Method and apparatus for separating carbon dioxide and other acid gases from methane by the use of distillation and a controlled freezing zone

A method for the separation of a feedstream containing methane and carbon dioxide in separation means comprising the steps of:

• maintaining a first distillation zone engineered to produce an enriched carbon dioxide liquid bottoms stream and a freezing zone vapor feedstream and operated at a temperature and pressure at which substantially no carbon dioxide solids are formed within said distillation zone,
• maintaining a freezing zone engineered to contact said freezing zone vapor feedstream with at least one freezing zone liquid feedstream containing methane at a temperature and pressure whereby both solids containing carbon dioxide and a methane-enriched vapor stream are formed,
• introducing said feedstream into said first distillation zone,
• producing said enriched carbon dioxide and said freezing zone vapor stream,
• introducing said freezing zone vapor feedstream into said freezing zone,
• contacting in said freezing zone said vapor feedstream with at least one said freezing zone liquid feedstream,
• forming in said freezing zone said solids containing carbon dioxide and said methane-enriched vapor stream,
• melting said solids containing carbon dioxide and introducing a liquid stream containing said melted solids into said first distillation zone,
• maintaining a second distillation zone engineered to produce at least one said freezing zone liquid feedstream and an overhead vapor stream and operated at a temperature and a pressure at which substantially no carbon dioxide solids are produced within said second distillation zone,
• condensing at least a portion of the overhead vapor stream and recycling at least a portion of said condensed overhead vapor stream as reflux in said second distillation zone, and
• recovering at least a portion of the remainder of the overhead vapor stream as a methane-enriched product stream.

A method for separation of a feedstream containing methane and carbon dioxide comprising the steps of:

• maintaining a first distillation zone engineered to produce an enriched liquid carbon dioxide bottoms stream and a first distillation zone vapor stream,
• maintaining a freezing zone engineered to contact said feedstream with said first distillation zone vapor stream at a temperature and pressure whereby both solids containing carbon dioxide and a methane-enriched vapor stream are formed,
• introducing said feedstream into the freezing zone,
• introducing said first distillation zone vapor stream into said freezing zone,
• contacting in said freezing zone said first distillation zone vapor stream with said feedstream,
• producing in said freezing zone said solids containing carbon dioxide and said methane-enriched vapor stream,
• condensing at least a portion of the methane-enriched vapor stream and forming at least one freezing zone reflux feedstream with at least a portion of said condensed vapor stream,
• recovering at least a portion of the remainder of the methane-enriched vapor stream as a methane-enriched product stream,
• melting said solids containing carbon dioxide, introducing a liquid stream containing said melted solids into said first distillation zone, and distilling said liquid stream in said first distillation zone at a temperature and pressure at which substantially no carbon dioxide solids are formed within said distillation zone, and
• recovering at least a portion of said enriched liquid carbon dioxide bottoms stream as a carbon dioxide-enriched product stream.

A method for the separation of a feedstream containing methane and carbon dioxide comprising the steps of:

• maintaining a first distillation zone engineered to produce an enriched carbon dioxide bottoms stream and a first distillation zone vapor stream,
• maintaining a second distillation zone engineered to produce at least one second distillation zone liquid stream and a methane-enriched overhead vapor stream,
• maintaining a freezing zone engineered to contact said feedstream and said second distillation zone liquid stream with said first distillation zone vapor stream and operated at a temperature and pressure whereby both solids containing carbon dioxide and a freezing zone vapor stream are formed,
• introducing said feedstream, said second distillation zone liquid stream and said first distillation zone vapor stream into the freezing zone,
• contacting said feedstream and said second distillation zone liquid stream with said first distillation zone vapor stream,
• producing in said freezing zone solids containing carbon dioxide and a freezing zone vapor stream,
• melting said solids containing carbon dioxide, introducing a liquid stream containing said melted solids into said first distillation zone, and distilling said liquid stream in said first distillation zone at a temperature and pressure at which substantially no carbon dioxide solids are formed within said distillation zone,
• recovering at least a portion of said enriched liquid carbon dioxide bottoms stream as a carbon dioxide-enriched product stream,
• introducing said freezing zone vapor stream into said second distillation zone, which zone is operated at a temperature and pressure at which substantially no carbon dioxide solids are produced within said second distillation zone,
• condensing at least a portion of the methane-enriched overhead vapor stream and recycling at least a portion of said condensed overhead vapor stream as reflux in said second distillation zone, and
• recovering at least a portion of the remainder of the overhead vapor stream as a methane-enriched product stream.