ironmaking/steelmaking routes, from the conventional blast furnace (BF)/BOF and
... Alternative Iron Sources (AISs)/steelmaking routes such as the FASTMET ...
FUTURE GREEN STEELMAKING TECHNOLOGIES Sara Hornby Anderson, Gary E. Metius, Jim M. McClelland Midrex Technologies Inc. 2725 Water Ridge Parkway, Suite 200 Charlotte, NC 28217 Fax: 704 373 1611
[email protected] tel: 704 378 3316
[email protected] tel: 704 378 3334
[email protected] tel: 704 378 3359 Key Words: Greenhouse Gases, Carbon Emissions, CO2 Emissions, Energy, BOF, EAF, EIF™, Alternative Iron Units, Hot Metal, DRI, HBI, Pig Iron, MIDREX®, FASTMET®, FASTMELT®, FASTIRON®, FASTEEL™, FASTOx®, ITmk3®, Mesabi Nuggets, Pig Pellets, COREX®, HIsmelt® ABSTRACT Use of the new direct reduction processes, natural gas-based or coal-based, will improve greenhouse gas emissions and lower steelmaking energy requirements while allowing steelmakers to meet end product quality requirements. Using steel mill wastes as feedstock will assist steelmakers to achieve zero waste status. This paper compares carbon dioxide (CO2)/carbon (C) emissions and energy requirements for various ironmaking/steelmaking routes, from the conventional blast furnace (BF)/BOF and MIDREX® Direct Reduction Process direct reduced iron (DRI)/hot briquetted iron (HBI)/EAF routes to the new innovative Alternative Iron Sources (AISs)/steelmaking routes such as the FASTMET Process, the ITmk3 process, FASTEEL, FASTOx, COREX and HIsmelt. Definitions of the process technologies considered herein can be found elsewhere in these proceedings in the paper titled “Influence of AIS Chemistry on EAF Steelmaking.” 1 INTRODUCTION The issue of greenhouse gases emissions is of growing world importance, mandating greenfield primary metals production facilities incorporate technologies with lower greenhouse gas generation potential. Brownfield steelmills, striving to improve their worldwide competitiveness, are adopting technologies to lower costs and improve efficiencies, while maintaining or improving product quality. In the electric arc furnace (EAF) sector, some of these technologies involve the increased use of chemical energy to reduce electrical energy requirements and to increase productivity, and alternative iron units (AIUs) to achieve high steel quality. The EAF sector is reviewing emerging AIU technologies, which will assist them in
achieving better cost competitiveness, production efficiency, and “zero waste” strategies, even without the need for higher steel quality. Although efficient operation of metals production facilities should decrease the generation of greenhouse gases, significant further emissions reduction requires a better understanding of how and where the greenhouse gases originate and what the impact of the new technologies and changing charge materials will be. In order to identify the options available for achieving a measurable reduction in CO2 emissions, it is necessary to assemble an overview of the typical levels of CO2 emissions generated in the various stages of steel production. Specifically, this paper provides an evaluation of CO2 emissions and energy consumption in steel production, from the receipt of basic raw materials to the tapping of a ladle of liquid steel. The production routes considered herein focus primarily on various AIS/EAF options and compare them to the conventional BF/BOF operations. The methodology used to analyze the alternative production routes is as follows. The BF/BOF route uses published data for energy inputs and outputs throughout the steelmaking operation and compares data both computed by the authors and presented in DOE report no. EE-0229 2,3,4,5. For the EAF route, an in-house EAF melt program has been used to predict, from first principles that we have fine tuned using practical experience, major operating parameters (for example, electrical, flux, oxygen, yield, thermal efficiency of melting, and levels of sulfur (S) and phosphorus (P) – Table I) given the input AIU composition, percentage charged, EAF slag “V” ratio, final carbon level in the steel, and the desired tap temperature. (It should be noted that productivity changes are partially reflected in the thermal coefficient of melting, but not fully). For each charge scenario, except the FASTMELT, FASTEEL, FASTOx, ITmk3, HIsmelt , COREX, and high (4%) C DRI scenarios, the practices reflect actual industrial data 6,7,8,9,10. In the case of FASTMET, FASTMELT, FASTEEL, ITmk3, and 4%C DRI, two internal mass balance design programs have been used, one for FASTMET, FASTEEL, FASTMELT, FASTOx, and ITmk3, which incorporates the Kakogawa FASTMET Demonstration Plant results 11,12,13, and one for gas-based DRI/HBI, which combines current operating data 6 with prior results for 3.5%C DRI 14 and extrapolates to 4%C DRI production. For FASTOx, where FASMELT HM (FASTIRON) is fed to a BOF, the internal FASTMET 11,12,13 analysis has been coupled with BOF published data 2,3,4,5. In all cases, the format used for the process operations’ energy input and output, is shown in Table IIa. The results from each individual process’ energy balance computations are then converted to greenhouse gas emissions using the conversion factors given in Appendix A. The bases for comparing the process routes are indicated in Tables IIb and IVb of this paper. ENERGY USE AND CARBON EMISSIONS Background Conventional technology based on BF/BOF operations has been the backbone of steel production. The preeminence of these high quality steelmaking operations is being challenged by EAF-based mini mills charging varying amounts of AIUs, primarily pig iron and DRI/HBI, with significant quantities of scrap. The need for cost effective, efficient, high quality steel production has led to many advances in EAF operations over the past 30 years. Most of these technologies involve the increasing use of chemical energy, such as C and O2 injection and hot, high energy charge materials, to reduce electrical energy requirements and increase productivity.
