Method and apparatus for processing incoherent plastics

Abstract

A method and apparatus are described for processing incoherent plastics to heat its mass and reduce its moisture content in three process stages, wherein the incoherent plastics enters and exits three containers arranged in series with a heated and dehumidified process gas entering and exiting the same three containers, and wherein a first actuator actuates a first flow rate of the process gas through the third container and a second actuator actuates a second flow rate of the process gas, equal to or less than the first flow rate, through the first two containers.

Description

Method and apparatus for processing incoherent plastics Background of the invention

[0001] The invention concerns a method and apparatus for processing incoherent plastics, i.e., plastics in the form of granules and / or microgranules and / or pellets and / or powder and / or flakes or the like, in particular for removing water (dehumidifying and / or drying) from the incoherent plastics.

[0002] Specifically, but not exclusively, the invention can be usefully applied in various sectors of incoherent plastics processing, such as injection, extrusion, thermoforming, calendering, etc.

[0003] As is known, incoherent plastics are generally dehumidified and / or dried before being transformed into the finished product. The prior art in this sector can be improved in various respects.

[0004] In particular, it would be desirable to be able to modulate the quality of the process gas used (typically dehumidified and heated air) more effectively, quickly, and flexibly depending on the various needs and circumstances that may arise at any stage of the dehumidification process.

[0005] Another requirement would be to be able to modulate not only the quality of the process gas but also the amount of energy consumed to implement the dehumidification process, depending on the needs and circumstances during the dehumidification process, with greater effectiveness, speed, and flexibility.

[0006] Another limitation of traditional dehumidification systems is the time required to achieve the desired objective, namely reducing a certain quantity of incoherent plastics below a predetermined humidity level.

[0007] It would also be desirable to increase productivity if a high number of production batch changes are required. It is known, in this regard, that before a new production batch can be processed, it is necessary to wait a time greater than or equal to the residence time of the material in the hopper where the process takes place. This drawback causes considerable economic and production losses in production systems that operate with frequent production batch changes (even twice a day), such as in contract manufacturing systems that mould only the preform according to the various formats required by the market.Summary of the Invention

[0008] One object of the invention is to provide a method and apparatus capable ofovercoming one or more of the aforementioned limitations and drawbacks of the prior art.

[0009] One object is to develop a method and apparatus that allow relatively rapid production batch changes.

[0010] One object is to improve the efficiency of energy transfer to the incoherent plastics compared to prior art systems.

[0011] One advantage is to significantly reduce the energy used for moving the process gas. In particular, a 40% to 60% reduction in process gas movement energy has been observed experimentally compared to traditional systems under the same process conditions.

[0012] One advantage is providing an apparatus suitable for processing incoherent plastics with relatively compact dimensions, particularly with a relatively low vertical elevation.

[0013] One advantage is reducing the flow rate of process gas required to adequately process incoherent plastics at each process stage, resulting in a significant reduction in energy consumption.

[0014] According to the invention, incoherent plastics are processed in at least three process stages arranged in series with respect to one another.

[0015] Laboratory tests on pilot plants have shown that processing the material within three or more distinct containment volumes allows the energy supplied by the process gas to be adjusted to the actual energy required by the material processed within each containment volume, thus reducing overall energy consumption for the same mass of processed material.

[0016] For example, in a traditional single-stage system, to obtain a temperature increase of the incoherent plastics of 150 °C and a reduction in humidity from 1500 ppm to 50 ppm, a power of at least approximately 65 W is required for each kg of material processed, while, using an experimental solution with three process stages, the same result was obtained with a variable power (depending on the hourly production) between approximately 45 and 55 W for each kg of material processed.

[0017] In one example, an apparatus for processing incoherent plastics, in particular for the purpose of reducing the moisture content of the incoherent plastics, comprises three process stages arranged in series with respect to one another, wherein each process stage comprises a respective container, wherein incoherent plastics enter and exit the three containers sequentially while a process gas enters and exits the same three containerssequentially, and wherein a first actuator actuates a first flow rate of the process gas through the third container and a second actuator actuates a second flow rate of the process gas (in particular, equal to or less than the first flow rate) through the first two containers. The process gas may comprise, in particular, a gas (e.g., air) that may be heated and dehumidified before being introduced into the third container.

[0018] The second actuator collects the process gas exiting the third container and relaunches it with sufficient power to allow the process gas to flow through both the second container and the first container, overcoming any pressure drops encountered along the way, thanks to the power supplied by the second actuator.

[0019] In practice, the incoherent plastics pass through the first container, the second container, and the third container in sequence, while the process gas (e.g., air) passes through the third container, the second container, and the first container in sequence. It is possible, in particular, to provide for a closed process gas circuit, so that the process gas exiting the first container is recirculated to a dehumidification device, which then sends the recirculated and dehumidified process gas back to the third container.

[0020] The dehumidification device may comprise, in particular, a condensation dehumidifier by cooling the process gas and / or an adsorption dehumidifier and / or a condensation dehumidifier by compression of the process gas and / or another type of dehumidifier.

[0021] In use, the dehumidification device generates a process gas with a dewpoint value that may be between -5°C and -60°C.

[0022] The second actuator may be controlled, in particular, based on signals provided by flow sensor means positioned along the path traversed by the process gas flow generated by the second actuator itself.

[0023] In particular, pressure sensor means may be arranged to detect the pressure in a section of the process gas path between the gas outlet of the second container and the gas inlet of the first container and in a section of the path exiting the first container. These pressure sensor means may be used, in particular, to monitor pressure drops in the process gas flow and, if necessary, also to control the second actuator in order to limit said pressure drops.

