Non-Isothermal Calcination Kinetics of Phosphate Rock

Abstract

The kinetics of thermal decomposition of the phosphate rock was studied by means of thermal analysis techniques (TG/DTG) in inert nitrogen (N2) atmosphere at heating rates of 2, 5, 10, and 20 K min-1. TG and DTG measurements indicated that calcination of the phosphate rock has single-stage degradation in between 873-1173 K. Kissinger–Akahira–Sunose (KAS) and Flynn-Wall-Ozawa (FWO) isoconversional methods were applied to the data obtained from TG and DTG curves and the activation energies were found as 170 ve 187 kJmol-1, respectively. It was determined that the thermal decomposition mechanism of phosphate rock was occurred via nucleation and growth (-ln(1-α)2/3) mechanism. Pre-exponentional factor (lnA) was determined as 20.47.

Keywords

• Phosphate rock, Isoconversional methods, Activation energy, Non-isothermal kinetic analysis.

Fosfat Kayasının İzotermal Olmayan Bozunma Kinetiği

Öz

Mazıdağı fosfat kayasının inert ( N2) ortamda ısıl bozunma kinetiği 2, 5, 10 ve 20 K dak-1 ısıtma hızlarında termal analiz teknikleri (TG/DTG) ile incelendi. TG ve DTG ölçümlerinde 873-1173 K sıcaklık aralığında fosfat kayasının ısıl bozunmasının tek basamaklı bozunma olduğu görüldü. TG ve DTG eğrilerinden elde edilen verilere eş dönüşüm metotları Kissinger–Akahira–Sunose (KAS) ve Flynn-Wall-Ozawa (FWO)uygulanarak aktivasyon enerjileri sırasıyla 170 ve 187 kJmol-1 olarak bulundu. Fosfat kayasının ısıl bozunmasının çekirdeklenme ve büyüme (-ln(1-α)2/3) mekanizmasına göre meydana geldiği belirlendi. Ön üssel faktör (ln A) ise 20.47 olarak tespit edildi.

Anahtar Kelimeler

• Fosfat kayası, Eş dönüşüm metotları, Aktivasyon enerjisi, İzotermal olmayan kinetik analiz.

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