JP2982889B2 - Equipment for collecting ultrafine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recovering ultrafine particles such as bentonite from muddy water or turbid water, and more particularly to an apparatus for recovering ultrafine particles from waste mud generated by a mud drilling method.

[0002]

2. Description of the Related Art A continuous underground wall method, a cast-in-place pile method, a mud shield method, and the like are known as methods for excavating the ground. These methods are so-called mud drilling methods using mud as a stable liquid. By filling the borehole with muddy water, the collapse of the borehole is prevented.

[0003] Bentonite is a typical muddy water material used in such a method. Bentonite is a clay mineral containing montmorillonite as a main component, and exhibits a negative potential on the surface in water to form a stable suspension.

[0004] The muddy water containing such clay particles is once discharged out of the hole by slurry transport together with excavation shearing, and coarse and fine sediment are removed by a sediment separator and a screw decanter, respectively. After that, it is returned to the borehole again and used for circulation.

However, the size of fine particles that can be separated by a screw decanter is about 10 μm or more, and fine particles (ultrafine particles) below this size are not removed and continue to increase in muddy water, which is one of the causes of deterioration of muddy water. Becomes

For this reason, muddy water degraded by circulating use undergoes coagulation treatment, dehydration treatment by a roll press or filter press, etc., and is then carried out as waste, and new muddy water is supplied instead.

[0007]

Here, in consideration of the natural environment and ecosystem, it is desirable that the amount of waste is as small as possible. There is also a growing demand to collect and reuse ultrafine particles contained in waste mud.
In addition, such ultra-fine particles are mixed not only with waste mud generated by the mud drilling method, but also with turbid water generated at quarries, aggregate for concrete, etc., and it is possible to classify and collect only ultra-fine particles. If possible, it will be possible to reuse it for various purposes.

However, as described above, it is impossible to classify ultrafine particles of 10 μm or less using a screw decanter, so that muddy water and turbid water containing such ultrafine particles are unavoidably discarded at present. is there.

The present invention has been made in view of the above circumstances, and provides an apparatus for recovering ultrafine particles such as bentonite from waste mud and the like, which can be reused. The purpose is to do.

[0010]

In order to achieve the above-mentioned object, an apparatus for recovering ultrafine particles according to the present invention contains treated water containing ultrafine particles such as bentonite. An ultrafine particle classifier in which fixed electrodes are arranged in a water tank in a substantially vertical and zigzag manner at predetermined intervals, and movable electrodes formed as endless belts are opposed to each other between the fixed electrodes; The mechanism comprises a mechanism provided near the outlet of the water tank for dropping the ultrafine particles attached to the water tank, and a dryer for drying the ultrafine particles dropped by the mechanism.

[0011]

In the apparatus for recovering ultrafine particles according to the present invention, the movable electrode is circulated while the treated water containing the ultrafine particles is placed in a water tank. Here, if the movable electrode is connected to the positive electrode side of the DC power supply and the fixed electrode is connected to the negative electrode side, ultra-fine particles of negative potential suspended between the movable electrode and the fixed electrode in the water tank will be electrically driven. It is attracted to the movable electrode on the positive electrode side by electrophoresis and adheres to the surface thereof. Then, the movable electrode circulates between the fixed electrodes while gradually growing an attached mass of ultrafine particles on the surface thereof. Next, the ultrafine particles attached to the movable electrode are dropped off by the action of a mechanism provided near the outlet of the water tank, and then the ultrafine particles dropped off by the mechanism are dried by a dryer.

The drying method may be appropriately selected from methods such as hot air heating, heat transfer heating, radiant heating, and high frequency heating.

The fine particles thus recovered can be reused as a mud making material in a muddy water method, and can also be reused as a raw material for porcelain and refractories, molding sand, papermaking additives, various fillers, and the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an apparatus for recovering ultrafine particles according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an apparatus for recovering ultrafine particles according to this embodiment, and FIG. 2 is a flowchart showing a procedure of a method for recovering ultrafine particles. As can be seen from FIG. 1, the apparatus for recovering ultrafine particles according to the present embodiment is configured such that a fixed electrode 12 is substantially vertically and staggered in a water tank 11 in which treated water containing ultrafine particles such as bentonite is put. An ultrafine particle classifier 7 which is arranged at intervals and has a movable electrode 13 formed as an endless belt facing each other between the fixed electrodes, and an ultrafine particle attached to the movable electrode 13 is subjected to vibration or air blowing. The mechanism comprises a mechanism 15 provided near the outlet of the water tank 11 for dropping by ultra-fine particles and the like, and a dryer 21 for drying the ultrafine particles dropped by the mechanism.

In the apparatus for recovering ultrafine particles according to the present embodiment, waste mud generated by the continuous underground wall construction method is used as the treated water. In the continuous underground wall construction method, as shown in FIG. 1, while excavating with an excavator 3 while filling the excavation hole 2 with the mud created by the mud making apparatus 1, the mud is temporarily excavated by slurry transport together with the excavation. After being discharged out of the hole and coarse particles are removed by the sediment separator 4, it is returned to the excavation hole 2 through the sand settling tank 5. Further, the muddy water put in the sand settling tank 5 is returned to the sand setting tank 5 for circulating use after the fine sediment is removed by the screw decanter 6.