The development of new AIUs offers even greater flexibility and competitiveness to EAF steelmakers than was available 10 years ago. These AIUs, including pig iron (PI), DRI, HBI, ITmk3 nuggets (“pig pellets” or PP), and hot metal (HM), are and/or would be used primarily to produce high steel quality. However, expanding upon the benefits of educated DRI/HBI use 1,6,7,8,9,10, the novel raw materials offer potential benefits such as charge make-up flexibility to ensure minimum cost, maximum productivity, and efficiency, while reducing greenhouse emissions over the conventional steelmaking techniques 3,4,5. The potential AIU/scrap combinations are limitless. Those considered herein were chosen to reflect a cross section of proven and future steelmaking operations. Due to the publication constraints, the lengthy nature of tabulating the computations, and prior publication of some of the same 3,4,5, the authors intend only to fully define the energy balance and greenhouse gas emissions data for the BF/BOF production processes 2,3,4,5 and those other production processes not previously considered elsewhere 2,3,4. A complete, detailed, analysis can be found at www.midrex.com. All references to tons herein are equivalent to metric tons (1000kg). Table I. Some EAF Melt Program Specifics for the EAF Charge Combinations Considered Process
Met’c Fe (%)
Total Iron (%)
89% BF HM - BOF 80% FI - BOF 80% Cold DRI 80% Hot DRI 80% Hi C CDRI 80% Hi C HDRI 50% CDRI 50% HBI 20% HBI/ 30% PI 50% PP 50% BF HM 50% FASTIRON 50% FASTEEL 50% COREX 50% HIsmelt 30% CDRI 30% Hi C CDRI 30% Hi C HDRI 30% HBI 10% FMWO/ 20% PI 10% FMWO/ 20% PP 30% CFMO 30% HFMO 30% PP (ITmk3) 30% Pig Iron 30% FASTIRON 30% FASTEEL 30% COREX 30% HIsmelt 100% Scrap
94.48 93.90 86.31 86.34 85.01 85.01 86.34 86.05 86.05 94.51 95.19 94.48 93.90 93.90 93.81 95.56 86.34 85.01 85.01 86.05 68.50 94.51 68.50 95.19 79.90 79.90 95.19 94.51 93.90 93.90 93.81 95.47 94.48
94.48 93.90 91.85 91.85 90.44 90.44 91.85 92.53 92.53 94.51 95.19 94.48 93.90 93.90 93.81 95.56 91.85 90.44 90.44 92.53 76.00 94.51 76.00 95.19 86.80 86.80 95.19 94.51 93.90 93.90 93.81 95.47 94.48
Blend %C in AIU Chge 4.0 4.4 2.5 2.5 4.0 4.0 2.5 1.5 1.5 4.0 3.5 4.0 4.4 4.4 4.6 4.0 2.5 4.0 4.0 1.5 2.5 4.0 2.5 3.5 2.5 2.5 3.5 4.0 4.4 4.4 4.6 4.0 0.04
Carbon Chg Inj (kg/tls)
Ther Melt efficy
Lime (kg/ tls)
O2 (Nm3/ tls) 56.80 59.28 22.27 22.27 38.80 38.80 22.05 19.68 28.59
Melt Power (kWh/ tls) -68.27 -50.83 546.40 407.02 499.50 357.96 527.11 561.77 447.83
Slag Vol (kg/ tls 125.81 154.38 110.52 110.52 110.45 110.45 102.33 102.07 90.69
Overall Yield (t/tls) 0.912 0.904 0.881 0.881 0.871 0.871 0.905 0.908 0.923
0 0 0 0 0 0 2 5 0
0 0 3.5 3.5 3.5 3.5 3.5 3.5 3.5
91.22 91.01 83.84 85.51 84.40 86.10 84.07 83.66 85.02
54.30 68.32 27.90 27.90 27.94 27.94 31.48 31.46 31.05
0 0 0 0 0 0 3 0 0 5 0
3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5
85.49 88.39 88.64 89.32 88.61 88.08 84.22 84.44 85.05 83.98 84.75
26.60 30.79 35.01 35.00 32.96 22.48 33.75 33.79 33.79 33.73 41.73
33.86 38.65 42.84 42.84 43.33 35.02 21.22 21.00 21.00 20.22 26.68
404.58 167.15 146.61 89.83 148.97 192.90 514.50 496.57 445.55 534.96 470.40
72.52 83.33 94.22 94.22 88.93 56.67 96.72 96.64 96.64 96.58 130.70
0.939 0.933 0.928 0.928 0.929 0.945 0.921 0.917 0.917 0.923 0.908
0
3.5
84.65
39.97
24.74
479.35
126.13
0.911
2 2 0 0 0 0 0 0 4
3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5
84.10 84.74 85.08 85.24 87.00 87.98 86.98 86.67 84.44
41.54 41.54 30.78 33.29 35.81 35.81 34.59 28.30 37.03
22.15 22.15 24.74 27.56 30.02 30.02 30.32 25.47 19.09
524.97 471.48 442.94 429.94 283.34 201.97 284.72 310.67 496.67
135.76 135.76 79.01 85.48 91.97 91.97 88.83 69.50 89.23
0.898 0.898 0.942 0.938 0.935 0.935 0.936 0.945 0.945
Table IIa – BF/BOF Energy Data US Data2
Description BF Pellet /t pellet
Sinter /t sinter
BF /t hot metal
BOF /t liq. steel
0.0 0.0 652.2 0.0 976.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1628.5
0.0 1282.4 342.4 0.0 0.0 47.5 0.0 278.2 0.0 0.0 0.0 13.9 0.0 1964.4
0.0 14555.7 243.7 1634.3 1048.9 0.0 133.4 0.0 2863.1 0.0 0.0 111.3 0.0 20590.4
