CA1091429A - Process for removing carbon dioxide containing acidic gases from gaseous mixtures - Google Patents
Process for removing carbon dioxide containing acidic gases from gaseous mixturesInfo
- Publication number
- CA1091429A CA1091429A CA292,708A CA292708A CA1091429A CA 1091429 A CA1091429 A CA 1091429A CA 292708 A CA292708 A CA 292708A CA 1091429 A CA1091429 A CA 1091429A
- Authority
- CA
- Canada
- Prior art keywords
- carbon dioxide
- absorbing solution
- amino
- psia
- regeneration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Gas Separation By Absorption (AREA)
- Treating Waste Gases (AREA)
Abstract
ABSTRACT
A process for the substantial removal of carbon dioxide from a normally gaseous mixture containing the same, which comprises:
(a) in an absorption step, contacting said normally gaseous mixture with an aqueous absorbing solution containing from about 5 to about 65 weight percent of at least one mildly sterically hindered water-soluble primary monoamine defined as having a secondary carbon atom attached to the amino group to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption step is conducted at temperatures in the range from about 20° to about 100°C and the partial pressure of the carbon dioxide in the feed gas is in the range from about 1 to about 1000 psia; and (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 50° to about 170°C and at pressures ranging from about 1 to about 50 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of mono-ethanolamine under the same conditions of regeneration. Aqueous solutions containing water-soluble primary monoamines having a secondary carbon atom attached to the amino group provide the same high cleanup and fast absorption rates as aqueous solutions containing monoethanolamine, with the advantages of slightly higher capacity and much easier regeneration than the monoethanolamine solutions.
A process for the substantial removal of carbon dioxide from a normally gaseous mixture containing the same, which comprises:
(a) in an absorption step, contacting said normally gaseous mixture with an aqueous absorbing solution containing from about 5 to about 65 weight percent of at least one mildly sterically hindered water-soluble primary monoamine defined as having a secondary carbon atom attached to the amino group to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption step is conducted at temperatures in the range from about 20° to about 100°C and the partial pressure of the carbon dioxide in the feed gas is in the range from about 1 to about 1000 psia; and (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 50° to about 170°C and at pressures ranging from about 1 to about 50 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of mono-ethanolamine under the same conditions of regeneration. Aqueous solutions containing water-soluble primary monoamines having a secondary carbon atom attached to the amino group provide the same high cleanup and fast absorption rates as aqueous solutions containing monoethanolamine, with the advantages of slightly higher capacity and much easier regeneration than the monoethanolamine solutions.
Description
~Q91429 ..
1 This invention relates to an improved prbces~ for
1 This invention relates to an improved prbces~ for
2' removing carbon dioxide containing acidic ga8es from nor-
3 mally gaseous mixtures containing them and more particularly'
4 relates to a process of accomplishing substantial removal of 'S carbon dioxide contalning acidic gases from normally gaseous 6 m~xture~ by contacting the rmally gaseous mixtures w~th a 7 concentrated aqueous solution containing a primary monoamine 8 wherein the amino group is attached to a secondary carbon 9 atom.
Carbon dioxide containing acidic gas-s are sub-11 8tantially removed from a n~rmally gaseous m~xture by a !2 proces8 comprising contacting the normally gaseous mixture 13 with an aqueous solution containing a water-soluble pr~mary monoamine having a secondary carbon atom attached to the amino group to ab80rb 8ubstantially sll of the carbon tiox-l6 ide containin~ acidic gases. The water-soluble primary .: . .
~ 17 monoamine i8 preferably an amino alcohol which is useful :, ~ .
' ~ l8 when a high degree of carbon'dioxide removal i8 desired,' li e.g., 4 mon~a manufacture, ethylene manufacture by steam cracking~and natural gas treating prior to liquefact~on.
21 ~ It is ~ell known in the art to treat gases and 22 llquids, such as mixtures containing acidic gases includ-..
23 ~ng 2- H2S, S02, S03, CS2j HCN, COS and oxygen and sulfur derivatives of Cl to C4 hydrocarbons with amine solutions to remove these acidic gases. The amine usually contacts 26 the acidic gases and the liquids as an aqueous solution containing the amine in an absorber tower with the aqueous amine solution contacting the acidic fluid countercurrently.
~ 29 The acid gas scrubbing processes known in the art '~ 30 can be generally broken into three (3) categories.
3l The first category is generally referred to as 32 the aqueous amine process where relatively concentrated ; - 2 - ~T~
~ 91 4~
j 1 amine solutions are employed during the absorption. This ¦ 2 type of process i8 often utillzed in the manofacture of 3 ammonia where nearly complete removal of the acid gas, such 4 as 2, is required. It i8 also used in those instances I S where an acid gas, such as C02, occurs with other acid 6 gases or where the partial pressure of the 2 and other 7 gases are low. Aqueous monoethanolamine (MEA) is widely uset in this type of process since it provides a high ' 9' degree of absorption. One of its trawbacks is the high sta-billty of its carSamat~, which causes its regeneration to be . .
I 11' ~low and incomplete.
2 A secont catègory i8 generally referred to as the 13 ~queous base scrubbing process or "hot pot" process. In this 14 type of process a 8mall level of an amine is incluted as an lS activator for the aqueous base used in the scrubbing solut~'on.
1~ . . .
16 This type of process is generally uset where bulk removal of 17 an acit gas, such as C02, is desiret. Thi~ process also 18 applies to situations where the C2 and feet gas pressures 19 are high. In such processes, useful results are achievet ~ using aqueous potassium carbonate solutions ant an amine ac-21 tivator.
~ A third category is generally referred to as the 23 nonaqueous solvent process. In this process, water is a ?4 mlnor constltuent of the scrubbing solution and the amine is dlssolved in ehe liquid phase containing the solvent. In 26 this' process, up to 50% of the amine is dissolved in the 27 liquid phase. This type of process is utilized for special-' ~ ized applications where the partial pressure of C02 is 2~ extremely high andior where many acid gases are present, e.g., COS, CH3SH and CS2.
31 The present invention pertains to an improved pro-32 cess for practicing the first category of the scid gas .
1C~3142~9 l scrubbing processes described above, namely, the aqueous 2 amine process where relatively large amounts of amine solu-3 tions are employed during the absorption. Many industrial 4 processes for the removal of carbon dioxide containing acidic S gases use regenerable aqueous solutions of amines which are 6 continuously circulated between an absorption zone where the 7 acidic gases, including the carbon diox~de, are absorbed and 8 a regeneration zone where the aqueous amine containing absorp-9 tion solution which is saturated with the acid~c components ls desorbed usually by pressure reduction and steam stripping.
ll The capital cost of these acid scrubbing processes is generally 2 controlled by the size of the absorption and regeneration l3 towers, the size of the reboilers for generating stripping l4 ~team, and the size of the condensers which condense spent lS ~tripping steam so that condensate may be returned to the 16 ~ystem to maintain proper water balance.
