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Mineral Flotation Process: 10 Common Problems (Part1)

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Identify common issues in mineral flotation, such as the impact of particle size and slimes on effectiveness, and explore solutions to improve flotation efficiency and concentrate quality.

Contents

  • The Impact of Grinding Particle Size on Flotation
  • Preventing and Mitigating Excessive Slimes in Grinding Pulp
  • Why Coarse Particles Are Difficult to Float and What Measures to Take
  • Difficulties in Flotation of Fine Particles and Measures to Take
  • The Impact of Slimes on Flotation and Solutions

The Impact of Grinding Particle Size on Mineral Flotation

Coarse particles (greater than 0.1mm) and extremely fine particles (less than 0.006mm) can negatively impact flotation effectiveness and recovery rates.

Flotation of Coarse Particles

When floating coarse particles, their significant weight increases the detachment force, making it difficult for them to adhere to bubbles, resulting in metal loss and affecting the grade of the concentrate. To address this, the following measures should be taken:

1. Use sufficient amounts of the most effective collectors.

2. Increase aeration of the pulp, producing larger bubbles and more microbubbles precipitated in water.

3. Ensure appropriate agitation intensity of the pulp.

4. Increase pulp density appropriately.

5. Ensure rapid and steady scraping of bubbles during froth scraping.

Flotation of Extremely Fine Particles

When floating extremely fine particles (usually less than 5-10μm), the following issues arise:

1. Fine particles easily adhere to bubbles, reducing the floatability of coarse particles, leading to poorer selectivity and separation efficiency, and lowering concentrate grade.

2. Fine particles have a large surface area, absorbing significant amounts of flotation reagents, reducing the reagent concentration in the pulp and disrupting the normal flotation process, thus lowering flotation indicators.

3. Fine particles have high surface activity, interacting easily with various reagents, making separation difficult. They have strong hydration, overly stabilizing the froth and making it difficult to concentrate, reducing the quality of the concentrate and the flowability and concentration efficiency of the froth product.

Preventing and Mitigating Excessive Slimes in Grinding Pulp

To prevent and mitigate excessive slimes, the following methods are commonly used:

1. Reduce and prevent the generation of slimes by adopting multi-stage grinding processes and staged beneficiation processes. Proper selection of grinding and classification equipment and improving the efficiency of classifiers is essential.

2. Add reagents to eliminate the harmful effects of slimes, such as water glass, soda, and caustic soda, to reduce the covering and flocculation effects of slimes. To mitigate the harmful impact of slimes absorbing large amounts of reagents, consider staged reagent addition.

3. Deslime the ground ore before flotation, discarding it as tailings. If the slimes contain valuable components, they can be treated separately by flotation or sent for hydrometallurgical processing.

Common desliming methods include:

-Classifier desliming.

-Hydrocyclone desliming.

-In special cases, add a small amount of frother before flotation to float and remove easily floatable slimes.

Why Coarse Particles Are Difficult to Float and What Measures to Take

Coarse grinding can save grinding costs and reduce expenses. In flotation plants processing ores with uneven dissemination, there is a trend towards coarser grinding sizes, provided that the rougher recovery rate is ensured. However, coarse particles are heavier and harder to suspend in the flotation cell, reducing the chances of collision with bubbles. Additionally, once attached to bubbles, the large detachment force makes them prone to falling off. To improve coarse particle flotation, the following measures can be taken:

1. Use collectors with stronger collecting power and add auxiliary collectors like kerosene or diesel to strengthen coarse particle collection, increasing the attachment and adhesion strength to bubbles, reducing detachment.

2. Increase the pulp density to enhance buoyancy. Ensure stable froth layers and appropriate agitation to promote coarse particle suspension and attachment to bubbles.

3. Increase aeration to create larger bubbles and “bubble clusters” formed by large and small bubbles, which have higher buoyancy to carry coarse particles upwards.

4. Use shallow flotation cells to shorten the flotation path and reduce particle detachment. Alternatively, use specialized flotation machines suited for coarse particles, such as cyclonic flotation cells and SkimAir flotation machines.

5. Utilize rapid and steady froth scrapers to promptly remove floated froth, reducing particle detachment.

Difficulties in Mineral Flotation of Fine Particles and Measures to Take

Fine particle separation in flotation is challenging due to:

1. Large specific surface area and increased surface energy, leading to non-selective aggregation between different mineral surfaces under certain conditions. Despite high reagent adsorption, selectivity is poor, making selective separation difficult.

2. Small volume reduces collision chances with bubbles. The small mass makes it difficult to overcome the hydration layer resistance between particles and bubbles, hindering attachment.

To address fine particle flotation challenges, the following measures can be implemented:

1. Selective flocculation flotation: Use flocculants to selectively flocculate target mineral micro-particles or gangue fines, then separate them by flotation.

2. Carrier flotation: Use regular flotation-sized particles as carriers to float target mineral fines. The carrier can be similar or different minerals. For example, pyrite can be used to float fine gold particles, and calcite to float micro-fine iron and titanium impurities in kaolin.

3. Agglomeration flotation, also known as emulsion flotation: Fine mineral particles treated with collectors form oil-coated froth under the action of neutral oils. The collector and neutral oil can be premixed into an emulsion and added to the pulp, or added separately into high-density pulp, agitated vigorously, then the upper froth is skimmed off. This method has been used for fine manganese, ilmenite, and apatite ores.

Mineral flotation site

The Impact of Slimes on Flotation and Solutions

If the flotation pulp contains excessive slimes, it negatively affects flotation in the following ways:

1. Slimes easily mix into froth products, reducing concentrate grade.

2. Slimes cover coarse particles, hindering their flotation.

3. Slimes absorb large amounts of reagents, increasing reagent consumption.

4. Slimes make the pulp viscous, worsening aeration conditions.

To solve these issues, the following measures can be taken:

1. Use dilute pulp to reduce viscosity, minimizing slime entrainment in froth products.

2. Add dispersants to disperse slimes, eliminating their harmful covering effect on other minerals.

3. Use staged reagent addition to reduce reagent consumption by slimes.

4. Deslime flotation materials before flotation.

Common desliming methods include hydrocyclone classification.

By understanding the impacts of particle size on flotation and implementing these measures, flotation efficiency and concentrate quality can be significantly improved.

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