JPH0731839A - Wet way exhaust gas desulfurization apparatus - Google Patents

Abstract

PURPOSE:To provide a desulfurization apparatus having a structure with which sprayed liquid drops can exist in a desulfurization tower as long as possible and the sprayed liquid drops can effectively work for desulfurization reaction. CONSTITUTION:A spray nozzle 4 to spray an absorbing liquid to a desulfurization tower is installed at the tip parts of side wall spray heads 14-16 installed in the side wall of a desulfurization tower main body 1 and at the tip of a ceiling spray head 17, and a spraying amount adjusting means of the absorbing liquid for the spray nozzle 4 is installed in each wall face or each part of the respective wall faces and no interior part is installed in the inside of a desulfurization tower. Since the desulfurization tower has a structure in which there is no spray pipeline and no support, the sprayed liquid drops can work effectively for desulfurization reaction without colliding against the interior parts and stopping the absorbing reaction with SO2 gas. It may be preferable either to install deflecting flow preventive plates in the tower or to increase the spraying absorbing liquid amount of the spray head 14 in the side wall in the inlet side more than those of other spray heads 15-17 in order to prevent gas deflecting flow or short pass from occurring in the desulfurization tower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet flue gas desulfurization apparatus, and more particularly to a high-performance wet flue gas desulfurization system in consideration of the arrangement structure of the nozzle when removing sulfur oxides in exhaust gas by droplets sprayed from a spray nozzle. The present invention relates to a flue gas desulfurization device.

[0002]

2. Description of the Related Art Sulfur oxides, especially sulfur dioxide (SO ₂ ), in flue gas produced by burning fossil fuels in thermal power plants, etc., are a major cause of global environmental problems such as air pollution and acid rain. It is one of the main causes. For this reason, research on a flue gas desulfurization method for removing SO ₂ from flue gas and development of a desulfurization device have become extremely important subjects. As the desulfurization method, recently, a simple dry desulfurization device having a low cost and a simple system has been developed, but the desulfurization rate is at most 70.
Since it is as low as -80%, the wet flue gas desulfurization method still predominates. This wet flue gas desulfurization method includes a soda method using a soda compound as an absorbent, a calcium method using a calcium compound, and a magnesium method using a magnesium compound. Of these, the soda method uses absorbent and S
While it has excellent reactivity with O ₂ , the soda used is very expensive. For this reason, a method using a relatively inexpensive calcium compound such as calcium carbonate is most often used for a flue gas desulfurization apparatus such as a large-scale boiler for power generation.

Desulfurization systems using this calcium compound as an absorbing liquid are roughly classified into three types, a spray system, a wetting wall system and a bubbling system, depending on the difference in gas-liquid contact method. Although each method has its own characteristics, the spray method, which has a proven track record and is highly reliable, is widely used worldwide. As the spray type desulfurization system, a cooling tower for cooling and removing dust from exhaust gas, an absorption tower for spraying an absorbing liquid to react with SO ₂ in the exhaust gas, and an oxidizing tower for oxidizing calcium sulfite produced in the absorbing tower have been used. It consisted of three towers. However, in recent years, the development of a single tower desulfurization tower in which the absorption tower has functions of cooling and oxidation has advanced, and recently, the single tower desulfurization system is becoming the mainstream of the spray method.

FIG. 5 shows an example of a conventional one-column tower desulfurization system using a spray method. The single tower type desulfurization tower mainly includes a desulfurization tower main body 21, an inlet duct 22, an outlet duct 23, a spray nozzle 24, a circulation pump 25 for absorbing liquid, and an oxidation tank 2.
6, a stirrer 27, an air blowing pipe 28, a demister 29, and the like. A plurality of spray nozzles 24 are installed in the horizontal direction, and a plurality of spray nozzles 24 are installed in the height direction. Normally, one circulation pump 25 is installed in each stage. The number of stages of the spray nozzle 24 is generally set to about 4 to 10, but in this figure, four stages are shown for simplification. Further, the stirrer 27 and the air blowing pipe 28 are installed in the oxidation tank 26 in the lower part of the desulfurization tower where the absorbing liquid stays, and the demister 29 is installed in the uppermost part in the absorption tower or in the outlet duct 23.

