In the fractionating column, the separation of oxygen and nitrogen is realized through the process of two-stage distillation in the upper and lower columns. The distillation process must have ascending air and downflow liquid, and the main function of the condensing evaporator is to exchange heat between the liquid oxygen returned from the bottom of the upper column and the nitrogen rising from the top of the lower column. Condensing evaporator is an indispensable heat exchange equipment in air separation distillation system. In a sense, condensing evaporator is the link between upper column and lower column.
The condensing evaporator is also called "main cooling". In the condensing evaporator, the liquid oxygen returned from the upper column absorbs heat and evaporates the gas oxygen; the rising nitrogen in the lower column is condensed into liquid nitrogen due to heat release. A part of the gas oxygen is sent out of the column as the product, and the rest is sent to the upper column as the rising steam of the distillation, while one part of the liquid nitrogen is directly used as the reflux of the lower column, and the other part is sent to the top of the upper column after throttling and depressurization, which is directly involved in the distillation process as the reflux liquid of the upper column.
