JP3453519B2 - Drying device of low humidity drying system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-humidity drying method in which low-humidity dry air is fed under pressure to a dryer for drying powder particles such as plastic pellets, for example, a hopper dryer. Regarding the device.

[0002]

2. Description of the Related Art As a conventional device of this type, a hopper dryer type drying device is widely known. There, it is composed of a hopper dryer installed on the upper part of the molding machine and an adjusting unit installed on one floor of the molding machine to dehumidify the dry exhaust gas and heat it to a predetermined temperature. The hopper dryer and the adjusting unit are connected via an air supply passage and a return passage, and perform pellet drying while circulating a drying exhaust gas. Equipment such as a dehumidifier, a heater, and a compressor is provided inside the adjustment unit. This type of adjusting unit is disclosed in, for example, Japanese Patent Laid-Open No. 8-2
See 07044.

[0003]

The drying rate of the plastic pellets contained in the hopper dryer increases in proportion to the amount of dry air passing through the hopper. Therefore, in order to increase the drying speed, it is necessary to feed a larger amount of pressurized dry air. However, larger compressors and circulation fans are required as the amount of air supplied increases. In the conventional apparatus, the dehumidification is adjusted by circulating the entire amount of the dry exhaust gas, which also contributes to the enlargement of each device. As a result, it is inevitable that the entire device becomes large and the introduction cost becomes high. Inevitably the running cost will be high. In addition to having to secure space for installing the adjustment unit,
Since large-diameter air piping is indispensable, a large space is required around the molding machine. The construction cost required for equipment installation is not small.

Incidentally, it is known that the moisture content of the dry exhaust gas which is circulated and returned to the adjusting unit after coming into contact with the plastic pellets is as low as around 1%. The present inventor has focused on this point, and has come up with the idea that the pellets can be dried by reusing the dry exhaust gas, and has proposed the present invention.

An object of the present invention is to circulate a dry exhaust gas having a sufficient drying capacity without dehumidifying adjustment, and to replace the dry exhaust gas with new dehumidified adjusted dry air to replace the dry exhaust gas. Keep the moisture content below a certain level,
Accordingly, it is an object of the present invention to provide a low-humidity drying type drying device capable of reducing the consumption of dry air whose dehumidification is adjusted, while exhibiting the same drying ability as that of a conventional device. Another object of the present invention is that the consumption of dry air that has been dehumidified is small, so that the equipment for dehumidification adjustment can be miniaturized, and the entire apparatus can be compactly configured as compared with the conventional apparatus,
It is an object of the present invention to provide a low-humidity drying type drying device that can save the manufacturing cost and the running cost required for drying plastic pellets and the like.

It is another object of the present invention to utilize the flow energy of dehumidified and conditioned pressurized dry air to circulate the dry exhaust or to mix fresh dry air evenly with the dry exhaust, thus It is an object of the present invention to provide a low-humidity drying type drying device that can realize the downsizing and cost reduction of the entire device at the same time by configuring the drying device with a simple device configuration as compared with the conventional device. Another object of the present invention is that a compressor having a smaller capacity can exhibit a drying capacity equivalent to that of using a large-sized compressor, whereby a dehumidifier, a heater and other adjusting devices are integrated with a hopper dryer, It is an object of the present invention to provide a low-humidity drying type drying device that can reduce the space required for equipment installation and further reduce the cost required for installation work.

[0007]

As shown in FIG. 1, a drying apparatus of the present invention includes a dryer main body 1 for accommodating an object to be dried,
An air supply device 2 for supplying dry air to the dryer body 1 is provided. The air supply device 2 includes a compressor 7 that pressurizes and feeds dry air, and a dehumidifier 8 that removes water in the dry air.
And a heater 10 for heating the dry air, and an air supply passage 11 that connects these devices 7, 8, 10 and guides the flow of the dehumidified and adjusted dry air to the dryer main body 1. An injector 9 including an inlet 25, an outlet 26, and a nozzle 24 is arranged in the middle of the air supply passage 11 as shown in FIG. A return passage 28 for drying and exhausting derived from the dryer main body 1 is connected to an inlet 25 of the injector 9. As a result, the drying exhaust is circulated and flowed between the dryer body 1 and the injector 9 by the flow energy of the pressurized dry air ejected from the nozzle 24 to perform drying.

Specifically, the compressor 7, the dehumidifying device 8, the injector 9, and the heater 10 are arranged in the order listed along the air supply passage 11. An exhaust passage 33 for discharging excess dry air from the dryer main body 1 is led out.

