Distillation tower
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When a distillation column is operating normally, the heavier components at the bottom of the column vaporize and rise to the top of the column. What impact does this have on the column pressure and the reflux drum? Does the control method of the tower also need to be considered for its impact on tower pressure?
The vaporization of the light components at the bottom of the tower to the top affects the quality of the product, and this is caused by two reasons: one is that the heat source is too strong, resulting in an excessively high temperature at the bottom of the tower； Second, the reflux is low and the top temperature is high. The column pressure depends on whether it is pressurized distillation, atmospheric distillation, or vacuum distillation
The reasons why heavy components evaporate to the top of the tower are: 1. High reboiling; 2. Low reflux; 3. An increase in heavy components in the feed; 4. An increase in feed temperature; 5. An increase in reflux temperature. The effect of heavy components evaporating to the top of the tower on the tower pressure should be an initial increase followed by a decrease. The increase occurs due to high reboiling, while the decrease happens because the heavy components that evaporate require more coolant. As a result, the liquid level in the reflux tank rises sharply. Is that correct? Posted the day before yesterday at 20:03. Your question involves too many variables; under normal operating conditions, there aren’t so many such factors. For example, either high reboiling or low reflux can cause heavy components to evaporate to the top of the tower, and this will lead to an increase in the liquid level in the reflux tank at the top of the tower and a decrease in the liquid level at the bottom of the tower, meaning that the equilibrium is disrupted； Furthermore, an increase in feed temperature is equivalent to a greater heat source for the reboiler; with all other operating conditions remaining unchanged, this will certainly result in higher levels of heavy components at the top of the tower and a higher liquid level in the reflux tank. So your question is too general; it’s necessary to identify the main cause and analyze it individually.
As clearly stated above, one more point to add: problems with the internals of the tower can also lead to a decrease in the tower’s separation capacity, resulting in an increase in the amount of heavy components in the product.