Drying device for synthetic resin molding material

Abstract

The purpose of the present invention is to provide a drying device for a synthetic resin molding material, which can effectively use heat energy and can dry the synthetic resin molding material such as resin particles in a shorter time in a temperature range in which the physical properties thereof are not susceptible to change. A drying device (1) is provided with: a drying hopper (2); generating units (8, 7A) for generating drying air for drying the synthetic resin molding material in the drying hopper (2); a dry air supply path (L1) for supplying dry air to the drying hopper (2); a discharge air discharge path (L2) for discharging, from the drying hopper (2), dry air from the drying hopper (2), said dry air having been used to dry the synthetic resin molding material; and a discharge air supply path (L7) for supplying a part of the discharge air flowing in the discharge air flow path (L2) to the drying hopper (2). The drying hopper (2) introduces dry air from the dry air supply path (L1) to the lower side, and introduces exhaust air from the exhaust air supply path (L7) to the upper side.

Description

Technical Field

[0001] This disclosure relates to a drying apparatus for removing moisture from synthetic resin molding materials, such as resin particles. Background Technology

[0002] Synthetic resin molding materials are typically fed to resin molding machines such as injection molding machines in granular form. Resin granules absorb moisture from the atmosphere; if they are in a high moisture content, hydrolysis will occur during the melt-mixing process, leading to reduced strength and impact resistance of the molded product, significantly lowering its quality. Furthermore, it can cause surface defects in the molded product. Therefore, resin granules are fed to injection molding machines after moisture removal.

[0003] As a means of removing moisture from resin particles, a drying apparatus is known, for example, that supplies high-temperature, low-dew-point dry air to a drying hopper containing resin particles, causing the dry air to contact the resin particles within the drying hopper. In this drying apparatus, the dry air heats the resin particles within the drying hopper, thereby vaporizing the moisture adhering to the surface of the resin particles and the moisture contained within them. The vaporized moisture is then carried away by the dry air, thereby removing moisture from the resin particles (see, for example, Patent Document 1).

[0004] Figure 5 A general outline of a conventional example of the aforementioned drying apparatus is shown. Dry air is generated by heating low-dew-point air to a high temperature in heater 101 and supplied to the drying hopper 100. Resin particles are supplied from the hopper loader 102 to the drying hopper 100. The resin particles within the drying hopper 100 are dried by the heating of the dry air. By opening the solenoid valve 103, the dried resin particles are discharged from the drying hopper 100 and supplied to the resin molding machine 105 via the conveying pipe 104.

[0005] The drying air used for drying resin particles in the drying hopper 100 decreases in temperature due to the heat carried away by the resin particles and increases in humidity due to the removal of moisture from the resin particles before being discharged from the drying hopper 100. The dried air discharged from the drying hopper 100 (exhaust air) is cleaned by a dust collector 107 to remove impurities, cooled by a cooler 108, compressed by a blower 109, and cooled again by a cooler 110 before being supplied to a dehumidifier 106. The exhaust air is then dehumidified by the dehumidifier 106 to become low-dew-point air and is used again as drying air for drying resin particles in the drying hopper 100.

[0006] Patent Document 1: Japanese Published Patent No. 7-19770 Summary of the Invention

[0007] (a) Technical problems to be solved Coolers 108 and 110 used for cooling exhaust air are typically water-cooled. While water-cooled coolers can efficiently cool exhaust air using cooling water, the cooling water, which recovers the heat energy of the exhaust air along with the cooling of the exhaust air, is cooled in a cooling tower. Therefore, although the exhaust air discharged from the drying hopper 100 is at a high temperature and contains heat energy, the heat energy of the exhaust air cannot be effectively utilized in existing drying devices.

[0008] Furthermore, for drying resin granules, higher drying air temperatures result in shorter drying times and higher temperatures in the dried resin granules, allowing for efficient and high-temperature supply to resin molding machines such as injection molding machines. However, if the drying air temperature increases, the resin granule temperature also rises accordingly, making them prone to decomposition (hydrolysis, oxidative decomposition, thermal decomposition, etc.) or degradation, leading to changes in their physical properties. Therefore, if an abnormality occurs in the drying equipment during resin granule drying, causing the resin granules to remain in the drying hopper at a high temperature for longer than the specified drying time, changes in the resin granule properties may occur. On the other hand, if the drying air temperature is low, the drying time for the resin granules will be longer.

[0009] This disclosure is made in view of the above circumstances, and its object is to provide a drying apparatus for synthetic resin molding materials that can effectively utilize thermal energy and dry synthetic resin molding materials in a shorter time within a temperature range that does not easily cause changes in the physical properties of synthetic resin molding materials such as resin particles.

[0010] (II) Technical Solution To address the aforementioned issues, the drying apparatus disclosed herein includes the drying apparatus described in item 1 below as the subject matter.

[0011] Item 1. A drying apparatus comprising: A drying hopper that contains synthetic resin molding material introduced from the top and discharges the synthetic resin material from the bottom; The generating section generates drying air for drying the synthetic resin molding material in the drying hopper; A dry air supply path for supplying the dry air to the dry hopper; An exhaust air path is provided for conveying exhaust air discharged from the drying hopper after the synthetic resin molding material has been dried within the drying hopper. An exhaust air supply path for supplying a portion of the exhaust air flowing in the exhaust air flow path to the drying hopper; and A heater, located in the exhaust air duct, heats the exhaust air supplied to the drying hopper. A drying air inlet is provided at the lower part of the drying hopper for introducing drying air from the drying air supply path, and an exhaust air inlet is provided at the upper part of the drying hopper for introducing exhaust air from the exhaust air supply path. In the drying hopper, the exhaust air inlet is located above the drying air inlet.