The dryer main body 1 is composed of a hopper dryer, and inside the case 2A (see FIG. 3) fixed to the outer surface of the drying tank 4, the respective devices 8.9.1 constituting the air supply device 2 are provided.
0s are collectively arranged.

[0010]

The dry air dehumidified and adjusted by the air supply device 2 is pressurized by the compressor 7 and has sufficient flow energy. This dry air is supplied to the nozzle 24 of the injector 9.
By injecting from the inlet 2 of the injector 9
The air around 5 is forcibly sucked and flown to the outlet 26 together with the jet flow. At this time, the inlet 25 communicates with the dryer main body 1 through the return passage 28. Therefore, the dryer body 1
The dry exhaust inside is sucked to the injector 9 side through the return passage 28, and by this suction action and the flow action of the dry air ejected from the nozzle 24, the dry exhaust can be forced to circulate and flow.

As described above, when the dry exhaust is circulated without being dehumidified and subjected to the drying process, the consumption of the dehumidified dry air is reduced as compared to the case where the entire amount of the dry exhaust is dehumidified and circulated. It can be significantly reduced. On the other hand, the humidity of the dry exhaust increases little by little, and the drying efficiency decreases. But,
Since the dehumidifying-adjusted dry air is constantly replenished to suppress the increase in humidity, the humidity of the circulating dry exhaust air is maintained below a predetermined value as a whole. A part of the dry exhaust is discharged from the dryer main body 1, and the dry exhaust is continuously updated at a constant rate.

When the drying exhaust air is repeatedly circulated as described above to perform the drying, the consumption of the dehumidified and adjusted dry air can be reduced, so that the device capacity of the compressor 7, the dehumidifying device 8, the heater 10 and the like can be reduced. . That is,
The air supply device 2 can be configured with smaller devices 7 to 10.
This also helps to provide the air supply device 2 integrally with the dryer main body 1.

Since the dry air dehumidified and adjusted by using the injector 9 is evenly mixed with the dry exhaust gas, the exhaust gas circulation function and the mixing operation can be simultaneously exerted only by the flow energy of the dry air, and therefore, the air supply device 2 The structure can be simplified. Since complicated control equipment is not required, the labor required for maintenance can be reduced.

According to the air supply device 2 in which the compressor 7, the dehumidifying device 8, the injector 9, and the heater 10 are arranged in the order described, the temperature control of the mixed dry air is ensured by the heater 10 provided at the final stage. Can be done.

Each of the devices 8 to 10 constituting the air supply device 2 is
According to the drying device collectively arranged in the case 2A provided on the outer surface of the drying tank 4, the space required for installing the drying device can be reduced. In particular, when the hopper dryer is arranged on the upper part of the molding machine for use, it is not necessary to secure a wide space around the molding machine.

[0016]

1 to 3 show an embodiment in which the present invention is applied to a hopper dryer type drying device. In FIG. 1, the drying device includes a dryer main body 1 that contains plastic pellets (objects to be dried), and an air supply device 2 that supplies dry air to the dryer main body 1. 3 is a material tank that is placed on the floor and stores the plastic pellets before drying.

A material feeder 5 is provided above the drying tank 4 of the dryer main body 1. This feeder 5 opens and closes a passage according to the fluctuation of the level of the plastic pellets in the tank, controls the pneumatic transportation state of the plastic pellets in the material tank 3, and maintains the level in the tank constant. Above the peripheral surface of the drying tank 4, a level sensor 6 for detecting the level inside the tank is provided.

The air supply device 2 includes a compressor 7 for feeding dry air under pressure, a dehumidifying device 8 for removing moisture in the dry air, an injector 9, a heater 10 for heating the dry air, and these devices 7 10 to 10 are connected to each other and configured by an air supply passage 11 for guiding the dehumidified and adjusted dry air to the drying tank 4. Between the compressor 7 and the dehumidifier 8, a drain separator 13, a micro mist separator 14, and a pressure adjusting valve 15 for maintaining a constant pressure of the pressurized air sent to the dehumidifier 8 are provided.

The dehumidifying device 8 removes water contained in the primary air sent from the compressor 7 to generate dry air whose humidity is adjusted to a predetermined value or less. As the dehumidifying device 8, various commercially available dehumidifying devices such as a dehumidifying device having a hollow fiber as a dehumidifying element and a dehumidifying device having an adsorbent as a dehumidifying element can be applied.

