Dryer unit for drying plastic granulate

Abstract

The invention relates to a dryer unit (1) for drying plastic granulate (2) in a granulate container (3), preferably provided with a capacity of at least 100 litres, the dryer unit (1) comprising: - a compressed air line system (4) having a compressed air inlet (5) for receiving compressed air and having a compressed air outlet (6) for transferring the compressed air into the granulate container (3); - a recirculating air line system (7) having a recirculating air inlet (8) for receiving recirculating air from the granulate container (3) and having a recirculating air outlet (9) for transferring the recirculating air into the granulate container (3); and - a recirculating air heater (10) arranged in the recirculating air line system (7) for heating the recirculating air, wherein the dryer unit (1) is designed as a unit which can be transported independently of the granulate container (3).

Description

[0001] Drying unit for drying plastic granules

[0002] The present invention relates to a dryer unit for drying plastic granules in a granule container, preferably with a capacity of at least 100 liters, wherein the dryer unit comprises a compressed air duct system with a compressed air inlet for receiving compressed air and with a compressed air outlet for passing the compressed air into the granule container, a recirculation duct system with a recirculation inlet for receiving recirculated air from the granule container and with a recirculation outlet for passing the recirculated air into the granule container, and a recirculation heater arranged in the recirculation duct system for heating the recirculated air.

[0003] Furthermore, the invention relates to a granule drying system with such a dryer unit and a method for manufacturing a granule drying system.

[0004] Drying units of this type are used to dry plastic granules before the granules undergo a plasticizing process for a shaping process such as injection molding, compression molding, pressing, extrusion, or blow molding. For such shaping processes, especially extrusion blow molding, the degree of dryness and therefore the drying capacity of the drying unit is crucial for the quality of the molded parts. To achieve the required dryness, it is advantageous to supply the plastic granules contained in the granule container of a granule drying system using a combination of compressed air and the exhaust air from the granule container, which is recirculated as air. This allows for high drying capacity regardless of the ambient humidity.

[0005] A disadvantage of such granule drying systems is that they are specifically designed and constructed for a particular forming machine, especially an extrusion blow molding machine, and their manufacture is quite complex. Furthermore, the drying units of these systems often take up a considerable amount of space, which can be particularly problematic given existing factory layouts. Older or alternative granule drying systems, in which drying is achieved either solely by means of compressed air or solely by means of recirculated air, often cannot be improved due to space constraints.

[0006] The object of the present invention is therefore to provide a dryer unit improved upon the prior art, which is easy to handle and retrofit, and in particular offers a plug-and-play solution for drying plastic granules using a granule container.

[0007] This problem is solved by the features of claim 1, namely with a dryer unit mentioned above, wherein the dryer unit is designed as a unit that can be transported independently of the granulate container.

[0008] A major advantage of the invention is that the dryer unit is a complete and self-contained unit that can be used with virtually any granule container. In other words, the dryer unit is compatible with virtually any granule container and can be integrated into an existing granule drying system, allowing for easy retrofitting and replacement. The dryer unit is particularly advantageous when used with a granule container with a capacity of at least 100 liters, and preferably up to 10,000 liters. In such a configuration, the energy consumption of the dryer unit can be drastically reduced, by up to 50%.

[0009] The drying unit is fundamentally suitable for drying all plastics, i.e., in particular both hygroscopic and / or non-hygroscopic plastic granules. It is especially suitable for drying hygroscopic polyethylene terephthalate (PET).

[0010] The dryer unit is particularly suitable for drying plastic granules in a fully sealable cylindrical and funnel-shaped granule container with a rotational symmetry axis vertically aligned in the operating position, wherein the granule container has a top and a bottom in an operating position.

[0011] The granule container preferably has a granule feed opening for adding undried plastic granules, wherein the granule feed opening is particularly located on the top of the granule container.

[0012] The granule container preferably has a granule dispensing opening for dispensing dried plastic granules, wherein the granule dispensing opening is preferably located on the underside of the granule container.

[0013] This means, in particular, that the granulate container is designed so that the plastic granules contained within it migrate from top to bottom and are dried in the process, until, after a residence time in the granulate container of, for example, approximately four hours, they are removed or passed on, or kept at a certain temperature.

