JPH07178347A - Wet classifier - Google Patents

Abstract

PURPOSE:To continuously an effectively classify granular in a slurry with high accuracy by installing a horizontal opening having the same height as the upper end of a nozzle over the whole vessel wall on the opposite side of partition of a secondary classifying vessel. CONSTITUTION:A classifying vessel 35 is divided into a primary classifying vessel 36 and a secondary classifying vessel 37 by a partition 3 having an opening 2 in the bottom part. In the secondary classifying vessel 37, a horizontal opening 39 having the same height as the upper end of a nozzle 41 is made over the whole vessel wall 38 on the opposite side of the partition 3. Outside the vessel wall 38, a trough 40 for discharging overflowing liquid is installed. The primary classifying vessel 36 is provided with the nozzle 41 in the upper part of the upstream end. The upstream end is provided with a horizontal flow outflow port 43 with a flow control valve 42 in a position having almost the same height as the nozzle 41. The nozzle 41 has a slurry inlet 44a, a confluent pipe 44 and a bend pipe line 45, and its outlet is provided with a horizontal flow guide 8. In this way, channeling hardly occurs, an the concentration and flow rate of the granular matter in the bend pipe line is made uniform. Thus horizontal straightening is formed and the classifying accuracy is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a wet classification apparatus for classifying powder particles contained in a slurry into multiple particles such as large particles, medium particles, small particles and fine particles.

[0002]

2. Description of the Related Art A wet classifying apparatus for classifying powder particles contained in a slurry into a large number, medium particles, small particles, fine particles, etc. is disclosed in Japanese Patent Laid-Open No. 4-11959 (Japanese Patent Publication No. 5-587).
No. 79). According to this technique, as shown in FIG. 8, the inside of the classification tank 1 of the wet classification device is partitioned by a partition wall 3 having an opening 2 at the bottom, and one partition wall 3 has a primary classification tank 4 and the other has a secondary classification tank. A bath 5 is formed.

In the primary classifying tank 4, a nozzle 6 is provided at the upper upstream (right side in FIG. 7) end in FIG. 7, and an overflow liquid outlet 7 having substantially the same height as the nozzle 6 is provided at the downstream end. To be The nozzle 6 is a nozzle that separately supplies the classified liquid that flows in from the classified liquid inlet 6a and the slurry that flows in from the slurry inlet 6b, and is guided by a horizontal flow guide 8 provided at the outlet of the nozzle 6 for horizontal straightening. And flows to the overflow liquid outlet 7. The interior of the primary classification tank 4 is divided into precipitation chambers 11, 12 and 13 by two partition plates 9 and 10 which are lower than the height connecting the nozzle 6 and the overflow liquid outlet 7.

At the bottom of the secondary classification tank 5, hoppers 14, 15, 16 facing the respective precipitation chambers 11, 12, 13 are arranged along the slurry flow direction, and the hoppers 14, 15, 16 are provided.
Are connected to the fluidized bed columns 20, 21, 22 by insertion tubes 17, 18, 19 respectively, and the fluidized bed columns 20, 21,
A rectifier 24 having a classification liquid inlet 23 is provided at the lower end of 22.

A hopper 15 is provided at the upper end of the fluidized bed column 20.
A bent tube 25 that opens above the fluidized bed column 2 is provided.
A bent tube 26 that opens above the hopper 16 is provided at the upper end of the fluidized bed column 22, and a secondary classification tank 5 is provided at the upper end of the fluidized bed column 22.
A bending pipe 30 that opens to an outlet pipe 29 with a regulating valve 28 provided on the downstream side wall 27 at the lower part of the is provided. Each of the fluidized bed columns 20, 21, 22 is provided with three sampling pipes 31 arranged in the height direction, and an opening / closing valve 32 is provided in each sampling pipe 31.

The classification by the wet classification device will be briefly described. When the classification liquid is supplied to the classification tank 1 from the classification liquid inlets 6a and 23, the classification liquid starts to overflow from the overflow liquid outlet 7, but it is adjusted. The valve 28 keeps the liquid level at the height of the upper end of the nozzle 6. In this state, when the slurry containing the powdery particles is supplied from the slurry inlet 6b, a horizontal flow is formed toward the overflow liquid outlet 7, and the powdery particles are separated into the settling chambers 11, 12, and 13 according to the particle size and settled. Therefore, the inside of the primary classification tank 4 is divided into a large particle group, a medium particle group, and a small particle group, and the fine particles can be collected from the overflow liquid outlet 7.

