METHOD OF SELECTIVELY REMOVING CYCLIC UREA FROM TREATING SOLUTION OF OBSTACLE AMINE GAS

摘要

Acid gases such as CO2 and H2S are scrubbed from a gas mixture in an absorption zone (2) employing an aqueous solution (22) comprising an alkali metal compound and a sterically hindered amine of formula: R-NH2-(CH2)m-NH2 in which R is a secondary or tertiary alkyl or cycloalkyl C4 to C20 hydrocarbon group and m is from 2 to 5, under elevated temperature and pressure causing the formation of a cyclic urea of formula: …… in which R is a secondary or tertiary C4 to C20 alkyl or cycloalkyl hydrocarbon and m is from 0 to 3. The solution containing absorbed acid gases is steam stripped in a regeneration zone (6, 8) and a portion of the resulting lean solution is cooled (in 19) to a temperature at which the cyclic urea selectively precipitates. The cooled portion of the solution is passed through a filter (16 or 17) to separate the cyclic urea solids before being recirculated (23) with the rest (21) of the lean solution to the absorption zone (2).