According to the quality standard of tungsten concentrate, except for the content gallery of WO3 is more than 65%, the content of other harmful impurities is lower than the corresponding standard, and the quality requirement of special grade tungsten concentrate is still high. There are corresponding standards for S, P, As, Mo, Ca, Mn, Cu, Sn, SiOl2 and other impurities in tungsten concentrate. When the physical beneficiation method fails to meet the requirements, the chemical beneficiation method is adopted, which can not only improve tungsten fines. The quality level of the mine can also be combined with other useful components.
(1) Tungsten concentrate removal tin method When tin in tin ore is present as a monomer of cassiterite, it can be separated from wolframite and scheelite by strong magnetic separation and electrification.
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↑ (under 850°C)
2FeWO4+2CaO+1/2O2 =2CaWO4+Fe2O3
2FeWO4+6CaCl2+1/2O2 =6CaWO4+4FeCl2+Fe2O3
Tungsten chloride coarse ore roasting tin chloride when other conventional agent is less corrosive and easy recovery of ammonium chloride, and ferric chloride. In order to ensure that the reaction is carried out in a reducing atmosphere, a certain amount of charcoal powder or sawdust is added to the ingredients, and the reaction formula is as follows:
SnO2 + 2NH4Cl+3C+O2 =SnCl2↑+2NH2↑+3CO↑H2O (under 850°C)
The amount of ammonium chloride added during calcination varies depending on the tin content of the tungsten concentrate. The chlorination roasting temperature is about 850 ° C, 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 to 4 hours, and the chlorination roasting is carried out for a period of time, the de-tinning rate can reach over 90%, and the tin content can be reduced to less than 0.2%.
(2) Methods for removing arsenic from tungsten concentrates The arsenic content in tungsten concentrates mainly exists in the form of toxic ore (FeAsS), realgar (AsS), orpiment (As2 S3), ochre (As2O3) and various arsenates. The methods for removing arsenic are:
1 floatation and flotation can remove most of the arsenic sulfide;
2 weak oxidative roasting or reduction roasting method for arsenic removal.
When added to the feed mass ingredients prior to firing the raw material according to the level of arsenic content of 2% to 6% of pulverized coal or charcoal powder, and calcined for 2 to 4 hours at a temperature of 700 ~ 800 ℃, 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
2As2 S3+10O2+C=2As2O3+6SO2+CO2
CaO·As2O5+C=As2O3+CaO+CO2
The suboxide of arsenic (As2O3) 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 argon roasting should be carried out in a weak oxidizing atmosphere or in a reducing atmosphere, in which case arsenic can be volatilized as a low-valent arsenic oxide, and high-priced arsenic oxide (or arsenate) can be reduced to low-priced arsenic. Oxide, thereby increasing the rate of arsenic removal.
(3) of tungsten concentrates dephosphorization method of phosphorus tungsten concentrates often apatite Ca5 (PO4) 3 (F, Cl, OH), YPO4 xenotime and monazite (Ce, La, Th) PO4 phosphate The form of salt exists. There are two methods for dephosphorization.
1 Dilute hydrochloric acid leaching dephosphorization method is suitable for removing apatite, generally using 1: (3 ~ 5) dilute hydrochloric acid as leaching agent, coarse grain concentrate by infiltration method, fine grain concentrate with stirring leaching, The phosphorus content can be reduced to less than 0.05%.
â‘¡ If the flotation dephosphorization tungsten concentrate to xenotime, alone presence of a phosphorus impurity stone shape, can not with dilute hydrochloric acid and phosphorus, phosphorus floating suppressing method available tungsten, arsenic acid and oleic acid with toluene catch Recipe , oxalic acid as an inhibitor, sodium carbonate as a regulator, can achieve the purpose of phosphorus reduction, and comprehensive recovery of xenotime.
(4) Removal of molybdenum from tungsten concentrates Molybdenum in tungsten concentrates is often present in the form of molybdenite and molybdenum oxides (calcium molybdate, molybdenum, etc.). Generally, lifting or flotation can be used to remove molybdenum sulfide or leaching with hypochlorous acid solution, and molybdenum in the form of molybdenite can also be removed. The leaching should be carried out at a temperature lower than 40 ° C. At this 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 cost-effective method. Generally, it can be treated by acid leaching or alkali leaching. For example, 20% to 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 are also transferred into the solution. The acid solubility of tungsten increases with increasing hydrochloric acid concentration and temperature.
(5) De-copper method of tungsten concentrate If the copper in the tungsten concentrate is in the form of sulfide, it is generally removed by flotation or floatation.
When a certain impurity is removed by the above method, a considerable amount of sulfur can be removed by removing a considerable portion of other impurities such as chlorination calcination or reduction roasting. 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 part of the copper, arsenic sulfide, and the like can be removed by removing the molybdenum with the sodium hypochlorite solution.
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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