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Proceedings Paper

In-Situ Measurement Of Lime Kiln Burden Temperature By Laser Induced Fluorescence
Author(s): Peter C. Ariessohn; Kelle R. Ryan
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Paper Abstract

A novel technique has been developed for measuring the temperature of the burden inside an operating industrial lime kiln. In this technique, trace quantities of a rare earth element are introduced into the input stream to the kiln. Conditions inside the kiln cause the rare earth ions to become incorporated as substitutional impurities in the crystal lattice of the calcium oxide product. This results in a product which exhibits strong fluorescence under ultra-violet excitation. The decay time constant of this fluorescence, which is strongly temperature dependent, serves as a measure of burden temperature. The spectral and temporal characteristics of the fluorescence of several rare earths have been studied over a temperature range of 800 to 1150°C which is the range of interest in an operating kiln. This work has led to the selection of praseodymium as the most suitable rare earth element and to the development of techniques to permit temperature measurements with an accuracy of approximately ±20°C to be performed at rare earth concentrations in the parts per million range. A prototype sensor employing this fluorescence technique has been developed. This sensor, which has been designed to survive in the harsh lime kiln environment, utilizes a frequency tripled Nd:YAG laser to provide high energy UV pulses at 355 nm and a specially designed telescope and fiber-optic light collection system to detect the emitted fluorescence. This device will provide the first accurate, in-situ measurement of lime kiln burden temperature which can be made on a continuous basis.

Paper Details

Date Published: 10 March 1989
PDF: 10 pages
Proc. SPIE 1012, In-Process Optical Measurements, (10 March 1989); doi: 10.1117/12.949339
Show Author Affiliations
Peter C. Ariessohn, Weyerhaeuser Company (United States)
Kelle R. Ryan, Weyerhaeuser Company (United States)

Published in SPIE Proceedings Vol. 1012:
In-Process Optical Measurements
Kenneth H. Spring, Editor(s)

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