Effects of Basicity Index on Incinerator Fly Ash Melting Process and Stabilization
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials, Reagents and Instruments
2.2. Basicity Index Adjustment Experiment
2.2.1. Basicity Index Adjustment with Glass through Melting Process
2.2.2. Basicity Index Adjustment with Silica Sand Powder through Melting Process
2.3. Leaching Property Test
2.4. Vitrified Slag Composition Test
3. Results and Discussion
3.1. Basicity Index Adjustment Experiment
3.1.1. Basicity Index Adjustment with Glass through Melting Process
3.1.2. High-Temperature Melting Process with Silica Sand Powder
3.2. Analysis
3.2.1. TCLP Tests
3.2.2. Composition Tests
4. Conclusions
- By adjusting the basicity index of the fly ash through the addition of silica, it was observed that the melting point of the fly ash could be effectively reduced from 1400 °C to 1200 °C when the basicity index was maintained below 1.28.
- The basicity indices for fly ash’s high temperature melting process were determined optimally by calculating the ratio of CaO/SiO2.
- Both kinds of fly ash, including industrial waste incinerator fly ash (FA1) and laboratory-waste-incinerator fly ash (FA2), could be melted and stabilized by the melting process after the adjustment of basicity indices.
- Even if the basicity index adjustment material was changed from glass to silica sand powder, this study proved that fly ash could be melted with a basicity index under 1.28. It did not make a difference in whether the fly ash could be melted if the SiO2 was in a crystalized phase or not.
- The leaching concentrations for all the vitrified slags were significantly low, including the ones from FA1 mixed with glass, FA1 mixed with silica sand, FA2 mixed with glass, or FA2 mixed with silica sand powder.
- Compared to the leaching concentration regulations in Taiwan, all of the vitrified slags were within the regulations. Thus, they were all considered stabilized.
- Through the ICP tests, the vitrified slags were all mainly composed of SiO2, CaO, Na2O, and a low amount of Al2O3.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Elements | FA1 | FA2 | Glass |
---|---|---|---|
Si | 2.71% | 2.60% | 28.73% |
Na | 4.66% | 9.60% | 2.81% |
Ca | 22.57% | 20.88% | 0.17% |
Al | 0.81% | 3.78% | 1.32% |
Mg | 0.47% | 0.45% | 0.11% |
Cu | 0.75% | 0.76% | 0.11% |
Zn | 0.81% | 0.56% | 0.10% |
Pb | 0.52% | 0.53% | 0.14% |
K | 1.56% | 1.21% | 0.46% |
Fe | 0.84% | 1.15% | 0.36% |
Oxides | FA1 | FA2 | Glass |
---|---|---|---|
5.8% | 7.55% | 88.59% | |
6.28% | 14.19% | 5.46% | |
CaO | 31.59% | 32.23% | 0.34% |
1.54% | 7.5% | 3.59% | |
MgO | 0.78% | 0.84% | 0.27% |
CuO | 0.94% | 0.94% | 0.19% |
ZnO | 1.01% | 0.81% | 0.18% |
Oxides | FA1 | FA2 | Glass |
5.8% | 7.55% | 88.59% | |
6.28% | 14.19% | 5.46% |
Ratio | FA1 | FA2 |
---|---|---|
1:0 | 5.45 | 4.27 |
6:1 | 1.54 | 1.54 |
5:1 | 1.35 | 1.28 |
4:1 | 1.13 | 1.09 |
3:1 | 0.90 | 0.87 |
2:1 | 0.63 | 0.62 |
1:1 | 0.34 | 0.34 |
Ratio | FA1 | FA2 |
---|---|---|
1:0 | 5.45 | 4.27 |
6:1 | 1.42 | 1.34 |
5:1 | 1.23 | 1.18 |
4:1 | 1.03 | 1.00 |
1:0 | 6:1 | 5:1 | 4:1 | 3:1 | 2:1 | 1:1 | |
---|---|---|---|---|---|---|---|
1100 °C | X | X | X | X | X | X | X |
1200 °C | X | X | X | O | O | O | O |
1300 °C | X | X | X | O | O | O | O |
1400 °C | O | O | O | O | O | O | O |
1:0 | 6:1 | 5:1 | 4:1 | 3:1 | 2:1 | 1:1 | |
---|---|---|---|---|---|---|---|
1100 °C | X | X | X | X | X | X | X |
1200 °C | X | X | O | O | O | O | O |
1300 °C | X | X | O | O | O | O | O |
1400 °C | O | O | O | O | O | O | O |
6:1 | 5:1 | 4:1 | |
---|---|---|---|
1100 °C | X | X | X |
1200 °C | X | O | O |
1300 °C | X | O | O |
1400 °C | O | O | O |
6:1 | 5:1 | 4:1 | |
---|---|---|---|
1100 °C | X | X | X |
1200 °C | X | O | O |
1300 °C | X | O | O |
1400 °C | O | O | O |
Regulation | FA1 4:1 | FA1 3:1 | FA1 2:1 | FA1 1:1 | |
---|---|---|---|---|---|
Ag | 5.0 | ND | ND | ND | ND |
As | 5.0 | ND | ND | ND | ND |
Cd | 1 | ND | ND | ND | ND |
