The Decomposition of Tungsten Chloride

Chloride metallurgy is the recent development of the new technology , with the chlorination process tungsten mineral raw materials have a number of advantages , mainly in:

( 1 ) Chlorine is very active , and thus the decomposition rate is very high, high metal recovery , in addition to deal with the general tungsten , but also especially suitable for processing lean tungsten ore, tungsten fine mud , tungsten ore tailings and polymetallic composite ore.

( 2 ) low boiling point of many of the metal fluoride , there is a gap between each other , and thus the vapor pressure can be used for separation and purification of different , easily obtained pure tungsten chloride.

( 3 ) Hydrogen chloride reduction process for the gas-phase reaction , easily accessible from tungsten chloride to obtain fine tungsten powder or plating .

( 4 ) easy recovery of other valuable elements .

Therefore, the method is the decomposition of tungsten chloride mineral raw materials promising methods. At present chlorination is mainly used in the decomposition of tungsten alloy scrap tungsten and tungsten minerals and thus obtain fine tungsten powder, has small-scale production .

Fundamental

Professor Li Honggui materials under thermodynamic system draws 1100K when W-Cl-O system and Fe-W-Cl-O system thermodynamic equilibrium diagram . In the W-Cl-O system exists WO2Cl2, WOCl4, WCl2 other compounds , oxygen -bit systems is higher, the higher the content of mixed vapor WO2Cl2 , to get WCl4 or WCl2, must reduce the oxygen -bit system , to ensure adequate reducing atmosphere . Therefore, scheelite or wolframite chloride , often adding carbon as a reducing agent.

For scheelite such as the use of sulfur dioxide as a reducing agent , the reaction is : CaWO4 (s) + Cl2 (g) + SO2 (g) = CaSO4 (s) + WO2Cl2 (g)

Scheelite chloride decomposition using carbon as a reducing agent , such as , you must add a certain amount of calcium fluoride decomposition rate was high : CaWO4 (s) +3 C (s) +2 Cl2 (g) + CaF2 (s) = 2CaClF (s ) + WOCl2 (g) +3 CO (g)

Process Lndicators

Tungsten with carbon and mineral raw materials are first additive (CaF2) and binder mixed group ; system group for the purpose of the charge to ensure good air permeability , dehydration briquettes sufficiently dried , and then chlorination, chlorination process is usually vertical chlorination furnace , the temperature controlled at 600 ~ 800 ℃ ( different materials , chlorination temperature is not the same ) , the chlorination of a mixed oxide vapor is condensed , and then purified by means of separation , can be used to obtain pure tungsten chloride obtained by hydrogen reduction of tungsten powder or coating can also be hydrolyzed acid .

Wolframite use chlorine chloride , the temperature to 800 ~ 900 ℃ only when a full , but adding carbon as a reducing agent , the reaction starts 400 ℃ , 500 ℃ under faster , to 600 ℃ has chlorination more completely .

Scheelite plus carbon oxidation , if not additive CaF2, then at 600 ℃, tungsten chlorination rate of only 65% , if by adding the theoretical amount of calcium fluoride , ingredients of carbon and scheelite ratio of 0.075,600 ℃ chlorination of tungsten chloride rate up to 99% .


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