JP2923436B2 - Classification method of suspended particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantitatively classifying suspended particles in a suspension based on the particle size related to the sedimentation speed of the particles, and more particularly, to a centrifugation method equipped with a rotary sedimentation tank. The present invention relates to a classification method in which a suspension is treated using a machine, and suspended particles having a specific particle size or more are settled in a rotary settling tank.
ADVANTAGE OF THE INVENTION According to the classification method of this invention, while being able to display the classification point of the suspended solid particles which settle and accumulate in a rotary sedimentation tank by Stokes diameter, the particle size distribution of the suspended solid particles in a suspension And the particle size distribution can be adjusted. Therefore, the present invention is useful in a wide range of industrial fields related to suspension processing.

[0002]

2. Description of the Related Art In a natural sedimentation method, a suspension is supplied to a sedimentation tank and allowed to stand to separate the suspension into a suspension (particles) and a suspension medium. In this case, the suspended particles can be classified according to the difference in sedimentation speed. However, in the natural sedimentation method, the processing speed is generally insufficient because the sedimentation speed of suspended particles is low. On the other hand, according to the centrifugal separation method, the suspension can be more efficiently separated into the suspended particles and the suspension medium because the acceleration of the rotational motion is used. Conventional centrifugation methods can be broadly classified into a centrifugal filtration method and a centrifugal sedimentation method. In the centrifugal filtration method, a suspension is supplied into a cylindrical, perforated wall rotating container provided with a filter medium on the peripheral wall, and the liquid is discharged through the filter medium by centrifugal force, and the suspended particles are deposited on the surface of the filter medium. Supplement in the form. In the centrifugal filtration method, classification can be performed by adjusting the opening degree of the filter medium. However, since clogging of the filter medium is inevitable, the cost of renewing the filter medium increases.

[0003] In the centrifugal sedimentation method, a suspension is supplied into a rotary sedimentation tank (bowl, non-porous wall basket) and rotated, and suspended particles are sedimented on the peripheral wall by centrifugal force. In the centrifugal sedimentation method, a rotary cylinder type (vertical type), a separation plate type, and a decanter type (horizontal type) centrifuge (centrifuge) are usually used. According to the centrifugal sedimentation method, not only can the sedimentation speed of the suspended solid particles be accelerated by the acceleration of the rotational movement, but also the sedimentation speed of the suspended solid particles can be increased by appropriately selecting the operation time and the magnitude of the angular velocity. And can be separated and collected according to the difference between them (fraction centrifugation). However, in fractionation centrifugation, it is difficult to perform high-precision fractionation, such as inevitable mixing of fine particles into coarse particles, and in fact, centrifuges
It is used mainly for the separation / collection or concentration of all suspended particles, or for the collection of clear liquid.

[0004] In the conventional centrifugal sedimentation method, it is difficult to set operating conditions because excessive or insufficient sedimentation of suspended particles greatly affects the properties and handling of the sediment. 2. Description of the Related Art Conventionally, in a rotary cylindrical type or decanter type centrifuge, the magnitude of centrifugal acceleration is taken up, and a centrifugal effect G is displayed as a parameter indicating how many times the centrifugal acceleration is a gravitational field. G = 0.00112 · r · n ² r: inner radius (m) of the widest point of the rotary sedimentation tank, n: number of revolutions (rpm) of the rotary sedimentation tank. The centrifugal effect on the maximum number of revolutions of the rotary sedimentation tank is a guide for selecting a centrifuge model. However, it is not possible to use the value of the centrifugal effect to make a quantitative design of the size of the sedimented suspended particles. Conventionally, for each type of centrifuge,
Attempts have been made to obtain sediment sediments that are easy to handle by selecting the centrifugal effect, liquid flow rate, residence time, etc. by trial and error, but all of these methods quantify the particle size related to the sedimentation speed of suspended solid particles. It does not control it. Moreover, the trial results can only be applied to a specific suspension to be treated, and cannot cope with fluctuations in the suspension and the type.

[0005] In a decanter type centrifuge (horizontal type centrifuge), when the rotation speed of the rotary sedimentation tank is increased or the treatment flow rate is decreased, the tendency of the particle size of the suspended solid particles flowing over to decrease tends to decrease. Are known. However, in the past, quantitative analysis of this tendency has not been performed, so that the characteristics are treated differently for each model or for each suspension to be treated. No proposal has been made for quantitative control of particle size. As described above, in the centrifugal sedimentation method of a suspension using a vertical or horizontal centrifuge, at present, the centrifuge is mainly used as a means for concentrating the suspension or a means for collecting fresh water,
It was considered unsuitable for use in quantitative classification of suspended particles, measurement of particle size distribution, adjustment of particle size distribution, and the like.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for quantitatively separating suspended particles in a suspension by using a centrifuge equipped with a rotary sedimentation tank based on the size of the sedimentation velocity. It is to provide a method for classification. Another object of the present invention is to provide a method for measuring the particle size distribution of suspended particles in a suspension using a centrifuge equipped with a rotary sedimentation tank, and the particle size distribution of the suspended particles in the suspension. It is to provide a method for adjusting. The inventor of the present invention has intensively studied to overcome the problems of the prior art, and as a result, the suspension to be treated is continuously supplied to a rotary sedimentation tank of a centrifuge and overflowed from the rotary sedimentation tank. By adjusting the flow rate of the overflowing suspension and the rotation speed of the rotary sedimentation tank according to a specific relational expression, suspended particles having a particle size equal to or larger than the desired particle diameter represented by the Stokes diameter are placed in the rotary sedimentation tank. I found that it could settle. In the present invention, a conventional vertical or horizontal centrifuge can be used as the centrifuge.However, the method of the present invention provides a quantitative classification, particle size Functions such as measurement of distribution and adjustment of particle size distribution are added. The present invention has been completed based on these findings.

