CA1304913C - Process for selectively removing hydrogen sulfide from a gas stream at high pressure - Google Patents
Process for selectively removing hydrogen sulfide from a gas stream at high pressureInfo
- Publication number
- CA1304913C CA1304913C CA000582943A CA582943A CA1304913C CA 1304913 C CA1304913 C CA 1304913C CA 000582943 A CA000582943 A CA 000582943A CA 582943 A CA582943 A CA 582943A CA 1304913 C CA1304913 C CA 1304913C
- Authority
- CA
- Canada
- Prior art keywords
- gas stream
- hydrogen sulfide
- solution
- gas
- carbon dioxide
- 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
Links
- 239000007789 gas Substances 0.000 title claims abstract description 33
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 title claims abstract description 23
- 229910000037 hydrogen sulfide Inorganic materials 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title claims abstract description 11
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 15
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 15
- 230000003068 static effect Effects 0.000 claims description 17
- 239000013522 chelant Substances 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 6
- YPFNIPKMNMDDDB-UHFFFAOYSA-K 2-[2-[bis(carboxylatomethyl)amino]ethyl-(2-hydroxyethyl)amino]acetate;iron(3+) Chemical compound [Fe+3].OCCN(CC([O-])=O)CCN(CC([O-])=O)CC([O-])=O YPFNIPKMNMDDDB-UHFFFAOYSA-K 0.000 claims description 2
- 239000007788 liquid Substances 0.000 abstract description 26
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 239000003345 natural gas Substances 0.000 abstract description 3
- 239000000243 solution Substances 0.000 description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 20
- 229910052742 iron Inorganic materials 0.000 description 10
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 9
- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 9
- 238000012360 testing method Methods 0.000 description 8
- 150000001412 amines Chemical class 0.000 description 7
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical class NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- CRVGTESFCCXCTH-UHFFFAOYSA-N methyl diethanolamine Chemical compound OCCN(C)CCO CRVGTESFCCXCTH-UHFFFAOYSA-N 0.000 description 4
- URDCARMUOSMFFI-UHFFFAOYSA-N 2-[2-[bis(carboxymethyl)amino]ethyl-(2-hydroxyethyl)amino]acetic acid Chemical compound OCCN(CC(O)=O)CCN(CC(O)=O)CC(O)=O URDCARMUOSMFFI-UHFFFAOYSA-N 0.000 description 3
- 102000018361 Contactin Human genes 0.000 description 3
- 108060003955 Contactin Proteins 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- -1 EDTA Chemical compound 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 2
- 239000001099 ammonium carbonate Substances 0.000 description 2
- 235000012501 ammonium carbonate Nutrition 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 235000013905 glycine and its sodium salt Nutrition 0.000 description 2
- NBZBKCUXIYYUSX-UHFFFAOYSA-N iminodiacetic acid Chemical compound OC(=O)CNCC(O)=O NBZBKCUXIYYUSX-UHFFFAOYSA-N 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- XFNJVJPLKCPIBV-UHFFFAOYSA-N trimethylenediamine Chemical compound NCCCN XFNJVJPLKCPIBV-UHFFFAOYSA-N 0.000 description 2
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 description 1
- GAWIXWVDTYZWAW-UHFFFAOYSA-N C[CH]O Chemical group C[CH]O GAWIXWVDTYZWAW-UHFFFAOYSA-N 0.000 description 1
- KXDHJXZQYSOELW-UHFFFAOYSA-N Carbamic acid Chemical class NC(O)=O KXDHJXZQYSOELW-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 description 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 1
- 239000004471 Glycine Substances 0.000 description 1
- 108010008488 Glycylglycine Proteins 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 235000011054 acetic acid Nutrition 0.000 description 1
- 150000001243 acetic acids Chemical class 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- GCPXMJHSNVMWNM-UHFFFAOYSA-N arsenous acid Chemical class O[As](O)O GCPXMJHSNVMWNM-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- ZTOGYGRJDIWKAQ-UHFFFAOYSA-N cyclohexene-1,2-diamine Chemical compound NC1=C(N)CCCC1 ZTOGYGRJDIWKAQ-UHFFFAOYSA-N 0.000 description 1
