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Quality molybdenum concentrate and molybdenum concentrate different non-premium prices, July 1, 1975 Chrysler Max molybdenum concentrate sales price of the company, quality of 2.5% to 17% higher than non-premium.
The standard for high-quality molybdenum concentrates developed by Claymax, USA is MoS 2 ≥ 95%, Cu < 0.15%, Pb < 0.05%, and CaO < 0.15%.
The flotation molybdenum concentrate produced by the copper -molybdenum plant usually contains more than 0.5% copper, and the lead and calcium oxide content often exceeds the standard. The flotation molybdenum concentrate produced by the molybdenum plant is mixed, and sometimes it is difficult to meet the quality standards.
In order to produce high-quality high-purity molybdenum concentrate, the following common production processes are as follows.
1. Enhanced beneficiation
Canada Ndakco obtained two products in the selection process: high-quality molybdenum concentrate containing 56.88% molybdenum and ordinary molybdenum concentrate containing 51% molybdenum.
Beijing Tianhe Chemical Plant uses a flotation column to carry out a seven-stage open-circuit flotation of molybdenum concentrate. While obtaining high-quality molybdenum concentrate (containing 97% of MoS and 37% of molybdenum recovery), it also produces a part of molybdenum ore. El Salvador uses a nine-stage selection to separate high-quality molybdenum concentrates (containing 97% of MoS 2 and 65% of molybdenum) from conventional molybdenum concentrates, while also producing a portion of common molybdenum concentrates.
The author uses TL agent to strengthen flotation, and produces high-quality molybdenum concentrate with molybdenum content of 57%~58% and molybdenum recovery rate≥97% from molybdenum concentrate containing 47% molybdenum, and also produces a small amount of molybdenum. Mine (Mo ≤ 2%).
2, hydrochloric acid leaching
When the flotation concentrate contains high CaO and PbS, it can be leached with hydrochloric acid.
Common calcium-containing minerals are calcite (CaCO 3 ), followed by fluorite (CaF 2 ). They are not easy to float and usually enter the molybdenum tailings. However, due to continuous organisms, oil contamination or mechanical inclusions, a small amount of molybdenum concentrate is often entered, causing its CaO content to exceed the standard.
Calcite is soluble in hydrochloric acid to form soluble CaCl 2 :
CaCO 3 +2HC1=CaC1 2 +CO 2 ↑+H 2 O
Canada Ndak has a flotation molybdenum concentrate with a CaO content of 0.4%. Before the filtration, hydrochloric acid is added to leaching at normal temperature and pressure to reduce the CaO content of the molybdenum concentrate to 0.03%.
Galena (PbS) can also react with hydrochloric acid to form PbCl 2 . PbCl 2 is insoluble in water, but when heated, PbCl 2 reacts with Cl - to form soluble PbCl 3 - :
2PbS+6HCl=2PbCl 3 +3H 2 S↑
The grade of molybdenum concentrate in the Henderson Molybdenum Plant in the United States is: 90% MoS 2 , 0.8% FeS 2 , 0.2% Pb, 0.5% CaO, 0.05% Cu, 6% acid insoluble (mostly silicate) . In order to reduce the content of lead and calcium oxide, high-quality molybdenum concentrate was produced. The 5% solution of HCl was used to leaching at 80 ° C for 16 h. PbCl - 3 entered the filtrate and cooled to crystallize PbCl 2 . The lead content in the molybdenum concentrate was reduced to 0.03%, and the calcium oxide content was lower, and a high-quality molybdenum concentrate was obtained.
When the calcium oxide is too high in the Yangjiazhangzi molybdenum selection plant, industrial hydrochloric acid is added to the concentrate chute before the molybdenum concentrate is filtered, and the content of calcium oxide in the product can also be lowered.
However, fluorite and calcium silicate (such as calcium Molybdenum ore calcium iron garnet), with the addition of hydrochloric acid is not immersed.
