CA1248462A - Method and arrangement for the selective removal of acid gases from a feed gas - Google Patents
Method and arrangement for the selective removal of acid gases from a feed gasInfo
- Publication number
- CA1248462A CA1248462A CA000456889A CA456889A CA1248462A CA 1248462 A CA1248462 A CA 1248462A CA 000456889 A CA000456889 A CA 000456889A CA 456889 A CA456889 A CA 456889A CA 1248462 A CA1248462 A CA 1248462A
- Authority
- CA
- Canada
- Prior art keywords
- permeator
- feed gas
- acid gases
- gas
- hydrogen sulfide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007789 gas Substances 0.000 title claims abstract description 177
- 239000002253 acid Substances 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 33
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 58
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910000037 hydrogen sulfide Inorganic materials 0.000 claims abstract description 32
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 29
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 29
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 27
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 27
- 239000012528 membrane Substances 0.000 claims description 43
- 239000013626 chemical specie Substances 0.000 claims description 16
- 229920000642 polymer Polymers 0.000 claims description 8
- 230000003190 augmentative effect Effects 0.000 claims description 7
- 239000011148 porous material Substances 0.000 claims description 7
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 4
- 239000003054 catalyst Substances 0.000 claims description 4
- 239000003518 caustics Substances 0.000 claims description 4
- 230000009257 reactivity Effects 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 4
- 238000010408 sweeping Methods 0.000 claims description 4
- 230000000694 effects Effects 0.000 claims description 2
- 229920000914 Metallic fiber Polymers 0.000 claims 1
- 230000002401 inhibitory effect Effects 0.000 claims 1
- 229920005594 polymer fiber Polymers 0.000 claims 1
- 239000000356 contaminant Substances 0.000 abstract description 22
- 239000000126 substance Substances 0.000 abstract description 7
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 4
- 239000003345 natural gas Substances 0.000 abstract description 2
- 238000000926 separation method Methods 0.000 description 19
- 239000004215 Carbon black (E152) Substances 0.000 description 10
- 239000007788 liquid Substances 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 9
- 239000003949 liquefied natural gas Substances 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 5
- 239000000835 fiber Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 239000002861 polymer material Substances 0.000 description 2
- 238000009877 rendering Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229920001400 block copolymer Polymers 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000008246 gaseous mixture Substances 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000011344 liquid material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- -1 polyxylylene Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/144—Purification; Separation; Use of additives using membranes, e.g. selective permeation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Water Supply & Treatment (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
METHOD AND ARRANGEMENT FOR THE SELECTIVE REMOVAL OF ACID GASES FROM A FEED GAS A method for the selective removal of acid gas contaminants from a feed gas and, more particularly, for the selective removal of acid gases from a feed gas essentially comprising hydrocarbons, hydrogen sulfide and carbon dioxide, produced during oil and gas field operations. More specifically, the invention relates to a method for the selective removal of acid gas components from a flow of natural gas containing such contaminants, wherein the acid gases are selectively removed by discriminating each gas component through its chemical potential difference and by allowing the acid gases to be separated out through a suitable permeator. The invention also relates to an arrangement for the implementation of the method of selectively removing acid gases from feed gas.
Description
12484~;2 F-2254 - l -METHOD AND ARRANGEMENT FOR THE SELECTIVE
REMOVAL OF ACID GASES FROM A FEED GAS
The present invention relates to a method for the selective removal of acid gas contaminants from a feed gas and, more particularly, relates to the selective removal of acid gases from a feed gas essentially comprising hydrocarbons, hydrogen sulfide and carbon dioxide, produced during oil and gas field operations. More specifically, the invention relates to a method for the selective removal of acid gas components from a flow of natural gas containing such contaminants, wherein the acid gases are selectively removed by discriminating each gas component through its chemical potential difference and by allowing the acid gases to be separated out through a suitable permeator. The invention also relates to an arrangement for the implementation of the method of selectively removing acid gases from the feed gas.
The selective removal of gaseous contaminants from a gas flow utilizing the technological concept of permeation to effect gas separation, such as permeating various gas components through a liquid, semi-liquid or solid material membrane structure, is well known in the technology. Numerous aspects and physical applications of the gas separation technology have been extensively researched and the process is commonly referred to as "facilitated transport", which is basically a process wherein the permeation of a solute across a membrane is chemically augmented. Generally, the gas separation is effected through permeation of the various gas components or gaseous contaminants which are to be separated from a flow of a feed gas by permitting the various contaminants to selectively permeate through a liquid film which has been chemically augmented. Although considerable research has been conducted in this field and numerous patents issued in connection with the permeation technology employing facilitated transport concepts, the physical phenomena are not all fully understood or comprehended at the present time. Moreover, in the selective removal of acid gas lZ4846~
contaminants from a feed gas which essentially comprises hydrocarbons, hydrogen sulfide and carbon dioxide obtained during oil and gas field operations, and wherein the treated feed gas is to be utilized in a liquid natural gas manufacturing facility, the selective separation of hydrogen sulfide and carbon dioxide contaminant gases from the feed gas, the socalled acid gases, the passage of these acid gases through a membrane, employing facilitated transport concepts, frequently leads to considerable loss of valuable hydrocarbons from the treated feed gas effluent, with a resultant reduction in gas quality and an increase in production costs.
