Metso Outotec High-Rate Thickener 20m Diameter

The Metso Outotec High-Rate Thickener with a 20-metre diameter is an industrial solid-liquid separation unit that uses gravity sedimentation with flocculant addition to dewater mineral slurry tailings and concentrates, producing a clarified overflow return water stream and a thickened underflow slurry for further processing or tailings disposal. High-Rate Thickeners differ from conventional thickeners by operating at significantly higher unit areas (t/m²/day) through the use of optimised feedwell hydrodynamics and high-efficiency flocculant addition systems, which accelerate particle flocculation and settling rates to produce denser underflow at smaller tank diameters than conventional designs.

The Metso Outotec feedwell design is central to the high-rate thickener's performance advantage. The feedwell uses a patented energy dissipation and flocculant distribution system that gently reduces feed slurry velocity from the incoming launder, promotes rapid and efficient flocculant mixing, and introduces the feed below the slurry surface to prevent short-circuiting to the overflow. The result is faster settling, higher underflow density (typically 55–75% solids by weight for phosphate tailings), and clearer overflow water. The raking mechanism uses a robust central drive with variable torque control and an automatic lift mechanism to prevent raking arm overload during high-density underflow conditions — a common operational challenge in remote mine sites.

Water recycling is a critical operational imperative for mining in Saudi Arabia's desert environment, where surface water is non-existent and groundwater is a finite, non-renewable resource shared with domestic and agricultural users. At Maaden's Wa'ad Al-Shamal phosphate complex in the Al-Jouf region — one of the most remote mine sites in the Kingdom — process water conservation is a licence-to-operate requirement. Thickener overflow clarified water is returned directly to the process as recycled water, reducing fresh water makeup requirements from the desalination plant that supplies the mine. A 20-metre high-rate thickener treating 500–800 t/h of phosphate tailings at 15% solids feed can recover 70–80% of the process water as recycled overflow, with the thickened underflow reporting to the tailings storage facility at 65–70% solids.

Razz Middle East supplies Metso Outotec thickeners and holds thickener rake mechanism wear parts, flocculant dosing system components, and drive unit assemblies for the Saudi mining sector. Our process engineers can conduct thickener performance assessments, flocculant selection trials, and underflow pump sizing consultations to optimise water recovery and tailings handling.