CA2059968A1 - Process for the extensive removal of acid gases from gaseous mixtures - Google Patents
Process for the extensive removal of acid gases from gaseous mixturesInfo
- Publication number
- CA2059968A1 CA2059968A1 CA 2059968 CA2059968A CA2059968A1 CA 2059968 A1 CA2059968 A1 CA 2059968A1 CA 2059968 CA2059968 CA 2059968 CA 2059968 A CA2059968 A CA 2059968A CA 2059968 A1 CA2059968 A1 CA 2059968A1
- Authority
- CA
- Canada
- Prior art keywords
- acid gases
- solvent
- weight
- promoter
- gaseous mixtures
- 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.)
- Abandoned
Links
Abstract
PROCESS FOR THE EXTENSIVE REMOVAL OF ACID GASES FROM GASEOUS MIXTURES.
ABSTRACT
A process is described for the extensive removal of acid gases such as H2S and/or CO2 from gaseous mixtures which contain them, comprising essentially absorption by a solvent and the regeneration of the spent solvent, in which the solvent consists of an aqueous mixture of dimethylethanolamine (DMEA) with a dimethylethanolamine concentration of between 30 and 70% by weight, and a promoter, produced by reacting formaldehyde with one or more polyalkylenepolyamines, in a quantity not exceeding 30% by weight of the total.
ABSTRACT
A process is described for the extensive removal of acid gases such as H2S and/or CO2 from gaseous mixtures which contain them, comprising essentially absorption by a solvent and the regeneration of the spent solvent, in which the solvent consists of an aqueous mixture of dimethylethanolamine (DMEA) with a dimethylethanolamine concentration of between 30 and 70% by weight, and a promoter, produced by reacting formaldehyde with one or more polyalkylenepolyamines, in a quantity not exceeding 30% by weight of the total.
Description
2~
PROCESS FOR THE EXTENSIVE REMOVAL OF ACID GASES FROM GASEOUS
MIXTURES
This invention relates to a process for the extensive removal of acid gases such as H2S and/or COz from gaseous mixtures by absorption.
The extensive removal of acid gases such as H2S and/or CO2 is a noted problem in industry which has as yet not found a solution always valid from both the technical and cost viewpoint. Its possible applications are numerous, a main but not exclusive example being the treatment oP synthesis gas used in NH3 preparation. The COz content of the Hz/N2 mixture concerned in this specific case can be of the order of 20% and has necessarily to be reduced to 100-500 ppm. This gas does not u~ually con-tain HzS, but in any event the specification for H2S content is very severe, being ~ 1 ppo.
The use of chemical absorption processes is well known in this field. These processes can be classified according to the type of solvent used and specifically can be divided into two basic classes:
a) the first comprises processes using aqueous solutions of primary and secondary amines such as MEA, DEA and diglycolamine;
,,, - ~, "
b) the second comprises processes using aqueous alkaline carbonate solutions activated by s~all concentrations of special compounds (promoters) such as primary and/or secondary amines, borates, amino acids etc. These favour the kinetics of the COz hydration reaction and thus its absorption by the solvent.
Both types of process are characterised essentially by two values, namely the investment cost and the operating cost per unit of acid gas eliminated. The invest~ent cost is substantially proportional to the column size (including reboiler and condenser) and hence to the required solvent throughput. Tbe operating cost is substantially proportional to the quantity of heat required to regenerate the solvent. It is also higher the greater the solvent throughput because of the greater energy consumed in pumping it.
The solvents of type a) are cnaracterised by higher operating costs than those of type b) because in the absorption stage they lead to the formation of carbaoate. The reverse reaction carried out in the regeneration column is decidedl~ more endothermic and hence more costly than that for forming bicarbonate for the - alternative solvents of type b).
Both types of process are characterised by high investment cost because the solvents have usually to be used in relatively low concentration to prevent serious corrosion phe~omena.
We have now found that the drawbacks of processes of the known art can be overcome by using as ~olvent an aqueous solution of dimethylethanolamine at suitably high concentration, to which a suitable promoter is added.
