JPH1015430A - Wet classifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate the next decantation process by recovering particles as slurry or cake of high concentration. SOLUTION: In a wet classifier using sedimentation by gravity provided with an upright classifying cylinder 1, an inflow pipe 3 for causing classifying liquid to flow in which is fitted to the lower end of the classifying cylinder 1, and an outflow pipe 4 for causing classifying liquid to flow out fitted to the upper end of the classifier 1, to the upper part of the inner wall of the classifying cylinder 1, one end of conveying piping 5 for conveying particle slurry which has been classified is connected, and also to a position a little above the conveying piping 5, one end of returning pipe 6 is connected, and the other end of the conveying piping 5 and the other end of the returning piping 6 are connected to a recovery vessel 7 for recovering particle slurry, allowing a slurry circulating route to be formed by the conveying piping 5, the recovery vessel 7 and the returning piping 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for so-called wet classification in which solid particles are separated in a liquid by utilizing sedimentation caused by gravity, and more particularly to a wet classification in which the recovery operation is greatly reduced. Related to the device.

[0002] Specifically, it is a device for separating particles of qualitatively uniform but different sizes according to their size. For example, they are made of glass or synthetic resin and have a diameter of about several micrometers. It is used in the process of producing spherical beads precisely aligned with values. In addition, the beads classified in this manner are used as a gap control material for a liquid crystal display panel,
It is used as standard particles, analytical packing materials, diagnostic drug carriers, various labeling materials, and the like.

[0003]

2. Description of the Related Art Processes of wet classification include those using an upward flow, those using a horizontal flow, those using a simple stationary method, and the like. Things.

[0004] In addition, the method using the upward flow is based on a batch operation (one in which particles charged at a time are successively taken out) and a continuous operation (one in which continuously supplied particles are continuously taken out). It is roughly divided into cases.

FIG. 8 shows a basic form of a classifier using a rising flow and a batch operation.

That is, FIG. 8 shows that the classifying liquid inlet 62 is provided at the lower part of the classifying cylinder 61 and the slurry outlet 6 containing fine particles.
Reference numeral 3 denotes a structure in which a slurry supply port 64 is provided in the upper part of the classification cylinder 61 and a slurry supply port 64 is provided in the middle of the classification cylinder 61.

The slurry supplied from the supply port 64 is often denser than the slurry retained in the apparatus. Therefore, the supply port 64 is often provided near the upper end of the classification cylinder 61 in order to disperse the supplied slurry in the classification liquid in the classification cylinder 61 well.

Usually, a liquid having a lower density than the particles to be classified is used as the classification liquid. The particles to be classified are in the classification liquid and settle down by the action of gravity, and therefore move downward relative to the classification liquid, but the classification liquid continuously flows from the inlet 62 at the lower part of the classification cylinder 61. Since the liquid is supplied and moves upward in the classification cylinder 61, the rise of the classification liquid and the sedimentation of the particles are offset, and the slurry-like particles stay in the classification cylinder 61 for a relatively long time.

In this case, the sedimentation speed of the slurry-like particles supplied into the classification cylinder 61 depends on the particle size, and the coarser particles sediment faster. That is, in comparison with the ascent rate of the classification liquid, the components that settle faster (coarse particles) move downward, and the particles that do not settle (fine particles) move upward.

As a result, in the classification cylinder 61, a layer having a larger diameter is formed in a lower layer corresponding to the diameter of the particle. At this time, the layered structure is affected by the supply and discharge of the classification liquid. It is necessary that the structure is not disturbed.

As a device satisfying such requirements, for example, a classifier described in Japanese Patent Publication No. 54-20028 (hereinafter referred to as prior art 1), a classifier disclosed in Japanese Patent Publication No. 59-292, and the like.
No. 99 gazette (this is described in Related Art 2
There is).

[0012] The classification device of the prior art 1 has a lower part of the main body,
A plate-like member having a large number of small-diameter holes is mounted, and a block having a plurality of vertical through-holes whose total opening area is smaller than the flow path cross-sectional area of the main body is provided below the member. A plate-shaped member having a large number of small-diameter holes is attached to the lower portion, and further, in each vertical through-hole portion of the block,
It has a structure in which a support member having a particle size slightly larger than the hole provided in the plate-like member is housed in a flowable manner.

