CA1091897A - 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
- CA1091897A CA1091897A CA272,392A CA272392A CA1091897A CA 1091897 A CA1091897 A CA 1091897A CA 272392 A CA272392 A CA 272392A CA 1091897 A CA1091897 A CA 1091897A
- Authority
- CA
- Canada
- Prior art keywords
- solvent
- gases
- polyethylene glycol
- mixture
- methyl isopropyl
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007789 gas Substances 0.000 title claims abstract description 42
- 229920001223 polyethylene glycol Polymers 0.000 claims abstract description 21
- RMGHERXMTMUMMV-UHFFFAOYSA-N 2-methoxypropane Chemical class COC(C)C RMGHERXMTMUMMV-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000000203 mixture Substances 0.000 claims abstract description 13
- 239000002253 acid Substances 0.000 claims abstract description 9
- 238000005406 washing Methods 0.000 claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000002904 solvent Substances 0.000 claims description 64
- 238000010521 absorption reaction Methods 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 15
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical class COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 claims description 6
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 claims description 4
- 239000003729 cation exchange resin Substances 0.000 claims description 3
- 229940023913 cation exchange resins Drugs 0.000 claims description 3
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 2
- 230000008929 regeneration Effects 0.000 claims description 2
- 238000011069 regeneration method Methods 0.000 claims description 2
- 239000002202 Polyethylene glycol Substances 0.000 claims 9
- 239000008246 gaseous mixture Substances 0.000 claims 3
- 238000010438 heat treatment Methods 0.000 claims 2
- 150000002170 ethers Chemical class 0.000 abstract description 8
- 239000003345 natural gas Substances 0.000 abstract description 7
- 239000000470 constituent Substances 0.000 abstract description 6
- 239000003795 chemical substances by application Substances 0.000 abstract 1
- 238000001035 drying Methods 0.000 abstract 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 27
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 15
- 238000003795 desorption Methods 0.000 description 13
- 239000006096 absorbing agent Substances 0.000 description 11
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 8
- 239000000243 solution Substances 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 5
- 150000005218 dimethyl ethers Chemical class 0.000 description 5
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 5
- -1 polyethylene Polymers 0.000 description 4
- 239000004698 Polyethylene Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000000306 component Substances 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 3
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 2
- VQTUBCCKSQIDNK-UHFFFAOYSA-N Isobutene Chemical compound CC(C)=C VQTUBCCKSQIDNK-UHFFFAOYSA-N 0.000 description 2
- BZLVMXJERCGZMT-UHFFFAOYSA-N Methyl tert-butyl ether Chemical compound COC(C)(C)C BZLVMXJERCGZMT-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 150000002334 glycols Chemical class 0.000 description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- UWHCKJMYHZGTIT-UHFFFAOYSA-N tetraethylene glycol Chemical compound OCCOCCOCCOCCO UWHCKJMYHZGTIT-UHFFFAOYSA-N 0.000 description 2
- 241000310637 Capillipedium spicigerum Species 0.000 description 1
- ZAFNJMIOTHYJRJ-UHFFFAOYSA-N Diisopropyl ether Chemical compound CC(C)OC(C)C ZAFNJMIOTHYJRJ-UHFFFAOYSA-N 0.000 description 1
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 1
- 239000004471 Glycine Substances 0.000 description 1
- QNAYBMKLOCPYGJ-REOHCLBHSA-N L-alanine Chemical compound C[C@H](N)C(O)=O QNAYBMKLOCPYGJ-REOHCLBHSA-N 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 208000036366 Sensation of pressure Diseases 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 235000004279 alanine Nutrition 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 150000005215 alkyl ethers Chemical class 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 235000019628 coolness Nutrition 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- CRVGTESFCCXCTH-UHFFFAOYSA-N methyl diethanolamine Chemical compound OCCN(C)CCO CRVGTESFCCXCTH-UHFFFAOYSA-N 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- JLFNLZLINWHATN-UHFFFAOYSA-N pentaethylene glycol Chemical compound OCCOCCOCCOCCOCCO JLFNLZLINWHATN-UHFFFAOYSA-N 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- CMXPERZAMAQXSF-UHFFFAOYSA-M sodium;1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate;1,8-dihydroxyanthracene-9,10-dione Chemical compound [Na+].O=C1C2=CC=CC(O)=C2C(=O)C2=C1C=CC=C2O.CCCCC(CC)COC(=O)CC(S([O-])(=O)=O)C(=O)OCC(CC)CCCC CMXPERZAMAQXSF-UHFFFAOYSA-M 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Water Supply & Treatment (AREA)
- Gas Separation By Absorption (AREA)
- Treating Waste Gases (AREA)
- Industrial Gases (AREA)
- Detergent Compositions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE: Acid constituents, eg. H2S and CO2 or their mixtures, are removed from industrial gases or natural gases by means of a washing agent which contains the unsymmetrical methyl isopropyl ethers of polyethylene glycols. The washing can be carried out with simultaneous drying of the gas , especially in the case of natural gases, since the anhydrous ethers are able to absorb water.
