How does the tower pressure change when the light component content in the feed to the distillation column increases? Why? I would appreciate your advice. Thank you

Changes in the feed composition have a direct impact on distillation operations; as the concentration of heavier components in the feed increases, the load on the distillation section rises. For a tower with a fixed number of rectification section plates, this will cause the heavier components to reach the top of the tower, resulting in substandard quality of the product at the top. If the concentration of the light components in the feed increases, the load on the stripping section increases. For a column with a fixed number of trays in the stripping section, this will result in incomplete evaporation of the light components in that section, leading to increased loss of light components in the bottom liquid. At the same time, changes in the feed composition will also cause changes in the material balance of the entire tower and the process conditions. As the composition becomes lighter, the overhead distillate increases while the amount of liquid discharged from the reactor decreases. At the same time, the temperature of the entire tower decreases while the tower pressure increases. The component becomes heavier; the situation is the opposite.

The pressure in the tower is determined by the gaseous substances present in the tower; when there is the most light components, the amount of vaporization increases, and consequently the tower pressure rises. In this case, feeding at a higher point is usually sufficient.

Changes in the properties of the raw materials cause changes in the gas and liquid load in the distillation section; as a result of this heat imbalance, the amount of vaporization increases while the volume of the liquid phase does not increase. Consequently, heat moves upward, leading to an increase in the top pressure

The increase in column pressure is mainly due to an increase in the amount of steam and an increase in the reflux flow. Assuming that all other conditions remain unchanged as mentioned by the original poster, there are two possible scenarios. In the first scenario, the heat input at the bottom of the column also remains constant; in this case, an increase in column pressure indicates that the vaporization latent heat of the light components is smaller than that of the heavy components, allowing more steam to be produced with the same amount of heat. In the second scenario, the conditions remain unchanged, meaning that the temperature of the tower stays constant. This makes it easier to understand, as an increase in the light components of the feedstock leads to an increase in the concentration of these light components at the bottom of the tower, which in turn lowers the temperature there. To maintain the same temperature, it is necessary to evaporate those extra light components; in other words, the heat load increases, and consequently the tower pressure also rises

The simplest way to understand this is that as the amount of light components in the feed increases, the amount of heavy components necessarily decreases. As a result, the load on the distillation section drops, while the amount of light components (in the gas phase) increases, which in turn raises the tower pressure

A simpler way to understand it is this: as the amount of light components increases, the boiling point of the feed drops. With the tower conditions remaining unchanged, the same amount of heat at the bottom of the tower will cause more material to vaporize, and thus the pressure inside the tower rises naturally.

Thank you all. Could you please share your QQ numbers so that I can consult you at any time in the future? Thank you

As the concentration of light components increases, the load on the stripping section increases. For a column with a fixed number of plates in the stripping section, when the amount of light component increases, under unchanged column conditions, the same amount of heat at the bottom of the column will cause more material to vaporize and evaporate, resulting in an increase in pressure within the column.