A study on composite carbonaceous reducing agent pellets based on low-order unbonded coal

Abstract

To minimize the cost of carbon-reducing agents and reduce the waste of powder in production, a novel composite carbonaceous reducing agent pellet was prepared through cold pressing, utilizing low-rank unbonded coal (NC) as the primary raw material and incorporating petroleum coke (PC) and high-bonding coal (HVC). This study investigated the influence of different material composition ratios, the addition of organic binder (OBD) and inorganic binder (IBD) (water glass solution), forming moisture ranging from 2 to 12 %, holding temperatures of 60 to 100 ℃, holding times of 2 to 6 h, and material particle sizes ranging from 40 to 250 mesh (0.063–0.420 mm). Additionally, forming pressures of 5 to 30 MPa were analyzed concerning their impact on the cold consolidation strength (CCS) of the resulting pellets. The primary and secondary effects of forming pressure, forming moisture, binder content, and raw material size on pellet strength were examined. According to the actual production situation, the optimum technological conditions were determined. The primary and secondary effects on CCS were ranked as follows: forming pressure > particle size of raw material > binder ratio of 4 % content > forming moisture. External morphology and internal structures of different carbon materials were characterized via FESEM, BET, FTIR, XRD, and XPS. Mechanisms affecting the pellet strength were analyzed. The newly developed composite carbon-reducing agent pellets were suitable for industrial silicon production. This study presented a pathway for the clean and efficient utilization of low-rank unbonded coal and low-viscosity coal, offering substantial economic and social benefits.