JPH10192646A - Horizontal flow and wet type flue gas desulfurization device with mist removing function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the sophistication of desulfurization performance without an increase in equipment cost by efficiently removing a scattered mist and thereby solving a problem with scaling. SOLUTION: A flue gas flow path for circulating a combustion flue gas in the horizontal or a non-vertical direction is provided on the upstream side of a circulation tank 6 for storing an absorbing solution, and spray nozzles 4 are arranged either in the flue gas flow path or near its wall so that the absorbing solution ejected from the nozzle 4 is brought into contact with a flue gas. In addition, a shielding plate 13 for dividing the flow of the flue gas horizontally is installed in the flue gas flow path positioned right above the circulation tank 6. The flow of the flue gas is shielded by the shielding plate 13 and divided into two horizontal parts. In this case, a scattered mist whose inertial force is higher than that of the flue gas runs into the shielding plate to be captured. Further, the two divided flue gas parts flow under rotating along a lateral wall, respectively. Consequently, the scattered mist whose irrential force is high runs into the lateral wall to be captured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wet flue gas desulfurization apparatus for removing sulfur oxides in an exhaust gas discharged from a combustion apparatus such as a boiler (such as SO _2), in particular gas is not horizontal or vertical In a horizontal flow type wet flue gas desulfurization unit that flows in one direction, the mist that flows into the outlet duct even under conditions where the gas flow rate in the absorption tower is increased and the amount of absorbing liquid injected from the spray nozzle is increased to improve performance The present invention relates to a wet flue gas desulfurization apparatus capable of improving desulfurization performance and reducing problems such as scaling without increasing the amount.

[0002]

2. Description of the Related Art In thermal power plants, sulfur oxides in flue gas generated by fossil fuel combustion, especially SO _2, are one of the main causes of environmental problems such as air pollution and acid rain. In recent years, the spread of flue gas desulfurization equipment on a global scale has been desired.

[0003] The current desulfurization system is dominated by the wet method based on the limestone-gypsum method, and the spray method, which is the most proven and highly reliable, is widely used worldwide. This spray type desulfurization device has high desulfurization performance, and the basic technology is almost established.

[0004] However, wet flue gas desulfurization equipment is expensive, and its penetration rate in developing countries is still low. Therefore, in order to increase the penetration rate of desulfurization equipment worldwide, it is important to greatly reduce the equipment cost and operation cost of the desulfurization equipment.

FIG. 11 shows an example of an apparatus for wet flue gas desulfurization employing a conventional spray method. FIG. 11 is a longitudinal sectional view of an absorption tower in a conventional horizontal wet flue gas desulfurization apparatus.
This wet flue gas desulfurization apparatus mainly includes an absorption tower main body 1, an inlet duct 2, an outlet duct 3, a spray nozzle 4, an absorbent extraction pipe 10, a spray header 11, an exhaust gas channel 12, and the like. The plurality of spray nozzles 4 are mounted near the wall of the inlet duct 2. Further, the stirrer 7 and the air blowing pipe 8 serve as a circulating tank 6 in which the absorption liquid at the bottom of the absorption tower stays.
The mist eliminator 9 is installed in the outlet duct 3.

Exhaust gas discharged from a boiler (not shown) is introduced into the absorption tower main body 1 from an inlet duct 2 by a desulfurization fan (not shown), and discharged from an outlet duct 3 through an exhaust gas passage 12. During this time, in the exhaust gas channel 12 of the absorption tower main body 1, the absorption liquid containing calcium carbonate sent to the absorption tower circulation pump 5 is jetted from the plurality of spray nozzles 4, and gas-liquid contact between the absorption liquid and the exhaust gas is performed. At this time, the absorbing liquid selectively absorbs SO ₂ in the exhaust gas and generates calcium sulfite. The absorbing solution that has generated calcium sulfite temporarily stays in the circulation tank 6 and is stirred by the oxidizing stirrer 7 while oxygen in the absorbing solution is oxidized by oxygen in the air supplied from the air blowing pipe 8, and (Plaster). Part of the absorption liquid in the circulation tank 6 where calcium carbonate and gypsum coexist is sent again to the spray nozzle 4 by the absorption liquid circulation pump 5, and part is discharged from the absorption liquid extraction pipe 10 to waste liquid treatment and gypsum recovery (not shown). Sent to the system. Further, in the absorbing liquid atomized by spraying from the spray nozzle 4,
Those having a small droplet diameter are entrained by the exhaust gas, but are collected by a mist eliminator 9 provided in the outlet duct 3.

