CA1340768C - Teritiary alkanolamine absorbent containing an ethyleneamine promoter and its method of use - Google Patents
Teritiary alkanolamine absorbent containing an ethyleneamine promoter and its method of useInfo
- Publication number
- CA1340768C CA1340768C CA000560222A CA560222A CA1340768C CA 1340768 C CA1340768 C CA 1340768C CA 000560222 A CA000560222 A CA 000560222A CA 560222 A CA560222 A CA 560222A CA 1340768 C CA1340768 C CA 1340768C
- Authority
- CA
- Canada
- Prior art keywords
- carbon dioxide
- absorbent
- absorbent solution
- tertiary alkanolamine
- ethyleneamine
- 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 - Fee Related
Links
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
- B01D53/1456—Removing acid components
- B01D53/1475—Removing carbon dioxide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1493—Selection of liquid materials for use as absorbents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/62—Carbon oxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/50—Carbon oxides
- B01D2257/504—Carbon dioxide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
-
- 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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
Absorption of carbon dioxide from gas mixtures with aqueous absorbent solutions of tertiary alkanolamines is improved by incorporating at least one alkyleneamine in the solution. The presence of the alkyleneamine promotes the rate of carbon dioxide absorption and the carbon dioxide capacity of the aqueous tertiary alkanolamine solution. As a result, absorption can be carried out in shorter absorber columns, and process energy requirements can be lowered by reducing the rate at which the absorbent solution is circulated.
Description
13407~~
TERTIARY ALKANOLAMINE ABSORBENT CONTAINING
AN ETHYLENEAMINE PROMOTER AND ITS METHOD OF USE
CKGROUND OF THE INVENTION
For many years, carbon dioxide has been removed from gaseous mixtures with various absorbent liquids.
Alkali metal. salts such as carbonates, phosphates, borates, and phenates of sodium and potassium are one category of absorbent liquid. The carbon dioxide absorption rates of such salts is, however, rather low, and, therefore, it has been necessary to add promoting agents to thesN salts. British Patent No. 798,856 to S.P.A. Vetrocoke discloses that an inorganic or organic compound of trivalent arsenic is useful in activating such salts. :In Astarita et al.'s "Promotion of C02 Mass Transfer In Carbonate Solutions", Chemical Enc~ineerina Science, Vol. 36, pp. 581-88 (1981.), it is mentioned that arsenious acid, ethanolamines, and amino acids promote the absorption of carbon dioxide by carbonate-bicarbonate salts. U.S. Patent No. 4,094,957 to Sartori et al., U.S. Patent No. 4,112,052 to Sartori et al., U.S. Patent. No. 4,217,237 to Sartori et al., U.S. Patent No. 4,405,577 to Sartori et al., U.S. Patent No. 4,405,578 to Sartori et al., U.S. Patent No.
4,405,579 to Sartori et al., and Sartori et al.'s "Sterically Hindered Amines for C02 Removal from Gases", ~ndustr~ial Engineering Chemical Fundamentals, Vol. 22, pp. 239-49 (1983) ("Sartori article") all disclose activating a basic salt for removing carbon dioxide from gaseous mixtures with sterically hindered 1340~~8 amines or amino acids (i.e. a primary amine in which the amino group is attached to a tertiary carbon atom or a secondary amine in which the amino group is attached to a secondary or tertiary carbon atom).
Alkanolamine:~ in aqueous solution are another class of absorbent liquid for removal of carbon dioxide from gaseous mixturEa. Alkanolamines are classified as pri-mary, secondary,, or tertiary depending on the number of non-hydrogen substituents bonded to the nitrogen atom of the amino group. Monoethanolamine (HOCH2CH2NH2) is an example of a well-known primary alkanolamine. Con-ventionally used secondary alkanolamines include diethanolamine ((HOCH2CH2)2NH) and diisopropanol amine ((CH3CHOHCH3)2NH). Triethanolamine ((HOCH2CH2)3N) and methyldiethanolamine ((HOCH2CH2)2NCH3) are examples of tertiary alkanolamines which have been used to absorb carbon dioxide from industrial gas mixtures. These alkanolamines are not only useful in absorbing carbon dioxide, but they have also been employed to absorb hydrogen sulfide or carbonyl sulfide from gas mixtures which may or ma~~ not contain carbon dioxide.
After absorption of carbon dioxide and/or hydrogen sulfide and/or carbonyl sulfide in an alkanolamine solution, the :solution is regenerated to remove absorbed gases. The regenerated alkanolamine solution can then be recycled for further absorption. Absorption and regeneration are usually carried out in different separatory columns containing packing or bubble plates for efficient operation. Regeneration is generally achieved in 2 stages. First, the absorbent solution's pressure is reduced so that absorbed carbon dioxide is vaporized from the solution in one or more flash regenerating columns. Next, the flashed absorbent is I3~0~6~
TERTIARY ALKANOLAMINE ABSORBENT CONTAINING
AN ETHYLENEAMINE PROMOTER AND ITS METHOD OF USE
CKGROUND OF THE INVENTION
For many years, carbon dioxide has been removed from gaseous mixtures with various absorbent liquids.
Alkali metal. salts such as carbonates, phosphates, borates, and phenates of sodium and potassium are one category of absorbent liquid. The carbon dioxide absorption rates of such salts is, however, rather low, and, therefore, it has been necessary to add promoting agents to thesN salts. British Patent No. 798,856 to S.P.A. Vetrocoke discloses that an inorganic or organic compound of trivalent arsenic is useful in activating such salts. :In Astarita et al.'s "Promotion of C02 Mass Transfer In Carbonate Solutions", Chemical Enc~ineerina Science, Vol. 36, pp. 581-88 (1981.), it is mentioned that arsenious acid, ethanolamines, and amino acids promote the absorption of carbon dioxide by carbonate-bicarbonate salts. U.S. Patent No. 4,094,957 to Sartori et al., U.S. Patent No. 4,112,052 to Sartori et al., U.S. Patent. No. 4,217,237 to Sartori et al., U.S. Patent No. 4,405,577 to Sartori et al., U.S. Patent No. 4,405,578 to Sartori et al., U.S. Patent No.
4,405,579 to Sartori et al., and Sartori et al.'s "Sterically Hindered Amines for C02 Removal from Gases", ~ndustr~ial Engineering Chemical Fundamentals, Vol. 22, pp. 239-49 (1983) ("Sartori article") all disclose activating a basic salt for removing carbon dioxide from gaseous mixtures with sterically hindered 1340~~8 amines or amino acids (i.e. a primary amine in which the amino group is attached to a tertiary carbon atom or a secondary amine in which the amino group is attached to a secondary or tertiary carbon atom).
Alkanolamine:~ in aqueous solution are another class of absorbent liquid for removal of carbon dioxide from gaseous mixturEa. Alkanolamines are classified as pri-mary, secondary,, or tertiary depending on the number of non-hydrogen substituents bonded to the nitrogen atom of the amino group. Monoethanolamine (HOCH2CH2NH2) is an example of a well-known primary alkanolamine. Con-ventionally used secondary alkanolamines include diethanolamine ((HOCH2CH2)2NH) and diisopropanol amine ((CH3CHOHCH3)2NH). Triethanolamine ((HOCH2CH2)3N) and methyldiethanolamine ((HOCH2CH2)2NCH3) are examples of tertiary alkanolamines which have been used to absorb carbon dioxide from industrial gas mixtures. These alkanolamines are not only useful in absorbing carbon dioxide, but they have also been employed to absorb hydrogen sulfide or carbonyl sulfide from gas mixtures which may or ma~~ not contain carbon dioxide.
After absorption of carbon dioxide and/or hydrogen sulfide and/or carbonyl sulfide in an alkanolamine solution, the :solution is regenerated to remove absorbed gases. The regenerated alkanolamine solution can then be recycled for further absorption. Absorption and regeneration are usually carried out in different separatory columns containing packing or bubble plates for efficient operation. Regeneration is generally achieved in 2 stages. First, the absorbent solution's pressure is reduced so that absorbed carbon dioxide is vaporized from the solution in one or more flash regenerating columns. Next, the flashed absorbent is I3~0~6~
stripped with steam in a stripping regenerating column to remove residual absorbed carbon dioxide. With primary and secondary alkanolamines, the nitrogen reacts rapidly and directly with carbon dioxide to bring the carbon dioxide into solution according to the following reaction sequence:
2RNH2 ~~ C02 ,~ RNHCOO- + RNH3 where R is an alkanol group. To obtain concentrations of carbon dioxide in solution which are greater than 0.5 mole of carbon dioxide per mole of alkanolamine, a portion of the' carbamate reaction product (RNHC00-) must be hydro7.yzed to bicarbonate (HC03-) according to the following reaction:
RNHCOO~ + H20 ~ RNH2 + HC03-There is a characteristic equilibrium between the carbamate (RNHCOO-) and bicarbonate (HC03-) ions for each alkanolamine which determines the vapor-liquid equilibrium or solution phase concentration of carbon dioxide for any gi en gas phase pressure of carbon dioxide. The alkanol substituent groups R which are attached to the nitrogen atom of any alkanolamine affect the basicity of the alkanolamine and its reactivity toward and vapor-liquid equilibrium with carbon dioxide.
In formin~~ a carbamate, primary and secondary alkanolamines ~sndergo a fast direct reaction with carbon dioxide which makes the rate of carbon dioxide absorp-tion rapid. However, considerable heat is required to break the bond between the alkanolamine and carbon dioxide in the carbamate and regenerate the absorbent.
