CA1212820A - Removal of co.sub.2 and/or h.sub.2s from gases - Google Patents
Removal of co.sub.2 and/or h.sub.2s from gasesInfo
- Publication number
- CA1212820A CA1212820A CA000438134A CA438134A CA1212820A CA 1212820 A CA1212820 A CA 1212820A CA 000438134 A CA000438134 A CA 000438134A CA 438134 A CA438134 A CA 438134A CA 1212820 A CA1212820 A CA 1212820A
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- Canada
- Prior art keywords
- flash
- stage
- absorption
- gas
- taken
- 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
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Classifications
-
- 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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/11—Purification; Separation; Use of additives by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
-
- 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)
- Organic Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Combustion & Propulsion (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Water Supply & Treatment (AREA)
- Gas Separation By Absorption (AREA)
- Treating Waste Gases (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Industrial Gases (AREA)
Abstract
Abstract of the Disclosure: CO2 and/or H2S are removed from gases which contain CO2 and/or H2S 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 con-taining from 20 to 70% by weighty of methyldiethanolamine, the treated gas is taken off at the top of the absorption stage, the aqueous absorption liquid laden with CO2 and/or H2S is taken off at the bottom of the absorption stage and then regenerated by being let down in one or more flash stages, the flash gases being taken off at the top of the flash stage or flash stages, the losses of water as a result of water present in the gas streams taken off at the top of the absorption stage and of the flash stage or flash stages are compensated by feeding in, at the bottom of the last flash stage or, where only one flash stage is used, at the bottom of this, and amount of steam corresponding to the water loss, and the regenerated absorption liquid is recycled to the absorption stage.
Description
2(~
O.z. 0050/36172 of C2 3nd/or H2S fr~_a~
The present ;nvention relates to a process for the remova~ of C02 and/or H2S from gases by means of an aqueous absorpt;on l;qu;d.
Ie has been d;sclosed, for exampLe in A.L. Kohl -F.C. Riesenfeld, ~as Purification, 3rd Edition, 1979, that aqueous solutions of monoethanolam;ne or diethanolamine or a mixture of cyclotetramethylenesulfone and an aqueous solution of diisopropanolamine can be used as solvents for removing C02 and~or HzS from gases~ In these pro-cesses, it is necessary for the solvent which is laden with 02 and-, where relevant, H2S to be regenerated in a stripping column by feeding in steam; this requires a substantial amount of energy. Where C02 and, ~here rele-vant~H2S are removed from na~ural gases conta;ning h;gherhydrocarbons by means of a mixture of cyclotetramethylene-sulfone and an aqueous solution of d;isopropanolamine, an add;ti~nal disadvantage ;s that the higher hydrocarbons have a relatively high solubility in this solvent, so that the acid gas taken off at the top of the-stripping column has a relat;vely h;gh hydrocarbon content wh;ch, if the acid gas contains H2S, can lead to difficulties in a do~nstream Clals unit. Furthermore, primary or secondary alkanolam;nes, eg. monoethanolamine or diethanolamine, can only be used in ~he form of rela~ively dilute aqueous solutions since h;gher concentrations can cause severe damage ~o plant components as a result of corrosion.
There has therefore been a need for a process for removing C02 and/or H2S from gases, by means of ~hich the disadvantages of the conventional processes can be avo1ded.
It is an object of the present invention to pro-vide a process for removing C02 and/or H2S from gases which contain C02 and/or H2S, ~hich requires a small amount of energy for ;ts operation and in which the loss of higher hydrocarbons can be kept low.
H;~U
- Z - O.Z. 0050/36172 We have found that th;s and other objects and advantages are ach1eved, ;n accordance w;th this inven-tion, by a process for remov;ng C0z and/or H2S from gases which contain COz and/or H2S, wherein the said gas is treated, ;n an absorption stage at from 40 to 100C, with an aqueous absorpt;on liquid contain;ng from Z0 to 70% by we;ght of methyld;ethanolamine, the treated gas ;s taken off at the top of the absorption stage, the aqueous absorpt;on l;qu;d laden with C0z and/or ~2S ;s taken off at the bottom of the absorption stage and then regenerated by being let down in one or more flash stages, the flash gases be;ng taken off at the top of the flash stage or flash stages, the losses of ~ater as a result of water present ;n the gas streams taken off at the top of the absorpt;on stage and of the flash stage or flash stages are compensated by feed;ng in, at the bottom of the last flash stage or, where only one flash stage ;s used, at the bottom of this, an amoun~ of steam correspond;ng to the water loss, and the regenerated - absorpt;on liqu;d ;s recycled to ~he absorption stage.
