EAF STEELMAKING ROUTE

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1 Opportunities for increasing productivity, lowering operating costs and reducing greenhouse gas emissions in EAF and BOF steelmaking Since almost 70% of the energy losses in EAF steelmaking are associated with the off-gas, improving energy use and reducing related CO 2 emissions means minimising off-gas sensible and chemical energy losses. EFSOP off-gas energy optimisation technology has already delivered significant operating cost savings and productivity improvements while reducing process greenhouse gas (GHG) emissions by an average of 18%. When EFSOP is combined with off-gas heat recovery, depending on the specific operating practice, direct and indirect CO 2 savings can increase 2 5 times, or 40, ,000t annually for a 1Mt/yr EAF. For the integrated process, increased scrap melting from enhanced BOF post combustion together with scrap and/or direct reduced iron charging to the BF will substantially increase productivity and reduce energy consumption while lowering total CO 2 emissions by 21 26%, or 382, ,000t/yr for a 1Mt/yr plant. Additional energy and GHG savings are possible in BOF plants where off-gas heat recovery is appropriate. Authors: Douglas J Zuliani, Vittorio Scipolo and Carsten Born Tenova Goodfellow Inc. and Tenova Re Energy GmbH Since carbon oxidation is the primary chemical reaction in all steelmaking processes, steelmakers are faced with the challenge of finding ways to reduce CO 2 emissions without seriously undermining process efficiency. This paper describes the development of process optimisation technology for both electric and oxygen steelmaking that is designed simultaneously to improve productivity, reduce operating costs and lower GHG emissions. EAF STEELMAKING ROUTE Modern EAF practices augment electricity with charged carbon and assorted hydrocarbon fuels to reduce energy costs and increase melting rates. However, inefficient use of these energy inputs will result in increased direct and indirect CO 2 emissions. Table 1 highlights an energy balance carried out for a modern 7m diameter EAF using both chemical and electrical inputs to process a scrap charge. The results indicate that when all energy sources are accounted for, total energy input amounts to about 722kWh per tonne liquid steel (tls). Surprisingly, these data indicate that less than 54% of the total input energy is actually required for melting and refining the liquid steel bath. Importantly, 70% of the lost energy is associated with the off-gas (15.5% as sensible heat and 16.9% as chemical energy in the form of un-combusted CO and H 2 ). Given the magnitude of the off-gas energy content, it is clear that a focus on minimising off-gas sensible and chemical energy losses is absolutely necessary if a step change reduction in EAF energy use and related GHG emissions is to be made. Off-gas chemical energy optimisation An initial study of EAF energy efficiency and related GHG emissions in 2000 by Thomson et al 1 reported direct CO 2 emissions of about 100kg/tls and additional indirect CO 2 emissions of kg/tls assuming power generation using 32% and 68% fossil fuels, respectively, as in the UK and USA. In order to improve process efficiency and reduce GHG emissions, Thomson used newly commercialised EFSOP continuous real-time off-gas analysis technology to measure and optimise in-furnace post combustion by altering burner, lance and injector practices. The authors reported that the resulting improved process energy use reduced electricity consumption by up to 40kWh/t. A further benefit was that combined direct and indirect GHG emissions were also reduced by 35kg CO 2 equivalent per tonne. Today EAF energy optimisation has evolved from simple post-combustion optimisation into a more holistic approach that aims to optimise the complete operating practice to achieve maximum total chemical and electrical savings, a 54

