WO2004048006A1

WO2004048006A1 - Method and device for separating dust particles from a granulate

Info

Publication number: WO2004048006A1
Application number: PCT/EP2003/013401
Authority: WO
Inventors: Manfred Butsch
Original assignee: Mbengineering Gmbh & Co. Kg
Priority date: 2002-11-28
Filing date: 2003-11-28
Publication date: 2004-06-10
Also published as: AU2003293738A1

Abstract

The invention relates to a method for separating dust particles from a granulate, according to which an air stream that entrains the dust particles is directed through the granulate. The granulate containing the dust particles is introduced into a container (10), the wall (11) of which is provided with passages (12) for the dust particles, is whirled up therein by the air stream (24, 60) that is introduced via an inlet, and is carried along to the container wall (11), where the dust particles are discharged through the passages (12) while the granulate remains inside the container. The invention also relates to a device for adequately carrying out the inventive method. The inventive method and device allow the granulate to be dried or granulates to be mixed if different types of granulates are used while the dust particles are separated.

Description

Method and device for separating dust particles from a granulate

description

The invention relates to a method for separating dust particles from a granulate.

Furthermore, the invention relates to a device for separating dust particles from a granulate.

Granules, which in the following are also to be understood as mixtures of different types or types of granules, can be found in a wide variety of applications. In particular in the manufacture of a wide variety of goods and components made of plastic, plastic granulate is widely used as the starting material.

Plastic dust often arises during the manufacture of the plastic granulate. The dust particles result from the cold cut when extruding into the new goods, since some granules cannot be produced by hot cut due to production. If goods or components are manufactured using an injection molding process, the actual product usually has a sprue attached to it. For ecological and economic reasons it is common to recycle this sprue, i.e. to regranulate it in a plastic mill and to feed it back into the product manufacturing process. A comparatively high proportion of plastic dust is usually contained in the regrind from such plastic mills.

In addition, the granules are usually not transferred directly from the manufacturer to the end product, but have to be transported to another location for further processing. During this transport, the granules rub against each other and the transport surface causes friction. holder is a fine-grained abrasion of the granules. The same happens when granules are transported in the pipelines of conveyor systems. Plastic dust is created again by internal friction between the granules and by friction on the inner walls of the pipe.

Plastic dust or dust that has been brought in from the environment can cause quality and processing problems in the production of plastic parts. If the proportion of dust in the new goods or the regrind is too high, this can lead to discoloration of the end product or dust inclusions in the auger of the spraying machine, which in turn leads to bridging in the feed of the screw, so that no further material is required can and the spraying machine fails. As a result, there is an increased amount of rejects and / or longer machine downtimes during production.

In addition, the dust contamination of the plastic granules leads to dust pollution in the workplace. In particular when using glass fiber reinforced materials or filled plastics, each of which secretes very small dust particles, inhalation of the dust is considered to be harmful to health. For the reasons mentioned, it is therefore necessary to dedust the plastic granulate before it is introduced into the production machines.

From DE-OS 20 08 480 a method is known in which the separation of dust particles from granules takes place in that an air stream carrying dust particles and granules is directed onto a partition which is only permeable to the air and the dust particles. The latter are carried through the sieve by the air flow, whereas the granulate is retained by the sieve and falls into a collecting container. A device is also known from the cited document, in which said partition is designed as a sieve.

A device is also known from DE 100 04 688 AI, in which an air classifier is integrated to separate the dust particles from the granulate. A stream of air flowing in from the side is guided here through falling granules, the dust particles being carried along due to their lower mass and being fed to a suction device.

In addition, a device for separating dust particles is known from US Pat. No. 6,004,404, in which a sieve drum is used. This is used to remove coarse impurities from the granulate. For this purpose, the contaminated granulate is first passed onto the sieve drum from the outside. Granules and dust particles penetrate through the openings in the sieve drum into the interior of the sieve drum, from where they in turn fall outwards. Coarse contaminants, on the other hand, cannot penetrate the sieve drum and are sorted out. The granules that have fallen through the sieve drum together with the dust particles are then fed to an air classifier, in which an air flow supplied carries the dust particles against gravity, while the granules fall downwards into a collecting container.

A disadvantage of the method mentioned or of the devices mentioned is that the degree of dust particle separation cannot be varied without modification of the devices or that different types of granules can be adapted. In the case of the device from DE-OS 20 08 4080, a cascading would have to be carried out in order to reduce the residual dust content in the granulate. rer devices required, in the device from DE 100 04 688 AI an extension of the wind sifting duct, possibly connected with additional air flows flowing in from the side, would have to take place.

