Chemical industry beginners don’t understand why vacuum needs to be created in the second-effect evaporation process
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The company has a secondary-effect evaporator; it creates a vacuum of -20 kPa in the primary effect. Why is a vacuum needed?
It is necessary to take into account the physical and chemical properties of the materials, and design them accordingly to environmental changes such as temperature and pressure, in order to achieve the production goals.
Shouldn’t the secondary steam coming out of the separator in the first stage be connected to the heater in the second stage, for evaporation under reduced pressure by vacuum?
Based on Xiaobai’s advice, it is recommended to learn Aspen simulation to improve understanding of chemical engineering principles and material properties. Multi-effect distillation generally requires energy optimization, that is, the condensation heat from the top of the preceding column is used as heating for the reboiler in the subsequent column. Read more and learn more; take a look at multi-effect distillation of methanol, with both three-effect and two-effect systems available, and also learn about heat pumps and similar technologies.
Vacuuming is generally done to reduce pressure, thereby lowering the temperature. Materials may decompose at high temperatures, etc.; it depends on their physical properties.
Vacuuming lowers the boiling point; the secondary steam from the first effect is used in the reboiler of the second effect. The ultimate goal is to achieve evaporation under reduced pressure, and making full use of the secondary steam also helps save energy
The evaporation efficiency is controlled by the varying vacuum levels among the various sections; by creating a vacuum, it is possible to better regulate the heat exchange rate, thereby achieving control over the vacuum level in each section
Reducing pressure lowers the boiling point, which not only helps save energy but also enables rapid concentration
It is estimated to be used for adjusting the reaction temperature