Research on Composite Binders for Pelletization in Pyrometallurgical Zinc Smelting

With the development of the zinc smelting industry, high-grade zinc ore resources are becoming increasingly scarce, and the costs associated with traditional pyrometallurgical zinc smelting processes such as the Imperial Smelting process (ISP) are gradually rising. Furthermore, conventional pelletizing processes predominantly utilize single inorganic binders, which tend to introduce impurities during sintering, leading to a decline in the final metal grade. To address these challenges, this study proposes blending zinc-containing solid waste generated during smelting with zinc concentrate. An organic–inorganic composite binder system was developed to replace conventional single inorganic binders. This approach aims to minimize impurity introduction, enable secondary resource utilization of zinc-containing solid waste, and thereby reduce overall zinc smelting costs. Results indicate that at an 8.5% moisture addition rate, using a binder composed of 0.3% hydroxypropyl methylcellulose (HPMC) blended with 1% water glass(sodium silicate) yields green ball properties of 4.3 times/0.5 m drop strength, 13.44 N P⁻¹ compressive strength, and 439°C bursting temperature. Calcination tests have demonstrated that the compressive strength and residual sulfur content of the pellets meet industrial production requirements. This approach reduced inorganic binder consumption while meeting green pellet strength requirements and minimizing impurity introduction. Kinetic studies revealed that the growth process of pellets prepared with an HPMC–water glass composite followed a first-order kinetic model. Further binder mechanism analysis indicated that HPMC enhances adsorption through hydrogen bonding and coordination bonds with metal ions. This research provides theoretical support and technical guidance for the efficient resource utilization of multi-source lead–zinc solid waste.