JPH08224436A - Compact type wet flue gas desulfurizer - Google Patents

Abstract

PURPOSE: To provide a desulfurizer in which an absorber is made compact without lowering the desulfurizing rate or without increasing the flying quantity of mist and which can cope with a high SO2 concentration and low in installation cost and operating cost, and of which desulfurizing performance is high. CONSTITUTION: In an absorber body 1, an upstream spray part 11 constituted of spray nozzles 4 on the upstream side of a gas flow and a downstream spray part 12 constituted of spray nozzles 4 on the downstream side thereof are provided, and an SO2 in waste gas absorbing part is divided into two regions by providing a space between the upstream spray part 11 and the downstream spray part 12 to make the gas flow velocity near the downstream spray part 12 smaller than that near the upstream spray part 11. Further, in a part near the upstream spray part 11 between the upstream spray part 11 and the downstream spray part 12, a waste gas flow passage for causing waste gas to flow almost in the same direction as the direction in which sprayed droplets of a liquid absorbent sprayed from the upstream spray part 11 are influenced by gravity and fall is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to SO in a boiler exhaust gas.
_{In connection} with a wet flue gas desulfurization device that removes ₂ , the absorption tower is made compact by increasing the gas flow rate in a part of the absorption tower to improve the absorption performance, and a high-performance wet exhaust gas that can handle high SO ₂ concentrations The present invention relates to a smoke desulfurization device.

[0002]

2. Description of the Related Art Sulfur oxides, especially sulfur dioxide (SO ₂ ) in flue gas generated by burning fossil fuels in thermal power plants is a main cause of environmental problems such as air pollution and acid rain. In recent years, it has been desired to spread flue gas desulfurization equipment on a global scale.

The current desulfurization system is dominated by the wet method based on the limestone-gypsum method, and the spray method, which has the most proven results and is highly reliable, is widely adopted all over the world. Although this spray desulfurization device has a high desulfurization performance and is an almost established technology, its spread rate is still low in developing countries because it is expensive. Therefore, in order to increase the popularity of desulfurization equipment worldwide, it is important to significantly reduce the cost of desulfurization equipment.

FIG. 6 shows an example of a conventional wet type flue gas desulfurization apparatus using a spray method. The desulfurization apparatus mainly includes an absorption tower body 1, an inlet duct 2, an outlet duct 3, a spray nozzle 4,
The absorption liquid circulation pump 5, the oxidation tank 6, the stirrer 7, the air blowing pipe 8, the mist eliminator 9, and the like.
A plurality of spray nozzles 4 are installed in a direction orthogonal to the gas flow, and a plurality of spray nozzles 4 are installed in the gas flow direction. Further, the agitator 7 and the air blowing pipe 8 are installed in the oxidation tank 6 in the lower part of the absorption tower where the absorbing liquid stays, and the mist eliminator 9 is installed in the outlet duct 3.

Exhaust gas discharged from a boiler (not shown) is introduced into the absorber main body 1 from the inlet duct 2 by a desulfurization fan (not shown) and discharged from the outlet duct 3. During this time, the absorption liquid containing calcium carbonate sent from the absorption liquid circulation pump 5 is sprayed from the plurality of spray nozzles 4 into the absorption tower, and the absorption liquid and the exhaust gas are brought into gas-liquid contact. At this time, the absorbing liquid selectively absorbs SO ₂ in the exhaust gas and forms calcium sulfite. The absorbing solution that has generated calcium sulfite is accumulated in the oxidation tank 6, and while being stirred by the oxidizing stirrer 7, oxygen in the air supplied from the air blowing pipe 8 oxidizes the calcium sulfite in the absorbing solution to remove gypsum. To generate. A part of the absorption liquid in the oxidation tank 6 in which calcium carbonate and gypsum coexist is sent to the spray nozzle 4 again by the absorption liquid circulation pump 5, and a part of the absorption liquid is taken out from the absorption liquid discharge pipe 10 to recover waste liquid / gypsum (not shown). Sent to the system. Further, among the absorbing liquids atomized and sprayed from the spray nozzle 4, those having a small droplet diameter are entrained in the exhaust gas, but are recovered by the mist eliminator 9 provided in the outlet duct 3.

