Effect of Electric Arc Vitrification of Bottom Ash on the Mobility and Fate of Metals

Ecke, Holger; Sakanakura, Hirofumi; Matsuto, Toshihiko; Tanaka, Nobutoshi; Lagerkvist, Anders

doi:10.1021/es0001759

Cited by 55 publications

(40 citation statements)

References 25 publications

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“…The melting process can lead to a reduction of ∼99% [5] or higher [2,6] of toxicity of dioxins, and also an approximate 10-15% (bottom ash) or 80-85% (fly ash) in volume by its high reaction temperature [7,8]. Although heavy metals are not destructed during thermal treatments such as sintering or vitrification, the mobility of heavy metals in ash can be drastically reduced [8,9].…”

Section: Introductionmentioning

confidence: 99%

Metal behavior during vitrification of incinerator ash in a coke bed furnace

Kuo

2004

Journal of Hazardous Materials

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Section: Introductionmentioning

confidence: 99%

Metal behavior during vitrification of incinerator ash in a coke bed furnace

Kuo

2004

Journal of Hazardous Materials

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“…Similar methods have been applied to estimate the phase distributions in our previous work and other reports. 8,13 When the slag is recycled, its properties deserve more investigation to insure environmental safety. In previous studies, the relation between the crystalline-phase formation in vitrified slag and the SiO 2 content was investigated.…”

mentioning

confidence: 99%

Effect of SiO₂ on Immobilization of Metals and Encapsulation of a Glass Network in Slag

Kuo

Lin

Tsai

2003

Journal of the Air & Waste Management Association

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The final disposal of ash from an incinerator is of special concern because of the possibility of its releasing toxic substances. Melting/vitrification has been regarded as a prospective technology of ash treatment. The object of this investigation was to evaluate the effect of silica (SiO 2 ) addition on the immobilization of hazardous metals and the encapsulation of a glass network during the vitrification process. Four specimens with SiO 2 /fly ash mixing ratios of 0, 0.1, 0.2, and 0.3, respectively, were tested. The mobility of metals in slag was then estimated by a sequential extraction procedure. X-ray diffraction analysis indicates that SiO 2 leads to the polymerization of silicates.The encapsulation of aluminum, calcium, and magnesium would not be observed unless adequate amount of SiO 2 was added. It was also found that SiO 2 addition enhances the formation of a compact and interconnected glass network structure and, thus, contributes to the chemical stability of metals in slag. After vitrification, the mobility of cadmium, copper, iron, chromium, nickel, lead, and zinc was significantly reduced. However, there is no significant correlation between the immobilization of these metals and the addition of SiO 2 . INTRODUCTIONIncineration, an important technology for the treatment of municipal solid waste (MSW), is used in many countries. 1 In addition to flue gas, MSW ashes (including fly ash and bottom ash) pose a big threat to the environment. 2 Direct landfilling of MSW ashes is no longer an appropriate strategy because of the dwindling number of final disposal sites and the risk of releasing organic toxics and heavy metals. Melting/vitrification has been developed as a proper technology in the further stabilization of ashes, radioactive waste, or sewage sludge. [3][4][5] This technology not only reduces the volume of waste and the mobility of metals but also destroys toxic substances such as polycyclic aromatic hydrocarbons (PAHs) or dioxins. 6 -9 The leaching of hazardous metals has been controlled by stringent regulations. 10 However, a leaching test does not preclude potential long-term pollution. On the other hand, the behavior of the main constituents in a glass network might serve as an indicator for prolonged structure deterioration in slag. During vitrification, the chemical composition of the ternary system (silica [SiO 2 ]-alumina [Al 2 O 3 ]-lime [CaO]) is a major factor controlling the formation of the slag structure. 3,11 Among these constitutes, SiO 2 is of the greatest importance for the main constituents in a glass network when fly ash is vitrified. 12 Therefore, this study focused on the effect of SiO 2 addition on vitrification.In this investigation, the mobility of anthropogenic metals was evaluated by a sequential extraction procedure. Similar methods have been applied to estimate the phase distributions in our previous work and other reports. 8,13 When the slag is recycled, its properties deserve more investigation to insure environmental safety. In previous studies, the ...

