Material Recovery Facilities (MRF) Copyright Anders Damgaard & Morton A. Barlaz, NC State University

Transcription

1 Material Recovery Facilities (MRF) Copyright Anders Damgaard & Morton A. Barlaz, NC State University 1

2 Lecture Objectives Explains MRFs and understand all the different types of separation equipment Define design parameters C&D Waste Copyright Anders Damgaard & Morton A. Barlaz, NC State University 2

3 Purpose of a MRF Where does a MRF fit in solid waste management? A MRF performs mechanical treatment/separation affects mechanical or physical characteristics, no conversion The MRF should have recyclable material as an end product (as well as a residual stream) A MRF is by necessity also a transfer station Role of environmental engineer Bid specs Copyright Anders Damgaard & Morton A. Barlaz, NC State University 3

4 MRF design will depend on.. How many types of recyclables are handled? Are recyclables presorted or to be sorted at MRF? (single/dual stream) Are recyclables separated from mixed waste? Endless combinations of materials to be processed Copyright Anders Damgaard & Morton A. Barlaz, NC State University 4

5 Simplest MRF Drop-Off Centers Drop-off centers in central locations Shopping centers Schools Transfer stations Participation is an issue Substitute for curbside recycling in areas that do not provide this service Maintaining neatness is critical Copyright Anders Damgaard & Morton A. Barlaz, NC State University 5

6 Drop-off Centers Copyright Anders Damgaard & Morton A. Barlaz, NC State University 6

7 Technologies in a MRF Separation separation according to a single or combined characteristic bag opening Size reduction reducing particle size Compaction increasing bulk density Copyright Anders Damgaard & Morton A. Barlaz, NC State University 7

8 Technology: Size reduction Hammer mills Impact crushers Cutters /shredders Cascade mills Jaw crushers Copyright Anders Damgaard & Morton A. Barlaz, NC State University 8

9 Hammer Mill - Glass A miniature hammer mill installed in a chute below a sorting conveyor used to reduce the volume of glass for shipment in bins or large boxes installation is based on transport, storage economics and market requirements Copyright: Anders Damgaard & Morton A. Barlaz, NC State University 9

10 Hammers for a hammer mill Copyright Anders Damgaard & Morton A. Barlaz, NC State University 10

11 Jaw crusher Copyright Anders Damgaard & Morton A. Barlaz, NC State University 11

12 Roll crusher Copyright Anders Damgaard & Morton A. Barlaz, NC State University 12

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

14 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 14

15 Technology: Separation Bag Opening Screens (size separation) Trommel screens Oscillating screens Bucket screens Ballistic screens Disc screens Air classifiers (heavy / light separation) Zig-zag air classifiers Rotary or cross current air classifiers Suction hoods (maybe manually assisted) Copyright Anders Damgaard & Morton A. Barlaz, NC State University 15

16 Technology: Separation Metal separators Magnets Eddy current (repels Al in alternating magnetic field) Optical sorters Liquid-based (water) separation Flotation Sedimentation Hydrocyclones Manual sorting Positive sorting (removing the product) Negative sorting (removing the dirt and contaminants) Copyright Anders Damgaard & Morton A. Barlaz, NC State University 16

17 Bag opening Typically applies to mixed waste Slitter/Trommel Bags fed by conveyor to a slitter Cut by 2 rotating blades Wheels with spikes Dropped onto a trommel where 75-95% of material (MSW or yard waste) is removed Trommel may have knives in front section Copyright Anders Damgaard & Morton A. Barlaz, NC State University 17

18 Bag Opening Augers Bags are dropped onto an auger by a loader or from a hopper Auger is at a 25 o angle Glass breakage is 5% 98% of contents are removed Auto-reverse feature to protect equipment Copyright Anders Damgaard & Morton A. Barlaz, NC State University 18

19 Size Separation - Trommels Uses bag opening broken glass/fines removal from commingled stream cleaning paper removal of materials from mixed (MSW) can have multiple openings along length container separation food waste/fines removal Copyright Anders Damgaard & Morton A. Barlaz, NC State University 19

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

21 Size Separation - Trommels Sizing is difficult Separation efficiencies are estimates Example Sizing These sizes are based on estimates from one vendor Ton/hr (TPH) Diam. (ft) Length (ft.) Copyright Anders Damgaard & Morton A. Barlaz, NC State University 21

22 This is a trommel prior to installation. Notice the different size openings in different sections of the trommel Copyright Anders Damgaard & Morton A. Barlaz, NC State University 22

23 Bucket screen Copyright Anders Damgaard & Morton A. Barlaz, NC State University 23

24 Size Separation - Screens Vibrating Screens useful for dry materials broken glass and dirt removal Copyright Anders Damgaard & Morton A. Barlaz, NC State University 24

25 Size Separation - Screens Disk Screens rotating disks with an interval between them to allow one component to fall between the disks while another component is carried over the top works well for separation of paper from containers or OCC from other paper the small material may be compostable in a mixed waste MRF Copyright Anders Damgaard & Morton A. Barlaz, NC State University 25

26 Disk screen Copyright Anders Damgaard & Morton A. Barlaz, NC State University 26

27 Size Separation Star Screens Star Screens - modification of disk screen Uses: Loosen up a fiber stream to ease manual sorts of mixed paper Separate OCC from ONP Separate fiber from containers when recyclables are collected as a single stream Copyright Anders Damgaard & Morton A. Barlaz, NC State University 27

28 Star Screen Copyright Anders Damgaard & Morton A. Barlaz, NC State University 28

29 Star and Disc Screens Design Parameters Distance between disks on axle Distance between axles Incline Limitations Wet weather/humidity Wire/string on shaft Copyright Anders Damgaard & Morton A. Barlaz, NC State University 29

30 Magnetic Separation Recovery of ferrous metal from A mixture of tin and aluminum cans Commingled recyclables Shredded MSW mixed waste MRF Depending on purity of inlet stream, two magnets in series, or a double throw magnet may be used Copyright Anders Damgaard & Morton A. Barlaz, NC State University 30

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

32 Copyright Anders Damgaard & Morton A. Barlaz, NC State University 32

33 Material passing under a magnet Copyright Anders Damgaard & Morton A. Barlaz, NC State University 33

34 Eddy Current Separation Use of magnetic fields to separate aluminum from other components Aluminum is repelled by magnetic force due to generation of a charge of opposite polarity Can be used to pull aluminum out of a stream of commingled recyclables or at the end of a belt to separate aluminum from residuals Copyright Anders Damgaard & Morton A. Barlaz, NC State University 34

35 Copyright: Anders Damgaard & Morton A. Barlaz, NC State University 35