CA2069380A1 - Method for removing permanent gases and light hydrocarbons from waste and process gas streams and petrochemical processes - Google Patents
Method for removing permanent gases and light hydrocarbons from waste and process gas streams and petrochemical processesInfo
- Publication number
- CA2069380A1 CA2069380A1 CA 2069380 CA2069380A CA2069380A1 CA 2069380 A1 CA2069380 A1 CA 2069380A1 CA 2069380 CA2069380 CA 2069380 CA 2069380 A CA2069380 A CA 2069380A CA 2069380 A1 CA2069380 A1 CA 2069380A1
- Authority
- CA
- Canada
- Prior art keywords
- gaseous
- boiling points
- components
- gas
- hydrocarbons
- 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
- 239000007789 gas Substances 0.000 title claims abstract description 180
- 229930195733 hydrocarbon Natural products 0.000 title claims abstract description 65
- 150000002430 hydrocarbons Chemical class 0.000 title claims abstract description 65
- 238000000034 method Methods 0.000 title claims description 36
- 239000002699 waste material Substances 0.000 title description 2
- 238000009835 boiling Methods 0.000 claims abstract description 120
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 24
- 238000000926 separation method Methods 0.000 claims abstract description 21
- 238000004508 fractional distillation Methods 0.000 claims abstract description 15
- 239000008246 gaseous mixture Substances 0.000 claims abstract description 15
- 230000000274 adsorptive effect Effects 0.000 claims abstract description 12
- 238000001179 sorption measurement Methods 0.000 claims description 52
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 18
- 239000003463 adsorbent Substances 0.000 claims description 15
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 14
- HSFWRNGVRCDJHI-UHFFFAOYSA-N Acetylene Chemical compound C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 12
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 239000001257 hydrogen Substances 0.000 claims description 8
- 229910052739 hydrogen Inorganic materials 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 7
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 6
- 238000011084 recovery Methods 0.000 claims description 6
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 5
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 5
- 238000003795 desorption Methods 0.000 claims description 5
- 239000000741 silica gel Substances 0.000 claims description 5
- 229910002027 silica gel Inorganic materials 0.000 claims description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 239000001569 carbon dioxide Substances 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 238000010926 purge Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 239000012530 fluid Substances 0.000 claims description 3
- 239000002808 molecular sieve Substances 0.000 claims description 3
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 3
- 239000010457 zeolite Substances 0.000 claims description 3
- 125000004432 carbon atom Chemical group C* 0.000 claims description 2
- 150000008282 halocarbons Chemical class 0.000 claims description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 claims 3
- 239000004215 Carbon black (E152) Substances 0.000 abstract description 12
- 239000000047 product Substances 0.000 description 57
- 239000002912 waste gas Substances 0.000 description 14
- 238000004821 distillation Methods 0.000 description 9
- 150000001875 compounds Chemical class 0.000 description 8
- 238000002485 combustion reaction Methods 0.000 description 7
- 239000006227 byproduct Substances 0.000 description 3
- -1 carbon dio~ide Chemical class 0.000 description 3
- 238000001311 chemical methods and process Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 description 2
- 239000001307 helium Substances 0.000 description 2
- 229910052734 helium Inorganic materials 0.000 description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 230000008929 regeneration Effects 0.000 description 2
- 238000011069 regeneration method Methods 0.000 description 2
- FGRBYDKOBBBPOI-UHFFFAOYSA-N 10,10-dioxo-2-[4-(N-phenylanilino)phenyl]thioxanthen-9-one Chemical compound O=C1c2ccccc2S(=O)(=O)c2ccc(cc12)-c1ccc(cc1)N(c1ccccc1)c1ccccc1 FGRBYDKOBBBPOI-UHFFFAOYSA-N 0.000 description 1
- 241000271566 Aves Species 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 241000518994 Conta Species 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 241000183024 Populus tremula Species 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 150000008280 chlorinated hydrocarbons Chemical class 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229940050176 methyl chloride Drugs 0.000 description 1
- 230000001473 noxious effect Effects 0.000 description 1
- 239000010908 plant waste Substances 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000002594 sorbent Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
Landscapes
- Separation By Low-Temperature Treatments (AREA)
- Separation Of Gases By Adsorption (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
0092G Dkt. No. 91A251 ABSTRACT OF THE DISCLOSURE
High boiling point gases, i.e. those having boiling points greater than above -80°C, are separated from a gaseous mixture containing, in addition to the high boiling gases, methane and/or a C2 hydrocarbon and one or more gases having boiling points less than -170°C by subjecting the gaseous mixture to adsorptive separation. If the gaseous mixture contains more than one high boiling component, these components may be further separated by fractional distillation.
High boiling point gases, i.e. those having boiling points greater than above -80°C, are separated from a gaseous mixture containing, in addition to the high boiling gases, methane and/or a C2 hydrocarbon and one or more gases having boiling points less than -170°C by subjecting the gaseous mixture to adsorptive separation. If the gaseous mixture contains more than one high boiling component, these components may be further separated by fractional distillation.
Description
CRR062091 PATEN~
0092G Dkt. Mo. 91A251 2~69380 METHOD ~OR REMOVING PERMA~ENT GA~E~ AND LIGHT
HYDROCAR~ONS FROM WASTE AND PROCESS GAS STREAMS
AND PETROCHEMICAL PROCESSES
BACKGROUND OF THE TNVENTION
This invention relates to the :removal of certain components from gas streams, and more particularly to the removal of valuable or environmentally unacceptable components from waste gas streams prior to relea5e of the waste gas streams to the atmosphere.
Waste gas streams fron~ chemical manufacturing or processing plants usually contain light gas elements or compounds which are not incompatible with the environment and thus can be released to the atmosphere. For e~ample, o~ygen, nitrogen, argon~ water vapor and carbon dioxide are commonly present in significant quantities in waste gas streams. It is also not uncommon for waste gas streams to contain trace amounts of hydrogen and helium. Since these gases are naturally occurring components of the atmosphere, they are environmentally acceptable and may be released to the atmosphere in reasonable quantities.
It often happens, however, that chemical plant waste gas streams contain higher boiling components which cannot be released to the atmosphere in concentrations above a specified tolerance limit. In such cases, the environmentally unacceptable gas components must be removed from the waste gas stream or converted to relatively harmless compounds, such as carbon dio~ide, prior to release of the waste gas stream to the atmosphere.
00921~; Dkt-2 ~q~9 One method of accomplishing the objective of rendering waste gas streams environmentally acceptable prior to releasing them to the atmosphere, is to burn the yases. This method can be employed when substantially all of the harmful components are removed from the gas streams and no other harmful gaseous substance are produced by incineration of the stream. For instance, when the gas stream originally contains only hydrocarbons as heavy gases, the gas stream may be burned, provided that combustion is sufficiently complete that the combustion by-products constitute substantially only water vapor and carbon dioxide.
