Formation of dioxins and furans during combustion of treated wood

As yet, very little is known about the PCDD/F fate and distribution in the woodchip-fuelled boilers. In this study, the feeding woodchips, stack flue gases and the ashes in different units of a woodchip-fuelled boiler are sampled to investigate their PCDD/F characteristics. The PCDD/F contents in the bottom residues and fly ashes ranged from 18.9 to 66.3 ng I-TEQ/kg, which are below the Taiwanese PCDD/F regulation for reutilization of bottom residues, but still higher than PCDD/F limitations on soils for agricultural use (10 ng I-TEQ/kg), which are adopted by several countries. From the PCDD/F output/input ratios, we found that combustion of woodchips in the boiler system is more favourable for the formations of PCDFs by de novo syntheses, especially for lower chlorinated PCDF congeners. Although about half of the input PCDD/Fs mass are destroyed in the combustion, the output PCDD/Fs toxicity are 6.9 times higher than the inputs. Fly ashes exhibited the highest PCDD/F distributions among the woodchip-fuelled boiler. Still 21.4% of total PCDD/F mass and 18.0% of total PCDD/F toxicity were emitted from the stack flue gases due to the lack of control devices for gaseous phase PCDD/Fs. Decreasing de novo syntheses among the boiler systems, deploying control devices for gaseous phase PCDD/Fs, and proper management on the reutilization of fly ashes will ensure woodchip-fuelled boilers as a sustainable and renewable biomass energy.

Section: Pcdd/f Contents (Concentrations) In the Feeding Woodchips Asupporting

confidence: 88%

Section: Introductionmentioning

confidence: 97%

Fate and Distribution of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in a Woodchip-fuelled Boiler

Chen

Shen

Hsieh

et al. 2011

“…Various PCDD/F congeners, both simple and complex (Jarmohamed and Mulder, 1994;Iino et al, 1999;Tame et al, 2007;Hajizadeh et al, 2011;Cheruiyot et al, 2015), can be suitable precursors, however, monocyclic aromatic compounds e.g., (chloro) phenols and (chloro) benzenes have been shown to be the most direct routes to the formation of PCDD/Fs (Altwicker and Milligan, 1993;Luijk et al, 1994;Altwicker, 1996). The formation reactions from these monocyclic aromatic compounds involve degradation of these precursors and the rearrangement of their structures.…”

Section: Formation and Decomposition Mechanisms Of Pcdd/fsmentioning

confidence: 99%

An Overview of PCDD/F Inventories and Emission Factors from Stationary and Mobile Sources: What We Know and What is Missing

Cheruiyot

Lee

Yan

et al. 2016

This overview attempts to outline what we currently know about the PCDD/F emission inventories and the source categories therein. Besides the best available control techniques, suggestions are offered on how to reduce the PCDD/F emission factors and emission quantity of some important PCDD/F emission sources. The PCDD/F combustion sources can be classified as either stationary or mobile or minimally/uncontrolled combustion sources. The major stationary sources of PCDD/Fs are metal production processes, waste incineration, heat and power plants, and fly ash treatment plant. Crematories, vehicles, residential boilers and stoves are of key concern due to their proximity to residential areas and their relatively lower lying stacks and exhaust gases, which may result in great impact to their surrounding environment.Moreover, we offered our perspectives on how to improve the quality and representative of the PCDD/F emission factors to attain PCDD/F inventories which correspond more to reality. These points of view include: (1) PCDD/F contributions during start-up procedures of MSWIs should be considered, (2) the sampling times of stack flue gases for EAFs and secondary metal smelters should correspond to whole smelting process stages, (3) longer flue gas sampling time should be executed for power plants, (4) direct exhaust samplings from tailpipes for mobile sources, (5) development of an open burn testing facility that can reflect the real open burning conditions, and (6) long-term sampling techniques like AMESA are suggested to used exclusively for the most contributed PCDD/F stationary sources.

“…The sources of PCDD/Fs are mainly human activities, including industrial and heat-treatment processes (Oh et al, 1999;Baker et al, 2000;Tame et al, 2007;, and are known to be persistent in the environment and animal tissue (Chao et al, 2007). The formation of PCDD/Fs in municipal solid waste incinerators had been researched in many countries (McKay, 2002;Altarawneh et al, 2009;Aurell and Marklund, 2009).…”

Section: Introdutionmentioning

confidence: 99%

The Emission and Distribution of PCDD/Fs in Municipal Solid Waste Incinerators and Coal-fired Power Plant

Lin

et al. 2010

The emission and distribution of polychlorinated debenzo-p-dioxins/dibenzofurans (PCDD/Fs) was investigated in two municipal solid waste incinerators (MSWIs) and one coal-fired power plant (PP) in southern Taiwan. Samples were collected from stack flue gases (SFG), bottom residues (BR), super heater (SH), economizer (EC), semi-dry absorber (SDA), bag filter (BF), and fly ash pit (FAP) in MSWIs. Stack flue gases, bottom residues and electrostatic dust collectors (ESD) in PP were also collected. In order to compare the difference between the results of MSWIs and PP, samples from SFG, BS, and FAP in a PP were also determined. Seventeen congeners of PCDD/Fs were analyzed by utilizing a highresolution gas chromatograph/high-resolution mass spectrometer (HRGC/HRMS). Distributions of total PCDD/F-I-TEQ in each unit of MSWI-A and MSWI-B were SFG (0.3%, 0.07%), BR (3.9%, 0.62%), SH (0.17%, 0.24%), EC (4.2%, 0.05%), SDA (1.29%, 7.06%), and BF (90.14%, 91.97%), respectively. However, those in SFG, BS, and FAP of PP were 99.58%, 0.17%, and 0.25%, respectively. The above results indicated 99.5% PCDD/Fs were trapped in the fly ash of MWSI. On the other hand, 99.7% PCDD/Fs was emitted to the atmosphere from PP. The results of this study provide useful information for controlling PCDD/Fs in MSWIs and PP.