Flowsheet grassroots-design optimization is one of the promising debottlenecking operations for energy conservation of large cryogenic air separation units. In this paper several air separation schemes including single-column, double-column, and triple-column cycles were theoretically compared and discussed to meet the diverse purity demands of industrial gases in different areas. All the proposed processes were rigorously verified via HYSYS platform processing the same amount of feed air of 10 000 N m(3)/h. Both single and triple column processes presented considerable energy saving potentials compared with conventional double-column process with an average specific energy consumption decrease of 12.3 similar to 25.9%. And triple column distillation scheme was more sensitive to oxygen product purity changes. A parametric sensitivity study was conducted using principal component analysis (PCA) method to investigate the influence of some important systematic parameters on novel triple-column cycle design. PCA method is fast enough to process large amounts of data, and is able to reflect more data essence compared with the sensitivity analysis method. The obtained results implied that the HP split ratio and oxygen purity have a greater impact on selection range of design parameter, whereas optimal MP split ratio existed under certain F-LP conditions. Subsystem contribution on the overall plant operation performance could be evaluated based on variance contribution. Heat-exchanger, distillation, and refrigeration subsystem accounted for 41%, 30%, and 24%, respectively. The obtained result has great engineering significance for air separation engineering conceptual design.