INJECTION PHENOMENA AND HEAT TRANSFER IN COPPER CONVERTERS by ALEJANDRO ...

298 Pages·2010·10.19 MB·English

INJECTION PHENOMENA AND HEAT TRANSFER IN
COPPER CONVERTERS
by
ALEJANDRO ALBERTO BUSTOS
Mining Eng., Universidad de Chile, 1972
M.Sc, Universidad de Chile, 1975
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
in
THE FACULTY OF GRADUATE STUDIES
(Department of Metallurgical Engineering)
We accept this thesis as conforming
to the_j^-quired standard
THE UNIVERSITY OF BRITISH COLUMBIA
December 1984
0 Alejandro Alberto Bustos, 1984
In presenting this thesis in partial fulfilment of the
requirements for an advanced degree at the University
of British Columbia, I agree that the Library shall make
it freely available for reference and study. I further
agree that permission for extensive copying of this thesis
for scholarly purposes may be granted by the head of my
department or by his or her representatives. It is
understood that copying or publication of this thesis
for financial gain shall not be allowed without my written
permission.
Department of Metallurgical Engineering
The University of British Columbia
1956 Main Mall
Vancouver, Canada
V6T 1Y3
Date February 18, 1985
ii
ABSTRACT
The injection dynamics and related accretion build up,
as well as bath motion and heat losses in copper converters,
have been investigated. The studies involved physical and
mathematical models coupled with plant trials at four copper
smelters to examine gas discharge phenomena, bath slopping
and heat transfer within the converter.
th
The laboratory work, performed on a 1|4 scale model
of a converter, indicated significant tuyere interaction. Air
discontinuously discharges into the bath with a frequency
which increases with gas flow rate and is affected by the
bath circulation velocity in the tuyere region. Measurements
have delineated slopping behaviour in terms of tuyere sub
mergence and the buoyancy power input to the bath.
The industrial trials were conducted in Peirce-Smith,
Hoboken and Inspiration converters under normal conditions.
A tuyerescope attached to the back of a tuyere permitted the
direct observation of accretion growth and the sampling of
accretions during blowing. The tests indicated that the copper
converter operates under bubbling conditions. Pressure pulses
from the tuyeres revealed that in non-ferrous submerged in
jection processes three regimes of gas-liquid interaction can
be identified: bubbling, unstable envelope and channelling.
i ii
The relative dominance of each regime is affected by tuyere
line erosion, viscosity of the bath and tuyere submergence.
Analysis of the accretion samples revealed that accretions
in the copper converter form mainly by the solidification of
bath at the tuyere tip. Oxygen enriched air does not prevent
accretion formation, but seems to produce a softer, easy-to-
punch accretion. The type of puncher as well as punching
frequency affect conditions inside the tuyere pipe and this
could have an influence on accretion formation.
The mathematical heat transfer model indicated that
when the converter is out of the stack, heat losses through
the mouth of the converter cause the internal surface to
cool rapidly which may lead to freezing at the tuyere line
and tuyere blockage when blowing is resumed. The temperature
gradient, localized to within 60-80 mm of the refractory
inside wall, changes markedly within the first minutes of
the converter being out of stack. This may generate thermal
stresses in the converter wall and contribute to refractory
erosion at the tuyere line. Covering the converter mouth
during out-of-stack periods significantly reduces the change
in temperature gradient at the inside wall as well as heat
losses from the converter.
iv
TABLE OF CONTENTS
Page
ii
ABSTRACT
TABLE OF CONTENTS iv
LIST OF TABLES viii
LIST OF FIGURES x
TABLE OF NOMENCLATURE xvii
ACKNOWLEDGEMENTS xx
CHAPTER I
INTRODUCTION: THE COPPER CONVERTING PROCESS 1
1.1 History of Copper Converting 2
1.2 Current Converting Practice 5
1.3 Problems in Copper Converting 9
CHAPTER II
LITERATURE REVIEW: STUDIES IN GAS INJECTION 13
2.1 Studies in Side-Blown Injection 14
2.2 Bubble Formation During Submerged
Injection 20
2.2.1 Bubble Formation in Low-Density,
