A mathematical model of the nickel converter: Part II. Application and analysis of converter operation
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I.
INTRODUCTION
N I C K E L converting is a complex process involving a large number of variables which are difficult to quantify, and hence, assessing their effects in the course of normal operation is not straightforward. A mathematical model of the nickel converter, assuming thermodynamic equilibrium, was developed and verified in Part I of this article, lu Empirical models of matte and slag solution thermochemistry were used in conjunction with equilibrium equations and mass and heat balances to describe the operation of the process through a series of equilibrium steps. The model was found to give a relatively good prediction of literature correlations and plant data from the Copper Cliff smelter of Inco Ltd. This model can be used to explore the effects of many different variables not easily changed in the field. The purpose of Part II is to carry out a preliminary analysis of various aspects of the nickel converting operation with the aim of identifying those variables which are important in controlling the productivity of the converter. In particular, this article will focus on heat distribution, the relative rates of iron and sulfur removal, and matte oxygen content as a function of operating variables. Before pursuing this, however, it is important to conduct a sensitivity analysis of the model to assess the effect of errors and/or uncertainties in the input values on the overall results. II.
SENSITIVITY ANALYSIS
AND CONVERTER THERMOCHEMISTRY A "standard" charge was developed based on Inco plant practice to allow direct comparisons between different A.K. KYLLO, Graduate Student, and G.G. RICHARDS, Associate Professor, are with The Centre for Metallurgical Process Engineering, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. S.W. MARCUSON, Supervisor of Process Development, is with the Copper Cliff Smelter, Inco Limited, Copper Cliff, ON POM INO, Canada. Manuscript submitted June 17, 1991. METALLURGICAL TRANSACTIONS B
values of the same variable. Details of this charge are given in Table I. It is not as complex as an actual charge and has a constant air rate, so that the effects of changes in a particular variable are not obscured by interactions with other variables and other considerations. A complete charge was chosen for this study in order to focus on the overall operation instead of specific chemical and thermal aspects of the process. The variables tested and the values used are given in Tables II and III. In order to assess the effect of each variable on converter operation, both bath temperature and composition should be considered. The effect on composition will be shown by the weight percent of iron in matte, which gives a good indication of the overall matte composition, as demonstrated in Part I. Ill In some cases, significant variations in the gas composition were seen, and where appropriate, these will be shown.
A. Metallurgy of the Standard Charge Figures 1 through 3 can be used to follow the progress of the standard charge. It should be noted that the idle time followin
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