Treatment of ash from Bavarian waste incineration plants
The grate ash is partly treated in on-site treatment plants, partly by external treatment service providers under the aspect of metal recovery and production of a low-quality construction material. Apart from the purest Fe and NE metal concentrates possible, a mineral material is also produced, which is suitable for landfill construction, road and path construction or as a basecourse in civil engineering or can be used as fill material. However, its use is not planned in Bavaria, either in road and path construction or as fill material. The new Substitute Construction Materials Ordinance ("Ersatzbaustoffverordnung") may set significantly higher requirements for future recovery of slag from waste incineration plants, including possible contaminant levels. Through further treatment of the grate ash with modern technology, it seems that not only a further significant increase in the yields of iron and NE metals is possible, but also quality improvement in the mineral constituents for possible use other than as fill material and landfill construction. If new recovery and recycling channels could be developed as a result, the existing gross landfill volume in Bavaria could be used for significantly longer. Through targeted treatment of the grate ash fines fraction < 2 mm, for example, additional metal fractions could be tapped. These mainly contain the "heavy" NE metals such as copper, silver and gold. The quantity is estimated to be 0.3 % to 0.6 % of the grate ash. Requirements for high-quality recovery of grate ash from which elutable contaminants have been removed are future legal permissibility and the creation of suitable sales markets.
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Dr. Karsten Wambach