Distillative separations of gas mixtures containing methane, carbon dioxide and other components

A distillative separation of a hydrocarbon feed mixture containing at least methane, carbon dioxide and hydrogen sulfide, comprising:

• a. introducing said feed mixture into a first distillation column;
• b. operating said first distillation column at conditions of pressure, temperature and composition sufficient to produce a methane-enriched overhead and a bottoms containing hydrogen sulfide and enriched in carbon dioxide based upon the methane and carbon dioxide present in said feed mixture, said conditions of pressure, temperature and composition creating a solids potential zone for carbon dioxide within said distillation column where said carbon dioxide would normally form solids;
• c. introducing a liquid solids-preventing agent into the solids potential zone in the upper portion of said first column in sufficient amount to eliminate carbon dioxide solids formation in the solids potential zone;
• d. withdrawing from the first distillation column said methane-enriched overhead;
• e. withdrawing the liquid solids-preventing agent with said bottoms enriched in carbon dioxide and containing the hydrogen sulfide;
• f. introducing said bottoms from the first distillation column into a second distillation column;
• g. operating said second distillation column at conditions of pressure, temperature and composition sufficient to produce a carbon dioxide-enriched overhead stream and a hydrogen sulfide-enriched bottoms stream based upon the carbon dioxide and hydrogen sulfide present in said bottoms from the first distillation column;
• h. introducing into said second distillation column at a location above the feed point thereto an agent for increasing the relative volatility of carbon dioxide to hydrogen sulfide;
• i. withdrawing from the second distillation column said carbon dioxide-enriched overhead;
• and,
• j. withdrawing from the second distillation column said bottoms enriched in hydrogen sulfide.

A distillative separation of a hydrocarbon feed mixture containing at least methane and one other light hydrocarbon and an acid gas capable of forming an azeotrope with said light hydrocarbon, comprising:

• a. introducing said feed mixture into a first distillation column;
• b. operating said first distillation column under conditions sufficient to produce a methane-enriched overhead and a bottoms containing the light hydrocarbon and enriched in acid gas based upon the methane and acid gas present in said feed mixture;
• c. withdrawing from the first distillation column said methane-enriched overhead;
• d. withdrawing from the first distillation column said bottoms enriched in acid gas;
• e. introducing said bottoms from the first distillation column into a second distillation column;
• f. operating said second distillation column at conditions of pressure, temperature and composition sufficient to produce an acid gas-enriched overhead stream and a light hydrocarbon-enriched bottoms based upon the acid gas and light hydrocarbon present in bottoms from said first distillation column, said conditions of temperature, pressure and composition also being sufficient normally for the formation of an acid gas/light hydrocarbon azeotrope which would limit the concentration of acid gas in said overhead stream to the azeotropic concentration, based upon a binary mixture of said acid gas and light hydrocarbon;
• g. introducing into the upper portion of said distillation column and above the point of introduction of bottoms from said first distillation column a liquid agent in an amount of greater than about 20 mole percent of the liquid agent based on the moles of liquids in the column at or below the point of introduction of the liquid agent and sufficient to provide a relative volatility of greater than 1 of said acid gas to said light hydrocarbon at or below the point of introduction of the liquid agent to provide an acid gas-enriched overhead stream having an acid gas concentration greater than the azeotropic concentration of a binary mixture of said acid gas and said light hydrocarbon;
• h. withdrawing said acid gas-enriched overhead from the second distillation column;
• and
• i. withdrawing said light hydrocarbon-enriched bottoms from the second distillation column.

A distillative separation of a hydrocarbon feed mixture containing at least methane, carbon dioxide and hydrogen sulfide, comprising:

• a. introducing said feed mixture into a first distillation column;
• b. operating said first distillation column at conditions sufficient to produce a methane-enriched overhead and a bottoms containing hydrogen sulfide and enriched in carbon dioxide based upon the methane and carbon dioxide present in said feed mixture;
• c. withdrawing from the first distillation column said methane-enriched overhead;
• d. withdrawing from the first distillation column said bottoms enriched in carbon dioxide;
• e. introducing said bottoms from the first distillation column into a second distillation column;
• f. operating said second distillation column at conditions of pressure, temperature and composition sufficient to produce a carbon dioxide-enriched overhead stream and a hydrogen sulfide-enriched bottoms stream based upon the carbon dioxide and hydrogen sulfide present in said bottoms from the first distillation column;
• g. introducing into said second distillation column at a location above the feed point thereof an agent for increasing the relative volatility of carbon dioxide to hydrogen sulfide, said agent being selected from a C.sub.3 -C.sub.6 alkane, SO.sub.2, SO.sub.3, and mixtures thereof;
• h. withdrawing from the second distillation column said carbon dioxide-enriched overhead;
• and
• i. withdrawing from the second distillation column said bottoms enriched in hydrogen sulfide.

