Abstract: This invention is related to so-called combined cycle co-generation installations, and it addresses present concerns of the industry. Among these, combustion stability, corrosion (due to large water content in the flue gases), large heat transfer areas, and the like. In some embodiments, an additional heat exchanger is added to heat combustion air with a portion of the exhaust gases resulting from an engine, preferably a gas turbine. As a result, the efficiency of the cycle will improve, the oxidant will be enriched by above 50% oxygen, the combustion process will be enhanced, and the dimensions of the boiler may be reduced. It is considered that the combustion air will require between 10% and 80% of the total flue gas volume, more preferably between 20% and 40%. This is the portion of the flue gases sent through the heat exchanger. A control system designed to optimize the flow of the different streams is also presented.