Extensive studies of selective gas separation techniques employing facilitated transport have been conducted in industry and at various universities. The studies have related to different physical and potential practical applications of these selective gas separation techniques. This is shown in the following publications which relate to the use of membranes consisting of chemically augmented polymer materials:
1) Science, Vol. 156, 1481-83
REMOVAL OF ACID GASES FROM A FEED GAS
The present invention relates to a method for the selective removal of acid gas contaminants from a feed gas and, more particularly, relates to the selective removal of acid gases from a feed gas essentially comprising hydrocarbons, hydrogen sulfide and carbon dioxide, produced during oil and gas field operations. More specifically, the invention relates to a method for the selective removal of acid gas components from a flow of natural gas containing such contaminants, wherein the acid gases are selectively removed by discriminating each gas component through its chemical potential difference and by allowing the acid gases to be separated out through a suitable permeator. The invention also relates to an arrangement for the implementation of the method of selectively removing acid gases from the feed gas.
The selective removal of gaseous contaminants from a gas flow utilizing the technological concept of permeation to effect gas separation, such as permeating various gas components through a liquid, semi-liquid or solid material membrane structure, is well known in the technology. Numerous aspects and physical applications of the gas separation technology have been extensively researched and the process is commonly referred to as "facilitated transport", which is basically a process wherein the permeation of a solute across a membrane is chemically augmented. Generally, the gas separation is effected through permeation of the various gas components or gaseous contaminants which are to be separated from a flow of a feed gas by permitting the various contaminants to selectively permeate through a liquid film which has been chemically augmented. Although considerable research has been conducted in this field and numerous patents issued in connection with the permeation technology employing facilitated transport concepts, the physical phenomena are not all fully understood or comprehended at the present time. Moreover, in the selective removal of acid gas lZ4846~
contaminants from a feed gas which essentially comprises hydrocarbons, hydrogen sulfide and carbon dioxide obtained during oil and gas field operations, and wherein the treated feed gas is to be utilized in a liquid natural gas manufacturing facility, the selective separation of hydrogen sulfide and carbon dioxide contaminant gases from the feed gas, the socalled acid gases, the passage of these acid gases through a membrane, employing facilitated transport concepts, frequently leads to considerable loss of valuable hydrocarbons from the treated feed gas effluent, with a resultant reduction in gas quality and an increase in production costs.
Extensive studies of selective gas separation techniques employing facilitated transport have been conducted in industry and at various universities. The studies have related to different physical and potential practical applications of these selective gas separation techniques. This is shown in the following publications which relate to the use of membranes consisting of chemically augmented polymer materials:
1) Science, Vol. 156, 1481-83
2) Ind. Eng. Chem., Process Des. Dev., Vol. 16, Nb. 3, 1977, 370-4.
3) AIChE Journal, Vol. 16, Nb. 3, 197û, 405-10.
4) AIChE Journal, Vol. 25, No. 1, 1979, 197-202.
5) AIChE Journal, Vol. 26, No. 1, 1980, 112-120.
Other feasibility studies involving facilitated transport have been conducted at various universities; for instance, the University of Michigan, Ann Arbor, Michigan, as reported in the AICHE Journal, May 1974, Volume 20, No. 3, pages 417 through 445;
the AICHE Journal, July 1974, Volume 20, No. 4, Pages 625 through 645; and the economic aspects as applied to the field of biotechnology, gas separation, metal extraction and other related technical areas, in the November 8, 1982 issue of Chemical &
Engineering News, pages 7 through 12. All of these publications indicate that although extensive research has been conducted in connection with selective gas separation through the employment of ~24~34~i~
F-2254 ~ 3 ~
facilitated transport techniques, at this time none of these techniques have found any extensive commercial application and, apparently, are still in the experimental and laboratory stages of research.