In the novel process, the solvent laden with C0z and/or H2S ;s regenerated w;thout the use of a stripping colu~n, simply by flashing ;n one or more flash stages, so that both capital costs and energy costs can be sub-stantially reduced. Furthermore, ;n the novel process it is possible to use relatively high methyldiethanolamine concentrations in the absorpt;on liquid without this en-tailing corrosion damase in the gas wash unit. Another advantage of the process is that water losses which arise in gas wash units as a result of water be;ng present in the gas streams taken off at the top of the absorption column and of the flash chambers are compensated by feed-ing in, at the bottom of the final flash stage, an amount of steam corresponding to the water loss. By means of this procedure, the water balance of the gas wash unit as well as its heat balance can be regulated, so that the heat exchanger provided for regulating the heat balance in the gas wash unit can be reduced in size or, if appro-priate, completely dispensed with.
O.z. 0050/36172 of C2 3nd/or H2S fr~_a~
The present ;nvention relates to a process for the remova~ of C02 and/or H2S from gases by means of an aqueous absorpt;on l;qu;d.
Ie has been d;sclosed, for exampLe in A.L. Kohl -F.C. Riesenfeld, ~as Purification, 3rd Edition, 1979, that aqueous solutions of monoethanolam;ne or diethanolamine or a mixture of cyclotetramethylenesulfone and an aqueous solution of diisopropanolamine can be used as solvents for removing C02 and~or HzS from gases~ In these pro-cesses, it is necessary for the solvent which is laden with 02 and-, where relevant, H2S to be regenerated in a stripping column by feeding in steam; this requires a substantial amount of energy. Where C02 and, ~here rele-vant~H2S are removed from na~ural gases conta;ning h;gherhydrocarbons by means of a mixture of cyclotetramethylene-sulfone and an aqueous solution of d;isopropanolamine, an add;ti~nal disadvantage ;s that the higher hydrocarbons have a relatively high solubility in this solvent, so that the acid gas taken off at the top of the-stripping column has a relat;vely h;gh hydrocarbon content wh;ch, if the acid gas contains H2S, can lead to difficulties in a do~nstream Clals unit. Furthermore, primary or secondary alkanolam;nes, eg. monoethanolamine or diethanolamine, can only be used in ~he form of rela~ively dilute aqueous solutions since h;gher concentrations can cause severe damage ~o plant components as a result of corrosion.
There has therefore been a need for a process for removing C02 and/or H2S from gases, by means of ~hich the disadvantages of the conventional processes can be avo1ded.
It is an object of the present invention to pro-vide a process for removing C02 and/or H2S from gases which contain C02 and/or H2S, ~hich requires a small amount of energy for ;ts operation and in which the loss of higher hydrocarbons can be kept low.
H;~U
- Z - O.Z. 0050/36172 We have found that th;s and other objects and advantages are ach1eved, ;n accordance w;th this inven-tion, by a process for remov;ng C0z and/or H2S from gases which contain COz and/or H2S, wherein the said gas is treated, ;n an absorption stage at from 40 to 100C, with an aqueous absorpt;on liquid contain;ng from Z0 to 70% by we;ght of methyld;ethanolamine, the treated gas ;s taken off at the top of the absorption stage, the aqueous absorpt;on l;qu;d laden with C0z and/or ~2S ;s taken off at the bottom of the absorption stage and then regenerated by being let down in one or more flash stages, the flash gases be;ng taken off at the top of the flash stage or flash stages, the losses of ~ater as a result of water present ;n the gas streams taken off at the top of the absorpt;on stage and of the flash stage or flash stages are compensated by feed;ng in, at the bottom of the last flash stage or, where only one flash stage ;s used, at the bottom of this, an amoun~ of steam correspond;ng to the water loss, and the regenerated - absorpt;on liqu;d ;s recycled to ~he absorption stage.
