According to the quality standard of tungsten concentrate, except for the content of WO 3 should be 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 impurities such as S, P, As, Mo, Ca, Mn, Cu, Sn, Si0 2 in tungsten concentrate. When the physical beneficiation method fails to meet the requirements, the chemical beneficiation method is adopted. This will not only improve the quality grade of tungsten concentrate, but also integrate other useful components of Lishengmin.
I. Tungsten concentrate removal tin method When tin in tin ore is present as a monomer of cassiterite, it can be separated from the 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:
850 ° C
SnO 2 +CaCl 2 +C ====== SnCl 2 ↑+CaO+CO↑
1
2FeW0 4 +2Ca0+——O 2 ==== 2CaW0 4 +Fe 2 O 3
2
1
2FeWO 4 +6CaC1 2 +1——O 2 ==== 6CaW0 4 +4FeC1 2 +Fe 2 0 3
2
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:
830 ° C
Sn0 2 +2NH 4 Cl+3C+O 2 ====== SnCl 2 ↑+2NH 3 ↑+3C0↑+H 2 0
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 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%. The ratio of ingredients in the chlorination roasting of a certain tungsten concentrate is shown in the table below.
Tin content (%) | Sawdust dosage (kg) | Ammonium chloride (kg) | Mineral quantity (kg) | Reduction roasting time (hours) | 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 concentrates arsenic removal method mainly tungsten concentrates containing arsenic arsenopyrite (FeAsS), realgar (AsS), orpiment (As 2 S 3), arsenic trioxide stone (As 2 0 3) and various arsenate The form exists. Method for removing arsenic:
(1) The platform floatation and flotation method 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 of the feedstock is added 2 to 6% by weight of pulverized coal or charcoal powder raw material, and calcined for 2 to 4 hours at a temperature of 700 ~ 800 ℃, calcination is carried out in a rotary kiln or a reflective guard. 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: [next]
2FeAsS+6O 2 +C ==== As 2 0 3 +Fe 2 O 3 +2S0 2 +CO 2
2As 2 S 3 +10O 2 +C ==== 2As 2 0 3 +6S0 2 +CO 2
Fe 3 (As0 4 ) 2 +C ==== As 2 0 3 +3Fe0+CO 2
CaO·As 2 O 5 +C ==== As 2 O 3 +CaO+CO 2
The suboxide of arsenic (As 2 0 3 ) is a volatile matter. Highly priced arsenic oxide (As 2 O 5 ) is less volatile and can form stable arsenates with certain basic oxides:
As 2 0 3 +Si0 2 +O 2 ==== As 2 O 5 +Si0 2
FeO(CaO)+As 2 O 5 ====Fe0·As 2 O 5 (or Ca0·As 2 O 5 )
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, the method of dephosphorization tungsten concentrates containing phosphorus tungsten concentrates often apatite Ca 5 (P0 4) 3 ( F, Cl. OH), PO 4 xenotime and monazite (Ce, La, Th) PO The form of 4 phosphates exists. 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 by infiltration method, fine-grained concentrate using stirring leaching, which can reduce phosphorus content to below 0.05%. .
(2) Dephosphorization by flotation. If there is phosphorus impurity in the form of phosphorus ore, monazite, etc. in tungsten concentrate, 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, sodium carbonate as a adjusting agent, can achieve the purpose of reducing phosphorus, and comprehensively recovers the 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, it is possible to remove the sulfide of molybdenum or to leach with a hypochlorous acid solution by means of floating or flotation, or to remove molybdenum in the form of molybdenite. 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 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 are also transferred into the solution. The acid solubility of tungsten increases with increasing hydrochloric acid concentration and temperature.
V. 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 floating method.
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, tin 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.
It is rare for other impurities in tungsten concentrate to exceed the standard. 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 of the standard.
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