Gas scrubbing is an industrial air pollution control process in which gaseous pollutants, particulate matter, or hazardous substances are removed from a gas stream by bringing it into intimate contact with a scrubbing liquid (typically water or a chemical solution) or a dry sorbent material. Gas scrubbing systems are widely deployed in mining and mineral processing operations across bauxite, gold, iron ore, and diamond sectors to protect worker health, minimize environmental impact, and ensure regulatory compliance.
Wet scrubbers operate by passing the contaminated gas stream through a chamber or tower where it contacts a liquid spray or liquid-filled packing. Pollutants are absorbed into or react with the scrubbing liquid, which is then treated and either recirculated or discharged. In bauxite refineries, wet scrubbers are used to capture caustic bauxite dust from crushing and grinding operations, and to absorb SO2 and HCl from calcination kiln off-gases. Alkaline scrubbing solutions (sodium hydroxide or lime slurry) are particularly effective for acidic gas removal.
In gold and base metal smelting operations, gas scrubbing systems remove sulfur dioxide generated during the roasting of sulfide concentrates or doré smelting. The SO2-laden gas is typically processed through double-absorption acid plants to produce sulfuric acid as a saleable by-product, or through wet limestone scrubbers to produce gypsum waste. Mercury vapour scrubbing is also essential in retort and roasting operations to prevent atmospheric mercury contamination.
In iron ore sintering plants, gas scrubbing addresses the complex mixture of SO2, NOx, dioxins, furans, heavy metals, and fine particulates generated during the sintering process. Advanced gas cleaning systems combining electrostatic precipitators (ESP), fabric filter baghouses, and multi-pollutant wet scrubbers are employed to achieve stringent emission limits.
In diamond processing operations involving kimberlite crushing and screening, wet scrubbing or dust suppression systems capture fine kimberlite dust, which can contain potentially hazardous mineral phases if the kimberlite is derived from asbestos-bearing geological formations.
Key performance parameters of gas scrubbing systems include removal efficiency, pressure drop, liquid-to-gas ratio, scrubbing liquid pH, and overall system availability. Selection of the appropriate scrubbing technology depends on the specific pollutants present, gas flow rate, temperature, and applicable regulatory limits.