초록 ▼

Carbon dioxide-containing gas such as flue gas and a carbon dioxide-rich stream are compressed and the combined streams are then treated to desorb moisture onto adsorbent beds and then subjected to subambient-temperature processing to produce a carbon dioxide product stream and a vent stream. The ve

Carbon dioxide-containing gas such as flue gas and a carbon dioxide-rich stream are compressed and the combined streams are then treated to desorb moisture onto adsorbent beds and then subjected to subambient-temperature processing to produce a carbon dioxide product stream and a vent stream. The vent stream is treated to produce a carbon dioxide-depleted stream which can be used to desorb moisture from the beds, and a carbon dioxide-rich stream which is combined with the carbon dioxide-containing gas.

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1. A method for recovering carbon dioxide comprising (A) providing a carbon dioxide-augmented feed gas by adding carbon dioxide to a flue gas produced by oxy-fuel combustion wherein the flue gas comprises at least carbon dioxide, water vapor, NOx and carbon monoxide, wherein the feed gas contains le

1. A method for recovering carbon dioxide comprising (A) providing a carbon dioxide-augmented feed gas by adding carbon dioxide to a flue gas produced by oxy-fuel combustion wherein the flue gas comprises at least carbon dioxide, water vapor, NOx and carbon monoxide, wherein the feed gas contains less than 0.1 vol. % hydrogen;(B) compressing the feed gas and then drying the compressed feed gas by contacting it with an adsorbent to form moisture-laden adsorbent and a dried gaseous feed stream;(C) subjecting the dried gaseous feed stream 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;(D) 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;(E) desorbing moisture from said moisture-laden adsorbent by contacting said moisture-laden adsorbent with said carbon dioxide-depleted stream to form a moisture-laden carbon dioxide-depleted stream and then separating said moisture-laden carbon dioxide-depleted stream from said adsorbent; and(F) combining said carbon dioxide-rich stream with said flue gas to form said carbon dioxide-augmented feed gas. 2. The method of claim 1 wherein refrigeration employed in step (C) is provided only by said expansion. 3. The method of claim 1 wherein at least a portion of said carbon dioxide-rich stream is contacted with said moisture-laden adsorbent to desorb moisture from said moisture-laden adsorbent and is then combined with said flue gas. 4. The method of claim 1 wherein said carbon dioxide-depleted stream is treated before or after expansion thereof to reduce its content of NOx. 5. The method of claim 1 wherein said carbon dioxide-depleted stream is treated before or after expansion thereof to reduce its content of carbon monoxide. 6. The method of claim 1 wherein said carbon dioxide-depleted stream is expanded before it is contacted with said moisture-laden adsorbent. 7. A method for recovering carbon dioxide comprising (A) providing a carbon dioxide-augmented feed gas by adding carbon dioxide to a flue gas produced by oxy-fuel combustion wherein the flue gas comprises at least carbon dioxide, water vapor, NOx and carbon monoxide, wherein the feed gas contains less than 0.1 vol. % hydrogen;(B) compressing the feed gas and then drying the compressed feed gas by contacting it with an adsorbent to form moisture-laden adsorbent and a dried gaseous feed stream;(C) subjecting the dried gaseous feed stream 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;(D) 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;(E) expanding said carbon dioxide-depleted stream to form an expanded carbon dioxide-depleted stream;(F) desorbing moisture from said moisture-laden adsorbent by contacting said moisture-laden adsorbent with a stream of nitrogen and then purging nitrogen from said adsorbent by contacting said adsorbent with said expanded carbon dioxide-depleted stream, and then separating said carbon dioxide-depleted stream from said adsorbent; and(G) combining said carbon dioxide-rich stream with said flue gas to form said carbon dioxide-augmented feed gas. 8. A method for recovering carbon dioxide comprising (A) providing a carbon dioxide-augmented feed gas by adding carbon dioxide to a flue gas produced by oxy-fuel combustion wherein the flue gas comprises at least carbon dioxide, water vapor, NOx and carbon monoxide, wherein the feed gas contains less than 0.1 vol. % hydrogen;(B) compressing the feed gas and then drying the compressed feed gas by contacting it with an adsorbent to form moisture-laden adsorbent and a dried gaseous feed stream;(C) subjecting the dried gaseous feed stream 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;(D) desorbing moisture from said moisture-laden adsorbent by contacting said moisture-laden adsorbent with said vent stream to form a moisture-laden vent stream and then separating said moisture-laden vent stream from said adsorbent;(E) 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(F) combining said carbon dioxide-rich stream with said flue gas to form said carbon dioxide-augmented feed gas. 9. Apparatus for recovering carbon dioxide comprising (A) compressor apparatus capable of compressing carbon dioxide-containing gas to produce a compressed carbon dioxide-containing stream;(B) dryer apparatus coupled to said apparatus for compressing to receive said compressed carbon dioxide-containing stream, and capable of reducing the water content of said compressed carbon dioxide-containing stream to produce a dried carbon dioxide-containing stream, wherein the dryer apparatus comprises one or more beds containing adsorbent for water which can alternately adsorb water and be desorbed of water by contact with a carbon dioxide-depleted stream produced in separation apparatus (D);(C) processing apparatus coupled to said dryer apparatus to receive said dried carbon dioxide-containing stream, and capable of producing therefrom at least one gaseous carbon dioxide product stream and at least one gaseous carbon dioxide-containing vent stream, by subambient-temperature processing;(D) separation apparatus coupled to said processing apparatus to receive said vent stream, and capable of producing from said vent stream a carbon dioxide-rich stream and a carbon dioxide-depleted stream by pressure swing adsorption or by physical or chemical absorption, and coupled to said compressor apparatus to pass said carbon dioxide-rich stream to said compressor apparatus, and coupled to said dryer apparatus so that said carbon dioxide-depleted stream can pass to said dryer apparatus. 10. Apparatus of claim 9 further comprising expander apparatus coupled to said separation apparatus to receive and expand said carbon dioxide-depleted stream and coupled to said dryer apparatus so that said expanded carbon dioxide-depleted stream can pass to said dryer apparatus. 11. Apparatus for recovering carbon dioxide comprising (A) compressor apparatus capable of compressing carbon dioxide-containing gas to produce a compressed carbon dioxide-containing stream;(B) dryer apparatus coupled to said apparatus for compressing to receive said compressed carbon dioxide-containing stream, and capable of reducing the water content of said compressed carbon dioxide-containing stream to produce a dried carbon dioxide-containing stream, wherein the dryer apparatus comprises one or more beds containing adsorbent for water which can alternately adsorb water and be desorbed of water by contact with a vent stream from processing apparatus (C);(C) processing apparatus coupled to said dryer apparatus to receive said dried carbon dioxide-containing stream, and capable of producing therefrom at least one gaseous carbon dioxide product stream and at least one gaseous carbon dioxide-containing vent stream, by subambient-temperature processing;(D) separation apparatus coupled to said dryer apparatus to receive said vent stream, and capable of producing from said vent stream a carbon dioxide-rich stream and a carbon dioxide-depleted stream by pressure swing adsorption or by physical or chemical absorption, and coupled to said compressor apparatus so that said carbon dioxide-rich stream can pass to said compressor apparatus.