IronIronIronIron OreOreOreOre ProductProductProductProduct DevelopmentDevelopmentDevelopmentDevelopment atatatat LKABLKABLKABLKABZUO Guangqing& HALLIN Mats

Marketing & Logistics Division, LKAB, Box 952, 97128, Luleå, Sweden

AbstractAbstractAbstractAbstract: Luossavaara-Kiirunavaara AB – LKAB, a wholly Swedish state-owned and a public limited company, is aninternational high-tech minerals group and one of the world’s leading producers of upgraded iron ore products. LKAB’smission is, based on the Swedish ore field, to manufacture and deliver upgraded iron ore products and services that createadded value for its customers.

LKAB’s iron ore product portfolio consists of blast furnace pellets, direct reduction pellet and sinter feeds for iron oresintering. As the No. 1 iron ore producer in Europe, who produces over 90% of iron ore products of Europe, LKAB does notown any commercial process for ironmaking. To be able to always provide customers with high-quality iron ore productsespecially iron ore pellets, product developments usually follow some special routines and are often conducted together withcustomers, for instance: laboratory test-pilot scale trials-final product launching for blast furnace pellet. This paper presentsbriefly some successful stories about the product development at LKAB.

Key works: LKAB, EBF®, iron ore pellet, iron ore product, AggloLab, blast furnace, iron making

1.1.1.1. IntroductionIntroductionIntroductionIntroductionLuossavaara-Kiirunavaara AB – LKAB is aninternational high-tech minerals group, one of theworld’s leading producers of upgraded iron oreproducts for the steel industry and a growingsupplier of industrial minerals products to othersectors. LKAB is wholly owned by the Swedishstate and a public limited company with headquarterin Luleå, Sweden. LKAB’s mission is, based on theSwedish ore field, to manufacture and deliverupgraded iron ore products and services that createadded value for customers.

LKAB’s iron ore products can be divided into threecategories; namely, blast furnace pellet constitutingof olivine and acid pellets; Direct Reduction pelletfor direct reduction processes; and fines as sinterfeed. The major market for LKAB’s iron ore productis in Europe but with more and more volumes duringthe recent years to China. The DR pellet is mainlydelivered to customers in Middle East and NorthAfrica.

The initial iron ore pellet at LKAB was developedand launched in 1980s for the use in a blast furnace

iron making process. Since then different types ofpellets were designed and tested during thedeveloping phase and some of them weresuccessfully put into the market. This paper mainlyreports the development of blast furnace pellets atLKAB.

2.2.2.2. ProductProductProductProduct DevelopmentDevelopmentDevelopmentDevelopment HistoryHistoryHistoryHistoryAs the No. 1 iron ore producer in Europe and the No.3 iron ore pellet manufacturer globally, LKAB doesnot own a commercial blast furnace for ironmaking.Iron ore pellet product development was conducteddirectly from laboratory tests to full scale trials atcustomer’s production furnace at LKAB before 1997.One of the present blast furnace pellet i.e.MPBOolivine pellet, which also was the prime BF pellet atLKAB,wasdeveloped through a tight cooperationbetween SSAB and LKAB, and initially introducedto blast furnace operation at SSAB in 1982[2].Outstanding operation results have been achievedsince the use of 100% MPBO pellet at SSAB LuleåWorks, and during the last decade the product hasbeen optimized to meet customers’ demands.

