JPH0242044B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a hopper dryer that can completely dry granular raw materials such as plastic raw materials while saving energy and supply the dried granular raw materials to a molding machine.

Most of the plastic raw materials used for molding plastic products are pellets, but if the pellets contain more moisture than the specified amount, hydrolysis will occur and the resin will deteriorate, causing the molded product to deteriorate. strength and toughness are reduced. Also, as the water content increases, the fluidity of the molten resin increases, and as a result,
Overfilling and burr formation occur in the mold, which adversely affects the shape accuracy and surface gloss of the molded product, so the pellet material must be thoroughly dried before use.

Therefore, in conventional plastic molding sites that require high dryness, hopper dryers are used to dry the pellet material before feeding it into the molding machine. It had the structure shown below.

That is, 1 is the hopper dryer main body,
Dry heat air is supplied into the hopper dryer body 1, and dehumidified air for drying the pellets contained in the hopper dryer body 1 is heated before being supplied into the hopper dryer body 1. A heating cylinder 5 and a dehumidifying device 2 are provided to produce dry heated air. This dehumidifying device 2 has two dehumidifying towers 3 and 4 filled with a dehumidifying agent, a cooler 6 and a heater 7 provided for intermittently drying the dehumidifying agent, and the above-mentioned cylinders are regenerated into a dehumidifying cycle. It has a three-way valve to switch between cycles. In addition, since high-temperature hot air of 300℃ or higher is sent into the dehumidifier to regenerate it, the dehumidifier reaches a high temperature and the dehumidifying effect cannot be obtained unless it is cooled down to near room temperature using a cooler. There is a problem in that the degree of dryness of the dehumidified air supplied to the par dryer varies considerably. Therefore, in this conventional hopper dryer, in order to supply dry heat into the hopper dryer main body 1, for example, a heater 7 with a power consumption of 6KW, a heating tube 5 with a power consumption of 3KW, and a cooler 6 with a power consumption of 3KW are operated. This led to the problem that a large amount of power was consumed. Furthermore, in the conventional example in which the dehumidifier 2 is incorporated in this circulation path, when the high temperature exhaust from the hopper dryer 1 is returned to the dehumidifier, the dehumidifying effect cannot be obtained unless the high temperature exhaust is first cooled by the cooler 10. There is a lot of wasted thermal energy. That is, there was a problem in that energy for driving the cooler was also required. In addition, in the conventional circulation system, the dehumidifying agent in the dehumidifying circuit is significantly contaminated and deteriorated due to the circulation of plasticizers and additives contained in the plastic, and maintenance costs are also high.

The present invention was made to solve these problems, and by effectively utilizing thermal energy, it is possible to reduce energy consumption to the necessary minimum, save energy, reduce equipment costs, and reduce maintenance costs. The purpose of this invention is to provide a hopper dryer with high performance.

The present invention will be explained in detail below based on the embodiment shown in FIG.

In the compressed air regeneration type dehumidification device 30 surrounded by a chain line, 11 and 12 are dehumidification tubes filled with a dehumidifier 13 inside, and both of these dehumidification tubes 11 and 12 are
have the same structure, and are both provided with two intake and exhaust ports 14 and 15. One intake/exhaust port 14 is communicated with a compressed air supply port 17 from a compressor and an exhaust port 18 via a three-way switching valve 16. In addition, both of the above intake and exhaust ports 15 are
Orifice 19 installed in parallel with each one-way valve 20
The nozzle 23 located between the blower 29 and the heating cylinder 22 communicates with the inside of the heating cylinder 22 through the nozzle 23 .
A heater 24 is disposed within the heating cylinder 22, and the ultra-dry air supplied into the heating cylinder 22 is mixed with the returned hot air to obtain dry heated air. The dry heat air obtained in this heating cylinder 22 is supplied by a blower 29 through a filter 25 into the hopper dryer main body 26, and the pellet material supplied into the hopper dryer main body 26 absorbs moisture to be dried. The exhaust gas passes through the filter 27, and the hot air led out from one exhaust port is sucked into the blower 29 again and returned to the heating cylinder. In addition, hygroscopic air equivalent to the entire amount of dehumidified air supplied by the one-way valve 28 is exhausted to the outside. The blower 29 has an appropriate air blowing capacity in order to suck in air as a heat medium in the hopper dryer 26, send it to the heating cylinder 22, reheat it, and heat the resin material in the hopper dryer 26.