Combustion of waste gas streams is not always a suitable method for the elimination of environmentally unacceptable components from the stream. For example, when the stream contains significant quantities of hydrocarbon, combustion of the stream will produce large quantities of CO2, the release of which to the environment will additionally burden an already overta~ed ecosystem. Furthermore, it often happens that the gas stream contains components which are not combustible, or which are combustible, but upon burning produce noxious combustion by-products. For example, many chlorinated hydrocarbons are not flammable, and others, although flammable, produce chlorine-containing by-products which themselves are not environmentally acceptable. It can readily be appreciated, therefore, that when a waste gas stream contains components which cannot be safely removed or destroyed from the stream by combustion, other techniques must be employed.
A commonly used technique for removing heavy gas components from waste gas streams is to separate the components by fractional distillation. Thus, high boiling gas components can often be separated from low boiling gases, such as o~ygen, nitrogen and argon, by cooling and compressing the gas stream to a temperature below the boiling point of the high boiling , . .
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0092G Dkt . ~o . 91A251 20~9~0 components at the e~isting pressure, and subsequently separating the components by means of distillation. When the gas mi~ture contains only the light gases mentioned above, a.e., nitrogen, oxygen, argon, etc., and the higher boiling compounds that are to be removed, i.e., ~ubstituted hydrocarbons ~nd C3 and higher unsubstituted hydrocarbons, a clean separation of the high boiling gases from the light gases can usually be effected by fractional distillation~ However, when methane or any of the C2 hydrocarbons are present in the gas mixture in addition to the low boiling and high boiling gases, it is o~ten difficult to obtain a clean separation by distillation. During the course of the distillation, the C
and C2 hydrocarbons, because of their low boiling points, distill off with the light gases. However, due to the solubility of the high boiling gas components in the light hydrocarbons, some of the high boiling compounds are also distilled off with the light gases. Thus, conventional fractional distillation cannot be effectively employed to separate high boiling hydrocarbons and substituted hydrocarbons from low boiling gases in gas mi~tures when the gas mi~tures also contain methane and/or C2 hydrocarbons.
Because of increasingly stringent environmental regulations, and because of the economic ad~antages offered by recovering and recycling high boiling hydrocarbons, there is a continuing effort to find improved methods for the removal of high boiling hydrocarbons from waste gas streams which additionally contain methane and/or one or more C2 hydrocarbons and low boiling environmentally acceptable gases.
The present invention provides an effective and efficient method for accomplishing this result~
~IMARY OF THE INVENTION
According to the invention, a gas mi~ture containing one or more high boiling gases, one or more low bo;ling gases and one :
0092G Dkt. No. 91A251 4 2 ~ 8 0 or more light hydrocarbons (all defined below) is subjected to adsorptive separation to produce an unadsorbed product gas stream that is enriched in low boiling gases and light hydrocarbons but substantially free of high boiling gases, and a desorbed gas product stream enriched in high boiling gases.
The two product gas streams can then be further treated, if desired, to separate the various components of each of the gas streams.
According to the process asplect of the invention, gases having boiling points ~reater than about -80~C are separated from a gas mixture containing one or more gaseous components having boiling points in the range of about -80C to about 50C, one or more hydrocarbons having boiling points between about -170C and about -80C, and one or more gaseous components having boiling points below about -170C. This is accomplished by passing the gaseous mixture through a bed of adsorbent which adsorbs the gaseous components having boiling points greater than about -80C more readily than it adsorbs gaseous components having boiling points lower than about -80C, thereby producing an unadsorbed gaseous product stream which is enriched in those components having boiling points less than about -80C and a desorbed gaseous product stream that is enriched in components having boiling points greater than about -80C.
In a preferred embodiment of the process of the invention, the adsorbent is activated carbon, silica gel, zeolites, carbon molecular sieves and mixtures of these.
In another preferred embodiment, the unadsorbed gaseous product stream is subjected to one or more additional adsorptive separations to recover methane and C2 hydrocarbons from the unadsorbed gaseous product stream.
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0092G Dkt. No. 91A251 2~380 In yet another preferred embodiment, applicable to the separation of gaseous mixtures which contain, in addition to low boiling gases and light hydrocarbons, two or more gaseous components having boiling points in the range of about -80C to about 50C, the invention comprises subjecting the high boiling gas-containing desorbed gaseous product stream to one or more fractional distillatisn steps to separately r~cover ~ome or all of the components of this stream.
In another preferred embodiment, hydrogen and/or carbon mono~ide present in the waste gas stream are o~idized to water and carbon dioxide, respectively.
In a most preferred embodiment, the process of the invention is applied to the recovery of two or more gases having boiling points in the range of about -80C to about 50C, one or more hydrocarbons selected from methane, ethane, ~thene and ethyne, and one or more light gaseous components selected from oxygen, nitrogen, argon, hydrogen and carbon mono~ide. According to this aspe~t of the invention, the gaseous mi~ture is subjected to a first adsorptive separation in a bed comprising an adsorbent selected from activated carbon, silica gel, zeolites, carbon molecular sieves or mi~tures of these, thereby producing an unadsorbed gaseous product stream enriched in low boiling gases and light hydrocarbons, but suostantially depleted of high boiling gases, and a desorbed gaseous product stream enriched in high boiling ~ases. The unadsorbed gaseous product stream is then subjected to a second adsorptive separation, thereby recovering an unadsorbed gas stream enriched in low boiling gases and a desorbed gaseous product enriched in one or more of methane, ethane~ ethene and ethyne. Also, according to this embodiment, the desorbed gaseous product enriched in the high boiling gaseous components can be subjected to one or more fractional distillation steps to separately recover the components of the high boiling gas mi~ture.
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0092G Dkt. No. 91A251 2~93~
-- 6 ~
BRIEF D~SCRIPTION OF THE DRAWING
Fig. 1 broadly illustrates, in a schematic diagram, apparatus iD which the process of the invention can be carried out.
Fig. 2 illustrates, in a schematic diagram, apparatus in which a preferred embodiment of the invention can be carried out.
DETAILED DES~R.IPTION OF T~E INVENTION
The invention provides an effective and efficient method for recovering high boiling gases from a gaseous mi~ture comprised of one or more hiyh boiling gases, one or more low boiling gases and one or more light hydrocarbons. To simplify the description of the invention, these terms are specifically define~ as follows:
The term Uhigh boiling gas , is used herein to denote an organic or inorganic gaseous element or compound which, in the liquid state, has a normal boiling point above about -80C.
E~amples of high boiling gases are unsubstituted hydrocarbons having three or more carbon atoms, halogenated hydrocarbons, nitrogen-substituted hydrocarbons, o~ygen-substituted hydrocarbons and sulphur-substituted hydrocarbons.
The term ~low boiling gas~ is used to denote a gaseous element or compound which, in the liquid state, has a normal boiling point below about -170C. Typical of the low boiling gases are the atmospheric gases such as o~ygen, nitrogen, argon, helium and hydrogen.
The term "light hydrocarbon~ is used to denote a hydrocarbon having a normal boiling point between about -170C
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. ,:
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0092G Dkt. No. 91A251 7_ 21~380 and -80C. Hydrocarbons having boiling points in this range include methane, ethane, ethene and ethyne.
The ~normal boiling point~ of an element or a compound is the boiling point of the element or compound at standard pressure, i.e. 760 mm barometric pressure.
