The drying rate is lower than the direct drying method. The temperature of the product during constant speed drying is not related to the temperature of the heating source. It is usually necessary to mechanically stir or rotate the container itself in order to increase or update the heat transfer surface of the material. Therefore, it is necessary to further study the adhesion problem of the heat transfer mechanism. The drying device itself is expensive, but it is characterized by a small load on the dust collecting system, high thermal efficiency, easy recovery of the solvent, and a total cost much less than the direct drying method. Water Gate Valve,Butterfly Check Valve ,Knife Valves Ritai Valve Group Co., Ltd. , http://www.stainless-steel-valve.com
Evaporated water vapor or organic solvent is extracted by vacuum or discharged with a small amount of air flow. The gas flow is the main carrier of moisture, and vacuum-operated operation is recommended for heat-sensitive granular materials. In conductive dryers, paddle dryers are used to dry paste materials. Rotary dryers with internal flow tubes have now been designed and put into use. The vacuum drying operation cost is noble, but the vacuum drying is recommended only when the material must be dried at a low temperature or in an oxygen deficient state, or when the material is dried in a heating medium and dried at a high temperature. For a certain evaporation efficiency, the use of high temperature operation is more effective, which can reduce the gas flow rate and reduce the equipment volume. Conduction drying is also called contact drying. In conductive heat transfer, it is very suitable for wet particles, and conduction dryer has higher thermal efficiency. For low-temperature drying operations, a suitable low-temperature waste heat or solar collector can be selected as the heat source, but the dryer has a relatively large volume. Freeze-drying is a special case of drying under vacuum conditions. Here, the temperature is below the three-state point of water, and water (or ice) sublimates directly into water vapor. Although the heat required for sublimation is several times lower than that of evaporation, the power consumption in other areas is relatively large. Therefore, the cost of vacuum drying is still noble. The heat is supplied to the dry material by jackets, stirring, heat transfer tubes, etc., and the heat medium is used instead of hot air. . A typical device is a trough type cylinder dryer. Cone stirring dryer, jacket and built-in heating tube rotary dryer, drum dryer, rake dryer, vacuum belt dryer, vacuum freeze dryer and so on. In hot air drying, the temperature during constant-rate drying corresponds to the wet bulb temperature. In conductive heat transfer drying, it is necessary to artificially invent the heating surface so that the heat transfer area is small and the heat transfer coefficient is increased. In this way, the structure is more complicated and the equipment investment is larger than the hot air dryer.
It is roughly the same as the saturation temperature of the gas pressure inside the device. In order to increase the drying rate and prevent uneven drying, the conductive drying method indirectly conveys the heat required for drying through the surface of a metal or the like. The drying rate is lower than the direct drying method. The temperature of the product during constant speed drying is not related to the temperature of the heating source. It is usually necessary to mechanically stir or rotate the container itself in order to increase or update the heat transfer surface of the material. Therefore, it is necessary to further study the adhesion problem of the heat transfer mechanism. The drying device itself is expensive, but it is characterized by a small load on the dust collecting system, a high thermal efficiency, and easy recovery of the solvent, and the total cost is much cheaper than the direct drying method.