DEVICE AND METHOD FOR DEDUSTING BULK MATERIALS

Description

I. Area of ​​application

[0001] The invention relates to the removal of dust from bulk materials, in particular by means of ionization, wherein the dust frequently adheres to the granules by means of electrostatic charging. II. Technical background

[0002] Especially in plastics technology, but also in pharmaceutical and food technology, raw materials in the form of bulk materials – such as granules, ground materials, coarse powders, etc. – often have to be handled. For the purposes of this application, all bulk materials are referred to by the abbreviated term "granules."

[0003] The transport of these bulk materials is often carried out by means of pneumatic conveying, in particular by means of air conveying, in which the granulate is transported to the desired location through conveyor lines by means of air flow and, for the most part, flying along with it.

[0004] The granulate should be as clean as possible for further processing, for example, use as raw material in a plastic injection molding machine, and especially free from dust-like contaminants. These dust-like contaminants can consist of foreign material that was inadvertently added to the granulate during production or transport, or they can be dust-like particles made of the same material as the granulate itself, which, however, may also be undesirable depending on the subsequent intended use.

[0005] Dust or dust-like impurities within the meaning of the present description should preferably have a particle size whose diameter is at most 1 / 10, better at most 1 / 30, better at most 1 / 100, better at most 1 / 1000 of the diameter of a granulate grain.

[0006] Therefore, the general aim is to separate such granules from the dust they contain before use.

[0007] Different techniques are available for this, from simple sieves to separating the transport air from granules and filtering the transport air to fraction separation using a cyclone.

[0008] One of the problems that arise is the strong adhesion of dust particles and granulate particles to each other, but also the adhesion of dust particles to device parts such as conveyor lines or granulate containers.

[0009] This strong adhesion is often caused by electrostatic charging, so that removal of the dust by mechanical means can usually only be carried out once these binding forces have been removed.

[0010] In principle, this is known to be possible by statically discharging the differently charged and thus mutually attracting particles, in this case dust particles on the one hand and granulate particles on the other, for example by grounding one fraction.

[0011] However, with a very large number of very small particles, as in the present case, this is difficult in practice.

[0012] For example, attempts have already been made to separate the granules by constantly swirling them upwards in a dedusting container sealed at the bottom, bringing them into close contact with ionized air. However, this can cause further abrasion and thus dust simply through the collision of granules.

[0013] EP 2 711 097 A1 shows a device for batchwise dedusting of a granulate, with a conveying flow generator arranged downstream of the dedusting container in the form of an ejector compressed air nozzle with a pressure connection and a dedusting container which has at least one granulate inlet opening for the granulate a granulate outlet opening in the lower part of the dust removal container, in particular in its base an air outlet opening, which is arranged in particular in the upper part of the dust removal container, an ionizer a fluidization unit for fluidizing the granulate in the dust removal container a control system which is able to control the fluidization unit and all moving parts, in particular valves, of the device the granulate outlet opening, preferably closable the peripheral walls surrounding the dust removal container, at least on the inner surfaces facing the interior, consist of an electrically non-conductive material, in particular glass the fluidization unit has an upwardly directed fluidization nozzle which is connected to a compressed air connection, in the lower part of the dust removal container, in particular in the granulate outlet opening.

[0014] In WO 2018 / 073053 A1, an attempt was made to extract the dust-laden air from the granule container through an air outlet opening rather than expelling it using overpressure. The air outlet opening was sealed by a sieve that prevented a granule grain from penetrating. In this case, the granule outlet opening is sealed by a flap.

[0015] WO 2016 / 041968 A1 discloses several nozzles in the outlet opening. However, these nozzles are part of the closure element. III. Description of the invention a) Technical task

[0016] It is therefore the object of the invention to provide a device for batchwise dedusting of a granulate, which is very compact and lightweight, is inexpensive to manufacture due to the fewest possible individual parts and, precisely for this reason, functions very reliably, as well as a method for operating such a device, which is very variable. b) Solution to the task

[0017] This task is solved by the features of the claims 1 and 9 solved. Advantageous embodiments emerge from the subclaims.

[0018] Regarding the Procedure This is achieved by generating a countercurrent flow in the dust removal container, which is known per se and directed from bottom to top, which is strong enough to move granules - which in the prior art were located as a batch on the closed closure element forming the bottom of the dust removal container - upwards with the countercurrent and thus to separate them.

[0019] Especially when the flow velocity of the counterflow decreases with altitude - which is the case, for example, when the cross-section of the air flow increases upwards - the upward force acting on the granules decreases until gravity prevails and the granules stop their rise in a reversal region occurring at a certain altitude and - usually outside the cross-section of the air flow or at its edge - sink back into the granule accumulation.

[0020] From there, if the countercurrent continues, you can get back into it and complete this cycle several times, depending on how long the air flow is maintained.