The particles classified in the primary classification tank 4 are guided to the hoppers 14, 15, 16 from the opening 2 and the insertion tube 1
From 7, 18, 19 enter the fluidized bed columns 20, 21, 22. The classifying liquid that passes through the rectifier 24 and rises quickly in the fluidized column 20, and small particles rise.
Then, slowly, the particles rise. Further, since a fluidized bed corresponding to the particle diameter is formed in the up-down direction in each fluidized bed column 20, 21, 22, it is possible to collect particles according to the particle diameter from the collection pipe 31.

[0008]

The above-mentioned wet classification device has the following problems. (1) When the flow rate of the supplied slurry changes, the liquid level changes,
Since a proper horizontal flow cannot be maintained and the classification performance is adversely affected, the adjusting valve 28 must be operated each time, which increases the human or power burden and the facility burden, resulting in equipment expenses and operating costs. To increase.

(2) When the concentration of the raw material slurry is high, or when it is necessary to reduce the horizontal flow velocity because the particle size of the granular material is also small, the relative amount of the raw material slurry with respect to the classification liquid increases and the nozzle When the slurries merge from the upper part of the classification liquid inside, the horizontal flow is disturbed, which causes a problem that the classification performance is adversely affected.

(3) When the flow velocity of the classification liquid in the fluidized bed column is not uniform and uneven in the cross-sectional direction of the fluidized bed column, small particles settle or large particles rise, which adversely affects the classification performance. was there. An object of the present invention is to solve such a problem, and the powder particles contained in the slurry are continuously and efficiently and accurately classified, and further, the human, power load, and equipment required for the liquid level control are required. A wet classification device that can reduce the burden.

[0011]

In order to achieve the above object, in the classification apparatus of the present invention, the inside of the classification tank is divided by a partition wall having an opening at the bottom, and one of the partition walls is used as a primary classification tank. The other of the partition walls is a secondary classifying tank, and the upstream end of the upper part of the primary classifying tank, a merging pipe for mixing a raw material slurry containing powder and a classifying liquid for adjusting the flow rate of a horizontal flow, and the merging pipe. A nozzle having a bent pipe for fluid homogenization is provided inside, and a horizontal outlet with a flow control valve is provided at the downstream end of the upper part of the primary classification tank, and the nozzle and the horizontal outlet are provided. A plurality of precipitation chambers partitioned by a partition plate lower than the height connecting the nozzle and the horizontal outlet is provided between the secondary classification tank and the entire tank wall surface opposite to the primary classification tank. A horizontal opening having the same height as the upper end of the supply nozzle of the primary classification tank, A gutter for discharging the overflow liquid is provided outside the flat opening, an outlet pipe with a regulating valve is provided at the downstream end of the lower part of the secondary classification tank, and a plurality of hoppers are provided at the bottom thereof, and the bottom end of each hopper is provided. Is connected to one end of a feed pipe, the other end of the feed pipe is connected to a fluidized bed column, a rectifier with a porous plate interposed at the lower end of the fluidized bed column, the lower end of the rectifier A classification liquid inlet was provided, an upper end of the fluidized bed column was opened to the downstream side of each hopper at the bottom of the secondary classification tank, and each fluidized bed column was provided with a plurality of collection tubes.

The porous plate is a flat plate having holes of a certain size and arrangement and provided on the inlet side of the rectifying section, and a second dispersion plate made of tatami-woven wire mesh and provided on the outlet side of the rectifier. It is preferable to use a dispersion plate.

[0013]

[Function] When the classification liquid is supplied into the classification tank from the nozzle and the classification liquid inlet of the wet classification device configured as described above, the classification liquid starts to flow from the outlet pipe with the adjusting valve and the horizontal outlet. However, the outflow amount of the classified liquid is suppressed by the adjusting valve of the outlet pipe and the flow control valve of the horizontal outflow port, and the classified liquid is also overflowed from the horizontal opening of the secondary classification tank. Since the horizontal opening is provided at the same height as the upper end of the nozzle of the primary classification tank, the liquid surface is kept at the same height as the upper end of the nozzle.

