The influence of mass transfer phenomena on the kinetic analysis for the thermal decomposition of calcium carbonate by constant rate thermal analysis (CRTA) under vacuum
✍ Scribed by N. Koga; J. M. Criado
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 202 KB
- Volume
- 30
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
The influence of the mass transfer phenomena on the thermal decomposition of calcium carbonate powders under vacuum was investigated through a detailed kinetic analysis by the constant transformation rate thermal analysis (CRTA). Reliable kinetic curves, free from the mass transfer problems, can be obtained by CRTA under vacuum, but within a restricted range of small sample sizes,
The influence of mass transfer phenomena on the Ͻ10 mg. apparent kinetic parameters is discussed in relation to the distribution of fractional reaction ␣ of the individual particles in a sample assemblage. Only when the distribution of ␣ is maintained constant among a series of experimental kinetic curves, can a reliable activation energy, E, be obtained by one of the isoconversion methods. In this respect, a single cyclic CRTA permits the ␣ distribution to be maintained constant between the two adjacent data points with different decomposition rates. In the present study, an apparent E value of about was obtained by the Friedman method from a series of CRTA curves with sample Ϫ1 223 kJ mol sizes less than and by the rate jump method from a single cyclic CRTA curve with sample 10 mg size of about
The first-order (F 1 ) law was determined to be the most appropriate kinetic 40 mg. model function, from a series of CRTA curves, instead of the ideal contracting geometry (R 3 ) law formalized for the three-dimensional shrinkage of the reaction interface in the respective particles. The particle size distribution of the sample particles is suggested to be one possible