In the case of the above-mentioned prior art, as means for achieving high performance, it is conceivable to increase the gas flow rate in the exhaust gas flow path 12 and increase the amount of circulating liquid, that is, the amount of absorbing liquid ejected from the spray nozzle 4. When the number of droplets ejected from the spray nozzle 4 is increased, the droplets are entrained in the gas flow and easily scatter as mist, and when the amount of circulating liquid is increased, the amount of scattered mist increases. When the amount of scattered mist increases in this way, the mist load increases at the entrance of the mist eliminator 9 installed in the exit duct 3, so that all mist cannot be removed, and in the exit duct 3 on the downstream side of the mist eliminator 9. It causes troubles such as scaling. For this reason, in order to reduce the load of the mist at the entrance of the mist eliminator 9, it is necessary to provide a large space for lowering the gas flow rate on the upstream side of the mist eliminator 9 and drop the scattered mist in this space. However, if such measures are taken, the absorption tower main body 1 inevitably becomes large, and it becomes difficult to reduce the equipment cost of the desulfurization device. Therefore, in order to achieve high performance with low equipment cost, it is an important issue how to reduce the amount of scattered mist at the entrance of the mist eliminator 9.

[0008]

In the above desulfurization apparatus of the prior art, sufficient consideration is given to increasing the gas flow rate in the absorption tower for higher performance and increasing the amount of scattered mist accompanying an increase in the amount of circulating liquid. In addition, there was a problem of scaling occurring at the outlet duct and a problem of an increase in equipment costs due to an increase in the size of the absorption tower. It is an object of the present invention to provide a wet flue gas desulfurization apparatus that efficiently removes scattered mist, eliminates scaling problems, and improves desulfurization performance without increasing equipment costs.

[0009]

The above object of the present invention is attained by the following constitution. That is, an exhaust gas passage for flowing exhaust gas discharged from a combustion device such as a boiler in a horizontal or non-vertical direction is provided above a circulation tank for storing an absorbing liquid, and a plurality of exhaust gas passages are provided inside or near the wall of the exhaust gas passage. A horizontal flow type wet type equipped with an absorption tower that arranges the spray nozzle, sends the absorbing liquid from the circulation tank to the spray nozzle by a pump, makes the absorbing liquid ejected from the spray nozzle contact exhaust gas, and treats sulfur oxides in the exhaust gas In the flue gas desulfurization device, a wet flue gas desulfurization device in which a shielding plate that divides the flow of exhaust gas in a horizontal direction is installed in an exhaust gas channel located directly above a circulation tank.

The shielding plate for blocking the flow of the exhaust gas of the present invention is a flat plate, a bent plate having a plurality of flat surfaces such that the upstream side of the gas flow is convex in the horizontal section, and the upstream side of the gas flow is convex in the horizontal section. And a cylindrical plate having a curved surface such that both the upstream and downstream sides of the gas flow are convex in the horizontal cross section.

In the case of the absorption tower employing the spray method, the mist eliminator is indispensable because the absorbing liquid ejected from the spray nozzle is easily accompanied by gas and scattered. Generally, a mist eliminator installed in an outlet duct of an absorption tower utilizes a difference in specific gravity between a droplet and a gas, that is, a difference in inertial force. If the gas flow rate in the absorption tower is increased and the amount of circulating liquid is further increased, the droplets sprayed from the spray nozzle are more likely to be entrained by the gas, and the amount of scattered mist increases. However, according to the present invention, since the shielding plate is installed so that the exhaust gas flows in the portion immediately above the circulation tank near the side walls on both sides, the exhaust gas is shielded by the shielding plate when passing through the upper portion of the circulation tank. And divided into two parts in the horizontal direction. At this time, the scattered mist having a larger inertia force than the gas collides with the shielding plate and is collected. In addition, since the exhaust gas divided into two flows while turning along the side wall, the scattered mist having a large inertia force collides with the side wall and is collected. Therefore, the mist load at the mist eliminator inlet increases even if the gas flow speed is increased and the circulating fluid amount is increased for higher performance. Also,
The spray nozzle arranged near the wall of the exhaust gas passage of the present invention can be constituted by a plurality of types of spray nozzles having different spray momentums.

The following configuration can be adopted as the spray nozzle having a different spray momentum. It consists of spray nozzles with different spray pressures. The spray nozzles have spray angles different from each other. It consists of spray nozzles with different spray flow rates. The spray nozzles having the same spray flow rate are configured so that the number of spray stages is different from each other on opposing wall surfaces. The spray nozzles are respectively disposed in the vicinity of opposing walls of the exhaust gas flow path, and the spray momentums of the spray nozzles of the adjacent spray stages are different from each other on at least one spray stage on the same side wall surface. The spray nozzles are arranged near the opposing walls of the exhaust gas channel, and the spray momentums of the opposing spray nozzles are different from each other for each spray stage. The spray nozzles having different spray momentums are configured such that the number of spray stages having spray nozzles having the same spray flow rate is different from each other on both opposing wall surfaces. The spray momentum of the spray nozzle of each spray stage on one side wall is different from the spray momentum of the spray nozzle of each spray stage arranged on the other side wall surface among the spray nozzles arranged near both opposing walls of the exhaust gas flow path. It is constituted by a spray nozzle.

