A plant for the heat treatment of solids containing titanium includes a fluidized bed reactor. The reactor includes at least one gas supply tube being at least partly surrounded by an annular chamber in which a stationary annular fluidized bed is located, and a mixing chamber being located above the upper orifice region of the gas supply tube. The gas flowing through the gas supply tube entrains solids from the stationary annular fluidized bed into the mixing chamber when passing through the upper orifice region of the gas supply system. The plant further includes a solids separator downstream of the reactor. The solids separator includes a solids conduit leading to the annular fluidized bed of the reactor.