[0012] Furthermore, as a preferred embodiment of the drying apparatus described in item 1 above, the drying apparatus disclosed herein includes the drying apparatus described in item 2 below.

[0013] Item 2. The drying apparatus according to item 1, characterized in that the generating unit comprises: a dehumidifying device for generating low dew point air; and a heater for heating the low dew point air to become the dried air.

[0014] In addition, as a preferred embodiment of the drying apparatus described in items 1 to 2 above, the drying apparatus disclosed herein includes the drying apparatus described in item 3 below.

[0015] Item 3. The drying apparatus according to item 1 or 2, characterized in that the temperature of the drying air supplied to the drying hopper is above 110°C and below 140°C.

[0016] (III) Beneficial Effects The drying apparatus disclosed herein can effectively utilize thermal energy and can dry synthetic resin molding materials in a shorter time within a temperature range that does not easily cause changes in the physical properties of synthetic resin molding materials such as resin particles. Attached Figure Description

[0017] Figure 1 This is a schematic structural diagram of a drying apparatus according to one embodiment of the present disclosure.

[0018] Figure 2 This is a schematic diagram of the drying hopper.

[0019] Figure 3 This is a schematic structural diagram of a drying apparatus according to another embodiment of the present disclosure.

[0020] Figure 4 This is a schematic structural diagram of a drying apparatus according to another embodiment of the present disclosure.

[0021] Figure 5 This is a schematic structural diagram of an existing drying apparatus. Detailed Implementation

[0022] This disclosure relates to a drying apparatus for removing moisture from synthetic resin molding materials used as raw materials during the manufacture of plastic molded articles, such as by injection molding or extrusion molding. Synthetic resin molding materials are hygroscopic and therefore absorb moisture from the atmosphere. If the synthetic resin molding material is supplied to a resin molding machine in a state containing a large amount of moisture, hydrolysis will occur during melt mixing, leading to a decrease in the strength and impact resistance of the molded article, significantly reducing its quality. Furthermore, it can cause appearance defects in the molded article. Therefore, it is necessary to remove moisture from the synthetic resin molding material before supplying it to the resin molding machine. The drying apparatus of this disclosure is a technique for drying synthetic resin molding materials to remove moisture from them.

[0023] Synthetic resin molding materials can take the form of powder, granules, or pellets, but their shape is not particularly limited. In the embodiments described below, the synthetic resin molding material is resin granules, but it is not limited to resin granules. The synthetic resin molding material uses thermoplastic resin as a raw material. Examples of thermoplastic resins include polyesters such as polyethylene terephthalate, polyethylene, polypropylene, polystyrene, ABS, and polyamide, but it is not limited to these.

[0024] Hereinafter, an embodiment of the drying apparatus of this disclosure will be described in detail with reference to the accompanying drawings.

[0025] like Figure 1 As shown, the drying device 1 includes a drying hopper 2 for holding resin particles. Figure 2 As shown, the drying hopper 2 has a receiving space 22 capable of containing resin particles. The resin particles are dried while contained in the drying hopper 2.

[0026] like Figure 1 and Figure 2 As shown, a resin particle inlet 20 is provided at the upper part of the drying hopper 2. A loading hopper 3, for example, is disposed above the drying hopper 2. Undried resin particles are conveyed from a raw material tank (not shown) to the loading hopper 3, and the undried resin particles are introduced from the loading hopper 3 into the drying hopper 2 through the inlet 20.

[0027] like Figure 1 and Figure 2 As shown, a portion of the lower end of the drying hopper 2 is, for example, conical or pyramidal in shape, and a resin particle discharge section 21 is provided at the lower end of the drying hopper 2. By, for example, opening the solenoid valve 4, the resin particles in the drying hopper 2 are discharged from the drying hopper 2 through the discharge section 21 and conveyed to the resin molding machine 6 through the conveying pipe 5. Furthermore, there is no particular limitation on the method of conveying or stopping the conveying of resin particles from the drying hopper 2 to the resin molding machine 6, and known methods can be used.

[0028] like Figure 1 and Figure 2 As shown, the upper part of the drying hopper 2 forms a tapered shape that tapers towards the bottom, and the accommodating space 22 within the drying hopper 2 is divided into a first region 22A on the lower side and a second region 22B on the upper side. At least one inlet portion 23, 24 is provided in the lower part of the drying hopper 2 to introduce drying air for drying the resin particles within the drying hopper 2. The end of the lower second inlet portion 24 preferably extends to near the lower end of the drying hopper 2.

[0029] Dry air is introduced into the lower part of the drying hopper 2 through the upper first inlet 23 and into the very bottom of the drying hopper 2 through the lower second inlet 24. The dry air contacts the resin particles within the drying hopper 2, thereby heating the resin particles and reducing their moisture content. The dry air rises within the drying hopper 2, primarily drying the resin particles contained in the lower part of the drying hopper 2. Because the dry air is introduced into the very bottom of the drying hopper 2 through the second inlet 24, the temperature drop of the resin particles accumulated in the lower part of the drying hopper 2 is suppressed. The humidity of the dry air increases as it carries away moisture from the resin particles, and its temperature decreases as heat is carried away by the resin particles.