[0014] The compressed air piping system can be referred to as the primary air system and the compressed air as primary air.

[0015] The pressure line system of the dryer unit is particularly suitable for receiving compressed air at pressures of up to 10 bar.

[0016] The recirculating air duct system can be referred to as the secondary air system and the recirculated air as secondary air.

[0017] The recirculation duct system of the dryer unit is designed to receive recirculated air, i.e., exhaust air, from the granulate container.

[0018] The exhaust air escapes from the granulate container, in particular from an exhaust air opening at the top of the granulate container.

[0019] Particularly preferably, the granule drying system has an exhaust air duct connected to the exhaust air opening and the recirculation air inlet, which is designed so that the exhaust air enters the recirculation duct system of the dryer unit as recirculation air, wherein the recirculation air is particularly extracted.

[0020] The top of the granulate container, especially the exhaust air opening, can be equipped with a dust filter for filtering the exhaust air and / or with a water separator.

[0021] The transportability of the dryer unit, independent of the granule container, is preferably also to be understood as meaning that the dryer unit can be easily separated from the granule container and, above all, can be easily transported to other locations for maintenance purposes, e.g., in a

[0022] A specialized workshop is required to be able to repair and / or maintain the product. Further advantageous embodiments of the invention are defined in the dependent claims.

[0023] The forced-air heating system can have one or more electric heating elements.

[0024] It is particularly preferred that the dryer unit is designed for fluidic and / or mechanical connection with the granulate container.

[0025] Preferably, the compressed air outlet, the recirculation air outlet, and the recirculation air inlet are detachably connected to the granule container. This allows for easy connection and / or disconnection of the dryer unit to and from the granule container, enabling the dryer unit to be easily retrofitted to an existing granule container and / or replaced or temporarily exchanged in case of a defect or for maintenance.

[0026] The recirculated air preferably has a pressure of approximately 0.5 bar at the recirculation outlet of the dryer unit.

[0027] A fluidic connection is understood to be, in particular, a connection to enable a fluid transfer between two components, whereby a mechanical connection is not necessarily required.

[0028] Mechanical connections can be achieved using fasteners such as screws, rivets, bolts, and / or bayonet systems. Welding is also a possibility.

[0029] It is preferred that the dryer unit be self-supporting. Self-supporting means, in particular, that the granule container is not subjected to the load of the dryer unit. This allows, for example, universal compatibility with existing granule containers, even if these are not designed to support additional components.

[0030] It is particularly preferred that the dryer unit has a housing within which the compressed air piping system and the recirculation piping system are arranged, in particular wherein the housing can contribute to the load-bearing capacity of the dryer unit and / or can also provide a visual screen for the dryer unit.

[0031] It may be provided that the dryer unit has a supporting structure such as a frame within which the compressed air piping system and the recirculation piping system are arranged, preferably wherein the supporting structure can contribute to the load-bearing capacity of the dryer unit.

[0032] Preferably, the housing and / or an enclosing outer contour of the supporting structure has or have a volume of between 0.5 and 5.0 m³. 3 , preferably between 1.0 and 2.0 m 3 , on. This ensures a particularly compact design of the dryer unit.

[0033] The dryer unit, in particular the housing and / or the supporting structure, may have a signal lamp to indicate an operating status of the dryer unit.

[0034] The dryer unit can be designed to be placed as a unit on a floor and / or on a support element, in particular so that the granulate container is not additionally burdened.

[0035] It is preferably provided that the drying unit is designed to dry the plastic granules in the granule container at a dew point between -70°C and +10°C and / or at a relative humidity between 0.1% and 99%, in particular wherein the granule container has a granule throughput of at least 40 kg / h, and more specifically at least 50 kg / h. This ensures sufficient dryness of the plastic granules to produce high-quality molded parts.

[0036] It is particularly preferred that the compressed air piping system includes a compressed air heater, in particular an electric one, for heating the compressed air.

[0037] The compressed air heating system can have one, two, three, four or more heating elements.

[0038] Preferably, the compressed air heating system is designed to heat the compressed air to 160–200 °C, particularly preferably to 170–190 °C. If, for example, PET plastic is involved, the compressed air is preferably heated to approximately 180 °C.

