Removal of hydrogen sulphide and carbon dioxide from a stream of fluid

A process for removing hydrogen sulfide and carbon dioxide from a fluid stream, the process comprising

• a) contacting the fluid stream with an absorbent comprising an aqueous solution of
• (i) an amine of fonnula (I)
• in which R1, R2and R3 are each independently C1-4-alkyl or C1-4-hydroxyalkyl;
• each R4 is independently hydrogen, C1-4-alkyl or C1-4-hydroxyalkyl;
• each R5 is independently hydrogen, C1-4-alkyl or C1-4-hydroxyalkyl;
• X is OH or NH(CR1R2R3);
• 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 a molar ratio of (i) to (ii) is greater than 0.05;
• wherein there is a partial hydrogen sulfide pressure of at least 0.1 bar and a partial carbon dioxide pressure of at least 1 bar in the fluid stream;
• wherein the fluid stream has a total pressure of at least 20 bar;
• wherein at least 90% of the hydrogen sulfide is removed from the fluid stream;
• wherein a CO2- and H2S-laden absorbent and a treated fluid stream are obtained;
• and
• wherein a selectivity S for hydrogen sulfide over carbon dioxide calculated as follows is not greater than 8:
• S
• =
• y
• ⁡
• (
• H
• 2
• ⁢
• S
• )
• feed
• -
• y
• ⁡
• (
• H
• 2
• ⁢
• S
• )
• treat
• y
• ⁡
• (
• H
• 2
• ⁢
• S
• )
• feed
• y
• ⁡
• (
• CO
• 2
• )
• feed
• -
• y
• ⁡
• (
• CO
• 2
• )
• treat
• y
• ⁡
• (
• CO
• 2
• )
• feed
• ,
• in which y(H2S)feed is a molar proportion of H2S in the fluid stream, y(H2S)treat is a molar proportion in the treated fluid stream, y(CO2)feed is a molar proportion of CO2in the fluid stream and y(CO2)treat is a molar proportion of CO2 in the treated fluid stream;
• b) regenerating at least a substream of the CO2- and H2S-laden absorbent;
• to obtain a regenerated absorbent;
• and
• c) recycling at least a substream of the regenerated absorbent into a)
• d′) treating a sub stream of a CO2- and H2 S-containing gas stream released in b) with the regenerated absorbent to obtain a second H2S-laden absorbent;
• and
• e′) passing the second H2S-laden absorbent into b).