Optimization of an Air Separation Unit (ASU) using Aspen Plus

Presenter(s)

Ian Park

Abstract or Description

Optimization of Air Separation Unit using Aspen Plus model

Air Separation Unit (ASU) is a facility that separates oxygen from the atmospheric air. The manufactured oxygen can be utilized in various types of chemical processes, including hydrogen production. To develop a feasible model of ASU that produces high-concentration oxygen, this study utilizes Aspen Plus and the relevant literatures to optimize the ASU operation.

The designed Aspen Plus model is a double-column unit with a feed entering the high-pressure column (HPC) and its distillate entering the low-pressure column (LPC). The feed is the cryogenic atmospheric air. The products are a gaseous oxygen stream (GOX) and a nitrogen-rich gas mixture (GAN).

The optimization of the ASU was investigated by testing varying inputs into the double-column unit. The manipulated variables included the operating pressures, feed locations, and numbers of stages of the columns. The values were considered optimized if the GOX concentration was greater than 99.9%.

The results indicate that the HPC number of stages (n=10) must be lower than LPC (n=30) to optimize oxygen concentration. The HPC reflux ratio (R=0.75) is lower than the LPC (R=3). The feed locations of the LPC were 13 (B) and 15 (Stream 3). Overall, these optimization process produced GOX with a concentration of 0.999005.

The study provides a generalized model of the ASU and its optimal conditions for oxygen production. This Aspen Plus model and data can be further utilized to develop a more complex ASU prototype.