Method and apparatus for liquefying a gas or cooling a feed gas at supercritical pressure

A method for liquefying a feed gas or cooling a feed gas at supercritical pressure, the method comprising the steps of:

• cooling the feed gas mixed with a cycle gas in a first heat exchanger to form a cooled fluid at a first pressure, wherein the cooled fluid is condensed within the first heat exchanger if the first pressure is below the critical pressure of the feed gas mixed with the cycle gas, wherein the cooled fluid is a supercritical fluid if the first pressure is above the critical pressure of the feed gas mixed with the cycle gas, wherein the feed gas mixed with the cycle gas is cooled against a single vaporizing fluid within the first heat exchanger;
• removing the cooled fluid from the first exchanger and expanding the cooled fluid to a second pressure lower than the first pressure to form an expanded flow;
• cooling a first portion of the expanded flow in a second heat exchanger to form a cooled first portion of the expanded flow;
• removing the cooled first portion of the expanded flow from the second heat exchanger;
• dividing the cooled first portion of the expanded flow into at least a first fraction and a second fraction, wherein the first fraction forms a liquefied product;
• and
• expanding the second fraction and vaporizing the expanded second fraction in the second heat exchanger to form at least a portion of the cycle gas that is then mixed with the feed gas and compressed in a compressor after or before being mixed with the feed gas;
• wherein a second portion of the expanded flow cools in the second heat exchanger to a temperature between the temperature of a cold end and a warm end of the second heat exchanger prior to being expanded again to form an expanded second portion;
• wherein a third portion of the expanded flow is expanded again, heated in the first heat exchanger and then sent to the compressor.