JPH03137486A - Method of drying and classifying powder particles - Google Patents

Abstract

PURPOSE:To enable an independent control of a degree of drying operation and a classified particle diameter by a method wherein an upper part and a lower part of an ascending pipe and a down-pipe are communicated by a flow passage, the upward flow passage is provided with a plurality of slits, powder particles are struck against the slits to classify the particles and at the same time the particles are dried with hot air. CONSTITUTION:Powder particles in a storing hopper 1 are fed onto a fluidized bed 4 through a rotary feeder 2 and a feeding port 3. The particles are fluidized by hot air 30 blown through punched holes in the fluidized bed 4, the particles rise up in an ascending pipe 15 and reach a classifier 5. The classifier 5 is comprised of several slits 14 and its width can be varied. Powder particles of small degree of particle are dried by hot air, almost of all the particles pass through the slits 14 and reach a cyclone 8. The powder particles of high degree of particle and the remaining powder particles not discharged pass through a discharging port 22 and settle in the down-pipe 6. Particle diameter can be controlled by adjusting a width of each of the slits 14. A circulating flow operation is repeated through a flow rate control device 25 and a supplying port 7 so as to promote a classifying operation and a sufficient drying and classification can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for drying and classifying powder and granules, and in particular,
The present invention relates to a method of accurately classifying particles with a particle size of about 100 to 1000 μm and drying at the same time.

(Prior Art) Conventionally, there have been the following fluidized dryers for drying and classifying powder and granular materials.

Fig. 6 shows a device disclosed in Japanese Patent Application Laid-Open No. 58-156179, in which a louver is provided in a cylindrical rotating body to feed hot gas from below, and the hot gas is passed through the wet material to dry it while fluidizing it. A classification zone is formed in a part of the dry zone to be formed, and the flow rate of the hot gas sent from the classification zone into the rotating body is controlled so that the hot gas passes through the material in the classification zone and is below the target particle size. A rotary flow dryer with a built-in heat transfer tube that has a drying function and a fine powder separation function by setting a flow rate that separates particles. In Figure 6, 51 is a rotating body, 5
2 is a charging port, 53 is a discharge port, 54 is a material outlet, and 55 is a louver. In addition, the following types of circulating fluidized beds for circulating powder and granules were available.

As shown in FIG. 7, a fluidization section 40, a cyclone 41,
In a circulating flow container in which a downcomer pipe 42 and a pneumatic feeder 43 are connected in a ring shape, powder and granules are fluidized at high speed and thrown out on an air current, and the flying particles are collected with a cyclone or the like. , recirculation method (multiphase flow 19
88. See December P, 270-271).

(Problems to be Solved by the Invention) However, these systems have had several problems as described below.

First, regarding the fluidized dryer that dries and classifies powder and granules, ■ In the fluidized bed from the inlet to the outlet, only the vicinity of the outlet is used for classification, so the outlet contains a considerable amount of fine powder and coarse particles. Grains are being discharged and sufficient classification cannot be expected.

■ A large horizontal space is required from the raw material charging inlet to the drying zone, nine classification zones, and the discharge outlet, making the equipment large.

■ The zone through which the powder and granules pass is divided into two sections, and classification is performed in the final zone, but since the particle size to be classified is determined by the amount of hot gas, the degree of drying and the classified particle size are independent. difficult to control.

In addition, regarding the circulating fluidized bed that circulates powder and granules, the flying particles are collected with a cyclone and circulated, and the classified particle size is 100 μm or less, and 100 to 100 μm.
In the case of a classified particle size of 0 μm, the size becomes large and the pressure loss in a cyclone etc. is large.The present invention was made in view of the problems of the prior art, and its purpose is to It has an efficient classification function, is compact, has drying and classification functions that can independently control the degree of dryness and the classified particle size, and has a classification function that can operate with a classified particle size of 100 to 1000 μm with low pressure drop. The objective is to provide drying and classification functions for powder and granular materials.

(Means for Solving the Problems) In order to achieve the object, the present invention provides a circulation flow vessel in which the upper and lower portions of an ascending pipe and a downcomer pipe are connected by flow passages, in which a plurality of pipes are provided in the middle of the upper passage. A slit is provided, and the powder and granule are charged into the fluidized bed at the bottom of the riser pipe, and hot air is supplied and circulated to cause the powder and granule to collide with the slit, classifying the powder and granule at the same time. , and dried with hot air.

