Waste Recycling & Utilization - Waste Plastic & Rubber

1. Waste Recycling & Utilization
~ Waste Plastic & Rubber ~

2. What is plastic?
 Plastics are macro molecules (synthetic or semi-
synthetic), formed by Polymerization and having the
ability to be shaped by the application of reasonable
amount of heat and pressure or some other form of force.
2 Global primary plastic production by polymer type

3. History
 Alexander Parkes in 1862 at exhibition in London presented a
semi synthetic plastic.
 Parkesine  organic material essentially cellulose nitrate and a
solvent.
 It could be heated, formed while it retained shape after cooling
down.
 Applications  buttons, combs, picture frames ad kinfe handles
 The cellulose nitrate (Parkesine) is essentially mostly you can
say nice and natural material, you can call that as well, but the
traditional plastic (synthetic) we use today was discover in 1907
by Leo Hendrik Baekeland.
 Thermosetting “Phenolic” plastic formed with a reaction
between phenol and formaldehyde under pressure and
hexamethylenetetramine catalyst.
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4. Classification of Plastics
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Plastics
Thermoplastics
Acrylics
ABS
Nylons
Polyethylene (PE)
PVC, PET, PP, etc.,
Properties:
low melting point,
softer, flexible.
Application:
bottles, food
wrappers, toys.
Thermosets
Melamine
formaldehyde
Epoxies & Resins
Phenolics (bakelite)
Polyimides
Properties:
durable, harder,
tough, light
Application:
auto-parts,
construction &
electrical materials
Elastomers
Natural rubbers
(latex)
Synthetic rubbers
Silicones
Polyurethanes
Properties:
thermosets with
rubber-like
properties
Application:
medical, gloves,
latex products, tire..

5. Types of common plastic
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6. Plastic Waste
 Plastic is not a perfect
material but a
necessary part of our
life.
 To replace all plastic
items with alternative
materials would be
highly costly and
need a lot of R&D.
How to Manage
Plastic Waste?
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Reversed Triangle 5R Waste Management Concept

7. Plastic Waste Recycling
Plastic Recycling is defined as “Using plastic waste as
material to manufacture a new product which involves
altering the physical form of a waste plastic material and
making a new product from the altered material.”
 There are many different types of plastic.
 So, It is important to know composition when recycling.
 Most plastic products are marked with a code or a number identifying
the type of plastic. This information is used by recyclers.
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8. Problems in Plastic Recycling
 Degradation during processing and lifetime
(Due to thermomechanical, photo-oxidation, etc.)
 Incompatibility between different polymers.
Other problems can arise from:
 Different melting points of the polymers in
mixed plastics
 Different size and shape of the materials
 Low apparent density.
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Recycling of
heterogeneous
plastics.
Recycling of
homogeneous
plastics.

9. Plastic Recycling Chain
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 The plastic recycling chain can be divided in the following
operations:
Collection is carried out adopting different systems, depending also on
the different sources, such as plastics from household waste and from
industrial waste.
Manual sorting is usually necessary at the beginning of the recycling
process for the preliminary removal of films, cardboard, and bulky items
and is usually carried out by operators checking the waste stream on the
conveyor belt.
Screening is applied to remove small objects such as glass and stones.
Typical screening equipment are drum or vibrating screens.

10. Plastic Recycling Chain
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Material/Polymer Sorting has the aim to obtain high-quality recycled
plastic products, preferably single polymer stream. Sorting technologies
are based on different physical-chemical properties of waste materials,
such as shape, density, size, color, or chemical composition of objects.
Size reduction is usually carried out by shredding or cutting techniques;
Plastics are usually shredded in flakes having a size of 5-10 mm.
Extrusion and granulation: this step is necessary to produce a
granulate which is easier to use for converters than flakes. The polymer
flakes are fed into the extruder, are heated, and then forced through a
die to form a continuous polymer product then cooled in a water bath
before being pelletized.

11. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Separation Techniques
Gravity Separation
Dry
Air classifiers
Ballistic
separators
Wet
Float-Sink
Jigging
Hydrocycloning
Electrostatic separation
Magnetic density separation
Flotation
Sensor-based sorting
Visible spectroscopy
Near infrared
spectroscopy
Hyperspectral imaging
X-ray fluorescence
Laser-induced
spectroscopy
Auxiliary separation
technologies
Magnetic
Edy current
For separation
of non-plastic
materials

12. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Gravity separation - Dry Methods
 Air classifiers use air as the medium to separate lighter materials
from heavier ones.
 Ballistic separation is based on a simple principle, that is, the
different movement characteristics of particles of different size, shape,
and weight, spatially defined as 2D or 3D materials.

13. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Gravity separation - Wet Methods
 Sink-float separation processes are based on the utilization of the
different density properties of materials. Separation is based on the
fact that when materials are introduced in a tank containing a fluid of
a specific density, lighter materials will float and heavier ones will sink
Densities of different plastics
Density
of
water
Float

14. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Gravity separation - Wet Methods
 Jigging can be defined as an “enhanced gravity based separation”, a
water stream is pulsed, or moved by plunger upward and downward,
through the material bed. Resulting, heavy and light plastics are
separated according to their densities.
 Hydrocycloning is a density sorting technology based on the
centrifugal/centripetal forces and fluid resistance of different particles
having different characteristics.
Jigging
Separator

15. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Electrostatic separation
 Electrostatic separation is usually applied when dielectric particles are
handled. Dielectric particles, when electrostatically charged, can be
separated according to their polarity charge. Plastic particles charging is
usually carried out utilizing the triboelectric effect.
 This effect is based on rubbing together plastic waste particles; as a
result they transfer their electrical charge and surfaces are thus
affected by different electrical charges allowing to perform separation
inside an electric field where charged electrodes are present.

16. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Electrostatic separation

17. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Magnetic density separation
 Magnetic density separation (MDS) is a density sorting process; utilizing
a “magnetic fluid” constituted by a liquid (i.e., water) and magnetic
particles (i.e., iron oxide / 10-20 nm) suspended in the liquid.
 Through a magnetic field an artificial gravity is produced. This artificial
gravity force varies exponentially in the vertical direction, and the
effective density of the liquid also varies accordingly.
 Resulting; waste plastic particles will float in the liquid at a level where
the effective density is equal to their own density. In other words,
particles are suspended at different heights according to their different
densities.

18. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Magnetic density separation

19. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Flotation
 Flotation processes are based on the different surface wettability properties of
materials. In principle, flotation works very similarly to a sink and float process,
where the density characteristics of the materials, with respect to that of the
medium where they are placed are at the base of the separation.
 Sometimes a centrifugal field is applied to enhance separation.

20. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Sensor-based sorting
The adoption of sensors to perform sorting means to follow a different approach,
requiring the utilization and the implementation of analytical logics and robots to
perform the separation. Materials in fact, have to be first detected, then identified
and topologically assessed in the stream; after these steps automated devices
realize the sorting.
 Visible spectroscopy
 Near infrared spectroscopy
 Hyperspectral imaging
 X-ray fluorescence
 Laser-induced breakdown spectroscopy

21. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Auxiliary separation technologies
 Auxiliary separation technologies, are those technologies allowing to clean the
plastic waste stream from other materials with different characteristics.
 Materials usually removed through such techniques are:
 ferrous metals, as low-grade stainless steel, nickel alloys, etc.,
 nonferrous metals, as aluminum.
 Magnets and Eddy current based separators, respectively, are commonly
utilized.

22. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Auxiliary separation technologies - Magnetic separators
(a) Overbelt magnetic separator; (b) Magnetic head pulley separator; (c) Magnetic drum separator.

23. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Auxiliary separation technologies - Eddy current separators
 Eddy current separation is based on the use of a high speed magnetic rotor
system and is used to remove nonferrous metals (i.e., aluminum and
copper) from waste plastic streams.
 Due to the high speed of the rotor, an electric current, called Eddy current,
is induced into conducting metals.
 The induced electric current produces a magnetic field, opposed by the
field created by the rotor, repelling the conducting metals. The remaining
materials such as plastics, glass, and other dry recyclables will simply
freefall over the rotor, separating them from the repelled metals.

