Mathematical model of chalcocite particle combustion
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A.A. SHOOK, formerly Graduate Student, The University of British Columbia, is Researcher, BHP Steel-New Technology Development, Wollongong, NSW 2500, Australia. G.G. RICHARDS, formerly Associate Professor, The University of British Columbia, is Senior Researcher, Cominco Research, Cominco Ltd., Trail, BC, Canada V1R 4S4. J.K. BRIMACOMBE, Alcan Chair in Materials Process Engineering and Director, The Centre for Metallurgical Process Engineering, is with The University of British, Columbia, Vancouver, BC, Canada V6T 1Z4. Manuscript submitted September 1, 1994. METALLURGICAL AND MATERIALS TRANSACTIONS B
Table I.
Chemical Analysis of MK Concentrate
Cu Ni S Typical assay 75 pct 3 to 4 pet 21 pct Table II.
Fe = 8
Model Predictions o
Data of Olero at ad.
gl D
0 600
700
BOO
900
1000
11O0
1200
1300
Furnace Temperature (K)
Fig. 8 ~ o m p a r i s o n between the mass loss measurements of Otero et al. [2] in oxygen and the predictions of the kinetic model. (fce = volume fraction copper).
the kinetic model predictions were compared with the mass loss data of Otero et al. t21 in an attempt to predict the ignition temperatures determined by these investigators. To make the predictions, the kinetic model was run with particle sizes of 10 to 100 microns, and the resulting series of computed mass loss values were averaged to give an estimate of the mass loss to be expected from the as-received concentrate. In these calculations, the parameter fcu, the fraction of the particle surface from which copper may vaporize, was assumed to be equal to the volume fraction of copper. This parameter was found to have no effect on the predictions of the ignition temperature, either in oxygen or in air. Owing to a systematic sampling error, the measurements of Otero et al.t21 exhibited a consistent mass loss of approximately 10 pct prior to ignition. To facilitate comparison with the mathematical model (and following the practice of Otero et al.), the experimental data plotted in Figures 7 and 8 have been corrected for this sampling error. This slight adjustment had no effect on the location of the experimentally measured ignition temperatures. The predictions of the model for the combustion of chalcocite in air and in oxygen are compared with the experimental data in Figures 7 and 8, respectively. These figures illustrate that the model is capable of predicting the ignition temperature of the MK concentrate (the inflection point in METALLURGICAL AND MATERIALS TRANSACTIONS B
Fig. 9--Predicted particle temperature and composition as a function of time for a 20 micron chalcocite particle combusting in oxygen. Furnace temperature = 1213 K.
the mass loss curve) with reasonable accuracy. This simultaneously provides some verification of the computer code and suggests that the values of the pre-exponential constant and the activation energy obtained from the data of Kim and Themelis t'3] are reasonably applicable to this system. The model appears to be much less successful in predicting the total mass loss after ignition, especially
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