In the classification device of the prior art 2, a plurality of lattice tubes are mounted in the classification tube in the longitudinal direction of the classification tube at intervals, and a wall between the vertically adjacent lattice tubes (the classification tube). (Wall surface) is provided with a resin outlet.

[0014]

By the way, if the flow rate of the classification liquid is gradually increased, the layered structure rises as a whole and flows out of the slurry 63 from the upper part in order, and is condensed to collect particles. It is possible.

However, in the classification cylinder 61, since the particles move upward while settling, there is a speed difference from the surrounding classification liquid. Therefore, what flows out of the outlet 63 is that a small part of the particles that have flowed out due to the gentle upward movement has been diluted into a large amount of supernatant generated in the classification cylinder 61.

[0016] For this reason, the decantation step of recovering only the particles from the dilute particle slurry flowing out in a large amount involves handling a large amount of liquid, and the recovery operation involves heavy labor.

The present invention has been conceived to solve such a problem, and its purpose is to recover the particles as a more concentrated slurry or cake, thereby eliminating the need for a subsequent decantation step. To provide a wet classification device.

[0018]

According to a first aspect of the present invention, there is provided a wet classification apparatus comprising: an upright cylindrical classification cylinder; and a classification liquid provided at a lower end of the classification cylinder. In a wet classification device using sedimentation by gravity, provided with an inflow means for inflow, and an outflow means for outflow of a classification liquid provided at the upper end of the classification cylinder, the classified particles are provided on the upper inner wall of the classification cylinder. One end of a discharge pipe for discharging the slurry is connected, and one end of a transport pipe is connected to a position slightly above the discharge pipe, and the other end of the discharge pipe and the other end of the transport pipe collect the particle slurry. By being connected to the collection container, a circulation path of the slurry is formed by the discharge pipe, the collection container, and the forwarding pipe.

The wet classification device according to a second aspect of the present invention is the wet classification device according to the first aspect, wherein the carry-out pipe and the forwarding pipe are inclined obliquely downward toward the collection container. This inclination angle is set to an angle exceeding the angle of repose of the particles to be classified in the classification liquid.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows the basic structure of the wet classification device of the present invention.

That is, an inverted conical end plate portion 2 is formed continuously from the lower end side opening edge 1a of the classifying cylinder 1 which stands upright.
A classification liquid inflow pipe 3 provided with an inflow means 3c is provided on the bottom 2a of the end plate portion 2, and an outflow pipe 4 is provided on the upper end 1b side of the classification cylinder 1. Further, a mixing section 10 for mixing the classification liquid and the granular material is provided inside the classification cylinder 1 and above the inflow pipe 3.

FIG. 1 to FIG. 3 show an embodiment of a wet classifier according to the present invention.

In the wet classification apparatus of the present invention, in the wet classification apparatus shown in FIG. 1, one end of a discharge pipe 5 for discharging the classified particle slurry is connected to the upper part of the inner wall of the classification cylinder 1 and this discharge is performed. On the inner wall slightly above the pipe 5,
One end of the forwarding pipe 6 is connected. The other end of the unloading pipe 5 and the other end of the forwarding pipe 6 are connected to a collection container 7 for collecting the particle slurry via opening and closing valves 51 and 61, respectively. That is, a circulation path of the slurry is formed by the unloading pipe 5, the collection container 7, and the forwarding pipe 6.

The unloading pipe 5 and the forwarding pipe 6 are inclined obliquely downward from the wall surface of the classifying cylinder 1, bent in the middle of the pipe, and the tip is directed vertically, and then connected to the collection container 7. At this time, if the inclination angle θ2 of the carry-out pipe 5 and the forwarding pipe 6 is small, the inside of the pipe is clogged due to sedimentation of the particles.

