Carbothermic reduction of misamis oriental chromite ores Erlinda O. Yape * and Nathaniel M. Anacleto College of Engineering, Mindanao State University, Marawi City, Philippines *Tel.: 09228466758 ; Email: erlyape@yahoo.com _____________________________________________________________________________ Abstract This study was conducted to determine the nonisothermal and isothermal reduction of chromium ores in the solid-state by reductants like solid carbon under argon and hydrogen-argon atmosphere. Two different chromite ores from local sources , sandy chromite ore from Opol, Misamis Oriental (SCO) and lumpy chromite ore from Manticao, Misamis Oriental (LCM) were used in the study. Isothermal and non-isothermal experiments were conducted in a fixed bed reactor heated in a vertical tube furnace in the temperature range 800 to 1000 o C. Raw chromite and reduced samples were subjected to phase analysis and morphology characterization using X-ray flouresence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDX). It was found that reduction does not go to completion at this temperature range. The early stage of reduction of iron was controlled by nucleation and the later by nucleation or chemical reaction or both. The activation energy at the early stage of reduction is estimated to be 44.76 kJ/mol and the later stage of reduction is 144 kJ/mol for SCO and 76.5 kJ/mol for LCM. The reduction of chromium was controlled by chemical reaction. 1. Introduction Chromium is found in different countries in the world but its presence is not so abundant. In 1989, Philippine chromite reserve registered 31.72 million metric tonnes (MGB, 2000). The early 90's posted growth rates, with 1992 registering the highest at 15.6%. In terms of volume, 1996 posted 45.68 million metric tons. For the regional reserves, Region III posted the highest at 15.79 million MT, followed by Region X at 15.27 million MT. The use of chromium to produce stainless steels and nonferrous alloys are two of its more important applications. Other applications are in alloy steel, plating of metals, pigments, leather processing, catalysts, and refractories. This study was conducted to determine the nonisothermal and isothermal reduction of chromium ores in the solid-state by reductants like solid carbon and hydrogen under argon and hydrogen-argon atmosphere. The findings of this study may contribute to further development of new ferroalloy technologies and to the development of technology in the stainless steel industry. Further, the findings of the study would serve as a tool for researchers who would try to conduct further research studies. 2. Materials and Methods Two chromite samples , sandy chromite from Opol, Misamis Oriental (SCO) and lumpy chromite ores from Manticao, Misamis Oriental (LCM) were used in the study with activated carbon as reductant . The composition of chromite samples were analyzed through XRF by HOLCIM Philipines Inc. in Iligan City. Isothermal and non-isothermal experiments were conducted for the two chromite samples (SCO and LCM) in a fixed bed reactor heated in a vertical tube furnace. The heating rate in nonisothermal experiment was 2.5 o C/min under Ar and H 2 -Ar atmospheres from 20 o C to 1000 0 C. A 2 – 3 g sample was mixed with carbon. Oxygen removed from the sample in the reduction experiment was calculated of CO and CO 2 content in the exit gas using the CO/CO 2 gas analyzer. The extent of reduction was determined as a ratio of oxygen loss to initial oxygen in the ore. The reduced and raw ores were also