The Use of Oxygen to Decrease Electrical Energy Usage in the Electric Arc Furnace

116 Pages·1999·4.84 MB·English

The Use of Oxygen to Decrease Electrical Energy Usage
in the Electric Arc Furnace
Nicholas George Kournetas
A thesis submitted in confomrty with the requirements for the degree of
Master of Applied Science
Graduate Deparbnent of the Facuity of Applied Science and Engineering
University of Toronto
@ Copyright by Nicholas George Koumetas, 1998
National Library Bibliothèque.n ationale
du Canada
Acquisiions and Acquisitions et
Bibliograph ic Services services bibliographiques
395 Wellington Street 395, nie Welngton
OîîawaûN K1AON4 OttawaON K l A W
Canada canada
The author has granted a non- Lfa uteur a accordé une licence non
exclusive licence dowing the exclusive permettant à la
National Library of Canada to Bibliotheque nationale du Canada de
reproduce, loan, distribute or sell reproduire, prêter, distribuer ou
copies of this thesis in microform, vendre des copies de cette thèse sous
paper or electronic formats. la forme de microfiche/fiim, de
reproduction sur papier ou sur format
électronique.
The author retains ownership of the L'auteur conserve la propriété du
copyright in this thesis. Neither the droit d'auteur qui protège cette thèse.
thesis nor substantial extracts fkom it Ni la thèse ni des extraits substantiels
may be printed or otherwise de celle-ci ne doivent être imprimés
reproduced without the author's ou autrement reproduits sans son
permission. autorisation.
The Use of Oxygen to ûecrease Elacal Energy Usage
in the Elecfnk Arc Furnaœ
Nicholas George Koumetas
Master of Applied Science and Engineering. 1998
Graduate Deparbrient of the Facuity of Applied Science and Engineering
University of Toronto
Abstract
The increased intensity of the Electnc Arc Fumace (EAF) steelrnaking process
has resulted in corresponding increases in energy losses. The reduction of
chernical energy losses, by the injection of targeted oxygen. has the potential to
become an enomous advantage in today's highly cornpetitive steel industry. A
variety of methods have been used for the addition of this supplemental oxygen.
including auxiliary lances, oxygen injectors and existing side wall bumen.
In this study the ratio of natural gas to oxygen, flowing through the existing side
wall burnerç, was modmed in order to increase the arnount of free oxygen flow to
the EAF ai Co-Steel Lasco. Decreases of 4.0% with respect to Specific
Electrical Energy Consumption. 42.7% with respect to Specific Natural Gas
Consumption, 5.0% wlh respect to Power on Time, and 4.5% with respect to
Tap to Tap Time were observed.
Acknowledgments
This project would not have corne to fruition without the assistance of certain key
individuals and institutions.
Financial assistance for this project was provided by the Natural Science and
Engineering Research Council of Canada and Goodfellow Technologies Inc.
(GTI).
I would like to thank Co-Steel Lasco for providing me with an industrial size
apparatus on which to conduct my experiments. The technical assistance,
provided by too many to narne, was invaluable.
I also owe a great deal of gratitude to my colleagues at GTI who always gave
generously of their tirne, expertise and equipment.
Financial and technical support was also received frorn my thesis supervisors:
Alex McLean, lain Sommerville and Murray Thomson. I thank them for ahnrays
encouraging me. and for their ability to always see the glass half full.
Finally, but most importantly, I would like to thank my friends, and especialiy my
family. who never let me loose sight of the most important things in life.
iii
Table of Contents
-tract .................................................................. ........................ .... ...-.. ................................................................................ ii
Acknowledgmnts. .................-.. ................................................................. .................................. .......................................ii.i
Table of c o m n... ................................................................................................................................................................. iv
List of Tables. ............................................................................................................................................................................ viii
List of Figure. .......................................................................................................................................................................... ix
List of Appendices. .................................................................................................................................................................. X
II. INTRODUCTION. ...................................................................................... ........l
.
2 THEORY .a...............~....................................................................................5.. ...
2-1 Energy In The Offgas 0.5
.....*u*.*.*.*....*.*.*...-..i..n..........*-..*..........*.-.*n..n*m..**...................-..-..
