Sains Malaysiana 51(5)(2022): 1511-1524

http://doi.org/10.17576/jsm-2022-5105-20

Volume Shrinkage during Carbothermic Reduction of Low-Grade Iron Ore Containing Goethite and Coal Composite

(Pengecutan Isi Padu Semasa Pengurangan Karbotermik Komposit Bijih Besi Gred Rendah yang Mengandungi Goetit dan Arang)

AGUNG SETIAWAN¹, INA ERMAWATI¹, FARRAS ANGGRAINI¹, FAIZINAL ABIDIN², ABDUL HAPID³, ADJI KAWIGRAHA³, SRI HARJANTO^1,* & M. AKBAR RHAMDHANI⁴

¹Department of Metallurgical and Materials Engineering, Faculty of Engineering, Universitas Indonesia, 16424 Kampus Baru UI Depok, West Java, Indonesia

²Directorate of Utilization of Research and Innovation by Government, Society, and Micro, Small, and Medium Enterprises- National Research and Innovation Agency (BRIN), Jakarta 10340, Indonesia

³Research Center for Mining Technology, National Research and Innovation Agency (BRIN), Building 820, Puspitek, Banten 15314, Indonesia

⁴Fluid and Process Dynamics (FPD) Research Group, Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Melbourne, VIC 3122, Australia

Received: 7 June 2021/Accepted: 20 October 2021

Abstract

The volume shrinkage and reduction behavior of low-grade iron ore goethite during the solid-state carbothermic process was studied and compared to synthetic goethite. The carbothermic reduction process using low-grade coal as a reducing agent was carried out in the temperature range 1000-1200 °C up to 60 min of reaction time. The results demonstrated that the volume shrinkage, reduction degree, and metallization degree of reduced samples increase with increasing temperature and reaction time. Compared to the reduced samples using synthetic goethite, the volume shrinkage, reduction degree, and metallization degree of the reduced samples using iron ore are lower due to the presence of impurities in Sebuku iron ore concentrates, which include Mg, Mn, Al, and Si. The highest volume shrinkage observed at 1200 °C for 60 min reaction time for the reduced samples using iron ore and synthetic goethite was 63.57±0.57 and 76.51±1.53%, respectively. The observed phases at this point were metallic iron (Fe_m) and spinel (Fe,Mg)Al₂O₄. The volume shrinkage of the reduced samples was caused primarily by the weight loss due to carbon, oxygen, and combined water evaporation, as well as the sintering of gangue oxides and metallic iron particles, and partial melting of these phases.

Keywords: Direct reduction; goethite; low-grade iron ore; rotary hearth furnace; volume shrinkage

Abstrak

Pengecutan isi padu dan tingkah laku pengurangan bijih besi kelas rendah yang mengandungi goetit semasa proses karbotermik keadaan pepejal dikaji berbanding dengan goetit sintetik. Proses pengurangan karbotermik menggunakan arang batu rendah sebagai agen pengurangan dilakukan dalam julat suhu 1000-1200 °C hingga 60 min masa reaksi. Hasil kajian menunjukkan bahawa pengecutan isi padu, tahap pengurangan dan tahap pengukuran sampel yang dikurangkan meningkat dengan peningkatan suhu dan tindak balas masa. Berbanding dengan sampel yang dikurangkan menggunakan goetit sintetik, pengecutan isi padu, tahap pengurangan dan tahap metalisasi sampel yang dikurangkan menggunakan bijih besi lebih rendah kerana beberapa kekotoran dalam pekatan bijih besi Sebuku, termasuk Mg, Al dan Si. Nilai pengecutan isi padu tertinggi yang dijumpai pada suhu 1200 °C selama 60 min masa reaksi bagi sampel yang dikurangkan menggunakan bijih besi dan goetit sintetik masing-masing adalah 63.57±0.57 dan 76.51±1.53%. Fasa yang diamati pada ketika ini adalah besi logam (Fe_m) dan spinel (Fe,Mg)Al₂O₄. Pengecutan jumlah sampel yang dikurangkan disebabkan terutamanya oleh penurunan berat badan karbon, oksigen dan air gabungan dan pertumbuhan sintering oksida gangue dan zarah besi logam dan pencairan sebahagian fasa gangue.

Kata kunci: Bijih besi bermutu rendah; goetit; pengecutan isi padu; pengurangan langsung; relau perapian putar

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^*Corresponding author; email: sri.harjanto@ui.ac.id