Description
897 o.z. 31,905 The present invention relates to a process for removin~ H2S
and/or C02 from gases which contain these constituents, especially as impurities, by washing the gases with a solvent whlch contains the methyl isopropyl ethers of polyethylene glycols.
The use of organi¢ solvents or aqueous solutions of organic solvents to remove undeslred acid constituents, eg. H2S and C02, from natural gases and synthesls gases, has been disclosed. A re-view article in H~drocarbon Processing, April 1975, pages 84 - 105, may be mentioned as representative of the extensive prior art, The solvents for the selective removal of H2S in the presence f C2 comprise two groups. Firstly, there are chemical solvents, r, eg. a~ueous solutions of methyldiethanolamine and solutions of salts of C~-aminocarboxylic acids, eg. glycine or alanine (Alkazid ~ ), the selectivity of whlch is due to the fact that they dlssolve H2S
; many times more rapidly than they dissolve C02. Secondly, there are physical solvents, eg. N-methylp~rrolidone (Purisol ~ ) and the di-methyl ethers of polyethylene glycols (Selexol ~ ), whlch thermo-dynamically dissolve more H2S-th~n C02.
~; In additlon to the solubility of a gas ln a solvent, from which the minimum amounts of circulating solvent are calculated, the rate o~ solution of the gas in the solvent is of great importance, since it determines the size of the absorber.
It is an ob~ect o~ the present invention to provide a solvent which not only exhibits a high rate of solution of H2S but in which H2S is also adequately soluble.
-` 1(~91897 The use of dimethyl ethers of polyethylene glycols or their mixtures to remove CO2 and/or H2S from gases is disclosed in ~.S. Patents 2,649,166, 3,362,133 and 3,533,732. Germain Laid-Open Application DOS 2,263,980 discloses alkylpolyethylene gly-col tert.-butyl ethers as solvents for acid gases.
It is true that as a rule the above solvents exhibit adequate absorption of H2S andtor CO2 and also satisfactory viscosity characteristics; according to the experiments describ-ed in German Laid-Open Application DOS 2,263,980 the unsymmetric-al ethers have somewhat higher absorption capacities than the dimethyl ethers described in the above U.S. Patents. However, the rate of absorption of H2S, both with dimethyl ethers and with methyl tert.-butyl ethérs of polyethylene glycols, is not satisfactory in every case.
We have found, surpr~singly, that the above object is achieved by the use of methyl isopropyl ethers of polyethylene ; glycols. These have a higher rate of solution of H2S than the conventional dimethyl ethers and alkyl tert.-butyl ethers; it ; is therefore possible to choose a relatively smaller absorber.
Accordingly, the invention relates to a process for removing CO2 and/or H2S from gases which contain these consti-tuents, by washing the gases in an absorption zone under pres-sure with a solvent comprising one or more alkyl ethers of polyethylene glycols of from 2 to 8 - /CH2-CH2-O/- units, to the temperature of the solvent at the top of the absorption zone not exceeding 50C, with subsequent regeneration of the solvent, methyl isopropyl ethers of ethylene glycols being used as the solvent.
Gases which may be purified in this way are coke oven gases, coal gasification gases, synthesis gases and, preferably, natural gases, from which H2S is to be removed selectively.
According to the invention, the methyl isopropyl ` 1(~9189 7 ethers of polyethylene glycols of the following formula, which contain from 2 to 8 ethylene glycol groups (i.e.
n = from 2 to 8) can be used as solvents:
H
H3C-O-(CH2~O)n-~-cH3 The use of ethers with from 3 to 7 ethylene glycol groups is preferred; from the point of view of the rate of solution of H2S, the compound with 3 ethylene glycol groups, ie. the methyl isopropyl ether of triethylene glycol, has proved'best, whereas compounds with 6 to 8 ethylene glycol groups are more suitable for removing CO2. However, in practice mixtures, obtained by synthesizing these compounds in the presence of stro'ngly acid ; cation exchange resins, are as a rule employed (cf. Berman printed Application 2,544,569). I mixtures of monomethyl ethers with 3 to 5 ethylene glycol,units are reacted with propylene in accordance with German printed Application
and/or C02 from gases which contain these constituents, especially as impurities, by washing the gases with a solvent whlch contains the methyl isopropyl ethers of polyethylene glycols.
The use of organi¢ solvents or aqueous solutions of organic solvents to remove undeslred acid constituents, eg. H2S and C02, from natural gases and synthesls gases, has been disclosed. A re-view article in H~drocarbon Processing, April 1975, pages 84 - 105, may be mentioned as representative of the extensive prior art, The solvents for the selective removal of H2S in the presence f C2 comprise two groups. Firstly, there are chemical solvents, r, eg. a~ueous solutions of methyldiethanolamine and solutions of salts of C~-aminocarboxylic acids, eg. glycine or alanine (Alkazid ~ ), the selectivity of whlch is due to the fact that they dlssolve H2S
; many times more rapidly than they dissolve C02. Secondly, there are physical solvents, eg. N-methylp~rrolidone (Purisol ~ ) and the di-methyl ethers of polyethylene glycols (Selexol ~ ), whlch thermo-dynamically dissolve more H2S-th~n C02.