[0007]

According to the present invention, a suspension to be treated is continuously supplied to a rotary sedimentation tank of a centrifugal machine, overflows the rotary sedimentation tank, and has the following general formula (1). The flow rate Q of the suspension flowing over and the number of revolutions n of the rotary sedimentation tank are adjusted, and the suspended solid particles having a sedimentation speed higher than the sedimentation velocity indicated by the particles having the Stokes diameter D or more are settled in the rotary sedimentation tank. Is provided. ^{D = k · r -3/2 · Q} 1/2 · n -1 (1) D: Stokes diameter of the suspended solids particles (μm) k: constant r: inner radius of the widest portion of the rotating sedimentation tank (m ) Q: Flow rate of the suspension flowing over the rotary settling tank (m ³ / H) n: Number of rotations of the rotary settling tank (rpm)

[0008] In one preferred embodiment of the present invention,
According to the following general formula (2), the flow rate Q of the suspension flowing over and the number of revolutions n of the rotary sedimentation tank are adjusted, and the suspended particles having a specific gravity of 2.60 and a sedimentation speed equal to or higher than the particles having a Stokes diameter of D or more are obtained. Is settled in a rotary settling tank. ^{D = 338 · r -3/2 · Q} 1/2 · n -1 (2) In formula (1), the case of k = 338 is the general formula (2).

Hereinafter, the present invention will be described in detail. General formula (1) The inventor of the present invention continuously supplies a suspension to be treated to a rotary sedimentation tank of a centrifuge and overflows the rotary sedimentation tank with an inner radius of r (m). When rotated at a rotation speed of n (rpm), the size of suspended particles that settles and accumulates on the side wall of the rotary sedimentation tank due to the action of acceleration, and exceeds the flow rate Q (m ³ / H) from the rotary sedimentation tank. As a result of earnest studies on the size of the suspended particles in the flowing suspension, the following findings were obtained. The particle size (classification point particle size) at the boundary of whether or not the suspended solid particles overflow the rotary sedimentation tank is determined by the rotational cross-sectional area S (πr
² ) It was found that the ratio was related to the ratio Q / GS of the value GS obtained by multiplying the centrifugal effect G to the flow rate Q of the suspension flowing from the rotary settling tank.

When a rotary sedimentation tank having an inner radius of rotation r is rotated at an angular velocity ω, a centripetal acceleration of rω ² acts on the center of the rotation axis, and suspended particles in a suspension in the rotary sedimentation tank include: Due to the centrifugal force of the reaction, the suspended solid particles settle on the side wall of the rotary settling tank. This centripetal acceleration is the gravitational acceleration g (= 9.
80 m / s ² ), which is rω ² / g times. This is called the centrifugal effect G. The rotation speed of the rotary sedimentation tank is n (r
pm), the angular velocity ω = 2πn / 60. Therefore, G is represented by the following equation (3). G = rω ² / g = r (2πn / 60) ² / g ∴G = 0.00112 · rn ² (3) Then, Q / GS is represented by the following equation (4). Q / GS = Q / (πr ² · 0.00112 · r · n ² ) ＧQ / GS = 285 · r ⁻³ · Q · n ^-2 (4) The Q / GS is a dimension of m / H ( Speed dimension),
Hereinafter, this is referred to as a classification effect.

[0011] The size of the settling suspended particles and the sedimentation speed thereof are affected by the shape of the particles. However, even in a centrifugal machine equipped with a rotary sedimentation tank, the suspended particles are practically formed into spherical particles. The assumed Stokes sedimentation velocity equation (5) can be applied. v = (1/18) · μ ⁻¹ · (ρ _s −ρ) · g · D ² (5) v: sedimentation velocity of suspended particles (m / H) μ: viscosity of suspension medium ρ _s : Specific gravity of suspended particles ρ: Specific gravity of suspension medium g: Gravitational acceleration D: Stokes diameter of suspended particles (μm)

Q / GS (dimension: m) in equation (4) of the classification effect
/ H) is the value of v (dimension: m / H) in the sedimentation velocity equation (5).
, Whereby the particle size (classification point size) at the boundary of whether the suspended particles overflow the rotary settling tank or not
Can be expressed as a function of r, Q and n.
That is, it is as follows. (1/18) · μ ⁻¹ · (ρ _s −ρ) · g · D ² = 285 · r ⁻³ · Q · n ^-2 D ² = 285 · r ^-3 · Q · n ^-2 · 18 · μ · (ρ _s −ρ) ⁻¹ · g ⁻¹ = 285 · 18 · μ · (ρ _s −ρ) ⁻¹ · g ⁻¹ · r ⁻³ · Q · n ^-2 where k ² = 285 · 18 · μ · (ρ _s -ρ) ^-1 · g ^-1 (6) The above equation becomes D ² = k ² · r ^-3 · Q · n ^-2 . (1) is obtained.

[0013] ^{D = k · r -3/2 · Q} 1/2 · n -1 (1)

The suspension to be treated is continuously supplied to a rotary sedimentation tank of a centrifuge and overflowed from the rotary sedimentation tank, and the flow rate Q of the overflowing suspension and the rotation speed n of the rotary sedimentation tank are adjusted. When adjusted according to the general formula (1), suspended particles having a particle size D or more corresponding to the Stokes diameter D can be settled in the rotary settling tank. That is, suspended solid particles having a sedimentation velocity equal to or higher than the particles having a Stokes diameter D or more can be sedimented in the rotary sedimentation tank. The particle size D in this case is called a classification point particle size. The general formula (1) quantitatively classifies the suspension according to the particle size using a centrifuge equipped with a rotary sedimentation tank.
What is useful for measuring the particle size distribution and adjusting the particle size distribution is specifically shown in Examples and the drawings.

