Molybdenum- calcium ore (CaMoO 4 ) is the same as the scheelite crystal form, as shown in Figure 1.
Figure 1 Crystal structure of molybdenum ore
Pure molybdenum ore has no unique industrial value. It is often symbiotic with molybdenite or scheelite. Comprehensive recovery can be considered when selecting molybdenum sulfide or scheelite.
The molybdenum-calcium ore in the molybdenum sulfide deposit is mainly a molybdenite oxidation product, which is often distributed in the oxidation zone of the molybdenum sulfide deposit and coexists with the molybdenite.
The oxidation-reduction phase transformation of molybdenite in a gas-water medium is shown in Figures 2 and 3. In the ash component, the molybdenite is first oxidized to a MoO 2 ·SO 4 complex ion, which is in contact with the calcium bicarbonate solution and reacts to precipitate calcium molybdate:
2MoS 2 + 9O 2 + 2H 2 O=2(MoO 2 SO 4 )+ 2H 2 SO 4
MoO 2 SO 4 + Ca(HCO 3 ) 2 = CaMoO 4 ↓ + H 2 SO 4 + 2CO 2
Molybdenum-calcium ore accounts for 5% to 40% of the total molybdenum content depending on the degree of oxidation of the molybdenum ore.
Figure 2 Eh-PH diagram of Mo-Fe-S-H2O system
Figure 3 Molybdenum changes with Eh-PH state in aqueous medium at 25 ° C, 0.1 MPa
Molybdenum-calcium ore is a typical oxoacid salt. The crystal lattice is tightly bonded by strong polar bonds and does not have natural floatability. When the molybdenum ore is captured by the hydrocarbon oil, the monolithic molybdenum-calcium ore is difficult to float and is lost through the tailings.
Among the molybdenum ore, the molybdenum-calcium ore is closely related to the molybdenum ore, and sometimes it is wrapped in the surface of the molybdenite grain, forming a molybdenite mineralized in the surface molybdenum-calcium mineral and losing the planktonic activity.
According to the determination, the former Soviet Union Barr Hashemi mineral processing plant in East Cohen de molybdenum sulfide ore, molybdenum final tailings about 0.01% to 0.02%, which was about 60% of molybdenum Mo presence of calcium deposit, the remaining molybdenum Molybdenum ore, a poor molybdenum ore body, and a muddy molybdenum deposit, which are mineralized by surface molybdenum and calcium. [next]
According to Tang Shunying, the Yangjiazhangzi Molybdenum Plant is generally containing 0.013%~0.015% of molybdenum in the final tailings produced by the Molybdenite. Among them, about 60% is molybdenum or molybdenum ore. mine. Because they are difficult to float, about 50% to 55% have been lost in the rough selection, and another 5% to 10% are re-grinded and then left by the tail. According to this calculation, 7.7% to 11.3% of the molybdenum content of the ore is a molybdenum ore mineralized by molybdenum ore or molybdenum. The reasons for the difficulty in recycling molybdenum-calcium ore are:
(1) The oxidized zone ore is subjected to surface mineralization, and the mineral lattice is damaged to some extent, and it is easy to be muddy when grinding.
(2) calcium-containing ores typically associated other minerals, such as calcite (CaCO 3), fluorite (CaF 2), apatite (Ca (PO 4) 2), etc., which are calcium and molybdenum ore (CaMoO 4) with the same The oxoacid salt containing the same cation (Ca 2+ ) (except CaF 2 , no oxygen), the floating property is very close, so that when the molybdenum-calcium ore is floated, it is difficult to separate from the calcium-containing gangue.
The practice or research on the recovery of molybdenum-calcium ore is still rare. It is only found in the study of the East Cohenrad ore by the former Soviet Union Mining Research Institute. The Balhas Concentrator has separate the molybdenum-calcium ore recovery practice and the molybdenum-calcium ore flotation process. Flotation and mixed flotation.
Separate flotation is a process for recovering molybdenum-calcium ore from molybdenite flotation tailings. 1950 Soviet Union И · A · Principal Strickland who first studied and gold for the first time Barr Hashemi concentrator, Cohen east of La molybdenum sulfide flotation tailings recovery of molybdenum calcium deposits.