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 229960002449 glycine Drugs 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000011133 lead Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- MGFYIUFZLHCRTH-UHFFFAOYSA-N nitrilotriacetic acid Chemical compound OC(=O)CN(CC(O)=O)CC(O)=O MGFYIUFZLHCRTH-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- AOHJOMMDDJHIJH-UHFFFAOYSA-N propylenediamine Chemical compound CC(N)CN AOHJOMMDDJHIJH-UHFFFAOYSA-N 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- RBWSWDPRDBEWCR-RKJRWTFHSA-N sodium;(2r)-2-[(2r)-3,4-dihydroxy-5-oxo-2h-furan-2-yl]-2-hydroxyethanolate Chemical compound [Na+].[O-]C[C@@H](O)[C@H]1OC(=O)C(O)=C1O RBWSWDPRDBEWCR-RKJRWTFHSA-N 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- IIACRCGMVDHOTQ-UHFFFAOYSA-N sulfamic acid Chemical class NS(O)(=O)=O IIACRCGMVDHOTQ-UHFFFAOYSA-N 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- 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
- Gas Separation By Absorption (AREA)
Abstract
PROCESS FOR SELECTIVELY REMOVING HYDROGEN SULFIDE
FROM A GAS STREAM AT HIGH PRESSURE
ABSTRACT
Hydrogen sulfide can be removed selectively from a gas stream also containing carbon dioxide at high pressure, such as those found at natural gas production wellheads, by contacting the gas stream with an alkaline liquid for a time period of less than about 80 milliseconds.
FROM A GAS STREAM AT HIGH PRESSURE
ABSTRACT
Hydrogen sulfide can be removed selectively from a gas stream also containing carbon dioxide at high pressure, such as those found at natural gas production wellheads, by contacting the gas stream with an alkaline liquid for a time period of less than about 80 milliseconds.
Description
13049~3 PROCESS FOR SELECTIVELY R~OVING HYDROOE N SULFIDE
FROM ~ GAS STR ~ I AT HIG~ PRESSURE
The present invention is directed tO the selective removal of hydrogen sulfide from a gas stream. In particular, the present s invention is directed to the selective removal of hydrogen sulfide from a high pressure gas stream which also contains carbon dioxide by using a metal chelate solution. Through operation at high pressures, the present invention may be used in situations where low pressure operation would be costly and time-consuming, such as in the removal of hydrogen sulfide from the gas stream of a natural gas production well.
The present invention provides a process for the removal of hydrogen sulfide from a gas stream containing hydrogen sulfide and carbon dioxide, which process co~prises contactin~ the gas stream with a stoichiometric excess of polyvalent retal chelate solution over the hydrogen sulfide, the solution having a p~ of about 8.0 to 9 2 for a time less than 0.08 sec. to absorb hydro~en sulfide and not carbon dioxide, by flowing the gas stream and the solution past from two to six mixing elements in a static mixer, the gas stream, which can be from the well head of a natural gas production well, being maintained at a pressure of 5340-6170 kPa (760-880 psig) during the contacting period. The polyvalent metal-chelate solution is preferably iron- HEDTA (N- hydroxyethylethylenediaminetriacetic acid).
- 25 Fig. 1 is a schematic representation of the equipment used in the experimental work described below, and Figs. 2-4 are graphical representations of the data obtained in the experimental work described below.
As noted above, the present process is directed to the selective removal of hydrogen sulfide from a gas stream at hi~h ~, "j 1~0~913 pressure. The following apparatus and procedure were used in conducting the high pressure removal of hydrogen sulfide with an alkaline absorbing solution. Referrin~ to Fig. 1, wellhead gas was contacted with absorbin~ solution in a static mixer and quickly separated in a gas/liquid separator. The gas/liquid separator was operated at the wellhead pressure, while the gas flow rate was varied throu~h the use of valve Vl. An orifice flange was set up to measure the gas flow rate downstream of valve Vl. The pressure gauge on the gas/liquid separator indicated wellhead pressure when valve Vl was shut and flowing pressure during testing. Valve V2 was opened slightly to allow a slo~ flow to the ~as chromatograph and the hydrogen sulfide tube samplers.
