2007 A record year for Consteel

Transcription

1 STEELMAKING 2007 A record yer for Consteel Nine new Consteel systems were ordered in This EAF technology is booming in Europe, Asi nd gin in the United Sttes, where it ws originlly conceived nd engineered 19 yers go. There re now 31 instlltions in plce or under construction in 13 countries. The drivers behind this remrkble success include the outstnding environmentl fetures, reduced electricity consumption nd n increse in productivity. Authors: Frncesco Memoli nd Muro Binchi Ferri Tenov Metl Mking C urrently there re 31 Consteel fcilities in opertion, under commissioning or in the construction phse (see Tble 1), equting to bout 27Mt/yr of cpcity. No other innovtive melting technology cn stte such trck record nd, since the first one ws instlled in 1990, more thn 82Mt of liquid steel hve been produced. New fetures hve been developed throughout this period leding to its gret success. The bsic technology hs been well documented[1,2] nd will not be discussed here. A cross-section through typicl fcility is shown in Figure 1 nd typicl plnt view is shown in Figure 2. In the erly 1990s, the system ws pplied mostly in the USA, where it ws originlly conceived nd engineered. The system s function of scrp preheting ws responding to the need for energy cost reduction. Since 2000 Consteel hs expnded t n impressive rte into Chin, with ten plnts to dte where, to meet the requirements of the growing Chinese steel industry, the process ws improved with focus on the continuous chrging function in order to chieve much higher productivity rtes thn conventionl EAFs. r Fig 1 Schemtic of Consteel equipment new plnts in Asi, including the highest instlled cpcity: 360t/hr for Tokyo Steel, currently under construction in Kurshiki, Jpn. The instlltion, due to commission in mid-2009, will hve nominl tpping weight of 300t nd totl cpcity of 420t. Two units re being supplied for the Asn By steelworks of Kore s Dong Bu Steel Co. The totl cpcity of the two units will be more thn 400t/h. The new plnt is expected to begin opertions in An exmple of retrofitting project in Chin is t the workshops of Anshn Hevy Mchine Mnufcturing Co, compny of the Anben Group bsed in Anshn. Anshn s Consteel will be unique s it will be integrted into n existing EAF with tpping sizes rnging from 60 to 120t. The EAF feeds csting mchine producing medium to r Fig 2 Consteel plnt t TSW, Germny SOME RECENT nd CURRENT PROJECTS Asi Tenov hs recently been contrcted to instll five 83

2 Fcility Loction Cpcity, t 1 Gerdu Ameristeel Chrlotte Chrlotte, NC, USA 40 2 Kyoei Steel Ltd Ngoy, Jpn Nucor Steel South Crolin Drlington, SC, USA Gerdu Ameristeel Syreville Syreville, NJ, USA 80 5 Nkornthi Strip Mills Public Co Ltd Chonburi, Thilnd ORI Mrtin SpA Bresci, Itly 85 7 Guiyng Steel Mills Corp Guiyng, Chin 60 8 Gerdu Ameristeel Knoxville Knoxville, TN, USA 60 9 Nucor Steel Hertford Hertford, NC, USA Xining Specil Steel Co Ltd Xining, Chin E Cheng Iron & Steel Works E Cheng, Chin Wuxi Xuefeng Iron & Steel Co Ltd Wuxi, Chin Shogun Iron & Steel Group Co Ltd (Shogng) Shogun, Chin Shndong Shiheng Specil Steel Co Ltd Shiheng, Chin Tonghu Iron & Steel Group Co Ltd Tonghu, Chin Ningxi Hengli Steel Wire Hengli, Chin Wheeling-Pittsburgh Corp Mingo Junction, OH, USA Jixing Dongfng Iron & Steel Compny Jixing, Chin Sonsid Société Ntionle de Sidérurgie Jorf Lsfr, Morocco Thép Viêt Compny Phu My, Vietnm Sovel SA, Hellenic Steel Processing Compny Volos, Greece TSW Trierer Sthlwerk GmbH Trier, Germny *Acciieri Arvedi SpA Cremon, Itly *CMC Steel Mes, AZ, USA *Cels Nordic Mo i Rn, Norwy *(privte investor) Hiphong, Vietnm *Angng Hevy Mchine Mnufcturing Angng, Chin *Tokyo Steel Mnufcturing Co Ltd Kurshiki, Jpn *Amet - Ashinskiy Metllurgicl works Ash, Russi *Dong-Bu Steel Co Ltd (No1) Asn By, South Kore *Dong-Bu Steel Co Ltd (No2) Asn By, South Kore *Dvsteel Cpe Gte Pty Ltd Vnderbijlprk, South Afric 75 *Currently t design, erection or commissioning stge r Tble 1 Consteel instlltions lrge-sized blooms. Strt-up is scheduled to tke plce by the end of In Vietnm, recent orders cme from two compnies, ech producing 400,00t/yr of billets; t one, the Thép Viêt Co Works locted close to Ho Chi Minh City, Tenov commissioned complete new steel plnt bsed on 60t Consteel, ldle furnce nd continuous csting mchine. Europe Environmentl nd lbour constrints in Europe hve not been incentives for steel compnies to invest in new meltshop technologies. In recent yers the steel industry hs not been considered s n importnt priority by governments. In this scenrio mny smll plnts hve been forced to close or convert production from rebr to specil steels in order to survive. Whenever money ws vilble for investment, priority ws generlly given to either new dedusting systems to mintin the production permits, or for finishing equipment. This investment strtegy is in some mesure the reson why Consteel ws not dopted in Europe for mny yers. The sitution hs now chnged nd the fct tht Consteel provides significnt environmentl nd energysving benefits is now crucil for the expnsion of this technology into Europe. A number of systems ordered in the pst few months will be locted in Europe, such s t Arvedi in Cremon, Itly, scheduled for strt-up t the beginning of This will be the Europe s lrgest unit: n 8.5m dimeter, 250t EAF designed to feed the new endless steel production (ESP) line. This integrted system is designed for up to 360t/h (430t/h mx), with scrp nd pig iron feeding vi 110m system comprising two chrging conveyors nd one preheting section. The trnsformer will be more thn 200MVA. The new fcility will be instlled in completely new building, 84