[0030] like Figure 1 and Figure 2 As shown, an exhaust vent 25 is provided at the upper part of the drying hopper 2, which discharges the drying air used for drying resin particles to the outside of the drying hopper 2. Additionally, an inlet vent 26 is provided at a position lower than the exhaust vent 25 at the upper part of the drying hopper 2, which guides a portion of the drying air (exhaust air) discharged to the outside of the drying hopper 2 into the drying hopper 2. The exhaust air inlet vent 26 is located higher than the drying air inlets 23 and 24. The end of the exhaust air inlet vent 26 preferably extends to the boundary between the lower and upper parts of the drying hopper 2.

[0031] The shape and structure of the drying hopper 2 are not particularly limited, and drying hoppers with previously known shapes and structures can be used.

[0032] like Figure 1 As shown, the drying apparatus 1 includes a generating unit that generates dry air for drying the synthetic resin molding material in the drying hopper 2. In this embodiment, the generating unit includes: at least one (two in this embodiment) dehumidifier 8 for generating low dew point air; and a first heater 7A for heating the low dew point air to become dry air. The dehumidifier 8 and the first heater 7A will be described later.

[0033] like Figure 1As shown, the drying apparatus 1 includes a drying air supply path L1 for supplying drying air to the drying hopper 2. In this embodiment, the drying air supply path L1 is divided into two paths at one end. One end of the drying air supply path L1 is connected to the first inlet 23 of the drying hopper 2. The other end of the drying air supply path L1 is connected to the second inlet 24 of the drying hopper 2. Drying air is supplied to the drying hopper 2 from the inlets 23 and 24 through the drying air supply path L1.

[0034] In this embodiment, the other end of the dry air supply path L1 is divided into two paths. One end of the other end of the dry air supply path L1 is connected to the exhaust section 80 of low dew point air provided on a dehumidifier 8. The other end of the other end of the dry air supply path L1 is connected to the exhaust section 80 of low dew point air provided on another dehumidifier 8. The low dew point air generated by the dehumidifier 8 is supplied from the exhaust section 80 of the dehumidifier 8 to the first heater 7A through the dry air supply path L1.

[0035] On the dry air supply path L1, between the drying hopper 2 and the dehumidification device 8, a first heater 7A, a first filter device 9A, and a first blower 10A are arranged in order of distance from the drying hopper 2 to the farthest point. The low dew point air discharged from the dehumidification device 8 passes sequentially through the first blower 10A, the first filter device 9A, and the first heater 7A.

[0036] The first blower 10A draws in low-dew-point air through the intake port, compresses the low-dew-point air, and discharges the compressed low-dew-point air through the outlet. The first filter device 9A removes foreign matter from the low-dew-point air. The first heater 7A heats the low-dew-point air, making it high-temperature, low-dew-point dry air. The first heater 7A heats the low-dew-point air to a temperature of, for example, 110°C to 180°C, preferably 110°C to 140°C. The first heater 7A, the first filter device 9A, and the first blower 10A can be conventionally known equipment.

[0037] like Figure 1 As shown, the drying device 1 includes an exhaust air outlet L2, which is used to discharge the drying air from the drying hopper 2 after drying the resin particles. The exhaust air outlet L2 supplies exhaust air from the drying hopper 2 to the dehumidification device 8.

[0038] One end of the exhaust air outlet path L2 is connected to the exhaust section 25 on the upper part of the drying hopper 2. In this embodiment, the other end of the exhaust air outlet path L2 is divided into two paths. One end of the other end of the exhaust air outlet path L2 is connected to the exhaust air inlet section 81 provided on a dehumidifier 8. The other end of the other end of the exhaust air outlet path L2 is connected to the exhaust air inlet section 81 provided on another dehumidifier 8. Exhaust air is supplied to the dehumidifier 8 from the inlet section 81 through the exhaust air outlet path L2.

[0039] On the exhaust air path L2, between the drying hopper 2 and the dehumidification device 8, a dust collector 11, a second blower 10B, and a cooler 12 are arranged in order of distance from the drying hopper 2 to the farthest point. The exhaust air discharged from the drying hopper 2 passes through the dust collector 11, the second blower 10B, and the cooler 12 in sequence.

[0040] The dust collector 11 removes foreign objects from the exhaust air flowing in the exhaust air discharge path L2. The dust collector 11 can be, for example, a cyclone dust collector, but is not limited to a cyclone type, and can be a conventionally known dust collector.

[0041] The second blower 10B draws in exhaust air through the intake port, compresses the exhaust air, and then discharges the compressed exhaust air through the outlet. The second blower 10B can be any conventionally known equipment.

[0042] Cooler 12 cools the exhaust air supplied to dehumidifier 8 to lower its temperature. Cooler 12 cools the exhaust air to a temperature of, for example, approximately 40°C. If the exhaust air discharged from drying hopper 2 is supplied to dehumidifier 8 at a high temperature, the dehumidification efficiency of the exhaust air in dehumidifier 8 will decrease. Therefore, by supplying the exhaust air cooled by cooler 12 to dehumidifier 8, the dehumidification efficiency of the exhaust air in dehumidifier 8 can be improved. This allows for the efficient generation of low dew point air in dehumidifier 8.