[0024] In particular, flow sensor means may be arranged to detect the flow rate (mass and / or volumetric) of the process gas. The measured values may be used to control the flow rate to ensure a desired energy supply to the incoherent plastics based on the differenttemperatures of the process gas (and / or material) present in the three stages and / or based on the actual hourly production (i.e., the actual flow rate of the incoherent plastics).

[0025] In particular, it is possible to have heating devices configured to heat the process gas at the inlet of the first process stage and / or at the inlet of the second process stage and / or at the inlet of the third process stage. These heating devices may be controlled to ensure a desired temperature of the process gas and / or the incoherent plastics processed for each process stage. It is possible to set a gradual increase in temperature of the incoherent plastics starting from the initial stage, moving on to the intermediate stage and then to the final stage, in particular to ensure a desired temperature (for example, 180°C) of the plastics at the inlet of the processing machine.

[0026] It is possible to use control devices configured with at least one setpoint value (of a process parameter, such as the temperature of the process gas or the plastics being processed) for each process stage in order to control the various process stages independently of each other. In particular, it is possible to set a setpoint value for the material temperature at the exit of the initial stage (for example, 100°C), a setpoint value for the material temperature at the exit of the intermediate stage (for example, 140°C), and a setpoint value for the material temperature at the exit of the final stage (for example, 180°C). The setpoint values may vary depending on the material mix, particularly the percentage of recycled material.

[0027] One advantage is allowing a significant reduction in the process gas flow rate required to adequately process the incoherent plastics at each process stage, resulting in a significant reduction in energy consumption.Brief description of the drawings

[0028] The invention can be better understood and implemented with reference to the attached drawings, which illustrate an exemplary and non-limiting embodiment thereof, in which:Figure 1 is a diagram of an example of an apparatus for processing incoherent plastics in accordance with the present invention.Detailed Description

[0029] With reference to the aforementioned figure, the numeral 1 generally indicates an apparatus for processing incoherent plastics, in particular for removing water (dehumidifying and / or drying) from the incoherent plastics.

[0030] Apparatus 1 comprises a first container 2 with a first material inlet forintroducing incoherent plastics into the first container 2. The first container 2 comprises a first material outlet for expelling incoherent plastics from the first container 2. The first container 2 comprises a first gas inlet for introducing process gas into the first container 2. The first container 2 comprises a first gas outlet for expelling process gas from the first container 2.

[0031] Apparatus 1 comprises a second container 3 with a second material inlet connected to the first material outlet for introducing incoherent plastics from the first container 2 into the second container 3. The second container 3 comprises a second material outlet for expelling incoherent plastics from the second container 3. The second container 3 comprises a second gas inlet for introducing process gas into the second container 3. The second container 3 comprises a second gas outlet for expelling process gas from the second container 3.

[0032] The apparatus 1 comprises a third container 4 with a third material inlet connected to the second material outlet for introducing incoherent plastics from the second container 3 into the third container 4. The third container 4 comprises a third material outlet for expelling incoherent plastics from the third container 4. The third container 4 comprises a third gas inlet for introducing process gas into the third container 4. The third container 4 comprises a third gas outlet for expelling process gas from the third container 4.

[0033] Each of the aforementioned three containers 2, 3, and 4 may comprise, in particular, a hopper configured to receive incoherent plastics (polymer granules) from above and to release incoherent plastics from below, and in which the incoherent plastics follow a descending path from top to bottom while the process gas follows a countercurrent path from bottom to top.

[0034] In each of the aforementioned three containers 2, 3, and 4, it is possible to provide, in particular, that the process gas enters the respective container through a central vertical conduit that ends at the bottom with a diffuser (for example, conical) arranged in a central and lower area of the container to diffuse the process gas which, after having passed through the mass of the incoherent plastics, can then exit from an upper outlet of the container.

[0035] The apparatus 1 comprises a first gas conduit 5 arranged to carry process gas from the third gas outlet of the third container 4 to the second gas inlet of the second container 3. The apparatus 1 comprises a second gas conduit 6 arranged to carry processgas from the second gas outlet of the second container 3 to the first gas inlet of the first container 2.

[0036] Apparatus 1 comprises a dehumidification device 7 configured to dehumidify the process gas. The dehumidification device 7 comprises a gas-to-be-dehumidified inlet and a dehumidified gas outlet.

[0037] Apparatus 1 comprises a gas supply conduit 8 arranged to carry process gas from the dehumidified gas outlet of the dehumidification device 7 to the third gas inlet of the third container 4.

[0038] Apparatus 1 comprises a first actuator 9 configured to actuate a flow of process gas along the gas supply conduit 8 towards the third gas inlet of the third container 4. The first actuator 9 may comprise, in particular, a fan or a blower. The first actuator 9 may comprise, in particular, a turbo blower capable of performing a centrifugal compression action on the process gas. It is possible, as in this specific example, for the first actuator 9 to be part of the dehumidification device 7.

[0039] The apparatus 1 comprises a second actuator 10 arranged in the first gas conduit 5 to implement a flow of process gas along the first gas conduit 5 towards the second gas inlet of the second container 3 and along the second gas conduit 6 towards the first gas inlet of the first container 2. The second actuator 10 may comprise, in particular, a blower, for example a turbo blower capable of performing a centrifugal compression action on the process gas.

[0040] As is known, a turbo blower (such as the first actuator 9 and / or the second actuator 10) is configured to take the process gas (air) with an axial flow at the center of an impeller equipped with radial blades and to push the gas with a radial flow due to the rotation of the impeller.