~; In additlon to the solubility of a gas ln a solvent, from which the minimum amounts of circulating solvent are calculated, the rate o~ solution of the gas in the solvent is of great importance, since it determines the size of the absorber.
It is an ob~ect o~ the present invention to provide a solvent which not only exhibits a high rate of solution of H2S but in which H2S is also adequately soluble.
-` 1(~91897 The use of dimethyl ethers of polyethylene glycols or their mixtures to remove CO2 and/or H2S from gases is disclosed in ~.S. Patents 2,649,166, 3,362,133 and 3,533,732. Germain Laid-Open Application DOS 2,263,980 discloses alkylpolyethylene gly-col tert.-butyl ethers as solvents for acid gases.
It is true that as a rule the above solvents exhibit adequate absorption of H2S andtor CO2 and also satisfactory viscosity characteristics; according to the experiments describ-ed in German Laid-Open Application DOS 2,263,980 the unsymmetric-al ethers have somewhat higher absorption capacities than the dimethyl ethers described in the above U.S. Patents. However, the rate of absorption of H2S, both with dimethyl ethers and with methyl tert.-butyl ethérs of polyethylene glycols, is not satisfactory in every case.
We have found, surpr~singly, that the above object is achieved by the use of methyl isopropyl ethers of polyethylene ; glycols. These have a higher rate of solution of H2S than the conventional dimethyl ethers and alkyl tert.-butyl ethers; it ; is therefore possible to choose a relatively smaller absorber.
Accordingly, the invention relates to a process for removing CO2 and/or H2S from gases which contain these consti-tuents, by washing the gases in an absorption zone under pres-sure with a solvent comprising one or more alkyl ethers of polyethylene glycols of from 2 to 8 - /CH2-CH2-O/- units, to the temperature of the solvent at the top of the absorption zone not exceeding 50C, with subsequent regeneration of the solvent, methyl isopropyl ethers of ethylene glycols being used as the solvent.
Gases which may be purified in this way are coke oven gases, coal gasification gases, synthesis gases and, preferably, natural gases, from which H2S is to be removed selectively.
According to the invention, the methyl isopropyl ` 1(~9189 7 ethers of polyethylene glycols of the following formula, which contain from 2 to 8 ethylene glycol groups (i.e.
n = from 2 to 8) can be used as solvents:
H
H3C-O-(CH2~O)n-~-cH3 The use of ethers with from 3 to 7 ethylene glycol groups is preferred; from the point of view of the rate of solution of H2S, the compound with 3 ethylene glycol groups, ie. the methyl isopropyl ether of triethylene glycol, has proved'best, whereas compounds with 6 to 8 ethylene glycol groups are more suitable for removing CO2. However, in practice mixtures, obtained by synthesizing these compounds in the presence of stro'ngly acid ; cation exchange resins, are as a rule employed (cf. Berman printed Application 2,544,569). I mixtures of monomethyl ethers with 3 to 5 ethylene glycol,units are reacted with propylene in accordance with German printed Application
2,544,569 and the low-boiling constituents are removed, the residual mixtuxe of monomethyl ethers and methyl isopropyl ethers may be employed as the solvent.
As a rule 7 the solvents are employed in a virtually , anhydrous form. If steam stripping is carried out in the desorption column, the water content of the solvent should not exceed 8% by weight, based on the solven~.
, From the point of view of the ability to dissolve CO2 and H2S, the!methyl isopropyl ethers of polyethylene glycols behave like physical solvents, ie. Henry's law applies as a good approximation, and thermodynamically more H2S than CO2 is dissol~ed, The process according to the invention can be carried out at normal or superatmospheric pressure, advantageously at H2S partial pressures greater than 0.05 bar and especially -2a-1C~91897 greater than O.S bar. When removing C02 from gases not containing H2S, the C02 partial pressure should advantageously be greater than 4 bars and especially greater than lO bars. The washing process may be carried out in one stage or two stages. The choice of washing process as a rule depends on the partial pressures of the gases to be washed out and on the final purity required, or on the permissible heat consumption or stripper gas consumption.
The process according to the invention may be carried out either with packed columns or with columns fitted with exchange trays. The temperature of the solvent at the top of the a ~ ber should not exceed 50C, since, the higher the temperatures, the lower is the gas loading of the solvent.
The absorption is as a rule carried out at from 20 to 40C.
The top temperature of the absorber iS fixed in accordance with the conventional criteria and as a rule depends on the desired degree of purity and on the temperature of the cool-ing water.
