Table Of ContentPOLLUTION CONTROL
AND RESOURCE
RECOVERY
POLLUTION CONTROL
AND RESOURCE
RECOVERY: MUNICIPAL
SOLID WASTES
INCINERATION
Bottom Ash and Fly Ash
ZHAO YOUCAI
Tongji University, Shanghai, China
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LIST OF CONTRIBUTORS
Zeng Chao
Tongji University, Shanghai, China
Niu Dongjie
Tongji University, Shanghai, China
Zhang Haiying
Tongji University, Shanghai, China; Shanghai Institute of Technology, Shanghai, China
Zhou Jiazhen
Tongji University, Shanghai, China
Su Lianghu
Tongji University, Shanghai, China; Nanjing Institute of Environmental Sciences of the
Ministry of Environmental Protection, Nanjing, Jiangsu, China
Song Lijie
Tongji University, Shanghai, China
Zhang Ruina
Tongji University, Shanghai, China
Dai Shijin
Tongji University, Shanghai, China
Chai Xiaoli
Tongji University, Shanghai, China
Zhao Youcai
Tongji University, Shanghai, China
Wei Yunmei
Kyushu University, Fukuoka, Japan
ix
PREFACE
Incineration technology has become predominant for pollution control
and resource reuse of municipal solid wastes (also namely as refuse, gar-
bage, municipal solid waste (MSW), domestic waste, etc.) in developed
countries and many developing nations. Currently, China has over 500
incineration plants with a scale of 1000 to 9000 t/d each plant. As a by-
product, around 25–30% bottom ash and 1.5–3% fly ash of those inciner-
ated will be generated in these incineration plants. The huge quantity of
bottom and fly ashes has become a great challenge for the development of
incineration technology.
Bottom ash (BA, or MSWI BA) contains mainly inert components
such as glass, synthetic ceramics, metals, silicates, phosphates, sulfates or
carbonates, and some unburned organic matters. 3.3–5.9 Zn, 1.2–2.4 Cu,
1.8–2.4 Pb, 0.6–1.1 Cr, 0.1–3 Ni, 0.022–0.06 Cd, 0.00003 Hg (all in g/kg)
may contain in the bottom ash. Over 60% of the bottom ash was >4 mm
in size, with a typical composition of SiO (35.3–42.3%), CaO (19–27.2%),
2
Al O (7.4–7.8%) and Fe O (3.9–5.1%). The contents of CaO, P O ,
2 3 2 3 2 5
MgO, TiO increase and SiO , Al O , Fe O , Na O, K O decrease, as the
2 2 2 3 2 3 2 2
particle size of the bottom ash decrease. Moreover, the concentrations of
heavy metals also increase as the particle size of bottom ashes decrease. It
may be considered that the coarser particles may originate from the wastes
incinerated and the smaller ones are formed during the incineration pro-
cess. The contents of heavy metals in both the bottom ash and fly ash are
found to be inter-related and depend on the volatilization of the heavy
metals involved. The heavy metals with low volatilization mainly remained
in the bottom ash, which present as carbonates and in residual forms with
high stabilization. As the leachability of heavy metals in the bottom ash are
lower than the leachability toxicity limit of wastes according to the China
leaching standard and USA TCLP, the bottom ash is considered to be a
non-hazardous waste in many countries and to use as building materials
for brick making and cement additives etc. Actually, however, most bottom
ash is being placed in landfills for it is in fact a lower quality waste, and the
physical and chemical and even biological changes will occur in the land-
fill during its long-term weathering and stabilization processes.
xiii
xiv Preface
Fly ash (FA, or MSWI FA) has been classified as a hazardous waste
due to the presence of leachable heavy metals Zn, Cu, Hg, Cd, Cr, As, Ni
and dioxins, which need to be disposed of carefully. Fly ash can be treated
with different ways. The most frequent means for fly ash treatment is to
stabilize the fly ash using organic and inorganic phosphorus and sulfur
chemicals and then placed in a security landfill. Immobilization and vit-
rification at high temperature and hydrometallurgical selective separation
of heavy metals by water washing, solvent extraction or by dissolution in
acidic or alkaline medium, or used as the ceramic additives, have also been
practiced, but limited due to their high costs. The fly ash used as cement
additive after water-washing had been extensively studied and pilot-tested,
but finally proved infeasible in engineering as the Cl present can not be
removed to an acceptable level.
