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US 5,330,557 AGranted
Fluid bed reduction to produce flowable molybdenum metal
AssigneeAmax Inc.
InventorWilliam A. May
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AssigneeAmax Inc.
InventorWilliam A. May
Estimating the term…
Flowable molybdenum metal powder of controlled particle size distribution is produced by stage-wise reduction wherein, in a first stage, molybdenum trioxide feed is preferably introduced at depth in a fluid bed of molybdenum dioxide and is reduced in an atmosphere containing at least 50% hydrogen, by volume, at a temperature between 560.degree. and 620.degree. C. and the product molybdenum dioxide is then reduced to molybdenum metal in a second stage fluid bed at a temperature between 1025.degree. C. and 1075.degree. C. in an atmosphere containing at least 50% hydrogen employed in amount of at least 2.75 times stoichiometric while controlling the off-gas dewpoint to be at least 21.degree. C. and controlling the off-gas hydrogen:water vapor ratio so as not to exceed 24:1 and removing the product spheroidal molybdenum metal particles from the bottom of the bed to prevent collapse of the bed.
A process for reducing molybdenum trioxide to molybdenum dioxide which comprises establishing a fluidized bed of molybdenum dioxide with a fluidizing gas containing at least about 50%, by volume, hydrogen, heating the fluidized bed to a temperature between about 560.degree. C. and 620.degree. C., feeding molybdenum trioxide into the fluidized bed at a point below the surface of the fluidized bed of at least about 20% of the depth of the fluidized bed, discharging molybdenum dioxide from the fluidized bed and adjusting the feeding and discharging steps to provide an average residence time sufficient to insure that the discharged molybdenum dioxide is reduced to the extent of at least about 95% compared to the starting molybdenum trioxide.
A process for reducing molybdenum trioxide to molybdenum dioxide which comprises establishing a fluidized bed of molybdenum dioxide with a fluidizing gas containing at least about 50%, by volume, hydrogen, heating the fluidized bed to a temperature between about 560.degree. C. and 620.degree. C., feeding molybdenum trioxide into the fluidized bed, discharging molybdenum dioxide from the fluidized bed and adjusting the feeding and discharging steps to provide an average residence time sufficient to insure that the discharged molybdenum dioxide is reduced to the extent of at least about 95% compared to the starting molybdenum trioxide, transferring said molybdenum dioxide to a second stage fluid bed and reducing said molybdenum dioxide at least 96% to molybdenum metal in a reducing gas atmosphere containing at least 50%, by volume, of hydrogen at a temperature of about 1025.degree. C. to 1075.degree. C. with an excess hydrogen of at least 2.75 times stoichiometric, while controlling the dewpoint of the off-gas to be at least 21.degree. C., said molybdenum metal being withdrawn from the bottom of said second stage fluid bed as substantially flowable particles.
The process for reducing molybdenum dioxide to molybdenum metal in a fluid bed reactor at a temperature of about 1025.degree. C., to 1075.degree. C. using hydrogen as the active reductant and controlling the off-gas such that the hydrogen:water vapor ratio does not exceed about 24:1 so that fluidization of the bed is maintained.
A process for reducing molybdenum trioxide to molybdenum dioxide which comprises establishing a fluidized bed of molybdenum dioxide with a fluidizing gas containing at least about 50%, by volume, hydrogen, heating the fluidized bed to a temperature between about 560.degree. C. and 620.degree. C., feeding molybdenum trioxide into the fluidized bed, discharging molybdenum dioxide from the fluidized bed and adjusting the feeding and discharging steps to provide an average residence time sufficient to insure that the discharged molybdenum dioxide is reduced to the extent of at least about 95% compared to the starting molybdenum trioxide, transferring said molybdenum dioxide to a second stage fluid bed and reducing said molybdenum dioxide at least 96% to molybdenum metal in a reducing gas atmosphere containing at least 50%, by volume, of hydrogen at a temperature of about 1025.degree. C. to 1075.degree. C. with an excess hydrogen of at least 2.75 times stoichiometric, while controlling the hydrogen to water vapor ratio in the off-gas so that it does not exceed 24:1, said molybdenum metal being withdrawn from the bottom of said second stage fluid bed as substantially spherical, flowable particles.
The process as described in 11 wherein said temperature is between about 570.degree. C. and 610.degree. C.
Dependencies are inferred from the claim text.