Bentonite-free pelletizing of iron ore particles via liquid binder: liquid bridge theoretical model and experimental study
摘要
Chinese iron ore pellets exhibit 2% lower iron content than global benchmarks. Reducing bentonite usage provides a viable pathway for iron grade enhancement. Current organic binder alternatives face limited adoption due to cost-effectiveness and applicability constraints, with insufficient theoretical guidance for binder development. The mechanical characteristics of interparticle bonding in iron ore pellets were investigated based on liquid bridge theory. A mathematical model was established to describe the formation and rupture of liquid bridges between iron ore particles. Theoretical calculations clarified the relationships among capillary force, viscous force, and key parameters including liquid bridge volume, contact angle, viscosity, and interparticle distance. A dual mechanism of viscous force generated by binders exists during pelletizing and collision–separation processes: Capillary force predominantly governs green pellet strength, while viscous force manifests only during relative particle motion. Higher liquid bridge viscosity enhances viscous force and adhesion, but excessive viscosity impedes particle aggregation during pelletizing, thereby increasing interparticle distance and reducing pellet strength. Experimental results demonstrate that when using liquid organic binders at concentrations of 0.7–0.8 wt.%, green pellets achieved a drop strength of 5.4 times/0.5 m and a compressive strength approaching 3000 N pellet−1, realizing bentonite-free pelletizing. However, binder concentrations exceeding 0.6 wt.% prolonged pelletizing time, while binder concentration of 1.0 wt.% caused excessive viscosity that increased interparticle distance and reduced drop strength.