In addition, primary and secondary alkanolamines have a limited capacity to absorb carbon dioxide due to the formation of atable carbamates. The Sartori article 1340~~8 teaches that loading of such alkanolamines is improved by incorporating sterically hindered amines. Meanwhile, British Patent No. ?98,856 activates primary alkanol-amines, like ethanolamine, with arsenious oxide.
Unlike primary and secondary alkanolamines, tertiary alkanolamines cannot react directly with carbon dioxide, because their amine reaction site is fully substituted with substituent groups. Instead, carbon dioxide is absorbed into solution by the following slow reaction with water to form bicarbonate:
R3N + C02 + 1H20 ~ HC03- + R3NH+
Because tertiary alkanolamines do not bond with carbon dioxide, they can be economically regenerated often by simply reducing pressure in the system (i.e. flash regenerating). little or no thermal regeneration is required. Although the absence of a direct reaction with carbon dioxide makes regeneration of tertiary alkanolamines more economical, large solvent circulation rates and high liquid to gas ratios (i.e. high liquid loadings) in tlae absorber are required due to the slow absorption of .carbon dioxide. Consequently, systems utilizing tertiary alkanolamines require absorption columns of increased height and diameter compared to systems employing either primary or secondary alkanolamines.
In order t.o increase the rate of carbon dioxide absorption by aqueous tertiary alkanolamine solutions, promoters have been added. In U.S. Patent No. 4,336,233 to Appl et al ("Appl patent"), a piperazine promoter is incorporated in an aqueous methyldiethanolamine solution. The process disclosed by the Appl patent "employs aqueous solutions of a bottom product obtained as a by-product from the synthesis of ethylenediamine 134Q7~~
_5-from monoethanolamine and ammonia. this material also contains 0.3 percent by weight, based on piperazine of the following by-products: NH3, ethylenediamine, MEA, and further nitrogen-containing products." The by-I
products are merely said to "not interfere with the process according to" the Appl patent.
Promoted met.hyldiethanolamine solutions have both an increased rate of carbon dioxide absorption and an increased capacity for carbon dioxide compared to unpromoted methyldiethanolamine. Improved rate of absorption is particularly evident at low levels of carbon dioxide loading and diminishes as such loading increases. The full benefit of the promoter is found in processes which employ thermal regeneration in addition to flash regeneration of the absorbent to maintain the low loading levels necessary to produce a gas product with low levels of carbon dioxide. Flash regeneration alone is sufficient for bulk removal of carbon dioxide from high pressure gases (i.e. carbon dioxide partial pressure greater than 50 psia) where low carbon dioxide specifications in the product gas are not needed.
DESCRIPTION OF THE INVENTION
The absorption of carbon dioxide from gas mixtures with aqueous absorbent solutions of tertiary alkanol-amines is improved by incorporating at least one alkyleneamine promoter in the solution. The alkylene-amine is incorporated in an amount sufficient to enhance substantially 'the carbon dioxide absorption rate by at least 10%, usually by 25-200 % and/or the capacity of the tertiary alkanolamine in water by as much as 70%.
The tertiary alkanolamines utilized can be any of a 1340'~~~
variety of compounds suitable for absorbing carbon dioxide from ~gas mixtures. Examples of these absorbent alkanolamines include: methyldiethanolamine, triethanol-amine, dimethylethanolamine, diethylethanolamine, methyldiisopropanolamine, and mixtures thereof. Methyl-diethanolamine and triethanolamine are the preferred tertiary alkanolamines with methyldiethanolamine being most preferred.
The promoter utilized by the present invention is generally at least one alkyleneamine defined by the formula:
H2N(CxH2xNH)nH
wherein x is 1 to 4, while n is 1 to 12. More preferably, the present promotion additive is at least one ethyleneamine or propyleneamine selected from a homologous series of polyamines, all of which contain two primary amino groups with other amino groups, if any, being secondary. Ethyleneamines which are useful in the present invention are defined by the formula:
H2N(C2H4NH)nH
where n is 1 to 12. Specific examples of such ethylene-amines include ethylenediamine, diethylenetriamine, tetraethylenepentamine, and mixtures thereof. Of these promoters, ethylenediamine is most preferred.
The alkyleneami.ne-promoted tertiary alkanolamine absorbents may additionally contain conventional corrosion inhibitors to prevent corrosion caused by carbon dioxide absorbed in the tertiary alkanolamine absorbent solution. When corrosion in the process is controlled, higher alkanolamine strengths can be utilized to reduce absorbent circulation rates, equipment size, and operating costs.
I34~~~8 _7_ The alkyleneamine-promoted tertiary alkanolamine absorbents of the present invention can be prepared as an aqueous solution which is ready to be used in the field. In ready-to-use form, the aqueous absorbent solution may contain 35-65 wt.% water, preferably 45-55 wt.% water, anc9 most preferably 50 wt.% water. The alkyleneamine promoter in the promotion additive is present in an amount sufficient to enhance the rate at which cool (to 100-130'F) aqueous tertiary alkanolamines absorb carbon dioxide from warm (150-200'F) gas mixtures in a gas-liquid contact apparatus. Such enhancement in the rate of carbon dioxide absorption is achieved when the alkyleneamine- promoted tertiary alkanolamine achieves at least 10%, usually 25-200%, faster carbon dioxide removal than the same absorbent without the alkyleneamine. This generally occurs when the alkyleneamine is 0.5-10 wt.% of the aqueous absorbent solution, preferably 2- .6 wt.%, and most preferably 3-4 wt.%. An effective amount of the corrosion inhibitor, if any, for purposes of the present invention is about 0.05-0.1 wt.% of the aqueous absorbent solution. The tertiary alkanolamine comprises the remainder of the absorbent solution.
Alternatively, the alkyleneamine-promoted tertiary alkanolamine can be prepared as a concentrate, shipped to the facility where it is to be utilized, and then diluted with water prior to use. In its concentrated, non-aqueous fo:-m, the absorbent contains 1.0-20 wt.% of alkyleneamine promoter, preferably 4-12 wt.%, and most preferably 5 t:o 8 wt.%. The tertiary alkanolamine con-stitutes the remainder of the concentrated absorbent.
The mole ratio of alkyleneamine to alkanolamine is 0.01 to 0.5, preferably 0.05 to 0.27, most preferably 0.07 to 0.17.
-g-In use, the aqueous ethyleneamine-promoted alkanol-amine solution (i.e. lean absorbent) at temperatures of 120°F to 200°F is contacted with an industrial gas containing carbon dioxide at partial pressures of 25 sia to 250 psia or higher in an absorption zone and P
both a product gas substantially free of carbon dioxide (i.e. 0.01 volume % to 0.1 volume % for trim gas removal and 3-5 volume % for bulk gas removal) and an aqueous alkyleneamine-promoted alkanolamine solution laden with absorbed carbon dioxide and optionally absorbed hydrogen sulfide or carbonyl sulfide (i.e. rich absorbent) are withdrawn from the absorption zone. In addition, the aqueous alkyleneamine-promoted alkanolamine can be used to treat gases with hydrogen sulfide and/or carbonyl sulfide containing little or no carbon dioxide. The absorption zone is preferably a gas-liquid contact column containing bubble plates or packing to improve absorption.
To conserve absorbent, the rich absorbent is regenerated in at least one regenerating column and then recycled to the absorption column. Such regeneration is achieved by first removing absorbed carbon dioxide from the rich absorbent by reducing the absorbent's pressure in at least one flash regenerating column (i.e. flash regenerating) t:o pressures as low as 7 psia and as high 20 psia and i=hen stripping the flashed absorbent with steam in a strapping regenerator column operating at 235 to 265°F to remove absorbed carbon dioxide to a residual loading of approximately 0.005 to 0.05, preferably 0.01 moles of carbon dioxide per mole of alkanolamine. The flash regenerating column and the stripping regenerator column both contain either packing or bubble plates for more efficient regeneration. The carbon dioxide-containing gas. produced in each regenerating column can ,.._.
i34o7ss _g-either be removed from the absorption/regeneration installation separately or the gas generated by the stripping regenerator column can be passed into the flash regenerating column and removed with the gas generated therein. Alternatively, regeneration can in some cases be ca~~ried out with just a flash regenerating step due to the ease with which tertiary alkanolamines are regenerated.
A wide variety of industrial gases (e. g. fuel gases, gasification product gases, refinery gases, synthesis gases, natural gas, and enhanced oil recover associated gases) can be treated with alkyleneamine promoted tertiary alkanolamine absorbent solutions utilizing the above-described absorption/regeneration scheme. These gases can include compounds in the range of amounts shown in Table 1.
TABLE
Compound mount (Volume percent) C02 10-40%
CO 20-40%
0-80%
C 0.1-90%
N2H2n + n(n=2-6) 0-20%
H2S 0-0.1%
COS
Synthesis gas containing the compounds in the amounts shown below in Table 2 is particularly well suited to treatment with absorbent solutions in accordance with present invention.
TABLE 2_ Co~~a mou t (Volume percent) C02 15-35%
CO 20-40%
H2 20-40%
0.1-5%
N2 0-20%
2 0-3%
COS 0-0.1%
Typically, contacting such gas with absorbents in accordance with the present invention reduces the carbon dioxide content: in the gas by between 75 and 100 vol.%
to yield gases of less than 3 vol.% carbon dioxide. The alkyleneamine-promoted tertiary alkanolamine also re-duces the hydrogen sulfide content in the gas by between 99.5 and 100 vol.% to less than 0.0004 vol.% and reduces the carbonyl sulfide content in the gas by 50-90 vol.%
to less than 0.001 vol.%.
