JPS586544B2 - Wind classifier that takes into account classification based on shape - Google Patents

Description

Detailed Description of the Invention The present invention separates fines (whisker-like, powder-like, or aggregation of these) that are generated in product pellets such as synthetic resins during pneumatic transportation, and separates them into product pellets. The present invention relates to improvements to classification equipment to maintain quality.

Generally, synthetic resins are made into pellets using an extruder after polymerization, but these are stored and transported by air between silos several times in order to equalize product quality or match various brands. is repeated until it reaches the shipping silo.

Regarding this, synthetic resin pellets have a relatively low melting point, so during repeated air transportation as described above, a part of the outer surface of the pellet melts due to the friction of the tube wall, producing whisker-like fines. Then, it grows into a tape-like fine.

If these fines are mixed into product pellets, their quality will be significantly impaired.

This can become a fatal defect during spinning, injection, or film production.

Therefore, methods to suppress the generation of fines include applying sandplast to the inner surface of the transport pipe or mechanically forming unevenness to reduce the friction area, but these methods are far from perfect. As a result of inner surface processing, even if the occurrence of whisker-like fines is reduced, the phenomenon in which the pellets are scraped by the tube wall occurs, and powder-like fines are generated, which aggregate in the silo and grow in clusters. New difficulties have arisen.

In this way, at present, synthetic resin pellets are mixed, stored,
It is difficult to prevent fines from being generated during the transportation process and mixed into the pellets.

Therefore, it is necessary to separate the generated fines from the pellets, but currently, sieving with a vibrating sieve or classification using wind power using an upright tower is generally adopted just before the shipping silo. be.

However, as mentioned above, the fines to be separated do not have a constant shape, and they are not necessarily in a separate state; rather, in terms of quantity, they are often grouped together in silos or the like during the process.

In other words, whisker-like substances become entangled with each other and form clumps, and powder-like substances accumulate and form clumps on the inner walls and ceilings of silos.

With the conventional vibrating sieve as described above, it is not only difficult to loosen and sieve the aggregated fines, but also to maintain the desired performance because the sieves often become clogged.

Furthermore, in conventional classification using wind power, it is possible to float and separate loose fines, but it is still difficult in principle to separate clustered fines from pellets.

In this regard, the present invention is composed of an inclined housing, a stationary rod screen that is also inclined in the middle of the housing, and a push-pull type airflow of approximately uniform velocity upward within the housing. , each mechanism works effectively in combination to separate the fines that are mixed in the pellets in various conditions, and contributes significantly to improving the quality of synthetic resin pellet products compared to various conventional devices for removing fines. It is something to do.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view thereof.

A prismatic classifier housing 3 is installed tilting to one side at a predetermined angle depending on the conditions, and several stages are arranged in a staggered manner approximately in the middle of the classifier housing 3 at right angles to the axis of the housing. A rod screen 4 with rods arranged in the flow direction is mounted.

This rod screen 4 has an angle θ of 5 with respect to the horizontal plane.
The angle is usually 30° to 45°, and as shown in Figure 3, the angle is approximately parallel to the flow direction.
In addition, as shown in FIG. 4, in this embodiment, they are arranged in a staggered manner in three stages: upper, middle, and lower.

Its arrangement dimensions are b, H≧(1.2-20)d usually,
3 to 10d, the pellets can easily pass through the rod screen, but the clustered fines 14 having a size of b or more cannot pass through.

A raw material pellet inlet 2 opens above the high side of the rod screen 4, and an inlet cyclone 1 and the like are mounted above it.

The inlet 2 has a built-in dispersion bar for dispersing raw material pellets during feeding.

A product cylinder 10 for storing the classified product pellets is provided below the vertical extension line of the inlet 2 by diagonally longitudinally cutting through the classifier housing 3 installed diagonally from the inlet 2. Airtightness is maintained.

A collective fine collection cylinder 12 is provided which hangs down vertically in an inverted pyramidal shape with one branch point at the intersection with the classifier housing 3 on the downstream side of the rod screen 4, and below the collection cylinder 12 is a collection cylinder 12.
It is sealed at 3.

This collective fine collection cylinder 12 is connected to the rod screen 4.
This is to accommodate fines that could not pass through and fines that adhere and re-grow in the upper classification duct 9, which will be described later, and accidentally fall.

The classifier housing 3 is divided into an upper part and a lower part, and is roughly divided into a lower classification duct 8 and an upper classification duct 9. At the lower end of the lower classification duct 8, an air source (not shown) is connected. A series of
A push air duct 5 has an air outlet with a built-in rectifying mechanism opened at right angles to the axis of the lower classification duct 8.
is connected.

Further, a pull air duct 6 having an inlet opposite to the outlet on the lower classification duct 8 side is connected to the upper end of the upper classification duct 9, and is connected to a dust collector via an exhaust fan (not shown).

The opening of the suction port of the pull air duct 5 is located at the upper end of the upper classification duct 9, on the vertical line of the collective fine collection cylinder 12, and further on the downstream side of the rod screen 4. All of them are located on the group fine collection cylinder 12 side when viewed from the vertical line of the intersection of the classifier housing 3.

That is, even if the fines that have reattached to the upper classification duct 9 and the suction port are peeled off whether the device is in operation or not, they will fall into the collective fines collection tube 12 and the product tube 10 will not be contaminated. The upper side of the suction port of the upper classification duct 9 is at least on the vertical extension of the intersection of the downstream side of the rod screen 4 and the classifier housing 3, or on the installation side of the collective fine collection cylinder 12. The length of the upper classification duct 9 is determined so that it opens with some margin.

Next, the set wind speed of the rectified classification airflow 7 flowing upward through the classifier housing 3 is the floating speed of the product pellets (U1).
Determined mainly by operating conditions.