Exhaust gas discharged from a boiler (not shown) is introduced into the desulfurization tower main body 21 through the inlet duct 22,
Finally, it is discharged from the outlet duct 23. During this period, the desulfurization tower receives the absorption liquid containing calcium carbonate sent from the circulation pump 25, and the spray pipe 3 arranged in the desulfurization tower.
Sprayed from a plurality of spray nozzles 24 attached to No. 0, gas-liquid contact between the absorbing liquid and the exhaust gas is performed. At this time, the absorbing liquid selectively absorbs SO ₂ in the exhaust gas to generate calcium bisulfite (Ca (HSO ₃ ) ₂ ). Fine calcium carbonate (limestone), which is an absorbent, is used for the limestone supply pipe 3
3 into the oxidation tank 26. The absorption liquid that has generated calcium bisulfite remains in the oxidation tank 26, and while being stirred by the stirrer 27, the air supplied from the air blowing pipe 28 oxidizes the calcium bisulfite in the absorption liquid to remove gypsum (CaSO ₄ ). To generate. Oxidation tank 2 in which calcium carbonate (CaCO ₃ ) and gypsum coexist
A part of the absorption liquid in 6 is sent to the spray nozzle 24 again by the circulation pump 25, and a part of the absorption liquid extraction pipe 34
Sent to the waste liquid treatment and gypsum recovery system. Moreover, in the absorbing liquid atomized and sprayed from the spray nozzle 24,
Those having a small droplet diameter are entrained in the exhaust gas, but are recovered by the demister 29 provided at the upper part of the desulfurization tower. The desulfurization reaction and the reaction in the oxidation tank 26 at this time are shown as follows.

(Spray part) SO ₂ + H ₂ O → H ₂ SO ₃ (1) CaCO ₃ + 2H ₂ SO ₃ → Ca (HSO ₃ ) ₂ + CO ₂ + H ₂ O (2) Ca (HSO ₃ ) ₂ + O ₂ + 2H ₂ O → CaSO ₄・ 2H ₂ O + H ₂ SO ₄ (Part) (3) (Oxidation tank) Ca (HSO ₃ ) ₂ + O ₂ + 2H ₂ O → CaSO ₄・ 2H ₂ O + H ₂ SO ₄ (3) CaCO ₃ + H ₂ SO ₄ + H ₂ O → CaSO ₄ · 2H ₂ O + CO ₂ (4) Further, the gypsum produced in the oxidation tank 26 is discharged as a slurry waste liquid from the absorption liquid extraction pipe 34, and the gypsum is recovered by the gypsum recovery device 35.

[0007]

In the conventional spray type desulfurization apparatus described in the above-mentioned prior art, in order to make the installation area of the desulfurization tower as small as possible, the desulfurization tower is raised and the number of spray nozzles 24 is set to a plurality of steps. This ensures the amount of spray liquid required for absorption. That is, since the amount of liquid sprayed from the spray nozzle 24 is determined in terms of desulfurization performance, it is necessary to increase the amount of spray liquid in order to increase desulfurization performance. The sprayed droplets fly in the desulfurization tower while absorbing SO ₂ in the gas, reach the side wall, the circulating liquid pipe in the tower or the liquid surface of the oxidation tank 26, and reach the SO ₂ by gas-liquid contact.
End the absorption reaction of. Sprayed droplet diameter is usually several mmφ
In order to maximize the reaction surface area of the liquid droplet per unit volume, the longer the flight time of the liquid droplet is SO
_{Since the amount of 2} gas is increased, the desulfurization performance is improved. However, as described above, when the number of stages of the spray nozzle 24 is set to a plurality of stages, the spray pipe 30 and the support of the spray pipe 30 (not shown) are present in the desulfurization tower, and thus the sprayed droplets are separated from these interior components. It collides and the absorption reaction with SO ₂ gas almost stops. Therefore, in order to improve the desulfurization performance, it is necessary to spray a considerably large amount of circulating liquid.
An object of the present invention is to provide a wet flue gas desulfurization apparatus having a structure in which sprayed droplets are present in a desulfurization tower as long as possible and the sprayed droplets effectively contribute to a desulfurization reaction.

[0008]

The above object of the present invention can be achieved by the following constitutions. That is, by contacting the exhaust gas discharged from the combustion device such as a boiler with the spray absorption liquid in the desulfurization tower, and recirculating the absorption liquid after contacting the exhaust gas from the tank at the bottom of the absorption tower into the absorption tower, In a wet flue gas desulfurization apparatus that treats sulfur oxides, a spray nozzle that sprays an absorbing liquid into the desulfurization tower is installed on the wall surface of the desulfurization tower main body, and there is no interior material inside the desulfurization tower. .

