Oxidation characteristics of calcium sulfite in sintering desulphurized ash

QIAN Dayi; WANG Yan; XING Yi; JIN Minghui; SU Wei; ZHANG Mengran; ZHENG Yuebo; LIU Yuanmeng; DUAN Shuya

doi:10.13374/j.issn2095-9389.2022.09.19.004

Volume 45 Issue 11

Nov. 2023

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Article Navigation > Chinese Journal of Engineering > 2023 > 45(11): 1985-1996

QIAN Dayi, WANG Yan, XING Yi, JIN Minghui, SU Wei, ZHANG Mengran, ZHENG Yuebo, LIU Yuanmeng, DUAN Shuya. Oxidation characteristics of calcium sulfite in sintering desulphurized ash[J]. Chinese Journal of Engineering, 2023, 45(11): 1985-1996. doi: 10.13374/j.issn2095-9389.2022.09.19.004

Citation:

QIAN Dayi, WANG Yan, XING Yi, JIN Minghui, SU Wei, ZHANG Mengran, ZHENG Yuebo, LIU Yuanmeng, DUAN Shuya. Oxidation characteristics of calcium sulfite in sintering desulphurized ash[J]. Chinese Journal of Engineering, 2023, 45(11): 1985-1996. doi: 10.13374/j.issn2095-9389.2022.09.19.004

Citation:

QIAN Dayi, WANG Yan, XING Yi, JIN Minghui, SU Wei, ZHANG Mengran, ZHENG Yuebo, LIU Yuanmeng, DUAN Shuya. Oxidation characteristics of calcium sulfite in sintering desulphurized ash[J]. Chinese Journal of Engineering, 2023, 45(11): 1985-1996. doi: 10.13374/j.issn2095-9389.2022.09.19.004

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Oxidation characteristics of calcium sulfite in sintering desulphurized ash

doi: 10.13374/j.issn2095-9389.2022.09.19.004

1.
School of Energy Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
2.
Key Laboratory of Pollutant Chemistry and Environmental Treatment, School of Chemistry and Environmental Science, Yili Normal University, Yining 835000, China

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Corresponding author: E-mail: qday@ustb.edu.cn
Received Date: 2022-09-19
Available Online: 2022-11-28
Publish Date: 2023-11-01

Abstract

Abstract

Considering the variation in dry heat oxidation of CaSO₃ in sintering semidry desulfurization ash under different reaction conditions, the effects of temperature, O₂ content and flow rate in gas, calcium compounds, iron oxide (Fe₂O₃), water vapor content, and flow rate on CaSO₃ oxidation were evaluated. It was determined that the reaction adheres to the Arrhenius equation. The oxidation rate of CaSO₃ increases from 380 ℃. Moreover, at 450 ℃, the oxidation rate of CaSO₃ exceeds 90%, and at 550 ℃, it is completely oxidized (98.2%). Under the condition of 10 ℃·min^?1 in the air atmosphere, the gas flow rate of 450 ℃ and 75 mL·min^?1 is the optimal process condition for economic dry heat oxidation. Water vapor is present on both sides of the CaSO₃ oxidation reaction. Moreover, the oxidation of CaSO₃ by calcium oxides was inhibited by inhibiting the generation of $ {\text{O}}_{\text{2}}^{-}\;\text{and }\;{\text{SO}}_{\text{3}}^{-} $ free radicals. The order of the inhibition of CaSO₃ oxidation by the three calcium oxides from weak to strong was CaCO₃ < Ca(OH) ₂ < CaCl ₂. The catalytic effect of Fe₂O₃ on the oxidation of CaSO₃ varies with temperature and concentration. When the temperature is less than 450 ℃ and the weight percentage of Fe₂O₃ is greater than 0.2%, it plays a certain catalytic role in the oxidation reaction. The doping of Fe₂O₃ accelerates the formation of $ {\text{O}}_{\text{2}}^{-} $ and $ \text{S}{\text{O}}_{\text{3}}^{-} $ free radicals. When the temperature exceeds 450 ℃ and the catalyst concentration is less than 0.2%, the catalyst concentration has no effect on the reaction process, and the temperature takes precedence. The microscopy analysis reveals that with the oxidation of CaSO₃ to CaSO₄, the morphology shifts from cluster to column. Furthermore, CaCl₂ inhibits not only the oxidation reaction but also the crystal form of CaSO₄. Fe₂O₃ aids the formation of CaSO₄ crystals. When the temperature exceeds 400 ℃, the internal temperature of desulfurized ash is higher than 500 ℃ for 5 min. Simultaneously, the conversion rate of CaSO₃ is greater than 85%, and the pilot test temperature is slower, which lacks this feature. The Gibbs free energy calculation results show that the most likely reaction is the oxidation of CaSO₃ and that decomposition of calcium below 600 ℃ is not feasible. The number of active sites in the process of CaSO₃ oxidation is proportional to temperature. Thus, when the temperature is between 623 and 723 K, the reaction is a first-order reaction. When the temperature exceeds 723 K, the reaction will be completed quickly in about 5 min, and the reaction order cannot be determined.
- semi-dry desulfurization,
- desulfurization ash,
- calcium sulfite,
- dry method,
- oxidation characteristics

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References(30)

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