CA2108892A1 - Treatment of acid gas using hybrid membrane separation systems - Google Patents
Treatment of acid gas using hybrid membrane separation systemsInfo
- Publication number
- CA2108892A1 CA2108892A1 CA002108892A CA2108892A CA2108892A1 CA 2108892 A1 CA2108892 A1 CA 2108892A1 CA 002108892 A CA002108892 A CA 002108892A CA 2108892 A CA2108892 A CA 2108892A CA 2108892 A1 CA2108892 A1 CA 2108892A1
- Authority
- CA
- Canada
- Prior art keywords
- membrane
- membranes
- hydrogen sulfide
- acid gas
- dehydration
- 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.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/02—Preparation of sulfur; Purification
- C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
- C01B17/0404—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process
- C01B17/0408—Pretreatment of the hydrogen sulfide containing gases
-
- 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
- B01D53/22—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 diffusion
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/16—Hydrogen sulfides
- C01B17/167—Separation
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
Abstract
2108892 9220431 PCTABS00017 A system and method for separating acid gas from natural gas which utilizes a hybrid membrane system comprising a hydrogen sulfide membrane assembly, an acid gas membrane assembly, and, optionally, a dehydration membrane assembly. This hybrid membrane system is preferably used together with a means for converting the separated hydrogen sulfide into elemental sulfur, i.e., a Claus sulfur plant. The hydrogen sulfide membrane assembly preferably comprises a gel polymer membrane, molten salt membrane and/or rubber copolymer membrane. The acid gas membrane assembly preferably comprises a cellulose acetate membrane, polyimide membrane, polysiloxane membrane, and/or pyrolone membrane. The dehydration membrane assembly preferably comprises a polysiloxane membrane.
Description
~092/20431 PCT/USg2/0402~ .
2 ~ 9 2 TKEATM~NT OF ACID C.AS USING_~YBRID
~M~A~X_~PARATION SYS~EMS -~
"
The present invention relates generally to the use of various hybrid me~brane separa~ion systems to separate hydrogen sulfide and carbon dioxide f~om natural gas feedstream~. In particulax, th~ hybrid membrane separation systems ~ombine an acid gas membrane system and at least one hydrogen sulfide m~brane sys~em in various configurations to provide for the separation of acid gas and concentration of hydrogen sulfide from a natural gas feedstream such that a hydrocarbon-rich retentate can be ~ent directly to a pipeline and wh~rein the r~sultant hydrogen sulfide-rich permeate stream is s~atisfactory for use in a Claus sulfur plant.
BACRÇRn~MD OF~T~E_IN~ ON
Mixtures of hydrogen sulfide with other gases, such as carbon dioxide and ~etha~e, are found in a number of gas str~ams. ~or exampIe, mixtures o~ hydrogen sul~ide, car~on dioxide, water, and methane are found in natural gases.
U.S. pipeline specifications for natural gas onl~y permi~ 2%
carbon dioxide and 4 ppm hydrogen sulfide. Therefore, it is necessary to remove hydrogen sulfide and carbon dioxide (also referred to as "acid gas") from the gas mixtures for the purpose of purif ying the gas mixture or recovering the WO92/~0431 PCT/USg2/W0~6 2~88~ 2 acid gas. Also, lt is often necessary to purify a gaseous :
hydrocarbon stream to produce sweet, dry gas which will not .
poison certain catalysts and which can meet the usual -.
pipeline specifications. It is also highly desirable to recover the hydrogen sulfide as a source of ~lemental sulfur. That is, during the separation of hydrogen sulfide from sour natural gas, it is desirable to selectively separate the hydrogen sulfide without removing all of the carbon dioxide. Usually, the separated hydr~gen sulfide and .portion of the carbon dioxide are deliv~red to a Claus sulfur plant for conversion to elemental sulfur.
Typical natural gas processing plant flow sheets are set forth in Figs. l and 2, attached hereto. Fig.~l depicts ~:.
a natural gas process wherein sour natural gas. is fed to a gas/li~uor separa:tion unit lO and the resultant gase~us product is sent to an amine absorption or cryogenic fractionation unlt 12 for the purpose of removing hydrogen sulfide and carbon dioxide from the gas. Amine absorption unit 12 separates the components and delivers hydrogen sulfide to Claus sulfur plant 14, carbon dioxide to compressor 16, and methane to dehydration unit 18. Claus sulfur plant 14 produces elemental sulfur which is sent to storage facility 20 and tail gases which are sent to cleanup unit 22. The methane which has been dehydrated in dehydration unit 1~ is sent to nitrogen rej ection unit 24 wher~in helium is recovered. The methane is then compressed WO92/20431 PCT/US92/~026
~M~A~X_~PARATION SYS~EMS -~
"
The present invention relates generally to the use of various hybrid me~brane separa~ion systems to separate hydrogen sulfide and carbon dioxide f~om natural gas feedstream~. In particulax, th~ hybrid membrane separation systems ~ombine an acid gas membrane system and at least one hydrogen sulfide m~brane sys~em in various configurations to provide for the separation of acid gas and concentration of hydrogen sulfide from a natural gas feedstream such that a hydrocarbon-rich retentate can be ~ent directly to a pipeline and wh~rein the r~sultant hydrogen sulfide-rich permeate stream is s~atisfactory for use in a Claus sulfur plant.
BACRÇRn~MD OF~T~E_IN~ ON
Mixtures of hydrogen sulfide with other gases, such as carbon dioxide and ~etha~e, are found in a number of gas str~ams. ~or exampIe, mixtures o~ hydrogen sul~ide, car~on dioxide, water, and methane are found in natural gases.
U.S. pipeline specifications for natural gas onl~y permi~ 2%
carbon dioxide and 4 ppm hydrogen sulfide. Therefore, it is necessary to remove hydrogen sulfide and carbon dioxide (also referred to as "acid gas") from the gas mixtures for the purpose of purif ying the gas mixture or recovering the WO92/~0431 PCT/USg2/W0~6 2~88~ 2 acid gas. Also, lt is often necessary to purify a gaseous :
hydrocarbon stream to produce sweet, dry gas which will not .
poison certain catalysts and which can meet the usual -.
pipeline specifications. It is also highly desirable to recover the hydrogen sulfide as a source of ~lemental sulfur. That is, during the separation of hydrogen sulfide from sour natural gas, it is desirable to selectively separate the hydrogen sulfide without removing all of the carbon dioxide. Usually, the separated hydr~gen sulfide and .portion of the carbon dioxide are deliv~red to a Claus sulfur plant for conversion to elemental sulfur.
Typical natural gas processing plant flow sheets are set forth in Figs. l and 2, attached hereto. Fig.~l depicts ~:.
a natural gas process wherein sour natural gas. is fed to a gas/li~uor separa:tion unit lO and the resultant gase~us product is sent to an amine absorption or cryogenic fractionation unlt 12 for the purpose of removing hydrogen sulfide and carbon dioxide from the gas. Amine absorption unit 12 separates the components and delivers hydrogen sulfide to Claus sulfur plant 14, carbon dioxide to compressor 16, and methane to dehydration unit 18. Claus sulfur plant 14 produces elemental sulfur which is sent to storage facility 20 and tail gases which are sent to cleanup unit 22. The methane which has been dehydrated in dehydration unit 1~ is sent to nitrogen rej ection unit 24 wher~in helium is recovered. The methane is then compressed WO92/20431 PCT/US92/~026
3 2~ ~'38`~ 2 `
in compressor 26 and the helium is sent to purification unit 28.
Fig. 2 depicts anoth~r process for car~on dioxide and hydrogen sulide removal which is combined with acid gas enrichment. According to this process flow sheet, sour natural gas i5 sent to a~ amine absorption or cryogeni~
fra~tiona~ion unit 30, wherein the separated acid gas '~omprises approximately 16% hydrog~n sulfide and the remainder substantially carbon dioxide. The separated acid gas is sent to acid gas enrichment unit 32 where the hydxogen sulfide is concentrated to approximately 60~ before delivery to Claus sulfur plant 34. Claus sùlfur plant 34 produces elementaI sulfur and re~idual gas which is hydrogenated ~36) and separa~ed~from residual hydrogen ;~
sul~ide(38) which is recycled to Claus~ sulfur plant 34.
Conventional methods for removing hydrogen sulfide and .
carbon dioxide from natural gas use amine absorption or cryogenic fractionation systems. Some examples of absQrption systems used in removing acid gas from 7as mixtures are set forth in ~.S~ Patent Nos.: 3,594,9B5 (~meen et al~), which issued JUly 27, 1971; 4,080,424 (Miller et al.), which issue~ March 21, 1978; and 3,664,091 (Hegwer), which issued May 23, 1972.
WO92/~0431 PCr/US9~/~02.6 Still others have attempted to separate acid gas from natural gas ~y combining absorption or fractionation columns and membranes, i.e., U.S.. Patent Nos. 4,374,657 (Schendel et ~:
al. ~, which issued February 22, 1983, and 4,466,946 (Goddin~ :
Jr. et al.), which issued August 21, 1984.
:, Schendel et al. discloses a process wherein methane i first separated fr~m a hydrocarbon feed~tream by low temperature distillation, and then acld gases are separated ~-~rom the remaining hydrocarbons by passing the residue tbrough a semipermeable membrane system. The semipermeable membrane used by Schendel et al. include~cellulose acetate,:~
cellulose diacetate, c~llulose triacetatej cellulose . , propionate, cellulose butyrate, cellulose cyanoethylate, cellulose methacrylate, or mixtures thereo~
The Goddin, Jr. et al. patent~includes one embodim~nt~ ~
wherein a process for treating a gaseous stream comprises: :
(a) separating a first portion of carbon~dloxide from the gaseous stream in a permeation zone by selective~permeation of car~on dioxide across a differentially permeable membrane to produce a carbon dioxide permeate stream and a hydrocarbon enriched first stream; and (b~ further separating carbon dioxide from the hydrocarbon enriched first str~am in at least one carbon~dioxide removal zone by cryogenically ~ractionating the hydrocar~on enriched first .
WO92J20431 PCT/US92/~026 s 21D3~ 2 stream to produce at least a carbon stream and ~ carbon ~`
dioxide stream.