However, in the course of developing a new type offluxed pellet during 1990s, difficulties through thisLab-BF development route was encountered. The

new type of pellet which appeared to have anexcellent properties in the laboratory tests did notfunction well in a commercial blast furnace process.Contrarily, it did caused some severe irregularitiesfor the BF process during the full scale trials, such ashigher pressure drop, higher fuel consumption butunstable process. The reason for the problemsoccurred in the blast furnace process could not beunderstood due to the difficulties in taking burdensamples on-line from a production furnace. It wasthen decided to conduct some pilot scale trials in asmall primitive pilot blast furnace of British Steel[2].The pilot blast furnace was quenched after finishingthe trials and excavated samples was taken forfurther laboratory examination. It was found that theabnormal process conditions occurred in theproduction furnace through the trial resulted fromthe catastrophic swelling of pellet during thereduction in the furnace. Metallic iron formed in theshape of whiskers in the blast furnace, butdid notappear in the standard swelling test. The result mayindicate that with the development of modern blastfurnace iron making technology, one step productdevelopment from laboratory to commercial blastfurnace can be too risky for a production furnace andtoo ineffective for product development. Toaccelerate the product development and to be able toalways provide customers with high-quality iron orepellets, it was decided in 1996 to build anExperimental Blast Furnace - EBF® for total 5campaigns of about 6 weeks each and 2-campaignper year for developing iron ore pellet productsbetween 1997 and 1999.

The EBF was built and commissioned in 1997.During the first 5 campaigns, both LKAB’s internalproduct development projects and external projectsfor optimizing the blast furnace process were carriedout. It became very obvious that the EBF is avaluable tool not only for iron ore pellet productdevelopment but for other research and developmentof blast furnace ironmaking technologies. As a result,the EBF with consecutive improvement wascontinued to use for product development and forexploring the blast furnace ironmaking technologiesafter 1999.So far 27 campaigns have been carried

out successfully for different purposes. New iron orepellet products have been designed and presented tocustomers as the commercial products; improvedburden structures were reconstructed for customerswithtrialsat EBF with desired raw materials ofcustomers for blast furnace operation.

3.3.3.3. TheTheTheThe ExperimentExperimentExperimentExperiment BlastBlastBlastBlast FurnaceFurnaceFurnaceFurnaceAlthough the EBF as shown in Figure 1 is not aslarge as a commercial blast furnace in size it is fullyequipped as a commercial one, or even better. Theon-line measurements of the top gas composition ofhigh accuracy as well as the gas temperaturemeasurements in crossed two diametrical directionscan provide valuable information about the gasutilization and distributions inside the furnace. Thehigh top pressure up to 2.5 bar makes it possible tooperate the furnace at high blast volume withoutdeteriorating process performance. The advancedtop charger developed by Z&J Technologies Gmbhand verified at LKAB’s EBF gives great flexibilityfor adjusting the burden distribution. ‘Livesampling’ during the operation through upper andlower shaft gas and burden probes, as well as theinclined burden probe can provide more detailed‘inside information’ for improved analysis of thefurnace process. Tuyere optical cameras can help theoperator to enhance the thermal state control to someextent.

Figure 2 shows a schematic layout of the EBF plant.Four ferrous material bins, slag former bins and onecoke bin facilitate greatly the test of different burdenstructure during a campaign. The charging systemwith skip car can serve the furnace well up to aproduction rate of about 1.85 t/h. Advanced flexibleinjection system can admit multiple injections ofpulverized coal together with other solid pulverizedmaterials, e.g. BOF slag and flue dust,simultaneously. Oil or reducing gas injection is alsopossible.

For heating up the cold blast two pebble heaters,functioning as hot stove, are used and are able toheat up the air from ambient temperature to atemperature of about 1250°C. High oxygen

enrichment ratio of up to 40% to blast was testedwithout any problem during one campaign. The gascleaning system with sampling function makes itvery easy to take flue dust and sludge samples forfurther analysis when necessary.

The taping system consists of a drilling machine foropening the tap hole and a mud gun for closing.Sampling of hot metal and slag as well as themeasurement of the hot metal temperature duringtapping are manually conducted. On-site chemicalanalysis of hot metal and slag can provide quickthermal information to process engineers forcontrolling the furnace.

