The municipal solid waste incinerators (MSWIs) in Taiwan generate about 300,000 tons of fly ash annually,
which is mainly composed of calcium and silicon compounds, and has the potential for recycling.
However, some heavy metals are present in the MSWI fly ash, and before recycling, they need to be
removed or reduced to make the fly ash non-hazardous. Accordingly, the purpose of this study was to
use a hydrocyclone for the separation of the components of the MSWI fly ash in order to obtain the recyclable
portion. The results show that chloride salts can be removed from the fly ash during the hydrocyclone
separation process. The presence of a dense medium (quartz sand in this study) is not only helpful
for the removal of the salts, but also for the separation of the fly ash particles. After the dense-medium
hydrocyclone separation process, heavy metals including Pb and Zn were concentrated in the fine particles
so that the rest of the fly ash contained less heavy metal and became both non-hazardous and
recyclable.