Unfortunately, the use of amine absoxption or cryogenic fractionation systems for acid gas removal is extre~ely :~
energy inefficient, costly and bulky. United States energy consumption for amine-based gas treatment is estimated at .
about 0.22 quads. M~reover, the shift in ga~ supply in the United States from larger gas fields to small~ir, lower ~quality~ remote gas fields will re~uire substantially downscaled processing plants. Amine-bas~d gas ~reatment sy~tems will be economically and struçturally lmpractical for use in these smaller fields.
Until recently, use of membrane technology for acid gas removal has not been considered for two primary reasons~
~ ranes have not been capable of separating sufficient ~hydrogen s~lfide to reach~the permlssible:level of 4 ppm;
and ~2) the compo3ition of acid gas contains too much carbon :~
dioxide to fit ~laus sulfur pIant feed specifications.
:
There are various known acid gas membranes which are capable of s~parating both carbon dioxide and hydrogen sulf~d2 from natural gas. The membranes are disclosed in th~ following U.S. Patent Nos.: 4,589~896 (CAen et al.) which issued May ~0, 1986; 4,659,343 (Kelly), which issued April 21, 1987; 4,435,191 (Graham), which issued March 6, WO9~/20431 PCT/US92/0~26 2~ 2 6 l9B4, and 4,857,078 (Watler), which issued on August 15 r `~
1989. All of which are incorporated h~rein by referenceO
Chen et al. disclose acid gac membranes such as spiral-wound cellulose scetate type or polysulfone hollow fiber type membranes. These membranes separate the bulk of carbon dioxide and essentially all the hydrogen sulfide from the ;~
hydrocarbon residual gas stream. Thereafter, the hydrogen sulfide is separated from the carbon dioxide via a ~ -~fractionation column~containing~an acld gas removal sol~ent. i/
.
Kelly discloses Yarious me~branes capable of separating carbon dioxide ~from hydr~car~on, i.e., cellulose acetate, `~`
~cellulose diacetate,;cellulose trlacetate, cellulose pr~pionate, cellulose~butyrate, cellulose cyanoethyIate, cellulose methacryl e and mixtures thereof. Similarly, Graham discloses various polysulfone~membranes which are useful for separatIng carbon~dioxide from methane. Watler ~ discloses a multilayer membrane comprising a microporous i support onto which is coated an ultrathin permselective layer of a rubbe~ry polymer for the separation of met~ane from acid gases and other hydrocarbons.
None of the aforementioned membranes are capable of adequately separating hydrogen sulfide from carbon dioxide ~o sa~isfy the ~laus sulfur plant requiremen~s. Only the Chen et al. patent provides a step for s~paratinq hydrogen WO92/20431 PCT/U~92/04026 7 2 ~ 2 ~:
sulfide from carbon dioxide and this step necessitates the -~
use of a fractionatlon column which is economically and structurally impractical for use in smaller natural gas fields.
Several attempts at removing hydroge~ sulfide from natural gas via hydrogen sulfide selec~ive membranes are set forth in U.S. Patent Nos. 3,819,806 (Ward et a~l.), which issued June 25, 1974, and 4,824,443 ~Matson et al.~), which ~ssued April 25, 1989. All of these patents are also incorporated here~n by reference.
.
:
Ward et al. discloses an immobilized liquid membrane : .
wherein acid gas~, e.g., hydrogen~sulflde, is transported therebetween due to the dissolving and dissociating of hydrogen :sulfide in a water sol~ble salt.
Matso~ et al. discloses an immo~ilized ~liquid membrane made of polymers that are compatible with and swellable by a class of high boiling point, highly polar sol~ents ::
containing nitrogen, oxygen, phosphorous or sulfur~atoms, the swollen liquid membrane being supported either on or in the pores of other microporous supports. This membrane is capable of selective removal of the acld gases, i.e., carbon dioxide and hydrogen sulflde, from other gases and gas .
mixtures, and furthe~ capable of selective removal of WO92/20431 PCT/US92~02$
21~88~2 hydrogen sulfide in preference to carbon dioxide and carbon dioxide in preference to hydrogen.
None of the aforementioned permselective membrane systems provide a method of separating a hydrogen sulfide- ~;
rich permeate stream from natural gas sufficient for use in a Claus sulfur plant. The present inventor has develop a unigue combined or hybrid membrane system which comprises both acid gas selective membranes and hydrogen sulfide . ..
~-~elective membranes that are capable of removing acid gas from natural gas feedstreams and separating the hydrogen sulfide to a level satlsfactory for use in the Claus~sulfur process. `
Moreover, the use of both a hydrogen sulfide selective membrane and an acid gas membrane;in the removal~ of acid gas and separation of~a hydrogen sulfide-rich permeate stream ~-from either the acid gas or natural gas feedstreams lS
extremely cost effective. Such membranes can be used in downscaled processing plants or in retrofitted amine absorption systems.
~';
Also, the me ~ rane-based process for natural gas sweetening does not require additional energy for acid gas removal, thexeby overcoming the high energy co t a~sociated with amine absorption systems. The use of high seIective, high.flux membranes will also result in minimal methane W092/20431 . PCT/U~9~/04~26 9 2~3 ~-s32 loss. Additional advantages of such a process are: (1) low capital investment, ~2) ease of installation, (3) simple opera~ion, (4) low weight and space requirements, (5) low environmental impact, 16) highly flexible membrane system, and (7) no power, water or air is required for operation.
The present invention also provides many additional .`
advantages w~ich shall become apparent as described below.
INVENTION
A hybrid membrane system for separating acid gas from natural gas which comprises a hydrogen sulfide membra~e ::
as embly and an acid gas mem~rane assembly. The hybrid membrane system according to the present invention is preferably used together with a means for converting the separated hydrogen sulflde-rich permeate into elemental sulfur, i.e., a Claus sulfur plant.
Optionally, a dehydration membrane assembly ca~ be attached to the system for removal of water prior to delivering the hydrocarbon gas to the pipeline.
Each of the aforementioned membrane assemblies include at least one membrane module. However, two and three stage membrane modules with retenta~e recycle means are pref erable if a higher separation factor is desired.
WOg2/20431 PCT/US92/~0~6 ~
~ ~8~92 lo Preferred membrane module desi~ns are, for example, c~-current membrane m~dules, counter-current membrane modules, and advantaged me~brane modules. Each membrane module includes a membrane having the appropriate selecti~ity, .
l.e., hydrogen sulfide, acid gas or water. These:membranes may be either spiral wound membranes, flat sheet membranes, hollow fiber me ranes, plate-and~frame membranes, or any other suitable membrane configuration.
,.
Accordin~ to another embodiment of the present invention, the hybrid membrane system for separating acid gas from natural gas may also:include an acid gas membrane assembly, a first hydrogen sulfide membrane assembly, and a se~ond~hydrogen sulfide membrane assembly.
Another object of the present invention~is a method for separating acid gas from a natural gas feedstream which :~
comprises: feeding~ the natural gas feedstream to a hydrogen sul~lde membr~ne assembly wherein hydrogen sulfide is ~ :
separated from the natural gas feedstream as a hydrogen :~
sulfide-rich permeate; feeding the natural gas retentate from the hydrogen~sUlfide membrane assembly to an acid gas membrane asse~bly wherein a car~on dioxide-rich permeate is separated fr~m the natural gas retentate and wherein a hydrocarbon-rich retentate is sent to a pipeline; and ~ -feeding the hydrogen sulfide-rich permeate to a mean~
capable of converting the hydrogen sulfide to elemental W092/~0431 PCT/US92/04026 ~:10~8~2 sulfur. This method may optionally include a step of feeding the hydrocarbon-rich retentate of the acid gas ~-membrane a~sembly to a dehydration membrane assemb}y to remove water prior to feeding the dehydrated hydrocarbon-rich r~tentate to a pipeline.
Ano~her method for separating acid gas~from a natural gas feedstream accordi~g to the present invention includes the steps of: feeding the natural gas feedstream to an acid ~gas me~brane assembly wherein hydrogen sulfide and carbon dioxide are separated from the natural gas feedstream as an acid gas permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline; feeding the acid gas permeate to a ~ydr~gen sulfide membrane assembly wherein hydrogen sulfide is separated from the acid gas permeate as a hydrogen ~- sulfide-rich permeate; and feeding the hydrogen sulfide-~ich permeate to a~means capable ~f convertlng the hydrogen sulfide to elemental sulfur. The hydrocarbon-rich retentate may optionally be fed to a dehydration membrane assembly to remove watex prior to feeding the dehydrated hydrocarbon-rich retentate to a pipeline.
A still further method for separating acid gas from a natural gas feedstream according to the present invention may include: f~ding the natural ga~ feedstream to an acid gas msmbran~i assembly wherein hydrogen sulflde and carbon dioxide are separated from the natural gas feedstream as an WO 92/20431 21~ ~ 8 9 2 PC~/US92~040.~6 arid gas permeate: feeding the acid gas permeate from the acid gas membrane assembly to a first hydrogen sulfide system membrane assembly wher~in hydrogen sulfide i5 separated from the acid ga~ permeate as a first hydrogen sulfide-rich permeate; feeding the natural gas retentate to a second hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from the natural gas retentate as a second hydrogen sul~ide-rich permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline; and ~-~eeding the first and second hydrogen sulfide-rich permeates to a means capable of converting said hydrogen sulfide to elemental sulfur. This method may optionally include a step o~-feeding the hydrocarbon ric~ retentate of the 6econd hydrogen sulfide membrane assembly to a dehydration membrane assembly to remove water prior to feeding the de~ydrated hydr~carbon-rich retentate to a pipeline.
,.
Any of the aforementioned systems or methods may optionally include at least one direct conversion device capable of separating residual hydrogen sulfide from the retenta~e of the me=brane assemblies.
