Effects of direct reduction process on the microstructure and reduction characteristics of carbon-bearing nickel laterite ore pellets

Abstract

A coal-based direct reduction process was used to recover the ferronickel from low-grade nickel laterite ore. The effects of basicity on the compressive strength, metallization rate, microstructure, and reduction characteristics of carbon-bearing nickel laterite ore pellets were investigated. The results show that the metallization rate of iron and the compressive strength of metallized pellets follow a parabolic function with increasing basicity. The optimal reduction temperature of the rotary kiln should be controlled at 1150 °C to 1250 °C with pellet basicity of 0.56 to prevent the ring-forming phenomenon. Under optimum process conditions, the metallized pellets mainly consist of ferronickel ([Fe,Ni]), forsterite ferroan (Mg1.38Fe0.61Ca0.01SiO4), and pigeonite ((Ca0.06Mg0.68Fe0.26)SiO3). The particle size of ferronickel can reach to 30 μm with a high nickel‑chromium concentrations. The compressive strength of metallized pellets is 5220 to 7223 N·Pellet−1, and the metallization rates of iron and nickel are 95.28% to 98.45%, 94.75 to 96.33%, respectively.