Fluidized bed process for preparing tungsten powder

Details Fluidized bed process for preparing tungsten powder Fluidized bed process for preparing tungsten powder

1990-09-10

1992-06-30

Andrews, Melvyn J.

Specialized metallurgical processes, compositions for use therei

Processes

Producing or purifying free metal powder or producing or...

75623, C22B 514, C22B 3436

Patent

active

051259648

ABSTRACT:
Tungsten metal powder of controlled particle sizes is obtained in a fluid bed process by reducing particles of tungsten oxide having the formula WO.sub.X where x is from 2.5 to 3.0. The WO.sub.X powder particles are heated to and then maintained at a temperature between 650.degree. and 1000.degree. C. in a reducing atmosphere, which is maintained by passing a mixture of hydrogen gas, water and optionally nitrogen gas through a fluid bed of the tungsten oxide particles until substantially all of the powder solid is tungsten dioxide, WO.sub.2. The ratio of water partial pressure to hydrogen partial pressure in the feed gas is equal to or slightly higher than the equilibrium partial pressure ratio. The flow of water vapor is then discontinued, either gradually or instantaneously, while maintianing the flow of hydrogen gas to reduce the WO.sub.2 to tungsten metal. By maintaining the ratio of water partial pressure to hydrogen partial pressure above the equilibrium value until the original WO.sub.X is substantially reduced to WO.sub.2, a product having a narrow particle size distribution is obtained. The WO.sub.X may be obtained by decomposition of ammonium paratungstate in the same reactor.

REFERENCES:
patent: 2993755 (1961-07-01), Redanz
patent: 3234007 (1966-02-01), Blocher, Jr. et al.
patent: 3236634 (1966-02-01), Lambdin, Jr. et al.
patent: 4402737 (1983-09-01), Kronenwetter

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