The Decomposition of Tungsten Concentrate Hydrochloric Acid Decomposition Method

Acid decomposition method in principle can be used to decompose scheelite, wolframite can be used to decompose . Decomposed with acid concentrates obtained crude acid can be obtained and then the ammonia dissolved ammonium tungstate solution , this solution can be prepared by crystallization of the pure compound of tungsten APT . Therefore, the acid decomposition process concentrates with short process, low cost. Mineral raw materials such as tungsten high impurity content , and ammonia dissolved in acid decomposition alone purification is difficult to obtain high -purity products . Therefore acid decomposition method used for processing low impurity content of scheelite . If the process to make appropriate adjustments for the poor quality of scheelite ( tungsten containing 40% to 60 %, including CaCO3 and other minerals less susceptible to acid dissolution ) can also be acid decomposition method.

Hydrochloric acid, nitric acid can be used to decompose scheelite . However, economic benefits, production results and other factors to consider, at present is generally used industrially acid decomposition method .

Thermodynamic Analysis

Tungsten minerals and chemical reaction of hydrochloric acid , and hydrochloric acid scheelite occurs when the following chemical reactions : CaWO4 (s) +2 HCl (aq) = H2WO4 (s) + CaCl2 (aq)

Wolframite and hydrochloric acid reaction : FeWO4 (s) +2 HCl (aq) = H2WO4 (s) + FeCl2 (aq); MnWO4 (s) +2 HCl (aq) = H2WO4 (s) + MnCl2 (aq)

Production practice, each larger than the concentration of the reaction solution , the concentration equilibrium constant at this time has more practical significance. Concentration equilibrium constant can be measured directly by experiment .

Acid decomposition process, the mineral raw materials of impurity elements in different reaction conditions with different chemical behavior .

Iron: elemental iron in tungsten minerals usually FeWO4, FeS2, Fe2O3, Fe3O4 and other forms exist. Concentrate milling , may also be part of the metal into iron .

Mo : Mo ore mainly CaMoO4 and molybdenite (MoS2) exists in the form of calcium molybdate molybdenum reacts with hydrochloric acid

CaMoO4 +2 HCl = H2MoO4 + CaCl2

MoS2 not with hydrochloric acid , but in the presence of an oxidizing agent can react molybdate :

MoS2 +2 HCl +6 NaNO3 = H2MoO4 +2 Na2SO4 +2 NaCl +6 NO ↑

Molybdate in hydrochloric acid greater than the solubility , and with the temperature increase and the concentration of hydrochloric acid increases. Therefore, improving concentration of hydrochloric acid , can make most of the molybdenum and tungsten into the solution to achieve separation .

In the acid decomposition process , you can also add to the addition of molybdenum ferrosilicon . Ferrosilicon (SiFe) as a reducing agent , where the silicon does not play a role with hydrochloric acid , and the iron will be oxidized to iron ions.

2H2MoO4 + SiFe +8 HCl = 2MoOCl3 + FeCl2 + Si +6 H2O

Treatment of high molybdenum content scheelite , the mother liquor by concentration of hydrochloric acid by acid and adding a reducing agent (SiFe) approach to the removal of molybdenum . Controls the right conditions , in addition to molybdenum ratio can reach 80%.


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