3. Chloride salt leaching
Chlorination leaching is the oxidation of chalcopyrite or galena with FeCl 3 or CuCl 2 with high oxidation properties:
CuFeS 2 +4FeCl 3 =CuC1 2 +5FeC1 2 +2S
PbS + 2FeC1 3 = PbC1 2 + 2FeC1 2 + S
The Fe 3+ ion oxidizes the sulfide, and the standard potential Eo(V) of S is:
Sulfide
FeS
ZnS
CuFeS 2
FeS 2
Cu 2 S
CuS
E 0 (V)
0.06
0.264
0.264
0.42
0.56
0.59
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In practice, leaching of sulfide minerals difficulty order: pyrrhotite <chalcocite <galena <sphalerite <chalcopyrite <pyrite. Immersion, in addition to iron chloride or copper chloride, an alkali metal added must often chloride salts (such as NaCl) or alkaline earth metal chloride (e.g. CaC1 2), which can enhance immersion in the boiling point of the leaching It can be carried out at a high temperature of 100~110 °C; it can provide a large amount of C1 - ions for PbCl 2 and CuCl, so that the insoluble PbCl 2 and CuCl form soluble complex ions into the liquid phase, and Cu and Pb leaching can be realized:
PbCl 2 +Cl - → PbC1 3 -
CuCl+CI - → CuCl 2 -
The immersion liquid is also added to the HCI to maintain a certain acidity.
Chlorination leaching of molybdenum concentrates has already been carried out in Brenda and put into production. This process is also commonly referred to as the Brenda method.
Brenda copper-molybdenum mine is the world's copper-molybdenum grade selection plant. The ore contains 0.183% copper and 0.049% molybdenum. The copper minerals in the ore are mainly chalcopyrite.
Brenda's flotation molybdenum concentrate contains an average of 54.97% molybdenum, 0.32% copper, and 0.38% lead (1974). Obviously, the content of copper and lead is high. After the bromo leaching process researched by Noranda Company Research Center in 1974, the grade of molybdenum concentrate increased to 55.89% Mo, 0.054% Cu, 0.033% Pb. . Its high quality was rare in the world at the time.
The immersion formulation is usually: CuCl 2 1%, FeC1 3 10%, CaCl 2 (or NaC1) 30%, HCl 10%. The leaching is carried out under normal pressure and the leaching temperature is usually controlled at 100 to 110 °C. Leaching is intermittent operation, each time 2~3h, after leaching, CuCl 2 - and PbCl 3 - are separated by filtration. The filtrate contains the reaction products CuCl 2 - , PbC1 3 - , FeC1 2 ... and also contains untreated agents. Usually, 30% of the filtrate is discarded to prevent Cu, Pb, etc. from accumulating in the immersion liquid, and the remaining filtrate is passed through chlorine gas, and the FeCl 2 is recycled to FeCl 3 and recycled.
The leaching cost is about 9-11 cents/kg molybdenum and the price is increased by 95 cents/kg molybdenum. Brenda has an annual profit of about $3 million.
Similar plants such as Chilean Andina, Canada's Haimont, and the United States' West Yalita have adopted a similar chlorine salt leaching process to reduce the copper content of molybdenum concentrate to less than 0.1%.
The chloride salt warming leaching process is in principle suitable for removing almost all sulfurized impurities. However, due to high drug consumption and high energy consumption, it is usually only used for leaching of hydrochloric acid and cyanide leaching of chalcopyrite which is difficult to remove. Of course, when removing chalcopyrite, it is naturally also immersed in other sulfurized impurities.
4, cyanide leaching
Cyanide reacts with copper ions on the surface of copper sulfide to form soluble copper ammine ions, which dissolve copper sulfide minerals. Molybdenite does not react with cyanide and is insoluble in sodium cyanide solution. According to this principle, copper-molybdenum separation can be carried out by cyanide leaching.
Different copper minerals have different solubility in cyanide solution, see table below.
