Gördes Lateritinin CO Atmosferinde İzotermal Olmayan İndirgenme Kinetiği

Nikel metaline yönelik her geçen gün artan talebe rağmen sülfit yataklarının tükeniyor oluşu sektörün yönünü düşük Ni içeriği ve yüksek enerji gerektirmesi dolayısıyla birincil kaynak olarak pek tercih edilmeyen laterit yataklarına çevirmiştir. Dolayısıyla hem maliyetleri hem de sera gazı emisyonları düşürerek bu cevherleri etkin şekilde işleyebilmek için alternatif yolların bulunması elzemdir. Lateritlerdeki nikelin kazanılması için katı faz indirgenmesi ve akabinde magnetik yolla ayırma cazip bir seçenektir. Bu nedenle bu çalışma Gördes lateritinin (Manisa, Türkiye) farklı ısıtma hızlarında (20, 25, 30, 35, ve 45 ºC/dak.) izotermal olmayan indirgenme kinetiğini konu almıştır. Aktivasyon enerjileri Friedman (FR), Kissinger-Akahira-Sunose (KAS), ve Flynn-Wall-Ozawa (FWO) yöntemleriyle, hızı kontrol eden mekanizmalar ise Sestak-Berggren Eşitliğinin Malek yorumu ile belirlenmiştir. İndirgenme prosesi, kinetik analiz sonuçlarına dayanılarak sırasıyla "0 ile 0,16", "0,16 ile 0,45", and "0,45 ile 0,7" indirgenme dereceleri arasında yer alan üç bölgeye ayrılmıştır. İlk bölgenin 53 kJ/mol’ lük bir aktivasyon enerjisiyle, arayüz reaksiyon kontrolü altında gerçekleştiği, ikinci ve üçüncü bölgelerin ise sırasıyla 126 kJ/mol ve 379 kJ/mol’ lik aktivasyon enerjisiyle, karışık kontrollü olarak gerçekleştiği belirlenmiştir.

Anahtar Kelimeler:

Nikel, laterit, izotermal olmayan TGA, kinetik modelleme, Sestak-Berggren eşitliği

Non-isothermal Reduction Kinetics of Gördes Laterite in CO Atmosphere

The growing demand for nickel metal and the depletion of high-grade sulfide ore reserves have turned the direction of industry towards laterites which are not desirable as the primary source due to their low Ni content and more energy-intensive processing. Thus, alternative routes are essential for effectively processing these ores while reducing the costs and greenhouse gas emissions. Solid-state reduction followed by magnetic separation is an attractive option for recovering the nickel in laterites. Hereby, this study analyzed the non-isothermal reduction kinetics of nickel laterite from Gördes (Manisa, Turkey) by CO at different heating rates of 20, 25, 30, 35, and 45 ºC/min. The activation energies were determined by Friedman (FR), Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO) methods, and the controlling mechanisms were determined by the Malek interpretation of the Sestak-Berggren Equation. The reduction process was divided into three stages which take place between "0 to 0.16", "0.16 to 0.45", and "0.45 to 0.7" reduction degrees respectively according to the kinetic analysis results. The first stage was determined to be interface reaction controlled (with "Ea" of 53 kJ/mol), while the second and third were determined to be mixed controlled (with "Ea" of 126 kJ/mol and 379 kJ/mol, respectively).

Keywords:

Nickel, laterite, non-isothermal TGA, kinetic modeling, Sestak-Berggren equation,

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