Abstract: A device for the indirect heating of air or another gas at high pressure to a high temperature, consisting of a heat exchanger of a special construction submerged in a fluid bed of the "classical type", through which flows a fluidized hot, finely powdered bed material which is introduced (2) below the bed surface (3) and discharged through an overflow (5). The heat exchanger surface is formed by hairpin-shaped tubes (6) with legs of unequal length, the shorter legs thereof discharging into the upper bottom of an inlet chamber (7) and the longer legs thereof extending down through a tubular lead-through (9) between the bottoms of said inlet chamber (7), which lead-through is concentric with said tube leg and opens into the upper bottom of an outlet chamber (8), with an annular channel between said tube (6) and said lead-through (9).

Abstract: Electrical energy is produced from solid fuels in an ACFBC steam generator with two gas turbines and a steam turbine. The fuel is pyrolyzed in a fluid pyrolysis bed (34) with a hot partial flow of the bed material from the ACFBC steam generator (30), which together with the formed pyro coke is returned to the generator (30) as a fuel. The formed pyro gas (35) is combusted in one of said gas turbines (10), the exhaust gas (16) from which is used for steam generation (17). The other gas turbine (20) is operated with compressed air from its high pressure compressor (22) partially heated in a heat exchanger (51) in a fluid bed (50) with a controlled partial flow of hot bed material from said generator (30). The compressed air is finally heated by burning (24) fuel directly therein, and the exhaust gas from the power turbine part (22) is used as combustion air in the generator (30) which produces super heated high pressure steam for the steam turbine (40).