[0041] It is possible to envisage, as in this specific example, that the first actuator 9 includes a turbo blower and that the second actuator 10 also includes a turbo blower and that the two aforementioned turbo blowers are connected in series one after the other along the same process gas flow.

[0042] The use of turbo blowers (for the first actuator 9 and for the second actuator 10) is particularly suitable for working, as in this case, with two or three or more process stages in which the process gas passes through the various stages in a series arrangement, i.e. with a flow that passes through the containers one after the other, since it has been seen that the energy consumption is relatively low, for the same process gas flow rate, comparedto other types of gas movement actuators.

[0043] In particular, it was noted that the energy efficiency is relatively high, in the example illustrated with three process stages with gas flow in series, for rotation speeds greater than 10,000 rpm (revolutions / minute) of the turbo blower impeller (for both the first actuator 9 and the second actuator 10).

[0044] Furthermore, it was found that a turbo blower generates relatively limited overheating of the process gas, even at high rotation speeds of the impeller.

[0045] It was also seen that a turbo blower maintains high efficiency even when the operating conditions vary, for example when the hourly production varies, i.e., the overall flow of incoherent plastics in the system.

[0046] Another advantage of a turbo blower is that, within a process gas circuit that supplies three or more process stages with a serial flow of process gas, two or more turbo blowers can be connected in series while still maintaining high energy efficiency.

[0047] However, it has been observed that, within a system with two or three or more process stages with a serial flow of process gas, in order to achieve a desired process gas flow rate, the use of one or more turbo blowers allows for a reduction in the overall number of blowers installed along the process gas flow compared to the use of other types of blowers (e.g., side channel blowers).

[0048] The third material outlet of the third container 4 may, in particular, be connected to a user device 11 configured to perform a transformation of incoherent plastics.

[0049] The user device 11 may comprise, in particular, an extruder and / or a molding machine (injection, compression, blow molding, etc.). The user device 11 may comprise, in particular, any device suitable for transforming incoherent plastics in any field of plastic processing (for example, molding, extrusion, blow molding, thermoforming, calendering, hot bending, etc.).

[0050] The apparatus 1 may be equipped with a handling system configured to move the incoherent plastics along a material path that proceeds from the feed to the first container 2 to the discharge from the third container 4, with the possible direct transfer to the user device 11.

[0051] The handling system (not illustrated) may comprise, in particular, discharge means arranged at the outlets of the three containers 2, 3, and 4 (for example, a discharge valve for each outlet) and configured to control the discharge of the incoherent plasticsfrom each of the three containers 2, 3, and 4 in such a way as to regulate the residence time of the incoherent plastics in each of the three containers 2, 3, and 4.

[0052] The three containers 2, 3, and 4 may be arranged, in particular, at substantially the same height with respect to each other (for example, all three resting on the ground). The handling system may comprise, in particular, a conveyor for lifting the plastics from the first material outlet of the first container 2 to the second material inlet of the second container 3 and another conveyor for lifting the plastics from the second material outlet of the second container 3 to the third material inlet of the third container 4.

[0053] The apparatus 1 may comprise, in particular, suction means configured to aspirate gas from a first suction outlet of the first container 2.

[0054] The apparatus 1 may comprise, in particular, suction means configured to aspirate gas from a second suction outlet of the second container 3.

[0055] The apparatus 1 may comprise, in particular, suction means configured to aspirate gas from a third suction outlet of the third container 4.

[0056] The suction means is configured to transport the incoherent plastics and to feed the incoherent plastics to the various containers 2, 3, and 4.

[0057] The suction means may comprise, as in this specific example, a first suction unit 12 connected to the first suction outlet via a first suction conduit 13 and a second suction unit 14 connected to the second suction outlet via a second suction conduit 15. The first suction unit 12 may comprise, in particular, a vacuum pump. The second suction unit 14 may comprise, in particular, a vacuum pump.

[0058] In use, it is possible to provide that the first suction unit 12 is controlled so that a vacuum at the inlet of the first suction unit 12 itself is between -250 mbar and -650 mbar (millibar) and / or that the second suction unit 14 is controlled so that a vacuum at the inlet of the second suction unit 14 itself is between -250 mbar and -650 mbar (millibar).

[0059] The apparatus 1 may comprise, in particular, a cooling device 16 arranged in the second suction conduit 15 configured to cool the gas, for example by means of a water / air exchanger.

[0060] In particular, it is possible to arrange a cooling device (not illustrated) in the first inlet conduit 13, configured to cool the gas, for example by means of a water / air water exchanger.

[0061] The apparatus 1 may comprise, in particular, a third suction conduit 17 that connects the third suction outlet to the second suction unit 14. The third suction conduit 17may open, as in this example, into the second suction conduit 15.

[0062] It is possible to arrange, as in this example, a cooling device (for example, the cooling device 16) between the third suction outlet and the second suction unit 14.

[0063] In other examples (not illustrated), it is possible to arrange a centralized vacuum system comprising a suction unit connected to the three suction conduits 13, 15 and 17 to simultaneously vacuum from the three containers 2, 3 and 4, thus simplifying the system and reducing energy consumption.

[0064] In other examples, it is possible to foresee that at least two containers are arranged in cascade in vertical extension in order to exploit gravity to transfer the plastics from one container to the other, for example from the first container 2 to the second container 3 and / or from the second container 3 to the third container 4, obtaining a certain energy saving for the movement of the plastics.

[0065] The apparatus 1 may comprise, in particular, a recirculation conduit 18 arranged to carry process gas from the first gas outlet of the first container 2 to the gas-to-be- dehumidified inlet of the dehumidification device 7.