2 Steelmaking and casting the highest productivity and minimum GHG emissions 11. Holistic optimisation is a well-accepted practice in the most efficient EAF shops including in conventional batch scrap melting furnaces, continuous scrap fed furnaces (CONSTEEL ) and continuous DRI fed furnaces. Since Thomson s original work, conducted 10 years ago, more than 45 EAFs worldwide have been equipped with EFSOP technology which uses a patented probe at the 4th hole, continuous off-gas analysis and a Level 2 SCADA interface to optimise EAF practice as shown schematically in Figure 1. In spite of the harsh operating conditions, EFSOP installations routinely demonstrate a probe life of more than 1yr with system maintenance of only about 30mins per week. The results in Table 2 indicate that EAF plant management have signed off on significantly lower total energy use and direct GHG emissions together with substantial operating cost savings and productivity improvements by using offgas analysis to: ` Optimise and dynamically control burner, lance and injector practice. ` Optimise charge bucket distribution and material sizing to improve charge carbon utilisation. ` Optimise and dynamically control fume system operation to minimise energy losses from excessive air in-leakage. ` Adjust electrical set points in tune with the optimised chemical energy inputs to increase melting rates, reduce power-on-times and maximise productivity. Energy input kwh/tls % total energy Electrical energy Chemical energy burners Chemical energy oxidation Oil + hydrocarbons Total energy inputs Energy output Steel Slag Off-gas sensible Off-gas chemical Water cooling Total energy outputs r Table1 Energy balance for a modern EAF practice As shown in Table 2, the average direct GHG savings from reduced carbon and fuels is about 18% or kg CO 2 / tls. Furthermore, this improved chemical energy utilisation also reduces electricity consumption by an average 14kWh/tls, thereby lowering indirect GHG emissions by an additional 3.1kg/tls for regions such as Canada where the power generation mix is 25% fossil fuels and by 8.4kg/ tls for the UK and USA, where the fossil fuel mix is about 68% (this calculation is based on a rule of thumb estimate for GHG emissions averaging about 8.8gm/kWh per % fossil fuel in the electrical generation mix 2 ). Off-gas sensible energy recovery As indicated by the energy balance shown in Table 1, approximately 15.5% of EAF energy inputs are lost as sensible heat in the offgas. When taken together with un-combusted CO which subsequently burns in the post-combustion chamber, the total thermal energy that can be used for heat recovery is well in excess of 25% of EAF energy inputs; the amount of off-gas energy needed for viable off-gas heat recovery. In spite of the potentially significant benefits, EAF off-gas heat recovery is not practised to any significant extent due, in part, to the harsh environment that exists in the fume r Fig 1 Application of EFSOP technology in EAF steelmaking system and the on-off batch nature of the process. Conventional EAF technology utilises water-cooled off-gas extraction systems with cooling water (4 5bar) being supplied at a sufficient flow to ensure that the hot (~1,300 C) off-gas is cooled to below 700 C before exiting the cooled part of the duct prior to final quenching. Since the heated cooling water is not at a high enough pressure and temperature to be of any practical use, it is typically pumped to evaporative cooling towers where the heat from the process is discharged to the atmosphere. Recognising the opportunity for significant energy savings, Tenova Re Energy GmbH has recently adapted Evaporative Cooling System (ECS) technology to heat recovery on the EAF. It is now possible to replace the conventional low pressure water-cooled ducting with high-pressure boiler a 55

3 Benefits Steel plant sign off on completion EFSOP completed installations as at Dec 2008 Operating cost cost savings (from electricity, carbon, Average US$/tls 2.14 fuels and oxygen) Minimum US$/tls 1.0 Energy Electricity saving 14.0kWh/tls Gas and fuel saving 1.1Nm 3 /tls Injected carbon saving 1.0kg/tls Charge carbon saving 1.4kg/tls Total in-eaf energy saving 29.0kWh/tls Productivity Power-on time (POT) reduction 2.1min per heat Productivity increase tls/pot 4.6% Yield increase 0.4% Environmental CO 2 reduction 17.9% r Table 2 Average benefits from off-gas based optimisation for all completed EFSOP EAF installations tubes designed to withstand the harsh EAF fume system conditions at pressures of 15 40bar. For example, at 20bar the boiling point of water increases to 216 C; the Tenova Re Energy ECS technology is designed to use the heat of evaporation to produce high-pressure steam at 216 C with the off-gas temperature exiting the cooled part of the waste gas duct reduced to about 600 C. The resulting high-pressure steam can be