7 The cost of operating such scrubbing plants i8 l8 generally related to the amount of heat required for the 19 removal of a given amount of acid gas, e.g., thermal effi-2~ ciency, sometimes expressed as cubic feet of acid gas removed 2l per pound of steam consumed. Means for reducing the costs 22- in operating these industrial processes have focused on the u~e of absorbing systems or combinations of chemical absorb-24 ënt~ which will operate mcre efficiently and effectively in acid-gas scrubbing processes using existing equipment.
26 - There are a number of patents which describe im-, . .
27 provements to-improve the efficiency of the above-described processes for removing acidic gases from gaseous mixtures.
Some of these improvements are described below.
Canadian Patent No. 619,193 teaches the use of 3l various aqueous solutions containing salts of aminoacids for 32 removing carbon dioxide containing gases from gaseous mixtures.
-` 1o~9~ 4Zx9 1 This patent is concerned with the same type of acid gas 2 scrubbing process as provided by the instant invention.
¦ 3 However, this Canadian patent does not disclose the use of . " i 4 aqueous solutions containing primary monoamines wherein the amino group is attached to a secondary carbon atom, and 6 particularly the amino alcohols.
7 U.S. Patent No. 1,783,901 to Bottoms is one of the 8 first patents to disclose a process for separating acidic 9 gases from acidic mixtures by contacting the gaseous mixture with an amine absorben~ agent and thereafter treating the ~~ ---1~ absorbent to separate the ab~orbed gas and regenerate the 12 absorbent. Various alkanolamines are disclosed in the patent 13 including monoethanolamine, diethanolamine, triethanolamine 14 and diethylaminoethyl alcohol.
U.S. Patent No. 2,139,123 discloses and claims the 16 compound 2-amino~l-pentanol. It is disclosed in the patent 17 that this amino alcohol, due to its basic nature, may be 18 utilized to absorb acids such as hydrogen sulfide and carbon 19 dioxide from industrial gases. The patent does not teach a process whereby the amino alcohol is substantially regener-21 ated in a continuous process.
22 - - Prior art workers have taught that sterically hin-23 dered amines would have low rates of combination with C2 24 and apparently concluded, although other explanations are possible, that such sterically hindered amines would be in-26 efficient in 2 scrubbing processes. For example, Sharma, 27 M.M.,-Trans. Faradav Soc., 61, 681-8 (1965) described the 28 kinetics of reaction between C02 and COS with 38 amines, 29 some of which are sterically hindered æmines. Other re-searchers have attributed relatively poor absorption rates 31 of CO~ by amines to steric hindrance. See, for example, J.L.
32 Frahn and J.A. Mills, Aust. J. Chem., 17, 256-73, 263 (1964), , . . .,,, ,~,,~
109~4Z9 and M.B. Jensen, Acta Chemica Scandinavia, 11, 499-505 (1957).
Shrier and Danckwerts, Ind. Eng. Chem. Fundamentals, 8, 415 (1969) discussed the use of amines as promoters for aqueous carbonate-bicarbonate buffers.
However, these researchers only ran initail absorption rate experiments and did not recognize the unique capacity advantages obtained by using sterically hindered amines in an acid gas scrubbing process. Also of interest is Danckwerts and Sharma The Chemical Engineer, Oct. 1966, pp.244-280.
In the prior art processes discussed above, it is apparent that the efficiency of processes employing absorbing solutions is generally limited by the relatively slow rate of transfer of molecules to the acid gas from the gas phase to the liquid phase as well as in the regeneration of the absorbing solution.
Many of the above-described prior art processes deal with means to render the acid gas scrubbing process mo e efficient.
In Dutch Patent Publication No. 7606979, there is disclosed and claimed processes and compositions useful for scrubbing acid gases comprising the use of sterically hindered amines. These sterically hindered amines unexpectedly improve the efficiency, efectiveness and working capacity of the acid gas scrubbing processes in all three of the above-mentioned process categories. Examples of amino alcohols which are primary monoamines disclosed in said patent application include the sterically hindered compounds: 2-amino-2-methyl-1-butanol; 2-amino-2-ethyl-l-butanol; 3-amino-3-methyl-1-butanol, and 2-amino-2-methyl-1-propanol.
This patent application does not, however, disclose amino alcohols having a secondary carbon atom attached to a primary .
~ 1Q9~429 1 amino group and/or their use in an aqueous scrubbing solu-2 tion to remove substantially all of the carbon dioxide 3 containing acidic gas from a gaseous mixture.
4 It has been observed that the sterically hindered amines, such as 2-amino-2^methyl-1-propanol, provide a broad-6 er cyclic capacity than monoethanolamine and higher rates of 7 regeneration in the aqueous amine acid gas scrubbing process, 8 i.e. the first process category described above. However, 9 the 2 cleanup with the 2-amino-2-methyl-1 propanol is in-ferior to that observed with monoethanolamine.
11 It ha~ now been unexpectedly discovered that aqueous 12 solutions containing watersoluble primary monoamines having 13 a secondary carbon atom attached to the amino group provide 14 the same high cleanup and fast absorption rates as aqueous solutions containing monoethanolamine, with the advantages 16 of slightly higher capacity and much easier regeneration 17 than the monoethanolami~e solutions. Wh~le not wishing to 18 be bound by any theory, it is believed that this behavior 9 i8 attributed to the fact that the water-soluble primary monoamines having a secondary carbon atom attached to the 21 amino group are mildly sterically hindered compared to 22 aqueous monoethanolamine, alth~ugh they do not possess the 23 degree of steric hindrance of the amines disclosed in Dutch 24 Patent Publication No. ?6069Z9 as used previously. In the latter patent application, steric hindrance is defined as 26 that of a primary amino group attached to a tertiary carbon 27 atom. -In-the case of monoethanolamine, the primary amino 28 group is attached to a primary carbon atom. The water-29 soluble primary monoamines used in the process of the in-stant invention have a secondary carbon atom attached to the 31 amino group, which apparently provides the proper amount of 32 steric hindrance for providing good cyclic capacity and high 4za rate of regeneration while retaining the exceIlent cIeanup character~stics of the aqueous monoethanolamine solutions.
Thus the present invention provides a process for the substantial removal of car~on diox~de from a normaIly gaseous mixture containing the same, which comprises:
(a) in an absorption step, contacting said nor-mally gaseous mixture with an aqueous absorbing solution containing from about 5 to about-65 weight percent of at least one mildly sterically hindered water-soluble primary monoamine defined as having a secondary carbon atom attached to the amino group to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption step is conducted at temperatures in the range from about 20~ to about 100C. and the partial pressure of the carbon dioxide in the feed gas is in the range from about 1 to about 1000 psia; and (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 50 to about 170C. and at pressures ranging from about 1 to about 50 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of monoethanolamine under the same conditions of regeneration.
In one embodiment of the present invention, there is provided a process for the substantial removal of carbon r~ 1[~91 42~9 dioxide containing acidic gases from a gaseous mixture, which comprises:
(a) contacting said gaseous mixture with an aqueous concentrated solution containing a water-soluble primary .. . .
monoamine having a secondary carbon atom attAched to the amino group to absorb the carbon dioxide containing acidic gases in the aqueous solution, and (b) desorbing substantially all of the absorbed carbon dioxide containlng acidic gases from said solution.
lo Desorption with the water-soluble primary mono-amines of the invention is more complete than monoethanol-amine under the same conditions of desorption (regeneration).
