A method for separating carbon dioxide from flue gas, the method comprising compressing the flue gas, cooling the compressed flue gas in at least a heat exchanger (3a, 3b) separating a carbon dioxide rich liquid from a carbon dioxide lean gas, supplying the carbon dioxide rich liquid and the carbon dioxide lean gas into a distillation column, separating in the distillation column non-condensable gas from carbon dioxide liquid, heating the carbon dioxide liquid discharged from the bottom of the distillation column at a cold side of a reboiler generating a purified carbon dioxide liquid (PCDL) and a mixture of residual non-condensable gas and carbon dioxide which is brought back from the cold side of the reboiler into the distillation column, expanding the purified carbon dioxide liquid (PCDL) discharged from the cold side of the reboiler and supplying the expanded carbon dioxide liquid (ECDL) to the at least a heat exchanger (3a, 3b) for cooling the at least a heat exchanger (3a, 3b), supplying the expanded carbon dioxide liquid (ECDL) from the at least a heat exchanger (3a, 3b) to a high pressure compressor to generate a compressed carbon dioxide vapor (CCDV), supplying at least a part of the compressed carbon dioxide vapor (CCDV) from the high pressure compressor to a warm side of the reboiler generating a cooled carbon dioxide liquid (CCDL), expanding the cooled carbon dioxide liquid (CCDL) discharged from the warm side of the reboiler and passing the cooled carbon dioxide liquid (CCDL) through the at least a heat exchanger (3a, 3b) for cooling the at least a heat exchanger (3a, 3b), characterized in that the purified carbon dioxide liquid (PCDL) discharged from the cold side of the reboiler and the cooled carbon dioxide liquid (CCDL) discharged from the warm side of the reboiler are not supplied into a buffer drum and mixed therein, but are each expanded separately and subsequently forwarded to the at least a heat exchanger (3a, 3b). compressing the flue gas, cooling the compressed flue gas in at least a heat exchanger (3a, 3b) separating a carbon dioxide rich liquid from a carbon dioxide lean gas, supplying the carbon dioxide rich liquid and the carbon dioxide lean gas into a distillation column, separating in the distillation column non-condensable gas from carbon dioxide liquid, heating the carbon dioxide liquid discharged from the bottom of the distillation column at a cold side of a reboiler generating a purified carbon dioxide liquid (PCDL) and a mixture of residual non-condensable gas and carbon dioxide which is brought back from the cold side of the reboiler into the distillation column, expanding the purified carbon dioxide liquid (PCDL) discharged from the cold side of the reboiler and supplying the expanded carbon dioxide liquid (ECDL) to the at least a heat exchanger (3a, 3b) for cooling the at least a heat exchanger (3a, 3b), supplying the expanded carbon dioxide liquid (ECDL) from the at least a heat exchanger (3a, 3b) to a high pressure compressor to generate a compressed carbon dioxide vapor (CCDV), supplying at least a part of the compressed carbon dioxide vapor (CCDV) from the high pressure compressor to a warm side of the reboiler generating a cooled carbon dioxide liquid (CCDL), expanding the cooled carbon dioxide liquid (CCDL) discharged from the warm side of the reboiler and passing the cooled carbon dioxide liquid (CCDL) through the at least a heat exchanger (3a, 3b) for cooling the at least a heat exchanger (3a, 3b), characterized in that the purified carbon dioxide liquid (PCDL) discharged from the cold side of the reboiler and the cooled carbon dioxide liquid (CCDL) discharged from the warm side of the reboiler are not supplied into a buffer drum and mixed therein, but are each expanded separately and subsequently forwarded to the at least a heat exchanger (3a, 3b).