In the wet flue gas desulfurization apparatus of the present invention,
A configuration may be employed in which the position at which the absorbents injected from the spray nozzles arranged near the opposing side wall surfaces of the exhaust gas flow path intersect is changed for each spray stage.

According to the present invention, when the absorbing liquid is sprayed into the exhaust gas flow path having a uniform gas flow, for example, at an arbitrary angle with respect to the gas flow direction, the gas flow changes according to the spray momentum. This is because the spray momentum of the absorbing liquid is transmitted to the gas, and the larger the spray momentum, the stronger the influence on the gas flow. In addition, as the spray momentum of the absorbing liquid in the direction perpendicular to the gas flow increases, the resistance of the absorbing liquid to the gas increases, which causes a change in the gas flow direction. In this way, the gas flow is achieved by changing the spray momentum in the direction orthogonal to the gas flow of the absorbing liquid ejected from the spray nozzle for each spray nozzle or spray stage, as well as for the effect of collecting scattering mist by using the shielding plate. The easy part can be changed. This prevents localized gas blow-through,
High desulfurization performance can be obtained.

In the wet flue gas desulfurization apparatus of the present invention, in addition to the wall-mounted spray nozzle disposed near the wall surface of the exhaust gas passage, a spray stage having a spray-installed nozzle installed in a tower perpendicular to the gas flow is provided. Can be installed at least one stage. As described above, even when the spray nozzles installed in the tower are scattered on the surface orthogonal to the gas flow, the change in the spray momentum in the surface orthogonal to the gas flow is small. It is prevented and high desulfurization performance can be obtained.

In the flue gas desulfurization apparatus according to the present invention, which has an exhaust gas flow path of a type that guides an exhaust gas flow in a horizontal direction or a direction that is not vertical, if the exhaust gas flow rate in the absorption tower is too low, the spray droplets are separated from the exhaust gas flow by gravity. Deviating and falling to the bottom of the tower, no matter how long the contact distance is in the horizontal or other direction, there is no gas-liquid contact. On the other hand, if the exhaust gas flow rate is too high, the amount of mist entrained is too large, causing a large loss of the absorbent and causing corrosion of the downstream duct, equipment, and instruments, and also a loss of ventilation. There is a problem such as becoming large. As described above, there is an optimum range of the gas flow velocity in the exhaust gas flow path for the conflicting problem caused by the difference in the gas flow velocity in the exhaust gas flow path.

FIGS. 11 and 12 show a gas amount of 3000 m ^3.
N / h, which was determined SO ₂ gas flow rate of the exhaust gas passage inlet under the conditions of a concentration 2000ppm and desulfurization rate, pressure drop and mist eliminator inlet mist of relationships in the exhaust gas passage outlet being disposed respectively However, the desulfurization rate increases as the gas flow rate increases, and is preferably 5 m / s or more. However, at 20 m / s or more, the desulfurization rate decreases again due to a decrease in the gas-liquid contact time. Similarly, the amount of mist at the inlet of the mist eliminator sharply increases as the gas flow rate increases. Therefore, in order to reduce the pressure loss and the mist amount at the mist eliminator inlet as much as possible and to increase the desulfurization rate, the gas flow rate at the inlet of the exhaust gas passage must be 5
It is desirable to set it to about 20 m / s. It was also found that the amount of mist at the inlet of the mist eliminator was smaller in the combination of the cocurrent spray and the countercurrent spray (curve b) than in the spray of the absorbing liquid only in the cocurrent direction (curve a). .

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of an absorption tower in a wet flue gas desulfurization apparatus according to an embodiment of the present invention, and FIG. 2 is a horizontal cross-sectional view of the absorption tower of FIG. 1, showing an embodiment using a flat plate as a shielding plate. It is.

