1. PB389 Integrated Solid Waste Management
Numfon Eaktasang, Ph.D.
Thammasat University

2. Solid Waste Management
generation
Waste reduction
and separation at the source
Collection
Transportation
Separation, processing & transformation
Disposal

3. Density separation – type of equipment
Separated based on the density and aero dynamic characteristics
Applied to the separation of shredded MSW into
Light fraction; paper, plastics and organics
Heavy fraction; metals, wood, etc..
Type
Air classification
Stoner
Flotation
Heavy media separation

4. Air classifier (1)
Lighter materials transport to the top of chute by the upward airflow
Control of the percentage split is accomplished by varying the waste loading, airflow rate, and the cross-sectional area of chute

5. Air classifier (2) Type of classfier Straight:
Zigzag: creates turbulence and allows bunched materials to be broken up.
Pulsed air: can achieve a greater discrimination
Straight
zigzag
Passive pulsed

6. Solid Waste Management: Chapter 5
Stoner (1)
Consists of a vibrating porous deck through which air is blown
Solid Waste Management: Chapter 5

7. Stoner (2) Initially designed to remove stones and other heavy rejects
Separate heavy grit from organic material in trommel underflow streams
Called inert separator
Actual separating criterion is terminal velocity, not density or weight.
Important operation variables are deck slope and air volumes

8. Flotation
Employs a fluid to separate two components of different densities.
Using water
Sink to bottom: glass chips, rocks, bricks
Float: light organics, plastics,…
Change the liquid, we can separate in a different density.

9. Heavy Media Separation
Shredded feedstock is dumped into a liquid stream that has a high specific gravity.
Aluminum separation (floating in a liquid)
After ferrous metal and glass have been removed.
Disadvantage
Optimum-size requirement: ton/d of feedstock
Increase success of source separation

10. Density separation – performance characteristics (2)
Solid Waste Management: Chapter 5

11. Density separation – design criteria (1)
Design based on
Air/solid ration (kg-air/kg-waste): 2 to 7
Required fluidizing velocity
Fluidizing velocity for pulsed air classifiers

12. Solid Waste Management: Chapter 5
Density separation
Solid Waste Management: Chapter 5

13. Density separation – Selection of equipment
Factors to be considered
Characteristics of material produced by the shredder or other separation device: particle size, shape, bulk specific weight, moisture content, particle size distribution, clumping tendency, fiber content
Materials specifications for light fraction: particle size and its distribution
Air classifier design parameters: air/solids ratio, fluidizing velocity, unit capacity, total air flow
Stoner design parameters: bet slope, fluidizing air, exhaust air
Operational characteristics: energy requirements, maintenance requirement, simplicity of operation, noise, air emission
Site considerations: floor space and height, access

14. Magnetic and Electric field separation
Magnetic separation
Based on magnetic permeability
Separate ferrous from nonferrous metals
Electrostatic separation
Based on differing surface charge characteristics
Separate plastics from paper
Eddy current separation
Varying magnetic fields are used to induce eddy currents in nonferrous metals such as aluminum

15. Magnetic separation
Permanent magnets or electromagnets can be used

16. Electrostatic separation
Use high-voltage electrostatic field to separate
Nonconductors of electricity such as glass, plastic and papers from conductors (metal)
Nonconductors from each other based on differences in their electrical pemittivity or ability to retain electrical charge
Separate paper from plastics
Different types of plastics from each other
Not widely used now, but promising technology
Plastic recycling

17. Electrostatic separation

18. Eddy current separation
Mechanism
Time-varying magnetic field
Voltage (eddy current) are generated in conductors
Magnetic force is produced.
Widely used
Aluminum separation from shredded waste
Waste
Non-metals
Nonferrous metals

19. Eddy current separation

20. Magnetic and Electric field separation – performance characteristics
Performance criteria
Recover, Purity, Efficiency
Magnetic separation devices
Generally, very high efficiency (>95%)
Design criteria
Based on mass loading and power consumption
Permanent magnets, comparing with electromagnets
Reduce operating cost, but need more capital costs

21. Magnetic and Electric field separation – Selection of equipment
Factors to be considered
Characteristics of material to be separated: particle size, shape, moisture content, material composition
Materials specifications for separated materials: purity, recovery and efficiency requirements
Device design parameters: unit capacity, power requirements (voltage and amperage), magnet strength, electrostatic field strength
Operational characteristics: energy requirements, maintenance requirement, simplicity of operation, noise, air emission
Site considerations: floor space and height, access

22. Densification (compaction)
Unit operation which increases the density of waste materials
Reduction of storage requirements of recyclables
Reduction of volume for shipping
Preparation of densified refuse-derived fuels (RDF)
Type of equipment
Stationary compactor
Prior to landfilling or combustion to reduce haul costs
Baling machine (Baler)
Processing recovered materials prior to sale
Cubing and pelleting equipment
Preparation of densified RDF

23. Stationary compactor
Compactor is categorized into stationary or movable.
Mechanism is same as a collection vehicle.
Usage of stationary compactor
Light duty
Commercial and light industry
Heavy industry
Transfer station
Low-pressure (<100lb/inch2)
High-pressure (>100lb/inch2)

24. Baling equipment Operating under high pressure Target materials
Typically, 100 to 200 lb/inch2
Target materials
Cardboard, newsprint, plastic,PET bottles, aluminum can
Baled materials
Easy to load with forklifts and economically shipped

25. Cubing and pelleting
Technology that can be used to produce densified refuse-derived fuels
Waste paper or shredded RDF is extruded through extrusion dies with and eccentric rotating presswheel.