The process according to the present invention for the extensive ~ 3 --removal of acid gases such as HzS and/or C02 from daseous mi~tures which contain them, and comprising essentially the absorption of the acid gases by a solvent and the regeneration of the spent solvent by stripping, is characterised by using a solYent consisting of Pn aqueous mixture of dimethylethanolamine (DMEA) with a dimethylethanolamine concentration of between 3~ and 70% by weight, preferably between 35 and 55X, and a promoter produced by reacting formaldehyde with one or more polyalkylenepolyamines in a quantity not exceeding 30% by weight, preferably between 3 and lOg, of the total (ie of the su~ of the water, the amine and the promoter~.
The promoter production reaction is conducted preferably with a formaldehyde/polyalkylenepolyamine molar ration of between 1/10 and 1/1.
This reaction can be conducted for example by reacting in the aforesaid molar ratio~ the polyalkylenepolyamine or polyalkylene-polyamines for about 1 hour with the formaldehyde, used in the form of an approximately 35 wt~ aqueous solution, at a temperature which is initially maintained around lOO C and is then progressively increased to a temperature around the boiling point of the polyalkylenepolyamine or polyalkylenepolyamines used.
The chosen polyalkylenepolyamines are preferably diethylenetriamine ~nd/or triethylenetetramine and/or tetraethylenepentamine. The analogous propylenepolyamines can also be used.
The product of the reaction between formaldehyde and a polyalkylenepolyamine can be easily regenerated thermally, so .
, 2~
oYercoming the stated difficulties encountered in directly using as promoter a polyalkylenepolyamine as such, such as tetraethylenepentamine or tetrapropylenepentamine iUS 4112050/US
4217237). This benefit is not penali~ed either by a reduction in the absorption capacity of the solution or by a reduction in its actual absorption kinetics.
A scheme for implementing the process according to the invention is described hereinafter by way of non-limiting example with reference to the Figure.
The gas to be treated is fed through the line 1 to the absorber 2, to which the absorbent solution is fed, a few plates below its top, through the line 3. The treated gas, having a very low H2S
content (< 1 ppm) and C02 content (~ 100 ppm), is withdrawn from the top through the line 4.
The spent solution 6 is discharged from the bottom and is fed to the regeneration column 12 after depressurization and preheating in 11.
To remove any small amine concentrations present in the gas, a water stream is fed $o the top of the column through the line 5.
This can be either fresh water or contain water-soluble high boiling acid compounds (organic or inorganic) haYing an acidity such that it can react with a basic compound such as dimethyl ethanol-amine without forming a particularly stable compound of poor water solubility which is difficult and costly to regenerate.
Malonic, succinic, oxalic, glmtaric, tetraboric and glycolic acid are non-limiting examples.
The fresh water (making up the balance between the gaseous streams a~
leaving and entering the cycle, ie [4~9] -[1]) is fed from the line 28. If required, the acidified water is fed from the line 27.
If only fresh water is used, no chimney plate is required in the upper section of the absorber and no regeneration circuit is required for the side stream 7 discharged from this plate. The column arrangement is the usual one for an absorber comprising a water stripping section at the top of the column.
If water acidified with a suitable additive is used, this additive and the DMEA must be recovered by the hot low pressure regeneration system ~reboiler 24) indicated schematically by 15.
The amine is recovered from the head of this (condenser 23, phase separator 16) and is recycled to the absorber through the lines 20 and 3. The aqueous acid solution~is recovered from its bottom an 16 is reused at the top of the column 2.
The vapour leaving the regenerator 12 i cooled in 21 and separated in 8 into a gaseous stresm 9 ~acid gases removed) and a liquid stream 10 (reflux aqueous phase).
- The solvent 14 discharged from the reboiler 13 is recycled by the pump 26 to near the top of the absorber 2. The absorber can be provided with supplementary intermediate heat exchangers 29 if strict temperature control i~ necessary.
Two examples are given below, one of which is comparative, for the purpo~e of better illustrating the invention but without in any way limiting it.
