JPH10128056A - Flue gas desulfurization apparatus and gypsum slurry treatment method - Google Patents

Abstract

(57) Abstract: A flue gas desulfurization device capable of achieving high filtration performance without increasing the filtration area when separating gypsum from gypsum slurry and wastewater slurry generated by desulfurization of exhaust gas. And a method for treating gypsum slurry. SOLUTION: As a gypsum separator, an endless filter cloth 56 is placed on a breathable belt 53 stretched between drums 52.
Is supported movably, and the mixed slurry supplied from the supply tank 60 on the filter cloth 56 is suctioned from the dehydration chamber 54 provided below the belt and maintained at a negative pressure to separate the filtrate into the filtrate and the gypsum. The vacuum vacuum dehydrator 50 is provided above the filter cloth 56 and is inserted into at least the upper fine particle layer of the cake made of the gypsum slurry and the drainage slurry to be conveyed, and is added to the upper fine particle layer of the cake with the conveyance. A fine particle layer breaking mechanism 51 for forming a groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flue gas desulfurization apparatus for removing sulfurous acid gas in an exhaust gas as gypsum, and a gypsum slurry produced in the flue gas desulfurization apparatus and a wastewater slurry produced in a wastewater treatment facility. The present invention relates to a method for treating a gypsum slurry for separating the gypsum from a mixed slurry.

[0002]

2. Description of the Related Art Conventionally, as one type of flue gas desulfurization apparatus for removing harmful components such as sulfurous acid gas from exhaust gas from boilers, various heating furnaces or incinerators, etc., sulfurous acid gas (SO ₂ ) The sulfur oxides mainly composed of an aqueous solution in which limestone (CaCO ₃ ) is dissolved or suspended are brought into contact with an absorbing solution to neutralize the sulfur oxides. Smoke desulfurization equipment is widely used. FIG. 4 shows a main part of this type of conventional wet flue gas desulfurization apparatus having a jet bubbling type reaction tank. In FIG. 4, reference numeral 1 in the figure indicates a reaction tank in this flue gas desulfurization apparatus.
Limestone (Ca) is formed in the reaction tank 1 by a disc-shaped or square-plate-shaped lower deck 2 and upper deck 3 serving as partition walls.
Absorbent solution 4 consisting of an aqueous solution in which CO ₃ is dissolved or suspended
And a storage section for storing the gas at a constant liquid level, an inlet plenum 6 between the upper and lower decks 2 and 3 to which an exhaust gas inlet duct 5 is connected, and an exhaust gas outlet duct 7 above the upper deck 3. Exit plenum 8. A large number of openings are formed in the lower deck 2, and sparger pipes 9 are suspended from each of the openings, and a lower outer periphery of each sparger pipe 9 in the absorbent 4. Exhaust holes for exhaust gas are drilled in the wall.
On the other hand, between the lower deck 2 and the upper deck 3, gas risers 10 are arranged to communicate a space on the absorbent surface of the storage section to the outlet plenum 8 side. Is provided with a mist eliminator 11. The symbol 12 in the figure indicates the absorption liquid 4 in the reaction tank 1.
An oxidation air supply pipe that introduces oxidation air into the
Reference numeral 13 denotes a stirrer that stirs the absorption liquid 4.

In addition, an absorbing solution 4 is provided at the bottom of the reaction tank 1.
A gypsum slurry discharge pipe 14 for extracting the gypsum slurry generated therein is provided. The gypsum slurry extracted from the gypsum slurry is supplied to the mixing tank 1 via a transfer pipe 17 by a pump 16.
8 is sent. On the other hand, wastewater extracted from this waste gas desulfurization device and the integrated wastewater treatment equipment in the power generation equipment and the like provided with the flue gas desulfurization device is neutralized by slaked lime etc. in a neutralization tank and concentrated in a concentration device. After that, the mixing tank 18 is drained through the drain slurry pipe 23.
To be sent to And the mixing tank 18
At the subsequent stage, a gypsum separator 25 for solid-liquid separation of a mixed slurry of gypsum slurry and drainage slurry via a supply pipe 24 is provided.