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“…The fractions of the three phases refer to the metals leached out from slags during the period of slag structure decomposition, possibly from no decomposition, partial decomposition, or thorough decomposition (Ecke et al, 2001). …”

Section: Sample Preparation and Vitrification Processmentioning

confidence: 99%

Evaluation of effect of reducing additives during vitrification via simulation and experiment

Cheng

Huang

et al. 2013

Journal of the Air & Waste Management Association

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This study investigates how reducing additives governed the vitrification of prepared specimens. In the experiments, pure CaO/ CaCO 3 and SiO 2 served as the major components of glassy matrix (basicity ¼ mass ratio of CaO/SiO 2 ¼ 2/3) with doping of hazardous metals (Cr, Cu, and Ni). The substitution ratio of CaCO 3 for CaO was used as an operating parameter. The specimens were vitrified at 1400 C and a sequential extraction protocol was used to determine the phase distribution of Cr, Cu, and Ni. The volume fractions of crystalline and amorphous phases were measured using semiquantitative x-ray diffraction (XRD) analysis. A commercial software package (HSC Chemistry 6.0) was used to simulate the experiment to acquire additional information. The simulation results showed the addition of CaCO 3 generated CO and CO 2 at high temperature . This reducing atmosphere might enhance Cu and Ni to be easily separated from slags and elevated the levels of Cu and Ni in ingots. At higher CaCO 3 mol(%), the polymerization of silicate (from sorosilicate to inosilicate) in slag rose and the CaSiO 3 amount increased. In addition, the immobilization of metals and the acid resistance of slags were improved. The results indicate that CaCO 3 addition is favorable for increasing the metal level in ingots and the metal encapsulation in slag in vitrification.Implications: Vitrification techniques are often used to treat hazardous materials. The additives used in vitrification processes play an important role in vitrification. This study combines simulations (based on HSC Chemistry) and experiments to evaluate the effect of CaCO 3 addition (creating a reducing atmosphere) on toxic metal stabilization in vitrification. This way, the effects of different parameters on toxic metal stabilization in vitrification can also be evaluated. IntroductionMelting hazardous waste with silicate additives at a high temperature, namely, vitrification, is a high-energy-consumption and high-cost technology. Nevertheless, it has been used to treat hazardous materials with high toxicity, such as electroplating sludge, spent batteries, fly ash, and nuclear waste, due to its unique advantages (Li et al., 2007;Kuo et al., 2009a; Sengupta, in press;. Previous studies reported that the vitrification can destroy organic toxics via high temperature (>1400 C) (Ito, 1996;Kuo et al., 2003). After vitrification, molten materials can be separated into slag and ingot, due to gravity. Metals with high boiling points and densities tend to gather in the ingot, while those with low boiling points are usually concentrated in particulate matter in the flue gas. The ingot and particulate matter with high levels of valuable metals, such as Cd, Cu, Fe, Ni, and Zn, can be recovered after refinement (Kuo et al., 2009a). The residual hazardous metals may be encapsulated/stabilized in the molten materials (slags) that are commonly reused as a building material or an additive for cement (Lubeck et al., 2012;Zhou et al., 2010;Kakimoto et al., 2004). In such cases, the immobilization of...

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Effect of Electric Arc Vitrification of Bottom Ash on the Mobility and Fate of Metals

Cited by 55 publications

References 25 publications

Metal behavior during vitrification of incinerator ash in a coke bed furnace

Metal behavior during vitrification of incinerator ash in a coke bed furnace

Effect of SiO₂ on Immobilization of Metals and Encapsulation of a Glass Network in Slag

Evaluation of effect of reducing additives during vitrification via simulation and experiment

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Effect of Electric Arc Vitrification of Bottom Ash on the Mobility and Fate of Metals

Cited by 55 publications

References 25 publications

Metal behavior during vitrification of incinerator ash in a coke bed furnace

Metal behavior during vitrification of incinerator ash in a coke bed furnace

Effect of SiO2 on Immobilization of Metals and Encapsulation of a Glass Network in Slag

Evaluation of effect of reducing additives during vitrification via simulation and experiment

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Effect of SiO₂ on Immobilization of Metals and Encapsulation of a Glass Network in Slag