Application of Pneumatic Flotation Column in Molybdenum Flotation Recovery

1.       Brief Description of Molybdenum Flotation Method

Molybdenite (MoS2), with a molybdenum (Mo) content of 60%, has good natural floatability and can be easily floated with non-polar oil, or even just with foaming agents. However, there are also refractory molybdenite ores that are difficult to float. Research has shown that molybdenite with larger lattice spacing is more difficult to float. For difficult-to-float molybdenite, it has been found that copper ions can be adsorbed at the crystal edges, so yellow drugs can be added to enhance its flotation by acting as collectors.

During low-temperature oxidation of molybdenite, soluble surface oxides that can be dissolved in water are formed, with approximate composition of MoO2.6~3. During high-temperature oxidation, insoluble surface oxide MoO3 is formed, which reduces the floatability of molybdenite. Washing with potassium hydroxide solution can remove the influence of such oxides on floatability.

The collectors for pure molybdenite include non-polar oils such as kerosene, transformer oil, and neutral oil. Emulsification can be done to enhance the effect of oil collectors. There are also patented reports of effective collectors for molybdenite, such as pentanol. Pine oil is preferred as a foaming agent. Regulators widely used include water glass, sodium carbonate, and caustic soda. Starch is commonly used as a depressant. In recent years, a sulfanilamide ester developed inChinahas been successfully applied in molybdenum flotation. This reagent, called "Synthex" (Syntex) in foreign countries, is an emulsifier that has both foaming and collecting properties, and can enhance the infiltration and diffusion ability of hydrocarbon oil collectors on the surface of molybdenite, thereby improving its floatability. (The above text is quoted from Chapter 5 of "Mineral Resources Processing Technology and Equipment").

The original ore content of molybdenite is relatively low, and the concentrate requires high grade and low impurity content, usually requiring 7-8 stages of concentration, and some mines even use more than a dozen stages of concentration to obtain qualified molybdenum concentrate.

2. Examples of Industrial Application of Flotation Columns

Analysis of the Application of Flotation Columns in a Molybdenum Mine in Shaanxi

The original flotation process of the beneficiation plant used one roughing, two scavenging, and eight cleaning stages. After all the flotation machines were replaced with flotation columns, the flotation process was changed to one roughing, three scavenging, and five cleaning stages.

The production indicators before and after the transformation are shown in the table below:

To verify the advantages of flotation columns in the recovery of fine-grained minerals, the particle size of the products before and after the transformation of flotation columns was analyzed in detail, and the specific results are shown in the table below.

From the analysis results, it can be seen that the recovery rate of flotation machines with a particle size above +0.074mm is significantly higher than that of flotation columns, especially for the +0.15mm (100 mesh) particle size, which is 11 percentage points higher.

In the particle size range of -0.074mm, flotation columns are superior to flotation machines, and the grade of the concentrate is much higher than that of flotation machines.

Due to the predominance of fine-grained molybdenite in the occurrence state of the scheelite-molybdenite orebody, flotation columns are more suitable for this orebody than flotation machines.

4. Analysis of the reasons:

From the perspective of industrial production indicators, the use of inflatable flotation columns in the recovery of the molybdenum ore in this mine is significantly better than that of flotation machines.

Under the same conditions, the flotation concentrate grade of the flotation column is slightly higher than that of the flotation machine, with an increase of about 5 percentage points, and the recovery rate is increased by 0.5 percentage points.

We analyzed the main reasons as follows:

A;The embedded particle size in the ore body is relatively fine, with a proportion of 52.31% below 0.019mm (625 mesh). In the 50-10 micron particle size range, the recovery effect of the flotation column is significantly better than that of the flotation machine.

B;The processing capacity of the flotation column per unit volume of pulp is far greater than that of the flotation machine, which leads to more complete recovery.

C;The number of bubbles in the flotation column is much larger than that of the flotation machine, and the contact probability between the target minerals and the bubbles is higher. Due to the low original content, a larger enrichment ratio is needed. Since the flotation column can produce a foam layer of about 1 meter thick at the top, the flotation accuracy is much higher than that of the flotation machine, and the flotation process can be effectively shortened.

D;The flotation column uses high-pressure gas to produce bubbles instantly, and the high-pressure gas instantly bursts to produce a large number of micro-nano bubbles. Under the combined action of continuous bubbles and micro-nano bubbles, the kinetic flotation rate constant K can be significantly improved. Molybdenum ore has good floatability and is suitable for rapid flotation.

E;The smaller the diameter of the bubbles, the bigger the surface energy and the longer the residence time in the pulp. Because the surface energy of micro-fine bubbles is high, it is easy to break through the water film on the surface of hydrophobic particles and adhere to the surface of hydrophobic particles. Due to the large number of micro-fine bubbles, the "bubble bridge" effect is generated, which can strengthen the aggregation of hydrophobic particles. This is also the reason why the recovery effect of micro-fine minerals in the flotation column is better than that of the flotation machine.

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