2.4 yilmaz glass defects heavy minerals
TRANSCRIPT
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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?