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US 5,292,493 AGranted
Clean up of ethanolamine solution by treating with weak ion exchange resins
AssigneeMobil Oil Corporation
InventorsCostandi A. Audeh, Tsoung Y. Yan
Life of this patent
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Abstract
The present invention provides a process for removing heat stable salts which accumulate in alkanolamine gas purification process units. Surprisingly, it has been found that weakly acidic cationic exchange resins are dramatically more effective for removing heat stable salts from alkanolamine solutions than strongly acidic cationic exchange resins. Specifically, it has been found in accordance with the invention that ion exchange resins are useful for purifying used aqueous alkanolamine solutions, in the following order of preference: Weak Acid IX>Weak Base IX>Strong Acid IX>Strong Base IX.
Claims13
A process for rejuvenating a spent aqueous alkanolamine solution comprising the steps of:
- (a) providing an aqueous alkanolamine solution having alkanolamine concentration sufficient to effectively sorb H.sub.2 S, CO.sub.2, or both from a gaseous hydrocarbon stream having H.sub.2 S, CO.sub.2, or both dissolved therein;
- (b) continuously contacting said aqueous alkanolamine solution with said hydrocarbon gas stream of step (a) whereby salts are accumulated in said aqueous alkanolamine solution, said salts exerting a deleterious effect on the acid gas sorption capacity of said aqueous alkanolamine solution;
- (c) contacting said aqueous alkanolamine solution of step (b) with a weak cationic exchange resin having a pKa of from about 1 to about 7 for time sufficient to sorb from said aqueous alkanolamine solution at least a portion of said accumulated salts;
- (d) repeating steps (b) and (c) to maintain the acid gas sorption capacity of said aqueous alkanolamine solution at a substantially constant value in the absence of fresh makeup alkanolamine;
- (e) regenerating said weak cationic exchange resins with an aqueous solution of (NH.sub.4).sub.2 CO.sub.3, NH.sub.4 HCO.sub.3, NH.sub.4 OH or a mixture thereof;
- and
- (f) removing counter-ions introduced by said regeneration solution by stripping said aqueous alkanolamine solution with steam and recycling said steam-stripped alkanolamine solution to step (b), wherein the corrosion rate in the presence of carbon steel is less than the same process using other ion exchange resins.
4 more elements
A process for purifying a hydrocarbon gas stream containing H.sub.2 S, CO.sub.2, or both comprising the steps of:
- (a) providing a hydrocarbon gas stream containing H.sub.2 S, CO.sub.2, or both;
- (b) contacting said hydrocarbon gas stream of step (a) with an aqueous alkanolamine solution having alkanolamine concentration sufficient to effectively sorb H.sub.2 C, CO.sub.2, or both from said hydrocarbon gas stream of step (a);
- (c) accumulating salts in said aqueous alkanolamine solution of step (b) to evolve a spent aqueous alkanolamine solution having decreased sorption affinity for H.sub.2 S, CO.sub.2, or both;
- (d) contacting said spent aqueous alkanolamine solution of step (c) with a weak cationic exchange resin having a pKa of from about 1 to about 7 for time sufficient to at least partially purify said aqueous alkanolamine solution to provide an intermediate stream having greater acid gas sorption affinity than said spent aqueous alkanolamine solution of step (c);
- (e) contacting said intermediate stream of step (d) with a weak anionic exchange resin having a pKa of from about 7 to about 14 for time sufficient to sorb from said intermediate stream of step (d) at least a portion of said accumulated salts to form a purified aqueous alkanolamine solution having greater acid gas sorption affinity than said intermediate stream of step (d);
- (f) recycling said purified aqueous alkanolamine solution of step (e) to said contacting step (b);
- (g) regenerating said weak cationic exchange resin and said weak anionic exchange resin with an aqueous regeneration solution of (NH.sub.4).sub.2 CO.sub.3, NH.sub.4 HCO.sub.3, NH.sub.4 OH, or a mixture thereof;
- (h) continuously repeating steps (b) through (g);
- and
- (i) removing counter-ions introduced by said generation solution by stripping said aqueous alkanolamine solution with steam and recycling said steam-stripped alkanolamine solution to step (b), wherein the corrosion rate in the presence of carbon steel is less than the same process using other ion exchange resins.
