Coal Combustion Products in
Constructed Landfills
Characteristics, Beneficial Use, Disposal, &
Impact on Geocomposite Leachate Collection
Systems
Dr. Tarunjit S. Butalia, PE
Research Scientist
Department of Civil, Environmental, and Geodetic Engineering
The Ohio State University
ccp.osu.edu
What are Coal Combustion Products
(CCPs)?
• CCPs are solid minerals that remain after
coal is burned to generate electricity or
steam
• Types:
•
•
•
•
Fly Ash
Boiler Slag
Bottom Ash
Flue Gas Desulfurization (FGD) Materials
• Dry FGD Materials (FBC, CFBC, SD)
• Wet FGD Materials (sulfite & sulfate)
How are CCPs generated?
Baghouse/ESP
Flue Gas
Desulfurization
(wet/dry)
Economizer
SCR for
removing
NOx
Smokestack
Coal Feed
Coal Boiler
BOTTOM ASH
BOILER SLAG
(dry bottom boilers) (wet bottom boilers)
FLY ASH
FGD MATERIALS
Fly Ash
• Fine powdery mineral collected by ESP or
baghouse
• Consists mainly of non-combustible
matter but also some unburned carbon
• Mostly silt size particles (with some fine
sand sized), mostly spherical (and
sometimes hollow)
• Types:
• Class F (non self-cementing)
• Class C (self-cementing)
• Handled dry or wet
Bottom Ash
• Fine to coarse material collected from
dry bottom boilers
• Consists of dark agglomerated ash
particles
• Sand size particles typ. angular
• Handled dry or wet
Boiler Slag
• Glassy material collected from wet
bottom boilers
• Black, dense, hard angular particles
Flue Gas Desulfurization (FGD) Materials
• Solid / semi-solid material obtained from
flue gas scrubbers (for SO2 control)
• Predominantly silt size particles
Stabilized
FGD material
• Wet or dry
• Types:
• Dry FGD Materials (CFBC, PFBC, SD)
• Wet FGD Materials
• Sulfite (Stabilized FGD material)
• Sulfate (FGD Gypsum)
FGD
Gypsum
CCPs
CCP
Type
Characteristics
Texture
Amount
Generated
Per Ton of
Coal Burned
(lbs)
Major
Constituents
Areas of Major Use
Cement/Concrete/Grout, Structural
Fill, Flowable Fill, Waste Stabilization,
Surface Mine Reclamation, Soil
Stabilization, Road Base, Mineral Filler,
Agriculture
Concrete Block, Road Subbase, Snow
and Ice Control, Structural Fill, Waste
Stabilization, Agriculture, Pipe
Bedding, Cement Manufacture
Fly Ash
Non-combustible
particulate matter
carried in stack
gases
Powdery,
silt like
160
Si, Al, Fe, Ca
Bottom
Ash
Material collected in Sand like
dry bottom boilers,
heavier than fly ash
40
Si, Al, Fe, Ca
Boiler
Slag
Material collected in Glassy
wet bottom boilers
angular
or cyclone units
particles
100
Si, Al, Fe, Ca
FGD
Solid/semi-solid
Material material obtained
from flue gas
scrubbers
Fine to
Coarse
(Dry or
Wet)
700
Blasting Grit, Roofing Granules, Snow
and Ice Control, Mineral Filler,
Construction Backfill, Water Filtration,
Agriculture, Drainage Media
Ca, S, Si, Fe, Al Wallboard, Road Base/Subbase,
Structural Fill, Surface Mine
Reclamation, Underground Mine
Injection, Livestock Pad, Agricultural
Liming Substitute
Typical Engineering Characteristics of
CCPs
Typical Characteristics
Fly Ash
FGD Material
Bottom
Ash /
Boiler Slag
Wet
Dry
0.001-0.05
0.002-0.075
Particle Size (mm)
0.001-0.1
0.1-10.0
Compressibility (%)
1.8
1.4
Dry Density (lb/ft3)
40-90
40-100
50-110
65-90
10-6-10-4
10-3-10-1
10-6-10-4
10-7-10-6
Cohesion (psi)
0-175
0
Angle of Internal Friction (degree)
25-45
25-45
0-1,600
40-2,250
Permeability (cm/sec)
Shear Strength
Unconfined Compressive Strength (psi)
Typical Engineering Properties of
