CA1295810C - Removal of co- and/or h-s from gases - Google Patents
Removal of co- and/or h-s from gasesInfo
- Publication number
- CA1295810C CA1295810C CA000507373A CA507373A CA1295810C CA 1295810 C CA1295810 C CA 1295810C CA 000507373 A CA000507373 A CA 000507373A CA 507373 A CA507373 A CA 507373A CA 1295810 C CA1295810 C CA 1295810C
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- Prior art keywords
- stage
- absorption
- steam
- gas
- flash
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1493—Selection of liquid materials for use as absorbents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
- B01D53/1462—Removing mixtures of hydrogen sulfide and carbon dioxide
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
- C10K1/00—Purifying combustible gases containing carbon monoxide
- C10K1/08—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors
- C10K1/10—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with aqueous liquids
- C10K1/12—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with aqueous liquids alkaline-reacting including the revival of the used wash liquors
- C10K1/14—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with aqueous liquids alkaline-reacting including the revival of the used wash liquors organic
- C10K1/143—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with aqueous liquids alkaline-reacting including the revival of the used wash liquors organic containing amino groups
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Analytical Chemistry (AREA)
- Combustion & Propulsion (AREA)
- Organic Chemistry (AREA)
- Gas Separation By Absorption (AREA)
- Treating Waste Gases (AREA)
Abstract
Abstract of the Disclosure: C02 and/or H2S are removed from gases which contain C02 and/or H2S by means of an aqueous alkanolamine-containing absorption liquid, by a process in which the said gas is treated, in an absorption stage, at from 40 to 100°C, with an aqueous absorption liquid containing from 20 to 70% by weight of methyl-diethanolamine, the treated gas is taken off at the top of the absorption stage, the aqueous absorption liquid laden with C02 and/or H2S is removed at the bottom of the absorption stage and is regenerated by being let down in two or more flash stages, the final flash stage being operated under reduced pressure and the latter being generated by means of a mechanical apparatus for producing reduced pressure and a steam-jet ejector, which are connected in series, and the regenerated absorption liquid is recycled to the absorption stage.
Description
i~35~
- 1 - O.Z. 0050/37728 Removal of C02 and/or H?S from gases The present invention relates to a process for removing C02 and/or H2S from gases by means of an aqueous absorption liquid.
It has been disclosed, for example by A.L. Kohl and F.C. Riesenfeld in Gas Purification, 3rd edition, 1979, that aqueous solutions of monoethanolamine or di-ethanolamine or m;xtures of cyclotetramethylene sulfone and an aqueous solut;on of d;isopro~anolamine can be used as solvents for remov;ng C02 and/or H2S from gases. In these processes, the solvent laden w;th C0z and, where relevant, H2S has to be regenerated in a stripp;ng column by feeding in steam, and this ;nvolves the consumpt;on of a cons;derable amount of energy. In the removal of C02 and, ;f necessary, H2S from natural gases containing higher hydrocarbons by means of a mixture of cyclotetra-methylene sulfone and an aqu00us solution of diiso-propanolamine, there is the additional disadvantage that the higher hydrocarbons have a relatively h;gh solubility ;n th;s solvent, so that the acid;c gas taken off at the top of the stripping column has a relatively high content of hydrocarbons, which, where the acidic gas contains H2S, can Lead to difficulties in a downstream Claus plant. Moreover, primary or secondary alkanolamines, such as monoethanolamine or diethanolamine, can as a rule only be used as aqueous solutions having a relatively low concentrat;on of these alkanolam;nes, s;nce the use of h;gher concentrat;ons may cause severe corrosion damage to parts of the plant.
There was therefore a need for a process for remov;ng C02 and/or H2S from gases, in which the dis-advantages of the conventional processes can be avoided.
It ;s an obj~ect of the present invention to pro-v;de a process for remov;ng C02 and/or H2S from gases, in which both capital costs and energy costs can be re-duced compared w;th the conventional processes~
We have found that this and other objects and .
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- 1 - O.Z. 0050/37728 Removal of C02 and/or H?S from gases The present invention relates to a process for removing C02 and/or H2S from gases by means of an aqueous absorption liquid.
