Method and apparatus for liquefaction of co2

A method for liquefaction of a gas containing at least 60% mol. of CO2 to produce at least one liquid product, the method comprising the steps of:

• cooling and compressing a feed gas from a first pressure to a second pressure to form a liquid or supercritical flow;
• cooling at least part of the liquid or supercritical flow in a heat exchanger to form a cycle liquid at the second pressure;
• dividing the cycle liquid or a liquid derived from the cycle liquid into at least two fractions including an auxiliary fraction, wherein at least one fraction is vaporized in the exchanger by exchange of heat with the part of the liquid or supercritical flow, and
• vaporizing at least two fractions each at a different pressure and then compressing and mixing the formed gas or gases with the first feed gas,
• wherein the auxiliary fraction either constituting the liquid product or one of the liquid products or being treated by separation at sub-ambient temperature in at least one separation means in order to form the liquid product or one of the liquid products,
• wherein the feed gas is compressed from the first pressure to the second pressure after having been mixed with at least one gas formed by vaporization of the cycle liquid, the gas formed by vaporization having been compressed from its vaporization pressure to the first pressure without having been mixed with the first gas.

An apparatus for liquefaction of a gas containing at least 60% mol. CO2 in order to produce at least one liquid product, the apparatus comprising:

• a heat exchanger;
• a compression means comprising at least two stages in series, a first stage and a second stage downstream of the first stage;
• a pipe configured to send a feed gas to the inlet of the second stage of the compression means in order to be compressed from a first pressure to a second pressure;
• means for cooling the gas at the second pressure in order to form a liquid or supercritical flow;
• a pipe configured to bring at least part of the liquid or supercritical flow to cool in the exchanger in order to form a cycle liquid at the second pressure;
• at least one pipe configured to send at least a fraction of the liquid to vaporize in the exchanger;
• at least one pipe configured to send the gas or gases formed to the compression means;
• a pipe for an auxiliary fraction of cycle liquid connected to the heat exchanger in order to transport either one of the liquid products or a liquid to be treated in order to form one of the liquid products;
• and
• a pipe configured to send the gas compressed in the first stage to the second stage,
• wherein the pipe configured to send the gas formed to the compression means is a pipe configured to send at least one gas formed at the inlet of the first stage in order to form a compressed gas.