In another embodiment of the invention, there i8 provided an aqueous acid scrubb~ng solution containing a mixture of 15 to about 65% by weight of a water-soluble primary monoamine having a secondary carbon atom attached to the amino group.
The term carbon dioxide containing acidic gas also includes H2S, S02, S03, CS2, HCN, COS and the oxygen and sulfur derivatives of Cl to C4 hydrocarbons in various ~ amounts as they frequently appear ln gaseous mixtureg These ; acid gases other than the carbon dioxide msy be present in trace amounts within a gaseous mixture or in major propor~kns.
The contacting of the absorbent mixture and the carbon dioxide containing acidic gas may take place in any suitable contacting tower. In such processes, the gaseous mixture from which the acid gases are ~o be removed may be brought into lntimate contact with the absorbing solution - 8a~
109~4~9 1 using conventional means, such 88 a tower packed wlth, for 2 xample, ceramic ring~ or satdles or with bubble cap plates 3 or sieve plates, or a bubble reactor.
4 In a preferred mode of practicin~ the ~nvention, S the absorption step is conducted by feeding the gaseous 6 mixture into the base of the tower while fresh absorblng 7 solution i5 fed into the top. The gaseous mixture freed 8 largely from acid gases emerges from the top. Preferably, 9 the temperature of the absorbing solution during the ~ absorption step is in the range from abcut 20- to about 11 100C, ~nd more preferably from 40 to about 60C. The 12 partial pressure of the acid gas, e.g., C02 in the feed gas 13 mixture will preferably be in the range from about 1 to about 14 1000 psia, and more preferably in the range from about 100 to about 500 psia. The contacting takes place under condi-16 tions such that the acid gas, e.g., C02, i8 absorbed by the 17 solution. During absorption the solution is maintained in a 18 single phase. ~ `
19 - The absorbing solution compri~ing the aqueous mixture containing the water-soluble primary monoamine 21 which is saturated or partially saturated with gases, such 2Z as 2 and H2S, may be regenerated so that it may be re-23 cyc~led back to the absorber. The regeneration should also 24 take place in a single liquid phase. The regeneration or desorption is accomplished by conventional means, such as -26 pressure retuction, which causes the acid gases to flash 27 off or by passing the solution into a tower of similar 28 conseruction to that used in the absorption step, at or near 29 the top of the tower, and passing an inert gas such as air 30 or nitrogen or preferably steam up the tower. The tempera-31 ture of the solution during the regeneration step should be 32 in the range fxom about 50 to about 170C, and preferably 1 80C to about 150C. The absorbing solution, after being 2 cleansed of at least a port~on of the acid bodies, may be 3 recycled back to the absorbing tower. Makeup absorbent may 4 be added as needed. - ~ -For example, during de80rption, the acid gas, e.g., 6 002-rich solution from the high pressure absorber is sent 7 first to a flash chamb~r where steam and some C02 are flashed 8 from solution at low pressure. The amount of C02 flashed off 9 will in general be about 35 to 447. of the net C02 recovered in the flash and stripper. This is increased somewhat, e.g., ~
11 to 40 to 50Z., with the high desorption rate owing to a closer 12 approach to equilibrium in the flash. Solution from the 13 flash drum i8 then steam stripped in the packed or plate 14 tower, stripping steam having been generated in the reboiler in the base of the stripper. Pressure in the flash drum ant 16 8tripper i8 usually 1 to about 50 ps~a, preferably 5 to about 17 30 psia, and the temperature is in the range from about 50 18 to about 170C, preferably 80 to about 150C. Stripper and 19 flash temperatures will, of course, depent on stripper pressure, thus at about 15 to 30 psia stripper pressures, 21 the temperature will be about 80 to about 150C during 22 desorption-23 ~ In the most preferred embotiment of the present 24 invention, substantiaIly complete removal of carbon dioxide containing acidic gases from gaseous mixtures is accomplished 26 by a process comprisin~ (1) contacting the gaseous mixture 27 with an aqueous concentratet solution containing a water-28 soluble primary monoamine having a secondary carbon atom 29 attached to the amino group, e.g., an amino alcohol, prefer-ably a water-soluble primary monoamine which is a member 31 selected from the group consisting of 2-amino-1-propanol, 32 2-am-no-1-butanol, 2-amino-3-methyl-1-butanol, 2-amino-1-, - ~ - 10 ., , 1C~31 42~9 .~ .
pentanol, 2-amino-1-hexanol, and 2~aminocyclohexanol, where-in the water-soluble primary monoamine ~s present Ln an ~mount ranging from about 5 to about 65 weight percent, and more preferably 15 to about 55 weight percent, said contact-ing being conducted at conditions whereby the carbon dioxide containing gas is absorbed in said solution, and preferably at a temperature ranging from about 20 to about 100C, more preferably from 40 to about 60C and at a pressure ranging from about 1 to about 1000 psia, and regenerating said lo aqueous solution at conditions whereby at least a portion of said carbon dioxide containing gases are desorbed from the 8crubbing solution. The regenerated scrubbing solution may thereafter be recycled to the ab80rber as is or it may be combined with fresh makeup scrubbing solution.
It is possible, of course, to employ the process of the present invention in con~unction with other acid gas 8crubbing processes. For example, solutions rich in carbon dioxide may be first scrubbed by a bulk scrubbing ~ process using the "hot pot" process, preferably the processes ; 20 disclosed in Dutch Patent PublLcation No. 7606979.
- .. ,.. ~. , I This coarsely pre-purified gas may then be ~reated in accor-dance with the teachings of the present invention to remové
the last residues of the carbon dioxide containing gases.
~- The aqueous amine containing solution of the presént invention may optionally include commonly used additives, such as antifoaming agents, antioxidants, corrosion inhibitors, etc. Examples of such additives in-clude arsenious anhydride, selenious and tellurous acid, protides, vanadium oxides, e.g., V203, chromates, e.g., 30 K2Cr207, etc.
The inventLon is illustrated further by the . 1C~31 42~9 1 following example~ which, however, are not to be taken as 1 2 lim$ting in any respect. All parts ana percentages, unless 3 expressly stated to be otherwise, are by weight.
4 EXAMPLE 1 I ~
Carbon dioxide containing acidic gas-s are sub-11 8tantially removed from a n~rmally gaseous m~xture by a !2 proces8 comprising contacting the normally gaseous mixture 13 with an aqueous solution containing a water-soluble pr~mary monoamine having a secondary carbon atom attached to the amino group to ab80rb 8ubstantially sll of the carbon tiox-l6 ide containin~ acidic gases. The water-soluble primary .: . .
~ 17 monoamine i8 preferably an amino alcohol which is useful :, ~ .
' ~ l8 when a high degree of carbon'dioxide removal i8 desired,' li e.g., 4 mon~a manufacture, ethylene manufacture by steam cracking~and natural gas treating prior to liquefact~on.
21 ~ It is ~ell known in the art to treat gases and 22 llquids, such as mixtures containing acidic gases includ-..