used to supplement or replace an in-plant steam generation boiler for existing applications within the plant such as for vacuum degassing or for in-plant DRI production using the HYL direct reduction process. By incorporating steam accumulator tanks to homogenise EAF process cycles, this technology has been shown to be capable of continuous steam production with an average rate of 20t/hr from a 140t/hr EAF. The associated boiler required to produce an equivalent amount of steam would consume almost 13,000kW/ hr. Hence, by employing the EAF off-gas heat recovery technology, boiler equivalent CO 2 emissions of almost 112,500t/yr with coal firing or 57,000 t/yr with natural gas firing would be eliminated. It is also possible to combine a second stage where the offgas temperature is reduced from ~600 C to ~200 C with a waste heat boiler instead of the standard off-gas quench. The combined heat recovery with the ECS and the waste heat boiler is 75-80% of the total energy content in the waste gas, approximately 20% of primary energy input. In cases where there is insufficient demand for steam from the EAF heat recovery, an Organic Rankine Cycle (ORC) turbine can be used for power generation. ORC generators are becoming commonplace in related industrial heat recovery applications. They typically operate at around 20% efficiency and could be expected to generate about 4MW of electrical power from an average-sized EAF. This translates to 24,000MWh/yr of electrical energy; a saving of 7.5% in net electrical energy usage in the EAF or 2.73t of GHG a yr per % fossil fuel in the power generation mix. Summary Given that almost 70% of the process energy losses are associated with the off-gas, a clear focus on minimising off-gas sensible and chemical energy loss is needed if a step change reduction in EAF energy use and GHG emissions is to be made. With more than 45 EFSOP off-gas based process control systems installed or underway worldwide, in-eaf energy optimisation is already delivering significant steel plant verified operating cost savings and productivity improvements plus substantial reductions in both direct and indirect GHG emissions. As indicated in Table 3, combining energy optimisation with heat recovery now affords the opportunity of augmenting the significant operating cost and productivity benefits from EFSOP with a substantial reduction in EAF energy use and GHG emissions. INTEGRATED BOF STEELMAKING ROUTE Based on a process mass balance model, it can be estimated that a typical integrated steel plant will emit approximately 1,844kg of CO 2 /tls from both direct and indirect sources, or 4-5 times more GHG than from an EAF plant. Of the total integrated process GHG emissions, approximately 71% are associated with the BF, 8% with the BOF and the balance with assorted raw materials production. It can be concluded that the major factor contributing to higher GHG emissions is the use of carbon to reduce iron oxides. Hence, increasing the proportional use of scrap and/or DRI could dramatically reduce specific GHG emissions/tls: the challenge facing steelmakers is how to efficiently increase the use of metallised iron in the integrated process. The potential to improve BF productivity and energy use while reducing GHG emissions In 1998, Austin et al 3 reported on the process dynamics of charging shredded scrap to the BF. Their results indicated that with optimum charging patterns, scrap addition could dramatically reduce fuel rate and increase productivity. Similarly, Knop et al 13 56

4 Steelmaking and casting 1 Mt/yr EAF Energy savings MWhr/ yr GHG savings t/yr EFSOP in-eaf optimisation Direct 15kWh(equiv)/ tls 15,000 10,000 20,000 Indirect 14kWh/tls 14,000 8,380* Off-gas heat recovery** Steam 20t/hr 93, ,130 continuous using coal firing, OR, Stage 2 electricity generation 28,800 20,970* r Table 3 Summary of potential energy and GHG savings for the EAF * Assumes 68% fossil fuel power generation. ** Assumes 300 operation days per year. have examined the economics, productivity and coke rate benefits associated with DRI use. Ryman and Larsson 4 recently used a GHG emissions model for the integrated process to examine the effects on GHG emissions/tls when charging scrap to the BF. Their results show that at a constant hot metal (HM) production rate, increasing the Total Scrap Ratio (TSR) from 20% to 50% by the addition of scrap to the BF at a rate of 