Abstract: In the boiler plant the flue gases coming from the firing space undergo division into at least two part-currents which are cooled to different degrees by giving up heat to a heat exchange medium and are then mixed together partly for producing a gas current with a desired temperature dependent on the rates of mixing of the two part-currents. The mixed current is then taken up by a heat user. Parts of the flue gases not going to the heat user are run through all heat absorbers of the system as far as the off-gas stack. The amounts of the part-currents of flue gases, used for forming the gas current with the desired temperature of mixing, are controlled dependent on the mixing temperature.

Abstract: In a process and apparatus for the continuous burning of a fuel, the fuel is run into a combustion space where it is burnt after being ignited, making use of oxygen-containing gas run into the space. The relation of gas to fuel is changed dependent on the adjustment, of a desired oxygen content in the flue gas current. For making certain of an unchanging combustion power, the fuel inlet rate is controlled to be directly dependent on the adjustment of the oxygen content in the flue gas while keeping up an unchanging rate of input of oxygen-containing gas into the combustion space.