[0021] As is well known, this separation makes it possible to suck the dust particles out of the granulate - even if they still adhere slightly to the granulate grains - upwards by means of a corresponding negative pressure, especially in or above the reversal area.

[0022] First, a distinction must be made between batch operation and continuous operation.

[0023] In the prior art, the dedusting of a granulate, in particular a pneumatically conveyed granulate, was carried out in batches, i.e. the granulate outlet opening at the lower end of the dedusting container was closed, a batch of granulate was filled into the dedusting container up to a predetermined fill level and then the granulate was removed upwards, for example by whirling up the granulate by means of the countercurrent flow directed against gravity and conveying it out, in particular by suctioning off the dust-laden air, but without the granulate grains.

[0024] Ionization of the air in the dust extraction container is also already known.

[0025] Subsequently, by opening the closure element of the granulate outlet opening, the dedusted granulate was allowed to fall into the intermediate container below.

[0026] According to the invention, in batch operation, even during the filling process, the lower granulate outlet opening is not closed by a closure element of the device, such as a closure flap, so that such a closure element is not present at all.

[0027] If no counterflow is generated during the filling process, the granules fall down to the surface of the granulate bed in the intermediate container, which is usually located below, whereby this surface can also be at the level of the lower granulate outlet opening of the dedusting container or even slightly above it, i.e. already in the dedusting container.

[0028] Only a slight degree of dust removal takes place due to the air introduced into the dust extraction container being pushed out or sucked out, preferably by means of a negative pressure, which, however, only sucks out dust particles that are freely suspended in the air.

[0029] If the surface of the bulk material in the intermediate container is very high or has even already reached the dedusting container, the newly filled batch collects in the dedusting container and can then be more easily dedusted by whirling it up.

[0030] Preferably, however, there is already a counterflow during the filling process. The structured process sequence according to the invention thus consists in the fact that for batch operation A) with or without countercurrent (32) in the dedusting container (9), granules (4) are filled into the dedusting container (9) up to a predetermined fill level, B) when the fill level is reached, the filling process is terminated, C) the dedusting of the filled batch (4') in the dedusting container (9) by means of introduced ionized gas, in particular ionized air, when the fill level of an intermediate container arranged below the granule outlet opening reaches the height of the granule outlet opening and the granules (4) are swirled up by a countercurrent (32) and conveyed out, in particular sucked off, the dust-laden gas, D) the dedusting container (9) is cleaned by flushing with an ionized gas, in particular ionized air, E) after the fill level has fallen below the predetermined fill level, at least steps A) to C) and E) are carried out again,

[0031] The strength of the counterflow, i.e. its flow velocity and / or its volume flow and / or pressure, is preferably controlled in step A) in such a way that the granulate is kept mostly above the granulate outlet opening, i.e., it floats, so to speak, without being appreciably whirled up.

[0032] Majority means that it is more than 70 percent by volume, better more than 80 percent by volume, better more than 90 percent by volume, better more than 95 percent by volume, better more than 98 percent by volume.

[0033] In this context, not significantly whirling up means that the majority of the granules are not whirled up above the height of the lower quarter, in particular not above the height of the lower third, of the dust collection container.

[0034] The counterflow should not be so strong that the pressure in the dust collector at the granulate inlet is greater than the pressure in the granulate filler neck, as this would interrupt the filling process. The upward counterflow is typically generated by injecting compressed air, but a weak counterflow can also be achieved by introducing ionized gas, especially ionized air.

[0035] The swirling in step C) can also be carried out several times in succession using short bursts of compressed air.

[0036] After the filling process has been completed, the batch introduced into the dedusting container is further dedusted by whirling the granules upwards, but in particular not so high that they reach the upper air outlet opening, and preferably also not the filling nozzle that may be located below it.

[0037] The granulate outlet opening therefore remains permanently open, which means that there is no closure element as part of the device that can close the granulate outlet opening.

[0038] If granules build up downstream of the granulate outlet opening, for example, from the downstream intermediate container, and reach the granulate outlet opening, this can be partially or completely closed, but without a tightly sealing closure element, which is part of the device. This allows the permeability of the granulate outlet opening to be controlled more or less continuously by varying the counterflow.

[0039] The granules are transported from the storage container into the dust removal container by means of overpressure.

[0040] On the other hand, the dust-laden air can certainly be removed from the dust extraction container, preferably upwards, by means of suction air, the suction effect of which, however, is adjusted in such a way that it cannot transport granules out of the air outlet opening, even if there is no sieve there to retain the granules.

[0041] Preferably, the whirling up by injecting compressed air and the suctioning of the dust-laden air from the dust extraction container by means of suction air always take place simultaneously.

[0042] However, it is not possible to suck the granulate through the dust removal container from the storage container using a vacuum source located downstream of the dust removal container, since this vacuum source would draw in false air through the always open granulate outlet opening and would not draw any granulate from the storage container.

