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    Slag Lecture

    Uploaded by

    Jojo Hany
    * Magnetite contains 95% Fe3O4 and 5% impurities * 1 ton of metallic iron requires: - 3.4 tons of Fe3O4 (since Fe3O4 produces 1 ton of Fe upon reduction with H2) - 3.4 * 0.05 = 0.17 tons of impurities * Therefore, the total quantity of magnetite required is: - Fe3O4 required = 3.4 tons - Impurities required = 0.17 tons - Total magnetite required = 3.4 + 0.17 = 3.57 tons Therefore, the quantity of magnetite containing 5% impurities required for the production of 1 ton of metallic iron is 3.

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    Slag Lecture

    Uploaded by

    Jojo Hany
    23 views39 pages
    * Magnetite contains 95% Fe3O4 and 5% impurities * 1 ton of metallic iron requires: - 3.4 tons of Fe3O4 (since Fe3O4 produces 1 ton of Fe upon reduction with H2) - 3.4 * 0.05 = 0.17 tons of impurities * Therefore, the total quantity of magnetite required is: - Fe3O4 required = 3.4 tons - Impurities required = 0.17 tons - Total magnetite required = 3.4 + 0.17 = 3.57 tons Therefore, the quantity of magnetite containing 5% impurities required for the production of 1 ton of metallic iron is 3.

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    the role of the slag

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    * Magnetite contains 95% Fe3O4 and 5% impurities * 1 ton of metallic iron requires: - 3.4 tons of Fe3O4 (since Fe3O4 produces 1 ton of Fe upon reduction with H2) - 3.4 * 0.05 = 0.17 tons of impurities * Therefore, the total quantity of magnetite required is: - Fe3O4 required = 3.4 tons - Impurities required = 0.17 tons - Total magnetite required = 3.4 + 0.17 = 3.57 tons Therefore, the quantity of magnetite containing 5% impurities required for the production of 1 ton of metallic iron is 3.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    23 views39 pages

    Slag Lecture

    Uploaded by

    Jojo Hany
    * Magnetite contains 95% Fe3O4 and 5% impurities * 1 ton of metallic iron requires: - 3.4 tons of Fe3O4 (since Fe3O4 produces 1 ton of Fe upon reduction with H2) - 3.4 * 0.05 = 0.17 tons of impurities * Therefore, the total quantity of magnetite required is: - Fe3O4 required = 3.4 tons - Impurities required = 0.17 tons - Total magnetite required = 3.4 + 0.17 = 3.57 tons Therefore, the quantity of magnetite containing 5% impurities required for the production of 1 ton of metallic iron is 3.

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    Outline

    The role of the slag phase in steelmaking


    Discussion of slag fundamentals
    Application of slag fundamentals to steelmaking
    Conclusions
    The importance of the slag phase

    Good steelmaking Good slag making

    Take of the slag and the steel will take care of


    itself

    Tools for good slag practices:


    Mass balance calculations for accurate estimations
    of slag compositions
    The role of the slag in steelmaking:
    Insulate the bath, maintaining steel temperature,
    chemistry and reduced off-grade heats.
    Protect the steel from oxidation and help to
    control steel chemistry
    Dephosphorization and desulfurization of steel
    Stabilize the arc to protect the refractory and sides
    from arc flare damage (EAF and LRF)
    Be compatible with the refractory material to
    minimize chemical erosion of the lining
    Good foaming slag reduces the amount of slag required to
    cover the arc, resulting in cost reductions in fluxes, slag
    handling, and electrical energy by reducing the heat loss to
    slag.
    Slag - Metal Reactions:

    Mn MnO + Fe
    Si SiO2 + Fe
    FeO +
    Al Al2O3 + Fe
    CaC2 CaO + Fe + CO(g)

    Si SiO2 + Mn
    MnO + Al Al2O3 + Mn
    CaC2 CaO + Mn + CO(g)

    SiO2 + Al Al2O3 + SiO(g)


    Al2O3 + [Si]
    Slag/Metal Interactions:

    FeO
    MnO SiO2

    Slag FeO, MnO, SiO2

    Metal Al, Si, Mn


    Slag/Metal Interactions:
    FeO

    Slag

    Metal Al, Si, Mn


    Slag/Metal Interactions:

    FeO

    Slag

    Metal Al, Si, Mn


    Slag/Metal Interactions:

    FeO

    Slag

    Al, Si, Mn
    Metal
    Slag/Metal Interactions:
    Al2O3
    SiO2
    MnO
    FeO

    Al, Si,
    Fe Mn
    Slag

    Metal
    (burp!)

    Fe Al2O3
    SiO2, MnO
    Slag

    Metal
    Slag/Metal Interactions:
    MnO

    Slag

    Metal Al, Si, Mn


    Slag/Metal Interactions:

    MnO

    Slag

    Metal Al, Si
    Slag/Metal Interactions:

    MnO

    Slag

    Al, Si
    Metal
    Slag/Metal Interactions:
    Al2O3
    SiO2
    MnO

    Mn Al, Si

    Slag

    Metal
    (hic!)

