Comparative study of the isothermal solid-state reaction systems of kaolinite–Na2CO3 and kaolinite–quartz–Na2CO3 for coal gangue activation. Issue 4 (December 2022)

• Record Type: Journal Article
• Authors: Yan, Kezhou; Guo, Yaru; Zhang, Yuanyuan; Guo, Yanxia; Cheng, Fangqin
• Is Part Of: Powder diffraction. Volume 37:Issue 4(2022)
• Page Start: 190
• Page End: 199
• Publication Date: 2022-12
• Subjects: kaolinite -- quartz -- sodium carbonate -- isothermal calcination -- XRD analysis -- phase transformation; Powder metallurgy -- Periodicals; Materials -- Analysis -- Periodicals; 620.1127
• DOI: 10.1017/S0885715622000434
• Languages: English
• ISSNs: 0885-7156

Abstract

Abstract : A clear understanding of the solid-state reaction of kaolinite (Kln), quartz (Qtz), and sodium carbonate (Na2 CO3 ) is of great significance for the process optimization of coal gangue calcined with Na2 CO3 . In this work, a comparative study of the isothermal solid-state reaction systems of Kln–Na2 CO3 and Kln–Qtz–Na2 CO3 was performed by means of X-ray diffraction (XRD), scanning electron microscope, and energy dispersion spectroscopy (SEM-EDS). The results showed that the calcined products both for these reaction systems mainly contain different kinds of sodium aluminum silicates (e.g., NaAlSiO4, Na1.55 Al1.55 Si0.45 O4, and Na1.95 Al1.95 Si0.05 O4 ) and various kinds of sodium silicates (e.g., Na2 Si3 O7, Na2 SiO3, and Na6 Si2 O7 ). The mass percentage of Na2 CO3 played a key role in the phase transformation, determining the Na/Al/Si molar ratio of the formed sodium aluminum silicates. Compared with the reaction system of Kln–Na2 CO3, the existence of Qtz inhibited the formation of sodium aluminum silicates in the reaction system of Kln–Qtz–Na2 CO3 . It should be noted that the formed phases both for these reaction systems were slightly different from that of the thermodynamical calculated results of Na2 O–SiO2 –Al2 O3 using FactSage™ software. According to both the experimental and calculated results, a reasonable batching area for coal gangue activation was proposed that the addition of Na2 CO3 should be in the range of 20–50% of the total mass of Kln, Qtz, and Na2 CO3 .