Environ. Sci. Technol. 1999, 33, 4318-4325
containing aromatic hydrocarbons and heavy metals (e.g.,
Analysis of Hydrocarbons and Ash
Particles Formed from Contaminated
Industrial Biowaste under
pulp and paper sludge, contaminated soil, or metallurgical
slag), the transfer of these environmentally detrimental
components into the combustion products is a major issue
of public concern (3, 4).
In this paper, the focus is on toxic heavy metals and
polycyclic aromatic compounds (PACs) that cannot be
captured by the classical air pollution control equipment.
Many PACs are carcinogenic. Therefore, even fractionally
small emissions of PAC may become substantial health
hazards. These hydrocarbons are often present in the vapor
phase, subsequently condensing onto fine particles. These
particles also contain heavy metals released during combus-
tion (5). Thus, the fine particles may act as carriers of both
the PACs and toxic metals.
Combustion-like Conditions
J A N U S Z A . K O Z I NÄ S K I * A N D
G U O H U I Z H E N G
Department of Metallurgical Engineering, McGill Metals
Processing Centre, McGill University, 3610 University Street,
Wong Building, Room 2160, Montreal, Quebec,
Canada H3A 2B2
As particle-PAC-heavy metal aerosol is known to be
mutagenic to bacterial and human cells (6), research directed
toward their formation and destruction is of interest to public
health officials and industries generating contaminated
wastes. It is particularly meaningful when residual materials
containing aromatic hydrocarbons and toxic metals are
burned. Such residual materials are often generated during
biological treatment of industrial solid wastes. The residues,
which are left after the biological treatment, are called
biowaste. They are still hazardous and have to be treated
prior to their disposal. Most of these residues (e.g., pulp and
paper sludges) contain enough combustibles to be considered
as low-grade fuel surrogates. Because of the energy conser-
vation and waste management problems, it is possible that
in the future more low-grade fuels will be used. All in all, it
is important to collect and interpret data related to the
properties of biowaste material in the high-temperature
environment existing during combustion.
In this research, a multizone temperature concept, shown
in Figure 1 (bottom), was applied to dispose of biowastes.
In this method, the biowaste is initially fed into the low-
temperature region (<1250 K) and then subjected to the high-
temperature treatment (1770 K), which is followed by sudden
quenching in a second low-temperature zone (,1250 K).
This type of burning process will be called the low-high-
low temperature process (LHL).
V I C U L O T H
Pulp & Paper Research Institute of Canada,
2711 Pulp Mill Road, Prince George, British Columbia,
Canada V2N 2K3
P E T E R G A N G L I †
FE 2000 Inc., 1000 Avenue Roche, Suite PH8, Vaudreuil,
Quebec, Canada J7V 8P5
W E S H U T N Y
Natural Resources Canada, CANMET Energy Technology
Centre, 555 Booth Street, Ottawa, Ontario, Canada K1A 0G1
A concept of multizone combustion of pulp and paper-
generated biowaste was investigated. The biowaste was
initially fed into the low-temperature region (<1250 K) and
then subjected to the high-temperature treatment (1770
K), which was followed by sudden quenching in a second low-
temperature zone (,1250 K). This type of burning is
called the low-high-low temperature process (LHL). It
was found that destruction of selected polycyclic aromatic
compounds occurred during the LHL process before
they were emitted into the atmosphere. The biowaste
material underwent dramatic morphological changes, which
influenced segregation of metals within ash particles
and their leachability. The heavy metals (Cr, Cd, Pb) were
encapsulated and immobilized within the ash particle
core surrounded by a compact shell consisting of condensed
layers of light nonhazardous metals (Si, Al, Na, K). It
seems that the multizone combustion of biowaste may be
an attractive and useful way for the clean and efficient
disposal of contaminated biowastes.
Experimental Section
Apparatus. The experiments simulating events occurring
during the LHL process were conducted in a computer-
controlled facility consisting of a high-temperature Cahn TG-
171 thermogravimetric furnace with maximum sample size
of 100 g coupled with a Mattson Galaxy 5020 Fourier
transform infrared spectrometer. This system has been
described in detail elsewhere (7); therefore, only brief
description is given here. Since the sample has to remain
stationary inside the cylindrical ceramic crucible (15 mm
diameter) placed in the combustion chamber (30 mm
diameter), biowaste “movement” through the LHL regions
was simulated by programming the temperature ramps as
illustrated in Figure 1 (top). The facility can relatively closely
simulate the residence time, temperature histories, and
chemical environment of commercial waste remediation
units allowing for a variety of solid-solid, solid-metal, and
solid-gas interactions. Changes in the sample weight and
temperature as well as the gas composition inside the furnace
are measured continuously. The reactor is designed for
operation at atmospheric pressure with the temperature limit
of 1970 K. The length of the heated zone is 300 mm with a
homogeneous temperature zone of 100 mm (in this zone the
radial temperature profiles are uniform). The extent and
Introduction
To remain faithful to environmental covenants, many
industrial sectors, e.g., pulp and paper and steel industries,
are facing new challenges. They generate contaminated
wastes that have to be disposed of. Combustion of wastes is
a proven disposal technology that permits the reduction of
hazardous material to a fraction of its original volume while
generating energy (1, 2). However, in the case of residues
* Corresponding author e-mail address: jkozin@po-box.mcgill.ca;
fax: (514)398-4492; tel.: (514)398-2432.
† Current address: National Utility Investors, 1760 Fortin Blvd.,
Laval, Quebec, Canada H7S 1N8.
9
4 3 1 8 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 33, NO. 23, 1999
10.1021/es990087s CCC: $18.00
1999 Am erican Chem ical Society
Published on Web 10/28/1999