ERIE;F DESCRIPTION OF THE DRAWINGS
Figure 1 is. a process flow diagram for an absozption and regeneration process utilizing a tertiary alkanol-amine absorbent containing an alkyleneamine promoter according to the present invention.
Figure 2 is a graph showing vapor-liquid equilibrium data and rate of absarption data for absorbent solutions with 50 wt% inethyldiethanolamine alone or with 3 wt% piperazine, ethylenediamine (i.e. EDA), or die-thylenetriamine (i.e. DETA).
AILED DESCRIPTION OF THE DRAWING
In a preferred embodiment, as shown in the process flow diagram of Figure 1, carbon dioxide is removed in two absorption columns connected fn series. Synthesis gas 8 is first directed into bulk C02 absorber 2 where it is contacted countercurrently with lean bulk absorbent ~. ~r bulk absorber product gas ~ from which 65 to 85% of the carbon dioxide in the synthesis gas has been removed is withdrawn from bulk C02 absorber 2 as an overhead product, while rich bulk absorbent p is withdrawn as a bottom product. The bulk absorbent product gas ~ is then conveyed into a lower portion of trim C02 absorber 4 and countercurrently contacted with lean trim, absorbent F which removes substantially all the remaining carbon dioxide. A substantially C02- free trial absorber product gas ~ is removed from trim C02 absorber 4 as an overhead product, while rich trim absorbent Ci is withdrawn as a bottom product.
Regeneration of the rich absorbent streams is also carried out in two columns. Rich bulk absorbent _D
undergoes a pressure drop through turbine 6 and then passes into flash regeneration column 8 having a top section 8A and a bottom section 8B. Gases g are conveyed by vacuum compressor 9 from bottom section 8B
to top section 8A, _while liquid O flows from top section 8A to bottom aection 8B by gravity. In flash regenera-tion column 8 which operates at pressure of 7 to 20 psia, some of the absorbed C02 flashes and is removed from flash regeneration column 8 as an overhead product Product ~ then passes through condenser 20 which is cooled (to 100-130°F) with water to permit non-condensibles to be separated and removed from reflux drum 10 as a gaseous product T, while condensibles ~C are withdrawn as a liquid product. Flash regenerated absorbent ~i i.s withdrawn from flash regeneration column 8 as a bottom product which can either be combined with rich trim absorbent ~ and directed by turbine 6 to bulk C02 absorber 2 as lean bulk absorbent $ or be conveyed by pump 12 t;o stripping regeneration column 14. In stripping regeneration column 14, residual carbon dioxide is rE:moved as stripping regeneration overhead product ~I which is then recycled to flash regeneration 13~O~1G~
column 8 from which carbon dioxide is removed from the system. Such recycling enhances the flashing of carbon dioxide in flash regeneration column 8. Stripping regeneration bottoms product ~1 is either conveyed through steam reboiler 16 and returned to stripping regeneration column 14 or combined with make-up water ~
and condensate ~C and recycled by pump 18 to trim Co2 absorber 4 as lean trim absorbent To reduce process energy requirements and improve absorption effic;iency, a portion of stripping regenera-tion bottoms product ~1 is cooled from about 250°F to 170°F by incoming flash regenerated absorbent ~i in heat exhanger 22. That portion of bottoms product ~1 which becomes lean trim absorbent ~ is further cooled (to 100-130°F) with water in cooler 24. As a result of its heat exchange contact with stripping regeneration bottoms product ~1, flash regenerated absorbent H_ is preheated (to 150-235°F) prior to entering stripping regeneration column 14.
~XAMPL~ 1 In commercial use, 142,333 standard cubic feet per minute of synthesis gas g produced by the partial oxidation of natural gas with steam and air could be treated in accordance with the process flow diagram of Figure 1 for ultimate use of the purified synthesis gas in a 1200 ton pe:r day ammonia product facility.
Synthesis gas ~ containing 41.9 mole % hydrogen, 41.0 mole % nitrogen, 15.7 mole % carbon dioxide, 0.7 mole % carbon monoxide, 0.5 mole % argon, 0.2 mole %
methane, and 0,.1 mole % helium enters the bottom of bulk C02 absorber 2 which is 11 feet in diameter and contains two 2!3 foot packed beds of structured stainless steel packing at 170°F and 400.0 psia. In bulk C02 absorber 2, synthesis gas ~ countercurrently contacts lean bulk absorbent $ which is an aqueous solution containing 47 weight percent methyldiethanolamine and 3 weight percent ethylenediamine. Lean bulk absorbent B
is fed to the top of bulk C02 absorber 2 at a rate of 6609 gallons per minute at a temperature of 155'F, and at a loading of 0.27 moles of carbon dioxide per mole of methyldiethanolamine. Carbon dioxide is removed from synthesis gas ~~ at a rate of 2746 moles per hour so that bulk absorbent product gas ~ which has a temperature of 155°F and 399 psia contains 3.95 mole % carbon dioxide.
Bulk absorbent product gas ~ then enters the base of the 36 tray trim C02 absorber 4 and is counter-currently contacted with lean trim absorbent ~ which is also an aqueous solution of 47 weight % methyldiethanol-amine and 3 weight percent ethylenediamine which has been regenerat~sd to a lean C02 solution loading of 0.01 moles o:E carbon dioxide per mole of. methyl-diethanolamine. Lean trim absorbent ~ is fed into the top of trim C02 absorber 4 at a temperature of 105°F
and at a flo~arate of 1368 gallons per minute. Carbon dioxide is removed from bulk absorber product gas C at a rate of 769.3 moles per hour so that the carbon dioxide content of the trim absorber product gas ~ is reduced to 1000 volumetric ppm or 0.1 mole %.
Rich bulk absorbent p which is discharged from the bottom of the bulk C02 absorber 2 at a temperature of 181°F, at a flowrate of 6935 gallons per minute, and with a molar carbon dioxide content of 0.48 is fed into top section 8A of column 8. Top section 8A is 11 feet in diameter, 39 feet. high, and filled with a 20 foot bed of stainless steel packing. This section operates at about 20.2 psia so that C02 is flashed at a rate of 1971.2 moles per hour which reduces the carbon dioxide 1340"ls~
loading in the absorbent to 0.33 moles of C02 per mole of methyldiethanolamine. This flashing reduces the absorbent temperature to 166'F. Flashed absorbent Q is then conveyed t:o bottom section 8B which is 42 feet high. In this section, the absorbent is vacuum flashed at 9.7 psia to remove another 750.7 moles of C02 per hour so that the flash regenerated absorbent ~I has a loading of 0.2'7 moles of C02 per mole of methyl-diethanolamine~and a temperature of 155°F.
A 81.6 percent portion of flash regenerated absorbent ~i is directly recycled to the top of bulk C02 absorber 2, while the remainder is heated to 233'F
by stripping regeneration bottom product ~1 in heat exchanger 22. From heat exchanger 22, preheated, flash regenerated absorbent ~i is fed into the top of stripping regeneration column 14 which is 11 feet in diameter and contains 17 sieve trays.
In stripping regeneration column 14, 793.5 moles of carbon dioxides per hour are produced as stripping regeneration overhead product ~I, so that the stripping regeneration bottom product ~1 has a carbon dioxide loading of 0.01 moles per mole of methyldiethanolamine.
Bottom product ~t is discharged at a rate 1388 gallons per minute and at a temperature of 253°F. Heat exchange with flash regenerated absorbent ~i reduces the tempera-ture of stripping regeneration bottom product ~1 to 168°F, while cooler 24 reduces the temperature of what is now lean trim absorbent ~ to 105°F.
Reboiler 16 heats bottom product Z1 at a rate of 55.9 MM BTUs per hour which is equivalent to 15.9 M BTUs per mole of carbon dioxide.
A series of experiments were conducted in a ,.~ 134flr1~8 specially desigr,~ed racking autoclave to determine the rate of carbon dioxide absorption and the vapor-liquid equilibrium for :several absorbent solutions.
The autoclave is a stainless steel cylinder which is I
surrounded by a steam jacket around which are electric heaters. Carbon dioxide is charged to an accumulator cell from a carbon dioxide cylinder. The carbon dioxide is then transferred from the accumulator cell to the autoclave through a port in the autoclave. A port is also provided :in the autoclave through which absorbent solution can b~. charged. The autoclave is rocked by an electric motor.
The head is provided with a port through which a thermocouple is inserted for measurement of the auto-clave temperature. The accumulator cell's pressure drop is used to calculate the gram-moles of carbon dioxide charged to the autoclave. Rate of absorption data is obtained by measuring the autoclave pressure vs. time.
The following aqueous absorbent solutions were prepared:
No. Agueous. Absorbent 1 50 wt.~. methyldiethanolamine alone 50 wt.~~ methyldiethanolamine plus 3.0 wt.$
pipera~; ine 3 50 wt.~s methyldiethanolamine plus 3.0 wt.~
diethy7.enetriamine 50 wt.3~ methyldiethanolamine plus 3.0 wt.$
ethylenediamine Each of the aqueous absorbent solutions was separately evaluated in the rocking autoclave by initially charging one of the absorbent solutions to the autoclave and heating the solution to a 70°C run 1340~~~
temperature. The autoclave was then pressurized with carbon dioxide from the accumulator cell, with the pressure change: of the accumulator cell being recorded.