If the area of the horizontal opening is small, the classification liquid overflowing will be concentrated in the horizontal opening, and a biased flow will be generated in the classification tank, which will be focused on the horizontal opening. Although it adversely affects the rate, since the horizontal opening of the present invention is provided on the entire wall surface of the secondary classification tank, the above effect is negligible.

In the nozzle, the raw material slurry and the classification liquid joined in the joining pipe have uneven concentration and uneven flow velocity in a plane perpendicular to the flow. The concentration and flow rate of are uniformized. Fluctuations in the slurry flow rate result in fluctuations in the amount of overflow from the horizontal opening, and the liquid surface from the nozzle toward the horizontal outflow port is always formed by horizontal flow straightening.

The granules in the slurry settle in a two-dimensional motion due to the combination of the horizontal speed and the sedimentation speed of the granules, and the granules with large particles are blocked by the partition plate on the upstream side and It passes through the opening and is collected by the hopper on the upstream side. The granular material with small particles is blocked by the partition plate on the downstream side, passes through the opening of the partition wall, and is collected by the hopper on the downstream side.

The classified liquid rising from the classified liquid inlet to the inside of the fluidized bed column through the rectifier has a uniform flow velocity in the cross section of the fluidized bed column due to the porous plate of the rectifier. Therefore, the powder and granules collected in the hopper flow into the fluidized bed column via the feed pipe, and the sedimentation speed based on the size of the powdery granules and the fluidized bed flow through the porous plate. Due to the relationship with the classifying liquid velocity, which is rectified to a uniform velocity and rises with respect to the cross-sectional direction of the column, the granular material group according to the grain size is arranged in the vertical direction of the fluidized bed column. Therefore, it is possible to classify and collect the powder and granules of each size from each sampling tube.

When the small-sized granular material flows into the large-sized fluidized bed column, it is sent from the opening at the upper end of the fluidized bed column to the hopper on the downstream side, and from the hopper on the downstream side to the downstream side via the inlet pipe. Sent to the fluidized bed column on the side.

[0019]

1 is a front view of a wet classification device, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a plan view of FIG. The present invention is an improvement of the conventional wet classification device, and the same parts as those of the conventional wet classification device are designated by the same reference numerals and detailed description thereof will be omitted. The inside of the classification tank 35 is partitioned into a primary classification tank 36 and a secondary classification tank 37 by a partition wall 3 having an opening 2 at the bottom, as in the conventional case.

In the secondary classification tank 37, a horizontal opening 39 having the same height as the upper end of a nozzle 41, which will be described later, is provided in the entire tank wall 38 on the opposite side of the partition wall 3, and overflows to the outside of this tank wall. A gutter 40 for discharging the liquid is provided. The primary classification tank 36 is provided with a nozzle 41 at the upper part of the upstream end (the right end in FIG. 1), and the nozzle 41 is provided at the upstream end (the right end in FIG. 1).
A horizontal outflow port 43 with a flow rate control valve 42 is provided at a position substantially the same height as.

The nozzle 41 has a merging pipe 44 having a slurry inlet 44a into which a raw material slurry containing a powdery fluid flows and a classification liquid inlet 44b into which a classification liquid for flow rate adjustment flows, and a merging pipe 4
A horizontal flow guide 8 is provided at the outlet, which has a bending conduit 45 that is connected to No. 4 and is bent four times at a right angle inside. Therefore, the slurry flowing from the slurry inlet 44a and the classified liquid inlet 44b
The classified liquid flowing in from is mixed in the merging pipe 44, and while being bent four times in the bending pipe line 45, the slurry concentration and flow velocity of each portion are made uniform, and guided by the horizontal flow guide 8 to make horizontal. It becomes a rectified state and flows to the horizontal outlet 43.

A nozzle 41 is provided on the inner wall surface of the primary classification tank 36.
The two partition plates 9 and 10 which are lower than the height connecting the horizontal outlet 43 to the horizontal outlet 43 are divided into the precipitation chambers 11, 12 and 13 from the nozzle 41 in order toward the horizontal outlet 43, and the side close to the nozzle 41. The partition plate 9 is lower than the partition plate 10 as in the conventional example. At the bottom of the secondary classification tank 37, a hopper 1 that is substantially opposed to each of the precipitation chambers 11, 12, and 13 is provided.
4, 15, 16 are provided.

