1 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006

2 IN THE WORLD OF GLASS..... AT HOME The Group..... Over 130 years of unbroken service to the Glass Industry

3 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Richard Sims Nikolaus Sorg GmbH & Co KG Glass conditioning for high quality production

4 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Glass conditioning for container manufacture Normally consists of thermal processes Increasingly acquiring a new component - temperature reduction - thermal homogenisation - chemical homogenisation to eliminate zircon cords

5 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Glass conditioning for high quality production Attainment of excellent chemical homogeneity extremely important Thermal processes generally not important - less temperature differential between entry and exit - much smaller quantities of glass

6 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Chemical homogeneity

7 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Glass conditioning for high quality production Elimination of chemical inhomogeneities by stirring Elimination of chemical inhomogeneities by draining Prevention of chemical inhomogeneities

8 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Elimination of chemical inhomogeneities by stirring

9 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Elimination of chemical inhomogeneities by stirring Chemical inhomogeneity (cord) is usually an area of differing chemical composition (= differing refractive index) We can render it invisible by equalisation of the composition We can render it invisible by distributing it in the glass body - this occurs mainly by diffusion

10 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Elimination of chemical inhomogeneities by stirring To facilitate diffusion we need Stirrers should either : - a large contact area between the cord and the base glass - time - increase contact area, OR - increase time available, OR - both Contact area is increased by application of shear forces Time is increased by modifying the flow pattern

11 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Spiral stirrer (blender)

12 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Good vertical glass transport ADVANTAGES Little horizontal glass transport Large vertical barrier area Spiral stirrer (blender) - the glass is not “pushed“ forwards

13 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Large vertical barrier area Spiral stirrer (blender)

14 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Good vertical glass transport ADVANTAGES Little horizontal glass transport Large vertical barrier area Spiral stirrer (blender) - the glass is not “pushed“ forwards Residence time of the glass is increased Low differential velocity DISADVANTAGES - low shear forces Little actual “mixing“ effect

15 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 two paddle - small Paddle stirrer - various types two paddle - large four paddle

16 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 ADVANTAGES High differential velocity - high shear forces Good “mixing“ effect DISADVANTAGES Horizontal glass transport - glass is “pushed“ forwards Paddle stirrer - large

17 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 side by side in-line Paddle stirrer - large

18 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 ADVANTAGES High differential velocity - high shear forces Good “mixing“ effect DISADVANTAGES Horizontal glass transport - glass is “pushed“ forwards Residence time of the glass decreased Paddle stirrer - large

19 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Rod stirrer - various types

20 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Rod stirrer - typical application

21 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 ADVANTAGES Very high differential velocity - very high shear forces Excellent “mixing“ effect DISADVANTAGES Needs vertical glass flow Rod stirrer Metallic = platinum alloy - VERY expensive Sometimes impractical

22 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Elimination of chemical inhomogeneities by stirring The combination of “mixing“ and increased residence time is necessary Stirrers and channel form must be matched BETTER results obtained with vertical flow BEST results obtained with rod stirrer in vertical channel Refractory stirrers wear = unstable operation

23 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Elimination of chemical inhomogeneities by draining

24 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Elimination of chemical inhomogeneities by draining If we cannot eliminate cord with stirrers it may be because it is not accessible In such cases selective draining can solve the problem - on or close to the surface - on or close to the bottom - refractory design to influence origin of drained glass - careful control of drained glass quantity

25 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Surface drain

26 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Surface drain Surface glass “skimmed“ off and removed by overflow drain Drain flow rate determined by overflow temperature Remaining glass of good quality

27 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Temperature controller Thyristor unit Counter electrode Thermocouple CONTI-DRAIN with nozzle Transformer Bottom drain - basic principle

28 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Bottom drain - details

29 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Bottom drain - mathematical model

30 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Bottom drain - in operation

31 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Elimination of chemical inhomogeneities by draining Selective draining can often solve problems that are not accessible to stirrers A surface drain can be used to remove glass contaminated by surface volatilisation Careful control of drain operation is vital for good results A bottom drain can be used to remove zircon-rich glass from furnace refractory corrosion

32 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities

33 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Chemical inhomogeneities can result from stagnant areas of glass in the forehearth channels - as a result of cold glass - as a result of poor flow patterns

34 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Avoid deep and wide channels Avoid sudden changes in channel width and depth Keep channel as short as possible Avoid flow barriers in the channels Avoid corners in the channels (as far as possible)

35 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Chemical inhomogeneities can result from stagnant areas of glass in the forehearth channels Chemical inhomogeneities can result from surface volatilisation - as a result of cold glass - as a result of poor flow patterns - for example, lead, fluorine, boron, alkalis

36 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Eliminate the glass bath surface

37 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Eliminate the glass bath surface - heating becomes a problem Indirect heating - gas or electric - forehearth is sluggish and control is difficult - forehearth is inflexible

38 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Non-contact cover - forehearth reaction and control are acceptable - compromise on quality ALTERNATIVE Eliminate the glass bath surface - heating becomes a problem Indirect heating - gas or electric - forehearth is sluggish and control is difficult - forehearth is inflexible

39 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Eliminate the glass bath surface - heating becomes a problem Indirect heating - gas or electric - forehearth is sluggish and control is difficult - forehearth is inflexible Direct heating - with electrodes - forehearth reacts well and control is good - possibility of glass quality problems from electrodes

40 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Prevention of chemical inhomogeneities Eliminate the glass bath surface - heating becomes a problem Indirect heating - gas or electric - forehearth is sluggish and control is difficult - forehearth is inflexible Direct heating - with electrodes - forehearth reacts well and control is good - possibility of glass quality problems from electrodes The combination - indirect heating (gas or electric) and direct heating by electrodes gives good results with few disadvantages

41 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 ? The answer

42 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006

43 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 The answer ? There isn't one There isn't ONE

44 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 If you want to make high quality production : Apply correctly designed stirrers Keep it as simple as possible If possible used combined indirect/direct heating - paddle stirrers - side-by-side - if possible in vertical channel Have drain facilities available

45 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 Always remember, there are 2 other major sources of glass quality problems that have not been mentioned here : - the furnace - the feeder bowl If you want to make high quality production :

46 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006

47 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006

48 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006 IN THE WORLD OF GLASS..... AT HOME The Group..... Over 130 years of unbroken service to the Glass Industry

49 XVIII ICF Technical Exchange Conference 7 th - 10 th October 2006