A pressure gauge 16, a pressure switch 17, and an orifice 18 are arranged between the dehumidifying device 8 and the injector 9. When the main valve 19 provided at the end of the air supply passage 11 on the compressor 7 side is opened, the pressure switch 17
Is switched to the ON state, and energization of the heater 10 in the subsequent stage is started. When the gas pressure in the air supply passage 11 drops, the pressure switch 17 is switched to the off state, and the power supply to the heater 10 is stopped. The orifice 18 stabilizes the dehumidifying action of the dehumidifying device 8 in cooperation with the above pressure adjusting valve 15 by keeping the air flow rate in the air supply passage 11 after dehumidifying constant. Air supply passage 1 on the rear side of the heater 10
1 is provided with a temperature sensor 20 for controlling the heat generation state of the heater 10.

In order to circulate the dry exhaust gas by using the flow energy of the dry air pressurized by the compressor 7, an injector 9 is arranged in the middle of the air supply passage 11 and its inlet 25 (see FIG. 2). ) And the drying tank 4 are connected by a return passage 28.

In FIG. 2, the injector 9 includes a venturi body 22, a suction case 23, and a nozzle 24 provided in the suction case 23.
An inlet 25 is provided on the upper surface side of the suction case 23, and an outlet 26 is provided on the side end of the venturi body 22. Inside the venturi body 22, there is provided an acceleration passage 27 having a narrowed middle portion. The nozzle 24 is arranged so that its tip portion is directed to the constricted portion of the acceleration passage 27. The injector 9 is interposed in the air supply passage 11 with the nozzle 24 positioned upstream of the air supply passage 11. Therefore, when the pressurized air is ejected from the nozzle 24 toward the acceleration passage 27, the air in the suction case 23 is sucked into the acceleration passage 27, so that the dry exhaust in the drying tank 4 is forced through the return passage 28. Can be circulated. A filter 29 for removing pellet powder contained in the dry exhaust gas and a flow rate adjusting valve 30 are provided in the middle of the return passage 28 (see FIG. 1).

In FIG. 1, reference numeral 32 is a screw cylinder of the injection molding machine, and 33 is an exhaust passage extending from the upper peripheral surface of the drying tank 4.

According to the drying device configured as described above,
Since pellet drying can be performed by repeatedly circulating the drying exhaust after contacting the plastic pellets inside the drying tank 4, it is possible to reduce the consumption of the dehumidified and adjusted dry air during pellet drying. Specifically, the flow rate of the dry exhaust gas circulating through the return passage 28 is several times the flow rate of the dry air ejected from the nozzle 24 in the injector 9. Therefore, even though a large amount of dry air is sent to the drying tank 4, the consumption of the dehumidified and adjusted dry air can be significantly suppressed. Further, dry air whose dehumidification is adjusted is continuously replenished to the dry exhaust gas, and a part of the dry exhaust gas is exhausted to the exhaust passage
Since it is discharged to the outside of the tank via 3, the humidity can be maintained below a certain amount even though the dry exhaust is repeatedly circulated.

The smaller the amount of dehumidified and adjusted dry air consumed, the smaller the capacity of each of the devices 7 to 10 constituting the air supply device 2, and the smaller the device, the more the air supply device 2 can be constructed.
Further, the dry air whose dehumidification is adjusted can be uniformly mixed with the dry exhaust while the dry exhaust is circulated by the injector 9 that does not require a power source. Therefore, as shown in FIG. 3, the case 2 in which the above devices 8 to 10 are fixed to the outer surface of the drying tank 4 is shown.
Most of the air supply devices 2 can be integrated with the dryer main body 1 without any trouble by arranging the air supply devices inside A together.

The actual values when the polyethylene terephthalate is dried using the above drying apparatus are as follows. Raw material plastic moisture content / moisture content 2000ppm / 0.2% Plastic moisture content after drying 100ppm Dew point of dry air after dehumidification (atmospheric pressure) -40 ℃ Dew point of dry air at hopper inlet (atmospheric pressure) -20 ℃ Dry Exhaust dew point (converted to atmospheric pressure) -12 ° C Dry air temperature at hopper inlet 160 ° C Dry air consumption 34m ³ / h Circulating air amount in hopper 60m ³ h Dry exhaust circulating air amount 34mh Drying treatment amount (hopper When the capacity is 60kg) 20kg / h

Depending on the plastic pellets to be dried, it is necessary to keep the dew point of the dry air at the inlet of the drying layer 4 below -30 ° C. In these cases,
The drying device can be configured as shown in FIG. 4 to lower the dew point of the dry air inside the drying layer. Specifically, the bypass passage 11a is branched from the air supply passage 11 at the stage subsequent to the dehumidifier 8, and the passage end is connected to the drying layer 4,
New dehumidified dry air is directly fed to the dry layer 4. An orifice 18 is provided in the bypass passage 11a. Further, although not necessarily required, a heater 10a can be separately provided for temperature control.