Other and ~urther objects, advantages and feature~ of the present invention will be understood by reference to the Xollowing specification in conjunction with the annexed drawings, wherein 'ike parts have been given like nu~bers.
wo g2/20431 ~2 ~ 2 PCTfUS92/~0~6 ~
13 ;-B~iEP~DESCRIPTION OF T9E DRAWINGS
Fig. 1 shows a conventional natural gas processing plant flow sheet;
Fig. 2 shows an amine absorption and acid gas enrichment pr~cess flow sheet;
Fig. 3a is a schematic representation of a counter-current membrane module;
Fig. 3b is a sche~atic representation of a counter-current membrane module wherein a portion of the retentate :
is used as a carrier gas for tbe permeate; ~ ~
;: Fig. 3c is a schematic representation of a counter- ~;
~:
~ current membran~ module wherein the permeate is carried out ::
of the module:by means of concentration difrerential;
:' Fig~ 3d is a schematic representation of a co-curreht m0mbrane module; : :
,:
Fig. 3e is a schematic representation of an advantaged or natural membrane module;
`:
Fig. 4a is a schematic representation of a two-stage membrane assembly according to ~he present invention;
WO 92/20431 PCI'/US92/0~026 2 ~ 3 9 2 14 ;`
Fig. 4~ is a schematic representation of a three-ctage membrane assembly aecording to th~ present invention, Fig. 5a i5 a schema~ic representation of a com~ined hydrogen sulfide and acid gas membrane system in accordance with one embodiment of the pre~ent invention;
Fig. 5b is a schematic representation of a combined hydrogen sulfide and acid gas membrane system according to ~-~hother embodiment of the present lnvention which also ncludes a dehydr~tion membrane assembly; ;~
:`
Flg. 6a is a schematic representatlon of a combined acid gas;and hydrogen sulfide membrane system according to another embodiment of the~ present invention;
;, Fig. 6b is a schemati representation of a combined acid gas and hydro~en sulfide membrane system according to :~
another embodiment of the present invention which also include a dehydration membran~ assembly and dlrect conversion means disposed throughout the system;
Fig. 7a is a schematic representation of a multiple membrane sy~tem according t~ still another embodiment of the present invention which c~mprises an acid gas membrane assembly and ~wo hydrogen s~lfide membrane assemblie~; and wog2/20431 15 ~2 PCT/~S92/040~6 Fig. 7b is a schematic representation of a multiple ;~
membrane system according to another embodiment of the present invention which comprises an acid gas membrane as~embly, two hydrogen sulfide membrane assemblies and a dehydration membrane assembly.
E~ ON O~_THE PREFERRED eN.BO ~ S :~
-Th~ present invention pro~ides a~hybrid membrane system ,~omprising a hydrogen sulfide membrane assembly having a membrane with a high preference toward hydrogen sulfide verses carbon dioxide and an acid gas membrane assembly having a membrane with a high preference toward acid gases verses hydrocarbons and water. The hybridization of a hydrogen sulfide membrane assembly with an acid gas membrane assembly results in a system exhibiting ~etter performance and lower construction cost than ronventional absorption and :
cryogenic plants; especially for small plants and in the treatment of gases~with high acid content.~ It also permits satisfactory concentration of hydrogen sulfide for use in a Claus sulfur plant, i.e., a system which converts hydrogen sulfide to elemental sulfur.
The unique hybrid membrane systems according ~o the present inventlon can best be described by reference to the a~tached drawings, wherein Fi~. 5a depicts a hybrid membrane syst~m for separating acid gas from natural gas which W~92/20431 PCT/US92/040.~.6 ;.
2~ 8~2 16 comprises a hydrogen sulfide membrane assembly 50 and an acid gas membrane assembly 52. This hy~rid membrane system :-is preferably used together with a means 54 for converting the separated hydrogen sulfide-rich permeate into elemental sulfur , i . e ., a Claus sulfur plant . .
As shown in Pig. 5b, a dehydration membrane assembly 56 can optionally be attached to the system for removal of :;
water prior to delivering a hydrocarbon-rich retentate to a peline.
}:ach membrane assembly 50, sa and 56 lncludes at least one membrane module. As demonstrated in Figures 4a and 4b, two and three stage membrane modules with retentate recycle means are preferable if a highcr~separation factor~is :
~desired.
Fig. 4a depicts a membrane assembly having two ;nembrane ~odules 60 and 6Z attach~d in series. ~odules 60 and 62 are connected via conduit 64 and compressor 66 wherein permeate from module 60 is delivered to module 62 ~nder sufficient pre~sure to promote 5atisfactory separation. Retentate from membrane module 62 is preferably recycled to module 60 via ~recycle conduit 68. The concentrated permeate exits the two stage membrane assembly via conduit 70 in a higher concentration than the concentration of the perme~te which exits first membrane module 60 via conduit 64.
,~092/20431 PCT/U~92/04026 17 ~ :~ U ~ 3 2 Fig~ 4b demonstrates a membrane assembly having threP
membrane modules 76, 78 and 80. Module 76 is cQnnected to module 78 via permeate conduit 8~ and compressor 84 wherein permeate from module 76 is sent to module 78 for additional separation. The retentate from module 78 is recy~led to ~-module 76 via recycle sonduit 86 for reprocessing.
Similarly, module 78 is connected to module 80 via permeate conduit 88 and compressor 90 wherein permeate from module 78 `~
is sent to module 80 for additional separation. The rçtentate from module 80 lS recycled to module 78 via ~;
recycle c~nduit 92 for reprocessing. The concentrated permeate exits m~dule 80 ~ia conduit 94 ln a~much higher concentration than the original feedstream delivered to .
~ module 76.
: Some of the preferred membrane module designs for use ~`
as any of ~he hydrogen sulfi~e, acid gas and dehydration membrane~modules are set forth in Figures 3a-3e. Figs. 3a- ~.
3c depict various counter-current designs wherein permeate .
is removed from the module in a directlon opposlte or~
counter to the dire~ion of the feeds~ream. : That is, Flg.
3a is a counter-current membrane module wherein an inert -carrier gas, e.g., nitrogen, lS supplied to remove the permeate from the module. Fig. 3b utilizes a portion of the retentate to remove the permeate from the module. The permeate is removed in the ccunter-current membrane modu~e WO9~/20431 PCT/US92/040~6 2~ ~ 8~ 18 shown in Fig. 3c due to the difference in concentration im ~-the permeate region.
Fig. 3d depicts a co-current membrane module wherein permeate is removed from the module in the same direction a~
the feedstream.
Fig. 3e depicts an advantaged membrane module wherein permeate is naturally or forcibly mixed to force average the ncentrations.
The systems of Figs. 5a and Sb operate such that a natural gas feedstream comprising methane, carbon dioxide, ,~
hydrogen sulfide, and water, is fed to hydrogen sulfide `
~embrane assembly S0 wherein the hydrogen sulfide-rich perm-ate includes hydrogen sulfide and carbon dioxide. The natural gas retentate from membrane assembly 50 includes met~ane, car~on dioxide and water. The hydrogen sulfide-rich peFmeate is deli~ered to a C1aus sulfur plant S4 wherein the hydrogen sulfide is converted to elemental sulfùr. The natural gas retentate from hydrogen su1fide membrane assembly 50 is sent to acid gas membrane assembly 52 wherein an aicid gas-rich permeate and a hydrocarbon-rich retentate compr1sing large amounts of methane and water are produced. If the wat-er concentration within the hydrocar~on-rich retentate meets pipelin~ specifications, thien the hydrocarbon-rîch retentate can be sent directly WO92/20431 2 ~ ,3 ~ 2 PCT/VS92/0~6 19 :.
from acid gas membrane assembly 52 to the pipeline. If, howe~er, the water concentration exceeds pipeline specifications, then the hydrocarbon-rich retentate must be sent to a dehydration membrane assembly 56, as shown in Fig.
5b, to remove water therefrom 5uch that a satisf actory ~;
hydrocarbon-rich feed can be sent t~ the pipeline. :.
Alternatively, the natural gas feedstream can be sent f irst to an acid gas membrane assembly wherein acid gases, .e., carbon dioxide and hydrogen sulfidej are separated therefrom as an a~id gas permeate which is then sent to hydrogen sulfide me~brane assembly 50 (see Fig. 6a). ~:
Hydrogen sulfide membrane assembly SQ pr~duces a hydrogen sulfide-rich permeate having a hydrogen sulfide concentration substantially higher than the acid gas permeate produced by acld gas membrane assem~ly 52, such that the hydrogen sulfide-rich permeate from assembly 50 can be sent to Claus sulfur plant 54 for conversion to elemental sulfur. As showr, in Fig. 6b, if the hydrocarbon-rich retentate produced by acid gas membrane assembly 52 contains ;~
a water concentration great than pipeline specification, ~:
then a dehydration mem~rane assembly 56 may be employed.
. .
Optionally, direct conversion devices 57, 58 and 59 can be used to further reduce the amount of hydrogen sulfide contained within the retent~te from acid gas me~brane assembly 52, the retentate from hydrogen sulfide memb~ane a5~emb1y 50, and the ex~aust from the Claus sulfur plant, WO92/20431 PcT/us92/~Q?~ ~
2 .~ 9 S ~
respecti~ely. These direct conversion devices typically in~lve the irreversible chemical scavenging of residual `-hydrogen sulfide by means of well known polishiny .`.
techniques.
According to another embodiment of the present invention as shown in Figs. 7a and 7b, the hybrid membrane syst~m for separating acid gas from natural gas may a}so :~
include an acid gas membrane assembly lOo, a first hydrogen ~ .
~-~ulfide membrane assembly 102, and a ~second hydrog~n sulfide -~
membrane assembly 104. These systems operate such that a natural gas comprising me~hane, carbon dioxlde, hydrogen sulfide and water is fed to acid gas membrane assembly :100:~
wherein the resultant acid gas permeate, i.e., hydrogen .
:sulfide and carbon dioxide, is sent to a first hydrogen sulfide membrane assembly 102. The acid gas permeate i5 ~: further separa~ed in first hydrogen sulfide~membrane ~
assembly to produce a hydrogen sulfide-rich permeate having~ :
an increased concentration of hydrogen~sulfide verses the acid gas permeate. The hydrogen sulflde-rich permeate is thereafter delivered to Claus sulfur plant 106 for conversion of the ~hydrogen sulfide to elemental sulfur. The hy~rocarbon-rich retentate from acid gas membrane assembly 100, i . e ., methane , water, and hydrogen sulfide, is sent to a second hydrogen sulfide membrane assembly 104 to separate most of the residual hydrogen sulfide contained therein such that the resultant hydrocarbon-rich retentate from membrane ,~
~092/2043l P ~/U~92/~026 2~ 3~
ass~mbly 104 meets pipeline specifications. Moreover, if .:
the hydrocarbon-rich retentate exiting ~econd hydrogen sulfide membrane ass~mbly 104 contains water in a quantity :~
in excess of pipeline specification, then it may be ;
desirable to send the hydrocarbon-rich retentate to a dehydration membrane assembly 10~ to remove unwanted water therefrom.