[0043] The cooler 12 is preferably an air-cooled heat exchanger. Within the cooler 12, exhaust air is introduced through the exhaust air inlet 120, and outside air is introduced through the outside air inlet 122. The cooler 12 cools the exhaust air by exchanging heat with the outside air. The cooled exhaust air is discharged from the exhaust air outlet 121 and supplied to the dehumidifier 8. The outside air heats up by exchanging heat with the exhaust air, carrying away its heat energy. The heated outside air is discharged from the outside air outlet 123, and a portion of the discharged outside air is supplied to the dehumidifier 8 as regeneration gas.

[0044] As long as the cooler 12 is an air-cooled heat exchanger, its shape and structure are not particularly limited, and conventionally known coolers can be used.

[0045] like Figure 1 As shown, the drying apparatus 1 includes an external air supply path L3 for supplying external air to the cooler 12. A second filter device 9B and a third blower 10C are provided on the external air supply path L3, upstream of the cooler 12. External air passes sequentially through the second filter device 9B and the third blower 10C.

[0046] The third blower 10C draws in outside air through the intake port, compresses the outside air, and then discharges the compressed outside air through the outlet. The second filter device 9B removes foreign matter from the outside air flowing in the outside air supply path L3. The second filter device 9B and the third blower 10C can be conventionally known equipment.

[0047] A temperature sensor 13 is installed on the exhaust air path L2, between the cooler 12 and the dehumidifier 8 (downstream of the cooler 12). The temperature sensor 13 measures the temperature of the exhaust air supplied to the dehumidifier 8 after being cooled by the cooler 12. In this embodiment, the temperature of the exhaust air measured by the temperature sensor 13 is monitored by the control device 14. That is, the temperature sensor 13 converts the measured temperature into an electrical signal and outputs it to the control device 14.

[0048] The control device 14 continuously monitors the temperature of the exhaust air supplied to the dehumidifier 8 and controls the airflow (air volume of the third blower 10C) of the external air supplied from the third blower 10C to the cooler 12 to ensure that the temperature of the exhaust air reaches a certain temperature, for example, 40°C. The control device 14, for example, uses a frequency converter to control the rotational speed of the motor built into the third blower 10C based on the exhaust air temperature. Thus, external air with an airflow corresponding to the exhaust air temperature is supplied to the cooler 12, adjusting the temperature of the exhaust air supplied to the dehumidifier 8 to a certain temperature. Furthermore, the airflow control of the third blower 10C can also be achieved by adjusting the damper.

[0049] In this embodiment, the drying apparatus 1 includes a temperature indicator regulator (TIC) as a control device 14. The temperature indicator regulator compares the electrical signal output from the temperature sensor 13 with a target value and calculates based on the deviation to control the third blower 10C. Alternatively, the control device 14 may also be a general-purpose computer.

[0050] like Figure 1As shown, the drying device 1 includes a dehumidifier 8. The dehumidifier 8 generates low dew point air by dehumidifying the exhaust air. The dehumidifier 8 contains an adsorbent. Exhaust air is introduced into the dehumidifier 8 from the exhaust air discharge path L2 through the inlet 81. Inside the dehumidifier 8, the exhaust air comes into contact with the adsorbent, and the moisture contained in the exhaust air is adsorbed by the adsorbent, thereby removing the moisture from the exhaust air. Thus, in the dehumidifier 8, the exhaust air is dehumidified to generate low dew point air.

[0051] The low dew point air generated in the dehumidifier 8 is discharged from the dehumidifier 8 through the exhaust section 80 and supplied to the first heater 7A through the dry air supply path L1. Then, in the first heater 7A, the low dew point air is heated to become high-temperature and low-dew-point dry air, which is then supplied to the drying hopper 2 through the dry air supply path L1. The adsorbent is not particularly limited as long as it can adsorb moisture from the gas; examples include silica gel, zeolite, activated carbon, and metal-organic framework (MOF) materials.

[0052] Additionally, regenerated gas is introduced into the dehumidifier 8 from the regenerated gas supply path L4 via the inlet 83. Inside the dehumidifier 8, the regenerated gas contacts the adsorbent, causing the adsorbed water to decompose and be removed from the adsorbent. Thus, the adsorbent is regenerated in the dehumidifier 8. The regenerated gas is not particularly limited, and can be, for example, high-temperature air at 200°C to 230°C. The regenerated gas (referred to in this disclosure as "regenerated gas") after the adsorbent has been regenerated in the dehumidifier 8 is discharged from the dehumidifier 8 via the exhaust 82.

[0053] The dehumidifier 8 is not particularly limited in shape or structure as long as it is configured to remove moisture contained in the exhaust air from the exhaust air by adsorption of the adsorbent to generate low dew point air, and to remove the moisture adsorbed by the adsorbent from the adsorbent by desorption of the regenerated gas to regenerate the adsorbent.

