Blog: Improve thickener operations by measuring density 1/3

Posted on Friday, 17 January 2020 at 03:01

In the next few weeks, we will share more about the important reasons for density measurement in the underflow, overflow and the feed of a thickener. This week we will give you more information about the water recovery.

In mineral processing operations, water is very important and therefore water recovery plants have an important position. According to CRC Care 2013, every year more than 10 billion tonnes of tailings are produced by mining activity. Thickeners can be used as a water recovery system, to meet requirements in the recovery and reprocess of water. Eventually, this can decrease water used from the environment. This environmental requirement can be encountered by an increase in the density of the underflow of thickeners. A growth of 1 or 2% in underflow density can return large amounts of water to the operating installations. The increasing of density is also important to avoid accidents in tailings dams, which can collapse when there is too much liquid pumping to the dams.

A thickener in Morocco, where the SDM is installed

Compared to other technologies, you can process high volumes of slurry at a quite low cost by sedimentation using thickeners. The two outputs, underflow and overflow, are not often prioritized at the same time. In tailings applications where water recovery is required, underflow will be targeted. But in concentrate applications, the overflow measurement is essential. Otherwise, the important material would be returned to the concentrator and lose recovery.

The Slurry Density Meter (SDM) can be used in many applications to measure the density of a slurry. A typical application for the mining industry is a thickener. With a thickener, the solid-liquid seperation is done by sedimentation. A thickener has several layers, the upper layer is clarified water. Below the clarified water is the interface, this is solids and water. Under this layer is mud and the lowest layer is heavy mud. Sedimentation is used to produce two phases by thicken the incoming feed stream. In the ideal situation, the overflow contains minimal solids and the underflow contains minimal liquid. That is why it is very important to measure the density.