In the novel process, the solvent laden with C0z and/or H2S ;s regenerated w;thout the use of a stripping colu~n, simply by flashing ;n one or more flash stages, so that both capital costs and energy costs can be sub-stantially reduced. Furthermore, ;n the novel process it is possible to use relatively high methyldiethanolamine concentrations in the absorpt;on liquid without this en-tailing corrosion damase in the gas wash unit. Another advantage of the process is that water losses which arise in gas wash units as a result of water be;ng present in the gas streams taken off at the top of the absorption column and of the flash chambers are compensated by feed-ing in, at the bottom of the final flash stage, an amount of steam corresponding to the water loss. By means of this procedure, the water balance of the gas wash unit as well as its heat balance can be regulated, so that the heat exchanger provided for regulating the heat balance in the gas wash unit can be reduced in size or, if appro-priate, completely dispensed with.
- 3 - O.Z. 0050/3617Z
Examples of gases wh;rh can be treated using the novel process are coal gasif;cat;on gases, synthes;s gases, coke oven gases and, preferably, natural gases. The pro-cess ;s advantageously used for removing C0z and/or H2S
from natural gases which conta;n h;gher hydrocarbons in addition to methaneq These higher hydrocarbons are in general C2-C30-hydrocarbons, preferably c2-c20-hydro~
carbons, ;n particular C2-C12-hydrocarbons, ~h;ch as a rule are al;phat;c, eg. ethane, propane, isobutane, n-1û butane, isopentane, n-pentane, the hexanes, heptanes, ottanes, non-anes and decanes and the hi~her homologs.
The higher hydrocarbons can contain, in addition to 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, ;n particular from 1 to 2û, mole X of the higher hydrocarbons.
The gases contain in general from 1 to 90, pre-ferably from 2 to 90O in particular from 5 to 60, mole of C02. They can also contain H2S as a further acid gas, or can contain H2S alone, for example in an amount of from a few mole ppm, for example 1 mole ppm, to 50 mole X.
The solvent used for the novel process ;s an aqueous absorption liquid containing from 20 to 79, pre-ferably from 30 to 65, in particular from 40 to 60, % by weight of methyldiethanolamine~ Advantageously, an aqueous methyldiethanolamine solution is employed, for example an aqueous solution of technical-grade methyl-diethanolamine. In an advantageous embodiment of the process, the aqueous methyldiethanolamine solution used additionally contains from 0~1 to 1, preferably from 0.2 to 0.8, in particular from 0.25 to 0.6, mole/liter of a secondary amine or alkanolamine~ preferably methylmono-ethanolamine, very part;cularly advantageously piperazine.
The novel process is carried out as follows: the gas con-taining C02 and/or H2S ;s first treated, in anabsorption stage, with the methyldiethanolamine-containing absorption liquid at from 40 to 100C, preferably from 50 -to 90C, in particular from 60 to 80C. The pressure in ~ 4 - O.Z. 0050/3617Z
the absorpt;on stage is ;n general from 10 to 110, prefer- -ably from 20 to 100, ;n part~cular from 30 to 90, bar. The absorpt;on stage ;s advantageously an absorption column, ;n general a packed column or a column equipped with trays.
Advantageously, the gas to be treated is fed in at the bottom and the absorpt;on l;qu;d is fed ;n at the top of the absorpt;on column, the acid gases C02 and/or H2S be;ng ~ashed out by a counter-current procedure. Wh;le any HzS
present ;s advantageously washed out to a substantial extent, ;n general so that the treated gas has an HzS
- content of not more than 1Z0, preferably not more than 10, ;n part;cular not more than 3, mole ppm, ;t may be advantageous to wash out the C02 from 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, mole X of C02.