The process is carried out in a column comprising 44 two-cap ,, 3~
plates and of 2" diameter using a mi~ture consisting of 50/50 by weight of DMEA/water. The feed gas (2 Nm3/h) contains 21.8% of - C02 and has a total pressure of 70 kg/cm2. Operating with a bottom temperature of 70C and top temperature of 0'C, the treated gas has a residual COz content of 0.5 volX for a solvent flow of 4.0 kg/h Operating in the same column with a feed gas containing 22% of C02 and at substantially the same temperature and pressure conditions but with a solvent stream consisting of 46 wt% of DMEA, 6 wt% of the product of the reaction between formaldehyde and tetra-ethylenepentamine in a 1:2 molar ratio and 48 wtX of water, and at a flow rate of 4.1 kg/h, an overhead gas having a C02 content of <
100 ppm is obtained.
The use of said promoter enables a significantly tighter specification (about 50 times) to be satisfied while using a substantially equal solvent throughput in both cases.
'' ' ' ' " - - ...
PROCESS FOR THE EXTENSIVE REMOVAL OF ACID GASES FROM GASEOUS
MIXTURES
This invention relates to a process for the extensive removal of acid gases such as H2S and/or COz from gaseous mixtures by absorption.
The extensive removal of acid gases such as H2S and/or CO2 is a noted problem in industry which has as yet not found a solution always valid from both the technical and cost viewpoint. Its possible applications are numerous, a main but not exclusive example being the treatment oP synthesis gas used in NH3 preparation. The COz content of the Hz/N2 mixture concerned in this specific case can be of the order of 20% and has necessarily to be reduced to 100-500 ppm. This gas does not u~ually con-tain HzS, but in any event the specification for H2S content is very severe, being ~ 1 ppo.
The use of chemical absorption processes is well known in this field. These processes can be classified according to the type of solvent used and specifically can be divided into two basic classes:
a) the first comprises processes using aqueous solutions of primary and secondary amines such as MEA, DEA and diglycolamine;
,,, - ~, "
b) the second comprises processes using aqueous alkaline carbonate solutions activated by s~all concentrations of special compounds (promoters) such as primary and/or secondary amines, borates, amino acids etc. These favour the kinetics of the COz hydration reaction and thus its absorption by the solvent.
Both types of process are characterised essentially by two values, namely the investment cost and the operating cost per unit of acid gas eliminated. The invest~ent cost is substantially proportional to the column size (including reboiler and condenser) and hence to the required solvent throughput. Tbe operating cost is substantially proportional to the quantity of heat required to regenerate the solvent. It is also higher the greater the solvent throughput because of the greater energy consumed in pumping it.
The solvents of type a) are cnaracterised by higher operating costs than those of type b) because in the absorption stage they lead to the formation of carbaoate. The reverse reaction carried out in the regeneration column is decidedl~ more endothermic and hence more costly than that for forming bicarbonate for the - alternative solvents of type b).
Both types of process are characterised by high investment cost because the solvents have usually to be used in relatively low concentration to prevent serious corrosion phe~omena.
We have now found that the drawbacks of processes of the known art can be overcome by using as ~olvent an aqueous solution of dimethylethanolamine at suitably high concentration, to which a suitable promoter is added.
The process according to the present invention for the extensive ~ 3 --removal of acid gases such as HzS and/or C02 from daseous mi~tures which contain them, and comprising essentially the absorption of the acid gases by a solvent and the regeneration of the spent solvent by stripping, is characterised by using a solYent consisting of Pn aqueous mixture of dimethylethanolamine (DMEA) with a dimethylethanolamine concentration of between 3~ and 70% by weight, preferably between 35 and 55X, and a promoter produced by reacting formaldehyde with one or more polyalkylenepolyamines in a quantity not exceeding 30% by weight, preferably between 3 and lOg, of the total (ie of the su~ of the water, the amine and the promoter~.
The promoter production reaction is conducted preferably with a formaldehyde/polyalkylenepolyamine molar ration of between 1/10 and 1/1.