Spray nozzles for spraying the absorbing liquid of the present invention into the desulfurization tower are provided on the side wall surface and the ceiling wall surface of the desulfurization tower,
It is possible to provide a means for adjusting the amount of the spray absorbed liquid of each spray nozzle for each wall surface. It is also possible to adopt a configuration in which a non-uniform flow preventing member for the spray absorbing liquid is arranged on the wall surface of the desulfurization tower. The present invention is suitable for a one-column type wet flue gas desulfurization apparatus in which the tank under the absorption tower is, for example, an oxidation tank, and the oxidation tank is provided with an air blowing pipe. However, the present invention is not limited to the one-column wet flue gas desulfurization apparatus, and can be applied to the case of a two-column wet flue gas desulfurization apparatus in which an oxidation tower is provided on the downstream side of the desulfurization tower.

[0010]

In the conventional method, in order to make the installation area of the desulfurization tower as small as possible, the desulfurization tower is raised and the number of stages of the spray nozzle is set to a plurality of stages to spray the slurry-like absorbing liquid as the absorbent. On the other hand, if the present invention is used,
Since there is no spray pipe or pipe support inside the desulfurization tower, the sprayed liquid droplets collide with these interior parts, and S
The sprayed droplets will remain in the desulfurization tower for a long time without stopping the absorption reaction with O ₂ gas, and the sprayed droplets can effectively contribute to the desulfurization reaction.

By providing the spray nozzles on the side wall surface and the ceiling wall surface of the desulfurization tower, the inner wall surface of the desulfurization tower can be effectively used. Also, the amount of absorbing liquid sprayed for each spray nozzle group separately arranged on each side wall and ceiling is changed according to the type of exhaust gas introduced into the desulfurization tower, the flow rate or the concentration of contained sulfur oxides. That is, it is possible to change the amount of the absorbing liquid sprayed for each part of the wall surface of a specific side surface part or for each part of the ceiling wall surface.

Further, in the case where a non-uniform flow of gas or a short path occurs in the desulfurization tower to deteriorate the desulfurization performance, a non-uniform flow prevention plate may be installed in the tower or the liquid amount of the inlet side wall nozzle may be increased. If a drift prevention plate is installed in the tower, the gas short path can be completely prevented. If the drift prevention plate is not installed, if the flow rate of the inlet side wall nozzle is made higher than the flow rate of the spray nozzle provided on the other wall surface, a liquid film will be formed by the sprayed droplets, which will cause gas flow resistance, so a short path Gas flow can be prevented.

Thus, according to the present invention, the absorption droplets sprayed in the desulfurization tower can be allowed to exist in the tower as long as possible, and as a result, the spray absorption droplets can effectively contribute to the desulfurization reaction and the desulfurization performance is improved. It will be dramatically improved. Further, since the sprayed droplets can effectively contribute to the desulfurization reaction, the amount of spray liquid can be reduced if the same desulfurization performance is to be obtained. Further, in the prior art, when installing a spray pipe or a pipe support in the desulfurization tower, since the absorbing liquid is strongly acidic, these members are made of high-grade materials such as stainless steel to prevent corrosion. However, according to the present invention, since the pipes are installed outside the desulfurization tower, it is not necessary to use such a high-grade material.

[0014]

The present invention will be explained in more detail by the following examples, but it should not be construed as being limited thereto.
FIG. 1 shows a schematic view of a desulfurization tower of a wet flue gas desulfurization apparatus according to an embodiment of the present invention. FIG. 1A is a schematic side sectional view of a desulfurization tower, and FIG. 1B is a schematic view looking downward from the line AA ′ in FIG. In FIG. 1, a box-shaped desulfurization tower body 1
An inlet duct 2 is provided in the upper part of the tower on one side wall, an outlet duct 3 is provided in the lower part of the central part, and a spray nozzle 4 is arranged on each of the four side walls. An oxidation tank 6 containing an absorbing solution is provided in the lower part of the desulfurization tower main body 1, and a stirrer 7, an air blowing tube 8, an absorbing solution withdrawing tube 1 are provided on a side wall of the tank 6.
0, a plurality of circulating liquid pipes 11 and a limestone supply pipe 13 are provided. A circulating pump 5 is provided in each circulating liquid pipe 11, and the absorbing liquid in the oxidation tank 6 is supplied to the spray nozzle 4. Each side wall spray nozzle 4 includes an inlet side wall spray head 14, an opposite side wall spray head 15 (above, FIG. 1A), and a side wall spray head 16 (see FIG. )) Supplies absorption liquid. A ceiling spray head 17 is provided on the spray nozzle 4 on the ceiling wall.

