Hydrogen sulfide is scrubbed from a gas stream to prepare dissolved alkali metal sulfide or hydrosulfide, which is used to prepare feed electrolyte solution for electrochemical processing to generate alkali metal hydroxide in catholyte and polysulfide in anolyte, which may be recovered from an electrochemical reactor and which may be subjected to further processing to precipitate elemental sulfur. Aqueous scrubbing solution may include alkali metal carbonate capture agent to capture hydrogen sulfide in alkali metal bicarbonate The gas stream may include carbon dioxide in addition to hydrogen sulfide, and a ratio of dissolved alkali metal carbonate to bicarbonate may be increased prior to electrochemical processing.

The present disclosure includes systems and methods that integrate a flare gas recovery process with a gas sweetening process used in oil and gas refining. A flare gas recovery system includes a primary gas sweetening unit and a liquid-driven ejector in continuous fluid communication with the primary gas sweetening unit. The ejector includes an inlet configured to receive a motive fluid including a regenerable amine solvent in a lean state from the primary gas sweetening unit, a gas inlet configured to receive a suction fluid including a gas, and a fluid outlet configured to either directly or indirectly discharge to the primary gas sweetening unit a two-phase fluid including a mixture of the suction fluid and the amine solvent in a rich state.

Method for extracting a gas from a gas mixture by: during a purification step, bringing a first sorption medium into contact with the gas mixture in order to extract the gas from the gas mixture, whereby an enriched first sorption medium is formed in which the gas is at least partially sorbed; during a regeneration step, bringing a second sorption medium into contact with the enriched first sorption medium in order to extract the gas from the enriched liquid first sorption medium; whereby for the contact in the purification step and/or in the regeneration step use is made of a separate venturi ejector.

Provided are a reclaimer 51 that introduces, through a branch line L.sub.11, and stores a part 17a of an absorbent 17 regenerated in a regenerator of a recovery unit that recovers CO.sub.2 or H.sub.2S in a gas, a first alkaline agent supply section 53A that supplies an alkaline agent 52 to the reclaimer 51, a heating section 54 that heats the absorbent 17 stored in the reclaimer 51 and to which the alkaline agent 52 has been mixed to obtain recovered vapor 61, a first vapor cooler 55A that cools the recovered vapor 61 discharged from the reclaimer 51 through a vapor line L.sub.12, a first gas-liquid separator 56A that separates a coexisting substance 62 entrained in the cooled recovered vapor 61 into a recovered absorption agent vapor (gas) 17b and the liquid coexisting substance 62 by gas-liquid separation, and an introduction line L.sub.13 that introduces the recovered absorption agent vapor 17b separated in the first gas-liquid separator 56A into a regenerator 20.

An absorbent is prepared by dissolving in water 1) monoethanolamine (MEA) and 2) a primary amine represented by the following formula (1) and having high steric hindrance. Releasability of CO.sub.2 or H.sub.2S during regeneration of the absorbent is thereby improved, and the amount of water vapor used during regeneration of the absorbent in a facility for recovering CO.sub.2 or H.sub.2S can be reduced. ##STR00001##
R.sub.1 to R.sub.3: H or a hydrocarbon group having 1 to 3 carbon atoms, at least one of R.sub.1 to R.sub.3 being a hydrocarbon.

Disclosed are systems and methods which provide a process stream comprising a gaseous component, capture the gaseous component from the process stream by an ionic liquid solvent of a separator, and recover a captured gaseous component from the ionic liquid solvent in a regenerator. A second gaseous component from the process stream may be captured by the ionic liquid solvent of the separator, and the second gaseous component may be recovered from the ionic liquid solvent in the regenerator. Alternatively, the second gaseous component from the process stream may be uncaptured by the ionic liquid solvent, and the uncaptured second gaseous component may be recovered from a membrane unit.

An absorbent liquid which absorbs at least one of CO.sub.2 and H.sub.2S from a gas, including a secondary linear monoamine; a tertiary linear monoamine or a sterically hindered primary monoamine; and a secondary cyclic diamine, wherein a concentration of each of the secondary linear monoamine, the tertiary linear monoamine or the sterically hindered primary monoamine; and the secondary cyclic diamine is less than 30% by weight.

Apparatuses, systems, and methods for removing acid gases from a gas stream are provided. Gas streams include waste gas streams or natural gas streams. The methods include obtaining a hypochlorite and a carbonate or bicarbonate in an aqueous mixture, and mixing the aqueous mixture with the gas stream to produce sulfates or nitrates from sulfur-based and nitrogen-based acidic gases. Some embodiments of the present disclosure are directed to produce the carbonate and/or bicarbonate scrubbing reagent from CO.sub.2 in the gas stream. Still others are disclosed.

An absorbent for selective removal of hydrogen sulfide from a fluid stream comprises an aqueous solution of a) a tertiary amine, b) a sterically hindered secondary amine of the general formula (I)

##STR00001##

in which R.sub.1 and R.sub.2 are each independently selected from C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl, with the proviso that at least one R.sub.4 and/or R.sub.5 radical on the carbon atom bonded directly to the nitrogen atom is C.sub.1-4-alkyl or C.sub.1-4-hydroxyalkyl when R.sub.3 is hydrogen; x and y are integers from 2 to 4 and z is an integer from 1 to 4; where the molar ratio of b) to a) is in the range from 0.05 to 1.0, and c) an acid in an amount, calculated as neutralization equivalent relative to the protonatable nitrogen atoms in a) and b), of 0.05 to 15.0%. One preferred amine of the formula I is 2-(2-tert-butylaminoethoxy)ethanol. The absorbent allows a defined H.sub.2S selectivity to be set at pressures of the kind typical in natural gas processing.

The invention concerns a method for treating a hydrocarbon feed gas stream containing at least CO.sub.2 and H.sub.2S to recover a high quality purified CO.sub.2 gas stream, comprising a. Separating said hydrocarbon feed gas stream into a sweetened hydrocarbon gas stream, and an acid gas stream; b. Introducing said gas stream into a Claus unit, c. Introducing the tail gas into a hydrogenation reactor and then into a quench contactor of the Tail Gas Treatment Unit (TGTU); d. Contacting said tail gas stream with a non-selective amine-based solvent into a non-selective acid gas absorption unit of the TGTU; e. Sending the off gas to an incinerator; f. Contacting said enriched gas stream (vii) with a selective H.sub.2S-absorption solvent into a selective H.sub.2S-absorption unit thereby recovering a highly purified CO.sub.2 gas stream and a H.sub.2S-enriched gas stream, as well as the device for carrying said method.