JPH11128670A - Belt-filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt-filter enabling to secure dehydration performance even when a fine particle layer of a gypsum cake is formed. SOLUTION: In a belt-filter 1 by which gypsum slurry 2 from a flue gas desulfurization device is sucked and dehydrated with vacuum dehydration devices 4, 5, plural stages of dams 10 whose lower ends extend to the upper layer of a gypsum cake 8, are provided in the longitudinal direction of the belt-filter 1 so that a fine particle layer formed on the surface of the gypsum cake 8 is stirred with them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a belt filter used for dewatering gypsum slurry in a flue gas desulfurization apparatus.

[0002]

2. Description of the Related Art A gypsum slurry dehydrator used in a flue gas desulfurization apparatus is changed from a centrifugal separator system to a basket type vacuum suction dehydrator system using a belt filter from the viewpoint of equipment costs, operation costs, maintenance costs and dewatering performance. Migrating. However, fine impurities contained in the slurry, such as unburned carbon, calcium fluoride, silica, aluminum hydroxide,
Fine particle dust made of iron hydroxide forms a fine particle layer 202 of about 1 to several mm on the surface of the dewatering cake 201 as shown in FIG. 2, thereby deteriorating air permeability during vacuum suction and deteriorating dewatering performance. Was to be caused.

[0003]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a belt filter capable of ensuring dewatering performance even when a fine particle layer of a gypsum cake is formed.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 is a belt filter in which gypsum slurry from a flue gas desulfurization unit is suction-dehydrated by a vacuum dehydration unit. Is characterized in that a plurality of weirs extending from the top of the gypsum cake are provided in the longitudinal direction of the belt filter so as to disturb the fine particle layer formed on the surface of the gypsum cake. According to a second aspect of the present invention, in the belt filter of the first aspect, a washing water supply device that supplies hot water, steam, or hot water and steam to a gypsum slurry or a gypsum cake on the belt filter is provided. I do.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A belt filter according to the present invention will be described below with reference to an embodiment shown in the accompanying drawings. As shown in FIG. 1, a belt filter 1 according to the present embodiment supplies a gypsum slurry 2 from a supply header 3, and includes a first vacuum box 4 and a second vacuum And a box unit 5. On the upper surfaces of the vacuum boxes 4 and 5, there is provided a transfer rubber belt 6 which moves and circulates in contact with the vacuum boxes. The rubber belt 6 supports a belt filter (filter cloth) main body 7 that moves and circulates. The belt filter body 7 has air permeability, and has an appropriate strength to hold the gypsum slurry 2 and the gypsum cake 8. Further, the present embodiment includes a cleaning water supply device 9. This device 9 is for washing out high-concentration chloride ions and other salts contained in the gypsum slurry 2 in order to obtain high-grade (purity) gypsum.

Further, the belt filter 1 according to the present embodiment has a weir 10. The weir 10 is a means for disturbing the fine particle layer formed on the surface of the gypsum cake 8. The weir 10 has a lower end extending to the upper layer of the gypsum cake 8 and is provided at three places in the longitudinal direction of the belt filter 1. Here, "the lower end extends to the upper layer of the gypsum cake 8" means that the crest 10 has a sufficient length in the vertical direction, and the lower end thereof disturbs the fine particle layer of the gypsum cake 8, and the dewatering performance is reduced. It means that it can be secured. The weir 10 can be made of rubber, plastic, bamboo, wood, metal, or the like, but is preferably made of rubber, that is, synthetic rubber. The weir 10 has a rectangular shape and is suspended in the width direction of the belt filter 1 by supporting means (not shown).

In the embodiment shown in FIG. 1, the gypsum slurry 2 is supplied from the supply header 3 to the belt filter body 7.
It is supplied to the upper part and is subjected to vacuum suction filtration in the first vacuum box section 4. Belt filter body 7 obtained by vacuum suction filtration
The upper gypsum cake 8 is sent to the second vacuum box section 5 by the rubber belt 6. At this time, the cleaning liquid is supplied onto the gypsum cake 8 from the cleaning water supply device 9. After the washing water is vacuum-suction-filtered in the second vacuum box section 5, the water in the gypsum cake 8 is dehydrated by vacuum suction for a further predetermined time. The dehydrated gypsum cake 8 is sent to the collection conveyor 11 side by the movement of the rubber belt 6, is separated from the belt filter body 7, and is collected by the collection conveyor 11. The belt filter body 7 from which the gypsum cake 8 has been peeled off is washed by the belt filter washing device 12 and then sent to the slurry supply unit again. The washing water supplied onto the gypsum cake 8 from the washing water supply device 9 is at the same temperature as the gypsum slurry or preferably at the slurry temperature +1.
0 ° C. Thereby, the temperature of the pore water in the gypsum cake 8 is raised, the viscosity and surface tension of the pore water are reduced, the resistance between particles is reduced, and the air permeability is improved.

