APPARATUS AND METHOD FOR DE-DUSTING BULK MATERIALS

Abstract

In batchwise operation, the granulate grains (4) are filled into the dedusting container (9), which has no closure element at the lower granule outlet opening (25) and in which the whirling nozzles (31) for introducing compressed air are arranged in a lower cone (28), and—in particular depending on the filling level in the intermediate container (14) below—are filled into the dedusting container (9)

either dropped downwards without counterflow (32), dedusting being effected by conveying out the introduced air, optionally due to the negative pressure at the upper air outlet opening, whereby only freely suspended dust particles are sucked off

or already during the filling process a counterflow (32) is introduced, which partially does not allow the filled granulate grains (4) to fall through the granulate outlet opening (25) but holds them quasi floating at the level of the lower third or lower quarter of the dedusting container (9).

By controlling the counterflow (32), the height of the reversal area (30) of the highly turbulent granulate grains (4) and also the residence time of the granulate grains (4) in the dedusting container (9) can be controlled, so that the device can also be operated in continuous operation.

Claims

1. A device (1) for dedusting a granulate (4), having a conveying flow generator arranged upstream of a dedusting container (9) in the form of an ejector compressed air nozzle (21a) with a compressed air connection and a dedusting container (9) comprising: at least one granulate inlet opening (8) for the granulate (4), a granulate outlet opening (25) in the lower part of the dedusting container (9) in its base, an air outlet opening (18) which is arranged in the upper part of the dedusting container (9), an ionizer (37), a whirling unit for whirling up the granulate (4) in the dedusting container (9), a controller (22) capable of controlling the whirling unit and all movable parts of the device, wherein the granulate outlet opening (25) is permanently open, peripheral walls surrounding the dedusting container (9) consist of an electrically non-conductive material at least on inner surfaces facing the interior, the whirling unit has upwardly directed whirling nozzles (31), which are connected to a compressed air connection, in the lower part of the dedusting container (9), in the granulate outlet opening (25).

2. The device according to claim 1, wherein the cross-section of the dedusting container (9) decreases in the lower part towards the granulate outlet opening (25) in the form of a cone surface (28′), and the compressed air nozzles (31) are arranged in the cone surface (28′).

3. The device according to claim 1, wherein the whirling nozzles (31) are controllable with respect to pressure or flow velocity or volume flow, are controllable by the controller (22).

4. The device according to claim 1, wherein the ionizer (37) comprises an ionizing tip which is arranged in a free end region of an air supply line and projects into a gas inlet opening (36) in the wall of the dedusting container (9) or even into the interior of the dedusting container (9).

5. The device according to claim 1, wherein the gas inlet opening (36) with ioniser (37) connected thereto is arranged either in the lower region of the dedusting container (9), above the outlet cone (28), or in the outlet cone (28), in or at a gas supply port (36), or or below the granulate outlet opening (25) in the intermediate container (14), in its upper region.

6. The device according to claim 1, wherein the air outlet opening (18) is permanent and completely open, in particular is not covered by a screen (5).

7. The device according to claim 1, wherein the height of the dedusting container (9) is at least 100 mm.

8. The device according to claim 1, wherein the peripheral wall of the dedusting container (9) is an upright glass tube which is open at the top and bottom, having a rotationally symmetrical cross-section, and the cross-section is unchanged over the entire length.

9. The device according to claim 1, wherein the device comprises a dust separator, in particular an exhaust air filter (2), or a vacuum generator, in particular an ejector compressed air nozzle (21b), which is arranged downstream of the dedusting container (9).

10. The device according to claim 1, characterized in that the granulate inlet opening (8) is arranged in the upper half of the height of the dedusting container (9).

11. The device according to claim 1, wherein the whirling nozzles (31) are capable of generating an upwardly directed counterflow (32) such that the granulate grains (4) thereby whirled up stop their upward movement mainly due to gravity before they reach the upper air outlet opening (18).

12. The device according to claim 1, wherein the controller (22) has operating modes for batchwise operation and continuous operation and the controller can be switched between these two operating modes or an intermediate container (14) is arranged below the granulate outlet opening (25) at the underside of the dedusting container (9).

