Reduksi Selektif Bijih Nikel Laterit Menggunakan Gas NH3 Sebagai Reduktan Dan CaSO4 Sebagai Agen Selektivitas

Ramadhan, Dolph Raikhan Shahrukh (2026) Reduksi Selektif Bijih Nikel Laterit Menggunakan Gas NH3 Sebagai Reduktan Dan CaSO4 Sebagai Agen Selektivitas. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Indonesia memiliki cadangan nikel terbesar di dunia dan menjadikannya sebagai komoditas strategis yang mendukung pertumbuhan ekonomi nasional dan transisi energi global. Namun, proses pengolahan bijih nikel laterit, khususnya metode pirometalurgi, masih bergantung pada bahan bakar fosil dan menghasilkan emisi CO2 yang tinggi, yaitu sekitar 18 ton CO₂-ekivalen/ton nikel. Salah satu metode alternatif yang dapat menurunkan emisi CO2 adalah penggunaan reduktan non-karbon, seperti gas amonia (NH₃) dan CaSO₄ sebagai aditif selektif dalam proses reduksi bijih nikel laterit. Penelitian ini bertujuan untuk menganalisis efektivitas proses reduksi bijih nikel lateritik menggunakan gas NH₃ dengan mengkaji pengaruh variasi penambahan CaSO₄, waktu tahan, laju alir NH₃, dan temperatur terhadap derajat reduksi, kandungan Ni dan Fe, karakteristik mineralogi dan morfologi produk reduksi, potensi pengurangan emisi CO2 secara teoritis guna mengoptimalkan pengembangan proses reduksi selektif serta mendukung teknologi pengolahan nikel yang efisien energi, rendah emisi karbon, dan ramah lingkungan. Variasi penelitian yang digunakan meliputi variasi jumlah aditif CaSO4 yang digunakan (0-20%), temperatur (700-900°C), waktu tahan (0-180 menit), dan laju alir NH3 (0,1-0,3 L/menit). Setelah seluruh proses reduksi selesai, perhitungan derajat reduksi, pengujian X-Ray Diffractometer (XRD), pengamatan Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) dilakukan untuk menganalisis produk hasil reduksi. Dari hasil penelitian diperoleh hasil bahwa variasi penambahan CaSO₄, temperatur, laju alir NH₃, dan waktu tahan berpengaruh signifikan terhadap derajat reduksi, transformasi mineralogi, serta morfologi produk reduksi bijih nikel laterit menggunakan gas NH₃. Kondisi optimum diperoleh pada penambahan 15 wt% CaSO₄, temperatur 850°C, laju alir NH₃ 0,2 L/min, dan waktu tahan 120 menit, yang menghasilkan derajat reduksi tertinggi. Pada kondisi tersebut terbentuk intensitas ferronickel (FeNi) tertinggi dengan keseimbangan pembentukan troilite (FeS) dan clinopyroxene (CaMgFeSi₂O₆), serta menghasilkan aglomerasi ferronickel yang lebih besar, homogen, dan distribusi Fe–Ni yang berlangsung lebih efektif. Sebaliknya, peningkatan CaSO₄, temperatur, laju alir NH₃, maupun waktu tahan di atas kondisi optimum meningkatkan pembentukan clinopyroxene yang lebih stabil sehingga menghambat difusi reduktan, dan menurunkan intensitas ferronickel. Selain itu, proses reduksi menggunakan gas NH₃ menghasilkan emisi sebesar 8,02 kg CO₂-eq/kg FeNi, lebih rendah dibandingkan proses produksi feronikel konvensional karena tidak menghasilkan emisi CO₂ secara langsung selama proses reduksi.
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Indonesia possesses the largest nickel reserves in the world, making nickel a strategic commodity that supports national economic growth and the global energy transition. However, the processing of lateritic nickel ores, particularly through pyrometallurgical routes, still relies heavily on fossil fuels and generates high CO2 emissions, reaching approximately 18 tons of CO2-equivalent per ton of nickel produced. One alternative approach to reducing CO2 emissions is the use of non-carbon reductants, such as ammonia gas (NH3), in combination with CaSO4 as a selective additive in the reduction of lateritic nickel ores. This study aims to analyze the effectiveness of lateritic nickel ore reduction using NH3 gas by investigating the effects of CaSO4 addition, holding time, NH3 flow rate, and temperature on the degree of reduction, Ni and Fe contents, mineralogical characteristics, and morphological features of the reduction products, as well as the theoretical potential for CO2 emission reduction. The results was expected to provide a basis for optimizing selective reduction processes and supporting the development of energy-efficient, low-carbon, and environmentally friendly nickel processing technologies. The experimental variables include variations in CaSO4 addition (0–20%), temperature (700–900°C), holding time (0–180 minutes), and NH3 flow rate (0.1–0.3 L/min). After the completion of the reduction process, the degree of reduction was calculated, and the reduction products were characterized using X-ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM-EDX), and Atomic Absorption Spectrophotometry (AAS). The results showed that variations in CaSO4 addition, reduction temperature, NH3 flow rate, and holding time significantly enhanced the reduction degree and improved the mineralogy and morphology of the reduced lateritic nickel ore. The highest reduction degree was achieved at 15 wt% CaSO4, a reduction temperature of 850°C, an NH3 flow rate of 0.2 L/min, and a holding time of 120 min. Under these optimum conditions, the highest ferronickel (FeNi) intensity was obtained, accompanied by a balanced formation of troilite (FeS) and clinopyroxene (CaMgFeSi2O6), which promoted larger and more homogeneous ferronickel agglomerates with overlapping Fe–Ni distributions, thereby improving the separation of metallic phases from the silicate matrix. In contrast, increasing the CaSO4 addition, reduction temperature, NH3 flow rate, or holding time beyond the optimum conditions promoted excessive clinopyroxene formation, hindering reductant diffusion and reducing ferronickel intensity. Moreover, the NH3-based reduction process resulted in lower CO2 emissions (8.02 kg CO2-eq/kg FeNi) compared to conventional processes, as no direct CO2 generation occurs during reduction.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Amonia, Nikel laterit, CaSO4, Waktu Tahan, Temperatur, Laju Alir, Ammonia, Laterite Nickel, CaSO4, Temperature, Holding Time, Flow Rate
Subjects:	T Technology > T Technology (General) > T58.8 Productivity. Efficiency T Technology > TD Environmental technology. Sanitary engineering > TD171.75 Climate change mitigation T Technology > TJ Mechanical engineering and machinery > TJ808 Renewable energy sources. Energy harvesting. T Technology > TN Mining engineering. Metallurgy T Technology > TN Mining engineering. Metallurgy > TN799.N6 Nickel--Metallurgy T Technology > TP Chemical technology > TP155.7 Chemical processes.
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Material & Metallurgical Engineering > 27101-(S2) Master Thesis
Depositing User:	Dolph Raikhan Shahrukh Ramadhan
Date Deposited:	04 Aug 2026 03:45
Last Modified:	05 Aug 2026 02:21
URI:	http://repository.its.ac.id/id/eprint/142927

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