The placement of fly ash in a security landfill will result to an irrevers-
ible effect on the environment, as the heavy metals in the ash would never
disappear in the landfill. Moreover, the cost for such a disposal method
is quite unacceptably high in many cases, as the investment for the land-
fill is always high. The immobilization using cement and other solidifica-
tion agents often show relatively low stabilization efficiency according to
its long-term leachability tests. The capability of cement matrix to cap-
ture and stabilize the heavy metals is limited and may deteriorate after
long-term storage in the landfill or recycling uses such as road pavement
materials. Moreover, the volume of the solidified products usually increases
considerably, leading to an increase of transportation cost. Modifications
have been used to raise the long-term stabilization effects for the cement
method. Three principally different cement solidification technologies
exist: (1) solidification of unwashed (original) fly ash; (2) solidification after
neutral/basic washing, and (3) solidification after acid washing. The first
method ends up with a residue with high chlorine and high heavy metals
contents. Consequently, a large amount of expensive high quality cement
with good hydraulic properties is used. In the second technology, the sol-
uble heavy metals chlorides are transformed to heavy metals hydroxides,
which precipitate. After filtration and solidification with a low amount of
cement, this process yields a residue with low chlorine content but high
heavy metals. However, the heavy metals will continuously release, though
slowly, in wet environment. Most heavy metals may be removed when the
fly ash is washed in an acidic medium, which is actually a hydrometallur-
gical process as most the metals may dissolve in the acidic solutions. The
post-solidification treatment for the resultant residue seems unnecessary.
Preface xv
The predominated fly ash disposal method currently practiced involves
the combined solidification/stabilization using chemical agents and
cement, and then the resultant products are placed at a security (dedicated)
landfill or at a sanitary landfill used for MSW disposal. If co-disposed with
MSW, the fly ash must be placed independently, without mixing with
MSW. However, the MSW landfill can become stabilized and be recycled
after closure for years, but the fly ash at landfill will be kept unchanged
forever and never become detoxified. When the fly ash is placed together
with MSW, this land might have to be closed forever without any recy-
cling possibility.
In this book, the general incineration process of refuse, characteriza-
tion, properties, stabilization and solidification, treatment and final disposal,
recycling of bottom ash and fly ash, is fully described, though focused on
and took China situation an example. The main contents include munici-
pal solid waste incineration process and its generation of incineration
ashes, characterization and recycling of bottom ashes, weathering process
and biological dechlorination of bottom ash at landfill, characterization of
heavy metals in fly ash, thermal characterization and use in ceramic tile
making of fly ash, chemical stabilization of fly ashes, and solidification/
stabilization process engineering design of fly ash. The readers include
solid waste engineers, managers, technicians and maintenance staff, recy-
cling coordinators and government officials, undergraduates and graduates,
and researchers.
ABBREVIATIONS
BA bottom ash, residue
BA-a (or A) bottom ash sample A
BA-b (or B) bottom ash sample B
CBz chlorinated benzene
FA fly ash
FA-a (or A) fly ash sample A
FA-b (or B) fly ash sample B
HCB hexachlorobenze
LOI loss on ignition
MSW municipal solid waste, or refuse, or domestic waste,
or garbage
MSWI municipal solid waste incineration
PAHs polycyclic aromatic hydrocarbons
PCB polychlorinated biphenyls
PCDD/Fs polychlorinated dibenzo-p-dioxins and dibenzofurans
PCDDs polychlorinated dibenzo-pdioxins
PCDFs polychlorinated dibenzofurans
POPs persistent organic pollutants
TDI tolerable daily intake
xvii
BIOGRAPHY
Zhao Youcai, is currently a Professor of environmental engineering at
School of Environmental Science and Engineering, Tongji University.
He got bachelor degree from Sichuan University (1984) and Ph.D. from
Institute of Chemical Metallurgy (now Institute of Process Engineering),
Chinese Academy of Sciences, Beijing (1989). After finished Post-
doctoral research work at Fudan University, Shanghai, he joined in
Tongji University in 1991. Meanwhile, he had ever worked at Aristotle
University, Greece, National University of Singapore, Tulane University,
USA, and Paul Scherrer Institute, Switzerland, for 4 years as a research fel-
low or visiting Professor. He had authored or co-authored 138 publica-
tions published in the peer-reviewed internationally recognized journals,
420 publications in China journals, authored or co-authored 75 books
(as an author or Editor-in-chief). Currently, his research interests include
treatment of municipal solid wastes, sewage sludge, hazardous wastes, pol-
luted construction wastes and industrial wastes.
xi
LIST OF ENVIRONMENTAL
CRITERIA & STANDARDS INVOLVED
“Standard for pollution control on municipal solid waste incineration”
(GBl8485-2014)
“Standard for pollution control on landfill sites for municipal solid waste”
(GB16889-2008)
“Safety regulations for belt conveyor” (GB14784-2013)
“Design specifications of low voltage distribution” (GB50054-95)
“Design specifications of power supply and distribution system”
(GB50052-95)
“Standard for lighting design of buildings” (GB50034-2004)
“Identification standards for hazardous waste-identification for extraction
toxicity” (GB5085.3-2007)
“Comprehensive wastewater discharge standard” (GB9878-1996)
“Emission standard for industrial enterprises noise at boundary”
(GB12348-2008)
“Occupational health and safety management system—Requirements”
(GB/T28001)
“Fired common brick” (GB5101-2003)
“Soil quality-Determination of total mercury-Cold atomic absorption
spectrophotometry” (GB/T 17136-1997)
xix
