METHOD AND APPARATUS FOR LIQUEFYING A CO2-RICH GAS

摘要

The invention relates to a method for liquefying a gas containing at least 60 mol % of CO2, in order to produce at least one liquid product, wherein the gas is cooled in order to form a fluid flow, at least a portion of the liquid or supercritical flow is cooled in a heat exchanger (E1) in order to form a cycle fluid having a cycle pressure, the cycle fluid is divided into at least two fractions including an auxiliary fraction, one of the fractions being expanded up to a first pressure in a valve (43) in order to form a biphasic mixture, and then sent to a phase separator (35). The liquid fraction of the phase separator is vaporized so as to form a vaporized gas in the exchanger, the vaporized gas then being expanded from the first pressure to a second pressure in an expansion means (45), and then compressed in the cycle compressor (C1, C2) and mixed with the first feed gas. The auxiliary fraction comprises the liquid product, and the first pressure is increased if the amount of impurities that are lighter than the carbon dioxide contained in the carbon-dioxide-rich gas increases.