Selective process modifications were considered among the possible process variations for carbon dioxide separation in natural gas fired combined gas and steam turbine power plants that differ greatly among themselves in terms of additional expense (efficiency losses, costs). The modifications considered effect an enrichment of the carbon dioxide content in the flue gas and a separation made easier (with various sorption media such as ammonia) instead of with amines (monoethanol amine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA). A carbon dioxide enrichment through exhaust gas recirculation coupled with a reduction of the oxygen content provides the challenge, to guarantee the combustion also under conditions with greater dilution (with "inert" gas components such as carbon dioxide and water) and low amounts of free oxygen and make the emissions of undesired byproducts such as NOx and CO extremely low (< 10 ppm). Through catalytic supported processes (in-situ partial catalytic oxidation) and through oxygen enrichment the stability of the release of heat at the same time can be maintained. It is to be expected that power plants running on, for example, natural gas will increase in efficiency and decrease in carbon dioxide emissions. The additional measures are to be made with little additional energy expense (efficiency loss of < 5%) and moderate additional costs of < 30 euros per tonne of separated carbon dioxide.