Patent ID: 7666251

Claim:
A method of purifying a feed stream containing carbon dioxide to obtain a carbon dioxide product, said method comprising: drying a feed stream having a superatmospheric pressure, in part with the use of a dryer; partially cooling the feed stream after having been dried in a main heat exchanger; reboiling a stripping column with the feed stream after having been partially cooled to further cool the feed stream and to initiate the formation of an ascending vapor phase within the stripping column; further cooling the feed stream in the main heat exchanger to at least partially liquefy the feed stream; expanding the feed stream after having been at least partially liquefied to an operational pressure of the stripping column that is less than that of the feed stream, thereby to lower a reboiling temperature at which the stripping column reboils to a level that is below the feed stream temperature after having been partially cooled; introducing at least part of the feed stream into the stripping column after having been expanded to initiate a descending liquid phase; contacting the descending liquid phase with the ascending vapor phase within the stripping column to strip impurities from the descending liquid phase and thereby to produce a carbon dioxide-lean column overhead and a carbon dioxide-rich, liquid column bottoms; utilizing a column overhead stream composed of the carbon dioxide-lean column overhead to recover refrigeration in the main heat exchanger; expanding a carbon dioxide product stream composed of the carbon dioxide-rich, liquid column bottoms at least at one pressure to generate the refrigeration; vaporizing the carbon dioxide product stream in the main heat exchanger; and compressing the carbon dioxide product stream in a compressor to obtain a compressed carbon dioxide stream as at least part of the carbon dioxide product.