The dryer of the present invention is not limited to the hopper dryer type installed in the molding machine, but can be applied to a box type dryer for batch processing. Furthermore, FIG.
It can also be applied to the conveyor type dryer shown in.

In FIG. 5, the conveyor type dryer has a belt conveyor 36 for transferring plastic pellets at a constant speed inside a closed drying tank 4, and is provided on each of the upper surface and the lower surface of the conveyor belt. Electrode plate 37.3
A high frequency voltage is applied between 8 to heat the plastic pellets on the belt from the inside. In order to remove the moisture in the drying tank 4 and accelerate the drying of the plastic pellets,
The air supply device 2 is provided, and the injector 9 and the drying tank 4 are connected by the return passage 28. Reference numeral 39 is a hopper for feeding materials. The same members as those in the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

[0030]

According to the drying apparatus of the present invention, the dehumidified and adjusted pressurized dry air is fed through the injector 9.
Since the dry exhaust gas can be forcibly circulated by the air feeding action of the injector 9, it is possible to significantly reduce the consumption amount of the dehumidified and adjusted dry air while supplying sufficient drying air to the dryer main body 1. Therefore, it is possible to reduce the size of the devices 7 to 9 that constitute the air supply device 2 without any hindrance, and simultaneously reduce the total cost required for manufacturing the drying device and the running cost. Compared with the conventional device, the air supply device 2 can be configured compactly, so that the space required for installing the drying device can be reduced. Particularly, according to the drying device in which the air supply device 2 is integrated with the dryer main body 1, the installation can be performed. It saves a lot of space and reduces the construction cost required for installation.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of a drying device.

FIG. 2 is a schematic sectional view of an injector.

FIG. 3 is a front view of the drying device.

FIG. 4 is a principle explanatory view showing another embodiment of the drying device.

FIG. 5 is a principle explanatory view showing another embodiment of the drying device.

[Explanation of symbols]

1 dryer main body 2 Air supply device 7 compressor 8 Dehumidifier 9 injectors 10 heater 11 Air supply passage 24 nozzles 25 entrance 26 exit 28 Return passage

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-78707 (JP, A) JP-A-6-71650 (JP, A) JP-A-7-190616 (JP, A) JP-A-8- 207044 (JP, A) JP-B 35-4289 (JP, B1) JP-B 49-47369 (JP, Y1) JP-A 8-500427 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F26B 17/10 B29B 13/02 B29B 13/06 F26B 3/04

Claims (3)

(57) [Claims] 1. A hopper dryer having an air supply port and an air exhaust port for containing plastic pellets; and an air supply device for supplying high-pressure dry air to the hopper dryer, wherein the air supply device is dry air. A compressor for feeding under pressure, a dehumidifier for removing moisture in dry air, a heater for heating dry air, the compressor, the dehumidifier, and the heater, and the air supply port of the hopper dryer. However, including an air supply passage for supplying the adjusted high-pressure dry air to the hopper dryer, and an injector arranged in the air supply passage, the dehumidification device, the injector and the heater are of the hopper dryer. The injector nozzles are centrally arranged inside the case fixed to the outer surface of the drying tank. Is connected to the upstream side of the air supply passage, the outlet of the injector is connected to the downstream side of the air supply passage, the inlet of the injector is connected to the exhaust port of the hopper dryer through the return passage. By the flow energy of high-pressure dry air introduced into the injector from the injector nozzle,
A low-humidity drying type drying device, wherein exhaust gas from the hopper dryer after the drying process is circulated between the hopper dryer and the injector for reuse. 2. The compressor, in order from the upstream side,
The low-humidity drying type drying device according to claim 1, wherein the dehumidifying device, the injector, and the heater are connected in series via the air supply passage. 3. The hopper dryer is provided with a second exhaust port, and the second exhaust port has an exhaust pipe line for exhausting excess exhaust gas after the drying process from the dry air main body to the outside. 3. The low-humidity drying type drying device according to claim 1, wherein the drying device is connected.