How to judge the flotation effect by flotation foams?

During flotation, it is important to observing the state of foams in flotation cells to adjust the flotation effect when equipment and technology is normal running. Workers need to decide whether and how it needs to adjust for the dosing of reagents, the output of concentrates and the recycling amount of middles depending on the state of flotation foams. We will analysis how to judge the state of foams in flotation cells in next paragraphs.

When foams shows up, we can observe some phenomena such as: empty and full, size, color, glossiness, shape, thickness, hardness, liquidity, voice and so on. These phenomena are depending on the type, amount, size, color of the ore on the foams and the type and amount of foaming agents.

The foams is full when there are much and heavy minerals on them, while them are empty when there are little and slight minerals on them. The foams is stable when there is a high grade of raw ores and suitable agent amount. The foams is sick and empty when there is too much inhibitor and less collector. It is usually full foams in rough separation and concentrating, and empty foams in scavenging. Besides, the foams can also be too full or empty because of unsuitable amount of inhibitor and collector.

The size of foams varies from the characteristic of ore, agents and the size of flotation area. Different ores and different flotation flow creates different size of foams. The size of foams is concerned about mineralization of ores. Middlings have a good mineralization. If over-mineralization, the foams can’t merge each other, creating abnormal small foams. If weak-mineralization, the foams merge too much, creating big foams, which is easily bursting when the surface waves. Small foams usually shows in scavenging. Too much foaming agents can also increase small foams.

The color of foams is depending on the color of ores on the foams. It is usually dark when roughing and concentrating, which means a good quality of concentration. It is usually like white water film when scavenging.

The foams show strong metal glossiness when roughing flotation of sulfide minerals and good mineralization of concentrating. If the foams show half-metal glossiness, it means a large loss of metal minerals. If there is much oxidized mineral in pulp, the foams will show half-metal or soil glossiness. If the foams in scavenging is weak mineralization, it will show glass glossiness like water.

When moderately hydrophobic granular mineralized foam is shaped on the surface, the pulp is sufficient with water and the shape of foams are clearer. The foams can stay long time on the surface of pulp and the minerals have large hydrophobic. The foam shape is vague for various and sophisticated minerals on foams.

The thickness of foams directly influence the recovery rate and the concentrate grade. It is mainly concerned with the amount of foaming agents and foam mineralization. The foam is thick when there is a large raw ore grade, a good mineralization or much foaming agents. If the granule of ore is too large, thick foams can’t be formed. The slurry level is low, the foam layer is thick and the concentrate grade is high. If there is a high slurry level, foamed minerals can be scraped in time. The foam layer is thin and the recovery rate is higher.

If the foams is high brittlement, it is unstable and easy to burst, sometimes even hard to be scraped. On the contrary, too much viscous foam and too much stabile foam will make the flotation machine "chute", and destroy the normal flotation process, leading to concentrate transport difficulties, and will also affect the concentrate grade or recovery rate. Excessive flotation agents, dropping of oil, slime or large amounts of soluble salt can make the foam too stable.

When scraping the foams, “rustle” can be heard. It means there are large amount of large proportion and large granule minerals on foams. It is normal state.

Here are eight aspects which can be reference as how to judge the flotation effect through foams in flotation cells. Although the foams varied from the size of flotation area, there still has specific phenomena in specific area. To observe the state of foams, some states of foams should be remembered: final concentration flotation cell, the first few flotation cells, adding flotation agent flotation tank, mop flotation tank, etc. it should be judged by different ore characteristic and ensure good recycling performance.

01.Vietnam 800t/d Graphite Flotation Plant

Xinhai Scheme: The process of "rough grinding and discarding tailings, multi-stage grinding and separation, and concentrated return of middle ore" was adopted, with a recovery rate of 92% and an estimated annual output value of 48 million us dollars. Xinhai Mining provides customers with the mineral processing EPC+M+O service, including mineral processing experiment, mine design, complete equipment manufacturing, installation and commission, worker training and so on.

02.Morocco 500t/d Silver Flotation Plant

Ore Characteristic: metal minerals are native silver, pyrite, limonite and so on. Gangue minerals are quartz, feldspar, clay and so on. silver is main recyclable element.

Xinhai Scheme: Two – stage and semi - closed - circuit crushing - two - stage grinding - flotation (one - stage roughing, three - stage sweeping, two - stage cleaning) - two - stage dehydration process. After grinding and through gravity separation and flotation, the silver recovery rate is up to 83.95%.

03.Columbia 100t/d Copper Flotation Plant

Ore Characteristic: The copper mine is dominated by oxidized ore and contains a small amount of sulfide ore.

Xinhai Scheme: Single flotation flow

After the raw ore is ground, the sulfide ore is treated with one primary concentration and two sweeps, and the oxidized ore is treated with one primary concentration, three sweeps and two picks. Finally, the mixed mineral rate of the concentrate is 30%, the copper concentrate grade is 25.95% and the recovery rate is 87.15%.

04.Uganda 720t/d Phosphorite Flotation Plant

Xinhai Scheme: A closed circuit grinding system is composed of ball mill, pump and classifying hydrocyclone. The flotation process is designed as a positive flotation process of one coarse and one fine cleaning. The flotation concentrate is transported to the concentrate pump box by the foam pump, and then to the concentrate dehydration system by the concentrate pump. The dehydrated product is phosphorus concentrate. The flotation tailings are transported by the tailings pump to the tailings dewatering and stockpiling system.