When autoclave pressurization is complete, a starting pressure is rE:corded, and a stop watch and the rocking motor are started simultaneously. The rate of carbon dioxide absorption is measured by recording the autoclave pres:~ure drop with time. Equilibrium in the autoclave is <sssumed when the autoclave pressure ceases to change. A:Eter the equilibrium autoclave pressure is recorded, the autoclave containing the carbon dioxide-laden absorbent solution is again pressurized with additional carlbon dioxide and the procedure is repeated until the final experimental solution loading or equili-brium vapor pressure of carbon dioxide is achieved.
This procedure is repeated several times for a given solution until a set of carbon dioxide absorption rate data and vapor-liquid equilibrium data is obtained.
Each of the 4 absorbent solutions are subjected to this testing technique.
For each charge of carbon dioxide to the autoclave, an equilibrium carban dioxide vapor pressure is measured subsequent to the change in autoclave pressure with time. Equilibrium solution loading is then calculated as the total moles of carbon dioxide charged to the autoclave from the accumulator (calculated from accumulator pressure drop using a non-ideal equation of state) minus the moles of carbon dioxide remaining in the autoclave vapor space (calculated from autoclave equilibrium vapor pressure again using a non-ideal equation of state). The resultant vapor liquid equilibrium data is plotted as carbon dioxide vapor pressure versu:~ solution loading.
The rate of absorption in moles of carbon dioxide absorbed per liter of solution in the autoclave per -minute are calculated from autoclave pressure change with time again using a non-ideal equation of state.
Gram-moles of carbon dioxide are converted to cubic feet, and the rate of absorption is divided by an average partial pressure driving force in atmospheres to obtain the final rate of absorption in terms of cubic feet of carbon dioxide per hour-liter-atmospheres. The rate of absorption data can then be plotted versus equilibrium solution loading.
From the carbon dioxide partial pressure, the absorbent solution's carbon dioxide loading, and the solution absorption rate values for each carbon dioxide pressurization, a pair of curves can be prepared for each of the absorbents as shown in Figure 2. One set of curves are the carbon dioxide partial pressure vs.
carbon dioxide loading curves having a generally increasing slope. Another set of curve are the rate of absorption vs. carbon dioxide loading curves having a generally decreasing slope.
The curves representing the equilibrium between carbon dioxide in the vapor phase (i.e. carbon dioxide partial pressure) and carbon dioxide loading in the solution (i.e. moles carbon dioxide per mole of amine) can be used to determine the absorbent solution's circulation rage, while the rate of carbon dioxide absorbed by the solution vs. the carbon dioxide loading curves are used to determine the mass transfer rates from which ab:~orbent column staging requirements can be ascertained.
~nhancement in the rate of absorption and solution capacity is most pronounced under trim absorber conditions where solution loadings are defined as lean and semi-rich. The difference between the commercially-1340~1G~
utilized lean solution loading of 0.01 nolss C02/mole amine and a semi-rich solution loading in ~guilibrium with a C02 partial pressure of 20 psia, as would exit the trim absorber and enter the bulk absorber, is then calculated using the curves from Figure 2 for each of the four absorbent solutions. J~s a result, the four solutions were found to have the following loading differentials, absorption rates, and required circulation rates set forth below in Table 3.
p 1 0.26 112.2 4.0 2.7 2 0.39 64.9 19 3.8 3 0.42 63.3 18 3.7 4 0.45 49.9 25 4.2 A= Aqueous Absorbent No.
B=Loading Differential--i.e. semi-rich minus lean (moles carbon dioxide per mole of amine).
C=Circulation Rate (gallons of solvent per pound-mole C02).
D~Lean Solution hbsorption Rate (cubic feet per hour-atmosphere).
E=Semi-Rich Solution J~rbsorption Rate (cubic feet per hour atmosphere).
From Table 3, it is apparent that the methyldiethanol-amine promotes! with ethylenediamine and diethylene-triamine unexpectedly have a higher carbon dioxide capacity compared to unpromoted methyldiethanolamine and ~34o~r~g to methyldiethanolamine promoted with piperazine. As a result, methy:ldiethanolamine solutions promoted with ethylenediamine and diethylenetriamine are capable of absorbing more carbon dioxide during trim absorption.
In addition, '.Cable 3 shows that methyldiethanolamine promoted with ~thylenediamine has lean and semi-rich carbon dioxide absorption rates unexpectedly higher than those of unpromoted methyldiethanolamine alone and methyldiethanolamine promoted with piperazine. The lean and rich carbon dioxide absorption rates of methyl-diethanol amine promoted with diethylenetriamine are unexpectedly better than those of methyldiethanolamine alone and about the same as those of methyldiethanol-amine promoted with piperazine.
Although the invention has been described in detail for the purpose of illustration, it is understood that such detail i:a solely for that purpose and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention which is defined by the following claims.
2RNH2 ~~ C02 ,~ RNHCOO- + RNH3 where R is an alkanol group. To obtain concentrations of carbon dioxide in solution which are greater than 0.5 mole of carbon dioxide per mole of alkanolamine, a portion of the' carbamate reaction product (RNHC00-) must be hydro7.yzed to bicarbonate (HC03-) according to the following reaction:
RNHCOO~ + H20 ~ RNH2 + HC03-There is a characteristic equilibrium between the carbamate (RNHCOO-) and bicarbonate (HC03-) ions for each alkanolamine which determines the vapor-liquid equilibrium or solution phase concentration of carbon dioxide for any gi en gas phase pressure of carbon dioxide. The alkanol substituent groups R which are attached to the nitrogen atom of any alkanolamine affect the basicity of the alkanolamine and its reactivity toward and vapor-liquid equilibrium with carbon dioxide.
In formin~~ a carbamate, primary and secondary alkanolamines ~sndergo a fast direct reaction with carbon dioxide which makes the rate of carbon dioxide absorp-tion rapid. However, considerable heat is required to break the bond between the alkanolamine and carbon dioxide in the carbamate and regenerate the absorbent.
In addition, primary and secondary alkanolamines have a limited capacity to absorb carbon dioxide due to the formation of atable carbamates. The Sartori article 1340~~8 teaches that loading of such alkanolamines is improved by incorporating sterically hindered amines. Meanwhile, British Patent No. ?98,856 activates primary alkanol-amines, like ethanolamine, with arsenious oxide.
Unlike primary and secondary alkanolamines, tertiary alkanolamines cannot react directly with carbon dioxide, because their amine reaction site is fully substituted with substituent groups. Instead, carbon dioxide is absorbed into solution by the following slow reaction with water to form bicarbonate:
R3N + C02 + 1H20 ~ HC03- + R3NH+
Because tertiary alkanolamines do not bond with carbon dioxide, they can be economically regenerated often by simply reducing pressure in the system (i.e. flash regenerating). little or no thermal regeneration is required. Although the absence of a direct reaction with carbon dioxide makes regeneration of tertiary alkanolamines more economical, large solvent circulation rates and high liquid to gas ratios (i.e. high liquid loadings) in tlae absorber are required due to the slow absorption of .carbon dioxide. Consequently, systems utilizing tertiary alkanolamines require absorption columns of increased height and diameter compared to systems employing either primary or secondary alkanolamines.
In order t.o increase the rate of carbon dioxide absorption by aqueous tertiary alkanolamine solutions, promoters have been added. In U.S. Patent No. 4,336,233 to Appl et al ("Appl patent"), a piperazine promoter is incorporated in an aqueous methyldiethanolamine solution. The process disclosed by the Appl patent "employs aqueous solutions of a bottom product obtained as a by-product from the synthesis of ethylenediamine 134Q7~~
_5-from monoethanolamine and ammonia. this material also contains 0.3 percent by weight, based on piperazine of the following by-products: NH3, ethylenediamine, MEA, and further nitrogen-containing products." The by-I
products are merely said to "not interfere with the process according to" the Appl patent.
Promoted met.hyldiethanolamine solutions have both an increased rate of carbon dioxide absorption and an increased capacity for carbon dioxide compared to unpromoted methyldiethanolamine. Improved rate of absorption is particularly evident at low levels of carbon dioxide loading and diminishes as such loading increases. The full benefit of the promoter is found in processes which employ thermal regeneration in addition to flash regeneration of the absorbent to maintain the low loading levels necessary to produce a gas product with low levels of carbon dioxide. Flash regeneration alone is sufficient for bulk removal of carbon dioxide from high pressure gases (i.e. carbon dioxide partial pressure greater than 50 psia) where low carbon dioxide specifications in the product gas are not needed.
DESCRIPTION OF THE INVENTION
The absorption of carbon dioxide from gas mixtures with aqueous absorbent solutions of tertiary alkanol-amines is improved by incorporating at least one alkyleneamine promoter in the solution. The alkylene-amine is incorporated in an amount sufficient to enhance substantially 'the carbon dioxide absorption rate by at least 10%, usually by 25-200 % and/or the capacity of the tertiary alkanolamine in water by as much as 70%.
The tertiary alkanolamines utilized can be any of a 1340'~~~
variety of compounds suitable for absorbing carbon dioxide from ~gas mixtures. Examples of these absorbent alkanolamines include: methyldiethanolamine, triethanol-amine, dimethylethanolamine, diethylethanolamine, methyldiisopropanolamine, and mixtures thereof. Methyl-diethanolamine and triethanolamine are the preferred tertiary alkanolamines with methyldiethanolamine being most preferred.