0.0 0.0 255.9 0.0 0.0 8.2 393.4 0.0 0.0 0.0 0.0 365.6 2257.1 3280.1
Energy Output (MJ/t) Coke for sale By-products for sale Metallic products Electrical power for sale Utilities for sale Low Btu Gas for sale Sub-total (b)
0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 2536.0 0.0 0.0 5509.3 8045.3
0.0 0.0 0.0 0.0 0.0 0.0 0.0
Sub-total Energy (a) - (b)
1628.5
1964.4
12545.1
3280.1
Energy Input (MJ/t) Metallurgical coal Metallurgical coke Electrical power Utilities Heavy Oil Low Btu gas O2/N2 Non-coking coal Pulverized coal Steam coal Limestone Natural gas Metallic feed Sub-total (a)
Total Energy (MJ/t) Total Energy (kWh/t) Limestone kg/t tons/t next processing step
16785.0 40.0 1.073
100.0 0.449
32.2 0.890
59.0 1.000
Table IIb – BF/BOF Production Conditions Operation
Sequence Step
BF-BOF
Pelletizing Sinter Blast Furnace BOF
Conditions • Oil-fueled induration, fluxed or acid pellet, 64% total iron • Coal fueled sintering, fluxed sinter, 56% total iron • Coke + coal injection + oil/nat.gas add. + O2 enrichment, 4.0% C, 0.6% Si, 1500oC • 89% HM, 11% Scrap, 0.04% C, 1620oC
Production Processes The following sections briefly describe the production processes chosen. The options considered fall into the following groups: • • • • •
80% AIU HM/20% scrap representative of economical integrated steelmaking practice 80% DRI/20% scrap representative of a captive DRI plant steelmaking practice 50% AIU/50% scrap representative of maximum HM usage in EAF steelmaking 30% AIU/70% scrap representative of the minimum AIU use for high quality steel production including 10% waste oxide AIU usage representing on-site auto-generation 100% scrap representing the EAF baseline
All of these are compared to 89% hot metal/11% scrap use in the BOF representing the BF/BOF baseline from the DOE report no. EE-022920 and from MIDREX computations. The process combinations represent the desire for hot and cold high %C (high chemical energy) charges, as well as cold “low” %C (conventional) charges. Carbon additions (both charge and foamy slag injected) to the EAF reflect current steelmaking practices 6,8,9,10,15, thus allowing the impact of the higher %C AIUs to be felt on the process. Charge C was added to heats to ensure a minimum O2 volume to reflect typical US practice of approximately 20 Nm3/tls. O2 usage has been allowed to “float” relative to the %C contained in each steelmaking system, in order to define the “least cost steelmaking” scenario 1. O2 values varied from 19.0 Nm3/t for 100% scrap to 43.3 Nm3/t for 50% COREX/ 50% scrap scenario. Table I outlines the blended analysis of the EAF feeds and the predicted thermal efficiency of melting, oxygen, and electrical energy required for steel production using a quaternary slag “V” ratio of 1.75. In order to simplify the comparison between various charge mixes, high quality scrap charge mixes were used. It should be noted that with the 80% and 50% AIU mixes, it might be possible to opt for cheaper scrap mixes, which would lower the cost/t liquid steel. Table III. Cost, Yield and Charge Make Up Assumptions for Scrap Charge EAF CHARGE MIX
$/Tonne
%Phos
%Sulf
Yield Est
Heavy #1 Heavy #2 Heavy Prime #1 Bushelling Turnings Shred #1 Bundles #2 Bundles Returns Skulls Municipal Shred Pit Scrap
$88.71 $77.82 $110.59 $113.58 $39.92 $104.21 $119.95 $62.40 $123.00 $64.42 $25.00 $113.00
0.020% 0.030% 0.025% 0.010% 0.030% 0.025% 0.020% 0.030% 0.020% 0.030% 0.030% 0.030%
0.040% 0.070% 0.025% 0.020% 0.080% 0.040% 0.025% 0.090% 0.040% 0.080% 0.090% 0.080%
92.00% 85.00% 95.00% 95.00% 92.00% 92.00% 95.00% 82.00% 98.00% 84.00% 80.00% 70.00%
Scrap Charge Make-Up 20% 50% 70% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 7.00% 19.00% 28.00% 0.00% 0.00% 0.00% 0.00% 6.00% 8.00% 7.00% 19.00% 28.00% 0.00% 0.00% 0.00% 4.00% 4.00% 4.00% 2.00% 2.00% 2.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Note: The scrap yield for the 20%, 50% and 70% scrap charges varied from 94.445% to 94.555%. An average of 94.5% has been used as the global scrap yield for all charge mixes to calculate % gangue.
