Exploring a new path of green and efficient utilization of sinter return fine to produce composite pellets

Efficient utilization of sinter return fine is an important measure to reduce cost, increase efficiency, save energy and reduce emission. A new path of green and efficient utilization of return fine was proposed to produce composite pellets. The metallurgical properties of composite pellets under the condition of hydrogen-rich blast furnace were studied. The experimental results indicate that the coated concentrate was consolidated for the composite pellets through normal Fe2O3 recrystallization. Near the surface of core return fine, the liquid phase formed due to its low-melting point, assimilated the adjacent concentrate, and then consolidated with the temperature decreasing. Compared with regular pellets, the compressive strength and reduction swelling index of composite pellets were decreased, but the reducibility index and softening–melting properties were improved. In addition, the reduction degradation index of composite pellets was significantly higher than that of sinter. Therefore, adding composite pellets was conducive to indirect reduction in blast furnace, reducing fuel ratio and improving production efficiency. According to the effect of the roasting system on the metallurgical properties, the roasting temperature and time were determined as 1250 °C and 30 min, respectively. The composite pellets can be produced under the traditional pelletizing process.