Patent ID: 8216344

Claim:
A process for treating gaseous carbon dioxide, comprising (A) providing a gaseous feed stream of carbon dioxide that also comprises NOx and sulfur dioxide, and that is at a pressure of at least 1.5 bar; (B) adsorbing SO 2 and NOx from said feed stream onto a washed first bed of activated carbon under oxidizing conditions to convert adsorbed sulfur dioxide to sulfur trioxide and to convert adsorbed NO to nitrogen dioxide, thereby forming SO 2 -depleted NOx-depleted carbon dioxide and a loaded first bed comprising SOx-loaded NOx-loaded activated carbon; (C) washing said loaded first bed with water to desorb sulfur trioxide and nitrogen dioxide therefrom into said water to form a mixture of sulfuric acid and nitric acid and a washed first bed of activated carbon, while adsorbing SO 2 and NOx from said feed stream onto a washed second bed of activated carbon under oxidizing conditions to convert adsorbed sulfur dioxide to sulfur trioxide and to convert adsorbed NO to nitrogen dioxide, thereby forming SO 2 -depleted NOx-depleted carbon dioxide and a loaded second bed comprising SOx-loaded NOx-loaded activated carbon; (D) washing said loaded second bed with water to desorb sulfur trioxide and nitrogen dioxide therefrom into said water to form a mixture of sulfuric acid and nitric acid, while adsorbing SOx and NOx from said feed stream onto said washed first bed of activated carbon in step (B); (E) subjecting the SO 2 -depleted NOx-depleted carbon dioxide to a subambient-temperature recovery process, employing refrigeration provided by expansion of at least one liquid carbon dioxide product stream formed by said recovery process to produce at least one gaseous carbon dioxide product stream and at least one gaseous carbon dioxide-containing vent stream; (F) separating the vent stream into a carbon dioxide-rich stream and a carbon dioxide-depleted stream, by pressure swing adsorption or by physical or chemical absorption; and (G) recycling said carbon dioxide-rich stream to said feed stream.