In the case of the desulfurizer shown in FIG. 6, the height of the absorption tower tends to be high, and when the inlet SO ₂ concentration is high, it is necessary to increase the number of spray stages by several stages, so the tower height is further increased. . As a concrete means for achieving a compaction of such a desulfurization device, a method of increasing the gas flow velocity in the absorption tower and reducing the size of the absorption tower can be considered. Since the SO ₂ absorption performance is improved by increasing the gas flow rate, it is possible to reduce the cross-sectional area and height of the absorption tower.

However, when the gas flow velocity is increased, the droplets ejected from the spray nozzle 4 are easily entrained in the gas and scattered, and the mist load at the inlet of the mist eliminator 9 increases. If the droplet amount at the inlet of the mist eliminator 9 exceeds the allowable value, problems such as scaling or corrosion in the outlet duct 3 will occur.
Therefore, in order to remove the scattered mist, it is conceivable to insert an insert or the like in the preceding stage of the mist eliminator 9 inside the absorption tower to roughly remove the mist, but it is necessary to use an expensive material for the interior. Therefore, the device cost becomes high.

Therefore, it is necessary to take measures to reduce the mist load at the entrance of the mist eliminator 9 without using structures such as interiors. As a specific method, a method may be considered in which the gas flow velocity near the spray nozzle 4 on the upstream side of the gas flow is set high and the gas flow velocity near the spray nozzle 4 on the downstream side is set low. Although it is different from this basic concept, it is the closest publicly known example, which is Shokai 61-71230.
The method described in Japanese Patent Publication can be used. In the device described in the above publication, a spray nozzle is installed in the vicinity of the inlet duct of the conventional absorption tower by the spray method, but the droplets ejected from the spray nozzle fall downward, whereas the exhaust gas rises upward, The contact time between the absorbent and exhaust gas is very short, and high desulfurization performance cannot be expected.

From the above, in order to make the desulfurization apparatus compact and low-cost, the gas flow rate in the absorption tower is increased and the gas flow rate is increased so that the mist load at the inlet of the mist eliminator 9 does not increase. It is important to increase the contact time between the droplets and the exhaust gas in the part so that high desulfurization performance can be maintained.

[0010]

The above-mentioned prior art does not consider improving the desulfurization performance and reducing the amount of mist scattered about the method for downsizing the wet flue gas desulfurization apparatus and reducing the cost. In order to maintain high desulfurization performance, there has been a problem that operating costs are high due to an increase in the amount of circulation of the absorbent.

The object of the present invention is to make the absorption tower compact without lowering the desulfurization rate or increasing the amount of mist scattered, capable of dealing with high SO ₂ concentration, low equipment cost and operating cost, and desulfurization performance. To obtain a high desulfurization device.

[0012]

The above object of the present invention can be achieved by the following constitutions. That is, by bringing the exhaust gas discharged from the combustion device such as a boiler into contact with the absorbing liquid ejected from the spray nozzles installed in a plurality of stages in the gas flow direction, an absorption tower for treating the sulfur oxides in the exhaust gas is provided. In a wet flue gas desulfurization apparatus provided with, in the absorption tower, an upstream spray section composed of at least one or more stage spray nozzles on the upstream side of the gas flow, and a downstream spray section composed of at least one or more stage spray nozzles on the downstream side. The absorption portion is divided into two regions by providing a space between the upstream spray portion and the downstream spray portion, and the gas flow velocity in the vicinity of the downstream spray portion is slower than the gas flow velocity in the vicinity of the upstream spray portion, Furthermore, in the portion near the upstream spray portion between the upstream spray portion and the downstream spray portion, the direction in which the droplets ejected from the upstream spray portion fall under the influence of gravity. When a compact wet flue gas desulfurization apparatus comprising an exhaust gas flow path for flowing the exhaust gas to approximately the same orientation.