[0066] The apparatus 1 may comprise, in particular, a bypass conduit 19 arranged to connect a section of the first gas conduit 5, i.e. a section between the third gas outlet of the third container 4 and the second actuator 10, to the gas-to-be-dehumidified inlet of the dehumidification device 7.

[0067] The bypass conduit 19 may be configured, in particular, to prevent a flow of gas towards the aforementioned section of the first gas conduit 5 and to allow a flow of gas towards the gas-to-be-dehumidified inlet of the dehumidification device 7 (for example with the use of unidirectional flow control means).

[0068] The bypass conduit 19 may be arranged, as in this specific example, to connect the aforementioned section of the first gas conduit 5 with the recirculation conduit 18.

[0069] The apparatus 1 may comprise, in particular, a bypass valve 20 arranged in the bypass conduit 19. The bypass valve 20 may comprise, in particular, a flow control valve, for example a flow regulator valve, or a pressure control valve.

[0070] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the bypass valve 20 so that a pressure in the aforementioned section of the first gas conduit 5 is positive while, during operation of the apparatus, the first actuator 9 actuates a flow of process gas towards the third gas inlet of the third container 4 and the second actuator 10 actuates a flow of process gas towards thesecond gas inlet of the second container 3.

[0071] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus (in particular, the system for moving the incoherent plastics) so that a residence time T1 of the incoherent plastics in the first container 2 is within the range T1 = 2 ± 0.5 hours.

[0072] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a residence time T2 of the incoherent plastics in the second container 3 is within the range T2 = 2 ± 0.5 hours.

[0073] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a residence time T3 of the incoherent plastics in the third container 4 is within the range T3 = 2 ± 0.5 hours.

[0074] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a residence time T1 of the incoherent plastics in the first container 2 is equal to a residence time T2 of the incoherent plastics in the second container 3 with a difference of less than 0.5 hours, i.e. T1 = T2 ± 0.5 hours.

[0075] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a residence time T1 of the incoherent plastics in the first container 2 is equal to a residence time T3 of the incoherent plastics in the third container 4 with a difference of less than 0.5 hours, i.e., T1 = T3 ± 0.5 hours.

[0076] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a residence time T2 of the incoherent plastics in the second container 3 is equal to a residence time T3 of the incoherent plastics in the third container 4 with a difference of less than 0.5 hours, i.e., T2 = T3 ± 0.5 hours.

[0077] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control a rotation speed of the first actuator 9 (turbo blower) and / or a rotation speed of the second actuator 10 (turbo blower), i.e. to control a flow rate of the process gas generated by the first actuator 9 and / or a flow rate generated by the second actuator 10, in particular by means of a feedback control as a function of the temperatures of the process gas detected at the outlet of the first container 2 and / or the second container 3 and / or the third container 4. This allows the flow rate of the process gasto be adjusted according to the actual energy requirement to process (heat and / or dehumidify) the incoherent plastics.

[0078] Apparatus 1 may comprise, in particular, a heater 21 arranged to heat the process gas (e.g., a thermostatically controlled heater 21) before the process gas is introduced into the third container 4 through the third gas inlet.

[0079] Apparatus 1 may comprise, in particular, a heater 21 arranged to heat the process gas (e.g., a thermostatically controlled heater 21) before the process gas is introduced into the second container 3 through the second gas inlet.

[0080] Apparatus 1 may comprise, in particular, a heater 21 arranged to heat the process gas (e.g., a thermostatically controlled heater 21) before the process gas is introduced into the first container 2 through the first gas inlet.

[0081] Apparatus 1 may comprise sensor means 22 arranged along the process gas path to detect at least one characteristic of the process gas.

[0082] The sensor means 22 may comprise, in particular, a first set of sensors arranged in the section of the first gas conduit 5 between the third gas outlet and the second actuator 10, for example at or near the bypass conduit 19, as in this example, although it is possible to arrange the first set of sensors before the bypass conduit 19 or after the bypass conduit 19, or it is possible to arrange two sets of sensors, one before and one after the bypass conduit 19. Each first set of sensors may comprise, in particular, a pressure sensor and / or a temperature sensor and / or a humidity sensor and / or a flow sensor.

[0083] The sensor means 22 may comprise, in particular, a second set of sensors arranged in the second gas conduit 6. This second set of sensors may comprise, in particular, a pressure sensor and / or a temperature sensor and / or a humidity sensor and / or a flow sensor.

[0084] The sensor means 22 may comprise, in particular, a third set of sensors arranged in the recirculation conduit 18 before the bypass conduit 19 (for example, near the first gas outlet of the first container 2). This third set of sensors may comprise, in particular, a pressure sensor and / or a temperature sensor and / or a humidity sensor and / or a flow sensor.

[0085] The sensor means 22 may comprise, in particular, a fourth set of sensors arranged in the recirculation conduit 18, for example, at or near the bypass conduit 19, as in this example, although it is possible to arrange the fourth set of sensors before the bypass conduit 19 or after the bypass conduit 19, or it is possible to arrange two sets ofsensors, one before and one after the bypass conduit 19. Each fourth set of sensors may comprise, in particular, a pressure sensor and / or a temperature sensor and / or a humidity sensor and / or a flow sensor.

[0086] The sensor means 22 may comprise, in particular, a fifth set of sensors (not shown) arranged in the bypass conduit 19.

[0087] A humidity sensor is understood to mean, for example, a dewpoint or absolute humidity or relative humidity sensor or another parameter suitable for defining the quantity of humidity contained in the process gas.

