An elevated-pressure cryogenic air separation unit based on self-heat recuperation technology for integrated gasification combined cycle systems

An advanced elevated-pressure cryogenic ASU (air separation unit) for IGCC (Integrated gasification combined cycle) system was proposed based on self-heat recuperation technology. In the proposed ASU, only one distillation column was used against the double columns in a conventional ASU. The N2 gas drawn from the top of the distillation column is first compressed to elevate the boiling temperature, and then undergo heat exchange with the liquid O2 stream from the bottom of the distillation column. Both the latent and the sensible heat of the process steams are recuperated in the proposed process, resulting in a large reduction of the energy requirement in ASU. We compared four different cryogenic air separation processes for IGCC systems: conventional low-pressure ASU, conventional elevated-pressure ASU, proposed low-pressure and elevated-pressure ASU based on self-heat recuperation technology. The simulation results show that the energy requirement of the proposed elevated-pressure ASU is the most suitable choice for IGCC systems, which was reduced by approximately 11.1% comparing with the conventional low-pressure ASU when only nitrogen injection is integrated with IGCC systems.