A combustion system including a bypass which opens to the open air during two different operating modes (conventional combustion; oxy-combustion), and which has the function, on the one hand, in the two operating modes, when the discharge valve is at least partially open and the recycling valve is closed or open, of allowing air to enter the recycling loop, and which has the function, on the other hand, in the second operating mode, when the discharge valve is closed and the recycling valve is open, of allowing a surplus of the combustion gas produced by the combustion device to be discharged from the recycling loop, the other fraction of the combustion gas produced by the combustion device supplying the mixer.

A carbon sequestration system includes a furnace having an oxy-combustion burner, a mill configured to receive a fuel and to provide the fuel to the oxy-combustion burner, a waste heat recovery exchanger configured to receive a flue gas from the furnace, the flue gas ultimately supplied to one or more of an overfire air port of the furnace, the oxy-combustion burner, the mill, and a CO.sub.2 purification unit, the CO.sub.2 purification unit configured to produce a purified CO.sub.2 stream.