IBA Aluminum Recovery: Why Ash Preparation Matters
Recovering aluminum from incinerator bottom ash (IBA) is not simply a matter of installing an eddy current separator. The ash contains minerals, glass, ceramics, iron and non-ferrous metals in different sizes and physical conditions. Some metal particles are free; others remain attached to slag or trapped in wet, fine material.
A study by Simon Mika, Julia Mühl and Jakob Lederer, published online in May 2026 and included in the September 2026 issue of Waste Management & Research, examined metallic aluminum recovery from two kinds of municipal waste incineration bottom ash. The researchers found that the way ash is discharged and the degree to which aluminum is liberated from mineral material affect recovery. Their full-scale results belong to the investigated treatment plant.
Start with the Ash, Not the Separator
IBA from a grate incinerator can differ substantially from ash produced by a fluidized-bed system. Cooling, storage, aging and prior handling also influence moisture, particle size and the condition of metal pieces.
For operators, the first question is whether valuable metal is physically accessible. An aluminum fragment enclosed in fused mineral material cannot be expected to behave like a clean, loose aluminum particle. Similarly, wet fines can stick together, making controlled feeding and separation more difficult.
Representative sampling should therefore identify the size distribution, moisture, ferrous content and the share of exposed non-ferrous pieces. This helps distinguish a preparation problem from a separator-setting problem.
Use Screening to Create Workable Size Fractions
A trommel screen separates IBA into size ranges before downstream recovery. This matters because a coarse metal fragment and a fine aluminum particle do not travel or respond identically in a sorting system.
Removing or separately handling excessive fines can also reduce the amount of ash carried into metal concentrates. Screen openings should be chosen from actual feed testing, not copied from another plant. Wet, sticky ash may blind apertures, while highly abrasive material increases wear and maintenance demands.
CurrenTek identifies IBA recycling as an application for its Trommel Screen, with size classification intended to support more stable downstream metal separation.
Remove Ferrous Metals, Then Recover Conductive Metals
A magnetic separator removes magnetically responsive iron and steel. Placing this stage before non-ferrous recovery helps prevent residual ferrous pieces from contaminating later fractions. Magnet arrangement, material depth and separation distance need to suit the size and abrasiveness of the ash.
An eddy current separator then uses a changing magnetic field to deflect exposed, conductive non-ferrous particles—especially aluminum—from predominantly non-conductive minerals. Copper and other conductive metals may also report to the recovered fraction, depending on particle characteristics and operating conditions.
The method is not a universal metal detector. Very small particles, irregular shapes, wet agglomerates and metal still bound to mineral matter can limit separation. Fine and coarse IBA fractions may require different settings or treatment routes.
Measure Both Metal Recovery and Mineral Quality
A successful IBA line should be evaluated on more than the amount of metal collected. Operators should also examine contamination in the metal concentrate, aluminum remaining in the mineral fraction, operating stability and the cost of preparation.
Removing metallic aluminum may improve the prospects for downstream mineral use, but it does not establish that treated ash is safe or compliant for construction. Leaching behavior, other contaminants and local regulatory requirements still need separate assessment.
For recycling facilities, the practical value is a process matched to the incoming ash: classify the material, remove iron, recover accessible conductive metal and verify both output streams. That is a more defensible route to improved recovery than relying on a single advertised efficiency figure.