23 ~ng 2- H2S, S02, S03, CS2j HCN, COS and oxygen and sulfur derivatives of Cl to C4 hydrocarbons with amine solutions to remove these acidic gases. The amine usually contacts 26 the acidic gases and the liquids as an aqueous solution containing the amine in an absorber tower with the aqueous amine solution contacting the acidic fluid countercurrently.
~ 29 The acid gas scrubbing processes known in the art '~ 30 can be generally broken into three (3) categories.
3l The first category is generally referred to as 32 the aqueous amine process where relatively concentrated ; - 2 - ~T~
~ 91 4~
j 1 amine solutions are employed during the absorption. This ¦ 2 type of process i8 often utillzed in the manofacture of 3 ammonia where nearly complete removal of the acid gas, such 4 as 2, is required. It i8 also used in those instances I S where an acid gas, such as C02, occurs with other acid 6 gases or where the partial pressure of the 2 and other 7 gases are low. Aqueous monoethanolamine (MEA) is widely uset in this type of process since it provides a high ' 9' degree of absorption. One of its trawbacks is the high sta-billty of its carSamat~, which causes its regeneration to be . .
I 11' ~low and incomplete.
2 A secont catègory i8 generally referred to as the 13 ~queous base scrubbing process or "hot pot" process. In this 14 type of process a 8mall level of an amine is incluted as an lS activator for the aqueous base used in the scrubbing solut~'on.
1~ . . .
16 This type of process is generally uset where bulk removal of 17 an acit gas, such as C02, is desiret. Thi~ process also 18 applies to situations where the C2 and feet gas pressures 19 are high. In such processes, useful results are achievet ~ using aqueous potassium carbonate solutions ant an amine ac-21 tivator.
~ A third category is generally referred to as the 23 nonaqueous solvent process. In this process, water is a ?4 mlnor constltuent of the scrubbing solution and the amine is dlssolved in ehe liquid phase containing the solvent. In 26 this' process, up to 50% of the amine is dissolved in the 27 liquid phase. This type of process is utilized for special-' ~ ized applications where the partial pressure of C02 is 2~ extremely high andior where many acid gases are present, e.g., COS, CH3SH and CS2.
31 The present invention pertains to an improved pro-32 cess for practicing the first category of the scid gas .
1C~3142~9 l scrubbing processes described above, namely, the aqueous 2 amine process where relatively large amounts of amine solu-3 tions are employed during the absorption. Many industrial 4 processes for the removal of carbon dioxide containing acidic S gases use regenerable aqueous solutions of amines which are 6 continuously circulated between an absorption zone where the 7 acidic gases, including the carbon diox~de, are absorbed and 8 a regeneration zone where the aqueous amine containing absorp-9 tion solution which is saturated with the acid~c components ls desorbed usually by pressure reduction and steam stripping.
ll The capital cost of these acid scrubbing processes is generally 2 controlled by the size of the absorption and regeneration l3 towers, the size of the reboilers for generating stripping l4 ~team, and the size of the condensers which condense spent lS ~tripping steam so that condensate may be returned to the 16 ~ystem to maintain proper water balance.
7 The cost of operating such scrubbing plants i8 l8 generally related to the amount of heat required for the 19 removal of a given amount of acid gas, e.g., thermal effi-2~ ciency, sometimes expressed as cubic feet of acid gas removed 2l per pound of steam consumed. Means for reducing the costs 22- in operating these industrial processes have focused on the u~e of absorbing systems or combinations of chemical absorb-24 ënt~ which will operate mcre efficiently and effectively in acid-gas scrubbing processes using existing equipment.
26 - There are a number of patents which describe im-, . .
27 provements to-improve the efficiency of the above-described processes for removing acidic gases from gaseous mixtures.
Some of these improvements are described below.
Canadian Patent No. 619,193 teaches the use of 3l various aqueous solutions containing salts of aminoacids for 32 removing carbon dioxide containing gases from gaseous mixtures.
-` 1o~9~ 4Zx9 1 This patent is concerned with the same type of acid gas 2 scrubbing process as provided by the instant invention.
¦ 3 However, this Canadian patent does not disclose the use of . " i 4 aqueous solutions containing primary monoamines wherein the amino group is attached to a secondary carbon atom, and 6 particularly the amino alcohols.
7 U.S. Patent No. 1,783,901 to Bottoms is one of the 8 first patents to disclose a process for separating acidic 9 gases from acidic mixtures by contacting the gaseous mixture with an amine absorben~ agent and thereafter treating the ~~ ---1~ absorbent to separate the ab~orbed gas and regenerate the 12 absorbent. Various alkanolamines are disclosed in the patent 13 including monoethanolamine, diethanolamine, triethanolamine 14 and diethylaminoethyl alcohol.
U.S. Patent No. 2,139,123 discloses and claims the 16 compound 2-amino~l-pentanol. It is disclosed in the patent 17 that this amino alcohol, due to its basic nature, may be 18 utilized to absorb acids such as hydrogen sulfide and carbon 19 dioxide from industrial gases. The patent does not teach a process whereby the amino alcohol is substantially regener-21 ated in a continuous process.
22 - - Prior art workers have taught that sterically hin-23 dered amines would have low rates of combination with C2 24 and apparently concluded, although other explanations are possible, that such sterically hindered amines would be in-26 efficient in 2 scrubbing processes. For example, Sharma, 27 M.M.,-Trans. Faradav Soc., 61, 681-8 (1965) described the 28 kinetics of reaction between C02 and COS with 38 amines, 29 some of which are sterically hindered æmines. Other re-searchers have attributed relatively poor absorption rates 31 of CO~ by amines to steric hindrance. See, for example, J.L.
32 Frahn and J.A. Mills, Aust. J. Chem., 17, 256-73, 263 (1964), , . . .,,, ,~,,~
109~4Z9 and M.B. Jensen, Acta Chemica Scandinavia, 11, 499-505 (1957).
Shrier and Danckwerts, Ind. Eng. Chem. Fundamentals, 8, 415 (1969) discussed the use of amines as promoters for aqueous carbonate-bicarbonate buffers.
However, these researchers only ran initail absorption rate experiments and did not recognize the unique capacity advantages obtained by using sterically hindered amines in an acid gas scrubbing process. Also of interest is Danckwerts and Sharma The Chemical Engineer, Oct. 1966, pp.244-280.
In the prior art processes discussed above, it is apparent that the efficiency of processes employing absorbing solutions is generally limited by the relatively slow rate of transfer of molecules to the acid gas from the gas phase to the liquid phase as well as in the regeneration of the absorbing solution.
Many of the above-described prior art processes deal with means to render the acid gas scrubbing process mo e efficient.
In Dutch Patent Publication No. 7606979, there is disclosed and claimed processes and compositions useful for scrubbing acid gases comprising the use of sterically hindered amines. These sterically hindered amines unexpectedly improve the efficiency, efectiveness and working capacity of the acid gas scrubbing processes in all three of the above-mentioned process categories. Examples of amino alcohols which are primary monoamines disclosed in said patent application include the sterically hindered compounds: 2-amino-2-methyl-1-butanol; 2-amino-2-ethyl-l-butanol; 3-amino-3-methyl-1-butanol, and 2-amino-2-methyl-1-propanol.
