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

Abstract

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.

Structural Optimization of Heat-Integrated Air Separation Column

“…The heat-integrated air separation column (HIASC) was proposed to overcome the energy consumption associated with conventional (CASC). , The HIASC reduced energy consumption by 60% compared to the CASC in a pilot plant scale application . Regardless of its potential for energy saving in the air separation process, it has not been implemented in industrial processes due to its extreme complexities among variables, high capital investment (CI), and design challenges due to the narrow physical space at the middle of both sections of the column. − A HIASC with insufficient dynamic performance characteristics may fail to satisfy product market specifications and violate operational and safety guidelines . In the last two decades, significant attention has been given to optimizing the HIASC with the primary goal of improving energy efficiency and reducing capital costs.…”