Bottom Ash & Boiler Slag
Property
Specific Gravity
Dry Unit Weight
Plasticity
Absorption
Bottom Ash
2.1 - 2.7
45 - 100 lb/ft3
NP
0.8 - 2.0%
Boiler Slag
2.3 - 2.9
60 - 90 lb/ft3
NP
0.3 - 1.1%
Maximum Dry Density, lb/ft3
Optimum Moisture Content, %
LA Abrasion Loss, %
Sodium Sulfate Soundness Loss, %
Friction Angle, degrees
California Bearing Ratio, %
Permeability Coefficient, cm/sec
75 – 100
12 – 24
30 - 50
1.5 – 10
32 – 45
40 - 70
10-2 - 10-3
82 – 102
8 – 20
24 – 48
1–9
36 – 46
40 – 70
10-2 - 10-3
(FHWA-RD-97-148)
Typical Engineering Properties of
FGD Materials
Property
Stabilized FGD
(Calcium Sulfite)
FGD Gypsum
(Calcium Sulfate)
Particle Sizing (%)
Sand Size
Silt Size
Clay Size
Specific Gravity
1
90
9
2.57
17
80
3
2.36
Property
Solids Content, %
Specific Gravity
Dry Density, lb/ft3
Friction Angle, degree
Permeability, cm/sec
UCS (28 days), psi
Stabilized FGD
55-80
2.25 – 2.60
75 – 95
35 – 45
10-6 – 10-7
25 - 50
(FHWA-RD-97-148)
Composition of Fly Ash & Cement
(CBRC, 2003)
Trace Elemental Composition
Element
(mg/kg)
Fly Ash
Mechanical
Range
Median
Bottom Ash/Boiler Slag
Dry FGD Material
ESP/Baghouse
Range
Median
Range
Median
Range
Median
Arsenic
3.3-160
25.2
2.3-279
56.7
0.50-168
4.45
44.1-186
86.5
Boron
205-714
258
10-1300
371
41.9-513
161
145-418
318
Barium
52-1152
872
110-5400
991
300-5789
1600
100-300
235
Cadmium
0.40-14.3
4.27
0.10-18.0
1.60
0.1-4.7
0.86
1.7-4.9
2.9
Cobalt
6.22-76.9
48.3
4.90-79.0
35.9
7.1-60.4
24
8.9-45.6
26.7
Chromium
83.3-305
172
3.6-437
136
3.4-350
120
16.9-76.6
43.2
Copper
42.0-326
130
33.0-349
116
3.7-250
68.1
30.8-251
80.8
Fluorine
2.50-83.3
41.8
0.4-320
29.0
2.5-104
50.0
---
---
Mercury
0.008-3.0
0.073
0.005-2.5
0.10
0.005-4.2
0.023
---
---
Manganese
123-430
191
24.5-750
250
56.7-769
297
127-207
167
Lead
5.2-101
13.0
3.10-252
66.5
0.4-90.6
7.1
11.3-59.2
36.9
Selenium
0.13-11.8
5.52
0.6-19.0
9.97
0.08-14
0.601
3.6-15.2
10.0
Silver
0.08-4.0
0.70
0.04-8.0
0.501
0.1-0.51
0.20
---
---
Strontium
396-2430
931
30-3855
775
170-1800
800
308-565
432
Vanadium
100-377
251
11.9-570
248
12.0-377
141
---
---
Zinc
56.7-215
155
14-2300
210
4.0-798
99.6
108-208
141
Leachate (TCLP) – Dry FGD and Fly Ash
Chemical
Constituent
(mg/L)
pH
TDS
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Dry FGD
Fly Ash
9.58-12.01
11,84013,790
<0.024
0.12-0.20
<0.005
0.543-2.17
<0.002
0.141-0.348
1,380-3,860
<0.003
<0.014-0.026
<0.005-0.028
<0.013
<0.029
<0.0002
1.3-22.1
----0.0-0.05
--0.026-0.4
0.5-92
0.30-2.0
<0.0001-0.015
--0.0-0.3
0.0-0.22
0.023-1.4
0.0-0.43
0.0-10.0
0.0-0.003
---
Chemical
Constituent
(mg/L)
Li
Mg
Mn
Mo
Na
Ni
P
Pb
S
Sb
Se
Si
Sr
V
Zn
Cl-
Dry FGD
Fly Ash
0.04-0.18
<0.04-1,360
<0.001
0.025-0.088
1.32-9.82
<0.01
<0.12
<0.001-0.017
132-979
<0.24
<0.001-0.005
0.10-0.33
0.83-3.38
<0.019-0.024
<0.006
19.6-67.8
----0.0-1.9
0.19-0.23
--0.0-0.12
--0.0-0.15
--0.03-0.28
0.011-0.869
------0.045-3.21
---
Leachate (Kosson Tier I, SPLP, TCLP)
FGD Gypsum
Element
As
B
Ba
Cd
Cr
Cu
Hg
K
Pb
Se
Tier I
SPLP
TCLP
(mg/mL)
<0.006
0.227
0.161
0.0017
0.0056
<0.001
7.9E-06
0.646
<0.003
<0.011
(mg/mL)
<0.006
0.130
0.101
0.002
0.0044
<0.001
3.60E-06
<0.4
<0.003
<0.011
(mg/mL)
<0.006
0.137
0.37
0.0017
0.0059
<0.001
1.8E-05
2.01
<0.003
0.012
Historical CCP Production & Beneficial Use
(American Coal Ash Association)
2010 CCP Production & Beneficial Use
(American Coal Ash Association)
Each Ton of Fly Ash in Concrete Equals...
