Air classifier: Zig-zag. Copyright Anders Damgaard & Morton A. Barlaz, NC State University 36

Transcription

1 Air classifier: Zig-zag Copyright Anders Damgaard & Morton A. Barlaz, NC State University 36

2 Material settling velocity Copyright Anders Damgaard & Morton A. Barlaz, NC State University 37

3 Optical sorting Glass can sort crushed glass by color can remove ceramic role will be at an intermediate processor collecting glass from multiple MRFs Plastic PET HDPE (translucent/pigmented) Copyright Anders Damgaard & Morton A. Barlaz, NC State University 38

4 Paper Sorting A lot of activity on sorted office pack (SOP) Tradeoff between quality and diversion high quality: 10-20% diversion SOP up to 75% of office waste What is the market for sorted vs. mixed paper? Copyright Anders Damgaard & Morton A. Barlaz, NC State University 39

5 Paper Sorting What can be done at a MRF? Labor intensive as mechanized sorting can only do so much Disc/star screens separate OCC from other paper Waterfall conveyors that flip stacks of paper every 30 contaminants are more visible to sorters Pneumatic suctions ducts over picking lines eliminate workers bending and turning reduces contamination Copyright Anders Damgaard & Morton A. Barlaz, NC State University 40

6 Star Disc Screen Copyright Anders Damgaard & Morton A. Barlaz, NC State University 41

7 Disc screen Copyright Anders Damgaard & Morton A. Barlaz, NC State University 42

8 Manual sorting: Positive and Negative sorting Copyright Anders Damgaard & Morton A. Barlaz, NC State University 43

9 Technology: Compaction Hydraulic compaction and containment (hydraulic plate or screw compacting against a wall in a container) Baling: hydraulic compaction and containment by wires, plastic or other wrapping Copyright Anders Damgaard & Morton A. Barlaz, NC State University 44

10 Balers (Densification) The major piece of equipment at many MRFs Used to prepare recyclables for market In some (rare) cases used to bale refuse prior to disposal Expensive, complex, and crucial to continuous operation Can be used for plastics, cans, fiber Size: 30 x 30 x 42 to 72 x 46 x 42 Moved by forklift Copyright Anders Damgaard & Morton A. Barlaz, NC State University 45

11 Balers (Densification) Vertical balers Small capacity TPD Horizontal baler Large capacity TPD 2 balers are desirable due to potential for downtime Specifications are critical!!! Materials to be baled Volume per day Size of largest material ONP, OCC, OFF > Al, plastics, ferrous Copyright Anders Damgaard & Morton A. Barlaz, NC State University 46

12 Inspector could be placed here Copyright Anders Damgaard & Morton A. Barlaz, NC State University 47

13 48 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 48

14 Can Compaction Crushers Crush cans between two rotating wheels Al: 250 lb/yd 3 May drop onto a conveyor or pneumatically blow them into a trailer Shredders (for Al) Shred and blow them into a trailer Copyright Anders Damgaard & Morton A. Barlaz, NC State University 49

15 Perforators Device to punch holes in plastic in order to facilitate flattening Can be mounted inside chutes 50 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 50

16 Wood grinders Primary use is upstream of a yard waste composting facility of for a C&D MRF Could be used to generate a fuel supplement from pallets, scrap lumber Tub grinder large tub with a revolving upper section, followed by a hammer mill Fed by a conveyor, front end loader or bucket May be portable and operated on diesel Copyright Anders Damgaard & Morton A. Barlaz, NC State University 51

17 52 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 52

18 Conveyors Transfer waste from one location to another - vertical and horizontal Vertical: < 40 degree angle to avoid accumulation of heavies (glass); use of flights On a picking line Wastes dropped onto conveyors by front end loaders tends to add to wear and tear require maintenance due to dusty environment adjustable speed to spread waste Also used to feed balers, ECS, screens, etc. Copyright Anders Damgaard & Morton A. Barlaz, NC State University 53

19 Pneumatic Conveyors used to convey materials large distances across a plant Copyright Anders Damgaard & Morton A. Barlaz, NC State University 54

20 Copyright: Anders Damgaard & Morton A. Barlaz, NC State University 55

21 Conveyor Feed Pit Photo Source: Ken Mills Engineering, Ltd. ( Copyright Anders Damgaard & Morton A. Barlaz, NC State University 56

22 Pit Length The higher the desired throughput the longer the pit Bulkier materials require longer pits At 5 tons/hr: pit length - 15 ft for OCC pit length - 10 ft for paper Throughput of conveyor/end point machinery is limited most by loading capability (the ability to keep material on the belt) Copyright Anders Damgaard & Morton A. Barlaz, NC State University 57

23 Picking Line 1 Well lighted and ventilated room enclosure for fresh air, noise protection dust control using misters at point where material drops vertically sort high volume materials first as number of materials goes up, so does residual Copyright Anders Damgaard & Morton A. Barlaz, NC State University 58

24 Picking Line 2 Adjustable speed ft/min Used to control material thickness, thinner is optimal for recovery efficiency 60 ft/min typical. Must have sufficient material for worker to maximize material recovery number of people on a material Copyright Anders Damgaard & Morton A. Barlaz, NC State University 59

25 Picking Line 3 Width 3-4 ft depending on whether there is access from both sides typically hand picked waste will be discharged to a chute which drops into a bin on a lower level (in line glass crusher) the bin may be the shipping container or an intermediate container (labor cost implications) Copyright Anders Damgaard & Morton A. Barlaz, NC State University 60

