A method 100 for treating a starting gas mixture comprising hydrogen sulphide and carbon dioxide comprises a gas conditioning step 10 to provide the gas mixture at an absorption pressure of between 4 and 10 bar (abs) and an absorption temperature of between -30 and -50°C and a gas separation step 20 comprising a physical absorption 21 at the absorption pressure and temperature level using an absorption liquid to generate at least two fractions, one of which predominantly or exclusively comprises carbon dioxide. A fraction comprising hydrogen sulphide and a fraction comprising hydrogen are preferably formed. The starting gas mixture may be a tail gas of a Claus process 1 or a hydrogenated gas mixture produced from a tail gas treatment unit 2. The gas conditioning step may comprise compressing 11 and cooling 12 the gas mixture. The absorption liquid is preferably methanol.
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