Routes to Recycling or Disposal of Thermoset Composites

Report
Routes to Recycling or Disposal
of Thermoset Composites
Steve Pickering
School of Mechanical, Materials and Manufacturing Engineering
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
Does not measure
recycling quality
(environmental benefit)
• Incineration
• with material and energy recovery
• with energy recovery
• without recovery
• Landfill
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
Mechanical
Recycling
(comminution)
Powdered
fillers
Fibrous
products
(potential
reinforcement)
Thermal
Processes
Combustion
with energy
recovery
(and material
utilisation)
Fluidised
bed process
Clean fibres
and fillers
with energy
recovery
Pyrolysis/
Gasification
Chemical
products,
fibres and
fillers
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
Thermal Processing
Combustion with energy and material recovery
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
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
Clean flue gas
To energy recovery
Scrap CFRP
Cyclone
Afterburner
300 mm
Fan
Recovered
Fibre
Electric Pre-heaters
Air Inlet
Fluidised
Bed
Air distributor
plate
Fluidised Bed Processing
Scrap
FRP
Clean Flue Gas
Fibres and
fillers carried in
gas flow
Fluidised
Bed
Materials and Energy Recovery
Separation
of fibres
and fillers
Secondary
Combustion
Chamber
Recovered Recovered
Fibres
Fillers
Heat
Recovery
Recovered
Energy
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 fibre
Moulding
Compounds
• Only effect is 25%
reduction in impact
strength
• no change to
processing conditions
• demonstrator
components produced
•Moulding - 50% recycled glass fibre
Outline Process Economics
Glass Fibre Recycling
Commercial Plant Schematic (5000 tonnes/year)
Outline Process Economics
Glass Fibre Recycling
5,000 tons/year
Annual costs:
Annual Income:
Capital £3.75million
£1.6 million
£1.3 million
Breakeven throughput: 10,000 tons/year
Fluidised Bed Process
Clean flue gas
To energy recovery
Scrap CFRP
Cyclone
Afterburner
300 mm
Fan
Recovered
Fibre
Electric Pre-heaters
Air Inlet
Fluidised
Bed
Air distributor
plate
Carbon Fibre Properties
• Little change in
modulus
• No oxidation of
carbon fibres
Fibre Strength
[GPa]
• Tensile strength
reduced by 25%
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Virgin
450 deg C 550 deg C
Carbon Fibre Properties
Fibre Quality
• Fibre surface quality similar
to virgin fibre
• Clean fibres produced
100mm
~200mm
100m
Recovered Fibre Composite
• Fibres made into polycarbonate composite
Strength
Stiffness
12
Tensile modulus [GPa]
Tensile strength [MPa]
250
200
150
100
50
10
8
6
4
2
0
0
Recovered
Fibre A
Recovered
Fibre B
Virgin
Carbon
Virgin Glass
Recovered
Fibre A
Recovered
Fibre B
Virgin
Carbon
Virgin Glass
Thermal Processing
Combustible Gases to
heat reactor
Pyrolysis Process
Scrap feed
Reactor
Solid Products
(fibres, fillers, char)
Hot
gases
Condenser
Solid and
Liquid
Hydrocarbon
Products
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
• Value of filler
• Value of glass fibre
• Value of carbon fibre
£1,000/tonne
£ 30/tonne
£1,000/tonne
£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
Fluidised Bed Process
Recycled Carbon Fibre
Life Cycle Analysis
Coal
• Energy use for
10% of virgin fibre
Lignite
Natural Gas
Other
Recovered
200
150
Energy (MJ/kg)
recovery process is
Crude Oil
production
100
50
0
Carbon Fibre Production
Fluidized Bed Recovery
-50
Coal
150
reduction observed for
100
recovered fibre
composites
Energy (MJ/kg)
• 40% to 45% energy
Crude Oil
Natural Gas
Lignite
Other
Recovered Energy
50
0
Virgin Carbon Fibre
Composite
-50
Equivalent Stiffness
Equivalent Strength

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