Abstract: Iron ore is introduced in a series of fluidized bed reactors, with a reducing gas that is heated before each bed and cooled after each bed and thereafter washed with water so as to remove from the gas the very fine powder of solids which otherwise would build up in the reactors. The reducing gas can be divided and fed to the reactors in parallel, the gas from all the reactors being recombined and subjected to washing, addition of make-up gas, and recompression, prior to recycling in a plurality of parallel streams. Alternatively, the reducing gas can proceed from the final reactor in reverse order to the passage of iron ore through the reactors, with heating of the gas before each reactor and cooling and washing of the gas after each reactor, followed by addition of make-up and recompression prior to recycling.