[0054] For example, the dehumidifier 8 is a rotary continuous dehumidifier. This type of dehumidifier 8 has a cylindrical adsorption wheel that can rotate around a rotation axis, and the adsorption wheel has adsorption elements with, for example, a honeycomb structure. The adsorption elements are loaded with adsorbent. The adsorption wheel is divided into an adsorption zone and a desorption zone along the circumference around the rotation axis, and the adsorption elements move alternately between the adsorption zone and the desorption zone by the rotation of the adsorption wheel.

[0055] Exhaust air is supplied to the adsorption zone of the adsorption rotor, where moisture in the exhaust air is adsorbed by the adsorbent as it passes through the adsorption elements located in the adsorption zone. This dehumidifies the exhaust air. Regeneration gas is supplied to the desorption zone of the adsorption rotor, where moisture is desorbed from the adsorbent as it passes through the adsorption elements located in the desorption zone. This regenerates the adsorbent.

[0056] Furthermore, the dehumidification device 8 is not limited to a rotary continuous dehumidification device, but may also use other conventionally known devices.

[0057] like Figure 1 As shown, the drying device 1 includes a regeneration gas supply line L4, which supplies regeneration gas to the dehumidifier 8 to regenerate the adsorbent in the dehumidifier 8. The regeneration gas is external air that has been heated in the cooler 12 through heat exchange with the exhaust air. The regeneration gas supply line L4 supplies the external air discharged from the cooler 12 to the dehumidifier 8.

[0058] One end of the regenerated gas supply path L4 is connected to the external air supply path L3, located downstream of the cooler 12. In this embodiment, the other end of the regenerated gas supply path L4 is divided into two paths. One end of the other end of the regenerated gas supply path L4 is connected to a regenerated gas inlet 83 provided on a dehumidifier 8. The other end of the other end of the regenerated gas supply path L4 is connected to a regenerated gas inlet 83 provided on another dehumidifier 8. External air discharged from the cooler 12 is supplied as regenerated gas from the regenerated gas supply path L4 to the dehumidifier 8 via the inlet 83.

[0059] On the regenerated gas supply path L4, between the cooler 12 and the dehumidifier 8, a preheater 15 and a third heater 7C are arranged in order of distance from the cooler 12 to the farthest point. The outside air discharged from the cooler 12 passes through the preheater 15 and the third heater 7C in sequence before being introduced into the dehumidifier 8.

[0060] The third heater 7C heats the outside air discharged from the cooler 12 (the outside air supplied to the dehumidifier 8 as regeneration gas) to increase the temperature of the outside air. The third heater 7C heats the outside air to a temperature of, for example, 200°C to 230°C. The third heater 7C can be a conventionally known device.

[0061] The preheater 15 preheats the outside air discharged from the cooler 12 (the outside air supplied to the dehumidifier 8 as regeneration gas) to increase the temperature of the outside air. The temperature of the outside air discharged from the cooler 12 is, for example, 51°C to 56°C. By preheating the outside air by the preheater 15, the heat energy applied to the outside air in the third heater 7C can be reduced.

[0062] The preheater 15 is preferably an air-cooled heat exchanger. External air discharged from the cooler 12 (external air introduced into the dehumidifier 8 as regeneration gas) is introduced into the preheater 15 through the regeneration gas inlet 150, and regenerated gas discharged from the dehumidifier 8 is introduced into the preheater 15 through the regeneration gas inlet 152. The regeneration gas is the regeneration gas after the adsorbent has been regenerated in the dehumidifier 8, and is at a high temperature (e.g., about 160°C). Therefore, the preheater 15 preheats the external air discharged from the cooler 12 by exchanging heat with the high-temperature regeneration gas. The heated external air, heated to, for example, 140°C to 150°C, is discharged from the regeneration gas outlet 151 and further heated by the third heater 7C.

[0063] After regeneration, the gas exchanges heat with the outside air discharged from the cooler 12, reducing its temperature to, for example, 55°C to 67°C, and is then discharged to the outside of the system from the regeneration gas discharge section 153.

[0064] The preheater 15 is an air-cooled heat exchanger, and its shape and structure are not particularly limited. It can use previously known equipment.

[0065] like Figure 1 As shown, the drying device 1 includes a regeneration gas discharge path L5 for discharging the regeneration gas from the dehumidification device 8. The regeneration gas discharge path L5 conveys the regeneration gas discharged from the dehumidification device 8 to the preheater 15.

[0066] One end of the regenerated gas flow path L5 is connected to the preheater 15. In this embodiment, the other end of the regenerated gas flow path L5 is divided into two paths. One end of the other end of the regenerated gas flow path L5 is connected to the exhaust section 82 of the regenerated gas provided on a dehumidifier 8. The other end of the other end of the regenerated gas flow path L5 is connected to the exhaust section 82 of the regenerated gas provided on another dehumidifier 8. The regenerated gas flows from the dehumidifier 8 through the exhaust section 82 in the regenerated gas flow path L5.

[0067] On the gas flow path L5 after regeneration, a fourth blower 10D and a preheater 15 are arranged in order of distance from the dehumidifier 8 from near to far. The regenerated gas discharged from the dehumidifier 8 passes through the fourth blower 10D and the preheater 15 in sequence.

[0068] The fourth blower 10D draws in the regenerated gas through the inlet, compresses the regenerated gas, and then discharges the compressed regenerated gas through the outlet. The regenerated gas discharged from the fourth blower 10D is supplied to the preheater 15, as described above, for preheating the outside air discharged from the cooler 12. The fourth blower 10D can be a conventionally known device.

