A process for removal of acid gases from fluid stream, wherein the fluid stream is brought into contact with an absorbent to obtain a treated fluid stream and a laden absorbent, the absorbent comprising a diluent and a compound of the general formula (I) wherein R.sup.1 is selected from C.sub.1-C.sub.8-alkyl and C.sub.2-C.sub.8-hydroxyalkyl; R.sup.2 is selected from hydrogen and C.sub.1-C.sub.8-alkyl; R.sup.3 is selected from hydrogen and C.sub.1-C.sub.8-alkyl; R.sup.4 is selected from hydrogen and C.sub.1-C.sub.8-alkyl; R.sup.5 is C.sub.1-C.sub.8-alkyl; with the proviso that at least one of the following conditions (i) and (ii) is met: (i) R.sup.5 is C.sub.3-C.sub.8-alkyl bound to the nitrogen atom via a secondary or tertiary carbon atom; (ii) when R.sup.4 is hydrogen, R.sup.3 is C.sub.1-C.sub.8-alkyl; or when R.sup.4 is C.sub.1-C.sub.8-alkyl, at least one of R.sup.2 and R.sup.3 is C.sub.1-C.sub.8-alkyl; and n is an integer from 0 to 6. Further provided is an absorbent for the absorption of acid gases from a fluid stream, comprising a diluent and a compound of the general formula (I) as defined above, as well as the use of a compound of the general formula (I) as defined above for removal of acid gases from a fluid stream. The absorbents are useful for the selective removal of hydrogen sulfide from fluid streams and have high acid gas loading capacity, high stability, and low volatility.

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An absorption solvent regeneration device includes: a regenerator for regenerating an absorption solvent by separating CO.sub.2 from the absorption solvent which has absorbed CO.sub.2; a main rich solvent line for supplying the absorption solvent which has absorbed CO.sub.2 to the regenerator; a first heating part for heating the absorption solvent flowing through the main rich solvent line, the first heating part being disposed on the main rich solvent line; and a branch rich solvent line for supplying a part of the absorption solvent flowing through the main rich solvent line to the regenerator, the branch rich solvent line branching from the main rich solvent line. The absorption solvent regeneration device further includes a regulating part for regulating a ratio between a first flow rate of the absorption solvent flowing through the first branch portion and a second flow rate of the absorption solvent flowing through the second branch portion.

A cooling absorption tower for a CO.sub.2 recovery device, comprises: an outer shell; a cooling section for cooling a flue gas, the cooling section being disposed in the outer shell; and an absorbing section configured to cause CO.sub.2 in the flue gas cooled by the cooling section to be absorbed in an absorption solvent, the absorbing section being disposed in the outer shell and above the cooling section.

A gas treatment method includes an absorption step in which a gas to be treated containing an acidic compound, such as carbon dioxide, is brought into contact, in an absorber, with a treatment liquid that absorbs the acidic compound; and a regeneration step in which the treatment liquid, having the acidic compound absorbed therein, is sent to a regenerator, and the treatment liquid is then heated to separate the acidic compound from the treatment liquid. In the regeneration step, a gas almost insoluble to the treatment liquid, such as hydrogen gas, is brought into contact with the treatment liquid.

A particulate material for removing an acid gas and/or mercury contaminant from a hydrocarbon gas is disclosed. The particulate material comprises a superabsorbent hydrogel comprising a cross-linked hydrophilic polymer network having from 0.1 mol % to 50 mol % cross-linking agent. The superabsorbent hydrogel has one or more compounds capable of binding the acid gas and/or mercury contaminant incorporated into the hydrophilic polymer network by absorbing said one or more compounds as a liquid phase or an aqueous solution. Methods for preparing the particulate material and using the particulate material to remove one or more acid gas and/or mercury contaminants from a hydrocarbon gas, dehydrating the hydrocarbon gas, and mitigating corrosion in gas flowlines are also disclosed.

A process for selectively separating H.sub.2S from a gas mixture which also comprises CO.sub.2is disclosed. A stream of the gas mixture is contacted with an absorbent solution comprising one or more amines, alkanolamines, hindered alkanolamines, capped alkanolamines, or mixtures thereof. The H.sub.2S/CO.sub.2 selectivity of the absorbent solution is preferably greater than about 4.0 for an acid gas loading [mol(CO.sub.2+H.sub.2S)/mol(amine)] between about 0.2 and about 0.6, and is achieved by reducing pH of the absorbent solution.

A method for recovering an acidic gas, includes: a step of bringing a gas to be treated that contains an acidic gas into gas-liquid into contact with an amine absorbing solution, allowing the amine absorbing solution to absorb the acidic gas, thereby removing the acidic gas from the gas to be treated; a step of allowing the amine absorbing solution that has absorbed the acidic gas to release the acidic gas, thereby regenerating the amine absorbing solution, and at the same time, recovering the released acidic gas; and an analysis step of calculating concentrations of iron ions and/or heavy metal ions in the amine absorbing solution.

A process for selectively separating H.sub.2S from a gas mixture which also comprises CO.sub.2 is disclosed. A stream of the gas mixture is contacted with an absorbent solution comprising one or more amines, alkanolamines, hindered alkanolamines, capped alkanolamines, or mixtures thereof. The H.sub.2S/CO.sub.2 selectivity of the absorbent solution is preferably greater than about 4.0 for an acid gas loading [mol(CO.sub.2+H.sub.2S)/mol(amine)] between about 0.2 and about 0.6, and is achieved by reducing pH of the absorbent solution.

The absorption agent of the present invention contains water, an amine compound, and an organic solvent, and a value obtained by subtracting a solubility parameter of the organic solvent from a solubility parameter of the amine compound is 1.1 (cal/cm.sup.3).sup.1/2 or more and 4.2 (cal/cm.sup.3).sup.1/2 or less. The method for separation and recovery of an acidic compound of the present invention includes the steps of: bringing a mixed gas containing an acidic compound into contact with an absorption agent containing water, an amine compound, and an organic solvent to absorb the acidic compound into the absorption agent; causing the absorption agent that has absorbed the acidic compound to be phase-separated into a first phase containing the acidic compound in a high content and a second phase containing the acidic compound in a low content; and heating the first phase to release the acidic compound from the first phase.

An alkanolamine gas treatment unit system that may comprise an absorber column, a regenerator column, and a once-through natural circulation vertical thermosyphon reboiler comprising a reboiler tube and a shell. The reboiler may be a steam driven one having a process side and a shell side, wherein the process side is inside the reboiler tube, the process side of the reboiler and the regenerator column are in fluid communication with one another, an inner surface of the reboiler tube, on the process side, has a surface roughness of 0.06 .Math.m or greater, the shell side of the reboiler is in fluid communication to a steam source, and the regenerator column and the absorber column are in fluid communication with one another. An absorbent regenerator system that may comprise the regenerator column and the once-through natural circulation vertical thermosyphon reboiler.