It has been disclosed, for example by A.L. Kohl and F.C. Riesenfeld in Gas Purification, 3rd edition, 1979, that aqueous solutions of monoethanolamine or di-ethanolamine or m;xtures of cyclotetramethylene sulfone and an aqueous solut;on of d;isopro~anolamine can be used as solvents for remov;ng C02 and/or H2S from gases. In these processes, the solvent laden w;th C0z and, where relevant, H2S has to be regenerated in a stripp;ng column by feeding in steam, and this ;nvolves the consumpt;on of a cons;derable amount of energy. In the removal of C02 and, ;f necessary, H2S from natural gases containing higher hydrocarbons by means of a mixture of cyclotetra-methylene sulfone and an aqu00us solution of diiso-propanolamine, there is the additional disadvantage that the higher hydrocarbons have a relatively h;gh solubility ;n th;s solvent, so that the acid;c gas taken off at the top of the stripping column has a relatively high content of hydrocarbons, which, where the acidic gas contains H2S, can Lead to difficulties in a downstream Claus plant. Moreover, primary or secondary alkanolamines, such as monoethanolamine or diethanolamine, can as a rule only be used as aqueous solutions having a relatively low concentrat;on of these alkanolam;nes, s;nce the use of h;gher concentrat;ons may cause severe corrosion damage to parts of the plant.
There was therefore a need for a process for remov;ng C02 and/or H2S from gases, in which the dis-advantages of the conventional processes can be avoided.
It ;s an obj~ect of the present invention to pro-v;de a process for remov;ng C02 and/or H2S from gases, in which both capital costs and energy costs can be re-duced compared w;th the conventional processes~
We have found that this and other objects and .
: ~ .
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- 2 - O.Z. OOS0/37728 advantages are achieved, in accordance with the invention, by a~process for removing C2 and/or H2S from a gas con-taining C02 and/or H2S by means of an aqueous alkanolamine-containing absorption liquid, wherein, in an absorption stage, the gas containing C02 and/or H2S is treated at from 40 to 100C with an aqueous absorption liquid which con-tains from 20 to 70 % by weight of methyl-diethanolamine, the treated gas is taken off at the top of the absorption stage, the aqueous absorption liquid laden with C02 and/or H2S is removed at the bottom of this stage and is regener-ated by being let down in two or more flash stages, the final ~lash stage being operated under reduced pressure and the latter being generated by means of a mechanical apparatus for producing reduced pressure and a steam-jet ejector, which are connected ;n series, and the regener-ated absorpt;on liquid is recycled to the absorption stage.
In an advantageous embodiment of the process, the water losses resulting from removal of water in the gas streams taken off at the top of the absorption stage and from the flash stages are compensated by feeding in, at the bottom of the penultimate flash stage, an amount of steam corresponding to the water loss.
In the novel process, the solvent laden with C02 and/or H2S is regenerated solely by flashing, without the use of a stripping column, so that a substantial reduction in both capital costs and energy costs is achieved.
Furthermore, the novel process permits the use of a rela-ti~vely high concentration of methyldiethanolamine in the 3~0 absorpt;on liqu1d, without resulting in corrosion damage in the gas washer. Another advantage of the process is that the water balance~of the gas washer can be controlled in~a slmple manner.~ Using this procedure, it is possible to regulate not only the water balance of the gas washer ~` 35 but also its heat balance, so that any heat exchanger pre-s;ent in the gas washer~for regulating the heat b~alance can be smaller or, if appropriate, can be omitted. The : ~: ~ : :
:
- 3 - O.Z. 0050/37728 procedure according to the invention gives a regenerated absorption l;quid which has a low C02 and/or HzS content, so that it is possible to circulate smaller amounts of absorption Liquid; this results in a corresponding saving of energy~
In another preferred embodiment of the process, the steam-jet ejector is downstream of the mechanical apparatus for generating reduced pressure. It may be advantageous if the gas taken off at the top of the final flash stage is fed in~ together with the steam used to operate the steam-jet ejector, at the bottom of the penultimate flash stage.