3 STEELMAKING r Fig 3 Off-gs tretment in Consteel plnt, compred to conventionl EAF plnt together with two dditionl ldle furnces, lso provided by Tenov. In lte 2007 two Consteel systems commenced opertion, one in Germny t Trierer Sthlwerk GmbH (TSW), nd one in Greece t Sovel Hellenic Steel Processing Compny SA. Like mny other steel compnies in Europe, some time go TSW decided to invest in new equipment, trining nd technology to increse the qulity of its steel production. Bsed on the experience nd the success of the meltshop t ORI Mrtin in Bresci, Itly, the first Europen Consteel instlled in 1998, TSW ordered complete meltshop, including 60t Consteel EAF, ldle furnce nd vcuum degssing sttion for its specil steel production. At Sovel the system ws retrofitted to n existing 130t EAF, which ws built in 1999 without the continuous scrp feeding equipment, but with the necessry provisions designed-in for its lter instlltion. The most recent Europen orders were wrded by Cels Nordic for its Mo i Rn works, Norwy nd by the Russin compny Amet. This ltter order is the first instlltion in the former CIS, n re with some of the lowest production costs in the world. Afric Tenov s ltest order hs been from Cpe Gte Pty Ltd for the Dvsteel meltshop t Vnderbijlprk. This will be the first system to be instlled in South Afric, in n re where Africn steel production is mostly concentrted. The system will be retrofitted to the existing Tenov EAF nd will provide the necessry productivity nd environmentl improvements to provide 650,000t/yr of steel for reinforcing brs, wire rods nd light sections. ENVIRONMENTAL PERFORMANCE At the ISS EAF conference held in Pittsburgh, USA in November 1999, the shre of newly built furnces incorporting scrp preheting technologies were expected to increse from 10% to 30% in the next decde. The min drivers behind this expected development were energy conservtion, shorter cycle times nd reduced operting costs. The technologies considered to eventully dominte the scrp preheting mrket were shft preheting with 50% of the instlltions nd twin shell preheting with 37%. Only 5% shre ws expected for Consteel. Time hs proved this prediction to be inccurte, s shft furnce technology hs been bndoned. Although the shft furnce hd cquired dominnt position it suffered from poor imge for environmentl performnce, which could only be corrected by expensive btement mesures nd restrictions on scrp types chrged[3]. In study on primry energy svings by the US Environmentl Protection Agency (EPA), shft furnce nd Consteel svings of 0.63GJ/t for the shft furnce nd 0.66GJ/t for Consteel were clculted[4]. Although in principle the shft concept hets the scrp to higher tempertures, for environmentl resons the need to tret fumes downstrem is expensive. As this is 85