The treated gas is advantageously taken off at the top of the absorption stage, expediently at a point above the feed of the absorption liqu;d. The absorption liquid laden with - the acid gases C02 and/or H2S is advantageously taken Z0 off at the bottom of the absorption zone~
The laden absorption liquid is then regenerated in one or more flash stages. In the last flash stage, or in the single flash stage where only one such stage is employed~ the pressure is advantageously let down to about 1 - 3, preferably from 1 to 1.8, in particular from 1 to 1.5, bar. It may also be advantageous to operate the last flash stage or the single flash stage under re-duced pressure, for example under from 0.5 to about 1, preferably from 0.8 to about 1, bar. It can be advan-tageous to use t~o or more, for example from Z to 5, pre-ferably 2 or 3, in particular 2, flash stages for the re-generation of the laden absorption l;quid. Preferably, the pressure of the latter is let down to not less than 5 bar in the first flash stage after the absorption stage.
It can be advantageous if the pressure to which the ab-sorption liquid is let down in this first flash stage is furthermore not less than the partial pressure of C0z or of HzS, or of the sum of the partial pressures of C02 and z~
- 5 - O.Z. 0050/3617Z
H2S, in the gas fed into the absorpt10n stage and con- -tain;ng C2 and/or H2S. In th;s procedure, the evapora tion of water and the assoc;ated energy losses as well as the losses of hydrocarbons can be kept particularly low. Flashing is advantageously carried out us;ng flash chambers which can, for example, also be in the form of columns. These flash chambers need not contain special-baffles. However~ it is also possible to use columns equipped with baffles, eg. packed columns.
10As a rule, heat is suppl;ed to the process to compensate for heat losses due to the process, for example those resulting from the flash. This is advantageously done in a hea~ exchange zone which is located upstream from the last flash stage, or from the single flash stage where only one such stage ;s used, and ;n which the laden absorption l;qu;d ;s heated before flashing in the last or single flash stage. As a rule, the absorption liquid is heated by not more than 20C in the exchange zone, reaching a temperature of in general not more than 90C, as a rule not more than 85C. In general heat exchangers, eg. a tubular heat exchanger, are used for the heat exchange zone.
To compensate for water losses which arise in the process as a result of the presence of water ;n the gas streams taken off at the top of the absorption stage and of the flash stage or flash stages, an amount of steam corresponding to the water loss is fed in at the bottom of the final flash stage or, where onLy one flash stage is used, at the bottom of this single flash stage.
As a rule, the water-present in the gas streams taken off is essentially removed in the form of steam. Low-pressure, medium-pressure or high-pressure steam, eg. steam under 1 - 100 bar, can be fed to the bottom of the flash s~age.
Preferably, low-pressure steam, eg. steam under 1.5 to 10, advant3geously from 1.5 to 5, bar, is used, since this steam is in general cheaply available. The feed, accord-ing to the invention, of steam to the flash stage permits control of the water balance as well as of the heat - 6 O.Z. 0050/36172 balance of the gas wash un;t. Accord;ngly, in a pre-ferred embod;ment of the process, ;n order to compensate for process-dependent heat losses the process ;s e;ther suppl;ed with heat both in the heat exchanger zone up-S stream from the f;nal flash stage or, where only oneflash stage is used, upstream from this single flash stage, and by means of the steam fed in at the bottom of the final flash stage or of the single flash stage, or supplied with heat solely by the latter method.
The acid gases C0z and/or H2S are advantage-ously taken off at the top of the last flash st3ge.
Where the acid gas removed contains HzS, it is advantage-ously worked up by oxidizing the H2S, for example in a Claus unit. The regenerated absorp~ion liquid taken off at the bottom of the last flash stage is recycled to the absorption zone~
The example which follows ;llustrates the ;nven- --t;on in more detail~ the course of the process being shown diagrammatically in the Figure~
Zû A gas which contains C02 and/or H2S, for example a natural gas containing h;gher hydrocarbons, eg. aliphatic c2-c10-hydrocarbons~ is passed under superatmospher;c pressure, v;a line 1, ;nto the bottom of absorption column 2. At the same time, an absorption liquid comprising from 20 to 70% strength by weight aqueous methyldiethanolamine solution is passed via line 3 to the top of the absorption column. The absorption liquid, which is fed counter-current to the gas, becomes laden with the acid gases C02 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 via line 13. The stream of laden absorption liquid 4 is then let down, advantageously to not less than S bar, ;n a flash chamber 6, for example via a valve or, preferably, an expansion turbine S~ In this stage, an intermediate flash gas containing hydrocarbons and C02 is liberated from the absorption liquid and is taken off at tne top - 7 - O.Z. 0050/36172 of flash chamber 6 v;a l;ne 7. At the bottom of flash chamber 6~ the absorpt;on liquid wh;ch has been part;ally let down ;s taken off v;a l;ne 8 and heated ;n heat exchanger 9, for example by from 1 to 15C, and the heated absorpt;on l;qu;d is let down, for example to 1 - 2 bar, ;n a second flash chamber 10. Th;s liberates a COz-r;ch flash gas, for example hav;ng a C02 concentrat;on of 98 mole %, and this gas is taken off at the top of flash chamber 10 via l;ne 11. To compensate for water losses of the system, steam, eg. low-pressure steam under Z.5 bar, is passed ;nto the bottom of flash chamber 10 via l;ne 14. ~he regenerated absorption liqu;d taken off at the bottom o' flash chamber 10 is recycled to the top of absorpt;on cslumn 2 with the aid of a c;rculatory pump 12.