[0004] With the flue gas desulfurization apparatus having the above structure,
For example, in order to remove sulfurous acid gas and the like contained in the exhaust gas of a boiler, the exhaust gas is supplied from an inlet duct 5 to an inlet plenum 6.
And spouts the sparger pipe 9 horizontally from the lower end spout hole. Then, the exhaust gas is absorbed by the absorbent 4
To form a jet bubbling layer having a liquid phase continuity. In this jet bubbling layer, highly efficient gas-liquid contact is performed to absorb SO _2, and the exhaust gas desulfurized in this manner is supplied to the gas riser 10. And is collected in the outlet plenum 8 through the outlet duct 7 and discharged through the mist eliminator 11 to the outside.

In parallel with this, by oxidizing and neutralizing SO ₂ , gypsum is formed in the absorbing solution 4, and the gypsum grows into coarse particles to form a gypsum slurry. Then, when this reaches a predetermined concentration, the reaction tank 1
From the bottom of the storage tube 1
After being stored in 5, it is sent from the transfer pipe 17 to the mixing tank 18 by the pump 16. On the other hand, the wastewater extracted from the system is neutralized in the neutralization tank and concentrated in a concentration device,
The slurry is sent from the drain slurry pipe 23 to the mixing tank 18. Then, the gypsum slurry and the drainage slurry sent to the mixing tank 18 are mixed here, sent to the gypsum separator 25 from the supply pipe 24, and separated into the mother liquor and the gypsum 26,
The gypsum component is provided as a raw material for a gypsum board or a cement mixture.

[0006]

In the above-mentioned conventional flue gas desulfurization apparatus, the gypsum separator 25 is
A centrifugal separator that mainly separates a mixed slurry of a gypsum slurry and a drainage slurry into solid and liquid by centrifugal force generated by high-speed rotation has been used. However, the flue gas desulfurization apparatus using the centrifugal separator as the gypsum separator 25 has a problem that the centrifugal separator is expensive. In addition, in the above-mentioned flue gas desulfurization device, when trying to reduce the amount of wastewater generated in the system related to the flue gas desulfurization device including the power generation equipment provided with the same, the chlorine concentration in the reaction tank increases, and as a result, Since the concentration of chlorine in gypsum as a by-product also increases, it is necessary to wash the gypsum in a gypsum separator to reduce the chlorine concentration in the gypsum. However, there is a problem that the above-mentioned gypsum cannot be washed.

Therefore, conventionally, it has been proposed to use a belt-type vacuum dehydrator as shown in FIG. 5 instead of the centrifugal separator as the gypsum separator 25. The belt-type vacuum dehydrator 30 includes drums 31 and 3 that are rotationally driven.
Belt 3 having a number of holes perforated and having air permeability
2 is stretched and a lower part of the upper belt is -30.
A dehydration chamber 33 that is evacuated to a vacuum of 0 to -600 mmHg is provided, and on the belt 32, an endless filter cloth 35 wound around a number of rollers 34. It is a schematic configuration, and above the filter cloth 35 on the belt 32, the filter cloth 35 indicated by an arrow in the drawing is provided.
Supply tank 37 for causing a mixed slurry of a gypsum slurry and a drainage slurry to flow down sequentially on the filter cloth 35 along the traveling direction of
And a cleaning spray 38 for cleaning the mixed slurry that is supplied onto the filter cloth 35 and moves while being filtered. A filtrate drainage pipe 39 for draining the filtrate removed by suction into a filtrate tank (not shown) is connected to the bottom of the dehydration chamber 33. Reference numeral 41 in the figure denotes a spray disposed on both sides of the filter cloth 35 for cleaning the filter cloth 35.

