Optimal Use of Liquefied Natural Gas (LNG) Cold Energy in Air Separation Units

Abstract

One of the solutions to utilizing liquefied natural gas (LNG) cold energy at import terminals is supplying it to an air separation unit (ASU), replacing an external refrigeration process and reducing the power consumption. Thus, two different options for the integration of a novel single column ASU process with LNG vaporization have been developed to achieve optimal use of the cold energy. After optimization of the heat integration part, both energy and exergy analyses have been performed to evaluate and compare the two integration options. The results indicate that the single column ASU process, precooled by an LNG stream, has a lower specific power consumption (0.281 kWh/kg) than the integration option with a liquid nitrogen production cycle (0.310 kWh/kg). The integration option with precooling also delivers a higher exergy efficiency for different LNG pumping pressure levels compared to the alternative with a liquid nitrogen production cycle.