Some Past OSU Demonstration Projects
• Highway Embankment Stabilization (1993, 1994)
• Stabilized FGD Material as Pond Liner (1997)
• Accelerated Loading of Newly Constructed Full-Scale
Pavements (2003)
• Full Depth Reclamation of Failing Asphalt Pavements (2006)
Use of Clean Coal Technology By-Products in
Construction of Low Permeability Liners
Filling of Pond with
water - 1997
During construction
Current
•
Constructed at OSU-OARDC Western Branch in
South Charleston, Ohio in Summer of 1997
•
Holding Capacity of 1 million gallons (6 months
storage capacity)
•
Primary Liner = 18” Compacted, Stabilized FGD
•
Leachate Collection System
Coefficient of Permeability (cm/sec)
Use of Clean Coal Technology By-Products in
Construction of Low Permeability Liners
Curing Time (days)
0
365
730
1095
1460
1825
2190
1.0E-03
Addition of swine
manure initiated
1.0E-04
1.0E-05
1.0E-06
1.0E-07
1.0E-08
1998
Full Scale Test
Laboratory Test on Laboratory Compacted Sample
Boutw ell(TP1)
Boutw ell(TP2)
Boutw ell(TP3)
Cored(TP1)
Cored(TP2)
Cored(TP3)
Ongoing OSU Projects
• Reclamation of Ohio Coal Mine Sites Using
FGD Byproducts
• Role of Remining in Mitigating Impacts of
Legacy Mining in Ohio
• Stability of Fly Ash During Cyclic Loading
• Effectiveness of Geocomposites as Drainage
Layer for CCPs
Effectiveness of Geocomposites
as Drainage Layer for CCP Landfills
2009-10 Research: Investigation of various CCP materials using non-woven
fabric (Alexis Semach MS Thesis)
Current Research: Study of various CCP materials using woven fabric
geocomposite drainage layer
Background
• Geocomposite leachate collection systems as possible
replacements for conventional graded sand filters in CCP
landfills
• Geocomposite drainage systems are attractive - not as
thick as graded sand filters
•
Geocomposite must
•
not restrict flow of leachate to collection system
•
prevent migration of CCP material to be retained through the
filter and into leachate collection system
Research Objective
•
To evaluate effectiveness of using geocomposites as
primary drainage layer for CCP landfills to study
potential
• clogging of leachate collection system, and
• migration of material into leachate collection system
2009-10 Research – Fill and Geocomposite
2009-10 Research – % Solids in Leachate
2009-10 Research – Fly Ash and Geocomposite
2009-10 Research – Laboratory Testing Summary
•
Measured permeabilities of the CCPs tested ranged from a high of slightly less than
1x10-4 cm/sec (silt) for FGD gypsum & Class F fly ash to 7x10 -6 cm/sec (silt or clay)
for stabilized FGD.
•
When CCPs were underlain by the geocomposite, effective permeability decreased,
typically by a factor of 5.
•
Quantity of material recovered in leachate was small and decreased after only one to
two pore volumes for FGD gypsum and stabilized FGD.
•
Quantity of fly ash recovered in leachate increased during tests until it was more than
the system could accommodate and testing had to be terminated.
•
Fly ash appears to not be adequately retained by sample non-woven geocomposite.
Even though initial permeabilities of fly ash and FGD gypsum were similar, the fly ash
particles went into the leachate at a much higher rate than did FGD gypsum. The
quantity of fly ash increased until laboratory tests on fly ash/geocomposite samples had
to be terminated.