Examples of gases which can be treated using the novel process are coal gasification gases, synthesis gases, coke oven gases and, preferably, natural gases. The process is advantageously used for removing C0z and/or H25 from natural gases which contain higher hydrocarbons in addition to methane. These higher ~ydrocarbons are in general C2-C30-hydrocarbons, in part;c~lar C2-C1z-hydrocarbons, which as a rule are aliphat;c, eg. ethane, propane, isobutane, n-butane, isopentane, n-pentane, the hexanes, heptanes, oc-tanes, nonanes ancl decanes and the higher homologs. The higher hydrocarbons can contain~ in addition to the ali-phatic hydrocarbons, aromatic hydrocarbons such as ben-zene. In general, the natural gases contain from 0.1 to 40, preferably from 0.5 to 30, in particular from 1 to 20, mol X of the higher hydrocarbons.
The gases contain in general from 1 to 90, prefer-ably from 2 to 90, in particular from 5 to 60, mol % of CQz. They can also contain H2S as a further acidic gas, or can contain HzS alone, for example in an amount from a few mol ppm,~for example 1 mol ppm, to 50 mol %, pre-- ferably from 10 mol ppm to 40 mol %O
The solvent used for the novel process is an aqueous absorption liquid which contains from 20 to 70, ~; ~ 35 ~preferably from 30 to 65, in particular from 40 to 60, %
by weight of methyldiethanolamine. An aqueous methyl-d1ethaAolamine solution is advantage~usly employed, for `~ ~295B-l~
In an advantageous embodiment of the process, the water losses resulting from removal of water in the gas streams taken off at the top of the absorption stage and from the flash stages are compensated by feeding in, at the bottom of the penultimate flash stage, an amount of steam corresponding to the water loss.
In the novel process, the solvent laden with C02 and/or H2S is regenerated solely by flashing, without the use of a stripping column, so that a substantial reduction in both capital costs and energy costs is achieved.
Furthermore, the novel process permits the use of a rela-ti~vely high concentration of methyldiethanolamine in the 3~0 absorpt;on liqu1d, without resulting in corrosion damage in the gas washer. Another advantage of the process is that the water balance~of the gas washer can be controlled in~a slmple manner.~ Using this procedure, it is possible to regulate not only the water balance of the gas washer ~` 35 but also its heat balance, so that any heat exchanger pre-s;ent in the gas washer~for regulating the heat b~alance can be smaller or, if appropriate, can be omitted. The : ~: ~ : :
:
- 3 - O.Z. 0050/37728 procedure according to the invention gives a regenerated absorption l;quid which has a low C02 and/or HzS content, so that it is possible to circulate smaller amounts of absorption Liquid; this results in a corresponding saving of energy~
In another preferred embodiment of the process, the steam-jet ejector is downstream of the mechanical apparatus for generating reduced pressure. It may be advantageous if the gas taken off at the top of the final flash stage is fed in~ together with the steam used to operate the steam-jet ejector, at the bottom of the penultimate flash stage.
Examples of gases which can be treated using the novel process are coal gasification gases, synthesis gases, coke oven gases and, preferably, natural gases. The process is advantageously used for removing C0z and/or H25 from natural gases which contain higher hydrocarbons in addition to methane. These higher ~ydrocarbons are in general C2-C30-hydrocarbons, in part;c~lar C2-C1z-hydrocarbons, which as a rule are aliphat;c, eg. ethane, propane, isobutane, n-butane, isopentane, n-pentane, the hexanes, heptanes, oc-tanes, nonanes ancl decanes and the higher homologs. The higher hydrocarbons can contain~ in addition to the ali-phatic hydrocarbons, aromatic hydrocarbons such as ben-zene. In general, the natural gases contain from 0.1 to 40, preferably from 0.5 to 30, in particular from 1 to 20, mol X of the higher hydrocarbons.
