Method and apparatus for separating a flow rich in carbon dioxide by distillation to produce liquid carbon dioxide

A process for the separation of a feed flow containing at least 95 mol % of carbon dioxide and also at least one impurity lighter than carbon dioxide by distillation, the process comprising the steps of:

• i. cooling the feed flow in a heat exchange means down to a first intermediate temperature of the heat exchange means, greater than that of a cold end and lower than that of a hot end of the heat exchange means, to form a liquid flow cooled to the first intermediate temperature and at a first pressure;
• ii. dividing the cooled liquid flow into at least two streams, thereby forming a first liquid fraction and a second liquid fraction;
• iii. expanding the first fraction in liquid form to a pressure of a distillation column, called second pressure, which is lower than the first pressure, and then sending the expanded first fraction to an intermediate level of the distillation column;
• iv. subcooling the second fraction in the heat exchange means down to the cold end, and then expanding the subcooled second fraction, in liquid form, to the pressure of the distillation column and then sending the expanded second fraction to a level of the distillation column above the point of arrival of the first fraction;
• and
• v. withdrawing a liquid flow containing at least 99 mol % of carbon dioxide from a bottom portion of the distillation column as a liquid product.

An apparatus for the separation of a feed flow containing at least 95 mol % of carbon dioxide and also at least one impurity lighter than carbon dioxide by distillation, the apparatus comprising:

• a heat exchange means;
• a distillation column;
• means for sending the feed flow to be cooled in the heat exchange means down to a first intermediate temperature greater than that of the cold end and lower than that of the hot end of the heat exchange means in order to form a liquid flow at the first intermediate temperature and at a first pressure;
• means for dividing the liquid flow into at least two in order to form a first liquid fraction and a second liquid fraction;
• means for expanding the first liquid fraction to the pressure of the distillation column, called second pressure, which is lower than the first pressure;
• means for sending the expanded first fraction to an intermediate level of the distillation column;
• means for exiting the second liquid fraction from the cold end of the heat exchange means after subcooling, means for expanding the subcooled second fraction to the pressure of the distillation column;
• means for sending the expanded second fraction from the distillation column at a level above the intermediate level and means for the withdrawal, from a bottom portion of the distillation column, of a liquid flow containing at least 99 mol % of carbon dioxide as liquid product.