Views: 147 Author: Site Editor Publish Time: 2019-09-24 Origin: Site
Strict control of moisture in raw materials is the key to the processing of high-quality plastics products. In the use of ordinary industrial dryers, there are often some problems. For example, the raw materials are not dried at one time and the raw materials in the industrial dryer are on fire. The dehumidifying dryer is a good solution to this type of problem. Why do you need a dehumidifying dryer?
A good drying efficiency is determined by four factors: drying temperature, residence time, air flow and dew point. Any change of conditions will affect the drying effect.
(1) Drying temperature refers to the temperature of the air entering the drying barrel. Each raw material has certain restrictions on the temperature during drying due to its physical properties such as molecular structure, specific gravity, specific heat and water content. If the temperature is too high, some additives in the raw material will be volatilized or agglomerated, and if the temperature is too low, some crystalline raw materials can not reach the required drying conditions, such as PC / 120 ° C, ABS / 80 ~ 95 ° C. In addition, insulation and heat preservation are needed in the selection of drying barrels to avoid the leakage of drying temperature, resulting in insufficient drying temperature or waste of energy.
(2) Residence time refers to the pre-drying time before the raw material is formed. If the residence time is too long, the raw material will deteriorate or agglomerate. If the residence time is too short, the water content will be too high.
(3) Air flow is the only medium to take away the moisture in the raw materials. The amount of air flow will affect the dehumidification effect. Too much air flow will cause the return air temperature to be too high, resulting in over heat and affecting the stability of the dew point. If the air flow is too little, the moisture in the raw material cannot be completely taken away. The air flow also represents the dehumidification capacity of the dehumidifying dryer.
(4) Dew point temperature refers to the temperature when the gas cools to condense the moisture into water droplets. It is a unit to measure the degree of dryness (humidity) of the gas. The less moisture in the gas, the lower the dew point temperature. A good dehumidifying dryer should have a dew point of -40 ° C dew point.
Only the above four factors can meet the requirements of the drying process, in order to obtain a satisfactory drying effect. The air flow is generated by the blower. As long as the correct blower is selected, the air flow is fixed. The drying temperature is controlled by the temperature controller. As long as the temperature is adjusted, it can be basically constant. Similarly, the residence time can be controlled by calculating the capacity of the drying hopper. The dew point temperature is affected by the humidity of the dry air heated by the external inhalation device.External air humidity is different because of the change of seasonal climate. The air humidity in winter is lower than that in summer. The air humidity in seaside is lower than that in inland. The air humidity in Meiyu season is higher than that in normal season. A high humidity point means a higher moisture content in the air or a higher dew point temperature in the air, and vice versa. When the dryer inhales air with higher dew point temperature and dries the resin material, the required moisture content can not be achieved. In this case, even if the drying time is prolonged, the required moisture content can not be achieved. On the contrary, the physical properties of raw materials will change due to excessive drying. The dew point temperature of dry air can be lowered and stabilized by using dehumidification device to remove moisture from air in advance and reduce moisture content. The ideal drying effect can be obtained by heating.
Compared with ordinary plastics, there are many new types of plastics with many excellent characteristics, the processing technology is relatively high. These raw materials are called "engineering plastics". Most engineering plastics are hygroscopic. When the plastic is taken out from the moisture-proof sealed bag and exposed to the atmosphere, it begins to absorb moisture from the atmosphere. If it is dried by a conventional hot air hopper dryer, because The external air with moisture is used to dry the plastic, so it is impossible to prevent the plastic from continuing to absorb moisture and obtain a satisfactory drying effect.
The use of a dehumidifying dryer has the following benefits:
(1) The moisture in the plastic raw material can be taken away to eliminate the generation of bubbles, so that the product can achieve the desired mechanical, electrical, dimensional stability and appearance.
(2) Prevent the generation of defective products, and reduce the generation of waste.
(3) Because the dehumidifying dryer uses very dry air for dehumidification, it can shorten the drying time and save man-hours.
(4) The air line of the dehumidifying dryer adopts a closed circulation system and is equipped with a filter, so it is not affected by the weather. And it can prevent dust from causing pollution in the factory and improve the working environment.
The use of dehumidifier can be divided into single-machine dehumidifying dryer and centralized dehumidifying dryer.
(1) Single-machine dehumidifying dryers typically include a dryer mainframe, a drying barrel, and a suction machine. Single-machine drying is suitable for a small amount of diverse drying, its advantages are good drying efficiency, and convenient and rapid material exchange.
(2) The centralized dehumidifying dryer consists of a dryer mainframe and several drying barrels. Each drying barrel has an independent heating controller that can simultaneously dry several different raw materials and cooperate with the air flow regulating valve to control the air flow of each drying barrel.
The dehumidifying dryer combines drying and dehumidification. It is especially suitable for the treatment of plastics with strong hygroscopicity. With the extensive use of engineering plastics, only dehumidifying dryers can be used to achieve drying requirements. Dehumidifying dryers have gradually replaced traditional industrial dryers.