Blog: Measuring density in grinding circuits 1/3

Posted on Friday, 20 March 2020 at 11:03

Are you struggling with your ball mill or cyclone operation? There are multiple reasons for measuring density in the grinding circuit, which differs per application. In the next few weeks we will share the purposes and benefits of measuring density at different applications in the grinding circuit.

In general lines, the grinding circuit is composed by a powdering or pulverizing process and a classification process. In most sites a ball mill is used for grinding, to produce fine particles, and a (hydro) cyclone is used for classification, to seperate the fine particles from larger particles. The main objectives when controlling the grinding circuit are to maximize the throughput and to decrease variability of product size and % solids. Material that meets the product size requirements is removed from the circuit and oversized material is recycled back to the grinding mill for further comminution. To achieve these objectives the slurry needs to be continuously monitored and controlled, allowing process stabilization and ensuring optimal grinding conditions.

Example of a Rhosonics density meter (SDM), installed in the ball mill discharge

Measuring technologies, such as density meters, efficiently help operators to monitor and control the grinding circuit, optimize it and prevent process failures. When used together with an advanced control system, density readings allow to automatically control valves, pumps and have an efficient water addition, resulting in the improvement of the process that can lead to a higher recovery.

In the grinding circuit possible installation points are in the ball mill discharge and feed (recirculation), (hydro) cyclone feed, overflow and underflow.

Measuring points in the grinding circuit

The grinding circuit can be considered as the first step of a processing plant, therefore, operators need to have a good control over it. One way to follow changes in the circuit is by measuring slurry density, which is done manually in many sites. The manually taken density sample can be used as parameter to indicate if the grinding process is operating steady.

However, manual sampling does not allow to have a trend for real-time control, so it is recommended to use an in-line measuring device, allowing to detect changes online (real-time) as it happens. As an example, a recommended application to efficiently dose grinding media (balls) and water into the ball mill is measuring density changes in the ball mill discharge.

Please contact Rhosonics if you want to have more information about our density meter (SDM).

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You can also read our other blogs or request our whitepapers to learn more about density measurement. We have written several blogs about the flotation circuit and thickening process.

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