Six Factors Affecting The Flotation of Lead-zinc Ore

The flotation process of lead-zinc ore is one of the important means to extract lead-zinc ore, mainly because its mineral composition elements are more and the floatability has obvious differences. Flotation can obtain better lead and zinc minerals, but there are many factors that affect the flotation effect. This article will explain the six major reasons that affect the flotation of lead-zinc ore.

1. Grinding Fineness

The flotation particle size is an adjustable factor, often expressed as grinding fineness, and is mainly achieved through crushing and grinding operations. During the flotation process, the ore needs to be fully crushed and ground to expose the floatable mineral surface. It requires the dissociation of the mineral monomers and the grinding to an appropriate fineness. If the ore particles are too coarse, even if the mineral monomers have been dissociated, they will not float because they exceed the buoyancy capacity of the bubbles. The upper limit of the flotation particle size of various minerals is different. For example, sulfide ores are generally 0.2~0.5mm, and non-sulfide ores are 0.25~0.3mm. If the ore particles are ground too finely, such as less than 0.01mm, they will not float well. Therefore, flotation grinding requires that the mineral monomers are dissociated, but not too coarse or “over-crushed”. For impregnated ores with extremely fine embedded particle sizes, since the monomer dissociation degree requires very fine grinding, it is usually necessary to add a slime dispersant during flotation, or use selective flocculation flotation (adding selective flocculants) or perform “mud and sand separation” (i.e., the process of treating fine mud and coarse sand separately).

2. Slurry Concentration

The adjustment of slurry before flotation is an important part of the flotation process. Before the slurry enters the flotation machine, it must be reasonably adjusted (i.e. “slurry adjustment”) so that the flotation machine can fully play its role. In most cases, the concentration of slurry adjustment and roughing operation is almost the same as the concentration of classification overflow. The adjustment of slurry concentration is also limited by fineness. When the fineness is required to be fine, the classification overflow is thinner; when the fineness is required to be coarse, the classification overflow is thicker. In actual production, the roughing operation uses a thicker slurry to save reagents; the use of a thinner concentration of ore for the fine selection is conducive to improving the grade of the concentrate; the concentration of the scavenging operation is affected by the roughing operation and is generally not controlled separately. The slurry concentration of the roughing and scavenging operation also affects the flotation time, because when the flotation machine is configured to a certain extent, its effective volume is a determined slurry concentration, and the flow time (i.e. flotation time) is longer; the thinner the slurry, the shorter the flow time.

flotation machine

3. Reagents

The adjustment of reagents in the flotation process includes exerting efficacy, reasonable addition, mixed-use, adjusting the concentration of reagents in the slurry, and controlling the pH value. Refer to these, we will provide more details about these in later blog updates.

4. Foam Adjustment

Froth flotation is a process of sorting at the liquid-gas interface, so foam plays an important role. The size and number of bubbles, the stability of the foam and the thickness of the foam layer are related to the type of flotation machine used (mainly the amount of aeration and the intensity of stirring), the properties of the ore, the reagent system and other factors. When other conditions remain unchanged, the thickness of the foam layer is mainly adjusted by controlling the slurry surface. Practice has shown that to stabilize the flotation operation, it is necessary to maintain a certain thickness of the foam layer. Once the foam layer is thicker, the concentrate grade is higher.

5. Temperature Influence

The slurry temperature can affect the chemical reaction rate between the mineral surface and the reagent and often plays an important role in the flotation process. However, most flotation plants currently perform flotation at room temperature, that is, the slurry temperature is not controlled and changes with the air temperature. Heating flotation comes from two requirements. One is the nature of the reagent. Some reagents can only play their effective role at a higher temperature. The other is that some special flotation processes require the temperature of the mineral to be increased to achieve the purpose of mineral separation. Steam or hot water is often used for slurry heating. With the development of the flotation process of complex sulfide ores. It is necessary to find a more effective separation method. Therefore, many studies have been conducted on the heating flotation separation of copper-lead, copper-molybdenum, zinc-sulfur, copper-nickel, etc., and they have been applied in some mineral processing plants at home and abroad. For example, in the separation of copper-sulfur mixed concentrate, steam heating can replace lime to suppress sulfur and float copper.

6. Influence of Water Quality

Flotation is carried out in water. The “hardness” of water (depending on the content of Ca2+ and Mg2+), the “turbidity” of water (the content of solid impurities per unit volume), and its composition also have an impact on flotation. The water used for flotation varies from place to place and from time to time. In the study of flotation technology, attention must be paid to the quality of water used for flotation. To save water resources, the utilization of return water has received more and more attention. The characteristic of flotation return water is that it contains more organic and inorganic reagents. The use of return water can save reagents; but due to its complex composition, improper use will affect the sorting effect. The practice has shown that the utilization of return water for the flotation of monometallic ores is relatively simple. When selecting polymetallic ores, the recycling of return water is more complicated. It is necessary to conduct a comprehensive analysis of the water quality of each flotation stage before a proper decision can be made on the utilization plan.

The above discusses the influence of different factors on the flotation process of lead-zinc ore from the aspects of grinding fineness, slurry concentration, reagents adding, foam adjustment, temperature, and water quality. I hope it will be helpful for your lead-zinc ore flotation process.