The rich solvent can be flashed in one or more stages, eg. using a flash turbine, before it is substantially regenera-ted in a packed desorption column or a desorption column equipped with trays, using stripping gas or steam which can be injected directly or can be generated by adding from 2 to 8%
by weight, especially from 3 to 5% by weight, of water to the solvent and employing indirect heat exchange. The solvent can also be stripped with an inert gas.
If, after flashing, the stripping is carried out in a column, it is advantageous to choose a pressure of from 1.1 to 1.5 bars in th ~ain flashing stage.
The solvent running into the desorption column can be heated by means of the solvent discharged, in a countercurrent heat exchanger. The temperature at the bottom of the absorber as a rule is from 110 to 140C, especially 115 to 130C. Thesolvent is conveyed by means of a pump to the top ~f the absorber via a cooler which can be used to set up the desired top tem-perature of the absorber.
If the wash is carried out in two stages, only a part of the ~olvent, coming from the desorption column, is fed to the top of the absorber, while the remainder is fed, at a some-what higher temperature, to another point of the absorber as it comes from the main flashing stage.
Figures 1 and 2 show two preferred process flow charts for carrying out a one-stage wash and a two-stage wash (rough wash and fine wash~, respectively.
The one-stage wash as shown in Fig. 1 is particu-larly suitable or gase~ with low partial pressures o the com-ponents to be washed out.
A rough wash using a flashing circuit may be carried out as follows (cf. Figure 1):-. ~he gas to be washed is supplied through line 11 tothe absorption column 1 through which it flows from bottom to top countercurrent to the solvent which is charged at the top od the column. The washed ~treated) gas leaves the absorption column 1 at the top via line 12. The solvent loaded with sour gas leaves column 1 at the bottom and is flashed through a - flash turbine 4 into a flash column 2. It is then supplied : via heat exchanger 7 to the desorption column 3. The degassed solvent leaves the desorption column at the bottom and is forced by pump 5 via solvent cooler 9 into the top of the absorption column. The flash gas from the flash stage leaves column 2 at the top through line 13. The off-gas from desorption column 3 leaves at the top and is then cooled in offgas cooler 10. The heat balance of the wash is matained by heat exchanger 8 at the bottom of column 3 .
In the Figures,thenumbers denote the following:
1. Absorption column 2, Flash column
As a rule 7 the solvents are employed in a virtually , anhydrous form. If steam stripping is carried out in the desorption column, the water content of the solvent should not exceed 8% by weight, based on the solven~.
, From the point of view of the ability to dissolve CO2 and H2S, the!methyl isopropyl ethers of polyethylene glycols behave like physical solvents, ie. Henry's law applies as a good approximation, and thermodynamically more H2S than CO2 is dissol~ed, The process according to the invention can be carried out at normal or superatmospheric pressure, advantageously at H2S partial pressures greater than 0.05 bar and especially -2a-1C~91897 greater than O.S bar. When removing C02 from gases not containing H2S, the C02 partial pressure should advantageously be greater than 4 bars and especially greater than lO bars. The washing process may be carried out in one stage or two stages. The choice of washing process as a rule depends on the partial pressures of the gases to be washed out and on the final purity required, or on the permissible heat consumption or stripper gas consumption.
The process according to the invention may be carried out either with packed columns or with columns fitted with exchange trays. The temperature of the solvent at the top of the a ~ ber should not exceed 50C, since, the higher the temperatures, the lower is the gas loading of the solvent.
The absorption is as a rule carried out at from 20 to 40C.
The top temperature of the absorber iS fixed in accordance with the conventional criteria and as a rule depends on the desired degree of purity and on the temperature of the cool-ing water.
The rich solvent can be flashed in one or more stages, eg. using a flash turbine, before it is substantially regenera-ted in a packed desorption column or a desorption column equipped with trays, using stripping gas or steam which can be injected directly or can be generated by adding from 2 to 8%
by weight, especially from 3 to 5% by weight, of water to the solvent and employing indirect heat exchange. The solvent can also be stripped with an inert gas.
If, after flashing, the stripping is carried out in a column, it is advantageous to choose a pressure of from 1.1 to 1.5 bars in th ~ain flashing stage.
The solvent running into the desorption column can be heated by means of the solvent discharged, in a countercurrent heat exchanger. The temperature at the bottom of the absorber as a rule is from 110 to 140C, especially 115 to 130C. Thesolvent is conveyed by means of a pump to the top ~f the absorber via a cooler which can be used to set up the desired top tem-perature of the absorber.
If the wash is carried out in two stages, only a part of the ~olvent, coming from the desorption column, is fed to the top of the absorber, while the remainder is fed, at a some-what higher temperature, to another point of the absorber as it comes from the main flashing stage.
Figures 1 and 2 show two preferred process flow charts for carrying out a one-stage wash and a two-stage wash (rough wash and fine wash~, respectively.
The one-stage wash as shown in Fig. 1 is particu-larly suitable or gase~ with low partial pressures o the com-ponents to be washed out.
