Method and plant for the heat treatment of solids containing iron oxide using a fluidized bed reactor

A method for the heat treatment of solids containing iron oxide, in which fine-grained solids are heated to a temperature of 700 to 1150° C. in a fluidized bed reactor, comprising introducing the solids into the reactor, introducing a first gas or gas mixture from below through at least one gas supply tube into a mixing chamber of the reactor located above the orifice region of the at least one gas supply tube, the at least one gas supply tube being at least partly surrounded by a stationary annular fluidized bed which is fluidized by supplying fluidizing gas, wherein the gas flowing through the at least one gas supply tube entrains solids from the stationary annular fluidized bed into the mixing chamber when passing through the upper orifice region of the at least one gas supply tube, and further comprising adjusting the gas velocities of the first gas or gas mixture and of the fluidizing gas for the annular fluidized bed such that the Particle-Froude-Number in the at least one gas supply tube are between 1 and 100, in the annular fluidized bed between 0.02 and 2, and in the mixing chamber between 0.3 and 30, and removing treated solids from the reactor.