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Geotechnical News • March 2013
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WASTE GEOTECHNICS
Characteristics of municipal solid waste incineration residues
and potential disposal methods in China
Ping Chen, Qimao Cai and G.W. Wilson
Introduction
In China, the rapid growth in the urban
population has resulted in the genera-
tion of an exceptionally large amount
of municipal solid wastes (MSWs).
At present, the annual generation of
MSWs is 245 million tonnes with an
annual increase of approximately 7%.
Because of rapid urban expansion and
limited land space, incineration has
become one of the primary methods
for MSW disposal. The latest statistics
show that incineration has accounted
for 15.8% of the total solid waste that
has been disposed of in 2011. Incin-
eration treatment not only significantly
reduces the volume of MSWs, but also
recovers energy from wastes (e.g.,
generating electricity). In addition,
support from government policies also
contributes to the rapid increase in the
proportion of incineration in China.
By the end of 2011, there were 109
MSW incineration plants that have
been put into operation in China.
Collectively, all of the plants are
capable of combusting 94,110 tonnes
of MSWs each day and 25,993,000
tonnes of MSWs each year. Most of
the incineration plants are located
in the eastern developed regions.
For example, the two provinces of
Zhejiang and Jiangsu in the east-
ern coastal region have 42 plants in
total. In Hangzhou, the capital city
of Zhejiang Province, there are two
incineration plants with a total daily
incineration capacity of 3,000 tonnes,
which accounts for 50% of the city’s
total daily waste generation. MSW
incineration plants are continuing to
increase rapidly both in number and
capacity. The latest information shows
that about 150 incineration plants were
built in China by the end of 2012.
The annual production of MSW incin-
eration residues in China is estimated
to be 5.2-7.8 million tonnes, 80% of
which are bottom ashes and 20% are
fly ashes. Compared to the fast devel-
opment of incineration technology, the
disposal technology for MSW incin-
eration residues in China falls behind.
Although some of the incineration
plants try to reuse the incineration
residues as engineering materials, the
feasibility of resource utilization relies
on an understanding of the characteris-
tics of the MSW incineration residues.
This paper mainly presents the particle
size distribution, mineralogical and
chemical composition, leaching toxic-
ity of heavy metals, and engineering
properties of the incineration residues
generated in representative cities
within China. Based on the observa-
tions, potential disposal methods for
the residues are discussed.
Characteristics of MSW
incineration residues
Production and classification of
MSW incineration residues
There are primarily two types of MSW
incinerators in China: mass burning
and fluidized bed, which accounts for
64% and 36% of the incinerators in
China, respectively. The incinerators
produce two types of residues, which
include bottom ash generated from the
furnace and fly ash collected from the
air pollution control system for flue
gas. The amount and characteristics of
the bottom and fly ashes depend on the
type of MSW incinerators producing
the residue. The bottom ash generated
from the mass burning incinerators
constitutes approximately 20-25% of
the waste, whereas fly ash constitutes
2-4% of the waste. The amount of
bottom ash and fly ash generated from
the fluidized bed incinerators is more
comparable, both being approximately
10-15% of the waste.
Table 1 shows the physical composi-
tion of bottom ash generated from
a mass burning MSW incineration
plant in Shanghai [1]. The bottom ash
is mainly composed of slag, brick,
glass, gravel, pottery, metals, and
other non-flammable organics. After
bulk materials larger than 10 mm are
removed, the bottom ash looks like a
sandy soil with gravel (see Figure 1).
The chemical composition, leaching
toxicity of heavy metals, and engineer-
Table 1. Physical composition of the bottom ash generated from a mass
burning MSW incineration plant in Shanghai.
Physical
composition
Slag Brick Glass Gravel Pottery Metals Organics
Percentage by
weight (%)
65 15.4 7.6 4.9
4.8
1.8
0.5