Current Distributions and Metal Flow in an Electric Arc Furnace

151 Pages·2016·23.37 MB·English

J'N At!
T:.LECJ'lUG ARC FUIU'-L\G}~
CURRENT DISTHIBU'fiON AND H.E'I'AL
FLO'I'! IN AN EL.F.C'rfliC ARC F'URNACE
by
l'J:J..,TON HARLBOHOUGH HUNR OE, B.A. Sc.
A Thesis
.Submitted tCJ the Fac•J.l ty of Grad:t~:l:~ Studisf3
iu FarLL~;l Jl'ulfj.lnont: of th\c K\qu:Lr.:•m:;;u·~I:J
for tlte D~gTe·a
Hcl~'later TJni verai ty
March 1972
!-lASTER OF' ENGINEERING (1972) gcMASTER UNIVERSITY
(Electrical lligineerillg) Onta:.:-io
Hamilton~
TITI,E: Current Distribution and Metal i.''l.. ow in an Electric Arc
Furnace
AUTilOR: Hilton l·a rlborough Hunroe, B.A.Sc. (Univ~~rsity o! Toron.t.o)
SUP:E:RVISOR: Dr. R.T.H. Alden
NU:mEH OF PAGES: 139 , X
SCOPE tlND CONTENTS:
Current Distribution and Metal Flow in the crucible of an
Electric Arc Furnace is investigated using a small-scale, three
dimensional model. Results obtained indicate that current
distribution for furMces of different sizes and ratings may be
predicted using one model. Naturally occurring metal flow is shown
to be related to phase rotation of the supply voltage. A two-phase,
four-electrode design is proposed as an alternati'Ce to the present
three-phase, three-electrode design.
(ii)
.· ..... ~ ;,
ACKNO\VLEWEHENTS
I would l ike to express IllY sincere thanks to Dr . R.T.H ..
Alden fer suggesting and supervising the topic.
I am also grateful to Dr. D.A.R. Kay and Hr. H. Ghosh of
the ~~etalhu·gy Department for the ma.ny di<;;cussions on the
metallurgical aspects of the subjact.
'lne assistance and. helpful suggest.i.ons giv n by Mr. B1ytho
viil.li 03'\IS and i".he at::~.ff of the Electrical Ene,inBnrin3 1-Jor.ks l''IJ :i.n t!10
construction of ~,he apparatus for this pl·ojcct is gratefvJ.ly
( :Ht)
TABLE o:F' CONTENTS
Pi\.CTJ:;
Descriptive Note :i.i
Acknowledt;ements i ii
CHAP'l'l!~ 1 THE ELECTRIC ARC FURNACE 1
1.1 INTIWDUCTION 1
1.2 IIIS'rORY AND DEV:E:LOP ENT OF 3
'!"HE ELEG'l'RIC ARC FURNACE
1.3 OVE.R4.TION AND CONTI?.OL OF 6
l'[E ELECTRIC ARC FUREACE
1.4 A.IH AND SCOPE OF THF..SIS
CI~A.Fi'ER 2 DEVr~OP ·1EN'r OF MODEL 17
2.1 CHOICE O.F MODEL 17
2.2 SCAJ,ING 18
2.2.1 DIHE;NSI ON SC,\LING IN HODEL 18
19
2.2~?:
2.2.3 THERI-l.AL SC.A..LU~G 21
2.3 D:S.SIUN CONS'r:iWCTIO;\; AND 23
9
OPERA~I'ION 0~~ MODEL
2.3.1 DESIGN 23
CONi:.WRUC'I'ION 25
CHAPI'B~R 3 CURRF:N'l' DIS1'HIBU7:ION 11-l
3.1 41
3.2 CURR:Sl4:P. Jli.STfC:J}U'J:'lO;·J IN 'l'Hl:EE 43
PITA.Sl<~ l,!ODEl,
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PAGE
3.3 CURRSNT DISTRIBUTION IN 'l'HE 51
!''IJO-PHASE MODEL
3.4 DIS·rRIBiJ'l'ION IN THE FURNACE 57
3 .. 5 H:tiliTING EFF'F~TS ?1
CHAPTER 4 .fl,UID MOTION 76
4.1 INHEID1'lT MOT! ON IN FURNACES 76
4.2 MOl'ION IN THE THREE-PHASE MODEL 77
4.3 HOTION IN TlvO-PHASE MODEL 79
4.4 EFFECT OF VANES ON HOTION 83
4.5 ELECTROKINETIC EFFECTS 85
CHAPTER 5 DISCUSSION AND CONCLUSIONS 93
5.1 DISCUSSION 93
5.1.1 THE AIM 93
5.1.2 CUHRENT DIS'l'RIBUTION 94
5.1.3 MOTION 99
5.1.4 TWO-PHASE SYSTEM 101
5.2 FUTURE WORK 103
5.3 CONCLUSIONS 104
APPENDIX A RELATION OF CURRENT DISTRIBUTION TO lo6
INPUT CURRENT
APPENDIX B THEORY OF ELECTROKINETIC EFFECTS ll4
APPENDIX C RECORD OF CURR~~T DENSITY MEASUREMENTS ll9
(v)
PAGE
GLOSSAHY OF f.'l.AIN TERMS 136
REFEHENCES 138
(vi)
LIST OF FIGURES
PAGE
Fig. 1.1 Early Designs of the Electric Arc Furnace 5
1.2 Electrical Supply Syst.em of a.n Electrical 8
Arc Furnace
1.3 Power Characteristics of a 150-ton Electric 10
Arc Furnace
1.4 Construction of the Threc-Fnase HeSoult 13
Electric Arc Furnace
:ne. 2.1 DieJDeter of Fura<.:tce Modelled in Rcla.tion to 24
Frequency
2.2 Dimcusiom~ of Hodel and Ring 29
2.3 Pro e Arm, with Holder and Probe 32
2.4 Po\ver Supplies for Hodel 35
2.5 Model Assembl ed i n a Fume Chn.ruber 37
2.6 App<u·atue for Cleaning and Sto:cage of 39
Hercury
Plan of Hodel Shm·ling SJ>sf~em of lr2
l1aa~urement o9f r~ e and ,5
Cur-re~'lt Distribution i n Tr...ree~Phasc Hodel 44
at 60 hz
Current Distribution in Three-Phase Hodel
at b,.QO hz
..
