Rigorous simulation and techno-economic evaluation on the hybrid membrane/cryogenic distillation processes for air separation

Background: At present, air separation has been mostly realized through cryogenic distillation, which uses a coupled process configuration and is very energy intensive. For the purpose of improving, this work proposes hybrid membrane/cryogenic distillation processes for producing multiple high/ultra-high purity products (i.e. 99.999 mol% nitrogen, 99.9 mol% oxygen and a 99.9 mol% nitrogen). Method: Rigorous simulation and techno-economic evaluation on the different hybrid membrane/cryogenic distillation processes are performed. Nine membrane samples with different oxygen permeability and selectivity are used for integration in two different coupling structures. Aspen Plus V11 and Aspen Custom Modeler are used for development of process and membrane, respectively. Significant Findings: Firstly, the internal rate of return of the 18 hybrid membrane/cryogenic distillation processes lie in between 11.30% and 14.17% (standalone cryogenic distillation: 14.93%), which could be economically attractive. Secondly, further discovering of membranes with high oxygen permeability is suggested, as using it for integration leads to promising economic performance. Lastly, the internal rate of returns for the best hybrid membrane/cryogenic distillation processes are around 8∼9% without considering the benefit from the secondary high-purity nitrogen (interest rate: 3.52%). It indicates the economic feasibility if the production focuses only on high/ultra-high purity products.