas-liquid contact portion 25b forms a downward flow, comes into gas-liquid contact with the absorbing liquid 26 sent from the circulation tank 21 by the pump 22, and becomes the processing gas 14.

The processing gas 14 is introduced into a mist eliminator (not shown), and after the mist is removed, is introduced into a gas-gas heat exchanger 15 for heating (FIG. 2). The height level at which the processing gas 14 is extracted from the absorption tower main body 24 is
A part of the horizontal projected cross-sectional area of the flue gas duct introduced into the absorber main body 24 and a part of the horizontal projected cross-sectional area of the duct for extracting the processing gas are arranged to be at the same height.

Comparing the conventional absorption tower configuration of FIG. 11 with the absorption tower configuration of the present invention, the ductwork can be simplified by lowering the processing gas extraction duct to the same height as the gas introduction duct, and the heat exchange for heating can be performed. Vessel (GGH heat recovery unit 1)
5) can be installed at a low height level, and the gantry supporting it can be reduced in weight.

The embodiment shown in FIG. 3 is an example in which a gas-liquid contact device of a spray type is installed in the gas-liquid contact portion of FIG. 1 in a plurality of stages in the height direction of the absorption tower. FIG. 3A is a side cross-sectional view of the absorption tower main body 24, and FIG.
3A has a circular horizontal cross-section, as shown in FIG. 3C, or has a rectangular horizontal cross-section, as shown in FIG. 3C.

The absorption liquid in the circulation tank 21 is supplied to the circulation pump 22
Most of the droplet diameter sprayed from the spray nozzle 25 becomes fine droplets of 1000 to 3000 microns, and sulfur oxidation in the combustion exhaust gas 12 introduced into the absorption tower main body 24 from the electrostatic precipitator 9 (FIG. 2). Absorb material and cool gas temperature.

Gas-liquid contact portion 25 on the introduction side of flue gas 12
The exhaust gas having risen in a is reversed in flow by the partition plate 23 to become a downward gas flow, and becomes the processing gas 14 via the gas-liquid contact portion 25b.

When a spray-type gas-liquid contact device is employed, the absorption performance can be adjusted by controlling the spraying conditions. In the embodiment shown in FIG. 4, droplets of the absorbing liquid are jetted at high speed into a gas stream containing sulfurous acid gas (SO ₂ ) in order to evaluate the mass transfer rate of the liquid droplets sprayed from the spray nozzle, and the liquid is ejected under the jetting conditions. It is the result of evaluating the SO ₂ absorption rate of the droplet.

The absorption rate of SO ₂ into the droplet is affected by the film resistance at the interface between the gas side film of the droplet and the droplet. In general, the mass transfer speed on the gas side of a droplet flying at a high speed can be increased as the relative speed between the droplet flight speed and the gas flow velocity increases.

Further, when the mass transfer speed at the interface of the droplet is examined from a flight experiment of the droplet, as shown in FIG. 4, the larger the Reynolds number based on the droplet, the larger the coefficient of mass transfer on the liquid side. Therefore, when spraying the absorbing liquid onto the gas flow system from the spray nozzle, it can be said that it is preferable to install a spray nozzle that increases the relative speed between the flight speed of the droplet and the gas flow speed.

The embodiment shown in FIG. 5 shows the results of comparison of the desulfurization rates in the case where the installation direction of the spray nozzle for spraying the gas flow is countercurrent (curve (a)) and cocurrent (curve (b)). It is. The type in which the absorption liquid is sprayed in the countercurrent direction from the spray nozzle in the gas flow direction is sprayed against the gas flow as compared with the type in which the absorption liquid is sprayed, so that it is effective to enhance the desulfurization performance.

Therefore, as shown in the embodiment of FIG. 6, the structure of the absorption tower is a spray nozzle structure in which both the gas-liquid contact portion 25a on the introduction side and the gas-liquid contact portion 25b of the descending flow are of countercurrent spray type. From the viewpoint of increasing the

However, the countercurrent spray method increases ventilation loss. Therefore, only the cocurrent spray method as shown in the schematic side sectional view of the absorption tower in FIG. 7 or the schematic side sectional view of the absorption tower in FIG. As shown, an absorption tower configuration by a combined spraying method of cocurrent and countercurrent is possible.