In the general formula (1), k is a constant. This k can be calculated from Equation (6) if the difference (ρ _s −ρ) between the medium viscosity μ and the specific gravity is known. A practical method for obtaining k is as follows. From the sedimentation velocity equations (5) and (6), the following equation (7) is obtained. v = (285 / k ² ) · D ² (7) An aqueous suspension having a specific concentration of particles having a specific gravity and a specific particle size is prepared, and the sedimentation velocity is determined experimentally at a specific temperature. Inserting into equation (7) gives 285 / k ² ,
Therefore, the k value can be calculated.

Stone flour is the most commonly occurring particle in nature. The specific gravity of the stone powder was 2.60. The stone powder was sieved and classified to collect particles having a size of 100 μm or less to prepare a 1% suspension. This suspension was filled in a test tube having a length of 15 cm, and the sedimentation speed of the particles was observed with a differential microscope in water at 14 ° C. The fastest settling particles are 7 cm in 10 seconds
(= 25 m / H). The particle diameter of the fastest settling particles was considered to be 100 μm, and these values were substituted into equation (7). 25 = (285 / k ² ) · 100 ² ∴285 / k ² = 0.0025

Therefore, the suspension to be treated has a specific gravity of 2.6.
In the case of an aqueous suspension containing 0 suspended particles, the Stokes sedimentation velocity equation can be expressed by the following equation (8). v = 0.0025D ² (8) Also, k ² = 285 ÷ 0.0025 = 1114 000∴k = 338. Therefore, when k = 338, the general formula (1)
Is represented by the following general formula (2). ^{D = 338 · r -3/2 · Q} 1/2 · n -1 (2)

This general formula (2) is applicable not only to an aqueous suspension containing only suspended particles having a specific gravity of 2.60,
Practically, the present invention can be applied to a case where various suspensions in which suspended particles having various specific gravities are mixed are targeted. Various types of suspensions rarely contain suspension particles having a single specific gravity, and often contain many types of suspension particles having different specific gravities. As a suspension medium, an organic solvent other than water, a mixed solution of water and an organic solvent, or the like may be used. In some cases, the specific gravity of the suspended particles contained in the suspension to be treated is unknown. However, in practice, the application of the general formula (2) is often sufficient for many suspensions to be treated, whereby the suspended particles having a sedimentation velocity equal to or greater than the sedimentation velocity indicated by the particles having the Stokes diameter D or more are obtained. It can be settled in a rotary settling tank. Of course, the specific gravity of the suspended particles is 2.60.
If the difference is very large or small, or if the specific gravity difference between the suspended particles and the suspension medium is very large,
If the respective k values are obtained, and a general expression having a new constant is derived from the general expression (1) and applied, more accurate classification processing can be performed.

Centrifuge equipped with a rotary sedimentation tank The centrifuge equipped with a rotary sedimentation tank used in the present invention includes:
Conventional vertical centrifuges and horizontal centrifuges can be used. The inner radius of the widest part of the rotary sedimentation tank is not particularly limited, but is usually 0.05 m (100 mmφ) to 0.1 mm.
Those up to 6 m (1200 mmφ) can be used.

Suspension The suspension to be treated in the present invention is not particularly limited.
The suspension (suspension particles) may be inorganic, organic, natural, or artificially synthesized. As for the suspension medium, a suspension using various liquid media such as water can be treated. Specific examples of the suspension include a suspension containing various mineral particles, a suspension of a yeast or a microorganism (a culture solution or a fermentation solution), sludge, a chemical reaction solution, and the like. As the chemical reaction liquid, for example, there is a suspension (for example, a suspension of pigment particles) obtained by adding an alkali to an acidic aqueous solution of a metal to precipitate metal hydroxide or oxide particles. In addition, the method of the present invention enables selective collection of particles grown to a desired size, for example, treatment of a suspension in a step of recovering magnesium hydroxide by reacting lime with seawater. Suitable for.

The method of the present invention is suitable for collecting deliquescent crystals and crystals that are easily decomposed by a change in temperature. In a method of separating a crystal by filtering a suspension containing such a crystal,
Even when the medium solution is removed and the crystals are decomposed, the method of the present invention does not remove the medium solution in the voids of the crystals, so that the chemical equilibrium is maintained and the crystals that do not decompose can be classified and separated. In addition, the method of the present invention is suitable for separating and collecting crystals, complex salts, double salts, and the like that are to be separated by a slight difference in chemical equilibrium. Therefore, it is suitable for collecting rare resources, particularly rare earth compounds.

With respect to the temperature of the suspension to be treated, water can be applied in the range of 0 to 100 ° C. But,
As the liquid temperature approaches 100 ° C., bubbles due to gasification (boiling) are likely to occur, and accurate classification is hindered.
It is preferable to maintain the temperature at 50 ° C. or lower. Further, since a change in the liquid temperature during the process causes convection, it is preferable to keep the temperature constant. The concentration of the suspension is not particularly limited, but when the suspension particles are classified according to the particle size, the lower the concentration, the better. The concentration of the suspension is usually
It is about 0.1 to 75% by weight. When treating a suspension having a low concentration of 5% by weight or less, it is preferable that the suspended particles are entangled by chemical adjustment to facilitate sedimentation.

As the suspending medium, any organic solvent other than water can be used as long as it can be expressed by the Stokes sedimentation system. Further, the suspension medium may be a mixture of water and an organic solvent. However, if the suspending medium is a flammable organic solvent, use an explosion-proof device. If the specific gravity of the suspended particles is smaller than the suspension medium, the suspended particles will float. In this case, if the sedimentation is replaced by levitation, the same can be applied. For example, a suspension of water and oil can be classified and collected according to the size of the dispersed particles of oil. When the suspended particles are organic polymers, high-performance particles can be collected by classification and collection according to the particle size. Thus, the method of the present invention comprises:
It is suitable for classifying a suspension polymerization solution containing an ion exchange resin, adhesive particles, printing material particles and the like.

