Jeffrey Ken B. Balangao ¹, Feven James C. Podiotan ², Aaron Exxon C. Ambolode ², Nathaniel M. Anacleto ², Consorcio S. Namoco ³

Affiliations
1 Department of Arts and Sciences, University of Science and Technology of Southern Philippines-Oroquieta Campus, Mobod, Oroquieta City, 7207 Misamis Occidental, PH
2 Department of Ceramics, Metallurgical and Mining Engineering, College of Engineering and Technology, MSU-Iligan Institute of Technology, 9200 Iligan City, PH
3 Department of Mechanical Engineering, College of Engineering and Architecture, University of Science and Technology of Southern Philippines-Cagayan de Oro Campus, Lapasan, Cagayan de Oro City, 9000 Misamis Oriental, PH

Abstract

Objective: To investigate the reduction of mixed chromite and laterite ores which were obtained from Zambales and Surigao Del Norte provinces to produce iron (Fe)-chromium (Cr)-nickel (Ni) metal alloys. Methods: Raw ores were mixed according to eutectic point of MgO-Al₂O₃-SiO₂ ternary phase diagram for which samples are melted at 1600ºC. Isothermal reduction of 12/88, 25/75 and 50/50 chromite/laterite samples was conducted at 1600ºC in one hour in vertical electric arc furnace using coconut charcoal as reductant under argon atmosphere. Non-isothermal reduction was conducted at 10ºC/min heating rate from 200ºC to 1500ºC to show reduction characteristics of the mixed sample. Findings: Metal recoveries were 69.70% (12/88), 78.99% (25/75) and 99.62% (50/50), respectively. Chromium contents increased at increasing percentages of chromite in the mixtures, i.e. from 12% to 50%. Nickel contents decreased at decreasing laterite contents from 88% to 50%. Scanning electron microscope (SEM) revealed presence of dark, light and some small black phases for 12/88 metal alloy; dark, light phase and gray phases for 25/75 and dark and light phases for the 50/50. According to EDS analyses, dark phases present in the metal alloys had 26.03-46.97% Fe, 35.39-59.41% Cr, 0.35-1.02%Ni and 10.14-12.44% C. Light phases consisted 62.31-67.33% Fe, 3.99-4.62% Cr, 12.05-15.75% Ni and 3.1-6.7% C. Results showed partial reduction at around 920ºC and maximum reduction at about 1450 ºC. Reduction was not completed at 1500ºC. Extent of reduction reached up to 32.16%. The extent of reduction was greatly attributed to the high concentrations of magnesia and silica and lower hematite (Fe₂O₃) in the sample. Improvements: Utilization of reductants such as graphite and activated carbon and other Philippine chromite/laterite mixing compositions that would result to higher chromium and nickel contents in alloys are recommended.

Full Text