2.1.1 Sensible Energy In The Offgas .......................................................................................................... 5
2-12 Sources Of Chemicai Energy In The Ongas. .................................................................................... 6
2.1 3 Offgas Volume .................................................................................................................................. -8
.... .........,....... ............ ... .*............. . ..... . .....-...
2.2 Chernical Energy Reactions 8
2.3 StafUs QUO... .. .................. ....... ...........n.....a.H........... ... .. ."....o.-..*.......... *......--. .........9
2.3.1 Chernical Energy Post Combustion ................................................................................................ IO
2.3 -2 Natural Post Combustion ................................................................................................................. 10
..,....,....... .............. .*...................... ....*.... ... ..............-.
2.4 Alternative: Post Corn bustion (PC) .**..*.*.*.* 11
2.4.1 PC in The Slag ............................................................................................................................ I l
2.4.1.1 Mechankms Of Heat Transfer .................................................................................................. 11
2-4-12P roblems ............................................................................................................................... 1 2
2.4.1 -3P ublished Results ..................................................................................................................... 13
2.42 PC In The FE Space. .................................. ..., ............................................................................... 13
2.4.2.1 Mechanisms Of Heat Tramfer ......................................................................................... 1 4
2.422 Strategies Employed ................................................................................................................. 14
2.4.2.3 Problems ................ ... ....... ............................................................................................. 14
..,
2.4.2.4 Published Results ................... .... ............................................................................................... 15
2.5 This Study. .........*...........*.O.....*..............*.....* * ........ ...U.....-*.......-**........*.....n......-..... *...*........... ...-.-.-. l7
3. METHODOLOGY. ......................................................................................... ..19
-. ................. .....-...........................-.
3.1 Outhe Of Cdteel Laso M -**e.*l..t.s.-h..o...p.. . 19
Table of Contents (continued)
-----..
3.2 Electric Arc Fu ..r..nI...a...c.l.e..--- --Y------- 9 1 - . .
........
....n3..3 .Ca.s- in-jepct.io-n .Eq.n.ip.m.en.t . 19
3 3.1 Lanciag System ............................................................................................................................... 20
............................................................................................................................................
33.2 Buniers 20
.....................................................................................................................
3 -32 .1 Burner Operation 20
3.3 2.2 Beak Burner. ............................................................................................................................ 1
3.5 Location Of Offgas Extraction Pro be...... ....,..... n....n........-.m..........W.-..C~. t.Ie....HHHHH21
RESULTS
4.1 CoUected Data ........ ............................ .................................... .......................... ..... .......................... 26
tt
4.1.1 Number Of Heats And Elhination Of Heats ................................................................................. 26
4.1 2 Averaghg And Nomaikation Rocess .................. .. ..................................................................... 27
4.1.3 Statistid Anaiysis .......................................................................................................................... 28
4.1.3.1 Linear Regression .................................................................................................................... 28
4.1.3.2 Two tailed t-test ....................................................................................................................... 28
...................... ... ....................................................................................................
4.2 Gas Injection 29
43.1 Bmer Operation ............................................................................................................................ 29
42.1.1 Bumers ..................................................................................................................................... 30
42.1.2 Burner Ratio .......................................................... ................................................... 31
4.22 Lancing .................................... .,., ..................................................................................................... 32
42.3 Free Oxygen Flow ............................................................................................................................ 33
................................................. ..........-.... ...... ......... ......
43 Offgas Analysis .......t.......................o.............. 35
4.3.1 CO Gas Profile ................................................................................................................................. 36
4.3 2 CO, Gas Profile ........ .............. , ................................................................................................. -37
4.3.3 O2 Gas Profile .................................................................................................................................3. 9
4.3.4 H, Gas ProfiIe .................................................................................................................................. 39
4.3.5 Total Carbon Containhg Gases Profile ...........................................................................................4 0
4.3.6 Post Combustion Ratio (PCR). ...................................................................................................... 41
4.3.7 N, Gas Profile ................................................................................................................................ 42
.. .............
