According to the quality standard of tungsten concentrate, except for the content of WO3 should be more than 65%, the content of other harmful impurities is lower than the corresponding standard, and the quality requirements of special grade tungsten concentrate are still high. S, P, As, Mo, Ca, Mn, Cu, Sn, SiO2 and other impurities in tungsten concentrate have corresponding standards. When the physical beneficiation method fails to meet the requirements, the chemical beneficiation method is adopted. This not only improves the quality grade of tungsten concentrate, but also makes use of other useful ingredients.

1. Method for removing tin from tungsten concentrate

When the tin in the tin ore is present as a monomer of cassiterite, it can be separated from the wolframite and scheelite by strong magnetic separation and electroselective methods, respectively.

In the production, a solid chlorinating agent is commonly used to chlorinate and roast the super-tungsten tungsten coarse concentrate to make the tin volatilize to achieve the purpose of removing tin. The main reactions of the process are:

SnO2+CaCL2 +C = SnCl2↑+CaO +CO↑(850)

2FeWO4+2CaO +1/2 O2 = 2CaWO4+Fe2O3

2FeWO4+6CaCl2 +3/2 O2 = 6CaWO4+ 4FeCl2 +Fe2O3

Tungsten chloride coarse ore roasting tin chloride when other conventional agent is less corrosive and easy recovery of ammonium chloride, ferric chloride and the like; in order to ensure the reaction is carried out in a reducing atmosphere, a certain amount of time to be added charcoal powder ingredients or Sawdust, the reaction formula is as follows:

SnO2 + 2NH4Cl +3C +O2 = SnCl2 ↑+2NH3↑ +3CO ↑+H2O

The amount of ammonium chloride added during calcination varies depending on the tin content of the tungsten concentrate. The chlorination calcination temperature is about 850, and the process can be carried out in a reverberatory furnace or a rotary kiln. In order to improve the de-tinning efficiency, the chlorination roasting can be turned over once after 2-4 hours, and the oxidizing roasting is carried out for a period of time, the de-tinning rate can reach more than 90%, and the tin content can be reduced to less than 0.2%.

Ingredient ratio of chlorination roasting of tin ore concentrate

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Tin content ( % )

Sawdust dosage (kg)

Ammonium chloride (kg)

Mineral quantity (kg)

Reduction roasting time

Oxidation roasting time (hours)

1-2

3

4

5

10-20

10-20

10-20

10-20

12

20

twenty four

28

175

175

175

175

2

3

4

4

2

3

4

4

Second, tungsten concentrate arsenic removal method

The arsenic content in tungsten concentrate is mainly in the form of toxic sand (FeAsS), realgar (AsS), orpiment (As2S3), ochre (As2O3) and various arsenates. Method for removing arsenic:

(1) Floatation and flotation can remove most of the arsenic sulfide:

(2) Desulfurization by weak oxidative roasting or reduction roasting.

According to the ingredients before firing low arsenic content in the raw material is added 2-6% by weight of the raw material powder coal or charcoal powder, calcined for 2-4 hours at a temperature of 700-800 degrees, calcination is carried out in a reverberatory furnace or a rotary kiln. If the charcoal powder does not meet the requirements for arsenic removal, a small amount of sulfur can be added. The main reaction of the process is:

2FeAsS+6O2 +C = As2O3+Fe2O3+2SO2+CO2

2As2S3+10O2 +C = 2As2O3+6SO2 +CO2

Fe3(AsO4)2+C =As2O3 +3FeO +CO2

CaO · As2O5 + C = As2O3 + CaO + CO2

The suboxide (As2O3) of arsenic is a volatile matter. Highly priced arsenic oxide (As2O5) is less volatile and can form stable arsenates with certain basic oxides:

As2O3 + SiO2 + O2 = As2O5 + SiO2

FeO·CaO)+As2O5 =FeO·As2O5 (or CaO·As2O5)

Therefore, the arsenic removal by roasting should be carried out in a weak oxidizing atmosphere or a reducing atmosphere, in which case arsenic can be volatilized as a low-valent arsenic oxide, and the high-priced arsenic oxide (or arsenate) can be reduced to low-priced arsenic. Oxide, thereby increasing the rate of arsenic removal.

Third, tungsten concentrates dephosphorization method

Phosphorus in tungsten concentrates is often present in the form of phosphates such as apatite Ca5(PO4)3 (F, Cl, OH), xenotime YPO4 and monazite (Ce, La, Th) PO4. Dephosphorization methods are:

(1) Dephosphorization by dilute hydrochloric acid leaching. This method is suitable for removing apatite, generally using 1:3-5 dilute hydrochloric acid as leaching agent, coarse-grain concentrate using infiltration method, and fine-grained concentrate using stirring leaching to reduce the phosphorus content to zero. 05%, below.

(2) Dephosphorization by flotation. If the tungsten concentrate contains phosphorus ore, monazite and other forms of phosphorus impurities, it is impossible to remove phosphorus with dilute hydrochloric acid. The method of floating phosphorus and tungsten can be used to mix the collector with toluene arsenic acid and oleic acid, and oxalic acid is used for suppression. The agent, the sodium carbonate adjuster, can achieve the purpose of reducing phosphorus, and comprehensively recovers the xenotime.

Fourth, in addition to molybdenum, tungsten concentrates method

The molybdenum in the tungsten concentrate is often in the form of molybdenite and molybdenum oxide (calcium molybdate, molybdenum, etc.). Generally, floating or flotation can be used to remove molybdenum sulfide or leaching with a hypohydrogen acid solution, and to remove molybdenum in the form of molybdenite. The leaching should be carried out at a temperature lower than 40 degrees, at which time the iron and copper sulfides are oxidized at a lower rate than the molybdenite and have a higher selectivity. If molybdenum exists in the form of oxides, molybdenum reduction is difficult, and there is currently no economically effective method. Generally, it can be treated by acid leaching or alkali leaching. For example, 20-30% hydrochloric acid can be used to convert all molybdate into calcium molybdate which is easily soluble in hydrochloric acid, and some copper and tungsten can also be transferred into the solution. The acid solubility of tungsten increases with increasing hydrochloric acid concentration and temperature.

V. Method for removing copper from tungsten concentrate

If the copper in the tungsten concentrate is present in the form of sulfide, it is generally removed by flotation reverse flotation.

When a certain impurity is removed by the above method, a considerable amount of other impurities such as chlorination roasting tin or reduction roasting arsenic can be removed to remove the equivalent amount of sulfur. In addition to acid leaching of molybdenum, phosphorus, can remove a substantial amount of calcium, bismuth, copper and other impurities. Sometimes, the ruthenium can be recovered from the acid leaching solution, and when the molybdenum is removed by the sodium hypochlorite solution, part of the copper, arsenic sulfide, and the like can be removed.

Excessive impurities in tungsten concentrates are rare. Generally, the physical beneficiation method is used for multiple selections and chemical beneficiation methods to remove impurities, so that the impurity content in the tungsten concentrate can be reduced below the standard value.

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