The invention was therefore based on the problem of providing a flexible method and a corresponding device with which the degree of separation of the dust particles from the granulate can be varied simply, in particular without structural changes to the devices using the method.

This problem is solved by a method which has the features of claim 1. Advantageous procedural variants are listed in the subordinate claims.

Furthermore, the stated problem is solved by a device with the features of claim 14. Advantageous further developments are described in the following subclaims.

The basic idea of the invention is that the granules contaminated with dust particles are introduced into a container, the container wall of which is provided with passage openings for the dust particles. In addition, an air stream, where air is generally understood to mean gases and gas mixtures, is conducted into the container, which whirls up granules and dust particles and carries them to the container wall. Air flow and dust particles pass through the container wall to the outside, while the granulate is retained in the container. In this way, there is a defined separation between dust particles and granules based on the geometry of the passage openings for the dust particles in the container wall. In addition, the granules can be of any length remain in the container and dust particles are continuously discharged so that the degree of separation of dust particles can be varied easily.

In addition, the granules are mixed by the air flow being stirred up. In particular, if the granules consist of several components, it is therefore advantageous to leave the granules in the container and to stir them up until homogeneous mixing has taken place.

The container can be made by joining solids or fibers or consist of at least one solid solid that is provided with through-openings, such as a perforated plate.

The container is preferably designed as a sieve drum. However, this serves a completely different purpose than the one mentioned above from US 6,004,404. In the device described there, the sieve drum is used to separate coarse impurities from the granulate. The separation of the

Dust particles from the granulate, on the other hand, take place in a wind sifter and not using the sieve drum. As a result, in contrast to the present invention, which uses the sieve drum to separate the dust particles, this device does not allow a simple variation in the degree of separation of the dust particles, nor does a defined separation between the granules and dust particles take place.

In the invention, all parts touching the granulate are preferably made of stainless steel, which enables these parts to be cleaned quickly and easily. This is particularly advantageous if different granules are to be treated in chronological order. In a further development of the invention, at least one suction device is arranged outside the container. Together with the supplied air, this creates an air flow that carries the dust particles and the granulate to the container wall. After the air flow has passed through the container wall, the air carrying the dust particles can be removed via the suction device.

It proves to be particularly advantageous to surround the container with an airtight housing to which at least one connection for the air supply and at least one connection for at least one suction device are attached. In this way, it is possible to prevent the dust particles from escaping into the external environment of the device and thus to stress the workplace.

A further development of the invention consists in generating the air flow with at least one turbine, which is preferably speed-controlled. In this way, a simple regulation of the amount of air supplied or its flow rate is possible, which influences the strength of the granulate or dust whirling up and the amount of dust particles discharged. In addition to the dwell time of the granules in the container, a further parameter is therefore available for varying the degree of separation of dust particles from the granules.

The air flow is preferably not fed continuously to the container, but rather is pulsed. In this way, the pressure in a housing surrounding the container is lower, so that the likelihood of dust escaping into the surroundings is reduced. In an advantageous embodiment of the invention, the air flow in the container is alternately generated either by the air introduced via the feed or by the suction device. In this way, dust particles that have been whirled up to a large extent can first be removed more efficiently. In addition, a pressure in the container that is higher than the environment and thus dust escape can be prevented in this way.

With regard to the exposure to dust particles in the workplace, it is advantageous if a vacuum is generated and / or maintained in the container while the dust particles are being separated from the external environment. In this way, the escape of dust particles into the external environment of the device can be prevented.

For the same reason, it is advantageous to suck the granules into the container by means of negative pressure. In this way, swirling up of dust particles cannot become one

Lead dust discharge into the environment.

In addition, a further development consists in vacuum-removing the granules from the container after separating the dust particles, i.e. in particular to suck it out of the container by means of negative pressure in a discharge line and to feed it for further processing.

An advantageous embodiment of the invention consists in at least part of the air forming the air flow before the

Introduce into the container to heat and / or dry. This can be realized, for example, in that the air flow is a heating and / or before being fed into the container Flows through drying device. In this way, in addition to separating the dust particles from the granules, they can also be dried. So far, this has been done by an additional, separate drying device, which was upstream or downstream of the device for separating the dust particles.

