A Basic principle NaF leaching method The reaction is:
CaW0 4 (s)+2NaF(aq)CaF 2 (s)+Na 2 W0 4 (aq)
At 225 ° C, the concentration equilibrium constant is 24.5.
Using F - tungsten leaching rate than white with CO 3 2-, PO 4 3- and other large (see below).
At less than 100 ° C, a CaF 2 film is formed on the surface of the ore particles, which hinders the reaction. Above 100 ° C, the film falls off. The apparent activation energies were 63.54 kJ/mol and 89.03 kJ/mol, respectively, at stirring speeds of 830 r/min and 510 r/min, respectively.
B Main technical indicators When Russian scholars deal with white tungsten in 33.7%~41.5% WO 3 , when the temperature is 225 °C and the amount of NaF is 1.8 times theoretical, the decomposition rate is 99.2%~99.8%, and Si0 2 in the leachate /W0 3 =0.2%~0.5%. Yao Zhengang waited for the treatment of Shizhuyuan scheelite concentrate under industrial conditions. When the amount of NaF was 1.2 times the theoretical amount and 1.5 hours at 190 °C, the decomposition rate was 98.87%, and the obtained Na 2 W0 4 solution contained P0.002g/ L, As 0.017 g / L, Si0 2 0.055 g / L.
The disadvantage of the NaF leaching method is that the solubility of NaF is limited, that is, the F - concentration in the leaching agent is limited, and accordingly the unit production capacity is low.
references:
1. Yao Zhengang. Study on the Process of Decomposing White Tungsten Concentrate by Sodium Fluoride. China Tungsten Industry, 1999(5-6): 166~170
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