FIGS. 3 to 10 show another embodiment of the present invention. FIG. 3 shows a shielding plate having a bent surface having a plurality of flat surfaces such that the upstream side of the gas flow is convex in a horizontal section. FIG. 4 is a vertical sectional view of an absorption tower showing an embodiment using a plate, and FIG. 4 is a horizontal sectional view of the absorption tower of FIG. FIG. 5 is a vertical sectional view of an absorption tower showing an embodiment using a plate having a curved surface such that the upstream side of a gas flow is convex in a horizontal section as a shielding plate, and FIG. It is a horizontal sectional view. FIG. 7 is a vertical sectional view of an absorption tower showing an embodiment using a cylindrical plate having a curved surface such that both the upstream side and the downstream side of the gas flow are convex in a horizontal section as a shielding plate, and FIG. It is a horizontal sectional view in the absorption tower of FIG. FIG. 9 shows an embodiment in which the present invention is applied to an absorption tower in which a spray nozzle 4 is disposed inside an exhaust gas passage. FIG. 10 is a horizontal sectional view of the absorption tower in FIG.

In the embodiment shown in FIGS. 1 and 2, a plate-shaped shielding plate 13 is provided so that exhaust gas flows in the portion immediately above the circulation tank 6 near the side walls on both sides, and the plane of the shielding plate 13 is substantially parallel to the gas flow. It differs from the prior art in that it is installed so that it is perpendicular to the surface and the plane faces in the vertical direction.
When the exhaust gas passes right above the circulation tank 6, the shielding plate 1
3, it is divided into two parts in the horizontal direction so as to go around the outside of the shield plate 13, flows along the side wall immediately above the circulation tank 6, and then merges again to enter the mist eliminator 9. First, when the exhaust gas is divided into two in the horizontal direction blocked by the shield plate 13, the scattered mist having a larger inertia force than the gas collides with the shield plate 13 and is collected. Subsequently, the divided exhaust gas is supplied to each of the circulation tanks 6.
Similarly, when the mist flows while turning along the side wall immediately above the mist, the scattered mist having a large inertial force collides with the shielding plate 13 and is collected. The shielding plate 13 used in this embodiment is a flat plate,
The structure is very simple.

FIGS. 3 and 4 show another embodiment of FIG. 1. FIG. 3 is a vertical sectional view of the absorption tower of this embodiment.
FIG. 4 is a horizontal sectional view of the absorption tower of FIG. Figure 1
In the embodiment of FIG. 2, the shielding plate 13 is a flat plate,
4 to 4 are different in that a bent plate having a plurality of planes such that the upstream side of the gas flow is convex in the horizontal cross section is used as the shielding plate 13. In this embodiment, FIG.
As can be seen from FIG.
A letter-shaped flat plate is used. Since the angle between the exhaust gas and the plane of the shielding plate when the plane collides with the plane of the shielding plate 13 is small,
Compared with the embodiment of FIGS. 1 and 2, the resistance to the flow of the exhaust gas is small and the power of the fan is small.

FIGS. 5 and 6 show another embodiment. FIG. 5 is a vertical sectional view of the absorption tower of this embodiment.
FIG. 6 is a horizontal sectional view of the absorption tower of FIG. 1 to 4
This embodiment differs from the third embodiment in that a plate having a curve such that the upstream side of the gas flow is convex in the horizontal section is used as the shielding plate 13. The other points are the same as those of the embodiment shown in FIGS.

FIGS. 7 and 8 show another embodiment. FIG. 7 is a vertical sectional view of the absorption tower of this embodiment.
FIG. 8 is a horizontal sectional view of the absorption tower of FIG.
The present embodiment differs from the embodiment in that a cylindrical plate having a curve such that both the upstream side and the downstream side of the gas flow are convex in the horizontal cross section is used as the shielding plate 13. In the embodiment shown in FIGS. 7 and 8, the flow of the exhaust gas when passing through the most downstream end portion of the shield plate 13 is small, so that the vortex on the downstream side of the shield plate 13 is small, and No worries about scaling.

Further, in each of the above embodiments, the spray nozzle 4 is arranged near the wall of the exhaust gas passage 12, but the spray nozzle 4 may be arranged inside the exhaust gas passage 12 as shown in FIGS. Almost the same effects can be obtained. In this case, as shown in FIG. 9, the spray nozzle 4 on the gas inlet side of the inlet duct 2 flows in parallel with the flow of the exhaust gas to promote the introduction of the exhaust gas, and the spray nozzle 4 on the downstream side therefrom is countercurrent to the flow of the exhaust gas. Thereby, the contact efficiency between the sprayed absorbing liquid and the exhaust gas can be increased.

[0025]

According to the present invention, the mist load accompanying the gas can be collected by the installation of the shielding plate, so that the mist load on the mist eliminator is reduced and the problem such as scaling at the outlet duct is solved. High desulfurization performance can be obtained without causing such a problem.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of an absorption tower in a wet flue gas desulfurization apparatus according to an embodiment of the present invention.

