Plural stage distillation of a natural gas stream
AssigneeThe Lummus Company
InventorStephen M. Solomon
Life of this patent
Estimating the term…
Abstract
Natural gas, containing carbon dioxide and nitrogen, is demethanized in a first fractional distillation tower to provide an overhead of nitrogen and methane free of carbon dioxide and components heavier than methane. A sidestream is withdrawn from the first tower at a point therein where carbon dioxide concentration is maximized and the sidestream is fractionated in a second tower to recover methane and carbon dioxide as overhead. Nitrogen is rejected from the carbon dioxide free overhead from the first tower by liquefaction of methane to provide a send-out gas free of nitrogen. The cold potential of various streams is used to provide cooling requirements for the process.
Claims14
A process for recovering a nitrogen-methane mixture from natural gas containing methane, nitrogen, carbon dioxide and materials heavier than methane, comprising:
- introducing the natural gas containing methane, nitrogen, carbon dioxide and materials heavier than methane into a first fractional distillation zone;
- fractionally distilling the natural gas in the first fractional distillation zone to recover solely by fractional distillation a first overhead consisting essentially of nitrogen and methane, essentially free of carbon dioxide and materials heavier than methane, and a first bottoms of materials heavier than methane and essentially free of methane;
- withdrawing a side-stream from the first fractional distillation zone at a point therein having a maximum concentration of carbon dioxide, said side-stream containing methane, carbon dioxide and materials heavier than methane, said side-stream being essentially free of nitrogen;
- introducing the side-stream into a second fractional distillation zone;
- and
- fractionally distilling the side-stream in the second fractional distillation zone to recover an overhead containing carbon dioxide and methane and a bottoms containing materials heavier than methane.
A process for recovering methane from natural gas containing methane, carbon dioxide, nitrogen and materials heavier than methane, comprising;
- a. introducing the natural gas containing methane, carbon dioxide, nitrogen and materials heavier than methane into a first fractional distillation zone;
- b. fractionally distilling the natural gas in the first fractional distillation zone to recover solely by fractional distillation a first overhead consisting essentially of methane and nitrogen essentially free of carbon dioxide and materials heavier than methane, and a first bottoms containing materials heavier than methane and essentially free of methane and nitrogen;
- c. withdrawing a side-stream from the first fractional distillation zone at a point therein having a maximum concentration of carbon dioxide, said side-stream containing methane, carbon dioxide and materials heavier than methane and being essentially free of nitrogen;
- d. introducing the side-stream into a second fractional distillation zone;
- e. fractionally distilling the side-stream in the second fractional distillation zone to recover a second overhead containing methane and carbon dioxide and a second bottoms containing materials heavier than methane;
- and
- f. cooling first overhead from the first fractional distillation zone to condense a major portion of the methane and to produce a liquid methane stream essentially free of nitrogen.
Dependencies are inferred from the claim text.