4.4 Periodic Sam ples ........ ...........U1u...n..-......n.nU...H.......-...U.n............H.............-...4~3 ...U....H-.
4.4.1 Bath Temperature Measurements .................................................................................................... 44
Table of Contents (continued)
...................................... .................
4.4.1.1 3: 1 Bmer Ratio 45
4-4-128 : 1 Burner Ratio ...................................................................................................................... 46
.................................................................................................................
44-13S tatisticd AnaIysis 46
4-42 Bath Chemistry Measurements ........................................................................................................ 47
4.42.1 3:l Bunier Ratio ............................................................................................................ ,.. ....... 48
4.4.2.2 8: 1 Burner Ratio ....................................................................................................................... 49
4.423 Statisticai Analysis ................................................................................................................... 49
4.4.3 Slag halysis ................................................................................................................................... 50
4.43.1 X-Ray Fluorescence Spectrometry Analysis (XRFS) ............................................................ 5 1
4.43.2 Powder X-Ray DitTiaction Analysis (PXRD) .......................................................................... 52
4.5 Operat ing Da ta ..... ........-.............U.U...-.n-.UU..-...-.n.-.......-.......5.2.. .
4.5.1 Gas Consumption ............................................................................................................................. 52
4.52 Tord Harmonic Distortion (THD).. ................................................................................................. 54
4.5.3 Electrode Consumption. ................................................................................................................... 55
4.5.4 Yield. ................................................................................................................................................ 56
4.5.5 Electrical Energy Consumption ....................................................................................................... 57
4.5.6 Power On Time And Tap To Tap The. .......................................................................................... 58
4.6 Observations .................. ...........-.... ...-. ..-. ... ".. ............. ..........-......-.-..n...-......H............o.w......5..9. .....
5 .D ISCUSSION ................................................................................................6..0
..................................................... ..........................................................................................
5.1 Ceneml -60
5.1.1 Gas Injection .................................. ., ............................................................................................ 61
................................................................................................................................
5.1 2 Offgas Analysis 62
5.1.3 Periodic Sampling ............................................................................................................................ 63
5.1 -4 Operating Data ................................................................................................................................ -64
...................................,.,..................,............... ....... ........... ......................
5.2 Cornparison Of ResuIts 66
.........................................................................................
53 Factors Contributing To Achieved Savings 66
5.3.1 lncrease In Scrap Hydrocarbons ...................................................................................................... 67
5.3.2 More Uniform Distribution Of Fuel And Oxygen Throughout Charge ........................................... 68
5.3.3 Reduced Air Inleakage. .......................................................................................... 70
5.3.4 Earlier Achievernent Of Flar Bath Conditions ................................................................................. 71
.
6 CONCLUSION ...............................................................................................7. 3
.........,... - ......
6.1 Cost And Energy Savings Were Achieved .........-...................-......o.................oH........ 73
6.2 Post Combustion Ratio Calcuhtions Can Be Misleading 74
..~.....~..~~.....~*~..wUo..~-..HHHHH.H..........W...H ...
........................ ...... ". ...................
6.3 Importance Of Targeted Olrygen Addition ...WWI...W...............U-. 74
Table of Contents (continued)
6-4 The ~ddition'oOf xygen Sboald Be Considemi In Conjiinrtion Wi The Addition Of F a c i 7 5
63S crap Chemistry Variations Have Significant Rarnifi~ti0ns,,-,-.---.~.~~~~~~~-.~~~~75
6.6 Offgas Anaiysis May Be Used To Characâerize Swap I-----HIII.-.UHI...--.u... 75
...................
7. FUTURE WORK m.........m....m.o..~....œ.~.œ............m.......-................œmm.m.m77
7.1 Increased Oxygen .--..,-----*-*-n---.n---.--n--.--.-...-n----------*"-*..-*-.77
-,,,,--.-...-------..-.-.
7.2 Hydrocarbon Combustion At The Burners Versus In The Scmp 77
73 Flow And Temperature Measurements -n.--...-----c-.n..Hlt..-....-.H-.HI.----.-.--.--U.....U-.7-8.- -.-.
7.4 Furttier Slag Aaalysis ....,,.~~+,..........-.U-~~t.UUI.~-M.-..-W..7.....+....8.
..... -,. ., .......,---.. ......++.
