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Steve PickeringSchool of Mechanical, Materials and Manufacturing Engineering
Routes to Recycling or Disposal of Thermoset Composites
Presentation Outline
• Need to Recycle
• Problems in recycling thermoset composites
• Recycling/Disposal Processes– mechanical recycling
– thermal processing
• Future Prospects
Need to Recycle
Pressure from legislation
• EU Directives
• Landfill
• End-of-Life Vehicles
• Waste Electrical and Electronic Equipment
• Construction and Demolition Waste
Recycling Heirarchy
• Prevent waste
• Reuse product
• Recycle material
• Incineration• with material and energy recovery
• with energy recovery
• without recovery
• Landfill
Does not measure recycling quality
(environmental benefit)
Problems in Recycling Thermoset Composites
• Technical Problems •Thermosetting polymers can’t be remoulded
• Long fibres
• Mixtures of materials (different compositions)
• Contamination
• Costs
• Collection and Separation
Recycling Processes for Thermoset Composites
Powdered fillers
Fibrous products (potential
reinforcement)
Combustion with energy
recovery (and material
utilisation)
Fluidised bed process
Pyrolysis/Gasification
Chemical products, fibres and
fillers
Clean fibres and fillers
with energy recovery
Thermal Processes
Mechanical Recycling
(comminution)
Mechanical Recycling
Size reduction • Coarse primary crushing
• Hammer milling followed by grading to give:
• Powder
• Coarser fractions (reinforcement rich)
All scrap material is contained in recyclate (incl. different polymers, contamination, paint….)
Mechanical Recycling
Recycling into new composites• Powdered recyclate useful as a filler
(up to 25% incorporated in new composite)
• Coarser recyclate has reinforcement properties
(up to 50% substitution of glass fibre)
Several companies have been founded to commercialise recycling – ERCOM (Germany), Phoenix Fiberglass (Canada)
Mechanical Recycling
Recycling into other products• Compounding with thermoplastics
• Production of reinforcement with recyclate core to allow resin flow during impregnation
• Using recyclate to provide damping (noise insulation)
• Alternative to wood fibre
• Asphalt
Thermal Processing
Combustion with Energy and Material Recovery • Calorific value of thermosetting resins ~ 30 MJ/kg
• Co-combustion with municipal waste in mass burn incinerators
• Co-combustion in cement kilns
• Co-combustion with coal in fluidised bed
Thermal Processing Combustion with energy recovery
• Calorific value depends on inorganic content (10 - 30 MJ/kg)
• Filler effects: • CaCO3 1.8 MJ/kg (+800 C)• ATH 1.0 MJ/kg
• ‘Cleaner than coal’• Bulky ash remaining
Cement manufacture
• energy recovery from polymer
• glass and fillers combine
usefully with cement minerals
• fuel substitution limited to <10%
by boron in E-glass
Potential savings <£20/tonne of GRP used
Thermal Processing Combustion with energy and material recovery
Thermal Processing Combustion with energy and material recovery
Fluidised Bed Coal Combustion
• (Limestone filled composites)
• energy recovery from polymer
• limestone filler absorbs oxides of
sulphur from coal
• commercial trial undertaken
Thermal Processing – Fluidised Bed Process
Cyclone
Air Inlet
Electric Pre-heaters
Fibre
Scrap CFRP
Recovered FluidisedBed
Air distributor
plate
300 mmAfterburner
Clean flue gas To energy recovery
Fan
Fluidised Bed Processing Materials and Energy Recovery
Fluidised
Bed
Scrap
FRP
Separation of fibres
and fillers
Recovered
FibresRecovered
Fillers
HeatRecovery
Recovered
Energy
Clean Flue Gas
Secondary
Combustion
Chamber
Fibres and fillers carried in gas flow
Fluidised Bed Operation• Temperature: 450 to 550 deg C• Fluidising air velocity: up to 1.3 m/s• Fluidising medium: silica sand 1mm
• Able to process contaminated and mixed composites eg: double skinned, foam cored, painted automotive components with metal inserts
Recovered Glass Fibres
Properties
• Strength: reduced by 50% (at 450 C)
• Stiffness: unchanged
• Purity: 80%
• Fibre length: 3 to 5 mm (wt)
Reuse of Recycled Glass Fibre Moulding Compounds