Here, the screw decanter 6 has a limit of removing fine particles of about 10 μm, and ultrafine particles smaller than this are not removed and exit from the screw decanter 6 in a state of being contained in the over muddy water. Come.

Therefore, in this embodiment, as shown by the broken line in FIG. 1, the over muddy water of the screw decanter 6 is taken out as treated water (FIG. 2, step 101). In addition, the muddy water in which the concentration of the ultrafine particles is high may be taken out from the sand settling tank 5.

Next, the extracted treated water is put into the ultra-fine particle classification device 7, and the ultra-fine particles are classified from the treated water (step 102).

Here, the movable electrode 1 of the ultrafine particle classifier 7
3 is a large number of sprockets 1 arranged inside and outside the water tank 11.
4 and is circulated inside and outside the water tank 11 by a predetermined driving mechanism (not shown) in the direction of the arrow shown in the figure. The fixed electrode 12 is electrically connected to the negative side of the DC power supply via the water tank 11 formed of a conductive material. On the other hand, the movable electrode 13 is connected to the positive side of the DC power supply via a brush or the like.

[0021]

In the ultrafine particle classifier 7, the water tank 11
The movable electrode 13 is slowly circulated in a state in which the treated water from the screw decanter 6 is charged. Here, since the movable electrode 13 is connected to the positive electrode side of the DC power supply and the fixed electrode 12 is connected to the negative electrode side, the negative potential suspended between the movable electrode 13 and the fixed electrode 12 in the water tank 11 is The ultrafine particles are attracted to the movable electrode 13 on the positive electrode side by electrophoresis and adhere to the surface thereof. And the movable electrode 13
Circulates between the fixed electrodes 12 while gradually growing an attached mass of ultrafine particles on the surface thereof.

When the movable electrode 13 comes out of the water tank 11 and reaches the mechanism 15, the ultrafine particles attached to the movable electrode 13 fall off by the action of the mechanism 15.

Next, as shown by the broken line in FIG.
The ultrafine particles dropped in step 5 are dried by the dryer 21 (step 103). The dryer 21 has a large number of steam heating tubes disposed in a cylindrical body that rotates slightly inclined.
The ultrafine particles can be dried by hot air and conduction heating while tumbling and stirring.

As described above, according to the apparatus for recovering ultrafine particles according to the present embodiment, ultrafine particles such as bentonite contained in waste mud are first classified by electrophoresis and then heated with hot air. Since it is configured to be recovered from the waste mud by drying by the method such as the above, it is possible to considerably reduce the amount of the mud which has conventionally only been discarded.

The recovered ultrafine particles can be reused again as a mud material for a muddy water method, and can be effectively used as a raw material for refractories such as bricks and tiles or a high-grade clay material for ceramics. Can also. Also, foundry sand,
It can also be reused for applications such as papermaking additives and various fillers.

In this embodiment, waste mud generated by the continuous underground wall method is used as the treated water.
Needless to say, waste mud generated by other mud drilling methods can be used, and turbid water generated at a quarry or the like may be used.
Moreover, when washing the aggregate of concrete, you may use it for collect | recovering the clay fine particle mixed in the said aggregate.

Further, the used casting sand may be once crushed and then slurried to prepare treated water.

In this embodiment, a dryer capable of drying ultrafine particles by both the action of hot air and heat transfer is used.
The drying method is not limited to such a method, and may be appropriately selected from various drying methods such as heating by hot air, heating by heat transfer, radiant heating using infrared rays, or heating using high frequency (electromagnetic waves). Further, the drying step may be performed under reduced pressure.

Further, in the present embodiment, the ultrafine particles attached to the movable electrode are dropped from the movable electrode by vibration or blow-off. However, the ultrafine particles may be dropped by electrode inversion.

[0031]

As described above, according to the apparatus for recovering ultrafine particles according to the present invention, ultrafine particles such as bentonite can be recovered from waste muddy water and reused.

[0032]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an apparatus for collecting ultrafine particles according to the present embodiment.

FIG. 2 is a flowchart showing the procedure of ultra-fine particle recovery using the apparatus for recovering ultra-fine particles according to the present embodiment.

[Explanation of symbols]

 7 Ultrafine particle classifier 21 Dryer 102 Classification process 103 Drying process

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E21D 9/06 301 B01D 57/02

Claims (1)

(57) [Claims] 1. A fixed electrode is disposed substantially vertically and in a staggered manner at a predetermined interval in a water tank containing treated water containing ultrafine particles such as bentonite, and an endless belt is formed between the fixed electrodes. An ultrafine particle classifier having a movable electrode opposed thereto, a mechanism provided near the outlet of the water tank for dropping the ultrafine particles attached to the movable electrode, and drying the ultrafine particles dropped by the mechanism. An apparatus for recovering ultrafine particles, comprising a dryer.