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Paste thickening

Paste thickening

Paste thickening is a process used in the mining and mineral processing industries to separate solid particles from liquid, typically in the form of a slurry. The primary purpose of paste thickening is to increase the solids concentration, reduce the volume of water, and create a paste-like material that is easier to transport, store, and dispose of. Paste thickening can be especially useful for tailings management, as it helps to reduce the environmental impact and increase the efficiency of water recycling in mining operations. The paste thickening process typically involves the following steps:

01 Slurry feed:

The slurry, a mixture of fine solid particles and water, is introduced into the paste thickener. This slurry is typically generated during the mineral processing phase, such as grinding, flotation, or leaching.

02 Sedimentation:

As the slurry settles within the thickener, the solid particles begin to separate from the liquid under the influence of gravity. The larger and denser particles settle faster, while the smaller and lighter particles settle more slowly.

03 Thickening:

The sedimentation process results in the formation of a concentrated layer of solids at the bottom of the thickener, known as the thickened solids or underflow. The liquid above the solids layer, known as the clarified liquid or overflow, is relatively free of solid particles and can be recycled or reused within the mining operation.

04 Rake mechanism:

In many paste thickeners, a rake mechanism is used to gently move the settled solids towards the center or discharge point of the thickener. The rake arms also help to prevent the solids from compacting or becoming too dense, which could hinder further settling and thickening.

05 Discharge:

The thickened solids are discharged from the bottom of the thickener, typically through a central discharge cone or pipe. The paste-like material can then be transported to a storage facility or disposal site.

06 Overflow collection and reuse:

The clarified liquid, or overflow, is collected from the top of the thickener and can be reused in the mining process or treated for disposal, depending on the quality and composition of the liquid.

Paste thickeners are designed to achieve high solids concentrations, often ranging from 55% to 75% by weight, which results in a non-settling, non-segregating paste. This is particularly beneficial for tailings management, as the paste can be easily pumped or transported to a tailings storage facility, where it can be spread in layers, reducing the risk of dam failures and minimizing the environmental impact. Additionally, the efficient water recovery provided by paste thickeners can lead to significant water savings, which is particularly important in arid regions where water resources are scarce.

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