In addition to molybdenum ores containing large amount of molybdenite and gangue, often also associated copper, lead, molybdenum, iron and other non-sulfide minerals. If the molybdenum ore is not strictly inhibited during flotation, they will be enriched in molybdenum concentrate to varying degrees, so that the product contains more than the standard. In 1979, in response to environmental protection requirements, Huairou Molybdenum Mine stopped adding cyanide, sulfide and other sulfide mineral inhibitors. The copper content of the molybdenum concentrate increased to 2.97%, which is 100 times more concentrated than the copper content in the ore (0.03% only). .
Most of the by-produced molybdenum concentrates are from copper-molybdenum ore. The valuable components are firstly copper minerals, which are obtained from copper-molybdenum mixed concentrates (usually containing 130% to 42% copper and 0.2% to 3% molybdenum). Qualified molybdenum concentrate, separation of copper and molybdenum is extremely important.
In molybdenum concentrate, non-molybdenum sulfide impurities are different from gangue, which not only reduces the molybdenum content of molybdenum concentrate (this effect is much smaller than the influence of gangue), but also in the deep processing of molybdenum concentrate. Molybdenum ore participates in the reaction together, affecting the quality of the product and causing great harm.
When molybdenum concentrate roasting, silicon impurities almost no change, but the metal sulfide (MeS) simultaneously with the oxidation of molybdenite oxidation to form the corresponding oxides (MeO). Firing the same environment, and then these metal oxides will oven gas with SO 3, P 2 O 5, As 2 O 3 ... the reaction to form the corresponding sulfates, phosphates, arsenates ....... Many salts are thermally stable, and they enter the molybdenum calcination to increase the content of harmful impurities such as S, P, and As in the molybdenum calcine. In the same roasting environment, these metal oxides will then react with the newly formed MoO 3 to form some stable molybdate. When preparing ammonium paramolybdate by ammonia leaching with these molybdenum-containing molybdenum calcine, CaMoO 4 is insoluble in ammonia water, and Fe 2 (MoO 4 ) 3 is insoluble in ammonia water, and they remain in the ammonia leaching residue and are discarded. Greatly reduce the ammonia leaching recovery rate of molybdenum. When high-purity molybdenum trioxide is produced by the sublimation method using these molybdenum-containing molybdenum calcines, the boiling points of PbMoO 4 and Bi 2 (MoO 4 ) 3 are consistent with the sublimation temperature of MoO 2 , which leads to an increase in lead and antimony content in the product. High and significantly affects the quality of molybdenum powder... The hazards of non-molybdenum sulfide impurities are far more than these.
For this reason, the content limit of non-molybdenum sulfide impurities is very strict in the quality standards of molybdenum concentrates formulated by various molybdenum countries or companies.
Common non-molybdenum sulfide impurities in molybdenum beneficiation are mainly copper minerals, lead minerals, iron minerals, especially chalcopyrite and chalcopyrite. The following will be introduced separately.
There are many kinds of copper minerals in nature, and the copper minerals in molybdenum ore or copper-molybdenum ore are mainly chalcopyrite and chalcopyrite.
Chalcopyrite (CuFeS 2 ) contains Cu 34.56 and S34.92%. It is the most common and the most valuable natural copper mineral in nature. Its crystal structure is shown in Figure 2-92.
Figure 2-92 Chalcopyrite crystal structure
The copper ore (Cu 2 S) contains Cu79.86% and S 20-14%, and has internal ore formation, but it is more found in the secondary enriched copper ore belt formed by oxidation leaching. It is the copper sulfide mineral with the highest copper content.
The porphyrite (Cu5FeS4) contains 63.3% Cu and S25.5%.
Copper blue (CuS) contains Cu67. 1%, S32.9%, which is also a common copper sulfide mineral, but the content is often very small.
The molybdenite produced by different molybdenum deposits or copper-molybdenum deposits has different ore-forming conditions and the flotation behavior is not the same. The distribution of molybdenite and copper sulfide minerals is different (the molybdenite is usually earlier than copper minerals). This has many adverse effects on copper-molybdenum separation. A common copper-molybdenum separation process is shown in the following table.
It should be noted that the inhibitors may be used singly or in combination, and in order to exert synergistic effects of the agents, the combination of several inhibitors is better.
Table 2-58 Common copper-molybdenum separation process
Classification | Craft or pharmacy | ||
Inhibitor only | Molybdenum floating copper | Dextrin inhibits molybdenum, xanthate captures copper minerals | |
Copper-free molybdenum | Cyanide | NaCN, KCN, Na 4 Fe(CN) 4 , Na 3 Fe(CN) 4 | |
Sulfide | Na 2 S, NaHS, (NH 4 ) 2 S | ||
Knox | P-Nokes (LR-744), As-Nokes (Anamol-D) | ||
Organic inhibitor | HSCH 2 COONa, HSCH 2 CHOH, etc. | ||
Oxidant + inhibitor | NaOC+Na 4 Fe(CN) 6 ;H 2 O 2 +Na 4 Fe(CN) 6 | ||
Nitrogen-filled + inhibitor | N 2 +Na 2 S(NaHS); N 2 +Nokes | ||
Heat treatment + inhibitor | Roasting method | Filtration-roasting-sorting | |
Steaming | Concentration-steaming-sorting | ||
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