According to a main embodiment of the process of the invention, the gas mi~ture being treated is initially subjected to a high boiling gas adsorptive separation in an adsorption bed which contains an absorbent that strongly adsorbs high boiling gases, thereby producing an unadsorbed gaseous product that is enriched in low boiling gases and light hydrocarbons but substantially depleted in high boiling gases, and an desorbed gaseous product that is enriched in high boiling gases.
There are a number of options available for treating the unadsorbed gas product stream obtained from the rough cut adsorptive separation step. One option, available when the unadsorbed gas product stream does not contain environmentally objectionable non-atmospheric gas components, e.g. carbon monoxide and light hydrocarbons, at concentrations above their ma~imum allowable limits, is to vent this stream to the atmosphere.
A second option is to incinerate this stream to burn carbon monoside, hydrogen and light hydrocarbons. This option is feasible only when the concentrations of these gases in the unadsorbed gaseous product stream are below the concentration levels that would make recovery of these components economically worth while.
A third alternative, worthwhile when the unadsorbed gaseous product stream contains significant concentrations of light hydrocarbons, is to subject this gas stream to a second adsorptive separation to recover the light hydrocarbons from . . ,; . .
. .
., .. . ~ , ~ .
0092G Dkt. No. 91A251 2~938~
the unadsorbed gas product ~tream. This is accomplished by introducing the unadsorbed gaseous product stream from the high boiling gas adsorptior zone into a second adsorption zone containing an adsorbent that adsorbs the light hydrocarbons conta~ned in the gas stream more strongly than it adsorbs the low boiling gases, thereby producing a ~econd unadsorbed gaseous product stream that is enriched in low boiling gases but depleted in light hydrocarbons and a desorbed gas product stream which is enriched in light hydrocarbons. The unadsorbed gaseous product stream from the light hydrocarbon adsorption section can be discharged to the atmosphere and the desorbed gaseous product stream can be used as fuel or as feed for a chemical process.
The high boiling gas components that were adsorbed in the high boiling gas adsorption section are desorbed during regeneration of the adsorbent. The desorbed high boiling gases can be incinerated if the resulting combustion gases do not contain components that are environmentally objectionable.
Alternatively, the high boiling components of this stream may be recovered or otherwise disposed of, if desired. When the desorbed gas stream from the high boiling gas adsorption section contains more than one component this stream may be suhjected to one or more fractional distillation steps to recover some or all of the components of the gas stream.
The invention can be better understood from the attached drawings. Only the principal components necessary for practicing the invention, together with connecting fluid transfer lines, are included in the drawings. Valves and auxiliary equipment that are not necessary for an understanding of the invention have been omitted.
Turning now to the drawings, Fig. 1 illustrates, in a schematic diagram, a system in which the process of the invention can be carried out. The major components included in 0092G Dkt, No. 91A251 - 9 2~9380 the equipment train shown in Fig. 1 are a high boiling gas adsorption ~ection, 4, a light hydrocarbon adsorption section, 12, and a cryogenic distillation ~ection, 28. Adsorption section 4 is provided with a feed gas line, 2, an unadsorbed gas product line, 6 a~d a desorbed product gas line, 22.
Unadsorbed product ~as line 6 joins vent line B and hydrocarbon adsorption section feed line 12. A low boiling gas product line 14 exits adsorption section 12 and connects to vent line 16 and rough cut adsorption zone purge gas line 18. Adsorption section 12 is also provided with a desorbed light hydrocarbon product gas line 20. Desorbed high boiling gas line 22 connects high boiling gas adsorption section 4 to both waste gas disposal line 24 and cryogenic distillation section feed line 26. Feed line 26 is, in turn, connected to cryogenic distillation section 28, which is provided with light product discharge line 30 and heavy product discharge line 32.
The high boiling gas adsorption section may comprise a single adsorption unit, but it generally comprises a battery of two or more adsorbers arranged in parallel and operated out of phase with each other so that unadsorbed product gas and desorbed product gas are continuously produced during the operation of this section. In other words while one adsorber of this section is in the adsorption mode another is in the depressurization mode, a third is in the desorption mode etc.
Similarly, the light hydrocarbon adsorption section may comprise a single adsorber but ~enerally comprises a battery of two or more adsorption units, likewise operated out of phase to provide a continuous flow of unadsorbed and desorbed product gases. The number, arr~ngement and design of the adsorbers in each of these adsorption section6 is a matter of choice and forms no part of this invention. Similarly, the operation of the sdsorption sections in a manner to produce a continuous flow of product streams is well known and likewise forms no part of the present invention.
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0092G Dkt . No . 91A251 2~69380 Fractional distillation section 28 may comprise a single distillation column or a battery of two or more columns arrange~ in series, depending on the number of components in the unadsorbed product gas stream and the degree of product separation desired. This section may be designed to operate at low temperatures, i.e. un~er cryogenic conditions, or at higher temperatures or at combinations of these conditions. The design and operation of fractional distillation sections suitable for use in the system of the invention are well known and form no part of the invention.
In practicing the process of the invention in the apparatus of Fig. 1, a feed gas mixture comprised of one or more high boiling gases, one or more light hydrocarbons and one or more low boiling gases is introduced into adsorber 4 via feed line 2. The high boiling gas components of the mixture are adsorbed onto the adsorbent in adsorber 4, while a large percentage of the low boiling gases and light hydrocarbons ~ntering adsorber 4 pass through the adsorbent bed and e~it adsorber 4 through line 6 as the unadsorbed gas product stream. If the unadsorbed gas product stream leaving adsorber 4 contains only trace amounts of light hydrocarbons, this stream may be incinerated or vented to the atmosphere. In this case, these gases exit the system through vent line 80 If, on the other hand, it is desired to subject the unadsorbed gas product stream leaving adsorber 4 to further adsorpti~e separation, this stream is introduced into adsorber 12 through line 10.
As the unadsorbed gas product stream e~iting high boiling gas adsorption section 4 passes through hydrocarbon adsorption section 12, the light gas components o the ~tream, comprised principally of low boiling gases, pass through the adsorbent bed, exit section 12 through unadsorbed gas product line 14 and leave the system through vent 16. If this gas stream does not contain environmentally objectionably high concentrations of hydrocarbon ~ases and carbon mono~ide it may be vented directly '-0092G Dkt. No. 91A251 11 2069~80 to the atmosphere. If, howe~er, it contains these components in higher than allowable concentrations, this gas stream must be further treated to remove the e~cess amounts.
The light hydrocarbons entering adsorption ~ection 12 are adsorbed onto the adsorbent. These components are removed from the a~sorbent bed during desorption of the bed and are discharged from the system through line 20. As noted ~bove, the desorbed gases can be incinerated or reco~ered for use in chemical process operations.
The adsorption process conducted in each adsorber of adsorption section 4 is permitted to continue until the high boiling gas front in the adsorber reaches the desired point.
At this point, which is prior to breakthrough of the component(s) being adsorbed through the product end of the adsorber in operation, the adsorption step in that adsorber is terminated and the adsorbed gases are desorbed from the bed by depressurization of the adsorber. During the desorption ~tep, the high boiling gases leave adsorber 4 through line 22.
Adsorber 4 can be purged with low boiling gas product from adsorber 12 via purge line 18. If the high boiling gases have little value and do not contain components which, upon combustion, result in the production of gas products that are harmful to the atmosphere, they may be discharged to an incinerator through line 24. hikewise, if this gas stream requires additional treatment (other than fractional distillation) or is comprised of a single high boiling component, it may be removed from the system for further processing or storage through line 24.
If the desorbed gas stream in line 22 contains more than one high boiling gas component, the stream components can be separated in fractional distillation unit 28, which, if desired, can be operated under cryogenic conditions. When this option is esercised, the desorbed gas stream enters fractional , 0092G Dkt. ~o. 91A251 - 12 - ~938~
distillation unit 28 through feed line 26, and the light and heavy product components leave unit 28 through lines 30 and 32, respectively. As indicated above, if the high boiling gas stream contains more than two components, multiple, serially-connected distillation UllitS may be used to effect recovery of the various components of the gas stream.
In some cases the desorbed gas stream from the high boiling gas adsorption sect;on may contain undesirably high concentrations of the low boiling gas components of the gas stream. In such cases, a portion of the desorbed gaseous product stream can be recycled to the feed stream. This will result in a reduction in the overall concentration of low boiling gases in the desorbed product stream.
Fig. 2 illustrates a simplified version of a preferred embodiment of the invention. The system of Fig. 2 is designed for the continuous ~eparation of high boiling gases and light hydrocarbons from low boiling gases contained in a gas stream comprised of these components. The equipment components of the system illustrated in Fig. 2 include a feed gas compressor 104, a rough cut adsorption zone 106, a light hydrocarbon adsorption zone 110, and a fractional distillation zone 124.
In practicing the process of the invention in the system illustrated in Fig. 2, the feed gas mi~ture, which typically contains the high boiling gases, the low boiling gases and one or more light hydrocarbons selected from methane, ethane, ethene and ethyne, is introduced into the system through feed line 102, ;s pressurized to the desired pressure in feed gas compressor 104 and is introduced into adsorption zone 106. The high boiling gas components of the mi~ture are adsorbed onto the bed contained in adsorber 106, while the unadsorbed gas stream, enriched in low boiling gases and light hydrocarbons passes through the adsorption bed and e~its the adsorption zone thxough product line 108. The unadsorbed gas stream ne~t enters light hyclrocarbon adsorption zone 110 wherein the C2 0092G Dkt. No. 91A251 2~6~80 - 13 ~
hydrocarbons and perhaps some or all of the methane contained in the gas stream are adsorbed onto the adsorbent in a~sorber 110 and the unadsorbed gas stream, enriched in low boiling gases, esits the adsorber and le!aves the ~ystem through line ~12.
When the beds in the adsorption modes in zones 106 and 110 become saturated with adsorbed gas, the ~eds are switched in the well known manner and the ~aturated beds are then regenerated, thereby producing the desorbed gas streams.
During the regeneration modes it may be desirable to purge the beds with the unadsorbed product gas from adsorption zone 110, which is comprised substantially of low boiliny gases. This can be accomplished by passing the low boiling gas stream produced in adsorption zone 110 through lines 116, 11~ and 120 and then counter-currently through adsorption zones 106 and 110.
The desorbed gas stream leaving adsorption zone 110, comprised predominantly of light hydrocarbons, can be incinerated or used in other chemical processes.
The desorbed gas stream leaving adsorption zone 106 during desorption of the adsorbers in this zone is cornprised predominantly of high boiling gases. This stream passes through line 122 and enters fractional distillation unit 124, which separates the gas com~onents into a light gas product and a heavy gas product. The light gas producit leaves unit 124 through line 126 and the heavy product leaves unit 124 through line 128. ~f the high ~oiling gas stream contains more than two components these may ~e separat~ly recovered by means o~
addition~l fractional distillation units arranged in series with unit 124.
The invention is further illustrated in the following hypothetical e~ample wherein, unless otherwise indicated, parts, psrcentages and ratios are on a volume basis.
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t::RR062091 PATENT
0092G Dkt . No . 91A251 ~ 14 - 2~693~0 ~ gas stream having the composition indicated in TABLE 1 is treated by the process of the invention in a simulated run to remove methyl chloride ~rom the stream. The equipment train used in the simulated run is æimilar to the equipment train illustrated in Fiy. 2 and ~ompris~es a first set of adsorbers containing silica gel and a second set of adsorbers containing activated carbon. The $eed stream entering each s0t of adsorbers is at a pressure in the range of about 20 - 25 psia.
The gases adsorbed in each set of adsorbers is desorbed at an absolute pressure of about 200 millibars. About 61% of the desorbed gas stream from the first set of adsorbers is recycled to the feed stream. The remainder of the desorbed gas stream from the first set of adsorbers is discharged from the system as desorbed product. The projected molar concentrations of the components in each stream is tabulated in the TABLE.
æu, ~ ~ ~tnr~lc~n ~ U ~ U
o~ C ~
o ~ U~
o ~ ~ ~ :o Zi ~ ....
a) ~ ~1 o o ~D
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0092~ Dkt. No. 91A251 2~38~
The above e~ample illustrates the projected efficiency of the invention for removing hi~h boiling gaseous components from a gas stream. In the process depicted in EX~MP~E 1, all of the me~hyl chloride in the feed stream will be adsorbed in the first ~et of adsorbers, while the non-adsorbed product from the second set of adsorbers will contain 16.9 moles of nitrogen (about 85.4~ of the nitrogen in the feed stream~.
Although the invention has been described with particular reference to the illustrated embodiments and a specific example, variations o these are contemplated. For example, other gas separation techniques, such as membrane separation and absorption can be used in the invention in combination with the adsorption steps depicted in the drawings. Furthermore, the efficiency of the disclosed process can be increaæed by conducting multiple adsorption steps in series and/or in parallel and by recycling any of the product streams from the various adsorbers. The scope of the invention îs limited only by the breadth of the appended claims.
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0092G Dkt. Mo. 91A251 2~69380 METHOD ~OR REMOVING PERMA~ENT GA~E~ AND LIGHT
HYDROCAR~ONS FROM WASTE AND PROCESS GAS STREAMS
AND PETROCHEMICAL PROCESSES
BACKGROUND OF THE TNVENTION
This invention relates to the :removal of certain components from gas streams, and more particularly to the removal of valuable or environmentally unacceptable components from waste gas streams prior to relea5e of the waste gas streams to the atmosphere.
Waste gas streams fron~ chemical manufacturing or processing plants usually contain light gas elements or compounds which are not incompatible with the environment and thus can be released to the atmosphere. For e~ample, o~ygen, nitrogen, argon~ water vapor and carbon dioxide are commonly present in significant quantities in waste gas streams. It is also not uncommon for waste gas streams to contain trace amounts of hydrogen and helium. Since these gases are naturally occurring components of the atmosphere, they are environmentally acceptable and may be released to the atmosphere in reasonable quantities.
It often happens, however, that chemical plant waste gas streams contain higher boiling components which cannot be released to the atmosphere in concentrations above a specified tolerance limit. In such cases, the environmentally unacceptable gas components must be removed from the waste gas stream or converted to relatively harmless compounds, such as carbon dio~ide, prior to release of the waste gas stream to the atmosphere.