Furthermore, although a number of patents have issued which are directed at the concept of selective gas separation through the utilization of facilitated transport techniques, these are primarily directed at relatively fundamental concepts and do not disclose the practical applications of these gas separation techniques, particularly with respect to the aspect of selectively removing acid gases, such as hydrogen sulfide and carbon dioxide, from a hydrocarbon feed gas flow as derived from oil and gas field operations and explorations without the loss of significant amounts of hydrocarbons and wherein the treated gas effluent is adapted to be further processed in a liquid natural gas manufacturing facility.
U.S. Patent No. 4,147,754 discloses a system for the selective removal of hydrogen sulfide from a mixture of gases, wherein a feed gas containing the hydrogen sulfide is conveyed through an immobilized liquid membrane providing for the facilitated transport of the hydrogen sulfide out of the gases while retaining carbon dioxide predicated on the system exhibiting a low permeability to carbon dioxide and a high permeability to hydrogen sulfide. Although the system described in this patent will readily facilitate the permeation or facilitated transport of hydrogen sulfide so as to separate out of a feed gas flow, the use of the immobilized liquid membrane as described herein will still retain the carbon dioxide acid gas component or contaminant in the feed gas and, moreover, will result in an appreciable degree of permeation and extensive concurrent loss of valuable hydrocarbons from any feed gas derived from oil and gas field operations, thereby rendering the techniques involved herein uneconomical with respect to such applications.
A similar concept is disclosed in U.S. No. Patent 4,089,653 wherein hydrogen sulfide is separated from a mixture of gases which include carbon dioxide, and wherein the immobilized liquid membrane F-2254 _ 4 _ 12484~i2 essentially corresponds in concept and use with that disclosed in U.S. Patent No. 4,147,754.
U.S. Patent No. 3,780,496 discloses the selective permeation of gases through a permselective rnembrane which is constituted of a sulfonated polyxylylene oxide in order to separate helium, hydrogen and oxygen from gas mixtures containing those elements. The particular membrane structure disclosed and described herein would not be appliable to the selective removal of hydrogen sulfide and carbon dioxide from a hydrocarbon feed gas containing such acid gases as derived in oil and gas field operations.
U.S. Patent No. 3,729,400 relates of a method to separating mixtures of gases employing a confined liquid membrane having an electrode in contact with each surface thereof, and provided with a concentration of a non-volatile transporting chemical specie in solution, wherein the specie is adapted to be either oxidized or reduced from a first to a second valence state. This will propagate the permeation of a specific gas element coming into contact with one surface of such a liquid membrane by means of an electrical potential which is produced across the electrodes, and thus allow for the selective permeation through the membrane of different gas components. There is no disclosure that this type of membrane is adapted for the permeation of acid gases, such as hydrogen sulfide and carbon dioxide, from a hydrocarbon feed gas in a mode as contemplated by the present invention. A similar method encompassing facilitated transport by means of an immobilized liquid membrane is disclosed in U.S. Patent No. 3,676,220, of which the hereinabove discussed U. S. Patent No. 3,729,400 is a divisional application.
U.S. Patent No. 3,653,180 discloses a block copolymer 3() membrane for the separation of polar gas contaminants from gaseous mixtures, wherein the gas mixture is conducted through a non-porous membrane constituted of a block polymer, and wherein particular polar gases or vapors of the gas mixtures may include hydrogen sulfide. However, there is no disclosure of a permeator for selectively removing hydrogen sulfide and carbon dioxide contaminant F-2254 ~ 5 ~
gases from a hydrocarbon feed gas without the permeation and resultant loss of any significant amounts of hydrocarbon, so as to adapt the membrane to the acid gas removal from feed gases derived from oil field operations, and in which such feed gas effluents are transportable to a liquid natural gas manufacturing facility for further processing thereof.
U.S. Patent No. 3,396,510 discloses an immobilized liquid membrane for use in the selective separation of gases through facilitated transport for the removal of carbon dioxide, hydrogen sulfide and oxygen gases from a gas mixture. However, the immobilized liquid membrane employed herein would not appear to be adapted to prevent the permeation through the membrane and loss of significant quantities of hydrocarbons from a hydrocarbon feed gas, thereby resulting in lower efficiencies and higher costs for the treated feed gas effluent.
In general, the facilitated transport processes and gas separation systems presently employed in the technology utilize gas permeation techniques wherein, for the gas separation, a substantial pressure differential is generated across the permeator or membrane which, in turn, causes the permeation and resultant loss of a significant proportion of valuable hydrocarbons from a hydrocarbon feed gas in conjunction with the separation out of any acid gases, such as hydrogen sulfide and carbon dioxide, and thereby renders the prior art processes uneconomical for large-scale commercial operations.
Pccordingly, the invention proposes to improve upon the selective separation of acid gas contaminants, such as hydrogen sulfide and carbon dioxide, from a feed gas flow essentially comprised of hydrocarbons and such acid gas contaminants, for example, a feed gas obtained during oil and gas field operations, and wherein the feed gas is adapted to be further processed in a liquid natural gas manufacturing facility.
