The contradiction between liquid phase formation and iron grain growth, which occurs during reduction roasting of copper slag pellets at high temperature, was resolved through changing the thermal history. The phase evolution of reduced products obtained at different thermal histories was examined using the analysis methods of morphology, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results indicate that prolonging the time promotes the increase of the metal ratio in the reduced products obtained at 1050 and 1100°C. A maximum metal ratio exceeding 90% is achievable in the reduced products obtained at 1100°C for more than 90 min, while the formation of liquid phase reduces the metal ratio in the reduced products obtained at 1150°C. When the copper slag pellet is reduced at 1100°C for ≥ 60 min followed by heating to 1150°C, the formation of liquid phase in the reduced products can be effectively suppressed and the metal ratio reaches a maximum value of over 90%. Meanwhile, the iron grain count and the volume with a size of + 20 μm reaches 17.07 and 91.53%, respectively. This study provides a new direction for effectively inhibiting liquid phase formation from copper slag pellet during reduction roasting.
Wang et al. (Tue,) studied this question.