[0008] The belt-type vacuum dehydrator 30 having the above configuration
In the above, while supplying the mixed slurry of the gypsum slurry and the drainage slurry onto the filter cloth 35 from the supply tank 37 while rotating the drum 31 to move the filter cloth 35 through the belt 32 in the arrow direction in the figure, , Cleaning spray 38
The washing water is spouted out of the filter cloth 35 to wash the cake transferred on the filter cloth 35. As a result, the moisture in the cake on the filter cloth 35 is sucked and removed to the dewatering chamber 33 side, and the separated gypsum 40 is collected from the right end of the filter cloth 35 to a belt conveyor or the like (not shown). The filtrate separated and removed in the dehydration chamber 33 is drained from the filtrate drain pipe 39 to the filtrate tank. According to such a flue gas desulfurization apparatus using the belt-type vacuum dehydrator 30 shown in FIG. 5 as the gypsum separator 25 in FIG. 4, the equipment cost is reduced as compared with the case where a centrifugal separator is used. In addition to being able to do, even when supplying gypsum slurry with high chlorine concentration,
This has the advantage that it can be cleaned.

However, the belt type vacuum dehydrator 3
6, as shown in FIG. 6, the mixed slurry 40 having a thickness of several centimeters composed of the mixed slurry supplied onto the filter cloth 35 is mixed with a gypsum component 40 a having a large specific gravity and a gypsum component 4.
0a has a two-layer structure with the fine particle layer 40b having a small specific gravity that covers the surface of the upper fine particle layer 4a.
Ob greatly reduces the air permeability of the mixed slurry 40 and reduces the filtration speed by suction from the dehydrating chamber 33, so that it becomes difficult to obtain gypsum having a water content of 15 to 20% by weight or less, which is generally required. There was a problem that it would. Therefore, when trying to increase the filtration area by reducing the thickness of the mixed slurry to improve the filtration performance, the width dimension of the required filter cloth becomes excessively large,
There is a problem that the apparatus becomes extremely large and cannot be practically used at all because of restrictions on the installation area and the like.

The present invention has been made to effectively solve the problems of the above-mentioned conventional flue gas desulfurization apparatus and the method for treating gypsum slurry in the flue gas desulfurization apparatus. An object of the present invention is to provide a flue gas desulfurization apparatus and a method for treating gypsum slurry that can achieve high filtration performance without increasing the filtration area when separating gypsum from wastewater slurry.

[0011]

According to a first aspect of the present invention, there is provided a flue gas desulfurization apparatus according to the present invention, wherein exhaust gas is brought into contact with an absorbent containing a Ca component which is circulated and supplied, and air is introduced into the absorbent. The sulfurous acid gas is removed from the exhaust gas as a gypsum slurry, the generated gypsum slurry is extracted, and a mixed slurry of the gypsum slurry and the wastewater slurry from the wastewater treatment equipment is solid-liquid separated in a gypsum separator to form gypsum. In the flue gas desulfurization device to be recovered, the gypsum separator has an endless filter cloth movably supported on a gas-permeable belt stretched between drums, and a supply tank is provided on the filter cloth. A belt-type vacuum dehydrator that sucks a mixed slurry of the supplied gypsum slurry and the drainage slurry from a dehydration chamber that is provided below the belt and is maintained at a negative pressure, and separates the filtrate and the gypsum; It is provided above the filter cloth of this belt-type vacuum dehydrator and is inserted into at least the upper fine particle layer of the mixed slurry composed of the gypsum slurry and the drainage slurry to be conveyed, and the upper fine particle layer of the mixed slurry accompanying the conveyance. And a fine particle layer breaking mechanism for forming a groove portion.

According to a second aspect of the present invention, the fine particle layer breaking mechanism according to the first aspect is fixed in a direction intersecting a running direction of the filter cloth, and is provided at a lower end portion in the upper fine particle layer. It is a synthetic resin plate on which a plurality of comb blades to be inserted are formed.