The promoter utilized by the present invention is generally at least one alkyleneamine defined by the formula:
H2N(CxH2xNH)nH
wherein x is 1 to 4, while n is 1 to 12. More preferably, the present promotion additive is at least one ethyleneamine or propyleneamine selected from a homologous series of polyamines, all of which contain two primary amino groups with other amino groups, if any, being secondary. Ethyleneamines which are useful in the present invention are defined by the formula:
H2N(C2H4NH)nH
where n is 1 to 12. Specific examples of such ethylene-amines include ethylenediamine, diethylenetriamine, tetraethylenepentamine, and mixtures thereof. Of these promoters, ethylenediamine is most preferred.
The alkyleneami.ne-promoted tertiary alkanolamine absorbents may additionally contain conventional corrosion inhibitors to prevent corrosion caused by carbon dioxide absorbed in the tertiary alkanolamine absorbent solution. When corrosion in the process is controlled, higher alkanolamine strengths can be utilized to reduce absorbent circulation rates, equipment size, and operating costs.
I34~~~8 _7_ The alkyleneamine-promoted tertiary alkanolamine absorbents of the present invention can be prepared as an aqueous solution which is ready to be used in the field. In ready-to-use form, the aqueous absorbent solution may contain 35-65 wt.% water, preferably 45-55 wt.% water, anc9 most preferably 50 wt.% water. The alkyleneamine promoter in the promotion additive is present in an amount sufficient to enhance the rate at which cool (to 100-130'F) aqueous tertiary alkanolamines absorb carbon dioxide from warm (150-200'F) gas mixtures in a gas-liquid contact apparatus. Such enhancement in the rate of carbon dioxide absorption is achieved when the alkyleneamine- promoted tertiary alkanolamine achieves at least 10%, usually 25-200%, faster carbon dioxide removal than the same absorbent without the alkyleneamine. This generally occurs when the alkyleneamine is 0.5-10 wt.% of the aqueous absorbent solution, preferably 2- .6 wt.%, and most preferably 3-4 wt.%. An effective amount of the corrosion inhibitor, if any, for purposes of the present invention is about 0.05-0.1 wt.% of the aqueous absorbent solution. The tertiary alkanolamine comprises the remainder of the absorbent solution.
Alternatively, the alkyleneamine-promoted tertiary alkanolamine can be prepared as a concentrate, shipped to the facility where it is to be utilized, and then diluted with water prior to use. In its concentrated, non-aqueous fo:-m, the absorbent contains 1.0-20 wt.% of alkyleneamine promoter, preferably 4-12 wt.%, and most preferably 5 t:o 8 wt.%. The tertiary alkanolamine con-stitutes the remainder of the concentrated absorbent.
The mole ratio of alkyleneamine to alkanolamine is 0.01 to 0.5, preferably 0.05 to 0.27, most preferably 0.07 to 0.17.
-g-In use, the aqueous ethyleneamine-promoted alkanol-amine solution (i.e. lean absorbent) at temperatures of 120°F to 200°F is contacted with an industrial gas containing carbon dioxide at partial pressures of 25 sia to 250 psia or higher in an absorption zone and P
both a product gas substantially free of carbon dioxide (i.e. 0.01 volume % to 0.1 volume % for trim gas removal and 3-5 volume % for bulk gas removal) and an aqueous alkyleneamine-promoted alkanolamine solution laden with absorbed carbon dioxide and optionally absorbed hydrogen sulfide or carbonyl sulfide (i.e. rich absorbent) are withdrawn from the absorption zone. In addition, the aqueous alkyleneamine-promoted alkanolamine can be used to treat gases with hydrogen sulfide and/or carbonyl sulfide containing little or no carbon dioxide. The absorption zone is preferably a gas-liquid contact column containing bubble plates or packing to improve absorption.
To conserve absorbent, the rich absorbent is regenerated in at least one regenerating column and then recycled to the absorption column. Such regeneration is achieved by first removing absorbed carbon dioxide from the rich absorbent by reducing the absorbent's pressure in at least one flash regenerating column (i.e. flash regenerating) t:o pressures as low as 7 psia and as high 20 psia and i=hen stripping the flashed absorbent with steam in a strapping regenerator column operating at 235 to 265°F to remove absorbed carbon dioxide to a residual loading of approximately 0.005 to 0.05, preferably 0.01 moles of carbon dioxide per mole of alkanolamine. The flash regenerating column and the stripping regenerator column both contain either packing or bubble plates for more efficient regeneration. The carbon dioxide-containing gas. produced in each regenerating column can ,.._.
i34o7ss _g-either be removed from the absorption/regeneration installation separately or the gas generated by the stripping regenerator column can be passed into the flash regenerating column and removed with the gas generated therein. Alternatively, regeneration can in some cases be ca~~ried out with just a flash regenerating step due to the ease with which tertiary alkanolamines are regenerated.
A wide variety of industrial gases (e. g. fuel gases, gasification product gases, refinery gases, synthesis gases, natural gas, and enhanced oil recover associated gases) can be treated with alkyleneamine promoted tertiary alkanolamine absorbent solutions utilizing the above-described absorption/regeneration scheme. These gases can include compounds in the range of amounts shown in Table 1.
TABLE
Compound mount (Volume percent) C02 10-40%
CO 20-40%
0-80%
C 0.1-90%
N2H2n + n(n=2-6) 0-20%
H2S 0-0.1%
COS
Synthesis gas containing the compounds in the amounts shown below in Table 2 is particularly well suited to treatment with absorbent solutions in accordance with present invention.
TABLE 2_ Co~~a mou t (Volume percent) C02 15-35%
CO 20-40%
H2 20-40%
0.1-5%
N2 0-20%
2 0-3%
COS 0-0.1%
Typically, contacting such gas with absorbents in accordance with the present invention reduces the carbon dioxide content: in the gas by between 75 and 100 vol.%
to yield gases of less than 3 vol.% carbon dioxide. The alkyleneamine-promoted tertiary alkanolamine also re-duces the hydrogen sulfide content in the gas by between 99.5 and 100 vol.% to less than 0.0004 vol.% and reduces the carbonyl sulfide content in the gas by 50-90 vol.%
to less than 0.001 vol.%.
ERIE;F DESCRIPTION OF THE DRAWINGS
Figure 1 is. a process flow diagram for an absozption and regeneration process utilizing a tertiary alkanol-amine absorbent containing an alkyleneamine promoter according to the present invention.
Figure 2 is a graph showing vapor-liquid equilibrium data and rate of absarption data for absorbent solutions with 50 wt% inethyldiethanolamine alone or with 3 wt% piperazine, ethylenediamine (i.e. EDA), or die-thylenetriamine (i.e. DETA).
AILED DESCRIPTION OF THE DRAWING
In a preferred embodiment, as shown in the process flow diagram of Figure 1, carbon dioxide is removed in two absorption columns connected fn series. Synthesis gas 8 is first directed into bulk C02 absorber 2 where it is contacted countercurrently with lean bulk absorbent ~. ~r bulk absorber product gas ~ from which 65 to 85% of the carbon dioxide in the synthesis gas has been removed is withdrawn from bulk C02 absorber 2 as an overhead product, while rich bulk absorbent p is withdrawn as a bottom product. The bulk absorbent product gas ~ is then conveyed into a lower portion of trim C02 absorber 4 and countercurrently contacted with lean trim, absorbent F which removes substantially all the remaining carbon dioxide. A substantially C02- free trial absorber product gas ~ is removed from trim C02 absorber 4 as an overhead product, while rich trim absorbent Ci is withdrawn as a bottom product.
Regeneration of the rich absorbent streams is also carried out in two columns. Rich bulk absorbent _D
undergoes a pressure drop through turbine 6 and then passes into flash regeneration column 8 having a top section 8A and a bottom section 8B. Gases g are conveyed by vacuum compressor 9 from bottom section 8B
to top section 8A, _while liquid O flows from top section 8A to bottom aection 8B by gravity. In flash regenera-tion column 8 which operates at pressure of 7 to 20 psia, some of the absorbed C02 flashes and is removed from flash regeneration column 8 as an overhead product Product ~ then passes through condenser 20 which is cooled (to 100-130°F) with water to permit non-condensibles to be separated and removed from reflux drum 10 as a gaseous product T, while condensibles ~C are withdrawn as a liquid product. Flash regenerated absorbent ~i i.s withdrawn from flash regeneration column 8 as a bottom product which can either be combined with rich trim absorbent ~ and directed by turbine 6 to bulk C02 absorber 2 as lean bulk absorbent $ or be conveyed by pump 12 t;o stripping regeneration column 14. In stripping regeneration column 14, residual carbon dioxide is rE:moved as stripping regeneration overhead product ~I which is then recycled to flash regeneration 13~O~1G~
column 8 from which carbon dioxide is removed from the system. Such recycling enhances the flashing of carbon dioxide in flash regeneration column 8. Stripping regeneration bottoms product ~1 is either conveyed through steam reboiler 16 and returned to stripping regeneration column 14 or combined with make-up water ~
and condensate ~C and recycled by pump 18 to trim Co2 absorber 4 as lean trim absorbent To reduce process energy requirements and improve absorption effic;iency, a portion of stripping regenera-tion bottoms product ~1 is cooled from about 250°F to 170°F by incoming flash regenerated absorbent ~i in heat exhanger 22. That portion of bottoms product ~1 which becomes lean trim absorbent ~ is further cooled (to 100-130°F) with water in cooler 24. As a result of its heat exchange contact with stripping regeneration bottoms product ~1, flash regenerated absorbent H_ is preheated (to 150-235°F) prior to entering stripping regeneration column 14.
