Critical conditions for zinc recovery in the FeOt-SiO2-CaO-Al2O3-ZnO slag system without metallic iron generation

• Published in: Journal of cleaner production 2024-03, Vol.443, p.141193, Article 141193
• Main Authors: Wang, Yannan, Xue, Zhenhong, Huang, Shuigen, Blanpain, Bart, Guo, Muxing
• Format: Article
• Language: English
• Subjects: calcium oxide; CaO; chemistry; Fe precipitation; oxygen partial pressure; pO2; Slag chemistry; slags; temperature; zinc; ZnO reduction
• ISSN: 0959-6526
• DOI: 10.1016/j.jclepro.2024.141193

The precipitation of metallic Fe from the FeOt-SiO2-CaO-Al2O3–ZnO-(Cr2O3) slag system can cause serious problems for the slag tapping and slag valorization. This study examines the impact of slag chemistry, oxygen partial pressure (pO2), and temperature on Fe generation and ZnO reduction in the FeOt-SiO2-CaO-Al2O3–ZnO-(Cr2O3) slag system and compares the results with those from FactSage calculation. Metallic Fe is observed in CaO-free slag with a FeO/(Al2O3+SiO2) ratio above 1.22 under pO2 of 1 × 10−12 atm at 1250 °C. As the CaO content increases to 29.7 wt%, the critical FeO/(Al2O3+SiO2) ratio for Fe generation decreases to 0.53. The critical temperature for Fe precipitation under pO2 of 1 × 10−12 atm is measured to be between 1200 and 1250 °C, while the critical pO2 to prevent the metallic Fe formation was calculated to be in excess of 5 × 10−13 and 1 × 10−12 atm at 1200 and 1250 °C, respectively. ZnO can be reduced into metallic Zn at 1250 °C under pO2 of 1 × 10−10 atm or below. The operational conditions for Zn fuming of the FeOt-SiO2-CaO-Al2O3–ZnO slags without Fe formation are recommended to be pO2 of 1 × 10−12 atm at 1200 °C. [Display omitted]