A fossil fuel fired combustion apparatus and a method for operating the fossil fuel fired combustion apparatus are provided which offer the flexibility to use carbon dioxide (CO
) both as a desirable end product and as support to the combustion process. The method includes the step of introducing a substantially pure oxygen feed stream into the fossil fuel fired combustion apparatus and the step of combusting a fossil fuel in the presence of the substantially pure oxygen feed stream to produce a flue gas having carbon dioxide and water vapor as its two largest constituent elements by volume. The method also includes the step of passing the flue gas through an oxygen feed stream pre-heater at which heat from the flue gas is transferred to the oxygen feed stream. Furthermore, the method includes the step of separating the flue gas into an end product portion and a recycling portion. The method additionally includes cooling and compressing the end product portion of the flue gas so as to yield carbon dioxide in a liquid phase and directing the recycling portion of the flue gas to the fossil fuel fired combustion unit to contribute to the combustion process therein.