The gases contain in general from 1 to 90, prefer-ably from 2 to 90, in particular from 5 to 60, mol % of CQz. They can also contain H2S as a further acidic gas, or can contain HzS alone, for example in an amount from a few mol ppm,~for example 1 mol ppm, to 50 mol %, pre-- ferably from 10 mol ppm to 40 mol %O
The solvent used for the novel process is an aqueous absorption liquid which contains from 20 to 70, ~; ~ 35 ~preferably from 30 to 65, in particular from 40 to 60, %
by weight of methyldiethanolamine. An aqueous methyl-d1ethaAolamine solution is advantage~usly employed, for `~ ~295B-l~
- 4 - O.Z. 0050/37728 example an aqueous solution of technical-grade methyl-diethanolamirie. In an advantageous embodiment of the pro-cess, an aqueous methyldiethanolamine solution ~hich addi-tionally contains from 0.05 to 1, in particular from 0.1 S to 0.8, in particular from 0.1 to 0.6, mole/liter of a primary amine or alkanolamine, such as monoethanolamine, or preferably a secondary amine or alkanolamine, advantage-ously methylmonoethanolamine, very particularly advantage-ously piperazine, ;s used.
The aqueous absorption liquid containing ~rom 20 to 70% by weight of methyldiethanolamine may additionally contain a physical solvent. SuitabLe physical solvents are, for example, N-methylpyrrolidone, tetramethylene sul-fone, methanol and oligoethylene glycol dialkyl ethers, such as oligoethylene glycol methyl isopropyl ether ~SEPASOLV MPE)~or oligoethylene glycol d;methyl ether ~SELEXOL)~ The physical solvent is present in the absorp-tion liquid in general in an amount of from 1 to 60, pre-ferably from 10 to 50, in particular from 20 to 40, % by weight.
The novel process is carried out as follows: the gas conta;ning C02 and/or H2S is first treated, in an absorption stage, with the methyldiethanolamine-containing absorption liquid. During this procedure, the temperature of the absorption l;quid in the absorption stage is main-tained at from 40 to 1û0C, preferably from 50 to 90C, in particular from 60 to 80C. In general, the pressure used in the absorption stage is from 10 to 110 bar. The absorption stage ;s advantageously an absorption column, in general a packed column or a column equipped ~;th trays.
Advantageously~ the gas to be treated is fed in at the bottom and the absorption liquid is fed in at the top of ~the absorption column, the acidic gases C02 and/or HzS
~being washed out by a countercurrent procedure. While any H2S present is advant~ageously washed out to a substantial extent, in general so that the treated gas has an H2S
~ content of not more than lZO, preferably not more than 10, :~:
The aqueous absorption liquid containing ~rom 20 to 70% by weight of methyldiethanolamine may additionally contain a physical solvent. SuitabLe physical solvents are, for example, N-methylpyrrolidone, tetramethylene sul-fone, methanol and oligoethylene glycol dialkyl ethers, such as oligoethylene glycol methyl isopropyl ether ~SEPASOLV MPE)~or oligoethylene glycol d;methyl ether ~SELEXOL)~ The physical solvent is present in the absorp-tion liquid in general in an amount of from 1 to 60, pre-ferably from 10 to 50, in particular from 20 to 40, % by weight.
The novel process is carried out as follows: the gas conta;ning C02 and/or H2S is first treated, in an absorption stage, with the methyldiethanolamine-containing absorption liquid. During this procedure, the temperature of the absorption l;quid in the absorption stage is main-tained at from 40 to 1û0C, preferably from 50 to 90C, in particular from 60 to 80C. In general, the pressure used in the absorption stage is from 10 to 110 bar. The absorption stage ;s advantageously an absorption column, in general a packed column or a column equipped ~;th trays.
Advantageously~ the gas to be treated is fed in at the bottom and the absorption liquid is fed in at the top of ~the absorption column, the acidic gases C02 and/or HzS
~being washed out by a countercurrent procedure. While any H2S present is advant~ageously washed out to a substantial extent, in general so that the treated gas has an H2S
~ content of not more than lZO, preferably not more than 10, :~:
- 5 - O.Z. 0050/37728 in particular not more than 3, mol ppm, it may be advan-tageous to wash out the C02 ~rom the gas so that the treated gas contains not more than about 0.5 - 6, preferably from 0.5 to 5, in particular from 1 to 4, mol X of C0~. The treated gas is advantageously taken off at the top of the absorption stage, expediently at a point above the feed of the absorption liquid. The absorption liquid laden with the acidic~gases C02 and/or H2S is advantageously taken off at the bottom of the absorption s~age.
