Apr 21, 2020
Thin film evaporators can be divided into three types: rising film evaporator, falling film evaporator, and wiped film evaporator according to the reasons of film formation and flow direction.
Thin film evaporator composition
The thin film evaporator unit is composed of three parts: an evaporator, a vapor-liquid separator, a preheater, and a simple separator. The evaporator is a rising film tube heat exchanger. The evaporator has the characteristics of large production capacity, high efficiency, and short heating time of materials. It is suitable for the concentration of dilute solutions in the pharmaceutical, food, chemical and other industries. The equipment and material contact parts are made of stainless steel, which has good corrosion resistance. Durable and meets the hygienic requirements of medicines.
Film evaporator performance characteristics
1. Small vacuum pressure drop
The vaporized gas of the material is sent to the external condenser from the heating surface, and there is a certain pressure difference. In general evaporators, this pressure drop (Δp) is usually relatively high, sometimes even unacceptably high. The scraper-type thin-film evaporator has a large gas through space. The pressure in the evaporator can be regarded as almost equal to the pressure in the condenser. Therefore, the pressure drop is very small, and the vacuum degree can reach 5mmHg.
2. Low operating temperature
Due to the above characteristics, this allows the evaporation process to be maintained at a higher vacuum. Due to the increase in vacuum, the boiling point of the corresponding material decreases rapidly, so the operation can be performed at a lower temperature, reducing the thermal decomposition of the product.
3. Short heating time
Due to the unique structure of the wiper film evaporator, the film wiper has a pumping effect, so that the residence time of the material in the evaporator is very short; in addition, on the heated evaporator due to the high-speed turbulent flow of the film, the product will not stay in the evaporation器 面。 The surface. Therefore, it is especially suitable for the evaporation of heat-sensitive materials.
4. High evaporation intensity
The lowering of the boiling point of the material increases the temperature difference of the same heat medium; the function of the film scraper reduces the thickness of the liquid film showing the turbulent state and reduces the thermal resistance. At the same time, in this process, the materials are inhibited from forming walls and scales on the heating surface, and accompanied by good heat exchange. Therefore, the total heat transfer coefficient of the scraped film evaporator is improved.
5. Large operation flexibility
It is precisely because of the unique performance of the scraped film evaporator that it is suitable for processing heat-sensitive and materials that require stable evaporation, high viscosity, and a sharp increase in viscosity with increasing concentration. The evaporation process can also evaporate smoothly. It can also be successfully applied to the evaporation and distillation of materials containing solid particles, crystallization, polymerization, scaling, etc.
How to choose the thin film evaporator
In the selection of thin film evaporators, various factors must be considered comprehensively, and generally need to be considered:
▲ Production capacity and operating parameters: including processing capacity, in and out concentration, temperature, annual operating hours, etc .;
▲ Product characteristics: including heat sensitivity, viscosity and fluidity (at operating temperature), foamability, solid content, crystallization and polymerization tendency, etc .;
▲ Operation medium: such as water vapor (pressure), cooling water (temperature), cleaning fluid (solvent), etc .;
▲ Material selection and surface polishing requirements;
▲ Site conditions: such as space, climate (outdoor), connection of energy and products, working platform, etc.
▲ Regulations: including safety, noise, environmental protection, etc.
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