The present invention is applicable to all fluids to which the Stokes sedimentation method can be applied. First, the present invention can be applied to a method for purifying mineral oils, animal and vegetable oils, and synthetic oils by removing suspended matter. In the refining of cooling oil and machine oil in the polishing step, the refining conditions can be optimally designed according to the characteristics of various suspended solids. In the separation of a suspension of water and oil, for example, in the purification of crude oil, the removal of water accumulated at the bottom of a product oil tank, and the recovery of oil spilled into the ocean, sedimentation and separation conditions can be quickly and optimally designed. Among suspensions, aqueous suspensions have a particularly wide application range. The suspended particles may be inorganic, organic, natural, or artificially synthesized. The size of the suspended particles, expressed as a Stoke diameter, can cover a wide range from clay fine particles of 2 μm or less to sand of 2 mm.

The method of the present invention is used for removing fine particles from coarse particles and fine particles to obtain purified particles having high fluidity, and conversely, for removing coarse particles contained in fine particles and clay particles. Are suitable. For example, when fine particles of clay such as kaolinite and pyrophyllite are peptized on the alkali side and then classified, the removal of particles not peptized on the alkali side becomes more complete. According to the method of the present invention, accurate classification can be performed in a factory where temperature and the like can be controlled without requiring elutriation equipment that requires a vast site. The suspension medium of the suspension to be treated in the present invention is usually water, but as a means for adjusting the specific gravity of the suspension medium to be small, isopropyl alcohol or the like is added or the specific gravity of the suspension medium is adjusted to be large. As a means, it is possible to classify several millimeters of particles by using seawater or adding clay fine particles such as kaolin and bentonite.

Classification Method In the classification method of the present invention, the suspension to be treated is continuously supplied to a rotary sedimentation tank of a centrifuge and overflowed from the rotary sedimentation tank. By adjusting the flow rate Q of the suspension and the rotation speed n of the rotary sedimentation tank, the suspended particles having a sedimentation speed higher than the sedimentation velocity of particles having a Stokes diameter D or more are settled in the rotary sedimentation tank. When the classification treatment is performed with variously changing the particle size corresponding to the Stokes diameter, the particle size distribution of the suspended particles in the suspension to be treated can be measured. The overflowing suspension contains suspended particles having a particle size smaller than the classification point particle size D. Therefore, it is possible to prepare a purified suspension from which suspended particles having a desired particle size or more are removed.

The suspension to be treated can be directly supplied to a rotary settling tank of a centrifuge. However, if the residence time of the suspension to be treated in the rotary sedimentation tank is insufficient, coarse particles having a particle size equal to or larger than the classification point may be mixed in the overflow.
Further, if the suspension having the increased viscosity due to the entanglement of the suspended particles is directly processed, the accuracy of the classification point particle size may be impaired. Therefore, as the suspension to be treated, a suspension previously stirred in a specific settling tank is used,
It is preferable that the overflow from the rotary settling tank of the centrifuge is returned to the settling tank so that coarse particles are completely captured.

More specifically, a settling tank for introducing a suspension and separating the suspension into a heavy liquid having a high concentration of suspended matter and a light liquid having a low concentration of suspended matter, A heavy liquid is collected by a pump means from a central part of the bottom of the settling tank in which a swirling flow that does not cause a short-circuit flow from the liquid level to the bottom of the tank in the tank is generated and maintained, and the heavy liquid is processed. As the suspension, a method of continuously supplying the suspension to a rotary sedimentation tank of a centrifuge can be used.
In this case, the heavy liquid collected by the pump means is branched into an upper circuit and a lower circuit, and the heavy liquid branched into the upper circuit is returned to the bottom of the settling tank, and the heavy liquid branched into the lower circuit. Is preferably continuously supplied to a rotary sedimentation tank of a centrifuge as a suspension to be treated. Further, it is preferable that the suspension flowing over the rotary settling tank is returned to the settling tank.
The sedimentation treatment tank and treatment method that can be used for such purposes include a suspension separation device (JP-A-4-346803) and a suspension separation / classification device (JP-A-5-468) proposed by the present inventors. No. 184815), and a method and a device for separating and separating a suspension (JP-A-6-55007).

<Basic Unit> FIG. 1 shows an example of a basic unit using the above settling tank in combination. The basic unit shown in FIG. 1 is constituted by a combination of a rotary sedimentation tank (vertical centrifuge) 10 rotated by a conductor M and a sedimentation treatment tank 3 in which the tank itself does not rotate but the contents liquid swirls. . The suspension 1 is introduced into a settling tank 3 through an injection pipe 2. The suspension is pumped up from the center of the bottom of the settling tank 3 by a pump means (submersible pump) 4, and the suspension is guided into a rotary settling tank 10 through a vertically raised conduit 5. In this case, the vertically raised conduit 5 is bent in the horizontal direction from the middle, the tip is branched up and down 6, and the suspension branched into the upward circuit (return circuit) 8 is placed on the bottom of the settling tank 3. It is preferable that the suspension is refluxed and blown out from the outlet 9 into a cylindrical settling tank to drive the swirling flow, while the suspension is injected from the downward circuit (injection port) 7 into the rotary settling tank 10.

In the settling tank 3, the suspension is separated into a heavy liquid having a high concentration of suspended matter and a light liquid having a low concentration of suspended matter. The heavy liquid is collected at the bottom of the settling tank 3, and the suspended particles are collected at the center of the bottom by centripetal force due to the swirling flow. The swirling flow is adjusted so that a short-circuit flow from the liquid level of the settling tank to the bottom does not occur. On the side wall of the rotary settling tank 10,
Large and heavy suspended particles settle 11 while small and light particles flow over the side wall weir together with the suspension. The flow rate of the overflowing suspension is measured by the flow meter F1. The overflowed suspension is transferred from the overflow trough 12 through the conduit 13 to the settling tank 3.
And preferably blown out in the tangential direction of the settling tank. According to this method, the residence time of the suspension to be treated in the rotary sedimentation tank is short, so that particles having a particle size equal to or higher than the classification point that have overflowed without sedimentation are repeatedly treated several times, and are surely sedimented and captured. You.

