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 (), 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
Cyclone
Afterburner
Scrap CFRP 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
Clean flue gas
Fluidised Bed Process
To energy recovery
Cyclone
Afterburner
Scrap CFRP 300 mm
Fan Recovered Fibre Electric Pre-heaters Air Inlet
Fluidised Bed Air distributor plate
Carbon Fibre Properties • Tensile strength reduced by 25% • Little change in modulus • No oxidation of carbon fibres
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
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 15% Waxes
(26%)…….
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