[0039] It is preferably provided that the compressed air inlet of the compressed air system is designed to receive compressed air from an existing compressed air system and / or compressed air compressor. This allows an existing on-site compressed air system and / or an existing on-site compressed air compressor to be advantageously used for operating the dryer unit as well.

[0040] It is also conceivable that the dryer unit itself includes a compressed air compressor.

[0041] It is also conceivable that waste heat from the compressed air compressor could be used for drying the plastic granules within the compressed air piping system and / or the recirculating air piping system. A compressed air drying device for drying and / or heating the compressed air can be arranged downstream of the compressed air inlet and preferably upstream of the compressed air heater. This can be advantageous, for example, if the compressed air available at the plant is particularly humid or if particularly high dryness requirements are placed on it.

[0042] It is preferably provided that the circulating air heater is designed to heat the circulating air to 160–200 °C, particularly preferably to 170–190 °C. If, for example, PET plastic is involved, the circulating air is preferably heated to approximately 180 °C.

[0043] The forced-air heating system preferably has three heating elements, but can also include one, two, four or more heating elements.

[0044] In some embodiments of the dryer unit, the compressed air outlet and the recirculated air outlet are arranged separately, so that the recirculated air and the compressed air can be passed on separately.

[0045] In other embodiments, the compressed air outlet leads into the recirculated air outlet, so that the compressed air and the recirculated air can be passed on together.

[0046] The compressed air piping system may be provided with a solenoid valve and / or a pressure reducer and / or a proportional valve for adjusting the pressure and / or flow rate of the compressed air downstream of the compressed air inlet and preferably upstream of the compressed air heater. This allows, for example, flexible compressed air control. The solenoid valve can, in particular, be used to open and close the compressed air inlet.

[0047] The pressure reducer serves in particular to reduce the pressure of the compressed air, especially to a value of 0 bar, so that a dew point of approximately -20 °C can preferably be achieved in the granulate container.

[0048] The proportional valve can be mechanically or electrically operated and is specifically designed to maintain the compressed air flow at a substantially constant value.

[0049] It is particularly preferred that the recirculation system upstream of the recirculation heater has a radial fan for drawing in the recirculated air and / or an air filter for filtering the recirculated air.

[0050] It is preferably provided that the dryer unit, in particular the compressed air piping system and the recirculation piping system, can be arranged next to and / or spaced apart from the granulate container.

[0051] The dryer unit may also include other components. Examples of other components are seals to prevent unwanted leakage of recirculated air and / or compressed air, thermal insulation to insulate the compressed air piping and / or recirculation piping systems, and sensors such as temperature and / or humidity sensors.

[0052] Furthermore, the dryer unit can include a control or regulating unit, in particular one configured to variably control or regulate the temperature and / or dew point of the recirculated air and / or compressed air, e.g., in the compressed air piping system and / or recirculated air piping system and / or in the granule container. Protection is also sought for a granule drying system comprising a dryer unit according to the invention and a granule container, in particular cylindrical and funnel-shaped and / or with a capacity of at least 100 liters, with a granule feed opening arranged on the top of the container in an operating position and a granule discharge opening arranged on the bottom of the container in an operating position, wherein the compressed air outlet and the recirculated air outlet of the dryer unit are fluidly connected to the granule container and preferably mechanically connected.

[0053] In an operating state of the granulate drying system, the granulate container is and / or is filled with plastic granulate via the granulate feed opening, whereby the plastic granulate, after drying by means of the dryer unit, is passed on through the granulate discharge opening, e.g. to an extrusion blow molding machine.

[0054] The granulate container is preferably made of stainless steel.

[0055] It is preferably provided that the granule drying system has a recirculating air line connected to the recirculating air outlet of the dryer unit, with a recirculating air discharge opening. The recirculating air discharge opening is located within the granule container and, in the operating state, in the lower third, preferably in the lower quarter, of the granule container, and is preferably designed to discharge the recirculated air downwards. In this way, the heated recirculated air can advantageously flow from bottom to top through the plastic granules, thereby drying them. It is also preferably provided that the granule drying system has a compressed air line connected to the compressed air outlet of the dryer unit, with a compressed air discharge opening for the direct or indirect discharge of compressed air into the granule container.

