Incinerator bottom ash is a product from waste-to-energy and incineration facilities; it’s the material that does not fully combust, and discharges after incineration. This bottom ash often contains precious metals and heavy metals that can be a challenge for disposal facilities. However, if these metals are selectively recovered, they can be sold directly to recyclers and metal refiners.
Sepro Mineral Systems has developed a proprietary system for wet processing of fine incinerator bottom ash (< 3mm or 1/8”), which has the following significant benefits:
of precious metals and heavy metals
which drastically reduces, if not eliminates, dust creation during processing
Simple to Retrofit
The ability to process either stockpiled or directly fed bottom ash
Simple to Retrofit
Easy integration into existing processes and small footprint requirements
Clean Construction Material
Cleaner final ash for use in construction materials
Modern incinerator bottom ash processing facilities are targeting the recovery of metals from coarse (+2 mm or coarser) fractions with ferrous, aluminum, copper, stainless steel and zinc being the main contributors. Valuable metals in the fine particle sizes (0 – 2 mm) were previously considered unrecoverable.
Sepro’s pioneering Fine Slag Treatment Plant (FSTP) module can now add a precious metals dimension. With today’s first world throw-away societies, increasing amounts of precious metals are found in fine IBA, tracing back to mainly electronics and jewelry. Fine incinerator bottom ash contains gold (0.3 – 1 ppm), silver (5 – 20 ppm) and platinum group metals (in minor amounts). At the same time, the plant helps meet environmental targets in terms of minimized heavy metals / leachable contaminants in the rejected bottom ash.
Sepro Urban Mining’s Fine Slag Treatment Plant
Raw bottom ash is fed into a wet operated jig or wet screen classifier, which separates the fines fraction (-2mm) as a slurry. The fine bottom ash fraction, containing most of the precious metals, is then transferred into the FSTP. First, the slurry is processed through low-intensity magnetic separation to remove fine iron. This step allows for the production of a saleable iron concentrate for special smelting applications. The non-magnetic slurry proceeds to gravity concentration in a low and high gravitational field in series, whereas, the low-G stage targets the recovery of fine copper, and the high-G stage targets the recovery of precious metals.
Three separate concentrates are produced and dewatered in bags. These concentrates are either sold directly to smelters or processed through a subsequent cleaning step. The reject stream is dewatered and can be landfilled with minimized remaining metals content.
- Pioneering fine IBA treatment (0 – 2 mm) with industry standard Falcon centrifugal concentrators optimised for IBA
- Possible adaptation to dry or wet IBA treatment plants
- Recovery of precious metals (Au, Ag, PGM) and heavy metals (Cu, Pb, Zn)
- High grade concentrates
- Low concentrate mass
- Concentrates for direct sale or further upgrading
- Minimized heavy metals content in rejects
- Fresh IBA and aged IBA can be treated by wet process
- Pre-assembled compact and modular plant design
- 0 – 2 mm feed particle size
- Available in 10 t/h and 20 t/h fines capacity per module
- Feed protection screen removes oversize
- Low-intensity magnetic separator produces iron product
- Falcon centrifugal concentrator produces precious metal concentrate
- Full automation
- Built to European or North American standards
Looking to recover fine metals from incinerator bottom ash?
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