A novel low-energy, low-cost air separation unit integrating heat pump recovery and off-peak cold storage: An energy, exergy, and economic performance analysis

Abstract

Air separation is a critical process in heavy industries, yet its high energy consumption and operational costs hinder the growth of downstream sectors. To address this, this study introduces the Low-Energy, Low-Cost Air Separation Unit (LEC-ASU), The LEC-ASU integrates a heat pump and a cold storage unit to reduce energy consumption and operational costs. The heat pump recovers compression heat, providing higher-grade thermal energy for molecular sieve regeneration, while the cold storage unit focuses the energy-intensive liquefaction process during off-peak periods. The energy consumption of LEC-ASU is reduced by approximately 9 %. Over 65 % of the energy consumption occurs during valley time, giving it a peak-shaving index of 4.0 MW, which could reach 6884 MW if implemented across all steel mills in China. Furthermore, LEC-ASU lowers operational costs by over 35 %. While the initial investment is higher than a standalone ASU, the net present value of LEC-ASU after 30 years is twice that of the standalone ASU, and its levelized cost of oxygen is reduced by 22.05 %. These findings highlight the potential for LEC-ASU to enhance energy efficiency and reduce costs, providing valuable insights for future air separation technologies.