Why is the pressure lower at the bottom of the tower than at the top?

By utilizing the pressure difference between the upper and lower towers, phase changes can be induced in the saturated fluids on both sides of the wall of the main condensation evaporator. The temperature of a saturated liquid/gas increases as pressure rises. By utilizing the pressure difference between the upper and lower towers, the saturated liquid (liquid argon) on the low-pressure side of the main condensation evaporator (upper tower) can be vaporized ； The saturated gas on the high-pressure side (lower column) of the main condensation evaporator is condensed and liquefied (into liquid nitrogen). As the gas from the lower column is liquefied and removed, the gas entering the bottom of the column rises upward; this rising gas serves as the vapor stream from the lower column, while part of the liquid nitrogen flows downward as the reflux stream from the column, thereby enabling distillation in the lower column ； In the upper tower section, the liquid oxygen from the main condensation evaporator absorbs the heat released by the nitrogen from the main condensation evaporator in the lower tower section (liquefaction of gaseous nitrogen) ； The liquid oxygen in the upper column section is evaporated to serve as the rising vapor during distillation in the upper column, while another portion of liquid oxygen and gaseous oxygen is taken out as products. Why is the pressure at the bottom of the tower higher than that at the top? It is mainly to enable the condensation evaporator to provide a pressure difference, thereby allowing for different temperature differences to be achieved. The fluids on both sides of the main condensation evaporator are condensed/evaporated. (For reference)

Well~ At first, I thought it was due to the airflow rising from the lower column and experiencing pressure drop as a result of resistance; sometimes I would just make guesses when I didn’t understand what was going on. Later on, I realized that it was related to the evaporation and condensation temperatures of oxygen and nitrogen on both sides of the main cooler. It became necessary to increase the pressure in the lower column in order to ensure the proper operation of the distillation tower

In the modified version, the pressure difference between the upper and lower towers can cause a phase change in the saturated fluid on both sides of the walls of the main condensation evaporator. The temperature of a saturated liquid/gas increases as pressure rises. By utilizing the pressure difference between the upper and lower towers, the saturated liquid (liquid oxygen) on the low-pressure side of the main condensation evaporator (the upper tower) can be evaporated ； The saturated gas on the high-pressure side (lower column) of the main condensation evaporator is condensed and liquefied (into liquid nitrogen). As the gas from the lower column is liquefied and removed, the gas entering the bottom of the column rises upward; this rising gas serves as the vapor stream from the lower column, while part of the liquid nitrogen flows downward as the reflux stream from the column, thereby enabling distillation in the lower column ； In the upper tower section, the liquid oxygen from the main condensation evaporator absorbs the heat released by the nitrogen from the main condensation evaporator in the lower tower section (liquefaction of gaseous nitrogen) ； The liquid oxygen in the upper column section is evaporated to serve as the rising vapor during distillation in the upper column, while another portion of liquid oxygen and gaseous oxygen is taken out as products. Why is the pressure at the bottom of the tower higher than that at the top? It is mainly to enable the condensation evaporator to provide a pressure difference, thereby achieving different temperature differences. The fluids on both sides of the main condensation evaporator are condensed/evaporated. (For reference)

I’m sorry; the answers above are not fully standard and are only for reference. It is recommended to check the standard for the answer to question 276 on page 146 of the newly compiled Q&A on oxygen workers.