A process simulator for design of a cryogenic air separation plant by packed columns with structured packing was developed by use of our heat and mass transfer model. The heat and mass transfer rates were estimated by correlations which were proposed in our previous work, Comparison of the predicted separation performance of a pilot-scale cryogenic air separation plant by the developed simulator with the observed data was made. Predicted concentration profiles in the low pressure column and the ones in the argon column showed good agreement with observed data. The effects of the side-cut location to the argon column, the liquid-feed location to the low pressure column, and the vapor-liquid ratio in the feeds to the low pressure column for a commercial-scale cryogenic air separation plant, which consisted of a high pressure column with 50 sieve trays, a 3,2-m diameter low pressure packed column with structured packing, and a 2.5-m diameter argon column with structured packing, on purity of the product nitrogen, oxygen and crude argon were also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.