This reaction can be conducted for example by reacting in the aforesaid molar ratio~ the polyalkylenepolyamine or polyalkylene-polyamines for about 1 hour with the formaldehyde, used in the form of an approximately 35 wt~ aqueous solution, at a temperature which is initially maintained around lOO C and is then progressively increased to a temperature around the boiling point of the polyalkylenepolyamine or polyalkylenepolyamines used.
The chosen polyalkylenepolyamines are preferably diethylenetriamine ~nd/or triethylenetetramine and/or tetraethylenepentamine. The analogous propylenepolyamines can also be used.
The product of the reaction between formaldehyde and a polyalkylenepolyamine can be easily regenerated thermally, so .
, 2~
oYercoming the stated difficulties encountered in directly using as promoter a polyalkylenepolyamine as such, such as tetraethylenepentamine or tetrapropylenepentamine iUS 4112050/US
4217237). This benefit is not penali~ed either by a reduction in the absorption capacity of the solution or by a reduction in its actual absorption kinetics.
A scheme for implementing the process according to the invention is described hereinafter by way of non-limiting example with reference to the Figure.
The gas to be treated is fed through the line 1 to the absorber 2, to which the absorbent solution is fed, a few plates below its top, through the line 3. The treated gas, having a very low H2S
content (< 1 ppm) and C02 content (~ 100 ppm), is withdrawn from the top through the line 4.
The spent solution 6 is discharged from the bottom and is fed to the regeneration column 12 after depressurization and preheating in 11.
To remove any small amine concentrations present in the gas, a water stream is fed $o the top of the column through the line 5.
This can be either fresh water or contain water-soluble high boiling acid compounds (organic or inorganic) haYing an acidity such that it can react with a basic compound such as dimethyl ethanol-amine without forming a particularly stable compound of poor water solubility which is difficult and costly to regenerate.
Malonic, succinic, oxalic, glmtaric, tetraboric and glycolic acid are non-limiting examples.
The fresh water (making up the balance between the gaseous streams a~
leaving and entering the cycle, ie [4~9] -[1]) is fed from the line 28. If required, the acidified water is fed from the line 27.
If only fresh water is used, no chimney plate is required in the upper section of the absorber and no regeneration circuit is required for the side stream 7 discharged from this plate. The column arrangement is the usual one for an absorber comprising a water stripping section at the top of the column.
If water acidified with a suitable additive is used, this additive and the DMEA must be recovered by the hot low pressure regeneration system ~reboiler 24) indicated schematically by 15.
The amine is recovered from the head of this (condenser 23, phase separator 16) and is recycled to the absorber through the lines 20 and 3. The aqueous acid solution~is recovered from its bottom an 16 is reused at the top of the column 2.
The vapour leaving the regenerator 12 i cooled in 21 and separated in 8 into a gaseous stresm 9 ~acid gases removed) and a liquid stream 10 (reflux aqueous phase).
- The solvent 14 discharged from the reboiler 13 is recycled by the pump 26 to near the top of the absorber 2. The absorber can be provided with supplementary intermediate heat exchangers 29 if strict temperature control i~ necessary.
Two examples are given below, one of which is comparative, for the purpo~e of better illustrating the invention but without in any way limiting it.
The process is carried out in a column comprising 44 two-cap ,, 3~
plates and of 2" diameter using a mi~ture consisting of 50/50 by weight of DMEA/water. The feed gas (2 Nm3/h) contains 21.8% of - C02 and has a total pressure of 70 kg/cm2. Operating with a bottom temperature of 70C and top temperature of 0'C, the treated gas has a residual COz content of 0.5 volX for a solvent flow of 4.0 kg/h Operating in the same column with a feed gas containing 22% of C02 and at substantially the same temperature and pressure conditions but with a solvent stream consisting of 46 wt% of DMEA, 6 wt% of the product of the reaction between formaldehyde and tetra-ethylenepentamine in a 1:2 molar ratio and 48 wtX of water, and at a flow rate of 4.1 kg/h, an overhead gas having a C02 content of <
100 ppm is obtained.
The use of said promoter enables a significantly tighter specification (about 50 times) to be satisfied while using a substantially equal solvent throughput in both cases.
'' ' ' ' " - - ...
