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Selective Glass BatchinggTo Dramatically Reduce Batch Free Time in Commercial Glasses
William CartyCh i t h Si tChristopher Sinton
Hyojin Lee
“The Shining Inferno –a Symposium on Glass Raw Materials”Glass Manufacturing Industry Council
20 October 2011Columbus OHColumbus, OH
IntroductionGlass batch reactions and refining are
inefficient processesinefficient processes. Theoretically, the energy required for melting
and refining (from batch to glass) should beand refining (from batch to glass) should be 2.2 million Btu/ton (energy consumption today: 5.5-8.6 MBtu/ton). ( gy p y )
Dramatic improvements in batch reaction ffi i ( d lt h it ) iblefficiency (and melt homogeneity) are possible by controlling reaction paths and reducing
segregationsegregation.
ClarificationThis is not briquetting or pelletizing. This is “selectively batching” to control
reaction pathways, by granulating a portion of the batch.
Also, this is not about the glass chemistry but the raw materials.
Typically the same raw materials, but there may be a reduction in particle size y pnecessary for granulation.
Typical Reaction Paths (assumed)
(Added as CaCO3)CaO
Typical ContainerGlass Composition
SiO2(Added as Quartz)
Na2O(Added as Na CO ) (Added as Quartz)(Added as Na2CO3)
Typical Reaction Paths(Added as CaCO3)
CaO
ReactionPath 1
Typical ContainerGlass Composition
EutecticPath 1
ReactionPath 2
Eutectic
Na2O(Added as Na CO )
SiO2(Added as Quartz)(Added as Na2CO3) (Added as Quartz)
Control reaction paths?pNa2CO3 + CaCO3 form a low viscosity
(4 mPa·s) eutectic melt ~780°C(4 mPa s) eutectic melt 780 C.Segregation of fluxes (low viscosity liquid)
from silica early in the reaction processfrom silica early in the reaction process. Proposed to prevent the reaction between
Na CO and CaCONa2CO3 and CaCO3
Force Na2CO3 to react first with SiO2.
A similar approach for borosilicate glasses (force reactions that create a higher viscosity borate liquid).
Forced Reaction Pathsvia Selective Batchingvia Selective Batching
(Added as CaCO3)CaO
ReactionPath 1b
Eutectic
Path 1b
ReactionPath 2
Eutectic
ReactionPath 1a
Na2O(Added as Na CO )
SiO2(Added as Quartz)Eutectic(Added as Na2CO3) (Added as Quartz)Eutectic
Two routes“Full Selective Batching”
Granulate both halves of the batch.Granulate both halves of the batch. Blend granulate prior to melting.
G1 + G2
“Partial Selective Batching”Granulate one half of the batch. Blend granulate with the balance of the
b h i l ibatch prior to melting.Batch balance = “matrix”
G1 + MG1 + M
Systems (evaluated using crucible melts)
System Generic Specific Success?
Container YesContainer es
Float Yes
Fiber (i l ti ) A ltFiber (insulation) Arc melt
Fiber (reinforcement) Yes
Flat Panel Display Yes
Nuclear Waste In discussion ??
Bio-Glass (45S5) Unclear
Art Glass UnclearArt Glass
Large melt trialsE-glass
UMR (2006)pilot scale, mimic tank, batchp
Container glassContainer glass Industrial partner (2011)500k t k500kg tank continuous feed/pull
Determining “Batch Free Time”g
Conventional batch and selective batch.Granules via dry pelletizing.25g & 2 kg crucibles 60 kg furnace25g & 2 kg crucibles, 60 kg furnace
melts.Temperature: 1350°CTemperature: 1350 CCrucibles or samples removed at various
intervals cooled and visually evaluatedintervals, cooled, and visually evaluated for evidence of reaction completion.
Example: Container (generic)(Na2CO3 + quartz) and (CaCO3 + quartz)
Mass Mole
Glass CompositionConventional, coarse
ass(%)
o e(%)
SiO2 75.1 71.6
Bat
ch
Selective (Full, Spray Dried; 12.5%)
Conventional, fine Unreacted batch at top
Na2O 14.3 13.2
CaO 10 7 15 2
B
Selective (Partial A granulated; 22%)
Selective (Full, Granulated; 15%)
CaO 10.7 15.2
Batch Free Time (minute)0 50 100 150 200 250
Selective (Partial, A, granulated; 22%)
SB ≡ Selective Batch
Approach for E-GlassApproach for E Glass
Two ternaries:
CaO-B2O3-SiO2
CaO-Al2O3-SiO22 3 2
Granule #1 Phase Diagramde
al
gch
ing
IdR
egio
nve
Bat
cor
king
RSe
lect
ivW
o
n 10% Al2O3
18 5% Al OGranule #2R
egio
nio
n)
18.5% Al2O3
33% CaO
erat
ure
mpo
siti
66.5% SiO2
Tem
peon
Com
49.5% SiO2
fera
ble
(Bas
ed
Pref (
Composition 280
Granule #1 Granule #2Granule #1 Granule #2
1:2.86
SB Composition #280; 1300°C
½ hour 1 hour 1½ hours 2 hours 2½ hours
3 hours
B.F.T. Reduction E-Glass
Total batch granulation
Conventional
Total batch granulation
E-Glass Granule #114% W t14% Water1% Na-SilicateEirich TV-02
1 mm
1 mm
Proposed reaction pathsp pConventional batch allows preferential
reaction between Na CO and CaCOreaction between Na2CO3 and CaCO3and gross segregation.
Boron segregation in borosilicate glasses promotes crystallization (anorthite).
Nepheline formation in nuclear waste glasses. Crystallization in a melt is evidence of
segregation.segregation.
Binary Reactions between N CO & C CONa2CO3 & CaCO3
1 hour at 800°C
2 hours at 800°C
1 hour at 800°CMelted shell
Crystalline corey
Particle Size Effects on BFT for E-Glass
Effect of particle size on melting time) 500
600(m
inut
es)
400
500B.F.T. = 20.519*e(0.0092*M.P.S.)
R2 = 0.9744
ree
Tim
e (
300
Bat
ch-F
r
100
200
0 50 100 150 200 250 300 350 4000
Mean Particle Size (m)
Optical Artifacts and Unreacted Batch Materials
0.5 cm0.5 cm
A B 0.5 cm
Optical Artifacts and Unmelted Batch Materials
0.5 cmA B 0.5 cm
Batch-Free Range Endpoints
Glass Quality: Refractive Index
Oil immersion test vian
C ti l E Gl 1 490Oil immersion test via optical microscopy(Becke line method)
Conventional E-Glass 1.490Selective Batched E-Glass 1.490Total granulated E-glass 1.490
Refractive index oils:
Average of five samplesNegligible standard Deviation
n=1.400 to 1.800
Index of Refraction
Independent benchmark
Glass powder usedFive random samples
Index of RefractionAlumina 1.740Silica 1.546Kaolin A 1.554p Kaolin A 1.554Kaolin B 1.554
Partial Selective BatchingPartial Selective BatchingGranulate to produce only G1 p y
(Typically, Na2CO3 + SiO2) Could also include minority additivesCould also include minority additives.
Most economical approach.G1 made on-site (ideal).Overall composition still controlledOverall composition still controlled
internally.
Partial Selective Batching, 4 hrs, 1350°CA C
Selective BatchingPartial Batching
G1 + coarse M (CaCO3+Quartz)
B
Traditional
Concerns & Potential Problems
Refractory “matrix” can lead to sintering lid t t ti ( t bl h )or solid-state reaction (→stable phase)
thwarting reaction/melting.Poor mixing/distribution of G1 can lead to
long diffusion paths and the potential for gsegregation.
Granulation may be expensive;Granulation may be expensive; the volumes are huge!
Obstacles (granulation)Primary Issues
SecondaryIssues
Minor IssuesIssues Issues Issues
Volume of material
Granulation efficiency / PSD
reductionmaterial ylosses reduction
C it l t Need for Granulate Capital cost Need for
binders size and distribution
Granulate strength
Granulate Drying
GranulationInitial work with spray drying b t t ibut too expensive
Granulation done using modified high intensity mixersmodified high-intensity mixers
Lower energy needs
Requires finer particles for flat/container glass
R id b t h i i 10 iRapid batch mixing ~10 min.
FiningSmaller bubbles formed, but volume of gas
i i ilis similar. Uniform distribution of bubbles in the melt,
versus “bubble gaps” and concentration gradients.
Foam formation reduced or eliminated. SB glass significantly more homogeneousSB glass significantly more homogeneous. Did not evaluate fining agents.
Bubble Distributions60
Conventional
3 Hours 1450°C
ht (m
m)
30
40
50
Selective Batch
3 Hours, 1450 C
3 hoursn = 432
Hei
gh
10
20
40
50
60
n 432
Bubble Diameter (mm)
0.0 0.1 0.2 0.3 0.4 0.50
Hei
ght (
mm
)20
30
3 hours n = 588
Bubble Diameter (mm)
0.0 0.1 0.2 0.3 0.4 0.50
10
“Bubble gap”
Bubble Distributions60
Conventional
5 Hours 1450°C
Hei
ght (
mm
)
30
40
50
Selective Batch
5 Hours, 1450 C
Bub
ble
H
10
20
5 hoursn = 434 m
m)
40
50
60
Bubble Diameter (mm)
0.0 0.1 0.2 0.3 0.4 0.5 0.60
n 434
5 hours
Bub
ble
Hei
ght (
m20
30
5 hours n = 517
Bubble Diameter (mm)
0.0 0.1 0.2 0.3 0.4 0.5 0.60
10
Summary and Conclusions
Dramatic reductions in BFT were observedSelective batching controls reaction paths and
prevents segregation during melt reactions by idi th f ti f l i it li idavoiding the formation of low viscosity liquid.
Particle size needs to be reduced and t ib t t d ti i BFTcontributes to reduction in BFT
Major obstacle to implementation appears to be l ti f th l i l dgranulation of the volumes involved.
Questions?Questions?