The bottom of the gutter 40 is formed into an inclined surface, and an overflow liquid outlet 46 for discharging the overflow liquid from the horizontal opening 39 is provided at the lower end of the inclined surface. One end of the feed pipe 17 is connected to the lower end of the hopper 14, the other end of the feed pipe 17 is connected to the fluidized bed column 20, and the lower end of the hopper 15 is connected to the fluidized bed column 21 via the feed pipe 18. However, the lower end of the hopper 16 is connected to the fluidized bed column 22 via the feed pipe 19 as in the conventional example.

A classified liquid inlet 23 and a rectifier 47 are attached to the lower ends of the respective fluidized bed columns 20, 21, 22. As shown in FIG. 4, the rectifier 47 includes the inlet side flange 47b and the outlet side flange 4 at the lower end and the upper end of the tubular body 47a.
7c is provided, the inlet side flange 47b and the classification liquid inlet 2
3, the first dispersion plate 48 is inserted between the flange 23a and the flange 23a, and the outlet side flange 47c and the fluidized bed columns 20, 21,
The second dispersion plate 50 is inserted between the lower end flange 49 of 22 and the lower end flange 49.

The first dispersion plate 48 is a flat plate in which holes 51 of a certain size are arranged at a constant interval (see the plan view of the main part of FIG. 5), and the classification liquid flowing into the classification liquid inlet 23 is Hole 51
By jetting from the nozzles substantially evenly, the unevenness of the flow velocity at each position in the cross section of the rectifier 47 is reduced. Second dispersion plate 5
No. 0 is made of tatami-woven wire mesh and has a large number of small holes formed at substantially equal intervals (see the longitudinal sectional view of the main part of FIG. 6).
This is to rectify the flow of the classified liquid in which the unevenness of the flow velocity is reduced.

A hopper 15 is provided at the upper end of the fluidized bed column 20.
A bending pipe 25 opening to the hopper 16 is provided at the upper end of the fluidized bed column 21, and a downstream side wall 27 of the secondary classification layer 37 is provided at the upper end of the fluidized bed column 22. Outlet pipe 29 with adjusting valve 28 provided in the
A bending tube 30 that opens to the inside is provided. Fluidized bed column 2
Each of 0, 21, 22 has three sampling tubes 3 in the vertical direction.
1 is provided and each collection pipe 31 is provided with an opening / closing valve 32 as in the conventional example (see FIGS. 1 and 2).

The operation of the wet classification device configured as described above will be described. When the classified liquid is supplied into the classified tank 35 from the classified liquid inlet 44b of the nozzle 41 and the classified liquid inlet 23 below each of the fluidized bed columns 20, 21, 22, the regulating valve 28
Although the classification liquid starts to flow from the attached outlet pipe 29 and the horizontal outlet 43, the adjusting valve 28 of the outlet pipe 29 and the horizontal outlet 43
The outflow amount of the classification liquid is suppressed by the flow rate control valve 42, and the classification liquid is overflowed from the horizontal opening 39 of the secondary classification tank 37. Since the horizontal opening 39 is provided at the same height as the upper end of the nozzle 41 of the primary classification tank 36, the liquid surface is kept at the same height as the upper end of the nozzle 41.

If the area of the horizontal opening 39 is small, the classification liquid overflowing will be concentrated in the horizontal opening 39, and a biased flow will be generated in the classification tank 35, which will focus on the horizontal opening 39. Although it has a bad influence on the recovery rate of the granular material, the horizontal opening 39 of the present invention is provided on the entire upper end of the tank wall 38 of the secondary classification tank 37, so that the above-mentioned effect is negligible.

In the nozzle 41, the raw material slurry and the classification liquid joined in the joining pipe 44 have uneven concentration and uneven flow velocity in a plane perpendicular to the flow, but when passing through the bent pipe 45. Because it bends at a right angle for four times and flows,
The concentration and flow velocity of the powder and granules are made uniform. Fluctuations in the slurry flow rate result in fluctuations in the amount of overflow from the horizontal opening 39, and
The liquid surface from 1 to the horizontal outflow port 43 is always formed by horizontal flow straightening.