On the other hand, the lower end of the weir 10 is a gypsum cake 8
And disturbs the upper layer of the gypsum cake 8 including the formed fine particle layer. Thereby, the air permeability of the gypsum cake 8 can be maintained and dehydration can be performed efficiently. The weir 10 also plays a role in retaining the aqueous phase. That is, at the position where the fine particle layer is formed, the water floating on the surface layer can be dammed, and at the same time, the fine particle layer can be disturbed and the water can be sucked out by vacuum suction. Can be prevented. In the present embodiment, since a plurality of weirs 10 are provided, the turbulence effect is large, the properties of the gypsum slurry 2 change, and the position where the fine particle layer is formed (water drainage position).
Can be dealt with by any of the weirs 10, which can be reliably disturbed and the dewatering performance can be ensured.

Other Embodiments In the above embodiment, the first vacuum section and the second vacuum section are provided. However, the first vacuum section is omitted, and only natural settling is performed in this section. You can also. In the embodiment of FIG. 1, three weirs 10 are provided. But,
In order to achieve the object of the present invention, it is sufficient that a plurality of steps are provided at the position where the fine particle layer is formed. Further, the number can be increased as compared with the embodiment of FIG. Further, the position set according to the difference in the position where the fine particle layer is formed can be variably configured. Strictly speaking, the effect of the cough 10 is most effective immediately before water is drained by dehydration (immediately before the fine particle layer is formed). For this reason,
In the case of a fixed type weir, a plurality of stages are provided. This is because the drainage position changes depending on the composition of the gypsum, as described in the embodiment of FIG. Further, instead of the fixed type as in the embodiment of FIG. 1, a movable type weir can be used. In this case, a function to automatically change the position by detecting the drainage position with a thickness sensor or the like is provided. Of course, at the position after the fine particle layer 202 is formed,
Although the effect can be expected even if it is provided, it is necessary that the material of the weir 10 is a relatively hard material. As a result, gypsum adheres or cough 10 becomes filter cloth (belt filter body).
There is a possibility that problems such as breaking this may occur.

The washing water supplied from the washing water supply device is
Good as steam. In short, it is sufficient that the temperature is high enough to reduce the viscosity and surface tension of the pore water. Hot water and steam can be used together. In the above-described embodiment, the weir 10 such as rubber is used to disturb the gypsum slurry.
However, any means such as a metal rake which can disturb the fine particle layer can be employed in the present invention. Further, a plurality of types of means can be used in combination.

[0011]

As is clear from the above description,
ADVANTAGE OF THE INVENTION According to this invention, even if the fine particle layer of a gypsum cake is formed, the belt filter which ensured the dehydration performance is provided. Further, in the embodiment employing a weir, at the position where the fine particle layer is formed, the water floating on the surface layer can be dammed, and at the same time, the fine particle layer can be disturbed and the water can be sucked out by vacuum suction. In addition, the water phase can be prevented from being discharged to the cake surface. Further, since a plurality of weirs are provided, the turbulence effect is large, and the properties of the gypsum slurry change, and even if the position where the fine particle layer is formed changes, it is possible to cope with any of the weirs, This can be reliably disturbed, and the dewatering performance can be ensured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of a belt filter according to the present invention.

FIG. 2 is a cross-sectional view illustrating a fine particle layer formed on a gypsum cake.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Belt filter 2 Gypsum slurry 3 Supply header 4 First vacuum box part 5 Second vacuum box part 6 Rubber belt 7 Belt filter body 8 Gypsum cake 9 Washing water supply device 10 Cough 11 Recovery conveyor 12 Belt filter cleaning device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Susumu Okino 4-22, Kannonshinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Masao Hino 4-chome Kannonshinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture No. 6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Laboratory

Claims (2)

[Claims] 1. A belt filter in which gypsum slurry from a flue gas desulfurization unit is suctioned and dewatered by a vacuum dewatering device, wherein a plurality of weirs whose lower end extends to the upper layer of the gypsum cake are provided in the longitudinal direction of the belt filter. A belt filter characterized by disturbing a fine particle layer formed on the cake surface. 2. The belt filter according to claim 1, further comprising a washing water supply device for supplying hot water, steam, or hot water and steam to a gypsum slurry or a gypsum cake on the belt filter.