0.289t/tHM would reduce the coke rate by 18% and correspondingly decrease direct and indirect GHG emissions by almost 20% or about 332kg/tls. Actual BF trials with scrap and metallised HBI/DRI confirm significant productivity and coke rate benefits 12. Small scale and commercial BF tests show that there will be a coke rate savings of about 310kg/tHM for every tonne of metallised iron added to the burden, irrespective of whether it is from scrap or HBI/DRI. Hot metal production rates also increase dramatically, for example production has been shown to increase on average by about 25% in cases where 30% of the iron in the burden is metallised. As reported by Duarte et al 14, DRI production from natural gas produces about kg of CO 2 /t DRI. Hence, the net CO 2 balance for the addition of 0.289t of metallised iron from HBI/tHM would represent a net reduction in BF GHG emissions by about 265kg/tls. Based on these results, in situations where scrap is not favourable, the addition of DRI to the BF is an effective alternative for reducing BF GHG emissions, decreasing coke rates and increasing productivity. In summary, the addition of metallised iron to the BF burden either as scrap or HBI/DRI will dramatically reduce coke rates, increase productivity and at the same time decrease GHG emissions by up to kg/tls. The potential to improve BOF productivity and reduce GHG emissions Whereas the EAF requires chemical and electrical energy inputs, BOF processes autogenously generate sufficient heat to support process dynamics from the oxidation of carbon and other elements such as iron, silicon and manganese. For a top-lance BOF operating under normal blowing conditions, 85 90% of the off-gas exiting the converter mouth is un-combusted CO 5,6 with the balance having been post-combusted to CO 2 inside the vessel. Depending on hot metal temperature, the typical top-blowing practice generates sufficient heat to process a charge containing up to about 25% solid scrap. Ryman and Larsson 4 used their GHG model to investigate the potential for reducing CO 2 emissions by increasing hot metal silicon levels so as to increase BOF converter scrap melting from the additional heat of oxidation. However, in this case the result was marginal at best since higher Si contributes additional GHG emissions from increased BF coke rates and higher BOF slag volumes, both of which are detrimental to efficient operations. Alternatively, Zuliani 8 has reported that enhancing in-converter post combustion of CO to CO 2 has been claimed to increase BOF scrap melting rates by 3 6%. The key factors for enhanced scrap melting rates include: ` Methods to effectively inject secondary O 2 to promote oxidation of CO to CO 2 in the converter. ` Methods to improve heat transfer efficiency between the off-gas and the liquid and solid phases within the converter. Because complete oxidation of carbon to CO 2 liberates 3.5 times more heat than partial oxidation to CO, increasing inconverter post combustion of CO can be an effective way to tap into a significant energy source that in many cases is under-used. Except for suppressed combustion situations where the off-gas chemical energy is used downstream as a fuel, in open combustion gap BOF plants most of the CO to CO 2 post-combustion takes place post-converter in the fume duct and the associated energy is typically recovered as low grade steam. In such situations, shifting more post combustion inside the converter provides a significant energy source available for additional scrap melting assuming the heat can be recovered efficiently before the off-gas exits the steelmaking furnace. a 57

5 BOF practice Baseline In-vessel post combustion BOF hot metal (%) BOF charged scrap (%) Metallic yield (%) * Total CO 2 emission integrated process Coke plant Kg CO 2 /kg coke ** Kg coke /tls Kg CO 2 /tls Pellet plant Kg CO 2 /kg pellet *** Kg pellet /tls 1,255 1,163 Kg CO 2 /tls BF Kg CO 2 /kg of HM **** Kg HM /tls Kg CO 2 /tls 1,304 1,209 BOF C removed Kg /tls Kg CO 2 /tls Total CO 2 Kg CO 2 /tls 1,844 1,609 Reduction (%) * 0.4% yield increase due to improved end-point control with EFSOP * * Queensland coke and power plant project environmental impact statement * * * CEPS task force sectoral industry approaches to address climate change baseline steel sector Brussels Oct, * * * * calculated using BF process mass balance model r Table 4 The effects on integrated