In the desulfurization tower of FIG. 1 having the above-mentioned components, the combustion exhaust gas containing SO ₂ enters the inside of the main body 1 of the desulfurization tower main body 1 from the inlet duct 2 at the upper part of the tower. In the desulfurization tower, the absorption liquid containing calcium carbonate sent from the circulation pump 5 is sprayed from a plurality of spray nozzles 4 provided on the side wall and the ceiling. Due to the gas-liquid contact of the absorbing liquid and the exhaust gas sprayed here, SO ₂ gas is absorbed and falls into the oxidation tank 6. On the other hand, fine calcium carbonate (limestone) that is an absorbent is supplied into the oxidation tank 6 through the limestone supply pipe 13. The absorption liquid that has generated calcium bisulfite is stored in the oxidation tank 6, and while being stirred by the stirrer 7, the air supplied from the air blowing pipe 8 oxidizes the calcium bisulfite in the absorption liquid to remove gypsum (CaSO ₄ ). To generate. A part of the absorption liquid in the oxidation tank 6 in which calcium carbonate (CaCO ₃ ) and gypsum coexist is sent to the spray nozzle 4 again by the circulation pump 5, and a part of the absorption liquid in the oxidation tank 6 is taken out as an absorption liquid discharge pipe. Gypsum recovery device 1 from 10
Sent to 2. Further, among the absorption liquids atomized by the spray nozzle 4 and atomized, those having a small droplet diameter are entrained in the exhaust gas, but are recovered by the demister 9 provided in the outlet duct 3 of the desulfurization tower. These reaction formulas are as shown in the above formulas (1) to (4).

Since the amount of liquid sprayed from the spray nozzle 4 is determined in terms of desulfurization performance, it is necessary to increase the amount of spray liquid in order to increase desulfurization performance. The sprayed droplets fly while absorbing SO ₂ in the gas in the desulfurization tower, reach the side wall, the spray pipe in the tower, or the liquid surface of the oxidation tank 6, and undergo SO ₂ absorption reaction by gas-liquid contact. Finish. The diameter of sprayed droplets is a few mmφ or less in a normal machine, and in order to maximize the reaction surface area of droplets per unit volume, the longer the flight time of droplets, the more SO ₂ gas is absorbed. Therefore, the desulfurization performance is high. Since the desulfurization tower of this embodiment has no structure such as the spray pipe 30 and the support (not shown) of the spray pipe 30 in the desulfurization tower shown in FIG. 5 of the conventional method, the sprayed droplets collide with these interior components. However, there is no possibility that the absorption reaction with SO ₂ gas will stop. Therefore, since the droplets sprayed according to this example can effectively contribute to the desulfurization reaction, the amount of spray liquid can be reduced if the same desulfurization performance as the conventional method is to be obtained.

Further, in the desulfurization tower of this embodiment, the spray heads 14 to 17 arranged on the side walls and the ceiling, respectively.
Since the circulation pump 5 is installed for each group, it becomes possible to change the amount of the spray absorbing liquid on a specific side wall or ceiling portion according to the type of exhaust gas, the flow rate, the SO ₂ content and the like. Although FIG. 1 shows a case where the cross-sectional shape of the desulfurization tower main body 1 is rectangular, it can be applied to a case of a round shape.

FIG. 2 shows a case where a drift prevention plate 18 is installed between the inlet duct 2 and the outlet duct 3 on the inlet side wall in the desulfurization tower. In FIG. 2, members having the same functions as the constituent members of the desulfurization tower shown in FIG. 1 have the same reference numerals. In the case where the gas desulfurization or short path occurs in the desulfurization tower and the desulfurization performance is deteriorated, the non-uniform flow prevention plate 18 may be installed in the desulfurization tower, or the amount of the spray absorption liquid of the inlet side wall spray head 14 may be increased. . If the drift prevention plate 18 is installed in the tower, the short path of gas can be completely prevented. In the case of FIG. 1 in which the non-uniform flow prevention plate 18 is not installed, if the amount of the spray-absorbed liquid in the inlet side wall spray head 14 is increased, a liquid film is formed by the spray droplets and becomes a flow resistance of the gas. Due to the same effect as the case where 18 is installed, the short path is eliminated and gas drift can be prevented.

