JPS6241050B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a horizontal vacuum dehydration method and apparatus for materials having thixotropic or dilatancy properties, which make filtration and dewatering extremely difficult. Substances with thixotropic properties undergo a reversible sol-gel transition by stirring and standing, but when such substances are filtered and dehydrated, the slurry, which has been dehydrated to some extent, gels as it stands on the filter cloth, and from then on Dehydration becomes extremely difficult. For example, in filtration using a hydrophilic colloid such as concentrated iron hydroxide, aluminum hydroxide, or special clay, the cake formed on the surface of the filter cloth is a gel with thixotropic properties, so (1) the moisture content of the cake after dehydration is high. (2) Cake cracking occurs, and cleaning water escapes through the cracks, resulting in a poor cake cleaning effect. (3) The peelability of the cake from the filter cloth is poor. (4) When the cake is moved, it turns into a sol, making it difficult to handle the cake. Problems such as this are occurring. A horizontal vacuum filtration machine is a device that supplies slurry of the filtered material onto a horizontally running filter cloth, and draws a vacuum from the bottom of the filter cloth to dehydrate the filtered material on the filter cloth. Even if the cake becomes fluid, it will not fall off because it rests on the horizontal filter cloth, making it suitable for filtering substances that easily undergo sol-gel transition. When the slurry is dehydrated and left to stand still, it turns into a gel. With ordinary substances, the cake is further dehydrated by drawing a vacuum from the bottom of the filter cloth, but the gelled cake is hardly removed, and furthermore, the cake cracks, causing the filter to become unusable. Since it passes (1)~
Various problems as described in (4) occur. The present invention has been made in consideration of these circumstances, and includes a part in the filter cloth running path of a horizontal vacuum filtration device, a part that dehydrates the cake on the filter cloth by drawing a vacuum, and a part that dehydrates the cake on the filter cloth by leaving it to dehydrate. To provide a method and an apparatus for efficiently filtering and dehydrating a substance having thixotropic properties by alternately providing a plurality of stages with parts that vibrate and stir a molten cake to sol it and make it easy to dehydrate. It is something. The present invention will be described in detail below with reference to the drawings. FIGS. 1 and 2 show an embodiment of a horizontal vacuum filtration device according to the present invention, and the reference numeral 1 in the figures is an endless filter cloth whose filtration portion is maintained horizontally. As shown in FIG. 1, the filter cloth 1 is supported by a number of intermediate rolls and is moved by a filter cloth drive drum 2 in the direction of the arrow in FIG. On the lower surface of the horizontal portion 1a of the filter cloth 1, a vacuum tray 3 for evacuating the upper surface of the filter cloth is placed on a rail 4 so as to be movable from side to side in FIG. These vacuum trays 3 are made of flexible vacuum hoses 5a.
Accordingly, a cutoff valve 5b connected to the vacuum system 5 to cut off between the vacuum system and the vacuum trays, and a release valve 5c to release each vacuum tray from the vacuum are provided. A support member 6a is provided between the vacuum trays, suspended by the vacuum trays 3 on both sides, and a tray support 6a is provided on the support member 6a.
b, Vibration tray 6 via coil spring 6c
are installed at the same level as the vacuum trays on both sides. A vibrator 6d is fixed to the lower part of the vibrating tray 6, and the vacuum tray 3 and the vibrating tray 6 are connected by a vibration-proof rubber material or the like. The tray group A formed by these connected vacuum trays 3 and vibrating trays 6 reciprocates on the rail 4 by a stroke length from side to side by a tray drive cylinder 7 provided at its end. It's becoming like that. Further, on the upper part of the filter cloth surface where the vibrating tray 6 reciprocates, a scroll 8 having a large number of fins 8a on its circumference is provided with a rotating shaft 8b perpendicular to and parallel to the traveling direction of the filter cloth surface 1a. Therefore, the cake on the vibrating tray 6 is stirred. Above the end of the horizontal portion 1a of the filter cloth 1,
A slurry supply port 9 is provided, and a scraper 10 for scraping off cake and a filter cloth cleaning spray 11 are attached to the other end. Next, the operation of the horizontal filtration device according to the present invention configured as described above will be explained. A slurry of thixotropic filtered material is
The slurry is supplied from the slurry supply port 9 to the horizontal portion of the filter cloth, and is evacuated and dehydrated by the vacuum tray 3 on the lower surface of the filter cloth. When the water is dehydrated to a certain level or less, the cake B on the filter cloth is in a static state and becomes a gel. At this time, the filter cloth is moved to the right in FIG.
is moved to the right by the tray drive cylinder at the same speed as the filter cloth, so each vacuum tray 3 and the filter cloth are in close contact, and efficient evacuation is possible. When the tray drive cylinder reaches its full stroke, the cutoff valve 5b closes and the release valve 5a opens, releasing the vacuum in the vacuum tray.The vacuum tray and filter cloth are no longer in close contact with each other, and the tray drive cylinder 7 closes the tray group. A slides on the lower surface of the horizontal filter cloth portion 1a, moves to the left, and returns to its original position. Next, the release valve is closed, the cutoff valve is opened, the vacuum tray becomes vacuum, the horizontal part 1a of the filter cloth is brought into close contact with the filter cloth, and the cake B is moved to the right again at the same speed as the filter cloth by the tray drive cylinder. Dehydrate. At this time, the cake B on the vibrating tray has been dehydrated and gelled by the vacuum tray 3 in the previous stage, but the gelled cake is on the vibrating tray 3.
The horizontal part 1a of the filter cloth is in close contact with the vibrating tray due to the vacuuming of the vacuum trays 3 on both sides, so that the cake B on the filter cloth is also directly attached to the vibrating tray. 6 and is stirred from above by the fins 8a of the scroll 8 to undergo sol transition. This vibrating tray 6 is suspended from the vacuum tray 3 on both sides via a lower spring 6c and a tray support 6b.
Since the vibrator 6d is attached to the vibrator 6d and is connected to the vacuum tray 3 by a vibration isolating material such as vibration isolating rubber, the vibration generated by the vibrator 6d is applied only to the vibrator tray 6, and the vacuum tray 3 It does not affect anything else. As described above, the cake B in the horizontal part 1a of the filter cloth alternately passes through the part where it is dehydrated and turned into a gel, and the part where it is turned into a vibratory sol (the cake is sometimes compacted and packed without being turned into a sol). The dehydration efficiency of the vacuum dehydration section is extremely good, the peelability between the cake and the filter cloth is good, and the cake does not crack, so washing with water can be carried out satisfactorily. Next, Examples will be given to concretely demonstrate the effects of the present invention. [Example] Dehydration filtration of aluminum silicate having thixotropic properties was carried out using a 28 m ² horizontal vacuum filter. In the filtration and dehydration method, 0 to 3 vibrating parts were provided between the vacuum parts of a horizontal vacuum filter, and vacuuming and vibration were performed alternately. The vibration rate of each vibration section is 20 seconds/time, and the speed of the filter cloth is constant, so the more vibrations, the shorter the evacuation time. The results are shown in the table below.