[0043] In step A) and / or C), the strength of the counterflow is controlled so that the granules do not reach the upper air outlet opening and / or the filler neck.

[0044] Once the dust removal process is complete, the counterflow is reduced or completely switched off so that the granules fall downwards and, depending on the fill level in the intermediate container below, fall into the intermediate container. In a non-stressed version, dust removal can also be carried out in continuous operation by a) granulate (4) is continuously filled into the dedusting container (9) in accordance with the consumption of granulate (4) from the dedusting container (9), b) simultaneously dedusting the granulate (4) in the dedusting container (9) by means of introduced ionized gas, in particular ionized air, and whirling up the granulate grains (4) by a counterflow (32) and Transport out, especiallySuction of the dust-laden gas is carried out c) whereby the average residence time of the granules (4) in the dedusting container (9) is determined by controlling the strength of the counterflow (32).

[0045] In both batch operation and continuous operation, the strength of the counterflow, in particular the flow velocity and / or the volume flow of the counterflow, can also influence the height to which the granulate is whirled up in the dedusting container.

[0046] During continuous operation, the filling process only needs to be interrupted if the granulate consumption downstream of the dust collection container is less than the amount of granulate delivered per unit of time through the supply line, i.e., in particular, if the intermediate container located below the dust collection container is completely filled and its contents would increase into the dust collection container. A permissible upper limit for the fill level in the intermediate container could be continuously monitored.

[0047] This can lead to a granule that has just fallen from the filler neck, i.e., the granule inlet, into the dust collection container, immediately falling through the granule outlet into the intermediate container without being moved upwards once, and the dust particles adhering to this granule are not yet completely removed. However, the statistical probability of this occurring is relatively low.

[0048] The procedure according to the invention therefore represents a compromise - both in batch and in continuous operation - between cost-effective dedusting in terms of manufacturing costs of the device and energy costs for the compressed air supply and an optimal dedusting result.

[0049] The ionization of the air in both batch and continuous operation in the dust collection container takes place in such a way that the ionizing tip of an ionizer is in contact with the interior of the dust collection container.

[0050] It is possible to switch between batch operation and continuous operation, i.e. both operating modes can be operated with the same device if the control system contains both operating modes.

[0051] Preferably, the ionizing tip is surrounded by a gas, particularly air, introduced into the dust collection container, thereby ionizing the air flowing past it into the container. The ionizing tip is preferably located at the mouth of such a gas supply line. This represents a particularly efficient way of ionizing the air being introduced.

[0052] Ionized gas, especially ionized air, can be introduced at several points: in the lower area of ​​the dedusting container through its peripheral wall, in particular as close as possible above the granulate outlet opening, in particular as close as possible above the outlet cone, and / or through a separate gas supply opening, i.e. not combined with the agitation nozzles, either in the outlet cone or at its lower end, i.e. at the level of the granulate outlet opening or even below it in the intermediate container and / or through the wall of an intermediate container located below the dedusting container.

[0053] This ensures that the counterflow generated by the turbulence nozzles contains as much ionized air as possible.

[0054] A special case, especially in batch operation, is the start of dedusting a larger quantity of granulate: In this case, the intermediate container located below the dedusting container is still empty and only fills up with each dedusted batch that falls into the intermediate container.

[0055] During normal operation, the intermediate hopper is filled up to the granulate outlet opening. The new batch to be dedusted can then be poured into the dedusting hopper and sits on the surface of the granulate in the intermediate hopper, so counterflow is not necessarily required during the filling process.

[0056] However, if the intermediate container is not filled up to the granulate outlet opening, this is usually essential, as otherwise the freshly filled granulate particles will immediately fall through into the intermediate container.

[0057] After dedusting and / or emptying the dedusting container by dropping the dedusted batch into the intermediate container, the dedusting container is rinsed with ionized air according to step D), wherein preferably a multiple of the volume of the interior of the dedusting container of ionized air is introduced and forced out or sucked out via the air outlet opening, thereby removing dust particles adhering to the inner circumferential surfaces of the dedusting container or loosening adhering granules.

[0058] To carry out a dust removal process, especially the one described so far, you need a device ,which, firstly - as is known for batch dedusting - has a dedusting container which has at least one granulate inlet opening and one granulate outlet opening as well as an air outlet opening for removing, in particular extracting, the air together with the dust to be removed.

[0059] The granulate inlet and / or the air outlet will preferably be located in the upper area, particularly in the upper half or upper third, with the air outlet preferably located in the upper lid of the dust removal container. The granulate outlet, on the other hand, will be located in the lower area, particularly in the lower third or preferably in the bottom of the granulate dust removal container.

