Scrubber Series - Introduction to the Workhorse of the Wash Plant

When it comes to preparing run-of-mine ore for downstream processing, few pieces of equipment work as quietly and tirelessly as

the rotary drum scrubber. These robust, rotating cylinders are a common sight in operations handling clay-rich or weathered ores.

In this first post of our "Scrubbers in Mineral Processing" series, we’ll explore what rotary drum scrubbers are, why they’re used, and how they fit into a plant. Later posts will dig deeper into selection criteria, sizing methods, liner materials, power calculations, and common operational challenges.

A rotary drum scrubber is essentially a large, rotating steel cylinder fitted with lifters to promote the tumbling and mixing of ore in the presence of water. As the drum rotates, the material is lifted and dropped repeatedly, allowing water and attrition between particles to loosen and break down clays, coatings, and other contaminants.

While they may resemble mills, their purpose is not to reduce the size of individual particles of ore, only to break apart aggregated clumps of soft ore or clay, and/or to ensure that superfine particles do not get released downstream after being handled by pumps or other aggressive mechanisms.

Why Use a Drum Scrubber?

In mineral processing, feed cleanliness can make or break downstream recovery efficiency. Many ores arrive at the plant contaminated with:

• Clay and laterite coatings that hinder screening and classification

• Organic material that can float in flotation circuits

• Soft, deleterious minerals like talc or mica that affect concentrate grade

• Surface-bound iron oxides or salts that can increase reagent consumption

Where They Fit in a Flowsheet

Drum scrubbers are usually located early in the process, often just after or before primary crushing and before screening or classification. Their output is typically split into:

• Cleaned coarse material → sent to crushers or mills

• Fine/clay-rich slurry → directed to classification or thickening circuits

In later articles, we’ll discuss how the choice of screen aperture, downstream density targets, and handling of fines can influence scrubber design.

Typical Industries and Applications

• Diamond recovery plants – freeing diamonds from clay-rich gravel or clay-like kimberlite ores.

• Bauxite processing – removing kaolinite before refining

• Gold operations – washing placer or saprolitic ores

• Base metals – preparing weathered ore for flotation

• Aggregate production – removing unwanted superfine coatings from stone

In the coming posts, we'll look at how the energy requirements of scrubbers are determined, the models used to calculate those requirements, and some general rules of thumb.