This patent application does not, however, disclose amino alcohols having a secondary carbon atom attached to a primary .
~ 1Q9~429 1 amino group and/or their use in an aqueous scrubbing solu-2 tion to remove substantially all of the carbon dioxide 3 containing acidic gas from a gaseous mixture.
4 It has been observed that the sterically hindered amines, such as 2-amino-2^methyl-1-propanol, provide a broad-6 er cyclic capacity than monoethanolamine and higher rates of 7 regeneration in the aqueous amine acid gas scrubbing process, 8 i.e. the first process category described above. However, 9 the 2 cleanup with the 2-amino-2-methyl-1 propanol is in-ferior to that observed with monoethanolamine.
11 It ha~ now been unexpectedly discovered that aqueous 12 solutions containing watersoluble primary monoamines having 13 a secondary carbon atom attached to the amino group provide 14 the same high cleanup and fast absorption rates as aqueous solutions containing monoethanolamine, with the advantages 16 of slightly higher capacity and much easier regeneration 17 than the monoethanolami~e solutions. Wh~le not wishing to 18 be bound by any theory, it is believed that this behavior 9 i8 attributed to the fact that the water-soluble primary monoamines having a secondary carbon atom attached to the 21 amino group are mildly sterically hindered compared to 22 aqueous monoethanolamine, alth~ugh they do not possess the 23 degree of steric hindrance of the amines disclosed in Dutch 24 Patent Publication No. ?6069Z9 as used previously. In the latter patent application, steric hindrance is defined as 26 that of a primary amino group attached to a tertiary carbon 27 atom. -In-the case of monoethanolamine, the primary amino 28 group is attached to a primary carbon atom. The water-29 soluble primary monoamines used in the process of the in-stant invention have a secondary carbon atom attached to the 31 amino group, which apparently provides the proper amount of 32 steric hindrance for providing good cyclic capacity and high 4za rate of regeneration while retaining the exceIlent cIeanup character~stics of the aqueous monoethanolamine solutions.
Thus the present invention provides a process for the substantial removal of car~on diox~de from a normaIly gaseous mixture containing the same, which comprises:
(a) in an absorption step, contacting said nor-mally gaseous mixture with an aqueous absorbing solution containing from about 5 to about-65 weight percent of at least one mildly sterically hindered water-soluble primary monoamine defined as having a secondary carbon atom attached to the amino group to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption step is conducted at temperatures in the range from about 20~ to about 100C. and the partial pressure of the carbon dioxide in the feed gas is in the range from about 1 to about 1000 psia; and (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 50 to about 170C. and at pressures ranging from about 1 to about 50 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of monoethanolamine under the same conditions of regeneration.
In one embodiment of the present invention, there is provided a process for the substantial removal of carbon r~ 1[~91 42~9 dioxide containing acidic gases from a gaseous mixture, which comprises:
(a) contacting said gaseous mixture with an aqueous concentrated solution containing a water-soluble primary .. . .
monoamine having a secondary carbon atom attAched to the amino group to absorb the carbon dioxide containing acidic gases in the aqueous solution, and (b) desorbing substantially all of the absorbed carbon dioxide containlng acidic gases from said solution.
lo Desorption with the water-soluble primary mono-amines of the invention is more complete than monoethanol-amine under the same conditions of desorption (regeneration).
In another embodiment of the invention, there i8 provided an aqueous acid scrubb~ng solution containing a mixture of 15 to about 65% by weight of a water-soluble primary monoamine having a secondary carbon atom attached to the amino group.
The term carbon dioxide containing acidic gas also includes H2S, S02, S03, CS2, HCN, COS and the oxygen and sulfur derivatives of Cl to C4 hydrocarbons in various ~ amounts as they frequently appear ln gaseous mixtureg These ; acid gases other than the carbon dioxide msy be present in trace amounts within a gaseous mixture or in major propor~kns.
The contacting of the absorbent mixture and the carbon dioxide containing acidic gas may take place in any suitable contacting tower. In such processes, the gaseous mixture from which the acid gases are ~o be removed may be brought into lntimate contact with the absorbing solution - 8a~
109~4~9 1 using conventional means, such 88 a tower packed wlth, for 2 xample, ceramic ring~ or satdles or with bubble cap plates 3 or sieve plates, or a bubble reactor.
4 In a preferred mode of practicin~ the ~nvention, S the absorption step is conducted by feeding the gaseous 6 mixture into the base of the tower while fresh absorblng 7 solution i5 fed into the top. The gaseous mixture freed 8 largely from acid gases emerges from the top. Preferably, 9 the temperature of the absorbing solution during the ~ absorption step is in the range from abcut 20- to about 11 100C, ~nd more preferably from 40 to about 60C. The 12 partial pressure of the acid gas, e.g., C02 in the feed gas 13 mixture will preferably be in the range from about 1 to about 14 1000 psia, and more preferably in the range from about 100 to about 500 psia. The contacting takes place under condi-16 tions such that the acid gas, e.g., C02, i8 absorbed by the 17 solution. During absorption the solution is maintained in a 18 single phase. ~ `
19 - The absorbing solution compri~ing the aqueous mixture containing the water-soluble primary monoamine 21 which is saturated or partially saturated with gases, such 2Z as 2 and H2S, may be regenerated so that it may be re-23 cyc~led back to the absorber. The regeneration should also 24 take place in a single liquid phase. The regeneration or desorption is accomplished by conventional means, such as -26 pressure retuction, which causes the acid gases to flash 27 off or by passing the solution into a tower of similar 28 conseruction to that used in the absorption step, at or near 29 the top of the tower, and passing an inert gas such as air 30 or nitrogen or preferably steam up the tower. The tempera-31 ture of the solution during the regeneration step should be 32 in the range fxom about 50 to about 170C, and preferably 1 80C to about 150C. The absorbing solution, after being 2 cleansed of at least a port~on of the acid bodies, may be 3 recycled back to the absorbing tower. Makeup absorbent may 4 be added as needed. - ~ -For example, during de80rption, the acid gas, e.g., 6 002-rich solution from the high pressure absorber is sent 7 first to a flash chamb~r where steam and some C02 are flashed 8 from solution at low pressure. The amount of C02 flashed off 9 will in general be about 35 to 447. of the net C02 recovered in the flash and stripper. This is increased somewhat, e.g., ~
11 to 40 to 50Z., with the high desorption rate owing to a closer 12 approach to equilibrium in the flash. Solution from the 13 flash drum i8 then steam stripped in the packed or plate 14 tower, stripping steam having been generated in the reboiler in the base of the stripper. Pressure in the flash drum ant 16 8tripper i8 usually 1 to about 50 ps~a, preferably 5 to about 17 30 psia, and the temperature is in the range from about 50 18 to about 170C, preferably 80 to about 150C. Stripper and 19 flash temperatures will, of course, depent on stripper pressure, thus at about 15 to 30 psia stripper pressures, 21 the temperature will be about 80 to about 150C during 22 desorption-23 ~ In the most preferred embotiment of the present 24 invention, substantiaIly complete removal of carbon dioxide containing acidic gases from gaseous mixtures is accomplished 26 by a process comprisin~ (1) contacting the gaseous mixture 27 with an aqueous concentratet solution containing a water-28 soluble primary monoamine having a secondary carbon atom 29 attached to the amino group, e.g., an amino alcohol, prefer-ably a water-soluble primary monoamine which is a member 31 selected from the group consisting of 2-amino-1-propanol, 32 2-am-no-1-butanol, 2-amino-3-methyl-1-butanol, 2-amino-1-, - ~ - 10 ., , 1C~31 42~9 .~ .
