Analysis of various liquid nitrogen pre-cooling schemes for large-scale helium liquefiers/refrigerators

Liquid nitrogen precooling is widely used in helium liquefier/refrigerator for increased liquefaction as well as providing initial cool-down up to 80 K. The advantages are reduction in plant size and in number of equipment. There are several configurations of liquid nitrogen precooling for helium plants have been proposed in literature and are being used in practice. The configurations mainly differ in number of equipment like heat exchangers, valves, dewars and the arrangement of helium and nitrogen streams. In this paper, through parametric analysis of some reported configurations using Aspen HYSYS® V7.3, design decisions for adopting a precooling scheme for given helium plant has been presented. Results have been analyzed for the adopted plant configuration to arrive at conclusion regarding optimum configuration for precooling in the helium plant.