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2011-Sustainable Industrial Processing Summit
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| Editors: | Florian K |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2012 |
| Pages: | 754 pages |
| ISBN: | 978-0-9879917-3-7 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Accretion Formation In Zinc Oxide Calcination Kiln
P. Chris Pistorius1; Regis Zagrocki2; Gabriel Gerson1;1CARNEGIE MELLON UNIVERSITY, Pittsburgh, United States; 2HORSEHEAD CORPORATION, Monaca, United States;
Type of Paper: Regular
Id Paper: 189
Topic: 12
Abstract:
Crude zinc oxide, the collected fume from a Waelz kiln, is calcined in a rotary kiln to remove volatile salts (such as lead chloride and potassium sulfate). Accretions develop in the calcination kiln. The work reported here examined the fundamental cause. It is found that a small amount of liquid forms at the calcination temperature, and binds together the zinc oxide, similar to the mechanism by which moisture increases the strength of wet sand. Both potassium sulfate and calcium silicate cause liquid formation. Laboratory trials tested whether the composition of the binding liquid responds to additions of silica and alumina. The calcium silicate appears to contain all of the calcium oxide and silica from the feed material (crude zinc oxide); it is possible to manipulate the composition and amount of the calcium silicate by silica additions to the feed, but the calcium silicate does not respond to alumina additions. While this work has clarified the likely causes of accretion formation, it does not lead to any obvious solutions. It does not appear possible to eliminate all liquid in this process, since potassium sulfate (with a melting point of 1069°C) is one of the binder liquids.