The Example which follows ;llustrates the inven-t;on.
EXAMPLE
In an absorption column, 3.15 kmol/hour of a C02-contain;ng natural gas are washed, under 75 bar, w;th a 50% strength by weight aqueous methyldiethanolamine solu-tion as the absorption liquid. The gas to be treated has the following composition:
C2 10.0 mole Z
CH4 75.0 mole X
higher hydrocarbons (C2-C1z-hydrocarbons) 15.0 mole ~.
The temperature of the absorption liqu;d in the feed to the absorption column is 70C. The C02 con-tent in the washed gas is 2.0 mole X. The laden washingagent which leaves the absorption column is let down to 20 bar ;n a f;rs~ flash chamber. In th;s procedure, 0.04 kmolJliter of a hydrocarbor,-rich intermediate flash gas having a G02 concentration of 34.3 mole X is liber-ated from the solution and is taken off at the top of the - first flash chamber. The partially let down absorption liquid is then heated in a heat exchanger. The heated absorpt;on liquid ;s let down to 1.3 bar in a second flash chamber. In this procedure 0.241 kmol/hour of a ~ 8 - O.Z. 0059/36172 COz-r;ch flash gas hav;ng a C02 concentrat;on of 97.55 mole X, a methane concentrat;on of 1~68 mole % and a con-centrat;on of higher hydrocarbons of 0.77 mole % is l;ber-ated and ;s taken off at the top cf the second flash S chamber. To compensate for the water losses of the system, lowopressure steam under 2.5 bar is passed ;nto the bottom of the second f lash chamber. The absorpt;on l;qu;d taken off at the bottom of the flash chamber ;s recycled to the top of the absorpt;on column with the aid of a circulatory pump.
Examples of gases wh;rh can be treated using the novel process are coal gasif;cat;on gases, synthes;s gases, coke oven gases and, preferably, natural gases. The pro-cess ;s advantageously used for removing C0z and/or H2S
from natural gases which conta;n h;gher hydrocarbons in addition to methaneq These higher hydrocarbons are in general C2-C30-hydrocarbons, preferably c2-c20-hydro~
carbons, ;n particular C2-C12-hydrocarbons, ~h;ch as a rule are al;phat;c, eg. ethane, propane, isobutane, n-1û butane, isopentane, n-pentane, the hexanes, heptanes, ottanes, non-anes and decanes and the hi~her homologs.
The higher hydrocarbons can contain, in addition to 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, ;n particular from 1 to 2û, mole X of the higher hydrocarbons.
The gases contain in general from 1 to 90, pre-ferably from 2 to 90O in particular from 5 to 60, mole of C02. They can also contain H2S as a further acid gas, or can contain H2S alone, for example in an amount of from a few mole ppm, for example 1 mole ppm, to 50 mole X.
The solvent used for the novel process ;s an aqueous absorption liquid containing from 20 to 79, pre-ferably from 30 to 65, in particular from 40 to 60, % by weight of methyldiethanolamine~ Advantageously, an aqueous methyldiethanolamine solution is employed, for example an aqueous solution of technical-grade methyl-diethanolamine. In an advantageous embodiment of the process, the aqueous methyldiethanolamine solution used additionally contains from 0~1 to 1, preferably from 0.2 to 0.8, in particular from 0.25 to 0.6, mole/liter of a secondary amine or alkanolamine~ preferably methylmono-ethanolamine, very part;cularly advantageously piperazine.