A rough wash using a flashing circuit may be carried out as follows (cf. Figure 1):-. ~he gas to be washed is supplied through line 11 tothe absorption column 1 through which it flows from bottom to top countercurrent to the solvent which is charged at the top od the column. The washed ~treated) gas leaves the absorption column 1 at the top via line 12. The solvent loaded with sour gas leaves column 1 at the bottom and is flashed through a - flash turbine 4 into a flash column 2. It is then supplied : via heat exchanger 7 to the desorption column 3. The degassed solvent leaves the desorption column at the bottom and is forced by pump 5 via solvent cooler 9 into the top of the absorption column. The flash gas from the flash stage leaves column 2 at the top through line 13. The off-gas from desorption column 3 leaves at the top and is then cooled in offgas cooler 10. The heat balance of the wash is matained by heat exchanger 8 at the bottom of column 3 .
In the Figures,thenumbers denote the following:
1. Absorption column 2, Flash column
3, Desorption column
4, Flash turbine
5. Solvsnt pump
6. Condensate pump
7. Solvent / solvent heat exchanger
8. Reboiler g. Solvent cooler 10. Off-gas cooler 11. Crude gas 12. Treated gas 13. Flashing gas ~inert ga~ ~ component washed out) 14, Off-gas ~component washed out) /
:, /
//
' /
/_ .
1C~91897 o.z, ~1,905 Figure 2 shows a pre~erred flow diagram for two-stage washing (rough and fine washing) with one flashing stage and one desorption stage (stripper)O The absorption column 1 comprises two sections 21 (rough wash) and 22 (rine wash). The solvent loaded with sour gas is flashed, as in Fig~ 1, in turbine 4 and column 2. The solvent leav-in~ flash column 2 at the bottom ls divided lnto two streams. One portlon Or the stream goes to rough wash column 21 after passlng through pump 25, while another portion of the flashed solvent passes through heat exchanger 7 to the top of desorption column ~. Reboiler 8 converts some of the solvent into vapor with which the solvent ~n column 3 is stripped from sour gas. The solvent stream thus regene-rated is pumped by pump 5 through heat exchangers 7 and 9 for cool-ing, and then fed to fine wash column 22. The off-gas leaving at the top of desorption column 3 is cooled in off-gas cooler 10.
In this Flgure, the numbers denote the following:
21. Rough wa~h column 22. Fine wash column 25, Solvent pump 2.
In addition to their ability to dlssolve H2S and C02, the methyl ~o lsopropyl ethers of polyethylene glycols are able to absorb water.
Hence, the solvents to be used accordlng to the lnventlon can also be used for conditlonlng natural gases. In that case, the water con-talned in the natural gas would be removed at the top or the stripper (compare position 3 in Figures 1 and 2). If the solvent of the in-vention is used for this purpose, the procedure followed would be as ; described in German Laid-Open Application DOS 2,4~7,576, whlch pro-poses a process for conditioning natural gases by means of solvents other than those now proposedO
The present invention is illustrated by Examples 1 and 2 whlch follow. Comparative Example 1 compares the rate of absorption of H2S
by methyl isopropyl ethers of polyethylene glycols wlth the rate of absorption by the ethers mentioned in U.S. Patent ~9~62,1~ (e) and German Laid-Open Application DOS 2,26~9980 (f)9 and Comparative Ex--- o.Z. ~1,905 ample ~ the stabllity of the methyl tertO-butyl ethers of ~OS
2,26~,98C wlth the methyl isopropyl ethers of the invention.
EXAMPLE 1 ~ Selective H2S removal 2C)0 m~(S.TOP.)/h of a dry synthesls gas at 16 bars and 50C
are supplied to a packed column of 00~ m diameter packed to a height of 7.5 m. The composition Or the gas is as follows (in % by vol.):
C~ 400 N2 0.2 Ar -4 H2 48.0 H S oO4 COS 24 vol. ppm The gas is washed countercurrently with 1.6 m3/h Or a solvent comprlsing 90~ w/w of asymmetrical methyl isopropyl ethers of poly-ethylene glyaols [26 w~.% trl, 36 tetra, 2~ penta, 11 hexa and 4 hepta~ , 6~ of slmllarly composed monomethyl ethers and 4% of wa-ter, the fe¢d temperature being relatively unfavorable at 50C.
The treated gas leaving the top of the absorber contalns 209% v/v ;~ 20 C02, 8 vol. ppm Or COS and o.8 vol.% H2S. The wash liquld loaded with sour gas has a temperature of 51C at the bottom of the ab-sorber. It is regenerated by flashing to 1025 bars and strlpping with steam in a desorption column (bottoms temperature 1~0C), al-:
- lowed to cool to 50 and returned to the top or the absorber.
i~i ` EXAMPLE 2 - Joint removal of H2S and C02 The method of Example 1 is followed, but 7 m~ (S.T.P.~ wash liquid is used per hourO At the top of the absorber the treated gas contains 1200 vol. ppm C02, ~ 1 vol. ppm H2S and ~-8 vol~ ppm COS.
