Optimization of a novel cryogenic air separation process based on cold energy recovery of LNG with exergoeconomic analysis

Oxyfuel combustion is deemed as one of the most potential technology to reduce CO2 emission from power plant. Exploring the technology of low-cost high-purity oxygen is a key issue to the implement of oxyfuel combustion. Cryogenic air separation is routinely used in large-scale production of high-purity oxygen. However, the relatively high power consumption of traditional cryogenic air separation no longer satisfies the requirement for cost-effective high-purity oxygen generation in the industrial field. A novel three-column cryogenic air separation process integrated with liquefied natural gas (LNG) regasification is introduced and evaluated in this paper. Waste nitrogen full utilization, cascade heat transfer and multi-column air distillation strategies are employed. To confirm the rationality and validity of the process, pinch point, energetic, exergetic and exergoeconomic analyses are performed. The obtained results indicate that the specific power consumption of liquid oxygen and liquid nitrogen are 0.252 kWh·kg-1 and 0.258 kWh·kg-1 in the proposed integrated system. The overall exergy efficiency and the LNG cold exergy utilization efficiency reach 0.7165 and 0.5318, respectively. Furthermore, sensitivity analysis is employed to investigate the effects of the outlet temperature of sub-coolers and stage number of low pressure column on total power consumption and equipment investment of the proposed process.