The combination of processes is not an exhaustive list of possible ironmaking/steelmaking combinations available to the EAF operator, but the typical performance characteristics of each respective option is presented. The scope of processing incorporated into each of the production methods begins with the receipt of feed metallics (iron ore and scrap), reductants (coal, natural gas, etc.), and energy (coal, natural gas and electricity) and ends with the tapping of a ladle of liquid steel (0.04% carbon and 1620°C) prior to any ladle furnace processing. BF/BOF - The blast furnace information included was based on data covering the average of four high volume, high technology (O2/fuel injection) BF operations in the US, reported in Iron & Steelmaker 2. The BF/BOF information is based on an overall integrated energy balance covering coking, pelletizing, sintering, and BOF steelmaking, which was presented at the 2001 COM Conference 3. The BF operations from the US were the basis for specific consumptions in the BF operations area. The energy balance for the BF/BOF operations is shown in Table IIa. The conditions assumed in the BF/BOF operations for comparison with other production methods are indicated in Table IIb. Since the original “green steelmaking” papers 3,4, a comparison between Midrex data and data from DOE publication EE-0229 5 has been performed to define any major difference in computations. There was close agreement between the two sets of data except for the electrical power energy conversion. Midrex data originally assumed 3,413 btu/kWh (net energy value for a kW of electrical power), while the DOE assumption was based on 10,500 btu/kWh (gross heat required to generate a kW of electrical power from coal). The Midrex basis was changed to use 10,500 btu/kWh to be consistent with the DOE assumption. With this change incorporated, the Midrex computations have been used as the basis for all production scenarios for liquid steel considered herein, and the energy balance format (Table IIa) was used. However, due to the volume of data, only the summaries for each computational results for “total energy requirements” for each step and the “tons/ton next processing step” are given in Table IVa. Details of the assumed production conditions for each production route, which allowed comparative analysis, are summarized in Table IVb. Each data source for the production route is defined here below. Full computational results are available at www.midrex.com DEFINITION OF DATA SOURCES FOR PRODUCTION ROUTES Results for “energy requirements per ton” for each step and the “total energy per ton liquid steel”, which factors in the feed ratios, are summarized in Table IVa. Details of the assumed production conditions for each production route, which allowed comparative analysis, are summarized in Table IVb. 80% FASTIRON HM/BOF (configuration known as FASTOx) –The production of FASTIRON, a liquid hot metal product, uses the FASTMET RHF direct reduction technology and close-links the hearth with an EIF (electric ironmaking furnace) to produce hot metal, which is then charged to a conventional BOF. The FASTIRON information is based upon an actual project quotation20. The BOF data was gathered from BOF operating data reported in Iron and Steelmaker and by DOE publication EE-0229 2,5. 80%, 50% and 30% hot or cold nominal C (2.5%) and high C (4%) DRI/EAF - The direct reduction information, using NG-based DRI, was gathered from material presented at the Midrex HBI/DRI Melting Seminar 6 and data provided for the Midrex 2000 Operations Report 7, which gathers direct reduction plants’ operating data. The high C DRI data is based on operational experience of producing 3.5%C DRI 14, which has been extended to cover 4% C DRI production. This data applies equally to all the percentages CDRI and HDRI used, at both the nominal (2.5%C) and high (4%C) carbon levels.
50% and 30% HBI/EAF – The hot briquetting information, using NG-based HBI, was gathered from material presented at the Midrex HBI/DRI Melting Seminar 6 and data provided for the Midrex 2000 Operations Report 7 , which gathers direct reduction plants’ operating data. 20% HBI + 30% PI/EAF – The hot briquetting information was gathered as specified above. The PI information is based on communications by Hornby-Anderson 8,9,15 with a steelmaker using high percentages of pig iron, and the average data taken from four high production, high technology BF operations in the US, reported in Iron & Steelmaker 2. 50% and 30% PP/EAF – The PP (“pig pellets”) refers to a new technology, ITmk3. Ore and coal fines are pelletized or cold briquetted and fed to an RHF, where the pellets/briquettes are reduced, and then proprietary technology is used to separate the gangue from the iron, producing iron nuggets. On discharge from the RHF, the gangue residue is separated from the nuggets, leaving pig iron quality iron nuggets (“pig pellets” [PP]) with a potential 3.0% to 4.0% C content. The ITmk3 information is based on data from the Kobe Steel demonstration plant (KDP) and the scale-up for the Mesabi Nugget demonstration plant in Minnesota 21. 50% BF hot metal/EAF – the BF information is based on data covering the average of four high volume, high technology (O2/fuel injection) BF operations in the US, reported in Iron & Steelmaker 2. The BF/BOF information is based on an overall integrated energy balance covering coking, pelletizing, sintering, and BOF steelmaking, presented at the 2001 COM Conference 3. BF operations from the US are the basis for specific consumptions in the BF operations area. 50% and 30% FASTIRON + 50% and 70% cold scrap/EAF – The production of FASTIRON, a liquid hot metal product, uses the FASTMET RHF direct reduction technology and close-links the hearth with an EIF ( configuration known as FASTMELT) to produce hot metal (FASTIRON) and thereby, reduce the slag compounds going to the EAF. The FASTIRON information is based on an actual project quotation to a European steelmaker20. 50% and 30% FASTIRON + 50% and 70% hot scrap/EAF (configuration known as FASTEEL) – This is a new process merging FASTMELT and CONSTEEL® technologies. The result is an EAF with constant feed of FASTIRON Hot Metal (FI HM) and preheated scrap. The FASTIRON information is based on an actual project quotation to a European steelmaker20. 50% and 30% HIsmelt HM/EAF – The HIsmelt Process reduces iron ore fines with coal and enriched hot air blast to produce HM. The HIsmelt information is based on a published paper by presented by Bates 18. 50% and 30% COREX HM/EAF – The COREX Process produces HM from reduced oxide pellets and/or lump ore and coal in a smelting furnace. The smelting furnace produces excess quantities of fuel rich off-gas, which is used to reduce the iron ore and optionally to produce power. The information is based on a VAI publication 19. 50% and 30% HBI/EAF - The hot briquetting information, using NG-based HBI, was gathered from material presented at the Midrex HBI/DRI Melting Seminar 6 and data provided for the Midrex 2000 Operations Report 7 , whichgathers direct reduction plants’ operating data. 10% Waste Oxide FASTMET + 20% PI/EAF – The FASTMET waste oxide (FM(WO)) information is based on the two commercial FASTMET installations at KSL and Nippon Steel and proposals for FM(WO) recycling projects in the US12,13,16. The PI information is based on the average data taken from four high
production, high technology BF operations in the US reported in Iron and Steelmaker discussions with steelmakers melting PI 8,15.
