Carbon dioxide removal from methane-containing gases

Claim 1

A process for removing carbon dioxide from a gas containing at least about 50% by volume of methane and at least about 5% by volume of carbon dioxide, which comprises compressing said gas, dehydrating the compressed gas, chilling the dehydrated compressed gas by indirect heat exchange with countercurrent discharge streams of product gas and separated carbon dioxide, both said streams being hereinafter identified, scrubbing the chilled dehydrated compressed gas at a pressure in the range of about 200 to 600 psia with cold recycled methanol supplied at a temperature in the range of about -40° F. to -70° F., said recycled methanol containing not more than about 2% on a molar basis of absorbed carbon dioxide at the start of said scrubbing, passing the scrubbed gas containing not more than about 2.5% by volume of carbon dioxide as the aforesaid discharge stream of product gas, cooling the methanol withdrawn from said scrubbing and passing the cooled methanol through a pressure reducing valve to effect a substantial pressure drop and a first flashing separation of absorbed carbon dioxide from said methanol, heating said methanol after said first flashing separation by indirect heat exchange with the aforesaid recycled methanol to effect solely with said heating a second flashing separation of absorbed carbon dioxide from said methanol, passing carbon dioxide from said first and said second flashing separation as the aforesaid discharge stream of separated carbon dioxide, further heating said methanol after said second flashing separation to effect solely with said further heating at least one further flashing separation of absorbed carbon dioxide from said methanol, venting the further flashed carbon dioxide, and pumping said methanol after said further flashing separation as the aforesaid recycled methanol to effect the aforesaid indirect heat exchange and scrubbing.

Claim 7

An apparatus for removing carbon dioxide from a pressurized gas containing methane as the principal component by scrubbing said gas with recycled methanol which comprises: a. a scrubbing column having a gas inlet in the bottom portion and a gas outlet in the top as well as a methanol inlet in the top portion and a methanol outlet in the bottom; b. a cooling exchanger connected to said methanol outlet and to a pressure reducing valve so that methanol withdrawn from said scrubbing column through said methanol outlet is cooled in flowing through said cooling exchanger to said reducing valve; c. a first gas-liquid separator connected to the discharge end of said reducing valve; d. a first warming heat exchanger connected to the liquid drain of said first separator and to a second gas-liquid separator so that liquid from said first separator is warmed in flowing through said first heat exchanger into said second separator; e. a second warming heat exchanger connected to the liquid drain of said second separator and a third gas-liquid separator so that liquid from said second separator is further warmed in flowing through said second heat exchanger into said third separator; f. a pump connected to receive liquid from said third separator and to recycle said liquid through said first heat exchanger in indirect exchange relation to the liquid passing through said first heat exchanger from said first separator; and g. a pipe connected to conduct the recycle liquid from said first heat exchanger to said methanol inlet.

Claim 8

An apparatus for removing carbon dioxide from a pressurized gas containing methane as the principal component by scrubbing said gas with recycled methanol which comprises: a. a scrubbing column having a gas inlet in the bottom portion and a gas outlet in the top as well as a methanol inlet in the top portion and a methanol outlet in the bottom; b. a cooling exchanger connected to said methanol outlet and to a pressure reducing valve so that methanol withdrawn from said scrubbing column through said methanol outlet is cooled in flowing through said cooling exchanger to said reducing valve; c. a first gas-liquid separator connected to the discharge end of said reducing valve; d. a first warming heat exchanger connected to the liquid drain of said first separator and to a second gas-liquid separator so that liquid from said first separator is warmed in flowing through said first heat exchanger into said second separator; e. a second warming heat exchanger connected to the liquid drain of said second separator and a third gas-liquid separator so that liquid from said second separator is further warmed in flowing through said second heat exchanger into said third separator; f. a pump connected to receive liquid from said third separator and to recycle said liquid through said first heat exchanger in indirect exchange relation to the liquid passing through said first heat exchanger from said first separator; and g. a pipe connected to conduct the recycle liquid from said first heat exchanger to said methanol inlet.