Why is the pressure in the lower tower of the air separation equipment higher than that in the upper tower?

The liquid air separation plant system uses the cold energy to produce liquid oxygen, liquid nitrogen and liquid argon in an air separation system, including an air compression pre-cooling system, an air purification system, an air separation system and a nitrogen circulation system for liquid air separation plant cold recovery. the nitrogen circulation system for liquid air separation plant cold recovery is placed in a separate cold box from the main cold box of the air separation system. the l...

In the process of operation, especially in the start-up and shutdown of the air separation unit, one-way force should be avoided on the instrument. During the start-up of the equipment, close the high pressure and low pressure valves firstly, then open the balance valve, and then slowly open the high pressure (or low pressure) valve, so that the measured medium can enter the positive (negative) pressure chamber of the transmitter. If the liquid is to be measured, the gas in the positive (negative) pressure chamber should be discharged from the upper vent. If the gas is measured, drain the liquid accumulated in the positive (negative) pressure chamber from the lower drain screw hole. After discharging the gas (liquid), close the balance valve, and then open the valve on the other side. When the equipment is shut down, the high pressure (or low pressure) valve should be closed first, then the balance valve should be opened, and then the valve should be closed on the other side. Someti