Each membrane module preferably includes membranes .having the desired selectivity, i.e., hydrogen sulflde, acid gas or water. These membranes may be either spiral wound membranes, flat sheet m~mbranes, hollow fiber membranes, plate-and frame membranes t or any other suitable membran~
configuration.
~YDRGGXN S~IFID~ SELECTIVE MEMBRAN~S ~;
Some examples of hydrogen sul~ide selective membranes are gel polymer membranes, molten salt membrane~ and rubber copolymer membranes.
One example of the preferred gel pol~mer membrane is described in U.S. Patent No. 4,824,443 (Matson et al.), which issued on April 2S, 1989, and which is incorporated herein by reference. This gel polymer membrane is a composite immobilized li~uid membrane which includes: (a) a microporous support, and (b) a solvent-swollen polymer compatible with and swella~le by at least one ~ol~ent WO~2/20431 PCT/US92/040~
2 1 ~ 3 2 ~2 ~.
selected from a class of solvents comprising tho~e ~olvents with a highly polar group in the molecular structure of the solv~nt, the highly polar group c~ntaining at lea t one atom `-selected from nitrogen, oxygen, phosphorous and sulfur, ~he solvents having a boiling point of at least lOO~C and a `~
solubility parameter of from about 7.5 to about 13.5 (cal/cm'-atm)~2 . ~ '`
,~, Molten salt hydrate membranes whlch c~n be used in the ,~separation of hydrogen sulfide gas from a gaseous feedstream are disclosed in U~S. Patent No. 4,780,114 (Quinn et al.~, sold by Air Products h C~emicals, Inc. of Allentown, Pennsylvania.
A rubber copol~mer membrane is set forth in U.S. Patent No. 4,857,07~ (Watler), which issued on August 15, 1989, and w~ich~is incorporated herein by reference. It is a ~i multilayer membrane comprising a~m1croporous support onto ~hich is coated an ultrathin permselective layer of a ruk~ery po~ymer.
::;
ACID GAS S~ECTIVE ~ RAN$S .
Acid gas selective mem~ranes are preferably selected from the group consisting of: cellulose acetate membranes, polyimide m~mbranes, polysiloxane membranes, and pyrolone '' ' `' ' W092/20431 ~i ~ @~ PCT/US92/04026 23 ~
membranes. H~wever, it is conceivable that many other ~;
polymeric membranes can also be used to separate acid gas from natural gas feedstreams.
Some examples of acid gAS selective membranes are set forth in U.S. Patent No. 4j589,89~ (Chen et al.), which issued May 20, 1986, U.S Patent No. 4,659,343 (Kelly), which ;~
- issued April 21l 1~87, and U.S Patent No. 4,435,191 (Graham), which issued March 6, 1984. Each of t~e ~:
aforementioned patents are incorporated herein by reference. ~`
Illustrative~polymer compositions suitable for use in :
acid gas membranes can be select~d from polysulfone, polyethersulfone, styrenic polymers and copolymers, ,:
polycarbonates, cellulosic polymers, polyamides, polyimides, polyethers, polyarylene oxides, polyurethanes, polyesters, poIyacrylates, polysulfides, polyolefins, polyvinyls and polyYinyl esters. Interpolymers, includlng block repeating ~ ~
units corresponding ~o the foregoing polymers, as well as ~.
. ~
graft polymers and blends of the foregoing, are als~
suitable for use in the membranes.
Preferred as membranes are cellulose esters, e.g., cellulose aceta~e, cellulose diacetate, cellulose triaceta~e, cellulose prcpionate, cellulose butyrate, cellulose cyanoethylate, cellulose methacrylate and mixtures thereof.
, .
'' :
WO92/20431 21~ ~ ~ 9 2 PCT/US92/040~ ~
~4 DBHYD~ATION SB~CTIVB ~ENB~EE `J"~
An example of one such dehydration selective membrane is a polysiloxane membrane manufactured by Bend Research Inc., of Bend, Oregon.
'~`'' While I have shown and described several embodiments in accordance with my invention, it is to be clearly understood ~`
that the same ar~ susceptible to numerous changes apparent ~.
~-to one skilled in the art. T~ere~ore, I do not wish to be~.
,~}imited to the~details shown and described, hut intend to -show all changes and modifications which come; within the .
scope of the appended claims.
~, -',:
`.
, . ~ .
in compressor 26 and the helium is sent to purification unit 28.
Fig. 2 depicts anoth~r process for car~on dioxide and hydrogen sulide removal which is combined with acid gas enrichment. According to this process flow sheet, sour natural gas i5 sent to a~ amine absorption or cryogeni~
fra~tiona~ion unit 30, wherein the separated acid gas '~omprises approximately 16% hydrog~n sulfide and the remainder substantially carbon dioxide. The separated acid gas is sent to acid gas enrichment unit 32 where the hydxogen sulfide is concentrated to approximately 60~ before delivery to Claus sulfur plant 34. Claus sùlfur plant 34 produces elementaI sulfur and re~idual gas which is hydrogenated ~36) and separa~ed~from residual hydrogen ;~
sul~ide(38) which is recycled to Claus~ sulfur plant 34.
Conventional methods for removing hydrogen sulfide and .
carbon dioxide from natural gas use amine absorption or cryogenic fractionation systems. Some examples of absQrption systems used in removing acid gas from 7as mixtures are set forth in ~.S~ Patent Nos.: 3,594,9B5 (~meen et al~), which issued JUly 27, 1971; 4,080,424 (Miller et al.), which issue~ March 21, 1978; and 3,664,091 (Hegwer), which issued May 23, 1972.
WO92/~0431 PCr/US9~/~02.6 Still others have attempted to separate acid gas from natural gas ~y combining absorption or fractionation columns and membranes, i.e., U.S.. Patent Nos. 4,374,657 (Schendel et ~:
al. ~, which issued February 22, 1983, and 4,466,946 (Goddin~ :
Jr. et al.), which issued August 21, 1984.
:, Schendel et al. discloses a process wherein methane i first separated fr~m a hydrocarbon feed~tream by low temperature distillation, and then acld gases are separated ~-~rom the remaining hydrocarbons by passing the residue tbrough a semipermeable membrane system. The semipermeable membrane used by Schendel et al. include~cellulose acetate,:~
cellulose diacetate, c~llulose triacetatej cellulose . , propionate, cellulose butyrate, cellulose cyanoethylate, cellulose methacrylate, or mixtures thereo~
The Goddin, Jr. et al. patent~includes one embodim~nt~ ~
wherein a process for treating a gaseous stream comprises: :
(a) separating a first portion of carbon~dloxide from the gaseous stream in a permeation zone by selective~permeation of car~on dioxide across a differentially permeable membrane to produce a carbon dioxide permeate stream and a hydrocarbon enriched first stream; and (b~ further separating carbon dioxide from the hydrocarbon enriched first str~am in at least one carbon~dioxide removal zone by cryogenically ~ractionating the hydrocar~on enriched first .
WO92J20431 PCT/US92/~026 s 21D3~ 2 stream to produce at least a carbon stream and ~ carbon ~`
dioxide stream.
Unfortunately, the use of amine absoxption or cryogenic fractionation systems for acid gas removal is extre~ely :~
energy inefficient, costly and bulky. United States energy consumption for amine-based gas treatment is estimated at .
about 0.22 quads. M~reover, the shift in ga~ supply in the United States from larger gas fields to small~ir, lower ~quality~ remote gas fields will re~uire substantially downscaled processing plants. Amine-bas~d gas ~reatment sy~tems will be economically and struçturally lmpractical for use in these smaller fields.
Until recently, use of membrane technology for acid gas removal has not been considered for two primary reasons~
~ ranes have not been capable of separating sufficient ~hydrogen s~lfide to reach~the permlssible:level of 4 ppm;
and ~2) the compo3ition of acid gas contains too much carbon :~
dioxide to fit ~laus sulfur pIant feed specifications.
:
There are various known acid gas membranes which are capable of s~parating both carbon dioxide and hydrogen sulf~d2 from natural gas. The membranes are disclosed in th~ following U.S. Patent Nos.: 4,589~896 (CAen et al.) which issued May ~0, 1986; 4,659,343 (Kelly), which issued April 21, 1987; 4,435,191 (Graham), which issued March 6, WO9~/20431 PCT/US92/0~26 2~ 2 6 l9B4, and 4,857,078 (Watler), which issued on August 15 r `~
1989. All of which are incorporated h~rein by referenceO
Chen et al. disclose acid gac membranes such as spiral-wound cellulose scetate type or polysulfone hollow fiber type membranes. These membranes separate the bulk of carbon dioxide and essentially all the hydrogen sulfide from the ;~
hydrocarbon residual gas stream. Thereafter, the hydrogen sulfide is separated from the carbon dioxide via a ~ -~fractionation column~containing~an acld gas removal sol~ent. i/
.
Kelly discloses Yarious me~branes capable of separating carbon dioxide ~from hydr~car~on, i.e., cellulose acetate, `~`
~cellulose diacetate,;cellulose trlacetate, cellulose pr~pionate, cellulose~butyrate, cellulose cyanoethyIate, cellulose methacryl e and mixtures thereof. Similarly, Graham discloses various polysulfone~membranes which are useful for separatIng carbon~dioxide from methane. Watler ~ discloses a multilayer membrane comprising a microporous i support onto which is coated an ultrathin permselective layer of a rubbe~ry polymer for the separation of met~ane from acid gases and other hydrocarbons.
None of the aforementioned membranes are capable of adequately separating hydrogen sulfide from carbon dioxide ~o sa~isfy the ~laus sulfur plant requiremen~s. Only the Chen et al. patent provides a step for s~paratinq hydrogen WO92/20431 PCT/U~92/04026 7 2 ~ 2 ~:
sulfide from carbon dioxide and this step necessitates the -~
use of a fractionatlon column which is economically and structurally impractical for use in smaller natural gas fields.
Several attempts at removing hydroge~ sulfide from natural gas via hydrogen sulfide selec~ive membranes are set forth in U.S. Patent Nos. 3,819,806 (Ward et a~l.), which issued June 25, 1974, and 4,824,443 ~Matson et al.~), which ~ssued April 25, 1989. All of these patents are also incorporated here~n by reference.
.
:
Ward et al. discloses an immobilized liquid membrane : .
wherein acid gas~, e.g., hydrogen~sulflde, is transported therebetween due to the dissolving and dissociating of hydrogen :sulfide in a water sol~ble salt.