In the compact type wet flue gas desulfurization apparatus of the present invention, a spray nozzle for spraying the absorbing liquid in a cocurrent flow with the exhaust gas is provided in the upstream spray portion, and the absorbing liquid is sprayed in the countercurrent flow with the exhaust gas in the downstream spray portion. Configuration with a spray nozzle,
Alternatively, the upstream spray unit is provided with a spray nozzle that sprays the absorbing liquid in a counterflow with the exhaust gas, and the downstream spray unit is provided with a spray nozzle that sprays the absorbing liquid in a cocurrent flow with the exhaust gas,
Or, by providing a difference in the exhaust gas flow passage cross-sectional area in the upstream spray section and the downstream spray section, the flow rate of the exhaust gas in the upstream spray section and the downstream spray section are mutually different, absorption between the upstream spray section and the downstream spray section The structure that deforms the horizontal ceiling wall of the tower body to regulate the flow direction of exhaust gas, hangs between the upstream spray section and the downstream spray section on the horizontal ceiling wall of the absorption tower body, and regulates the flow direction of exhaust gas with a partition plate It can be configured such as The absorbing liquid used in the present invention comprises a slurry of an alkali metal compound such as limestone, quick lime, slaked lime, and magnesium carbonate, or an alkaline compound such as an alkaline earth compound.

[0014]

[Function] Although various factors affect the desulfurization performance in the wet flue gas desulfurization device, the area that contributes to the reaction between the gas and the absorbing liquid, that is, the gas-liquid contact area has a large influence. If the contact area can be increased, the desulfurization performance can be easily increased. As a method of increasing the gas-liquid contact area, a method of decreasing the droplet diameter of the spray absorbing solution or a method of increasing the residence time of the droplets of the spray absorbing solution in the absorption tower can be considered. In order to reduce the droplet diameter with the same spray nozzle, it is necessary to reduce the capacity of the spray nozzle or increase the spray pressure of the absorbing liquid.

However, when the capacity of the spray nozzle is reduced, the number of spray nozzles increases, which increases the equipment cost and the construction cost. Further, in order to increase the spray pressure of the absorbing liquid, it is necessary to increase the pump power, and therefore the operating cost. Becomes expensive. Therefore, in order to increase the gas-liquid contact area between the gas and the absorbing liquid by an inexpensive method, the residence time of the droplet in the absorption tower is increased rather than decreasing the spray droplet diameter of the absorbing liquid. The method of doing is considered desirable.

Although there are some differences depending on the direction of the spray nozzle, the droplets ejected from the spray nozzle fall while drawing a parabola due to gravity. Therefore, as in the present invention, by flowing the exhaust gas between the upstream spray portion and the downstream spray portion in a direction substantially the same as the direction in which the droplets ejected from the upstream spray portion fall, the retention time of the droplets, that is, absorption The contact time between the liquid and the exhaust gas can be extended. Generally, since the liquid droplets drop downward or obliquely downward, the exhaust gas also flows downward or obliquely downward.

Further, if the gas flow velocity in the vicinity of the upstream spray portion is made high in order to make the absorption tower compact, the droplets are easily scattered and the mist load at the inlet of the mist eliminator increases, but immediately before the mist eliminator, that is, downstream By reducing the gas flow velocity near the spray part, the scattered mist entrained in the exhaust gas can be dropped, and if the direction of the exhaust gas flow is changed between the upstream spray part and the downstream spray part, that is, just above the oxidation tank. The scattered mist can be shaken off, and its effect is further enhanced.

