Why does increasing the top pressure of a tower raise the bottom temperature? What principle?

The principle that increasing the top pressure can raise the bottom temperature is based on the flashing principle in thermodynamics. Vaporization refers to the instantaneous boiling that occurs in a liquid when its pressure is reduced. As the pressure at the top of the tower increases, the pressure difference throughout the tower increases as well, and the pressure at the bottom of the tower also rises accordingly. According to the principle of flashing, when the pressure of a liquid is reduced, some of its molecules rapidly evaporate into gas. Therefore, at the bottom of the tower, the liquid will flash, with part of it evaporating rapidly to form gas. The evaporation process requires heat energy, so flashing causes the temperature at the bottom of the tower to drop. However, as the pressure at the top of the tower increases, the pressure in the bottom part of the tower also rises. Because the temperature at the bottom of the tower is low, the gas under high pressure is easily reabsorbed by the liquid, causing the liquid to return to its liquid state. In this way, the flash conversion rate of the liquid decreases, which reduces the heat energy required for evaporation and leads to an increase in the temperature at the bottom of the tower. Therefore, increasing the top pressure of the tower can raise the temperature in the bottom section, as it increases the heat energy required during the flashing process and reduces the likelihood of liquid reabsorption. .

It’s just like the pressure cooker you bought for your home.

Vapor pressure is a function of temperature; to increase the vapor pressure at the top of the tower, the temperature at the bottom of the tower must also be increased in order to achieve equilibrium

You can think of a distillation tower as a large container with a constant volume. According to the gas law PV=nRT, when V and R are constant, P is directly proportional to T. When considering the heat enthalpy values at different temperatures, the relationship is not ideally proportional; however, the trend of change is definitely in the form of a monotonic basis function.