JP2005125272A - Classifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for highly efficient classification by repeatedly circulating at least two kinds of powders different in separation efficiency in a separator such as a cyclone in a circulation fluidized layer. <P>SOLUTION: A classifier for a mixed sample comprising at least two kinds of the powders is provided with a flow-down pipe connected to the lower part of a separator, and the circulation fluidized layer is formed by connecting the flow-down pipe to the separator with a transfer pipe and further by connecting to the transfer pipe to an air blowing pipe. A powder recovery container is provided to the down stream side of an exhaust pipe installed at the upper part of the separator, and a sample charge opening is provided to the flow-down pipe. Therein, a powder with high separation efficiency is condensed in the flow-down pipe and a powder with low separation efficiency is condensed in the powder recovery container, thereby highly efficient classification can be realized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a classification apparatus for classifying two or more kinds of powders, and relates to a circulating fluidized bed type classification apparatus for classifying two or more kinds of mixed powders having different separation efficiencies for a separator such as a cyclone with high efficiency. .

In general, two or more types of powders are classified using a sieving method that uses different particle sizes, a gravity classification method that uses different sedimentation rates of solid particles, and an inertia classification that uses the difference in inertial force. There is a method such as a cyclone classification method using a centrifugal force instead of a gravity method, and a technique combining these alone or a plurality of them has been proposed and put into practical use. The cyclone classification method can easily create a sedimentation speed from several hundred times to several thousand times compared to the case of gravity by using centrifugal force, so the classification time can be greatly shortened and compared with other gravity classification methods. It has the advantage of being able to make the device compact and, above all, its simple structure, and is widely used. Usually, these classifiers only collect the separated ones by providing a collection bottle or the like.

In addition, solid-gas, solid-liquid, or gas-liquid-solid fluidized beds have been used for a long time as one of the solid handling techniques. Among them, the circulating fluidized bed handles a relatively large amount of fluid (mainly gas). Often used in systems. For example, devices such as coal combustion boilers and FCC catalytic reactors have been put into practical use and are widely used.
JP-A-6-142615 Japanese Patent Laid-Open No. 6-267938

  When there are a large number of powders to be classified, the sieving method is laborious and continuous operation is difficult. Considering increasing classification accuracy, there are limits to gravity classification and inertial classification. In the gravity classification method, the inertia classification method, or the cyclone classification method, separation may be difficult although the density is small but the particle size is large and the density is large but the particle size is small. In any classification method, the classification efficiency is fixed once designed.

  In the present invention, two or more kinds of powders are made to have different separation efficiencies for a separator such as a cyclone, and are circulated a plurality of times in the circulating fluidized bed, so that both high and low separation efficiency powders can be obtained. An object is to provide a classifying apparatus that performs separation with high efficiency.

The classifying device of the present invention connects a downcomer to the lower part of the separator and connects the downcomer and the separator with a transport pipe communicating with a blower to form a circulating fluidized bed, and an exhaust connected to the separator. In a classification apparatus for a mixed sample containing two or more kinds of powders, in which a powder recovery device is provided on the downstream side of the tube and a sample inlet is provided in the downcomer, the mixed sample is circulated a plurality of times in the circulating fluidized bed. Thus, the powder having a high separation efficiency among the powders having different separation efficiencies is concentrated in the downcomer.
In addition, the classifying device of the present invention puts the powder collected by the powder recovery device provided on the downstream side of the circulating fluidized bed again into the sample inlet, and circulates the circulating fluidized bed multiple times, thereby improving the separation efficiency. It is characterized by concentrating low powder with a powder collector.
The classifying device of the present invention is characterized in that a circulating fluidized bed is provided in multiple stages and a mixed sample containing three or more kinds of powders can be classified simultaneously.

The present invention has the following excellent effects.
(1) The powder separated by the separator is circulated a plurality of times in the circulating fluidized bed, thereby enabling highly efficient classification.
(2) In the gravity classification method, the inertia classification method or the cyclone classification method, separation is difficult although the density is small but the particle size is large and the particle size is large but the particle size is small, but according to the present invention, Classification is possible even for powders that have been considered difficult in the past. In other words, when the separation efficiency of the mixed powder to be classified is close to each other, the classification efficiency for the separator can be changed by changing the fluid. is there.
(3) By employing a circulating fluidized bed, continuous processing and large-scale processing can be performed.
(4) No special skill is required for classification operation.

  The best mode for carrying out the classification apparatus according to the present invention will be described below with reference to the drawings based on the embodiments.