:7;- 4 Cun·cnt Density Profil es in Ttn:·ec·,Phase 46
Hockl at 60 hz.
3 .:;c>: CtaTent D3nsi ty Profil ea in T!1reer•Phar;e 48
Model at l+OO hz
3.6 Cu ...·. re:lt StroaMli r::s at 60 hz ill 1'hree~PhF-:c-:::
Ho::1el
C:.trrent Stroaml:i.m~n i n Three·~.c :..,ace '~lodel ac 50
lJ.QO hz
( vi:i.)
PAGE
Fig. 3.8 Electrode Configurat i ons in Two-Phase 52
Hodel
3.9 Cu:t·rent Distri'btlti on in 'ltro-Phase 1-iodel. 53
Electrodes of Same Phase Adjacent (400 hz)
3.10 Current Distribution in T'.to-Phase f.iode1. 5L~
Electrodes of Same Phase 0 posite (400 hz)
3.11 Current Density Profiles i n Two-Phase ioiodel. 55
Electrodes of Same Phase Adjacent (/+00 hz)
3.12 Cur rent Density Profi l es i n Two-Phase Model. 56
Electrodes of Same Phase Op~osite (400 hz)
3.13 Current St reaml ines in T\-ro-Pha.se Hodel . 58
Electrodes o: Same Pl1.ase P.djacenc ( 1;')0 hz,)
3.14 Current Streamlines i n 'I\:o-P'nase Hodel .. 59
Elect rodes of Same Phase Opposite ( !iOO hz)
3.15 Relationship Between Furnace Si ze and 62
Transform8r Rating
3.16 Correlati on Bet..-Jeen Furnace 'l'raneforn1er Rat ine 63
and Maximum Elect rode Current
c
3.1'1 Current Scal ing F-ctor , 6!1.
1
3.18 Gra.ph of IJ i vs I 66
3.19 Graph of l og I J I l og f 67
Vf]
3.20 Variation of Normalt zed VaJues of IJI with 69
Depth (i+OO and 1000 , z)
3.21 Heasured and Predicted Val ues cf Phsse at 70
400 c nd 1000 z
3.22 Current Path Boloi'J Hercury Surface in 'l"llree 72
Elect rode Mac.~].
Natural Flm:~ Pu.ttern i n 'I'h:r.ee-l'naue }iodel 78
(Phase Sequence A-B-C)
4.2 n~.tw:-al Flo1t Patter!l i n ri\c:o~J?hase l.odel. 81
E:iectrodes of Samo Phase Adjacent (Phase
Sequence A-D~JJ-C)
(viii)
PAGE
I'ig. 4.3 Natural Flow Pattern in Two-Phase Model. 82
1lectrodes of Same l~ase Opposite (Phase
Sequence A-B--n.-C)
4 ·"''~ Effect of Vanes on Flo~ Pattern (Phase 84
Sequence A-B-C)
4"5 Electrocapillary Action Using Alternating 87
Current
4.6 Electrocapillary Action Using Direct 90
Cv.rrent
4.7 Stages in Development of Electrocapillary 91
Action on Direct Current
Fi.g. 5.1 Forces on Surface under Foot of Arc 95
5.2 Features of a Typical Electroslag 98
Remelting Furnace
Fig. Al The Model as a Cylinder of Infinite Length 107
Fig. Bl The Electrocapillary Curve 115
B2 Production of Surface Oscillations by 11?
Alternating Current
B3 Hcvement of Mercury Sur face by 118
Electrocapillary Action, Using Direct
Current
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