[0060] Furthermore, a known dedusting device comprises a fluidizing unit for fluidizing the granulate in the dedusting container by injecting compressed air, as well as a control system, in particular an electronic control system, which is capable of controlling the entire device, i.e. in particular all moving parts, in particular valves and / or all pneumatically or electrically or electronically functioning parts of the device.

[0061] According to the invention, however, there is no activatable or deactivatable closure element at the granulate outlet opening, so it remains permanently open. This significantly simplifies the device's design and maintenance requirements.

[0062] Furthermore, the peripheral walls surrounding the dust collection container, at least on the inner surfaces facing the interior, are made of an electrically non-conductive material, in particular glass. As a result, ionized air molecules that are introduced into the dust collection container to electrically neutralize electrostatically charged dust particles and that come into contact with the interior surfaces are not immediately neutralized. Preferably, the peripheral walls of the dust collection container are made entirely of glass, in particular a piece of a cylindrical glass tube.

[0063] The agitation unit comprises upwardly directed agitation nozzles which are connected to a compressed air connection and are arranged in the lower part of the dedusting container close to the granulate outlet opening, preferably in an outlet cone forming the lower part of the dedusting container, the cross-section of which decreases towards the bottom and which can be made of metal.

[0064] As a result, the counterflow generated by the agitation nozzles, moving from bottom to top, can widen above the granulate outlet opening in the area of ​​the outlet cone, whereby the flow velocity automatically decreases with increasing widening until, at a certain height, the so-called reversal area, it is too low to move granulate grains against gravity or to keep them at a constant height.

[0065] By controlling the pressure applied to the agitation nozzles and / or the volume flow through the nozzles, it is possible to control how strongly and how high the granulate located above the agitation nozzles is agitated in the dust extraction container.

[0066] The agitation nozzles are designed and supplied with compressed air in such a way that they can generate a counterflow that keeps the granules suspended at least in a position above the granule outlet opening by swirling them upwards.

[0067] The ionizer used preferably has an ionizing tip that is arranged in the free end region of a gas supply line, in particular an air supply line, and projects into an opening in the wall of the dust removal container or even through this opening into the interior of the dust removal container. The ionizer is preferably arranged on the outside of the wall of the dust removal container. Preferably, only a single ionizer is present.

[0068] A gas supply opening, particularly an air supply opening, can be provided in the lower area of ​​the dust collection container, particularly above the outlet cone. The air introduced via the fluidization nozzles can also be ionized by an ionizer upstream of the fluidization nozzles. This allows the interior of the dust collection container to be optimally flooded with ionized air.

[0069] The air outlet opening is preferably completely open and, in particular, not covered by a screen. This prevents the screen from becoming clogged with dust or angel hair.

[0070] The negative pressure downstream of the air outlet opening is controlled in such a way that it is not able to suck granules into the air outlet opening.

[0071] For this purpose, the dust extraction container has a height of at least 100 mm, preferably at least 200 mm, preferably at least 300 mm, preferably at least 400 mm, so that the whirling up of the granules can be stopped at a sufficient distance below the air outlet, so that the reversal area of ​​the whirled up granules is still a sufficient distance above the lower granule outlet opening, which is sufficient to electrically neutralize the dust adhering to the granules and remove it from the granules.

[0072] The dust-laden air passing through the air outlet pushed out or is sucked away, is fed to a dust separator, in particular a filter, which can also be arranged far away from the dust extraction container.

[0073] For this purpose, a vacuum generator, for example a so-called compressed air ejector nozzle, is preferably provided between the air outlet and the dust separator, or a vacuum generator, in particular a blower, is provided downstream of the dust separator. Compressed air flows into such a well-known compressed air ejector nozzle, thereby entraining the surrounding air and creating a negative pressure upstream of the compressed air ejector nozzle and an overpressure downstream.

[0074] The device comprises a flow generator arranged in the feed line for granules in the form of a known compressed air ejector nozzle, which is arranged in the free end area of ​​the feed line, which can be designed in the form of a suction lance. There, the granules are sucked into a storage container and away the flow generator with overpressure in the conveyor line to the dust extraction container.

[0075] According to the invention, an intermediate container is arranged below the granulate outlet opening of the dust removal container, into which the granulate can fall through the granulate outlet opening.

[0076] The device comprises one, preferably only one, level sensor in the dedusting container and / or in the intermediate container.

[0077] In order to be able to produce granulate mixtures from two components, two suction lances for different storage containers can be connected to the dust removal container via one conveying capacity each, which either end in two separate granulate inlet openings in the dust removal container or whose conveying lines are combined outside the dust removal container to form a single conveying line and granulate inlet opening. c) Examples of implementation

[0078] An embodiment of a device for dedusting granules according to the invention is described below by way of example with reference to the figures in various functional states. They show: figure 1a, b :the device during the first filling of the intermediate container, shown in side view, partly in vertical section, Figure 2 :the device for filling the dust container, shown in side view, partly in vertical section Figure3 :the device for dedusting the granulate in the dedusting container, Figure 3.1: a detail enlargement Figure 3 , figure 4 :the device at the end of the dust removal process, Figure 5 :the device for emptying the dust container, Figure 6 :the device for rinsing the empty dust container, Figure 7: a view of the dust extraction container.

