Should Traditional Pot Materials Be Replaced by Modern Materials in Glass Manufacturing Process?

1. Can Traditional Pot Materials be Substituted by Modern Materials?Bo Jonson School of Technology andDesign Departmentof Chemistry – Glass Group

2. Contents • Pot furnace – still alive ? • Clay pretreatment requirements • Glass contact performance of clay type materials • Requirements and objectives for new materials • Performance during glass contact of candidate materials • Conclusions Bo Jonson ICF 2004

3. Retro .. Tank*and pot furnace campaign times* tank data from M Maquet, Proc. ICG, Brazil 2003 Bo Jonson ICF 2004

4. Why are pot furnaces still in use? Pros: • Flexibility in operation - rapid change of glass composition/colour • Low investment/ repair costs Bo Jonson ICF 2004

5. … but there are disadvantages ! • Complicated pre-treatment of clay pots • Batch charging => thermal shock • Worse glass quality compared to continous melting • Higher specific energy consumption (up to 10 kWh/kg glass !) Bo Jonson ICF 2004

6. ..(2nd) but why not develop/adopt a new refractory pot material ?? • EU Craft project with this objective initiated 2003 • RTD – Sweden and UK • SME partner representing: • Glass industry • Furnace and refractory manufactures • Sweden, UK, France, (….Italy) Bo Jonson ICF 2004

7. Novel pot project - workpackages • Fault inspection - statistics and defect analyses • Material selection - corrosion studies - material data - FEA studies - coating/glazing development • Prototype development • Industrial validation Bo Jonson ICF 2004

8. Clay pot pretreatment requirements <-Tempering 7 days -> Densefiring and Glazing 20 hours Bo Jonson ICF 2004

9. Clay material glass contact performance – lab. experience • Alumina-silica type materials containing approx. 5 % other elements • Lab experiments indicate corrosive volume losses ranging from 10 – 40% the first 24 hours Chemistry in wt-% Bo Jonson ICF 2004

10. Clay material glass contact performance – industrial experiences/defect composition • Stones  Primarily consist of unreacted SiO2, Al2O3 and TiO2 . Reactions with K2O in glass form leucite or other feldsparic compounds Cords • EDX analysis show enrichment in Al2O3 (TiO2) • Defects are of clay origin Feldsparic crystals Al2O3 37% SiO2 46 % K2O 10% Na2O 4% TiO2 2 % Bo Jonson ICF 2004

11. Clay material glass contact performance – industrial production experiences • Rejects/2nds is as much as up to 30% (s =10%) of produced glass • Defects originating from clay amounts to around 50% of the glass faults • Contributing to large variance of process performance –very difficult to apply statistical process control ! Al2O3 - SiO2 69 % K2O 9% Na2O 7% TiO2 - PbO 9 % Al2O3 12% SiO2 63 % K2O 12% Na2O 5% TiO2 1 % PbO 3 % Bo Jonson ICF 2004

12. SV & OF Clay material dissolution • Lab study show a continous dissolution without formation of any protective phases • Crystallography of clay – mainly quartz, cristoballite, sillimanite, caolinite and mullite SiO2 phase Al2O3 needles Bo Jonson ICF 2004

13. Requirements and objectives for new pot materials • Resistant to thermal shock • Mechanical stability • Superior performance in terms of corrosion • Suitable for room temperature coating • Less complicated pretreatment • Suitable for pot manufacturing Bo Jonson ICF 2004

14. Candidate materials ! Chemistry in wt-% • Frisil H -sillimanite type • AZS G6 • CAZ 20 • Tialite G10 • R (recycled) AZS Bo Jonson ICF 2004

15. Performance testing of new materials • Dynamic corrosion in molten glass • Thermal shock • Thermal expansion • Thermal conductivity • E-modulus • Stress/strain behaviour Corrosive volume loss Bo Jonson ICF 2004

16. Other project activities • FE analysis • Coating/glazing development and testing Bo Jonson ICF 2004

17. Testing of crucibles made from new materials - 24% PbO crystal 5 days- 8 weeks 5 kg crucible trials Bo Jonson ICF 2004

18. 5 kg crucible trials 2% reduction of wall thickness 5% reduction of wall thickness Bo Jonson ICF 2004

19. What more to do in the project ?? • Trials with 5 kg crucible glazed at room temperature • Prototype development – production of full sized pot • Industrial validation Bo Jonson ICF 2004

20. Preliminary conclusions • Clay material is low performing in terms of corrosion resistance towards molten glass • Clay material shows a continous dissolution without forming protective phases • All candidate materials show an improved corrosion resistance towards molten glass • Thermo mechanical properties of candidate indicate promising performance for CAZ20 and Frisil– industrial scale performance to be verified Bo Jonson ICF 2004

21. Q & A • Can Traditional Pot Materials be Substituted by Modern Materials? • In lab/small scale – YES ! • In industrial scale – ?? - to be answered Bo Jonson ICF 2004

22. Acknowledgements –I would like to Thank.. • The novel pot consortium for technical and suggestive input to the paper and their permission to present some results • The ECfor permission to publish project results and financial support • Mr Jonathan Schneider for performing a lot of lab studies in his diploma work, Bo Jonson ICF 2004