[0088] The apparatus 1 may comprise sensor means (not shown) arranged along the path of the incoherent plastics to detect at least one characteristic of the incoherent plastics.

[0089] The sensor means of the incoherent plastics may comprise, in particular, a temperature sensor arranged at the inlet of the first container 2 and / or a temperature sensor arranged between the first container 2 and the second container 3 and / or a temperature sensor arranged between the second container 3 and the third container 4 and / or a temperature sensor arranged at the outlet of the third container 4.

[0090] The sensor means of the incoherent plastics may comprise, in particular, a humidity sensor arranged at the inlet of the first container 2 and / or a humidity sensor arranged between the first container 2 and the second container 3 and / or a humidity sensor arranged between the second container 3 and the third container 4 and / or a humidity sensor arranged at the outlet of the third container 4.

[0091] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a temperature of the incoherent plastics at the outlet of the third container 4 is greater than 140 °C, in particular within the range of 180 ± 20 °C.

[0092] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a temperature of the process gas at the outlet of the third container 4 is greater than 140 °C, in particular within the range of 180 ± 20 °C.

[0093] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a temperature of the incoherent plastics at the outlet of the first container 2 is greater than 40 °C, in particular within the range of 80 ± 20 °C.

[0094] The apparatus 1 may comprise, in particular, control means (electronic andprogrammable) configured to control the apparatus so that a temperature of the process gas at the outlet of the first container 2 is greater than 40 °C, in particular within the range 80 ± 20 °C.

[0095] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a temperature of the incoherent plastics at the outlet of the second container 3 is greater than 100 °C, in particular within the range 140 ± 20 °C.

[0096] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the apparatus so that a temperature of the process gas at the outlet of the second container 3 is greater than 100 °C, in particular within the range 140 ± 20 °C.

[0097] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the first actuator 9 and the second actuator 10 so that a flow rate of process gas to the second gas inlet of the second container 3 is no greater than a flow rate of process gas to the third gas inlet of the third container 4.

[0098] The apparatus 1 may comprise, in particular, control means (electronic and programmable) configured to control the second actuator 10 based on a setpoint value of a process gas flow rate.

[0099] The second actuator 10 may be configured, in particular, to implement a gas flow rate of between 100 and 4000 m3 / h (cubic meters per hour) with a delivery pressure of between 1 and 150 mbar. The second actuator 10 is configured to overcome the pressure drops encountered by the process gas along the path through the second container 3 and the first container 2.

[0100] The first actuator 9 may be configured, in particular, to implement a gas flow rate between 100 and 5000 m3 / h.

[0101] The first container 2 may have, in particular, a maximum volume VI less than 6000 dmc (cubic decimeters), specifically between 2000 dmc and 6000 dmc. The second container 3 may have, in particular, a maximum volume V2 less than 6000 dmc (cubic decimeters), specifically between 2000 dmc and 6000 dmc. The third container 4 may have, in particular, a maximum volume V3 less than 6000 dmc (cubic decimeters), specifically between 2000 dmc and 6000 dmc.

[0102] The first container 2 may have, in particular, a maximum volume VI equal to the maximum volume V2 of the second container 3 with a difference of less than 500 dmc(cubic decimeters), i.e., VI = V2 ± 500 dmc. The first container 2 may have, in particular, a maximum volume VI equal to the maximum volume V3 of the third container 4 with a difference of less than 500 dmc (cubic decimeters), i.e., VI = V3 ± 500 dmc. The second container 3 may have, in particular, a maximum volume V2 equal to a maximum volume V3 of the third container 4 with a difference of less than 500 dmc (cubic decimeters), i.e. V2 = V3 ± 500 dmc.

[0103] The operation of the apparatus 1 comprises the steps of introducing incoherent plastics into the first container 2, expelling the incoherent plastics from the first container 2, and introducing the incoherent plastics, which have been expelled from the first container 2, into the second container 3.

[0104] The operation of the apparatus 1 comprises the steps of expelling incoherent plastics from the second container 3, introducing the incoherent plastics, which have been expelled from the second container 3, into the third container 4, and expelling incoherent plastics from the third container 3. The incoherent plastics expelled from the third container 3 may be sent directly to the user device 11, which will perform a transformation of the incoherent plastics.

[0105] The operation of the apparatus 1 comprises the steps of dehumidifying a process gas by means of the aforementioned dehumidification device 7, of using the first actuator 9 to actuate a flow of process gas along the gas supply conduit 8 towards the third gas inlet of the third container 4, and of using the second actuator 10 to actuate a flow of process gas along the first gas conduit 5 towards the second gas inlet of the second container 3 and then along the second gas conduit 6 towards the first gas inlet of the first container 2.

[0106] The operation of the apparatus 1 may comprise, in particular, the step of withdrawing gas from the first suction outlet of the first container 2 along the first suction conduit 13. The operation of the apparatus 1 may comprise, in particular, the step of withdrawing gas from the second suction outlet of the second container 3 along the second suction conduit 15. The operation of the apparatus 1 may comprise, in particular, the step of withdrawing gas from the third suction outlet of the third container 4 along the third suction conduit 17. The suction of gas along the suction conduits 13, 15, 17 allows the transport and feeding of the incoherent plastics to the respective containers 2, 3, 4.

[0107] It is possible to provide, as in this specific example, that the process gas exiting the first gas outlet of the first container 2 is conveyed to the gas-to-be-dehumidified inlet ofthe dehumidification device 7 along the recirculation conduit 18.

