Zinc recovery from Waste-to-Energy fly ash – A pilot test study
Journal article, 2020

Zinc recovery from MSWI fly ash using acidic leaching and chemical precipitation was studied at pilot scale. The leached fly ash was re-incinerated in order to destroy toxic dioxins. 75–150 kg/h of fly ash from a Swedish Waste-to-Energy plant was mixed with scrubber liquids from the same flue gas treatment system in a continuously stirred vessel. The resulting slurry was dewatered in a vacuum belt filter. Hydroxide precipitation of the produced leachate, at a pH of around 9, followed by filtration of the formed crystals in a membrane filter press produced a filter cake with up to 80 wt% Zn(OH)2 in dry solids, calculated from Zn(tot). Up to 70% of the zinc content in the fly ash could be recovered. Two 4-hour full scale ash re-incineration tests were performed: leached fly ash was mixed with the waste at a ratio corresponding to a situation where all the fly ash was continuously re-incinerated. The tests showed only an 8% mass increase of produced fly ash, which means that most of it ended up in the bottom ash, although some elements could potentially accumulate in the system if all the fly ash was to be continuously re-incinerated. No negative effects were observed on the bottom ash quality, which suggests that a large portion of the toxic fly ash could be transformed into the bottom ash fraction.

Waste-to-Energy

Zinc recovery

Fly ash

Precipitation

Leaching

Author

Karin Karlfeldt Fedje

Renova

Chalmers, Architecture and Civil Engineering, Water Environment Technology

Sven Andersson

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Environmental Inorganic Chemistry

Babcock and Wilcox Vølund AB

Waste Management

0956-053X (ISSN)

Vol. 118 90-98

Subject Categories

Materials Engineering

Bio Materials

Chemical Process Engineering

DOI

10.1016/j.wasman.2020.07.017

PubMed

32892098

More information

Latest update

1/5/2021 2