recycling in waste management
DESCRIPTION
RECYCLING in waste management. Total waste production in EU countries. Total amount of 2.62 billion tonnes (2008) European Parliament passed a resolution on Resource Efficien Europe ( zero waste by 2020). Source: Eurostat. Per capita waste generation in EU by individual countries. - PowerPoint PPT PresentationTRANSCRIPT
RECYCLING in waste management
Total waste production in EU countries
• Total amount of 2.62 billion tonnes (2008)
• European Parliament passed a resolution on Resource Efficien Europe (zero waste by 2020)
Source: Eurostat
Per capita waste generation in EU by individual countries
Per capita hazardous waste generation in EU by individual countries
Municipal solid waste (MSW) composition in EU
Total amount: 221 million tonnes
MSW composition for the USTotal MSW generation: 234 million tonnes
Source: US EPA
State of the art: landfilling• Health and sanitary risks at dump sites, and at their vicinity
(microorganisms, insects, rodents)• Groundwater contamination by landfill leachate, incl. heavy
metals and pesticides• Airborne pollution on burning and incineration• Release of greenhouse gases (CH4, CO2, etc.)• The problem can be at least partially solved by recycling
Recovery options for various waste: an American case study
Paper
Glass
Steel
AluminiumPlas
tics
Rubber and le
ather
Textile
WoodFo
od0
10
20
30
40
50
60
70
80
90Production, mln tonnesRecycling, mln tonnes The lowest
recovery:• Plastics• Food waste
US EPA, 2005
Recycling development• First recorded ideas on recycling
originated from Plato (ca. 400 BC)• Archeology shows that recycling
was popular in the antiquity (why?)• 18th-19th centuries – recycling of
dust and ash from burning wood and coal (bricks), scrap metal, glass• World Wars – literally everything• Next upsurge – 1970s (greatly
increased prices for oil and energy)• Increased environmental awareness
Proposed complete recycling schemeCollection
Sorting at conveyor beltOrganics + rejects
PaperMetal Textile
Glass
Plastics
Press Crushing
Composting
Rejects Compost
Bricks, interlocks, wheels, tables, manholes, road ramps, etc.
Sand
Thin filmplastics
Hardplastics
Paper recycling
Paper recycling stages• Paper sorting• Metal removal by magnet (staples etc.)• Pulping• Cleaning and screening• De-inking• froth flotation• wash deinking (detergent addition)
• Washing• Bleaching• Paper production• It is considered (US EPA, 2012) that paper can be recycled 5-7
times before cellulose fibres become too short
Paper sorting: main paper categories
• High-grade paper for printing and writing• Newsprint• Paperboard and packaging paper• Tissues and paper towels
• De-inking is required for most paper types in course of recycling
Pulping and screening• Mechanical defragmentation• pH adjusted to 8.5-10• H2O2 / O3 for bleaching• Ca2+ compunds as fillers• Fatty acids/soap• Obtained slurry undergoes
centrifugal cleaning and screening to remove particles heavier and larger than pulp fibres
De-inking: froth flotation
• Chemicals can be added to faciliate ink removal
• This is done primarily in tissue paper production
Image source: en.wikipedia.org
Recycling 1 t of paper saves:• 1 t of wood (ca 17 trees)• 26 m3 of water• 320 L of oil• 4100 kW h of energy (6-months consumption of an average US
house)• 2.3 m3 of landfill space
Plastic recycling
Most commonly used plastic types• PET/PETE (polyethylene terephtalate) – soft drink bottles, food
containers• HDPE (high density polyethylene) – bottles for beverages with
short life (milk, juices)• LDPE (low-density PE) – cable insulation, flexible bottles• PVC (polyvinylchloride), V (vinyl) – packaging sheets, wire and
cable insulation, floor tiles• PP (polypropylene) – packaging film, bottles for hot liquids• PS (polystyrene) – protective packaging
Basic recycling steps• Cleaning (hot water)• Sorting • Cutting• Shredding• Agglomeration• Pelletizing• Reprocessing
Plastic waste
Washing
Sorting
Agglomeration Shredding
Pelletizing
