Refractory application for extreme firing condition in … application for extreme firing condition in the regenerator of glass melting furnaces Sandra ... Magnesia 97 direct bonding

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Refractory application for extreme firing condition

in the regenerator of glass melting furnaces

Sandra Fischer, Rongxing Bei, RHI Glas GmbH, Germany

For part of “thermal chemical regenerator”: Joaquín de Diego, Praxair, Inc., USA

2017 ICG Annual Meeting & 32nd Şişecam Glass Symposium, Istanbul, October 22-25th 2017

Refractory for extreme firing condition in regenerator

2017 ICG Annual Meeting & 32nd Şişecam Glass Symposium, Istanbul, Oct 22-25th 2017

Content

• Pet-coke firing

• Sodium silicate glass

• Thermal chemical regenerator

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Content

• Pet-coke firing



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Pet-coke firing

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Sample 1 Sample 2 Sample 3 Sample 4 Sample 5

Cr2O3 11.9 9.0 1.1

Fe2O3 24.9 14.3 20.9 11.0 9.8

NiO 7.6 6.7 6.7 4.4

V2O5 30.1 7.3 29.3

From the pet-coke ash:

High amount of Cr, Fe, Ni, and V

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Pet-coke firing

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V2O5 total in flue gas (Kg / ton glass)



Pet-coke firing

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Problem for glass production The unburned pet coke powder can go into the regenerator,

A re-firing within regenerator can happen:

High temperature and strong thermoshock

Destruction of the regenerator crown, wall and checker



Pet-coke firing

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Magnesia Zircon (RUBINAL VZ) :

Forsterite formation during brick production

ZrSiO4 + 2MgO Mg2SiO4+ ZrO2

Protection of the Periclase (1) by matrix out of Forsterite and ZrO2



Pet-coke firing

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Example Magnesia zircon brick (Rubinal

VZ) shows corrosion of half

layer after 6 years



Pet-coke firing

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Corrosion Test

Hot face not corroded

excellent resistance against carryover and V2O5

Chrome corundum with 10% Cr2O3 (DURITAL RK10)



Pet-coke firing

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Corundum (1) is protected by chrome corundum solid solution (2)



Pet-coke firing

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Checker Lining Recommendation

Top Layer: Magnesia Zircon and Chrome Corundum

Hot zone (>1100 °C): Magnesia Zircon

DURITAL RK10

RUBINAL VZ



Content

• Pet-coke firing



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Sodium silicate glass

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Component ratio

SiO2 : Na2O

Name

3,9 to 4,1 High silicic acid water glass

3,3 to 3,5 Neutral soda glass

2,0 to 2,2 Basic water glass

Sodium silicate (water glass):

Amorphous melts of alkali silicates

Waste Gas containing:

NaOH (gas firing)

Na2SO4 (oil firing)




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For gas firing:




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Gas firing:

Condensation zone,

MgO (ANKER DG1)

After 5 years




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NaOH had no effect on MgO – it entered

the Magnesia-crystal to form a „ring“ on

the surface




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Oil firing:

Condensation zone,

magnesia-Zircon

After 12 years




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1: cavity

A and B:

matrix of forsterite and

ZrO2

C: ZrO2

Even after 12 years of

application the matrix

has done a good job!




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Content

• Pet-coke firing



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Process of thermochemical regenerator

CH4, H2O, CO2, CO and H2 exist in

different height of checker work

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Test setup

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Test setup

Different refractory samples

• installed in doors

• installed in ports

• for 8 months

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Refractories in the temperature-range of 1150-1200°C

All wall samples containing

mullite:

zirconia mullite

fused mullite

sintered mullite

are damaged!

Reason:

Na2O (out of waste gas) +

Mullite

Nepheline formation

zirconia mullite

Baddeleyite, syn ZrO2 +++

Corundum, syn Al2O3 +++

Mullite, syn Al6Si2O13 +

Nepheline NaAlSiO4 +

SO3 0,30

Na2O 4,16

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Checker sample

in TCR

Magnesia and

magnesia zircon:

• no interaction with Na2O

• no damage

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Magnesia 97




What is important for magnesia with C2S-bonding?

MgO-MgO-direct bonding!

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Case Example

Magnesia 97

direct bonding

Magnesia 97 direct bonding used as checker in one float furnace:

• 14 years

• Firing with heavy oil and gas

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Case Example

Magnesia 97

direct bonding

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Case Example

2CaO.SiO2 disappeared (corroded by Na2O and V2O5)

MgO-MgO direct bonding

remains (circles)

Magnesia 97

direct bonding

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Conclusion

Pet-coke firing (Vanadium attack):

• Magnesia zircon (RUBINAL VZ) has good performance.

• Chrome corundum (DURITAL RK10) even better

Sodium silicate glass (Strong NaOH attack):

• Magnesia zircon (RUBINAL EZ) for oil firing

• Magnesia (ANKER DG1) for gas firing

Thermal chemical regenerator:

(Changing between reducing and oxidising atmosphere):

• Basic materials showed no attack

• MgO-MgO direct bonding is important

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Thank you for your attention

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Refractory application for extreme firing condition in … application for extreme firing condition in the regenerator of glass melting furnaces Sandra ... Magnesia 97 direct bonding