The invention contemplates employment of the basic technology of facilitated transport in selectively separating the hydrogen sulfide and carbon dioxide acid gas components from the ~248~6;~
feed gas through the intermediary of a permeator which consists of a porous membrane having a chemical specie immobilized in the pores thereof in order to augment the permeation therethrough of the acid gases; in essence, the hydrogen sulfide and carbon dioxide.
Concurrently, the membrane inhibits the through-passage of the valuable hydrocarbons which are contained in the feed gas so as to essentially allow for the formation of a relative pure feed gas effluent without significant hydrocarbon losses, which is then directed the liquid natural gas manufacturing facility in a highly efficient and economical manner.
~ith respect to the foregoing, the acid gases which are separated in the permeator from the feed gas may be removed through the intermediary of a flow of air which is passed through the permeator or, alternatively, removed from the permeator through physically soluble solutions, by sweeping of the permeator with steam, or through the action of chemically reactive solutions.
In a more specific aspect of the invention, the permeator for removing the acid gas contaminants from the feed gas flow consists of a porous membrane which has the pores thereof provided with a chemical specie which is immobilized therein, and wherein the membrane may be constituted of a polymer material in the form of one or more porous polymer sheets, porous hollow polymer tubes or fibers or, alternatively, constituted of porous hollow metallic sheets or porous metallic tubes or fibers. The chemical species which are immobilized in the pores of the membrane may be constituted any one or a combination of chemical species such as alkanolamines, physical solvents for carbon dioxide and/or hydrogen sulfide, and reactive chemicals such as carbonates and caustics which are reactive with carbon dioxide and hydrogen sulfide. If desired, the reactivity of these chemical species may be further augmented with the aid of catalysts to still further enhance the rate of separation and permeation of the acid gases.
Referring now in detail to the single figure of drawing which is illustrative of a schematic representation of the inventive acid gas separating arrangement for selectively removing acid gas contaminants, such as hydrogen sulfide and/or carbon dioxide, from a feed gas flow essentially comprising hydrocarbons and the acid gas contaminants, for instance a feed gas flow derived from oil and gas field operations, which is adapted to be possessed and liquefied in a liquid natural gas manufacturing facility.
Basically, the arrangement 10 includes a first gas infeed conduit 12 wherein a continual flow of a feed gas is conducted in the direction of the arrow from, for example an oil and gas field operation. The feed gas substantially comprises hydrocarbons and significant amounts of acid gas contaminants, such as hydrogen sulfide and/or carbon dioxide. The gas infeed conduit 12 connects into a permeator 14, which in accordance with the invention, incorporates porous membranes 16 adapted to permit the acid gas contaminants to selectively permeate therethrough. The permeator membranes 16 consists of one or more polymer or metallic porous sheets, or may be constituted of polymer or metallic hollow tubes or fibers. Immobilized within the pores of each of the membranes 16 is a suitable chemical specie, such as an alkanolamine, physical solvents for carbon dioxide and/or hydrogen sulfide, or reactive chemicals such as carbonates and caustics whic~ are reactive with carbon dioxide and hydrogen sulfide, and which will enhance the permeation of these acid gas contaminants through the membranes towards an outlet conduit 18. The reactivity of these chemical species may, if desired, be also augmented with the aid of suitable catalysts.
An air blower 20 receiving a supply of air from an inlet conduit 22 communicates through a further conduit 24 with the permeator 14 so as to cause the flow of air to expel the permeated and selectively separated acid gas components through the porous membranes towards the acid gas discharge conduit 18, while allowing the treated feed gas effluent to be discharged from the permeator 14 into the outlet conduit 26 for further processing, such as in a liquid natural gas manufacturing facility.
Pursuant to the invention, the permeator operates whereby the outlet conduit 26 is at a pressure which is practically - \
12~8~62 identical with the pressure of the feed gas flow in the inlet conduit 23 inasmuch as the permeator 14 does not operate on a difference in pressure across the membrane phase of the permeator, but rather utilizes the chemical species which are immobilized in 5 the membrane pores to provide for the permeation and selective separation of the acid gas contaminants from the feed gas.
Furthermore, the utilization of the permeator in the form of porous polymer or metallic membranes having the chemical species immobilized therein inhibits the permeation of any significant amounts of hydrocarbons from the feed gas along with the separated acid gases, and thus facilitates that practically all of the hydrocarbon components in the feed gas flow are recovered in the treated feed gas effluent being discharged into outlet conduit 26, thereby rendering the entire operation efficient and economical.