2
and on private
30% CDRI 30% Hi C CDRI 30% Hi C HDRI 30% HBI 10% FM(WO)/ 20% PI 10% FM(WO)/ 20% PP 30% CFM (O) 30% HFM (O) 30% PP (ITmk3) 30% BF HM 30% FASTIRON 30%FI/H Scrap FASTEEL) 30% COREX
Tot Energy KWh/tl.s
RHF /t DRI/PP
CDRI/HDRI /tDRI
546
3397
911
4624
892 1949 1634 1956 1633 1907
4545 5065 4592 5124 4766 3893 4204 4007 4447 3284 3419
80
2705
529 529 529 529 529 452
1321
2695 2570 2795 2670 2795
529 529
80
2705
1321
1924 1606 1516 1003 980
80
2705
1321
805
3243
987 1046
4217 3856
1735 1716 1600 1817
2901 2891 2734 3163
1631
2970
1645
3174
1787 1687 1541 1520
3092 2926 3294 3000
546
3341 3341
3857
511 452
4744 546
3485
452
5342 5310 529 529 529 529
452
EAF /t l.s.
503
BOF /t l.s.
4663
SF /t HM
911
EIF /t HM
3485
HBI /t HBI
546
CBP /t pellet
452
CBQ /t briq
BF /t HM/PI
50% HBI 20%HBI/30%PI 50% PP 50% BF HM 50% FASTIRON 50%FI/H scrap (FASTEEL) 50% COREX 50% HIsmelt
Sinter /t sinter
89% BF HM MTI 89% BF HM DOE 80%FI-FASTOx 80% Cold DRI 80% Hot DRI 80% Hi C CDRI 80% Hi C HDRI 50% CDRI
DR Pellet /t pellet
Energy for each Process Step & Total Energy per t liquid steel.*
BF Pellet /t pellet
Table IVa. Summary of Energy Data for all Steelmaking Options (kWh/t)
2695 2795 2670 3341 91 91
546
3857
2759 4744 3750 3550 4744
511
91 91 511 452
2759
546
3485
80
2705
1321
1210
2662
80
2705
1321
973
2423
5342
1217
3140
5310
1272 1647
2957 1647
452
30% HIsmelt 100% Scrap * Note: Total Energy per t liquid steel. requires feed ratio information from computational tables.
10% waste oxide FASTMET + 20% PP/EAF – The FASTMET waste oxide (FM(WO)) information is based on the two commercial FASTMET installations at KSL and Nippon Steel and proposals for FM(WO) recycling projects in the US12,13,16. The PP (“pig pellets”) are produced by a new technology, ITmk3. Ore and coal fines are pelletized or cold briquetted and fed to an RHF, where the pellets/briquettes are reduced, and then proprietary technology is used to separate the gangue from the iron, producing iron nuggets. On discharge from the RHF, the gangue residue is separated from the nuggets, leaving pig iron quality iron nuggets (“pig pellets” [PP]) with a potential 3.0% to 4.0% C content. The ITmk3 information is based on data from the Kobe Steel demonstration plant (KDP) and the scale-up for the Mesabi Nugget demonstration plant in Minnesota 21. 30% ore based cold and hot FASTMET/EAF – The ore-based FASTMET (FM(O)) information is based on the two commercial FASTMET installations at KSL and Nippon Steel and FM proposals 13,16. 30% PI/EAF – The pig iron information is based on communication with a steelmaker by Hornby-Anderson using high percentages of pig iron, and the average data taken from four high production, high technology BF operations in the US, reported in Iron & Steelmaker 2. 8,15
100% scrap/EAF - The scrap information is based on discussions with steelmakers by Hornby-Anderson 6,8,15. The information is being primarily presented to show the background scrap results, which are used in nearly all of the case comparisons. For the purpose of this paper, scrap has been chosen to best represent high steel quality production to enable a better comparison with the AIU/EAF practices. In reality, 50% and 80% AIU mixes could use lower scrap qualities, which would change energy and greenhouse gas computations, making them higher. Table IVb. Summary of Operating Conditions for the Various Liquid Steel Production Scenarios Operation
Sequence Step
BF HM-BOF
Pelletizing Sinter Blast Furnace BOF
80% FASTIRONBOF (FASTOx)
CDRI/HDRI-EAF
Conditions • Oil fueled induration, fluxed or acid pellet, 64% total iron • Coal fueled sintering, fluxed sinter, 56% total iron • Coke + coal injection + oil/nat.gas add. + O2 enrichment, 4.0% C, 0.6% Si, 1500°C • 89% HM, 11% Scrap, 0 kg added carbon, 56.80 Nm3/t oxygen, 0.04% C, 1620°C
Cold Briquetting
• Coal reductant, organic binders
Direct Reduction
• NG-fueled, RHF, 1000°C
EIF®
• AC furnace, 4.4% C, 0.8 Si, 1500°C
BOF
• 80% HM, 20% Scrap, 0 kg added carbon, 59.28 Nm3/t oxygen, 0.04% C, 1620°C
Pelletizing Direct Reduction
• NG-fueled induration, DR pellet, 67% total Fe • CDRI NG-based, shaft furnace, 2.5% carbon • HDRI NG-based, shaft furnace, 2.5% carbon, 700oC
Operation
Sequence Step
EAF
Hi C CDRI/HDRIEAF
Pelletizing Direct Reduction
EAF HBI-EAF
Pelletizing Direct Reduction
20% HBI +30% PIEAF
• NG-fueled induration, DR pellet, 67% total Fe • • • •