Claims (5)
1. A process for the extensive removal of acid gases such as H2S and/or CO2 from gaseous mixtures which contain them, comprising essentially the absorption of the acid gases by a solvent and the regeneration of the spent solvent by stripping, characterised by using a solvent consisting of an aqueous mixture of dimethylethanolamine (DMEA) with a dimethylethanolamine concentration of between 30 and 70% by weight, and a promoter, produced by reacting formaldehyde with one or more polyalkylenepolyamines, in a quantity not exceeding 30% by weight of the total.
2. A process as claimed in claim 1, wherein the concentration of DMEA in the aqueous solution is between 35 and 55% by weight.
3. A process as claimed in claim 1, wherein the promoter quantity is between 3 and 10% by weight of the total.
4. A process as claimed in claim 1, wherein the chosen polyalkylenepolyamines are diethylenetriamine and/or triethylenetetramine and/or tetra-ethylenepentamine.
5. A process as claimed in claim 1, wherein the reaction for preparing the promoter is conducted with a formaldehyde/
polyalkylenepolyamine molar ratio of between 1/10 and 1/1.
polyalkylenepolyamine molar ratio of between 1/10 and 1/1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ITAO910170 | 1991-01-24 | ||
| IT91A000170 | 1991-10-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2059968A1 true CA2059968A1 (en) | 1992-07-25 |
Family
ID=28460718
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2059968 Abandoned CA2059968A1 (en) | 1991-01-24 | 1992-01-23 | Process for the extensive removal of acid gases from gaseous mixtures |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2059968A1 (en) |
-
1992
- 1992-01-23 CA CA 2059968 patent/CA2059968A1/en not_active Abandoned
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1090098A (en) | Removal of co.sub.2 and/or h.sub.2s and/or cos from gases containing these constituents | |
| US4999031A (en) | Removing CO2 and, if necessary, H2 S from gases | |
| EP0368423B1 (en) | Removal and recovery of sulphur dioxide from gas streams | |
| GB2252307A (en) | Process for the removal of acid gases from gaseous mixtures | |
| US5733516A (en) | Process for removal of hydrogen sulfide from a gas stream | |
| EP1059109B1 (en) | Carbon dioxide recovery with composite amine blends | |
| US6939393B2 (en) | Method for neutralizing a stream of fluid, and washing liquid for use in one such method | |
| EP1654052B1 (en) | Low energy so2 scrubbing process | |
| WO2002009849A2 (en) | Method and installation for the recovery of pure co2 from flue gas | |
| US20110146489A1 (en) | Ammonia removal, following removal of co2, from a gas stream | |
| EP0215505B1 (en) | Removing h2s from a sour gaseous stream | |
| JP2003535209A (en) | Deoxidation of hydrocarbon fluid streams. | |
| Appl et al. | Removal of CO2 and/or H2S and/or COS from gases containing these constituents | |
| AU2012210998B2 (en) | Method for removing heat stable base salts from a contaminated basic solution, and use thereof in a process for recovering acid gas from an acid gas stream | |
| EP0013151B1 (en) | Process for maintaining the performance of aqueous hindered amine scrubbing liquid in acid gas scrubbing | |
| CA1291627C (en) | Removal of acid gases from a sour gaseous stream | |
| EP0067013B1 (en) | Process for removal of cyclic urea reaction product from amine gas - treating solution | |
| JPH01231921A (en) | Tertiary alkanolamine absorbent containing ethyleneamine promoter and its use | |
| CA1085590A (en) | Process for the removal of acid gases | |
| US4871520A (en) | Process and composition for H2 S removal | |
| US3959451A (en) | Recovery of sulfur dioxide from gas mixtures | |
| CA2059968A1 (en) | Process for the extensive removal of acid gases from gaseous mixtures | |
| GB2252308A (en) | Process for removing acid gases from gaseous mixtures | |
| EP0956141B1 (en) | Amine heat stable salt neutralization having reduced solids | |
| EP0125358B1 (en) | A non-sterically hindered - sterically hindered amino co-promoted acid gas scrubbing solution and a process for using same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |