Accretion growth on single-pipe tuyeres: Part II. Model results and discussion
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I.
INTRODUCTION
T H E mathematical model of accretion growth detailed in Part I of this article t~J can be used to simulate the formation of accretions in single-pipe injection systems. This article will study two such cases in detail: the copper converter and inert gas injection into steel. The injection into steel considers both ladle stirring and bath stirring in a combined blowing converter. In Part I of this paper, tll it was shown that pipe accretions in the copper converter only form under extreme conditions, while the hemispherical accretions formed in a steel ladle stirring application required 600 seconds to reach a steady-state size. The primary source of heat to the accretions is the bath flow. However, in the case of accretions in the copper converter, the oxygen-matte reaction at the tip also plays a role in controlling accretion length. The conditions under which these results were obtained are given in Table I. A sensitivity analysis considering the effects of the assumptions and less well-known input data is essential. This serves to aid in assessing the validity of the model, which is particularly important in this case, since there is very little industrial data which can be used for that purpose. It can also help increase the understanding of the complexities of accretion formation. The second objective of this article is to assess the effects of the most important operating parameters on accretion growth. The parameters studied are those which are the most likely to affect the heat balance at the tuyere/accretion A . K . K Y L L O , Graduate Student, is with the Centre for Metallurgical Process Engineering, University of British Columbia, Vancouver, BC Canada V6T 1Z4. G.G. RICHARDS, formerly Associate Professor, University of British Columbia, Vancouver, is Senior Research Scientist, Cominco Metals, Trail, BC Canada V1R 4L8. Manuscript submitted October 16, 1992. METALLURGICAL TRANSACTIONS B
tip in the case of a pipe accretion and on the accretion. surface in the case of a hemispherical accretion. The analysis of copper converting accretions uses a bath superheat of 5 K as the base. This is to ensure that the accretion formed is significant and will better illustrate the effects of the parameters studied. II.
SENSITIVITY ANALYSIS
A. Copper Converter The parameters studied in the sensitivity analysis of accretion formation in the copper converter are given in Table II. In Part I, m it was shown that copper converter slag accretions took about 300 seconds to reach steady state. This may be longer than the time between tuyere punching in those installations which employ it, so in those cases, steady state may not be attained. However, the effects of the variables considered can best be shown using the steady-state accretion profiles. The bath velocity in a converter is not well known. A previous model of pipe growth in a copper converter 12~ used a value of 0.25 ms -l, and this value was used in the present model. Figure l(a) indicates that a decrease in the bath velocity of 40 pct causes an
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