[0079] The dust removal of the granulate 4 takes place batchwise or continuously in the dust removal container 9.

[0080] First, batch operation is explained.

[0081] In ongoing batch operation, the first step is to Figure 2the dedusting container 9 is filled with a charge 4' of granulate 4, wherein the intermediate container 14, which is open at the top and is arranged below the dedusting container 9 and its lower granulate outlet opening 25, is filled up to the granulate outlet opening 25, so that the charge 4' newly introduced into the dedusting container 9 can be deposited on the upper side of the filling of the intermediate container 14 made of granulate 4 and is supported by it.

[0082] For this purpose, a suction lance 16 is inserted into a supply of granules 4 located in a storage container 7. Via the conveying line 15 connected to the suction lance 16, which terminates at its other end in an inlet nozzle 24, the free, open end of which, the granule inlet opening 8, is located in the dedusting container 9, the granules are pressed from the storage container 7 to the dedusting container 9 by the conveying air 3 flowing in the flow direction 10, which entrains the granule grains 4. This is achieved by an ejector compressed air nozzle 21a driven by compressed air in or near the suction lance 16.

[0083] The inlet nozzle 24 here is an angled piece of pipe which runs sealed through the wall of the dust removal container 9, and whose free end points downwards in the dust removal container 9, so that the granulate 4 supplied via the conveyor line 15 flows downwards out of the granulate inlet opening 8 and remains on the upper side of the filling of the intermediate container 14 in the height range above the granulate outlet opening 25, approximately in the height range of the outlet cone 28 and slightly beyond up to the height position of the fill level sensor 19a, which triggers the shutdown of the delivery of granulate 4. The compressed air supply to the ejector compressed air nozzle 21a in the suction lance 16 is then terminated.

[0084] During the filling process, the conveying air 3 leaves the dedusting container 9 via its air outlet opening 18, which is arranged in the lid 27 of the dedusting container 9 and which can be spanned by a sieve 5, through which the conveying air 3 and any dust 11 contained therein can flow, but not by granulate grains 4.

[0085] From there, the conveying air 3, now exhaust air 6, flows in the flow direction 10 along a dust line 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 to the dust 11.

[0086] The flow of the exhaust air 6 is optionalby a vacuum generator downstream of the air outlet opening 18 or at least reinforced, in this case again an ejector compressed air nozzle 21b, which is either already arranged immediately downstream of the air outlet opening 18 in the dust line 20 or can also be arranged downstream of the exhaust air filter 2.

[0087] 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 line, and thereby creates a negative pressure in the transport line upstream of the ejector compressed air nozzle 21 and thus a flow of the transport air in this flow direction 10.

[0088] In the sectional view of the Figures 1a to 6 and based on the supervision of the Figure 7It becomes clear that the dust removal container 9 is an upright, essentially cylindrical container, i.e. with rotationally symmetrical inner peripheral walls, which approach each other in the lower region towards the granulate outlet opening 25, which is preferably arranged centrally therein, in the form of a conical surface 28'.

[0089] The peripheral wall of the cylindrical part of the dust removal container 9 is formed by a piece of pipe made of an electrically non-conductive material, preferably glass, on whose open upper side the lid 27 sits and whose open underside rests on the cone 28, in which the inner conical surface 28' is formed. Fluidizing nozzles 31 open into this conical surface 28', through which compressed air can be injected into the interior of the dust removal container 9 to fluidize the granulate 4 contained therein. This air, along with electrical control signals and electrical current, is provided to the individual components by a controller 22.

[0090] Preferably, the outlet cone 28 comprises an annular channel 33 arranged concentrically to the granulate outlet opening 25, which is connected on the one hand to the compressed air supply and on the other hand to the swirling nozzles 31.

[0091] How Figure 7As can be seen, the area of ​​the particularly circular granulate outlet opening 25 can be substantially smaller than the inner free, particularly circular, cross-section of the dust removal container 9, and the cross-section of the particularly circular granulate inlet opening 8, i.e. the mouth at the end of the inlet nozzle 24, is generally also smaller than the inner free, particularly circular, cross-section of the dust removal container 9, although both of these are by no means a condition for the implementation of the invention.

[0092] The batch in the granulate dedusting container 9 is then dedusted as in Figure 3 and the enlargement of the Figure 3 . 1 shown: For this purpose, a negative pressure is optionally first generated in the dust line 20, i.e. the ejector compressed air nozzle 21b there is pressurized with compressed air.