Table of solubility of several copper sulfide in cyanide solution 1
mineral
Dissolution rate
(%)
Temperature (°C)
Copper ore
(Cu 2 S)
Copper ore
(Cu 5 FeS 4 )
Sulfur arsenic copper ore
(Cu 3 AsS 4 )
Beryllium copper mine
(Cu 12 Sb 4 S 13 )
Chalcopyrite
(CuFeS 2 )
twenty three
45
90.2
100.0
70.0
100.0
65.8
75.1
21.9
43.7
5.6
8.2
10.1% NaCN, 24h
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Obviously, secondary copper minerals such as chalcopyrite have high solubility in cyanide solution, and can be well leached at normal temperature and normal pressure. The solubility of molybdenum ore in cyanide solution is very low and it is difficult to leach. The cyanidation leaching method is also only suitable for leaching secondary molybdenum minerals in molybdenum concentrates.
Leaching is carried out at normal temperature and normal pressure. The amount of sodium cyanide is 1~1.5kg/t.
Several large copper-molybdenum mines in Chile are mining secondary enriched copper belts, which are selected in the ore and the main copper mineral is copper (Cu 2 S). After copper-molybdenum separation, the obtained molybdenum concentrate contains about 0.5% to 1.0% of copper. In order to reduce the copper content to less than 0.3%, most of the simple cyanide leaching process is adopted.
Chile's Chuquicamata flotation molybdenum concentrate contains 52.5% molybdenum and 1.5% copper (bronze ore). After continuous and batch two-stage cyanidation leaching, the final product contains 54% molybdenum and 0.1% copper. The first stage leaching consumes 0.8 kg/t of sodium cyanide and the second stage consumes 0.4 kg/t of sodium cyanide.
Copper-molybdenum mines such as Salvador, Kwajung and Pakpara in Chile also use a cyanide leaching process to leach the copper ore in the flotation molybdenum concentrate, so that the final product contains less than 0.3% copper.
The cyanide leaching drug has low consumption and can work under normal temperature and normal pressure, and the immersion liquid is less corrosive and easy to implement. However, sodium cyanide is too toxic, which seriously affects its promotion.
5, fluorination leaching
Flotation molybdenum concentrate (even high-purity molybdenum concentrate) also often contains a certain amount of quartz or silicate. In the preparation of MOS 2 lubricant, hydrofluoric acid must be added to remove it.
The mechanism by which hydrofluoric acid leaches off silicon-based impurities is to form soluble silicates:
SiO 2 +6HF=H 2 SiF 4 +3H 2 O
Ca 3 Fe 2 (SiO 4 ) 3 +8HF+6HCl=3CaSiF 6 +2FeC1 3 +12H 2 O
HF is a medium-strong acid with a low degree of ionization (3.53 × 10 -4 ). In order to increase the F - ion concentration, the reaction is accelerated. In 1978, the Romanian patent changed to ammonium fluoride (NH 4 F) instead of HF.
Both HF or NH 4 F are added with HC1 (H 2 SO 4 ) and heated under heating. Conventional glass-lined reactors are challenged by the dissolution of F - silicates.
A chemical plant in Shanghai consumes 350% of hydrofluoric acid and 30% of 30% hydrochloric acid per 1 t of product containing MoS 2 97%. The final product contains SiO 2 <0.5%,
The authors fluorinated and leached in a glass fiber reinforced plastic (PMRP) reactor. The HF concentration in the immersion liquid was 3% to 5%, the concentration of HC1 was 1%, the reaction solution was 1:1, and the reaction temperature was 75 to 80 °C. After immersion for 3~4h, the content of SiO 2 in the product decreased to 0.0275%, and the content of molybdenum was over 59%.
Fluorinated leaching cannot remove non-molybdenum sulfide impurities in molybdenum concentrate. When MoS 2 lubricant (Molykote) is produced, it is sometimes necessary to increase the process of chlorination of copper sulfide and iron before fluorination and leaching.
Chemical dressings such as cyanide leaching, chlorination leaching, and fluorination leaching generally produce high-purity molybdenum concentrates that cannot be achieved by flotation processes.