Cr | 5 | 0.16 | 0.15 | 0.21 | 0.14 |
Cu | 15 | 0.10 | 0.09 | ND | ND |
Hg | 0.2 | ND | ND | ND | ND |
Pb | 5 | ND | 0.05 | ND | ND |
Se | 1 | 0.04 | 0.05 | 0.03 | 0.02 |
Ba | 100 | 0.50 | 0.40 | 0.23 | 0.22 |
Cr(VI) | 2.5 | ND | ND | ND | ND |
Regulation | FA1 5:1 | FA1 4:1 | |
---|---|---|---|
Ag | 5.0 | ND | ND |
As | 5.0 | ND | ND |
Cd | 1 | ND | ND |
Cr | 5 | ND | ND |
Cu | 15 | ND | ND |
Hg | 0.2 | ND | ND |
Pb | 5 | ND | ND |
Se | 1 | 0.05 | 0.01 |
Ba | 100 | 0.51 | 0.14 |
Cr(VI) | 2.5 | ND | ND |
Regulation | FA2 5:1 | FA2 4:1 | FA2 3:1 | FA2 2:1 | |
---|---|---|---|---|---|
Ag | 5.0 | ND | ND | ND | ND |
As | 5.0 | ND | ND | 0.10 | ND |
Cd | 1 | ND | ND | ND | ND |
Cr | 5 | 0.11 | 0.11 | 0.14 | 0.12 |
Cu | 15 | ND | ND | ND | 0.29 |
Hg | 0.2 | ND | ND | ND | ND |
Pb | 5 | ND | ND | ND | ND |
Se | 1 | 0.18 | 0.13 | 0.12 | 0.19 |
Ba | 100 | 0.33 | 0.24 | 0.23 | 0.11 |
Cr(VI) | 2.5 | ND | ND | ND | ND |
Regulation | FA1 5:1 | FA1 4:1 | |
---|---|---|---|
Ag | 5.0 | 0.01 | ND |
As | 5.0 | ND | ND |
Cd | 1 | ND | ND |
Cr | 5 | 0.21 | 0.14 |
Cu | 15 | ND | ND |
Hg | 0.2 | ND | ND |
Pb | 5 | ND | ND |
Se | 1 | 0.01 | 0.01 |
Ba | 100 | 0.17 | 0.63 |
Cr(VI) | 2.5 | ND | ND |
FA1 4:1 | FA1 3:1 | FA1 2:1 | FA1 1:1 | |
---|---|---|---|---|
37.35% | 37.45% | 47.84% | 51.75% | |
CaO | 4.58% | 16.55% | 13.63% | 16.44% |
4.90% | 3.06% | 3.04% | 4.40% | |
0.04% | 0.27% | 0.16% | 0.37% |
FA1 5:1 | FA1 4:1 | |
---|---|---|
21.94% | 27.38% | |
CaO | 20.83% | 18.52% |
3.11% | 3.18% | |
0.50% | 0.85% |
FA2 5:1 | FA2 4:1 | FA2 3:1 | FA2 2:1 | FA2 1:1 | |
---|---|---|---|---|---|
33.66% | 35.93% | 40.17% | 52.80% | 60.49% | |
CaO | 4.03% | 3.61% | 4.95% | 6.20% | 7.02% |
9.72% | 9.53% | 10.40% | 7.87% | 6.85% | |
0.03% | 0.03% | 0.04% | 0.03% | 0.36% |
FA1 5:1 | FA1 4:1 | |
---|---|---|
31.84% | 25.54% | |
CaO | 17.69% | 21.42% |
6.41% | 6.79% | |
0.63% | 0.71% |
Method | Narrative |
---|---|
Thermal treatment | The thermal treatment could stabilize the heavy metals in fly ash by melting it into vitrified slags and the slags could be further used as other materials. Yet, the high energy consumption of the method still needs to be solved. |
Solidification/stabilization | This method is the most commonly used method in all fly ash treatments due to its simple operation and low processing costs. However, it does lead to the problems of low heavy-metal stability and increase in waste volume. |
Leaching process | This method is the only method that is able to effectively recycle the Zn, Pb, Cu, Cd and other metals from the fly ash. Yet, the residues of this method would still require further treatments before landfilling. |
Pyrolysis process | This method shows good results in its dioxins degradation and PCDD/Fs decomposition. Nonetheless, it still presents the problems of high energy consumption and high TEQ residues. |
Hydrothermal treatment | The hydrothermal method can significantly dichlorination and degradation the POPs in fly ash and is a relatively mature method. Nevertheless, the leaching of some heavy metals such as Pb and Cd could then become even more severe, causing further problems. |
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Chen, W.-S.; Chen, G.; Lee, C.-H. Effects of Basicity Index on Incinerator Fly Ash Melting Process and Stabilization. Sustainability 2023, 15, 11610. https://doi.org/10.3390/su151511610
Chen W-S, Chen G, Lee C-H. Effects of Basicity Index on Incinerator Fly Ash Melting Process and Stabilization. Sustainability. 2023; 15(15):11610. https://doi.org/10.3390/su151511610
Chicago/Turabian StyleChen, Wei-Sheng, Gregory Chen, and Cheng-Han Lee. 2023. "Effects of Basicity Index on Incinerator Fly Ash Melting Process and Stabilization" Sustainability 15, no. 15: 11610. https://doi.org/10.3390/su151511610
APA StyleChen, W.-S., Chen, G., & Lee, C.-H. (2023). Effects of Basicity Index on Incinerator Fly Ash Melting Process and Stabilization. Sustainability, 15(15), 11610. https://doi.org/10.3390/su151511610