Use of FGD Byproducts in Agriculture: DOE Perspective
Workshop on Research and Demonstration of Agricultural Uses of Gypsum and Other FGD Materials
St. Louis, MO
September 13, 2006
William W. Aljoe, Project ManagerU.S. Department of Energy, National Energy Technology Laboratory
OARDC FGD Workshop, September 12-14, 2006
DOE Terminology: CUBs
Coal Utilization By-products Includes Fly ash, Bottom ash, Boiler slag, FGD solids Other acronyms: CCBs, CCPs, CCW, FFCW, CCR ...
Utilization includes: Combustion Gasification & Hybrid systems
By-products because: $ from electricity sales >> $ from CUB sales Become “Products” when sold or beneficially used Become “Wastes” when sent to a permanent disposal site
Can still become “products” after disposal
OARDC FGD Workshop, September 12-14, 2006
Outline
Types of FGD Systems & By-products Wet FGD Systems Dry FGD Systems Fluidized Bed Combustion (FBC)
FGD By-product Characteristics FGD Gypsum vs. “Mixtures” (wet & dry)
Production and Use Recent and future trends Effect of SO2 and Hg regulations
OARDC FGD Workshop, September 12-14, 2006
Byproducts from Wet FGD Systems
Pulverized Coal
Bottom Ash or Boiler Slag
Boiler
ESP or Fabric Filter
Fly Ash
Wet FGD Absorber
Wet FGD By-product
Lime or Limestone Slurry
Flue Gas
Stack Emissions
OARDC FGD Workshop, September 12-14, 2006
Wet FGD System Alternatives
Reagent Limestone or Lime Sodium-based (rare)
Oxidation method Inhibited or Natural In-situ External
2 major classes of By-products Older systems: Sulfite sludge (CaSO3 · ½ H2O)
Must be “stabilized” or “fixated” before disposal or use Newer systems: Gypsum (CaSO4 · 2H20)
No stabilization needed
OARDC FGD Workshop, September 12-14, 2006
FGD Byproduct Formation: Sulfite Sludge Basic Chemical Reaction (Limestone Reagent)
SO2 + CaCO3 → CaSO3·½ H2O (s) + CO2 (g)↑
Source: http://www.worldbank.org/html/fpd/em
/power/EA/mitigatn/aqsowet.stmUnstabilized
FGD Byproduct(CaSO3 · ½H2O)Stabilized (Fixated)Stabilized (Fixated)
FGD ByproductFGD Byproduct
OARDC FGD Workshop, September 12-14, 2006
FGD Gypsum Formation Basic Chemical Reaction (Limestone Reagent)
SO2 + CaCO3 → CaSO3 · ½ H2O + CO2 (g)
Source: http://www.worldbank.org/html/fpd/em/power/EA/mitigatn/aqsowet.stm
+ O2 → CaSO4 ·2H20 (Gypsum)
Forced Oxidation (In-Situ)
Air
FGD GypsumFGD Gypsum
Forced Oxidation (External)
Air
Slurry
OARDC FGD Workshop, September 12-14, 2006
Byproducts from Dry FGD Systems(Spray Dryers)
Pulverized Coal
Bottom Ash or Boiler Slag
Boiler
Spray Dryer
Absorber
ESP or Fabric Filter
Dry FGD Byproduct =Fly Ash + CaSO3 + CaSO4 + Ca(OH)2
Lime Slurry
Flue Gas
Stack Emissions
OARDC FGD Workshop, September 12-14, 2006
Byproducts from Fluidized Bed Combustion (FBC)
Coal, Refuse, or other Fuel
Limestone
FBC Boiler
Bottom Ash + CaSO4 + CaSO3 +CaO
ESP or Fabric Filter
Fly Ash + CaSO4 + CaSO3 +CaO
Flue Gas
Stack Emissions
OARDC FGD Workshop, September 12-14, 2006
U.S. CUB Production and Use – 2004(Data from American Coal Ash Association)
2004 Fly Ash Bottom AshFGD
GypsumOther Wet
FGD Boiler Slag Dry FGD FBC Ash Total
Production (million tons) 70.8 17.2 12.0 17.5 2.2 1.8 0.9 122.5Total Use (million tons) 28.1 8.2 9.0 1.2 2.0 0.2 0.5 49.1
Percent of production utilized 39.6% 47.4% 75.7% 6.8% 89.6% 9.7% 54.6% 40.1%
0
10
20
30
40
50
60
70
80
Fly Ash BottomAsh
FGDGypsum
OtherWet FGD
BoilerSlag
Dry FGD FBC Ash
Production (million tons)
Total Use (million tons)
OARDC FGD Workshop, September 12-14, 2006
U.S. FGD Byproduct Production and Use – 2004(Data from American Coal Ash Association)
2004FGD
GypsumOther Wet
FGD Dry FGD FBC Ash
Production (million tons) 12.0 17.5 1.8 0.9Total Use (million tons) 9.0 1.2 0.2 0.5
Percent of production utilized 75.7% 6.8% 9.7% 54.6%
FGD Gypsum
Other Wet FGD Dry FGD
FBC Ash
(54%)
(37%)
(6%)
(3%)
OARDC FGD Workshop, September 12-14, 2006
Fate of FGD Gypsum – 2004(Data from American Coal Ash Association)
FGD Gypsum
Cement, concrete, grout
Raw feed for cement clinker
Wallboard
Agriculture
Other
Disposal
OARDC FGD Workshop, September 12-14, 2006
Fate of “Other” (Sulfite) Wet FGD Byproducts – 2004(Data from American Coal Ash Association)
Other Wet FGD
Raw feed for cement clinker
Structural fill
Mining applications
Agriculture
Other
Disposal
OARDC FGD Workshop, September 12-14, 2006
