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An Experimental Study of Calcination of South Australian Caroline Limestone
Author(s) -
Telfer M.,
Zhong Z.,
Xu Y.,
Li D.,
Zhang M.,
Zhang D. K.
Publication year - 2000
Publication title -
developments in chemical engineering and mineral processing
Language(s) - English
Resource type - Journals
eISSN - 1932-2143
pISSN - 0969-1855
DOI - 10.1002/apj.5500080306
Subject(s) - calcination , thermogravimetric analysis , partial pressure , particle size , mineralogy , diffusion , decomposition , particle (ecology) , analytical chemistry (journal) , chemistry , materials science , thermodynamics , metallurgy , geology , chromatography , catalysis , physics , oxygen , organic chemistry , oceanography
Calcination experiments were conducted on Caroline Limestone from 53μm to 1.0 mm in size, under a range of partial pressures of CO 2 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 diffusion 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 MgCO 3 . The calcination of Caroline Limestone conducted under a variety of partial pressures of CO 2 was found to be proportional to the equilibrium partial pressure of CO 2 minus the partial pressure of CO 2 at interface, PCO 2 e ‐ PCO 2 i , for the 0.21–0.35 and 0.5–0.6mm particle size fractions. For the larger particle size fractions between 0.85–1.0mm and 0.5–0.6mm in N 2 environment under higher pressures (up to 5 atm), the use of a constant mole fraction y 1 , was necessary to correlate the calcination rates with effect of CO 2 partial pressure. The calcination rate under these conditions was therefore found proportional to PCO 2 e ‐ PCO 2 i ‐ Py 1 . Calcination rates calculated from data up to 100% conversion for the 0.2–0.35mm particles also required the inclusion of y 1 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 1 clearly indicates that it is included to account for heat and mass transport processes which supports previous justification for its introduction in the rate equation.