Air separation operation

The air is mainly composed of 78.03% nitrogen and 20.93% oxygen and other gases. Air separation is to cool the air to a certain low temperature firstly and liquefy it into liquid air. Reuse two liquids oxygen and nitrogen with different boiling points (At atmospheric pressure, the boiling point of oxygen is - 183.98°C and that of nitrogen is - 195.8°C), separation is carried out in an air fractionator equipped with sieve plates. The air separation column is also called distillation column. Air distillation column can be divided into single-stage distillation column and double-stage distillation column, and single-stage distillation column can only produce one kind of pure product. Two stage distillation column is used to produce high purity nitrogen and oxygen in common air separation unit.

In the air separation unit, the water cooling column is a hybrid heat exchange equipment which uses the crude nitrogen to reduce the temperature of the cooling water from the air cooling column after cooling air, so as to provide the air cooling column with recycling. In the water cooling column, the crude nitrogen from the reversible heat exchanger (or accumulator) is 27-28 ℃ and the relative humidity is about 30%, while the temperature of the cooling water from the air cooling column is 35-45 ℃. When the crude nitrogen meets the hot water sprayed, it absorbs heat, thus reducing the water temperature. Generally, the structure of water cooling column is packed column, cyclone plate column and sieve plate column.