CDRI NG-based, shaft furnace, 4.0% C HDRI NG-based, shaft furnace, 4.0% C, 700oC All 3.5kg/t foamy slag C; 0.04%C; 1620oC 80% Hi C CDRI/HDRI, 20% Scrap, 0 kg charge carbon, 38.80Nm3/t O2 • 30% Hi C CDRI/HDRI, 70% scrap, 0 kg charge carbon, 21.00Nm3/t O2 • NG-fueled induration, DR pellet, 67% total Fe • NG-based, shaft furnace, 1.5% C
EAF Pelletizing
• Oil fueled induration, fluxed or acid BF pellet, 64% total Fe
Blast Furnace Pelletizing Direct Reduction EAF
• Coal fueled sintering, fluxed sinter, 56% total Fe • Coke + coal injection + oil/NG add. + O2 enrichment, 4.0% carbon, 0.6% silicon • NG-fueled induration, DR pellet, 67% total Fe • NG-based, shaft furnace, 1.5% C • 3.5kg/t foamy slag C; 0.04%C; 1620oC • 20% HBI, 30% PI, 50% Scrap, 0 kg charge carbon, 28.59 Nm3/t O2
Pelletizing/Cold briquetting
• Coal reductant, organic binders
Direct Reduction
• NG-fueled RHF, 3.5% C
EAF 50% BF HM-EAF
• All 3.5kg/t foamy slag C; 0.04%C, 1620o • 80% CDRI/HDRI, 20% Scrap, 0 kg charge carbon, 22.27 Nm3/t oxygen • 50% CDRI, 50% Scrap, 2.0 kg charge carbon, 22.05 Nm3/t oxygen • 30% CDRI, 70% Scrap, 3.0 kg charge carbon, 21.22 Nm3/t oxygen
• All 3.5kg/t foamy slag C; 0.04%C, 1620oC • 50% HBI, 50% Scrap, 5.0 kg charge carbon, 19.68 Nm3/t O2 • 30% HBI, 70% Scrap, 5.0 kg charge carbon, 20.22 Nm3/t O2
Sinter
ITmk3 (PP)-EAF
Conditions
Pelletizing Sinter Blast Furnace EAF
• All 3.5 kg/t foamy slag C, 0.04% C, 1620°C • 50% PP, 50% Scrap, 0 kg charge carbon, 33.86 Nm3/t O2 • 30% PP, 70% scrap, 0 kg charge carbon, 24.74 Nm3/t O2 • Oil fueled induration, fluxed or acid BF pellet, 64% total Fe • Coal fueled sintering, fluxed sinter, 56% total Fe • Coke + coal injection + oil/NG add. + O2 enrichment, 4.0% carbon, 0.6% silicon, 1500°C • 50% HM, 50% Scrap, 3.5 kg/t foamy slag C, 0 kg charge carbon, 38.65 Nm3/t O2 0.04% carbon, 1620°C
Operation
Sequence Step
FASTIRON-EAF
Cold Briquetting
• Coal reductant, organic binders
Direct Reduction
• Natural gas-fueled, rotary hearth furnace, 1000°C
FASTIRON-EAF w/Scrap Preheat (FASTEEL™)
COREX-EAF
EIF®
• AC furnace, 4.4% carbon, 0.8% Si, 1500°C
EAF
• All 3.5 kg/t foamy slag C, 0.04% carbon, 1620°C • 50% FI HM, 50% Cold Scrap, 0 kg charge carbon, 42.84 Nm3/t O2 • 30% FI HM, 70% Cold Scrap, 0 kg charge carbon, 30.02 Nm3/t O2
Cold Briquetting
• Coal reductant, organic binders
Direct Reduction
• Natural gas-fueled, rotary hearth furnace, 1000°C
EIF®
• AC furnace, 4.4% carbon, 0.8% Si, 1500°C
EAF
• • • •
Pelletizing
•
Smelting Furnace
•
EAF
HIsmelt-EAF
Smelting Furnace
EAF 10% FM(WO) +20% PI-EAF
Pelletizing Sinter Blast Furnace
• • • • • • •
Scrap preheated to 600oC All 3.5 kg/t foamy slag C, 0.04% carbon, 1620°C 50% FI HM, 50% Hot Scrap, 0 kg charge carbon, 42.84 Nm3/t O2 30% FI HM, 70% Hot Scrap, 0 kg charge carbon, 30.02 Nm3/t O2 Oil fueled induration, acid BF pellet, 64% total iron BF grade pellets, Coal and O2 for smelt reduction, HM at 4.5% C, 0.7% Si, 1500°C. 13.2 GJ/t off gas credit. All 3.5 kg/t foamy slag C, 0.04% carbon, 1620°C 50% HM, 50% Scrap, 0 kg charge carbon, 43.33 Nm3/t O2 30% HM, 70% Scrap, 0 kg charge carbon, 30.32 Nm3/t O2 Iron ore fines, Coal, 30% O2 enriched hot blast, HM at 4% C, 0.2% Si, 1500°C. “Power Balanced Flowsheet” All electrical & O2 power is produced from off gas. All 3.5 kg/t foamy slag C, 0.04% C, 1620°C 50% HIS HM, 50% Scrap, 0 kg charge carbon, 35.02 Nm3/t O2 30% HIS HM, 50% Scrap, 0 kg charge carbon, 25.47 Nm3/t O2
• Oil fueled induration, fluxed or acid BF pellet, 64% total Fe • Coal fueled sintering, fluxed sinter, 56% total Fe • Coke + coal injection + oil/NG add. + O2 enrichment, 4.0% carbon, 0.6% silicon
Cold Briquetting
• Coal reductant, organic binders
Direct Reduction
• NG-fueled, RHF, 2.5% C, 1000°C
EAF 10% FM(WO) +20% PP-EAF
Conditions
• 10% FM(WO) DRI, 20% PI, 70% Scrap, 3.5 kg/t foamy slag C, 0 kg charge carbon, 26.68 Nm3/t O2, 0.04% C, 1620°C
Pelletizing/Cold briquetting
• Coal reductant, organic binders
Direct Reduction
• NG-fueled RHF, 3.5% C
Cold Briquetting
• Coal reductant, organic binders
Direct Reduction
• NG-fueled, RHF, 1000°C, 2.5% C
Operation
30% CFM(O)/HFM(O)EAF
Sequence Step
Conditions
EAF
• 10% FM(WO) DRI, 20% PP, 70% Scrap, 3.5 kg/t foamy slag C, 0 kg charge carbon, 24.74 Nm3/t O2, 0.04% C, 1620°C
Cold Briquetting Direct Reduction
EAF
30% Pig Iron-EAF
Pelletizing Sinter Blast Furnace EAF
Scrap-EAF
EAF
• Coal reductant, organic binders • • • •
CFM NG-fueled, RHF, 2.5%C HFM NG-fueled, RHF, 2.5%C, 1000°C All 3.5 kg/t foamy slag C, 0.04% C, 1620°C 30% CFM(O) DRI, 70% Scrap, 2.0 kg charge carbon, 22.15 Nm3/t O2 • 30% HFM(O) DRI, 70% Scrap, 2.0 kg charge carbon, 22.15 Nm3/t O2