Liquid was pumped to the static mixer by a variable speed Zenith ~ear pump. A two-liter cell was used for the liquid reservoir, and wellhead pressure pressurized the liquid reservoir which fed the pump. The wellhead gas which pressurized the liquid reservoir first passed through a methyldiethanol amine scrubber whi h removed the acid gases from the gas. Wellhead temperature was monitored by a thermocouple, in-line with a pyrometer.
Three solutions were tested. The first solution was 50~ by wei~ht methyldiethanol amine. The amine was purchased from Pfaltz and Pauer, Inc. The remaining two solutions were dilutions of Dow Chemical's'~ersenor'S~ iron chelate solution, and iron-HEDTA chelate solution. The concentrations of the solutions were 0.32 molar and 0.11 molar, and the pH of each was adiusted to 9.2 with ammonium carbonate solution.
The gas tested had a composition of 95.3 mole percent methane, l.S mole percent ethane, 0.3 mole percent propane, 0.4 mole percent nitrogen, 1.8 mole percent carbon dioxide, 0.1 mole percent hydrogen sulfide and 0.6 mole percent other hydrocarbons. The gas was tested at pressures from 5340 to 6170 kPa (760 to 880 psig).
Four different sizes of static mixers were used during the test:
12.7 mm (1/2") diameter by 152.4 mm (6") long; 9.5 mm (3/8") *Trade mark 7, ~30~913 F-2765 --3~~
diameter by 114.3 mm (4-1/2") long; 6.4 mm (1/4") diameter by 63.5 mm (2-1/2") lon~; and 6.4 mm (1/4") diameter by 127 m~ (5") long.
In the first test, the 50~ by wei~ht amine solution was used with the 12.7 mm (1/2") static mixer. The ~as flow rate was set at 8~D00 standard liter per hour (3,0~0 standard cubic feet per hour), which resulted in a gas- liquid contact time in the static mixer of 100 milliseconds. This was the maxirum flow rate that could be run with this equipment because of pressure drop limitations in the equipment. Five liquid flow rates were run, and the results are shcwn in Fi~. 2. This fi~ure shows the percent of hydro~en sulfide removed as a function of excess mo1ar amine pumped. Approximately 9~ of the carbon dioxide also was removed with the hydrogen sulfide. This was not unexpected, because of the relatively lon~ contact time between the liquid and the gas. About 70~ of the hydro~en sulfide was removed with a pumped amine stoichiometric excess of 300%.
To reduce the ~as-liquid contact time, the 9.5 mm (3/8') static mixer was used. With a ~as flow rate of 59400 standard liter/hour (2,100 scfh), a contact time in the static ~ixer of 17 milliseconds was maintained for the second test. As can be seen in Fig. 2, at the shorter contact time, the hydrogen sulfide still was removed, but not as efficiently as at the lon~er contact time.
Carbon dioxide was also removed (about 8) which was not expected.
These results illustrate th~t both the amine/hydro~en sulfide and - 2s amine/carbon dioxide reactions are kinetically limited. Other work has shown that carbon dioxide removal is diffusion limited, and can be controlled by limiting the gas-liquid contact time to under 80 milliseconds.
A concentrated iron chelate solution also was run to determine if selective hydro~en sulfide absorption could be achieved at the hi~her pressures. ~ecause of limited pumpin~ rates, less gas was processed in this test. The 6.4 mm x 63.5 mm (1/4" x 2-1/2") static mixer was used to obtain a short ~as-liquid contact time of ~3 D
130~9~3 F-2765 ~~4~~
17 milliseconds. Fig. 3 shows that in contactin~ the gas with a 12-fold stoichiometric excess of iron, 89% of the hydrogen sulfide was removed with no carbon dioxide absorption. For either iron chelate or amine solutions, a stoichiometric excess over the hydro~en sulfide is necessary, since the ~ixin~ does not provide for a stoichiometric reaction.