FBC Ash Structural fill
Soil modification
Mining applications
Waste stabilization
Other
Disposal
Fate of Dry FGD and FBC Byproducts – 2004(Data from American Coal Ash Association)
Dry FGD Cement, concrete, grout
Flowable fill
Mining applications
Agriculture
Aggregate
Disposal
OARDC FGD Workshop, September 12-14, 2006
Recent Trends in FGD Byproduct Production & Use
0
2
4
6
8
10
12
14
16
18
20
2002 2003 2004
Mill
ion
To
ns
FGD Gypsum Production FGD Gypsum Use
Other Wet FGD Production Other Wet FGD Use
OARDC FGD Workshop, September 12-14, 2006
Effect of CAIR on FGD Byproducts
CAIR Requirements 44% reduction in SO2 emissions by 2010
56% reduction in SO2 emissions by 2015
Total volume of FGD byproducts will increase Most “new” wet FGD systems will produce gypsum Many “old” (sulfite-producing) FGD systems will continue to
operate More dry FGD systems will be added
Less efficient for SO2 removal than wet FGD Dry: 70-90%; Wet: 95%+ (BACT considerations)
Will be used mostly for for low-S coals, where water is scarce
OARDC FGD Workshop, September 12-14, 2006
Future Trends in FGD Byproduct Production
FGD Byproduct Production (All Types)
0
10
20
30
40
50
60
1996 1998 2000 2002 2004 2006 2008 2010 2012 2014
Mill
ion
To
ns
CAIR Phase II
CAIR Phase I
OARDC FGD Workshop, September 12-14, 2006
Potential Impact of Power Plant Mercury Emission Regulations (CAMR) on CUBs
Fly Ash Loss of all reuse applications
~ $908 M/yr impact
FGD Solids Loss of all reuse applications
~ $213 M/yr impact
Hazardous designation of all CUBs could cost more than $11 billion/year
Fly Ash FGD Byproduct
Mercury
OARDC FGD Workshop, September 12-14, 2006
Mercury Partitioning Across Coal Power Plants(Annual Nationwide Estimates based on 1999 EPA ICR Data)
Sorbent Injection
EnhancedScrubbing
Typical Control Technologies
In 2018: ~94T Hg
~6T Hg ~73 T Hg
15T Hg CAMR Phase II
After CoalCleaning
BoilerParticulate
ControlFGD
System
48T Hg
StackBottom Ash~5T Hg
Pre-CAMR: ~75T Hg
Fly Ash FGD Byproduct
~22T Hg
OARDC FGD Workshop, September 12-14, 2006
Effects of CAMR on Hg in Wet FGD Byproducts Points to consider
1. Wet FGD systems already remove oxidized Hg
Byproducts already contain 70-90% of initial Hg2+
ESP or Fabric Filter
Flue gas from boiler Hg2+
Hg0
Wet FGD Absorber Stack Emissions
Hg2+ Hg2+
Hg0 Hg0
Fly Ash Wet FGD By-product
OARDC FGD Workshop, September 12-14, 2006
Effects of CAMR on Hg in Wet FGD Byproducts Points to consider
2. Hg concentration in wet FGD byproducts will be slightly higher if SCR is added or if “oxidation enhancement additives” are used
SCR+additives+scrubber won’t be chosen ($$) if incoming Hg is primarily Hg0
Flue gasfrom boiler
SCR ESP or Fabric FilterHg2+
Hg0
Hg2+ Hg2+
Hg0 Hg0
Fly Ash Wet FGD By-product
Hg2+
Hg0
Oxidation Enhancement Additive
OARDC FGD Workshop, September 12-14, 2006
Effects of CAMR on Hg in Wet FGD Byproducts Points to consider
3. Hg concentration in wet FGD byproducts may be lower if powdered Hg sorbents are used for Hg control
Hg Sorbent
ESP or Fabric Filter
Flue gasfrom boiler or SCR
Hg2+
Hg0
Hg2+ Hg2+
Hg0 Hg0
Fly Ash Wet FGD By-product
More Hg in fly ash = less in FGD byproduct
OARDC FGD Workshop, September 12-14, 2006
Effects of CAMR on Hg in Dry FGD Byproducts
Powdered sorbents will probably be the Hg control method of choice
FGD byproduct will have some more Hg but much more carbon than before
Flue gas from boiler
Stack
Spray Dryer
Hg Sorbent
FGD Sorbent
ESPor FF
Fly ash +
FGD byproduct +
Sorbent
OARDC FGD Workshop, September 12-14, 2006
Environmental Release of Hg from FGD Byproducts R&D Must “Check all the Boxes”
FGD Source
Landfill ImpoundmentUtilization
Hg (g)
Hg (aq)
Hg (g)
Hg (aq)
+ +
LandfillHg (g)
Hg (aq)
+
Manufactured Products
Roads/Fills/Land Application
Hg (aq)
Hg (g)Hg (g)
Hg (aq)
+
Hg (p)
Hg (g) = VolatilizationHg (aq) = LeachingHg (p) = Dust+ = Microbial activity/methylation
OARDC FGD Workshop, September 12-14, 2006
Near-Term R&D Goals Hg Release from FGD Byproducts
Determine the stability of Hg and other metals under simulated end-use environments Disposal and re-use
Explain the chemistry underlying metal stability
Drywall ready for landfill
FGD solids ready for disposal
OARDC FGD Workshop, September 12-14, 2006
Where Does the Hg Go upon Capture ?