13. The device according to claim 1, wherein the dedusting container (9) has a plurality of granulate inlet openings (8), each of which is connected via a conveyer pipe (15) to a suction lance (16) in which an ejector compressed air nozzle (21a) is arranged, or the dedusting container (9) has only one granulate inlet opening (8), the conveyer pipe (15) of which has outside the dedusting container (9) a branch to two suction lances (16), in each of which an ejector compressed air nozzle (21a) is arranged.

14. A method for removing dust from a granulate (4) by means of a device according to claim 1 whereby the dust (11) adhering to the granulate grains (4) is to be removed, and wherein either for batchwise operation with or without counterflow (32), granulate (4) is filled into the dedusting container (9) up to a predetermined filling level, the filling process is terminated when the filling level is reached, the dedusting of the filled batch (4′) in the dedusting container (9) is carried out by means of introduced ionized air, and whirling up the granule grains (4) by means of a counterflow (32) and conveying out, the dust-laden gas, the dedusting container (9) is cleaned by flushing with an ionised gas, in particular ionised air, after the filling level has fallen below the specified level, the previous steps can be carried out again, or for continuous operation granulate (4) is continuously filled into the dedusting container (9) according to the consumption of granulate (4) from the dedusting container (9), the granulate (4) is simultaneously de-dusted in the de-dusting container (9) by means of introduced ionized air, and the granulate grains (4) are swirled up by a counterflow (32) and conveyed out, in particular sucked out, of the dust-laden gas wherein the average residence time of the granulate grains (4) in the dedusting container (9) is determined by controlling the force of the counterflow (32).

15. The method according to claim 14, wherein in bathwise operation the force of the counterflow (32) is adjusted by controlling the whirling nozzles (31) with respect to pressure and/or flow velocity and/or volume flow, or the counterflow (32) is effected by, in particular only by, the ionized gas introduced in the lower region of the dedusting container (9).

16. The method according to claim 14, wherein the sucking out of the dust-laden gas from the dedusting container (9) and the introduction of air via the whirling nozzles (31) is carried out simultaneously.

17. The method according to claim 14, wherein the granulate grains (4) are whirled up several times in succession.

18. The method according to claim 14, wherein the majority of the granulate grains (4) do not reach the upper air outlet opening (18), in particular also the inlet stub (24).

19. The method according to claim 14, wherein the granulate outlet opening (25) is not closed in any operating state by a closure element attached to the device.

20. The method according to claim 14, wherein the control (22) of the device can be switched between batchwise operation and continuous operation.

21. The method according to claim 14, wherein after the filling level has dropped, the filling process is only started after a specified time delay.

22. The method according to claim 14, wherein the height of the reverse zone (30), up to which the granulate (4) is swirled up, can be adjusted by the force of the counterflow (32).

23. The method according to claim 14, wherein flushing is only started after dedusting has been completed, in particular after the filling level has dropped below the specified level.

24. The method according to claim 14, wherein a multiple volume of the total dedusting container (9) of ionized gas (34) is introduced during flushing, or the gas (34), which is meanwhile at least partly no longer ionised, is continuously removed from the dedusting container (9) by suctioning out.

25. The method according to claim 14, wherein the counterflow (32) is terminated or at least reduced to such an extent that the granulate (4) located in the dedusting container (9) falls out downwards through the granulate outlet opening (25) after dedusting a granulate charge (4′).

26. The method according to claim 14, wherein the granulate (4) is transported by compressed air to the dedusting container (9) or the dust (11) is removed from the dedusting container (9) by means of suction air.

27. The method according to claim 14, wherein the ionizing tip of the ionizer (37) is circulated around by a gas, in particular air, which is to be introduced into the dedusting container (9).

28. The method according to claim 14, wherein ionised gas is supplied in the lower region of the dedusting container (9), above the outlet cone (28) or through the outlet cone (28) or below the granulate outlet opening (25) into the intermediate container (14).

Description

C) EMBODIMENT CONTAINERS EXAMPLES

[0092] A design of a device for removing dust from a granulate according to the invention is described in the following exemplarily on the basis of the figures in different functional states. The figures show:

[0093] FIGS. 1a, b: the device for the first filling of the intermediate container, shown in the side view, partly in vertical section,

[0094] FIG. 2: the device during filling of the dedusting container, shown in the side view, partly in vertical section

[0095] FIG. 3: the device for dedusting the granulate contained in the dedusting container,

[0096] FIG. 3.1 an enlargement from FIG. 3,

[0097] FIG. 4: the device at the end of the dedusting process,

[0098] FIG. 5: the device for emptying the dust container,

[0099] FIG. 6: the device when flushing the empty dust collector,

[0100] FIG. 7: a view from above onto the dedusting container.