In a particularly advantageous development of the invention, at least one heat source is arranged in the container, with which the granulate therein or the air flowing through the container is heated or dried. This can be done in addition or as an alternative to the above-mentioned heating / drying of the air flow outside the container.

Depending on the type of granulate to be dusted and / or dried, electrostatic charging of the granulate can occur, particularly in the case of plastic granules, due to internal friction of the granulate, or if the container is manufactured from corresponding materials, also due to friction of the granulate against the container wall. The charged granulate then interacts with charged dust particles. This leads to electrostatic attraction of dust particles, which consequently adhere to the granulate and are difficult to separate. For this reason, an advantageous development of the invention consists in ionizing at least part of the air forming the air flow before it is introduced into the container. For example, this is achieved in that the air flow flows through a known ionization device before being fed into the container. The ionized air subsequently at least partially reduces the electrostatic adherence of dust particles to the granulate by reducing the electrostatic charges and thus facilitates the separation of the dust particles. In a further embodiment of the invention, the container is rotatably mounted along at least one axis, preferably in the operating position, ie the arrangement during the process of separating the dust particles, and does not run vertically, and rotates at least temporarily circumferentially or reversing about at least one of these axes. This rotational movement enables a homogeneous separation of the dust particles or homogeneous drying of the granules to be achieved more quickly. In addition, when the container is filled with different types of granulate or when admixtures are added, homogeneous mixing of the various components results more quickly. In addition, the container can be placed in different positions for filling or emptying.

An advantageous further development consists in providing the inside of the container with webs on the container wall. When the container rotates, these prevent the granules from slipping off the inner container wall, which hinders mixing. If, on the other hand, webs are attached, such a sliding movement is interrupted, the granulate is deflected, falls over the webs and is consequently better mixed. The webs are preferably designed such that they run parallel to that axis of rotation of the container around which the container rotates during the separation of the dust particles.

When arranging the webs, it makes sense to take the orientation of the container into account during emptying. If, at this point in time, the container is tilted by 90 ° relative to a horizontal axis in relation to the operating position, the preferred arrangement of the webs mentioned above is particularly advantageous since no granules are emptied by the webs when emptying is withheld. In other operating or emptying positions of the container or other positions of the axes of rotation, the webs m can be arranged in a correspondingly advantageous manner.

The container is expediently filled volumetrically or gravimetrically with valves or sliders via supply lines and / or storage containers. In particular, the valves can be designed entirely or partially as pinch valves.

Furthermore, it is advantageous to empty the container way via at least one discharge line, which is preferably separated from the container via a valve or slide control. In particular, individual or all valves in these discharge lines can be designed as pinch valves.

Air contaminated with dust particles must generally not be released into the environment. It is therefore advantageous to integrate at least one filter device of a known type into the invention, through which the air stream carrying dust particles is guided in the container walls after flowing through the passage openings.

At least one of the filters in the above is preferred

Filter device designed as a cartridge filter, through which the air is conducted from the outside into the interior of the filter and extracted there. In an advantageous development, a compressed air supply is arranged in the interior of the filter, which is opened via a valve, in order to remove the dust particles deposited on the outer filter wall during air filtering and thus to clean the filter. In an advantageous embodiment of the invention, the various units are electronically controlled and are able to communicate electronically with one another. In this way, the time sequence of individual control signals and individual process steps can be optimized and automated with regard to their efficiency.

It also appears expedient to integrate a suction device, as is known per se, into the device and to use it to clean the device.

The invention is explained in more detail below with reference to the exemplary embodiment shown in the figures. Show it:

Fig. 1 loading the sieve drum

Fig. 2 sieve drum during the dedusting / drying

Fig. 3 emptying the sieve drum

Fig. 4 Integration of the screening drum from Figures 1 to 3 in a granulate processing system

In Figure 1, the device is shown in a vertical position, as it seems appropriate for the introduction of the granules 40 contaminated with dust particles into the container, which is designed here as a sieve drum 10. The sieve drum 10 is surrounded by an airtight housing 20, to which a material / air supply 24 and a connection for the suction device 22 are attached. The airtight housing 20 and the sieve drum 10 are rotatably mounted about the tilt axis 6 mounted on the axles 30. By tilting it, the device is moved from the loading position to the operating position shown in FIG. To separate the dust particles or to dry the granules, air 50 is now introduced via the material / air supply 24 and air 50a via a second supply 60, which extends over the entire length of the sieve drum. The second feed 60 is provided along its length with outlet openings from which the air 52 flows into the sieve drum. In addition, this second feed 60 can be regulated via the feed valve 62. At the same time as the air supply is sucked off via the connection of the suction device 22. The air stream that forms swirls up granules and dust particles in the sieve drum 10 and carries them to the wall 11 of the sieve drum 10 provided with through-openings 12. The air 55 carrying dust particles is fed via the connection of the suction device 22 to a filter device known per se.

