2.4 yilmaz glass defects heavy minerals

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  • 8/17/2019 2.4 Yilmaz Glass Defects Heavy Minerals

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    "Glass Defects Related with Heavy

    Mineral & Clay Bearing Raw Materials"

    Sener YILMAZ , E.Burak IZMIRLIOGLU

    Glass Research Center  

    Glass Trend Istanbul Seminar4  – 6 November 2013, Turkey 

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    OUTLINE

    Chromite stones originated from sand

    Zircon stones originated from feldspar

    Quartz-Mullite  defects originated from

    clay (kaolinite) in sand

    Conclusion

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     Chromite stones originated from sand 

    Chromite [Fe,Mg) (Cr, Al, Fe)2O4 ] :

    occurs especially in ultramafic rocks (i.e.,

    peridotite, ophiolite)

    has a density of 4.5 - 4.8 g/cm3

    has a melting point of 1850 –

     2200 0C 

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    Case:  Chromite inclusions in float glass due to

    silica sand containing coarse chromite grains.

    History: Silica sand used in float glass batch has been

    mined from sandstone deposit.

    Chromites were concentrated with quartz inlarge amounts during the formation of the

    deposit by sedimentation process. 

    Chromite stones originated from sand 

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     Chromite stones originated from sand 

    SEM-SEI image of chromite stone defects in float glass

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      Na2O MgO Al2O3 SiO2 Cr2O3 Fe2O3

    Chromite (%) 0,34 13,18 7,22 1,92 66,68 10,66

    Chromite (%) 0,58 13,44 7,49 3,33 68,6 6,55

    Chromite(%) 0,35 12,82 7,74 1,72 66,37 11

    Chromite (%) 0,55 13,71 8,16 3,21 69,26 5,11

    Chromite stones originated from sand 

    EDS analysis of some chromite stones in float glass

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     Chromite stones originated from sand 

    SEM-SEI images of some rounded chromite grains in silica sand

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     Chromite stones originated from sand 

    EDS analysis of some chromites (Mg-Chromites)in sand

    MgO Al2O3 Cr2O3 Fe2O3

    Chromite (1) 7.68 16.18 60.94 14.45

    Chromite (2) 2.93 12.54 53.75 29.31

    Chromite (3) 10.02 22.94 42.32 23.35

    Chromite (4) 5.69 13.68 47.31 31.17

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     Chromite stones originated from sand 

    Melting Behaviour of A Single Chromite GrainIn Glass Melt

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     Chromite stones originated from sand 

    Particle size

    (µm)

    Chromitespecification

    (Number / ton)

    Chromite grainsin silica sand

    (Number / ton)

    + 400 0 20

    + 300 40 300

    + 200 1000 1500

    Specifications for chromite in float glass sandvs.

    chromite grains in silica sand (sandstone)

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     Chromite stones originated from sand 

    Cure: To remove chromite particles from sand 

    Reduce product size of sand below to 0.400 mm 

    Use gravity separation techniques

    (i.e., Humphrey Spiral)

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    Humprey Spiral is the most effective gravity

    separation technique for removing of chromite

    mineral from sand.

    Chromite stones originated from sand 

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     Zircon stones originated from feldspar  

    Zircon (ZrSiO4):

    Its small crytals can be found in all type rocks (igneous,

    metamorphic and sedimentary ) as accessory mineral

    Its large crytals (up to 1 cm) occur especially in

    pegmatites and granites (Nepheline syenite)

    Has a density of 4.6 –

     4.7 gr/cm3

    Has a melting point of over 2500 0C (It dissociates to

    zirconia and quartz over 1550 0C)

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     Zircon stones originated from feldspar  

    Case: The brekage of bottles during pressuretests because of coarse zircon inclusion.

    History: Nepheline syenite, like feldspar, supplies

    alumina and also provides alkalis that act as a

    flux to lower the melting temperature in

    glassmaking. It is a kind of feldspathic rock. 

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     Zircon stones originated from feldspar  

    SEM-SEI image and EDS analysis of zirconinclusions in green bottle samples.

    Formula Zircon stone (%)  

    SiO2 31.11

    ZrO2 68.89

    Formula Zircon stone (%)  

    SiO2 30.88

    ZrO2 69.12

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     Zircon stones originated from feldspar  

    Mineralogical investigation results show that

    feldspar contains:

    ~ 20 free zircon grains, which is coarser than0.500 mm, per 1 kg feldspar

    Grain size distribution of zircon in feldspar is between

    0.4 –

     0.7mm (mostly coarser than 0.5 mm)

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     Zircon stones originated from feldspar  

    Zircon stone inclusions due to feldspar which ismined from nepheline syenite deposit.

    a b

    a) Free zircon grains

    b) Nepheline syenite rock fragments

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     Zircon stones originated from feldspar  

    X-ray elemental mapping of coarse zircon grains

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     Zircon stones originated from feldspar  

    Cure:

    The most effective and economic way is

    to reduce product size of feldsparbelow to 0.400 or 0.500 mm to preventcoarse zircon grains from entering furnace

    with feldspar. 

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    Kaolinite [Al2Si2O5(OH)4]:

    One of the member of kaolinite group (kaolinminerals)

    Formed by the alteration of feldspars in granites or

    extrusive igneous rocks either hydrothermally or by

    weathering  On heating up to 1000 ºC, the mullite phase is

    formed

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    Case: Quartz  –  Mullit inclusions in float glass

    ribbon due to high content clay (kaolinite) in glass

    sand.

    History: Glass sand produced from sandstone

    which contains high content kaolinite (~ 5 % wt).

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    Stone

    (Quartz)

    (%)

    Knot

    (Mullite)

    (%)

    Na2O 0.53 6.72

     Al2O3  0.66 13.4

    SiO2  98.68 79.0

    K2O -- 0.49

    CaO 0.13 --

    Microanalysis of quartz  – mullite inclusion

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    Thermal Behaviour of Kaolinite Clays

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    Al2O3 SiO2Na2O

    + K2O

    Fe2O3 TiO2 CaO + MgO L.O.I

    2.1  – 2.3 95 - 96 0.2  – 0.8 0.1 0.05 0.2 0.6  – 0.9

    Chemical composition of glass sand (% wt)

    Mineralogical composition of glass sand (% wt)

    QUARTZ CLAY FELDSPAR OTHERS

    93 % 5 % 1 % 1 %

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    Mineralogical analysis shows that glass

    sand is a kind of «kaolinitic sand»,

    NOT

    a feldspathic sand.

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    SEM image of fine kaolinite particles coating on

    quartz grains

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     Quartz  –  Mullite defects originated

    from clay (kaolinite) in sand 

    Cure: To remove clay particles from sand, some

    mineral processing techniques can be applied in

    the plant.These techniques are namely,

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    Scrubbing

    Attrition scrubbers

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    Classification & Separation

    Hydrocylones

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    Drying & Screening

    Vibrating Sieves

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     Conclusion 

     Apart from incompletely melted quartz

    grains, "heavy minerals" and "clays" may

    also precipitate the formation of stones

    that originate in the glass raw materials.The most harmful minerals are especially

    those

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     Conclusion (1) 

    that dissolve in the glass at a slower

    rate than the quartz ,

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     Conclusion (2) 

    that are transformed into chemically

    more resistant phases at high

    temperatures (kaolinite mullite)

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     Conclusion (3) 

    That release low-solubility components

    into the glass during their dissolution

    ( chromite escolaite)( zircon zirconia + quartz)

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    THANK YOU !

    Questions?