JPH04243582A - Air separator - Google Patents

Abstract

PURPOSE:To prevent the mixing of a coarse powder with a fine powder in a final classifying stage to the utmost by making the height of a cylinder vertically suspended around a fine powder discharge port controlling tertiary classification variable to set the height of the cylinder so as to obtain the optimum tertiary classification and discharging the coarse powder excluded by the tertiary classification from the through-hole of a rotary impeller. CONSTITUTION:A rotary impeller 8A wherein a plurality of rotary blades 8 are provided to the periphery of a drive shaft 8 is arranged within a fixed blade 6 and a fine powder discharge port 9 is provided directly above the rotary impeller 8A. A cylindrical slide gate 20 freely movable up and down is provided to the lower part of the fine powder discharge port 9 and the rotary impeller 8A is formed as a conical disc having a stepped part and through-holes 80 discharging a coarse powder are provided to the stepped part. As a result, a classicying point is more transferred toward a fine powder side and the mixing of the coarse powder with a fine powder in a final classifying stage is prevented to the utmost and sharp classifying capacity can be obtained.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention uses an air flow to convert materials to be crushed (hereinafter referred to as classified raw materials) such as cement raw materials, clinker, blast furnace slag, and chemicals that are crushed in a crusher and a crushing section into fine powder and coarse powder. This relates to an air separator that separates the air.

0002

[Prior Art] An air separator is a classification device whose purpose is to use airflow to sort powder and granules crushed by a crusher into powders of a desired particle size and produce products.The classification principle is based on gravity. It is broadly divided into classification, inertial force classification, and centrifugal force classification. Centrifugal force classification is suitable for bulk classification of powder.
It is a combination of two types: a free-vortex type in which the airflow is swirled by creating a spiral shape in the classification chamber, and a forced-vortex type in which the airflow is forcibly swirled by rotating blades installed in the classification chamber. There is a shared type of free vortex and forced vortex.

FIG. 7 shows an embodiment of a conventional air separator, which is a combination of free vortex and forced vortex. In the figure, the classified raw material is introduced from the raw material supply port 3a, and is introduced into the classified air in a dispersed state via a dispersion plate 4a and a collision plate 20 which rotate at high speed. The classification air flows tangentially from the classification air intake port 5a along the spiral inner wall of the casing, passes through the fixed blades 6a to form a primary swirling airflow, and is further passed through the rotating rotary impeller 8a. Forms a secondary swirling airflow.

[0004] Classification is first carried out in the primary swirling airflow, and then in the secondary swirling airflow, by balancing the centrifugal force and the drag force of the inwardly flowing air. It is taken out of the system as a fine powder.

On the other hand, aggregates of coarse particles larger than the required particle size and fine particles smaller than the required particle size are bounced off toward the outer periphery of the rotary impeller 8a by the centrifugal force of the secondary swirling airflow, and are scattered along the inside of the fixed blade 6a. While descending, the fixed wing 6a
When exposed to the classification air that enters the inside through the air, the aggregates of fine particles are decomposed, broken up, and subjected to a dispersion action, but the coarse particles continue to fall toward the coarse powder outlet 11. Then, the dispersed fine particles are again transported together with the classification air into the secondary swirling airflow and classified.

[0006]

[Problem to be solved by the invention] However, in centrifugal force classification, although there is a solid theory that classification is performed by the balance between fluid drag and centrifugal force, the conventional technology It is difficult to extract only particles as fine powder, and there are many cases where coarse particles are mixed into the fine powder side. Regarding the difference between theory and practice,
While theory deals with single particles, in reality the powder to be classified is not a single particle, but collisions between particles or particles colliding with classification blades occur. It is thought that this is due to the fact that

[0007] Conventionally, in order to prevent coarse particles from being mixed into the fine powder side, the actual rotation speed of the classification blade has been set higher than the theoretical rotation speed required to obtain fine powder of the required particle size. Countermeasures have been taken, such as setting the impeller at high speed and installing a member on the outer circumference of the rotary impeller that rotates together with the impeller to prevent coarse particles from entering. Therefore, as the rotation speed of the rotary impeller increases and the weight of the outer circumference of the impeller increases,
There was a problem in that the electric power required to drive the rotary impeller was excessive.

[0008] Furthermore, in this type of air separator,
Primary classification is performed in the space between the fixed blade and the rotating blade, and secondary classification is performed in the space with the radial width of the rotating blade. A classification action called tertiary classification is performed, but
Since no consideration has been given to the route for returning the coarse powder sorted in this tertiary classification, this coarse powder is discharged as is along with the fine powder, and as a result, tertiary classification is not performed, and as a result, sharp classification is hindered. This resulted in a product with a gradual particle size curve. The air separator of the present invention takes full advantage of such tertiary classification and is designed to reliably return the coarse powder after the tertiary classification.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the separator of the present invention has a
It has a rotary impeller equipped with a rotatably supported vertical drive shaft and a number of classification blades that rotate integrally around the shaft, and above the rotary impeller there is a fine powder that communicates with the inside of the rotary impeller. A fixed blade having a discharge port and a large number of slit-like openings on the outer periphery of the rotary impeller for giving swirl to the classified air is fixedly installed in a concentric circle at an appropriate distance apart, and connected to the fixed blade. In an air separator equipped with an inverted conical guide cone, a cylindrical slide gate that can be moved vertically downward from the fine powder discharge port is provided, and the rotary impeller is connected to a substantially conical guide cone. A disc was formed, and a step was provided at the intermediate diameter portion of the conical disc so that the outer diameter side was higher than the inner diameter side, and a through hole was provided in the step portion to pass through the disc.