steelmaking CO 2 emissions from a 5% increase in BOF scrap melting by enhanced in-converter post combustion The major factor determining the effectiveness of inconverter post combustion for increased scrap melting is the heat transfer efficiency (HTE) between the off-gas and the liquid and solid phases. Farrand et al 15 developed a heat transfer model that predicts that liquid steel temperatures should rise by 10 C for every 1% increase in post combustion for a KOBM converter if the heat transfer efficiency is 100%. In practice the HTE actually averages only about 44% and that the steel temperature actually rises on average by 4.9 C for every 1% increase in inconverter post combustion. To increase post combustion and the HTE in the BOF process, O 2 must be introduced into the converter in a way that allows it effectively to come in contact with CO. This can be accomplished by: ` Raising the lance height this has been shown to increase in-converter post combustion; however, it also reportedly increases refractory wear in the cone and has little or no beneficial effect on increasing the HTE 6,7,15. ` Introducing secondary oxygen either through inclined nozzles located at some height above the primary lance tip or through specially designed nozzles located adjacent to the primary O 2 ports at the lance tip. Lance modifications have been shown effectively to promote both higher scrap melting rates from enhanced post combustion and increased the HTE. Kato et al 16 mathematically modelled the effectiveness of various design characteristics for inclined injection of secondary O 2 through nozzles located at a fixed height above the lance tip. Their results indicated that this height, the angle of nozzle inclination and the flow rate of the secondary O 2 all had a significant impact on post combustion and the HTE. Takashiba et al 7,17 conducted a similar investigation with an altered lance configuration that introduced secondary O 2 through specially designed angled ports at the lance tip. Their results indicated that in order to maximise HTE and minimise damage to the vessel refractory and lance, it is important to locate the optimum combustion zone just above the molten steel surface about 1m from the refractory side walls and at a short distance from the lance tip. A correct balance between secondary and primary O 2 flow rates was required to achieve the optimum flow characteristics and scrap melting benefits. US Patent 18 also 58

6 Steelmaking and casting discloses specific lance design characteristics to promote efficient post combustion and heat transfer. Based on industry data, a 5% increase in scrap rates is reasonable with an optimised in-converter post-combustion practice. Table 4 summarises the calculated effects of this 5% increase in BOF scrap melting on CO 2 emissions/tls for the integrated route. Increasing the scrap to hot metal ratio at the BOF reduces the demand for hot metal, coke and pellets, all of which combine to reduce CO 2 emissions by about 7% or 135kg CO 2 /tls Off-gas heat recovery Unlike the EAF, evaporative cooling technology is widely used on BOF converters equipped with open gap combustion systems. In suppressed combustion situations, some plants use the CO off-gas as a fuel while many others simply lose the energy by flaring the gas. As an alternative to flaring, a waste heat boiler can be installed to produce steam with the CO. Because the amount of steam generation can be regulated by the amount of CO burnt in the boiler, this configuration can be readily designed to generate a very constant steam flow rate with much less steam buffering than is the case for EAF off-gas heat recovery. For example, during oxygen blowing periods when CO flow is high, only a portion of the CO is burnt in the boiler with the remainder being stored. To maintain a steady steam flow during periods when there is no oxygen blowing, the previously stored portion of the CO from earlier heats is subsequently burnt. i BOF technology Tenova Goodfellow is currently commercialising the next generation intelligent BOF (i BOF ) technology (see Figure 2); designed to reduce GHG emissions while improving yield, productivity, scrap melting capability and operating costs 8. It is modular and can be configured in a number of ways to meet the specific requirements of each BOF shop. It can be supplied either as a complete package or as individual modules as required