As another method, a container is provided in place of the slit, an air-adding classifier is provided in the middle of the descending pipe, air is introduced into the classifier, and the air is directed from downward to upward through a perforated plate. The above problem was solved by classifying in an anti-transfer style.

(Function) A feature of the present invention is that the granular material circulates and flows in a vertical flow container. Therefore, the powder in the flow container is efficiently classified by circulating through the slit and the downcomer several times.

In the case of the slit type, the powder collides with the slit and coarse particles fall, descend down the downcomer pipe, and circulate. Fine particles pass through the slit and are discharged out of the flow vessel. In other words, the particles are classified into particle sizes commensurate with the flow rate passing through the slit.

In the case of the air addition type, air is blown from bottom to top on particles that stall and fall during circulation to discharge fine particles out of the fluidized vessel.

Coarse particles continue to fall and circulate. In other words, the particles are classified into particle sizes commensurate with the flow rate of the gas flowing from bottom to top.

In addition to the amount of hot air supplied, the flow rate at which the particles are scattered can be adjusted by increasing or decreasing the slit angle and the amount of air flowing into the air-added classifier, and the classified particle size can be independently controlled. Furthermore, by reducing the passing flow rate, classification of 100 μm or more is possible with low pressure loss.

(Example) Hereinafter, the case of drying and classifying coal will be explained as an example.

It goes without saying that the method of drying and classifying powder and granular material specified herein can also be used for any other granular material. FIG. 1 illustrates a system for drying and classifying coal powder (hereinafter referred to as coal) in a first embodiment of the present invention.

The riser pipe 15 has a fluidized bed 4 at the lower part, the upper part is connected to the upper part of the downcomer pipe 6 by a slit type classifier 5 equipped with a large number of slits 14, and the lower part has a supply lower and a flow rate adjustment device 25. It is connected to the lower part of the downcomer pipe 6 to form a circulation path. This part is called the circulation flow vessel.

Coal stored in storage hopper 1 (particle size 10 μm ~
Number 101011I is the loading port 3 by the rotary feeder 2.
via the fluidized bed 4. The fluidized bed 4 is made of punched metal with punched holes. The coal charged onto the fluidized bed is brought into a high-speed fluidized state by the hot air 30 blown from below through the punch holes in the fluidized bed, rises through the riser pipe 15, and reaches the classifier 5.

FIG. 2 is an enlarged view showing details of the slit type classifier shown in FIG. 1.

The classifier is composed of a large number of slits 14, and the width of the slits is variable and can be changed via a lever 16.

The small-sized coal is dried by the hot air, and most of it passes through the slit and is discharged to the cyclone 8. The large-grained coal and the remaining small-grained coal that has not been discharged stall, pass through the outlet 22, and settle down the downcomer 6.

The particle size of the coal passing through the slit can be controlled within the range of 100 to 1000 μm at the most downstream side by adjusting the width of the slit.

The method according to claim 2 is shown in Figure i3. This is the second aspect of the present invention.
It shows the system in the example.

The large particle size coal in Example 2 and the remaining small particle size coal that was not discharged were stored in a container 21 equipped with a discharge port 17 and an outlet port 22, which was attached to a circulation flow container instead of the slit type classifier. It stalls at the point where it passes through the outlet 22 and reaches the air-addition type classifier 18. The air addition type classifier shown in detail in FIG. 4 also includes a perforated plate 19 and an air inlet 2.
0 and is connected to the downcomer pipe.

Air flowing in from the outside through the air inlet 20 passes through the perforated plate, collides with the coarse particles that have fallen and accumulated in the downcomer, reverses itself and rises inside the downcomer, passes through the outlet 22, and enters the container 21. leading to.

Here, other gases (N2, Co2, etc.) may be used instead of air. The coal that has settled out of the container 21 and the outlet 22 is a mixture of coarse particles and fine powder, and the rising air separates the fine powder with a particle size commensurate with the air flow velocity, and the coal is returned to the outlet 22 and the container. 21 and passes through the discharge port 17 to reach the cyclone 8.

The settled large-grained coal moves downward through the downcomer pipe 6, is returned to the fluidized bed through the supply lower, and is recirculated by hot air. By recirculating, the fine-grained coal adhering to the large-grained coal is discharged again through the slit or through the air-addition classifier in Example 2, improving classification accuracy and promoting drying. be done.

