A method of preparing an oxidant stream comprising: burning a combustion mixture comprising (a) one or more fuel composition and (b) oxidant comprising a first oxygen content of about 10 mole % or more and a first carbon dioxide (CO2) gas content of about 68 mole % or more on a dry basis, the burning producing a flue gas comprising CO2 gas, water vapor, and unreacted oxygen; separating from the flue gas a recycle stream; mixing at least a portion of the recycle stream having a first pressure with a sufficient amount of an oxygen stream having a second pressure which is sufficiently higher than the first pressure to entrain at least a portion of the recycle stream in the oxidant stream and to produce the oxidant stream having a second oxygen content of 10 mole % or more and a second CO2 gas content of about 68 mole % or more on a dry basis.