To provide such operating method that dust does not stick even in the continuous operation for long time in spite of the obstruction to the operation of a fluidized bed type pre-reduction furnace caused by sticking of the dust to a straightening nozzle arranged on a dispersion plate in the case of forming the fluidized bed by using high temp. process gas containing the dust in the conventional method.

In the operating method of the fluidized bed pre-reduction furnace 1 for preheating and/or pre-reducing ore by blowing the process gas from the straightening nozzle 4 arranged on the dispersion plate 3 to form the ore fluidized bed 7, grain of carbonaceous material in the process gas is contained with ≥3g/Nm3 concn. At this time, it is desirable to introduce the straightened gas into the fluidized bed pre-reducing furnace in substantially parallel direction to the gas flowing direction from the straightening nozzle.