Carbothermic Reduction Roasting of a Low-Grade Nickel Laterite Ore in the Modified Caron Process

Carbothermic reduction-roasting of a low-grade Ni-lateritic was investigated under the modified Caron process. Roasting parameters of reductant (coal), additive (Na2SO4), temperature, and time were varied to optimize an efficient reduction of laterite to metallic nickel and cobalt. The degree of phase transformation characterized using XRD revealed a positive effect of additive that improved reduction with respect to increasing temperatures. The laterite mixture (with 10% coal + 9% Na2SO4) roasting at 800 degrees C for a duration of 120 min showed >90% nickel and 68% cobalt in an ammoniacal solution of NH4OH-(NH4)(2)CO3. The calculated reduction rate indicates the occurrence of a 3-steps reaction, comprising surface-diffusion followed by intermediate-diffusion, and finally the product-diffusion. Subsequently, leaching kinetics of roast-reduced laterite fit to the shrinking core model by following a mixed- and diffusion-controlled mechanism for nickel and cobalt, respectively.

Automated summary

The carbothermic reduction-roasting process of low-grade Ni-lateritic under the modified Caron process was investigated. Optimal conditions were found to efficiently reduce laterite to metallic nickel and cobalt, with the use of additives showing a positive effect on the reduction process. Leaching kinetics of the roast-reduced laterite were found to follow a shrinking core model with a mixed- and diffusion-controlled mechanism for nickel and cobalt, respectively.