Sun Peimei

Caustic decomposition of scheelite and scheelite-wolframite concentrates through mechanical activation

Based on physicochemical study of the reaction between scheelite and NaOH, a new decomposition process for scheelite and scheelite-wolframite concentrate, i. e., mechenically activating caustic decomposition has been developed, and it has been successfully used on a commercial scale in 11 tungsten plants in our country. Industrial practice has shown that a tungsten recovery higher than 98% for sheelite concentrate and 99% for scheelite-wolframite mixed concentrate is obtained, under the conditions of NaOH/WO3 mole ratio of 3.6–4.8, 160–170 °C, and it is suitable to treat almost any sort of tungsten ore concentrates, including low grade complex concentrate, and it is more effective than the traditional soda ash digestion process.Based on physicochemical study of the reaction between scheelite and NaOH, a new decomposition process for scheelite and scheelite-wolframite concentrate, i. e., mechenically activating caustic decomposition has been developed, and it has been successfully used on a commercial scale in 11 tungsten plants in our country. Industrial practice has shown that a tungsten recovery higher than 98% for sheelite concentrate and 99% for scheelite-wolframite mixed concentrate is obtained, under the conditions of NaOH/WO3 mole ratio of 3.6–4.8, 160–170 °C, and it is suitable to treat almost any sort of tungsten ore concentrates, including low grade complex concentrate, and it is more effective than the traditional soda ash digestion process.

A new technology for production of high purity paratungstate ammonium from low grade tungsten concentrate

A new technological process for production of paratungstate ammonium from low grade tungsten concentrate with a high content of calcium and impurities has been studied. The experiments show that average tungsten leaching efficiency of more than 96.92% can be obtained with a low NaOH consumption by using the mechanical activating caustic decomposition, and the content of main impurities (P, As, Si) in Na2WO4 solution obtained is competitive with that from standard wolframite concentrate by traditional caustic decomposition. After recovering caustic soda by crystallization, impure Na2WO4 solution is changed to (NH4)2WO4 solution by ion exchange method. Molybdenum may be removed from (NH4)2WO4 solution by new ion exchange method. Finally, paratungstate ammonium of high purity is obtained. This technology has the advantages of short technological process, high recovery of tungsten, high economic and social benifits.A new technological process for production of paratungstate ammonium from low grade tungsten concentrate with a high content of calcium and impurities has been studied. The experiments show that average tungsten leaching efficiency of more than 96.92% can be obtained with a low NaOH consumption by using the mechanical activating caustic decomposition, and the content of main impurities (P, As, Si) in Na2WO4 solution obtained is competitive with that from standard wolframite concentrate by traditional caustic decomposition. After recovering caustic soda by crystallization, impure Na2WO4 solution is changed to (NH4)2WO4 solution by ion exchange method. Molybdenum may be removed from (NH4)2WO4 solution by new ion exchange method. Finally, paratungstate ammonium of high purity is obtained. This technology has the advantages of short technological process, high recovery of tungsten, high economic and social benifits.

Soda decomposition of low-grade tungsten ore through mechanical activation

Leaching of low-grade refractory tungsten ore was carried out through mechanical activation. The effect of temperature, amount of Na2CO3, addition of NaOH, ratio of liquid to solid and leaching time on the recovery of WO3 was studied. The WO3 recovery upto 96%–99% has been achieved when the tungsten ore was digested by soda not more than three times stiochiometric amount at 185–195 °C for 1.0–2.0 h. The WO3 recovery can increase 10%–15% compared to that of conventional soda autoclave process.Leaching of low-grade refractory tungsten ore was carried out through mechanical activation. The effect of temperature, amount of Na2CO3, addition of NaOH, ratio of liquid to solid and leaching time on the recovery of WO3 was studied. The WO3 recovery upto 96%–99% has been achieved when the tungsten ore was digested by soda not more than three times stiochiometric amount at 185–195 °C for 1.0–2.0 h. The WO3 recovery can increase 10%–15% compared to that of conventional soda autoclave process.

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 °C, 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.