Method of treating carbon-dioxide-containing natural gas

A method for separating carbon dioxide from a carbon-dioxide-containing natural gas mixture having a high carbon dioxide content comprising:

• (1) providing a natural gas mixture containing about 10 to 70% methane and having a carbon dioxide content of 30 to 90 mol percent and liquefying a major portion of the carbon dioxide in the natural dioxide in the natural gas mixture by cooling the gas mixture, at an elevated pressure above about 700 psig,
• (2) thereafter separating the cooled natural gas mixture of step (1) into a condensed liquid carbon-dioxide-containing stream and non-condensed vapor,
• (3) subcooling the liquid carbon-dioxide-containing stream,
• (4) rectifying the subcooled liquid carbon-dioxide-containing stream to provide methane-containing overhead vapor and a kettle liquid having an increased carbon dioxide content,
• (5) vaporizing a minor portion of the carbon-dioxide-containing kettle liquid of step (4) by heating so as to provide reflux vapor for rectifying the subcooled liquid carbon-dioxide-containing stream of step (4),
• (6) separating a carbon-dioxide-enriched liquid from the vapor of step (5),
• (7) combining the methane-containing overhead vapor separation of step (4) with the non-condensed vapor separated in step (2) to provide a methane-containing gas mixture,
• (8) cooling the methane-containing gas mixture of step (7) and rectifying the cooled mixture to provide a methane-enriched overhead vapor and a kettle liquid containing carbon dioxide, the steps (1) through (8) being conducted at a pressure below the critical pressure and at a temperature above the triple point temperature for each composition involved.