Jiang et al. / J Zhejiang Univ-Sci A (Appl Phys & Eng) 2010 11(7):530-537
530
Combustion characteristics of tannery sludge and
volatilization of heavy metals in combustion
*
Xu-guang JIANG
†
, Chun-yu LI, Zhen-wei FEI, Yong CHI, Jian-hua YAN
(State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China)
†
E-mail: jiangxg@zju.edu.cn
Received July 7, 2009; Revision accepted Dec. 25, 2009; Crosschecked June 11, 2010
Abstract: Incineration is considered one of the most readily available techniques for sewage sludge disposal, including tannery
sludge, which often contains significant amounts of volatile heavy metals. The combustion characteristics and kinetic analysis of
tannery sludge were investigated using thermogravimetric analysis (TGA) at a heating rate of 30 °C/min in 50–950 °C. In addition
to confirming that tannery sludge has a high content of volatile material and ash, it was further discovered that almost all the zinc
(Zn) in tannery sludge is volatilized at 900 °C. The degree of volatilization for heavy metals at 900 °C followed the order of
Zn>Cd>Cu>Mn>Pb>Cr. Moreover, the volatilization of these heavy metals increased with temperature. It is thus concluded that,
to avoid heavy metal volatization during incineration disposal, 800 °C is a reasonable incineration temperature.
Key words: Tannery sludge, Combustion, Heavy metal volatilization, Thermogravimetric analysis (TGA), Combustion kinetics
doi:10.1631/jzus.A0900414 Document code: A CLC number: X705
1 Introduction
Tannery sludge, the essential by-product of the
tanning industry, contains chromium in amounts high
enough such that is classified as hazardous waste.
Landfilling and ocean dumping are the simplest
methods for disposal of this waste sludge, but there is
an increasing call to cease these methods because of
environmental consequences (Saxena and Jotshi,
1996). Waste sludge has been widely used as agri-
cultural organic fertilizer, but application of heavy
metal-contaminated sewage sludge significantly in-
creases the risk of soil contamination with toxic met-
als contamination and metals transfer to freshwater
and plants. The use of sewage sludge for agricultural
applications is thus less appealing and less often used
(Jensen and Jepsen, 2005; Toribio and Romanya,
2006; Dai et al., 2007).
Organic sludge has generally good combustion
characteristics, and sludge incineration technology
has reached a commercial level of operation (Mahesh
et al., 2006). Incineration has been well recognized as
the most available pretreatment technique for waste
sludge before landfilling, because of the effective
volume reduction and detoxification. In addition,
waste energy can be recovered by incineration for
economic and environmental benefits, and the ash
residue may be also used in the ceramic and building
material industries (Mahesh et al., 2006).
The combustion characteristics of sewage sludge
have been investigated (Ferrasse et al., 2003), and
two maxima patterns of volatile matter and fixed
carbon were found in sludge combustion (Ogada and
Werther, 1996; Magalhães et al., 2008). Temperature
and residence time were found as the dominant pa-
rameters determining the volatilization of heavy
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering)
ISSN 1673-565X (Print); ISSN 1862-1775 (Online)
www.zju.edu.cn/jzus; www.springerlink.com
E-mail: jzus@zju.edu.cn
*
Project supported by the National High-Tech Research and Devel-
opment (863) Program of China (Nos. 2007AA061302 and
2007AA06Z336), the Key Project of Science and Technology of
Zhejiang Province, China (No. 2007C13084), the Zhejiang Provincial
Natural Science Foundation of China (Nos. X506312 and R107532),
the Project on Science and Technology of Zhejiang Province
(No. 2008C23090), China, the Program for New Century Excellent
Talents in University (No. NCET-05-0524), and the Y. C. TANG
Disciplinary Development Fund of Zhejiang University, China
© Zhejiang University and Springer-Verlag Berlin Heidelberg 2010