[0101] Dedusting of granulate 4 is carried out in batches or continuously in the dedusting container 9.

[0102] At first the batchwise operation is explained.

[0103] During batchwise operation, the dedusting container 9 is first filled with a batch 4′ of granulate 4 as shown in FIG. 2, whereby the intermediate container 14, which is open at the top and is arranged under the dedusting container 9 and its lower granulate outlet opening 25, is filled up to the granulate outlet opening 25, so that the batch 4′ newly introduced into the dedusting container 9 can deposit on the upper side of the fill of the intermediate container 14 of granulate 4 and is supported by this.

[0104] For this purpose, a suction lance 16 is inserted in a storage of granulate 4, which is located in a storage container 7. Via the conveyer pipe 15 connected to the suction lance 16, which ends with its other end in an inlet stub 24, the free open end of which, the granulate inlet opening 8, is located in the dedusting container 9, the granulate is pressed from the storage container 7 to the dedusting container 9 by means of the conveying air 3 flowing in the direction of flow 10, which entrains the granulate grains 4 to the dedusting container 9. This is achieved by means of a compressed air operated ejector compressed air nozzle 21a in or near the suction lance 16.

[0105] The inlet stub 24 here is an angled pipe section which runs through the wall of the dedusting container 9 in a sealed manner and whose free end points downwards in the dedusting container 9, so that the granulate 4 fed via the conveyer pipe 15 flows downwards out of the granulate inlet opening 8 and remains lying on the upper side of the fill of the intermediate container 14 in the height region above the granulate outlet opening 25, approximately in the height region of the outlet cone 28 and slightly beyond that to the height position of the filling level sensor 19a, which triggers the switching off of the delivery of granulate 4. Then the compressed air supply to the ejector compressed air nozzle 21a in the suction lance 16 is terminated.

[0106] During the filling process, the conveying air 3 leaves the dedusting container 9 via its air outlet opening 18, which is located in the lid 27 of the dedusting container 9 and which can be spanned by a screen 5, through which the conveying air 3 and any dust 11 contained in it can flow, but not granulate grains 4.

[0107] From there the conveying air 3, now exhaust air 6, flows in flow direction 10 along a dust pipe 20 to a dust collection container 12 and through an exhaust air filter 2, which is preferably arranged in an outlet opening in the lid of the dust collection container 12 and which is not permeable for the dust 11.

[0108] The flow of the exhaust air 6 is optionally effected or at least intensified by a vacuum generator downstream of the air outlet opening 18, in this case again an ejector compressed air nozzle 21b, which is either already arranged directly downstream of the air outlet opening 18 in the dust pipe 20 or can also only be arranged downstream of the exhaust air filter 2.

[0109] Such an ejector compressed air nozzle 21a, b shoots compressed air usually taken from an existing stationary compressed air network 17—in the desired flow direction 10 into the respective transport pipe, and thereby generates a negative pressure in the transport pipe upstream of the ejector compressed air nozzle 21 and thus a flow of the transport air in this flow direction 10.

[0110] In the sectional view of FIG. 1a to 6 and from the view of FIG. 7 it becomes clear that the dedusting container 9 is an upright, essentially cylindrical container, i.e. with rotationally symmetrical inner circumferential walls, which approach one another in the lower region to the granulate outlet opening 25, preferably arranged centrally therein, in the form of a cone surface 28′.

[0111] The circumferential wall of the cylindrical part of the dedusting container 9 is formed by a tube piece of an electrically non-conductive material, preferably of glass, on the open upper side of which the lid 27 is seated and the open underside of which is seated on the cone 28, in which the inner cone surface 28′ is formed. In this cone surface 28′, whirl-up nozzles 31 open out, through which compressed air can be injected into the interior of the dedusting container 9 to whirl up the granulate 4 inside, which is made available to the individual components by a controller 22, as are electrical control signals and electrical current.

[0112] The outlet cone 28 preferably comprises a ring channel 33 arranged concentrically to the granulate outlet opening 25, which is connected on the one hand to the compressed air source and on the other hand to the whirling nozzles 31.