The above is the configuration of this embodiment.Next, to describe its operation, compressed air supplied from the compressor is passed from the air supply port 17 of the compressed air regeneration dehumidifier 30 to the switching valve 16, and then to one of the dehumidifying tubes. For example, when the air is supplied to the dehumidifying cylinder 1
After being dehumidified by the dehumidifier 13 in 1, it passes through the intake/exhaust port 15 and the one-way valve 20 to the heat exchange tube 21.
It absorbs the heat that escapes to the outside and becomes high temperature, which is supplied from the nozzle 23 into the heating cylinder 22. On the other hand, a part of the dehumidified air is branched and supplied to the dehumidifying cylinder 12 from the intake/exhaust port 15, and the dehumidifying agent in the dehumidifying cylinder 12 is Dehumidify 13,
The dehumidifier 13 is discharged to the outside air through the discharge pipe 14, the switching valve 16, and the exhaust port 18, and the dehumidifier 13 is regenerated.
12 alternately repeats dehumidification/regeneration to supply dehumidified air to the heating tube 22, and the hot air returned from the blower 29 in the heating tube 22 has a temperature of about 80% of the temperature blown into the main body 26. For example, if the blowing temperature is set at 100°C, the return temperature is about 80°C, and the heater 24 only needs to supply enough heat to raise the temperature by 20°C. I will also discuss the problem of whether ultra-dry air, which is the main objective of the present invention, can be made into dry heat air by absorbing moisture and mixing it with returned moisture. For example, for a hopper dryer that takes in outside air for drying, if the outside air conditions are humid air with a temperature of 20℃, an absolute pressure of 760mmHg, and a relative humidity of 75%, the amount of moisture contained in 1 ^m3 is as much as 10.521g. Therefore, if air is introduced under the above conditions with a blower of 2.5 m ³ per minute, it will be 2630.25 g per hour.
Since moisture will pass through the resin, in the case of materials such as nylon, which have a high water absorption rate, the result may be more moisture than drying. Therefore, a dehumidifying device is required for such resins, but conventional equipment was large-scale and had the problem of high running costs.However, according to the present invention, dehumidifying equipment that contains, for example, 0.3% water, was problematic. The 50kg of 6.6 nylon resin contains only 150g of water, but since the moisture content recommended by the resin manufacturer is around 0.1%, the initial value of 0.3 is reduced in 3 hours.
% resin to a moisture content of 0.1%, it is necessary to expel 33.3g of moisture per hour.
As an example, suppose that 5.4 m 3 of ultra-dry air with a dew point of -53°C is fed per hour into a circulation system equipped with a hot air circulation blower ²⁹ at a flow rate of 4.7 m ³ /min to raise the temperature of resin pellets. The dew point temperature inside the hopper body 26 is below -20℃, so if the temperature is -20℃ and there is 90 resin in the hopper, the actual volume of resin can be calculated as follows:
If it is 60%, the resin volume is 50, and the volume of the hopper dryer including the hopper body 26, heating tube 22, blower 29, etc. is 110, so the air volume inside the hopper is 56, and the dew point is minus 20°C.
The amount of water contained in it is 0.049476g in 56.

Here, the amount of air exhausted is equal to the amount of air injected, so 5.4 m ³ per hour and 0.09 m ³ per minute are exhausted from the exhaust port 28, but according to experiments, the dew point at the time of exhaust For nylon with a temperature of 6.6,
For the first two and a half hours, the temperature was around +5℃, so the amount of water contained in that time was 36.7092g.
5.4 of ultra-dry air blown at -53℃
The amount of water contained in m ³ /Hr is 0.14364g, so the amount of water reduced per hour is 36.7092-
0.14364=36.56556g, so 109.69g in 3 hours
becomes. When installed in a molding machine that uses an injection rate of 15 kg per hour, the molding conditions can be met in less than 3 hours, and the dry state can be maintained even when new undried resin is introduced. becomes. or,
Since the compressed air regeneration type dehumidifier, which is the dehumidified air supply source, is installed outside the circulation system, the dehumidifier inside the dehumidifying cylinder will not be contaminated or deteriorated by additives such as plasticizers contained in the plastic. . For this reason, according to this example, the power consumption of the heater to obtain dry heat air is 1KW/Hr or less.
Compressor for dehumidifying air supply
1.5KW/Hr or less, blower 0.4KW/Hr, total
In addition to bringing about a significant energy saving effect of less than 2.9KW/Hr, the amount of heat exhausted has also been reduced.
Since only 20% of the power consumption of the 1KW/Hr heater is exhausted, indoor air conditioning is also significantly energy efficient. Furthermore, there is no reduction in dehumidification ability, which means that maintenance and maintenance costs are significantly reduced.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a conventional hopper dryer, and FIG. 2 is an explanatory diagram showing an embodiment of the hopper dryer according to the present invention. 11, 12... Dehumidifying cylinder, 13... Dehumidifying agent, 1
4, 15...Intake/exhaust port, 16...Switching valve, 17...
...Compressed air supply port, 18...Regeneration air exhaust port,
19... Orifice, 20... One-way valve, 21...
...Heat exchange tube, 22...Heating cylinder, 23...Dehumidifying air blowing nozzle, 24...Heater, 25...
... Filter, 26 ... Hopper dryer body, 27 ... Filter, 28 ... Exhaust one-way valve, 29 ... Blower, 30 ... Compressed air regeneration type dehumidification device.

Claims (1)

[Claims] 1. A circulating heating type hopper dryer in which one end of the heating cylinder 22 connected to the hopper-shaped drying cylinder 26 is connected to the drying cylinder, and an air blower 29 is further provided between the other end of the heating cylinder and the drying cylinder, and a circulating heating type hopper dryer. A compressed air regeneration type dehumidifier 30 is operated using compressed air from an air compressor installed outside the circulation system so as not to be contaminated by air, and uses the compressed air to remove and regenerate adsorbed water of a dehumidifier and to generate dehumidified air. A hopper dryer configured to inject dehumidified air into the circulation system.