Microwave Pyrolysis of Plastic Waste

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03/07/2006 Horizon Green Frontiers 1

Department of Chemical Engineering

University of Cambridge

Microwave pyrolysis oflaminate wastes:

spinning out researchinnovation

Strange Things to do with aMicrowave Oven

Howard Chase

Carlos Ludlow-Palafox


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University of CambridgeMotivation for Recycling

70 Mtonnes/y of plastics produced in Europe, 58% of which is

disposed of as post-consumer waste.

Only 50% of the waste is recycled, the rest goes to landfill

To landfill plastic wastes is simply not sustainable. It results in the

complete loss of their energetic and chemical value and does notsolve the problem; it merely transfers it to future generations.


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University of CambridgeRecycling options

There are basically three methods to recycle plastics or

plastic-containing wastes:

Mechanical recycling:Remelting and remoulding ofthe plastics.

Energy recovery by Incineration:Burning of theplastic in order to recover the energetic value of the

waste.

Feedstock recycling by Pyrolysis:Cleaving of the

polymer molecules to small hydrocarbons in order to

recover the energetic and chemical value of the waste.


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University of CambridgeComparison

Mechanical recycling

Expensive since it requires clean and sorted waste

Not suitable for food packaging Incineration

No need to sort the waste

Difficult control of dangerous emissions

Contribution to the greenhouse effect Chemical value lost

Pyrolysis

Reduction by a factor of 5 to 20 in the amounts ofgaseous products compared to incineration

Recovery of the chemical products within the plastic

Can deal with unsorted waste


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University of CambridgeThe packaging

laminates issue

Aluminium foil (5 30 microns thick) laminated with

paper and/or plastics e.g. TetraPak Used in drink cartons and other packaging

Advantages: very low weight to volume ratio, long-life

protection from UV light, aseptic nature, low transportcosts

800,000 tonnes of drink cartons produced per annum

- Polyethylene - protects against outside moisture - Paper - for stability and strength - Polyethylene - adhesion layer - Aluminium foil - oxygen, flavour and light barrier - Polyethylene - adhesion layer - Polyethylene - seals in the liquid

Overall composition 75% Paper, 20% Plastic & 5% Aluminium.


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University of CambridgePackaging laminates

opportunity

In Europe

Member states have to recycle 55% of packaging waste by 2008

(including 50% of metals and 22.5 % of plastics)

Potential recovery of 40,000 tonnes/y of aluminium metal from

drinks packaging alone

Waste is already in specific locations waiting for someone to do

something

Current recycling processes incapable of recycling this waste


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University of CambridgeDrink cartons life cycle

Europe: 2005

280, 000 tonnes 70%800, 000 tonnes40,000 tn Al

30%Country Carton Recycling Rate (2003)

Germany 65%

Belgium 68%

Sweden 44%

United Kingdom 1%

EU Average 28%

Solution needed

Aluminium:

14,000 tonnes


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University of CambridgeSolution found

Microwave induced pyrolysis is capable of

recovering the aluminium from laminates waste andpyrolysing the plastic into hydrocarbon oils and gases


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University of CambridgeMicrowave heating

Microwave radiation was developed intensively for radar during

WWII and subsequently used for heating water-containing

foodstuffs. Modern industrial microwave heating systems are used for a

diversity of processes in the food industry, tempering and

thawing, continuous baking, vacuum drying, pasteurisation andsterilisation

Advantages over conventional surface heating include:

Even distribution of heat

Easy control over the temperature

High temperatures and high heating rates

Excellent efficiency in conversion electricity-heat

Reliable and competitive with other heating methods


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University of CambridgeMicrowave Pyrolysis

How are plastics thermally degraded usingmicrowaves when they are known to have a very

high transparency to this kind of radiation

The Enval process combines the advantages of

microwave heating with the environmental benefits and

commercial opportunities arising from the pyrolysis

wastes.


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University of CambridgeThe use of carbon particles

Particulate carbon is a very efficient receptor ofmicrowave radiation

Add plastic-containing waste to an agitated bed ofcarbon that is subjected to microwave radiation.

