How can you optimize particle size distribution to improve flotation circuit recovery and grade?

1 Why PSD matters

The PSD of the feed material affects the flotation kinetics, the bubble-particle collision, attachment, and detachment probabilities, the froth stability and drainage, and the entrainment and detachment of gangue particles. Generally, coarse particles have lower collision and attachment probabilities, higher detachment probabilities, and lower entrainment rates than fine particles. However, coarse particles also have higher mass and grade, and lower surface area and reagent consumption than fine particles. Therefore, there is an optimum PSD range that balances these factors and achieves the best recovery and grade for each mineral species.

2 How to measure PSD

Measuring the PSD of the feed material requires different methods and instruments, depending on the size range, accuracy, and frequency needed. Sieving is a simple and inexpensive method, but it is labor-intensive and prone to errors. Laser diffraction is fast and automated, but it is expensive and sensitive to particle shape. Image analysis is accurate and non-destructive, but it is complex and limited by the resolution of the device. Each method has its own advantages and disadvantages, so careful consideration should be taken when selecting the appropriate method for your needs.

4 How to control PSD

Optimizing the PSD of the feed material requires controlling the comminution and classification processes that precede the flotation circuit. This can be done by adjusting the crusher or mill settings, such as changing the gap, speed, pressure, or load. Additionally, you can adjust the classifier settings by altering the cut size, overflow rate, underflow rate, or pressure. Lastly, adding or removing grinding media to the mill such as steel balls, rods, or pebbles can modify the grinding action and product size. For example, increasing the gap or decreasing the speed of a jaw crusher will produce coarser particles, while decreasing the cut size or increasing the underflow rate of a screen will produce finer particles in the underflow.

5 How to monitor PSD

To ensure that the PSD of the feed material is within the optimum range, you need to monitor it continuously or periodically. You can do this using online or offline instruments, such as laser diffraction analyzers, image analysis cameras, ultrasonic probes, cross-cut samplers, rotary splitters, and riffle dividers. Measuring and analyzing the PSD of your flotation circuit feed material allows you to optimize the flotation performance and improve the recovery and grade of your concentrate. Additionally, this process can reduce reagent consumption, energy consumption, and environmental impact.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?