Abstract: In a process for the low-pollutant conversion of thermal energy produced by burning fossil fuels into power, the thermal energy produced by burning fossil fuels is delivered directly to the cyclic process by virtue of the fact that in the cyclic process the fuels are burned with oxygen in the presence of carbon dioxide recycled from the cyclic process to form gas turbine operating substances having a temperature of from 800.degree. to 1500.degree. C. Furthermore, according to the invention, the pressure difference between the combustion chamber (1) and the carbon dioxide recycling process is compensated by condensation (11), on the one hand, and evaporation (4, 8) and pre-heating (3) of the carbon dioxide to be recycled and the combustion chamber (1), on the other, by compression (7) and expansion (6) which are performed during the process, preferably with a high-performance gas turbocharger (6, 7).

Abstract: A compact, unfired, staggered tube, once-through steam generator or boiler of simple construction intended primarily for combined cycle power plants in which the thermal energy utilized to generate steam is obtained from the exhaust gases of a gas turbine engine. The boiler provides steam at two different pressure levels, which maximizes recovery of thermal energy; and all wettable components in the steam/water loop are fabricated of corrosion resistant materials. This eliminates the need for controlling the pH of the feedwater and the need for chemically controlling its dissolved oxygen content, thereby reducing maintenance and operating costs and making automatic, unattended, remotely controlled operation of the boiler practical as well as eliminating the need for blowing down the boiler and minimizing requirements for make-up water. The boiler can be operated dry to remove gas side fouling; and feedwater flow rates can be directly controlled.