4 r Fig 4 Electricl energy demnd of top chrge EAF vs Consteel EAF not necessry with Consteel, its overll energy recovery efficiency is higher. Since then Tenov hs further improved the preheting cpbilities. For instnce reserch hs demonstrted tht the EAF off-gses flow into the preheting tunnel (see Figure 1) t temperture consistently bove 900 C nd prehet the scrp chrge up to surfce temperture bove 600 C nd n verge temperture in the rnge of C, depending on the type of scrp chrged[5]. Moreover, in study on methods to reduce the volume of dust generted during steelmking by the Center for Mteril Production nd the Steel Mnufcturers Assocition in the USA, the Consteel process ws proven to reduce dust dischrged from the furnce by eliminting bck chrge[6]. Also, s bucket chrging is not required, the dimensions of the dedusting system cn be minimised (see Figure 3), so reducing the cost of ssocited off-gs equipment in green field plnts, or voiding dditionl expenses of such equipment in cse of n increse in production in existing plnts. As the preheting tunnel hs lrger cross-section thn norml off-gs duct, the speed of the fumes in the tunnel section is much lower thn in fourth hole elbow in n EAF. This mens tht the lrger dust prticles deposit on the bottom of the tunnel nd re picked up by the scrp being conveyed towrds the furnce. In this wy n estimted 20-30% of the totl EAF dust produced is recycled, resulting in considerble reduction in environmentl costs. The EAF roof remins closed t ll times in order to reduce energy losses nd cut emissions of gses nd other pollutnts. ELECTRICAL ENERGY Averge electricity consumption in EAFs is typiclly 400kWh/t. Using the Consteel process, this figure cn be decresed to pproximtely kWh/t[7]. As well s the preheting effect which reduces energy demnd the 30-50% of hot heel employed, compred to the more usul 10-15% in conventionl furnces, provides therml inerti which ids scrp melting without the need for oxyfuel burners. In res of the world where electricl energy is problemtic, Consteel is prticulrly beneficil becuse the trnsformer cn be one third smller thn with conventionl EAF. This is illustrted in Figure 4, which compres dt from the sme furnce with nd without Consteel. (Consteel cn produce up to 2.5t/hr of liquid steel t 1,620 C with 1MW of ctive power). A conventionl 100t/hr EAF would require 60MW trnsformer, while 100t/hr Consteel furnce requires bout 40MW. Figure 4 lso illustrtes more uniform electricl energy profile, so reducing the costs ssocited with lod demnd. Reduction of flicker nd hrmonics re two of the min drivers for Consteel instlltions in plnts where the electricl power supply network is n issue. This is of prticulr concern to those plnts locted in populted neighbourhoods. EAF opertors need to limit electricl disturbnce to the network nd, in mny cses, dditionl investment in electricl equipment is necessry to reduce flicker voltge fluctutions. By feeding scrp continuously, the rc is more stble nd, being covered by fomy slg, considerbly reduces electricl disturbnces flicker, hrmonics nd noise to the network with minimum cpitl cost[8]. The noise level is very importnt issue to resolve sometimes even more importnt thn flicker. Noise emissions of top-chrged EAF nd continuous melting EAF re compred in Figure 5, illustrting significnt reduction in noise. PROCESS CONTROL The environmentl fetures of the Consteel system hve now been enhnced with one of the most innovtive products of Tenov, nmely Goodfellow s EFSOP technology, introduced in Cnd in the lte 1990s[9,10]. EFSOP is closed-loop control system tht continuously nlyses the composition of the off-gses crbon monoxide, crbon 86

5 STEELMAKING r Fig 5 Noise emissions nd flicker of top-chrge EAF vs Consteel EAF dioxide, oxygen nd hydrogen nd performs the necessry retro-ction to the chemicl injection system. This optimises chemicl energy use within the furnce, nd lso detects possible wter lekges, giving significnt contribution to sfer melting opertions. One of the improvements of Consteel coupled with EFSOP is the possibility of monitoring the crbon content of the liquid steel by mesuring the off-gs composition. In this wy the decrburistion is totlly under control, optimising the use of injected oxygen. The possibility of using dditionl post-combustion oxygen permits optimistion of the combustion of the crbon monoxide generted in the steel bth. The generted energy is then used to prehet the scrp long the preheting tunnel, enhncing the preheting effect of the stndrd system. As result, the mount of CO in the off-gses is minimised. The ORI Mrtin plnt hs lso been n importnt development site for mny of the technologies which tody complement the bsic system, such s utomtic scrp speed control bsed on the on-line mesurement of the EAF weight nd thus the clcultion of specific energy consumption. This utomtion feture ws successfully implemented t ORI Mrtin, leving the EAF opertor only with the tsk of supervising the process, without ny rel mnul intervention during the phses of melting nd refining. An dditionl technologicl detil which ws dded t ORI is continuous belt chrging of lump crbon nd lime onto the connecting cr conveyor, design solution tody implemented on ll new Consteel systems. SCRAP QUALITY Scrp density nd grde hve lwys been of concern to EAF users. This ws of specific concern to Chinese steel mkers s scrp qulity, vilbility, selection nd preprtion hve lwys been n issue. Following instlltion of Consteel plnts, however, they soon relised tht they could chrge ny type of scrp from 100% hevy to 100% turnings, nd from rolls of wire to tundish skulls. This provides gret flexibility of opertion when scrp supplies re vrible. HOT METAL CHARGING The first users to dd hot metl to Consteel furnce were the Chinese. Hot metl provides dditionl het to the bth such tht with bout 30% hot metl nd oxygen injection, it will reduce electricl power consumption by more thn 80kWh/t[2,13]. Furthermore, when hot metl is chrged, lrge mount of CO will be vilble for 87