7.5 Scrap Characterization , tt..~..-..H---.-......... 7 9
REFERENCES ...œ..~.............o........m.....m.....m........mmm...........~...m0..m...m....œ..~.-mm.mm...~.8..1.
vii
List of Tables
Table 2.4. Sumrnary of Post Combustion trial resub fmm BSW using ALARCPCn"
-
Pstc mhstion technology .-*-..-..-.-----..-.------....-- -.------.-------------.--.--------..----. -- -.---.--.-.1-.7 .-
**** -.- * *-*-* ** *----- *
Table 4.1, Statistical Analysis results for Temperature vs. kWh into heat data..---..--47
Table 4.5, Average gas consumption. on a per ton basis, for both Bumer Trials...--54
Table 4.7, Power on and Tap to Tap time results for both bumer ratio trials ..-.-.-.-..5-.9.
Table 6.1. Summary of savings realized by CoSteel Lasw during this study ...-.---7.-3.
viii
List of Figures
Figure 2.1, Typical EAF offgas profile, showhg the metldown and refining perîods of the
heat. .....................~...~.~.......~...~.~-.........,,........... 6
Figure 4.1. Nonnalkeâ bumer profile at a 3:1 Bumer Ratio. ...................... ...... .....-3 0
Figure 4.2, Nomiaked bumer profile at a 8:l Bumer Ratio. ...................-...--.--3.-1- ----.
Figure 4.3, Nonnalized burner ratio profiles for both bumer ratio trials. ... .. . .. . .. -.. . . . . . 32
Figure 4.4, Nomalized oxygen lance profile for both bumer raüo trials. .................. 33
Figure 4.5, Nomalized free oxygen flow for both bumer ratio trials. ........................ 34
Figure 4.6, Normalized offgas profile for the 3:1 bumer ratio trial. ........................... 35
Figure 4.7, Nomalized ornas profile for the 8:1 bumer ratio trial. ....... .................... 36
Figure 4.8. Normalized CO offgas conœntration profile for both bumer ratio trials.. 37
Figure 4.9, Nonnalked CO2 offgas concentration profile for both bumer ratio trials.38
Figure 4.10, Normalked 02 offgas concentration profile for both burner ratio trials. 39
Figure 4.1 1, Nomalized H2 offgas concentration profile for both burner ratio trials. 40
Figure 4.1 2, Norrnal~edto tal carbon containing ornas concentration profile for both
. .
bumer rat10t nals .................~~~~..~~~~~.~..~..~.~..~.~~~~..4.1.~ ~....~..................................
Figure 4.1 3, Normalued Post Combustion Ratio (PCR) profile for both bumer ratio
trials. .. .. . .. .,. .. .. . . . . .. ... .. ... .. . .. ... ., ,,......-........... ................................ . . .. . .. . .. .. . . . . ... .. - 42
Figure 4.14, Nomalized Nq offgas concentration profile for both bumer ratio trials. 43
Figure 4.1 5, Temperature vs. kWh into heat measurements for 3:1 bumer ratio trials,
including line of best fit. ......................... ........ .. .................................. 45
Figure 4.16, Temperature vs. kWh into heat measurements for 8:l burner ratio trials.
including Iine of best fit. ......................... ........ .. ................................ 46
Figure 4.1 7, Dissolved carbon concentration vs. kWh into heat measurements for 3:l
bumer ratio trial, including line of best fit ..... .... .. . ... ...........-... ... .. . . . . . - -. ..- 4 8
Figure 4.1 8, Dissolved carbon concentration vs. kWh into heat measurements for 8:1
burner ratio trial, including line of best fit ................................................... 49
Figure 4.19, Nomialized THD profile for both bumer ratios. .....................................5 5
Figure 4.20, Monthly Eledrode Consumption figures, including month of June, 1997
when bumer ratio trials were conducted. ..................................................... 56
Figure 4.21, Monthly yield figures, including month of June, 1997 when bumer ratio
trials were conducted. ............~............................................... ........... 57