Further, in the method for treating a gypsum slurry according to the present invention according to the third aspect, the exhaust gas and Ca circulated and supplied are provided.
While contacting the absorbing solution containing the components, air is introduced into the absorbing solution to remove the sulfurous acid gas from the exhaust gas as a gypsum slurry, the generated gypsum slurry is extracted, and the contents in the gypsum slurry and the exhaust gas are removed. A method of treating a gypsum slurry in which a mixed slurry with a collected wastewater slurry is solid-liquid separated in a gypsum separator and collected as gypsum, wherein the gypsum slurry is a belt-type vacuum dehydrator according to claim 1 or 2. Supplied from the dehydration chamber while forming a groove by the fine particle layer breaking mechanism, at least the upper fine particle layer of the mixed slurry composed of the gypsum slurry and the drainage slurry that is supplied on the filter cloth, By separating, gypsum having a desired moisture content or less is obtained.

In the flue gas desulfurization apparatus according to the first or second aspect and the method for treating a gypsum slurry according to the third aspect using the apparatus, the drum is rotated to move the filter cloth supported on the belt. Meanwhile, a mixed slurry of a gypsum slurry and a drainage slurry is supplied from a supply tank onto the filter cloth, and the mixed slurry is transported together with the filter cloth. Then
Along with this transport, a part of the upper fine particle layer is broken by a fine particle layer breaking mechanism inserted into the upper fine particle layer of the mixed slurry, and a groove is formed. As a result, air permeability in the mixed slurry is ensured by the grooves, so that the water in the mixed slurry is smoothly sucked and removed from the dewatering chamber below the filter cloth, thereby being dewatered to a desired water content. Gypsum, and is collected from the filter cloth.

Therefore, according to the flue gas desulfurization apparatus and the method for treating gypsum slurry, it is possible to continuously process the mixed slurry composed of the gypsum slurry and the waste slurry by continuous operation, and to increase the filtration area without increasing the filtration area. Filtration performance can be achieved, and therefore, gypsum whose water content has been reduced to a desired value can be easily obtained. At this time, according to the invention described in claim 2,
As the fine particle layer breaking mechanism, a synthetic resin plate fixed in the direction intersecting the running direction of the filter cloth and formed with a plurality of comb blades inserted at the lower end into the upper fine particle layer is used, It is a device and does not cause corrosion.
Therefore, in the continuous treatment of the mixed slurry, the above-mentioned remarkable effects can be obtained over a long period of time, which is preferable.

[0016]

1 and 2 show a main part of an embodiment of a flue gas desulfurization apparatus according to the present invention. Other parts are the same as those shown in FIG. For this reason, the same reference numerals are given in the description, and the description is omitted. FIG. 1 shows a configuration of a gypsum separator in the present flue gas desulfurization apparatus, and this gypsum separator is schematically constituted by a horizontal belt type vacuum dehydrator 50 and a fine particle layer destruction mechanism 51. . Here, the horizontal belt type vacuum dehydrator 50
A rubber belt 53 having a large number of holes and having air permeability is rotatably stretched together with the drum 52 between the rotatably driven drums 52, 52. At the bottom of 53, the inside is -300 to -60
A dehydration chamber 54 maintained at a vacuum of 0 mmHg is provided. Then, a large number of rollers 55 are placed on the belt 53.
.. An endless filter cloth 56 made of polypropylene, polyester, or the like, which is wrapped freely between them, is supported along with the belt 53 in the direction shown by the arrow in FIG. A filtrate drainage pipe 57 for draining the filtrate removed by suction into a filtrate tank (not shown) is connected to the bottom of the dehydration chamber 54.

