Factors influencing the production rate and quality of lead sinter
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I.
INTRODUCTION
IDEALLY, a lead sinter machine should be able to produce strong, uniform, low-sulfur sinter at high production rates. The "strong gas" for sulfuric acid production should have a high and uniform SO2 content, and the dust content of the sinter should be low. However, a number of difficulties occur in actual operation to prevent these ideal conditions. Almost all of these difficulties can be traced to three characteristics of conventionally prepared feed: low permeability, variable permeability, and incomplete charge mixing. The present work was undertaken to examine the effect of a number of independent sintering variables on 24 different characteristics of either the sintering process or the fifial sinter. Most of the experiments were statistically designed so as to give an empirical quantitative model of the sintering process for a typical Missouri lead concentrate. Particular emphasis was placed on the method of charge preparation before sintering. In about half of the experiments, the charge was prepared in the conventional way, by mixing the ingredients in a rotating drum while adding moisture. In the other half of the experiments, the charge was carefully pelletized* *In this work, the term "pelletize" is synonymous with the terms "green bailing" and "nodulizing" used by other authors.
in such a way that the center of each pellet was a piece of coarse return sinter. The experimental work on a pelletized charge actually had two main objectives. First was an exploration of the pelletizing process itself to determine conditions necessary for formation of strong green balls from the charge materials. Second was an exploration of the sintering process, conducted in a manner similar to the sintering investigation for a conventionally prepared charge. This paper is confined primarily to the sintering research. The sintering results are expressed primarily in the form of graphs and equations, and in the British system of JOHN R. KNOEPKE is with Kennecott Process Technology, P. O. Box 11248, Salt Lake City, UT 84147; HUNG-YANG TSAI is with China Steel Corporation, Hsiao-Kang, Kaohsiung 812, Taiwan, Republic of China; and ARTHUR E. MORRIS is with the Department of Metallurgical Engineering, University of Missouri-Rolla, RoUa, MO 65401. Manuscript submitted June 1, 1981. METALLURGICALTRANSACTIONS B
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units. This was done so as to make the results directly comparable to industrial sinter plant data. The Appendix contains conversion factors for certain dependent variables to SI units.
II.
LITERATURE REVIEW AND T H E O R E T I C A L CONSIDERATIONS
The sintering process consists of the passage of a heat and reaction front through a packed bed of solids. In general, the objective is to attain a temperature wave passing through the bed in such a way that a zone of incipient or partial fusion passes through the bed in order to agglomerate (sinter) the fines in the bed to a porous lumpy material. The theoretical development of the sintering process has mainly been developed by workers interested in iron o
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