A question about the distillation tower
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Recently reading a book on multi-effect distillation columns. I read such a sentence in the book ； Increasing the operating pressure of the distillation tower increases the content of volatile components in the non-volatile products at the bottom of the tower. Could any friend help explain this?
As the column pressure increases, the relative volatility decreases, thereby increasing the content of light components at the bottom of the column
According to Raoult’s law, increasing the operating pressure causes the volatile components to increase in concentration in the liquid phase in order to achieve phase equilibrium.
As pressure increases, the partial pressures increase as well; the boiling point rises. If the light components are not easily volatile or evaporative, this leads to an increase in the concentration of these light components in the material at the bottom of the tower.
Specifically, the original poster can take a close look at the distillation chapter in the textbook on chemical engineering principles.
There is a prerequisite for this: the tower pressure must increase, while all other conditions remain unchanged, such as the heat load at the bottom of the tower not increasing and the cold reflux at the top of the tower not decreasing.
Look again! In fact, I misunderstood “increase the operating pressure” as “increase the negative pressure”. It’s been over a decade since I graduated, and I have to start studying distillation from scratch again.
It can be thought of this way: increasing the tower pressure prevents the light components from being distilled out, and they remain in the heavy materials at the bottom of the tower
As the column pressure increases, the relative volatility decreases, making it difficult to separate the more volatile components. It must be related to this, haha