The granules in the slurry settle in a two-dimensional motion due to the combination of the horizontal velocity and the sedimentation speed of the granules, and the granules having large grains are blocked by the partition plate 9 on the upstream side, and the partition wall is formed. After passing through the opening 2 of No. 3, it is collected by the hopper 14 on the upstream side. The small particles are blocked by the partition plate 10 on the downstream side, pass through the opening 2 of the partition wall 3, and pass through the hopper 15 on the downstream side.
To be collected by. Partitioning plate 10
After passing through, it descends and is collected in the most downstream hopper 16.

The classified liquid which passes through the rectifier 47 from the classified liquid inlet 23 and rises in the fluidized bed columns 20, 21, 22 is
Porous plate of the rectifier 47 (first dispersion plate 48 and second dispersion plate 5
By 0), the flow velocity in the cross section of the fluidized bed column 20, 21, 22 is made uniform and rectifies and rises. Therefore, the granular material collected in the hopper 14 flows into the fluidized bed column 20 via the feed pipe 17, passes through the porous plate and the sedimentation speed based on the particle size of the granular material. In view of the relationship with the classifying liquid velocity that is rectified and rises in the fluidized bed column 20, the group of powder particles according to the size of the particles is arranged in the vertical direction of the fluidized bed column 20.

Similarly, the particles collected in the hopper 15 are vertically arranged in the fluidized bed column 21 according to the size of the particles, and the particles collected in the hopper 16 are The particles are arranged vertically in the fluidized bed column 22 according to the size of the particles. Therefore, it is possible to classify and collect the powder or granular material of each size from each of the sampling tubes 31.

When the small-sized powder particles flow into the fluidized bed column 20, they are sent from the opening at the upper end of the fluidized bed column 20 to the hopper 15 via the bending tube 25, and then from the hopper 15 to the fluidized bed column 21. Sent. Further, when small-sized powder particles flow into the fluidized bed column 21, the bending tube 26, the hopper 1
When the fine powder particles are sent to the fluidized bed column 22 via 6 and flow into the fluidized bed column 22, the bent pipe 30
Although it is collected from the outlet pipe 29 via the flow path, if necessary, the rising flow velocity of the final fluidized bed column 22 can be adjusted to match the particle size range of the fine particle group flowing out from the horizontal flow outlet 43. it can.

In this embodiment, the number of fluidized bed columns (or the number of settling chambers) is three, but it is possible to increase the number to three or more, and one fluidized bed column has three collection tubes. Although 31 is provided, the number can be increased to 3 or more, and by increasing these, finer classification can be performed.

Table 1 shown below is an example of comparison between the wet classification device of the present invention and a conventional wet classification device. Saturated saline was used as the classification liquid, and commercially available salt having a mean particle size (50% diameter of lognormal probability distribution) of 407 μm and a deviation (84% diameter-50% diameter of lognormal probability distribution) of 121 μm was used as a powder sample. The feed rate of the raw material slurry was 400 liters / hr, the amount of classified liquid in the horizontal flow was 1.1 m ³ / hr, and the amount of classified liquid in the upward flow was 1.0 m ³ / hr, 0 in the order of the fluidized bed columns 20, 21, 22. .
From the stable state by setting the conditions of 8 m ³ / hr and 0.6 m ³ / hr, the raw material slurry was increased to 500 liters / hr, and the powder fluid was collected from the lower collection pipe 31 for each fluidized bed column. Gathered.

The weight in Table 1 is the ratio to the total amount of the powder or granules collected from each fluidized bed column.

[0037]

[Table 1]

The test shown in Table 1 was performed by the conventional apparatus, and the liquid level was increased by 5 mm due to the increase of the raw material slurry, and the flow velocity was decreased due to the widening of the cross-sectional area of the horizontal flow. On the other hand, in the test, the same nozzle as the conventional device was attached, and the horizontal opening 3
9, the liquid level is properly adjusted by increasing the overflow amount of the horizontal opening 39, so that the classification effect is increased as compared with the test of the conventional device, and the small particles are the third fluidized bed column. It has reached 22. Further, in the test, the nozzle of the present invention was attached to the test device, and the classification effect was further increased as compared with the test.

Table 2 shown below is an embodiment showing the rectifying effect of the first dispersion plate 48 and the second dispersion plate 50 of the rectifier 47. Water was used as the classification liquid to the fluidized bed column 20 at 2.0 m ³ /
It is the result of investigating the state of the ascending flow by mixing the red ink into the classification liquid while supplying the flow rate of hr to form the ascending flow, and by mounting the first dispersion plate 48 and the second dispersion plate 50. , The rectification effect is increasing.