Further, when a spray pipe or a support for the pipe is installed in the desulfurization tower, since the slurry liquid is strongly acidic, a high-grade material such as stainless steel is used for the pipe in order to prevent corrosion. However, when the present invention is used, since the circulating liquid pipe 11 and the like are installed outside the desulfurization tower, it is not necessary to use such a high-grade material. As described above, according to the embodiment of the present invention, if the same desulfurization performance as that of the conventional method is to be obtained, the amount of spray liquid can be reduced, so that the operating cost can be reduced. In addition, since there is no interior material in the desulfurization tower, the cost for manufacturing the device can be reduced.

In the embodiment shown in FIG. 3, combustion exhaust gas containing SO ₂ is introduced into the desulfurization tower main body 1 from the inlet duct 2 at the bottom of the tower. In FIG. 3, members having the same functions as the constituent members of the desulfurization tower shown in FIG. 1 are given the same numbers. Figure 3
In the case of, since the combustion exhaust gas is supplied from the lower part of the desulfurization tower into the tower, the ceiling spray head 17 installed at the top of the tower.
The absorbing droplets sprayed from the spray nozzle 4 and the gas come into countercurrent contact with each other, and further improvement in desulfurization performance can be expected compared with the case of FIG.

FIG. 4 shows a comparison of the desulfurization performance between the conventional method and the present invention. Combustion exhaust gas amount: 15,000 Nm ³ / h, using a pilot device, SO ₂ concentration: 750 ppm, calcium excess rate: 2%, the experimental results using limestone from the Ikura region of # 325 pass 95% Indicates. When the present invention is used, the desulfurization rate is higher in the present invention at all liquid gas ratios, which shows the effectiveness of the present invention. As described above, by using the embodiment of the present invention, the desulfurization performance is improved, so that the amount of spray liquid can be reduced and the operating cost can be reduced. Further, since the interior is not inside the desulfurization tower and the pipes are installed outside the desulfurization tower, it is not necessary to use a high-grade material such as stainless steel, and the cost for manufacturing the device can be reduced.

[0022]

According to the present invention, the operating cost can be reduced, and at the same time, since the interior is not inside the tower, the pipes are installed outside the desulfurization tower, and it is necessary to use a high-grade material such as stainless steel. Can be eliminated, and the cost for manufacturing the device can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a desulfurization tower of a wet flue gas desulfurization apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a desulfurization tower of a wet flue gas desulfurization apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a desulfurization tower of a wet flue gas desulfurization apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a liquid gas ratio and a desulfurization rate of a wet flue gas desulfurization apparatus according to an embodiment of the present invention.

FIG. 5 is a schematic view of a desulfurization tower of a conventional wet flue gas desulfurization apparatus.

[Explanation of symbols]

1 ... Desulfurization tower main body, 2 ... Entrance duct, 3 ... Exit duct, 4
... Spray nozzle, 6 ... Oxidation tank, 11 ... Circulating liquid piping, 14 ... Inlet side wall spray head, 17 ... Ceiling spray head, 18 ... Drift prevention plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B01D 53/34 ZAB B01D 53/34 125 Q (72) Inventor Hirofumi Yoshikawa 3 Takaracho, Kure City, Hiroshima Prefecture No.36 Babcock Hitachi Kure Research Institute

Claims (4)

[Claims] 1. An exhaust gas discharged from a combustion device such as a boiler is brought into contact with a spray absorption liquid in a desulfurization tower, and the absorption liquid after contacting the exhaust gas is recirculated from a tank at the bottom of the absorption tower into the absorption tower. In a wet flue gas desulfurization device that treats sulfur oxides in exhaust gas, a spray nozzle that sprays an absorption liquid into the desulfurization tower is installed on the wall surface of the desulfurization tower main body, and the interior is not provided inside the desulfurization tower. Wet flue gas desulfurization equipment that does. 2. A spray nozzle for spraying the absorbing liquid into the desulfurization tower is provided on a side wall surface and a ceiling wall surface of the desulfurization tower, and the amount of the spray absorbing liquid of each spray nozzle for each wall surface or each wall portion. The wet flue gas desulfurization apparatus according to claim 1, further comprising: 3. The wet flue gas desulfurization apparatus according to claim 1, wherein a non-uniform flow preventing member for the spray absorbing liquid is arranged on the wall surface of the desulfurization tower. 4. The wet flue gas desulfurization apparatus according to claim 1, wherein the tank below the absorption tower is an oxidation tank, and the oxidation tank is provided with an air blowing pipe.