PROCESS AND SYSTEM FOR CONTROLLING A CRYOGENIC AIR SEPARATION UNIT DURING RAPID CHANGES IN PRODUCTION

摘要

A process and system for controlling acryogenic air separation unit during rapid changes inproduction. During operation of an air separation unit,demands for oxygen will vary and the pressure of the feedair will fluctuate. The changes in oxygen demand andfeed air pressure translate into a ramping, either up ordown, of the distillation system pressure in the airseparation unit. Because the product streams have tightpurity requirements, the ramping system pressure (whichcould adversely affect product purity) is compensatedfor. This compensation is by way of a net transfer ofrefrigeration, in the form of liquid nitrogen, into andout of the distillation system. This transfer ofrefrigeration is implemented using a storage vessel ofliquid nitrogen connected to the reflux path of thedistillation system. Liquid nitrogen via the reflux pathis removed and stored or added to the distillation systemto decrease or increase the refrigeration, respectively.