The present invention relates to a process for producing metal oxide from metal compounds, in particular metal hydroxide or metal carbonate, in which the metal compound is conveyed into a reactor (25) with fluidized bed, heated there to a temperature of 650 15 to 1150° C. by combustion of fuel, and metal oxide is generated, as well as to a corresponding plant. To improve the utilization of energy, it is proposed to introduce a first gas or gas mixture from below through a gas supply tube (26) into a mixing chamber (20) of the reactor (25), the gas supply tube (26) being at least partly surrounded by a stationary annular fluidized bed (27) which is fluidized by supplying fluidizing gas, and 20 to adjust the gas velocities of the first gas or gas mixture and of the fluidizing gas for the annular fluidized bed (27) such that the Particle-Froude numbers in the gas supply tube (26) lie between 1 and 100, in the annular fluidized bed (27) between 0.02 and 2, and in the mixing chamber (20) between 0.3 and 30.