IPTF Trommel Studies

Operation-Based Improvements through the Use of
Trommel Screens for Processing and Contaminant
Reduction across Various Seasons
Ali Rajabpour, Ph.D. Candidate
Daryl McCartney, Ph.D., P.Eng.
17 September, 2015
The National Compost Conference
Gatineau, Québec
1
Background: Rotary Screen (Trommel)
3
• Originally adapted from
1
mineral processing
h
– Diameter
ω
– Length
– Inclination angle
– Rotational velocity
– Shape and size of apertures
– Feed rate
R
• Screening of organic fines
2
• Final screening of compost
product
• …
2
Background: North American Case Studies
AB
CA
MD
LA
Case Studies
Berkeley, CA (Glaub et al.,1982)
Average Temperatre (oC)
30
20
10
0
-10
Baltimore, MD
Bereckley, CA
New Orleans, LA
Edmonton, AB
-20
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
New Orleans, LA (Glaub et al.,1982)
Baltimore, MD (Hannon et al.,1983)
Edmonton, AB (Rajabpour et al., 2015)
3
Integrated Processing and Transfer Facility (IPTF)
1
MSW
Trommel
1st Hand
Sorting
Recyclables,
Rejects and
bulky items
2
>9 inch
>9 inch
2nd Hand
Sorting
D
2 to 9 inch
2
5 to 9 inch
5 to 9 inch
<2 inch
2
2
<2 inch
Disc Screen
Pre-processing Line #1
2
D
Pre-processing Line #2
C- 502
2 to 5 inch
2 to 5 inch
1
D
C- 401 D
C- 600
Common conveyors and belt-scales
D
D
To ECF
C- 700
To RDF
Note: The flow of ferrous metals separated by overhead magnets from both undersize
waste streams are not shown for simplicity
4
Weekly variation of <2” in 2013
Winter
Spring
Summer
Fall
5
Areas of improvement
• Variation in recovery of <2” waste stream over time
• Feed rates exceeding the designed throughput (summer)
• Clogging of 2” apertures (especially in winter)
• Non-biodegradable contaminants in compost feedstock
• Available options:
– Increase the screen size
– Control the feed rates
6
Objectives
• To assess the effectiveness of screening with larger
screen size (i.e., 3”)
• To quantify the feed rate that:
1. Maximizes the screening of the organic-rich fines (<2”); and/or
2. Maximizes the waste processing throughput
7
Methodology (1): Trials and feed rate calibration
• Preliminary trials: three full-day tests at minimum,
average and maximum feed rates (i.e., 40, 55, 70-tph)
with 2” screen in March
• 4 trials were scheduled in June-July:
– Feed rate: 40 and 70 tph (nominally)
– Screen size (of 1st stage): 2 and 3 inch
• Trial duration: 4 hours in summer
• Feed rate calibration:
– Random sampling from waste pile for scoop measurement
– Setting time intervals between waste loads
8
Methodology (2): Data collection and sampling
• Data collection:
– Data recording in every 15 minutes
– Operation downtime
• calculation of feed rate, system availability and
recovery ratios
• A single sampling (ASTM D5231) from:
– First unders (<2″ WS): 15-kg
– Second unders (2 to 9″ WS): 75-kg
– Overs (>9″ WS): 20-kg
9
Methodology (3): Waste characterization
• Particle size distribution (PSD) analysis
– 9, 7, 6, 5, 3.5 (or 3) and 2 inch sieves
– Further sieving of <2” fraction into 35 mm (1.4”) and
15 mm (0.6”).
• Composition of post-sieved size fraction:
– 1) Paper & cardboard; 2) rigid plastics; 3) film plastic;
4) yard; 5) food; 6) other combustible; 7) glass; and,
8) non-combustible wastes.