The other ends of the discharge pipe 5 and the feed pipe 6 are connected to the bottom surface 7c of a recess 7b formed in the lid 7a of the collection container 7, and the tip 5a of the discharge pipe 5
Is inserted through the bottom surface 7c to a slightly lower position. Further, the distal end portion 6a of the forwarding pipe 6 is connected to the opening of the bottom surface 7c. That is, inside the collection container 7, the tip 5 a of the unloading pipe 5 is provided so as to open at a position higher than the tip 6 a of the forwarding pipe 6.

The classification liquid is an inorganic or organic liquid, specifically, water, n-pentane, n-hexane, acetone,
It is selected from liquids such as ethyl acetate, methanol, tetrahydrofuran, toluene, silicone oil, and aqueous solution of polyethylene oxide monoether, mainly from the viewpoint of the sedimentation speed when the powder is dispersed and the dispersibility.

From the viewpoint of the sedimentation velocity, a liquid which is low in both density and viscosity and which can rapidly sediment the granules is desired.

Further, from the viewpoint of dispersibility, it is necessary that the classification liquid sufficiently wets the surface of the powdery granules. In actual selection, consideration must be given to satisfy such requirements, and it is also possible to use a surfactant or the like for improving dispersibility.

In addition, it is also a necessary condition that the classification liquid does not dissolve the powder or swell significantly.

Next, more specific shapes, structures, and dimensions of the wet classification device of the present invention will be described with reference to FIGS.

The inclination angle θ of the end plate 2 is set so as to be slightly larger than the angle of repose of the granular material in the classification liquid.

That is, since the end plate portion 2 is a portion that slides or rolls after a part of the granular material settles thereon, its inclination angle θ1 is larger than the angle of repose of the granular material in the classification liquid. There is a need to. However, when the inclination angle θ1 is extremely increased, the horizontal cross-sectional area becomes relatively small, so that the processing capacity is reduced. In addition, it is conceivable that the height of the apparatus is increased to the extent that the horizontal cross-sectional area is reduced, but in this case, even though the processing amount per batch is the same, the processing time is increased by the height of the apparatus. It will take.

Therefore, it is appropriate to minimize the above-mentioned problems by setting the inclination angle θ1 of the end plate portion 2 to be slightly larger than the angle of repose of the granular material in the classification liquid.

The height ratio k between the classifying cylinder 1 and the end plate 2 is k.
(= H ₁ / H ₂ ) is preferably about 1.0 to 5.0. If the value of k is larger than this range (k> 5.0),
When the time required for forming a layered structure described later increases, and when the value of k is smaller than this range (k <1.0), the ratio of the amount of particles that can be recovered after the layered structure is once formed to the total number of particles is reduced. In any case, it is not practically preferable.

Here, the charged amount per batch (actual volume)
Where V is the ratio of the charged amount V to the volume W of the classification device, and x is in the range of 5 to 50%, which is the most excellent in classification accuracy and efficiency. If x is smaller than this range (x <5%), the efficiency is remarkably reduced, and if x is larger than this range (x> 50%), troubles such as cake formation may occur.

The volume W of the classifier is

[0038]

[Number 1] W = V / x ≒ (1/8 ) (k + 1/3) (π · tanθ1) · D 1 3 is a ... (1), use this formula (1) of the relationship, described above from the various requirements and the necessary charge amount V, it is possible to obtain the design value of the inner diameter D ₁ of the cylindrical portion 1. The dimensions of the other parts, the D ₁
Can be determined based on the value of

In the present embodiment, the outflow pipe 4 has a horizontal end plate 5 connected to the upper end 1b of the classification tube 1, and a central opening 5a of the end plate 5 serving as an outflow port 4a.

The inner diameter D _{4 of the} outlet 4 a should not be too large, and is approximately 15% or less of the inner diameter D ₁ of the classification cylinder 1. If it exceeds this, the accuracy will deteriorate. Unless the outlet 4a is clogged, there is little problem due to being too thin.

FIG. 7 is an enlarged view showing a specific shape of the inflow port 3a of the inflow pipe 3.

