METHOD FOR DRYING BULK MATERIALS, IN PARTICULAR SOLIDS, SUCH AS GRANULATES, POWDERS, GRAINS, FOILS, SHAVINGS OR THE LIKE, PREFERABLY PLASTIC GRANULATE

Abstract

A method for drying bulk material, in particular solids, preferably for plastics-processing machines, in drying devices and containers, interconnected to form an assembly. Depending on the material used, the drying time specified, is transmitted or set by the operator or i-s-present in the controller. A consumer transmits the material consumption or the shot weight per production cycle, respectively, or the individual or cumulated shot weights for several production cycles or other values indicative of the material consumption to the drying device(s) and/or material container(s). Each material container consists, on the control side, of several loading batches, preferably with time stamps, and the drying or residence time, respectively, for the respectively lowest loading batch in the material container results from the difference between the current time of the respective material removal by the consumer and the time stamp associated with the oldest loading batch.

Claims

1. A method for drying bulk material, in particular solids, such as granule materials, powders, grains, films, chips, or the like, preferably for plastics-processing machines, in a single or several drying devices and containers, in particular material containers, which are interconnected to form an assembly, wherein, depending on the material or bulk material, respectively, used, the drying time specified by the manufacturer or set by the user, in particular the residence time, is either transmitted by a superordinate controller or by the consumer or is set in the controller of the container or of the drying device by the operator or is present in the controller of the container or of the drying device in the form of a local database, wherein the consumer transmits the material consumption or the shot weight per production cycle, respectively, or the individual or cumulated shot weights for several production cycles or other values which are indicative of the material consumption to the drying device(s) and/or material container(s), directly or indirectly via the superordinate controller, whereby each material container consists on the control side of several loading batches, preferably with time stamps, and for the respectively lowest loading batch, in particular material batch, in the material container the drying or residence time results from the difference between the current time of the respective material removal by the consumer and the time stamp associated with the preferably oldest loading batch.

2. The method according to claim 1, wherein both the consumer, preferably one or several injection-molding machines, and the drying device or devices and material containers function autonomously from each other and are mutually interconnected via communication interfaces.

3. The method according to claim 1, wherein the controller or controllers of the drying device(s) or of the material container or containers keep the respective entries for the loading batches, at least the time stamps in the form of a ring buffer.

4. The method according to claim 1, wherein a new loading batch and thus an entry in the ring buffer for a specific material container results from a conveying cycle of the bulk material conveying device associated for the loading of this material container.

5. The method according to claim 1, wherein the current material consumption transmitted by the consumer is subtracted from the respectively oldest loading batch in the ring buffer until this loading batch is completely used up, whereby the next oldest loading batch, i.e. the next entry in the ring buffer, is subsequently used for the calculation.

6. The method according to claim 1, wherein the minimum number of loading batches of a ring buffer results from the ratio of the volume of the material container and the volume of the associated bulk material conveying device.

7. The method according to claim 1, wherein the physical size of a loading batch results from the volume of the bulk material conveying device associated with a material container, from which the material consumption transmitted by the consumer is subtracted in each case.

8. The method according to claim 1, wherein the drying device or devices can select from among various strategies for drying the material in the container or containers by predetermined selection or automatically when the predetermined or determined residence time of the material or bulk material, respectively, is not reached or exceeded.

9. The method according to claim 1, wherein the process temperature is changed, preferably reduced, to an adjustable or automatically determined value for the duration of an exceedance of the residence time in the container(s) predetermined or determined for the respective plastic or bulk material, respectively.

10. The method according to claim 1, wherein the drying device or devices equipped with a frequency converter for varying the air volume or air quantity, respectively, automatically vary the air volume through the container or containers for the duration of an undershoot or exceedance of the residence time predetermined or determined for the respective material.

11. The method according to claim 1, wherein a material container equipped with a throttle valve for varying the air volume flowing through said container automatically varies the air volume through the container for the duration of an undershoot or exceedance of the residence time predetermined or determined for the respective material.

12. The method according to claim 1, wherein the material supply or the quantity of bulk material, respectively, in the material container or containers can be automatically adapted to the predetermined residence time in order to achieve an optimum and constant residence time in the material container for the respective material.

