High Cullet Levels In container glass - GlassTrend

High cullet levels in container glassobservations, 

challenges, solutions 

09-10-2012 

Sven-Roger Kahl 

Hans Hilkes 

Ardagh Group 

© Ardagh Group 2012

Overview 

> Use of recycled cullet in container glass – a 

success story. 

> Cullet levels in container glass – where are we? 

> Classic contamination: CSP and metal 

> Organic contamination and redox – problems 

and solutions 

> “New“ contaminations: Glass ceramics, lead 

glass 

> Where to go in the future? 

© Ardagh Group 2012 2

Cullet recycling in container glass – a 

success story. 

• Cullet is used more and 

more in all of Europe 

• Since 2002 the EU 

target of 60% recycling 

is achieved 

• Until 100% is reached 

there is still a huge 

potential to save 

material and energy 

Source: FEVE statistics 


Where are we today ? 

• Flint glass: 

• 10…15% for high colour demands (domestic 

cullet only) 

• 50% for standard colour (40% external cullet) 

• 80% is possible (preheater) 

• Emerald glass: 

• 50%...95% depending on availability and quality 

demands (lead, inclusion rates) 

• Amber: 

• 30% … 80% depending on availability 

• More and more alternatives are used: plate 

cullet, special glasses, … 


What are the main problems? 

> Classical contamination: CSP, metal, loose 

organics and plastic 

> Cullet’s influence on redox, based on 

contamination and grain size 

> “New” contamination: glass ceramics, heat 

resistant glasses 

> Increasing demands from customers and 

authorities result in increasing quality demands 

> In most EU countries there is a lot of political 

influence on the cullet market 


Classic contamination 

Type CSP Metal Loose 

organics 

Actual limit 

for cullet 

Detection > 8 

mm 

Detection < 8 

mm 

Quality 

control 

Sticky organics 

< 20 ppm < 5 ppm < 200 ppm COD 

Good Good Good Not detectable 

Reasonable 

until 3 mm 

Statistical 

control 

Good Not reliable Not detectable 

Statistical 

control 

Statistical 

control 

Measurement 

of COD, LOI 


Quality demands only increase… 


Organics, grain size and redox 

• Above 60% cullet level redox 

is mainly influenced by the 

cullet quality 

• “Bad” cullet can completely 

upset a stable furnace within 

hours 

• Fine cullet leads to foam and 

influences redox as well 

Fe 2+ /Fe tot. 

Crown 

Time 

Bottom 


Problem solutions… 

1. If you want to control redox you must measure it 

- Optical methods off-line 

- Electrochemical methods on-line 

2. MPC can smooth the effect of redox on 

temperatures 

- MPC is the better operator and works as an autopilot 


Practical example 

> ± 2001: Redox change leads to dropping crown 

temperatures and operator reactions – bottom 

temperature increases 40K within 3 hours 

> ±2002: new instruction – let the crown go, bottom 

temperature still increased 25K 

> ±2004: online redox sensor in the fore hearth helped 

to manage the process, bottom temperature stayed 

stable within 10K 

> 2010: implementation of MPC – the on line sensor 

still showed a redox change, bottom temperature 

remains flat 


“New” contamination 

• Glass-ceramics 

• Partly crystallized glasses of special composition 

• Produced since 1968 in Germany and Japan 

• Appearance: transparent, glass like, not to be found 

by naked eye 

• Glass-ceramics do not melt in the furnace but 

“follow the process” 

• Due to crystal growth the inclusion turns flint 

• Main problems are: irregularities with gobs, 

blocked spinning nozzles 


Glass-ceramics – detection techniques 

• Since the mid 90ies various techniques became 

available 

1. X-ray based systems 

2. UV-light detection 

3. Hyper spectral imaging (under development) 

• Techniques 1 and 2 are for the cullet recycling 

plant, technique 3 can also be used as on-site 

control 

• Since 2010 more and more cullet is treated for 

glass-ceramics and the efficiency is proven 


Heavy metals (lead) 

• Within the EU glass packaging may 

not contain more than 200 ppm 

heavy metals (average over 12 

month) 

• In 32 states of the USA the limit is 

lowered to 100 ppm (Soil Protection 

Act) 

• Recycling cullet in Europe actually 

contains about 150…170 ppm lead 

• Lead sorting is possible with the same 

techniques applied for glassceramics. 

• Calculations show that it will take 

years to “clean” recycling cullet from 

lead glass 


Future solutions 

• Cullet grinding – the solution for inclusions? 

• Grinded cullet (0.8-1.2 mm) is a real solution for 

classic CSP inclusions 

• Corundum will deliver a total mess of inclusions ± 

1mm – be aware of your incoming material 

• Grinded cullet gives loads of foam 

• Grinded cullet give a lot of carryover and the dust is 

literally everywhere in the plant 


The “Best Available Future” scenario 

• Dry cullet before processing 

• Focus on the > 8mm fraction for cleaning from 

contamination 

• Apply 100% colour sorting, glass-ceramics and lead 

detection 

• Grind the sub 8 mm fraction to 0.8-1.2 mm and 

pelletize this cullet. 

• Use filter powder (CaSO 4 ) as a free binder, add if 

possible other fine fraction (limestone, dolomite)

High Cullet Levels In container glass - GlassTrend

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