Above the filter cloth 56 of the belt-type vacuum dehydrator 50, the supply pipe 24
A supply tank 60 for supplying the mixed slurry of the gypsum slurry and the drainage slurry sent by the above to the filter cloth 56 is provided, and the bottom surface of the supply tank 60 is provided with the fine particle layer breaking mechanism 51. ing. As shown in FIG. 2, the fine particle layer breaking mechanism 51 is a plate-like member made of a synthetic resin such as nylon fixed in a direction orthogonal to the running direction of the filter cloth 56. A number of comb blades 62 to be inserted into the upper fine particle layer 40b of the slurry 40 are formed. In addition, as the fine particle layer breaking mechanism, for example, as shown in FIG. 3, a plurality of plate members 63 made of synthetic resin are arranged so that their respective plate surfaces are along the conveying direction of the mixed slurry, and the lower end is formed. The mixed slurries may be arranged at a fixed interval from each other so as to be inserted into the upper fine particle layer. And the above-mentioned supply tank 6
0 and the filter cloth 56
A cleaning spray 64 for cleaning the mixed slurry conveyed above is provided.

In the flue gas desulfurization apparatus having the gypsum separator having the above configuration, the gypsum slurry produced in the absorbing solution 4 of the reaction tank 1 and the wastewater obtained by being extracted from the system and concentrated. In order to process the mixed slurry with the slurry, first, the gypsum slurry and the drainage slurry are supplied to the mixing tank 18 from the transfer pipe 17 and the drainage slurry pipe 23, respectively, and mixed therein. Send to In parallel with this, the drum 51 of the horizontal drum type vacuum dehydrator 50 is rotationally driven to rotate the belt 5.
2, a mixed slurry of a gypsum slurry and a drainage slurry is supplied from the supply tank 60 onto the filter cloth 56 while moving the filter cloth 56 in the direction of the arrow in the drawing.
0 is conveyed together with the filter cloth 56. Then, as shown in FIG. 2, a part of the upper fine particle layer 40b is broken by the comb blades 62 of the fine particle layer breaking mechanism 51 inserted into the upper fine particle layer 40b of the mixed slurry 40 with this conveyance. A groove 70 is formed. As a result, the groove 7
0, the upper fine particle layer 40 partially covering the gypsum component 40a
b is destroyed, air permeability in the mixed slurry 40 is secured, and water in the mixed slurry 40 is sucked and removed from the dewatering chamber 54 below the filter cloth 56, whereby the mixed slurry 40 is dehydrated to a desired water content. The gypsum 71 is separated and collected from the filter cloth 56 to the belt conveyor 72.

Therefore, according to the flue gas desulfurization apparatus and the method for treating gypsum slurry, continuous processing of the gypsum slurry, the drainage slurry and the mixed slurry by continuous operation can be performed, and further, the fine particle layer destruction mechanism 5 can be used.
According to 1, since high filtration performance can be achieved without increasing the filtration area, gypsum whose moisture content has been reduced to a desired value can be easily obtained. Moreover,
The fine particle layer breaking mechanism 51 is a synthetic resin plate fixed in a direction perpendicular to the traveling direction of the filter cloth 56 and having a plurality of comb blades 62... Inserted into the upper fine particle layer 40b at the lower end. The above-mentioned remarkable effects can be obtained over a long period of time with a simple device without requiring a large-scale device.

In the above embodiment, only the case where the flue gas desulfurization apparatus in which the gypsum separator according to the present invention is improved is applied to a wet flue gas desulfurization apparatus having a jet bubbling type reaction tank has been described. Without being limited to this, while contacting the exhaust gas and the absorbent containing the Ca component to be circulated and supplied, air is introduced into the absorbent to remove sulfurous acid gas from the exhaust gas as a gypsum slurry,
A so-called wet lime-gypsum method flue gas desulfurization device, in which the generated gypsum slurry is withdrawn by a slurry pump, solid-liquid separated in a gypsum separator and collected as gypsum,
Various forms can be similarly applied.

