Mixed plastic waste (MPW) may be a mixture of two ... · Mixed plastic waste (MPW) may be a mixture...

Mixed plastic waste (MPW) may be a mixture of two thermoplastics

or a variety of thermoplastics

Commingled plastic waste

Plastic wastes from domestic refuse collection

generally have the following composition,

Polyolefins 70%

PS 9%

PVC 11%

EPS 3%

other 7%

Source

separation


mixtures of different plastics considerably reduce the quality

of the products made from them

contamination with other nonplastic waste fractions

such as paper, metal, glass, food residues etc.

separation is most difficult

Thermodynamic

incompatibility Application

incompatibility

Problems:

Thermodynamic incompatibility


J. Brandrup, M. Bittner, W. Michaeli, G. Menges, Recycling and Recovery of Plastics, New York, 1996, p. 376.

Application incompatibility



Processing temperature will be

dictated by,

the need to obtain suitable

rheological behavior of the melt

the need to avoid excessive

degradation of any single

component

Commingled plastic waste recycling

Reprocessing Use as fillers

Feedstock

recycling

Energy

recovery


Re-processing for commingled plastics recyclate


Commingled plastic waste recycling : Reprocess

Pretreatment of mixed plastics sorting

preliminary size reduction

grinding

agglomeration of film flake

mixing and interim storage

Processing of mixed plastics

intrusion process

extrusion process

injection molding

sinter molding process


Sorting

Mixed & contaminated wastes need to be sorted before qualified

recycling processes can begin.

Sorting plant

Various separated fractions

- plastic bottles

- film

- mixed plastics

- tinplates

- aluminums

- papers


Sorting


Preliminary size reduction & Grinding

reduce plastic waste in size easily feed into plasticating unit

5 x 5 mm has becomes customary

Rotary cutter

- High flexibility for variation of

plastic types and forms

- screen is set at an exist of

regrinding chamber

- mesh size determines size of

regrind


agglomeration of film flake

Ground film material bond together by pressing or fusion process

- bulk density & grain size greatly increase

- ensure good feeding into plasticating unit

- only slightly thermally stress for a short time


Processing of mixed plastics

Intrusion process

Extrusion process

Injection molding process

Sinter-molding process

large-surface, thick-walled products can be produced

products can be painted, pigmented, laminated or coated to

improve the surface quality and appearance


Intrusion process

- combination of injection molding &extrusion

- mixed plastics are plasticated in extruder, filled in metal mold

and then cooled until product solidifies

- high-melting thermoplastics, foreign matters and contaminants

become embedded in the melt & predominantly in core of product

Demands on feed material:

- Minimum polyolefins proportion ~ 40 wt.%

- Total amount of foreign matters should be


Intrusion process

The Real process


Intrusion process

Recycled plastic lumber

- replace wood products

- have typical advantages of plastics


Intrusion process

Recycled plastic lumber

has properties similar to wood with distinguished advantages -

high chemicals resistance

- wide variety of possible products

can be used substitute wood under following conditions

- applications which wood is endangered by living organisms

- in animal husbandry applications

- fences

- in applications which high wear resistance is required

- in applications which electrical resistance is required


Extrusion process


- minimum polyolefins proportion should be as high as 50 wt.%

- total amount of foreign matters; paper, thermosets, aluminium,

rubber should be


Extrusion process The Greiner & Sohne process


Extrusion process

Product: thin-walled hollow profiles (wall thickness ~5 mm.)

- coloring with masterbatch pigment

- reinforcement by addition of wood or paper fibers

(elastic modulus increases 30-80%)

- surface improvement by coextrusion and film coating

- additives addition to improve UV resistance, thermal stability

& modify cold impact resistance

improve the physical & chemical

properties by


Extrusion process: Product

Typical applications:

- building construction

- civil engineering

- sewers & road building

- agriculture & transportation

- horticulture

- traffic control




- may have moisture content of 7 wt.%

- total amount of foreign matters; paper, aluminium, copper,

wood, metal, vet. Oil, paint, sand & rubber should be



The Remaplan GmbH process




- demand on the composition of raw mat. are low

- raw mats. are not required to wash

-foreign matters; aluminium & paper are easily processed along

with plastics

- sink fraction (PS, PVC, PET, others) from plastic waste sorting

can be processed without further additives



The Wegner & Co. (Weco) Schweisswerk-Behalterbau process


Sinter-molding process: Products surface is often multicolored

- panels (semi-finished products in similar way to chipboard)