Matso~ et al. discloses an immo~ilized ~liquid membrane made of polymers that are compatible with and swellable by a class of high boiling point, highly polar sol~ents ::
containing nitrogen, oxygen, phosphorous or sulfur~atoms, the swollen liquid membrane being supported either on or in the pores of other microporous supports. This membrane is capable of selective removal of the acld gases, i.e., carbon dioxide and hydrogen sulflde, from other gases and gas .
mixtures, and furthe~ capable of selective removal of WO92/20431 PCT/US92~02$
21~88~2 hydrogen sulfide in preference to carbon dioxide and carbon dioxide in preference to hydrogen.
None of the aforementioned permselective membrane systems provide a method of separating a hydrogen sulfide- ~;
rich permeate stream from natural gas sufficient for use in a Claus sulfur plant. The present inventor has develop a unigue combined or hybrid membrane system which comprises both acid gas selective membranes and hydrogen sulfide . ..
~-~elective membranes that are capable of removing acid gas from natural gas feedstreams and separating the hydrogen sulfide to a level satlsfactory for use in the Claus~sulfur process. `
Moreover, the use of both a hydrogen sulfide selective membrane and an acid gas membrane;in the removal~ of acid gas and separation of~a hydrogen sulfide-rich permeate stream ~-from either the acid gas or natural gas feedstreams lS
extremely cost effective. Such membranes can be used in downscaled processing plants or in retrofitted amine absorption systems.
~';
Also, the me ~ rane-based process for natural gas sweetening does not require additional energy for acid gas removal, thexeby overcoming the high energy co t a~sociated with amine absorption systems. The use of high seIective, high.flux membranes will also result in minimal methane W092/20431 . PCT/U~9~/04~26 9 2~3 ~-s32 loss. Additional advantages of such a process are: (1) low capital investment, ~2) ease of installation, (3) simple opera~ion, (4) low weight and space requirements, (5) low environmental impact, 16) highly flexible membrane system, and (7) no power, water or air is required for operation.
The present invention also provides many additional .`
advantages w~ich shall become apparent as described below.
INVENTION
A hybrid membrane system for separating acid gas from natural gas which comprises a hydrogen sulfide membra~e ::
as embly and an acid gas mem~rane assembly. The hybrid membrane system according to the present invention is preferably used together with a means for converting the separated hydrogen sulflde-rich permeate into elemental sulfur, i.e., a Claus sulfur plant.
Optionally, a dehydration membrane assembly ca~ be attached to the system for removal of water prior to delivering the hydrocarbon gas to the pipeline.
Each of the aforementioned membrane assemblies include at least one membrane module. However, two and three stage membrane modules with retenta~e recycle means are pref erable if a higher separation factor is desired.
WOg2/20431 PCT/US92/~0~6 ~
~ ~8~92 lo Preferred membrane module desi~ns are, for example, c~-current membrane m~dules, counter-current membrane modules, and advantaged me~brane modules. Each membrane module includes a membrane having the appropriate selecti~ity, .
l.e., hydrogen sulfide, acid gas or water. These:membranes may be either spiral wound membranes, flat sheet membranes, hollow fiber me ranes, plate-and~frame membranes, or any other suitable membrane configuration.
,.
Accordin~ to another embodiment of the present invention, the hybrid membrane system for separating acid gas from natural gas may also:include an acid gas membrane assembly, a first hydrogen sulfide membrane assembly, and a se~ond~hydrogen sulfide membrane assembly.
Another object of the present invention~is a method for separating acid gas from a natural gas feedstream which :~
comprises: feeding~ the natural gas feedstream to a hydrogen sul~lde membr~ne assembly wherein hydrogen sulfide is ~ :
separated from the natural gas feedstream as a hydrogen :~
sulfide-rich permeate; feeding the natural gas retentate from the hydrogen~sUlfide membrane assembly to an acid gas membrane asse~bly wherein a car~on dioxide-rich permeate is separated fr~m the natural gas retentate and wherein a hydrocarbon-rich retentate is sent to a pipeline; and ~ -feeding the hydrogen sulfide-rich permeate to a mean~
capable of converting the hydrogen sulfide to elemental W092/~0431 PCT/US92/04026 ~:10~8~2 sulfur. This method may optionally include a step of feeding the hydrocarbon-rich retentate of the acid gas ~-membrane a~sembly to a dehydration membrane assemb}y to remove water prior to feeding the dehydrated hydrocarbon-rich r~tentate to a pipeline.
Ano~her method for separating acid gas~from a natural gas feedstream accordi~g to the present invention includes the steps of: feeding the natural gas feedstream to an acid ~gas me~brane assembly wherein hydrogen sulfide and carbon dioxide are separated from the natural gas feedstream as an acid gas permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline; feeding the acid gas permeate to a ~ydr~gen sulfide membrane assembly wherein hydrogen sulfide is separated from the acid gas permeate as a hydrogen ~- sulfide-rich permeate; and feeding the hydrogen sulfide-~ich permeate to a~means capable ~f convertlng the hydrogen sulfide to elemental sulfur. The hydrocarbon-rich retentate may optionally be fed to a dehydration membrane assembly to remove watex prior to feeding the dehydrated hydrocarbon-rich retentate to a pipeline.
A still further method for separating acid gas from a natural gas feedstream according to the present invention may include: f~ding the natural ga~ feedstream to an acid gas msmbran~i assembly wherein hydrogen sulflde and carbon dioxide are separated from the natural gas feedstream as an WO 92/20431 21~ ~ 8 9 2 PC~/US92~040.~6 arid gas permeate: feeding the acid gas permeate from the acid gas membrane assembly to a first hydrogen sulfide system membrane assembly wher~in hydrogen sulfide i5 separated from the acid ga~ permeate as a first hydrogen sulfide-rich permeate; feeding the natural gas retentate to a second hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from the natural gas retentate as a second hydrogen sul~ide-rich permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline; and ~-~eeding the first and second hydrogen sulfide-rich permeates to a means capable of converting said hydrogen sulfide to elemental sulfur. This method may optionally include a step o~-feeding the hydrocarbon ric~ retentate of the 6econd hydrogen sulfide membrane assembly to a dehydration membrane assembly to remove water prior to feeding the de~ydrated hydr~carbon-rich retentate to a pipeline.
,.
Any of the aforementioned systems or methods may optionally include at least one direct conversion device capable of separating residual hydrogen sulfide from the retenta~e of the me=brane assemblies.
Other and ~urther objects, advantages and feature~ of the present invention will be understood by reference to the Xollowing specification in conjunction with the annexed drawings, wherein 'ike parts have been given like nu~bers.
wo g2/20431 ~2 ~ 2 PCTfUS92/~0~6 ~
13 ;-B~iEP~DESCRIPTION OF T9E DRAWINGS
Fig. 1 shows a conventional natural gas processing plant flow sheet;
Fig. 2 shows an amine absorption and acid gas enrichment pr~cess flow sheet;
Fig. 3a is a schematic representation of a counter-current membrane module;
Fig. 3b is a sche~atic representation of a counter-current membrane module wherein a portion of the retentate :
is used as a carrier gas for tbe permeate; ~ ~
;: Fig. 3c is a schematic representation of a counter- ~;
~:
~ current membran~ module wherein the permeate is carried out ::
of the module:by means of concentration difrerential;
:' Fig~ 3d is a schematic representation of a co-curreht m0mbrane module; : :
,:
Fig. 3e is a schematic representation of an advantaged or natural membrane module;
`:
Fig. 4a is a schematic representation of a two-stage membrane assembly according to ~he present invention;
WO 92/20431 PCI'/US92/0~026 2 ~ 3 9 2 14 ;`
Fig. 4~ is a schematic representation of a three-ctage membrane assembly aecording to th~ present invention, Fig. 5a i5 a schema~ic representation of a com~ined hydrogen sulfide and acid gas membrane system in accordance with one embodiment of the pre~ent invention;
Fig. 5b is a schematic representation of a combined hydrogen sulfide and acid gas membrane system according to ~-~hother embodiment of the present lnvention which also ncludes a dehydr~tion membrane assembly; ;~
:`
Flg. 6a is a schematic representatlon of a combined acid gas;and hydrogen sulfide membrane system according to another embodiment of the~ present invention;
;, Fig. 6b is a schemati representation of a combined acid gas and hydro~en sulfide membrane system according to :~
another embodiment of the present invention which also include a dehydration membran~ assembly and dlrect conversion means disposed throughout the system;
Fig. 7a is a schematic representation of a multiple membrane sy~tem according t~ still another embodiment of the present invention which c~mprises an acid gas membrane assembly and ~wo hydrogen s~lfide membrane assemblie~; and wog2/20431 15 ~2 PCT/~S92/040~6 Fig. 7b is a schematic representation of a multiple ;~
membrane system according to another embodiment of the present invention which comprises an acid gas membrane as~embly, two hydrogen sulfide membrane assemblies and a dehydration membrane assembly.
E~ ON O~_THE PREFERRED eN.BO ~ S :~
-Th~ present invention pro~ides a~hybrid membrane system ,~omprising a hydrogen sulfide membrane assembly having a membrane with a high preference toward hydrogen sulfide verses carbon dioxide and an acid gas membrane assembly having a membrane with a high preference toward acid gases verses hydrocarbons and water. The hybridization of a hydrogen sulfide membrane assembly with an acid gas membrane assembly results in a system exhibiting ~etter performance and lower construction cost than ronventional absorption and :
cryogenic plants; especially for small plants and in the treatment of gases~with high acid content.~ It also permits satisfactory concentration of hydrogen sulfide for use in a Claus sulfur plant, i.e., a system which converts hydrogen sulfide to elemental sulfur.
The unique hybrid membrane systems according ~o the present inventlon can best be described by reference to the a~tached drawings, wherein Fi~. 5a depicts a hybrid membrane syst~m for separating acid gas from natural gas which W~92/20431 PCT/US92/040.~.6 ;.
2~ 8~2 16 comprises a hydrogen sulfide membrane assembly 50 and an acid gas membrane assembly 52. This hy~rid membrane system :-is preferably used together with a means 54 for converting the separated hydrogen sulfide-rich permeate into elemental sulfur , i . e ., a Claus sulfur plant . .
As shown in Pig. 5b, a dehydration membrane assembly 56 can optionally be attached to the system for removal of :;
water prior to delivering a hydrocarbon-rich retentate to a peline.