The angle between the introduction direction of the gas to be treated 12 and the extraction direction of the treatment gas 14 can be appropriately selected at the same height level depending on the location of the absorption tower main body 24 and the chimney. The embodiment shown in FIG. 9 (FIG. 9 (a) is a schematic sectional side view of the absorption tower, and FIG. 9 (b) is a view taken along the line AA in FIG. 9 (a)) This is an example in which the angle formed by the direction of extraction of the processing gas 14 is 90 °.

In the embodiment shown in the schematic side sectional view of the absorption tower in FIG. 10, a heat exchanger 30 is installed above the absorption tower, and a refrigerant 31 (such as air) is passed through the heat exchanger 30. In addition, the water vapor in the combustion exhaust gas in the absorption tower main body 24 is partially condensed, and scale generation due to dry-up of the wall of the tower can be prevented.

[0044]

According to the present invention, since the height of the duct at the outlet of the absorption tower is the same as that of the gas introduction duct, the heat exchanger for heating the gas at the outlet of the absorption tower is installed. Since the height can be reduced, the weight of the supporting stand can be reduced, and the ductwork can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an absorption tower according to an embodiment of the present invention.

FIG. 2 is a diagram of an integrated smoke exhaust treatment system of a thermal power plant to which the present invention pertains.

FIG. 3 is a diagram showing a typical example when a spray method is adopted for a gas-liquid contact portion of an absorption tower according to an embodiment of the present invention.

FIG. 4 is a diagram showing test results for evaluating the mass transfer rate of droplets sprayed from a spray nozzle having an absorption tower configuration according to an embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a method of spraying an absorbent and a desulfurization rate according to the embodiment of the present invention.

FIG. 6 is a diagram showing a combination (No. 1) of the spraying method of the absorbing liquid according to the embodiment of the present invention.

FIG. 7 is a view showing a combination (No. 2) of the spraying method of the absorbing liquid according to the embodiment of the present invention.

FIG. 8 is a diagram illustrating a combination (No. 3) of the spraying method of the absorbing liquid according to the embodiment of the present invention.

FIG. 9 is a diagram showing a combination (No. 4) of the spraying method of the absorbing liquid according to the embodiment of the present invention.

FIG. 10 is a diagram showing an example in which a scale prevention device is arranged on the upper wall surface of the absorption tower according to the embodiment of the present invention.

FIG. 11 is a configuration diagram of a conventional absorption tower.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Boiler 2, 4, 6, 8, 10, 12, 16 Combustion exhaust gas 3 Air preheater 5 Denitration device 7, 15 Heat exchanger 9 Electric dust collector 11, 17 Desulfurization fan 13 Absorption tower 14 Processing gas 17 Desulfurization fan 19 Chimney 21 Circulation tank 22 Circulation pump 23 Partition plate 24 Absorbent liquid body 25, 25a, 25b Gas-liquid contact part, spray type gas-liquid contact device 26 Absorbent liquid 30 Heat exchanger 31 Refrigerant

Continued on the front page (72) Inventor Akira Kato 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Hisao Yamashita 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shigeru Shozuhata 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shigeru Nozawa 6-9 Takaramachi, Kure City, Hiroshima Prefecture No. F-term (reference) in Babcock Hitachi Kure Works 4D002 AA02 AC01 BA02 BA12 BA13 BA14 BA16 CA01 CA13 DA05 DA16 EA02 FA03 GA02 GA03 GB01 GB02 GB03 GB04 HA05 HA08 4D020 AA06 BA02 BA09 BB05 BC06 CB27 CC01 CD01 DA01 DB12 DB20

Claims (10)