by each plant. For example: ` Enhanced end-point detection This basic module uses a combination of the EFSOP off-gas analysis system together with proprietary process models. Endpoint detection was significantly improved, thereby reducing the number of turndowns and reblows, which increases yield as shown in Figure 3. ` Early warning slop detection This optional module continuously monitors high and low frequency changes in lance vibration to obtain an advance warning of the onset of a slop event and an indication of impending slop severity. ` Enhanced post-combustion This optional module enhances in-bof post combustion for increased scrap melting capacity by using a combination of the EFSOP r Fig 2 i BOF technology features off-gas analysis system together with dual-flow lance technology. This technology is being designed to use real-time off-gas analysis for lance height control and for independent flow rate control between primary O 2 for decarburisation and secondary O 2 for post combustion. The net result is optimised post combustion, heat transfer efficiency, scrap melting and productivity in real-time. If installed with the slop detection module, i BOF is designed to mitigate the effects of the slop event in real time by dynamically increasing secondary O 2 flow to enhance post combustion and accelerate slag heating to destabilise the foam by lowering viscosity 8. ` Automated tapping control This optional module provides control technology for operator assist or for full automated tapping control to improve safety, minimise slag carry-over and reduce operating costs. i BOF results from recent installations The first installation was the end-point detection module on a 165 short ton top-blown converter at US Steel Hamilton Works 9,19. US Steel was able to predict end-point carbon to within ± % carbon for 90% of heats and within ± % carbon for 97% of heats. Table 5 summarises consumable cost benefits associated with improved endpoint detection as confirmed by US Steel. i BOF end-point prediction also reduced the standard deviation for end-point carbon on 0.1% carbon heats by almost 60% which has enabled US Steel to successfully implement a catch carbon practice when producing high carbon heats. Ultimately, the objective is to completely eliminate the need for Celox bombs to further reduce consumable costs. A second installation on a 360t BOF converter with top blowing and Ar/N 2 bottom injection included the improved end-point prediction and the slop detection a 59

7 Yield # Turndowns r Fig 3 Effect of the number of BOF turndowns on % yield together with a significant reduction in GHG emissions. Increasing yield by 0.4% through improved end-point detection together with increasing the scrap melting capacity by 5% from improved in-vessel post combustion will reduce GHG emissions from the integrated process by more than 7% (see Figure 4 and Tables 7 & 8). MS Doug Zuliani is Director of Sales and Business Development and Vittorio Scipolo is Manager of Research and Development, both at Tenova Goodfellow Inc., Mississauga, Ontario, Canada. Carsten Born is with Technical Sales for the heat recovery team of Tenova Re Energy GmbH, Düsseldorf, Germany. CONTACT: doug.zuliani@ca.tenovagroup.com Items Change (%) Oxygen consumption -0.7 Carbon ladle addition -2.7 Aluminium -4.0 Ferro-alloys -1.6 r Table 5 Cost benefits using i BOF endpoint detection at US Steel Hamilton Works modules 20. This BOF was equipped with a sublance system with the normal practice being two sublance readings per heat, the first in-blow and the second confirmatory before tapping. The objective was to improve end-point prediction ultimately to allow the plant to eliminate the second sublance reading, thereby reducing operating cost and the associated production delays. Table 6 confirms that the predicted end-point C and temperature are in excellent agreement with the final inmelt sublance reading, thereby providing confidence for the plant to eliminate this second sublance reading and to proceed with a blow and tap practice. A second objective for this installation was to provide advanced warning of the onset of a slop event to avoid yield and productivity losses associated with metal ejection from the converter. Extensive trials demonstrated an 87% slop detection rate with about 20 40secs of advance warning before the visual onset of metal ejection. This warning provides sufficient