Cryogenic distillative removal of CO.sub.2 from high CO.sub.2 content hydrocarbon containing streams

Process for cryogenic distillative fractionation of a feedstream comprising methane, carbon dioxide, and an indigenous light oil component variable in composition, the process comprising:

• maintaining a predetermined carbon number range in a light lean oil stream while the hydrocarbon content of the feedstream varies by removing a first hydrocarbon fraction containing lower boiling point constituents in a stabilizer column and a second hydrocarbon fraction containing higher boiling point constituents in a topping distillation column from the feedstream to produce a light lean oil stream of predetermined average carbon number range by the steps of
• (a) introducing a feedstream comprising methane, carbon dioxide, and an indigenous light lean oil component variable in composition into the topping column and removing the second hydrocarbon fraction containing higher boiling point constituents from the feedstream therein to produce a topped feedstream;
• (b) introducing the topped feedstream into a first distillation column and removing methane therefrom to produce an enriched methane overhead stream and a first bottoms stream;
• (c) introducing the first bottoms stream into a second distillation column and removing carbon dioxide therefrom to produce an enriched carbon dioxide overhead stream and a second bottoms stream;
• (d) introducing the second bottoms stream into the stabilizer column and removing the first hydrocarbon fraction of lower boiling point constituents therefrom to produce an overhead stream enriched in the lower boiling point constituents and, as a bottoms stream, the light lean oil stream of predetermined average carbon number range;
• and
• returning at least a portion of the light lean oil stream of predetermined carbon number range to at least one of the first distillation column and the second distillation column.

Process for cryogenic distillative fractionation of a feedstream comprising methane, carbon dioxide, and an indigenous light oil component variable in composition, the process comprising:

• maintaining a predetermined carbon number range in a light lean oil stream while the hydrocarbon content of the feedstream varies by removing a first hydrocarbon fraction containing lower boiling point constituents in a stabilizer column and a second hydrocarbon fraction containing higher boiling point constituents in a topping distillation column from the feedstream to produce a light lean oil stream of predetermined carbon number range by the steps of
• (a) introducing a feedstream comprising methane, carbon dioxide, and an indigenous light lean oil component variable in composition, into a distillation column and removing methane therefrom to produce an enriched methane overhead stream and a bottoms stream;
• (b) introducing the first bottoms stream into a second distillation column and removing carbon dioxide therefrom to produce an enriched carbon dioxide overhead stream and a second bottoms stream;
• (c) introducing the second bottoms stream into the stabilizer column and removing the first hydrocarbon fraction containing lower boiling point constituents therefrom to produce an overhead stream enriched in the lower boiling point constituents and a third bottoms stream;
• (d) introducing a portion of the third bottoms stream into the topping distillation column to remove the second hydrocarbon fraction containing higher boiling point constituents from the third bottoms stream to produce the light lean oil stream of predetermined carbon number range;
• and
• returning at least a portion of the light lean oil stream of predetermined carbon number range to at least one of the first distillation column and the second distillation column.