,- , Table 1 which follows shows the transfer coefficients Kg for the solvents of the lnvention and for varlous solvents of the prior ~0 art. The Kg values were determined in a ~et stream chamber, the Kg .., O.Z. 31J905 ~ e Or the met~lyl isoprlopyl ether of triethylene glycol being taken arbltraril~ as 1.
relative mass transfer ~a~ Metl-yl isopropyl ether of tr~ethylene glycol (b~ Methyl isopropyl ether of tetraethylene glycol o.86 ~c) Methyl isopropyl ether of pentaethylene glycol 0.79 (d~ Undistilled m~xture of a, b and c 0.72 ~e) Mixture of dimethyl ethers of polyethylene 0 57 glycols with low-boiling constituents 10 (f) Methyl tert.-butyl ether of triethylene glycol 0.79 (g) Methyl tert~-butyl ether of tetraethylene glycol o.58 COMPARhTIVE EXAMPLE 2 (a) Table 2 which follows shows the results of' comparative experiments on the decomposition of~ the methyl tert.-butyl ether Or tetrae~hylene glycol (A~ and of the corresponding methyl iso-p~opyl ether ~) with sulfurlc acid. In each case, 30 g of the ether (A) or (B) were heated with 2 drops of concentrated sulfuric acld at 140C (A) or 270C (B only) for 1 hourO In the case of compound (B), a further 2 drops of concentrated sulfuric acid were after-ward added at the higher temperature and the material was heated 0 for a further 2 hours at 270C. In each case, the isobutene or iso-propylene eliminated was determined.
Proportion decomposed A B
in ~
Amount of concentrated H2S04 140C, arter 1 hour 100~ O
-- _.
after 1 hour - O
after 3 hours _ 2~
Table 2 shows that the solvents to be used according to the invention are substantially more stable in an acid medium than 1(~918~7 OOZ. 31,905 the solvents of the prlor art~ as may be seen rrom the low degree of decomposltion~
~b) In a rurther experimentJ the rate of decomposition of the : ethers (A) and (B) was determlnedO For this purpose, 100 g portions of the ethers were heated wlth 5% of the acld lon exchanger used rOr the manufacture of the ether (B) (a sulfonated crosslinked poly-styrene resln ln the H+ form) at 70C, and the rate of elimlnation of olefins was measuredO If the rate constant of the decomposition reactlon for (B) is taken as = 1, a value o~ 562 is ~ound ror the compounds (A) of the prlor art~
~
., '' '
:, /
//
' /
/_ .
1C~91897 o.z, ~1,905 Figure 2 shows a pre~erred flow diagram for two-stage washing (rough and fine washing) with one flashing stage and one desorption stage (stripper)O The absorption column 1 comprises two sections 21 (rough wash) and 22 (rine wash). The solvent loaded with sour gas is flashed, as in Fig~ 1, in turbine 4 and column 2. The solvent leav-in~ flash column 2 at the bottom ls divided lnto two streams. One portlon Or the stream goes to rough wash column 21 after passlng through pump 25, while another portion of the flashed solvent passes through heat exchanger 7 to the top of desorption column ~. Reboiler 8 converts some of the solvent into vapor with which the solvent ~n column 3 is stripped from sour gas. The solvent stream thus regene-rated is pumped by pump 5 through heat exchangers 7 and 9 for cool-ing, and then fed to fine wash column 22. The off-gas leaving at the top of desorption column 3 is cooled in off-gas cooler 10.
In this Flgure, the numbers denote the following:
21. Rough wa~h column 22. Fine wash column 25, Solvent pump 2.
In addition to their ability to dlssolve H2S and C02, the methyl ~o lsopropyl ethers of polyethylene glycols are able to absorb water.
Hence, the solvents to be used accordlng to the lnventlon can also be used for conditlonlng natural gases. In that case, the water con-talned in the natural gas would be removed at the top or the stripper (compare position 3 in Figures 1 and 2). If the solvent of the in-vention is used for this purpose, the procedure followed would be as ; described in German Laid-Open Application DOS 2,4~7,576, whlch pro-poses a process for conditioning natural gases by means of solvents other than those now proposedO
The present invention is illustrated by Examples 1 and 2 whlch follow. Comparative Example 1 compares the rate of absorption of H2S
by methyl isopropyl ethers of polyethylene glycols wlth the rate of absorption by the ethers mentioned in U.S. Patent ~9~62,1~ (e) and German Laid-Open Application DOS 2,26~9980 (f)9 and Comparative Ex--- o.Z. ~1,905 ample ~ the stabllity of the methyl tertO-butyl ethers of ~OS
2,26~,98C wlth the methyl isopropyl ethers of the invention.