FIG. 1 is a conceptual diagram of a circulating fluidized bed type classification apparatus according to an embodiment of the present invention.

Examples of the mixed sample containing two or more kinds of powders classified in the embodiment of the present invention include various types such as waste plastic dust containing valuable metals or mixed plastic made of different materials such as polyethylene terephthalate and polypropylene. is there.

In FIG. 1, a hopper 1 serving as a sample inlet is connected to the downcomer 2 via a chute 7 and a valve 8 so that a sample can be supplied to a downcomer (also referred to as a downcomer) 2.

The upper part of the downcomer 2 is connected to the lower part of the separator 5, and the powder separated by the separator is accommodated in the downcomer 2. For example, a cyclone centrifuge 5 is suitable as the separator 5.
The downcomer 2 and the cyclone centrifuge 5 are connected by a transport pipe (also referred to as a riser pipe) 3, and fluid is supplied to the vertical portion of the transport pipe 3 from below through a blower pipe 9 by a blower 4. A circulating fluidized bed is formed by the downcomer 2, the transporter 3 and the cyclone centrifuge 5. In order to transport the powder from the downcomer pipe to the horizontal portion of the transport pipe 3, the powder is transported by a pneumatic transport system or a mechanical transport system such as the screw feeder 11. Further, the upper end of the transport pipe 3 is connected toward the tangential direction of the cylindrical portion of the cyclone centrifuge 5.

An exhaust pipe 10 is connected and arranged upward from the center of the cyclone centrifuge 5, and a powder collector 6 is provided on the downstream side of the exhaust pipe 10. As the powder recovery unit 6, a known one such as a bag filter is used.

  A mixed sample 12 containing two or more kinds of powders to be classified is supplied from the hopper 1 to the downcomer 2. The mixed sample 12 in the downcomer 2 is transported to the vertical portion of the transport tube 3 by the screw feeder 11 and is transported upward by the fluid 13 from the blower 4 toward the tangential direction of the cylindrical portion of the cyclone centrifuge 5. Supplied at a constant rate. The powder separated by the cyclone centrifuge 5 returns to the downcomer 2 connected to the lower part thereof. The powder that has not been separated is conveyed to the fluid 13 and enters the recovery device 6 through the exhaust pipe 10, and is separated and recovered from the fluid by the filter of the recovery device 6 or the like. This apparatus is a circulating fluidized bed in which the mixed powder returns from the downcomer 2 to the downcomer 2 via the conveying tube 3 and the cyclone centrifuge 5.

Now, it is assumed that there is a sample in which two types of powder P1 having a separation efficiency of 0.9 for the cyclone centrifuge 5 and powder P2 having a separation efficiency of 0.1 are mixed in equal amounts. When the sample passes through the cyclone centrifuge 5 once, it is defined as one cycle, and when 10 cycles is a unit of continuous operation, the powder P1 having a separation efficiency of 0.9 in 10 cycles is almost 100%. Can be obtained in the downcomer 2 below the cyclone centrifuge 5 (see FIG. 2). Furthermore, if the continuous operation of 10 cycles is defined as one trial, the ratio of the powder P2 in the sample collected by the collection machine 6 at the end of one trial is about 60%. Only the mixed sample recovered by the recovery machine 6 is put into the hopper 1 again and a retry is performed. By repeating this, almost 100% of the powder P2 can be recovered after about 10 trials (see FIG. 3).
The above procedure is schematically shown in FIG. The present invention does not aim to improve the separation efficiency for a separator such as a cyclone, but the separation efficiency for the separator is made different for each powder to be classified and is circulated in a circulating fluidized bed. It is characterized by high-efficiency classification using the property that high things are concentrated in the layer.
In the case of the three mixed powders, in the first trial, the powder with the highest separation efficiency for the separator is circulated until it is concentrated in the downcomer. Medium and low-efficiency powders are concentrated in the collector, so that if they are handled again as binary mixed powders, the tertiary mixed powders can be classified into each. It is possible to classify various kinds of mixed powders by the same procedure.
The above procedure is for the case where a single-stage circulating fluidized bed is used. However, the operation can be made more efficient by using, for example, a multi-stage circulating fluidized bed as shown in FIG. At that time, depending on the separation efficiency, only the cyclone centrifuge 5 and the descending pipe 2 may be provided, and the circulation paths such as the transport pipe 3 and the screw feeder 11 may be omitted.

