Method and facility for purifying a feed gas stream comprising at least 90% CO2

A process for purifying a feed gas stream comprising at least 90% of CO2 on a dry basis, at least 20% relative humidity and at least one impurity chosen from chlorinated, sulfur-bearing, nitrated or fluorinated compounds, comprising the following successive steps:

• a) subjecting the feed gas stream to catalytic oxidation in such a way as to produce a gas stream comprising at least one acid impurity chosen from HCl, NOx, SOx or hydrofluoric acid;
• b) maintaining the temperature of the gas stream from step a) above the highest value between the dew point of water and the dew point of the acid(s) contained in the gas downstream of the catalytic process;
• c) removing at least a part of the acid impurities by bringing the gas stream from step b) into contact with at least one corrosion-resistant heat exchanger in such a way as to condense the acid compounds while regulating the temperature of the gas stream exiting below the dew point of water;
• and
• d) separating the acid condensates from the gas stream from step c) by means of a corrosion-resistant separator in such a way as to produce a CO2-enriched gas stream.