0010

[Operation] In the air separator of the present invention, a primary swirling airflow is formed by the fixed blades, and a secondary swirling airflow is formed by the rotating impeller. In addition, the classified raw material is classified in the primary swirling airflow and the secondary swirling airflow in the same manner as in the past, with the balance between centrifugal force and drag force caused by inwardly flowing air.

[0011] Now, considering the space in which classification is performed, in conventional air separators, primary classification is performed in a space surrounded by fixed blades and classification blades, and secondary classification is performed in a space surrounded by the width of the classification blades. It was said to take place in or near space.

[0012] However, the present invention is based on the discovery of the present applicant that further classification, which should be called tertiary classification, is also carried out in a space closer to the center from the classification blade, and this tertiary classification is By making the height of the cylinder that hangs vertically downward around the controlled fine powder outlet variable, it is possible to set the cylinder height that provides the optimal tertiary classification, and to remove the coarse particles that are eliminated by the tertiary classification. In order to return the powder to powder, it is dropped onto the conical disc of the rotary impeller and discharged to the outside of the rotary impeller via a through hole provided in the stepped portion of the conical disc.

As a result, the fine powder that has passed through the air separator of the present invention excludes the coarse powder of the primary classification, secondary classification, and tertiary classification, and is a product with a sharp classification performance curve (particle size distribution curve). is obtained.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings. 1 to 6 relate to an embodiment of the present technology, FIG. 1 is a side sectional view of an air separator, FIG. 2 is a side sectional view of an air separator showing another embodiment, and FIG. 3 is a third embodiment of FIG. 1.
- A cross-sectional plan view from III view, Figure 4 is a perspective view of the rotary impeller,
FIG. 5 is a coarse powder distribution ratio curve diagram of the air separator of the present invention, and FIG. 6 is a coarse powder distribution ratio curve diagram of another embodiment of the air separator of the present invention.

The separator of the present invention is constructed inside a cylindrical classification chamber 1 and a downward diameter-reduced dispersion chamber 2, and has a vertical drive shaft 7 rotatably supported at the center of the classification chamber 1. It has a rotary impeller 8A around which a large number of classification blades 8 are attached which integrally rotate, and a fine powder discharge port 9 communicating with the inside of the rotary blade 8A is arranged above the impeller 8A. On the outer periphery of the rotary impeller 8A, fixed blades 6 having a large number of slit-like openings for giving swirl to the classification air are fixedly installed concentrically at appropriate intervals, and are connected to the fixed blades 6. It is provided with a guide cone 10 whose diameter is reduced downward.

Inside the dispersion chamber 2, a dispersion plate 4 is provided on the drive shaft 7 in the lower part of the rotary impeller 8A, and a classified material supply port 3 is provided.
The classified raw material supplied from the classification chamber 1 is classified in the classification chamber 1, and together with the fine particle aggregates falling along the inner walls of the fixed blades 6 and the guide cone 10, is passed from the classification air intake 5 through the slit 5A. It has a structure in which it is thrown into the incoming classification air and dispersed.

The fine powder discharge port 9 has a long cylindrical slide gate 20 inside a short cylindrical fixed tube 12.
is fitted so that it can move vertically and slide freely, and the slide gate 2
A wire cord or metal chain 22 attached to the upper end flange of the casing 1A is taken out of the air separator via a pulley 21, and is connected to an electric winch 23 installed on the top plate of the casing 1A so that it can move up and down. has been done. The height h of the slide gate 20 can be controlled within a range of 5 to 50% of the total height H of the rotating blade 8. Also, slide gate 20
The inner diameter d is selected to be 30 to 70% of the outer diameter D of the rotary impeller 8A.

On the other hand, as shown in FIG. 1, the rotary impeller 8A is a conical disk having a high step on the outside at the intermediate diameter position, and a plurality of through holes 8B are formed in the step portion around the circumference. They are arranged at a uniform pitch, and the coarse powder or grains that have fallen into the inner conical disk of the through hole 8B can fall downward. The diameter of the through hole 8B is approximately 5 to 10 mm, but it is made as small as possible to avoid clogging. The reason why the rotary impeller 8A is made of a conical disk with steps is to ensure that the coarse powder that falls onto the conical disk is discharged from the through hole 8B.
This is to prevent it from passing through the through hole 8B and passing between the rotating blades from the inside to the outside.

