Decomposing scheelite and scheelite-wolframite mixed concentrate by caustic soda digestion

Scheelite and scheelite-wolframite mixed concentrates with different grades were decomposed by caustic soda digestion, and the effects of caustic soda（NaOH） dosage, the ratio of water to ore and the stirring rate on tungsten recovery were studied. The results show that under the conditions that the ratio of water to ore is （0.8,） stirring rate is 500 r·min-1 and the heating time is 2.0 h at （160 ℃,） the recovery of tungsten reaches 98% for scheelite （w（WO3） is （65.04%）） and wolframite containing high proportion of calcium （w（WO3） is 65.58%, w（Ca） is （7.53%）,） when caustic soda dosage is 2.2 and 2.0 times of theoretical value, respectively; the recovery of tungsten can be more than 98%,98% and 96% respectively for low-grade scheelite-wolframite mixed concentrate with （55.78%,） 45.32% and 25.21% WO3, when caustic soda dosage is 2.6,3.2 and 5.5 times of theoretical value, respectively.