Abstract: A method and apparatus for producing a high energy fluid of high temperature and pressure substantially not containing physiologically harmful substances, such as nitrogen oxides NO.sub.x and carbon monoxide CO, by combusting a fluid-type or a fine powder-type fuel.Volume-controlled fuel is introduced together with volume-controlled pure oxygen through a nozzle into a closed pressure-tight container from its bottom and the mixture thereof is ignited therein for substantially complete combustion to provide an up-going jet flame of high temperature. Volume-controlled stream of de-aired water is forced into this container from its top toward the flame for heat exchange with the heat from the jet flame to produce steam of high temperature and pressure and to simultaneously lower the temperature of the combustion gas.

Abstract: A method and an apparatus for performing combustion in a closed system employing recirculated exhaust gas, by the use of a combustion chamber and an exhaust gas cleaning chamber connected by an exhaust gas duct and a recirculation pipe to the combustion chamber. The exhaust gas cleaning chamber has an oxygen supply pipe, means for supplying a pressurized aqueous solution (or oxidant-absorbing pressurized aqueous solution), a carbon dioxide supplying means, and a mixing fan. A safety pressure valve is provided on said exhaust gas cleaning chamber for discharging excess exhaust gas that becomes present in this chamber to the outside of the apparatus. The oxygen supply pipe has an oxygen flow rate regulator. An oxygen content sensor is provided in the recirculation pipe leading from the cleaning chamber to the combustion chamber and this sensor is operably connected to the oxygen flow rate regulator.