Method and apparatus for liquefaction of co2

Abstract

In a method for the liquefaction of a gas containing at least 60 mol % of CO2, in order to produce at least one liquid product, a first feed gas is compressed from a first pressure to a second pressure and cooled so as to form a liquid or supercritical flow, at least part of the liquid or supercritical flow is cooled in a heat exchanger in order to form a cyclic liquid at the second pressure, the cyclic liquid is divided into at least two fractions, including an auxiliary fraction, at least one fraction being vaporized in the exchanger by means of heat exchange with the liquid or supercritical flow part, and where there are at least two fractions, each one is vaporized at a different pressure, and the at least one gas formed is then compressed and mixed with the first feed gas, the auxiliary fraction either forming the liquid product or one of the liquid products, or being treated by separation at a sub-ambient temperature in at least one separating means in order to form the liquid product.

1 - 15 . (canceled) 
     
     
         16 . A method for liquefaction of a gas containing at least 60% mol. of CO 2  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.   
     
     
         17 . The method as claimed in  claim 16 , in which the liquid derived from the cycle liquid is derived by separation in a phase separator in order to produce a gaseous fraction and a liquid fraction, the liquid fraction constituting the liquid derived from the cycle liquid. 
     
     
         18 . The method as claimed in  claim 16 , in which a fraction of the liquid or supercritical flow is not cooled in the heat exchanger and serves as a product. 
     
     
         19 . The method as claimed in  claim 16 , in which a second feed gas is purified in the separation means or at least one of the separation means, without having been compressed with the first feed gas. 
     
     
         20 . The method as claimed in  claim 16 , in which at least one fraction of the cycle gas is vaporized at a pressure lower than the first pressure and compressed to the first pressure before being mixed with the first feed gas. 
     
     
         21 . The method as claimed in  claim 16 , in which the auxiliary fraction and/or the second feed gas is/are purified in order to form the liquid product or one of the liquid products by separation in at least one phase separator and/or at least one distillation column. 
     
     
         22 . The method as claimed in  claim 16 , in which the feed gas mixed with the cycle gas at the second pressure is cooled upstream of the heat exchanger in order to supply the liquid or supercritical flow and the liquid or supercritical flow is next sent to the heat exchanger. 
     
     
         23 . The method as claimed in  claim 22 , in which the feed gas at the second pressure is cooled upstream of the heat exchanger in order to form a single liquid or supercritical flow and no gaseous flow. 
     
     
         24 . The method as claimed in  claim 22 , in which the liquid or supercritical flow is sub-cooled. in the exchanger. 
     
     
         25 . 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.   
     
     
         26 . The apparatus as claimed in  claim 25 , in which at least one said pipe configured to send a gas form by vaporization to the compression means is connected to a point of the compression means upstream of the entrance of the first feed gas in the compression means. 
     
     
         27 . The apparatus as claimed in  claim 25 , comprising a cold box containing the exchanger and means of expanding a liquid to be vaporized in the exchanger, as well as means for treating the auxiliary fraction of the cycle liquid, consisting of at least one phase separator and/or at least one distillation column. 
     
     
         28 . The apparatus as claimed in  claim 27 , comprising a pipe configured to send a second feed gas to the treatment means without having been compressed in the compression means. 
     
     
         29 . The apparatus as claimed in  claim 28 , in which the pipe configured to send a second feed gas to the treatment means is connected to the exchanger. 
     
     
         30 . The apparatus as claimed in  claim 25 , further comprising a pipe configured to bring some of the liquid or supercritical flow to serve as a product without passing through the heat exchanger. 
     
     
         31 . The apparatus as claimed in  claim 25 , further comprising means for vaporizing the at least two fractions each at a different pressure for the case where several fractions vaporize therein.