New plant to boost bottom ash processing at Irish recycler

Germany’s recycling solutions provider Eggersmann Anlagenbau has commissioned a new plant for the processing of incineration bottom ash (IBA) at Knockharley landfill, north of Dublin, Ireland.

The new plant can handle 59 tonnes of IBA per hour. With a planned eight-hour, single-shift operation on 255 days per year, over 120 000 tonnes of IBA will be processed, claims Eggersmann.

The facility aims to recover valuable metals from the ash, both ferrous and non-ferrous. The non-ferrous metals are separated into sizes of 0 to four mm, four to 30mm and 30 to 150 mm while the ferrous fraction is separated into a fraction smaller than 150 mm and one larger.

500-metre conveyor

Eggersmann supervised the project as general contractor and was responsible for every phase, from planning to installation and commissioning. This also included the production of the 527 metres of conveyor technology.

The biggest challenge in the recovery process is the sintered bottom ash, says Eggersmann. ‘This mineralised material, which is produced by heating and then cooling the ash, is crushed in an impact mill so that the trapped metals are released. Using strong magnets, sieving machines and other separation solutions, further metals can now be extracted in a targeted manner.’

Processing fine fractions

‘After thermal treatment, the bottom ash and slag are first cooled in a water bath,’ explains project supervisor Jens Thomas. ‘Then either the very moist and still highly abrasive fresh slag can be treated directly, or it is first stored and dried.’

At the Knockharley landfill plant, the IBA is dried for two to three weeks until it has a residual moisture content of 16 to 19%. ‘The fine fraction of the ash from zero to four mm is also processed here to extract all valuable materials. This follows a general trend in the market which is associated with special challenges. But with the right concept, that’s not a problem either.’

Full turn-key solution

Knockharley landfill has been processing IBA for subsequent landfill on the site since 2014. Until now, the company has relied on a mobile modular solution. ‘The customer approached us because the previous mixture of mobile machines and stationary process technology was no longer sufficient for this demanding material and these high throughputs,’ Thomas explains. ‘The time was right for a full turn-key recycling solution. A plant that not only offers a higher degree of automation but can also cope with highly abrasive materials. This significantly minimises maintenance and down time.’