Current Research
Focus: Study of Fly Ash (silo and ponded), FGD gypsum, and stabilized
FGD material underlain by woven fabric geocomposite system
• Laboratory Experiments
• Permeability of CCP fill material with & without geocomposite
• Percent solids in leachate of CCP fill with & without geocomposite
• Field Testing
• Permeability and leachate quality of as installed CCP fills with geocomposite
Laboratory Testing
• Geocomposite with top woven geotextile layer
• CCP Materials
 Class F Fly Ash (silo and ponded)
 FGD Gypsum
 Stabilized FGD (sulfite) material
• Tests conducted
 Falling head permeability tests on CCP fill materials
only (porous stone at top and bottom of sample)
 Falling head permeability tests on drainage system
(bottom porous stone replaced by geocomposite)
• Test results
 Permeability and percent solids in leachate as a
function of pore volume
Sample
Geotextile Fabric
Geo-Grid
Geotextile Fabric
PVC Layer
Hole in PVC for Drainage
CCP Fill and Geocomposite Test System
Sample
Geotextile Fabric
Geo-Grid
Geotextile Fabric
PVC Layer
Hole in PVC for Drainage
Silo Fly Ash M
1.00E-02
2
4
6
8
porous stone (dry
density=79.97pcf)
1.00E-03
geocomposite (dry
density=83.16pcf)
1.00E-04
12
10
1.00E-05
Pore Volume Fraction
Percent Solids (%)
Hydraulic Conductivity (cm/s)
0
porous stone (dry
density=79.97pcf)
8
geocomposite (dry
density=83.16pcf)
6
4
2
0
0
2
4
Pore Volume Fraction
6
8
Ponded Fly Ash C
1.00E-02
2
4
6
8
porous stone (dry
density=95.37pcf)
geocomposite (dry
density=95.15pcf)
1.00E-03
1.00E-04
1.00E-05
12
porous stone (dry
density=95.37pcf)
Pore Volume Fraction
10
Percent Solids (%)
Hydraulic Conductivity (cm/s)
0
8
geocomposite (dry
density=95.15pcf)
6
4
2
0
0
2
4
Pore Volume Fraction
6
8
FGD Gypsum M
1.00E-02
2
4
6
8
geocomposite (dry
density=85.03pcf)
porous stone (dry
density=84.47pcf)
1.00E-03
1.00E-04
12
1.00E-05
Pore Volume Fraction
porous stone (dry
density=84.47pcf)
10
Percent Solids (%)
Hydraulic Conductivity (cm/s)
0
geocomposite (dry
density=85.03pcf)
8
6
4
2
0
0
1
2
3
4
Pore Volume Fraction
5
6
7
FGD Gypsum C
1.00E-02
2
4
6
8
porous stone (dry
density=77.97pcf)
geocomposite (dry
density=77.70pcf)
1.00E-03
1.00E-04
12
10
1.00E-05
Pore Volume Fraction
Percent Solids (%)
Hydraulic Conductivity (cm/s)
0
porous stone (dry
density=77.97pcf)
8
geocomposite (dry
density=77.70pcf)
6
4
2
0
0
2
4
Pore Volume Fraction
6
8
Post-test Geocomposite Inspection
Sample
Top Geotextile Fabric
Geo-Grid
Bottom Geotextile Fabric
PVC Layer
Hole in PVC for Drainage
Top of “top geotextile fabric”
Top of “top geotextile fabric” Bottom of “top geotextile” fabric
Top of “geo-grid”
CCP
Typical
field
basin
constructed
at OSU
Olentangy
River
Wetland
Research
Park
CCP
Plan View
of Field
Test
Basins
Field Construction
Field Construction
Ponded Fly Ash C
Silo Fly Ash M
FGD Gypsum M
Stabilized FGD C
Field Testing
Permeability - Silo Fly Ash M
1.00E-02
Hydraulic Conductivity (cm/s)
0
2
4
6
8
porous stone (dry
density=79.97pcf)
1.00E-03
geocomposite (dry
density=83.16pcf)
1.00E-04
1.00E-05
Pore Volume Fraction
Laboratory Measured Permeability
Field Basin Permeability* = 4 x 10-4 cm/sec
Permeability - Ponded Fly Ash C
1.00E-02
Hydraulic Conductivity (cm/s)
0
2
4
6
8
porous stone (dry
density=95.37pcf)
geocomposite (dry
density=95.15pcf)
1.00E-03
1.00E-04
1.00E-05
Pore Volume Fraction
Laboratory Measured Permeability
Field Basin Permeability* = 2 x 10-3 cm/sec
Permeability - FGD Gypsum M
1.00E-02
Hydraulic Conductivity (cm/s)
0
2
4
6
8
geocomposite (dry
density=85.03pcf)
porous stone (dry
density=84.47pcf)
1.00E-03
1.00E-04
1.00E-05
Pore Volume Fraction
Laboratory Measured Permeability
Field Basin Permeability* = 2 x 10-2 cm/sec
Total Suspended Solids - Field
Total Dissolved Solids - Field
Turbidity - Field
Current Research – Preliminary Conclusions