~XAMPL~ 1 In commercial use, 142,333 standard cubic feet per minute of synthesis gas g produced by the partial oxidation of natural gas with steam and air could be treated in accordance with the process flow diagram of Figure 1 for ultimate use of the purified synthesis gas in a 1200 ton pe:r day ammonia product facility.
Synthesis gas ~ containing 41.9 mole % hydrogen, 41.0 mole % nitrogen, 15.7 mole % carbon dioxide, 0.7 mole % carbon monoxide, 0.5 mole % argon, 0.2 mole %
methane, and 0,.1 mole % helium enters the bottom of bulk C02 absorber 2 which is 11 feet in diameter and contains two 2!3 foot packed beds of structured stainless steel packing at 170°F and 400.0 psia. In bulk C02 absorber 2, synthesis gas ~ countercurrently contacts lean bulk absorbent $ which is an aqueous solution containing 47 weight percent methyldiethanolamine and 3 weight percent ethylenediamine. Lean bulk absorbent B
is fed to the top of bulk C02 absorber 2 at a rate of 6609 gallons per minute at a temperature of 155'F, and at a loading of 0.27 moles of carbon dioxide per mole of methyldiethanolamine. Carbon dioxide is removed from synthesis gas ~~ at a rate of 2746 moles per hour so that bulk absorbent product gas ~ which has a temperature of 155°F and 399 psia contains 3.95 mole % carbon dioxide.
Bulk absorbent product gas ~ then enters the base of the 36 tray trim C02 absorber 4 and is counter-currently contacted with lean trim absorbent ~ which is also an aqueous solution of 47 weight % methyldiethanol-amine and 3 weight percent ethylenediamine which has been regenerat~sd to a lean C02 solution loading of 0.01 moles o:E carbon dioxide per mole of. methyl-diethanolamine. Lean trim absorbent ~ is fed into the top of trim C02 absorber 4 at a temperature of 105°F
and at a flo~arate of 1368 gallons per minute. Carbon dioxide is removed from bulk absorber product gas C at a rate of 769.3 moles per hour so that the carbon dioxide content of the trim absorber product gas ~ is reduced to 1000 volumetric ppm or 0.1 mole %.
Rich bulk absorbent p which is discharged from the bottom of the bulk C02 absorber 2 at a temperature of 181°F, at a flowrate of 6935 gallons per minute, and with a molar carbon dioxide content of 0.48 is fed into top section 8A of column 8. Top section 8A is 11 feet in diameter, 39 feet. high, and filled with a 20 foot bed of stainless steel packing. This section operates at about 20.2 psia so that C02 is flashed at a rate of 1971.2 moles per hour which reduces the carbon dioxide 1340"ls~
loading in the absorbent to 0.33 moles of C02 per mole of methyldiethanolamine. This flashing reduces the absorbent temperature to 166'F. Flashed absorbent Q is then conveyed t:o bottom section 8B which is 42 feet high. In this section, the absorbent is vacuum flashed at 9.7 psia to remove another 750.7 moles of C02 per hour so that the flash regenerated absorbent ~I has a loading of 0.2'7 moles of C02 per mole of methyl-diethanolamine~and a temperature of 155°F.
A 81.6 percent portion of flash regenerated absorbent ~i is directly recycled to the top of bulk C02 absorber 2, while the remainder is heated to 233'F
by stripping regeneration bottom product ~1 in heat exchanger 22. From heat exchanger 22, preheated, flash regenerated absorbent ~i is fed into the top of stripping regeneration column 14 which is 11 feet in diameter and contains 17 sieve trays.
In stripping regeneration column 14, 793.5 moles of carbon dioxides per hour are produced as stripping regeneration overhead product ~I, so that the stripping regeneration bottom product ~1 has a carbon dioxide loading of 0.01 moles per mole of methyldiethanolamine.
Bottom product ~t is discharged at a rate 1388 gallons per minute and at a temperature of 253°F. Heat exchange with flash regenerated absorbent ~i reduces the tempera-ture of stripping regeneration bottom product ~1 to 168°F, while cooler 24 reduces the temperature of what is now lean trim absorbent ~ to 105°F.
Reboiler 16 heats bottom product Z1 at a rate of 55.9 MM BTUs per hour which is equivalent to 15.9 M BTUs per mole of carbon dioxide.
A series of experiments were conducted in a ,.~ 134flr1~8 specially desigr,~ed racking autoclave to determine the rate of carbon dioxide absorption and the vapor-liquid equilibrium for :several absorbent solutions.
The autoclave is a stainless steel cylinder which is I
surrounded by a steam jacket around which are electric heaters. Carbon dioxide is charged to an accumulator cell from a carbon dioxide cylinder. The carbon dioxide is then transferred from the accumulator cell to the autoclave through a port in the autoclave. A port is also provided :in the autoclave through which absorbent solution can b~. charged. The autoclave is rocked by an electric motor.
The head is provided with a port through which a thermocouple is inserted for measurement of the auto-clave temperature. The accumulator cell's pressure drop is used to calculate the gram-moles of carbon dioxide charged to the autoclave. Rate of absorption data is obtained by measuring the autoclave pressure vs. time.
The following aqueous absorbent solutions were prepared:
No. Agueous. Absorbent 1 50 wt.~. methyldiethanolamine alone 50 wt.~~ methyldiethanolamine plus 3.0 wt.$
pipera~; ine 3 50 wt.~s methyldiethanolamine plus 3.0 wt.~
diethy7.enetriamine 50 wt.3~ methyldiethanolamine plus 3.0 wt.$
ethylenediamine Each of the aqueous absorbent solutions was separately evaluated in the rocking autoclave by initially charging one of the absorbent solutions to the autoclave and heating the solution to a 70°C run 1340~~~
temperature. The autoclave was then pressurized with carbon dioxide from the accumulator cell, with the pressure change: of the accumulator cell being recorded.
When autoclave pressurization is complete, a starting pressure is rE:corded, and a stop watch and the rocking motor are started simultaneously. The rate of carbon dioxide absorption is measured by recording the autoclave pres:~ure drop with time. Equilibrium in the autoclave is <sssumed when the autoclave pressure ceases to change. A:Eter the equilibrium autoclave pressure is recorded, the autoclave containing the carbon dioxide-laden absorbent solution is again pressurized with additional carlbon dioxide and the procedure is repeated until the final experimental solution loading or equili-brium vapor pressure of carbon dioxide is achieved.
This procedure is repeated several times for a given solution until a set of carbon dioxide absorption rate data and vapor-liquid equilibrium data is obtained.
Each of the 4 absorbent solutions are subjected to this testing technique.
For each charge of carbon dioxide to the autoclave, an equilibrium carban dioxide vapor pressure is measured subsequent to the change in autoclave pressure with time. Equilibrium solution loading is then calculated as the total moles of carbon dioxide charged to the autoclave from the accumulator (calculated from accumulator pressure drop using a non-ideal equation of state) minus the moles of carbon dioxide remaining in the autoclave vapor space (calculated from autoclave equilibrium vapor pressure again using a non-ideal equation of state). The resultant vapor liquid equilibrium data is plotted as carbon dioxide vapor pressure versu:~ solution loading.
The rate of absorption in moles of carbon dioxide absorbed per liter of solution in the autoclave per -minute are calculated from autoclave pressure change with time again using a non-ideal equation of state.
Gram-moles of carbon dioxide are converted to cubic feet, and the rate of absorption is divided by an average partial pressure driving force in atmospheres to obtain the final rate of absorption in terms of cubic feet of carbon dioxide per hour-liter-atmospheres. The rate of absorption data can then be plotted versus equilibrium solution loading.
From the carbon dioxide partial pressure, the absorbent solution's carbon dioxide loading, and the solution absorption rate values for each carbon dioxide pressurization, a pair of curves can be prepared for each of the absorbents as shown in Figure 2. One set of curves are the carbon dioxide partial pressure vs.
carbon dioxide loading curves having a generally increasing slope. Another set of curve are the rate of absorption vs. carbon dioxide loading curves having a generally decreasing slope.
The curves representing the equilibrium between carbon dioxide in the vapor phase (i.e. carbon dioxide partial pressure) and carbon dioxide loading in the solution (i.e. moles carbon dioxide per mole of amine) can be used to determine the absorbent solution's circulation rage, while the rate of carbon dioxide absorbed by the solution vs. the carbon dioxide loading curves are used to determine the mass transfer rates from which ab:~orbent column staging requirements can be ascertained.
~nhancement in the rate of absorption and solution capacity is most pronounced under trim absorber conditions where solution loadings are defined as lean and semi-rich. The difference between the commercially-1340~1G~
utilized lean solution loading of 0.01 nolss C02/mole amine and a semi-rich solution loading in ~guilibrium with a C02 partial pressure of 20 psia, as would exit the trim absorber and enter the bulk absorber, is then calculated using the curves from Figure 2 for each of the four absorbent solutions. J~s a result, the four solutions were found to have the following loading differentials, absorption rates, and required circulation rates set forth below in Table 3.
p 1 0.26 112.2 4.0 2.7 2 0.39 64.9 19 3.8 3 0.42 63.3 18 3.7 4 0.45 49.9 25 4.2 A= Aqueous Absorbent No.
B=Loading Differential--i.e. semi-rich minus lean (moles carbon dioxide per mole of amine).