Furthermore, the permeator provides for an arrangement which requires less energy for its operation and thus becomes even more economical in use.
In lieu of the air blower 20, the selectively separated and permeated acid gases may be removed from the permeator 14 in physically soluble solutions, by sweeping of the permeator with steam, or through the intermediary of chemically reactive solutions.
Cenerally, although not necessarily, the entire process is effectuated in a substantially isothermal manner and at an essentially constant pressure with regard to the inlet feed gas conditions in the conduit 12. Furthermore, it is assumed that the output conditions of the feed gas effluent in the outlet conduit 26 are at the same temperatures and pressures as those of the inlet feed conditions. Conceivably, although not limited thereto, such feed gas pressure may be within the range from atmospheric pressure up to about 48263.3 kPa (7000 psia), and at temperatures of from about -73.3C to 204C (-100F to 400F).
Although the invention has been described with regard to the separation of acid gas contaminants from a hydrocarbon feed gas which is to be utilized in a liquid natural gas manufacturing facility, the acid gases being selectively separated from the feed ~248~6Z
F-2254 ~ 9 ~
gas by discriminating each gas component through its chemical potential difference7 other applications may readily suggest themselves to one skilled in the art besides those of gas streams in oil and gas field operations. Thus, the invention may be readily applied to other gas flows in chemical and refinery plants and can readily compete with present permeation processes as well as with conventional acid gas removing processes, with the additional advantage of affording a considerably lower energy consumption.
Other feasibility studies involving facilitated transport have been conducted at various universities; for instance, the University of Michigan, Ann Arbor, Michigan, as reported in the AICHE Journal, May 1974, Volume 20, No. 3, pages 417 through 445;
the AICHE Journal, July 1974, Volume 20, No. 4, Pages 625 through 645; and the economic aspects as applied to the field of biotechnology, gas separation, metal extraction and other related technical areas, in the November 8, 1982 issue of Chemical &
Engineering News, pages 7 through 12. All of these publications indicate that although extensive research has been conducted in connection with selective gas separation through the employment of ~24~34~i~
F-2254 ~ 3 ~
facilitated transport techniques, at this time none of these techniques have found any extensive commercial application and, apparently, are still in the experimental and laboratory stages of research.
Furthermore, although a number of patents have issued which are directed at the concept of selective gas separation through the utilization of facilitated transport techniques, these are primarily directed at relatively fundamental concepts and do not disclose the practical applications of these gas separation techniques, particularly with respect to the aspect of selectively removing acid gases, such as hydrogen sulfide and carbon dioxide, from a hydrocarbon feed gas flow as derived from oil and gas field operations and explorations without the loss of significant amounts of hydrocarbons and wherein the treated gas effluent is adapted to be further processed in a liquid natural gas manufacturing facility.
U.S. Patent No. 4,147,754 discloses a system for the selective removal of hydrogen sulfide from a mixture of gases, wherein a feed gas containing the hydrogen sulfide is conveyed through an immobilized liquid membrane providing for the facilitated transport of the hydrogen sulfide out of the gases while retaining carbon dioxide predicated on the system exhibiting a low permeability to carbon dioxide and a high permeability to hydrogen sulfide. Although the system described in this patent will readily facilitate the permeation or facilitated transport of hydrogen sulfide so as to separate out of a feed gas flow, the use of the immobilized liquid membrane as described herein will still retain the carbon dioxide acid gas component or contaminant in the feed gas and, moreover, will result in an appreciable degree of permeation and extensive concurrent loss of valuable hydrocarbons from any feed gas derived from oil and gas field operations, thereby rendering the techniques involved herein uneconomical with respect to such applications.
A similar concept is disclosed in U.S. No. Patent 4,089,653 wherein hydrogen sulfide is separated from a mixture of gases which include carbon dioxide, and wherein the immobilized liquid membrane F-2254 _ 4 _ 12484~i2 essentially corresponds in concept and use with that disclosed in U.S. Patent No. 4,147,754.
U.S. Patent No. 3,780,496 discloses the selective permeation of gases through a permselective rnembrane which is constituted of a sulfonated polyxylylene oxide in order to separate helium, hydrogen and oxygen from gas mixtures containing those elements. The particular membrane structure disclosed and described herein would not be appliable to the selective removal of hydrogen sulfide and carbon dioxide from a hydrocarbon feed gas containing such acid gases as derived in oil and gas field operations.