FIG. 2 shows another embodiment of the present invention, and FIG.
The part corresponding to the classification chamber of the air separator is applied to a vertical roller mill. The vertical roller mill is the same as the conventional one, and its explanation will be omitted. The structure of each member of the separator is the same as that of the separator described above.

FIGS. 5 and 6 show partial classification efficiency determined from samples obtained by classification using the air separator of the present invention. The classification experiment shown in Figure 5 was conducted under two conditions: with and without a slide gate provided at the fine powder discharge port using the same air separator, and the internal diameter of the fine powder discharge port, the rotation speed of the rotary impeller, The operating conditions of the separator, such as the amount of air for classification and the amount of supplied raw material for classification, were kept constant. Ordinary Portland cement was used as the raw material for classification.

Looking at this figure, even if the operating conditions of the separator are constant, by providing a slide gate at the fine powder outlet, the proportion of coarse particles recovered to the coarse powder side increases.
In other words, it is clear that the amount of coarse particles recovered on the fine powder side has decreased, and furthermore, the classification point has become smaller.

The classification experiment shown in FIG. 6 was conducted using the same air separator under two conditions: with and without a slide gate provided at the fine powder outlet, and by adjusting the inner diameter of the fine powder outlet and the rotary impeller. When the rotational speed is constant, the amount of supplied raw material for classification and the amount of air for classification are 100% when no slide gate is provided, and increased to 150% when an annular member is provided.

Looking at this figure, it can be seen that by providing a slide gate, even if the amount of classification air is increased, classification can be performed at the same level as when there is no slide gate.
Furthermore, it can be seen that it is also possible to increase the throughput of raw materials.

[0024] From the above experiments, generally speaking, by providing a cylindrical tube such as a slide gate at the fine powder discharge port, the particle size distribution of the product after classification changes, and the particle size shifts to the fine powder side. However, it can be seen that sharp classification is performed. Therefore, in order to achieve the desired product particle size distribution in the space from the rotary vane 8 to the fine powder discharge port 9, which can be called tertiary classification, the separator of the present invention is optimized by raising and lowering the slide gate 20. In order to be able to select the point and to quickly discharge the coarse powder sorted by the tertiary classification from this space,
The rotary impeller 8A has a conical shape with a step so that the coarse powder is discharged from the through hole 8B in the step.

[0025]

[Effects of the Invention] As explained above, the air separator of the present invention shifts the classification point to the finer powder side, prevents the introduction of coarse powder (mixing of coarse powder into fine powder) in the final classification stage, and sharpens the air separator of the present invention. Excellent classification with a classification curve can be achieved. Furthermore, even if the amount of air for classification is increased, the same classification as before can be ensured, so the amount of classification processing per hour can be increased.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an air separator of the present invention.

FIG. 2 is a side sectional view showing another embodiment of the air separator of the present invention.

FIG. 3 is a cross-sectional plan view taken along III-III in FIG. 1;

FIG. 4 is a perspective view of a rotary impeller of the air separator of the present invention.

FIG. 5 is a coarse powder distribution ratio curve diagram of the air separator of the present invention.

FIG. 6 is a coarse powder distribution ratio curve diagram showing another embodiment of the air separator of the present invention.

FIG. 7 is a side sectional view of a conventional air separator.

[Explanation of symbols]

1 Classification chamber 1A Classification chamber casing 2 Dispersion chamber 2A Dispersion chamber casing 3 Classified raw material port 3a Classified raw material port 4 Dispersion plate 4a Dispersion plate 5 Air intake port for classification 5a Air intake port for classification 5A Slit 6 Fixed blade 6a Fixed blade 6A Slit 7 Drive shaft 8 Rotating blade (classifying blade) 8A Rotating impeller 8B Through hole 9 Fine powder outlet 10 Guide cone 11 Coarse powder outlet 12 Fixed tube 18 Collision plate 20 Slide gate 21 Pulley 22 Wire cord (or metal chain) 23 Electric winch 30 Reducer 31 Grinding table 32 Hydraulic cylinder 33 Roller arm 34 Grinding roller 50 Air flow

Claims (1)

[Claims] Claim 1: A rotary impeller having a rotatably supported vertical drive shaft and a large number of classifying blades that rotate integrally around the rotary impeller is provided in the center of the classification chamber, and above the rotary impeller. A fine powder discharge port communicating with the inside of the rotary impeller is arranged, and fixed blades having a large number of slit-like openings on the outer periphery of the rotary impeller are arranged concentrically and spaced apart for an appropriate distance. In the air separator, which is fixedly installed in the air separator and is connected to the fixed blade and is equipped with an inverted conical guide cone, a cylindrical slide gate that is movable vertically downward from the fine powder discharge port is provided. The rotary impeller is formed into a substantially conical disk, and a step is provided at an intermediate diameter portion of the conical disk such that the outer diameter side is higher than the inner diameter side, and the step portion is provided with a step that penetrates the disk. An air separator characterized by having through holes.