In FIG. 1, from the upper part of the settling tank, the light liquid is collected as a purified suspension from the collection port 17 through the overflow gutter 16. Further, the flow rate of each suspension branched from the branch point 6 is adjusted by the flow control valves 14 and 15. The rotational speed n of the rotary sedimentation tank is measured by the rotational measuring machine SI,
The flow rate Q of the suspension flowing over is measured by the flow rate measuring device F1, and the classification point particle size is controlled using the measured data. By the way, when the suspension is fluidized, the entanglement between the suspended particles is usually released and the viscosity is reduced. The suspension is treated in a settling tank that keeps the swirling flow in the horizontal plane from mixing up and down, and its viscosity is reduced before it is supplied to the rotary settling tank. Classification can be performed more accurately than when supplied. When the suspension flowing over the rotary sedimentation tank of the centrifuge is returned to the original sedimentation treatment tank that maintained the swirling flow, and the circulation treatment is repeated,
Due to the capacity of the rotary sedimentation tank, coarse particles having a particle size equal to or larger than the classification point and leaking during overflow due to insufficient residence time can be reliably captured in the rotary sedimentation tank.

In the settling tank, the suspension is swirled in a plane limited to the bottom, and the swirling flow is short-circuited and does not mix up and down. The suspension is swirled in a fluid state, and the gravitational field acts, so that the centripetal force and the gravity work to cause the sedimentation of the suspended particles and the concentration of the suspension at the center of the bottom of the settling tank. . In the settling tank, the suspension is kept in a fluidized state, so that the viscosity of the suspension is reduced, the interaction between the suspended particles is reduced, and each particle tends to behave independently.

<Classification System> The classification method of the present invention can be performed by combining a plurality of sedimentation tanks and a plurality of centrifuges. FIG. 2 shows a specific example of such a classification system. In the mixing tank (1) at the upper left of FIG.
1) is mixed to prepare a suspension. At this time, the recovery medium liquid (12) may be mixed. The suspension prepared in the mixing tank (1) is introduced into the reaction tank (2). This reaction tank is a settling tank in which a swirl flow limited to the bottom portion is generated and maintained. In the reaction tank (2), the suspension is chemically adjusted, for example, by supplying oxygen from the gas bottle (10) to oxidize the suspended particles. In the reaction tank (2), a heterogeneous chemical reaction that forms a complex phase of gas, liquid, and solid can be performed.

The suspension (heavy liquid) pumped by the pump means from the bottom of the reaction tank (2) is branched into an upper circuit and a lower circuit, and the suspension in the lower circuit is supplied to the reaction tank (2). The liquid is refluxed at the bottom of 2) to generate a swirling flow, and the suspension in the upward circuit is introduced into the next classification tank (3). In the classification tank (3), coarse particles in the suspension are settled
Concentrate and store. The concentrated and stored coarse particle suspension is guided to a vertical centrifuge (8) or (9). In a vertical centrifuge, the number of revolutions of the rotary sedimentation tank and the flow rate of the overflowing suspension are adjusted according to the general formula (1) of the present invention, whereby the predetermined particle size that is accurately designed with the Stokes diameter is exceeded. Only the particles are classified and collected.

If a plurality of classifying tanks (3) are installed and connected in parallel sequentially by an overflow circuit or the like (not shown), classified suspensions having different particle diameters from the respective classifying tanks in the same manner as described above. Solid particles are collected. The water surface area of each classification tank is S (m ² )
When overflowing at a speed of Q (m ³ / H), the rising speed of the water surface in each classification tank is Q / S (m / H). This rise rate value is below the settling rate of the desired particle size, for example,
If it is 0.25 m / H or less, particles of 10 μm or more cannot be passed through the weir and are stored in the weir. The classification particle size is quantitatively designed based on the Stokes diameter, and the particle size in the range of 2 to 50 μm can be classified. Therefore, it is possible to design with a Stokes diameter from a small-scale test to a large-scale operation, and the same classification process can be performed.

The suspension flowing from the classification tank (3) is led to the concentration tank (4). This concentrating tank (4) is a settling tank in which a swirl flow limited to the bottom portion is generated and maintained. In the concentration tank (4), the fine particles in the suspension are settled, concentrated and stored. The suspension containing the concentrated fine particles is sent to a horizontal centrifuge (7) through a branch circuit, and only particles having a predetermined particle size or more are appropriately dehydrated and collected. The particles are
When the coagulant is added from the chemical liquid inlet (17), the particles become entangled with each other and apparently become large particles. Therefore, in the case of an aqueous medium, the dehydrated and collected liquid in the centrifuge (7) becomes clear water. The apparent size of the aggregated particles is represented by the Stokes diameter, and the operation of the centrifuge (7) is performed.

The overflow from the concentration tank (4) is led to the final storage tank (5). This storage tank (5) becomes a storage tank for the suspension medium liquid. A swirling flow is generated and maintained at the bottom so that even a small amount of particles does not settle and accumulate in the storage tank, and the liquid at the center of the bottom is returned to the previous stage. The above classification system is merely an example, and various modifications are possible.
If a plurality of basic units each including a centrifuge equipped with a rotary sedimentation tank and a sedimentation treatment tank are combined and used, it is possible to classify and collect suspended particles having a desired particle size from the suspension to be treated. . Therefore, such a classification system can be applied to a classification process of a suspension or a dry-pulverized powder generated in a chemical reaction process.

The flow rate of the suspension is usually measured by volume flow. Basically, the flow rate is measured using a volume measurement mass with a bypass circuit provided. As an automatic measuring device, an orifice flow meter, a float type flow meter, an electromagnetic flow meter, an ultrasonic flow meter, or the like can be used. The place where the flow rate of the suspension flowing from the rotary sedimentation tank is measured is preferably after the centrifuge, but may be provided before the centrifuge when the flow rate of the suspension flowing over is kept constant.