}:ach membrane assembly 50, sa and 56 lncludes at least one membrane module. As demonstrated in Figures 4a and 4b, two and three stage membrane modules with retentate recycle means are preferable if a highcr~separation factor~is :
~desired.
Fig. 4a depicts a membrane assembly having two ;nembrane ~odules 60 and 6Z attach~d in series. ~odules 60 and 62 are connected via conduit 64 and compressor 66 wherein permeate from module 60 is delivered to module 62 ~nder sufficient pre~sure to promote 5atisfactory separation. Retentate from membrane module 62 is preferably recycled to module 60 via ~recycle conduit 68. The concentrated permeate exits the two stage membrane assembly via conduit 70 in a higher concentration than the concentration of the perme~te which exits first membrane module 60 via conduit 64.
,~092/20431 PCT/U~92/04026 17 ~ :~ U ~ 3 2 Fig~ 4b demonstrates a membrane assembly having threP
membrane modules 76, 78 and 80. Module 76 is cQnnected to module 78 via permeate conduit 8~ and compressor 84 wherein permeate from module 76 is sent to module 78 for additional separation. The retentate from module 78 is recy~led to ~-module 76 via recycle sonduit 86 for reprocessing.
Similarly, module 78 is connected to module 80 via permeate conduit 88 and compressor 90 wherein permeate from module 78 `~
is sent to module 80 for additional separation. The rçtentate from module 80 lS recycled to module 78 via ~;
recycle c~nduit 92 for reprocessing. The concentrated permeate exits m~dule 80 ~ia conduit 94 ln a~much higher concentration than the original feedstream delivered to .
~ module 76.
: Some of the preferred membrane module designs for use ~`
as any of ~he hydrogen sulfi~e, acid gas and dehydration membrane~modules are set forth in Figures 3a-3e. Figs. 3a- ~.
3c depict various counter-current designs wherein permeate .
is removed from the module in a directlon opposlte or~
counter to the dire~ion of the feeds~ream. : That is, Flg.
3a is a counter-current membrane module wherein an inert -carrier gas, e.g., nitrogen, lS supplied to remove the permeate from the module. Fig. 3b utilizes a portion of the retentate to remove the permeate from the module. The permeate is removed in the ccunter-current membrane modu~e WO9~/20431 PCT/US92/040~6 2~ ~ 8~ 18 shown in Fig. 3c due to the difference in concentration im ~-the permeate region.
Fig. 3d depicts a co-current membrane module wherein permeate is removed from the module in the same direction a~
the feedstream.
Fig. 3e depicts an advantaged membrane module wherein permeate is naturally or forcibly mixed to force average the ncentrations.
The systems of Figs. 5a and Sb operate such that a natural gas feedstream comprising methane, carbon dioxide, ,~
hydrogen sulfide, and water, is fed to hydrogen sulfide `
~embrane assembly S0 wherein the hydrogen sulfide-rich perm-ate includes hydrogen sulfide and carbon dioxide. The natural gas retentate from membrane assembly 50 includes met~ane, car~on dioxide and water. The hydrogen sulfide-rich peFmeate is deli~ered to a C1aus sulfur plant S4 wherein the hydrogen sulfide is converted to elemental sulfùr. The natural gas retentate from hydrogen su1fide membrane assembly 50 is sent to acid gas membrane assembly 52 wherein an aicid gas-rich permeate and a hydrocarbon-rich retentate compr1sing large amounts of methane and water are produced. If the wat-er concentration within the hydrocar~on-rich retentate meets pipelin~ specifications, thien the hydrocarbon-rîch retentate can be sent directly WO92/20431 2 ~ ,3 ~ 2 PCT/VS92/0~6 19 :.
from acid gas membrane assembly 52 to the pipeline. If, howe~er, the water concentration exceeds pipeline specifications, then the hydrocarbon-rich retentate must be sent to a dehydration membrane assembly 56, as shown in Fig.
5b, to remove water therefrom 5uch that a satisf actory ~;
hydrocarbon-rich feed can be sent t~ the pipeline. :.
Alternatively, the natural gas feedstream can be sent f irst to an acid gas membrane assembly wherein acid gases, .e., carbon dioxide and hydrogen sulfidej are separated therefrom as an a~id gas permeate which is then sent to hydrogen sulfide me~brane assembly 50 (see Fig. 6a). ~:
Hydrogen sulfide membrane assembly SQ pr~duces a hydrogen sulfide-rich permeate having a hydrogen sulfide concentration substantially higher than the acid gas permeate produced by acld gas membrane assem~ly 52, such that the hydrogen sulfide-rich permeate from assembly 50 can be sent to Claus sulfur plant 54 for conversion to elemental sulfur. As showr, in Fig. 6b, if the hydrocarbon-rich retentate produced by acid gas membrane assembly 52 contains ;~
a water concentration great than pipeline specification, ~:
then a dehydration mem~rane assembly 56 may be employed.
. .
Optionally, direct conversion devices 57, 58 and 59 can be used to further reduce the amount of hydrogen sulfide contained within the retent~te from acid gas me~brane assembly 52, the retentate from hydrogen sulfide memb~ane a5~emb1y 50, and the ex~aust from the Claus sulfur plant, WO92/20431 PcT/us92/~Q?~ ~
2 .~ 9 S ~
respecti~ely. These direct conversion devices typically in~lve the irreversible chemical scavenging of residual `-hydrogen sulfide by means of well known polishiny .`.
techniques.
According to another embodiment of the present invention as shown in Figs. 7a and 7b, the hybrid membrane syst~m for separating acid gas from natural gas may a}so :~
include an acid gas membrane assembly lOo, a first hydrogen ~ .
~-~ulfide membrane assembly 102, and a ~second hydrog~n sulfide -~
membrane assembly 104. These systems operate such that a natural gas comprising me~hane, carbon dioxlde, hydrogen sulfide and water is fed to acid gas membrane assembly :100:~
wherein the resultant acid gas permeate, i.e., hydrogen .
:sulfide and carbon dioxide, is sent to a first hydrogen sulfide membrane assembly 102. The acid gas permeate i5 ~: further separa~ed in first hydrogen sulfide~membrane ~
assembly to produce a hydrogen sulfide-rich permeate having~ :
an increased concentration of hydrogen~sulfide verses the acid gas permeate. The hydrogen sulflde-rich permeate is thereafter delivered to Claus sulfur plant 106 for conversion of the ~hydrogen sulfide to elemental sulfur. The hy~rocarbon-rich retentate from acid gas membrane assembly 100, i . e ., methane , water, and hydrogen sulfide, is sent to a second hydrogen sulfide membrane assembly 104 to separate most of the residual hydrogen sulfide contained therein such that the resultant hydrocarbon-rich retentate from membrane ,~
~092/2043l P ~/U~92/~026 2~ 3~
ass~mbly 104 meets pipeline specifications. Moreover, if .:
the hydrocarbon-rich retentate exiting ~econd hydrogen sulfide membrane ass~mbly 104 contains water in a quantity :~
in excess of pipeline specification, then it may be ;
desirable to send the hydrocarbon-rich retentate to a dehydration membrane assembly 10~ to remove unwanted water therefrom.
Each membrane module preferably includes membranes .having the desired selectivity, i.e., hydrogen sulflde, acid gas or water. These membranes may be either spiral wound membranes, flat sheet m~mbranes, hollow fiber membranes, plate-and frame membranes t or any other suitable membran~
configuration.
~YDRGGXN S~IFID~ SELECTIVE MEMBRAN~S ~;
Some examples of hydrogen sul~ide selective membranes are gel polymer membranes, molten salt membrane~ and rubber copolymer membranes.
One example of the preferred gel pol~mer membrane is described in U.S. Patent No. 4,824,443 (Matson et al.), which issued on April 2S, 1989, and which is incorporated herein by reference. This gel polymer membrane is a composite immobilized li~uid membrane which includes: (a) a microporous support, and (b) a solvent-swollen polymer compatible with and swella~le by at least one ~ol~ent WO~2/20431 PCT/US92/040~
2 1 ~ 3 2 ~2 ~.
selected from a class of solvents comprising tho~e ~olvents with a highly polar group in the molecular structure of the solv~nt, the highly polar group c~ntaining at lea t one atom `-selected from nitrogen, oxygen, phosphorous and sulfur, ~he solvents having a boiling point of at least lOO~C and a `~
solubility parameter of from about 7.5 to about 13.5 (cal/cm'-atm)~2 . ~ '`
,~, Molten salt hydrate membranes whlch c~n be used in the ,~separation of hydrogen sulfide gas from a gaseous feedstream are disclosed in U~S. Patent No. 4,780,114 (Quinn et al.~, sold by Air Products h C~emicals, Inc. of Allentown, Pennsylvania.
A rubber copol~mer membrane is set forth in U.S. Patent No. 4,857,07~ (Watler), which issued on August 15, 1989, and w~ich~is incorporated herein by reference. It is a ~i multilayer membrane comprising a~m1croporous support onto ~hich is coated an ultrathin permselective layer of a ruk~ery po~ymer.
::;
ACID GAS S~ECTIVE ~ RAN$S .
Acid gas selective mem~ranes are preferably selected from the group consisting of: cellulose acetate membranes, polyimide m~mbranes, polysiloxane membranes, and pyrolone '' ' `' ' W092/20431 ~i ~ @~ PCT/US92/04026 23 ~
membranes. H~wever, it is conceivable that many other ~;
polymeric membranes can also be used to separate acid gas from natural gas feedstreams.
Some examples of acid gAS selective membranes are set forth in U.S. Patent No. 4j589,89~ (Chen et al.), which issued May 20, 1986, U.S Patent No. 4,659,343 (Kelly), which ;~
- issued April 21l 1~87, and U.S Patent No. 4,435,191 (Graham), which issued March 6, 1984. Each of t~e ~:
aforementioned patents are incorporated herein by reference. ~`
Illustrative~polymer compositions suitable for use in :
acid gas membranes can be select~d from polysulfone, polyethersulfone, styrenic polymers and copolymers, ,:
polycarbonates, cellulosic polymers, polyamides, polyimides, polyethers, polyarylene oxides, polyurethanes, polyesters, poIyacrylates, polysulfides, polyolefins, polyvinyls and polyYinyl esters. Interpolymers, includlng block repeating ~ ~
units corresponding ~o the foregoing polymers, as well as ~.
. ~
graft polymers and blends of the foregoing, are als~
suitable for use in the membranes.