[0040]

[Table 2]

[0041]

Since the present invention is constructed as described above, it has the following effects. (1) In the secondary classification tank, a horizontal opening with the same height as the upper end of the nozzle was provided in the entire tank wall on the opposite side of the partition wall, so a proper horizontal flow was maintained and the classification performance was improved. Further, it is not necessary to operate the adjusting valve as in the conventional example, and the human or power load and the facility load are reduced.

(2) Even when the concentration of the raw material slurry is high or the granular material also reduces the horizontal flow speed in accordance with the particle size, the slurry and the classification liquid can be separated by the nozzle in which the confluent pipe is connected to the bent pipe. Since it is uniformly mixed and rectified, the classification performance is improved. (3) Since the classification liquid in the fluidized bed column rectifies and rises, the powder and granules in the fluidized bed column are correctly gathered at the positions according to the size of the particles, and the classification performance is improved.

[Brief description of drawings]

FIG. 1 is a front view of a wet classification device.

FIG. 2 is a side view of FIG.

FIG. 3 is a plan view of FIG.

FIG. 4 is a front view of a rectifier.

FIG. 5 is a plan view of an essential part of a first dispersion plate.

FIG. 6 is a vertical cross-sectional view of a main part of a second dispersion plate.

FIG. 7 is a front view of a conventional wet classification device.

FIG. 8 is a side view of FIG. 7.

[Explanation of symbols]

 2 Openings 3 Partition walls 8 Horizontal flow guides 9, 10, Partition plates 11, 12, 13 Precipitation chambers 14, 15, 16 Hoppers 17, 18, 19 Inlet pipes 20, 21, 22 Fluidized bed columns 23 Classification liquid inlets 25, 26 , 30 Bending pipe 28 Adjusting valve 29 Outlet pipe 31 Sampling pipe 32 Opening / closing valve 35 Classification tank 36 Primary classification tank 37 Secondary classification tank 38 Tank wall 39 Horizontal opening 40 Gutter 41 Nozzle 42 Flow control valve 43 Horizontal outlet 44 Confluence pipe 44a Slurry inlet 44b Classification liquid inlet 45 Bending pipe line 46 Overflow liquid outlet 47 Rectifier 48 First dispersion plate 50 Second dispersion plate

Claims (2)

[Claims] 1. The inside of the classification tank is divided by a partition wall having an opening at the bottom, one of the partition walls serves as a primary classification tank, the other partition wall serves as a secondary classification tank, and the upstream end of the upper part of the primary classification tank is defined. A raw material slurry containing powder and granules and a confluent pipe for mixing a classifying liquid for adjusting the flow rate of a horizontal flow, and a nozzle connected to the confluent pipe and having a bent pipe line for fluid homogenization provided therein. A horizontal outlet with a flow control valve is provided at the downstream end of the upper part of the primary classification tank, and a partition plate lower than the height connecting the nozzle and the horizontal outlet between the nozzle and the horizontal outlet. A plurality of partitioned precipitation chambers are provided, and in the secondary classification tank, a horizontal opening having the same height as the upper end of the supply nozzle of the primary classification tank is provided on the entire tank wall surface opposite to the primary classification tank, A gutter for draining the overflow liquid is provided outside the horizontal opening, and at the downstream end of the lower part of the secondary classification tank. An outlet pipe with a regulating valve is provided, a plurality of hoppers are provided at the bottom thereof, one end of a feed pipe is connected to the lowermost end of each hopper, and the other end of the feed pipe is connected to a fluidized bed column, A rectifier interposing a porous plate is provided at the lower end of the fluidized bed column, a classification liquid inlet is provided at the lower end of the rectifier, and a downstream side of each hopper at the bottom of the secondary classification tank is provided at the upper end of the fluidized bed column. The wet classification device is characterized in that each fluidized bed column is provided with a plurality of collection tubes. 2. The porous plate comprises a first dispersion plate provided on the inlet side of the rectifier provided with holes of a fixed size and arrangement on the flat plate, and a first distribution plate made of tatami-woven wire mesh and provided on the outlet side of the rectifier. The wet classification device according to claim 1, wherein the wet classification device is constituted by two dispersion plates.