Heat transfer between carbon and plastic induces

pyrolysis Hot carbon maintains a chemically reducing environment

with beneficial effect on the chemistry of the pyrolysisproducts alkanes and alkenes


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University of CambridgeEnvals project time line

1998 - 2001

Understandingof thephysicochemical

process.EPSRC funded


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University of CambridgeBatch equipment

Batch Equipment for Microwave Induced Pyrolysis


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University of CambridgeBatch equipment

6- Oil/wax main collection7- Warm condensers

8- Cold trap (0C)

9- Cold trap (-72C)

10- Filter

1- Microwave oven2- Quartz reactor

3- Motor

4- Top feeder

5- N2 flowmeter


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University of CambridgeBatch pyrolysis results

0

10

20

30

40

0 100 200 300 400Time (seconds)

Volume

(ml)

500C

600C

Rate of degradation

Cumulative yield of products from HDPE pellets pyrolysis at 500 and 600C.

Mass balance Liquid/Solid Gases Residues500C 81% 19% 0%

600C 79.1% 20.9% 0%


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University of CambridgeResults

Distribution of degrees of polymerisation (oils/waxes)

Pyrolysis of HDPE pellets with a flow of 1 l/min of carrier gas.

500C

0%

1%

2%

3%

4%

5%

6%

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69

Carbon number

Massfraction

600C

0%

1%

2%

3%

4%

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57

Carbon number

Massfractio

n

700C

0%

1%

2%

3%

4%

5%

6%

7%

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57

Carbon number

Massfraction

Temperature

(C)

wMw

(amu)500 21.8 305

600 29 406

700 20.6 289

R l


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University of CambridgeResults

Chemical composition of the products (oils/waxes)

Temperature (C) 500 600 700

Linear Hydrocarbons 81.1 92.8 88

Of which: Alkanes 37 29.5 11.8

Alkenes 52.2 60.1 60

Dialkenes 10.9 10.4 28.2

The rest is a mixture of many aliphatic and aromatic compounds

including cyclohexene, benzene, toluene, ethyl-benzene and xylene.

E l j t ti li


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2002 - 2004

Funding searchto proveconcept

1998 - 2001


process.

D f Ch i l E i i2002 2004


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University of Cambridge2002 - 2004

Invention disclosure

Patent drafting and initial filing

Cambridge Enterprise Seed Funds (formelyUniversity Challenge Fund) 10k pathfinder

Other small grants to keep project going Development of Business Plan

Victims of too commercial for researchcouncils but too early for private investors

D t t f Ch i l E i iE l j t ti li


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2002 - 2004 2005 June 2006

Funding searchto proveconcept

Building and testingprototype

Enval Ltd.incorporated

1998 - 2001


process.

Department of Chemical Engineering2005 June 2006


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University of Cambridge2005 June 2006

Cambridge Enterprise Proof of Concept grant (DTI)

Patent published

Winners of 2005 Cambridge EntrepreneursBusiness Plan Competition

Cambridge Enterprise Seed Funds investment

Development of a continuous treatment prototype

Department of Chemical EngineeringNew reactor design


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University of CambridgeNew reactor design

Microwave applicator

Feeding air lock

Exit air lock

Agitation system

Microwave system

Continuous Equipment for Microwave Induced Pyrolysis

Department of Chemical EngineeringNew equipment


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University of CambridgeNew equipment

Continuous Equipment for Microwave Induced Pyrolysis

Department of Chemical EngineeringRecovered aluminium


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University of CambridgeRecovered aluminium

Aluminium from the Enval process

Department of Chemical EngineeringEnvals project time line


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p g g

University of CambridgeEnval s project time line

2002 - 2004 2005 June 2006

Funding searchto proofconcept

Building and testingprototype

Enval Ltd.incorporated

1998 - 2001 June 2006 -


process.

Building and testingpilot plant.Trailer mounted unit

that can be taken todepulping mills



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Microwave Pyrolysis of Plastic Waste