The 6.4 mm x 127 mm (1/4" x 5") static mixer then was tested and operated at the same gas rate. This produced a gas-liquid contact time of 30 milliseconds in the static mixer, doubling not only the contact time, but also the number of mixin~
elements in the static mixer. Fig. 3 shows that a slight increase in hydrogen sulfide absorption was achieved with no carbon dioxide absorption. This shows that the six mixin~ elements in the 6.4 mm x 63.5 mm (1/4" x 2-1/2") static mixer were sufficient to obtain the needed liquid dispersion to assure kinetic control of the reaction.
In the next test, the iron chelate solution was diluted to yield a final iron chelate concentration of 0.11 ~, as opposed to the 0.32 ~ solution tested previously. Again, no carbon dioxide was absorbed during the test. As shown in Fig. 3, to achieve 80%
hydrogen sulfide removal, a 380~ molar excess of iron chelate was needed. The data from all the tests are ~iven in the Table on the following page ~30~g~3 E
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Fig. 4 shows the same data as Fig. 3, but as a function of pumping rate. The dilute solution is not as efficient in this case. However, only a 5~ increase in hydro~en sulfide removal is seen over the dilute solution. Since concentration appears to make very little difference, the limiting factor for the concentrations tested is the total liquid surface area. The total li~uid surface area is a function of the mean drop diameter and the volume of liquid pumped. The mean drop diameter is controlled by the type and number of static mixer elements used alon~ with the velocity of the fluids and the physical properties of both the li~uid and ~as. This is described in U.S. Patent 4,499,059. Using static mixers with a gas-liquid system, a stable mean drop diameter is obtained with two to six static mixer elements. Additional elements do not reduce the mean drop diameter. Thus, with six mixing elements, the total liquid surface area can be controlled by varying the liquid flow rate, and hence at constant ~as rates and solution ~'s, the hydro~en removal efficiency can be controlled by varyin~ the liquid flow rate.
The polyvalent metal chelate solution must have a pH of at least 7, preferably 8-9, and may be a polyvalent metal chelate solution, with pff adjusted by sodiu~ or ammonium carbonate. The polyvalent metal ~ay be selected from iron, copper, manganese, lead, mercury, palladium, platinum, tungsten, nickel, chromium, cobalt, vanadium, titanium, tantalum, zirconium, molybdenum and tin, preferably iron, copper and manganese, and most preferably iron.
The chelating agent may be selected from amino acetic acids derived from ammonia or 2-hydroxyalkylamines, such as glycine, diglycine (aminodiacetic acid), nitrilo triacetic acid, 2-hydroxyalkylglycine, di-hydroxyalkylglycine and hydroxyethyl or 3~ hydroxypropyldiglycine, amino acetic acids derived from ethylene diamine, diethylenetriamine, 1,2-propylenediamine and 1,3-propylenediamine, such as EDTA, 2-hydroxy EDTA, and diethylene tria~ine pent2aceticacid, amino acetic acid derivatives of cyclic 1~0~1~13 1,2-diamines, such as 1,2-diaminocyclohexane-N, N- tetraacetic acid, and amides of polyamino acetic acids, as disclosed in U. S. Patent No. 3,580,950 to Bersworth. E~T~ and N-hydroxyethylethylenediaminetriacetic acid (HEDTA) are particularly preferred. The alkaline liquid also may be selected from aqueous solutions of inorganic salts having an alkaline reaction, such as alkali metal hydroxides, rhosphates, borates, metaborates or arsenites, solutions of or~anic bases, svch as alkanolamines, like monoethanol amine, diethanolamine, triethanolamine, N-methyldiethanolamine, alkanoldiamines, alkenylpolyamines, or solutions of salts of weak or~anic acids, such as amino carboxylic acids and aminosulfonic acids, or other alkaline liquids. Alkali metal hydroxides and alkanolamines are preferred, particularly diethanola~ine and N- methyldiethanolamine.