7 more elements
A continuous process for purifying a hydrocarbon gas stream containing H.sub.2 S, CO.sub.2, or both comprising the steps of:
- (a) providing a hydrocarbon gas stream containing H.sub.2 S, CO.sub.2, or both;
- (b) contacting said hydrocarbon gas stream of step (a) with an aqueous diethanolamine solution having diethanolanine concentration sufficient to effectively sorb H.sub.2 S, CO.sub.2, or both from said hydrocarbon gas stream of step (a);
- (c) accumulating salts in said aqueous diethanolamine solution of step (b) to evolve a spent aqueous diethanolamine solution having decreased sorption affinity for H.sub.2 S, CO.sub.2, or both;
- (d) contacting said spent aqueous diethanolamine solution of step (c) with a weak cationic exchange resin having a pKa of from about 1 to about 7 for time sufficient to sorb from said aqueous diethanolamine solution at least a portion of said accumulated salts to form a purified aqueous diethanolamine solution having greater acid gas sorption affinity than said spent aqueous diethanolamine solution of step (c);
- (e) recycling said purified aqueous diethanolamine solution of step (d) to said contacting step (b);
- (f) repeating steps (b) through (e) until said weak cationic exchange resin is deactivated;
- (g) regenerating said weak cationic exchange resin by contacting said weak cationic exchange resin aqueous solution containing at least one selected from the group consisting of (NH.sub.4).sub.2 CO.sub.3, NH.sub.4 HCO.sub.3 and NH.sub.4 OH;
- and
- (h) repeating steps (b) through (g) with said regenerated weak cationic exchange resin of step (g), wherein the corrosion rate in the presence of carbon steel is less than the same process using other ion exchange resins.
6 more elements
A method for mitigating the corrosivity of an aqueous diethanolamine solution comprising the steps of:
- (a) providing an aqueous diethanolamine solution characterized by a first rate of corrosive attack, R.sub.1, on A.S.T.M. 1018 carbon steel;
- (b) circulating said aqueous diethanolamine solution of step (a) in contact with a hydrocarbon gas having H.sub.2 S, CO.sub.2, or both dissolved therein to remove H.sub.2 S, CO.sub.2, or both from said hydrocarbon gas thereby altering the composition of said aqueous diethanolamine solution to increase the rate of corrosive attack of said aqueous diethanolamine solution on A.S.T.M. 1018 carbon steel to a second rate of corrosive attack, R.sub.2 ;
- (c) withdrawing a portion of said circulating aqueous diethanolamine solution of step (b);
- (d) contacting said withdrawn aqueous diethanolamine solution of step (c) with a weak cationic exchange resin having a pKa of from about 2 to about 6 to evolve a rejuvenated aqueous diethanolamine solution exhibiting a third rate of corrosive attack on A.S.T.M. 1018 carbon steel, R.sub.3, wherein R.sub.1 <R.sub.3 <R.sub.2 ;
- (e) continuously recycling said rejuvenated aqueous diethanolamine solution of step (d) to said circulating step (b).
- (f) repeating steps (b) through (e) until said weak cationic exchange resin is deactivated;
- (g) regenerating said weak cationic exchange resin by contacting said weak cationic exchange resin aqueous solution containing at least one selected from the group consisting of (NH.sub.4).sub.2 CO.sub.3, NH.sub.4 HCO.sub.3 and NH.sub.4 OH;
- and
- (h) repeating steps (b) through (g) with said regenerated weak cationic exchange resin of step (g), wherein the corrosion rate in the presence of carbon steel is less than the same process using other ion exchange resins.
6 more elements
Dependencies are inferred from the claim text.