When the inlet 3a has a simple shape, the diameter of the inlet 3a must be extremely small in order to prevent the backflow of the granular material. However, if the inflow port 3a is too small, there is a problem in that the inflow port 3a is easily blocked by the granular material and the passage of the flow path. Therefore, in order to solve such a problem, in the present embodiment, the bottom 2a of the end plate 2 is used.
The horizontal cross-sectional shape (inner diameter D ₂ ) of the inner wall of the connection portion 3b of the inflow port 3a connected to the
Is formed into a nozzle shape narrower than the horizontal cross-sectional shape (inner diameter D ₃ ) of the inner wall. This makes it possible to prevent backflow in the vicinity of the bottom 2a of the end plate 2.

Here, each inner diameter D ₂ , D ₃ ,
And the values of the nozzle tip width (height) H _3, the following condition (2), (3), is set to a value satisfying the expression (4).

[0044]

## EQU2 ## D_Two≦ 0.05 ・ Φ^1/3・ (Η ・ ρ)^1/9・ (X ・ g ・ ρΔ)^-2/9 ... (2) D_Three≧ 1.2D_Two ... (3) 0 ≦ H_Three≤0.5D_Two (4) where Φ: flux of inflow, η: viscosity of classified liquid, ρ: classified
Density of liquid, x: slurry concentration (volume in wet state
Rate; 0 to 1), g: gravitational acceleration, ρΔ: classification liquid and particles
(Lubricated state). However, these are MSK
Depends on unit. In addition, the expressions (2) to (4), particularly the expression (2)
Coefficient of silica beads of several micrometers
Underwater classification experiment (ρΔ = 1,200kg / m^Three, Device diameter
(Inner diameter) D ₁= 60-240mm)
ing.

It should be noted that the influx flux Φ is closely related to the sedimentation velocity of the particles and the order is defined.
The sedimentation rate v, the diameter of the device (inside diameter) and D _1,

[0046]

Φ = (π / 4) · v · D ₁ ² (5) is a condition for balancing.

The sedimentation velocity v is determined based on the infinite dilution sedimentation velocity v ₀ of the particle in question and is influenced by the complex effects of other particles. Is approximately expressed by the following equation.

[0048]

V = f · v ₀ (6) v ₀ = (g · ρΔ · d ² ) / (18 · η) (7) Equation (7) is the Stokes sedimentation velocity equation It is. It holds well when the Reynolds number for sedimentation does not exceed 2. In the same range, the concentration factor f is approximated by the following equations.

[0049]

F = ε− ^4.65 (ε ≧ 0.7) (8) f = 6 · (1−ε) / ε ³ (ε ≦ 0.7) (9) ε (= 1-x) is the porosity, and what is effective as the concentration x here is that in the vicinity of the outlet 4a of the upper end 1b of the classification cylinder 1 during operation. This is a value somewhat smaller than the charged concentration.

The simplest configuration of the mixing section 10 is based on a simple horizontal stirring blade. As a stirring blade in this case, a rod-shaped blade having a low stirring force and causing only the horizontal movement of the classification liquid is suitable.

FIG. 6 shows an example of a more preferable structure of the mixing section 10. That is, the whole is cylindrical, the inlet 11 is formed at the lower end, and the outlet 12 is formed at the upper end.
Is formed, and the stirring blade 13 is housed therein.

The inlet 11 of the mixing section 10 is located above the inlet 3a. The outlet 12 of the mixing section 10
Is most preferably provided at substantially the same height as the seam 1a between the classification tube 1 and the end plate portion 2.

As such a cylindrical mixing section 10,
Specifically, there are a case where the stirring blade 13 is forcibly driven by power and a case where a static mixer is used.
FIG. 7 illustrates the case of a static mixer.

In the case of a static mixer, an upflow can be obtained without the need for positive power, for example, on the same principle as that of a strong upflow in a chimney. In this case, in particular, the length of the mixing section 10 is preferably long as long as the inflow port 11 on the lower end side is not too close to the bottom 2a of the end plate section 2 and does not block the flow of the classification liquid. Is good. In addition, the shape and dimensions of the element become coarse,
It is not preferable that the number of repetitions is too small. Further, an umbrella 19 may be provided at the lower end of the mixing unit 10 to ensure that the upward flow passes through the static mixer.

The dimensional requirements of the static mixer are as follows from Bernoulli's theorem.

