Optimization of Number of Stages for Energy Conservation and Economic Feasibility of the Heat-Integrated Air Separation Column

The number of stages is a basic structural parameter for the heat-integrated air separation column (HIASC) to improve its energy-saving potential. This paper, therefore, aims at the optimization of the number of stages of the HIASC regarding energy conservation and economic feasibility. A basic optimization problem is carried out showing the existence of an optimal number of stages regarding energy consumption with a fixed heat-transfer capacity. It is shown by the results that the energy use is reduced with an increased number of stages in a certain range, and a smaller heat-transfer capacity should be selected in the meantime. The heat-transfer capacity is taken as a variable in further optimization to exploit the energy-saving potential and evaluate its economic feasibility based on total annual costs. Results show that the HIASC can reduce energy consumption by 43.6% or the total annual costs by 18.7% compared with a conventional column.