Calculation Method and Apparatus In the method of the present invention, when a specific centrifuge is used, the size of the rotary sedimentation tank is set to a constant (r = constant), and the value of the rotation speed n and / or the overflow Q Is used as a variable signal, and it is preferable to calculate based on the measured values so as to be able to display the classification point granularity, the separation effect, the classification effect, and the like. The calculation is performed by, for example, a manual calculation, a conversion table, a conversion graph, a numerical table, an analog calculator, a microcomputer, or the like. Accurately measuring the number of revolutions and the flow rate of the rotary sedimentation tank of the centrifuge, and recording and storing the information, the particle size of the classified sample can be accurately grasped. Operating conditions often fluctuate between their rise and stop times. The length of the fluctuating period is more important than the magnitude of the fluctuation, and the allowable range of the fluctuation should be determined based on the ratio of the fluctuating period to the entire operating period. Therefore, instantaneous measurement accuracy is not necessarily required.

From such a viewpoint, it is preferable to employ a measurement / navigation record (meter / logger) system. In addition to the measurement of flow rate and rotation speed related to particle size, many measurement / navigation records such as meteorological factors such as temperature and humidity, and water quality environmental factors such as pH, conductivity, turbidity, and dissolved oxygen concentration can be performed. For example, if it is stored on a floppy, it functions as an accurate work log. Since the transmission and duplication of the floppy can be freely performed, the examination and consideration of the operation result can be objectively performed on many occasions. Long-term storage of data and easy search and investigation, product quality control,
Useful for solving various problems at production sites.

[0041]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to only these examples.

[Example 1] The maximum rotation speed was 5000 rpm,
The classification point particle size was designed using a 100 mmφ (r = 0.05 m) rigid centrifuge. When using the above centrifuge,
The general formula (2) is expressed as follows. ^{D = 338 · 0.05 -3/2 · Q} 1/2 · n -1 D = the 30200 · Q ^1/2 · n ^-1 centrifuge speed n of the (rpm) horizontal axis, the flow rate Q (m
³ / H) are (g) 0.2, (h) 0.1, (i)
Stokes diameter D (μ) for 0.05 and (j) 0.02
The above equation was graphed using the calculation result of m) as the vertical axis (FIG. 3). FIG. 3 shows that the specific gravity of the suspended particles is 5.6.
Also in the case of 0 and 3.60, the relationship among n, Q and D was shown.

1 kg of stone powder by-produced during quarrying at a quarry is mixed with 19 kg of water to form a suspension having a concentration of 5% by weight of about 20%.
One liter was prepared and stored in a relay tank. This suspension was supplied to the rotary sedimentation tank of the vertical centrifuge at a constant rate of 0.2 m ³ / H, and the overflow was returned to the original relay tank for circulation treatment.
From the graph of FIG. 3 [straight line (g), specific gravity 2.60], the number of revolutions 660 rpm required for classification with a particle size of 20 μm was read, the number of revolutions n of the centrifuge was adjusted, and the apparatus was operated for 20 minutes. After terminating the supply of the suspension to be treated, in order to accelerate sedimentation, the number of revolutions was increased to 3000 rpm, and the system was operated for 5 minutes. The tap water was gently drained to obtain 23 g of sediment. As a result of observation with an optical microscope at a magnification of 100 times, the sediment was particles of 20 μm or more, and almost no fine particles of less than 20 μm were observed.

Similarly, the number of revolutions required for classification of a particle size of 10 μm was read from FIG. 3, and the same operation as above was carried out except that the number of revolutions of the centrifuge was adjusted to 1030 rpm to obtain 525 g of sedimentary sediment. Was. When observed with an electron microscope at a magnification of 1000 times, the sediment
Particles of 0 μm or more and fine particles of less than 10 μm were hardly observed. By the same operation, 145 g (670 g in total) of sedimentation sediment having a particle size of 10 μm or more was collected.

Similarly, the number of revolutions required for classification with a particle size of 5 μm was read at 2700 rpm, and the number of revolutions of the centrifuge was set to 2700 rpm.
Except that it was adjusted to rpm, operate in the same way as above,
230 g of sedimented sediment were obtained. As a result of observation with an electron microscope at a magnification of 1000 times, the sedimented sediment was about 5 μm to 10 μm.
Of the particles smaller than m, particles smaller than 5 μm were hardly observed. The remaining suspension was dried to obtain 70 g of particles. In this way, the suspended particles were classified into respective particle sizes and could be collected (cumulative 993 g). Therefore, information on the particle size distribution was obtained together with classification according to the particle size of the suspended particles.

[Second Embodiment] The maximum rotation speed is 6000 rpm,
The classification particle size was designed using a horizontal centrifuge having a diameter of 228 mmφ (r = 0.114 m). When the above-described centrifuge is used, the general formula (2) is expressed as follows. D = 338 · 0.114 ^-3/2 · Q rotational speed of ^{1/2 · n -1 = 8780 · Q} 1/2 · n -1 centrifuge n the (rpm) horizontal axis, the flow rate Q (m
³ / H) are (d) 2.0, (e) 1.0, (f)
The above equation was graphed with the vertical axis representing the calculation result of the Stokes diameter D (μm) in the case of 0.5, (g) 0.2, and (h) 0.1 (FIG. 4). FIG. 4 also shows the relationship among n, Q, and D when the specific gravity of the suspended particles is 5.60 and 3.60.

10 kg of stone powder was mixed with 190 kg of water to prepare 200 liters of a suspension having a concentration of 5% by weight and stored in a relay tank. At a flow rate of 2.0 m ³ / H, the number of rotations required to classify suspended particles having a particle size of 5 μm or more was read from FIG. 4 [straight line (d), specific gravity 2.60].
It was 00 rpm. 5 wt% concentration in the above horizontal centrifuge
Is supplied at a flow rate of 2.0 m ³ / H, and the number of rotations is 250.
The operation was performed at 0 rpm for 20 minutes. The overflowed suspension was returned to the relay tank and used for circulation. As a result of this experiment,
Although the overflow liquid contained 15% of particles having a size of 5 μm or more, the particles could be roughly classified as designed.

