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?