    Mn Al2O3
    SiO2
    Slag

    Metal
    Slag/Metal Interactions:
    SiO2

    Slag

    Metal Al
    Slag/Metal Interactions:

    SiO2

    Slag

    Metal Al
    Slag/Metal Interactions:

    SiO2
    Slag

    Al
    Metal
    Slag/Metal Interactions:

    Al2O3
    SiO2

    Al
    Si

    Slag

    Metal
    Si
    Al2O3
    Slag

    Metal
    Typical slag components
    Oxide Melting Point (C) Optical Basicity
    SiO2 1720 0.48
    CaO 2600 1.0
    MgO 2800 0.78
    Al2O3 2030 0.61
    FeO 1370 0.51
    MnO 1850 0.59
    Cr2O3 2260 0.55
    CaF2 1420 0.67
    Fluxes for MgO and CaO

    Possible fluxes for MgO and CaO are:


    SiO2
    Al2O3
    CaF2
    FeO
    Fluxing is necessary to form liquid slags at
    steelmaking temperatures
    MgO MgO
    MgO MgO
    MgO slag MgO slag
    MgO CaO, SiO2 MgO MgO, CaO, SiO2
    MgO 1600 C MgO 1600 C
    Melting point Melting point
    1350C 1450C
    Melting Point Melting point
    2800C 2800C

    MgO
    MgO slag
    MgO MgO CaO, SiO2
    MgO MgO 1600 C
    MgO Melting point
    1350C

    Melting Point formation of low


    2800C melting phases
    Slag : Balance of refractory and fluxing oxides

    Refractory Oxides Fluxing Oxides


    (CaO & MgO) (SiO2, Al2O3, CaF2)
    Good foamy slag can be controlled by HBI
    continuous feeding
    Too much CaO and MgO

    Fluxing Oxides

    Refractory Oxides
    Too little CaO and MgO

    Refractory Oxides

    Fluxing Oxides
    Balance of refractory and fluxing oxides

    Refractory Oxides Fluxing Oxides


    (CaO & MgO) (SiO2, Al2O3, CaF2)
    Slag Requirements:
    High fluidity, but not watery - Slags with a
    creamy consistency

    Saturated with refractory oxides to minimize


    chemical wear

    Maximum amount of dissolved lime for optimum


    desulfurization and inclusion removal
    Consider the balance again:

    Refractory Oxides Fluxing Oxides


    (CaO & MgO) (SiO2, Al2O3, CaF2)
    The use of CaF2 and SiO2 as fluxes

    Fluorspar is very effective to bring lime in


    solution. However, it is equally effective in
    bringing MgO into solution.

    If MgO is not added as a flux it will be dissolved


    from the refractories.

    The addition of Al2O3 increases the solubility


    of CaO in the slag but it also decreases the
    solubility of MgO in the slag.
    The composition of a slag is usually expressed in terms of the
    component oxides (or flourides) on
    a weight percent basis. For example a slag could have the following
    composition:
    wt% CaO 55
    wt% SiO2 20
    wt% MgO 8
    wt% Al2O3 12
    wt% CaF2 5
    Where do these components come from?
    CaO - Lime (98 % CaO)
    - Dolomite (58 % CaO & 39 % MgO)
    - Ca-Aluminate (45% CaO & 53% Al2O3)
    - Refractories (dolomite)
    MgO - Dolomite (58 % CaO & 39 % MgO)
    - Magnesia (> 92% MgO)
    - Refractories (Mag-C & Dolomite)
    SiO2 - Oxidation of the Si in the scrap (Si + O2 = SiO2)
    - Steel deoxidation (2O + Si = SiO2)
    - Sand and dirt
    - Refractories (High Alumina)
    Al2O3 - Oxidation of the Al in the scrap (2Al +3/2O2 = Al2O3)
    - Steel deoxidation (3O + 2Al = Al2O3)
    - Ca-Aluminate (45% CaO & 53% Al2O3)
    - Bauxite (>80% Al2O3)
    - Refractories (High Al2O3 sidewalls & bottoms)
    FeO - Scrap (2Fe + O2 = 2FeO)
    MnO - Scrap (2Mn + O2 = 2MnO)
    - Steel deoxidation (O + Mn = MnO)
    CaF2 - Fluorspar (90% CaF2)
    The mass-balance approach is used to calculate contributions of the various
    components.
    CaO Contributions
    Lime: 700 x 1 = 700
    Dolomite: 500 x 0.6 = 300
    Ca-Aluminate: 500 x 0.45 = 225
    1225
    MgO Contributions
    Dolomite: 500 x 0.4 = 200
    Al2O3 Contributions
    Ca-Aluminate: 500 x 0.55 = 275
    Steel deoxidation 340 x 0.75 x 1.89 = 485
    760

    Total Slag Amount: 1225 + 200 + 760 = 2185


    % CaO = 1225/2185 x 100 = 56.1
    % MgO = 200/2185 x 100 = 9.1
    % Al2O3 = 760/2185 x 100 = 34.8
    Calculate the quantity of pure CaCo3 required
    to produce 1 ton of Cao .
    The atomic mass of Ca, C and O are
    40.1,12,and 16.
    Estimate the quantity of magnetite contains
    5% impurities (SiO2,CaO,MgO,Al2O3)
    required for the production of 1 ton metallic
    iron. Consider the reduction done by using
    H2.

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