Thus, the present invention provides a process for the selective removal of hydrogen sulfide from a gas stream also containing carbon dioxide, at high pressure, by contactin~ the gas stream with an alkaline liquid. A limited gas-liquid contact time of less than 0.08 sec. allows selective removal of hydro~en sulfide.
Althou~h a detailed description of the present invention has been provided above, the present invention is not limited thereto. ~odifications will be apparent to those of ordinary skill which are not outside the scope of the invention, which is defined in the following claims.
FROM ~ GAS STR ~ I AT HIG~ PRESSURE
The present invention is directed tO the selective removal of hydrogen sulfide from a gas stream. In particular, the present s invention is directed to the selective removal of hydrogen sulfide from a high pressure gas stream which also contains carbon dioxide by using a metal chelate solution. Through operation at high pressures, the present invention may be used in situations where low pressure operation would be costly and time-consuming, such as in the removal of hydrogen sulfide from the gas stream of a natural gas production well.
The present invention provides a process for the removal of hydrogen sulfide from a gas stream containing hydrogen sulfide and carbon dioxide, which process co~prises contactin~ the gas stream with a stoichiometric excess of polyvalent retal chelate solution over the hydrogen sulfide, the solution having a p~ of about 8.0 to 9 2 for a time less than 0.08 sec. to absorb hydro~en sulfide and not carbon dioxide, by flowing the gas stream and the solution past from two to six mixing elements in a static mixer, the gas stream, which can be from the well head of a natural gas production well, being maintained at a pressure of 5340-6170 kPa (760-880 psig) during the contacting period. The polyvalent metal-chelate solution is preferably iron- HEDTA (N- hydroxyethylethylenediaminetriacetic acid).
- 25 Fig. 1 is a schematic representation of the equipment used in the experimental work described below, and Figs. 2-4 are graphical representations of the data obtained in the experimental work described below.
As noted above, the present process is directed to the selective removal of hydrogen sulfide from a gas stream at hi~h ~, "j 1~0~913 pressure. The following apparatus and procedure were used in conducting the high pressure removal of hydrogen sulfide with an alkaline absorbing solution. Referrin~ to Fig. 1, wellhead gas was contacted with absorbin~ solution in a static mixer and quickly separated in a gas/liquid separator. The gas/liquid separator was operated at the wellhead pressure, while the gas flow rate was varied throu~h the use of valve Vl. An orifice flange was set up to measure the gas flow rate downstream of valve Vl. The pressure gauge on the gas/liquid separator indicated wellhead pressure when valve Vl was shut and flowing pressure during testing. Valve V2 was opened slightly to allow a slo~ flow to the ~as chromatograph and the hydrogen sulfide tube samplers.
Liquid was pumped to the static mixer by a variable speed Zenith ~ear pump. A two-liter cell was used for the liquid reservoir, and wellhead pressure pressurized the liquid reservoir which fed the pump. The wellhead gas which pressurized the liquid reservoir first passed through a methyldiethanol amine scrubber whi h removed the acid gases from the gas. Wellhead temperature was monitored by a thermocouple, in-line with a pyrometer.
Three solutions were tested. The first solution was 50~ by wei~ht methyldiethanol amine. The amine was purchased from Pfaltz and Pauer, Inc. The remaining two solutions were dilutions of Dow Chemical's'~ersenor'S~ iron chelate solution, and iron-HEDTA chelate solution. The concentrations of the solutions were 0.32 molar and 0.11 molar, and the pH of each was adiusted to 9.2 with ammonium carbonate solution.
The gas tested had a composition of 95.3 mole percent methane, l.S mole percent ethane, 0.3 mole percent propane, 0.4 mole percent nitrogen, 1.8 mole percent carbon dioxide, 0.1 mole percent hydrogen sulfide and 0.6 mole percent other hydrocarbons. The gas was tested at pressures from 5340 to 6170 kPa (760 to 880 psig).
