Hydrogen sulfide is removed from a gas stream by bubbling a gas stream having ≥100 ppm hydrogen sulfide through a scavenging mixture. The scavenging mixture includes: 1) at least one sweetener selected from the group consisting of triazines, oxazolidines, hemiacetals, and mixtures thereof, and 2) at least one reaction catalyst selected from the group consisting of dipropyl amine (DPA), diethyl amine (DEA), dimethyl amine (DMA), pyrrole, and mixtures thereof. The scavenging mixture interacts with the hydrogen sulfide to produce a cleaned gas stream having ≤ 5 ppm hydrogen sulfide.

A composite amine absorbent according to the present invention is an absorbent for absorbing CO.sub.2 or H.sub.2S, or both of CO.sub.2 and H.sub.2S in a gas. The absorbent is obtained by dissolving (1) a linear monoamine, (2) a diamine, and (3) propylene glycol alkyl ether, for example, represented by the following chemical formula (I) in water. In the composite amine absorbent, the components complexly interact, and the synergistic effect thereof provides good absorbability of CO.sub.2 or H.sub.2S, or both of CO.sub.2 and H.sub.2S and good releasability of CO.sub.2 or H.sub.2S absorbed during regeneration of the absorbent. Furthermore, the amount of water vapor in a reboiler 26 used during regeneration of the absorbent in a CO.sub.2 recovery unit 12 can be reduced.
R.sup.1—O—(R.sup.2—O).sub.n—R.sup.3  (I)

The invention relates to a low-cost and high-efficiency absorption-desorption decoupling method for contaminant-CO.sub.2 synergistic capture. According to the method, an optimization model of absorption-desorption decoupling control for contaminant-CO.sub.2 synergistic capture under different working conditions is built, the optimization objective is to obtain high-purity liquid contaminants and CO.sub.2 at low cost and efficiently, and an adaptive penalty function is constructed to transform a solution of a constrained optimization problem into that of an unconstrained optimization problem, thereby controlling parameters in a real-time, precise and stable manner. Moreover, supported by means of flue gas pre-scrubbing and cooling, multi-stage intercooling and column-top demisting, the method of the present invention achieves efficient capture of contaminants and CO.sub.2. According to the invention, the absorption process is decoupled from the desorption process, and the coordinated control of temperature-pH-liquid-gas ratio and rich liquid flow-desorption temperature in all cycles is carried out to realize the synergistic capture-regeneration-concentration of contaminants and CO.sub.2 with high efficiency and low energy consumption, thereby reducing the high cost of the traditional method where a flue gas cleaning system and a carbon capture system operate separately.

An aqueous solvent composition is provided, comprising a nucleophilic component having one or more sterically unhindered primary or secondary amine moieties, a Brønsted base component having one or more basic nitrogen moieties, a water-soluble organic solvent, and water. A biphasic composition is provided, comprising one or more carbamate compounds, one or more conjugate acids of Brønsted base, a water-soluble organic solvent, and water. A biphasic CO.sub.2 absorption process is also provided, utilizing the biphasic solvent composition.

The present invention relates to a process for removing acid compounds contained in a gaseous effluent which consists in bringing a gaseous effluent into contact, in the absorption column, with an absorbent solution comprising water, between 20% and 28% by weight of pentamethyldipropylenetriamine and between 5% and 35% by weight of N-methyldiethanolamine.

To provide a carbon dioxide separation composition which is excellent in carbon dioxide desorption efficiency (desorption amount/absorption amount) and durability to nitrogen oxides, and a method for separating carbon dioxide.

A carbon dioxide separation composition, containing at least one amine compound selected from the group consisting of an amine compound represented by the following formula (1):

##STR00001## wherein R.sup.1 to R.sup.3 each independently represent a hydrogen atom or a C.sub.1-4 alkyl group, and an amine compound represented by the following formula (2):

##STR00002## wherein R.sup.10, R.sup.11, R.sup.12, R.sup.13 and R.sup.14 each independently represent a hydrogen atom, a C.sub.1-4 alkyl group, a hydroxy group, a hydroxymethyl group, a 2-hydroxyethyl group or a C.sub.1-4 alkoxy group, a and b are each independently 0 or 1 and satisfy the relation a+b=1, and R.sup.15 is a hydrogen atom, a C.sub.1-4 alkyl group, a methoxymethyl group, a methoxyethoxymethyl group or a 2-hydroxyethyl group.

Provided is a method of introducing a scavenger composition into a fluid contaminated with a sulfur contaminant, mixing the scavenger composition with the fluid in a vessel, and recovering the fluid containing a reduced amount of sulfur contaminant from the effluent. The scavenger composition comprises a hydrogen sulfide scavenger and a linear anionic polymer. The linear anionic polymer is present in an amount of about 0.1% to about 50% by weight of the scavenger composition and has a number average molecular weight of about 1.0×10.sup.3 to about 2.0×10.sup.4 Daltons.

Disclosed is an adsorbent containing a metal oxide for adsorption of hydrogen sulfide in biogas, and a biogas purification system using the same.

The invention provides a method for the capture of at least one acid gas in a composition, the release of said gas from said composition and the subsequent regeneration of said composition for re-use. The method comprises the step of capturing an acid gas by contacting said acid gas with a capture composition comprising at least one salt of a carboxylic acid dissolved in a solvent system consisting substantially of water.

Disclosed is a process comprising: step a) contacting a feed stream comprising a contaminant with an absorbent stream in a counter-current flow to produce a contaminant depleted product stream depleted in the molar quantity of the contaminant relative to the molar quantity of said contaminant in the feed stream, and a contaminant enriched absorbent stream enriched in the molar quantity of the contaminant relative to the molar quantity of said contaminant in the absorbent stream; and step b) treating the contaminant enriched absorbent stream to form a gaseous stream comprising said contaminant and a regenerated absorbent stream lean in the molar quantity of said contaminant relative to the molar quantity of said contaminant in the contaminant enriched absorbent stream; herein said absorbent stream comprises at least 15 wt. % of at least one compound (A) of general formula (I) or a mixture (M) comprising at least one compound (B) of general formula (II) and at least one compound (C) of general formula (III).