concentrator

A concentrator is a gravity or pneumatic separator that processes finely crushed ore to remove gangue, the worthless rock surrounding valuable minerals. The machine exploits density differences, size differences, or both. Ore enters as a stream of particles ranging from dust to coarse sand. Air jets, vibration, or flowing water then selectively carry away the lighter waste while heavier mineral-bearing particles settle or collect at a discharge point.

The simplest form, the pneumatic concentrator, uses pulsed air jets blown upward through a gently sloped deck or through a column. As intermittent puffs of compressed air strike the ore bed from below, lighter particles are suspended and carried away by overflow while denser material remains on the deck or falls through to a catch. This design works best on dry ore and requires careful control of air pressure, typically 15 to 30 pounds per square inch, and pulse frequency to avoid either blowing away valuable minerals or allowing too much waste to settle with the concentrate.

Other concentrator types include the spiral concentrator, which uses centrifugal force as slurry flows down a grooved helical channel, and the shaking table, which vibrates ore particles across an inclined, riffled surface while water spray carries fines to waste. Jig concentrators, common in coal and mineral separation, work by pulsing water vertically through ore in a chamber, causing repeated settling and resuspension. Each type suits different ore densities and particle size distributions.

Separation by density, not chemistry

Concentrators do not dissolve or chemically alter minerals. They separate solely on the basis of physical properties. A concentrator cannot distinguish magnetite from hematite if both have the same density and size; downstream magnetic separation or flotation cells must do that work. Concentrators are therefore middle-stage equipment, following primary crushing and screening, and preceding chemical beneficiation or smelting.

The term concentrator reflects the machine's purpose: it concentrates the valuable mineral fraction by removing bulk waste, raising the ratio of ore to gangue. Industrial concentrators range from bench-scale laboratory units handling a few kilograms per hour to large plant concentrators processing hundreds of tons daily. Efficiency depends heavily on matching the concentrator type and settings to the specific ore characteristics, particle size distribution, and target mineral density.