time for the plant operators to take preventative action to mitigate the effects of the slop event. Summary When these BOF practice enhancements are combined with changes at the BF, the net effect can be a substantial improvement in energy use and productivity REFERENCES 1 M J Thomson, E J Evenson, M J Kempe and H D Goodfellow, Control of greenhouse gas emissions from electric arc furnace steelmaking: evaluation methodology with case studies, Ironmaking and Steelmaking, 2000, 27, 4, p National Inventory Report, : Greenhouse Gas Sources and Sinks in Canada, annex 9 electricity intensity tables: /a9_eng.cfm#ta9_1 3 P R Austin, H Nogami and J-I Yagi, Computational investigation of scrap charging to the BF, ISIJ International 1998, 38, 7, p C Ryman and M Larsson, Reduction of CO 2 emissions from integrated steelmaking by optimised scrap strategies: application of process integration models on the BF-BOF System, ISIJ International, 2006, 46, 12, p1, H Okuda, H Take, T Yamada and K Frits, Thermal compensation by post combustion in converter, TRANS ISIJ, 1985, 25, 11, B, p D A Vensel, H Henein and P H Dauby, A thermodynamic analysis of decarhurisation and post combustion in the BOP, Proceedings of the 68th Steelmaking Conference, Iron & Steel Society, Detroit, April 14-17, 1985, p67. 7 N Takashiba, S Kojima, H Take and H Okuda, Postcombustion of converter gases, Steel Technology Int., 1989, p D J Zuliani, Post combustion in electric and oxygen steelmaking, Metal Producing and Processing, March- April 2009, p13. 9 J Maiolo and D J Zuliani, BOF endpoint prediction, Metal Producing and Processing, 2008, Nov/Dec, p V Scipolo, J Maiolo, C W Li, B Goldberg and D Zuliani, Application of EFSOP holisitic optimisation technology to oxygen steelmaking, AISTECH 2008, Pittsburg,

8 Steelmaking and casting Average sublance Average i BOF prediction Standard error Number of heats Temperature ( C) 1,678 1, Carbon (wt %) r Table 6 i BOF endpoint detection compared to end-of-blow sublance readings in a 360t BOF Process Action GHG savings (%) GHG savings (%) BOF 5% Increase scrap charge by enhanced post combustion 7 7 BF Scrap 0.29t /t HM, OR 20 DRI/HBI 0.29t iron equiv/t HM 15 Total GHG reduction potential r Table 7 GHG savings potential from increased use of metallised iron in integrated steelmaking 1Mt/yr integrated plant GHG savings kg/t GHG savings t/yr i BOF end-point and post combustion ,000 combined savings; BOF, BF, coke & pellet plants BF metallic Fe charging ,000 scrap charging at a rate of 0.29kg/kg HM DRI at a rate of 0.29kg Fe/kg HM ,,000 Total GHG reduction , ,000 r Table 8 Summary of potential GHG savings in integrated route 11 D J Zuliani, H D Goodfellow and M Bianchi Ferri, EFSOP holistic optimization of electric arc furnaces past, present and future, AISTech Conference, Pittsburgh, Direct reduced iron technology and economics of production and use, (ed) Jerome Feinman and Donald R Mac Rae, The Iron & Steel Society, 1999, chapter 10, Use of DRI in Ironmaking, pp K Knop, P Duarte, E Zendejas and U Gerike, Technical, economical and ecological aspects for optimized use of fossil primary energies in integrated steel plants for crude steel production METEC Congress 03, 3rd International Conference on Science and Technology of Ironmaking Proceedings, Düsseldorf, June 2003, pp P E Duarte, A Tavano and E Zendejas, Achieving carbon free emissions via the ENERGIRON DR process, to be published in AISTech Conference, Pittsburgh, B L Farrand, J E Wood and F L Goetz, Post combustion trials at Dofasco s KOBM furnace, 1992 Steelmaking Conference Proceedings, p Y Kato, J-C Grosjean, J-P Reboul and P Riboud, Influence of lance design and operating variables on post combustion in the converter with secondary flow nozzles, Trans ISIJ, 1988, 28, p US Patent 4,746,103: Takashiba et al, Lance for blow refinement in converter. 18 US Patent 5,681,526: Zhang, Method and apparatus r Fig 4 Enhanced integrated practice for post-combustion of gases during the refining of molten metal. 19 S Gillgrass, V Scipolo, B Goldberg, J Maiolo, P Hole, J Spence and R Roudabush, Application of EFSOP holistic optimization technology to oxygen steelmaking, AISTech 2009, St Louis, USA. 20 O Davis, V Scipolo and A Vazquez, Mathematical modeling of the BOF for endpoint prediction using EFSOP technology, ABM 41st Steelmaking Seminar International, May 23-26, 2010 Resende, Rio de Janeiro, Brazil. 61