Download - Environmentally Conscious Design & Manufacturing (ME592) Date: April 17, 2000 Slide:1 Environmentally Conscious Design & Manufacturing Class 18: Recycle

Environmentally Conscious Design & Manufacturing (ME592)

Date: April 17, 2000 Slide:1

Environmentally Conscious Design & Manufacturing

Class 18: Recycle

Prof. S. M. Pandit



Agenda

• Definition of recycling• Hierarchy of recycling• Design for recycling• Recycling metals, plastics & forest products• Economics



Definition of Recycling

American Automobile Manufacturers Association’s definition

A series of activities, including collection, separation, and processing, by which products or other materials are recovered from or otherwise diverted from the solid waste stream for use in the form of raw materials in the manufacture of new products.



Some Myths - 1

• Recycling should pay for itself- Bias in data collected, and the inability to

recognize large scale impact has led to reports of “expensive recycling”

- $200 of energy is saved per ton of material recycled



Some Myths - 2

• Environmental impacts of manufacturing are included in the products- Cost = function of:

» supply & demand» governmental policy» problems with assigning cost



Source: Bishop, “Pollution Prevention: Fundamentals and Practice”

Life Cycle of a Product



Recycling World

• Categories:- Portable high value (computers, auto parts)- Metals- Plastics- Paper- Chemicals & glass- Food waste- Used equipment- Building material



Typical Value for Vehicles



Hierarchy of Recycling Options




Steps of Recycling

For remanufacture and reuse:

• Disassembly• Cleaning• Sorting and inspection• Part renewal• Re-assembly



For material recycling:

• SeparationDiscrete subassemblies /

joining techniques

• SortingGroup or classify

• Reprocessing technology

Steps of Recycling (cont.)



Possible Separation for Materials




Example: Polymer Recycling



Design for Recycling

Multiple objectives

• Minimize variety of materials & components

• Avoid use of toxic materials • Ease of disassembly of dissimilar

materials



Disassembly

• Design for Disassembly (DFD)

• Ease of Disassembly

- Preferred design: snap-fit, pop-in, pop-out, bolted

or screwed components

- Difficult design: welded, adhesive, threaded

connections



Disassembly (cont.)

• Simplified Design

- Reduce the number and types of parts

- Reduce product complexity

• Modularity Design

• Material Selection

- Facilitate identification of materials (e.g. Marking plastics)

- Use fewer types of materials

- Use similar or compatible materials



Disassembly (cont.)• Non-Destructive Disassembly (NDD)

- Minimize the destruction of the product

- Maximize the potential of material resource and

sub-component reuse

• Destructive Disassembly (DD)

- Destroy one or more components so that the others

can be disassembled

- Save more expensive components- Recycle materials



Disassembly (cont.)

• Disassembly Strategy

- Analyze feasibility of part reuse and materials recovery

- Generate optimal disassembly sequence

- Disassembly optimization (Lower disassembly cost,

higher rate of component reuse, higher rate of material

recycling, etc.)



Recycling Metals

• Mixed metals (plating) - expensive• Pure metals - very inexpensive• Separation techniques:

- Manual- Automated magnetic separation- Chemical separation

» Pyrometallurgy, hydrometallurgy, electrometallurgy



Recycling Plastics

• Thermoplastics - easy- Polyethylene terepthalate, polyvinyl chloride,

low density polyethylene, polypropylene

• Thermoset plastics- Phenolics, polyesters, epoxides: -

crosslinking, need pyrolysis / hydrolysis to reduce mol. Wt.



Recycling Rubber

Mechanical Recycling

Feed StockRecycling

Energy Recovery

Use as is(Retreaded tired, fishing banks, etc.)

Powdered rubber(Block, road paving, etc.)

Reclaimed rubber(Devulcanization by the PAN reclaiming

Thermal decomposition, etc

Recovery of heat energy

Source: Otsuka et al., SAE 2000 world congress



Recycling Forest Products

• Paper- Fibers get shorter with use & recycling

» White bond» Colored bond» newspaper» grocery bags» toilet paper



Economics

• Recycling must be profitable

• Revenue from recycling:- High value, reusable subassembly and parts - Recycled materials and energy

• Cost incurred by recycling:- Investments in recycling equipment- Labor cost- Other cost such as transportation, equipment

operating



Economics (cont.)

Number of Disassembly Steps

Co

st

Landfilling Cost

Disassembly cost



References

• Graedel & Allenby, Industrial Ecology, 1995• http://minerals.usgs.gov/minerals/pubs/commodity/recycle/

index.html• http://doemetalsrecycle.ornl.gov/• http://www.edf.org/pubs/reports/armythfin.html• http://www.recycle.net/recycle/• http://mime1.marc.gatech.edu/Courseware/autorecycling/

MatRecyc.html• http://srl.marc.gatech.edu/education/Recycle/EnergRec.

html



Homework #6

1 How is the manufacturing economics affected by environmental considerations? (Illustrate your answer by using machining as an example)

2 What steps would you take in a quantitative decision making process? What are the different tools available in this process?

3 Compare and contrast traditional and ECDM guidelines for material selection.



Homework #6

4 Why is recycling of plastics so important for the ECDM efforts? Give relevant statistics to support your answer.

5 What are the major hurdles in recycling of plastics? How can they be overcome?

Download - Environmentally Conscious Design & Manufacturing (ME592) Date: April 17, 2000 Slide:1 Environmentally Conscious Design & Manufacturing Class 18: Recycle

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