TRS helps Swiss partner make the most of incinerator bottom ash

TRS, a specialist in turnkey systems for incinerator bottom ash (IBA), has just completed a new treatment and metal recovery plant for a customer in Switzerland.

AIB Deponieanlage Elbisgraben’s site near Basel has a capacity of 30 tonnes per hour. The goal of the project is to reduce all IBA material to an end-fraction of less than 5mm and to recover as many metals as technically possible. TRS points out that Switzerland forbids the use of bottom ash for road construction and other applications. Even when it is landfilled, the material must not contain more than 1% non-ferrous metals. The new recycling plant achieves a value under 0.22%.

How does it work?

The unprocessed and pre-conditioned IBA is loaded into a bunker where fractions greater than 250 mm are separated on a tilting grid before the fraction smaller than 250 mm is sieved at 40mm. The fraction from 40-250 mm continues to an electromagnet and manual sorting cabin for the recovery of ferrous, non-ferrous, stainless steel, copper coils, unburned and mineral components.

The 0-40mm fraction is further sieved at 5 mm, creating two fractions to achieve optimal metal recovery using the latest spreading and metal recovery techniques. These include active clean vibratory feeders, low intensity magnetic separation and high intensity eddy current separation.

Immediately after sieving, the 5-40mm fraction is treated by an electro over band magnet to take out clean ferrous and is then processed by an active clean vibratory feeder. After that, the eddy current recovers non-ferrous metals that are directed towards the metal storage bay.

The remaining mineral fraction from the eddy current is forwarded to an impact crusher, releasing more metals that are bound with minerals and cleaning any stainless steel not separated by the conventional magnets and eddy current. The crushed material is then looped back into the 5 mm sieve and sent back to the non-ferrous metals separation stages.

The stainless steel parts, mostly between 5-40 mm (including bigger pieces such as cutlery) travel through the plant until being released into a container by a reversing conveyor belt.

The 0-5 mm fraction is separately forwarded into a ‘waterfall’ distribution and separation set-up, consisting of an active clean vibration feeder to ensure the best possible separation, both on the low intensity magnetic separator module and in the 2 000 mm wide high magnetic density and frequency eddy current separator.

This results in a clean and smaller IBA fraction to be sent to landfill.