[0069] After regeneration, the exhaust gas L5 is connected to a branch path L6 between the fourth blower 10D and the preheater 15. The branch path L6 is connected to the regeneration gas supply path L4. The connection point of the branch path L6 to the regeneration gas supply path L4 is between the preheater 15 and the third heater 7C.

[0070] The splitter L6 mixes a portion of the regenerated gas discharged from the dehumidifier 8 with the outside air discharged from the cooler 12 (the outside air supplied to the dehumidifier 8 as regeneration gas). Since the regenerated gas is at a high temperature (e.g., about 160°C), mixing it with the outside air discharged from the cooler 12 raises the temperature of the outside air. This reduces the heat energy applied to the outside air in the third heater 7C.

[0071] like Figure 1 As shown, the drying device 1 includes an exhaust air supply passage L7, which supplies a portion of the exhaust air discharged from the drying hopper 2 and flowing in the exhaust air discharge passage L2 to the drying hopper 2. One end of the exhaust air supply passage L7 is connected to a position downstream of the dust collector 11 in the exhaust air flow passage L2, and the other end of the exhaust air supply passage L7 is connected to the inlet section 26 at the top of the drying hopper 2. The exhaust air supply passage L7 supplies the exhaust air discharged from the drying hopper 2 as preheated gas from the exhaust air discharge passage L2 to the drying hopper 2. The preheated gas is introduced from the exhaust air supply passage L7 into the top of the drying hopper 2 through the inlet section 26.

[0072] The undried resin particles supplied to the drying hopper 2 have a temperature of, for example, 20°C to 25°C and a moisture content of, for example, approximately 3000 ppm. The exhaust air discharged from the drying hopper 2, having already been used for drying the resin particles within the drying hopper 2, has a lower temperature and higher humidity compared to the drying air introduced into the drying hopper 2, but still maintains a relatively high temperature and low humidity. Therefore, by introducing the exhaust air discharged from the drying hopper 2 into the upper part of the drying hopper 2, the resin particles can be preheated in the upper part of the drying hopper 2 before being formally dried using dry air in the lower part of the drying hopper 2. This preheating of the resin particles increases their temperature and allows for preliminary drying, reducing the moisture content to, for example, approximately 150 ppm. This reduces the amount of heat energy required to dry the resin particles to, for example, a moisture content of approximately 50 ppm or less in the lower part of the drying hopper 2. Therefore, the drying of the resin particles does not require a large amount of heat energy, achieving energy savings.

[0073] On the exhaust air supply path L7, a second heater 7B, a third filter device 9C, and a fifth blower 10E are arranged in order of distance from the drying hopper 2 from closest to furthest. The exhaust air discharged from the drying hopper 2 passes through the fifth blower 10E, the third filter device 9C, and the second heater 7B in sequence from the exhaust air discharge path L2.

[0074] The fifth blower 10E draws in low dew point air through the intake port and, after compressing the exhaust air, discharges the compressed exhaust air through the outlet. The third filter device 9C removes foreign matter from the exhaust air. The second heater 7B heats the exhaust air. The second heater 7B, the third filter device 9C, and the fifth blower 10E can be conventionally known equipment.

[0075] Furthermore, in this embodiment, a portion of the exhaust air discharged from the drying hopper 2 is returned to the drying hopper 2 after being heated by the second heater 7B. However, it is not mandatory for a portion of the exhaust air discharged from the drying hopper 2 to be returned to the drying hopper 2 after being heated by the second heater 7B; it may also be returned directly to the drying hopper 2 without being heated.

[0076] After preheating the resin particles in the drying hopper 2, the exhaust air is discharged from the drying hopper 2 through the exhaust section 25 at the top of the drying hopper 2.

[0077] In the above Figure 1In the drying apparatus 1 shown, high-temperature, low-dew-point dry air heats the synthetic resin molding material, such as resin particles, at the lower part of the drying hopper 2, thereby removing moisture from the synthetic resin molding material and drying it. The dried synthetic resin molding material at the lower part of the drying hopper 2 is discharged from the drying hopper 2 through the discharge section 21 at the lower end of the drying hopper 2 and conveyed to the resin molding machine 6. Synthetic resin molding material is replenished from the upper part of the drying hopper 2 to the lower part of the drying hopper 2. By using dry air at the lowest part of the drying hopper 2 through the second inlet section 24, the temperature drop of the dried synthetic resin molding material at the lower part of the drying hopper 2 is suppressed. Therefore, the dried synthetic resin can be discharged from the drying hopper 2 at a high temperature and conveyed to the resin molding machine 6. Therefore, the drying apparatus 1 according to this embodiment can supply the resin molding machine 6 with dehydrated synthetic resin molding material.

[0078] In addition, Figure 1 In the drying apparatus 1 shown, after the synthetic resin molding material is dried, a portion of the exhaust air discharged from the drying hopper 2 is supplied to the dehumidification device 8 through the exhaust air discharge path L2. After being dehumidified in the dehumidification device 8, it is supplied to the drying hopper 2 again for drying the synthetic resin molding material. On the other hand, a portion of the exhaust air discharged from the drying hopper 2 is supplied to the upper part of the drying hopper 2 through the exhaust air supply path L7.