The small particle size coal discharged together with the exhaust gas is collected by a cyclone 8 and a bag filter 9 and stored in a small particle size hopper. Coal having a coarse particle size that cannot be fluidized in the upper layer on the fluidized bed remains on the fluidized bed for a certain period of time, and then is discharged from the coarse particle discharge port 10 by the discharge feeder 13.

Further, the dried and classified coal is discharged from the discharge port 11 by the discharge feeder 12, and depending on the purpose, it is mixed with the above-mentioned coarse particles and used.

Furthermore, the flow rate adjustment device 25 in the downcomer section can adjust the circulation flow rate of coal, and also change the concentration and residence time of coal in the circulation flow vessel.

Further, according to the present invention, it is also possible to perform classification using a slit and classification using an air addition type classifier at the same time, depending on the desired classification particle size, as in the third embodiment shown in FIG. In this case, after classification by the slit, the coarse particles and fine particles that have settled in the outlet 22 are classified by rising air from the air-addition classifier into particle sizes commensurate with the air flow rate. The fine powder rises again, collides with the slit, and is classified again.

(Effects of the Invention) As explained above, in the present invention, by repeating circulating flow, drying in a circulating flow container and classification in a slit type classifier or an air addition type classifier are repeated and promoted. Therefore, sufficient drying and classification can be performed.

In addition, the width of the slit and the amount of air flowing from the perforated plate are
By changing it, the classified particle size can be adjusted even with the same hot air flow rate, and the degree of drying and the classified particle size can be controlled independently. Furthermore, since it is possible to change the coal concentration and residence time in the circulating flow vessel, there is a large degree of freedom in terms of equipment design and operation.

In addition, the present invention provides powder and granular materials with a wide range of particle sizes (several tens of μm).
Classification and drying is also possible for particles with a diameter of several tens of mm. Furthermore, even when the particle size is 100 to 1000 μm, classification can be performed with a small size and low pressure loss.

Furthermore, since drying and classification are performed in a vertical circulation flow container,
This has the effect of reducing the installation space.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of the first embodiment of the present invention, Fig. 2 is a partially enlarged view showing details of the slit type classifier shown in Fig. 1, Fig. 3 is a system diagram of the second embodiment, and Fig. 4 is a detailed view of the air addition type classifier shown in Fig. 3, Fig. 5 is a system diagram of the third embodiment, Fig. 6 is a cross-sectional view of the structure of a conventional horizontal fluidized bed dryer, and Fig. 7 is a circulating flow diagram. FIG. 3 shows a diagram of the structure of an example of layers. 1...Storage hopper 2...Rotary feeder 3.
...Charging port 4...Fluidized bed 5...Slit type classifier 6...Downcomer pipe 7...Supply port
8... Cyclone 9... Bag filter 10
... Coarse particle discharge port 11 ... Discharge port 12
...Discharge feeder 12...Discharge feeder 14
...Slit 15...Rising pipe 16...
・Lever 17...Discharge port 18...Air addition type classifier 19...Perforated plate 20...
Gas inlet 21... Container 22... Outlet 25... Flow rate adjustment device 30... Hot air 40
...Fluidization section 41...Cyclone 42.
...Downcomer pipe 43...Pneumatic feeder 51...Rotating body 52...Charging port 53...
...Discharge port 54...Material outlet 55 River louver Figure 1 12: FR, Output feeder I3: Discharge feeder

Claims (1)

[Scope of Claims] 1. In a circulating fluid vessel in which the upper and lower sides of a riser pipe and a downcomer pipe are connected by a flow path, a plurality of slits are provided in the middle of the upper flow path, and a fluidized bed at the bottom of the riser pipe is A granular material characterized by charging the granular material and supplying hot air to circulate and flow the granular material so that the granular material collides with the slit, classifies the granular material, and simultaneously dries the granular material with the hot air. How to dry and classify the body. 2. In the circulating fluidized container according to claim 1, a container is provided in the middle of the upper flow path, an air-addition type classifier is provided in the middle of the descending pipe, and the granular material is charged into the fluidized bed at the bottom of the rising pipe. , supplying hot air to circulate and flow it, and making air flow into the air addition type classifier, and redirecting the air from downward to upward through the perforated plate, classifying the powder and granules, and at the same time drying with the hot air. A method for drying and classifying powder and granular materials.