Purification of acidic gaseous streams can be of interest because often required in running different kinds of industrial plants, such as power plants, natural gas production plants, … In the case here presented the aim is to remove H2S and CO2 in order to purify a sour gas containing these acid gases and to obtain a CO2-rich gaseous stream containing at least 90% vol. CO2, with a maximum content of H2S of 200 ppm (v).
In order to limit the amount of H2S, the absorption plant has been divided in two sections: the gas is fed to a first absorber where most of H2S is removed, and then it is treated in a subsequent section, where most of CO2 is absorbed. The H2S concentration in the H2S-rich gas, moreover, has been chosen to be at least the one required for feeding a Claus plant. Because of its high selectivity towards H2S, fundamental to run this plant configuration, a MDEA solution in water has been selected.
A possible scheme for the purification section, able to meet the specifications for the purified gas and for the concentrated acid gas streams, while allowing a reasonable energy requirement, has been studied. Two absorption sections, with two different amine concentrations and two different regeneration sections have been designed, each one with particular features aimed at meeting all the required specifications, considering an overall CO2 removal of 95%.
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