The laden absorption liquid is then regenerated in 2 or more, advantageously from 2 to 5, preferably 2 or 3, flash stages, the final flash stage being operated under reduced pressure, and the latter being generated by means of a mechanical apparatus for producing reduced pressure and a steam-jet ejector, which are connected in series, and any water losses resulting from removal of water in the gas streams taken off at the top of the absorption stage and of the flash stages may be compensated by simultaneously feeding in, at the bottom of the penultimate flash stage, an amount of steam corresponding to the water loss. Pre-ferably, a pressure of from about 0.3 to about 1, prefer-ably from 0.4 to about 1, in particular from 0.5 to about 0.9, bar is maintained in the final flash stage. Examples of suitable mechanical apparatus for producing reduced pressure are vacuum pumps and, preferably, compressors, eg. screw compressors or centrifugal compressors. The steam-jet ejector is preferably downstream of the mechani-cal apparatus for producing reduced pressure. In general, the flash stages are operated at from 35 to 100C, prefer-ably fram 45 to 90C, in particular from 55 to 85C.
To compens~ate for water losses which ar;se in theprocess as a result of water being removed in the gas streams taken off at the top of the absorption stage and from the flash stages, an amount of steam corresponding 35~ to the water loss is ~advantageously fed in at the bottom of the penultimate flash stage. As a rule, the water ~; present in the gas streams taken off is substantially "
`' ~.;~5~
.
The laden absorption liquid is then regenerated in 2 or more, advantageously from 2 to 5, preferably 2 or 3, flash stages, the final flash stage being operated under reduced pressure, and the latter being generated by means of a mechanical apparatus for producing reduced pressure and a steam-jet ejector, which are connected in series, and any water losses resulting from removal of water in the gas streams taken off at the top of the absorption stage and of the flash stages may be compensated by simultaneously feeding in, at the bottom of the penultimate flash stage, an amount of steam corresponding to the water loss. Pre-ferably, a pressure of from about 0.3 to about 1, prefer-ably from 0.4 to about 1, in particular from 0.5 to about 0.9, bar is maintained in the final flash stage. Examples of suitable mechanical apparatus for producing reduced pressure are vacuum pumps and, preferably, compressors, eg. screw compressors or centrifugal compressors. The steam-jet ejector is preferably downstream of the mechani-cal apparatus for producing reduced pressure. In general, the flash stages are operated at from 35 to 100C, prefer-ably fram 45 to 90C, in particular from 55 to 85C.
To compens~ate for water losses which ar;se in theprocess as a result of water being removed in the gas streams taken off at the top of the absorption stage and from the flash stages, an amount of steam corresponding 35~ to the water loss is ~advantageously fed in at the bottom of the penultimate flash stage. As a rule, the water ~; present in the gas streams taken off is substantially "
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- 6 - O.Z. 0050/37728 removed in the form of steam. Low-pressure, medium-pressure or high-pressure steam, eg. steam under 1~5-100 bar, can be fed to the bottom of the penultimate flash stage. Preferably, low-pressure steam, eg. steam under 1.5-10~ advantageously 1.5-S, bar, is used, since this steam is in general cheaply available.
The gas taken off at the top of the final flash stage can be released to the atmosphere or, if it still contains HzS, can be worked up by oxidizing the H2S, for example in a Claus unit. In an advantageous embodiment of the process, the steam-jet ejector is do~nstream of the mechanical apparatus for producing reduced pressure, and, expediently, the gas taken off at the top of the final flash stage ;s fed ;n, together with the steam used to operate the steam-jet ejector, at the bottom of the penultimate flash stage.
Where the steam used to operate the steam-jet ejector ;s fed in at the bottom of the penultimate flash stage, the ejector is advantageously operated using an amount of steam corresponding to that required to compen-sate the water losses in the process. However, it ;s also possible to operate the steam-jet ejector with an amount of steam smaller than that required to compensate the water losses, and in add;tion to feed in the lacking amount of steam at the bottom of the penultimate flash stage. The steam-jet ejector can be operated using medium-pressure or high-pressure steam. Medium-pressure steam, eg. under 5-Z0, preferably 5-10, bar, is preferably ; used.
The penultima~e flash stage is advantageously oper-ated under a pressure of about 1-30, preferably about 1-25, in particular about 1-Z0, bar.