26. Densification – design criteria (1)

27. Densification

28. Densification – Selection of equipment
Factors to be considered
Purpose of densification: compaction, cubing and pelleting, baling
Characteristics of material to be processed: particle size and its distribution, shape, moisture content, material composition, specific weight
Equipment design parameters: unit capacity, power requirements (voltage, amperage, horsepower), compaction ratio, unit specific weight, bulk specific weight, bale weight, operating pressure
Operational characteristics: energy requirements, maintenance requirement, simplicity of operation, noise, air emission
Site considerations: floor space and height, access

29. Development and implementation of MRFs
Engineering consideration
Definition of the functions of the MRF
Selection of the materials to be separated (now and future)
Identification of the material specifications
Development of separation process flow diagram
Determination of process loading rates
Layout and design of the physical facilities
Selection of the equipment and facilities
Environmental controls and aesthetics considerations
Nonengineering implementation issues
Siting
Environmental emissions: traffic, noise, odor, dust, airborne debris, liquid discharge, visual unsightliness, vector control
Public health and safety: workers, public access
economics

30. Functions of MRF (1) Depend on For source-separated wastes
Role of the MRF in the waste management system
Types of materials to be recovered
Form in which the materials to be recovered will be delivered to the MRF
Containerization and storage of processed materials for the buyer
For source-separated wastes
Mixed paper and cardboard:
Manual separation of cardboard, newspaper, high-value paper or of contaminants from commingled paper types. Baling of separated materials for shipping. Storage of baled materials.
PETE and HDPE plastics:
Manual separation of PETE and HDPE from commingled plastics. Baling of separated materials for shipping. Storage of baled materials.

31. Functions of MRF (2) For source-separated wastes Mixed plastics:
Manual separation of PETE, HDPE and other plastics from commingled plastics. Baling of separated materials for shipping. Storage of baled materials.
Mixed plastics and glass:
Manual separation of PETE, HDPE and glass by color from commingled mixture. Baling of plastics for shipping. Storage of separated materials.
Mixed glass:
Manual separation of clear, green and amber glass. Storage of separated materials.
Aluminum and tin cans:
Magnetic separation of tin cans from commingled mixture. Baling of separated materials for shipping. Storage of separated materials.

32. Functions of MRF (3) For source-separated wastes
Plastics, glass, aluminum and tin cans:
Manual or pneumatic separation of PETE, HDPE and other plastics. Manual separation of glass by color. Magnetic separation of tin cans. Baling of plastics, aluminum and tin cans, and crushing of glass for shipping. Storage of separated materials.
Yard wastes:
Manual separation of plastic bags and other contaminants from commingled yard wastes. Grinding of clean yard wastes. Size separation. Storage of oversized materials for biomass facility or mulch. Composting of the undersized materials.

33. Functions of MRF (4) For commingled MSW
Recovery of recyclable materials
Preparation for use as a fuel
Preparation for use as a feedstock for composting
Manual separation of bulky items, cardboard, PETE, HDPE, other plastics, and large ferrous items. Mechanical or manual separation of glass by color and aluminum cans. Magnetic separation of tin cans and other ferrous materials.
Baling of cardboard, plastics, aluminum and tin cans, and crushing of glass for shipping. Storage of separated materials.
Fuel preparation

34. Development of separation process flow diagrams
Assemble of unit operations
Important factors
Characteristics of the waste materials to be processed
Specifications for recovered materials now and future
Available types of equipment and facilities

35. Flow diagrams for source-separated waste (1)
Paper and cardboard
Plastics and glass
Aluminum and tin cans
Process for mixed paper 

36. Materials balances and loading rate
Design of MRF
Appropriate design loading rate
Loading rate (ton/h)
= total loading (ton/yr or ton/d)
/ operating hours (h/yr or h/d)
Total loading is estimated based on mass balance.
Quantities of materials that can be recovered is essential to consider mass balance.

37. Material recovery rates for source-separated materials
Materials recovery rates
For input of MRFs
Indicate the effectiveness or performance of the recycling program
Material recovery rate
　　　　　= composition factor * recovery factor * participation factor
Composition factor= fraction of waste component in total
Recovery factor= fraction of material recovered
Participation factor= fraction of the public that participates

38. System layout and design
Important factors
Methods or means by which the wastes will be delivered to the MRF
Materials delivery rates
Materials loading rates
Material flows and handling pattern within the MRF
Performance criteria for the selection of equipment and facilities
Overall MRF layout includes
Sizing of the unloading and presorting area
Placement of conveyor lines, screens, magnets, shredders and other unit operations.
Sizing of storage and outloading areas
Sizing and desing of parking areas and traffic flow patterns in and out of the MRF

39. Selection of Equipment and facilities
Factors that should be considered
Capabilities: can we improve conventional practice?
Reliability
Service: maintenance can be done by local trained personnel?
Safety of operation, health hazard
Efficiency: specific energy consumption
Environmental effects
Economics

40. Thank You for Your Attention