Hg in Zimmer WFGD ProductsND set to 0.0
0
2
4
6
8
10
12
14
16
18
Hg
, p
pm
(dry
)
Zimmer-Fines
Zimmer-Slurry
Zimmer-Gypsum
“… the mercury compound formed in the wet scrubber is associated with the fines and is not tied to the larger gypsum crystals.”
Source: “FULL-SCALE TESTING OF ENHANCED MERCURY CONTROL TECHNOLOGIES FOR WET FGD SYSTEMS” Final Report, DE-FC26-00NT41006, BABCOCK & WILCOX CO. and McDERMOTT TECHNOLOGY, INC. May 7, 2003
OARDC FGD Workshop, September 12-14, 2006
Leaching of FGD Byproducts Using Continuous Stirred Tank Reactor (CSTX)
FGD Gypsum Gypsum totally dissolved
Leachate: No Hg Residue
< 1% of original material Fe, Al, and all Hg
Wallboard Gypsum totally dissolved
Leachate: ~1% of Hg Residue
~ 2% of original material Fe, Al, and majority HgContinuous stirred tank
reactor
OARDC FGD Workshop, September 12-14, 2006
CSTX Results Summary
An iron-containing phase, probably introduced with limestone, is responsible for sorption of mercury
Hg content of FGD gypsum appears to correlate with Fe content
Rapid Hg leaching is unlikely in typical disposal and land-application (agricultural) environments
OARDC FGD Workshop, September 12-14, 2006
FGD Byproducts in Agriculture and Land Applications Relevant CBRC Projects
Website: http://wvwri.nrcce.wvu.edu/CBRC/
Project Title Performer Total Project Value
Start Date End Date
Environmental Effects of Large-Volume FGD Fill GAI Consultants, Inc. $206,800 4/15/2001 12/31/2004Power Plant Combustion Byproducts for Improved Crop Productivity of Agricultural Soils
New Mexico State University Agricultural Science Center at Farmington
$119,008 9/1/2004 8/31/2005
Flue Gas Desulfurization Byproducts Provide Sulfur and Trace Mineral Nutrition for Alfalfa and Soybean Ohio State University $97,300 1/3/2000 8/31/2003
Boron Transport from Coal Combustion Product Utilization and Disposal Sites Southern Illinois University $118,241 11/1/1999 8/31/2003
The Impact of Adsorption on the Mobility of Arsenic and Selenium Leached from Coal Combustion Products
Southern Illinois University $138,412 9/1/2002 12/31/2004
Qualifying CCBs for Agricultural Land ApplicationUniversity of North Dakota $105,613 9/1/2002 7/31/2005
Field Testing of Arsenic and Mercury Bioavailability Model from Land-Applied CCBs Tennessee Valley Authority $142,300 7/1/2006
National Network of Research and Demonstration Sites for Agricultural and Other Land Application Uses of FGD Products
Ohio State University $575,677 7/1/2006
Community-based Social Marketing: the tool to get target audiences to use CCBs University of Tennessee $275,193 7/1/2006
OARDC FGD Workshop, September 12-14, 2006
FGD Byproduct Reuse: Economics 101
Producer (Utility) Perspective: Recycling occurs when cost of reuse < Cost of disposal
In theory: new technology reduces cost of reuse In practice: reuse becomes “economical” when disposal costs
rise
User Perspective: Recycling occurs when cost of reuse < cost of alternative
materials Need specifications for reuse (not always available) Need consistent supply and quality of material Need support from material supplier
OARDC FGD Workshop, September 12-14, 2006
How Can FGD Byproduct Use in Agriculture Be Increased?
Education
Communication Finding “Win-Wins”
Diligence Don’t quit ‘til you get it right
OARDC FGD Workshop, September 12-14, 2006
For More Information
DOE-NETL CUB Website http://www.netl.doe.gov/technologies/coalpower/ewr/co
al_utilization_byproducts/