Two-wavelength pyrometry study of the combustion of sulfide minerals: Part III. The influence of oxygen concentration on
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I.
INTRODUCTION
IRON sulfides are a common constituent of most commercial concentrates of lead and other mineral sulfides, and their presence influences the combustion of these solids during flash smelting. The combustion behavior of pyrite has been studied by a number of researchers, tl-51 Jorgensen has investigated the combustion of individual particles of pyrite extensively using two-wavelength radiation pyrometry techniques similar to those adopted in the present study, tl,2,31The effect of oxygen concentration and gas temperature on the reactions has been reportedJ ~1 The maximum particle temperature for the combustion of a 37- to 53-/xm screen fraction of pyrite in a furnace at 973 K was found to increase from - 1 9 0 0 K at 14 pct oxygen to a maximum of --2600 K in pure oxygen, while average particle stream temperatures were 300 to 600 K lower. In part I of this series of articles,t61 examples of pyrometry pulses recorded during the combustion of pyrite and pyrrhotite in air were presented. Jorgensen has also published t2J a few pyrometer traces of the combustion of individual particles which show similar combustion pulse shape
N.E. TUFFREY, formerly Graduate Student, Centre for Metallurgical Process Engineering, University of British Columbia, is Senior Research Metallurgist, Sherritt Inc., Fort Saskatchewan, AB, Canada T8L 3W4. G.G. RICHARDS, formerly Associate Professor, Department of Metals and Materials Engineering, University of British Columbia, is Senior Research Scientist, Cominco Research Ltd., Trail, BC, Canada V1R 4S4. J.K. BRIMACOMBE, Alcan Chair in Materials Process Engineering, and Director, Centre for Metallurgical Process Engineering, is with the University of British Columbia, Vancouver, BC, Canada V6T 1Z4. Manuscript submitted April 13, 1994. METALLURGICAL AND MATERIALS TRANSACTIONS B
and maximum temperatures. A sudden three- to tenfold increase in particle energy was observed, and it was postulated to be due to the formation of a large, thin-walled iron oxide cenosphere frequently obtained in the product. Jorgensen proposed that cenospheres formed due to the freezing of a low-temperature skin, and particle expansion was the result of gaseous products from the residual sulfur being generated beneath this skin. The limitations seen to the particle temperature were thought to be the result of FeO or Fe vaporization at high temperature.[2.3~ Jorgensen also suggested from a simple modeling study of iron sulfide combustiont2.41 that despite thermodynamic considerations, sulfur monoxide rather than sulfur dioxide was the major reaction product. The present study investigated the effect of oxygen concentration in the atmosphere on the temperature of pyrite combustion and the reaction phenomena occurring. The much higher data sampling rate of the pyrometer and data acquisition system used in this study gave greater resolution than the results previously reported, such that changes in temperature of the individual particles during combustion could be determined.
II.
EXPERIMENTAL
The effect o
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