pentanol, 2-amino-1-hexanol, and 2~aminocyclohexanol, where-in the water-soluble primary monoamine ~s present Ln an ~mount ranging from about 5 to about 65 weight percent, and more preferably 15 to about 55 weight percent, said contact-ing being conducted at conditions whereby the carbon dioxide containing gas is absorbed in said solution, and preferably at a temperature ranging from about 20 to about 100C, more preferably from 40 to about 60C and at a pressure ranging from about 1 to about 1000 psia, and regenerating said lo aqueous solution at conditions whereby at least a portion of said carbon dioxide containing gases are desorbed from the 8crubbing solution. The regenerated scrubbing solution may thereafter be recycled to the ab80rber as is or it may be combined with fresh makeup scrubbing solution.
It is possible, of course, to employ the process of the present invention in con~unction with other acid gas 8crubbing processes. For example, solutions rich in carbon dioxide may be first scrubbed by a bulk scrubbing ~ process using the "hot pot" process, preferably the processes ; 20 disclosed in Dutch Patent PublLcation No. 7606979.
- .. ,.. ~. , I This coarsely pre-purified gas may then be ~reated in accor-dance with the teachings of the present invention to remové
the last residues of the carbon dioxide containing gases.
~- The aqueous amine containing solution of the presént invention may optionally include commonly used additives, such as antifoaming agents, antioxidants, corrosion inhibitors, etc. Examples of such additives in-clude arsenious anhydride, selenious and tellurous acid, protides, vanadium oxides, e.g., V203, chromates, e.g., 30 K2Cr207, etc.
The inventLon is illustrated further by the . 1C~31 42~9 1 following example~ which, however, are not to be taken as 1 2 lim$ting in any respect. All parts ana percentages, unless 3 expressly stated to be otherwise, are by weight.
4 EXAMPLE 1 I ~
- 5 This example demonstrates that the mildly hindered ,
6 amines of the invention give the same high C02 cleanup as
7 monoethanolamine, but their desorption i8 more complete than
8 monoethanolamine.
9 To a l-liter autoclave equipped with a stirrer, inlee and outlet tubes for gases (the entering gases are~
lI saturatet wlth water and the outgoing gases pass through a 12 condenser) and liqui~ sampling device there is charged an - 13 squeous scrubbing solution consisting of 222 g of 2-amino-1-14 butanol and 278 g of water. The solutlon in the autoclave ~: 15 i8 approximately 5 M. The temperature i8 brought to 100F
~ ~ 16 (37.7 ~ and a gas mixture containing 0.2 mole X C2 and ¦ 17 99.8 mole X He is slowly blown through the solution, under a 18 pressure of 50 psla, until gas chromatography shows that the I ~
19 composition of the outgoing gas i~ the same as that of the entering gas. At this point equilibrium has been reached.
21 Analysis gives a ~2 content of 8.2% and a nitrogen content 22 of 6.4%, from which a C02/amine molar ratio of 0.41 is cal-23 culated.
24 ~ Under the same equilibrium conditions, a 5 M 801u-tion of monoethanolamine gives about the same C02/amine ratio.
26 Under the experimental conditions, i.e., low temperature and . . ~.. ... . . ............ .
27 low C02 partial pressure, the COz/amine ratio is taken as an 28 indication of cleanup ability.
29 The above experiment i8 repeated, using the same jgas mixture but operating at 250F (121.1C), i.e., under 31 conditions simulating desorption. Only about 1 g of C02 32 remains in solution in the case of 2-amino-1-butanol, where-~l8 5 M monoethanolamine retains a sizable amount of C02 2 under the same conditions. This is indicative that the 3 desorption is more complete in the case of 2-amino-1-butanol.
4 Specifically, vaIues for the mole ratio of C02/amine corres-5 ponding to the various values of the partial pressure of C2 6in the gas phase at 250F are as follows: `~
8Partial Pressure of C02 9at Equilibri~1m 1035 5 0.
11~ psia P8 ia 12 Amine(C02/amine) in the Solution 13 2-amino-1-butanol0.33 0.14 0.01 14 monoethanolamine0.44 0.30 0.03 15 EXA~LE 2 16 This example demonstrates the easier regeneration 17 of th~ water-soluble primary monoamine having a ~econdary 18 carbon atom attached to the amino group by the following 19 ~bsorption-desorption cycle at atmospheric pressure.
The absorber is a stirret vessel, having a capacity 21 of 2.5 liters and a diameter of 10 cm. A pump removes liquid 22 from the bottom of the reactor and feeds it back above the 23 surface through a sparger. A stirrer further increases con-24 tact between liquid and gas.
The desorber i8 a l-liter reactor, equipped with 26 teflon-blade stirrer, gas sparger, reflux condenser and 27 thermometer. 296 g of 2-amino-1-butanol is dissolved in 28 enough water to give a volume of 670 ml. The solution is 29 5 M. It -is put ~nto;-the reactor and heated to 100F
30 (37.7C) . The reactor is evacuated and then pure C02 is 31 admitted until no more gas is absorbed. The amount absorbed 32 is 75 g. Analysis gives a C02 content of 10.1%. The rich 33 solution is transferred to the desorber and bo~led for 15 `1091429 ¦ 1 minutes while 810wly blow~ng n~trogen. The 2 content trops 2 to 2.7%.
3 The experiment is repeated, using 670 ml of 5 M
. ., 4 monoethanolamine. Absorption is pract~cally the same as with 2-amino-1-butanol. However, when desorption is carried 6 out, the rich monoethanolamine solution must be boiled ant 7 strippet for 60 minutes in order for the C02 content to trop ` 8 to 2.r%. This shows that regeneration is easier with 2-amin~
9 l-butano~. -. - "
11 To the same l-liter autoclave as described in 12 Ex~mple 1, there is charged a solution of 134 g of 2-amino-13 l-butanol in 366 ml of water. Tho solution is about 3 M
14 wIth tespect to 2-amino-1-butanol. The autocIave is closed ~nd brought to 100F (37.7C); a gas mixture dontaining ~ ~ 16 0.2 mole % 2 and 99.8 mole % He i8 810wly blown through ¦ 1~ 17 the solution under a pressure of 50 psia. until gas chroma-18 tography shows that the composition of the ouegoing ga~ is ~ ~ .