[0018]

EXAMPLE A wet flue gas desulfurization apparatus according to an example of the present invention is shown in FIG. Similar to the conventional absorption device shown in FIG. 6, the absorption device of this embodiment has an absorption tower body 1, an inlet duct 2, an outlet duct 3, a spray nozzle 4, a circulation pump 5, an oxidation tank 6, an agitator 7, and an air blower. Inlet tube 8, Mist eliminator 9
Etc. However, in this embodiment, the spray portion is divided into the upstream spray portion 11 and the downstream spray portion 12, and the upper spray portion 11 is provided with the co-current spray nozzle 4 for ejecting the absorbing liquid droplets in substantially the same direction as the gas flow, and further downstream. Spray part 12
A counter-current spray nozzle 4 for ejecting spray-absorption droplets (hereinafter, sometimes simply referred to as droplets) against the gas flow is installed in. Further, the gas flow velocity in the vicinity of the downstream spray unit 12 is made slower than the gas flow velocity in the vicinity of the upstream spray unit 11, and the exhaust gas passing through the upstream spray unit 11 is caused to flow in a direction substantially the same as the drop direction of the droplets. The exhaust gas is turned into a V shape between the portion 11 and the downstream spray portion 12, and the exhaust gas passing through the downstream spray portion 12 is caused to flow in the direction opposite to the spray droplets, that is, the countercurrent direction. As a means for turning the exhaust gas into a V shape, in this embodiment, the vertical section of the ceiling of the absorption tower body 1 is formed into a doglegged shape, and the exhaust gas flows obliquely downward in the upstream spray section 11 and upward in the downstream spray section 12. Flowing toward.

The droplets ejected from the upstream spray section 11 fall while drawing a parabola due to the influence of gravity. Therefore, by flowing the exhaust gas passing through the upstream spray section 11 in almost the same direction as the direction in which the droplets drop (in the case of FIG. 1, obliquely downward), the retention time of the droplets, that is, the contact between the absorbing liquid and the exhaust gas The time can be lengthened. Since the SO ₂ absorption performance is improved when the gas flow velocity is increased, it is possible to obtain high desulfurization performance if the gas-liquid contact time can be lengthened.

In this embodiment, since the gas flow velocity in the upstream spray section 11 is set high, the amount of scattered mist is large, but the liquid level in the oxidation tank 6 between the upstream spray section 11 and the downstream spray section 12 is high. Since the flow of exhaust gas is turned in a V shape in the vicinity, coarse scattered mist is shaken off in this part,
Further, since the gas flow velocity in the vicinity of the downstream spray section 12 is slowed down, the scattered mist can be dropped also here, and the mist collecting load of the mist eliminator 9 in the outlet duct 3 can be reduced. Further, the countercurrent spray nozzle 4 of the downstream spray section 12 has an effect of removing scattered mist. In this embodiment, since the parallel spray is used in the upstream spray section 11, the pressure loss can be reduced.

Another embodiment according to the present invention is shown in FIGS. 2, 3, 4 and 5. In the embodiment shown in FIG. 2, the spray direction of the droplets sprayed from each spray nozzle 4 in the upstream spray section 11 and the downstream spray section 12 in the embodiment described in FIG. 1 is changed. That is, in the embodiment shown in FIG. 2, the spray nozzle 4 of the upstream spray section 11 has a countercurrent spray type in which the absorbing liquid spraying direction is directed in the direction opposite to the gas flow, and the direction of the spray nozzle 4 of the downstream spray section 12 is changed. It is a co-current spray type that ejects droplets in the same direction as the gas flow.

In the counter-current spray nozzle 4 of the upstream spray section 11, the droplets ejected from the spray nozzle 4 once fly to the upstream side and then reverse and are entrained in the gas flow. Therefore, as compared with the co-current spray type of the embodiment shown in FIG. 1, the retention time of the liquid droplets becomes longer, and the desulfurization performance is further improved. Further, in the co-current spray nozzle 4 of the downstream spray section 12, the liquid droplets ejected from the spray nozzle 4 once rise toward the downstream side, and then reverse and fall in a form against the gas flow. Therefore, the dwell time of the droplet becomes long,
The desulfurization performance in this part is also improved. In particular, this is an effective example when the inlet SO ₂ concentration is high.