Flashing is advantageously carried out using flash chambers which can, for example, also be in the form of columns. These flash chambers need not contain special baffles,~ although columns equipped with baffles, eg.
packed columns, may also be used.
: :
` ~295;~1~
The gas taken off at the top of the final flash stage can be released to the atmosphere or, if it still contains HzS, can be worked up by oxidizing the H2S, for example in a Claus unit. In an advantageous embodiment of the process, the steam-jet ejector is do~nstream of the mechanical apparatus for producing reduced pressure, and, expediently, the gas taken off at the top of the final flash stage ;s fed ;n, together with the steam used to operate the steam-jet ejector, at the bottom of the penultimate flash stage.
Where the steam used to operate the steam-jet ejector ;s fed in at the bottom of the penultimate flash stage, the ejector is advantageously operated using an amount of steam corresponding to that required to compen-sate the water losses in the process. However, it ;s also possible to operate the steam-jet ejector with an amount of steam smaller than that required to compensate the water losses, and in add;tion to feed in the lacking amount of steam at the bottom of the penultimate flash stage. The steam-jet ejector can be operated using medium-pressure or high-pressure steam. Medium-pressure steam, eg. under 5-Z0, preferably 5-10, bar, is preferably ; used.
The penultima~e flash stage is advantageously oper-ated under a pressure of about 1-30, preferably about 1-25, in particular about 1-Z0, bar.
Flashing is advantageously carried out using flash chambers which can, for example, also be in the form of columns. These flash chambers need not contain special baffles,~ although columns equipped with baffles, eg.
packed columns, may also be used.
: :
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- 7 - O.Z. OOS0/37728 The acidic gases CO2 and/or H2S are advantageously taken off at the top of the final flash stage or (where the gas taken off at the top of this stage is fed in, to-gether with the steam for operating the steam-iet ejector, at the bottom of the penultimate flash stage) at the top or the penuLtimate flash stage. The regenerated absorption liquid taken off at the bottom of the final flash stage is recycled to the absorption stage.
The Example which follows ilLustrates the invention in more detail, the course of the process being shown diagrammatically in the figure.
In the-figure, a gas which contains COz and/or HzS, for example a natural gas containing higher hydro-carbons, eg. aliphatic C2-C10-hydrocarbons, is passed under superatmospheric pressure, via line 1, into the bottom of absorption column 2~ At the same time, 20-70% strength by weight aqueous methyldiethanolamine solution is passed, as an absorption liquld, v;a line 3 to the top of the absorpt;on column. The absorption liquid, which is fed countercurrent to the gas, becomes laden with the ac;dic gases C2 and/or H2S, and the laden absorption liquid is taken off at the bottom of the absorption column via line 4. The washed gas is taken off at the top of the absorption column v;a l;ne 11. The stream 4 of laden absorption liquid is then let down into a flash chamber 5, for example via a valve or, preferably, an expansion tur-bine. In this stage, a flash gas is liberated from the absorpt;on l;quid and ;s taken off at the top of flash chamber 5 v;a l;ne 6.~ At the bottom of flash chamber 5, the absorpt;on l;qu;d which has been p~rtially let down is taken off v;a line 7 and~ if necessary, heated in heat exc~hanger 8, for example by from 0 to 15C, and the absorp-t;on l;quid, wh;ch may or may not have been heated, is let down into a second flash chamber 9 in which reduced pres-sure down to, for example, 0.3 bar is maintained by meansof the mechanical apparatus 14 for producing reduced pressure, for example a compressor, and the steam-jet :~:
.
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The Example which follows ilLustrates the invention in more detail, the course of the process being shown diagrammatically in the figure.