U.S. Patent No. 3,729,400 relates of a method to separating mixtures of gases employing a confined liquid membrane having an electrode in contact with each surface thereof, and provided with a concentration of a non-volatile transporting chemical specie in solution, wherein the specie is adapted to be either oxidized or reduced from a first to a second valence state. This will propagate the permeation of a specific gas element coming into contact with one surface of such a liquid membrane by means of an electrical potential which is produced across the electrodes, and thus allow for the selective permeation through the membrane of different gas components. There is no disclosure that this type of membrane is adapted for the permeation of acid gases, such as hydrogen sulfide and carbon dioxide, from a hydrocarbon feed gas in a mode as contemplated by the present invention. A similar method encompassing facilitated transport by means of an immobilized liquid membrane is disclosed in U.S. Patent No. 3,676,220, of which the hereinabove discussed U. S. Patent No. 3,729,400 is a divisional application.
U.S. Patent No. 3,653,180 discloses a block copolymer 3() membrane for the separation of polar gas contaminants from gaseous mixtures, wherein the gas mixture is conducted through a non-porous membrane constituted of a block polymer, and wherein particular polar gases or vapors of the gas mixtures may include hydrogen sulfide. However, there is no disclosure of a permeator for selectively removing hydrogen sulfide and carbon dioxide contaminant F-2254 ~ 5 ~
gases from a hydrocarbon feed gas without the permeation and resultant loss of any significant amounts of hydrocarbon, so as to adapt the membrane to the acid gas removal from feed gases derived from oil field operations, and in which such feed gas effluents are transportable to a liquid natural gas manufacturing facility for further processing thereof.
U.S. Patent No. 3,396,510 discloses an immobilized liquid membrane for use in the selective separation of gases through facilitated transport for the removal of carbon dioxide, hydrogen sulfide and oxygen gases from a gas mixture. However, the immobilized liquid membrane employed herein would not appear to be adapted to prevent the permeation through the membrane and loss of significant quantities of hydrocarbons from a hydrocarbon feed gas, thereby resulting in lower efficiencies and higher costs for the treated feed gas effluent.
In general, the facilitated transport processes and gas separation systems presently employed in the technology utilize gas permeation techniques wherein, for the gas separation, a substantial pressure differential is generated across the permeator or membrane which, in turn, causes the permeation and resultant loss of a significant proportion of valuable hydrocarbons from a hydrocarbon feed gas in conjunction with the separation out of any acid gases, such as hydrogen sulfide and carbon dioxide, and thereby renders the prior art processes uneconomical for large-scale commercial operations.
Pccordingly, the invention proposes to improve upon the selective separation of acid gas contaminants, such as hydrogen sulfide and carbon dioxide, from a feed gas flow essentially comprised of hydrocarbons and such acid gas contaminants, for example, a feed gas obtained during oil and gas field operations, and wherein the feed gas is adapted to be further processed in a liquid natural gas manufacturing facility.
The invention contemplates employment of the basic technology of facilitated transport in selectively separating the hydrogen sulfide and carbon dioxide acid gas components from the ~248~6;~
feed gas through the intermediary of a permeator which consists of a porous membrane having a chemical specie immobilized in the pores thereof in order to augment the permeation therethrough of the acid gases; in essence, the hydrogen sulfide and carbon dioxide.
Concurrently, the membrane inhibits the through-passage of the valuable hydrocarbons which are contained in the feed gas so as to essentially allow for the formation of a relative pure feed gas effluent without significant hydrocarbon losses, which is then directed the liquid natural gas manufacturing facility in a highly efficient and economical manner.
~ith respect to the foregoing, the acid gases which are separated in the permeator from the feed gas may be removed through the intermediary of a flow of air which is passed through the permeator or, alternatively, removed from the permeator through physically soluble solutions, by sweeping of the permeator with steam, or through the action of chemically reactive solutions.
In a more specific aspect of the invention, the permeator for removing the acid gas contaminants from the feed gas flow consists of a porous membrane which has the pores thereof provided with a chemical specie which is immobilized therein, and wherein the membrane may be constituted of a polymer material in the form of one or more porous polymer sheets, porous hollow polymer tubes or fibers or, alternatively, constituted of porous hollow metallic sheets or porous metallic tubes or fibers. The chemical species which are immobilized in the pores of the membrane may be constituted any one or a combination of chemical species such as alkanolamines, physical solvents for carbon dioxide and/or hydrogen sulfide, and reactive chemicals such as carbonates and caustics which are reactive with carbon dioxide and hydrogen sulfide. If desired, the reactivity of these chemical species may be further augmented with the aid of catalysts to still further enhance the rate of separation and permeation of the acid gases.
Referring now in detail to the single figure of drawing which is illustrative of a schematic representation of the inventive acid gas separating arrangement for selectively removing acid gas contaminants, such as hydrogen sulfide and/or carbon dioxide, from a feed gas flow essentially comprising hydrocarbons and the acid gas contaminants, for instance a feed gas flow derived from oil and gas field operations, which is adapted to be possessed and liquefied in a liquid natural gas manufacturing facility.