[Claims] A combustion exhaust gas is introduced and brought into contact with an absorbent containing lime slurry to absorb sulfur oxides in the exhaust gas.
In the absorption tower of the desulfurization unit to be removed, the gas flows from the gas inlet provided on the side wall of the absorption tower to the gas flow path on the upstream side, which forms the upward flow of the gas introduced into the tower, and the gas outlet provided on the side wall of the absorption tower. Partitioning the gas flow path on the downstream side to form a downward flow of gas, and installing a partition plate on the ceiling to form a gas flow path connecting the upstream side and the downstream side. A gas-liquid contact device is provided in the gas flow path on the side, and further arranged so that a part of the horizontal projected sectional area of the gas inlet part and a part of the horizontal projected sectional area of the gas outlet part are at the same height level. An absorption tower for a desulfurization device, comprising: 2. A gas-liquid contact device of a spray type for spraying an absorbing liquid with respect to an exhaust gas flow as a gas-liquid contact device provided in a gas flow path on the upstream and downstream sides. 2. The absorption tower of the desulfurization apparatus according to 1. 3. The spraying method of the absorbing liquid of the gas-liquid contact device is a counter-current spraying method in which the upstream side has a direction opposite to the gas flow direction, and a co-current spraying method in which the downstream side has the same direction as the gas flow direction. 3. The method according to claim 2, wherein a co-current spray method is used on the upstream side and a counter-current spray method is used on the downstream side.
The absorption tower of the desulfurization apparatus according to the above. 4. The spraying method of the absorbing liquid of the gas-liquid contacting device is characterized in that the gas is sprayed on the upstream side and the downstream side in a co-current spraying mode or a counter-current spraying mode. The absorption tower of a desulfurization device according to claim 2. 5. The desulfurization apparatus according to claim 1, wherein a lower end of the partition plate is disposed so as to be immersed in an absorbing solution in a circulating tank for storing the absorbing solution provided in a lower portion of the absorbing tower. Tower. 6. The absorption tower according to claim 1, further comprising a spraying device for spraying a part of the absorbing liquid from a gas-liquid contact portion toward an inner wall of a ceiling of the absorption tower. 7. The absorption tower of a desulfurization apparatus according to claim 1, wherein a cooling device is arranged on a ceiling of the absorption tower. 8. A combustion exhaust gas is introduced and brought into contact with an absorbent containing lime slurry to absorb sulfur oxides in the exhaust gas.
An absorption tower to be removed, a circulation tank provided at a lower portion of the absorption tower for storing the absorption liquid, an absorption liquid circulation flow path for supplying a part of the absorption liquid in the circulation tank to a gas-liquid contact portion of the absorption tower, In a desulfurization apparatus having a gas flow path for the processing gas discharged from the tower, a gas flow path on the upstream side forming an upward flow of gas introduced into the tower from a gas inlet provided on the side wall of the absorption tower, and the absorption tower A partition plate that partitions into a downstream gas flow path that forms a downward flow of gas toward the gas outlet provided on the side wall, and that forms a gas flow path that connects the upstream and downstream sides to the ceiling. Installed, gas-liquid contactors are provided in the gas flow path on the upstream and downstream sides, and a part of the horizontal projected sectional area of the gas inlet and a part of the horizontal projected sectional area of the gas outlet are the same. At a height level, and place the processing gas in the gas flow path of the processing gas discharged from the absorption tower. Providing a processing device, and arranging the gas inlet and gas outlet of the absorption tower on the side wall of the absorption tower such that the gas flow path connecting the post-processing device and the absorption tower is the shortest. A desulfurization device. 9. The mist eliminator unit is installed at a plurality of height levels at the gas outlet, and a heat exchanger for heating the gas is installed in the gas flow path on the downstream side. Desulfurization equipment. 10. A lower end of the partition plate is disposed so as to be immersed in an absorption liquid in a circulation tank storing an absorption liquid provided in a lower part of the absorption tower, and draws out the absorption liquid in the circulation tank on the gas outlet side. 9. The desulfurization apparatus according to claim 8, wherein an absorption liquid supply path for supplying the liquid to the gas-liquid contact portion of the absorption tower is provided.