Inviscid Liquids 22
2.2.2 Bubble Formation in Liquid Metals 28
2.3 Pressure Fluctuations at the Tuyere .... 33
2.4 The Bubbling-Jetting Transition 44
2.5 Accretion Formation and Tuyere Blockage . 47
2.6 Bath Surface Movement. Splashing
and Slopping 53
2.7 Summary 63
V
CHAPTER III
OBJECTIVES 66
CHAPTER IV
EXPERIMENTAL TECHNIQUES 69
4.1 Laboratory Experimental Work 69
4.1.1 The isothermal Model ^
4.1.2 Experimental Apparatus 77
4.1.2.1 Converter-Shaped Vessel 79
4.1.2.2 Tuyeres 82
4.1.2.3 Gas-Delivery System 85
4.1.2.4 Pressure Measurements 86
4.1.2.5 High-Speed Cinematography 86
4.1.3 Conditions for the Tests and
General Procedure 88
4.2 Industrial Work 91
4.2.1 Smelters Selected for the Tests 92
4.2.2 Scope of the Industrial Tests 96
4.2.3 Equipment and Procedure 97
CHAPTER V
EXPERIMENTAL RESULTS 103
5.1 Laboratory Results 103
5.1.1 Dynamic Pressure Measurements 103
5.1.1.1 Effect of the Air Flow Rate 104
5.1.1.2 Effect of Tuyere Spacing 110
5.1.1.3 Tuyere Interaction 113
5.1.1.4 Effect of Tuyere Submergence 115
5.1.2 High-Speed Cinematography 117
5.1.2.1 Observations at the Tuyere Line 117
5.1.2.2 Slopping Observations 120
5.1.3 Slopping Measurements 121
vi
5.2 Industrial Results 128
5.2.1 Dynamic Pressure in the Tuyeres 128
5.2.1.1 Effect of the State of the Refractory
at the Tuyere Region 129
5.2.1.2 Effect of the Tuyere Submergence 132
5.2.1.3 Effect of Tuyere Blockage 132
5.2.2 Accretion Growth at the Tuyere Tip 136
5.2.2.1 Dynamics of Accretion Growth 136
5.2.2.2 Effect of Oxygen Enrichment of
the Blast 138
5.2.2.3 Analysis of Accretion Samples 142
5.2.2.4 Influence of the 4B5 Punching System 144
5.2.2.5 Tuyere Pipes. Metallographic Work 148
5.2.3 Bath Surface Movement and Splashing 151
CHAPTER VI
HEAT LOSSES FROM COPPER CONVERTERS.
A MATHEMATICAL MODEL 154
6.1 Scope of the Heat Transfer Model 154
6.2 The Mathematical Model 155
6.2.1 Radiation Heat Transfer in
Copper Converters 158
6.2.2 Transient Conduction in the
Elements in the Model 162
6.2.3 Computer Program 166
6.2.4 Range of Variables Studied in the Model 168
6.3 Accuracy of the Heat Transfer Model 169
6.4 Influence of the Refractory Emissivity 171
6.5 Model Predictions 175
6.5.1 Effect of the Converter Mouth Position 175
6.5.2 Thermally Active Zone in the Refractory .... 179
6.5.3 Effect of the Converter Diameter 182
6.5.4 Effect of the Area of the Converter Mouth .. 184
6.5.5 Influence of the Coverage of the Mouth 187
vii
CHAPTER VII
DISCUSSION 195
7.1 Injection Dynamics at the Tuyere Tip 195
7.2 Bath Movement and Slopping 209
7.3 Accretion Formation and Tuyere Blockage 213
7.4 Heat Losses from the Converter 218
CHAPTER VIII
SUMMARY AND CONCLUSIONS 221
8.1 Summary 221
8.2 Suggestions for further Work 225
REFERENCES 228
APPENDIX I THE PLATE ORIFICE 240
APPENDIX II PRESSURE TRACES FOR DIFFERENT CHARGES
OF THE COPPER CONVERTER 251
APPENDIX II RADIATION SHAPE FACTORS IN THE
HEAT TRANSFER MODEL 253
APPENDIX IV THERMAL CONDUCTANCES FOR THE DIFFERENT
NODES IN THE MODEL 257
APPENDIX V HEAT TRANSFER COEFFICIENT FOR THE
EXTERNAL SURFACE OF THE CONVERTER 261
APPENDIX VI TEMPERATURE PROFILES IN THE CONVERTER
WALL WITH VARIABLE THERMAL CONDUCTIVITY.. 267
APPENDIX VII HEAT TRANSFER MODEL PROGRAM 269
viii
LIST OF TABLES
Table 4.1 Physical Properties of Some Fluids 72
Table 4.1 Details of Copper Converter Practice
in North America 80
Table 4.3 Characteristics of the Average 13 x 30
Converter and Three Other Plants 81
Table 4.4 Scaled-Down Characteristics for
Different Models 89
Table 4.5 Range of Variables 90
Table 4.6 Conditions for the Industrial Trials 95
Table 6.1 Parameters in the Heat Transfer Model 170
Table 1.1 Characteristic Dimensions of Orifice
and Comparison with Recommended
Design Variables 241
Table 1.2 Values for Use in Equation (1.2) to
Obtain Discharge Coefficients for
2-inch Plate Orifices 245
Table 1.3 Calibration of the Plate Orifice with
a Diameter Ratio of 0.4 246
Table 1.4 Calibration of the Plate Orifice with
a Diameter Ratio of 0.6 247
ix
Table V.l Properties of Dry Air at
Atmospheric Pressure 264
Table V.2 Heat Transfer Coefficient for
Different Converter Diameters 265
Table V.3 Heat Losses by Convection and Radiation
as Compared with Conductive Heat Flow
Inside the Wall 266