• Oil-fueled induration, acid pellet, 64% total Fe pellet • Coal fueled sintering, fluxed sinter, 56% total iron • Coke +coal injection +oil/NG add.+O2 enrichment, 4.0% carbon, 0.6% silicon • 30% PI, 70% Scrap, 3.5 kg/t foamy slag C, 0 kg charge carbon, 27.56 Nm3/t O2, 0.04% carbon, 1620°C • 100% Scrap, 3.5 kg/t foamy slag C, 4.0 kg charge carbon, 19.09 Nm3/t O2, 0.04% carbon, 1620°C
RESULTS Energy & Emissions Figures 1, 2, and 3 summarize the results of the energy and emissions evaluation for the production methods assessed. The graph includes the total energy required to produce the liquid steel, energy for conversion from iron to steel (BOF or EAF energy inputs), and the carbon dioxide emissions generated throughout the production process. The units of energy are given in kWh/t of liquid steel, and the emissions are given in kgCO2/t liquid steel. Due to the number of cases studied, the results are divided into three graphs which represent the 80% AIU, 50% AIU and 30%AIU usage, respectively. In order to highlight the significant impact of feed materials on the EAF energy balance, the conversion energy line has been expanded by using the same scale as for the CO2 emissions.
Figure 1 – Total Energy, EAF Energy and CO2 Emissions (80% AIU) Total Energy EAF Energy CO2 Emissions
AI-EAF Comparison
4500
5124
4765
2500
2000 1959
4000 1922
3500
1500
3000
1066
1195
1647
2000
1065
2500
1163
1467
kWh/t LS (Total Energy)
4592
4545
4624
5000
4662
5065
5500
1000
1500 500 441
1000 500 0
kWh/t LS (EAF Energy), kg CO2/t LS (CO2 Emissions)
3000
6000
0 BF-BOF (DOE)
BF-BOF (Midrex)
FASTMELTBOF
100% SCRAP
80% CDRI
80% HDRI
80% HI C CDRI
80% HI C HDRI
Figure 2 – Total Energy, EAF Energy and CO2 Emissions (50% AIU) Total Energy EAF Energy CO2 Emissions
AI-EAF Comparison 6000
3243
3419
3300
3887
2000
1880
4217
4435
1959
1922
3500
2500
4017
3893
4000
3000 1259
1041
1507
1085
1500
1198
991
2000
912
1647
1320
1467
1500
2500
1000
500 441
1000 500
M FA ST IR O N 50 % FA ST EE L 50 % C O R EX 50 % H IS M EL T
50 %
BF
H
K3 50 %
IT M
PI 50 %
0%
H BI +3
H BI 20 %
50 %
R I C D IC H 50 %
10 0%
SC R
F TBO
x)
FA ST M EL
(M id re
O
F
(D BF -B O
AP
0 E)
0
BF -B O F
kWh/t LS (Total Energy)
4500
4207
5000
4545
4624
4662
5500
kWh/t LS (EAF Energy), kg CO2/t LS (CO2 Emissions)
3000
Figure 3 – Total Energy, EAF Energy and CO2 Emissions (30% AIU) Total Energy EAF Energy CO2 Emissions
AI-EAF Comparison
3000
2500
500
2957
3140
918
749
811
876
811
1165
1286
2410
2662
3003
3294
2926
3092 852
2972
3174 826
1000
500
)+ 20 % )+ PI 20 % IT M 30 K3 % C FM 30 (O % ) H FM (O 30 ) % IT M K3 30 30 % % PI FA ST IR 30 O % N FA ST E 30 EL % C O 30 R EX % H IS M EL T
BI
I
I
H
30 %
FM
(W
O
O (W FM 10 %
10 %
30 %
H
IC
IC
H
D R
D R C
C D H
30 %
30 %
10 0%
R I
0 SC R AP
0 BF -B O F BF (D -B O E) O F (M FA id ST re x) M EL TBO F
1500
441
1000
997
3163 766
2734 632
1500
693
2000
702
1647
2500
1467
3000
2891
2901
3500
2000 1959
4000 1922
kWh/t LS (Total Energy)
4500
4545
4662
5000
4624
5500
kWh/t LS (EAF Energy), kg CO2/t LS (CO2 Emissions)
6000
The results of this study indicate that: • For a 80% iron ore-based steelmaking facility, DRI consumes slightly more overall energy but produces significantly less carbon emissions than the BF/BOF technology because of its use of natural gas for iron ore reduction. • The EAF production routes, which utilize greater amounts of scrap, have lower total energy and carbon emissions than the conventional BF/BOF route. • To minimize total energy consumption and CO2 emissions, scrap use must be maximized. • Since many steel products cannot be made with a 100% scrap feed, a portion of alternative iron is charged to the EAF to meet quality requirements. • As the amount of AIUs charged to the EAF increases, so do the total energy consumptions and CO2 emissions. • AIUs produced by natural gas-based reduction (DRI & HBI) promote lower total energy consumptions and significantly less CO2 emissions than (cold) pig iron. • In the 80% AIU group, Hi C HDRI & HDRI have lower CO2 and EAF energy, and compare equally for total energy with the BF-BOF route. • In the 50% AIU group, FASTIRON, FASTEEL, and BF HM have the lowest total energy and EAF energy, while BF HM and COREX have the highest CO2 emissions. • In the 30% AIU group, FASTEEL has the lowest Total energy and EAF energy, followed by FASTIRON. The highest CO2 emissions from the group fall to the PI and COREX scenarios. • All of the HM scenarios have the lowest EAF energy for any given group. • EAF operations need to consider the global picture rather than operate in isolation.
