Thermal analysis kinetics of non-free water removal in nickel laterite

Abstract

Differential scanning calorimetric(DSC) data during non-free water removal in nickel laterite were determined with a NETZSCH STA 449 C thermal analyzer. Experiments were carried out at four heating rates of 10,15,20 and 25℃·min-1. According to these DSC curves at different heating rates,the activation energies were calculated by five different calculation methods of conversion rate,namely the Flynn-Wall-Ozawa(FWO),Hu-Gao-Zhang(Hu GZ),Boswell,Starink,and Friedman-Reich-Levi(Friedman)methods. The pre-exponential factor(A) and the most probable mechanism function were determined by the Malek method,then the relationship between reaction degree and time under an isothermal condition was derived and the energy consumptions at different temperatures were analyzed and compared. The average activation energy of non-free water removal in nickel laterite is 181.50 k J·mol-1. The average lnA is 21.95 min-1. The most probable mechanism function fits the Zhuralev-Lesokin-Tempelman(Z-L-T)equation well. The non-free water removal is controlled by three-dimensional diffusion. The average power decreases with increasing temperature.

Keywords

• nickel laterite
• dewatering
• thermal analysis
• kinetics
• activation energy