FIG. 2 is a horizontal sectional view of the absorption tower of FIG. 1, showing an embodiment using a flat plate as a shielding plate.

FIG. 3 is a vertical sectional view of an absorption tower showing an embodiment of the present invention using a plate having a plurality of flat surfaces such that the upstream side of a gas flow is convex in a horizontal section as a shielding plate.

FIG. 4 is a horizontal sectional view of the absorption tower of FIG.

FIG. 5 is a vertical sectional view of an absorption tower showing an embodiment of the present invention using a plate having a curved surface such that an upstream side of a gas flow is convex in a horizontal section as a shielding plate.

FIG. 6 is a horizontal sectional view of the absorption tower of FIG.

FIG. 7 is a vertical sectional view of an absorption tower showing an embodiment of the present invention using a cylindrical plate having a curved surface such that both the upstream side and the downstream side of a gas flow in a horizontal section are convex as a shielding plate.

8 is a horizontal sectional view of the absorption tower of FIG.

FIG. 9: A spray nozzle is arranged inside the exhaust gas channel,
It is a vertical sectional view of an absorption tower showing an example of the present invention to an absorption tower using a cylindrical plate which has a curved surface so that both the upstream side and the downstream side of the gas flow in the horizontal section are convex as a shielding plate.

FIG. 10 is a horizontal sectional view of the absorption tower of FIG.

FIG. 11 is a diagram showing the relationship between the gas flow rate at the inlet of the absorption tower and the desulfurization rate according to one embodiment of the present invention.

FIG. 12 is a diagram showing the relationship between the gas flow rate at the inlet of the absorption tower and the amount of mist at the mist eliminator (demister) inlet in one embodiment of the present invention.

FIG. 13 is a vertical sectional view of an absorption tower in a conventional wet-type flue gas desulfurization apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Absorption tower main body 2 Inlet duct 3 Outlet duct 4 Spray nozzle 5 Absorption tower circulating pump 6 Circulation tank 7 Oxidizing stirrer 8 Air blowing pipe 9 Eliminator 10 Absorbing liquid extraction pipe 11 Spray header 12 Exhaust gas flow path 13 Shield plate

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Noriaki Taniguchi 6-9 Takaracho, Kure City, Hiroshima Prefecture Inside Babcock Hitachi Kure Plant

Claims (8)

[Claims] 1. An exhaust gas passage for flowing exhaust gas discharged from a combustion device such as a boiler in a horizontal direction or a non-vertical direction above a circulation tank for storing an absorbing liquid,
A plurality of spray nozzles are arranged inside or near the wall of the exhaust gas flow path, the absorbing liquid is sent from the circulation tank to the spray nozzle by a pump, and the absorbing liquid ejected from the spray nozzle is brought into contact with the exhaust gas to remove sulfur oxides in the exhaust gas. In a horizontal flow type wet flue gas desulfurization device equipped with an absorption tower for processing, a shielding plate is installed in the exhaust gas flow path located directly above the circulation tank to divide the flow of exhaust gas horizontally. Flue gas desulfurization equipment. 2. The wet flue gas desulfurization apparatus according to claim 1, wherein a flat plate is used as a shielding plate for blocking the flow of the exhaust gas. 3. The wet-type wet plate according to claim 1, wherein a bent plate having a plurality of flat surfaces such that the upstream side of the gas flow is convex in a horizontal cross section is used as a shielding plate that blocks the flow of the exhaust gas. Flue gas desulfurization equipment. 4. The wet flue gas desulfurization apparatus according to claim 1, wherein a plate having a curved surface such that the upstream side of the gas flow is convex in a horizontal cross section is used as a shielding plate for blocking the flow of the exhaust gas. . 5. The shielding plate according to claim 1, wherein the shielding plate for blocking the flow of the exhaust gas is a cylindrical plate having a curved surface such that both the upstream side and the downstream side of the gas flow are convex in a horizontal cross section. Wet flue gas desulfurization equipment. 6. The wet flue gas desulfurization apparatus according to claim 1, wherein the spray nozzle disposed near the wall of the exhaust gas flow path comprises a plurality of types of spray nozzles having different spray momentums. 7. The spray nozzle according to claim 6, wherein at least one spray stage having a spray nozzle installed inside the tower is installed on a surface orthogonal to the gas flow, in addition to the wall-installed spray nozzle arranged near the wall surface. Wet flue gas desulfurization equipment. 8. The gas flow rate in the exhaust gas passage is set to 5 m / s to 2 m / s.
The wet flue gas desulfurization apparatus according to any one of claims 1 to 7, wherein the velocity is 0 m / s.