The novel process is carried out as follows: the gas con-taining C02 and/or H2S ;s first treated, in anabsorption stage, with the methyldiethanolamine-containing absorption liquid at from 40 to 100C, preferably from 50 -to 90C, in particular from 60 to 80C. The pressure in ~ 4 - O.Z. 0050/3617Z
the absorpt;on stage is ;n general from 10 to 110, prefer- -ably from 20 to 100, ;n part~cular from 30 to 90, bar. The absorpt;on stage ;s advantageously an absorption column, ;n general a packed column or a column equipped with trays.
Advantageously, the gas to be treated is fed in at the bottom and the absorpt;on l;qu;d is fed ;n at the top of the absorpt;on column, the acid gases C02 and/or H2S be;ng ~ashed out by a counter-current procedure. Wh;le any HzS
present ;s advantageously washed out to a substantial extent, ;n general so that the treated gas has an HzS
- content of not more than 1Z0, preferably not more than 10, ;n part;cular not more than 3, mole ppm, ;t may be advantageous to wash out the C02 from 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, mole X of C02.
The treated gas is advantageously taken off at the top of the absorption stage, expediently at a point above the feed of the absorption liqu;d. The absorption liquid laden with - the acid gases C02 and/or H2S is advantageously taken Z0 off at the bottom of the absorption zone~
The laden absorption liquid is then regenerated in one or more flash stages. In the last flash stage, or in the single flash stage where only one such stage is employed~ the pressure is advantageously let down to about 1 - 3, preferably from 1 to 1.8, in particular from 1 to 1.5, bar. It may also be advantageous to operate the last flash stage or the single flash stage under re-duced pressure, for example under from 0.5 to about 1, preferably from 0.8 to about 1, bar. It can be advan-tageous to use t~o or more, for example from Z to 5, pre-ferably 2 or 3, in particular 2, flash stages for the re-generation of the laden absorption l;quid. Preferably, the pressure of the latter is let down to not less than 5 bar in the first flash stage after the absorption stage.
It can be advantageous if the pressure to which the ab-sorption liquid is let down in this first flash stage is furthermore not less than the partial pressure of C0z or of HzS, or of the sum of the partial pressures of C02 and z~
- 5 - O.Z. 0050/3617Z
H2S, in the gas fed into the absorpt10n stage and con- -tain;ng C2 and/or H2S. In th;s procedure, the evapora tion of water and the assoc;ated energy losses as well as the losses of hydrocarbons can be kept particularly low. Flashing is advantageously carried out us;ng flash chambers which can, for example, also be in the form of columns. These flash chambers need not contain special-baffles. However~ it is also possible to use columns equipped with baffles, eg. packed columns.
10As a rule, heat is suppl;ed to the process to compensate for heat losses due to the process, for example those resulting from the flash. This is advantageously done in a hea~ exchange zone which is located upstream from the last flash stage, or from the single flash stage where only one such stage ;s used, and ;n which the laden absorption l;qu;d ;s heated before flashing in the last or single flash stage. As a rule, the absorption liquid is heated by not more than 20C in the exchange zone, reaching a temperature of in general not more than 90C, as a rule not more than 85C. In general heat exchangers, eg. a tubular heat exchanger, are used for the heat exchange zone.
To compensate for water losses which arise in the process as a result of the presence of water ;n the gas streams taken off at the top of the absorption stage and of the flash stage or flash stages, an amount of steam corresponding to the water loss is fed in at the bottom of the final flash stage or, where onLy one flash stage is used, at the bottom of this single flash stage.
As a rule, the water-present in the gas streams taken off is essentially removed in the form of steam. Low-pressure, medium-pressure or high-pressure steam, eg. steam under 1 - 100 bar, can be fed to the bottom of the flash s~age.
