Patent ID: 8806891

Claim:
A method for cooling and optionally liquefaction of a product gas, based on a closed loop of multi-component refrigerant with a joined composition of a more volatile fraction and a less volatile fraction, in heat exchange with the product gas to be cooled and optionally condensed, said method comprising: directing the product gas to be cooled through a primary two-flow heat exchanger; directing the refrigerant with the joined composition from a first secondary two-flow heat exchanger through a compressor; removing heat absorbed by the refrigerant by heat exchange in a pre-cooling heat exchanger so as to cool the refrigerant; passing the cooled refrigerant into a first phase-separator for separating the refrigerant into the more volatile fraction and the less volatile fraction; cooling the more volatile fraction in heat exchange with low pressure refrigerant of the joined composition by passing the more volatile fraction through the first secondary two-flow heat exchanger; further cooling the more volatile fraction in heat exchange through a second secondary two-flow heat exchanger; directing a first part of the further cooled more volatile fraction to a first throttling device, and directing the first part from the first throttling device into heat exchange in the second secondary two-flow heat exchanger as a first low pressure refrigerant; directing the remaining part of the further cooled more volatile fraction to a second throttling device so as to become a remaining low pressure refrigerant, and directing the remaining low pressure refrigerant into heat exchange with the product gas to be cooled through the primary two-flow heat exchanger; throttling by means of a third throttling device the less volatile fraction from the first phase-separator so as to become a second low pressure refrigerant, and directing all of the second low pressure refrigerant, combined with the remaining low pressure refrigerant from the primary heat exchanger and the first low pressure refrigerant from the second secondary two-flow heat exchanger, into heat exchange and complete vaporization through the first secondary two-flow heat exchanger, wherein the second low pressure refrigerant with the less volatile fraction, the first low pressure refrigerant with the first part of the more volatile fraction and the remaining low pressure refrigerant with the remaining part of the more volatile fraction form the total amount of the joined composition; and closing the loop by directing the vaporized refrigerant to the compressor, wherein only the primary two-flow heat exchanger receives the product gas, and wherein only the refrigerant is passed through the first and second secondary two-flow heat exchangers.