[0079] The exhaust air supplied to the drying hopper 2, together with the drying air rising from the bottom of the drying hopper 2, preheats and initially dries the undried synthetic resin molding material accumulated in the upper part of the drying hopper 2. Therefore, the synthetic resin molding material, having undergone preheating and initial drying, resulting in a higher temperature and lower moisture content, is supplied from the upper part of the drying hopper 2 to the lower part of the drying hopper 2.

[0080] Thus, according to Figure 1 The drying apparatus 1 shown in the diagram effectively utilizes the heat energy of the exhaust air—which is not wasted—by returning a portion of the exhaust air from the drying hopper 2 to the upper part of the hopper 2, thus preheating and initially drying the synthetic resin molding material. Therefore, although the synthetic resin molding material is still heated and dried in the lower part of the drying hopper 2, the heat energy required for drying the synthetic resin molding material is reduced. Consequently, the drying of the synthetic resin molding material does not require a large amount of heat energy, achieving energy savings.

[0081] In addition, according to Figure 1The drying apparatus 1 shown reduces the heat load on the exhaust air generated by cooling, dehumidifying, and heating the exhaust air in devices such as the cooler 12, dehumidifier 8, and first heater 7A, since a portion of the exhaust air discharged from the drying hopper 2 is returned to the upper part of the drying hopper 2. Therefore, it reduces the heat energy required to generate dry air, achieving energy savings.

[0082] In addition, according to Figure 1 The drying apparatus 1 shown, located at the lower part of the drying hopper 2, dries the synthetic resin molding material even at lower temperatures (e.g., 110°C to 140°C) where changes in the properties of the synthetic resin molding material are unlikely to occur. Because the synthetic resin molding material, having undergone preheating and preliminary drying, has increased in temperature and decreased in moisture content, is supplied from the upper part of the drying hopper 2 to the lower part, the time required to dry the synthetic resin molding material can be shortened compared to the prior art. Thus, according to the drying apparatus 1 of this embodiment, even when drying the synthetic resin molding material at lower temperatures (e.g., 110°C to 140°C), drying can be completed in a short time. Even if an abnormality occurs in the drying apparatus 1 during the drying process, causing the synthetic resin molding material to remain continuously in the drying hopper 2, changes in the properties of the synthetic resin molding material are unlikely to occur.

[0083] In addition, according to Figure 1 The drying apparatus 1 shown has a first heater 7A for heating the drying air (low dew point air) supplied to the lower part of the drying hopper 2 and a second heater 7B for heating the exhaust air supplied to the upper part of the drying hopper 2, which are separately provided. Therefore, the temperature of the drying air and the temperature of the exhaust air can be set independently. As a result, over-drying of the synthetic resin molding material in the lower part of the drying hopper 2 can be prevented, and dried synthetic resin molding material with a temperature that meets the molding conditions of the resin molding machine 6 can be easily obtained.

[0084] The embodiments of the drying apparatus of this disclosure have been described above, but the drying apparatus of this disclosure is not limited to the above. Figure 1 The embodiments shown can be modified in various ways without departing from the spirit of this disclosure. For example, the following modifications can be made. In addition, the key points of the following modifications can be appropriately combined.

[0085] For example, in the above embodiment, the drying apparatus 1 includes two dehumidifying devices 8. As a variation, the drying apparatus 1 may include one or more dehumidifying devices 8.

[0086] Furthermore, in the above embodiment, the drying apparatus 1 includes a second filter device 9B, through which external air is filtered to remove foreign matter before being introduced into the cooler 12. As a variation, the drying apparatus 1 may also omit the second filter device 9B.

[0087] Furthermore, in the above embodiment, the drying device 1 includes a circulation path L6, in which a portion of the regenerated gas discharged from the dehumidifier 8 is mixed with the external air discharged from the cooler 12 (the external air supplied to the dehumidifier 8 as regeneration gas). As a variation, the drying device 1 may also lack the circulation path L6, in which case all the regenerated gas discharged from the dehumidifier 8 may be introduced into the preheater 15 and then discharged to the outside of the system.

[0088] In addition, in the above embodiment, the drying device 1 includes a preheater 15, and the external air discharged from the cooler 12 (the external air supplied to the dehumidifier 8 as regeneration gas) is preheated by exchanging heat with the regenerated gas discharged from the dehumidifier 8 before being supplied to the third heater 7C. As a variation, the drying device 1 may also omit the preheater 15, and the external air discharged from the cooler 12 (the external air supplied to the dehumidifier 8 as regeneration gas) may be supplied to the third heater 7C without preheating. Furthermore, in this variation, a portion of the regenerated gas discharged from the dehumidifier 8 may be mixed with the external air discharged from the cooler 12 (the external air supplied to the dehumidifier 8 as regeneration gas) through the circulation path L6, or it may be completely discharged to the outside of the system.

[0089] In addition, in the above embodiment, a portion of the external air discharged from the cooler 12 is released to the outside of the system, while the other portion is supplied to the dehumidifier 8 as regeneration gas. As a variation, a portion of the external air discharged from the cooler 12 is supplied to the dehumidifier 8 as regeneration gas, and the other portion can be... Figure 3 As shown, the preheating gas is supplied to the storage hopper 16.