SUMMARY The most greenhouse gas and energy friendly steelmaking process is EAF melting of 100% scrap. As this practice is not conducive to high quality steelmaking, AIUs must be used. NG-based reduction maintains its position as the minimum CO2 route, but availability and cost of NG make this option unattractive in many regions. Coal-based reduction, with hot metal charging to the EAF, offers the next best option by reducing total and EAF energy and only slightly increasing CO2 emissions over the NG scenarios. FASTEEL, incorporating both coal-based reduction, hot metal, and preheated scrap charging to the EAF, might present the best picture of future steelmaking. ACKNOWLEDGEMENTS The authors would like to acknowledge the kind support of Midrex Technologies, Inc., Kobe Steel Ltd., MIDREX Process Licensees, and contributing steelmakers for providing their operating data to enable the continued improvement in steelmaking operations.
REFERENCES 1. S.A. Hornby Anderson, G.E. Metius, R.L. Hunter, “Influence of AIS Chemistry on EAF Steelmaking Economics”, to be presented at the Electric Furnace Conference, San Antonio, TX Nov 10-13, 2002, Iron and Steel Society 2. “2000 Blast Furnace Roundup”, Iron & Steelmaker, Vol. 27, No. 8, August, 2000 3. S. Hornby-Anderson, J. Kopfle, G. Metius and M. Shimizu, “Green Steelmaking with the MIDREX® and FASTMET® Processes”, Paper presented at COM: The Conference of Metallurgists “Greenhouse Gases in the Metallurgical Industries: Policies, Abatement, and Treatment“, Toronto, Canada, August 26-29, 2001 4. J.M. McClelland, G.E. Metius, S.A. Hornby Anderson, “Future Green Steelmaking”, 32nd SEAISI Conference Proceedings, Tokyo, Japan, April 2002 5. “Energy and Environmental Profile of the U.S. Iron and Steel Industry”, DOE report no EE-0229, August 2000 6. Plant data submitted for Midrex Melting Seminar, May, 2000, Tuscaloosa, AL, USA 7. Plant data submitted for Midrex Operations Report, January, 2000, Unpublished 8. S. Hornby-Anderson, Private Communications, Midrex Technologies, Inc., March, 2001 9. Midrex Technologies Inc./BHP, “HBI & DRI Melting Seminar”, held in conjunction with 30th SEAISI Conference, Singapore, May 2001 10. S.A. Hornby Anderson, “Educated Use of DRI/HBI Improves EAF Energy Efficiency and Yield and Downstream Operating Results”, European Electric Steelmaking Congress proceedings, Venice, Italy, May 26-29, 2002 11. G. E. Hoffman, “FASTMELT - The Preferred Choice”, Paper presented at the Gorham Conference “Beyond the Blast Furnace”, Atlanta, GA, USA, 7 June 2000 12. J. M. McClelland, Private Communications addressing waste oxide recycling at a North American steel mill, October 2000 13. J. M. McClelland, “Proven FASTMET® Process: Right for India”, The Indian Institute of Metals and Tata Steel’s Conference “Direct Reduction and Direct Smelting”, Jamshedpur, India, Oct. 5th – 6th, 2001 14. G. Metius, Authors personal experience, April 1990, and subsequent technology developments. 15. S.A. Hornby Anderson, Private Communications with MIDREX Licensees’ steelmills 16. J. M. McClelland, Private Communications, Midrex Technologies, Inc., March, 2001 17. S. Montague, “HOTLINK™ - Hot Charging DRI for Lower Cost and Higher Productivity”, ISS 57th Electric Furnace Conference Proceedings, Pittsburgh, PA, USA, Nov. 14-16, 1999 18. Peter Bates and Andrew Coad, “HIsmelt, The Future In Ironmaking Technology”, 4th European Coke & Ironmaking Conference, Paris, June 2000 19. VAI publication, “The COREX® C-3000 Generation” 20. Kobe Steel Proposal for FASTIRON facility at a European Steelmill 21. Estimated consumptions from design calculations for Mesabi Nugget Project, to be verified during demonstration plant operation.
APPENDIX A Energy & Carbon Conversion Factors The conversion factors used in the paper, shown below, are based on continental US operating conditions Conversion Factors Item to Convert
Factor
Natural gas to energy & carbon
2646 kcal/kWh*, 0.208 kg-C/kWh for composite grid power** 0.281 kg-C/kWh for coal generated power 9,518 kcal/Nm3, 0.065 kg-C/Mcal
Coke to energy & carbon
7,149 kcal/kg, 0.122 kg-C/Mcal
Coal to energy & carbon
7,492 kcal/kg, 0.106 kg-C/Mcal
Coke to coal equivalent
1.0 kcal coke : 1.3 kcal coal
Fuel oil to energy & carbon
9,801 kcal/kg, 0.087 kg-C/Mcal
Oxygen to electricity
1.2 kWh/Nm3
Limestone to carbon
0.12 kg-C/kg
Electricity to energy & carbon
* Equivalent Thermal Energy required to generate delivered electricity 15 ** Calculated from “Electrical Power Annual 2000 – Volume 1”, Energy Information Administration2