Principles of IronmakingSung-Mo JungGraduate Institute of Ferrous TechnologyPohang University of Science and Technology(1/58)Course(Chapter1-An outline of the process)

Iron and Steelmaking Processes(4/58)

Production Flow of Steel Product

Fine OreCoalSinteringCoke makingBlast Furnace OperationIron Ore Blast furnace Ironmaking ProcessSintered Ore Coking CoalCoke

(Molten Iron)(Hot Metal)(Pig Iron)(Vergin Iron)

Raw Materials & Blast Furnace FINEX ProcessIronmaking Technology

OrePelletClassifier Fine CoalPellet(Import)p/pLumpy CoalShaft FurnaceMelter GasifierO2OreBriquetterPCIp/pBriquetted CoalFluidized ReactorMelter GasifierO2PCI HCI (Hot Compacted Iron)Fine ore< COREX >< FINEX >CO2 removall Steaming Coal Steaming Coal New Ironmaking Process Technology

Principles of IronmakingObjectives Easy understanding of complicated processes occurring in the BF To determine from theory as well as from practice the ways and means of increasing blast furnace productivity To briefly familiarize the reader with the process of ironmaking in the blast furnace

Contents Outline of the process Physico-chemical principles Systems of importance in ironmaking The temperature profile Raw materials and their properties Reactions in the blast furnace Blast furnace slags The removal of sulfur The coke rate and fuel efficiency Blast furnace productivity RIST diagram Materials and Heat Balances

Blast Furnace High production rate: 12,000 THM per day Efficient counter-current heat exchanger: 85-90% of heat utilization Source of ironClassification of iron ore

Source of IronOxide Hematite (For pure hematite, Fe content: 70%) Magnetite (For pure magnetite, Fe content: 72.4%) Limonite: 2Fe2O33H2O (T.Fe=60%)Rich ore (T.Fe=50-65%)Hydroxide Goethite: FeO(OH)Carbonate Siderite: FeCO3 (T.Fe=48.3%)Lean ore (T.Fe=30-50%)Sulfide Pyrites: FeS2 (T.Fe=46.6%) Pyrrhotite: FeS (T.Fe=63.5%)

Section of Iron Blast FurnaceBurden charging part[charge cycle, stock line, bell rim(=rip)] Shaft (Refractory: Fire-clay brick)Hearth (Refractory: Carbon brick) (Mag-C)

Temp. distribution of gas & solids

Reactions in the Upper zone Upper zone Called preheating or preparation zone Temp. of the gas ascending from the middle zone falls rapidly from 800 -1000oC to 100-250oC Main reactions in the upper zone Decomposition of carbonates other than that of Ca Vaporization of moisture and hydrated water of the burden Carbon deposition: 2CO=CO2+C Partial or complete reduction of hematite and magnetite to their lower oxides

ReactionsCO/CO201000.2580

Reactions in the Middle zone Middle zone Temp. of the solids and gas are near identical (800-1000oC) Called isothermal or thermal reserve zone Chemical inactive zone: Very little oxygen between the ore and the gas Water-gas shift reaction CO+H2O=CO2+H2

ReactionsCO/CO22.330

Reduction of Iron oxide in upper & middle zone Equilibrium at 900oC CO-utilization factor

ReactionsCO/CO201000.25802.330

Reactions in the lower zone

Reactions in the lower zone Compositional change of BF slags

CompositionSlagBasicityLiquidus temp.FeO-SiO2-Al2O3-MnOPrimary slagVery high1200CaO-SiO2-Al2O3-MnOBosh slag1.5-1.61250-1350CaO-SiO2-Al2O3-MgOHearth slag0.9-1.21400-1450

Reactions in the lower zone Important chemical reactions in the lower zone

NameChemical reactionsEndothermic or exorthermicCalcination of limestoneCaCO3=CaO+CO2EndothermicDirect reduction of FeOFeO+C=Fe+COEndothermicDirect reduction of SiO2SiO2+2C=Si+2COEndothermicDirect reduction of MnOMnO+C=Mn+COEndothermicDirect reduction of P2O5P2O5+5C=2P+5COEndothermicSulfur removalFeS+CaO+C=CaS+Fe+COEndothermicCombustion of carbonC+O2(air)=CO2+N2ExothermicReduction of CO2CO2+C=2CO(1000oC)EndothermicReduction of moistureH2O+C=CO+H2(1000oC)endothermic

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