Thermodynamics of copper matte converting: Part III. Steady-state volatilization of Au, Ag, Pb, Zn, Ni, Se, Te, Bi, Sb,
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I.
INTRODUCTION
THERMODYNAMIC models of copper-matte converting have been recently formulated. 1.2 As an example of the application, the models were demonstrated to predict the behavior of five major elements I (Cu, Fe, S, O, SiO2) and also ten minor elements 2 in the condensed phases of the Noranda Process. These models not only provide plausible explanations for the commercial operation data, but also reveal many important fundamentals that are useful in controlling the commercial process. The models were based on the assumption that molten phases in the Noranda Process reactor are in equilibrium with each other as well as with the reacted tuyere gas, or SO2-N2 gas. The remarkable success of these equilibrium modelings encouraged a further thermodynamic analysis of the process with the aims of assessing the volatilization of the minor elements in the reactor, and establishing eventually the overall performance of the reactor as to the ten minor elements. The present work consists of three studies: the first is a critical review and compilation of the related thermodynamic data (Part III), the second the derivation of a mathematical formula for steady-state volatilization (also Part III), and the third a demonstration of how to apply the steady-state reactor model to the commercial Noranda Process (Part IV). The present model can provide a set of predictions for the overall reactions of minor elements as functions of process parameters. The predictions are presented in the form of tables (Part IV). This tabular method coupled with computer techniques allows the analysis of a complex multicomponent system, which is practically impossible with graphical methods. It will be self-evident in the course of the present modeling that the ultimate purpose of the present study is not merely to explain the commercially observed data M. NAGAMORI, formerly Associate Professor, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT, is now with Centre de Recherches Mindrales, Quebec Government, 2700 Einstein, Ste-Foy, Quebec G1P 3W8, Canada. P.C. CHAUBAL is Graduate Student, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112. Manuscript submitted September 8, 198l. METALLURGICALTRANSACTIONS B
of the Noranda Process, but to demonstrate a new computermodeling concept and technique which can certainly be applied in the analyses of many pyrometallurgical process reactors where steady-state or equilibrium conditions prevail.
II.
THERMODYNAMIC DATA
Some of the required basic free energy data were compiled elsewhere. 1,2 Table 13-32 provides additional thermochemical data for important gaseous species. Several values of AH~98, S~98, and Cp that are still missing in the literature were estimated by the authors, and the details of the calculation are given in the Appendix A. Using the data listed in Table I, the free energy (AG ~ data were calculated by the relation: AG~ --- dlH2~ +
fl~ AcpdT -
TASk98 - T
98
f~ ---T-dT z~c; 98
[201] The AG~ values were calculated at
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