The EBF has been fully financed and is owned byLKAB, but situated on the MEFOS premises.Design of campaign and process control during eachcampaign are usually conducted by LKAB’sengineers and researchers, and sometimes jointlywith partners if a trial was for a joint project.Dissection of the EBF after each campaign,sampling the burden materials during the excavation,as well as the further evaluations of the probing andexcavation samples are carried out independently byLKAB.

Inclined

- 4.3 m

Upper shaft

Lower shaft

-3.45 m

Tuyere-6 m

-1 m

Inclined

- 4.3 m

Upper shaft

Lower shaft

-3.45 m

Tuyere-6 m

-1 m

Technical Data of EBFWorking volume 9 m³Hearth diameter 1.4 mWorking height 6.0 m3 Tuyeres 54 mmMax. top pressure 1.5 barThroat diameter 1.0 m

Typical production figuresBlast volume 1700m³/hO2 in blast 25%Blast temp. 1250°CFuel rate 530 kg/tHMTop pressure 1.0 barProduction 36 t/d

Inclined

- 4.3 m

Upper shaft

Lower shaft

-3.45 m

Tuyere-6 m

-1 m

Inclined

- 4.3 m

Upper shaft

Lower shaft

-3.45 m

Tuyere-6 m

-1 m

Technical Data of EBFWorking volume 9 m³Hearth diameter 1.4 mWorking height 6.0 m3 Tuyeres 54 mmMax. top pressure 1.5 barThroat diameter 1.0 m

Typical production figuresBlast volume 1700m³/hO2 in blast 25%Blast temp. 1250°CFuel rate 530 kg/tHMTop pressure 1.0 barProduction 36 t/d

Figure 1: The LKAB’s experimental blast furnace

Figure 2:Schematic diagram of the LKAB’s EBF

4.4.4.4. IronIronIronIron OreOreOreOre ProductProductProductProduct DevelopmentDevelopmentDevelopmentDevelopment

4.1.4.1.4.1.4.1. DevelopmentDevelopmentDevelopmentDevelopment ofofofof thethethethe LKABLKABLKABLKAB AcidAcidAcidAcidPelletPelletPelletPellet[5][5][5][5]

LKAB’s olivine pellets were introduced to themarket in the early 1980s and great successes havebeen attained in commercial blast furnaces with100% olivine pellet operations. For the first timebetter operating results were achieved with pelletsthan with sinter in terms of productivity and fuelrate[5]. Theappropriate highsoftening andmelting propertiesmake it possible forblast furnaces with100% pellet asferrous burden todecrease the fuelconsumption.

At the end of the last century demand on acid pelletswhich could be used together with sinter in mixedburden was quite strong. A new acid blast furnacepellet called KPBA with higher iron content thanprevious acid pellet and appropriate metallurgicalproperties was then designed and tested in thelaboratory. Thanks to the EBF, KPBA was testedand optimized before successfully introducing tocustomers. In the year of 2000, the new product –KPBA with quartzite as main additive and specially

aimed for blast furnace operation with sinter, waslaunched. Table 1presents the major chemicalcompositions of one olivine pellet and KPBA.Currently KPBA has been in regular use inEuropean steel works for more than 10 years. Onceagain, the improved operation stability in theproduction blast furnaces – Table 2, demonstratedeffectiveness of EBF in pellet development at LKAB.

4.2.4.2.4.2.4.2. BurdenBurdenBurdenBurden StructureStructureStructureStructure DevelopmentDevelopmentDevelopmentDevelopment[6][6][6][6]After the KPBA pellet was launched customers werenot 100% convinced by the properties of the newacid pellet, especially one customer demandedfluxed pellet with a basicity of about CaO/SiO2=1.05for use to mix with its own sinter. To fullydemonstrate the fitness of KPBA to the mixedburden with sinter for blast furnace operation trialsof two periods with mixed burdens ofsinter/KPBA/lump ore (SKL) and sinter/fluxedpellet/lump ore (SFL) were carried outrespectivelyat EBF in 2002. To facilitate the evaluation of thetrial results the operational process parameters werekept as identical as possible for two trial periods;and the pellet ratio in the burden mix was about 38%following the customer’s request.

