What is the relationship between the bubble point temperature of a distillation column and the feed conditions of the column?

I think there are multiple uncertainties regarding the answer to this question, as it’s not clear whether the person who asked it is indeed the one who needs an answer. First, let’s talk about the energy consumption associated with the bottom reboiler: when the feed temperature is low, in order to achieve distillation effects, it’s necessary to heat this feed so that it vaporizes. It then needs to condense at certain temperatures and pressures at different tray levels. The substance A desired is obtained at the top of the tower, while substance B is obtained at the bottom. In essence, this increases the losses incurred by the reboiler. Additionally, the state of the feed also plays a role; if it’s in liquid form, it needs to absorb heat in order to vaporize. In such cases, feeding is usually done from the middle of the tower, which also allows the vapor to be cooled. Gaseous substances, on the other hand, are generally fed from the bottom of the tower, where they exchange heat with the liquid phase that has condensed there. Well, these are just surface-level considerations; I hope experts can provide further answers.

At a certain pressure, the temperature at which the first bubble forms when a multi-component liquid is heated is known as the boiling point, which represents the temperature at which boiling begins. If your sample is a multi-component liquid, then feeding it at the boiling point is certainly related to this boiling point temperature

Thank you. By the way, do you know the relationship between the feed temperature and the bubble point of the mixture? And then there’s how to determine the bubble point temperature of a mixture.

The bubble point temperature can be calculated using ASPEN; it depends on the composition of the material, not on its temperature

The boiling point generally applies to mixed liquids； The boiling point of a pure liquid remains constant; for example, water boils at 100 degrees Celsius at one atmosphere of pressure. Boiling begins when the first bubbles appear in the liquid, at a temperature of 100 degrees ； The temperature is also 100 when the first droplets of water begin to form in the water vapor ； In the gas-liquid coexistence state, the temperature remains stable at 100 degrees Celsius regardless of the proportion of each phase. Mixed liquids are different; the first bubble to appear in them is what is known as the bubble point. Continuing to heat the mixture corresponds to a certain temperature range, during which the proportions of various components in the gas-liquid mixture change as the temperature rises. When the temperature reaches a certain level, the heat in the mixed liquid causes it to heat further, and the composition of the gas and liquid phases changes accordingly, until everything turns into a gas phase.