[0090] Figure 3 The drying apparatus 1 shown includes a storage hopper 16 for temporarily storing resin particles. The storage hopper 16 is positioned above the drying hopper 2. The storage hopper 16 has an internal space for storing resin particles supplied from a raw material tank via a supply pipe 162. The resin particles supplied from the raw material tank are undried resin particles. The resin particles are supplied to the storage hopper 16 from a supply section located at the top of the storage hopper 16. The lower part of the storage hopper 16 is, for example, conical or pyramidal in shape, and a resin particle discharge section 164 is provided at the lower end of the storage hopper 16. By, for example, opening a solenoid valve 163, the resin particles in the storage hopper 16 are supplied from the discharge section 164 to the drying hopper 2.

[0091] The resin particles are preheated while stored in the storage hopper 16. An inlet 160 is provided on the storage hopper 16 to introduce preheating gas used to preheat the resin particles within the storage hopper 16. Additionally, an outlet 161 is provided on the storage hopper 16, positioned above the inlet 160, to discharge the preheating gas used to preheat the resin particles from the storage hopper 16.

[0092] For the preheating gas, external air that has been heated in the cooler 12 through heat exchange with the exhaust air is used. At least a portion of the external air discharged from the cooler 12 is supplied to the storage hopper 16 through the preheating gas flow path L8. One end of the preheating gas flow path L8 is connected to the external air flow path L3 downstream of the cooler 12, and the other end of the preheating gas flow path L8 is connected to the inlet 160 of the storage hopper 16. The resin particles in the storage hopper 16 are preheated by the preheating gas and supplied to the drying hopper 2 at an elevated temperature.

[0093] Thus, according to Figure 3 The drying apparatus 1 shown supplies external air discharged from the cooler 12 as preheating gas to the storage hopper 16. This avoids wasting the heat energy recovered from the exhaust air during cooling within the cooler 12, effectively using it to preheat synthetic resin molding materials such as resin particles. Therefore, although the synthetic resin molding material is still heated and dried in the drying hopper 2, the heat energy required for drying the synthetic resin molding material is reduced. Thus, drying the synthetic resin molding material does not require a large amount of heat energy, achieving energy savings.

[0094] In addition, Figure 3 In the drying device 1 shown, all the external air discharged from the cooler 12 may be supplied to the storage hopper 16 as preheating gas, while other external air different from the external air discharged from the cooler 12 may be introduced into the dehumidification device 8 as regeneration gas.

[0095] In addition, as other variations, Figure 4 The drying apparatus 1 shown may also include a heat exchanger 17 for heat exchange between the low dew point air supplied from the dehumidification device 8 and the exhaust air discharged from the drying hopper 2.

[0096] The low dew point air supplied from the dehumidifier 8 has a temperature of, for example, about 55°C. This low dew point air is heated in the first heater 7A and then supplied to the drying hopper 2. Since the temperature of the exhaust air discharged from the drying hopper 2 is relatively high, the low dew point air supplied from the dehumidifier 8 is heated in the heat exchanger 17 by exchanging heat with the exhaust air discharged from the drying hopper 2, thereby enabling the low dew point air to be supplied to the first heater 7A at an elevated temperature.

[0097] Low-dew-point air carries away heat through heat exchange with exhaust air, thus warming up to, for example, about 60°C to 70°C. Therefore, in Figure 4 In the drying apparatus 1 shown, not only is the heat energy applied to the low dew point air in the first heater 7A reduced, but the heat energy of the exhaust air discharged from the drying hopper 2 is not wasted, but can be effectively used to generate dry air. Therefore, according to Figure 4 The drying device 1 shown can effectively suppress energy loss and improve energy efficiency.

[0098] The exhaust air supplied to the heat exchanger 17 may be the exhaust air before passing through the dust collector 11, preferably the exhaust air after passing through the dust collector 11. The low dew point air supplied to the heat exchanger 17 may be the low dew point air before passing through the first filter device 9A, preferably the low dew point air after passing through the first filter device 9A.

[0099] Explanation of reference numerals in the attached figures 1. Drying device 2. Drying hopper 7A First heater (generation section) 7B Second Heater 8. Dehumidification unit (generation section) L1 Dry Air Supply Path L2 exhaust air path L7 exhaust air supply path

Claims

1. A drying apparatus comprising: A drying hopper that contains synthetic resin molding material introduced from the top and discharges the synthetic resin material from the bottom; The generating section generates drying air for drying the synthetic resin molding material in the drying hopper; A dry air supply path for supplying the dry air to the dry hopper; An air exhaust path is provided for discharging the dried air from the drying hopper after the synthetic resin molding material has been dried. An exhaust air supply path is provided for supplying a portion of the exhaust air flowing in the exhaust air flow path to the drying hopper; as well as A heater, which is provided in the exhaust air vent, heats the exhaust air supplied to the drying hopper; A drying air inlet is provided at the lower part of the drying hopper for introducing drying air from the drying air supply path, and an exhaust air inlet is provided at the upper part of the drying hopper for introducing exhaust air from the exhaust air supply path. In the drying hopper, the exhaust air inlet is located above the drying air inlet.

2. The drying apparatus according to claim 1, characterized in that, The generating unit includes: a dehumidifier for generating low dew point air; and a heater for heating the low dew point air to become dry air.

3. The drying apparatus according to claim 1, characterized in that, The temperature of the drying air supplied to the drying hopper is above 120°C and below 130°C.

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