The trial results as shown briefly in Table 3indicated that operation with mixed burden SKL didconsume lesser reducing agents than that with SFL,but still had higher hot metal temperature - Figure 3.Comparisons of other process parameter e.g. top gasutilization, burden descent and permeability of theburden column, etc. also demonstrated a more stableprocess with mixed burden SKL. Therefore, it couldbe concluded that KPBA is indeed a more favorable

Table 1: LKAB’s BF pellets

wt% KPBO KPBA

Fe 66.6 67.1SiO2 2.05 2.30CaO 0.46 0.55MgO 1.55 0.52Al2O3 0.22 0.22

Figure 3: Variations in coke rate and hot metal temp

Table 2: Some comparisions between the EBF and

an industrial BF

EBF (1.2 m) BremenNo. 2 (12m)

KPBO KPBA KPBO KPBA

ηco 45.7 47.2 48.1 48.6

σ(ηco) 2.90 0.7 2.4 2.1

PV bosh 6.6 6.7 6.7 6.7σ(PV 0.25 0.17 0.81 0.66

ηco: Top gas utilization ηco=CO2/(CO2+CO);

σ: standard deviation of ηco

PV bosh: permeability index of burden column

choice in formulating the mixed burden for blastfurnace operation.

Softening and melting tests of mixed burdens usedduring trial excluding the lump ore were performedin the laboratory. In-depth analysis of the EBFprocess phenomena and the laboratory test resultsindicated that when using mixed burden SFL re-solidification of primary slag might have occurred inthe course of slag formation. The reason might bethe gradual reduction of wüstite in the primary slag,and as a result raising melting temperature ofprimary slag. When the re-solidification occurred inthe coke layers around the cohesive zone smoothoperation of the furnace process would be disturbed.After the trials with two types of mixed burden asmentioned above the customer was indeedconvinced by the appropriate properties of KPBAand certainly accepted KPBA as the excellentferrous material in its mixed burden. Actually KPBAhas been in regular use in European steel works formore than 10 years.

4.3.4.3.4.3.4.3. ImprovingImprovingImprovingImproving thethethethe PropertiesPropertiesPropertiesProperties ofofofofOlivineOlivineOlivineOlivine PelletPelletPelletPellet[5][5][5][5][7][7][7][7]

To further improve the performance of a blastfurnace with 100% olivine pellets as the ferrousburden material a new ideas of coating the olivine

pellets with slag formers, which was inspired by the

successful technique of coating direct reduction ironore pellets, was put forward in the year of 2000.After a series of theoretical investigations andlaboratory tests, pellets coated with different fluxmaterials were produced and put into trials atLKAB’s EBF. Table 4 presents a comparison ofsome major process parameters of the trials.

In comparison with the operation of standard olivinepellet – MPBO-3, the performance of the EBF wasindeed improved by the use of the coated olivinepellets. The gas utilization was increased, while thefuel rate was decreased as shown in the table. Thereason could be that the coating materials may haveenhanced the slag formation process in the furnaceand permeability of the burden column.

4.4.4.4.4.4.4.4. TheTheTheThe AggloLabAggloLabAggloLabAggloLabAs well-known the properties of the original iron oreas well as the wet green pellets during theagglomeration process can affect significantly thequality of the final pellet product. To be able toalways supply customers with high quality ironpellet product and to maintain the leading position inthe iron ore market, LKAB in 2011 complementedthe EBF with an Agglomeration laboratory – calledAggloLab in Malmberget. It was expected toconduct cutting-edge research in a modern facilitythat has everything needed, including full-scaleequipment for agglomeration. It will further enhancethe product development process and accelerate thetransfer of know-how from research result to highquality of iron ore pellet products.

