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Production of lightweight fillers (LWFs) from recycled glass and paper sludge ash (PSA)
Charikleia Spathi a,b, Luc Vandeperre a, Chris Cheeseman b
a Department of Materials, Imperial College Londonb Department of Civil and Environmental Engineering, Imperial College London
Symbiosis 2014 International Conference, Athens
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Background to the project
• EPSRC Industrial Case PhD Award
• Mixed colour glass cannot be reprocessed
• Sustainable solutions for PSA required as an alternative to landfill
• Manufacturing LWFs from waste glass and PSA would be a novel re-use application
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Background to the project
• EPSRC Industrial Case PhD Award
• Mixed colour glass cannot be reprocessed
• Sustainable solutions for PSA required as an alternative to landfill
• Manufacturing LWFs from waste glass and PSA would be a novel re-use application
• Industry demand for lightweight fillers (LWFs) and cenospheres
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Industrial Project Collaborators
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End users
DistributionPrinting
Paper
Chemical pulp
Energy productionPSA
RECOVERED PAPER PULP
ENER
GY
PAP
ER SLU
DG
ELife cycle of paper
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End users
DistributionPrinting
Paper
Chemical pulp
Energy production
RECOVERED PAPER PULP
ENER
GY
PAP
ER SLU
DG
ELife cycle of paper
PSA
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Paper Sludge Ash (PSA)
Residue from combustion of wastepaper sludge
125,000 tonnes of PSA was produced in 2006
88,000 tonnes beneficially reused in UK markets
37,000 tonnes landfilled
Increasing volumes produced and opportunity for new applications
Material for combustion Amount (tonnes/year)
Paper sludge 275,000
Biomass (virgin and clean non-virgin timber) 120,000
Plastics 17,000
Waste Protocols Project: A technical report on the production and use of PSA (2007)
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Waste glass & PSA: Chemical and mineralogical composition
X-Ray Diffraction data
X-Ray Fluorescence data
SiO2 CaO Na2O MgO Al2O3 K2O Fe2O3 SO3 TiO2 P2O5 OthersWaste glass 75.8 12.0 7.3 2.3 1.4 0.6 0.3 0.2 nd nd -
PSA 21.2 61.2 nd 2.8 12.6 0.4 0.9 0.2 0.3 0.1 0.1
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PSA: Microstructure
• Agglomerated particles• Loosely bonded• Porous
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PSA: Dilatometer results
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-10
-5
0
0 200 400 600 800 1000 1200 1400
dL/
Lo (
%)
Temperature (°C)
As-received PSA
Samples fall apart at T= 1180 °CInadequate sintering
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PSA and recycled glass: Dilatometer results
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-20
-15
-10
-5
0
0 200 400 600 800 1000 1200 1400
dL/
Lo (
%)
Temperature (°C)
Recycled Glass
As-received PSA
Tonset = 594 °C, Tend = 664 °CdL/Lo = 23.2 %
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PSA: Thermogravimetric Analysis (TGA)
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PSA: Thermogravimetric Analysis (TGA)
Tonset = 600 °C, Tend = 780 °C
mloss = 5.5 wt%
CaCO3 CaO + CO2
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Mechanisms for expansion during rapid sintering
Green particle
particle packing
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Mechanisms for expansion during rapid sintering
Green particle Liquid phase sintering
particle packing vitreous phases formed
Heating
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Mechanisms for expansion during rapid sintering
Green particle Liquid phase sintering
Gas evolution
particle packing vitreous phases formed
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Mechanisms for expansion during rapid sintering
Green particle Rapidly sintered particle
Liquid phase sintering
Gas evolution
particle packing vitreous phases formed
closed cell structure
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Specifications of potential LWF products
Desired properties• Low density ~ < 1 g cm-3
• Relatively low water absorption • High strength• Particle size ranging from ~ 60µm to 2mm
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Industrial manufacturing process
Raw materials (recycled glass)
Ball milling
Mixing
Pan pelletising
Sintering (rotary kiln)
As used by Poraver, Liaver and Ecoglassmanufacturers
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Laboratory manufacturing process
Fine glass powder PSA
1. Raw materials
2. Grinding
1-4 hours
3. Mixing
Water
4. Pelletising
Angle and rotation speed adjusted
5. Rapid sintering
Temp.: 800 °CTime: < 40 min
6. Sieving
Size: 1 – 7 mm
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Effect of PSA content on density and water absorption
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80
100
120
140
160
0.0
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0.6
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1.0
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2.0
0 10 20 30 40 50
Wat
er a
bsor
ptio
n (w
t.%
)
part
icle
den
sity
( g
cm
-3)
PSA content (wt. %)
Commercial LWFs
Commercial LWFs
Wet milled for 1 hour, Tsint= 800 °C, tsint= 20 minutes
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par
ticl
e d
en
sity
(g
cm-3
)
Sintering time (min)
Commercial LWF
Effect of sintering time: 20% PSA-80% glass mix
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par
ticl
e d
en
sity
(g
cm-3
)
Sintering time (min)
Stable phase
Effect of sintering time: 20% PSA-80% glass mix
HeatingGlass softeningGas evolution
Potential coarsening
Commercial LWF
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0
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0 5 10 15 20 25 30 35 40
Wat
er a
bso
rpti
on
(%
)
par
ticl
e d
en
sity
(g
cm-3
)
Sintering time (min)
Commercial LWF
Commercial LWF
Effect of sintering time: 20% PSA -80 % glass mix
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Sintering time: 5 minutes Sintering time: 10 minutes
Effect of sintering time on microstructure
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Sintering time: 15 minutes Sintering time: 20 minutes
Effect of sintering time on microstructure
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20% PSA-80% glass mix: Effect of pellet size on CS (10)
0
0.5
1
1.5
2
2.5
3
3.5
1-2mm 2-5mm 5-7mm
Cru
shin
g St
ren
gth
(1
0)
(MP
a)
Pellet size
20% PSA_800 C_15min Commercial LWF
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Conclusions
• Identified LWFs as the target product – cenosphere-type products
• PSA can be mixed with glass (1:4) to form LWFs
• Laboratory production process mimics industrial manufacturing
• Promising results to date:
- Light weight fillers are produced at particle sizes ranging from 1-7 mm
- Relatively low sintering temperature (800 °C) and time (15 min)
- Optimum PSA-glass LWFs have higher crushing strength than commercial LWFs
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Questions and Answers
Thank you!