10
Min rate (41 tph)
Mean rate (60 tph)
Max rate (75 tph)
40
-20°C
30
+7°C
20
°C
~0
10
Operation Time (min)
0
66
0
60
0
54
0
48
0
42
0
36
0
30
0
24
0
18
0
12
60
0
0
Total recovery (%, by wet weight)
Recovery of <2” at different feed rates in March-14
11
Rosin-Rammler PSD of combined feed in summer
season (June-July 2015)
Cumulative Passed (%, wet weight)
100
96%
80
R2= 0.993
66%
60
52%
40
20
Ave
Max
Min
0
0.01
0.1
1
2" 3"
10
100
Particle Size (inch)
12
Recovery of <2” and <3” waste streams
60
Recovery (%, wet weight)
2" Screen 52%
3" Screen 66%
50
40
30
20
T1 @ 2" & 82.4 tph
T2 @ 2" & 45.8 tph
T3 @ 3" & 75.9 tph
T4 @ 3" & 55.2 tph
10
0
0
60
120
Operation time (min)
180
240
13
Recovery of 2-9” and 3-9” waste streams
70
2" Screen 44%
3" Screen 30%
Recovery (%, wet weight)
60
50
40
30
20
T1 @ 2" & 82.4 tph
T2 @ 2" & 45.8 tph
T3 @ 3" & 75.9 tph
T4 @ 3" & 55.2 tph
10
0
0
60
120
Operation time (min)
180
240
14
Recovery of >9” waste stream
Recovery (%, wet weight)
20
T1 @ 2" & 82.4 tph
T2 @ 2" & 45.8 tph
T3 @ 3" & 75.9 tph
T4 @ 3" & 55.2 tph
15
2" Screen 4%
3" Screen 4%
10
5
0
0
60
120
Operation time (min)
180
240
15
Composition of <2” and <3” streams
Size Sample # Paper
3" Screen
2" Screen
1
2
3
4
Average
5
6
7
8
Average
4%
7%
10%
7%
7%
8%
8%
9%
13%
10%
T-Test results NS
Rigid Film
Plastic Plastic
3%
3%
4%
2%
7%
4%
4%
4%
4%
3%
5%
6%
4%
4%
5%
5%
5%
5%
5%
5%
NS
S
42%
47%
36%
45%
42%
29%
41%
39%
37%
37%
20%
12%
15%
9%
14%
14%
16%
8%
14%
13%
Diap. &
Nap.
8%
10%
11%
14%
11%
19%
9%
12%
7%
12%
NS
NS
NS
Yard Food
Other
NonGlass
Comb.
Comb.
13%
2%
6%
12%
1%
4%
12%
1%
4%
11%
1%
6%
12%
1%
5%
12%
1%
6%
8%
1%
9%
15%
1%
6%
12%
1%
6%
12%
1%
7%
NS
NS
S
Biodeg. Non-Biodeg.
74%
76%
72%
74%
74%
70%
74%
68%
71%
71%
26%
24%
28%
26%
26%
30%
26%
32%
29%
29%
NS
NS
NS: Not significantly different
S: Significantly different
16
Composition of <2” and <3” streams
Size Sample # Paper
3" Screen
2" Screen
1
2
3
4
Average
5
6
7
8
Average
1%
2%
2%
2%
2%
2%
3%
6%
4%
4%
T-Test results NS
Rigid Film
Plastic Plastic
1%
0%
1%
0%
1%
0%
0%
0%
1%
0%
4%
0%
1%
0%
1%
0%
2%
1%
2%
1%
NS
54%
69%
71%
88%
70%
42%
57%
63%
53%
54%
23%
12%
9%
1%
11%
21%
19%
9%
17%
16%
Diap. &
Nap.
6%
4%
4%
2%
4%
11%
6%
9%
8%
8%
S
NS
S
Yard Food
S
Other
NonGlass
Comb.
Comb.
5%
4%
6%
6%
2%
4%
5%
3%
5%
2%
2%
4%
4%
3%
5%
10%
3%
7%
6%
3%
5%
7%
3%
3%
11%
1%
3%
8%
2%
5%
S
NS
NS
Biodeg. Non-Biodeg.
83%
87%
87%
93%
87%
75%
85%
86%
81%
82%
17%
13%
13%
7%
13%
25%
15%
14%
19%
18%
NS
NS
NS: Not significantly different
S: Significantly different
17
Maximum Foreign Matter Particles Allowed in
Composts
Contamination level in the final compost produced in June & July of 2015
was 0.14% DW of plastic (average of 3 tests)
Country
Recommended levels (% of dry weight)
Australia
< 0.5% foreign matter (glass, metals, plastic) for
>2mm fraction
US: Los Angeles, CA
0.1% film plastic
US: Portland, OR
0.5% film plastic
Germany
< 0.5% for >2mm of foreign matter
Italy
<3 % in total
Switzerland:
1) < 0.5% for >2mm fraction; 2) max 0.1% plastic
United Kingdom
1) < 1% > 2mm; 2) < 0.5% if plastic
18
Correlation between feed rate & system availability
Availablity % =
100
Net peration time
×
Total Time
100
System Availability (%)
95
R2=0.7
90
85
80
75
70
65
20
30
40
50
60
70
80
90
Feed Rate (tph)
19
Maximum achievable processing throughput
Processing Throughput tpd = Feed rate tph × Duration (hpd) × Aavailability %
Amount of waste processed (tpd)
700
8 hpd
9 hpd
10 hpd
600
500
400
300
200
40
50
60
70
80
90
100
Feed Rate (tph)
20
Summary
• Challenges of studying at full-scale operation.
• Effectiveness of larger screen size vs. lower feed rate
on screening performance
– Larger screen  more consistent screening
– Lower feed rate  higher recovery ratios
• The practical feed rate to be applied was between 45
and 75 tph.
– What’s the objective? Priority?
• Concerns on quality of compost product
– Which facility to target?
21
Acknowledgements
22
Thank you!
Questions?
23