Preferred as membranes are cellulose esters, e.g., cellulose aceta~e, cellulose diacetate, cellulose triaceta~e, cellulose prcpionate, cellulose butyrate, cellulose cyanoethylate, cellulose methacrylate and mixtures thereof.
, .
'' :
WO92/20431 21~ ~ ~ 9 2 PCT/US92/040~ ~
~4 DBHYD~ATION SB~CTIVB ~ENB~EE `J"~
An example of one such dehydration selective membrane is a polysiloxane membrane manufactured by Bend Research Inc., of Bend, Oregon.
'~`'' While I have shown and described several embodiments in accordance with my invention, it is to be clearly understood ~`
that the same ar~ susceptible to numerous changes apparent ~.
~-to one skilled in the art. T~ere~ore, I do not wish to be~.
,~}imited to the~details shown and described, hut intend to -show all changes and modifications which come; within the .
scope of the appended claims.
~, -',:
`.
, . ~ .
Claims (76)
1. A multiple membrane assembly system for separating acid gas including carbon dioxide and hydrogen sulfide from natural gas which comprises:
a hydrogen sulfide membrane assembly comprising at least one hydrogen sulfide selective membrane which is capable of separating hydrogen sulfide from said natural gas and/or said acid gas; and an acid gas membrane assembly comprising at least one acid gas selective membrane which is capable of separating said acid gas from said natural gas.
a hydrogen sulfide membrane assembly comprising at least one hydrogen sulfide selective membrane which is capable of separating hydrogen sulfide from said natural gas and/or said acid gas; and an acid gas membrane assembly comprising at least one acid gas selective membrane which is capable of separating said acid gas from said natural gas.
2. The system according to claim 1 further comprising a means for converting hydrogen sulfide into elemental sulfur.
3. The system according to claim 1 further comprising a dehydration membrane assembly.
4. The system according to claim 1, wherein said hydrogen sulfide membrane assembly comprises at least one hydrogen sulfide membrane module.
5. The system according claims 4, wherein said hydrogen sulfide membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
6. The system according to claim 5, wherein said hydrogen sulfide membrane module comprises a hydrogen sulfide selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
7. The system according to claim 6, wherein said hydrogen sulfide selective membrane is selected from the group consisting of: gel polymer membranes, molten salt membranes and rubber copolymer membranes.
8. The system according to claim 1, wherein said acid gas membrane assembly comprises at least one acid gas membrane module.
9. The system according claims 8, wherein said acid gas membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
10. The system according to claim 9, wherein said acid gas membrane module comprises an acid gas selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
11. The system according to claim 10, wherein said acid gas selective membrane is selected from the group consisting of: cellulose acetate membranes, polyimide membranes, polysiloxane membranes, and pyrolone membranes.
12. The system according to claim 3, wherein said dehydration membrane assembly comprises at least one dehydration membrane module.
13. The system according claims 12, wherein said dehydration membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
14. The system according to claim 13, wherein said dehydration membrane module comprises a dehydration selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
15. The system according to claim 14, wherein said dehydration selective membrane is a polysiloxane membrane.
16. The system according to claim 1 wherein said hydrogen sulfide membrane assembly is disposed within said system so as to receive as its feed the acid gas permeate from said acid gas membrane assembly, and wherein said system further comprises a second hydrogen sulfide membrane assembly comprising at least one hydrogen sulfide selective membrane which is capable of separating hydrogen sulfide from the natural gas retentate of said acid gas membrane assembly.
17. The system according to claim 16 further comprising a means for converting hydrogen sulfide into elemental sulfur.
18. The system according to claim 16 further comprising a dehydration membrane assembly.
19. The system according to claim 16, wherein said first and second hydrogen sulfide membrane assemblies each comprise at least one hydrogen sulfide membrane module.
20. The system according claims 19, wherein said hydrogen sulfide membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
21. The system according to claim 20, wherein said hydrogen sulfide membrane module comprises a hydrogen sulfide selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
22. The system according to claim 21, wherein said hydrogen sulfide selective membrane is selected from the group consisting of: gel polymer membranes, molten salt membranes and rubber copolymer membranes.
23. The system according to claim 16, wherein said acid gas membrane assembly comprises at least one acid gas membrane module.
24. The system according claims 23, wherein said acid gas membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
25. The system according to claim 24, wherein said acid gas membrane module comprises an acid gas selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
26. The system according to claim 25, wherein said acid gas selective membrane is selected from the group consisting of: cellulose acetate membranes, polyimide membranes, polysiloxane membranes, and pyrolone membranes.
27. The system according to claim 18, wherein said dehydration membrane assembly comprises at least one dehydration membrane module.
28. The system according claims 27, wherein said dehydration membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
29. The system according to claim 28, wherein said dehydration membrane module comprises a dehydration selective membrane selected from the group consisting of:
spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
30. The system according to claim 29, wherein said dehydration selective membrane is a polysiloxane membrane.
31. A method for separating acid gas including carbon dioxide and hydrogen sulfide from a natural gas feedstream which comprises:
feeding said natural gas feedstream to either (a) a hydrogen sulfide membrane assembly comprising at least one hydrogen sulfide selective membrane wherein hydrogen sulfide is separated from said natural gas feedstream as a hydrogen sulfide-rich permeate, or (b) an acid gas membrane assembly comprising at least one acid gas selective membrane wherein carbon dioxide and hydrogen sulfide are separated from said natural gas-feedstream so as to produce an acid gas permeate and a hydrocarbon-rich retentate; and/or feeding said hydrogen sulfide-rich permeate from said hydrogen sulfide membrane assembly to a means capable of converting said hydrogen sulfide to elemental sulfur; and/or feeding said hydrocarbon-rich retentate from said acid gas membrane assembly to a pipeline; and/or feeding said acid gas permeate to said hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from said acid gas permeate as a hydrogen sulfide-rich permeate.
feeding said natural gas feedstream to either (a) a hydrogen sulfide membrane assembly comprising at least one hydrogen sulfide selective membrane wherein hydrogen sulfide is separated from said natural gas feedstream as a hydrogen sulfide-rich permeate, or (b) an acid gas membrane assembly comprising at least one acid gas selective membrane wherein carbon dioxide and hydrogen sulfide are separated from said natural gas-feedstream so as to produce an acid gas permeate and a hydrocarbon-rich retentate; and/or feeding said hydrogen sulfide-rich permeate from said hydrogen sulfide membrane assembly to a means capable of converting said hydrogen sulfide to elemental sulfur; and/or feeding said hydrocarbon-rich retentate from said acid gas membrane assembly to a pipeline; and/or feeding said acid gas permeate to said hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from said acid gas permeate as a hydrogen sulfide-rich permeate.
32. The method according to claim 31 further comprising the step of feeding said hydrocarbon-rich retentate of said acid gas membrane assembly to a dehydration membrane assembly to remove water prior to feeding the dehydrated hydrocarbon rich retentate to said pipeline.
33. The method according to claim 31, wherein said hydrogen sulfide membrane assembly comprises at least one hydrogen sulfide membrane module.
34. The method according claims 33, wherein said hydrogen sulfide membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
35. The method according to claim 34, wherein said hydrogan sulfide membrane module comprises a hydrogen sulfide selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
36. The method according to claim 35, wherein said hydrogen sulfide selective membrane is selected from the group consisting of: gel polymer membranes, molten salt membranes and rubber copolymer membranes.
37. The method according to claim 31, wherein said acid gas membrane assembly comprises at least one acid gas membrane module.
38. The method according claims 37, wherein said acid gas membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
39. The method according to claim 38, wherein said acid gas membrane module comprises an acid gas selective membrane selected from the group consisting of spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
40. The method according to claim 39, wherein said acid gas selective membrane is selected from the group consisting of: cellulose acetate membranes, polyimide membranes, polysiloxane membranes, and pyrolone membranes.
41. The method according to claim 32, wherein said dehydration membrane assembly comprises at least one dehydration membrane module.
42. The method according claims 41, wherein said dehydration membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
43. The method according to claim 42, wherein said dehydration membrane module comprises a dehydration selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
44. The method according to claim 43, wherein said dehydration selective membrane is a polysiloxane membrane.
45. A method for separating acid gas from a natural gas feedstream which comprises:
feeding said natural gas feedstream to an acid gas membrane assembly wherein hydrogen sulfide and carbon dioxide are separated from said natural gas feedstream as an acid gas permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline;
feeding said acid gas permeate to a hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from said acid gas permeate as a hydrogen sulfide-rich permeate; and feeding said hydrogen sulfide-rich permeate to a means capable of converting said hydrogen sulfide to elemental sulfur.
feeding said natural gas feedstream to an acid gas membrane assembly wherein hydrogen sulfide and carbon dioxide are separated from said natural gas feedstream as an acid gas permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline;
feeding said acid gas permeate to a hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from said acid gas permeate as a hydrogen sulfide-rich permeate; and feeding said hydrogen sulfide-rich permeate to a means capable of converting said hydrogen sulfide to elemental sulfur.
46. The method according to claim 45 further comprising the step of feeding said hydrocarbon-rich retentate of said acid gas membrane assembly to a dehydration membrane assembly to remove water prior to feeding the dehydrated hydrocarbon-rich retentate to said pipeline.
47. The method according to claim 45, wherein said hydrogen sulfide membrane assembly comprises at least one hydrogen sulfide membrane module.
48. The method according claims 47, wherein said hydrogen sulfide membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
49. The method according to claim 48, wherein said hydrogen sulfide membrane module comprises a hydrogen sulfide selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
50. The method according to claim 49, wherein said hydrogen sulfide selective membrane is selected from the group consisting of: gel polymer membranes, molten salt membranes and rubber copolymer membranes.
51. The method according to claim 45, wherein said acid gas membrane assembly comprises at least one acid gas membrane module.
52. The method according claims 51, wherein said acid gas membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
53. The method according to claim 52, wherein said acid gas membrane module comprises an acid gas selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
54. The method according to claim 53, wherein said acid gas selective membrane is selected from the group consisting of: cellulose acetate membranes, polyimide membranes, polysiloxane membranes, and pyrolone membranes.
55. The method according to claim 46, wherein said dehydration membrane assembly comprises at least one dehydration membrane module.
