Civil Engineering Reference
In-Depth Information
10 mm
10 mm
2/8 mm
8/16 mm
10 mm
16/32 mm
12.3
Municipal solid waste incinerator ash separated into size
fractions After Rübner et al. (2008).
fired pottery fragments, cement and concrete, brickbat and porcelain. They
further describe the magnetic components as dominantly magnetite (Fe
3
O
4
),
haematite (Fe
2
O
3
) and wustite (FeO), noting that strictly only magnetite is
ferromagnetic (see Fig. 12.5). Amongst the diamagnetic particles, copper
and its alloys are noted and especially aluminium, which in its various forms
represents over 90% by mass of the free metals. Numerous minor phases
have been reported, amongst which are wollastonite, (CaSiO
3
) Mayenite
('C
12
A
7
' - Ca
12
Al
14
O
33
) and gehlenite ('C
2
AS' - Ca
2
Al
2
SiO
7
) (Qiao et al.
2008a).
The glassy particles are largely derived from container glass fragments
incorporated in the waste, although of more variable composition after cooling,
owing to incorporation of other elements whilst fused in the incinerator.
Rübner et al. (2008) estimate the glass content comprises around 15% by
mass of the bottom ash.
Also incorporated in the bottom ash is unburned carbonaceous material
