Systems and methods for converting BHEEU to DGA are provided. An exemplary system includes an amine unit; a reclaimer configured to receive a lean DGA stream including BHEEU and DGA exiting the amine unit and a reclaimer steam stream to convert at least a portion of the BHEEU to DGA; a sparge line connected a steam source and to the reclaimer configured to introduce sparge steam to restore accumulated DGA at the bottom of the reclaimer; and an output stream comprising DGA.

Disclosed are a carbon dioxide absorbent composition in which an N-alkylaminoalkanol; a polyhydroxyamine-based compound; and ethylenediamine and/or diethylenetriamine are mixed, a method for preparing the same, and a method and an apparatus for carbon dioxide absorption/separation using the same. Since the carbon dioxide absorbent according to the present disclosure has superior carbon dioxide absorption capacity and remarkably lower absorbent recycling temperature as compared to the existing absorbents such as monoethanolamine, etc., total energy consumption in the capturing process can be reduced greatly. In addition, since carbon dioxide is recovered at low recycling temperature, contamination by water or absorbent vapor may be prevented.

A natural gas refining apparatus including a first separation membrane unit including a first separation membrane; and a second separation membrane unit provided in a subsequent stage of the first separation membrane unit. The second separation membrane unit includes a second separation membrane that allows an amine solution to circulate through the second separation membrane unit, and the natural gas refining apparatus refines raw natural gas containing CO.sub.2 by passing the raw natural gas through the first and second separation membrane units, separating CO.sub.2-rich gas with the first and second separation membranes, and absorbing CO.sub.2 with the amine solution circulating through the second separation membrane unit.

An absorbing liquid which absorbs the CO.sub.2 or H.sub.2S or both contained in a gas, and which comprises 1) at least one tertiary-monoamine main agent selected from a tertiary-monoamine group and 2) at least one secondary-diamine first additive selected from a secondary-diamine group, the secondary-diamine concentration being within the range of 0.05 to 0.5 in terms of the additive concentration index represented by the following expression (I).

(Additive concentration index)=[(secondary-diamine acid dissociation index) (pKa)/(tertiary-monoamine acid dissociation index) (pKa)](index ratio)×[(secondary-diamine molar concentration) (mol/L)/(tertiary-monoamine molar concentration) (mol/L)](molar ratio)  (I).

According to embodiment, a carbon dioxide capturing system cools a regenerator discharge gas discharged from a regenerator 5 containing carbon dioxide by a cooling unit 8, and then sends the gas to a cleaner 9. The cleaner 9 receives condensed water generated from the regenerator discharge gas cooled by the cooler 9, and a gaseous cooled regenerator discharge gas, and cleans the cooled regenerator discharge gas by a cleaning liquid. The cleaner 9 has a first liquid reservoir 9b configured to store the condensed water, and a second liquid reservoir 9c configured to store the cleaning liquid having cleaned the cooled regenerator discharge gas.

The present invention relates to a method for using, as a carbon dioxide absorbent, a secondary amine having a nitrile group, that is, a 3-(alkylamino)propionitrile compound. The absorbent based on the 3-(alkylamino)propionitrile compound and the carbon dioxide absorption method and separation method using same, according to the present invention, not only have an excellent carbon dioxide absorption capacity and a rapid carbon dioxide absorption rate, but also allow absorbent regeneration even at a considerably low temperature compared with a conventional alkanolamine-based absorbent and thus can significantly reduce the entire energy consumption required for an absorption process, and can also prevent recovered carbon dioxide from being contaminated with moisture and absorbent vapor, owing to the low regeneration temperature.

Disclosed is a process for regenerating a hybrid solvent used to remove contaminants from a fluid stream and to provide an improved yield of purified fluid. Said process comprises at least one purification unit (12) and at least one regeneration unit (40) wherein condensed water 62 from the regeneration unit is recycled back into the purification unit and none of the condensed water is reintroduced into the regeneration unit.

The present invention relates to an apparatus and method for recovering carbon dioxide (hereinafter also referred to as “CO.sub.2”) contained in a combustion exhaust gas, and more specifically relates to: an apparatus and method for reactively absorbing CO.sub.2 contained in a combustion exhaust gas into an amine compound-containing absorption liquid; an apparatus and method for desorbing CO.sub.2 contained in an amine compound-containing absorption liquid from the amine compound-containing absorption liquid; an apparatus and method for evaporating and separating impurities from the amine compound-containing absorption liquid containing the impurities; an apparatus and method for performing a pretreatment such as desulfurization, dust removal, and cooling on a combustion exhaust gas; and a carbon dioxide-recovering apparatus and method utilizing the above apparatuses and methods.

The invention relates to a method of selectively removing hydrogen sulfide H.sub.2S from a gaseous effluent comprising at least H.sub.2S and CO.sub.2, wherein a stage of selective absorption of hydrogen sulfide over CO.sub.2 is carried out by contacting said effluent with a solution comprising (a) water and (b) at least the following diamine: 1,2-bis(2-dimethylaminoethoxy)ethane ##STR00001##
and wherein the absorption selectivity is controlled by adding (c) a viscosifying compound to the absorbent solution.

A process for removing hydrogen sulfide and carbon dioxide from a fluid stream comprises a) an absorption step in which the fluid stream is contacted with an absorbent comprising an aqueous solution (i) of an amine of the general formula (I)

##STR00001##

in which R.sub.1, R.sub.2 and R.sub.3 are each independently selected from C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; each R.sub.4 is independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; each R.sub.5 is independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; X is OH or NH(CR.sub.1R.sub.2R.sub.3); m is 2, 3, 4 or 5; n is 2, 3, 4 or 5; and o is 0 or 1; and optionally (ii) at least one tertiary amine, where the molar ratio of (i) to (ii) is greater than 0.05; wherein at least 90% of the hydrogen sulfide is removed from the fluid stream and selectivity for hydrogen sulfide over carbon dioxide is not greater than 8, wherein a CO.sub.2- and H.sub.2S-laden absorbent is obtained; b) a regeneration step in which at least a substream of the CO.sub.2- and H.sub.2S-laden absorbent is regenerated and a regenerated absorbent is obtained; and c) a recycling step in which at least a substream of the regenerated absorbent is recycled into the absorption step a). The process allows a high level of hydrogen sulfide removal with a simultaneously high coabsorption of carbon dioxide.