00921~; Dkt-2 ~q~9 One method of accomplishing the objective of rendering waste gas streams environmentally acceptable prior to releasing them to the atmosphere, is to burn the yases. This method can be employed when substantially all of the harmful components are removed from the gas streams and no other harmful gaseous substance are produced by incineration of the stream. For instance, when the gas stream originally contains only hydrocarbons as heavy gases, the gas stream may be burned, provided that combustion is sufficiently complete that the combustion by-products constitute substantially only water vapor and carbon dioxide.
Combustion of waste gas streams is not always a suitable method for the elimination of environmentally unacceptable components from the stream. For example, when the stream contains significant quantities of hydrocarbon, combustion of the stream will produce large quantities of CO2, the release of which to the environment will additionally burden an already overta~ed ecosystem. Furthermore, it often happens that the gas stream contains components which are not combustible, or which are combustible, but upon burning produce noxious combustion by-products. For example, many chlorinated hydrocarbons are not flammable, and others, although flammable, produce chlorine-containing by-products which themselves are not environmentally acceptable. It can readily be appreciated, therefore, that when a waste gas stream contains components which cannot be safely removed or destroyed from the stream by combustion, other techniques must be employed.
A commonly used technique for removing heavy gas components from waste gas streams is to separate the components by fractional distillation. Thus, high boiling gas components can often be separated from low boiling gases, such as o~ygen, nitrogen and argon, by cooling and compressing the gas stream to a temperature below the boiling point of the high boiling , . .
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0092G Dkt . ~o . 91A251 20~9~0 components at the e~isting pressure, and subsequently separating the components by means of distillation. When the gas mi~ture contains only the light gases mentioned above, a.e., nitrogen, oxygen, argon, etc., and the higher boiling compounds that are to be removed, i.e., ~ubstituted hydrocarbons ~nd C3 and higher unsubstituted hydrocarbons, a clean separation of the high boiling gases from the light gases can usually be effected by fractional distillation~ However, when methane or any of the C2 hydrocarbons are present in the gas mixture in addition to the low boiling and high boiling gases, it is o~ten difficult to obtain a clean separation by distillation. During the course of the distillation, the C
and C2 hydrocarbons, because of their low boiling points, distill off with the light gases. However, due to the solubility of the high boiling gas components in the light hydrocarbons, some of the high boiling compounds are also distilled off with the light gases. Thus, conventional fractional distillation cannot be effectively employed to separate high boiling hydrocarbons and substituted hydrocarbons from low boiling gases in gas mi~tures when the gas mi~tures also contain methane and/or C2 hydrocarbons.
Because of increasingly stringent environmental regulations, and because of the economic ad~antages offered by recovering and recycling high boiling hydrocarbons, there is a continuing effort to find improved methods for the removal of high boiling hydrocarbons from waste gas streams which additionally contain methane and/or one or more C2 hydrocarbons and low boiling environmentally acceptable gases.
The present invention provides an effective and efficient method for accomplishing this result~
~IMARY OF THE INVENTION
According to the invention, a gas mi~ture containing one or more high boiling gases, one or more low bo;ling gases and one :
0092G Dkt. No. 91A251 4 2 ~ 8 0 or more light hydrocarbons (all defined below) is subjected to adsorptive separation to produce an unadsorbed product gas stream that is enriched in low boiling gases and light hydrocarbons but substantially free of high boiling gases, and a desorbed gas product stream enriched in high boiling gases.
The two product gas streams can then be further treated, if desired, to separate the various components of each of the gas streams.
According to the process asplect of the invention, gases having boiling points ~reater than about -80~C are separated from a gas mixture containing one or more gaseous components having boiling points in the range of about -80C to about 50C, one or more hydrocarbons having boiling points between about -170C and about -80C, and one or more gaseous components having boiling points below about -170C. This is accomplished by passing the gaseous mixture through a bed of adsorbent which adsorbs the gaseous components having boiling points greater than about -80C more readily than it adsorbs gaseous components having boiling points lower than about -80C, thereby producing an unadsorbed gaseous product stream which is enriched in those components having boiling points less than about -80C and a desorbed gaseous product stream that is enriched in components having boiling points greater than about -80C.
In a preferred embodiment of the process of the invention, the adsorbent is activated carbon, silica gel, zeolites, carbon molecular sieves and mixtures of these.
In another preferred embodiment, the unadsorbed gaseous product stream is subjected to one or more additional adsorptive separations to recover methane and C2 hydrocarbons from the unadsorbed gaseous product stream.
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0092G Dkt. No. 91A251 2~380 In yet another preferred embodiment, applicable to the separation of gaseous mixtures which contain, in addition to low boiling gases and light hydrocarbons, two or more gaseous components having boiling points in the range of about -80C to about 50C, the invention comprises subjecting the high boiling gas-containing desorbed gaseous product stream to one or more fractional distillatisn steps to separately r~cover ~ome or all of the components of this stream.
In another preferred embodiment, hydrogen and/or carbon mono~ide present in the waste gas stream are o~idized to water and carbon dioxide, respectively.
In a most preferred embodiment, the process of the invention is applied to the recovery of two or more gases having boiling points in the range of about -80C to about 50C, one or more hydrocarbons selected from methane, ethane, ~thene and ethyne, and one or more light gaseous components selected from oxygen, nitrogen, argon, hydrogen and carbon mono~ide. According to this aspe~t of the invention, the gaseous mi~ture is subjected to a first adsorptive separation in a bed comprising an adsorbent selected from activated carbon, silica gel, zeolites, carbon molecular sieves or mi~tures of these, thereby producing an unadsorbed gaseous product stream enriched in low boiling gases and light hydrocarbons, but suostantially depleted of high boiling gases, and a desorbed gaseous product stream enriched in high boiling ~ases. The unadsorbed gaseous product stream is then subjected to a second adsorptive separation, thereby recovering an unadsorbed gas stream enriched in low boiling gases and a desorbed gaseous product enriched in one or more of methane, ethane~ ethene and ethyne. Also, according to this embodiment, the desorbed gaseous product enriched in the high boiling gaseous components can be subjected to one or more fractional distillation steps to separately recover the components of the high boiling gas mi~ture.
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0092G Dkt. No. 91A251 2~93~
-- 6 ~
BRIEF D~SCRIPTION OF THE DRAWING
Fig. 1 broadly illustrates, in a schematic diagram, apparatus iD which the process of the invention can be carried out.
Fig. 2 illustrates, in a schematic diagram, apparatus in which a preferred embodiment of the invention can be carried out.
DETAILED DES~R.IPTION OF T~E INVENTION
The invention provides an effective and efficient method for recovering high boiling gases from a gaseous mi~ture comprised of one or more hiyh boiling gases, one or more low boiling gases and one or more light hydrocarbons. To simplify the description of the invention, these terms are specifically define~ as follows:
The term Uhigh boiling gas , is used herein to denote an organic or inorganic gaseous element or compound which, in the liquid state, has a normal boiling point above about -80C.
E~amples of high boiling gases are unsubstituted hydrocarbons having three or more carbon atoms, halogenated hydrocarbons, nitrogen-substituted hydrocarbons, o~ygen-substituted hydrocarbons and sulphur-substituted hydrocarbons.