C=Circulation Rate (gallons of solvent per pound-mole C02).
D~Lean Solution hbsorption Rate (cubic feet per hour-atmosphere).
E=Semi-Rich Solution J~rbsorption Rate (cubic feet per hour atmosphere).
From Table 3, it is apparent that the methyldiethanol-amine promotes! with ethylenediamine and diethylene-triamine unexpectedly have a higher carbon dioxide capacity compared to unpromoted methyldiethanolamine and ~34o~r~g to methyldiethanolamine promoted with piperazine. As a result, methy:ldiethanolamine solutions promoted with ethylenediamine and diethylenetriamine are capable of absorbing more carbon dioxide during trim absorption.
In addition, '.Cable 3 shows that methyldiethanolamine promoted with ~thylenediamine has lean and semi-rich carbon dioxide absorption rates unexpectedly higher than those of unpromoted methyldiethanolamine alone and methyldiethanolamine promoted with piperazine. The lean and rich carbon dioxide absorption rates of methyl-diethanol amine promoted with diethylenetriamine are unexpectedly better than those of methyldiethanolamine alone and about the same as those of methyldiethanol-amine promoted with piperazine.
Although the invention has been described in detail for the purpose of illustration, it is understood that such detail i:a solely for that purpose and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention which is defined by the following claims.
Claims (56)
1. A concentrated absorbent for removing carbon dioxide from industrial gases comprising:
at least one tertiary alkanolamine and at least one promotion additive comprising at least one alkyleneamine in an amount sufficient to increase the carbon dioxide absorption rate or the carbon dioxide loading of said at least one tertiary alkanolamine in an aqueous solution of 35-65 wt.% water by 25-200% or by as much as 70%, respectively, said at least one alkyleneamine being defined by the formula:
H2N(C x H2x NH)n H
where x is 1 to 4 and n is 1 to 12.
at least one tertiary alkanolamine and at least one promotion additive comprising at least one alkyleneamine in an amount sufficient to increase the carbon dioxide absorption rate or the carbon dioxide loading of said at least one tertiary alkanolamine in an aqueous solution of 35-65 wt.% water by 25-200% or by as much as 70%, respectively, said at least one alkyleneamine being defined by the formula:
H2N(C x H2x NH)n H
where x is 1 to 4 and n is 1 to 12.
2. A concentrated absorbent according to claim 1, wherein said at least one tertiary alkanolamine is selected from the group consisting of methyldiethanolamine, triethanolamine, dimethylethanolamine, diethylethanalamine, methyldiisopropanolamine, and mixtures thereof.
3. A concentrated absorbent according to claim 2, wherein said at least one tertiary alkanolamine is methyldiethanolamine.
4. A concentrated absorbent according to claim 2, wherein said at least one tertiary alkanolamine is triethanolamine.
5. A concentrated absorbent according to claim 1, wherein the at least one alkyleneamine is at least one ethyleneamine defined by the formula:
H2N(C2H4NH)n H
where n is 1 to 12.
H2N(C2H4NH)n H
where n is 1 to 12.
6. A concentrated absorbent according to claim 5, wherein the at least one ethyleneamine additive is selected from the group consisting of ethylenediamine, diethylenetriamine, tetraethylenepentamine, and mixtures thereof.
7. A concentrated absorbent according to claim 6, wherein the at least one ethyleneamine is ethylenediamine.
8. A concentrated absorbent according to claim 7, wherein said at least one tertiary alkanolamine is methyldiethanolamine.
9. A concentrated absorbent according to claim 5, wherein said concentrated absorbent contains 1-20 wt.%
of the at least one ethyleneamine.
of the at least one ethyleneamine.
10. A concentrated absorbent according to claim 5, wherein said concentrated absorbent contains 5-8 wt.% of the at least one ethyleneamine.
11. A concentrated absorbent according to claim 8, wherein said concentrated absorbent contains 5-8 wt.%
of ethylenediamine.
of ethylenediamine.
12. An absorbent solution for removing carbon dioxide from industrial gases comprising:
an inert carrier;
at least one tertiary alkanolamine; and at least one promotion additive comprising at least one alkyleneamine in an amount sufficient to enhance the carbon dioxide absarption rate or the carbon dioxide loading of said at least one tertiary alkanolamine in said inert carrier by 25-200 % or by as much as 70%, respectively, said at least one alkyleneamine being defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12.
an inert carrier;
at least one tertiary alkanolamine; and at least one promotion additive comprising at least one alkyleneamine in an amount sufficient to enhance the carbon dioxide absarption rate or the carbon dioxide loading of said at least one tertiary alkanolamine in said inert carrier by 25-200 % or by as much as 70%, respectively, said at least one alkyleneamine being defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12.
13. An absorbent solution according to claim 12, wherein said inert carrier is water.
14. An absorbent solution according to claim 13, wherein said at least one tertiary alkanolamine is selected from the group consisting of methyldiethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, methyldiisopropanolamine, and mixtures thereof.
15. An absorbent solution according to claim 14, wherein said at least one tertiary alkanolamine is methyldiethanolamine.
16. An absorbent solution according to claim 14, wherein said at least one tertiary alkanolamine is triethanolamine.
17. An absorbent solution according to claim 13, wherein the at least one alkyleneamine is at least one ethyleneamine defined by the formula:
H2N(C2H4NH)nH
where n is 1 to 12.
H2N(C2H4NH)nH
where n is 1 to 12.
18. An absorbent solution according to claim 17, wherein the at least one ethyleneamine is selected from the group consisting of ethylenediamine, diethylenetriamine, tetraethylenepentamine, and mixtures thereof.
19. An absorbent solution according to claim 18, wherein the at least one ethyleneamine is ethylenediamine.
20. An absorbent solution according to claim 19, wherein said at least one tertiary alkanolamine is methyldiethanolamine.
21. An absorbent solution according to claim 17, wherein said absorbent solution contains 0.5-10 wt.% of the at least one ethyleneamine.
22. An absorbent solution according to claim 21, wherein said absorbent solution contains 3-4 wt.% of the at least one ethyleneamine.
23. An absorbent solution according to claim 20, wherein said absorbent solution contains 3 wt.% of ethylenediamine.
24. An absorbent solution according to claim 13, wherein said absorbent solution contains 35-65 wt.% of said water.
25. An absorbent solution according to claim 13, wherein said absorbent solution contains 45-55 wt.% of said water.
26. An absorbent solution according to claim 23, wherein said absorbent solution contains 45-55 wt.% of said water.
27. A process of absorbing carbon dioxide from an industrial gas comprising:
passing said industrial gas containing carbon dioxide into an absorption zone;
contacting acid industrial gas with a lean absorbent solution in the absorption zone to absorb carbon dioxide from said industrial gas, wherein said lean absorbent solution containing substantially no absorbed carbon dioxide comprises:
water:
at least one tertiary alkanolamine: and at least one alkyleneamine promotion additive in an amount sufficient to enhance the carbon dioxide absorption rate and the carbon dioxide loading of said tertiary alkanolamine in said water by 25-200% or by as much as 70%, respectively, said at least one alkyleneamine being defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12;
withdrawing a product gas containing substantially no carbon dioxide from the absorption zone: and withdrawing said absorbent solution from the absorption zone as a rich absorbent solution containing absorbed carbon dioxide.
passing said industrial gas containing carbon dioxide into an absorption zone;
contacting acid industrial gas with a lean absorbent solution in the absorption zone to absorb carbon dioxide from said industrial gas, wherein said lean absorbent solution containing substantially no absorbed carbon dioxide comprises:
water:
at least one tertiary alkanolamine: and at least one alkyleneamine promotion additive in an amount sufficient to enhance the carbon dioxide absorption rate and the carbon dioxide loading of said tertiary alkanolamine in said water by 25-200% or by as much as 70%, respectively, said at least one alkyleneamine being defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12;
withdrawing a product gas containing substantially no carbon dioxide from the absorption zone: and withdrawing said absorbent solution from the absorption zone as a rich absorbent solution containing absorbed carbon dioxide.
28. A process according to claim 27, wherein said at least one tertiary alkanolamine is selected from the group consisting of methyldiethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, methyldiisopropanolamine, and mixtures thereof.
29. A process according to claim 28, wherein said at least one tertiary alkanolamine is methyldiethanolamine.
30. A process according to claim 28, wherein said at least one tertiary alkanolamine is triethanolamine.
31. A process according to claim 27, wherein said at least one alkyleneamine is at least one ethyleneamine defined by the formula:
H2N(C2H4NH)nH
where n is 1 to 12.
H2N(C2H4NH)nH
where n is 1 to 12.
32. A process according to claim 31, wherein said at least one ethyleneamine is selected from the group consisting of ethylenediamine, diethylenetriamine, tetraethylenepentamine, and mixtures thereof.
33. A process according to claim 32, wherein said at least one ethyleneamine is ethylenediamine.
34. A process according to claim 32, wherein said at least one tertiary alkanolamine is methyldiethanolamine.
35. A process according to claim 27, wherein said contacting of said industrial gas and said lean absorbent solution in the absorption zone is countercurrent.
36. A process according to claim 27 further comprising:
regenerating said rich absorbent solution to produce a regenerated absorbent solution containing substantially no carbon dioxide and a waste gas rich in carbon dioxide.
regenerating said rich absorbent solution to produce a regenerated absorbent solution containing substantially no carbon dioxide and a waste gas rich in carbon dioxide.