Preferably, low-pressure steam, eg. steam under 1.5 to 10, advant3geously from 1.5 to 5, bar, is used, since this steam is in general cheaply available. The feed, accord-ing to the invention, of steam to the flash stage permits control of the water balance as well as of the heat - 6 O.Z. 0050/36172 balance of the gas wash un;t. Accord;ngly, in a pre-ferred embod;ment of the process, ;n order to compensate for process-dependent heat losses the process ;s e;ther suppl;ed with heat both in the heat exchanger zone up-S stream from the f;nal flash stage or, where only oneflash stage is used, upstream from this single flash stage, and by means of the steam fed in at the bottom of the final flash stage or of the single flash stage, or supplied with heat solely by the latter method.
The acid gases C0z and/or H2S are advantage-ously taken off at the top of the last flash st3ge.
Where the acid gas removed contains HzS, it is advantage-ously worked up by oxidizing the H2S, for example in a Claus unit. The regenerated absorp~ion liquid taken off at the bottom of the last flash stage is recycled to the absorption zone~
The example which follows ;llustrates the ;nven- --t;on in more detail~ the course of the process being shown diagrammatically in the Figure~
Zû A gas which contains C02 and/or H2S, for example a natural gas containing h;gher hydrocarbons, eg. aliphatic c2-c10-hydrocarbons~ is passed under superatmospher;c pressure, v;a line 1, ;nto the bottom of absorption column 2. At the same time, an absorption liquid comprising from 20 to 70% strength by weight aqueous methyldiethanolamine solution is passed via line 3 to the top of the absorption column. The absorption liquid, which is fed counter-current to the gas, becomes laden with the acid gases C02 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 via line 13. The stream of laden absorption liquid 4 is then let down, advantageously to not less than S bar, ;n a flash chamber 6, for example via a valve or, preferably, an expansion turbine S~ In this stage, an intermediate flash gas containing hydrocarbons and C02 is liberated from the absorption liquid and is taken off at tne top - 7 - O.Z. 0050/36172 of flash chamber 6 v;a l;ne 7. At the bottom of flash chamber 6~ the absorpt;on liquid wh;ch has been part;ally let down ;s taken off v;a l;ne 8 and heated ;n heat exchanger 9, for example by from 1 to 15C, and the heated absorpt;on l;qu;d is let down, for example to 1 - 2 bar, ;n a second flash chamber 10. Th;s liberates a COz-r;ch flash gas, for example hav;ng a C02 concentrat;on of 98 mole %, and this gas is taken off at the top of flash chamber 10 via l;ne 11. To compensate for water losses of the system, steam, eg. low-pressure steam under Z.5 bar, is passed ;nto the bottom of flash chamber 10 via l;ne 14. ~he regenerated absorption liqu;d taken off at the bottom o' flash chamber 10 is recycled to the top of absorpt;on cslumn 2 with the aid of a c;rculatory pump 12.
The Example which follows ;llustrates the inven-t;on.
EXAMPLE
In an absorption column, 3.15 kmol/hour of a C02-contain;ng natural gas are washed, under 75 bar, w;th a 50% strength by weight aqueous methyldiethanolamine solu-tion as the absorption liquid. The gas to be treated has the following composition:
C2 10.0 mole Z
CH4 75.0 mole X
higher hydrocarbons (C2-C1z-hydrocarbons) 15.0 mole ~.
The temperature of the absorption liqu;d in the feed to the absorption column is 70C. The C02 con-tent in the washed gas is 2.0 mole X. The laden washingagent which leaves the absorption column is let down to 20 bar ;n a f;rs~ flash chamber. In th;s procedure, 0.04 kmolJliter of a hydrocarbor,-rich intermediate flash gas having a G02 concentration of 34.3 mole X is liber-ated from the solution and is taken off at the top of the - first flash chamber. The partially let down absorption liquid is then heated in a heat exchanger. The heated absorpt;on liquid ;s let down to 1.3 bar in a second flash chamber. In this procedure 0.241 kmol/hour of a ~ 8 - O.Z. 0059/36172 COz-r;ch flash gas hav;ng a C02 concentrat;on of 97.55 mole X, a methane concentrat;on of 1~68 mole % and a con-centrat;on of higher hydrocarbons of 0.77 mole % is l;ber-ated and ;s taken off at the top cf the second flash S chamber. To compensate for the water losses of the system, lowopressure steam under 2.5 bar is passed ;nto the bottom of the second f lash chamber. The absorpt;on l;qu;d taken off at the bottom of the flash chamber ;s recycled to the top of the absorpt;on column with the aid of a circulatory pump.
