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This post was last edited by goldliyang on 2019-7-26 at 18:16. Rotary Drum Evaporator I. Structure and Principle The basic structure of this type of evaporator consists of multiple layers of rotating tubes arranged inside a horizontal cylinder. The material forms a film on the surface and is continuously renewed. It has a high heat transfer coefficient, no pressure drop during evaporation, and a small effective temperature difference, making it particularly suitable for use as evaporators and reboilers in high-vacuum distillation and fractionation processes. Years of use and the processing of dozens of different materials have shown that the heat transfer coefficients of these two types of evaporators are about twice higher than those of external-circulation falling-film reboilers, and two to three times higher than those of rising-film thermosyphon reboilers. Various industries handle high-viscosity, high-boiling-point, heat-sensitive materials (material fill factor 40%). II. Scope of Application High (low) vacuum evaporation and concentration of thermosensitive substances with high viscosity and high solid content, such as those used in the petroleum, chemical, pharmaceutical, food, and health product industries. III. Performance and Features 1. Compact design with excellent sealing performance. It can operate continuously for long periods under conditions ranging from normal pressure to high vacuum (absolute pressure of 1 Pa). 2. The processing is carried out under high vacuum and at low temperatures, which prevents phenomena such as decomposition, carbonization, and polymerization, thereby ensuring the quality and color of the product. 3. The material forms a uniform film, has a high heat transfer coefficient, and offers high production capacity: one set of this evaporator can replace ten sets of batch distillation units of the same size, resulting in significant energy savings. Model, Heat Transfer Area (m²), Evaporation Capacity: kg of water/(h·m²) at △t=50°C, External Dimensions: Diameter × Length × Height (mm), Equipment Weight (KG), Power (KW): XBZ33320: 500×1250×1100, 1.5; XBZ66320: 900×1350×1600, 2.2; XBZ99320: 900×1650×2100, 4.0; XBZ1212320: 1200×1650×3100, 5.5; XBZ1818320: 1400×2250×4100, 7.5; XBZ3636320: 1400×3200×5600, 11; XBZ4848320: 1400×4200×6100, 15; XBZ6060320: 1600×4500×7600, 18.5. Note: If the viscosity of the material affects film formation, the tube bundle is replaced by a cylinder, and additional auxiliary devices are used to ensure proper film formation of the material. Application of rotary evaporators in high-vacuum distillation High-vacuum fractionation refers to the fractionation process carried out at absolute pressures in the range of (5–500) Pa. When a falling-film evaporator is used as a reboiler in vacuum distillation, it indeed exhibits many excellent properties compared to various other types. However, its performance still has shortcomings. As the material vaporizes due to heating in the falling film evaporator, the resulting secondary steam carries along the liquefied material, flowing through the entire tube at a speed of hundreds of meters per second, thereby causing a significant pressure drop and raising the boiling point of the material. To maintain an effective temperature difference for heating, it is necessary to raise the temperature of the heating medium outside the tube. Typically, the temperature of the heating medium is much higher than the vaporization temperature of the material inside the tube, sometimes exceeding 100°C, which is very detrimental to heat-sensitive materials. It accelerates the processes of decomposition, carbonization, polymerization, and scaling of materials within the pipe. It not only wastes materials but also significantly reduces heat transfer, **lowering the evaporation capacity. The higher the vacuum level during system operation, the more severe this phenomenon becomes. Furthermore, excessively high temperatures cause the quality of heat transfer oil to deteriorate rapidly. Oil degradation leads to carbonization, thickening, precipitation, and scarring, which not only reduces the service life of heat transfer oil but also causes a significant decrease in the heat transfer coefficient. In summary, this is why the heat transfer coefficient of falling film evaporators is very high during evaporation at atmospheric pressure or low vacuum, but drops significantly when operating under high vacuum; rotary evaporators are particularly suitable as reboilers and distillation vessels in high-vacuum conditions.