A distillative separation of a hydrocarbon feed mixture containing methane, carbon dioxide, ethane, and at least one C.sub.3 -C.sub.6 alkane, comprising:

• a. precooling said feed mixture;
• b. introducing said precooled feed mixture into a first distillation column;
• c. operating said first distillation column at conditions of pressure, temperature and composition sufficient to produce a methane-enriched overhead and a bottoms containing ethane and C.sub.3 -C.sub.6 alkane and enriched in carbon dioxide based upon the methane and carbon dioxide present in the feed mixture, said conditions of pressure, temperature and composition creating a solids potential zone for said carbon dioxide within said first distillation column where carbon dioxide solids would normally form;
• d. introducing a liquid solids-preventing agent comprising one or more C.sub.3 -C.sub.6 alkanes into the solids potential zone in the upper portion of said first distillation column in sufficient amount to eliminate carbon dioxide solids formation in said solids potential zone;
• e. withdrawing said methane-enriched overhead;
• f. condensing a portion of said methane-enriched overhead and directing said condensed portion back to said first distillation column as reflux;
• g. withdrawing the balance of said methane-enriched overhead as methane product,
• h. withdrawing said bottoms enriched in carbon dioxide;
• i. reboiling a portion of said bottoms and redirecting it to said first distillation column;
• j. introducing the balance of bottoms from said first distillation column into a second distillation column;
• k. operating said second distillation column at conditions of pressure, temperature and composition sufficient to produce a carbon dioxide-enriched overhead stream and an ethane-enriched bottoms based upon the carbon dioxide and ethane in bottoms from said first distillation column, said conditions of pressure, temperature and composition also being sufficient normally for the formation of a carbon dioxide/ethane azeotrope which would limit the concentration of carbon dioxide in said overhead to the azeotropic concentration, based upon a binary mixture of said acid gas and said light hydrocarbon;
• l. introducing into the upper portion of said second distillation and above the point of introduction of bottoms from said first distillation column a liquid agent sufficient to provide a relative volatility of greater than 1 of said acid gas to said light hydrocarbon at or below the point of introduction of said liquid agent to provide a carbon dioxide-enriched overhead stream having a carbon dioxide concentration greater than the azeotropic concentration of a binary mixture of carbon dioxide and ethane, said agent comprising one or more C.sub.3 -C.sub.6 alkanes;
• m. withdrawing said carbon dioxide-enriched overhead from said second distillation column;
• n. condensing a portion of said carbon dioxide-enriched overhead and redirecting it to said second distillation column as reflux;
• o. withdrawing the balance of said carbon dioxide-enriched overhead as a carbon dioxide product;
• p. withdrawing said ethane-enriched bottoms from the second distillation column;
• q. reboiling a portion of said ethane-enriched bottoms and redirecting said portion back to said second distillation column;
• r. introducing the balance of said ethane-enriched bottoms from the second distillation column into a third distillation column;
• s. operating said third distillation column under conditions sufficient to produce a bottoms product enriched in a C.sub.3 -C.sub.6 alkane based upon the feed thereto;
• and
• t. recycling said bottoms product enriched in a C.sub.3 -C.sub.6 alkane from said third distillation column to both of said first distillation column as liquid solids-preventing agent and to said second distillation column as liquid agent sufficient to provide a relative volatility of greater than 1 of said carbon dioxide to said ethane therein.

A distillation separation of a hydrocarbon feed mixture containing at least methane, carbon dioxide, hydrogen sulfide and a C.sub.3 -C.sub.6 alkane, comprising:

• a. precooling said feed mixture;
• b. introducing said precooled feed mixture into a first distillation column;
• c. operating said first distillation column at conditions of pressure, temperature and composition sufficient to produce a methane-enriched overhead and a bottoms containing hydrogen sulfide and C.sub.3 -C.sub.6 alkane and enriched in carbon dioxide based upon the methane and carbon dioxide present in said feed mixture, said conditions of pressure, temperature and composition creating a solids potential zone for said carbon dioxide within said first distillation column where carbon dioxide solids would normally form;
• d. introducing a liquid solids-preventing agent comprising one or more C.sub.3 -C.sub.6 alkanes into the solids potential zone in the upper portion of said first distillation column in sufficient amount to eliminate carbon dioxide solids formation in said solids potential zone;
• e. withdrawing said methane-enriched overhead;
• f. condensing a portion of said methane-enriched overhead and directing said condensed portion back to said first distillation column as reflux;
• g. withdrawing the balance of said methane-enriched overhead as methane product;
• h. withdrawing said bottoms enriched in carbon dioxide;
• i. reboiling a portion of said bottoms and redirecting it to said first distillation column;
• j. introducing the balance of bottoms from said first distillation column into a second distillation column;
• k. operating said second distillation column at conditions of pressure, temperature and composition sufficient to produce a carbon dioxide-enriched overhead stream and a bottoms stream containing C.sub.3 -C.sub.6 alkane and enriched in hydrogen sulfide based upon the carbon dioxide and hydrogen sulfide present in bottoms from the first distillation column;
• l. withdrawing said carbon dioxide-enriched overhead stream from said second distillation column;
• m. condensing a portion of said carbon dioxide-enriched overhead and redirecting it to said second distillation column as reflux;
• n. removing the balance of carbon dioxide-enriched overhead as carbon dioxide product;
• o. withdrawing said bottoms enriched in hydrogen sulfide from said second distillation column;
• p. reboiling a portion of said hydrogen sulfide-enriched bottoms product and directing said reboiled portion back to said distillation column;
• q. introducing the balance of withdrawn hydrogen sulfide-enriched bottoms from said second distillation column into a third distillation column;
• r. operating said third distillation column under conditions sufficient to produce an overhead enriched in hydrogen sulfide and a bottoms enriched in one or more C.sub.3 -C.sub.6 alkanes based upon the hydrogen sulfide and C.sub.3 -C.sub.6 alkanes present in feed thereto;
• and
• s. recycling bottoms from said third distillation column to both of said first distillation column as liquid solids-preventing agent and to said second distillation column as agent for raising the relative volatility of carbon dioxide to hydrogen sulfide therein.