6 STEELMAKING r Fig 6 Hot metl chrging t Wheeling-Pittsburgh Co, USA production in the bth, which ssists slg foming. Tody, hot metl ddition plys significnt role t Shogun. It is the only EAF plnt ble to consistently use hot metl rte exceeding 85% due to oxygen injection improvements. The good experience with the continuous chrge of scrp nd hot metl in the six Chinese plnts now using this procedure hs helped to design the melting process of the new steel plnt t the Wheeling-Pittsburgh Mingo Junction plnt in the USA. This is the first EAF built in the USA to replce one of the existing blst furnces nd its supporting coke btteries[12,13]. Wheeling-Pittsburgh is the lrgest Consteel unit in opertion in the world nd the first unit built in the USA designed to continuously feed hot metl long with scrp into new EAF. The furnce hs nominl cpcity of 250t/h, which cn be incresed to 300t/h when fed with 40% hot metl nd 60% scrp mix (see Figure 6). CONCLUSIONS Twenty yers fter the first instlltion Consteel hs eventully shown the secret of its success: simplicity. As John Vllomy the inventor of the Consteel technology used to sy: If you hve boiling wter pot on fire you cn grdully dd ice nd the wter will keep boiling. Consteel is s simple s tht. MS Frncesco Memoli nd Muro Binchi Ferri re with Tenov Metl Mking, Miln, Itly. References [1] G Fnutti et l, Environmentl Control nd the Consteel process, Millennium Steel 2004, pp [2] Tng Jemin et l, Chrging hot metl to the EAF using Consteel. Millennium Steel 2006, pp [3] JP Birt, A futures study nlysis of the technologicl evolution of the EAF by 2010, Irsid-Usinor Recherche, L Revue de Métllurgie-CIT, Nov 2000, p1,355. [4] E Worrell, N Mrtin nd L Price, Energy efficiency nd crbon dioxide emissions reduction opportunities in the US iron nd steel sector, LBNL-41724, Energy Anlysis Deprtment, Environmentl Energy Technologies Division, Ernest Orlndo Lwrence Berkeley Ntionl Lbortory, University of Cliforni, July 1999, pp9-11, pp [5] U De Mirnd, A Di Donto, V Volponi, U Znusso, P Argent nd M Pozzi, Scrp continuous chrging to EAF, ISSN , no Europen Commission, Luxembourg, 2003, pp1-41. [6] MA Brown, MD Levine nd WD Short, Inter-lbortory Working Group on Energy-Efficient nd Clen-Energy Technologies, Scenrios for clen energy future, Ok Ridge Ntionl Lbortory; Lwrence Berkeley Ntionl Lbortory; Ntionl Renewble Energy Lbortory, Nov. 2000, for US Deprtment of Energy. [7] T Considine, C Jblonowsky, DMM Considine, PG Ro, The industril ecology of steel, Finl Report to Office of Biologicl nd Environmentl Reserch, US Dept of Energy, Awrd No.DE-FGO2-97ER62496, Mrch 26, 2001, pp [8] JA Vllomy, C Fllon, Continuous melting in EAF A wy to minimise flicker nd hrmonics, MPT Metllurgicl Plnt nd Technology Interntionl, Vol 20(4), Aug 1997, pp [9] L Ferro et l, EAF process control, Millennium Steel 2006, pp [10] M Pozzi et l, Operting results of Goodfellow EFSOP t Riv, Veron, Itly, Millennium Steel 2008, pp [11] W Snwu, Z Shoujun nd T Risheng Appliction of hot metl chrging for 90t Consteel-EAF t SGIS, Consteel Interntionl Symposium Proceedings, Metllurgicl Industry Press, Beijing, 2004, pp [12] JG Brdley, HL Pge, DE Ketin, T Brown nd SD Guzy, Wheeling-Pittsburgh steel, Mingo Junction plnt: Revitlized with new continuous steelmking process, Iron & Steel Technology 2005, 2(6), pp [13] M Ferri nd F Memoli, EAF Integrtion into the blst furnce route t Wheeling-Pittsburgh Millennium Steel 2007, pp