Four different sizes of static mixers were used during the test:
12.7 mm (1/2") diameter by 152.4 mm (6") long; 9.5 mm (3/8") *Trade mark 7, ~30~913 F-2765 --3~~
diameter by 114.3 mm (4-1/2") long; 6.4 mm (1/4") diameter by 63.5 mm (2-1/2") lon~; and 6.4 mm (1/4") diameter by 127 m~ (5") long.
In the first test, the 50~ by wei~ht amine solution was used with the 12.7 mm (1/2") static mixer. The ~as flow rate was set at 8~D00 standard liter per hour (3,0~0 standard cubic feet per hour), which resulted in a gas- liquid contact time in the static mixer of 100 milliseconds. This was the maxirum flow rate that could be run with this equipment because of pressure drop limitations in the equipment. Five liquid flow rates were run, and the results are shcwn in Fi~. 2. This fi~ure shows the percent of hydro~en sulfide removed as a function of excess mo1ar amine pumped. Approximately 9~ of the carbon dioxide also was removed with the hydrogen sulfide. This was not unexpected, because of the relatively lon~ contact time between the liquid and the gas. About 70~ of the hydro~en sulfide was removed with a pumped amine stoichiometric excess of 300%.
To reduce the ~as-liquid contact time, the 9.5 mm (3/8') static mixer was used. With a ~as flow rate of 59400 standard liter/hour (2,100 scfh), a contact time in the static ~ixer of 17 milliseconds was maintained for the second test. As can be seen in Fig. 2, at the shorter contact time, the hydrogen sulfide still was removed, but not as efficiently as at the lon~er contact time.
Carbon dioxide was also removed (about 8) which was not expected.
These results illustrate th~t both the amine/hydro~en sulfide and - 2s amine/carbon dioxide reactions are kinetically limited. Other work has shown that carbon dioxide removal is diffusion limited, and can be controlled by limiting the gas-liquid contact time to under 80 milliseconds.
A concentrated iron chelate solution also was run to determine if selective hydro~en sulfide absorption could be achieved at the hi~her pressures. ~ecause of limited pumpin~ rates, less gas was processed in this test. The 6.4 mm x 63.5 mm (1/4" x 2-1/2") static mixer was used to obtain a short ~as-liquid contact time of ~3 D
130~9~3 F-2765 ~~4~~
17 milliseconds. Fig. 3 shows that in contactin~ the gas with a 12-fold stoichiometric excess of iron, 89% of the hydrogen sulfide was removed with no carbon dioxide absorption. For either iron chelate or amine solutions, a stoichiometric excess over the hydro~en sulfide is necessary, since the ~ixin~ does not provide for a stoichiometric reaction.
The 6.4 mm x 127 mm (1/4" x 5") static mixer then was tested and operated at the same gas rate. This produced a gas-liquid contact time of 30 milliseconds in the static mixer, doubling not only the contact time, but also the number of mixin~
elements in the static mixer. Fig. 3 shows that a slight increase in hydrogen sulfide absorption was achieved with no carbon dioxide absorption. This shows that the six mixin~ elements in the 6.4 mm x 63.5 mm (1/4" x 2-1/2") static mixer were sufficient to obtain the needed liquid dispersion to assure kinetic control of the reaction.
In the next test, the iron chelate solution was diluted to yield a final iron chelate concentration of 0.11 ~, as opposed to the 0.32 ~ solution tested previously. Again, no carbon dioxide was absorbed during the test. As shown in Fig. 3, to achieve 80%
hydrogen sulfide removal, a 380~ molar excess of iron chelate was needed. The data from all the tests are ~iven in the Table on the following page ~30~g~3 E
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Fig. 4 shows the same data as Fig. 3, but as a function of pumping rate. The dilute solution is not as efficient in this case. However, only a 5~ increase in hydro~en sulfide removal is seen over the dilute solution. Since concentration appears to make very little difference, the limiting factor for the concentrations tested is the total liquid surface area. The total li~uid surface area is a function of the mean drop diameter and the volume of liquid pumped. The mean drop diameter is controlled by the type and number of static mixer elements used alon~ with the velocity of the fluids and the physical properties of both the li~uid and ~as. This is described in U.S. Patent 4,499,059. Using static mixers with a gas-liquid system, a stable mean drop diameter is obtained with two to six static mixer elements. Additional elements do not reduce the mean drop diameter. Thus, with six mixing elements, the total liquid surface area can be controlled by varying the liquid flow rate, and hence at constant ~as rates and solution ~'s, the hydro~en removal efficiency can be controlled by varyin~ the liquid flow rate.
