Carbon dioxide compression system and method with multiphase compression and supercritical pump

A method for compressing a fluid comprising at least 80% carbon dioxide, the method comprising at least the following steps:

• a) compressing (Comp) the fluid in one or more compression stages to a pressure (P1) greater than 8 bar and strictly less than 50 bar,
• b) cooling (Ref1) the compressed fluid to a temperature (T1′) of between −50° C. and 15° C., fluid pressure (P1) being maintained greater than 8 bar and strictly less than 50 bar, so as to partly liquefy the carbon dioxide of the fluid, the gas volume fraction of the fluid ranging between 1% and 99%,
• c) carrying out multiphase compression (PP) of the cooled compressed fluid to a pressure (P3) strictly below the critical pressure of the fluid, multiphase compression being carried out in one or more multiphase compression stages,
• d) preferably cooling (Ref2) the fluid from the multiphase compression so as to totally liquefy at least the carbon dioxide of the fluid,
• e) compressing (PSP) the fluid so that the pressure (P4) of the fluid exceeds the critical point of the fluid, preferably to a temperature below 60° C.