Molybdenum ore calcium collectors commonly used oleic acid (about 100g / t) simultaneously recovering molybdenite, must kerosene was added (200g / t), using a foaming agent xylenol. The flotation production process includes rough selection, sweep selection, coarse concentrate with water glass (1300g/t), steaming (temperature treatment at 85 °C for 30~40min), filtration, drug removal, and mixing with fresh water for four Selected. The recovery of kerosene and oleic acid is weak and the selectivity is poor. Therefore, the grade and recovery rate of molybdenum-calcium ore in foam products are low, and it is impossible to produce qualified molybdenum concentrate, which can only obtain 7.5%~15% of molybdenum. Copper, 2% to 3%, 30% to 35% calcium, 3% to 8% iron , and 4% to 6% sulfur. The medium mine is also subjected to a calcination-leaching extraction process to prepare calcium molybdate (CaMoO 4 ).
The former Soviet Union Institute of Mining Research studied the use of sodium alkyl sulfate as a dispersant for oleic acid and kerosene. The effect is shown in Figure 4 and Figure 5.
Figure 4 Effect of emulsifier (sodium alkyl sulfate) on flotation of molybdenum ore
Figure 5 Effect of dispersant on flotation of molybdenum-calcium ore
Obviously, the addition of a small amount of dispersant sodium alkyl sulfate can increase the recovery rate and floating speed of molybdenum ore.
The “separate†flotation failed to obtain qualified molybdenum concentrate, and the flotation equipment increased. To this end, the former Soviet Union Institute of Mining Research studied the process of "mixing" the collection of molybdenum sulfide and molybdenum oxide. [next]
The "separate" flotation and "mixed" flotation kinetic curves are compared, as shown in Figures 6 and 7.
Figure 6 Flotation kinetics curve of molybdenum oxide
Figure 7 Total molybdenum flotation kinetics curve
It can be seen from the figure that the “mixing†and “separate†flotation process indicators are the same, but the flotation speed is faster and the flotation time is shortened. Obviously, molybdenum sulfide and molybdenum oxide minerals can be mixed and floated without reducing the quality of the concentrate.
The molybdenum or molybdenum-calcium ore mixed flotation was industrially tested in 1963. The test was carried out on the original sulfide ore flotation series. The ball mill was added with soda (600g/t) and kerosene (200g/t). The mixture was added with sodium oleate (100g/t) and alkyl sulfate (10g/t). Kerosene was added to the selection and sweeping. The sodium oleate and alkyl sulfate were also foaming, and the amount of the foaming agent xylenol was reduced by 50%. The steaming and selection processes have not changed much. The test confirmed that the mixed flotation ratio was “separate†flotation, and the molybdenum recovery rate was increased by 5% on average.
Whether to adopt mixed flotation, first of all depends on whether a qualified mixed molybdenum concentrate can be obtained, and the molybdenum-calcium ore concentrate produced by the “separate†flotation contains 7.5 % to 20% of molybdenum. According to this calculation, the molybdenum in the mixed concentrate is calculated. The calcium ore fraction cannot exceed 13% to 18% of the total molybdenum. That is to say, the proportion of molybdenum-calcium ore in the original ore cannot be too high, otherwise it is difficult to ensure the quality of the mixed concentrate.
The molybdenum-calcium ore in the molybdenum deposit is mainly a product of tungsten in the molybdenum-like substitution of scheelite (CaWO 4 ), and a rare molybdenum-calcium ore containing no tungsten is rare. Molybdenum enters the tungsten mineral lattice to replace tungsten, and as the substitution amount increases, scheelite, tungsten molybdenum ore, molybdenum tungsten ore, molybdenum ore is formed. Its crystal form is the same as scheelite and molybdenum calcium; its planking performance is similar to that of scheelite and molybdenum ore. The tungsten ore containing molybdenum ore is in the flotation, the molybdenum-calcium ore and the scheelite cannot be separated, and at the same time enter the tungsten concentrate, and then the leaching-extraction process is used to separate and purify the molybdenum product.
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