13. The method according to claim 1, wherein, if the residence time specified or determined for the respective material is not reached, an error message can be produced after an adjustable or fixed period of time.

14. The method according to claim 1, wherein the size of the container or containers is adjustable or determinable and thus the total supply of material in the container or containers can be determined.

Description

[0040] The figures show:

[0041] FIG. 1—an overview illustration of a plastics-processing industrial installation in a work cell; simplified, for illustrative purposes only;

[0042] FIG. 2—a schematic representation of a plastics industry system whose production resources are connected as part of a central conveyor system; simplified, for illustrative purposes only.

[0043] FIG. 3—schematic illustration of the design of the drying plant; simplified, for illustrative purposes only;

[0044] FIG. 4—a schematic representation of a material container of a drying plant with several loading batches; simplified, for illustrative purposes only;

[0045] FIG. 5—a further schematic representation of an embodiment of a material container of a drying plant with several inflow points for the supply of air to different areas, in particular to the loading batches; simplified, for illustrative purposes only;

[0046] It should be stated by way of introduction that, in the individual embodiments, the same parts are provided with the same reference numbers or same component designations, wherein the disclosures contained in the entire description can, by analogy, be transferred to identical parts with identical reference numbers or identical component designations, respectively. The position details selected in the description, such as, e.g., top, bottom, lateral, etc., likewise relate to the figure described, and in the event of a change of position, they are to be transferred to the new position by analogy. Individual features or feature combinations from the exemplary embodiments shown and described may also represent independent inventive solutions.

[0047] FIGS. 1 to 5 show an industrial installation 1 for plastics applications, in which the individual production resources 2 for producing one or several products/semi-finished products or injection-molded parts 3 are connected.

[0048] For example, it is possible that for the production of an injection-molded part 3 plastic granules or powder are fed to the processing machine 4 via a granule conveyor 9 and possibly via a metering device 11 or from a granule dryer 10. By means of a temperature control unit 13 and/or cooling unit, the injection mold 7 can be kept at operating temperature by feeding a temperature control medium, or heated or cooled accordingly, respectively, so that optimum processing of the plastic granules or powder, which must be plasticized for injection into the injection mold 7, is made possible.

[0049] In addition, the system can be equipped with a monitoring device 15, in particular a camera system, in order to be able to carry out an automatic quality control of the manufactured product 3. Very often there are also upstream or downstream automation systems 16 present, e.g. sprue cutter 17, centering, separating, feeding, crate and pallet stacking stations, etc., which are directly integrated into the robot controller or industrial installation 1, respectively, and controlled by it via digital or analog signals or other communication interfaces. The creation of the flow and control logic for the robot 5 or handling robot 5, respectively, and any connected automation components 16 or systems, respectively, is typically carried out in a teach-in procedure, for which an appropriate teachbox 18 or robot controller, respectively, can be used.

[0050] In order for the individual devices to be adjustable or programmable, respectively, they are preferably equipped with corresponding control electronics or controller, respectively, 19, as shown schematically, wherein the setting or programming, respectively, is entered and displayed via displays arranged on the devices or the teachbox 18. Of course, it is also possible to program or adjust, respectively, the devices via an external component connected to the production resources 2 via an interface.

[0051] For the sake of completeness, it is also mentioned that all devices are connected to corresponding lines, in particular power supply, network and connection lines, liquid supply lines, material lines, etc., which in the interest of clarity were not displayed in the representation shown. Moreover, such production resources 2 are preferably combined into one or several work cells 20, wherein the communication of the production resources 2 within the work cells 20 can be directly done with the machine 4 or via a work cell controller 21. In this context, the industrial installation can have one or several control rooms 23, in which, in particular, one or several control units 24 or computers, respectively, can be arranged, whereby cell phones 25 and/or tablets 26 can also be used. To ensure that the plastics-processing production resources 2 are supplied with bulk material 12, the corresponding production resources 2 can be supplied via a central conveyor system 27, as shown for example in FIG. 2, via corresponding supply lines 28.

