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Effect of co-contaminated soil mixtures as fixed/fluidized bed media on pollutants emission under thermal treatment
Samaksaman, U.; Kuo, J.-H.; Peng, T.-H. & Wey, M.-Y.
Abstract
Thermal treatment of soil polluted by lube oil and
heavy metals (cadmium, chromium, copper, and lead) was
carried out by using a laboratory-scale incinerator. The effect
of co-contaminated soil mixtures as fixed/fluidized bed media
was studied with different ratios of sand bed amount to soil
feeding. Additionally, the effect of soil moisture content on
incineration system was further investigated. The reduction in
air input altered the mode of fluidized bed to fixed bed which
resulted in an increase in organic pollutants such as benzene,
toluene, ethylbenzene, xylene, and polycyclic aromatic
hydrocarbons. The combustion efficiency of fixed bed mode
was observed to be relatively high at a lower ratio of sand bed
amount to soil feeding, whereas high combustion efficiency
was found in fluidized bed mode at a higher ratio of sand bed
amount to soil feeding. Much higher concentration of organic
pollutants in both gas phase and bottom ash is found under a
higher soil moisture content. In addition, the increase in
moisture content has resulted in an increase in lead, cadmium,
and chromium in fly ash while copper was decreased. An
important consideration is that the partitioning of heavy
metals was randomly distributed in particle sizes of bottom
ash. The highest concentration of heavy metals was deposited
on fine-sized particle. The distribution of heavy metals in
medium-sized and coarse-sized particles to form eutectic
species might be produced by the soil–sand aggregation.
Keywords
Heavy metals; Incineration; Moisture; Organic pollutants
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