[0093] Ionized air is introduced into the dust removal 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 granules 4. To ensure that this works well, compressed air is injected from the cone walls 28', in particular diagonally upwards, into the interior of the dust removal container 9 via the turbulence nozzles 31, thereby creating a counterflow 32 directed against gravity, which whirls up the granules 4 and separates them, as shown in Figure 3 shown.

[0094] The upward swirling is controlled in such a way that the granules 4 end their upward movement in a reversal area 30 and fall back down towards the outlet cone 28, whereby the reversal area 30 is still located below the inlet nozzle 24 in order to avoid the granules 4 from colliding with the inlet nozzle 24. As a result, the granules 4 do not reach the upper air outlet opening 18 and cannot be sucked into the exhaust air line 20 by the negative pressure prevailing there, even if this is Figure 1a is not covered by a sieve 5, i.e. is completely open, as is the case alternatively in Figure 1b is shown.

[0095] Preferably, the introduction of compressed air into the turbulence nozzles 31 is coupled via the control 22 with the introduction of compressed air into the compressed air ejector nozzle 21b for generating the negative pressure in the dust line 20.

[0096] Depending on the duration of the counterflow 32, the granules 4 undergo several such cycles. Preferably, however, the counterflow 32 is switched on and off several times in succession.

[0097] The counterflow 32 thus flows through the charge 4', which was previously supported downwards by the top of the bed in the intermediate container 14 approximately at the level of the granulate outlet opening 25, and has such a force that the majority of the 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 dedusting container 9, until the flow velocity in this air flow is no longer sufficient, due to the widening of this counterflow 32, to further lift the granulate grains 4 carried therein or even to hold them in this raised state.

[0098] Below the granulate outlet opening 25 and thus below the dust collection container 9 is the intermediate container 14, which is also usually essentially an upright cylinder. This intermediate container 14 is often located on top of a consumer 50, such as an injection molding machine, which only Figure 1a is indicated, and serves as an intermediate storage device from which - when the lower opening of the intermediate container 14 is open - the granulate 4 is fed to the consumer 50.

[0099] After this dust removal of the granulate has been carried out for a sufficient time, it is stopped so that according to Figure 4 the now dedusted granulate charge 4' accumulates again in the lower area of ​​the dedusting container 9, particularly in the area of ​​the outlet cone 28.

[0100] As soon as the filling level in the intermediate container 14 has dropped so far due to the consumption of granulate 4 by the consumer 50 that the upper side of the bed has reached, for example, the lower granulate outlet opening 25, as in Figure 5 shown, a batch 4' of granulate 4 can be introduced into the dedusting container 9 and dedusted as described above with reference to the Figures 2 and 3 explained.

[0101] In practice, a new batch 4' is added as soon as the fill level sensor 19 can no longer detect a fill level at its height, and a predefined waiting time has elapsed. This eliminates the need for another fill level sensor.

[0102] Preferably, however, before introducing a new batch 4', the now empty dust removal container 9 is first freed from the dust 11 deposited mainly on the inside of its walls, as can be seen from the Figure 6 recognizable.

[0103] For this purpose, the dust removal container 9 is flushed with ionized air 34, preferably with a multiple of the volume of the dust removal container 9, i.e. ionized air 34 is introduced via the air inlet opening 36, which is preceded by an ionizer 37, and sucked out via the negative pressure prevailing in the exhaust air line 20.

[0104] A pressure control valve 29 can be present in each compressed air line 26 from the controller 22 to the respective air inlet opening 36.

[0105] All described processes are controlled by a central control 22: This supplies compressed air via compressed air lines 26 controlled with regard to pressure and / or quantity and / or time the at least one ejector compressed air nozzle 21a in the at least one suction lance 16, the air supply opening 36, the optionally available at least one ejector compressed air nozzle 21b for generating negative pressure in the dust line 20.

[0106] Furthermore, the control system is connected via electrical lines 13 to all existing fill level sensors 19a, b on the dust removal container 9 and on the intermediate container 14 in order to, for example, end the filling process at the right time depending on their measuring signals.

[0107] In addition, the ionizer 37 is also supplied with electrical current and controlled by the controller 22.

[0108] In order to achieve a filling level in the intermediate container 14 which supports the next batch 4' introduced into the dedusting container 9 during batch operation, this intermediate container 14 must first be filled for the first time at the beginning of the entire dedusting process, as shown in the Figures 1a , bshown: 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 line 20 generates negative pressure and compressed air is injected via the swirling nozzles 31 and an upward counterflow 32 is generated against the direction of fall of the granulate particles 8.

[0109] As a result, the granules 4 falling from the inlet nozzle 24 are partially dedusted on their way down to the granule outlet opening 25.