[0056] Preferably, the compressed air discharge opening is located inside the granulate container and in the lower quarter, preferably in the lower fifth, of the container when in operation, and is preferably designed to discharge the compressed air downwards. This allows the heated compressed air to advantageously flow from bottom to top through the plastic granules, thereby drying them.

[0057] It is also possible for the compressed air outlet to open into the recirculating air line outside the granule container. This allows the compressed air to be released into the granule container together with and mixed with the recirculating air.

[0058] The granule drying system may include a compressed air compressor connected to the compressed air inlet of the dryer unit.

[0059] A dryer unit according to the invention can also be used in previously known designs of granule containers and can be retrofitted.

[0060] Protection is also sought for a method for manufacturing a granule drying system, in particular a granule drying system according to the invention, comprising the following steps:

[0061] Providing a granule container, in particular cylindrical and funnel-shaped, comprising a granule feed opening arranged on the top of the container in an operating position, a granule discharge opening arranged on the bottom of the container in the operating position, and an exhaust air opening arranged on the top of the container for releasing exhaust air obtained by drying the plastic granules; providing a dryer unit according to the invention;

[0062] Establishing a fluidic and preferably mechanical connection between the exhaust air opening of the granulate container and the recirculated air inlet of the dryer unit and

[0063] Establishing a fluidic and preferably mechanical connection between the recirculated air outlet of the dryer unit and the granulate container and

[0064] Establishing a fluidic and preferably mechanical connection between the compressed air outlet of the dryer unit and the granulate container.

[0065] The exhaust air released from the granulate container corresponds to the recirculated air passed through the dryer unit.

[0066] It is particularly preferred that, in order to convert an existing granule drying system, existing drying components connected to the granule container are removed before the aforementioned fluidic and preferably mechanical connections are made.

[0067] This means, in particular, that existing connections of a recirculation system and a compressed air system are closed off, and then new direct and / or indirect connections are made between the exhaust air opening of the granulate container and the recirculation air inlet of the dryer unit, and between the recirculation air outlet of the dryer unit and the granulate container, and between the compressed air outlet of the dryer unit and the

[0068] Granule containers are manufactured.

[0069] Essentially, an existing, e.g. outdated, granule drying system can be retrofitted with a dryer unit according to the invention and / or a granule drying system according to the invention can be manufactured.

[0070] Further advantages and details of advantageous variants of the invention will become apparent from the figures and the accompanying figure description. These show:

[0071] Fig. 1-2 shows a first embodiment of a dryer unit according to the invention.

[0072] Fig. 3 shows a first variant of a granule drying system.

[0073] Fig. 4 shows a second variant of a granule drying system.

[0074] Fig. 5 shows a second embodiment of a device according to the invention.

[0075] dryer unit and

[0076] Fig. 6 shows a third variant of a granule drying system.

[0077] In the following description of the exemplary embodiments of the dryer unit 1 and the granule drying system 19 shown in the following figures, the differences between the subsequent exemplary embodiments and the first exemplary embodiment will be discussed primarily to avoid repetition. The description of the first exemplary embodiment also applies, where applicable, to the exemplary embodiments described subsequently.

[0078] Fig. 1 shows a schematic representation of a first embodiment of a dryer unit 1 according to the invention for drying plastic granules 2 in a granule container 3, wherein the dryer unit 1 comprises a compressed air duct system 4 with a compressed air inlet 5 for receiving compressed air and with a compressed air outlet 6 for passing the compressed air into the granule container 3, a recirculation duct system 7 with a recirculation inlet 8 for receiving recirculated air from the granule container 3 and with a recirculation outlet 9 for passing the recirculated air into the granule container 3, and a recirculation heater 10 arranged in the recirculation duct system 7 for heating the recirculated air, wherein the dryer unit 1 is designed as a unit that can be transported independently of the granule container 3.

[0079] The dryer unit 1 is also preferably designed to be self-supporting.

[0080] In this embodiment, the compressed air piping system 4 has a compressed air heater 13, in particular an electric one, which is designed to heat the compressed air to 160 - 200 °C, particularly preferably to 170 - 190 °C.