[0056]

[6] _{(π / 4) · D 6} 2 = k · (1 + N E · α E) · Φ / 2 · H 4 · x · ρΔ / ρ) 1/2 ··· (10) However, k ≧ 2 (desirably k ≧ 5), N _E : number of elements, α _E : pressure loss coefficient per element, Φ: minimum value of inflow of classified liquid.

As a static mixer, the whole is smoothly finished so that particles do not accumulate due to sedimentation, and the internal inclination angles are all larger than the angle of repose of the particles, that is, the element has no extreme twist. It is desirable that

Next, a description will be given of a classification method using the wet classification apparatus having the above-described configurations.

That is, if the classification liquid is continued to flow from the inflow pipe 3 at a constant flow rate that is not too high after the powder to be classified is charged into the apparatus as a slurry, a gentle layered structure is formed in the classification cylinder 1. The layered structure here means
Larger diameter particles mean lower, higher volume fractions and smaller particles have higher, lower volume fractions in an orderly arrangement.

Thereafter, when the slurry rises to a level at which the discharge pipe 5 in the classification cylinder 1 is opened, a part of the slurry flows into the discharge pipe 5. As described above, since the carry-out pipe 5 is inclined, the inflowing slurry flows toward the collection container 7 according to gravity. This flow then attracts the subsequent slurry, creating a strong flow.

The slurry that has entered the collection container 7 fills the interior of the collection container 7, but the sedimentation of the slurry causes the supernatant to accumulate at the top of the collection container 7, which enters the forwarding pipe 6. Since the density of the slurry entering the forwarding pipe 6 is lower than that of the slurry in the discharge pipe 5, an upward flow toward the classification cylinder 1 is created. As a result, the slurry having a low density rises in the forwarding pipe 6 and is returned into the classification cylinder 1.

Since the slurry returned to the classification cylinder 1 is diluted by the supernatant when it exits the collection container 7,
There is a steady concentration difference between the inside of the carry-out pipe 5 and the inside of the forwarding pipe 6, and this concentration difference is used as a starting force.
A circulating flow around the classifying cylinder 1-carry-out pipe 5-collection vessel 7-forwarding pipe 6-classifying cylinder 1 is continuously generated.

Therefore, inside the classification cylinder 1, the slurry located at a position higher than the opening of the discharge pipe 5 circulates along this circulation flow, and is finally collected in the collection container 7.

Next, the following experiment was conducted using the wet classification device of the present invention. [Embodiment] In accordance with FIGS.
₁ = 480 mm, D ₂ = 1.5 mm, D ₃ = 3 mm, D
₄ = 53 mm, D ₅ = 6 mm, H ₁ = 320 mm, H ₂
= 320 mm, H ₃ = 30 mm, H ₄ = 130 mm, H
₅ = 0.5 mm, H ₆ = 260 mm, θ1 = 53 °, θ
At 2 = 45 ° (minimum), the volume was 77.2 liters. The supply of the classification liquid was performed by a metering pump, and the number of elements of the static mixer used as the mixing unit 10 was 22. The inner diameter of the collection container 7 is 120 m.
m, the capacity is about 2.2 liters, the inner diameter of the discharge pipe 5 and the forwarding pipe 6 is about 5 mm, the minimum inclination angle is 45 °, and the discharge pipe 5
The drop between the opening on the classifying cylinder 1 side and the opening on the collection container 7 side was 280 mm. Further, the tip 6a of the forwarding pipe 6 does not protrude inward from the lid 7a of the collection container 7, and the tip 5a of the unloading pipe 5 is 3 mm away from the inner surface of the lid 7a.
It extended 0 mm below.

At room temperature, water (η = 1.0 × 1)
0 ^-3 Pas · sec, ρ = 1000 kg / m ³ ), and ρ = 1130 kg / m ³ (ρΔ = 130 kg /
m ³ ) of the thermosetting resin beads were classified. The particle size is d =
An average value of 9.9 μm, d = 8.2 μm to d = 1
A substantially normal distribution having a weight of 90% within 2.1 μm was used. The charged amount is apparently 19.3 liters (for the volume below the connection of the outlet pipe 5 of the classification cylinder 1, 25
%), And the actual volume was 13.5 liters.