で表される。ここで、ηは分離効率、ρ_ｐは粒子密度、ρ_ｆは流体密度、ｄ_ｐは粒子径、ｕ_ｉはサイクロン入口流体速度、μは流体粘度、及びＤはサイクロン直径である。
この式（１）から、分離効率ηは、粒子密度と流体密度との差、粒子径及びサイクロン入口流体速度が大きい程、分離効率ηは大きく、反対に流体粘度及びサイクロン直径が大きい程、分離効率ηは小さくなることわかる。その際、粒子密度は１乗、粒子径は２乗で効くことがわかる。
Here, the cyclone centrifuge 5 will be supplementarily described.
The separation efficiency of the cyclone centrifuge 5 is

It is represented by Here, η is the separation efficiency, ρ _p is the particle density, ρ _f is the fluid density, d _p is the particle diameter, u _i is the cyclone inlet fluid velocity, μ is the fluid viscosity, and D is the cyclone diameter.
From this formula (1), the separation efficiency η indicates that the separation efficiency η increases as the difference between the particle density and the fluid density, the particle diameter and the cyclone inlet fluid velocity increases, and conversely, as the fluid viscosity and the cyclone diameter increase. It turns out that efficiency (eta) becomes small. It can be seen that the particle density is 1st power and the particle diameter is 2nd power.

FIG. 6 shows the relationship between the particle diameter d _p and the density difference (ρ _p −ρ _f ) using the separation efficiency η as a parameter. When the mixed powder to be classified has a large particle size and a small density, and a mixed powder having a small particle size and a large density, and the separation efficiency is almost the same, classification is difficult as it is. Therefore, consider changing the fluid side. For example, if the fluid is air and has the same separation efficiency, the density difference can be reduced by equal amounts by changing the fluid to water. Since the particle diameter d _p and the density difference (ρ _p −ρ _f ) are curves as shown in FIG. 6, if the density difference (ρ _p −ρ _f ) decreases by the same width, the larger the particle diameter, the larger the particle diameter. The separation efficiency decreases more significantly than the smaller one, and the separation efficiency of the two can be different. Accordingly, when separation is difficult, the separation efficiency for the cyclone can be changed by changing the fluid, that is, changing the fluid density ρ _f, and as a result, classification can be performed by the method of the present invention. Furthermore, if the difference in separation efficiency can be increased, the time required for classification can be shortened. Examples of the fluid include air, hydrogen, carbon dioxide and the like in the gas phase system, and water, oil, alcohol and the like in the liquid phase system.

1 is a conceptual diagram of a circulating fluidized bed type classification apparatus according to an embodiment of the present invention. It is the figure which showed the change with respect to the frequency | count of circulation of the abundance ratio which occupies in the mixed powder in the downcomer of the powder P1 whose separation efficiency with respect to a separator is 0.9. It is the figure which showed the change with respect to the frequency | count of trial of the abundance ratio which occupies in the mixed powder in the powder collector of the powder P2 whose separation efficiency with respect to a separator is 0.1. FIG. 4 is a diagram schematically showing how P1 and P2 are separated by integrating the procedures of FIGS. 2 and 3. The conceptual diagram of the circulating fluidized bed type | mold classification apparatus at the time of making a circulating fluidized bed multistage is shown. It is the figure which showed an example of the relationship between the particle diameter computed from Formula (1) of separation efficiency, and a density difference.

Explanation of symbols

1 Hopper 2 Downcomer (also called downcomer)
3 Transport pipe (also called riser pipe)
4 Blower 5 Cyclone centrifuge 6 Powder collector

7 Shoot

8 Valve

9 Air duct

10 Exhaust pipe

11 Screw feeder

12 Mixed sample containing two or more powders

13 Fluid

Claims (3)

A downcomer is connected to the lower part of the separator and the downcomer and the separator are connected by a conveying pipe connected to a blower to form a circulating fluidized bed, and a powder is formed downstream of the exhaust pipe connected to the separator. In a classification apparatus for a mixed sample including two or more kinds of powders provided with a recovery device and provided with a sample inlet in the downcomer, the separation efficiency differs by circulating the mixed sample a plurality of times in a circulating fluidized bed. A classifier that concentrates powder with high separation efficiency in a downcomer.   The powder collected by the powder collector provided downstream of the circulating fluidized bed is put into the sample inlet again and circulated in the circulating fluidized bed several times, so that the powder with low separation efficiency is collected in the powder collector. The classifier according to claim 1, wherein the classifier is concentrated. The classification apparatus according to claim 1 or 2, wherein the circulating fluidized bed is provided in multiple stages, and a mixed sample containing three or more kinds of powders can be classified simultaneously.

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