Cryogenic distillation air separation procedure and plant uses lightening gas formed at least partly from purging gas drawn from vaporizer-condenser

摘要

The air separation procedure consists of transferring at least one liquid via a rising duct with a pressure reducing valve from a first stage operating at one pressure to a second stage operating at a lower pressure. The air separation procedure consists of transferring at least one liquid via a rising duct (6, 9, 12) with a pressure reducing valve (7, 10, 13) from a first stage operating at one pressure to a second stage operating at a lower pressure. In advance of the reducing valve a lightening gas is injected, delivered at a pressure greater than the sum of the second pressure and the pressure created by a column of liquid between the point of the injection and the point at which the liquid is introduced into the second stage. A flow of air (5) is sent to one column (2) of a double separating column, and a fluid rich in nitrogen and another rich in oxygen are drawn from the low-pressure column of the double separation column. At least part of the aforementioned lightening gas consists of a purging gas drawn from the vaporizer-condenser, the gas containing at least one component that does not condense at the lowest operating temperature of the vaporizer-condenser.