How Many Things Do You Know About Flotation Process?

In the process of analyzing the ore properties, if the mineral disseminated grain size is found to be extremely fine and the physical and chemical properties of the mineral surface are highly different, flotation process is the perfect separation method. The flotation process is a mineral processing technology with a wide application range and strong adaptability,and the finest particle size flotation can process can reach 5~10μm.

Flotation process can be applied to almost all kinds of minerals such as non-ferrous metals, rare metals and non-metals. It can be used in the processing of more than 100 kinds of minerals, especially for gold extraction. At the same time, the flotation process is also a relatively complex mineral processing process, and there are many factors affecting the flotation effect,such as ore size, ore properties, pulp pH and reagent.

The basic theoretical knowledge of the flotation process flow is described below, along with a brief description of the operation techniques.

Flotation process mainly includes grinding, pulp conditioning and dosing, flotation separation and dewatering of foam products and tailings products after flotation. Before the flotation operation, the ore needs to be ground to optional particle size range, and generally needs to be ground to less than 0.1 mm. When the flotation is too coarse, the ore particles(greater than 0.1 mm) will increase the exfoliation force of the ore due to the larger weight. Very fine particles (usually means the particle size of ore less than 5-10 μm), due to the small weight of the mineral particles, it is easy to adhere to the surface of the coarse particles, so that the floatability of the coarse particles is reduced. So if the ore particles are too big or too fine,the recovery rate of ore would reduce.

When the ore particles are too coarse, we should

1) Use a collector with strong collecting power, you can also add auxiliary collectors such as kerosene and diesel to strengthen the collection of coarse particles and increase the adhesion of the ore particles to the bubbles, thus reduce the falling of mineral particles.

2) Appropriately increase the mass fraction of the pulp and increase the buoyancy of the pulp.

Under the premise of ensuring the stability of the foam layer, the mixture should be appropriately stirred to promote the suspension of the coarse particles and the chance of adhesion to the bubbles.

In the flotation of fine ore particles, we should

1) Use selective flocculation flotation, the flocculant is used to selectively flocculate the target mineral particles or gangue fine mud, and then separate them by flotation.

2) Use carrier flotation, using the ore particles of general flotation size as a carrier, so that the fine particle of target mineral cover is floating on the carrier.

The carrier may be of the same type or a heterogeneous mineral. For example, pyrite may be used as a carrier for flotation of fine gold. The calcite may be used as a carrier to float the fine iron and titanium impurities in the kaolin.

In the process of pulp conditioning and dosing, it is necessary to control the pulp within proper concentration and pH value. Adjust the concentration of the slurry, add the required water and flotation reagents,and make the slurry concentration meet the flotation requirements. Add a collector or activator to increase the hydrophobicity of the surface of the mineral to be floated, or add an inhibitor to cause the surface of the mineral that is not tend to float to become more hydrophilic, inhibits their floating,or add a blowing agent to promote bubble formation and separation. In practice,the concentration of the slurry needs to be determined according to the property of the flotation ore and related technical requirements.

When the ore is coarsely selected, the slurry concentration should be 25% to 35%. During the flotation process of fine particles and the ore containing high mud, the slurry concentration should be 10% to 20%. The larger the particle size is, the thicker the slurry concentration should be. When the flotation density is small, the fine and muddy minerals should use a relatively thin pulp.

The pH of the pulp has a great influence on the flotation index. The mineral can only be fully floated or suppressed at a suitable pH value. The pH value is controlled by adjusting reagents such as lime, sodium sulfate and sulfuric acid.There are usually two methods for controlling the pH:

 1) Use fixed-value adjustment to keep the pH constant. This is a method that is commonly used in some domestic factories.

2) Track the changes of ore properties and adjust the pH value in time to obtain better flotation indicators. For example, adjust the pH in the process of copper-nickel mixed flotation to achieve the maximum possible recovery.

In the process of pulp conditioning and dosing, it is necessary to prepare slurry of suitable concentration for the next process.

When the adjusted slurry is sent to the flotation tank,the mineral particles with strong hydrophobic surface adhere to the surface of the bubble and are carried by the bubble to float up to the surface of the slurry, form a foam layer, and then being scraped out to be a concentrate. And the particles which stay in the slurry and are excluded from the tank along with the slurry flow are tailings.

In the process of flotation separation, it is necessary to pay attention to the pH value of the slurry at all times. The pH value should be measured with the test paper at intervals to ensure that the pH value is maintained at a stable value.

Moreover, the concentration of the slurry and the liquid level need to be stable to ensure the amount of scraping and the foam should be scraped off the board completely. The stability of the entire process is important during the separation process.

It can be seen that the flotation process is highly complex.

In order to achieve the best results in the flotation separation operation, the staff in the mineral processing plant needs to have a holistic understanding of the entire process. Both initial grinding operation and the control of the overall process stability during the flotation separation process are essential.