Graphical unit block approach for complex PSA cycle scheduling of parallel interacting trains of columns and tanks

Abstract

A simple, graphical, unit block approach for complex pressure swing adsorption (PSA) cycle scheduling has been developed for parallel interacting trains of PSA columns, possibly assisted by trains of tanks. For parallel interacting trains of PSA columns, this new methodology involves a priori specifying for each train the cycle steps, their sequence, and the number of beds, and then following a systematic procedure that requires filling in a 2-D grid for each of these coupled trains. For parallel interacting trains of PSA columns assisted by trains of tanks, a similar methodology has been developed; however, the number of tanks to include and their steps is an output from the methodology rather than an input to it. The reason for this is that tanks are inherently required when the coupling between steps is otherwise impossible or leads to the generation of undesirable idle steps. The overall outcome is a unit block for each train that can easily be extended to form its complete cycle schedule, thereby forming the grand cycle schedule of the coupled train–train or train-tank system. Three heuristics were also discovered about the minimum number of beds required to satisfy the number and types of steps in the cycle step sequence. These new methodologies and heuristics should be very useful for quickly scrutinizing different PSA cycle schedules for complex PSA processes comprising any number of parallel interacting trains of PSA columns, including the possibility of being assisted by one or more trains of tanks.