Large- and Particle-Scale energy assessment of reduction roasting of nickel laterite ore for Ferronickel production via the rotary Kiln-Electric furnace process

Abstract

• Mineralogical composition and moisture content govern energy consumption. • Dehydroxylation and drying use around one-third of the energy input. • Energy and exergy efficiencies amount to 66.4% and 32.3%, respectively. • Dehydroxylation, drying, and size define intraparticle temperature gradient. Ferronickel is essential in manufacturing austenitic stainless steels, nickel alloy steels, batteries, electronics, and gas turbines, among other crucial products. The Rotary Kiln-Electric Furnace process is a widely recognized pyrometallurgical route for ferronickel production. This paper focuses on the rotary kiln furnace, an intermediate stage in which partially dried minerals convert into calcine, ready for smelting in an electric arc furnace. This paper uses a unique industrial database that contains operation variables and minerals composition of a 180 t h −1 rotary kiln furnace. As a distinguishing feature, this work incorporates the effects of dehydroxylation reactions and uses intraparticle energy analysis to gain further insights into the reduction roasting process. Goethite and serpentine dehydroxylation reactions consume around 18% of the energy input of the rotary kiln furnace. Flue gases and shell losses represent around 25% and 8% of the energy input, respectively, while the vaporization of free moisture consumes nearly 15% of the energy input. The rotary kiln furnace shows energy and exergy efficiencies of 66.4% and 32.3%, respectively, leaving room for waste heat recovery. Particles with surface-to-center distances lower than 5.0 mm could behave as isothermal, while coarser particles could present significant temperature gradients. These results can assist in optimizing operating conditions and provide insights into the thermal effects of the ore mineralogical composition.