[Embodiment 3] Maximum rotation speed 16,000 rpm
m, a classifying particle size was designed using a vertical centrifuge having a diameter of 200 mmφ (r = 0.100 m). When the above-described centrifuge is used, the general formula (2) is expressed as follows. D = 338 · 0.10 ^-3/2 · Q rotational speed of ^{1/2 · n -1 = 10700 · Q} 1/2 · n -1 centrifuge n the (rpm) horizontal axis, the flow rate Q (m
³ / H) are (g) 0.2, (h) 0.1, (i)
The above equation was graphed using the calculation result of the Stokes diameter D (μm) in the case of 0.05 as the vertical axis (FIG. 5). In addition,
FIG. 5 also shows the relationship among n, Q, and D when the specific gravity of the suspended particles is 1.60.

A red organic pigment having a specific gravity of 1.60 was dispersed in deionized water to which a small amount of alcohol and a surfactant had been added by stirring with a stirrer. The suspension was used as a water-based paint. As a result, there was color unevenness, and when the coated article was wet with rain, the coating film swelled. The suspension of the red organic pigment is supplied to the above vertical centrifuge at a flow rate of 0.05 m ³ / H, and operated at a rotation speed of 10,000 for 20 minutes, and an overflow containing particles having a particle size of less than 0.4 μm is performed. The liquid was discarded. On the other hand, a paint was prepared using the cake settled and deposited in the rotary settling tank of the centrifuge. The coated product coated with this coating material had no color unevenness, exhibited a very favorable glossy appearance, and had a favorable feeling. Also. Even if the painted articles get wet in the rain, the swelling of the paint film does not occur, durability,
Rust prevention effect was improved.

[Embodiment 4] The maximum rotation speed is 3000 rpm,
The classification particle size was designed using a vertical centrifuge having a diameter of 658 mmφ (r = 0.329 m). When the above-described centrifuge is used, the general formula (2) is expressed as follows. ^{D = 338 · 0.329 -3/2 · Q} 1/2 · n -1 D = 1790 · Q -1/2 · n -1 speed n of the centrifuge (rpm) horizontal axis, the flow rate Q ( m
³ / H) are (a) 20.0, (b) 10.0,
(C) 5.0, (d) 2.0, (e) 1.0, (f)
The above equation was graphed with the vertical axis representing the calculation result of the Stokes diameter D (μm) in the case of 0.5, (g) 0.2, and (h) 0.1 (FIG. 6). FIG. 6 also shows the relationship among n, Q, and D when the specific gravity of the suspended particles is 3.60 and 5.60.

Called sericite, phlogopite and muscovite powder;
There is a clay mineral powder that exhibits pearl luster. Since clay used for ceramics contains sericite, the conditions for separating and collecting this from clay are shown. The clay containing sericite was dispersed in water to prepare a 5% by weight suspension. Although flaky mica particles are large in the plate direction, they are considered small particles because they float and hardly settle. First, in order to remove lump particles of mica that have not been loosened on a thin plate, the specific gravity is 2.60 and the particle size is 10 μm.
Operating conditions under which sedimentary particles of m or more were sedimented and collected were set, and the sedimented cake was discarded.

The overflow liquid obtained in the above treatment was subjected to a specific gravity of 2.6.
The conditions for sedimentation and collection of particles having a particle size of 2 μm or more at 0
When the mixture was treated with a vertical centrifuge at 00 rpm and at a flow rate of 2.0 m ³ / H, a cake of flaky particles excellent in silky luster could be collected. The overflow liquid obtained by this classification treatment is a cloudy liquid that does not settle as it is,
When adjusted to the following acidity, the clear water layer separated. When the clear water was separated, a coagulated cake of kaolinite-rich fine clay mineral particles having a particle size of less than 2 μm could be collected.

Embodiment 5 The maximum rotation speed is 3000 rpm,
A vertical centrifuge having a diameter of 658 mmφ (r = 0.329 m) and a settling tank shown in FIG. 1 were used in combination. An aqueous suspension containing 5% by weight of a stone powder having a specific gravity of 2.60 is supplied to the settling tank 3 shown in FIG.
From the outlet 9 to the bottom of the settling tank 3 in the tangential direction of the tank,
A swirl flow without short-circuit flow limited to the bottom part was generated and maintained. Then, the flow control valve 15 below the branch 6 is operated to flow 2.0 m ³ / flow from the downward circuit (inlet) 7.
At H, the suspension was supplied to the rotary sedimentation tank 10 of the vertical centrifuge. On the other hand, the rotary settling tank was rotated at 1200 rpm.
The overflow liquid from the rotary settling tank 10 was returned to the settling tank 3. When operated under the above conditions for 1 hour, the particle size was 2 μm.
1100 g of the above suspended particles were settled and deposited in the rotary settling tank. Observation of the particles collected with an electron microscope at a magnification of 1000 times revealed that particles having a particle size of less than 2 μm were hardly observed.

[0054]

According to the present invention, the following remarkable effects can be obtained. 1. According to the method of the present invention, it is possible to quantitatively design the classification point particle size related to the sedimentation velocity of particles, which cannot be achieved by the conventional method of adjusting the centrifugal effect (G = 0.00112 rn ² ). Moreover, the method of the present invention can be applied to any type of centrifuge and its size. 2. According to the method of the present invention, the particle size of the classification point can be quantitatively expressed by the Stokes diameter, so that the particle quality of the product is improved. Further, according to the method of the present invention, the particle size distribution of the product can be measured simultaneously with the classification. 3. According to the method of the present invention, particles having a desired classification point particle size can be collected by automatically controlling the flow rate and the rotation speed. Also, the particle size distribution of the suspension can be automatically adjusted. 4. The sediment whose particle size quality is quantitatively controlled is easy to scrape out and handle. 5. In the case of a horizontal centrifuge, although the sedimentation is disturbed by the scraping screw and the range of the particle size to be classified is widened, it is sufficiently practical. 6. In the case of a vertical centrifuge where scraping is batch operation,
It can be classified exactly as calculated and can be used for the classification of suspensions with a concentration of 0.1-75% by weight. 7. In a field where sieve or filtration separation is difficult, a new classification and purification method can be provided. 8. It can also be used in areas where conventional equipment and methods have been unprofitable, for example, in the treatment of low-grade resources or waste.

