A method and its related plant for the thermal treatment of iron containing oxide, in which fine-grained solids are heated in a preheating calcining stage and exposed to a reduction gas in a subsequent reduction stage. Off-gas from the reduction stage is guided through a separation device wherein water originating from the reduction stage is separated. The water separated in the separation device is recycled into a water treatment section, from which the recycled water is supplied to a water electrolysis plant and/or a steam reforming plant producing hydrogen, and the produced hydrogen is supplied to the reduction stage as reductant and/or to the preheating calcining stage as fuel and/or to the gas heater as fuel and/or from which the recycled water is supplied to the separation device.