19 the same as that of the entering gas. At this point, quilibrium has been reached. Analysis giv s a C02 content 21 of 8.2% and a nitrogen content~of 4.3% from which a C02/amine 22 ~olar ratio of ~.41 is calculatet. Under the same conditions, 23 a 3 N solution of monoethanolamine gives about the same 24 002/amine ratio. Under the experimental conditions, i.e., low tempera;ture and low C02 partial pressure, the 002/amine 26 ratio ~8 taken as an indication of cleanup ability.
27 The above experiment is repeatet, using the same ~ , .
28 gas mixture, but operating at 250F (121.1C), i.e., under 29 conditlons simulating desorption. Only about 2 g of 2 remain in solution in the case of 3 M 2-amino-1-butanol, 31 whereas 3 M monoethanolamine r¢tains about 6 g of C02 32 under the same conditions. This indicates that desorp~n ,- , ' 1~91429 1 is more complete in the ca~e of 2-ami -l-butanol.
3 Example 3 is repeated, using 3M 2-amino-1-propanol 4 or ~ M 2-amino-3-methyl-1-butanol. The results obtained are very similar to those obtained with-3 M 2-amino-}-butanol.
.
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,. .: . . : ..i, -:. - ..., ., - . . . .
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lI saturatet wlth water and the outgoing gases pass through a 12 condenser) and liqui~ sampling device there is charged an - 13 squeous scrubbing solution consisting of 222 g of 2-amino-1-14 butanol and 278 g of water. The solutlon in the autoclave ~: 15 i8 approximately 5 M. The temperature i8 brought to 100F
~ ~ 16 (37.7 ~ and a gas mixture containing 0.2 mole X C2 and ¦ 17 99.8 mole X He is slowly blown through the solution, under a 18 pressure of 50 psla, until gas chromatography shows that the I ~
19 composition of the outgoing gas i~ the same as that of the entering gas. At this point equilibrium has been reached.
21 Analysis gives a ~2 content of 8.2% and a nitrogen content 22 of 6.4%, from which a C02/amine molar ratio of 0.41 is cal-23 culated.
24 ~ Under the same equilibrium conditions, a 5 M 801u-tion of monoethanolamine gives about the same C02/amine ratio.
26 Under the experimental conditions, i.e., low temperature and . . ~.. ... . . ............ .
27 low C02 partial pressure, the COz/amine ratio is taken as an 28 indication of cleanup ability.
29 The above experiment i8 repeated, using the same jgas mixture but operating at 250F (121.1C), i.e., under 31 conditions simulating desorption. Only about 1 g of C02 32 remains in solution in the case of 2-amino-1-butanol, where-~l8 5 M monoethanolamine retains a sizable amount of C02 2 under the same conditions. This is indicative that the 3 desorption is more complete in the case of 2-amino-1-butanol.
4 Specifically, vaIues for the mole ratio of C02/amine corres-5 ponding to the various values of the partial pressure of C2 6in the gas phase at 250F are as follows: `~
8Partial Pressure of C02 9at Equilibri~1m 1035 5 0.
11~ psia P8 ia 12 Amine(C02/amine) in the Solution 13 2-amino-1-butanol0.33 0.14 0.01 14 monoethanolamine0.44 0.30 0.03 15 EXA~LE 2 16 This example demonstrates the easier regeneration 17 of th~ water-soluble primary monoamine having a ~econdary 18 carbon atom attached to the amino group by the following 19 ~bsorption-desorption cycle at atmospheric pressure.
The absorber is a stirret vessel, having a capacity 21 of 2.5 liters and a diameter of 10 cm. A pump removes liquid 22 from the bottom of the reactor and feeds it back above the 23 surface through a sparger. A stirrer further increases con-24 tact between liquid and gas.
The desorber i8 a l-liter reactor, equipped with 26 teflon-blade stirrer, gas sparger, reflux condenser and 27 thermometer. 296 g of 2-amino-1-butanol is dissolved in 28 enough water to give a volume of 670 ml. The solution is 29 5 M. It -is put ~nto;-the reactor and heated to 100F
30 (37.7C) . The reactor is evacuated and then pure C02 is 31 admitted until no more gas is absorbed. The amount absorbed 32 is 75 g. Analysis gives a C02 content of 10.1%. The rich 33 solution is transferred to the desorber and bo~led for 15 `1091429 ¦ 1 minutes while 810wly blow~ng n~trogen. The 2 content trops 2 to 2.7%.
3 The experiment is repeated, using 670 ml of 5 M
. ., 4 monoethanolamine. Absorption is pract~cally the same as with 2-amino-1-butanol. However, when desorption is carried 6 out, the rich monoethanolamine solution must be boiled ant 7 strippet for 60 minutes in order for the C02 content to trop ` 8 to 2.r%. This shows that regeneration is easier with 2-amin~
9 l-butano~. -. - "
11 To the same l-liter autoclave as described in 12 Ex~mple 1, there is charged a solution of 134 g of 2-amino-13 l-butanol in 366 ml of water. Tho solution is about 3 M
14 wIth tespect to 2-amino-1-butanol. The autocIave is closed ~nd brought to 100F (37.7C); a gas mixture dontaining ~ ~ 16 0.2 mole % 2 and 99.8 mole % He i8 810wly blown through ¦ 1~ 17 the solution under a pressure of 50 psia. until gas chroma-18 tography shows that the composition of the ouegoing ga~ is ~ ~ .
19 the same as that of the entering gas. At this point, quilibrium has been reached. Analysis giv s a C02 content 21 of 8.2% and a nitrogen content~of 4.3% from which a C02/amine 22 ~olar ratio of ~.41 is calculatet. Under the same conditions, 23 a 3 N solution of monoethanolamine gives about the same 24 002/amine ratio. Under the experimental conditions, i.e., low tempera;ture and low C02 partial pressure, the 002/amine 26 ratio ~8 taken as an indication of cleanup ability.
27 The above experiment is repeatet, using the same ~ , .
28 gas mixture, but operating at 250F (121.1C), i.e., under 29 conditlons simulating desorption. Only about 2 g of 2 remain in solution in the case of 3 M 2-amino-1-butanol, 31 whereas 3 M monoethanolamine r¢tains about 6 g of C02 32 under the same conditions. This indicates that desorp~n ,- , ' 1~91429 1 is more complete in the ca~e of 2-ami -l-butanol.
3 Example 3 is repeated, using 3M 2-amino-1-propanol 4 or ~ M 2-amino-3-methyl-1-butanol. The results obtained are very similar to those obtained with-3 M 2-amino-}-butanol.
.
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. . . . ~ . ; , . . .
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,. .: . . : ..i, -:. - ..., ., - . . . .
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Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the substantial removal of car-bon dioxide from a normally gaseous mixture containing the same, which comprises:
(a) in an absorption step, contacting said nor-mally gaseous mixture with an aqueous absorbing solution containing from about 5 to about 65 weight percent of at least one mildly sterically hindered water-soluble primary monoamine defined as having a secondary carbon atom attached to the amino group to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption step is conducted at temperatures in the range from about 20° to about 100°C. and the partial pressure of the carbon dioxide in the feed gas is in the range from about 1 to about 1000 psia; and (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 50° to about 170°C. and at pressures ranging from about 1 to about 50 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of monoethanolamine under the same conditions of regeneration.