The term ~low boiling gas~ is used to denote a gaseous element or compound which, in the liquid state, has a normal boiling point below about -170C. Typical of the low boiling gases are the atmospheric gases such as o~ygen, nitrogen, argon, helium and hydrogen.
The term "light hydrocarbon~ is used to denote a hydrocarbon having a normal boiling point between about -170C
:
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0092G Dkt. No. 91A251 7_ 21~380 and -80C. Hydrocarbons having boiling points in this range include methane, ethane, ethene and ethyne.
The ~normal boiling point~ of an element or a compound is the boiling point of the element or compound at standard pressure, i.e. 760 mm barometric pressure.
According to a main embodiment of the process of the invention, the gas mi~ture being treated is initially subjected to a high boiling gas adsorptive separation in an adsorption bed which contains an absorbent that strongly adsorbs high boiling gases, thereby producing an unadsorbed gaseous product that is enriched in low boiling gases and light hydrocarbons but substantially depleted in high boiling gases, and an desorbed gaseous product that is enriched in high boiling gases.
There are a number of options available for treating the unadsorbed gas product stream obtained from the rough cut adsorptive separation step. One option, available when the unadsorbed gas product stream does not contain environmentally objectionable non-atmospheric gas components, e.g. carbon monoxide and light hydrocarbons, at concentrations above their ma~imum allowable limits, is to vent this stream to the atmosphere.
A second option is to incinerate this stream to burn carbon monoside, hydrogen and light hydrocarbons. This option is feasible only when the concentrations of these gases in the unadsorbed gaseous product stream are below the concentration levels that would make recovery of these components economically worth while.
A third alternative, worthwhile when the unadsorbed gaseous product stream contains significant concentrations of light hydrocarbons, is to subject this gas stream to a second adsorptive separation to recover the light hydrocarbons from . . ,; . .
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0092G Dkt. No. 91A251 2~938~
the unadsorbed gas product ~tream. This is accomplished by introducing the unadsorbed gaseous product stream from the high boiling gas adsorptior zone into a second adsorption zone containing an adsorbent that adsorbs the light hydrocarbons conta~ned in the gas stream more strongly than it adsorbs the low boiling gases, thereby producing a ~econd unadsorbed gaseous product stream that is enriched in low boiling gases but depleted in light hydrocarbons and a desorbed gas product stream which is enriched in light hydrocarbons. The unadsorbed gaseous product stream from the light hydrocarbon adsorption section can be discharged to the atmosphere and the desorbed gaseous product stream can be used as fuel or as feed for a chemical process.
The high boiling gas components that were adsorbed in the high boiling gas adsorption section are desorbed during regeneration of the adsorbent. The desorbed high boiling gases can be incinerated if the resulting combustion gases do not contain components that are environmentally objectionable.
Alternatively, the high boiling components of this stream may be recovered or otherwise disposed of, if desired. When the desorbed gas stream from the high boiling gas adsorption section contains more than one component this stream may be suhjected to one or more fractional distillation steps to recover some or all of the components of the gas stream.
The invention can be better understood from the attached drawings. Only the principal components necessary for practicing the invention, together with connecting fluid transfer lines, are included in the drawings. Valves and auxiliary equipment that are not necessary for an understanding of the invention have been omitted.
Turning now to the drawings, Fig. 1 illustrates, in a schematic diagram, a system in which the process of the invention can be carried out. The major components included in 0092G Dkt, No. 91A251 - 9 2~9380 the equipment train shown in Fig. 1 are a high boiling gas adsorption ~ection, 4, a light hydrocarbon adsorption section, 12, and a cryogenic distillation ~ection, 28. Adsorption section 4 is provided with a feed gas line, 2, an unadsorbed gas product line, 6 a~d a desorbed product gas line, 22.
Unadsorbed product ~as line 6 joins vent line B and hydrocarbon adsorption section feed line 12. A low boiling gas product line 14 exits adsorption section 12 and connects to vent line 16 and rough cut adsorption zone purge gas line 18. Adsorption section 12 is also provided with a desorbed light hydrocarbon product gas line 20. Desorbed high boiling gas line 22 connects high boiling gas adsorption section 4 to both waste gas disposal line 24 and cryogenic distillation section feed line 26. Feed line 26 is, in turn, connected to cryogenic distillation section 28, which is provided with light product discharge line 30 and heavy product discharge line 32.
The high boiling gas adsorption section may comprise a single adsorption unit, but it generally comprises a battery of two or more adsorbers arranged in parallel and operated out of phase with each other so that unadsorbed product gas and desorbed product gas are continuously produced during the operation of this section. In other words while one adsorber of this section is in the adsorption mode another is in the depressurization mode, a third is in the desorption mode etc.
Similarly, the light hydrocarbon adsorption section may comprise a single adsorber but ~enerally comprises a battery of two or more adsorption units, likewise operated out of phase to provide a continuous flow of unadsorbed and desorbed product gases. The number, arr~ngement and design of the adsorbers in each of these adsorption section6 is a matter of choice and forms no part of this invention. Similarly, the operation of the sdsorption sections in a manner to produce a continuous flow of product streams is well known and likewise forms no part of the present invention.
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0092G Dkt . No . 91A251 2~69380 Fractional distillation section 28 may comprise a single distillation column or a battery of two or more columns arrange~ in series, depending on the number of components in the unadsorbed product gas stream and the degree of product separation desired. This section may be designed to operate at low temperatures, i.e. un~er cryogenic conditions, or at higher temperatures or at combinations of these conditions. The design and operation of fractional distillation sections suitable for use in the system of the invention are well known and form no part of the invention.
In practicing the process of the invention in the apparatus of Fig. 1, a feed gas mixture comprised of one or more high boiling gases, one or more light hydrocarbons and one or more low boiling gases is introduced into adsorber 4 via feed line 2. The high boiling gas components of the mixture are adsorbed onto the adsorbent in adsorber 4, while a large percentage of the low boiling gases and light hydrocarbons ~ntering adsorber 4 pass through the adsorbent bed and e~it adsorber 4 through line 6 as the unadsorbed gas product stream. If the unadsorbed gas product stream leaving adsorber 4 contains only trace amounts of light hydrocarbons, this stream may be incinerated or vented to the atmosphere. In this case, these gases exit the system through vent line 80 If, on the other hand, it is desired to subject the unadsorbed gas product stream leaving adsorber 4 to further adsorpti~e separation, this stream is introduced into adsorber 12 through line 10.
As the unadsorbed gas product stream e~iting high boiling gas adsorption section 4 passes through hydrocarbon adsorption section 12, the light gas components o the ~tream, comprised principally of low boiling gases, pass through the adsorbent bed, exit section 12 through unadsorbed gas product line 14 and leave the system through vent 16. If this gas stream does not contain environmentally objectionably high concentrations of hydrocarbon ~ases and carbon mono~ide it may be vented directly '-0092G Dkt. No. 91A251 11 2069~80 to the atmosphere. If, howe~er, it contains these components in higher than allowable concentrations, this gas stream must be further treated to remove the e~cess amounts.