- pallets

- packaging materials

- partition walls

- soundproof walls


Properties of commingled plastics recyclate

Important variables: - composition of mixed plastics

- composition of contaminants

- type, size & concentration of foreign matters

Addition of fillers or fibers to commingled plastics waste provides

a further means of improving the mechanical properties.

Glass fibers improves strength at break, stiffness

Talc improves stiffness

Compatibilizer improves overall mechanical properties


Properties of commingled plastics recyclate

Properties Stark Italian Thomas New

Jursey

Tensile strength [Mpa]

Ultimate stress [Mpa]

Elastic modulus [Mpa]

Flexural modulus [Mpa]

Compression modulus [Mpa]

Elongation at break [%]

Notched impact strength [kJ/m2]

Impact resistance [kJ/m2]

13.9-15.6

250-1280

2.8-15.0

3.9-6.7

5.2-17.4

20.5

950

6.8

11.5

14.2

933

811

20.7

7.3

17.1

21.9

794



Feedstock

recycling

Energy

recovery

Commingled plastic waste recycling : Fillers

use as plastic fillers cost reduction

properties drop down

use as aggregate in concrete for construction materials


Advantages for using MPW in building materials

low thermal conductivity thermal insulation components

lightweight dense concrete aggregate

less wear of conveyor equipment

lowering E-modulus with retention of strength

enhances crack resistance of plasters

high intrinsic strength relative to density


Restrictions for using MPW in building materials

flammability high contents of plastics restrict the scope for

application

DIN 4102: building materials used for load-bearing components are

subject to stringent requirements for non- flammability

not all building sectors are wiling to use plastics

considerable effort to obtain approved status;

technical properties, environmental compatibility, hygiene and

industrial medicine


Plastic aggregate in concrete

Aggregate is the granular structure that is cemented together

with the aid of the water/binder matrix. It consists either of

natural or artificial dense, porous stone or of metals or organic

compounds with particular sizes suitable for making concrete,

and is used as a mixture of particles of the same or different

size


Plastic aggregate in concrete (plastic grain): Sicowa process

Raw materials: contaminated commingled plastics waste

20-40% contaminants; paper, metals, glass, food scraps, etc.

MPW Preparation

Compression,

compaction

Thermal treatment

in autoclave

Semi-finished

Plastics products

Size reduction,

Drying & milling

Plastic grains

& flour

Cleaned

plastic regrind



Preparation

shredding of the compressed baled

separation of heavy metals

size reduction & washing

separation of plastics according to polymer (optional)

drying

Cleaned plastic regrind



Thermal treatment (Autoclaving)

wet plastics (residual moisture of 20-40 wt.%) are treated

hydrothermally in autoclave

with presence of steam, plastics are plastified at set

temperature

( 170 oC) & intensively sterilized and re-cleaned

yielding homogeneously melted semi-finished plastics with a dry

density of 700 kg/m3



Size reduction, Manufacture of Grains & Flours

semi-finished products are sized-reduced in cutting mills to

coarse granules (max. diameter = 8 mm)

residual moisture is driven out @ T< 70 oC moisture < 1 wt.%

dried coarse granules are reduced further in size to fine grains

and flours by disc mills



Feedstock

recycling

Energy

recovery

Commingled plastic waste recycling : Feedstock recycling

Examples of MPW feed stock recycling

Texaco gasification process

Polymer cracking process

BASF conversion process

Used as reducing agent in blast furnace

Veba combi cracking process

Pressurized fixed bed gasification

Akzo Nobel steam gasification process

Linde gasification process

NKT pyrolysis process PVC-rich waste



Combination 2 process steps,

- liquefaction step : plastic waste is cracked under relatively

mild thermal condition

depolymerization results in synthetic

heavy oil & gas fraction

- entrained bed gasifier: @ 1200-1500 oC with steam & O2



Raw materials:

process can deal well with up to 10% PVC in feedstock

non-plastic materials is thought to be around 10%

Material texture Dry, not stick, free

flowing

Plastics content > 90 wt%

Physical

description

Shredded or chipped Free metals < 1 wt%

size < 10 cm PVC content < 10 wt%

Physical fine

content

< 1% under 250 mm Ash content < 6 wt%

Bulk density > 100g/l Residual moisture < 5 wt%

Form @ delivery Baled or agglomerated Paper content < 10 wt%



Products:

synthesis gas (mainly H2/CO)

pure sulfur

saleable NH4Cl

vitrified slag secondary building materials

fines quality matches the fly ash


Polymer cracking process (BP Chemicals)

basic separation of non-plastic fraction & size reduction is

required

fluidized bed reactor operates @ 500 oC in absence of air


Polymer cracking process (BP Chemicals)

Polyolefins 70-80 wt% Moisture 0.5-1 wt%

Polystyrene 15-30 wt% Metal pieces Max. 1 wt%

PET 3-5 wt% size 1-20 mm

PVC 2-4 wt% Fines sub-250 micron Max. 1 wt%

Total plastic

content

90-95 wt% Bulk density 300-400 kg/m3

Ash 2-5 wt%

Other inputs into a process are;

electric power: approximately 60 kW/ton feed plastic

cooling water: 40 m3/ton feed plastic

steam: 1.2 ton/ ton feed plastic


The BASF conversion process

developed for packaging waste recycling

Cl content is recovered as HCl, NaCl & CaCl2

separation Grinding &

agglomeration

dehalogenation conversion

@400 oC

MPW

products


The BASF conversion process

Products:

HCl which is for a small part neutralized or processed in a

HCl acid production plant

naptha to be treated in a steam cracker

monomers, e.g. ethylene & propylene, which can be used for

the production of virgin plastic materials

high boiling oil, which can be processed into synthesis gas or

conversion coke & then transferred for further use

residues


The Akzo nobel steam gasification process

can handle variety of materials; wood,

biomass, MPW or pure PVC waste

process is centred around two separate circulating fluid bed

(CFB) reactors which are operated at atm pressure

Gasifier Combustor

- fast pyrolysis @ 700-900 oC with

steam

- products: gaseous (fuel gas & HCl)

residual tar

- burn residual tar to provide

heat for gasification



Feedstock

recycling

Energy

recovery

Commingled plastic waste recycling : Energy recovery

Complete combustion: O2 3T

heat energy

600-1000 CC ( 850 CC)

Incineration

3T

-Temperature excess air water

spray T

-Residence time

-Turbulence

O2


Incineration


Incineration

(Incineration process)

(Residue handling process)

(Flue gas cooling process)

(Flue gas treatment process)

(Wastewater treatment process)

(Heat utilization process)

Incineration

Type of Incinerator

- (Stoker type incinerator)


Incineration

Type of Incinerator

- (Rotary kiln incinerator)


Incineration

Type of Incinerator

- Fluidized bed incinerator

()

(turbulent)


Incineration


Incineration

(Residue handling process)

2

- (Bottom ash)

- (Fly ash)

(Cyclone) (Baghouse

filter) Electrostatic precipitator (ESP)


Incineration

(Flue gas cooling process)

250-300 oC

- Water spray

heat energy

-

(Flue gas treatment process)

2

- Dust treatment Cyclone, Baghouse filter, Electrostatic

precipitator (ESP)

- Wet scrubber-Gas treatment Wet scrubber

(NaOH) (Ca(OH)2) HCl, SOx, CO, NOx


Incineration

(Wastewater treatment process)

- (Chemical precipitation)

-

(Activated sludge: AS)


Incineration

(Heat utilization process)

- (Electricity generation)

- (Hot water use)


Incineration

- 80-90%

-

-

-

-

-

-


Incineration


Cement kiln

( Zero landfill)

1450 oC

Date post:	28-Jul-2018
Category:	Documents
Author:	nguyenthuy
View:	213 times
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Mixed plastic waste (MPW) may be a mixture of two ... · Mixed plastic waste (MPW) may be a mixture...

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