•Moulding - virgin glass fibreMoulding - virgin glass fibre
•Moulding - 50% recycled glass fibreMoulding - 50% recycled glass fibre
Moulding Compounds
• Only effect is 25% reduction in impact strength
• no change to processing conditions
• demonstrator components produced
Outline Process EconomicsGlass Fibre Recycling
Commercial Plant Schematic (5000 tonnes/year)
Outline Process EconomicsGlass Fibre Recycling
5,000 tons/year Capital £3.75million
Annual costs: £1.6 millionAnnual Income: £1.3 million
Breakeven throughput: 10,000 tons/year
Fluidised Bed Process
Cyclone
Air Inlet
Electric Pre-heaters
Fibre
Scrap CFRP
Recovered FluidisedBed
Air distributorplate
300 mmAfterburner
Clean flue gas To energy recovery
Fan
Carbon Fibre Properties
•Tensile strength reduced by 25%
•Little change in modulus
•No oxidation of carbon fibres
00.5
11.5
22.5
33.5
44.5
Virgin 450 deg C 550 deg C
Fibr
e S
treng
th
[GP
a]
Carbon Fibre Properties Fibre Quality
• Fibre surface quality similar to virgin fibre
• Clean fibres produced
~200mm~200mm
100mm100mm
100100mm
Recovered Fibre Composite
0
50
100
150
200
250
RecoveredFibre A
RecoveredFibre B
VirginCarbon
Virgin Glass
Tens
ile s
treng
th [M
Pa]
0
2
4
6
8
10
12
RecoveredFibre A
RecoveredFibre B
VirginCarbon
Virgin Glass
Tens
ile m
odul
us [G
Pa]
• Fibres made into polycarbonate composite
StrengthStrength StiffnessStiffness
ReactorScrap feed Condenser
Hot gases
Solid and Liquid
Hydrocarbon Products
Combustible Gases to heat reactor
Solid Products (fibres, fillers, char)
Pyrolysis Process
Thermal Processing
Thermal Processing
Pyrolysis Processes • Heating composite (400 – 800°C) in absence of air to give
• hydrocarbon products – gases and liquids
• fibres
• Some char contamination on fibres
• Hydrocarbon products potential for use as fuels or chemical feedstock
• Low temperature (200°C) catalytic pyrolysis for carbon fibre
Gasification – limited oxygen – no char, fuel gases evolved
Thermal Processing
Products from Pyrolysis (450°C)
Polyester Composite (30% glass fibre, 7% filler, 63% UP resin)
6% Gases: CO2 & CO (75%) + H2, CH4 …….
40% Oils hydrocarbons, styrene (26%)…….
15% Waxes phthalic anhydride (96%)…..
39% Solids glass fibre & fillers (CaCO3), char (16%)
What is best Recycling Route??
• Established hierarchy and ELV Directive favour mechanical recycling techniques – but are these the best environmentally??
• Detailed Life Cycle Analysis needed to identify environmental impact
• Recent project in Sweden (VAMP18) has considered best environmental and cost options for recycling a range of composites
Prospects for Commercial Success?
• ERCOM and Phoenix – viable levels of operation not
achieved
• Recyclates too expensive to compete in available markets
• Need to develop higher grade recyclates for more
valuable markets
• Legislation and avoidance of landfill are new driving forces
Value in Scrap Composites
• Energy value of polymer £ 30/tonne
• Value of polymer pyrolysis products
Maleic Anhydride, Bisphenol A £1,000/tonne• Value of filler £ 30/tonne• Value of glass fibre £1,000/tonne• Value of carbon fibre £10,000/tonne
New Initiative
• EuCIA (GPRMC) initiative
• ECRC (European Composites Recycling Concept)
• Scheme to fund recycling to meet EU Directives
• A guarantee that composites will be recycled
Conclusions
• A range of technologies is under development• material recycling
• thermal processing
• Key barriers to commercial success are markets at right cost
• Need for environmental analysis to identify best options
• Future legislation is driving industry initiatives
Recycled Carbon Fibre Life Cycle Analysis
• Energy use for
recovery process is
10% of virgin fibre
production
• 40% to 45% energy
reduction observed for
recovered fibre
composites
-50
0
50
100
150
200
Carbon Fibre Production Fluidized Bed Recovery
Ene
rgy
(MJ/
kg)
Coal Crude Oil Lignite Natural Gas Other Recovered
-50
0
50
100
150
Virgin Carbon FibreComposite
Equivalent Stiffness Equivalent Strength
En
erg
y (M
J/kg
) Coal Crude Oil Natural Gas Lignite Other Recovered Energy
Fluidised Bed Process