[Table] That is, the water content decreases by 6 to 7% when the vibration is performed three times compared to when there is no vibration. As described above, the horizontal vacuum filtration method and apparatus according to the present invention can efficiently dehydrate thixotropic substances that undergo sol-gel transition.
In addition, since cake cracking is eliminated, suction leakage from the vacuum pump is reduced, allowing the vacuum pump to be used more effectively.Also, since there is no shot pass during cleaning, cleaning efficiency is improved, and the moisture content in the cake is reduced, which promotes solidification. Therefore, it has many advantages such as improved separation of the cake from the filter cloth.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a horizontal vacuum filtration device showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken in the E-Y direction of FIG. DESCRIPTION OF SYMBOLS 1...Filter cloth, 1a...Filter cloth horizontal part, 2...Filter cloth drive drum, 3...Vacuum tray, 4...Rail, 5...Vacuum system, 5a...Flexible vacuum hose, 5b...Shutoff valve, 5c...Release valve, 6 ...Vibration tray, 6
a...Support member, 6b...Tray support, 6c...Spring, 7...Tray drive cylinder, 8...Scroll, 8a...Scroll fin, 8b...Scroll shaft, 9...Slurry inlet, 10...Scraper,
11... Water spray, A... Tray group, B... Cake.

Claims (1)

[Claims] 1. In horizontal vacuum filtration, the cake formed on the filter cloth by vacuuming is subjected to an external force such as vibration and/or stirring by interrupting vacuuming,
A horizontal vacuum filtration method characterized in that the operation of drawing a vacuum again is performed one or more times. 2. In a horizontal vacuum filtration device, a vacuum section is provided on the lower surface of the horizontal section of the traveling filter cloth between a vacuum section formed by a vacuum tray that dehydrates the cake on the filter cloth, and the vacuum section is provided to dehydrate the cake on the filter cloth. A horizontal vacuum filtration device comprising: a vibrating portion formed by a vibrating tray that applies an external force.