In the-figure, a gas which contains COz and/or HzS, for example a natural gas containing higher hydro-carbons, eg. aliphatic C2-C10-hydrocarbons, is passed under superatmospheric pressure, via line 1, into the bottom of absorption column 2~ At the same time, 20-70% strength by weight aqueous methyldiethanolamine solution is passed, as an absorption liquld, v;a line 3 to the top of the absorpt;on column. The absorption liquid, which is fed countercurrent to the gas, becomes laden with the ac;dic gases C2 and/or H2S, and the laden absorption liquid is taken off at the bottom of the absorption column via line 4. The washed gas is taken off at the top of the absorption column v;a l;ne 11. The stream 4 of laden absorption liquid is then let down into a flash chamber 5, for example via a valve or, preferably, an expansion tur-bine. In this stage, a flash gas is liberated from the absorpt;on l;quid and ;s taken off at the top of flash chamber 5 v;a l;ne 6.~ At the bottom of flash chamber 5, the absorpt;on l;qu;d which has been p~rtially let down is taken off v;a line 7 and~ if necessary, heated in heat exc~hanger 8, for example by from 0 to 15C, and the absorp-t;on l;quid, wh;ch may or may not have been heated, is let down into a second flash chamber 9 in which reduced pres-sure down to, for example, 0.3 bar is maintained by meansof the mechanical apparatus 14 for producing reduced pressure, for example a compressor, and the steam-jet :~:
.
~;~g5~
- 8 - O.Z. 0050/37728 ejector 13. The steam-jet ejector 13 ;s advantageously supplied~ via line 12, with the amount of steam required to compensate the water losses of the system. The gas taken off at the top of flash chamber 9 is fed, together with the steam used for operating the steam-jet ejector 13, via line 1û to the bottom of the f;rst flash chamber 5~
The Example which follows illustrates the invention.
EXAMPLE
The gas washer used comprises an absorption column and, downstream from this, three flash chambers in succes-s;on. In the absorpti~n column, 3.15 kmol/h of a C02-containing natural gas are washed, under 75 bar, with a 50% strength by weiyht aqueous methyldiethanolamine solu-tion as the absorption liquid.
The gas to be treated has the following composition:
C2 10.0 mol%
CH4 75.0 mol%
higher hydrocarbons (C2 C12-hydrocarbons) 15.0 mol~
The temperature of the absorption liquid in the feed to the absorption column is 70C. The C02 content in the washed gas iS less than 2 mol %. The laden wash liquid leaving the absorption column is let down to 30 bar in a first flash chamber. In this procedure, 0.011 mol/h of a hydrocarbon-rich intermediate flash gas having a C02 concentration of less than 4 mol ~ is liberated from the solution and taken off at the top of the first flash chamber. The partially let down absorption liquid is then heated in a heat exchanger, after which it is let down to 1.5 bar in a second flash chamber. In this procedure, 0.26 kmollh of a C02-rich flash gas having a C0z concen-tration of more than 99 mol % is liberated, and removed from the top of the second flash chamber.
The absorption liquid taken off at the bottom of the second flash chamber is passed through a heat exchanger and ~hen finally let down in a third fLash chamber in which a pressure of 0.7 bar is m~intained by means of a :: : :
~ .
;:
5~
The Example which follows illustrates the invention.
EXAMPLE
The gas washer used comprises an absorption column and, downstream from this, three flash chambers in succes-s;on. In the absorpti~n column, 3.15 kmol/h of a C02-containing natural gas are washed, under 75 bar, with a 50% strength by weiyht aqueous methyldiethanolamine solu-tion as the absorption liquid.
The gas to be treated has the following composition:
C2 10.0 mol%
CH4 75.0 mol%
higher hydrocarbons (C2 C12-hydrocarbons) 15.0 mol~
The temperature of the absorption liquid in the feed to the absorption column is 70C. The C02 content in the washed gas iS less than 2 mol %. The laden wash liquid leaving the absorption column is let down to 30 bar in a first flash chamber. In this procedure, 0.011 mol/h of a hydrocarbon-rich intermediate flash gas having a C02 concentration of less than 4 mol ~ is liberated from the solution and taken off at the top of the first flash chamber. The partially let down absorption liquid is then heated in a heat exchanger, after which it is let down to 1.5 bar in a second flash chamber. In this procedure, 0.26 kmollh of a C02-rich flash gas having a C0z concen-tration of more than 99 mol % is liberated, and removed from the top of the second flash chamber.
The absorption liquid taken off at the bottom of the second flash chamber is passed through a heat exchanger and ~hen finally let down in a third fLash chamber in which a pressure of 0.7 bar is m~intained by means of a :: : :
~ .
