Method and apparatus for low-temperature separation of a gas containing co2 to produce a co2-rich fluid

A process for the low-temperature separation of a feed gas containing CO2, at least one component lighter than CO2 and at least one component heavier than CO2 to produce a CO2-rich fluid, the process comprising the steps of:

• compressing the feed gas in a compressor comprising at least two stages to form a compressed gas;
• cooling the compressed gas in a first heat exchanger to form a cooled gas;
• separating the cooled gas at low temperature at least by distillation in a first distillation column to produce a liquid enriched in CO2 and depleted in the at least one component lighter than CO2 and a gas depleted in CO2 and enriched in the at least one component lighter than CO2;
• heating the gas depleted in CO2 in the first heat exchanger;
• pressurizing the liquid enriched in CO2 and depleted in the at least one component lighter than CO2 in a pump;
• expanding a first portion of the liquid enriched in CO2 and depleted in the at least one component lighter than CO2 and introducing the expanded first portion into a second distillation column in liquid phase;
• vaporizing a second part of the liquid enriched in CO2 in the first heat exchanger and then introducing the vaporized second part in the gaseous phase into first point that is located at a bottom of the second distillation column;
• withdrawing a fluid depleted in CO2 and enriched in the at least one heavier component from a second column;
• and
• withdrawing a top gas enriched in CO2 and depleted in the at least one heavier component at a top of the second column as product,
• wherein the first part of the liquid being sent to the second distillation column is at a level above the first point.

An appliance for the low-temperature separation of a feed gas containing CO2 , at least one component lighter than CO2 and at least one component heavier than CO2 to produce a CO2-rich fluid, the apparatus comprising:

• a compressor comprising at least two stages;
• a first heat exchanger, a first distillation column, a second distillation column;
• a first conduit for sending the feed gas to be compressed in the compressor comprising at least two stages;
• a second conduit configured to send the compressed gas to be cooled in the first heat exchanger;
• means for sending the gas cooled in the first heat exchanger to be separated at low temperature at least by distillation in the first distillation column to produce a liquid enriched in CO2 and depleted in the at least one component lighter than CO2 and a gas depleted in CO2 and enriched in the at least one component lighter than CO2 ;
• a third conduit configured to send the gas depleted in CO2 to be heated in the first heat exchanger;
• an expansion means;
• means for withdrawing a liquid depleted in CO2 and enriched in the at least one heavier component from the second column and means for withdrawing a gas enriched in CO2 and depleted in the at least one heavier component at the top of the second column as product;
• a fourth conduit configured to send a first part of the liquid enriched in CO2 to be expanded in the expansion means;
• a fifth conduit configured to send the expanded first part to the second distillation column in the liquid form;
• a sixth conduit configured to send a second part of the liquid enriched in CO2 to be vaporized in the first heat exchanger;
• and
• a seventh conduit configured to send the vaporized second part into the bottom of the second distillation column at an arrival point, the first part of the liquid being sent to the second column at a level above the arrival point of the second part of the liquid.