Injection molding Film blowing Extrusion
Sorting plastic types• Water-alcohol solution:• = 925 kg m-3: HDPE sinks, PP floats• = 930 kg m-3: HDPE sinks, LDPE floats
• Water-salt solution:- separating PS (polystyrene) and PVC
• Resin identification code (RIC)• Near-infrared analysis (NIR)
Resin identification code
PET PP
HDPE PS
PVC Other
LDPE
A few words on infrared analysis
Graph: Khayet et al., J. Membr. Sci. 263 (2005) 77-95Spectrometers: Google
Extrusion
1. rotating screw2. plastic pellets
addition3. breaker plate4. extruded plastic
Image source: en.wikipedia.org
Injection molding
Film blowing
http://www.hipf.edu.sa/HIPF_English/Courses-BFE.html
Thermal depolymerisation (TDP)• Plastic waste is cut or shredded• Water addition• Temperature risen to 250 C at constant volume, pressure rises to
4 MPa, 15 min• Pressure is released, water evaporates• Second stage reactor: 500 C, breaking up long hydrocarbon
chains• Destillation• Light crude oil produced• Plastic bottles can produce up to 70 % oil and 16 % gases from
their initial mass
Products from recycled plastic
• PET:• Storage containers, including food containers, fabrics
• HDPE• Tables, roadside curbs, benches, truck cargo liners, trash
receptacles• PS• Metal casting operations, concrete
• Others• Bricks, tiles, plastic railroad ties, additives to ashalt
Glass recycling
Main glass types• Container glass• Flat glass• Fibreglass• Domestic glass• Special glass types: fused silica, borosilicate glass, etc.
Glass composition (1):
• Soda-lime-silica glass: 72 % SiO2, 14.2 % Na2O ,2.5 % MgO, 10.0 % CaO, 0.6 % Al2O3; high thermal expansion, low heat resistance (melts at 500-600 C) – windows, containers, glassware, etc.
• Borosilicate glass (incl. Pyrex): 81 % SiO2, 12 % B2O3, 4.5 % Na2O, 2.0 % Al2O3; very low thermal expansion – laboratory ware, optics, household cookware
• Fused/vitreous silica glass: SiO2; low thermal expansion, very hard, resists heat (melts at 1000-1500 C) and weathering – furnace tubes
• Crystal glass: 59 % SiO2, 2.0 % Na2O, 25 % PbO, 12 % K2O, 0.4 % Al2O3, 1.5 % ZnO; high elasticity, poor heat resistance - glassware
Glass composition (2)
• Aluminosilicate glass: 57 % SiO2, 16 % Al2O3, 4.0 % B2O3, 6.0 % BaO, 7.0 % MgO, 10 % CaO – fibreglass, glass-reinforced plastics, halogen bulb glass
• Oxide glass: 90 % Al2O3, 10 % GeO2; extremely clear, used for fibre optics
Glass recycling stages• Sorting• By colour: glass of different colour generally has different
properties• By glass types – borosilicate and other special glass types should
be dealt with separately: these should be disposed of separately• Crushing into cullet• Melting• Production
• Part of glass containers can be reused
Optical glass separator
Glass production• Glass and cullet storage• Melting in furnace (up to 1575 C)• Forming• Cutting molten glass into cylinders a.k.a. gobs (1050-1200 C)• Blow and blow method: glass is blown into ring mould with all the
container details (parisons), and then blown to full container shape
• Press and blow method: parisons are formed by pressing• Done by individual section (IS) machines
• Inner surface dealkalization (high-temperature S- and F-containing gas)
• Annealing (580 C)• Cooling down (20-6000 min)
Foam glass production• Foaming agent is added to the glass• CaSO4
• Coal• CaCO3
• Aluminium slag• Mixing (foaming agent particle size ca. 75-150 µm)• Heating: gas bubbles form and expand (700-900 C)• Annealing• Cutting into details
Implementation of recycled glass• Glassware• Insulation• Ceramic sanitary ware• Brick manufacturing• Artificial turf• Recycled glass worktops• Foam glass filters• Abrasive materials• Construction aggregate for concrete
Laminated plastic recycling
Laminated plastics• Usually a plastic made of superposed layers of paper, wood,
glass, metal or fabric bonded or impregnated with resin and compressed under heat
• Perhaps one of the most challenging material in terms of recycling is PE/Al composite (chip bags, milk/juice containers, etc.)