That is, U1 of the pellet is 7 to 9 m/sec,
Since the fine U2 is 0.1 to 2 m/sec, the speed U3 of the classifying airflow 7 may be set to an appropriate speed between these, for example, U3 = 3 to 5 m/sec, depending on the given conditions. By bringing the wind speed U3 closer to the pellet U1, the quality of the product pellets can be improved, and by lowering the wind speed U3 to the fine U2, the yield of the product pellets can be improved.

The present invention configured as described above operates as follows.

First, raw material pellets to be classified reach the inlet cyclone 1 by pneumatic transport or other suitable means, pass through the dispersion bar, and fall into the classifier housing 3 from the inlet 2. At some points, the clustered fines 14 are prevented from falling, proceed downstream on the screen, and finally fall from the lower end of the screen into the clustered fines collecting cylinder 12.

At this time, since the classification airflow 7 is directed upward through the rod screen 4, the clustered fines 14 are slightly disentangled as they roll around the screen due to this upward airflow, and are disentangled into the inside of the cluster. It has the effect of separating mixed pellets into the product.

On the other hand, the pellets that have passed through the rod screen 4 obliquely descend through the lower classification duct 8 against the direction of the classification airflow 7 and fall into the product tube 10.

In this classification device, the required length of the pellets to be exposed to the classification air stream is set in advance, and during this time, fines mixed or attached to the pellets are sufficiently separated or detached.

The classification airflow 7 that has undergone the above actions in the lower classification duct 8 passes through the rod screen 4 and advances to the upper classification duct 9, carrying the separated fines with it.
, the cross-sectional area has become larger due to the provision of the collective fine collection tube 12, so the wind speed of the classification airflow 7 becomes slower as shown by the arrow in the figure, and the uniformity is particularly marked on the group fine collection tube 12 side. It is no longer a fast airflow.

As a result, a part of the fines that had been moving upward along with the classification airflow 7 lose their buoyancy and sink into the collective fines collecting cylinder 12 located directly below.

In addition, due to the slow wind speed, the collective fine collection tube 1
The separated fines re-adhere and accumulate on the side wall A of the classifier housing 3 on the second side, but even if they accidentally fall off, they fall into the collective fines collection tube 12, so there is no risk of contamination of the product pellets. .

The airflow for classification is reduced in wind speed and accompanied by fines.
Eventually, it is sucked into the suction port of the pull air duct 6, passes through a dust collector (not shown), and is dissipated into the atmosphere by an exhaust fan.

In addition, the suction air volume by the pull air duct 6 takes into consideration the amount of air introduced when air for air transportation is introduced from the raw material pellet inlet 2 in addition to the classification air flow 7 from the push air duct 5. There must be.

As described above, the present invention enables the separation and classification of fines mixed in various states in pellets using the inclined housing, inclined rod screen, and rectified upward airflow, which improves product quality. This greatly contributes to improvement.

Additionally, this type of classification device is often installed in a high place, such as on top of a shipping silo, due to the nature of the device, but the device of the present invention does not involve vibration, so special consideration is not required for the strength of the structure. This is also a big advantage.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG. Fig. 3 is a plan view of the rod screen section shown in the direction of arrow BB;
Further, FIG. 4 is a partially enlarged view showing the arrangement of the screen rod as viewed from the CC arrow. 1... Inlet cyclone, 2... Inlet, 3... Classifier housing, 4... Rod screen, 5...・Push air duct, 6...
...Pull air duct, 7... Air flow for classification,
8... Lower classification duct, 9... Upper classification duct, 10... Product tube, 11...
Airlock, 12... Collective fine collection tube, 1
3...Shattata, 14...Global fine.

Claims (1)

[Scope of Claims] 1. In a classification device for separating fines (whisker-like, powder-like, or aggregates thereof) mixed in pellets or chips (hereinafter referred to as pellets) of synthetic resin, etc. from the pellets, a prismatic type The housing is installed tilted in one direction, and a rod screen is installed in the middle of the housing, in which several stages of ronds are arranged in parallel in a single stage or in a staggered manner, approximately perpendicular to the axis of the housing. A raw material inlet is opened above the high side where the rod screen is tilted in the vertical direction, and the pellets are stored below the vertical extension line of the inlet that runs diagonally across the housing from the inlet. a collection tube for collecting fines that hangs down vertically in an inverted pyramid shape with one side branching point at the intersection with the housing on the lower side of the rod screen;
A push air duct is connected to the lower part of the casing and has an air outlet that is oriented obliquely upward in the direction of the tilted axis of the casing and has a built-in rectifying mechanism. This is a device that connects pull air ducts each having an opening to form a fluidized bed flow through cooperation between diagonally upward push and pull airflows that are rectified into a substantially uniform uniform flow velocity distribution between the two, and the following: A wind classifier that takes into account classification based on shape, and is characterized by having specified angle, dimension, and speed instruction conditions. 5°≦θ≦70° d<b, h<D U2≦cos θU3<U1 where θ=angle of inclination of the rod screen with respect to the horizontal plane. b = pitch between parallel rods arranged substantially parallel. h = vertical pitch between each rod. d=maximum major axis of product pellet. D = diameter of clustered fine nodules. U1 = Floating speed of product pellets. U2 = Floating speed of whiskers or powdery fines. U3=average flow velocity of push air flow. 2. A device according to claim 1, comprising:
The opening of the suction port of the pull air duct is on the vertical line of the collective fine collection tube, and on the upper side of the inclined housing, it is located at the intersection of the lower side of the rod screen and the housing, that is, the intersection of the housing and the collective fine. A wind classifier that takes into account classification based on a shape characterized by an opening on the collection cylinder side of the collective fine when viewed from the vertical line at a branch point on one side of the collection cylinder.