Claims
1. A process for removing CO2 and/or H2S from a gas which contains CO2 and/or H2S by means of an aqueous absorption liquid containing an alkanolamine, wherein 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 methyldiethanclamine, the treated gas is taken off at the top of the absorption stage, the aqueous absorption liquid laden with CO2 and/or H2S is taken off at the bottom of the absorption stage and then regenerated by being let down in one or more flash stages, the flash gases being taken off at the top of the flash stage or flash stages, the losses of water as a result of water present in the gas streams taken off at the top of the absorption stage and of the flash stage or flash stages are compensated by feeding in, at the bottom of the last flash stage or, where only one flash stage is used, at the bottom of this, an amount of steam corres-ponding to the water loss, and the regenerated absorption liquid is recycled to the absorption stage.
Drawing.
Drawing.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3236601.9 | 1982-10-02 | ||
| DE19823236601 DE3236601A1 (en) | 1982-10-02 | 1982-10-02 | METHOD FOR REMOVING CO (DOWN ARROW) 2 (DOWN ARROW) AND / OR H (DOWN ARROW) 2 (DOWN ARROW) S FROM GASES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1212820A true CA1212820A (en) | 1986-10-21 |
Family
ID=6174827
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000438134A Expired CA1212820A (en) | 1982-10-02 | 1983-09-30 | Removal of co.sub.2 and/or h.sub.2s from gases |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0107783B1 (en) |
| JP (1) | JPS5990616A (en) |
| AT (1) | ATE26409T1 (en) |
| CA (1) | CA1212820A (en) |
| DE (2) | DE3236601A1 (en) |
| NO (1) | NO159474C (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| DE3432213A1 (en) * | 1984-09-01 | 1986-03-13 | Basf Ag, 6700 Ludwigshafen | METHOD FOR REMOVING CO (DOWN ARROW) 2 (DOWN ARROW) AND / OR H (DOWN ARROW) 2 (DOWN ARROW) S FROM GASES |
| IT1191805B (en) * | 1986-06-11 | 1988-03-23 | Snam Progetti | PROCESS FOR SELECTIVE REMOVAL OF SULPHIDIC ACID |
| DE10139453A1 (en) * | 2001-08-10 | 2003-02-20 | Basf Ag | Acid content removed from gaseous flow by aqueous absorbent containing methyl-diethanolamine and piperazine |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2551717C3 (en) * | 1975-11-18 | 1980-11-13 | Basf Ag, 6700 Ludwigshafen | and possibly COS from gases |
| US4100257A (en) * | 1977-02-14 | 1978-07-11 | Exxon Research & Engineering Co. | Process and amine-solvent absorbent for removing acidic gases from gaseous mixtures |
-
1982
- 1982-10-02 DE DE19823236601 patent/DE3236601A1/en not_active Withdrawn
-
1983
- 1983-09-22 AT AT83109425T patent/ATE26409T1/en not_active IP Right Cessation
- 1983-09-22 DE DE8383109425T patent/DE3370765D1/en not_active Expired
- 1983-09-22 EP EP83109425A patent/EP0107783B1/en not_active Expired
- 1983-09-30 CA CA000438134A patent/CA1212820A/en not_active Expired
- 1983-09-30 NO NO833566A patent/NO159474C/en not_active IP Right Cessation
- 1983-10-03 JP JP58183229A patent/JPS5990616A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| NO159474C (en) | 1989-01-04 |
| NO159474B (en) | 1988-09-26 |
| ATE26409T1 (en) | 1987-04-15 |
| EP0107783B1 (en) | 1987-04-08 |
| DE3236601A1 (en) | 1984-04-05 |
| JPS5990616A (en) | 1984-05-25 |
| DE3370765D1 (en) | 1987-05-14 |
| JPH0456649B2 (en) | 1992-09-09 |
| NO833566L (en) | 1984-04-03 |
| EP0107783A1 (en) | 1984-05-09 |
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