EXAMPLE 1 ~ Selective H2S removal 2C)0 m~(S.TOP.)/h of a dry synthesls gas at 16 bars and 50C
are supplied to a packed column of 00~ m diameter packed to a height of 7.5 m. The composition Or the gas is as follows (in % by vol.):
C~ 400 N2 0.2 Ar -4 H2 48.0 H S oO4 COS 24 vol. ppm The gas is washed countercurrently with 1.6 m3/h Or a solvent comprlsing 90~ w/w of asymmetrical methyl isopropyl ethers of poly-ethylene glyaols [26 w~.% trl, 36 tetra, 2~ penta, 11 hexa and 4 hepta~ , 6~ of slmllarly composed monomethyl ethers and 4% of wa-ter, the fe¢d temperature being relatively unfavorable at 50C.
The treated gas leaving the top of the absorber contalns 209% v/v ;~ 20 C02, 8 vol. ppm Or COS and o.8 vol.% H2S. The wash liquld loaded with sour gas has a temperature of 51C at the bottom of the ab-sorber. It is regenerated by flashing to 1025 bars and strlpping with steam in a desorption column (bottoms temperature 1~0C), al-:
- lowed to cool to 50 and returned to the top or the absorber.
i~i ` EXAMPLE 2 - Joint removal of H2S and C02 The method of Example 1 is followed, but 7 m~ (S.T.P.~ wash liquid is used per hourO At the top of the absorber the treated gas contains 1200 vol. ppm C02, ~ 1 vol. ppm H2S and ~-8 vol~ ppm COS.
,- , Table 1 which follows shows the transfer coefficients Kg for the solvents of the lnvention and for varlous solvents of the prior ~0 art. The Kg values were determined in a ~et stream chamber, the Kg .., O.Z. 31J905 ~ e Or the met~lyl isoprlopyl ether of triethylene glycol being taken arbltraril~ as 1.
relative mass transfer ~a~ Metl-yl isopropyl ether of tr~ethylene glycol (b~ Methyl isopropyl ether of tetraethylene glycol o.86 ~c) Methyl isopropyl ether of pentaethylene glycol 0.79 (d~ Undistilled m~xture of a, b and c 0.72 ~e) Mixture of dimethyl ethers of polyethylene 0 57 glycols with low-boiling constituents 10 (f) Methyl tert.-butyl ether of triethylene glycol 0.79 (g) Methyl tert~-butyl ether of tetraethylene glycol o.58 COMPARhTIVE EXAMPLE 2 (a) Table 2 which follows shows the results of' comparative experiments on the decomposition of~ the methyl tert.-butyl ether Or tetrae~hylene glycol (A~ and of the corresponding methyl iso-p~opyl ether ~) with sulfurlc acid. In each case, 30 g of the ether (A) or (B) were heated with 2 drops of concentrated sulfuric acld at 140C (A) or 270C (B only) for 1 hourO In the case of compound (B), a further 2 drops of concentrated sulfuric acid were after-ward added at the higher temperature and the material was heated 0 for a further 2 hours at 270C. In each case, the isobutene or iso-propylene eliminated was determined.
Proportion decomposed A B
in ~
Amount of concentrated H2S04 140C, arter 1 hour 100~ O
-- _.
after 1 hour - O
after 3 hours _ 2~
Table 2 shows that the solvents to be used according to the invention are substantially more stable in an acid medium than 1(~918~7 OOZ. 31,905 the solvents of the prlor art~ as may be seen rrom the low degree of decomposltion~
~b) In a rurther experimentJ the rate of decomposition of the : ethers (A) and (B) was determlnedO For this purpose, 100 g portions of the ethers were heated wlth 5% of the acld lon exchanger used rOr the manufacture of the ether (B) (a sulfonated crosslinked poly-styrene resln ln the H+ form) at 70C, and the rate of elimlnation of olefins was measuredO If the rate constant of the decomposition reactlon for (B) is taken as = 1, a value o~ 562 is ~ound ror the compounds (A) of the prlor art~
~
., '' '
Claims (7)
1. A process for removing H2S or CO2 or both from a gaseous mixture containing H2S or CO2 or both which comprises washing the gases in an absorption zone under pressure with a solvent comprising one or more polyethylene glycol methyl isopropyl ethers containing from 2 to 8 ?CH2CH2-O? units, the temperature of the solvent at the top of the absorption zone not exceeding 50°C, with subsequent regeneration of the solvent.
2. A process according to claim 1, wherein a solvent comprising a mixture of polyethylene glycol methyl isopropyl ethers containing from 2 to 8 ?H2CH2-O? units is used.
3. A process according to claim 1, wherein a solvent comprising one or more polyethylene glycol methyl isopropyl ethers containing from 3 to 7 ?CH2CH2-O? units is used.
4. A process according to claim 1, wherein a solvent comprising a mixture of polyethylene glycol methyl isopropyl ethers containing from 3 to 7 ?CH2CH2-O? units is used.