In order to be able to dry the granules simultaneously with the separation of the dust particles, an infrared heater 15 is axially mounted in the sieve drum, which heats the granules or the air flowing through them.

The process of separating the dust particles and / or drying is supported by at least occasionally rotating or reversing rotation of the sieve drum 10 about the axis of rotation 5, as a result of which homogeneous separation or drying of the granules is achieved more quickly.

If the filled granules 40 also consist of different types of granules, the rotational movements about the axis of rotation 5 contribute to a faster homogeneous mixing of the granules. FIG. 3 shows a possible unloading position. Housing 20 and sieve drum 10 were tilted about the tilt axis 6 in such a way that the material / air supply 24 points downward. The granules 70, which have been separated from and dried by dust particles, fall out downwards and can be sent for further processing. The emptying process can be supported or accelerated by rotating the screening drum 10 about the axis of rotation 5.

FIG. 4 shows the sieve drum 110 from FIGS. 1 to 3 in cooperation with advantageous developments. From three storage containers 140a, 140b, 140c, metered via a weighing device 142 and the valves of the storage containers 145a, 145b, 145c, various granules or admixtures are filled into the collecting container 141. After opening the valve of the material feed 144, this mixture of granules is sucked via a vacuum generated by the suction device 180 through the feed line 143 into the sieve drum 110, which is surrounded by the airtight housing 120. In addition, the screen drum 110 is rotatably mounted as described in FIGS. 1 and 3, so that it can be tilted in the indicated directions 106 and temporarily rotates in the direction 105.

After the sieve drum 110 has been filled in the loading position shown in FIG. 1, the sieve drum 110 is tilted into the operating position shown in FIG. 2, the valve of the material feed 144 is closed and instead the valve for the air feed 154 is opened, so that air 150 initially flows

Flows through drying device 152 and then gets into the rotating sieve drum 110, where it whirls up granules and dust particles, the dust particles described in the above be separated and the granules are dried at the same time.

In the meantime, the air carrying dust particles after flowing through the through openings 12 is extracted via the suction line 155 and fed to the filter device 181, which is equipped with two cartridge filters 185a and 185b, on the outer walls of which the dust particles settle.

Is the desired degree of drying or separation of the

Dust particles reached from the granules, the sieve drum 110 is tilted into the unloading position shown in Figure 3. After switching off the suction device or closing the suction valve 187 and opening the valve for the material discharge 177, the granules 170 separated and dried from dust particles are removed from the screening drum in the manner described above with reference to FIG. 3 and / or sucked off via the material discharge line 175 ,

Furthermore, the cartridge filters 185a and 185b are cleaned via compressed air feeds arranged inside them, the detached dust particles being collected in a collecting container 190.

Reference character list

5 axis of rotation 6 tilting axis

10 screening drum

11 Wall of the sieve drum

12 passage opening 15 infrared heater 20 airtight housing

22 Suction device connection

24 Material / air supply

30 axles for tilt axis storage

40 Granules contaminated with dust particles 50 Air, supplied via 24

50a additional air, supplied over 60

52 through openings in 60 exiting air

55 Airflow carrying dust particles

60 Additional air supply 62 Supply valve

70 Dried granules separated from dust particles

105 direction of rotation

106 direction of tilt

104a granulate storage container a 104b granulate storage container b

104c granulate storage container c

141 collecting container for granules

142 weighing device

143 Material feed line 144 Material feed valve

145a Valve reservoir a

145b valve reservoir b

145c valve reservoir c 150 air t

152 drying device

154 Air supply valve

155 Suction line for air carrying dust particles 170 Dried granules separated from dust particles

175 Material discharge line

177 Material discharge line valve

180 suction device

181 filter device 185a cartridge filter a

185b cartridge filter b

187 suction valve

190 dust container

Claims

claims

1. A method for separating dust particles from a granulate, in which an air stream is passed through the granulate, which carries the dust particles with it, so that the granules (40) containing the dust particles are placed in a container

(10) is introduced, the container wall (11) of which is provided with passage openings (12) for the dust particles, and whirled up there by the air flow introduced via a feed (24; 60) and to the container wall

(11) is carried along where the dust particles are subsequently discharged through the passage openings (12), while the granules remain in the container.

