How does an air separation unit work

An air separation unit (ASU) works based on the principle of the fractional distillation of air. The air is compressed to high pressures and cooled to extremely low temperatures by passing through a series of heat exchangers. The compressed and cooled air mixture is then fed into a distillation column, where the different components of air (nitrogen, oxygen, argon, and other trace gases) are separated based on their boiling points.

The distillation column contains a top condenser and a bottom reboiler. The compressed and cooled air mixture is fed into the upper section of the column. As the air rises through the column, it experiences a gradual decrease in temperature, allowing the different components to condense into liquid form at different levels within the column. The condensed liquids are then collected and removed from their respective trays.

The bottom of the column contains the reboiler, which heats up the liquid argon and pumps it back into the column, helping to provide the necessary heat for the distillation process. The produced oxygen and nitrogen gases are then recovered from the top of the column and separated for commercial use. The trace gases are also collected and recovered from the bottom of the column.

Overall, the air separation unit process uses the physical properties of the different components of air to effectively separate them into their respective products. This process is widely used in various industries, including metal production, chemical manufacturing, new energy and healthcare.