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Abstract

A process for producing high-purity methane is disclosed wherein a mixture containing predominantly methane, and at least one higher hydrocarbon, such as ethane or propane, and nitrogen is liquefied and fed to a first fractionation column that removes nitrogen and other light gases from the mixture through the top of the first fractionation column as a vapor. The remainder of the mixture is fed to a second fractionation column that removes the higher hydrocarbons and other heavier components through the bottom of the second fractionation column as a liquid producing high-purity methane out the top of the second fractionation column as a vapor. The high-purity methane vapor is warmed, compressed, and liquefied by heat exchange. The liquid leaving the second fractionation column can be further purified in a stripping column to remove non-hydrocarbon components such as carbon dioxide.

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First Claim