Lecture 6 - Recycling of common materials (Ch. 5.1-5.5) Flashcards
Which stage in the typical waste management system has the lowest efficiency?
The source separation
Explain the term “recovery” in relation to recycling of paper and cardboard
o Recovery: amounts collected separately or otherwise recovered in a region for recycling.
Explain the term “utilization” in relation to recycling of paper and cardboard
o Utilization: amount of recovered paper which is used as a raw material in new products.
What is the typical utilization of recovered paper?
o Packaging paper (Case materials, carton boards, wrapping paper, other packaging papers)
o Graphic paper (Newsprint and other graphic paper)
o Tissue paper (Household and sanitary)
o Paper for technical and other purposes
What are the generic recycling steps for paper and cardboard?
o Removal of scraps and leftovers and cleaning o Pulping o Flotation and Washing o Screening and Cleaning o Dewatering
The typical reprocessing to packaging paper is different from the reprocessing of other papers, because of what?
- Two layers of different strength are processed.
- Long fibre fraction is used in the high strength layer
What requires the reprocessing to graphical paper besides the generic steps?
– Requires more extensive treatment
– Deinking -printing inks removed by flotation
– Bleaching –for products of high optical quality (agents such as sodium hydroxide)
Mention two EoL-options for glass
Reuse: Returnable glass bottles or containers:
o + highly sustainable – low environmental impacts
o – uneconomical and impractical in terms of logistic (for remote locations)
Closes-loop material recycling
o Feeding waste glass (cullet) into the glassmaking furnace
o Low/no loss of material property
o Color sorting is required for quality assurance
What are the methods used for sorting and preparation the glass for closed-loop recycling?
- Hand sorting –to remove obvious contamination
- Crushing
- Sieving –to also remove foreign material
- Magnetic sorting –to remove ferrous metals
- Eddy current sorting
- Vacuum sorting.
What are typical utilizations of glass from Open-loop recycling?
Ballotini:
Highly reflective small glass sphere –road signs, clothing, screens Colorless –only flint cullets can be used
Glass wool insulation:
Short glass fibers, no color requirement
Up to 80% cullet can be used
Foamed glass:
Varying shape/size, up to 98% cullet
Abrasive media
Filtration media
In other products:
Ceramics, Construction aggregate,
Concrete and cement
What is the main characteristic of thermoplast? Mention types of this plastic.
Thermoplasts do not undergo chemical changes when heated and can be molded again.
- PE,PP,PS,PVC;
- HDPE, LDPE and LLDPE.
What is the main characteristic of thermosets? Mention types of thermoset plastic.
Thermosets can melt and take shape once, a chemical reaction occurs that cannot be reversed.
- PUR.
What are the main users of plastic?
Packaging and constructions
What are the main steps of mechanical recyling of plastic?
Sorting (fx induction sorting, eddy current separator, drum separator, sink-float separation)
Shredding
Washing
Reprocessing
(fx agglomeration, extrusion, injection molding, blow molding, film blowing, fiber extrusion)
Explain the terms:
1) Agglomeration
2) Extrusion
3) Injection moulding
4) Blow moulding
5) Film blowing
6) Fiber extrusion
1) Agglomeration: Heating the plastic just below its melting point to reduce size, before cutting into pieces.
2) Extrusion: Used to homogenize the plastic pieces with heat
3) Injection moulding: The pellets are molten again and the polymer is pressed into a split mold
4) Blow moulding: The plasticized polymer is forced through a die.
5) Film blowing: Blowing compressed air into a thin tube to expand it (plastic bags)
6) Fiber extrusion: Filaments are spun to be drawn, dried, cut into staple fiber and baled for sale.