[0110] Depending on the setting of the pressure and / or volume flow through the swirling nozzles 31, i.e. depending on the strength of the counterflow 32, a larger or smaller part of the granulate grains 4 falling from the filling nozzle 24 will not immediately fall through the granulate outlet opening 25, but will first be swirled up once or twice and thus be better dedusted before they fall down into the intermediate container 14.

[0111] The strength of the counterflow 32 can therefore be adjusted depending on the desired dedusting quality and / or depending on the quantity of granulate 4 consumed by the consumer 50 per unit of time.

[0112] For batch operation, the aim is to allow the fill level in the intermediate container 14 to rise to the height of the granulate outlet opening 25 of the dedusting container 9 according to Figure 1b, in order to then begin batchwise dedusting, whereby the fill level should preferably return to this level after dedusting a batch 4'. However, the consumption of granulate 4 by the downstream consumer cannot generally be influenced, and this goal can only be achieved by a similar feed of granulate into the dedusting container 9 and dedusting of the granulate.

[0113] However, continuous operation can also be carried out with this device in this way by adjusting the counterflow 32 and also the - preferably continuous - filling of granules into the dedusting container 9 in such a way that the surface of the bed of granules 4 in the intermediate container 14 never reaches its lower end, but preferably also does not rise above the granule outlet opening 25 of the dedusting container 9. LIST OF REFERENCE SYMBOLS

[0114] 1 Device for dust removal 2 Exhaust air filter 3 Conveying air 4 granules, granule accumulation, granule grain 4' Batch 5 Sieve 6 exhaust air 7 storage container 8 Granule inlet opening 9 Dust extraction container 10 Flow direction 11 Dust 12 Dust collection container 13 Electrical cable 14 Intermediate container 15 conveyor line 16 suction lance 17 Compressed air source 18 Air outlet opening 19 Level sensor 20 Dust line 21a, b Ejector compressed air nozzle, vacuum generator 22 steering 23 24 Inlet nozzle 25 Granule outlet opening 26 Compressed air line 27 Lid 28 Outlet cone 28' Conical surface 29 Pressure control valve 30 Reversal area 31 agitation nozzle32 Countercurrent 33 Ring canal 34 ionized gas 36 Gas supply opening 37 Ionizer 50 consumer

Claims

1. Device (1) for the batchwise dedusting of a granulate (4), with a conveying flow generator arranged upstream of the dedusting container (9) in the form of an ejector compressed air nozzle (21a) with a compressed air connection and a dedusting container (9), which comprises - 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 particular in its base, - an air outlet opening (18) which is arranged in particular in the upper part of the dedusting container (9), - an ioniser (37), - a whirling unit for whirling the granulate (4) in the dedusting container (9), - a controller (22) which is able to control the whirling unit and all moving parts, in particular valves, of the device, - wherein an intermediate container (14) is arranged below the granulate outlet opening (25) of the dedusting container (9), into which the granulate can fall through the granulate outlet opening (25), and a level sensor connected to the controller (22) via electrical lines (13) is arranged in the intermediate container (14), - wherein the peripheral walls surrounding the dedusting container (9) consist of an electrically non-conductive material, in particular glass, at least on the inner surfaces facing the interior, characterised in that - the closure-less granulate outlet opening (25) is permanently open, - 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 particular in the granulate outlet opening (25), - whereby, when the filling level in the intermediate container (14) measured by the filling level sensor rises to the level of the granulate outlet opening (25) of the dedusting container (9), the controller (22) initiates batchwise dedusting.

2. Device according to claim 1, characterised in that - the cross-section of the dedusting container (9) decreases in the lower part towards the granulate outlet opening (25) in the form of a conical surface (28'), - the compressed air nozzles (31) are arranged in the conical surface (28').

3. Device according to one of the preceding claims, characterised in that - the whirling nozzles (31) can be controlled as regard pressure and / or flow rate and / or volume flow, in particular can be controlled by the controller (22), and / or - the ioniser (37) comprises an ionising tip which is arranged in the free end region of an air supply line and protrudes into a gas supply opening (36) in the wall of the dedusting container (9) or even into the interior of the dedusting container (9).

4. Device according to one of the preceding claims, characterised in that the gas supply opening (36) with the ioniser (37) connected thereto - is arranged either in the lower region of the dedusting container (9), in particular above the outlet cone (28) or in the outlet cone (28), in particular in or on a gas supply opening (36), - or is arranged below the granulate outlet opening (25) in the intermediate container (14), in particular in its upper region.

5. Device according to one of the preceding claims, characterised in that - the air outlet opening (18) is permanently and in particular is completely open, in particular is not covered by a sieve (5), and / or - the height of the dedusting container (9) is at least 100 mm, better at least 200 mm, better at least 300 mm, better at least 400 mm, and / or - the peripheral wall of the dedusting container (9) is an upright glass tube open at the top and bottom, in particular having a rotationally symmetrical cross-section, and the cross-section is in particular unchanged over the entire length.