Basically, the arrangement 10 includes a first gas infeed conduit 12 wherein a continual flow of a feed gas is conducted in the direction of the arrow from, for example an oil and gas field operation. The feed gas substantially comprises hydrocarbons and significant amounts of acid gas contaminants, such as hydrogen sulfide and/or carbon dioxide. The gas infeed conduit 12 connects into a permeator 14, which in accordance with the invention, incorporates porous membranes 16 adapted to permit the acid gas contaminants to selectively permeate therethrough. The permeator membranes 16 consists of one or more polymer or metallic porous sheets, or may be constituted of polymer or metallic hollow tubes or fibers. Immobilized within the pores of each of the membranes 16 is a suitable chemical specie, such as an alkanolamine, physical solvents for carbon dioxide and/or hydrogen sulfide, or reactive chemicals such as carbonates and caustics whic~ are reactive with carbon dioxide and hydrogen sulfide, and which will enhance the permeation of these acid gas contaminants through the membranes towards an outlet conduit 18. The reactivity of these chemical species may, if desired, be also augmented with the aid of suitable catalysts.
An air blower 20 receiving a supply of air from an inlet conduit 22 communicates through a further conduit 24 with the permeator 14 so as to cause the flow of air to expel the permeated and selectively separated acid gas components through the porous membranes towards the acid gas discharge conduit 18, while allowing the treated feed gas effluent to be discharged from the permeator 14 into the outlet conduit 26 for further processing, such as in a liquid natural gas manufacturing facility.
Pursuant to the invention, the permeator operates whereby the outlet conduit 26 is at a pressure which is practically - \
12~8~62 identical with the pressure of the feed gas flow in the inlet conduit 23 inasmuch as the permeator 14 does not operate on a difference in pressure across the membrane phase of the permeator, but rather utilizes the chemical species which are immobilized in 5 the membrane pores to provide for the permeation and selective separation of the acid gas contaminants from the feed gas.
Furthermore, the utilization of the permeator in the form of porous polymer or metallic membranes having the chemical species immobilized therein inhibits the permeation of any significant amounts of hydrocarbons from the feed gas along with the separated acid gases, and thus facilitates that practically all of the hydrocarbon components in the feed gas flow are recovered in the treated feed gas effluent being discharged into outlet conduit 26, thereby rendering the entire operation efficient and economical.
Furthermore, the permeator provides for an arrangement which requires less energy for its operation and thus becomes even more economical in use.
In lieu of the air blower 20, the selectively separated and permeated acid gases may be removed from the permeator 14 in physically soluble solutions, by sweeping of the permeator with steam, or through the intermediary of chemically reactive solutions.
Cenerally, although not necessarily, the entire process is effectuated in a substantially isothermal manner and at an essentially constant pressure with regard to the inlet feed gas conditions in the conduit 12. Furthermore, it is assumed that the output conditions of the feed gas effluent in the outlet conduit 26 are at the same temperatures and pressures as those of the inlet feed conditions. Conceivably, although not limited thereto, such feed gas pressure may be within the range from atmospheric pressure up to about 48263.3 kPa (7000 psia), and at temperatures of from about -73.3C to 204C (-100F to 400F).
Although the invention has been described with regard to the separation of acid gas contaminants from a hydrocarbon feed gas which is to be utilized in a liquid natural gas manufacturing facility, the acid gases being selectively separated from the feed ~248~6Z
F-2254 ~ 9 ~
gas by discriminating each gas component through its chemical potential difference7 other applications may readily suggest themselves to one skilled in the art besides those of gas streams in oil and gas field operations. Thus, the invention may be readily applied to other gas flows in chemical and refinery plants and can readily compete with present permeation processes as well as with conventional acid gas removing processes, with the additional advantage of affording a considerably lower energy consumption.
Claims (22)
1. A method for the selective removal of acid gases from a flow of feed gas substantially comprising hydrocarbons and acid gases comprising carbon dioxide and hydrogen sulfide, comprising conducting a flow of the feed gas through a permeator having at least one chemical species selected from the group consisting of alkanolamine, physical solvents for carbon dioxide and hydrogen sulfide, or carbonates and caustics which are chemically reactive with carbon dioxide and hydrogen sulfide immobilized therein to effect the permeation of the acid gases while substantially inhibiting the permeation of hydrocarbons from the feed gas so as to selectively separate the acid gases from the permeator in a flow separate from an effluent flow of treated feed gas discharged from the permeator.
2. A method as claimed in Claim 1, wherein the permeator comprises a porous membrane, the chemical species being immobilized in the pores of the membrane.