[0113] As FIG. 7 shows, the area of the granulate outlet opening 25, which is in particular circular, may be substantially smaller than the internal free cross-section, which is in particular circular, of the dedusting container 9, and the cross-section of the granulate inlet opening 8, which is in particular circular, the mouth at the end of the inlet stub 24, is in general also smaller than the internal free cross-section, which is in particular circular, of the dedusting container 9, which, however, is by no means a condition for the realisation of the invention.

[0114] The batch in the granulate dedusting container 9 is then deducted as shown in FIG. 3 and the enlargement of FIG. 3.1:

[0115] For this purpose, a vacuum is optionally first generated in the dust pipe 20, i.e. compressed air is applied to the ejector compressed air nozzle 21b there.

[0116] Ionized air is introduced into the dedusting container 9 via the gas inlet opening 36, which is intended to neutralize the static charge of the dust particles 11 as well as the granulate grains 4. In order for this to work well, compressed air is injected into the interior of the dedusting container 9 via the whirling nozzles 31 from the cone walls 28′, in particular obliquely upwards, and thus a counterflow 32 directed against gravity is generated, which whirls up and separates the granulate grains 4 as shown in FIG. 3.

[0117] The high turbulence is controlled in such a way that the granulate grains 4 stop their upward movement in a reverse zone 30 and fall down again in the direction of the outlet cone 28, whereby the reverse zone 30 is still below the inlet stub 24, in order to avoid a collision of granulate grains 4 at the inlet stub 24. As a result, the granulate grains 4 do not reach the upper air outlet opening 18 and cannot be sucked into the exhaust air pipe 20 by the negative pressure prevailing there, even if it is not covered by a screen 5 as shown in FIG. 1a, i.e. it is completely open, as shown in FIG. 1b alternatively.

[0118] Preferably, the control 22 is used to introduce compressed air into the whirling nozzles 31 coupled with the introduction of compressed air into the compressed air ejector nozzle 21b to generate the negative pressure in the dust pipe 20.

[0119] Depending on the duration of the counterflow 32, the granulate grains 4 pass through several such circuits. Preferably, however, the counterflow 32 is switched on and off several times in succession.

[0120] The counterflow 32 thus flows through the charge 4′, which was previously supported downwards by the top of the bulk material in the intermediate container 14 at approximately the level of the granulate outlet opening 25, and has such a force that most granulate grains 4 do not fall downwards through the granulate outlet opening 25, but are transported upwards by the counterflow 32 at least in the middle of the cross-section of the granulate de-dusting container 9 until the flow velocity in this air flow is no longer sufficient, due to the widening of this counterflow 32, to raise the granulate grains 4 carried in it further or even to maintain them in this raised state.

[0121] Below the granulate outlet opening 25 and thus below the dedusting container 9 is the intermediate container 14, which is also mostly an upright cylinder. This intermediate container 14 is often placed on the top of a consumer 50, such as an injection moulding machine, which is only indicated in FIG. 1a, and serves as an intermediate storage from which—when the lower opening of the intermediate container 14 is open—the granulate 4 is fed to the consumer 50.

[0122] After this dedusting of the granulate has been carried out for a sufficient period of time, it is terminated so that, according to FIG. 4, the now dedusted granulate batch 4′ accumulates again in the lower area of the dedusting container 9, in particular in the area of the outlet cone 28.

[0123] As soon as the level in the intermediate container 14 has been reduced to such an extent that, for example, the upper side of the bulk material has reached the lower granulate outlet opening 25, as shown in FIG. 5, as a result of consumption of granulate 4 by the consumer 50, a batch of 4′ of granulate 4 can again be introduced into the dedusting container 9 and be dedusted, as explained above in FIGS. 2 and 3.

[0124] In practice, a new batch of 4′ is filled as soon as the level sensor 19 can no longer detect a level at its height and a specified waiting time has elapsed since then. This eliminates the need for an additional level sensor.

[0125] Preferably, however, before introducing a new batch 4′, the now empty dedusting container 9 is first freed of the dust 11 deposited mainly on the inside of its walls, as shown in FIG. 6.

[0126] For this purpose, the dedusting container 9 is flushed with ionized air 34, preferably with a multiple of the volume of the dedusting container 9, i.e. via the air inlet opening 36, which is preceded by an ionizer 37, ionized air 34 is introduced and sucked off via the negative pressure prevailing in the exhaust air pipe 20.