;:
5~
- 9 - O.Z. 0050/}7728 steam-jet ejector and a compressor. The gas taken off at the top of the third flash chamber is passed, together with the steam used for operating the steam-jet ejector, into the bottom of the second flash chamber. The absorption liquid S taken off at the bottom of the third flash chamber is recycled to the top of the absorption column with the aid of a circuLatory pump.
.
. ~
..
; ~ .
~:
'; '
.
. ~
..
; ~ .
~:
'; '
Claims (3)
1. A process for removing CO2 and/or H2S from a gas containing CO2 and/or H2S by means of an aqueous alkanolamine-containing absorption liquid, wherein, in an absorption stage, the gas containing CO2 and/or H2S is treated at from 40 to 100°C with an aqueous absorption liquid which contains from 20 to 70% by weight of methyl-diethanolamine, the treated gas is taken off at the top of the absorption stage, the aqueous absorption liquid laden with CO2 and/or H2S is removed at the bottom of this stage and is regenerated by being let down in two or more flash stages, the final flash stage being operated under reduced pressure and the latter being generated by means of a mechanical apparatus for producing reduced pressure and a steam-jet ejector, which are connected in series, and the regenerated absorption liquid is recycled to the absorption stage.
2. A process as claimed in claim 1, wherein the steam-jet ejector is downstream of the mechanical apparatus for producing reduced pressure.
3. A process as claimed in claim 2, wherein the gas taken off at the top of the final flash stage is fed in, together with the steam used for operating the steam-jet ejector, at the bottom of the penultimate flash stage.
Drawing
Drawing
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19853518368 DE3518368A1 (en) | 1985-05-22 | 1985-05-22 | METHOD FOR REMOVING CO (DOWN ARROW) 2 (DOWN ARROW) AND / OR H (DOWN ARROW) 2 (DOWN ARROW) S FROM GASES |
| DEP3518368.3 | 1985-05-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1295810C true CA1295810C (en) | 1992-02-18 |
Family
ID=6271343
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000507373A Expired - Lifetime CA1295810C (en) | 1985-05-22 | 1986-04-23 | Removal of co- and/or h-s from gases |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0202600A3 (en) |
| JP (1) | JPS61271016A (en) |
| CA (1) | CA1295810C (en) |
| DE (1) | DE3518368A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2451157C3 (en) * | 1974-10-28 | 1983-05-19 | Aluminium Norf Gmbh, 4040 Neuss | Process for cleaning exhaust air produced in large quantities during the operation of rolling stands |
| DD119610A1 (en) * | 1975-04-11 | 1976-05-05 | ||
| GB2088240B (en) * | 1980-11-28 | 1984-02-22 | British Gas Corp | Regenerating solvents in gas absorption |
| DE3308088A1 (en) * | 1983-03-08 | 1984-09-27 | Basf Ag, 6700 Ludwigshafen | METHOD FOR REMOVING CO (DOWN ARROW) 2 (DOWN ARROW) AND / OR H (DOWN ARROW) 2 (DOWN ARROW) S FROM GASES |
| DE3445063A1 (en) * | 1984-12-11 | 1986-06-12 | Basf Ag, 6700 Ludwigshafen | METHOD FOR REMOVING CO (DOWN ARROW) 2 (DOWN ARROW) AND / OR H (DOWN ARROW) 2 (DOWN ARROW) S FROM GASES |
-
1985
- 1985-05-22 DE DE19853518368 patent/DE3518368A1/en not_active Withdrawn
-
1986
- 1986-04-23 CA CA000507373A patent/CA1295810C/en not_active Expired - Lifetime
- 1986-05-14 JP JP61108768A patent/JPS61271016A/en active Pending
- 1986-05-14 EP EP86106575A patent/EP0202600A3/en not_active Withdrawn
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| US20110308388A1 (en) * | 2009-05-06 | 2011-12-22 | Uop Llc | Absorption method for recovering gas contaminants at high purity |
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Also Published As
| Publication number | Publication date |
|---|---|
| DE3518368A1 (en) | 1986-11-27 |
| EP0202600A3 (en) | 1988-09-21 |
| JPS61271016A (en) | 1986-12-01 |
| EP0202600A2 (en) | 1986-11-26 |
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