2. The method according to claim 1, characterized in that an extraction device (180) located outside the container (10) together with the air (50; 52) introduced via the feed (24; 60), an air flow through the container wall (11) generated and after the air flow has passed through the container wall (11) removes the dust particles carrying air (55).

3. The method according to claim 1, wherein the air flow is generated by at least one turbine, which is preferably speed-controlled.

4. The method according to any one of claims 1 to 3, d a d u r c h g e k e n n z e i c h n e t that at least part of the air stream is pulsed.

BESTATIGUNGSKOPIE

5. The method according to any one of claims 1 to 4, so that the air flow is generated alternately solely by the air (50; 52) introduced via the feed (24; 60) or the suction device (180).

6. The method according to any one of claims 1 to 5, so that a vacuum is generated and / or maintained in the container (10) during the separation of the dust particles with respect to the external environment.

7. The method according to any one of claims 1 to 6, that the granules (40) are sucked into the container (10) by negative pressure and or the granules are sucked out of the container (10) by negative pressure.

8. The method according to any one of claims 1 to 7, so that at least part of the air (50; 50a) forming the air flow is heated and / or dried before being introduced into the container (10).

9. The method according to any one of claims 1 to 8, so that at least a portion of the air (50; 50a) forming the air flow is ionized before being introduced into the container (10).

10. The method according to any one of claims 1 to 9, characterized in that the granules in the container (10) or which flow through the container de air (50; 52) is heated with a heat source (15) arranged in the container.

11. The method according to any one of claims 1 to 10, d a d u r c h g e k e n n z e i c h n e t that the container rotates at least temporarily rotating or reversing.

12. The method according to any one of claims 1 to 11, that a mixture of different granules and admixtures is introduced into the container (10) and this remains in the container until a homogeneous mixture has formed.

13. The method according to any one of claims 1 to 12, so that the air flow (55) carrying the dust particles after flowing through the passage openings (12) is passed through a filter device (181) after flowing through the passage openings (12).

14. The method according to claim 13, so that at least one filter of the filter device is cleaned by compressed air ejection inside the filter.

15. Device for separating dust particles from a granulate with at least one feed for an air stream that carries the dust particles, so that the a

Granulate (40) containing container (10), in the container wall (11) of which at least in places there are passage openings (12) for the dust particles, with mmdes- At least one air supply (24; 60) is provided, which allows an air flow from the inside of the container (10) at least through parts of the container wall (11), from which granules and dust particles can be carried, the passage openings (12) in the The container wall (11) are dimensioned such that they allow a defined separation between the granulate and dust particles when the air flow carrying the particles passes through and only the dust particles can be removed from the container (10).

16. The apparatus of claim 15, d a d u r c h g e k e n e z e i c h n e t that at least one suction device (180) is arranged outside the container (10).

17. The device according to any one of claims 15 to 16, that the container (10) is designed as a sieve drum.

18. Device according to one of claims 15 to 17, characterized in that the container (10) is enclosed by an airtight housing (20) on which at least one connection for the air supply (24; 60) and at least one connection for the suction device ( 22) are attached.

19. Device according to one of claims 15 to 18, characterized in that at least one turbine for generating the air flow is arranged in front of the air supply (24; 60), which is preferably speed-controlled.

20. Device according to one of claims 15 to 19, so that a heating and / or drying device (152) is arranged in front of the air supply (24; 60), through which the air to be supplied (50; 50a) can flow.

21. Device according to one of claims 15 to 20, so that at least one ionization device is arranged in front of the air supply (24; 60).

22. Device according to one of claims 15 to 21, so that at least one heat source (15) is arranged in the container (10).

23. Device according to one of claims 15 to 22, so that the container (10) is rotatably mounted along at least one axis that is not arranged vertically (5; 6) in the operating position.

24. Device according to one of claims 15 to 23, so that it is provided with a filter device (181) through which the air (55) carrying dust particles after flowing through the passage openings (12) can be passed.

25. The device according to claim 24, so that the filter device is provided with at least one cartridge filter (185a; 185b).

26. Device according to one of claims 24 to 25, characterized in that a closable compressed air supply is attached inside at least one filter.