3. A method as claimed in Claim 1, comprising separating the acid gases from the feed gas in the permeator substantially isothermally and at an essentially constant pressure relative to the inlet conditions of the feed gas.
4. A method as claimed in Claim 1, comprising conveying the feed gas to the permeator at pressures within the range of from atmospheric pressure to 48263.3 kPa, and at temperatures within the range of -73.3°C to 204.4°C.
5. A method as claimed in Claim 1, comprising conducting a flow of air through the permeator to expel the separated acid gases from the permeator.
6. A method as claimed in Claim 1, comprising removing the separated acid gases from the permeator through the intermediary of physically soluble solutions.
7. A method as claimed in Claim 1, comprising removing the separated acid gases from the permeator through the intermediary of chemically active solutions.
8. A method as claimed in Claim 1, comprising removing the separated acid gases from the permeator by sweeping the permeator with steam.
9. A method as claimed in Claim 1, comprising augmenting the reactivity of the chemical species with at least one catalyst.
10. An apparatus for the selective removal of acid gases comprising carbon dioxide and hydrogen sulfide from a feed gas substantially comprising hydrocarbons and the acid gases; comprising a permeator having at least one chemical species selected from the group consisting of alkanolamine, physical solvents for carbon dioxide and hydrogen sulfide, or carbonates and caustics which are chemically reactive with carbon dioxide and hydrogen sulfide immobilized therein adapted to facilitate the permeation of the acid gases while substantially inhibitng the permeation of the hydrocarbons from the feed gas so as to selectively separate the acid gases from the feed gas;
means for conducting a flow of the feed gas into the permeator; and means for removing the separated acid gases from the permeator in a flow separate from an effluent flow of treated feed gas discharged from the permeator.
means for conducting a flow of the feed gas into the permeator; and means for removing the separated acid gases from the permeator in a flow separate from an effluent flow of treated feed gas discharged from the permeator.
11. An apparatus as claimed in Claim 10, wherein the permeator separates said acid gases substantially isothermally from the feed gas at an essentially constant pressure relative to the inlet conditions of the feed gas.
12. An apparatus as claimed in Claim 10, wherein the permeator comprises a porous membrane, the chemical species being immobilized in the pores of the membrane.
13. An apparatus as claimed in Claim 10, comprising conveying the feed gas to the permeator at pressures within the range of atmospheric pressure to 48263.3 kPa, and at temperatures in the range of -73.3 to 204.4°C.
14. An apparatus as claimed in Claim 10, the means for removing the separated acid gases from the permeator comprising a blower for passing a flow of air through the permeator.
15. An apparatus as claimed in Claim 1, comprising means for sweeping the permeator with steam for removing the separated acid gases from the permeator.
16. An apparatus as claimed in Claim 12, comprising catalysts for augmenting the reactivity of the chemical species in the permeator.
17. An apparatus as claimed in Claim 12, the porous membrane comprising at least one porous polymer sheet.
18. An apparatus as claimed in Claim 12, the porous membrane comprising a plurality of porous, hollow polymer tubes.
19. An apparatus as claimed in Claim 12, the porous membrane comprising a plurality of porous polymer fibers.
20. An apparatus as claimed in Claim 12, the porous membrane comprising at least one porous metallic sheet.
21. An apparatus as claimed in Claim 12, the porous membrane comprising a plurality of porous hollow metallic tubes.
22. An apparatus as claimed in Claim 12, the porous membrane comprising a plurality of porous metallic fibres.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50691883A | 1983-06-22 | 1983-06-22 | |
| US506,918 | 1984-06-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1248462A true CA1248462A (en) | 1989-01-10 |
Family
ID=24016480
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456889A Expired CA1248462A (en) | 1983-06-22 | 1984-06-19 | Method and arrangement for the selective removal of acid gases from a feed gas |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1248462A (en) |
| DE (1) | DE3422941A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5149340A (en) * | 1991-03-12 | 1992-09-22 | Marathon Oil Company | Process and apparatus for separating impurities from hydrocarbons |
| DE4109267C1 (en) * | 1991-03-21 | 1992-10-08 | Still Otto Gmbh, 4630 Bochum, De | Hydrogen sulphide, ammonia and hydrogen cyanide absorption from process gas - by using circulating wash contg. aq. ammonium soln. and clean water and working up loaded absorption soln. obtd. from hydrogen sulphide absorber by reverse osmosis |
-
1984
- 1984-06-19 CA CA000456889A patent/CA1248462A/en not_active Expired
- 1984-06-20 DE DE19843422941 patent/DE3422941A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE3422941A1 (en) | 1985-01-03 |
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