The light hydrocarbons entering adsorption ~ection 12 are adsorbed onto the adsorbent. These components are removed from the a~sorbent bed during desorption of the bed and are discharged from the system through line 20. As noted ~bove, the desorbed gases can be incinerated or reco~ered for use in chemical process operations.
The adsorption process conducted in each adsorber of adsorption section 4 is permitted to continue until the high boiling gas front in the adsorber reaches the desired point.
At this point, which is prior to breakthrough of the component(s) being adsorbed through the product end of the adsorber in operation, the adsorption step in that adsorber is terminated and the adsorbed gases are desorbed from the bed by depressurization of the adsorber. During the desorption ~tep, the high boiling gases leave adsorber 4 through line 22.
Adsorber 4 can be purged with low boiling gas product from adsorber 12 via purge line 18. If the high boiling gases have little value and do not contain components which, upon combustion, result in the production of gas products that are harmful to the atmosphere, they may be discharged to an incinerator through line 24. hikewise, if this gas stream requires additional treatment (other than fractional distillation) or is comprised of a single high boiling component, it may be removed from the system for further processing or storage through line 24.
If the desorbed gas stream in line 22 contains more than one high boiling gas component, the stream components can be separated in fractional distillation unit 28, which, if desired, can be operated under cryogenic conditions. When this option is esercised, the desorbed gas stream enters fractional , 0092G Dkt. ~o. 91A251 - 12 - ~938~
distillation unit 28 through feed line 26, and the light and heavy product components leave unit 28 through lines 30 and 32, respectively. As indicated above, if the high boiling gas stream contains more than two components, multiple, serially-connected distillation UllitS may be used to effect recovery of the various components of the gas stream.
In some cases the desorbed gas stream from the high boiling gas adsorption sect;on may contain undesirably high concentrations of the low boiling gas components of the gas stream. In such cases, a portion of the desorbed gaseous product stream can be recycled to the feed stream. This will result in a reduction in the overall concentration of low boiling gases in the desorbed product stream.
Fig. 2 illustrates a simplified version of a preferred embodiment of the invention. The system of Fig. 2 is designed for the continuous ~eparation of high boiling gases and light hydrocarbons from low boiling gases contained in a gas stream comprised of these components. The equipment components of the system illustrated in Fig. 2 include a feed gas compressor 104, a rough cut adsorption zone 106, a light hydrocarbon adsorption zone 110, and a fractional distillation zone 124.
In practicing the process of the invention in the system illustrated in Fig. 2, the feed gas mi~ture, which typically contains the high boiling gases, the low boiling gases and one or more light hydrocarbons selected from methane, ethane, ethene and ethyne, is introduced into the system through feed line 102, ;s pressurized to the desired pressure in feed gas compressor 104 and is introduced into adsorption zone 106. The high boiling gas components of the mi~ture are adsorbed onto the bed contained in adsorber 106, while the unadsorbed gas stream, enriched in low boiling gases and light hydrocarbons passes through the adsorption bed and e~its the adsorption zone thxough product line 108. The unadsorbed gas stream ne~t enters light hyclrocarbon adsorption zone 110 wherein the C2 0092G Dkt. No. 91A251 2~6~80 - 13 ~
hydrocarbons and perhaps some or all of the methane contained in the gas stream are adsorbed onto the adsorbent in a~sorber 110 and the unadsorbed gas stream, enriched in low boiling gases, esits the adsorber and le!aves the ~ystem through line ~12.
When the beds in the adsorption modes in zones 106 and 110 become saturated with adsorbed gas, the ~eds are switched in the well known manner and the ~aturated beds are then regenerated, thereby producing the desorbed gas streams.
During the regeneration modes it may be desirable to purge the beds with the unadsorbed product gas from adsorption zone 110, which is comprised substantially of low boiliny gases. This can be accomplished by passing the low boiling gas stream produced in adsorption zone 110 through lines 116, 11~ and 120 and then counter-currently through adsorption zones 106 and 110.
The desorbed gas stream leaving adsorption zone 110, comprised predominantly of light hydrocarbons, can be incinerated or used in other chemical processes.
The desorbed gas stream leaving adsorption zone 106 during desorption of the adsorbers in this zone is cornprised predominantly of high boiling gases. This stream passes through line 122 and enters fractional distillation unit 124, which separates the gas com~onents into a light gas product and a heavy gas product. The light gas producit leaves unit 124 through line 126 and the heavy product leaves unit 124 through line 128. ~f the high ~oiling gas stream contains more than two components these may ~e separat~ly recovered by means o~
addition~l fractional distillation units arranged in series with unit 124.
The invention is further illustrated in the following hypothetical e~ample wherein, unless otherwise indicated, parts, psrcentages and ratios are on a volume basis.
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t::RR062091 PATENT
0092G Dkt . No . 91A251 ~ 14 - 2~693~0 ~ gas stream having the composition indicated in TABLE 1 is treated by the process of the invention in a simulated run to remove methyl chloride ~rom the stream. The equipment train used in the simulated run is æimilar to the equipment train illustrated in Fiy. 2 and ~ompris~es a first set of adsorbers containing silica gel and a second set of adsorbers containing activated carbon. The $eed stream entering each s0t of adsorbers is at a pressure in the range of about 20 - 25 psia.
The gases adsorbed in each set of adsorbers is desorbed at an absolute pressure of about 200 millibars. About 61% of the desorbed gas stream from the first set of adsorbers is recycled to the feed stream. The remainder of the desorbed gas stream from the first set of adsorbers is discharged from the system as desorbed product. The projected molar concentrations of the components in each stream is tabulated in the TABLE.
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The above e~ample illustrates the projected efficiency of the invention for removing hi~h boiling gaseous components from a gas stream. In the process depicted in EX~MP~E 1, all of the me~hyl chloride in the feed stream will be adsorbed in the first ~et of adsorbers, while the non-adsorbed product from the second set of adsorbers will contain 16.9 moles of nitrogen (about 85.4~ of the nitrogen in the feed stream~.
Although the invention has been described with particular reference to the illustrated embodiments and a specific example, variations o these are contemplated. For example, other gas separation techniques, such as membrane separation and absorption can be used in the invention in combination with the adsorption steps depicted in the drawings. Furthermore, the efficiency of the disclosed process can be increaæed by conducting multiple adsorption steps in series and/or in parallel and by recycling any of the product streams from the various adsorbers. The scope of the invention îs limited only by the breadth of the appended claims.
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Claims (12)
1. A process for the recovery of gases having boiling points greater than about -80° C. from a gaseous mixture comprising one or more gaseous components having boiling points in the range of about -80° C. to about 50° C., one or more hydrocarbons having boiling points between about -170° C. and about -80° C. and one or more gaseous components having boiling points below about -170° C. comprising subjecting said gaseous mixture to adsorptive separation in a bed of adsorbent selected from activated carbon, silica gel and mixtures of these, thereby producing an unadsorbed gaseous product enriched in components having boiling points less than about -80° C. and a desorbed gaseous product enriched in components having boiling points greater than about -80° C.
2. The process of Claim 1, wherein said gaseous mixture contains two or more gaseous components having boiling points in the range of about -80° C. to about 50° C.