[0081] In this embodiment, the compressed air piping system 4 has a solenoid valve 14 and / or a pressure reducer 15 and / or a proportional valve 16 for adjusting a pressure and / or a flow rate of the compressed air downstream of the compressed air inlet 5 and preferably upstream of the compressed air heater 13.

[0082] In this embodiment, the recirculation system 7 upstream of the recirculation heater 10 has a radial fan 17 for drawing in the recirculated air and / or an air filter 18 for filtering the recirculated air.

[0083] Figure 2 shows a further illustration of the first embodiment. Here it is shown that the compressed air piping system 4 has a compressed air inlet 5, a solenoid valve 14, a pressure reducer 15, a proportional valve 16, a compressed air heater 13, and a compressed air outlet 6, with the compressed air flowing through the system in this order. The arrows represent the flow direction of the recirculated air or compressed air at the inlet and outlet of the dryer unit 1.

[0084] Furthermore, it is shown that the recirculation system 7 has a recirculation inlet 8, an air filter 18, a radial fan 17, a recirculation heater 10 with three heating elements and a recirculation outlet 9, wherein the recirculation flows through the system in this order.

[0085] The convection heating system 10 is designed in particular to heat the convection air to 160 - 200 °C, especially preferably to 170 - 190 °C.

[0086] In this first embodiment, the compressed air outlet 6 and the recirculated air outlet 9 are arranged separately from each other.

[0087] In this embodiment, the compressed air inlet 5 is designed to receive compressed air from an existing compressed air system and / or compressed air compressor.

[0088] It is also possible that the dryer unit 1 itself includes a compressed air compressor.

[0089] Fig. 3 shows a first variant of a granule drying system 19 with a granule container 3, in particular cylindrical and funnel-shaped and / or with a capacity of at least 100 liters, and a dryer unit 1 fluidically and indirectly mechanically connected to it according to the first embodiment (Figs. 1 and 2), in particular wherein the dryer unit 1 is designed for fluidic and / or mechanical, in particular detachable, connection with the granule container 3.

[0090] The granule container 3 of the granule drying system 19 has a granule feed opening 21 arranged on a container top 20 in an operating position of the granule container 3 and a granule discharge opening 23 arranged on a container bottom 22 in the operating position .

[0091] The compressed air outlet 6 and the recirculated air outlet 9 of the dryer unit 1 are fluidically and preferably mechanically connected to the granulate container 3.

[0092] In particular, the compressed air outlet 6, the recirculated air outlet 9 and the recirculated air inlet 8 can be connected directly and / or indirectly to the granulate container 3.

[0093] The dryer unit 1 is specifically designed to dry plastic granules 2 in a granule container 3 with a granule throughput of at least 40 kg / h, in particular at least 50 kg / h.

[0094] In this embodiment, the dryer unit 1 has a housing 11 and / or a support structure 12, within which the compressed air piping system 4 and the

[0095] Circulation system 7 are arranged.

[0096] In this preferred embodiment, the granule drying system 19 has a recirculating air line 24 connected to the recirculating air outlet 9 of the dryer unit 3, with a recirculating air discharge opening 25 being located inside the granule container 3 and in the lower third, preferably in the lower quarter, of the granule container 3 when it is in operation, and preferably discharges the recirculated air downwards. In this embodiment, the granule drying system 19 has a compressed air line 26 connected to the compressed air outlet 6 of the dryer unit 3, with a compressed air discharge opening 27 for direct or indirect discharge of the compressed air into the granule container 3.

[0097] In this variant, the compressed air discharge opening 27 leads outside the granulate container 3 into the recirculated air line 24 .

[0098] In this variant, the granule drying system 19 has an exhaust air line 29 connected to the exhaust air opening 28 of the granule container 3, through which the exhaust air passes as recirculated air through the recirculated air inlet 6 of the dryer unit 3 into the recirculated air line system 7 of the dryer unit 1, in particular being drawn in.