37. A process according to claim 36, wherein said regenerating is effected by flashing said rich absorbent solution.
38. A process according to claim 36, wherein said regenerating is effected by flashing said rich absorbent solution to remove carbon dioxide and then steam stripping said rich absorbent solution after flashing to remove additional. carbon dioxide.
39. A process according to claim 36 further comprising:
recycling said regenerated absorbent solution to the absorption zone as said lean absorbent solution.
recycling said regenerated absorbent solution to the absorption zone as said lean absorbent solution.
40. A process according to claim 27, wherein said industrial gas contains a substantial quantity of hydrogen which is withdrawn from the absorption zone in the product gas.
41. A process according to claim 27, wherein said industrial gas additionally contains hydrogen sulfide and carbonyl sulfide which are also removed by said lean absorbent solution in the absorption zone.
42. A process according to claim 34, wherein said industrial gas additionally contains hydrogen sulfide or carbonyl sulfide which are also removed by said lean absorbent solution in the absorption zone.
43. A process according to claim 36, wherein said industrial gas additionally contains hydrogen sulfide or carbonyl sulfide which are also removed by said lean absorbent solution in the absorption zone.
44. A process according to claim 27, wherein said lean absorbent containing said industrial gas is at 120°F to 200'F.
45. A process according to claim 38, wherein said flashing reduces the pressure of said rich absorbent solution to pressures as low as 7 psia.
46. A process according to claim 38, wherein said steam stripping occurs at temperatures of 235°F to 265°F.
47. A concentrated absorbent for removing carbon dioxide from industrial gases comprising:
at least one tertiary alkanolamine and at least one promotion additive comprising at least one ethyleneamine in an amount sufficient to increase by 25-200% or try as much as 70% the carbon dioxide absorption rate or carbon dioxide loading, respectively, of said at least one tertiary alkanolamine in 35-65 wt%
water, wherein said at least one promotion additive contains substantially no piperazine.
at least one tertiary alkanolamine and at least one promotion additive comprising at least one ethyleneamine in an amount sufficient to increase by 25-200% or try as much as 70% the carbon dioxide absorption rate or carbon dioxide loading, respectively, of said at least one tertiary alkanolamine in 35-65 wt%
water, wherein said at least one promotion additive contains substantially no piperazine.
48. An absorbent solution for removing carbon dioxide from industrial gases comprising:
an inert carrier:
at least one tertiary alkanolamine; and at least one promotion additive comprising at least one ethylenediamine in an amount sufficient to enhance by 25-200% or by as much as 70% the carbon dioxide absorption rate or carbon dioxide loading, respectively, of said at least one tertiary alkanolamine in said inert carrier, wherein said at least one promotion additive contains substantially no piperazine.
an inert carrier:
at least one tertiary alkanolamine; and at least one promotion additive comprising at least one ethylenediamine in an amount sufficient to enhance by 25-200% or by as much as 70% the carbon dioxide absorption rate or carbon dioxide loading, respectively, of said at least one tertiary alkanolamine in said inert carrier, wherein said at least one promotion additive contains substantially no piperazine.
49. An absorbent solution according to claim 48, wherein said inert carrier is water.
50. A concentrated absorbent for removing carbon dioxide from industrial gases comprising:
1-20 wt% of at least one alkyleneamine, wherein said at least one alkyleneamine is defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12 and 80-99 wt% of at least one tertiary alkanolamine.
1-20 wt% of at least one alkyleneamine, wherein said at least one alkyleneamine is defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12 and 80-99 wt% of at least one tertiary alkanolamine.
51. A concentrated absorbent according to claim 50, wherein said at least one ethyleneamine is present in the at least one ethyleneamine in an amount of 5-8 wt%, while said at least one tertiary alkanolamine is present in an amount of 92-94 wt%.
52. An absorbent solution for removing carbon dioxide from industrial gases comprising:
44-55 wt% of an inert carrier:
41-53 wt% of a tertiary alkanolamine; and 3-4 wt% of at least one alkyleneamine, wherein said at least one alkyleneamine is defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12.
44-55 wt% of an inert carrier:
41-53 wt% of a tertiary alkanolamine; and 3-4 wt% of at least one alkyleneamine, wherein said at least one alkyleneamine is defined by the formula:
H2N(CxH2xNH)nH
where x is 1 to 4 and n is 1 to 12.
53. An absorbent solution according to claim 52, wherein said inert carrier is water, said tertiary alkanolamine is methyldiethanolamine, and said ethyleneamine is ethylenediamine.
54. An absorbent solution for removing carbon dioxide from industrial gases comprising:
an inert carrier;
at least one tertiary alkanolamine: and at least one promotion additive comprising at least one ethyleneamine in an amount sufficient to enhance appreciably the carbon dioxide absorption rate of said at least one tertiary alkanolamine in said inert carrier, wherein said ethyleneamine is defined by the formula:
H2N(C2H4NH)n H
where n is 1 to 12.
an inert carrier;
at least one tertiary alkanolamine: and at least one promotion additive comprising at least one ethyleneamine in an amount sufficient to enhance appreciably the carbon dioxide absorption rate of said at least one tertiary alkanolamine in said inert carrier, wherein said ethyleneamine is defined by the formula:
H2N(C2H4NH)n H
where n is 1 to 12.
55. An absorbent solution according to claim 54, wherein said inert carrier is water.
56. A concentrated absorbent for removing carbon dioxide from industrial gases comprising:
at least one tertiary alkanolamine and at least one promotion additive comprising at least one ethyleneamine in an amount sufficient to enhance appreciably they carbon dioxide absorption rate of said at least one tertiary alkanolamine in water, wherein said ethyleneamine is defined by the formula:
H2N(C2H4NH)n H
where n is 1 to 12.
at least one tertiary alkanolamine and at least one promotion additive comprising at least one ethyleneamine in an amount sufficient to enhance appreciably they carbon dioxide absorption rate of said at least one tertiary alkanolamine in water, wherein said ethyleneamine is defined by the formula:
H2N(C2H4NH)n H
where n is 1 to 12.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000560222A CA1340768C (en) | 1988-03-01 | 1988-03-01 | Teritiary alkanolamine absorbent containing an ethyleneamine promoter and its method of use |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000560222A CA1340768C (en) | 1988-03-01 | 1988-03-01 | Teritiary alkanolamine absorbent containing an ethyleneamine promoter and its method of use |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1340768C true CA1340768C (en) | 1999-09-28 |
Family
ID=33315108
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000560222A Expired - Fee Related CA1340768C (en) | 1988-03-01 | 1988-03-01 | Teritiary alkanolamine absorbent containing an ethyleneamine promoter and its method of use |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1340768C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9566539B2 (en) | 2010-06-02 | 2017-02-14 | Statoil Petroleum As | CO2 desorption without stripper |
-
1988
- 1988-03-01 CA CA000560222A patent/CA1340768C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9566539B2 (en) | 2010-06-02 | 2017-02-14 | Statoil Petroleum As | CO2 desorption without stripper |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4814104A (en) | Tertiary alkanolamine absorbent containing an ethyleneamine promoter and its method of use | |
| US6165433A (en) | Carbon dioxide recovery with composite amine blends | |
| AU2006325350B2 (en) | Process for the recovery of carbon dioxide | |
| US8388855B2 (en) | Polyamine/alkali salt blends for carbon dioxide removal from gas streams | |
| US4217237A (en) | Process for removing carbon dioxide containing acidic gases from gaseous mixtures using a basic salt activated with a hindered amine | |
| CA2777326C (en) | Acid gas absorbent, acid gas removal method, and acid gas removal device | |
| US4892674A (en) | Addition of severely-hindered amine salts and/or aminoacids to non-hindered amine solutions for the absorption of H2 S | |
| US20130269525A1 (en) | Absorption Media for Scrubbing CO2 from a Gas Stream and Methods Using the Same | |
| EP2679296B1 (en) | Acid gas absorbent comprising diamine, acid gas removal method, and acid gas removal device | |
| JPS637813B2 (en) | ||
| AU2011302569B2 (en) | Solvent and method for CO2 capture from flue gas | |
| CA2843316A1 (en) | Aminopyridine derivatives for removal of hydrogen sulfide from a gas mixture | |
| US4961873A (en) | Absorbent composition containing a severely-hindered amine mixture with amine salts and/or aminoacid additives for the absorption of H2 S | |
| WO2015167729A1 (en) | Carbon dioxide scrubbing process | |
| JPH0644972B2 (en) | Tertiary alkanolamine absorbers containing ethylene amine promoters and methods of use thereof | |
| US4510124A (en) | System for recovery of CO2 from flue gases containing SO2 | |
| EP0544515A1 (en) | Process and apparatus for removing acid gas from a gas mixture | |
| CA1340768C (en) | Teritiary alkanolamine absorbent containing an ethyleneamine promoter and its method of use | |
| CA2617610C (en) | Polyalkyleneacrylamide salt for acid gas scrubbing process | |
| KR101335603B1 (en) | Absorbent with high Carbon dioxide Loading Ratio | |
| EP0034901B1 (en) | Acid gas scrubbing process using hindered amine solution with hindered amine recovery from side-product cyclic urea | |
| CA1179828A (en) | Sterically hindered amino acid promoted acid gas scrubbing process | |
| US9533253B2 (en) | Amine solvent blends | |
| CA1189050A (en) | Non-sterically hindered-sterically hindered amine co- promoted acid gas scrubbing solution and process for using same | |
| MX2008006371A (en) | Process for the recovery of carbon dioxide |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |