Extractive stripping of inert-rich hydrocarbon gases with a preferential physical solvent

Claim 2

In a process for treating a natural gas stream containing methane, heavier hydrocarbons, and an inert gas, an improvement comprising selectively extracting natural gas liquids from said natural gas stream with a preferential physical solvent which provides selective capability for recovery according to said selected degree of: (a) ethane in amounts ranging from 2-98%, (b) propane in amounts ranging from 2-99%, (c) butanes in amounts ranging from 2-100%, or (d) pentanes and higher molecular weight hydrocarbons in amounts ranging up to 100%, said improvement comprising the following steps: A. selecting said preferential physical solvent which is selective for ethane and heavier hydrocarbon components of said gas stream such that: (1) relative volatility of methane over ethane is at least 5.0 and the hydrocarbon loading capacity, defined as solubility of ethane in said solvent, is at leas 0.25 standard cubic feet of ethane per gallon of said solvent, or (2) the preferential factor, determined by the multiplication of relative volatility of methane over ethane by the solubility of ethane in solvent, in standard cubic feet of ethane per gallon of solvent, is at least 1.25; B. selectively extracting and stripping said natural gas stream with said physical solvent to produce an inert gas stream and a rich solvent stream containing methane and said hydrocarbons heavier than methane; and C. distilling said rich solvent stream to produce a stream of said methane and said selected hydrocarbons heavier than methane and a stream of said physical solvent.

Claim 3

In a process for selectively extracting hydrocarbons from a natural gas stream by extractive stripping with a preferential physical solvent which provides selective capability for recovery according to a selected degree of (a) ethane in amounts ranging from 2-98%, (b) propane in amounts ranging from 2-99%, (c) butane in amounts ranging from 2-100%, and (d) pentanes and higher molecular weight hydrocarbons in amounts ranging up to 100%, wherein said natural gas stream comprises methane and more than 3 mol. % of an inert gas, the improvement which comprises: A. selectively extracting and stripping said natural gas stream with said physical solvent to produce: (1) a stream of said methane and said inert gas, and (2) a rich solvent stream containing said selected hydrocarbons heavier than methane, said physical solvent being selective for ethane and heavier hydrocarbon components of said inert gas stream such that: (1) the relative volatility of methane over ethane is at least 5.0 and the hydrocarbon loading capacity, defined as solubility of ethane in solvent, is at least 0.25 standard cubic feet of ethane per gallon of solvent, or (2) the preferential factor, determined by the multiplication of relative volatility of methane over ethane by the solubility of ethane in solvent, in standard cubic feet of ethane per gallon of solvent, is at least 1.25; B. distilling said rich solvent stream to produce said selected hydrocarbons heavier than methane and said physical solvent; C. extracting and stripping said stream of said methane and said inert gas with a stream of a preferential physical solvent to produce said inert gas as an overhead stream and said methane in a rich solvent stream; and D. recovering said methane from said rich solvent stream.

Claim 4

In a process for selectively extracting hydrocarbons from a natural gas stream by extractive stripping with a preferential physical solvent which provides selective capability for recovery according to a selected degree of (a) ethane in amounts ranging from 2-98%, (b) propane in amounts ranging from 2-99%, (c) butane in amounts ranging from 2-100%, and (d) pentanes and higher molecular weight hydrocarbons in amounts ranging up to 100%, wherein said natural gas stream comprises methane and more than 3 mol. % of an inert gas, the improvement which comprises: A. selectively extracting and stripping said natural gas stream with said physical solvent to produce: (1) a stream of said methane and said inert gas, and (2) a rich solvent stream containing said selected hydrocarbons heavier than methane, said physical solvent being selective for ethane and heavier hydrocarbon components of said inert gas stream such that: (1) the relative volatility of methane over ethane is at least 5.0 and the hydrocarbon loading capacity, defined as solubility of ethane in solvent, is at least 0.25 standard cubic feet of ethane per gallon of solvent, or (2) the preferential factor, determined by the multiplication of relative volatility of methane over ethane by the solubility of ethane in solvent, in standard cubic feet of ethane per gallon of solvent, is at least 1.25; B. distilling said rich solvent stream to produce said selected hydrocarbons heavier than methane and said physical solvent; C. extracting and stripping said stream of said methane and said inert gas with a stream of a preferential physical solvent to produce said inert gas as an overhead stream and said methane in a rich solvent stream; and D. recovering said methane from said rich solvent stream.

Claim 5

In a process for the removal of hydrocarbons heavier than methane from a natural gas stream comprising methane and an inert gas, wherein a need exists for recovering said inert gas and separately recovering to any selected degree and at extremely high recoveries a selected hydrocarbon component and heavier hydrocarbons within the group consisting of ethane, propane, butanes, and pentanes, without the need simultaneously to recover hydrocarbons lighter than said selected hydrocarbon component from said natural gas stream, the improvement comprising: providing the capability of separately extracting said inert gas and said selected hydrocarbon component and heavier hydrocarbons from said natural gas stream with a preferential physical solvent according to said selected degree of (a) ethane in amounts ranging from 2-98%, (b) propane in amounts ranging from 2-99%, (c) butane in amounts ranging from 2-100%, or (d) pentanes and higher molecular weight hydrocarbons in amounts ranging up to 100% by the following steps: A. selectively extracting and stripping said natural gas stream with a stream of a preferential physical solvent, at flow rates within the range of 0.001-0.5 gallon of solvent per standard cubic foot of natural gas, to produce a stream of said inert gas as product and a rich solvent stream containing said methane and said hydrocarbons heavier than methane, said solvent being selective for ethane and heavier hydrocarbon components of said gas stream such that: (1) the relative volatility of methane over ethane is at least 5.0 and the hydrocarbon loading capacity, defined as solubility of ethane in solvent, is at least 0.25 standard cubic feet of ethane per gallon of solvent, or (2) the preferential factor determined by the multiplication of relative volatility of methane over ethane by the solubility of ethane in solvent, in standard cubic feet of ethane per gallon of solvent, is at least 1.25; B. distilling said rich solvent stream to produce said hydrocarbons as an overhead stream and said physical solvent as a bottoms stream; C. selectively extracting and stripping said overhead stream of said Step B to produce said selected hydrocarbon component and said heavier hydrocarbon components in a rich solvent stream and said methane in an overhead stream; and D. distilling said rich solvent stream to recover said solvent and produce said selected hydrocarbon components.

Claim 6

In a process for the removal of hydrocarbons heavier than methane from a natural gas stream comprising methane and an inert gas, wherein a need exists for recovering said inert gas and separately recovering to any selected degree and at extremely high recoveries a selected hydrocarbon component and heavier hydrocarbons within the group consisting of ethane, propane, butanes, and pentanes, without the need simultaneously to recover hydrocarbons lighter than said selected hydrocarbon component from said natural gas stream, the improvement comprising: providing the capability of separately extracting said inert gas and said selected hydrocarbon component and heavier hydrocarbons from said natural gas stream with a preferential physical solvent according to said selected degree of (a) ethane in amounts ranging from 2-98%, (b) propane in amounts ranging from 2-99%, (c) butane in amounts ranging from 2-100%, or (d) pentanes and higher molecular weight hydrocarbons in amounts ranging up to 100% by the following steps: A. selectively extracting and stripping said natural gas stream with a stream of a preferential physical solvent, at flow rates within the range of 0.001-0.5 gallon of solvent per standard cubic foot of natural gas, to produce a stream of said inert gas as product and a rich solvent stream containing said methane and said hydrocarbons heavier than methane, said solvent being selective for ethane and heavier hydrocarbon components of said gas stream such that: (1) the relative volatility of methane over ethane is at least 5.0 and the hydrocarbon loading capacity, defined as solubility of ethane in solvent, is at least 0.25 standard cubic feet of ethane per gallon of solvent, or (2) the preferential factor determined by the multiplication of relative volatility of methane over ethane by the solubility of ethane in solvent, in standard cubic feet of ethane per gallon of solvent, is at least 1.25; B. distilling said rich solvent stream to produce said hydrocarbons as an overhead stream and said physical solvent as a bottoms stream; C. selectively extracting and stripping said overhead stream of said Step B to produce said selected hydrocarbon component and said heavier hydrocarbon components in a rich solvent stream and said methane in an overhead stream; and D. distilling said rich solvent stream to recover said solvent and produce said selected hydrocarbon components.

Claim 7

The process of claims 1, 2 or 3, wherein said contacting of said step A is at 200-1300 psig and wherein said flow rate of said physical solvent is selectively adjusted in response to market conditions.

Claim 8

The process of claim 4, wherein additional selectivity is provided by using a reboiler and a stripping section in an extraction column for carrying out said selectively extracting and stripping of said natural gas stream with said preferential physical solvent.

Claim 9

The process of claim 5, wherein said additional degree of freedom is effectively utilized by appropriately selecting the reboiling temperature at the bottom of said column in order to produce said rich solvent stream consisting essentially of only said desirable hydrocarbons.

Claim 10

The process of claim 6, wherein said stream of undesirable hydrocarbons, flowing upwardly through said stripping section of said column, contains some desirable hydrocarbons which are recovered preferentially by mass transfer principles by transfer to said physical solvent.

Claim 11

The process of claim 7, wherein said hydrocarbons, stripped from said rich solvent, leave said stripping section of said column and join the incoming natural gas stream and flow together upwardly within said extraction section of said column, whereby said lean solvent preferentially recovers any contained desirable hydrocarbons.

Claim 12

The process of claim 8, wherein said extracting is done in separate extractive stripping (ES) columns.

Claim 13

The process of claim 9, wherein a first said ES column produces an inert gas stream, as an overhead stream, and a first rich solvent stream, at a bottoms stream, which is separated into a C 1 30 hydrocarbon stream and a first lean solvent stream by said distilling step.

Claim 14

The process of claim 10, wherein said C 1 + hydrocarbons stream is fed to a second said ES column which produces a C 1 gas product and a second rich solvent stream, containing C 2 + hydrocarbons, which is separated into a C 2 + hydrocarbons product and a second lean solvent stream by said distilling step.

Claim 15

The process of claim 11, wherein said first lean solvent stream and said second lean solvent stream are different solvents.

Claim 16

The process of claim 9, wherein a first said ES column produces an overhead mixed stream of said inert gas and said C 1 and a first rich solvent stream which is separated into a C 2 + hydrocarbon product and a first lean solvent stream.

Claim 17

The process of claim 13, wherein said mixed stream is fed to a second said ES column which produces an inert gas stream and a second rich solvent stream.

Claim 18

The process of claim 14, wherein said second rich solvent stream is separated into a C 1 gas product and a second lean solvent stream.

Claim 19

The process of claim 15, wherein said first solvent stream and said second lean solvent stream are different solvents.

Claim 20

The process of claim 15, wherein said inert gas stream and said C 1 gas product are passed through a power recovery turbine.

Claim 21

The process of claim 14, wherein said second rich solvent stream is flashed to produce a C 1 gas product stream and a solvent stream which is pumped to the top of said first ES column.

Claim 22

The process of claim 18, wherein said inert gas stream and said mixed stream are passed through a power recovery turbine.

Claim 23

The process of claim 8, wherein said rich solvent leaving the bottom of said column is let down in pressure to a pressure level that is consistent with the operation of a distillation column for conducting said distilling of said step B.

Claim 24

The process of claim 20, wherein said aromatic streams comprise a C 9 heart cut or extract of catalytically reformed naphtha which is enriched in C 9 alkylbenzenes.

Claim 25

The process of claim 21, wherein said C 9 aromatics extracted from a naphtha reformate are characterized as having an initial boiling point range of 230°-280° F., an end boiling point range of 350°-425° F., and an API gravity of 35-60.

Claim 26

The process of claim 20, wherein said rich solvent is heated before entering said distillation column in order to lower the reboiler heat load on said distillation column.

Claim 27

The process of claim 23, wherein said distillation column is a fractionation-type column which separates recovered hydrocarbons from said physical solvent.

Claim 28

The process of claim 24, wherein said recovered hydrocarbons leave the top of said distillation column and are condensed to form liquid hydrocarbon product and said lean solvent leaves the bottom of said distillation column.

Claim 29

The process of claim 25, wherein the temperature at the bottom of said distillation column is selected to ensure the recovery of all desirable hydrocarbons and is no higher than the boiling point of said physical solvent at said operating pressure.

Claim 30

The process of claim 26, wherein said column overhead is refluxed with a portion of said liquid hydrocarbon product in order to minimize loss of said physical solvent with said natural gas liquid product.

Claim 31

The process of claim 27, wherein said lean physical solvent is cooled before recycling to said step A as said preferential physical solvent.

Claim 32

The process of claim 23, wherein said rich solvent is heated by lean/rich solvent heat exchanging.

Claim 33

The process of claim 4, wherein said preferential physical solvent is selected from the group consisting of dialkyl ethers of polyalkylene glycol and streams rich in C 8 -C 10 aromatic compounds having methyl, ethyl, or propyl aliphatic groups.

Claim 34

The process of claim 4 wherein said solvent is selected from the group consisting of mesitylene, n-propyl benzene, n-butyl benzene, o-xylene, m-xylene, p-xylene, and mixtures thereof, and aromatic streams rich in mixed xylenes and other C 8 -C 10 aromatics.

Claim 35

The process of claim 31, wherein said C 8 -C 10 aromatic streams are C 9 alkylaromatics derived from gasoline producing processes.

Claim 36

The process of claim 32, wherein said C 8 -C 10 aromatic streams are C 9 alkylaromatics derived from conversion of methanol to gasoline.

Claim 37

The process of claim 32, wherein said C 8 -C 10 aromatic streams are C 9 alkylaromatics derived from conversion of syngas to gasoline.

Claim 38

The process of claim 31, wherein said C 8 -C 10 aromatic streams are C 9 alkylaromatics derived from pyrolysis of coal to produce coke.

Claim 39

The process of claim 31, wherein said C 8 -C 10 aromatic streams are alkylaromatic streams which contain substantial quantities of alkylbenzenes and are produced by petroleum processing operations selected from the group consisting of transalkylation, isomerization, and disproportionation.

Claim 40

The process of claim 1, wherein said inert gas is up to 75 mol percent nitrogen.