[0108] It is possible to provide, as in this specific example, that a part of the process gas flowing along the first gas conduit 5, in a section of the first gas conduit 5 between the third gas outlet of the third container 4 and the second actuator 10, is bypassed towards the gas-to-be-dehumidified inlet of the dehumidification device 7 so that a pressure in the aforementioned section is positive during operation, while the second actuator 10 implements a gas flow rate of process gas towards the second gas inlet of the second container 3 and then sequentially towards the first gas inlet of the first container 2, while the first actuator 9 actuates a flow of process gas towards the third gas inlet of the third container 4.

[0109] The operation of the apparatus 1 may include, in particular, that a flow rate of process gas actuated by the second actuator 10 is between 100 and 4000 m3 / h with a delivery pressure between 1 and 150 mbar. The operation of the apparatus 1 may include, in particular, that a flow rate of process gas actuated by the first actuator 9 is between 100 and 5000 m3 / h.

[0110] The operation of the apparatus 1 may comprise, in particular, that a flow rate of process gas actuated by the first actuator 9 is greater than or equal to a flow rate of process gas actuated by the second actuator 10.

[0111] It is possible to control the various actuators of the apparatus 1 - namely the first actuator 9, the second actuator 10, the dehumidification device 7 which dehumidifies the process gas, the heater 21 which heats the process gas, the bypass valve 20 which controls the flow in the bypass conduit 19, the suction means (first suction unit 12 and second suction unit 14), the system for moving the incoherent plastics (which controls the residence time of the incoherent plastics in the various containers 2, 3 and 4) - so as to obtain, based on measurements carried out by temperature sensor means, the desired temperatures of the incoherent plastics (at the material outlet of the first container 2 and / or at the material outlet of the second container 3 and / or at the material outlet of the third container 4) and / or the desired process gas temperatures (in particular, at the gas outlet of the third container 4 and / or at the gas outlet of the second container 3 and / or at the gas outlet of the first container 2).

[0112] It has been seen that this possibility, combined with the possibility of controlling the residence time of the incoherent plastics in the three containers 2, 3 and 4, allows for increasing the efficiency of heat exchange between the process gas and theincoherent plastics, reducing thermal energy consumption and overall process time.

[0113] Furthermore, it has been seen that the solution of adopting the second actuator 10, capable of boosting the flow rate of the process gas exiting the third container 4 and producing a desired flow rate of process gas that passes sequentially first through the second container 3 and then the first container 2, achieves a certain saving in energy consumption for the movement of the process gas compared to a traditional solution (single-stage) with a single container or dehumidification hopper, with the same volume of treated material and removal of humidity from the material itself.

[0114] When changing production batches, it is possible to begin loading the first container 2 (emptied of material from the previous production batch) with material from the new production batch while the material from the previous production batch is still being processed in the second container 3 and the third container 4. That is, it is possible to begin processing the material from the new production batch in the first container 2 without having to wait for all three containers 2, 3, and 4 to be emptied of material from the previous production batch.

[0115] When the second container 3 is emptied of material from the previous production batch, it will be possible to begin feeding the second container 3 with material from the new production batch (while the third container 4 still contains material from the previous production batch).

[0116] This results in an undoubted time saving.

[0117] In the specific example illustrated here, apparatus 1 is equipped with only three process stages. Other examples, not illustrated, may be envisaged with a number of process stages equal to four, or five, or more than five, where the second actuator 10 may be configured to actuate a process gas flow rate that relays the flow through more than two process stages, or an additional actuator (or two or more additional actuators) may be provided capable of relaying the flow rate for the additional process stages.

[0118] In other examples, not illustrated, it is possible to provide that the incoherent plastics are subjected to radio frequency waves inside the first container 2 and / or inside the second container 3 and / or inside the third container 4, by means of means for generating radio frequency waves arranged in addition to or in place of the respective heaters 21 operatively associated with the aforementioned containers 2, 3, 4.

[0119] The aforementioned radio frequency waves, to which the incoherent plastics can be subjected, may have, in particular, a frequency between 300 KHz and 300 GHz, orbetween 1 MHz and 1 GHz, or between 10 MHz and 100 MHz, or between 1 MHz and 50 MHz, or between 10 MHz and 50 MHz.

[0120] The aforementioned radio frequency waves may be generated, in particular, by means of at least one electrode located inside the respective container and in contact with the incoherent plastics. The aforementioned radio frequency waves may be controlled, in particular, to maintain a desired value of a temperature measured inside the respective container.

[0121] It has been found that the aforementioned use of radio frequency waves to heat the incoherent plastics results in improved energy efficiency compared to other types of heating, especially when used in the second container 3, but also when used in the third container 4, for the purpose of removing moisture and / or other contaminants from the particles of incoherent plastics. Heating the plastics with radio frequency waves may, however, also be performed in the first container 2.

[0122] Furthermore, it is possible to provide that the incoherent plastics are subjected to a process pressure lower than ambient pressure (in the presence or absence of the aforementioned radio frequency waves) inside the first container 2 and / or inside the second container 3 and / or inside the third container 4, by means of means for generating vacuum (arranged in addition to or in place of the aforementioned suction means for transporting and feeding the incoherent plastics).

[0123] The aforementioned process pressure lower than ambient pressure may be, in particular, lower than 7.5 x 104 absolute Pascal, or lower than 5 x 104 absolute Pascal, or lower than 2.5 x 104 absolute Pascal, or lower than 1.4 x 104 absolute Pascal. The aforementioned process pressure lower than ambient pressure may be, in particular, higher than 2 x 103 absolute Pascal.