The upstream spray section 11 and the downstream spray section 1
Although the combination of 2 is set to the co-current spray type and the counter-current spray type in FIG. 1 and the counter-current spray type and the co-current spray type in FIG. 2, the combination is not limited to this combination, but the upstream spray section 11 and the downstream spray section 12 are not limited to this combination. As a combination of the above, substantially the same effects can be obtained even if they are set to a co-current spray type and a co-current spray type or a counter-current spray type and a counter-current spray type.

In another embodiment shown in FIG. 3, a partition plate 13 protruding downward from the horizontal ceiling portion of the absorption tower main body 1 between the upstream spray portion 11 and the downstream spray portion 12 makes the exhaust gas U-shaped. It was made to turn. In this embodiment, FIG.
Similar to the embodiment shown in FIG. 3, the co-current spray nozzle 4 is installed in the upstream spray section 11 and the countercurrent spray nozzle 4 is installed in the downstream spray section 12, and the same effect as that of the embodiment shown in FIG. 1 can be obtained.

In another embodiment shown in FIG. 4, the upstream spray portion 11 in the embodiment shown in FIG. 3 is changed to a countercurrent spray. The combination of the upstream spray section 11 and the downstream spray section 12 is not limited to the combination of FIG. 3 and FIG. 4, but may be a combination of a co-current spray type and a co-current spray type, or a combination of a counter-current spray type and a co-current spray type. Even if set, almost the same effect can be obtained.

In the other embodiment shown in FIG. 5, the exhaust gas is not turned between the upstream spray portion 11 and the downstream spray portion 12, but the exhaust gas is turned into a V shape after passing through the downstream spray portion 12. It is a thing. Therefore, the vertical cross-sectional shape of the absorption tower main body 1 is formed in a vertical tube shape between the upstream spray section 11 and the downstream spray section 12, and the exhaust gas passage after passing through the downstream spray section 12 is formed in a horizontal tube shape. In the present embodiment, since the droplets scattered from the downstream spray portion 12 can be shaken off near the liquid surface, the mist collecting load at the inlet of the mist eliminator 9 can be further increased as compared with the embodiments shown in FIGS. It can be reduced. The combination of the upstream spray section 11 and the downstream spray section 12 is not limited to the combination of FIG. 5, but may be a combination of a co-current spray type and a co-current spray type, or a combination of a counter-current spray type and a co-current spray type. Even if set, almost the same effect can be obtained.

[0027]

EFFECTS OF THE INVENTION According to the present invention, the SO ₂ absorption reaction in the portion where the gas flow velocity is high can be utilized without reducing the gas-liquid contact time, so that the absorption performance per unit absorption tower volume is improved and the high SO 2 It is a compact desulfurizer that can handle _two concentrations. Further, since it is not necessary to increase the amount of the absorbing liquid ejected from the spray nozzle, that is, the liquid-gas ratio in order to improve the desulfurization performance, the power of the circulation pump, that is, the operating cost can be significantly reduced. Further, since the mist load at the mist eliminator inlet can be reduced, it is possible to prevent scaling and corrosion from occurring in the outlet duct, and it is possible to use the mist eliminator with low pressure loss. Therefore, since the power of the desulfurization fan can be lowered, it is possible to provide a desulfurization device having a lower operating cost.

[Brief description of drawings]

FIG. 1 is a schematic view of a wet flue gas desulfurization apparatus according to an embodiment of the present invention in which exhaust gas is turned into a V shape between an upstream spray section and a downstream spray section.

FIG. 2 is a schematic view of a wet flue gas desulfurization apparatus according to another embodiment of the present invention in which the directions of spray nozzles in the upstream spray section and the downstream spray section are changed in the embodiment of FIG.

