Liquid air separation design

In the distillation column of air separation, the air is usually pre separated in the lower column, and then distilled into oxygen rich liquid air and pure nitrogen, and then further distillation in the upper column to obtain oxygen and nitrogen products. As a condensing evaporator connecting the upper and lower columns, the pressure nitrogen of the lower column is used to heat the liquid oxygen of the upper column. When the liquid oxygen is evaporated, the gas nitrogen is condensed. The two-stage distillation column can make oxygen and nitrogen products obtain higher extraction rate and higher purity. The working principle of single-stage distillation column is similar to that of the lower column of two-stage distillation column. Oxygen enriched liquid air is at the bottom of the column, and pure nitrogen gas can be obtained at the top of the column. The single-stage distillation column can't separate the air perfectly, so it is seldom used in practice. However, because of its simple

Distillation is using the different boiling points of the two substances to condense the mixed steam and vaporize the mixed liquid repeatedly to achieve gas separation. For a mixed liquid composed of two substances with different boiling points, when the heat absorption part evaporates, the volatile components will evaporate more, while the mixed steam will give off heat and partially condense, the non volatile components will condense more. If the saturated steam with higher temperature is mixed with the saturated liquid with lower temperature, the steam will release heat and partially condense, and the liquid will absorb heat part of it evaporates. If after a round of partial evaporation and partial condensation, the steam and liquid with higher concentration will contact with the steam and liquid with different temperature respectively, and then partial condensation and partial evaporation will occur again. This process will be repeated for many times, and finally gas separation