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Zinc recovery from Waste-to-Energy fly ash - A pilot test study
Karin Karlfeldt Fedje1, Sven Andersson2
1Recovery and Management, Renova AB, Box 156, SE-401 22 Gothenburg, Sweden; Department of Architecture and Civil Engineering, Division of Water Environment Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
This study recovers zinc from municipal solid waste incineration (MSWI) fly ash using pilot-scale acidic leaching and precipitation. Re-incineration of leached ash effectively reduces toxic dioxins and transforms fly ash into bottom ash.
Area of Science:
- Environmental Engineering
- Chemical Engineering
- Waste Management
Background:
- Municipal solid waste incineration (MSWI) fly ash contains valuable metals like zinc but also toxic pollutants.
- Effective treatment methods are needed to recover resources and mitigate environmental risks associated with fly ash.
Purpose of the Study:
- To investigate the pilot-scale recovery of zinc from MSWI fly ash.
- To evaluate the effectiveness of re-incineration for dioxin destruction and ash transformation.
Main Methods:
- Acidic leaching of fly ash followed by hydroxide precipitation at pH 9.
- Dewatering using a vacuum belt filter and filtration with a membrane filter press.
- Pilot-scale re-incineration tests of leached fly ash mixed with waste.
Main Results:
- Achieved up to 70% zinc recovery, yielding a filter cake with up to 80 wt% zinc hydroxide.
- Re-incineration tests showed an 8% mass increase in fly ash, with most mass ending up in bottom ash.
- No negative impacts on bottom ash quality were observed, indicating potential for toxic fly ash transformation.
Conclusions:
- Acidic leaching and precipitation are effective for zinc recovery from MSWI fly ash.
- Re-incineration of leached fly ash can reduce dioxins and transform hazardous ash into a less problematic bottom ash fraction.