5. A process according-to claim 2, wherein the mixture of polyethylene glycol methyl isopropyl ethers has been obtained by reacting a mixture of polyethylene glycol monomethyl ethers containing from 2 to 8 ?CH2CH2-O? units in the presence of strongly acid cation exchange resins with propylene.
6. A process according to claim 4, wherein the mixture of polyethylene glycol methyl isopropyl ethers has been obtained by reacting a mixture of polyethylene glycol monomethyl ethers containing from 3 to 7 ?CH2CH2-O? units in the presence of strongly acid cation exchange resins with propylene.
7. A process for removing H2S or CO2 or both from a gaseous mixture containing H2S or CO2 or both, which comprises (a) contacting said gaseous mixture in an absorption zone with a solvent comprising a mixture of polyethylene glycol methyl isopropyl ethers containing from 2 to 8 ?H2CH2-O? units to effect absorption of substantially all of the H2S or CO2 or both and a minor portion of other gases, the temperature of the solvent at the top of the absorption zone not exceeding 50°C, (b) passing the solvent containing the absorbed gases to a second zone maintained at a pressure substantially lower than that in the absorption zone to effect liberation of at least a portion of the absorbed gases, (c) withdrawing from said second zone gases liberated therein, (d) withdrawing solvent containing H2S or CO2 or both from said second zone, (e) and introducing the solvent to a third zone to effect removal of substantially all of the H2S or CO2 or both therefrom by heating the solvent or by stripping with steam or inert gases or by heating and stripping, (f) returning at least a portion of the desorbed solvent to the top of the absorption zone after adjusting the water content to not more than 8% by weight, based on the solvent, if steam has been added to the solvent in step (e).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2611613A DE2611613B2 (en) | 1976-03-19 | 1976-03-19 | Process for the separation of CO2 and / or H25 from gases containing these components |
| DEP2611613.2 | 1976-03-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1091897A true CA1091897A (en) | 1980-12-23 |
Family
ID=5972880
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA272,392A Expired CA1091897A (en) | 1976-03-19 | 1977-02-21 | Removal of co.sub.2 and/or h.sub.2s from gases |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5945034B2 (en) |
| BE (1) | BE852612A (en) |
| CA (1) | CA1091897A (en) |
| DE (1) | DE2611613B2 (en) |
| FR (1) | FR2344322A1 (en) |
| GB (1) | GB1574646A (en) |
| NL (1) | NL7702916A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2909335A1 (en) * | 1979-03-09 | 1980-09-18 | Linde Ag | METHOD AND DEVICE FOR DISASSEMBLING NATURAL GAS |
| DE2923012A1 (en) * | 1979-06-07 | 1980-12-18 | Basf Ag | METHOD FOR THE SIMULTANEOUS REMOVAL OF WATER AND SULFURIUM FROM GASES |
| US4741745A (en) * | 1986-05-07 | 1988-05-03 | Norton Company | Process for separation of carbon dioxide from other gases |
| JPH0698262B2 (en) * | 1987-11-06 | 1994-12-07 | 株式会社日本触媒 | Acid gas absorbent composition |
| US8435325B2 (en) | 2008-10-23 | 2013-05-07 | Hitachi, Ltd. | Method and device for removing CO2 and H2S |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2139375A (en) * | 1937-06-14 | 1938-12-06 | Shell Dev | Removal of so from gases |
| US3591641A (en) * | 1968-10-28 | 1971-07-06 | Allied Chem | Production of dialkyl ethers of polyalkylene glycols |
| US3737392A (en) * | 1969-06-11 | 1973-06-05 | Allied Chem | Solvent composition useful in acid gas removal from gas mixtures |
| DE2544569C3 (en) * | 1975-10-04 | 1984-06-07 | Basf Ag, 6700 Ludwigshafen | Methyl isopropyl ether of tri-, tetra- and / or pentaethylene glycol |
-
1976
- 1976-03-19 DE DE2611613A patent/DE2611613B2/en not_active Withdrawn
-
1977
- 1977-02-21 CA CA272,392A patent/CA1091897A/en not_active Expired
- 1977-03-15 JP JP52027686A patent/JPS5945034B2/en not_active Expired
- 1977-03-17 NL NL7702916A patent/NL7702916A/en not_active Application Discontinuation
- 1977-03-18 FR FR7708184A patent/FR2344322A1/en active Granted
- 1977-03-18 GB GB11542/77A patent/GB1574646A/en not_active Expired
- 1977-03-18 BE BE852612A patent/BE852612A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS52125502A (en) | 1977-10-21 |
| NL7702916A (en) | 1977-09-21 |
| GB1574646A (en) | 1980-09-10 |
| JPS5945034B2 (en) | 1984-11-02 |
| FR2344322A1 (en) | 1977-10-14 |
| DE2611613A1 (en) | 1977-10-20 |
| DE2611613B2 (en) | 1979-04-26 |
| BE852612A (en) | 1977-09-19 |
| FR2344322B1 (en) | 1982-07-16 |
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