Apparatus for removing CO and NO from flue gas comprising carbon dioxide, CO, NO and at least one non-condensable gas, said apparatus comprising: an oxyfuel combustion system for generating said flue gas by oxyfuel combustion of a carbonaceous fuel; a removal system for removing water soluble components and solid particulates from said flue gas; a compression system for compressing said flue gas; a SO 2 removal system for removing SO 2 from said flue gas; a water adsorption system comprising at least one adsorbent bed for drying said flue gas; a low temperature carbon dioxide purification system for purifying dried flue gas to produce liquid carbon dioxide and a NO/CO-containing gas that is depleted in carbon dioxide; a pressurizable catalytic reactor system comprising at least one catalyst bed comprising a CO-oxidation catalyst, for converting CO and NO in said NO/CO-containing gas in the presence of O 2 at a first elevated temperature and at a first elevated pressure to carbon dioxide and NO 2 respectively, to produce NO 2 /carbon dioxide-enriched gas comprising at least a portion of said non-condensable gases; a heat exchange system for recovering heat from said NO 2 /carbon dioxide-enriched gas by indirect heat exchange with said CO-containing gas as feed to said pressurizable catalytic reactor system; a membrane separation system for separating said NO 2 /carbon dioxide-enriched gas into a carbon dioxide-rich permeate fraction that is rich in O 2, and a non-condensable gas(es)-enriched retentate fraction containing NO 2; a conduit arrangement for recycling said carbon dioxide-rich permeate fraction to said oxyfuel combustion system, optionally via at least one adsorbent bed in said water adsorption system; and a NO 2 removal system for removing NO 2 from said non-condensable gas(es)-enriched retentate fraction. an oxyfuel combustion system for generating said flue gas by oxyfuel combustion of a carbonaceous fuel; a removal system for removing water soluble components and solid particulates from said flue gas; a compression system for compressing said flue gas; a SO 2 removal system for removing SO 2 from said flue gas; a water adsorption system comprising at least one adsorbent bed for drying said flue gas; a low temperature carbon dioxide purification system for purifying dried flue gas to produce liquid carbon dioxide and a NO/CO-containing gas that is depleted in carbon dioxide; a pressurizable catalytic reactor system comprising at least one catalyst bed comprising a CO-oxidation catalyst, for converting CO and NO in said NO/CO-containing gas in the presence of O 2 at a first elevated temperature and at a first elevated pressure to carbon dioxide and NO 2 respectively, to produce NO 2 /carbon dioxide-enriched gas comprising at least a portion of said non-condensable gases; a heat exchange system for recovering heat from said NO 2 /carbon dioxide-enriched gas by indirect heat exchange with said CO-containing gas as feed to said pressurizable catalytic reactor system; a membrane separation system for separating said NO 2 /carbon dioxide-enriched gas into a carbon dioxide-rich permeate fraction that is rich in O 2, and a non-condensable gas(es)-enriched retentate fraction containing NO 2; a conduit arrangement for recycling said carbon dioxide-rich permeate fraction to said oxyfuel combustion system, optionally via at least one adsorbent bed in said water adsorption system; and a NO 2 removal system for removing NO 2 from said non-condensable gas(es)-enriched retentate fraction.