Mechanism and structure-activity relationship of a new composite binder to improve the quality of green pellets

Reducing bentonite consumption is one of the effective ways to improve the grade of pellets and realize energy saving and emission reduction. Based on the new high-efficiency composite binder, the effect of the composite binder on the quality of green pellets and structure-activity relationship with important indexes were studied by means of green pellet preparation, linear fitting analysis, and green pellet mechanical characteristics analysis. Moreover, the mechanism of the composite binder to improve the quality of the green pellets was expounded. Results show that the composite binder pellet, with a ratio of 1.2% bentonite and 0.028% organic binder, has a drop number (dropped from 0.5 m height) of 6.2, a average crushing strength of 14.5 N, and a shock temperature of 542 ℃. Compared with the pellet with 2.0% bentonite, the mass of the green pellets is similar; however, the bentonite consumption is reduced by 40%. Based on the analysis of the structure-activity relationship, the organic binder has a considerable effect on the drop number and the shock temperature of the green pellets, and the bentonite has a greater effect on the dry-crushing strength. The organic binder strengthens the drop number of the pellets by enhancing the hydrophilicity, capillary force, and viscosity, and it forms small amounts of pores on the surface layer during drying, which is beneficial for discharging water in the pellets and improving the shock temperature of the pellets. After drying, the organic binder strengthens the pellets in the form of a solid connection bridge; however, the site and the size of the pores may reduce the dry-crushing strength. Therefore, bentonite plays a decisive role in the strength of the dry pellets, and the influence of the organic binder on the strength of the dry pellets is multifaceted.