[0124] For each container subjected to the aforementioned process pressure lower than ambient pressure, it is possible to arrange one or more vacuum pumps, one or more vacuum-tight valves (upstream and / or downstream of the respective container), and one or more buffer volumes (upstream and / or downstream of the respective container) to manage the aforementioned relatively intense vacuum in the container itself.

[0125] It has been found that the aforementioned use of a process pressure lower than ambient pressure improves the removal of moisture and / or other contaminants from the particles of the incoherent plastics, especially when used in the second container 3, butalso when used in the first container 2. The aforementioned process pressure lower than ambient pressure may, however, also be used in the third container 4.

[0126] It is possible to envision an embodiment, not illustrated, identical to the examples described above and claimed below, except that the first container 2 is absent (as are consequently the first suction conduit 13 and the second gas conduit 6) and the recirculation conduit 18 is connected directly to the second gas outlet of the second container 3.

[0127] Legend:1 Apparatus for processing incoherent plastics2 First container3 Second container4 Third container5 First gas conduit6 Second gas conduit7 Dehumidification device8 Gas supply conduit9 First actuator10 Second actuator11 User device12 First suction unit13 First suction conduit14 Second suction unit15 Second suction conduit16 Cooling device17 Third suction conduit18 Recirculation conduit19 Bypass conduit20 Bypass valve21 Heaters22 Sensor means

Claims

CLAIMS1. Apparatus for processing incoherent plastics, said apparatus (1) comprising: a first container (2) with a first material inlet for introducing incoherent plastics into said first container (2), a first material outlet for expelling incoherent plastics from said first container (2), a first gas inlet for introducing process gas into said first container (2), and a first gas outlet for expelling process gas from said first container (2); a second container (3) with a second material inlet connected to said first material outlet for introducing incoherent plastics from said first container (2) into said second container (3), a second material outlet for expelling incoherent plastics from said second container (3), a second gas inlet for introducing process gas into said second container (3), and a second gas outlet for expelling process gas from said second container (3); a third container (4) with a third material inlet connected to said second material outlet for introducing incoherent plastics from said second container (3) into said third container (4), a third material outlet for expelling incoherent plastics from said third container (4), a third gas inlet for introducing process gas into said third container (4), and a third gas outlet for expelling process gas from said third container (4); a first gas conduit (5) for conveying process gas from said third gas outlet to said second gas inlet; a second gas conduit (6) for conveying process gas from said second gas outlet to said first gas inlet; a dehumidification device (7) with a gas-to-be-dehumidified inlet and a dehumidified gas outlet; a gas supply conduit (8) for conveying process gas from said dehumidified gas outlet to said third gas inlet; a first actuator (9) configured to actuate a flow of process gas along said gas supply conduit (8) towards said third gas inlet; and a second actuator (10) arranged in said first gas conduit (5) to actuate a flow of process gas along said first gas conduit (5) towards said second gas inlet and along said second gas conduit (6) towards said first gas inlet.

2. Apparatus according to claim 1, wherein said third material outlet is connected to a user device (11) configured to perform a transformation of incoherent plastics, in particular for processes such as moulding, extrusion, blowing, thermoforming, calendering, hot bending.

3. Apparatus according to claim 1 or 2, comprising suction means configured to suck gas from a first suction outlet of said first container (2) and / or from a second suction outlet of said second container (3) and / or from a third suction outlet of said thirdcontainer (4); said suction means comprising, in particular, at least one suction unit (12; 14) connected to said first suction outlet by a first suction conduit (13) and / or connected to said second suction outlet by a second suction conduit (15) and / or connected to said third suction outlet by a third suction conduit (17); said apparatus comprising, in particular, a cooling device (16) arranged to cool gas sucked by said suction means.

4. Apparatus according to any one of the preceding claims, comprising a recirculation conduit (18) for conveying process gas from said first gas outlet to said gas-to-be- dehumidified inlet.

5. Apparatus according to any one of the preceding claims, comprising a bypass conduit (19) arranged to connect a section of said first gas conduit (5) between said third gas outlet and said second actuator (10) with said gas-to-be-dehumidified inlet; said bypass conduit (19) being configured, in particular, to prevent a flow of gas towards said section.

6. Apparatus according to claims 5 and 4, wherein said bypass conduit (19) connects said first gas conduit (5) with said recirculation conduit (18).

7. Apparatus according to claim 5 or 6, comprising control means configured to control said bypass conduit (19) such that a pressure in said section is positive while said first actuator (9) actuates a flow of process gas to said third gas inlet and said second actuator (10) actuates a flow of process gas to said second gas inlet.

8. Apparatus according to any one of the preceding claims, wherein said first actuator (9) is part of said dehumidification device (7).

9. Apparatus according to any one of the preceding claims, wherein said first actuator (9) comprises a turbo blower and / or wherein said second actuator (10) comprises a turbo blower.

10. Apparatus according to any one of the preceding claims, comprising control means configured to control said apparatus such that a residence time of the incoherent plastics in each of said first, second and third containers (2; 3; 4) is in the range 2 ± 0.5 hours.

11. Apparatus according to any one of the preceding claims, comprising a heater (21) arranged to heat the process gas before the process gas is introduced into said third container (4) through said third gas inlet and / or before the process gas is introduced into said second container (3) through said second gas inlet and / or before the processgas is introduced into said first container (2) through said first gas inlet.