Currently the operational areas of the AggloLabcovers:

• Ore preparation – crushing, comminution,screening, separation, concentration,

flotation, dewatering,characteriza-tion, structuralanalysis and ore base inventory

• Agglomeration – micro balling,balling circuit development,oxidation, sintering,development of binding additives,thermo analysis, simulation of

Table 3: Reducing agent consumption

Burden KPBA+sinter

Fluxed P+sinter

Coke rate, kg/tHM 415 421Oil rate, kg/tHM 114 113Red. rate, kg/tHM 529 534EtaCO, % 44.87 43.38Slag rate, kg/tHM 236 236

Table 4.... Some main process parameters in the EBF trials

MPBO-3 MPBO-O MPBO-D MPBO-Qηco 46.8 47.2 48.2 47.0PV bosh 8.9 9.0 8.3 8.3Prod., t/m³⋅d 4.18 4.25 4.37 4.15Fuel rate, kg/tHM 552 541 537 549

firing process, coating• Training – of process engineers, process

operators, junior researchers etc.

In the near future, an experimental pelletizing plantand probably also an experimental direct reductionplant, will be constructed too. The world-classunique leading product development for iron orepellet will be formulated.

5.5.5.5. SummarySummarySummarySummaryDuring the last decade LKAB, as the world leadingiron ore product producer and supplier, has putconsiderable efforts on the product development.The erection of the EBF® in 1997 and its useafterwards for exploring the optimized pellet qualityas well as the burden structure for blast furnaceironmaking process have given great helps forLKAB in developing new iron ore pellet productsand in the meantime enhancing properties of theexisting pellet. As a result, LKAB currently is ableto supply the steel industry with world’s best ironore product package, enabling the optimal functionof the modern, larger and fewer blast furnaces ofsteel producers.

To satisfy the customers’ further demands on ironore pellet products, an AggloLab was started to buildin 2011 and will be commissioned soon. Anexperimental pelletizing plant and maybe anexperimental direct reduction plant will beconstructed too. A world leading research centre foriron ore product development and for testing themodern ironmaking technology will be erected atLKAB.

ACKNOWLEDGEMENTSACKNOWLEDGEMENTSACKNOWLEDGEMENTSACKNOWLEDGEMENTSThe authors are grateful to all colleagues and staff atLKAB, MEFOS and project partners as well ascontractors that contributed to the EBF operationand campaigns.

ReferencesReferencesReferencesReferences[1] M. Tottie, “LKAB’s Experimental Blast

Furnace at MEFOS”, 1998ICSTI/Ironmaking Conference Proceedings,

vol 57, Toronto, Ontario Canada 1998,pp1587-1590

[2] A. Dahlstedt, M. Hallin and M Tottie;“LKAB’s Experimental Blast Furnace forEvaluation of Iron Ore Products”,Proceedings of Scanmet 1, 1999, Luleå, pp.235-245

[3] J. Sterneland and P-G. Jönsson; “The Use ofCoated Pellet in Optimising the Blastfurnace Operation”, ISIJ International, Vol.43 (2003), No. 1, pp26-35

[4] U Leimalm, L Sundqvist, A Brännmark andBo Björkman; “Correlation Between PelletReduction and Some Blast FurnaceOperation Parameters”,AISTech 2006Proceedings - Volume 1, pp 39-50

[5] M. Hallin, L. Hooey, J. Sterneland and D.Thulin; “LKAB’s experimental blastfurnace and pellet development”, La Revuede Métallurgie, April 2002, pp. 311-316.

[6] Eklund N.: Trials with mixed burden in theLKAB’s experimental blast furnace;ScanMet II, 2nd International Conference onProcess Development in Iron andSteelmaking, June 6-9, 2004, Luleå Sweden

[7] Hallin M.; BF Inside Story ThroughQuenching; John Floyd InernationalSymposium on Sustainable Developmentsin Metals Processing, 3-6 july, 2005,Melbourne Australia