METHOD OF AND SYSTEM FOR CONTROLLING A DEVICE FOR CRYOGENIC SEPARATION OF AIR DURING QUICK CHANGES IN PRODUCTION

摘要

A process and system for controlling a cryogenic air separation unit during rapid changes in production. During operation of an air separation unit, demands for oxygen will vary and the pressure of the feed air will fluctuate. The changes in oxygen demand and feed air pressure translate into a ramping, either up or down, of the distillation system pressure in the air separation unit. Because the product streams have tight purity requirements, the ramping system pressure (which could adversely affect product purity) is compensated for. This compensation is by way of a net transfer of refrigeration, in the form of liquid nitrogen, into and out of the distillation system. This transfer of refrigeration is implemented using a storage vessel of liquid nitrogen connected to the reflux path of the distillation system. Liquid nitrogen via the reflux path is removed and stored or added to the distillation system to decrease or increase the refrigeration, respectively.