12. Apparatus according to any one of the preceding claims, comprising control means configured to control said apparatus so that:a temperature of the incoherent plastics at the outlet of said third container (4) is greater than 140 °C, in particular within the range 180 ± 20 °C, and / or so that a temperature of the process gas at the outlet of said third container (4) is greater than 140 °C, in particular within the range 180 ± 20 °C; and / or a temperature of the incoherent plastics at the outlet of said first container (2) is greater than 40 °C, in particular within the range 80 ± 20 °C, and / or so that a temperature of the process gas at the outlet of said first container (2) is greater than 40 °C, in particular within the range 80 ± 20 °C; and / ora temperature of the incoherent plastics at the outlet of said second container (3) is greater than 100 °C, in particular within the range 140 ± 20 °C, and / or so that a temperature of the process gas at the outlet of said second container (3) is greater than 100 °C, in particular within the range 140 ± 20 °C.

13. Apparatus according to any one of the preceding claims, comprising control means configured to control said first and second actuators (9; 10) such that a flow rate of process gas actuated by said second actuator (10) to said second gas inlet is no greater than a flow rate of process gas actuated by said first actuator (9) to said third gas inlet.

14. Apparatus according to any one of the preceding claims, comprising control means configured to control said second actuator (10) based on a setpoint value of a flow rate of process gas.

15. Apparatus according to any one of the preceding claims, wherein said second actuator (10) is configured to actuate a flow rate of between 100 and 4000 m3 / h with a delivery pressure of between 1 and 50 mbar and said first actuator (9) is configured to actuate a flow rate of between 100 and 5000 m3 / h.

16. Apparatus according to any one of the preceding claims, wherein said first container (2) has a maximum volume of less than 6000 dmc, in particular between 2000 dmc and 6000 dmc, wherein said second container (3) has a maximum volume of less than 6000 dmc, in particular between 2000 dmc and 6000 dmc, and wherein said third container (4) has a maximum volume of less than 6000 dmc, in particular between 2000 dmc and 6000 dmc.

17. Apparatus according to any one of the preceding claims, comprising means for generating radio frequency waves and subjecting the incoherent plastics in said first container (2) and / or in said second container (3) and / or in said third container (4) to said radio frequency waves; said radio frequency waves having, in particular, a frequency between 300 KHz and 300 GHz, or between 1 MHz and 1 GHz, or between 10 MHz and 100 MHz, or between 1 MHz and 50 MHz, or between 10 MHz and 50 MHz; said means for generating radio frequency waves comprising, in particular, at least one electrode which is arranged in the respective container (2; 3; 4) and which is in contact with the incoherent plastics.

18. Apparatus according to any one of the preceding claims, comprising means for generating vacuum and subjecting the incoherent plastics to a process pressure lower than ambient pressure in said first container (2) and / or in said second container (3) and / or in said third container (4); said process pressure lower than ambient pressure is, in particular, lower than 7.5 x 104Pascal absolute, or lower than 5 x 104Pascal absolute, or lower than 2.5 x 104Pascal absolute, or lower than 1.4 x 104Pascal absolute.

19. Use of an apparatus according to any one of the preceding claims, said use comprising the steps of introducing incoherent plastics into said first container (2), expelling incoherent plastics from said first container (2) and introducing said incoherent plastics expelled from said first container (2) into said second container (3), expelling incoherent plastics from said second container (3) and introducing said incoherent plastics expelled from said second container (3) into said third container (4), expelling incoherent plastics from said third container (4), dehumidifying a process gas by said dehumidifying device (7), actuating a flow of process gas by said first actuator (9) towards said third gas inlet, and actuating a flow of process gas by said second actuator (10) towards said second gas inlet and towards said first gas inlet.

20. Use according to claim 18, wherein said incoherent plastics expelled from said third container (4) is sent to a user device (11) which carries out a transformation of said incoherent plastics.

21. Use according to claim 19 or 20, comprising the step of aspirating gas from a first suction outlet of said first container (2) and / or from a second suction outlet of said second container (3) and / or from a third suction outlet of said third container (4).

22. Use according to any one of claims 19 to 21, wherein said process gas is conveyed from said first gas outlet to said gas-to-be-dehumidified inlet along a recirculation conduit (18).

23. Use according to any one of claims 19 to 22, wherein a portion of the process gas flowing in said first gas conduit (5), in a section between said third gas outlet and said second actuator (10), is bypassed towards said gas-to-be-dehumidified inlet so that a pressure in said section is positive while said second actuator (10) actuates a flow rate of process gas towards said second gas inlet and towards said first gas inlet and said first actuator (9) actuates a flow rate of process gas towards said third gas inlet.

24. Use according to any one of claims 19 to 23, wherein a residence time of the incoherent plastics in each of said first, second and third containers (2; 3; 4) is included in the range 2 ± 0.5 hours.

25. Use according to any one of claims 19 to 24, wherein:a temperature of the incoherent plastics at the outlet of said third container (4) is greater than 140 °C, in particular within the range 180 ± 20 °C and / or a temperature of the process gas at the outlet of said third container (4) is greater than 140 °C, in particular within the range 180 ± 20 °C; and / ora temperature of the incoherent plastics at the outlet of said first container (2) is greater than 40 °C, in particular within the range 80 ± 20 °C, and / or a temperature of the process gas at the outlet of said first container (2) is greater than 40 °C, in particular within the range 80 ± 20 °C; and / ora temperature of the incoherent plastics at the outlet of said second container (3) is greater than 100 °C, in particular within the range 140 ± 20 °C, and / or a temperature of the process gas at the outlet of said second container (3) is greater than 100 °C, in particular within the range 140 ± 20 °C.

26. Use according to any one of claims 19 to 25, wherein a process gas flow rate actuated by said second actuator (10) is between 100 and 4000 m3 / h with a delivery pressure between 1 and 50 mbar and wherein a process gas flow rate actuated by said first actuator (9) is between 100 and 5000 m3 / h.

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