Recycling process stages• Shredding• Magnetic and Foucaul current separation• Foucault or eddy curent arise when the magnetic current passing
through conducting material changes• This slows down passing metallic objects
• Aluminium-rich fraction (up to 50 %) is thus obtained• Fraction is treated thermally to remove PE• Rotating kiln• Moving bed pyrolysis oven
• Al is remelted and recycled into new foil
Alternative recovery• Shredding• Addition of diluted acid (HCl or H2SO4) or NaOH
2 Al + 6 HCl → 2 AlCl3 + 3 H2 ↑2 Al + NaOH → 2 NaAlO2 + H2 ↑
• PE slurry is separated by filtration• Hydrogen can be used as fuel gas
Biodegradable organic waste recycling (including food waste)
Organic part recycling• Anaerobic fermentation coupled with biogas production• Methane tanks
• Optimal temperature for biogas production is around 37 °C• Composition: methane and carbon dioxide, may have hydrogen
• Composting • Sludge from methane tanks is aerated, dewatered (when necessary), and mixed
with peat (when necessary)• Left for further decomposition• Used as soil for food-unrelated purposes upon rejects removal (if any)
Recycling MSW rejects
Rejects • Contaminated plastic bags• Clening not cost efficient
• Small pieces of glass• May be dangerous for those who sort waste
• The rejects are usually separated from compost after maturation of piles • Drum separator with cutting tools• Organic material is shredded into smaller prices an exits through
openings in drum walls• Rejects are transported further and exit at the end of the drum• Alternative: screen separator
• Can be incinerated or recycled
Separated rejects• Agglomeration• Cutting• Sand addition• Heating up to 140-240 °C• Plastic rejects melt,
forming silica-plast mass that can be molded and pressed into various products
Compost with rejects
SeparatorCompost
Rejects
Agglomerator
Mixing and heating
Sand
Sand screens
MoldHydraulic pressProducts
Silica-plast products from MSW rejects• 20-60 % of sand• Compressive strength 10-23 Mpa• Density of 1.12-1.68 g cm-3
• Low water adsorption
• Bricks• Poor adhesion (plastic)• Higher density• Hard material (bulletproof)
• Interlocks• Yards, floors, pavements, etc.• Cost is 30-50 % of ceramic interlocks
• Maintenance hole covers• Cheaper and not prone to corrosion, as metal covers
Recycling in iron and steel industry
Blast furnace1. Hot blast2. Melting zone3. FeO reduction4. Fe2O3 reduction5. Pre-heating6. Feed7. Exhaust gases8. Ore, coke and
limestone9. Removal of slag10. Molten pig iron11. Waste gases
collectionFe2O3 + 3CO → 2Fe + 3CO2
Pig iron• 2.14-6.97 % C• 0.2-0.8 % Si• 0.08-0.18 % P• 0.01-0.04 % S• Mn, etc.
• Brittle due to high carbon content• Refinig into steel is needed
Basic oxygen furnace• Hot pig iron is poured
into converter• Magnesium for sulphur
removal• Oxygen stream (99 %)• Outcome: low-carbon
steel • 0.3-0.6 % C• 0.05-0.1 % Mn• 0.01-0.03 % Si• 0.01-0.03 % S and P
Slag• Blast furnace: 20-40 % by mass of pig iron produced• Basic oxygen furnace: 5-22 % of steel produced• Generates SO2, on contact with water H2S and H2SO4
• Recycling: iron re-smelting, addition to glassware and ceramics (from Antiquity on), cement production, road filling, insulating materials (slag wool)
• Part of iron in the slag can be reduced and extracted by magnet
Recycling statistics
Waste recovery in EU