[0099] Such a granule drying system 19 can be produced using the following process steps:

[0100] - Providing a granule container 3, in particular cylindrical and funnel-shaped, comprising a granule feed opening 21 arranged on a container top 20 in an operating position of the granule container 3, a granule discharge opening 23 arranged on a container bottom 22 in the operating position, and an exhaust air opening 28 arranged on the container top 20 for the discharge of exhaust air obtained by drying the plastic granules;

[0101] - Providing a dryer unit 1 according to the invention;

[0102] - Establishing a fluidic and preferably mechanical connection between the exhaust air opening 28 of the granulate container 3 and the recirculation air inlet 8 of the

[0103] Dryer unit 1 and - Establishing a fluidic and preferably mechanical connection between the recirculated air outlet 9 of the dryer unit 1 and the granulate container 3 and

[0104] - Establishing a fluidic and preferably mechanical connection between the compressed air outlet 6 of the dryer unit 1 and the granulate container 3 .

[0105] For the conversion of an existing granule drying system to a granule drying system 19 according to the invention, it is preferably provided that, prior to establishing the fluidic and preferably mechanical connections between the exhaust air opening 28 of the granule container 3 and the recirculation air inlet 8 of the dryer unit 1, between the recirculation air outlet 9 of the dryer unit 1 and the granule container 3 and between the compressed air outlet 6 of the dryer unit 1 and the granule container 3, existing drying components connected to the granule container 3 are removed.

[0106] Figure 4 shows a second variant of a

[0107] Granule drying system 19 with a dryer unit 1 according to the first embodiment (Fig. 1 and 2).

[0108] In this variant, the compressed air release opening 27 is located inside the granule container 3 and in the lower quarter, preferably in the lower fifth, of the granule container 3 when in the operating state, in particular wherein the compressed air is released downwards.

[0109] Fig. 5 shows a second embodiment of a dryer unit 1 according to the invention, which differs from the first embodiment in particular in that the compressed air outlet 6 opens into the recirculated air outlet 9, so that the

[0110] Compressed air and recirculated air can be passed on together.

[0111] Figure 6 shows a third variant of a

[0112] Granule drying system 19 with a dryer unit according to the second embodiment (Fig. 5) .

[0113] Here, the compressed air is mixed with the ambient air and delivered via the ambient air line 24 into the granulate container 3. A compressed air line 26 is therefore not required.

Claims

Patent claims 1. Drying unit (1) for drying plastic granules (2) in a granule container (3) preferably equipped with a capacity of at least 100 liters, wherein the drying unit (1) - a compressed air piping system (4) with a compressed air inlet (5) for receiving compressed air and with a compressed air outlet (6) for transferring the compressed air into the granulate container (3) , - a recirculation system (7) with a recirculation inlet (8) for receiving recirculated air from the granule container (3) and with a recirculation outlet (9) for passing the recirculated air into the granule container (3) and - a recirculating air heater (10) arranged in the recirculating air system (7) for heating the recirculated air, characterized in that the dryer unit (1) is designed as a unit that can be transported independently of the granulate container (3).

2. Dryer unit (1) according to claim 1, wherein the dryer unit (1) is designed for fluidic and / or mechanical, in particular detachable, connection with the granulate container (3), in particular wherein the compressed air outlet (6) , which recirculation outlet (9) and the recirculation inlet (8) with the Granule containers (3) can be connected. Dryer unit (1) according to one of the preceding claims, wherein the dryer unit (1) is self-supporting.

4. Dryer unit (1) according to one of the preceding claims, wherein the dryer unit (1) comprises a housing (11) and / or a support structure (12), wherein the Compressed air piping system (4) and the recirculation piping system (7) are arranged, preferably wherein the housing (11) and / or an enclosing outer contour of the supporting structure (12) has a volume of between 0.5 and 5.0 m³ 3 , preferably between 1.0 and 2.0 m 3 exhibits or exhibits.

5. Drying unit (1) according to one of the preceding claims, wherein the drying unit (1) is configured to dry the plastic granules (2) in the granule container (3) at a dew point between -70°C and +10°C, in particular wherein the granule container (3) has a granule throughput of at least 40 kg / h, in particular of at least 50 kg / h.

6. Dryer unit (1) according to one of the preceding claims, wherein the compressed air piping system (4) comprises a compressed air heater (13), in particular an electric one, which is designed to heat the compressed air to 160 - 200°C, particularly preferably to 170 - 190°C.

7. Dryer unit (1) according to one of the preceding claims, wherein the compressed air inlet (5) is designed to receive compressed air from an existing compressed air system and / or compressed air compressor and / or wherein the dryer unit (1) comprises the compressed air compressor.