[0127] A pressure control valve 29 may be provided in each of the compressed air lines 26 from control 22 to the respective air inlet opening 36.

[0128] All described processes are controlled by a central control 22:

[0129] This supplies compressed air via compressed air lines 26 controlled with regard to pressure and/or quantity and/or time. [0130] the at least one ejector compressed air nozzle 21a in the at least one suction lance 16, [0131] the air inlet opening 36, [0132] the optionally available at least one ejector compressed air nozzle 21b for generating negative pressure in the dust pipe 20.

[0133] In addition, the control system is connected via electric cables 13 with all existing filling level sensors 19a, b at the dedusting container 9 and at the intermediate container 14 in a signal-technical connection in order to terminate the filling process at the right time, for example, depending on their measurement signals.

[0134] In addition, the ionizer 37 is also supplied with electrical current and controlled by the control 22.

[0135] In order to achieve such a filling level in the intermediate container 14, which supports the next batch 4′ introduced into the dedusting container 9 during batchwise operation, this intermediate container 14 must first be filled at the beginning of the entire dedusting process, as shown in FIGS. 1a, b:

[0136] By activating the ejector compressed air nozzle 21a in the suction lance 16, granulate 4 is introduced into the dedusting container 9 via the granulate inlet opening 8, while at the same time both the ejector compressed air nozzle 21b in the exhaust air pipe 20 generates vacuum and compressed air is injected via the whirling nozzles 31 and an upwardly directed counterflow 32 is generated against the falling direction of the granulate grains 4.

[0137] This means that the granulate grains 4 falling down from the inlet stub 24 are partially de-dusted on their way down to the granulate outlet opening 25.

[0138] Depending on the setting of the pressure and/or volume flow through the whirling nozzles 31, i.e. depending on the force of the counterflow 32, a larger or smaller part of the granulate grains 4 falling out of the inlet stub 24 will not immediately fall through the granule outlet opening 25, but will first be whirled up once or twice and thus better de-dusted before they fall downwards into the intermediate container 14.

[0139] The force of the counterflow 32 can thus be set depending on the desired dedusting quality and/or depending on the amount of granulate 4 consumed by the consumer 50 per time unit.

[0140] For batchwise operation, the aim is to raise the filling level in the intermediate container 14 to the level of the granulate outlet 25 of the dedusting container 9 as shown in FIG. 1b, in order to then be able to start dedusting batchwise, whereby the filling level should preferably be at this level again after dedusting a batch of 4″. However, the consumption of granulate 4 cannot normally be influenced by the downstream consumer, and this aim can only be achieved by analogous feeding of granulate into the dedusting container 9 and dedusting of granulate.

[0141] However, continuous operation with this device can also be carried out in this way by adjusting the counterflow 32 and also the—preferably continuous—filling of granulate into the dedusting container 9 in such a way that the surface of the granulate filling 4 in the intermediate container 14 never reaches its lower end, but preferably does not rise above the granulate outlet opening 25 of the dedusting container 9.

REFERENCE SIGN LIST

[0142] 1 dedusting device

[0143] 2 exhaust air filter

[0144] 3 conveying air

[0145] 4 granulate, granulate filling, granulate grain

[0146] 4′ batch

[0147] 5 screen

[0148] 6 exhaust air

[0149] 7 storage container

[0150] 8 granulate inlet opening

[0151] 9 dedusting container

[0152] 10 direction of flow

[0153] 11 dust

[0154] 12 dust-collection container

[0155] 13 electric cable

[0156] 14 intermediate container

[0157] 15 conveyer pipe

[0158] 16 suction lance

[0159] 17 compressed air source

[0160] 18 air outlet opening

[0161] 19 level sensor

[0162] 20 dust pipe

[0163] 21a, b ejector compressed air nozzle, vacuum generator

[0164] 22 control

[0165] 23

[0166] 24 inlet stub

[0167] 25 granulate outlet opening

[0168] 26 compressed air line

[0169] 27 lid

[0170] 28 outlet cone

[0171] 28′ cone surface

[0172] 29 pressure control valve

[0173] 30 reverse zone

[0174] 31 whirling nozzle

[0175] 32 counterflow

[0176] 33 ring channel

[0177] 34 ionized gas

[0178] 36 gas supply port

[0179] 37 ionizer

[0180] 50 consumer