Molybdenum is a very important non-ferrous metal with high hardness, corrosion resistance, and the third-highest melting point (2,623°C) of all metals. It is one of the most valuable alloying agents in steels and cast irons.1. Molybdenum mining
Molybdenum exists in many minerals, but only molybdenite is suitable for the industrial production of molybdenum products.
Molybdenite can be the only mineralization in a single ore body, but it often co-exists with other metals, especially copper. The molybdenum content of various ore bodies is 0.01-0.25%.
If molybdenum ore is close to the surface, open-pit mining is used to dig the overburden to expose the ore body for easy mining.
If molybdenum ore is located deep underground, the underground ore block caving is used. Large ore blocks are cut from the bottom and collapse under their weight. The resulting ore is moved to the ground for the processing.
2. Extraction of Molybdenum
The molybdenum production process is Crushing - Grinding - Molybdenum flotation - Roasting.
Please adopt the segmented grinding and multi-stage separation process. No excessive grinding.
2.1 Stage I Crushing and screening (Three-stage closed-circuit crushing)
(1) Large molybdenum ore is fed into a jaw crusher by a vibrating feeder for coarse crushing;
(2) It is screened by a vibrating screen, and sent to a cone crusher for medium crushing;
(3) Then it is sent to a sand maker for fine crushing. The final particle size is 12-15 mm.
2.2 Stage II Grinding (Two-stage and one-closed grinding)
(1) The crushed ore is sent to a ball mill for grinding. The molybdenum disulfide powder has a diameter of only a few microns.
(2) Then it is screened by a spiral classifier. The qualified powders are sent to the floatation machine, while the rest continues to be ground.
2.3 Stage III Molybdenum flotation ( Preferential flotation)
Molybdenum and gangue powder are mixed with floatation agents and aerated. Then the molybdenum concentrate is obtained, containing 85%-92% molybdenum disulfide.
How are the floatation reagents used?
Collectors: Non-polar oils, such as Syntex, Xanthate Ester.
Regulators: Lime.
Inhibitors: Water glass, cyanide or sulfide.
Inhibitors depend on the impurities contained in molybdenum concentrate.
Copper and iron: Use sodium sulfide or sodium hydrosulfide, cyanide or ferricyanide.
Lead: Use dichromate, Nokes.
Calcium oxide: Use water glass, sodium hexametaphosphate or organic glue as inhibitors, and finally leach with hydrochloric acid.
Carbon minerals: Use sodium hexametaphosphate and CMC. Or use ferric chloride, water glass, and sodium hexametaphosphate.
Silica (Sio2): Use CMC.
If necessary, chemical beneficiation is used.
1. Secondary copper sulfide is leached with cyanide.
2. Chalcopyrite is leached with ferric chloride solution.
3. Galena is leached with hydrochloric acid and ferric chloride solution.
2.4 Stage IV Roasting
Molybdenum concentrate is roasted in a rotary kiln at 500-650?. Roasting converts it into Molybdenum Calcine (MoO3), also called Industrial Molybdenum Oxide (MoOx).
Industrial molybdenum oxide contains 57% molybdenum and less than 0.1% sulfur.
A multi-hearth furnace is used for roasting.
(1) Gas and heated air are blown from the bottom.
(2) The large rotating rake arm continuously flips the molybdenum concentrate to promote chemical reactions.
(3) The discharged roasting furnace gas is passed through a desulfurization system or lime washing device to remove sulfur dioxide.