[0021]

As described above, claim 1 or claim 2
According to the flue gas desulfurization apparatus described in the above, and the method for treating the gypsum slurry according to the third aspect using the same, the fine particle layer destruction mechanism inserted into the upper fine particle layer accompanying the transport of the mixed slurry causes the above-mentioned upper part to be removed. It is possible to form a groove by partially destroying the fine particle layer, and as a result, the groove allows the mixed slurry to have air permeability, so that high filtration performance can be achieved without increasing the filtration area. An effect is thus obtained such that gypsum having a reduced water content to a desired value can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a gypsum separator in one embodiment of a flue gas desulfurization device of the present invention.

FIG. 2 is a front view of a main part showing a fine particle layer breaking mechanism of FIG. 1;

FIG. 3 is a perspective view of a main part showing another embodiment of a fine particle layer breaking mechanism.

FIG. 4 is a schematic configuration diagram showing a conventional flue gas desulfurization device.

FIG. 5 is a schematic configuration diagram showing a gypsum separator in another conventional flue gas desulfurization apparatus.

FIG. 6 is a longitudinal sectional view showing a state of a mixed slurry on a filter cloth in the gypsum separator of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank 4 Absorbing liquid 12 Oxidation air supply pipe 17 Gypsum slurry transfer pipe 18 Mixing tank 23 Drain slurry pipe 40 Mixed slurry 40a Gypsum component in mixed slurry 40b Upper fine particle layer in mixed slurry 50 Horizontal belt vacuum dehydrator Reference Signs List 51 particulate layer destruction mechanism 52 drum 53 belt 54 dehydration chamber 56 filter cloth 60 supply tank 62 comb blade 64 cleaning spray 70 groove 71 gypsum

Claims (3)

[Claims] 1. A gypsum slurry produced by contacting an exhaust gas with an absorbent containing a Ca component to be circulated and supplied, and introducing air into the absorbent to remove a sulfurous acid gas from the exhaust gas as a gypsum slurry. In a flue gas desulfurization apparatus for collecting a gypsum by solid-liquid separation of a mixed slurry of the gypsum slurry and the wastewater slurry from the wastewater treatment equipment by a gypsum separator, the gypsum separator is stretched between drums. An endless filter cloth is supported movably on a belt having air permeability, and a mixed slurry of the gypsum slurry and the drainage slurry supplied from a supply tank on the filter cloth is provided below the belt. A belt-type vacuum dehydrator that separates the filtrate and the plaster by suction from the dehydration chamber held at a negative pressure, and a belt-type vacuum dehydrator that is provided above the filter cloth of the belt-type vacuum dehydrator. A fine particle layer destruction mechanism that is inserted into at least the upper fine particle layer of the mixed slurry composed of the gypsum slurry and the drainage slurry to be transported and forms a groove in the upper fine particle layer of the mixed slurry with the transport. A flue gas desulfurization device comprising: 2. The synthetic resin plate, wherein the fine particle layer breaking mechanism is fixed in a direction intersecting a running direction of the filter cloth, and has a plurality of comb blades formed at a lower end thereof to be inserted into the upper fine particle layer. The flue gas desulfurization device according to claim 1, wherein: 3. The gypsum slurry produced by bringing exhaust gas into contact with an absorbent containing a Ca component that is circulated and supplied, and introducing air into the absorbent to remove sulfurous acid gas from the exhaust gas as a gypsum slurry. A gypsum slurry, wherein a mixed slurry of the gypsum slurry and the wastewater slurry from the wastewater treatment facility is solid-liquid separated in a gypsum separator and collected as gypsum. Supplying on the filter cloth of the belt-type vacuum dehydrator according to the above, at least in the upper fine particle layer of the mixed slurry composed of the gypsum slurry and the drainage slurry to be conveyed, while forming a groove by the fine particle layer breaking mechanism By sucking from the dehydration chamber and separating the water, a gypsum having a desired moisture content or less is obtained and a desired filtration is performed. Processing method of the gypsum slurry and obtaining a degree.