FIG. 3 is a schematic view of a wet flue gas desulfurization apparatus according to another embodiment of the present invention when exhaust gas is turned into a U shape by a partition plate between the upstream spray section and the downstream spray section.

FIG. 4 is a schematic view of a wet flue gas desulfurization apparatus according to another embodiment of the present invention in which the direction of the spray nozzle of the upstream spray section is changed in the embodiment of FIG.

FIG. 5 is a schematic view of a wet flue gas desulfurization apparatus according to another embodiment of the present invention when the direction of exhaust gas is not changed between the upstream spray section and the downstream spray section.

FIG. 6 is a schematic diagram of a conventional wet flue gas desulfurization apparatus.

[Explanation of symbols]

1 ... Absorption tower body, 2 ... Entrance duct, 3 ... Exit duct, 4
... Spray nozzle, 5 ... Circulation pump, 6 ... Oxidation tank, 7
... Stirrer, 8 ... Air blowing pipe, 9 ... Mist eliminator, 10 ... Absorbing liquid withdrawing pipe, 11 ... Upstream spray part, 12
... Downstream spray section, 13 ... Partition plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirofumi Yoshikawa, No. 36 Takaracho, Kure City, Hiroshima Prefecture Babcock-Hitachi Co., Ltd. Kure Research Institute (72) Shigeru Nozawa, No. 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock-Hitachi Ltd. Kure Factory

Claims (6)

[Claims] 1. A sulfur oxide in the exhaust gas is treated by bringing the exhaust gas discharged from a combustion device such as a boiler into contact with an absorbing liquid ejected from a spray nozzle installed in a plurality of stages in the gas flow direction. In a wet flue gas desulfurization apparatus equipped with an absorption tower, in the absorption tower, an upstream spray section composed of at least one or more stages of spray nozzles on the upstream side of the gas flow and a downstream composed of at least one or more stages of spray nozzles on the downstream side. By providing a spray portion, the absorption portion is divided into two regions by providing a space between the upstream spray portion and the downstream spray portion, and the gas flow velocity in the vicinity of the downstream spray portion is made higher than that in the vicinity of the upstream spray portion. It is slowed down, and the droplets ejected from the upstream spray part fall under the influence of gravity in the part near the upstream spray part between the upstream spray part and the downstream spray part. Compact type wet flue gas desulfurization apparatus characterized by comprising an exhaust gas flow path for flowing the exhaust gas in a direction substantially the same orientation. 2. The upstream spray section is provided with a spray nozzle for spraying the absorbing solution in a cocurrent flow with the exhaust gas, and the downstream spray section is provided with a spray nozzle for spraying the absorbing solution in a counterflow with the exhaust gas. 1. The compact type wet flue gas desulfurization device according to 1. 3. The upstream spray section is provided with a spray nozzle that sprays the absorbing solution in a counterflow with the exhaust gas, and the downstream spray section is provided with a spray nozzle that sprays the absorbing solution in a cocurrent flow with the exhaust gas. The compact type wet flue gas desulfurization apparatus according to 1 or 2. 4. The exhaust gas flow passage cross-sectional areas of the upstream spray section and the downstream spray section are made different from each other, and the flow rates of the exhaust gas in the upstream spray section and the downstream spray section are changed from each other. The compact type wet flue gas desulfurization device according to any one of the above. 5. The horizontal direction of the ceiling wall of the absorption tower body is deformed between the upstream spray section and the downstream spray section to regulate the flow direction of the exhaust gas, according to any one of claims 1 to 4. Compact wet flue gas desulfurizer. 6. The exhaust gas flowing direction is regulated by a partition plate which hangs down between the upstream spray section and the downstream spray section on the horizontal ceiling wall surface of the absorption tower body.
4. The compact wet flue gas desulfurization device according to any one of 4 above.