56. The method according claims 55, wherein said dehydration membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
57. The method according to claim 56, wherein said dehydration membrane module comprises a dehydration selective membrane selected from the group consisting of:
spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
58. The method according to claim 57, wherein said dehydration selective membrane is a polysiloxane membrane.
59. A method for separating acid gas from a natural gas feedstream which comprises:
feeding said natural gas feedstream to an acid gas membrane assembly wherein hydrogen sulfide and carbon dioxide are separated from said natural gas feedstream as an acid gas permeate;
feeding said acid gas permeate from said acid gas membrane assembly to a first hydrogen sulfide system membrane assembly wherein hydrogen sulfide is separated from said acid gas permeate as a first hydrogen sulfide-rich permeate;
feeding the natural gas retentate to a second hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from said natural gas retentate as a second hydrogen sulfide-rich permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline;
feeding said first and second hydrogen sulfide-rich permeates to a means capable of converting said hydrogen sulfide to elemental sulfur.
feeding said natural gas feedstream to an acid gas membrane assembly wherein hydrogen sulfide and carbon dioxide are separated from said natural gas feedstream as an acid gas permeate;
feeding said acid gas permeate from said acid gas membrane assembly to a first hydrogen sulfide system membrane assembly wherein hydrogen sulfide is separated from said acid gas permeate as a first hydrogen sulfide-rich permeate;
feeding the natural gas retentate to a second hydrogen sulfide membrane assembly wherein hydrogen sulfide is separated from said natural gas retentate as a second hydrogen sulfide-rich permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline;
feeding said first and second hydrogen sulfide-rich permeates to a means capable of converting said hydrogen sulfide to elemental sulfur.
WO 92/20431 PCT/US92/04026 63. The method according to claim 59 further comprising the step of feeding said hydrocarbon-rich retentate of said second hydrogen sulfide membrane assembly to a dehydration membrane assembly to remove water prior to feeding the dehydrated hydrocarbon-rich retentate to said pipeline.
61. The method according to claim 59, wherein said hydrogen sulfide membrane assembly comprises at least one hydrogen sulfide membrane module.
62. The method according claims 61, wherein said hydrogen sulfide membrane module is selected from the qroup consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
63. The method according to claim 62, wherein said hydrogen sulfide membrane module comprises a hydrogen sulfide selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
64. The method according to claim 63, wherein said hydrogen sulfide selective membrane is selected from the group consisting of: gel polymer membranes, molten salt membranes and rubber copolymer membranes.
65. The method according to claim 59, wherein said acid gas membrane assembly comprises at least one acid gas membrane module.
66. The method according claims 65, wherein said acid gas membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
67. The method according to claim 66, wherein said acid gas membrane module comprises an acid gas selective membrane selected from the group consisting of: spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
68. The method according to claim 67, wherein said acid gas selective membrane is selected from the group consisting of: cellulose acetate membranes, polyimide membranes, polysiloxane membranes, and pyrolone membranes.
69. The method according to claim 60, wherein said dehydration membrane assembly comprises at least one dehydration membrane module.
70. The method according claims 69, wherein said dehydration membrane module is selected from the group consisting of co-current membrane modules, counter-current membrane modules, and advantaged membrane modules.
71. The method according to claim 70, wherein said dehydration membrane module comprises a dehydration selective membrane selected from the group consisting of:
spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
spiral wound membranes, flat sheet membranes, hollow fiber membranes, and plate-and-frame membranes.
72. The method according to claim 71, wherein said dehydration selective membrane is a polysiloxane membrane.
73. The method according to any of claims 31 wherein residual hydrogen sulfide is separated from the retentate of any membrane assembly by means of direct conversion, said direct conversion involving the irreversible chemical scavenging of said residual hydrogen sulfide.
74. The system according to any of claims 1 further comprising at least one direct conversion device capable of separating residual hydrogen sulfide from the retentate generated from an acid gas membrane assembly and/or a hydrogen sulfide membrane assembly, said direct conversion involving the irreversible chemical scavenging of said residual hydrogen sulfide.
75. The method according to claim 31 wherein said natural gas feedstream is feed to said acid gas membrane assembly, and wherein said system further comprises feeding the hydrocarbon-rich retentate of said acid gas membrane assembly to a second hydrogen sulfide membrane assembly comprising at least one hydrogen sulfide selective membrane wherein hydrogen sulfide is separated from said hydrocarbon-rich retentate as a second hydrogen sulfide-rich permeate, and wherein a hydrocarbon-rich retentate is sent to a pipeline.
76. The method according to claim 75 wherein said hydrogen sulfide membrane assembly and said second hydrogen sulfide membrane assembly are connected in parallel such that the hydrogen sulfide-rich permeates therefrom are feed to a means capable of converting said hydrogen sulfide to elemental sulfur.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US70351891A | 1991-05-21 | 1991-05-21 | |
| US703,518 | 1991-05-21 | ||
| PCT/US1992/004026 WO1992020431A1 (en) | 1991-05-21 | 1992-05-14 | Treatment of acid gas using hybrid membrane separation systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2108892A1 true CA2108892A1 (en) | 1992-11-22 |
Family
ID=24825696
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002108892A Abandoned CA2108892A1 (en) | 1991-05-21 | 1992-05-14 | Treatment of acid gas using hybrid membrane separation systems |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0641244A1 (en) |
| JP (1) | JPH06504949A (en) |
| CA (1) | CA2108892A1 (en) |
| NO (1) | NO934178L (en) |
| WO (1) | WO1992020431A1 (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5332424A (en) * | 1993-07-28 | 1994-07-26 | Air Products And Chemicals, Inc. | Hydrocarbon fractionation by adsorbent membranes |
| US5407466A (en) * | 1993-10-25 | 1995-04-18 | Membrane Technology And Research, Inc. | Sour gas treatment process including membrane and non-membrane treatment steps |
| GB2289286B (en) * | 1994-05-11 | 1998-10-14 | Ici Plc | Sulphur removal |
| EP0880992B1 (en) * | 1997-05-26 | 2004-12-15 | Kabushiki Kaisha Toshiba | Desulfurization apparatus |
| US6776974B1 (en) | 1999-10-22 | 2004-08-17 | Monsanto Enviro-Chem Systems, Inc. | Process for the production of sulfur |
| DE60024866T2 (en) * | 1999-10-22 | 2006-08-17 | Mecs, Inc. | PROCESS FOR OBTAINING SULFUR |
| EP1642864A3 (en) * | 1999-10-22 | 2006-05-17 | MECS, Inc. | Process for the production of sulfur |
| US6926829B2 (en) | 2000-03-06 | 2005-08-09 | Kvaerner Process Systems A.S. | Apparatus and method for separating fluids through a membrane |
| DE10208253A1 (en) * | 2002-02-26 | 2003-09-04 | Lurgi Ag | Process for the removal of mercaptan from raw gas |
| US20040099138A1 (en) * | 2002-11-21 | 2004-05-27 | L'air Liquide, Societe Anonyme A Directoire Et Conseil De Surveillance Pour L'etude Et | Membrane separation process |
| EA025596B9 (en) * | 2011-12-27 | 2018-03-30 | Эвоник Файберс Гмбх | Method for separating gases |
| US8722003B1 (en) | 2013-02-13 | 2014-05-13 | General Electric Company | Apparatus and method to produce synthetic gas |
| US9533260B2 (en) | 2013-07-03 | 2017-01-03 | Centro De Investigacion En Quimica Aplicada | Method and system for obtaining sweet gas, synthetic gas and sulphur from natural gas |
| WO2015002523A1 (en) * | 2013-07-04 | 2015-01-08 | Centro De Investigación En Química Aplicada | Method and system for obtaining sweet gas, synthesis gas and sulphur from natural gas |
| EP3586941B1 (en) | 2014-04-16 | 2021-08-25 | Saudi Arabian Oil Company | Improved sulfur recovery process and apparatus for treating low to medium mole percent hydrogen sulfide gas feeds with btex in a claus unit |
| KR101658448B1 (en) | 2014-06-27 | 2016-09-30 | 한국에너지기술연구원 | Multi-step hybrid apparatus for removal of acidic gas and moisture from natural gas and the method therewith |
| US20160184771A1 (en) | 2014-12-31 | 2016-06-30 | L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude | Polyimide membrane for h2s removal |
| US9962646B2 (en) * | 2016-01-04 | 2018-05-08 | Saudi Arabian Oil Company | Sour gas feed separations and helium recovery from natural gas using block co-polyimide membranes |
| US10913036B2 (en) | 2017-05-31 | 2021-02-09 | Saudi Arabian Oil Company | Cardo-type co-polyimide membranes for sour gas feed separations from natural gas |
| US10765995B2 (en) * | 2017-06-08 | 2020-09-08 | Saudi Arabian Oil Company | Helium recovery from gaseous streams |
| KR20220011679A (en) | 2019-05-17 | 2022-01-28 | 사우디 아라비안 오일 컴퍼니 | Improved sulfur recovery operation with improved carbon dioxide recovery |
| CN113289462A (en) * | 2021-05-19 | 2021-08-24 | 华南理工大学 | Hydrate membrane device and method for gas separation |
| CN115337795B (en) * | 2022-06-22 | 2023-12-12 | 宁德师范学院 | ZTIF-1/cellulose acetate blend membrane and preparation method and application thereof |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3534528A (en) * | 1969-05-26 | 1970-10-20 | Abcor Inc | Gas well sulfur removal by diffusion through polymeric membranes |
| US4130403A (en) * | 1977-08-03 | 1978-12-19 | Cooley T E | Removal of H2 S and/or CO2 from a light hydrocarbon stream by use of gas permeable membrane |
| FR2540396B1 (en) * | 1983-02-04 | 1988-09-23 | Petroles Cie Francaise | GAS DEHYDRATION PROCESS |
-
1992
- 1992-05-14 WO PCT/US1992/004026 patent/WO1992020431A1/en not_active Application Discontinuation
- 1992-05-14 JP JP5500178A patent/JPH06504949A/en active Pending
- 1992-05-14 CA CA002108892A patent/CA2108892A1/en not_active Abandoned
- 1992-05-14 EP EP92912590A patent/EP0641244A1/en not_active Withdrawn
-
1993
- 1993-11-18 NO NO934178A patent/NO934178L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| WO1992020431A1 (en) | 1992-11-26 |
| EP0641244A1 (en) | 1995-03-08 |
| NO934178D0 (en) | 1993-11-18 |
| NO934178L (en) | 1993-11-18 |
| JPH06504949A (en) | 1994-06-09 |
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