[0052] Here FIG. 3 shows a detail of the design of a drying plant 29 for illustrating the process for drying bulk material 12, in particular solids, such as granule materials, powders, grains, films, chips, or the like, preferably plastic granules in a single drying device or several drying devices 30 and containers 10, 31, in particular material containers 10, 31, connected together to form an assembly.

[0053] As mentioned before, the production resources 2, in particular the drying device 30 and the container 10, 31 are connected via a line 22 for communication via their controllers 19, whereby the controller 19 controls or regulates, respectively, the individual components, sensors. Furthermore, all drying devices 30 and vessels 10, 31 located in the drying plant 29 are mutually interconnected via an air supply line 32 and air return line 33. In this process, the drying devices 30 dehumidify the moist air 34 and then feed dry air 34 into the air supply line 32 so that it is taken from the containers 10, 31 for drying the bulk material 12 and heated accordingly by a process heater 35 and subsequently conveyed through the storage system 36 filled with granules 12 so that the air 34 can absorb the moisture of the bulk material 12, whereupon the moist air 34 is fed into the air return line 33. This allows the drying equipment 30 to remove the moist air 34 from the air return line 33 and deliver it via a pump/compressor 37 to a drying device 38, which removes the moisture in the air 34. For the extraction and supply of air 34, the individual devices are equipped with flaps or valves 39, which are controlled accordingly via the controller 19.

[0054] According to the present invention, it is now envisioned that a process temperature 40 set for the respective material 12 or bulk material 12 in the container(s) 10, 31 or the loading 41 of the container(s) 10, 31 with material 12 or bulk material 12, respectively, or the air volume 42 of the drying device(s) 30 is adapted on the basis of the transmission of at least the material consumption 43 from the consumer 2, preferably one or several plastics-processing machines to the drying device(s) 30 or containers 10, 31, i.e., that all consumers or production resources, respectively, which require or process, respectively, bulk material 12 communicate the material consumption 43, so that the drying process can be adapted accordingly to the conditions by the drying device or devices 30 or containers 10, 31.

[0055] In order to ensure a smooth supply of sufficient dry bulk material 12, the consumers 2 transmit their material consumption or shot weight per production cycle or the individual or cumulated shot weights for several production cycles to the drying device or devices 30 and material containers 10, 31, which are further processed by their controller 19, i.e., the required material consumption 43 is determined or calculated, respectively, from all the transmitted data, so that a corresponding controller or regulator, respectively, is carded out to increase or decrease the required dry bulk material 12. Here, the container 10, 31 and/or the drying device 30 can determine or calculate, respectively, a residence time 45 of the bulk material 12 present in the storage system 36 of the container 10, 31 to prevent an excessively short or unnecessarily long storage time 46 for optimal plasticizing and material properties of the bulk material 12. Indeed, if the bulk material 12 is dried for too long and/or at too high temperatures, for example, it may result in the bulk material 12 becoming too dry and no longer being able to be optimally processed by the plastics-processing machines, which may lead to defective production parts. In the process, the controllers 19 also include other parameters, such as the material type or type of plastic, respectively, material size, etc.

[0056] It is essential that, depending on the material or bulk material, respectively, 12 used, the optimum residence time is either transferred by a superordinate controller or database, or is set by the operator in the controller 19 of the container 10, 31 or of the drying device 30, or is available in the controller 19 of the container 10, 31 or of the drying device 30 in the form of a local database.

[0057] As previously mentioned, a wide variety of control and regulating methods can be used, with the paramount goal always being to provide consistent bulk material quality to the plastics-processing devices.

[0058] In this context, it is possible that different materials 12 or bulk materials 12, respectively, are processed, in particular dried, in different containers 10, 31, in particular in their storage system 36, the parameters of which, in particular the process temperature 40, can be set for each container 10, 31, i.e., the individual containers 10, 31 supplied with different bulk material 12 can have different parameters which are regulated or controlled, respectively, independently of one another, so that a bulk material 12 of consistently equally good quality is always made available for further processing. In this context, it is also possible for several containers 10, 31 to be connected in parallel in the drying plant 29, as this allows more material 12 and thus more consumers to be supplied simultaneously.

