Transforming Palm Waste into Renewable Reductant: Torrefied Palm Kernel Shell as a Sustainable Reductant for Low-Carbon Ferronickel Production

¹ Department of Chemical Engineering, Faculty of Industrial Technology, Bandung Institute of Technology, Indonesia 40132
² Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Indonesia 40132

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Indonesia, with the world’s largest nickel ore reserves of approximately 55 million tons, plays a significant role in the global nickel supply chain. To support the national downstream strategy, efficient utilization of nickel ore, particularly through ferronickel production, is crucial. However, the conventional use of coal as a reductant poses the risk of increased carbon emissions in line with growing ferronickel demand, challenging Indonesia’s Net Zero Emissions 2060 target. On the other hand, Indonesia also produces around 12.8 million tons of palm kernel shell (PKS) waste annually, which has potential as a low- carbon biomass reductant. Nevertheless, its low fixed carbon content limits its direct use in metallurgical processes. This research studied the torrefaction of PKS at 300 °C for 1 hour, which increased its fixed carbon content from 17.43% to 40.16%. The torrefied PKS was then used as a reductant for reducing saprolite nickel ore at a 1:4 w/w (reductant:ore) ratio, at temperatures of 500 °C, 700 °C, and 900 °C for 60 – 120 minutes. The reduced solids were characterized using XRD and SEM-EDS. Metallic phases were detected in samples reduced at 700 °C and 900 °C for 120 minutes, with iron (Fe) contents of 96.17% and 95.67%, respectively. These samples were subsequently smelted at 1373 °C, 1473 °C, and 1573 °C, and the resulting solids were analyzed using SEM-EDS. Increasing reduction temperatures indicated enhanced metallic formation. The metal produced at 1573 °C smelting process from the 500 °C reduction sample contained 79.30% Fe and 15.59% nickel (Ni), while the 700 °C and 900 °C reduction samples contained 74.62% Fe and 14.88% Ni, and 75.57% Fe and 13.77% Ni, respectively.