[Brief description of the drawings]

FIG. 1 is a flowchart of a basic unit which is one embodiment of a classification method of the present invention.

FIG. 2 is a flowchart of a classification processing system according to an embodiment of the present invention.

FIG. 3 is a graph showing a classification point particle size designed using a rigid centrifuge with an inner radius r = 0.05 m.

FIG. 4 is a graph showing a classification point particle size designed using a horizontal centrifuge having an inner radius r = 0.114.

FIG. 5 is a graph showing a classification point particle size designed using a rigid centrifuge with an inner radius r = 0.100 m.

FIG. 6 is a graph showing a classification point particle size designed using a rigid centrifuge with an inner radius r = 0.329 m.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suspension 2 Injection pipe 3 Sedimentation tank 4 Submersible pump 5 Pumping pipe 6 Upper and lower branches 7 Injection port to centrifuge (downward circuit) 8 Return circuit (upward circuit) 9 Swirling flow drive outlet 10 Centrifuge Rotary sedimentation tank of machine 11 Classified sediment 12 Overflow toy of rotary sedimentation tank 13 Circuit to return overflow 14 Flow control valve 15 Flow control valve 16 Overflow gutter from sedimentation tank 17 Purified suspension sampling port M Conductor F1 Flow meter SI rotation meter (1) Mixing tank (2) Reaction tank (3) Classification tank (4) Concentration tank (5) Storage tank (6) Circulation circuit (7) Horizontal centrifuge (8) Vertical Centrifuge (9) Vertical centrifuge for alternate operation (10) Gas bottle (11) Medium liquid (12) Reflux purified liquid (13) Powder (14) Purified suspension collection (15) Purified suspension collection (16) Purification suspension (Shimizu) collection

Claims (8)

(57) [Claims] 1. A suspension to be treated is continuously supplied to a rotary sedimentation tank of a centrifuge and overflowed from the rotary sedimentation tank, and a flow rate of the suspension flowing over according to the following general formula (1). A method for classifying suspended particles, wherein Q and the number of rotations n of the rotary sedimentation tank are adjusted to suspend sediment particles having a sedimentation speed equal to or higher than the sedimentation velocity of particles having a Stokes diameter of D or more in the rotary sedimentation tank. ^{D = k · r -3/2 · Q} 1/2 · n -1 (1) D: Stokes diameter of the suspended solids particles (μm) k: constant r: inner radius of the widest portion of the rotating sedimentation tank (m ) Q: Flow rate of the suspension flowing over the rotary settling tank (m ³ / H) n: Number of rotations of the rotary settling tank (rpm) 2. The sedimentation velocity of a particle having a specific gravity of 2.60 or more and a Stokes diameter D or more is adjusted according to the following general formula (2) by adjusting the flow rate Q of the overflowing suspension and the rotation speed n of the rotary sedimentation tank. The classification method according to claim 1, wherein the suspended particles are settled in a rotary settling tank. ^{D = 338 · r -3/2 · Q} 1/2 · n -1 (2) 3. A sedimentation treatment tank for introducing a suspension and separating the suspension into a heavy liquid having a high concentration of suspended matter and a light liquid having a low concentration of suspended matter. A heavy liquid is collected by a pump from the center of the bottom of the settling tank, which generates and maintains a swirling flow that does not cause a short-circuit flow from the liquid surface to the bottom of the suspension,
3. The classification method according to claim 1, wherein the heavy liquid is continuously supplied as a suspension to be treated to a rotary settling tank of a centrifuge. 4. The heavy liquid collected by the pump means is branched into an upper circuit and a lower circuit, and the heavy liquid branched into the upper circuit is returned to the bottom of the settling tank so as to have a driving force for turning. The classification method according to claim 3, wherein the heavy liquid branched to the downward circuit is continuously supplied as a suspension to be processed to a rotary sedimentation tank of a centrifuge. 5. The classification method according to claim 3 , wherein the suspension flowing over the rotary settling tank is refluxed to the settling tank. 6. A rotary sedimentation tank of a centrifuge and means for calculating and displaying the value of the Stokes diameter D (μm) of suspended particles according to the formula (1) or (2) according to claim 1 or 2. Equipment for classifying suspended particles. 7. The Stokes diameter D (μm) of the suspended solid particles according to the rotary settling tank of the centrifuge and the formula (1) or (2) according to claim 1 or 2 is set to a preset value. Then, the flow rate Q (m ³ / H) of the suspension flowing over the rotary settling tank
And / or means for controlling the number of revolutions n (rpm) of the rotary sedimentation tank. 8. A settling tank for introducing a suspension and separating the suspension into a heavy liquid having a high concentration of suspended matter and a light liquid having a low concentration of suspended matter, comprising: According to the equation derived from the relationship, the Stokes diameter D (μ
m) becomes a preset value, and the water surface area is S
An apparatus for classifying suspended particles, comprising means for controlling an overflow flow rate Q (m ³ / H) from the settling tank in the settling tank (m ² ). v = Q / S v = 0.0025D ² Q = 0.0025 D ² · S [where v is the maximum sedimentation velocity (m / H) of the suspended solid particles flowing from the sedimentation treatment tank, and This corresponds to the minimum settling velocity (m / H) of suspended particles retained in the tank. ]