[0059] As shown schematically in FIG. 3 by a dashed arrow 43 in the area of the line 22, the consumer(s) 2 transmit(s) the material throughput 43 or the shot weight per production cycle, respectively, or the individual or cumulated shot weights for several production cycles or other values that directly or indirectly indicate the material throughput to the drying device(s) 30 and/or material container(s) 10, 31. This allows the drying device(s) 30 and/or material container(s) 10, 31 to calculate the residence time 45 of the material or bulk material, respectively, 12 present in the container(s) 10, 31 from the transmitted material throughputs or shot weights per production cycle or cycles.

[0060] FIG. 4 schematically shows the relationship between ring buffer 49 and loading batch 48, 48a,48b,48c. On the control side, the ring buffer 49 serves for storage and management of the time stamps 50, in particular the time stamps 50a to c of the most varied loading batches 48a to c, and possibly further information, e.g. size of the loading batch 48a to c, the effective drying time 51a,51b,51c of a loading batch 48a to c or additional information 53a,53b,53c, of the loading batches 48a to c. A new loading batch 48, on the control side in the ring buffer 49 and physically in the material container 10, 31, results from a material conveying cycle of a conveying device 9, which is mounted on the material container 10, 31. The current time and optionally further information is stored in an entry in ring buffer 49. The physical loading batches 48a through c are schematically indicated in FIG. 4 by different orientations of the bulk material grains and are different layers, as schematically separated by dashed lines, in the material container 10, 31. By design, the material moves through a material container 10, 31 according to the FIFO (First-In, First-Out) principle. The respectively “oldest” loading batch 48a in the ring buffer 49 is used to calculate the residence time 45 of the material. In discontinuous operation, as is the case with an injection-molding machine, for example, the consumer reports the corresponding material consumption for each injection cycle via various physical variables. The residence time 45a of the respectively lowest material batch 48a in the material container 10, 31 that is used for the injection-molding cycle results from the difference of the current time at the time of the consumer's demand 2 and the time stamp 50a of the oldest loading batch in the ring buffer 49.

[0061] If such a drying plant is used for the operation of an extrusion facility, the material consumption is preferably transmitted continuously and at presettable time intervals in order to determine the residence time 45.

[0062] Furthermore, it is possible, as shown schematically in FIG. 5, that the air supply for the most diverse loading batches 48,48a to 48c can be controlled or regulated, respectively, i.e. that several inflow points 54 for the supply of the dried air 34 are arranged on the container 10,31, in particular on the storage system 36, so that the required air 34 is fed in per calculated residence time 45,45a to c of the most diverse loading batches 48,48a to c. For example, it is possible that the air supply is reduced for the oldest, i.e. lowest, loading batch 48a and increased for the next loading batch or loading batches 48b, 48c, respectively.

[0063] As previously stated, if the material or bulk material 12 falls below or exceeds the predetermined or determined residence time 45,45a,45b,45c, the drying device or devices 30 may select from among various strategies for drying the material, respectively, 12 in the container or containers 10, 31 by predetermined selection or automatically. In this context, for example, the process temperature 40 can be changed, preferably reduced, to an adjustable or automatically determined value during the duration of an exceedance of the residence time 45,45a,45b,45c in the container(s) 10, 31 predetermined or determined for the respective plastic or bulk material 12, respectively. However, it is also possible for a material container 10,31 equipped with a throttle valve 46 for varying the air volume 47 flowing through said container 10,31 to automatically vary the air volume through the container during the period of time when the residence time 45,45a,45b,45c predetermined or determined for the particular material 12 is not reached or exceeded. In this regard, it is also possible for the drying device or devices 30, which are equipped with a frequency converter for changing the air volume or air quantity, respectively, 42, to automatically change the air volume 42 through the container or containers 10, 31 for the duration of an undershoot or exceedance of the residence time 45 specified or determined for the respective material. Of course, other strategies for drying known from the prior art are possible. It is also possible that, if the residence time 45 specified or determined for the respective material 12 is not reached, an error message can be generated after an adjustable or fixed period of time.

[0064] For the sake of completeness, it is pointed out that all devices or production resources, respectively, 2 can be designed as so-called stand-alone devices and thus operate independently of others.

[0065] It is pointed out that the invention is not limited to the embodiments shown, but may comprise further embodiments and designs.