As a pyro-metallurgical process, a fluidized-bed process can be employed because of its high transfer rates of heat and mass between gas and powder particles. The metal powder production usually needs to be divided to a few steps to obtain an efficiency of stepwise control or to solve some operational difficulties. In these cases, a multi-stage fluidized-bed system can be used to meet different operating conditions of steps. Hydrogen reduction processes of oxides by a two-stage fluidized-bed reactor are investigated in this study for the metal powder productions of molybdenum and nickel. For the molybdenum powder production, before the hydrogen reduction, a serial use of a single fluidized-bed reactor for the calcination of an ammonium molybdate to make a molybdenum oxide, is also investigated. As results, optimal or desirable operational conditions (temperature, residence time and gas consumption rate) for each fluidized-bed step are provided, as well as the process conceptions of the hydrogen reduction by the two-stage fluidized-bed reactors.Keywords: Fluidized-bed, multi-stage, molybdenum oxide, nickel oxide, hydrogen reduction.
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