Abstract: A fluidized bed combustion system that can be operated or controlled under pressure is provided. To eliminate the erosion or abrasion to which heat exchangers located in a fluidized bed combustion chamber are subjected due to the flue dust contained in the flue gas, no thermal withdrawal or exchange takes place in the combustion chamber of the inventive fluidized bed combustion system, although the reaction conditions remain the same. At least one controllable line for returning to the combustion chamber part of the flue gas, if necessary cooled by heat exchangers variously arranged outside the combustion chamber, branches off from the flue gas line downstream of a dust separator that is disposed in the flue gas line downstream of the combustion chamber. The main area of application is the production of electrical energy and heat for the generation of steam, as process heat, or as heat for a remote site, by means of a fluidized bed combustion system that can be operated or controlled under pressure.

Abstract: A coal-fired steam generator that has a water-steam circulation and a low pressure-heat carrier-circulation which, via a heater that is disposed in the flue gas flow of the steam generator and that has at least one heat transfer surface, absorbs heat from the flue gas flow and conveys this heat to a process that utilizes heat, especially a gas turbine process in conjunction with a coal-combination unit having a steam turbine connected in the water-steam circulation. To optimize the position of the heater for the low pressure-heat carrier-circulation, especially a sodium circulation, there are provided at least two flue gas passes that are connected in parallel with a combustion chamber of the steam generator, whereby the flue gas flow coming from the combustion chamber is distributed to these flue gas passes, at least one of which is associated with a water-steam circulation, while the other is associated with the low pressure-heat carrier-circulation.