The polyvalent metal chelate solution must have a pH of at least 7, preferably 8-9, and may be a polyvalent metal chelate solution, with pff adjusted by sodiu~ or ammonium carbonate. The polyvalent metal ~ay be selected from iron, copper, manganese, lead, mercury, palladium, platinum, tungsten, nickel, chromium, cobalt, vanadium, titanium, tantalum, zirconium, molybdenum and tin, preferably iron, copper and manganese, and most preferably iron.
The chelating agent may be selected from amino acetic acids derived from ammonia or 2-hydroxyalkylamines, such as glycine, diglycine (aminodiacetic acid), nitrilo triacetic acid, 2-hydroxyalkylglycine, di-hydroxyalkylglycine and hydroxyethyl or 3~ hydroxypropyldiglycine, amino acetic acids derived from ethylene diamine, diethylenetriamine, 1,2-propylenediamine and 1,3-propylenediamine, such as EDTA, 2-hydroxy EDTA, and diethylene tria~ine pent2aceticacid, amino acetic acid derivatives of cyclic 1~0~1~13 1,2-diamines, such as 1,2-diaminocyclohexane-N, N- tetraacetic acid, and amides of polyamino acetic acids, as disclosed in U. S. Patent No. 3,580,950 to Bersworth. E~T~ and N-hydroxyethylethylenediaminetriacetic acid (HEDTA) are particularly preferred. The alkaline liquid also may be selected from aqueous solutions of inorganic salts having an alkaline reaction, such as alkali metal hydroxides, rhosphates, borates, metaborates or arsenites, solutions of or~anic bases, svch as alkanolamines, like monoethanol amine, diethanolamine, triethanolamine, N-methyldiethanolamine, alkanoldiamines, alkenylpolyamines, or solutions of salts of weak or~anic acids, such as amino carboxylic acids and aminosulfonic acids, or other alkaline liquids. Alkali metal hydroxides and alkanolamines are preferred, particularly diethanola~ine and N- methyldiethanolamine.
Thus, the present invention provides a process for the selective removal of hydrogen sulfide from a gas stream also containing carbon dioxide, at high pressure, by contactin~ the gas stream with an alkaline liquid. A limited gas-liquid contact time of less than 0.08 sec. allows selective removal of hydro~en sulfide.
Althou~h a detailed description of the present invention has been provided above, the present invention is not limited thereto. ~odifications will be apparent to those of ordinary skill which are not outside the scope of the invention, which is defined in the following claims.
Claims (3)
1. A method for selectively removing hydrogen sulfide from a gas stream containing hydrogen sulfide and carbon dioxide, comprising contacting the gas stream with a stoichiometric excess of a polyvalent metal chelate solution over said hydrogen sulfide said solution having a pH of about 8.0 to 9.2 for a time period less than 80 milliseconds to absorb hydrogen sulfide and not carbon dioxide, by flowing said gas stream and said solution past from two to six mixing elements in a static mixer, said gas stream being at a wellhead pressure of about 760-880 psig during said contacting period.
2. A method according to claim 1, wherein said polyvalent metal chelate solution is an iron-HEDTA solution.
3. A method according to claim 1 or 2, wherein the gas stream and the solution flow past six mixing elements.
0001A/0388h
0001A/0388h
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2014201487A1 (en) | 2013-06-20 | 2014-12-24 | Technische Universität Wien | Process and apparatus for desulfurizing gas mixtures |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2014201487A1 (en) | 2013-06-20 | 2014-12-24 | Technische Universität Wien | Process and apparatus for desulfurizing gas mixtures |
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