3. The process of Claim 2, wherein said two or more gaseous components having boiling points in the range of about -80° C. to about 50° C. are further separated by fractional distillation subsequent to desorption from said adsorbent.
4. The process of Claim 1 or Claim 3, wherein the gaseous components present in said gaseous mixture having boiling points in the range of about -80° C.to about 50° C. include one or more members selected from the group consisting of hydrocarbons having three or more carbon atoms, halogenated hydrocarbons, nitrogen-substituted hydrocarbons, oxygen-substituted hydrocarbons and sulfur-substituted hydrocarbons.
5. The process of Claim 1, wherein said gaseous mixture contains one or more components selected from the group 0092G Dkt.No. 91A251 consisting of oxygen, nitrogen, argon, hydrogen and carbon monoxide.
6. The process of Claim 1, wherein hydrogen is present in said gaseous mixture and it is ozidized to water subsequent to the adsorption step.
7. The process of Claim 1, wherein carbon monoxide is present in said gaseous mixture and it is oxidized to carbon dioxide subsequent to the adsorption step.
8. The process of Claim 1, wherein at least one of said gaseous hydrocarbons is separated from said unadsorbed gaseous product in a second adsorptive separation step.
9. A process for the recovery of gases having boiling points greater than about -80° C. from a gaseous mixture comprising one or more heavy gaseous components having boiling points in the range of about -80° C. to about 50° C. one or more hydrocarbons selected from methane, ethane, ethene and ethyne, and one or more light gaseous components selected from oxygen, nitrogen, argon, hydrogen, and carbon monoxide, comprising subjecting said gaseous mixture to adsorptive separation in a bed comprising adsorbent selected from activated carbon, silica gel, zeolites, carbon molecular sieves and mixtures of these, thereby producing an unadsorbed gaseous product enriched in said hydrocarbons and light gaseous components and a desorbed gaseous product enriched said heavy gaseous components.
10. The process of Claim 9, wherein said unadsorbed gaseous product is subjected to a second adsorptive separation thereby producing a light product phase enriched in said light gas components and a desorbed phase enriched in one or more of methane, ethane, ethene and ethyne.
0092G Dkt. No. 91A251.
0092G Dkt. No. 91A251.
11. Apparatus useful for the recovery of gases having boiling points greater than about -80°C from a gaseous mixture comprising one or more gaseous components having boiling points in the range of about -80°C to about 50°C, one or more hydrocarbons having boiling points between about -170°C and about -80°C and one or more gaseous components having boiling points below about -170°C comprising:
(a) a first adsorption zone containing an adsorbent which adsorbs gases having boiling points greater than about -80°C more readily than it adsorbs gases having boiling points less than about -80°C;
(b) a second adsorption zone whose inlet is in fluid communication with the product end of said first adsorption zone, and containing an adsorbent which adsorbs hydrocarbons having boiling points in the range of about -170°C to about -80°C, more readily than it adsorbs gases having boiling points less than about -80°C;
(c) a cryogenic gas separation unit having an inlet in fluid communication with the feed end of said first adsorption zone, and adapted to receive and separate by fractional distillation a multi-component gas stream that is desorbed from said first adsorption zone;
(d) means for introducing said gas mixture into said first adsorption zone at super atmospheric pressures;
(e) means for recovering product gas from said second adsorption zone;
0092G Dkt. No. 91A251 (f) means for recovering desorbed gas from said second adsorption zone; and (g) means for separately recovering the components separated in the cryogenic gas separation unit.
(a) a first adsorption zone containing an adsorbent which adsorbs gases having boiling points greater than about -80°C more readily than it adsorbs gases having boiling points less than about -80°C;
(b) a second adsorption zone whose inlet is in fluid communication with the product end of said first adsorption zone, and containing an adsorbent which adsorbs hydrocarbons having boiling points in the range of about -170°C to about -80°C, more readily than it adsorbs gases having boiling points less than about -80°C;
(c) a cryogenic gas separation unit having an inlet in fluid communication with the feed end of said first adsorption zone, and adapted to receive and separate by fractional distillation a multi-component gas stream that is desorbed from said first adsorption zone;
(d) means for introducing said gas mixture into said first adsorption zone at super atmospheric pressures;
(e) means for recovering product gas from said second adsorption zone;
0092G Dkt. No. 91A251 (f) means for recovering desorbed gas from said second adsorption zone; and (g) means for separately recovering the components separated in the cryogenic gas separation unit.
12. The apparatus of Claim 11 additionally comprising means for purging said first adsorption zone with product gas from said second adsorption zone.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71987791A | 1991-06-24 | 1991-06-24 | |
| US07/719,877 | 1991-06-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2069380A1 true CA2069380A1 (en) | 1992-12-25 |
Family
ID=24891739
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2069380 Abandoned CA2069380A1 (en) | 1991-06-24 | 1992-05-25 | Method for removing permanent gases and light hydrocarbons from waste and process gas streams and petrochemical processes |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH0623221A (en) |
| AU (1) | AU663502B2 (en) |
| CA (1) | CA2069380A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0639399A1 (en) * | 1993-08-06 | 1995-02-22 | Dow Corning Corporation | Process for treatment of by-product gaseous mixture resulting from the reaction of methyl chloride with silicon |
| US5740682A (en) * | 1994-02-13 | 1998-04-21 | Ram Lavie | Method for the recovery of organic vapors |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5551257A (en) * | 1992-10-01 | 1996-09-03 | The Boc Group, Inc. | Production of ultrahigh purity nitrogen |
| AUPN195295A0 (en) * | 1995-03-24 | 1995-04-27 | Colcard Pty. Limited | Refrigerant separation using zeolite molecular sieves |
| CN112122327B (en) * | 2020-08-20 | 2022-02-22 | 广州市番禺环境工程有限公司 | Prosthetic devices based on soil thermal desorption repair technique |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3122701A1 (en) * | 1981-06-06 | 1982-12-23 | Bergwerksverband Gmbh, 4300 Essen | METHOD FOR SEPARATING GAS MIXTURES BY MEANS OF PRESSURE CHANGE TECHNOLOGY |
| US4761167A (en) * | 1986-12-12 | 1988-08-02 | Air Products And Chemicals, Inc. | Hydrocarbon recovery from fuel gas |
| GB8803767D0 (en) * | 1988-02-18 | 1988-03-16 | Ici Plc | Desulphurisation |
-
1992
- 1992-05-25 CA CA 2069380 patent/CA2069380A1/en not_active Abandoned
- 1992-06-18 AU AU18393/92A patent/AU663502B2/en not_active Ceased
- 1992-06-24 JP JP4166345A patent/JPH0623221A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0639399A1 (en) * | 1993-08-06 | 1995-02-22 | Dow Corning Corporation | Process for treatment of by-product gaseous mixture resulting from the reaction of methyl chloride with silicon |
| US5740682A (en) * | 1994-02-13 | 1998-04-21 | Ram Lavie | Method for the recovery of organic vapors |
Also Published As
| Publication number | Publication date |
|---|---|
| AU663502B2 (en) | 1995-10-12 |
| AU1839392A (en) | 1993-01-07 |
| JPH0623221A (en) | 1994-02-01 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Dead |