(a) in an absorption step, contacting said nor-mally gaseous mixture with an aqueous absorbing solution containing from about 5 to about 65 weight percent of at least one mildly sterically hindered water-soluble primary monoamine defined as having a secondary carbon atom attached to the amino group to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption step is conducted at temperatures in the range from about 20° to about 100°C. and the partial pressure of the carbon dioxide in the feed gas is in the range from about 1 to about 1000 psia; and (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 50° to about 170°C. and at pressures ranging from about 1 to about 50 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of monoethanolamine under the same conditions of regeneration.
2. The process of claim 1 wherein the water-soluble primary monoamine is an aminoalcohol.
3. The process of claim 2 wherein said amino alcohol is selected from the group consisting of 2-amino-1-propanol, 2-amino-1-butanol, 2-amino-3-methyl-l-butanol, 2-amino-l-pentanol, 2-amino-1-hexsnol and 2-aminocyclohexanol.
4. The process of claim 3 wherein said amino alcohol is 2-amino-l-butanol.
5. The process of claim 1 wherein the absorption step (a) takes place at temperatures ranging from about 40°
to about 60°C. and carbon dioxide partial pressures ranging from about 100 to about 500 psia, and the regeneration step (b) takes place at temperatures ranging from about 80° to about 150°C. and at pressures ranging from about 15 to about 30 psia.
to about 60°C. and carbon dioxide partial pressures ranging from about 100 to about 500 psia, and the regeneration step (b) takes place at temperatures ranging from about 80° to about 150°C. and at pressures ranging from about 15 to about 30 psia.
6. The process of claim 5 wherein the water-soluble primary monoamine is present in an amount ranging from about 15 to about 55 weight percent.
7. The process of claim 1 wherein the regenerated absorbing solution is continuously recycled.
8. The process of claim 1 wherein said absorbing solution additionally includes additives selected from the group consisting of antifoaming agents, antioxidants and corrosion inhibitors.
9. A process for the substantial removal of car-bon dioxide from a normally gaseous mixture containing the same, which comprises:
(a) in an absorption step, contacting said nor-mally gaseous mixture with an aqueous absorbing solution containing from about 15 to about 55 weight percent of 2-amino-1-butanol to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption of the carbon dioxide is carried out at temperatures ranging from about 40° to about 60°C. and carbon dioxide partial pressures ranging from about 100 to about 500 psia, and, (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 80° to about 150°C. ant at pressures ranging from about 15 to about 30 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of mono-ethanolamine under the same conditions of regeneration.
(a) in an absorption step, contacting said nor-mally gaseous mixture with an aqueous absorbing solution containing from about 15 to about 55 weight percent of 2-amino-1-butanol to absorb the carbon dioxide in said aqueous absorbing solution, wherein the absorption of the carbon dioxide is carried out at temperatures ranging from about 40° to about 60°C. and carbon dioxide partial pressures ranging from about 100 to about 500 psia, and, (b) in a regeneration step, desorbing absorbed carbon dioxide from said absorbing solution at temperatures in the range from about 80° to about 150°C. ant at pressures ranging from about 15 to about 30 psia until at least more carbon dioxide is desorbed from the absorbing solution than would be desorbed from an absorbing solution containing the same amount of mono-ethanolamine under the same conditions of regeneration.
10. The process of claim 1 wherein the regener-ated absorbing solution is continuously recycled.
11. The process of claim 9 wherein said absorb-ing solution additionally includes additives selected from the group consisting of antifoaming agents, antioxidants ant corrosion inhibitors.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US75744777A | 1977-01-06 | 1977-01-06 | |
| US757,447 | 1991-09-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1091429A true CA1091429A (en) | 1980-12-16 |
Family
ID=25047863
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA292,708A Expired CA1091429A (en) | 1977-01-06 | 1977-12-08 | Process for removing carbon dioxide containing acidic gases from gaseous mixtures |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1091429A (en) |
| NL (1) | NL7800153A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6036931A (en) * | 1992-02-27 | 2000-03-14 | The Kansai Electric Power Co., Inc. | Method for removing carbon dioxide from combustion exhaust gas |
| WO2000018492A1 (en) * | 1998-09-30 | 2000-04-06 | The Dow Chemical Company | Composition and process for removal of acid gases |
| WO2000018493A1 (en) * | 1998-09-30 | 2000-04-06 | The Dow Chemical Company | Composition and process for removal of acid gases |
| US6497852B2 (en) * | 2000-12-22 | 2002-12-24 | Shrikar Chakravarti | Carbon dioxide recovery at high pressure |
| MD20120034A2 (en) * | 2012-03-29 | 2013-09-30 | Государственный Университет Молд0 | Process for biohydrogen cleaning from impurity gases |
| MD784Z (en) * | 2012-03-29 | 2015-01-31 | Государственный Университет Молд0 | Process for biohydrogen cleaning from impurity gases |
| US20150132207A1 (en) * | 2012-05-11 | 2015-05-14 | Mitsubishi Heavy Industries, Ltd. | Complex amine absorbent, and device and method for removing one or both of co2 and h2s |
-
1977
- 1977-12-08 CA CA292,708A patent/CA1091429A/en not_active Expired
-
1978
- 1978-01-05 NL NL7800153A patent/NL7800153A/en not_active Application Discontinuation
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6036931A (en) * | 1992-02-27 | 2000-03-14 | The Kansai Electric Power Co., Inc. | Method for removing carbon dioxide from combustion exhaust gas |
| WO2000018492A1 (en) * | 1998-09-30 | 2000-04-06 | The Dow Chemical Company | Composition and process for removal of acid gases |
| WO2000018493A1 (en) * | 1998-09-30 | 2000-04-06 | The Dow Chemical Company | Composition and process for removal of acid gases |
| US6165432A (en) * | 1998-09-30 | 2000-12-26 | The Dow Chemical Company | Composition and process for removal of acid gases |
| US6207121B1 (en) | 1998-09-30 | 2001-03-27 | The Dow Chemical Company | Composition and process for removal of acid gases |
| AU749665B2 (en) * | 1998-09-30 | 2002-07-04 | Ineos Americas Llc | Composition and process for removal of acid gases |
| US6497852B2 (en) * | 2000-12-22 | 2002-12-24 | Shrikar Chakravarti | Carbon dioxide recovery at high pressure |
| MD20120034A2 (en) * | 2012-03-29 | 2013-09-30 | Государственный Университет Молд0 | Process for biohydrogen cleaning from impurity gases |
| MD784Z (en) * | 2012-03-29 | 2015-01-31 | Государственный Университет Молд0 | Process for biohydrogen cleaning from impurity gases |
| US20150132207A1 (en) * | 2012-05-11 | 2015-05-14 | Mitsubishi Heavy Industries, Ltd. | Complex amine absorbent, and device and method for removing one or both of co2 and h2s |
| US10137407B2 (en) * | 2012-05-11 | 2018-11-27 | Mitsubishi Heavy Industries Engineering, Ltd. | Complex amine absorbent, and device and method for removing one or both of CO2 and H2S |
Also Published As
| Publication number | Publication date |
|---|---|
| NL7800153A (en) | 1978-07-10 |
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