• Laboratory testing to date indicates that the new
geocomposite woven fabric:
• retains fly ash and other CCP fill particles
• does not restrict the flow of leachate to collection system
• prevents migration of CCP material into leachate collection
system
• Field test basin verifies laboratory observations
Resources Available to You
Our online library collection has been subdivided into the following categories:
Material Characterization
Applications
Economics of Beneficial Use
Our library listing of journal articles, conference papers and published information
sources is related to Coal Combustion Products research. Many of our documents
can be downloaded (typ. as pdf files). For references not available online and not
subject to copyright restrictions, a paper copy can be provided by contacting Carol
Scott at [email protected].
You are welcome to submit articles for inclusion in our reference library. Contact
Dr. Tarunjit S. Butalia at [email protected].
Graduate Student Research
M.S. Thesis
Dorothy Adams, Swelling characteristics of dry sulfur dioxide removal waste products
Jeffreys Chapman, Stress Model Verification with Reclaimed Asphalt Pavement
Malcolm Hargraves, The effect of freeze-thaw cycles on the strength of stabilized flue gas desulfurization sludge
James Howdyshell, Strain compatibility analysis in slope stability modeling
Jun Huang, Degradation of resilient modulus of saturated clay due to pore water pressure buildup under cyclic loading
Na Jin, Fly Ash Applicability in Pervious Concrete
James Kirch, Potential Use of Flue Gas Desulfurization Gypsum (FGD) in a Flowable Grout for Re-mining of Abandoned Coal Mines
Jangguen Lee, The Behavior of Pore Water Pressure in Cohesive Subgrade Soils
Jung Woo Lee, Beneficial reuse of FGD by-products as flowable fill
Yong-Woong Lee, Measurement and Prediction of Resilient Modulus of Lime-Fly Ash Stabilized Cohesive Subgrade Soils
Aleia Long, Evaluating material properties of fly ash modified concrete plates under low velocity impact
Ryan Mackos, Environmental Analysis of Full Depth Reclamation Using Coal Combustion By-Products
Deepa Modi, Potential Utilization of FGD Gypsum for Reclamation of Abandoned Highwalls
Jennifer Myers, Stabilization of sludge using spray dryer absorber ash
Salman Nodjomian, Clean-coal technology by-products used in a highway embankment stabilization demonstration project
Xueling Pan, The Effect of Freeze Thaw Cycling on the Permeability of Stabilized Flue Gas Desulfurization (FGD) Materials
Rachel Pasini, An Evaluation Of FGD Gypsum For Abandoned Mine Land Reclamation
Renee Payette, Landslide Remediation Using Clean Burning Coal Technology By- Products
Gloria Rodgers, Resilient modulus predictions using engineering properties and neural networks
Alexis Semach, Geotextiles for Use in Drainage Systems in Coal Combustion Product Landfills
Sharon Studer, Seepage analysis of a highway embankment constructed from the Flue Gas Desulfurization by-product
Wei Tu, Evaluation of Full-Scale CCP Pavement Performance Using Accelerated Loading Facility
Michael Nuhfer, Use of flue gas desulfurization by-product as a lake-bed liner
Ph.D. Dissertations
Dong-Gyou Kim, Development of a Constitutive Model for Resilient Modulus of Cohesive Soils
Sung Hwan Kim, A decision support system for highway embankment design using FGD by-products
J.W. Lee, Real-Time Monitoring of Landslide Using Wireless Sensor Network
Panuwat Taerakul, Characterization of trace elements in dry flue gas desulfurization (FGD) by-products
Wei Tu, Response Modeling of Pavement Subjected to Dynamic Surface Loading Based on Stress-Based Multi-layered Plate Theory
Chin-Min Cheng, Leaching of coal combustion products: field and laboratory studies
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