An Experimental Study of Calcination of South Australian Caroline Limestone

Abstract

~~Calcination experiments were conducted on Caroline Limestonefrom 53jm to 1.0 mm in size, under a range of partial pressures of C02 and total pressures and temperatures between 700-900°C using both an atmospheric and a pressurised thermogravimetric apparatus. Results revealed that under these conditions the calcination of Caroline Limestone was unaffected by particle size. The behaviour was attributed to particle explosion that allowed less difision resistances for the larger particles. It still needs to be determined whether the explosion was a result of thermally induced fractures (TIFs) or low-temperature decomposition of MgC03 The calcination of Caroline Limestone conducted under a variety of partial pressures of COz was found to be proportional to the equilibrium partial pressure of C02 minus the partial pressure of C02 at interface, PCO; -PCO,' for the 0.21-0.35 and 0.5-0.6mm particle size fractions. For the larger particle size fractions between 0.85-I.0mm and 0.5-0.6mm in N2 environment under higher pressures (up to 5 atm), the use of a constant mole fraction y], was necessary to correlate the calcination rates with effect of C02 partial pressure. The calcination rate under these conditions was therefore found proportional to PCO? -PCO; -Pyl. Calcination rates calculated from data up to 100% conversion for the 0.2-0.35mm particles also required the inclusion of y1 and its value was also found to increase from 0.03 at 850°C to 0.22 at 900°C. The observed trends in the value and requirement of the constant mole fraction, y,, clearly indicates that it is included to account for heat and muss transport processes which supports previous justifcation for its introduction in the rate equation.

Calcination Behaviour of Nsuta Rhodochrosite Ore in the Presence and Absence of End-of-Life High Density Polyethylene

“…In another development, a study conducted by O'Shaughnessy et al (2004) concluded that Nsuta manganese carbonate is still acceptable in its nature for manganese ferroalloy production. The thermal decomposition of metal carbonates and or hydroxides have been investigated before (Borgwardt, 1985;Chen et al, 2009;Kim and Kwon, 1998;Li et al, 2005;Samtani et al, 2002;Telfer et al, 2000;Wang et al, 2007;Yamaguchi et al, 1980). The effect of CO2 partial pressure on the thermal decomposition kinetics of metal carbonates such as CdCO3, MnCO3, PbCO3 and ZnCO3 were investigated by Criado et al, 1998;Criado et al, 1987;Criado et al, 1982;Yamada et al, 2009;Yamaguchi et al, 1980).…”