26 Picking Line 4 Negative Sorts All facilities must be designed to minimize repetitive motion injuries (ergonomics) pushing versus pulling material head on sorting off of a shaking table lets workers see an item coming longer and use both hands more efficiently Copyright Anders Damgaard & Morton A. Barlaz, NC State University 61

27 Double vs Single side sorting Sorting Line Considerations Photo source: Is single side preferable over double side? Photo source: - Double side: need at least 2 people for good efficiency; higher throughput - Single side: need only 1 sorter with no loss in efficiency Copyright Anders Damgaard & Morton A. Barlaz, NC State University 62

28 Sorter Line Ergonomics Angled sideboards for armrest & protection Width: Single side = 24 typ. (36 max.) Double side = typ. (72 max.) Burden depth = 6 Speed adjust for sort efficiency & # workers Length based on Negative sort for # workers, space, etc. heavier items Copyright Anders Damgaard & Morton A. Barlaz, NC State University 63

29 This is an enclosed picking room so workers are insulated from the general plant noise. Picked materials are dropped in here. Copyright Anders Damgaard & Morton A. Barlaz, NC State University 64

30 dust curtain at entrance to enclosed picking room Vacuum supply Copyright Anders Damgaard & Morton A. Barlaz, NC State University 65

31 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 66

32 This is an example of head on sorting Copyright: Anders Damgaard & Morton A. Barlaz, NC State University 67

33 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 68

34 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 69

35 Other Requirements Scales Typically trucks are weighed on entering and leaving May need smaller scales to weigh bins of materials as are prepared for shipment Storage May be in roll off containers, boxes, tractor trailers, piles, bales Must allow for storage between collection and sale Depending on the material, the market and the flow rate, this could be 1-5 weeks (or higher if small portions) Vehicles Forklifts Bobcats/loaders Copyright Anders Damgaard & Morton A. Barlaz, NC State University 70

36 Other Requirements 3 Office space Flexibility!! Increase the number of shifts Leave room for another processing train Movable chutes and bins to vary materials recovered Heat and ventilation Fire protection Copyright Anders Damgaard & Morton A. Barlaz, NC State University 71

37 Other Requirements 4 Traffic patterns and size of tipping floor to minimize unload time and congestion Public access Separate commercial haulers from pickup trucks Material Purification second sort of materials sorted from mixed waste, or, a picking line for checking recyclables sorted at point of collection (negative sort) Some MRFs may cater to commercial waste/ office waste only Copyright Anders Damgaard & Morton A. Barlaz, NC State University 72

38 MRF Design The design process 1. Formulation of a design basis What will be delivered and from where? How much will be delivered? 2. Recovery factor How reliable are people in source curbside programs? (lb/house-wk) How good are pickers in a mixed waste MRF? Optimize personnel vs. efficiency Copyright Anders Damgaard & Morton A. Barlaz, NC State University 73

39 MRF Design 2 3. Development of a process flow diagram 4. Material balance All material must be accounted for at each step 5. Size equipment Operating hours Allow for cleanup time Copyright Anders Damgaard & Morton A. Barlaz, NC State University 74

40 MRF Design 3 6. Specify equipment Interaction with vendors Demonstrations, site visits Write performance specifications and send out for bid Performance guarantees MSW is more abrasive than many other solid materials 7. Equipment and facility layout Traffic pattern Minimize backing up Number of trucks to be accommodated at one time Typically will not be spread evenly Copyright Anders Damgaard & Morton A. Barlaz, NC State University 75

41 MRF Design 8. OSHA Personnel on the tipping floor moving around heavy equipment Noise levels Gloves/respirators Repetitive motion Lifting Dedicated dust control Ventilation for dust/bacteria Curtains where waste falls on conveyors Around trommel Copyright Anders Damgaard & Morton A. Barlaz, NC State University 76

42 MRF Economics 1 MRFs typically require a tipping fee Fee may vary by type of load Presorted vs. Commingled Commercial vs. Residential Recyclables vs. mixed refuse MRF profitability versus total system cost Many companies will build a MRF and then recruit business Copyright Anders Damgaard & Morton A. Barlaz, NC State University 77

43 MRF Economics 2 City s perspective Additional collection plus MRF operation costs money Write contracts carefully so city is not trapped in a bad situation Contract can include revenue sharing between the city and MRF owner which protects both parties from price fluctuations Is there a cost savings by not using landfill? Refuse plus recyclables costs are not linear Copyright Anders Damgaard & Morton A. Barlaz, NC State University 78

44 C&D Waste Recycling Material Composition (%) Dirt/Fines 25 Brick 5 Concrete 10 Asphalt 6 OCC 7 Ferrous Metal 3 Non-Ferrous Metal 2 Wallboard 8 Wood 22 Miscellaneous 12 Copyright: Anders Damgaard & Morton A. Barlaz, NC State University 79

45 C&D Waste Recycling Separate from a traditional MSW MRF Special Equipment excavator with a permanent magnet head used to scavenge metal on receipt finger screen to do a size split small material (<12 ) to a trommel large air suction for paper removal larger material hand sorted Copyright Anders Damgaard & Morton A. Barlaz, NC State University 80

46 C&D Waste Recycling Trommel: <2 fines landfill cover 2-4 magnet, rock and bricks >4 hand sorting for: Rugs Wood Tires Plastic buckets OCC wallboard Copyright Anders Damgaard & Morton A. Barlaz, NC State University 81

47 C&D Waste Recycling Rock and brick is crushed, passed under a magnet and sized for use in gravel can be processed by sink/float system to remove small pieces of wood Wallboard causes significant dust problems Copyright Anders Damgaard & Morton A. Barlaz, NC State University 82

48 Typical Flow Diagram 83 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 83

49 84 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 84

50 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 85

51 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 86