6. Device according to one of the preceding claims, characterised in that - the device comprises a dust separator, in particular an exhaust air filter (2), and / or a vacuum generator, in particular an ejector compressed air nozzle (21b), which is arranged downstream of the dedusting container (9), and / or - the granulate inlet opening (8) is arranged in the upper half, in particular in the upper third, of the height of the dedusting container (9).

7. Device according to one of the preceding claims, characterised in that - the whirling nozzles (31) are able to generate such an upwardly directed counterflow (32) that the granulate grains (4) whirled up thereby stop their upward movement mainly due to gravity before they reach the upper air outlet opening (18), and / or - the controller (22) has operating modes for batchwise operation and continuous operation and the controller can be switched between these two operating modes and / or - an intermediate container (14) is arranged on the underside of the dedusting container (9) below the granulate outlet opening (25).

8. Device according to one of the preceding claims, characterised in that - the dedusting container (9) has multiple granulate inlet openings (8), each of which is connected via a conveyor line (15) to a suction lance (16) in which is arranged an ejector compressed air nozzle (21a) or - the dedusting container (9) has only one granulate inlet opening (8), the conveyor line (15) of which has a branch outside the dedusting container (9) to two suction lances (16), in each of which is arranged an ejector compressed air nozzle (21a).

9. Method for the batchwise dedusting of a granulate (4) by means of a device according to one of the preceding claims, wherein in particular the dust (11) adhering to the granulate grains (4) is to be removed and wherein, A) when the filling level of the intermediate container (14) arranged below the granulate outlet opening (25) reaches the height of the granulate outlet opening (25), granulate is filled into the dedusting container (9) with or without counterflow in the dedusting container up to a predetermined filling level. B) when the filling level is reached, the filling process is terminated, C) the dedusting of the filled batch (4') in the dedusting container (9) is carried out by means of introduced ionised gas, in particular ionised air, and whirling up of the granulate grains (4) by a counter-current (32) and outward conveyance, in particular suctioning off, of the dust-laden gas, D) the dedusting container (9) is cleaned by flushing with an ionised gas, in particular ionised air, E) after the filling level drops below the specified filling level, at least the steps A) to C) and E) are repeated.

10. Method according to claim 9, characterised in that in step A) - the strength of the counterflow (32) is adjusted by controlling the whirling nozzles (31) as regards pressure and / or flow rate and / or volume flow, or - the counterflow (32) is effected by, in particular only by, the ionised gas introduced in the lower region of the dedusting container (9).

11. Method according to one of the preceding method claims, characterised in that - the suctioning of the dust-laden gas from the dedusting container (9) and the introduction of air via the whirling nozzles (31) is carried out simultaneously, in particular always only simultaneously, and / or - in step C) the whirling up of the granulate grains (4) is carried out several times in succession.

12. Method according to one of the preceding method claims, characterised in that - the granulate outlet opening (25) is not closed by a closure element attached to the device in any operating state, and / or - in step A) and / or C) the majority of the granulate grains (4) do not reach the upper air outlet opening (18), in particular also the filling neck (24).

13. Method according to one of the preceding method claims, characterised in that - after the filling level has dropped according to step E), the filling process according to step A) is started only after a predetermined time delay, and / or - as desired, either batchwise or continuous operation can be employed, in particular using the same device, and in particular the controller (22) of the device can be switched between batchwise operation and continuous operation.

14. Method according to one of the preceding method claims, characterised in that - the height of the reversal region (30) up to which the granulate (4) is whirled can be adjusted by the strength of the counterflow (32), and / or - the flushing according to step D) is only started after the dedusting according to step C) has ended, in particular after the filling level has fallen below the predetermined filling level according to step E).

15. Method according to one of the preceding method claims, characterised in that - during flushing according to step D), a multiple volume of the entire dedusting container (9) of ionised gas (34) is introduced, and / or - the gas (34), which meanwhile is at least partially no longer ionised, is continuously removed from the dedusting container (9), in particular by suction.

16. Method according to one of the preceding method claims, characterised in that after the dedusting of a granulate batch (4'), the counterflow (32) is terminated or at least reduced to such an extent that the granulate (4) present in the dedusting container (9) falls downwards through the granulate outlet opening (25).

17. Method according to one of the preceding method claims, characterised in that - the granulate (4) is transported to the dedusting container (9) by means of compressed air and / or - the dust (11) is removed from the dedusting container (9) by means of suction air.

18. Method according to one of the preceding method claims, characterised in that a gas, in particular air, to be introduced into the dedusting container (9) flows around the ionising tip of the ioniser (37).

19. Method according to one of the preceding method claims, characterised in that ionised gas, in particular ionised air, - is fed in the lower region of the dedusting container (9), in particular above the outlet cone (28) or through the outlet cone (28) or - below the granulate outlet opening (25), into the intermediate container (14).