The flow rate condition was consistently 30 ml / min, but first the formation of the layered structure was waited for 14 days. During this period, once a day, the collection container 7 was replaced with an empty one. 1
After the fourth day, once every 12 hours, 2 ml each time, 1
The flow was increased to 70 ml / min over 0 days and the sample was collected. Sampling was performed once every 12 hours (recovery container 7 was replaced with an empty one), and a sample for 20 minutes was obtained.
Although a part of the sample was in the form of a slurry, the collection container 7 was obtained as a cake-like one that had accumulated at the bottom of the collection container 7 by being left overnight. The total amount (apparent volume) of the cake was 11.1 liter. The range of the average particle size of each sample is from 8.1 μm to 10.2 μm, and the CV value (coefficient of variation) indicating the distribution width of each fraction is 3.
Good values were obtained, ranging from 2% to 3.8%. However,
The definition of the CV value is

[0067]

[Mathematical formula-see original document] CV value = standard deviation of particle size / average value of particle size. The outflow from the outflow pipe 4 was hardly seen at all. [Comparative Example] The same operation as in the above embodiment was carried out except that the open / close valves 51 and 61 in the middle of the carry-out pipe 5 and the forwarding pipe 6 were closed, and the collection container 7 was not replaced.

As a result, the flow rate was set to 32 ml / min.
After the day, the particles flowed out of the outflow pipe 4 violently.

[0069]

According to the wet classification device of the present invention, one end of a discharge pipe for discharging the classified slurry is connected to the upper part of the inner wall of the classification tube, and one end of the feed pipe is located slightly above the discharge pipe. And the other end of the carry-out pipe and the other end of the feed pipe are connected to the collection vessel that collects the particle slurry, so that the slurry circulates through the carry-out pipe, the collection vessel, and the feed pipe, and sedimentation occurs in the process. The particles can be collected in the collection container. That is, conventionally, it was unnecessary to separate particles from a large amount of dilute slurry flowing out of the outflow pipe. However, in the wet classification device of the present invention, a high-concentration slurry or cake can be recovered in a relatively small recovery container. Therefore, the collection work is greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a wet classification device of the present invention.

FIG. 2 is a longitudinal sectional view of a simplified state of a lid portion of the collection container.

FIG. 3 is a partially enlarged cross-sectional view illustrating a connection structure between a cover of a collection container, a discharge pipe, and a forwarding pipe.

FIG. 4 is a diagram showing a basic configuration of a wet classification device of the present invention.

FIG. 5 is a schematic configuration diagram of a wet classification device of the present invention, which is displayed in a dimension.

FIG. 6 is a partially enlarged cross-sectional view showing a structure of a mixing unit.

FIG. 7 is a partially enlarged sectional view showing a specific shape of an inflow port of the wet classification device of the present invention.

FIG. 8 is a schematic configuration diagram showing a basic form of a classifier using a rising flow and a batch operation.

[Explanation of symbols]

 Reference Signs List 1 Classification cylinder 2 End plate 3 Inflow pipe 3a Inflow port 4 Outflow pipe 4a Outflow port 5 Outgoing pipe 5a Tip 6 Retransmission pipe 6a Tip 10 Mixing

Claims (2)

[Claims] 1. A classification cylinder having an upright cylindrical shape, an inflow means provided at a lower end of the classification cylinder for inflowing a classification liquid, and an outflow means provided at an upper end of the classification cylinder for flowing out the classification liquid. In a wet type classification device utilizing sedimentation caused by gravity, one end of a discharge pipe for discharging the classified particle slurry is connected to an upper portion of the inner wall of the classification cylinder, and a return pipe is disposed at a position slightly higher than the discharge pipe. Is connected, and the other end of the carry-out pipe and the other end of the feed pipe are connected to a collection vessel for collecting the particle slurry, thereby forming a slurry circulation path by the carry-out pipe, the collection vessel, and the feed pipe. Wet classifier characterized by being performed. 2. The discharge pipe and the transfer pipe are inclined obliquely downward toward the collection container, and the inclination angle is an angle exceeding a repose angle of the particles to be classified in the classification liquid. 2. The wet classification device according to 1.