24. Plastic Waste Separation & Sorting
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Plastic Waste Separation Technologies
Auxiliary separation technologies - Eddy current separators

25. Recycling Methods
Category Methods ISO 15270
Material
recycling
Recycling to make:
• Plastic raw material
• Plastic products
Mechanical
recycling
Chemical
recycling
Monomerization
Feedstock
recycling
Blast furnace reducing agent
Coke oven chemical feedstock recycling
• Gasification
• Liquefaction
Chemical feedstock
Thermal
recycling
Fuel
Energy Recovery
Cement kiln
Waste power generation
RPF (Refuse Paper & Plastic Fuel)
RDF (Refuse Derived Fuel)
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26. Mechanical Recycling
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 Mechanical recycling is a way of making new products out of
unmodified plastic waste. It was developed in the 1970s, and is now
used by several hundred manufactures around the world.
 Mechanically recycled waste has until now consisted largely of
industrial plastic waste. Industrial plastic waste generated in the
manufacture, processing and distribution of plastic products is well
suited for use as the raw material for mechanical recycling thanks to
clear separation of different types of resins, a low level of dirt and
impurities and availability in large quantities.
 Used plastics can also be recycled, such as PET bottles and expanded
polystyrene, are turned into textile products, packaging materials, bottles,
stationery, daily necessities, and similar products.

27. Mechanical Recycling
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 Extrusion molding: Resin is melted and continually extruded through
a mold by a screw to form a molded product. Products include pipes,
sheets, film and wire covering.
 Injection molding: Heated melted resin is injected into a mold and
solidifies to form a molded product. Products made this way range from
washbowls, buckets and plastic models to larger products such as
bumpers and pliers.

28. Mechanical Recycling
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 Blow molding: A parison obtained by extrusion or injection molding is
clamped into a mold and inflated with air to make bottles for all kinds.
PET bottles are made by stretch blow molding so as to make them less
likely to rupture.
Parison

29. Mechanical Recycling
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 Vacuum molding: A heat-softened
sheet is sandwiched in a mold and the
space between the sheet and mold
sealed and evacuated to form
products such as travel bags, cups
and trays.
 Inflation method: This is a type of
extrusion molding where a melted
resin is inflated into a cylinder to form
a film. This method is used to make
products such as shopping bags.

30. Mechanical Recycling
Example of PET Bottles Recycling
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31. Mechanical Recycling
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32. Chemical Recycling
 Plastic waste seems to be a very promising feed in the production of
valuable chemicals and fuels. The current interest is not only in
recovering energy or in mechanical recycling but also in the
production of valuable products such as monomers or petrochemical
feedstock.
 Chemical recycling is an accepted recycling method that follows the
principles of ‘‘sustainable development”.
 Chemical recycling methods are opening newer pathways for using
waste as a precursor in generating pure value-added products for
various industrial and commercial applications.
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33. Chemical Recycling
Monomerization
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EG: Ethylene glycol
BHET: Bisydroxyethyl-terephthalate
DMT: Dimethyl-terephthalate
PTA: Purified terephtalic acid

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Chemical Recycling
Blast Furnace Feedstock Recycling
In the blast furnace,
gas is introduced
laterally at a high
velocity through a
port, called Tuyere.

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Chemical Recycling
Coke Oven Feedstock Recycling

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Chemical Recycling
Gasification process

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Chemical Recycling
Liquefaction process

38. Thermal Recycling
Thermal conversion methods such as Incineration (combustion),
pyrolysis and gasification are recognized as thermal feedstock recycling
technologies when the products are used for the production of fuels or raw
chemicals.
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Higher
Calorific
Value

39. Thermal Recycling
Energy Recovery via Incinerator
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Thermal Recycling
Energy Recovery via Gasification

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Exhaust Heat from
Incineration / Gasification
Thermal Recycling
Power Generation from Exhaust Heat

42. Recycling of Waste Tires
Mechanical Methods:
 Cryogenic Tire Recycling
This process is called “cryogenic” because whole tires or tire chips are cooled
down to a temperature of below –80 C (-112 F). At this temperature, rubber
becomes nearly as brittle and glass and size reduction can be accomplished by
crushing and breaking. This type of size reduction requires less energy and
fewer pieces of machinery. Another advantage of the cryogenic process is that
steel and fiber liberation, is much easier, leading to a cleaner end product.
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43. ELVs Recycling
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De-pollution process