8. Dryer unit (1) according to one of the preceding claims, wherein the circulating air heating (10) comprises three heating elements and / or is designed to heat the circulating air to 160 - 200°C, particularly preferably to 170 - 190°C.

9. Dryer unit (1) according to one of the preceding claims, wherein the compressed air outlet (6) and the recirculated air outlet (9) are arranged separately from each other and / or wherein the The compressed air outlet (6) opens into the recirculated air outlet (9), so that the compressed air and the recirculated air can be passed on together.

10. Dryer unit (1) according to one of the preceding claims, wherein the compressed air line system (4) has a solenoid valve (14) and / or a pressure reducer (15) and / or a proportional valve (16) for adjusting a pressure and / or a flow rate of the compressed air downstream of the compressed air inlet (5) and preferably upstream of the compressed air heater (13).

11. Dryer unit (1) according to one of the preceding claims, wherein the recirculation system (7) is located upstream of the The recirculating air heater (10) has a radial fan (17) for drawing in the recirculated air and / or an air filter (18) for filtering the recirculated air.

12. Granule drying system (19) comprising a dryer unit (1) according to one of the preceding claims and a granule container (3), in particular cylindrical and funnel-shaped and / or equipped with a capacity of at least 100 liters, with a granule feed opening (21) arranged on the upper side (20) of the container in an operating position and a granule discharge opening (23) arranged on the lower side (22) of the container in the operating position, wherein the compressed air outlet (6) and the recirculated air outlet (9) of the dryer unit (1) are connected to the Granule containers (3) are fluidly connected and preferably mechanically connected.

13. Granule drying system (19) according to claim 12, wherein the granule drying system (19) has a recirculation line (24) connected to the recirculation outlet (9) of the dryer unit (3) with a recirculation discharge opening (25), wherein the The recirculated air discharge opening (25) is located inside the granule container (3) and in the lower third, preferably in the lower quarter, of the granule container (3) when the granule container (3) is in its operating state, and preferably discharges the recirculated air downwards.

14. Granule drying system (19) according to claim 12 or 13, wherein the granule drying system (19) has a compressed air line (26) connected to the compressed air outlet (6) of the dryer unit (3) with a compressed air discharge opening (27) for direct or indirect discharge of the compressed air into the granule container (3).

15. Granule drying system (19) according to claim 14, wherein the compressed air discharge opening (27) is located inside the granule container (3) and in the lower part of the granule container (3) during operation. quarter, preferably in the lower fifth, of the granulate container (3) and preferably releases the compressed air downwards.

16. Granule drying system (19) according to claim 14, wherein the The compressed air discharge opening (27) outside the granulate container (3) leads into the recirculated air line (24).

17. Method for manufacturing a granule drying system (19) , in particular according to any one of claims 12 to 16, comprising the following steps: - Providing a granule container (3), in particular cylindrical and funnel-shaped, comprising a granule feed opening (21) arranged on the top of the container (20) in an operating position of the granule container (3), a granule discharge opening (23) arranged on the bottom of the container (22) in the operating position, and a [missing information] arranged on the top of the container (20). Exhaust air opening (28) for the release of exhaust air obtained by drying the plastic granules; - Providing a dryer unit (1) according to any one of claims 1 to 11; - Establishing a fluidic and preferably mechanical connection between the exhaust air opening (28) of the granulate container (3) and the recirculated air inlet (8) of the dryer unit (1) and - Establishing a fluidic and preferably mechanical connection between the recirculated air outlet (9) of the dryer unit (1) and the granulate container (3) and - Establishing a fluidic and preferably mechanical connection between the compressed air outlet (6) of the dryer unit (1) and the granulate container (3) .

18. Method according to claim 17, wherein, in order to convert an existing granule drying system, existing drying components connected to the granule container (3) are removed before the fluidic and preferably mechanical connections between the exhaust air opening (28) of the granule container (3) and the recirculation air inlet (8) of the dryer unit (1), between the recirculation air outlet (9) of the dryer unit (1) and the granule container (3) and between the compressed air outlet (6) of the dryer unit (1) and the granule container (3).

Images