EPA/600/R-09/152 

December 2009 

Evaluating the Thermal Stability of 

Mercury and Other Metals in Coal 

Combustion Residues Used in the Production 

of Cement Clinker, Asphalt, and Wallboard 

Susan Alice Thorneloe-Howard 

Principal Investigator
 

Office of Research and Development 

National Risk Management Research Laboratory
 

Air Pollution Prevention and Control Division 

Research Triangle Park, NC 27711
 

U.S. Environmental Protection Agency 

Washington, D.C. 
 

Acknowledgements 

Technical support for the preparation of this report was provided by ARCADSIS-US, Inc., 4915 Prospectus 

Drive, Suite F, Durham, NC under EPA Contracts EP-C-04-023 and EP-C-09-027 (Work Assignment 0-27). 

ARCADIS personnel participating in the research included Kevin Bruce, Peter Kariher, and Elizabeth Lee of 

ARCADIS. 

Also, Connie Senior with Reaction Engineering International is acknowledged for assistance in obtaining 

coal combustion residue samples and related background information for this project. 
Table of Contents 

Page i 

Table of Contents 

List of Tables.............................................................................................................................................. iii
 

List of Figures ............................................................................................................................................ iv
 

List of Acronyms........................................................................................................................................ vi
 

Executive Summary ................................................................................................................................. viii
 

Chapter 1 Introduction.................................................................................................................................. 1-1
 

1.1 Coal Combustion Residues from Multi-Pollutant Control Technology ...................................... 1-1
 

a

Calcium sulfate hemihydrate or gypsum produced by the FGD system.................................................... 1-5
 

b

Solid phase from hydroclone overflow stream sent to disposal................................................................. 1-5
 

c

Liquid phase from hydroclone overflow stream sent to disposal. ............................................................. 1-5
 

1.1.1 CCR Use in Cement Clinker...................................................................................................1-5
 

1.1.2 CCR Use as Aggregate in Asphalt .........................................................................................1-5
 

1.1.3 FGD Gypsum Use in Wallboard ............................................................................................1-6
 

1.2 Objective ........................................................................................................................................ 1-7
 

Chapter 2 Materials and Methods ................................................................................................................ 2-1
 

2.1 CCR Materials for Evaluation....................................................................................................... 2-1
 

2.1.1 Brayton Point ..........................................................................................................................2-2
 

2.1.2 Salem Harbor ..........................................................................................................................2-3
 

2.1.3 Pleasant Prairie........................................................................................................................2-5
 

2.1.4 Facility A.................................................................................................................................2-5
 

2.1.5 Facility B .................................................................................................................................2-6
 

2.1.6 Facility E .................................................................................................................................2-6
 

2.1.7 Facility M ................................................................................................................................2-6
 

2.1.8 Facility N.................................................................................................................................2-7
 

2.1.9 Facility O.................................................................................................................................2-7
 

2.1.10 Facility S .................................................................................................................................2-7
 

2.1.11 Facility T .................................................................................................................................2-7
 

2.1.12 Facility W................................................................................................................................2-8
 

2.1.13 Facility X.................................................................................................................................2-8
 
 

 

Table of Contents 

Page ii 

2.1.14	 Facility Aa ...............................................................................................................................2-8
 

2.1.15	 Facility Da ...............................................................................................................................2-9
 

2.1.16	 FGD Gypsum Sample from U.S. Gypsum...........................................................................2-12
 

2.2 Thermal Stability Protocols.........................................................................................................2-13
 

2.3 Analytical Methods......................................................................................................................2-16
 

2.3.1	 Mercury (CVAA Method 7471A, Method 3052, Method 7473, Method 30B)..................2-16
 

2.3.2	 Arsenic, Selenium and Lead (ICP-MS, Method 3052, Method 6020)................................2-16
 

2.3.2.1 Severn Trent Laboratories, Inc. (STL)........................................................................2-17
 

2.3.2.2 Oxford Laboratories ....................................................................................................2-17
 

Chapter 3 Results and Discussions............................................................................................................... 3-1
 

3.1 Cement Simulations....................................................................................................................... 3-1
 

3.2 Asphalt Simulations....................................................................................................................... 3-2
 

3.2.1	 Asphalt Simulation Tests for Mercury Thermal Stability on ADA Fly Ashes.....................3-2
 

3.2.2	 Asphalt Simulation Tests for Non-Mercury Metals Thermal Stability on ADA Fly Ashes.3-3 

3.2.3	 Asphalt Simulation Tests for Mercury Thermal Stability on Non-ADA Fly Ashes.............3-5
 

3.2.4	 Asphalt Simulation Tests for Non-Mercury Metals Thermal Stability on Non-ADA Fly 

Ashes .......................................................................................................................................3-8
 

3.2.5	 Correlation of Carbon Content and Mercury Volatilization................................................3-10
 

3.3 Wallboard Simulations ................................................................................................................3-10
 

3.3.1	 Wallboard Simulation Tests for Mercury Thermal Stability on USG FGD Gypsum.........3-11
 

3.3.2	 Wallboard Simulation Tests for Non-Mercury Metals Thermal Stability on USG FGD 

Gypsum .................................................................................................................................3-11
 

3.3.3	 Additional Wallboard Simulation Tests for Mercury Thermal Stability on Gypsum Samples
 

...............................................................................................................................................3-12
 

3.3.4 Wallboard Simulation Tests for Mercury Thermal Stability at Various Temperatures......3-14
 

Chapter 4 Conclusions and Future Considerations...................................................................................... 4-1
 

Chapter 5 Quality Assurance / Quality Control........................................................................................... 5-1
 

5.1 Quality Indicator Goals ................................................................................................................. 5-1
 

5.2 Ontario Hydro and Method 29 Mercury Analyses ....................................................................... 5-1
 

5.3 Method 29 Analyses for Arsenic, Lead, and Selenium ................................................................ 5-3
 

Chapter 6 References.................................................................................................................................... 6-1
 

Appendix A DOE NETL Full-Scale Test Site Flow Diagrams...................................................................... 1
 

Appendix B Non-DOE NETL Full-Scale Test Site Flow Diagrams ............................................................. 1
 

Appendix C Detailed Results for Additional Wallboard Simulation Tests ................................................... 1
 
 

 

Table of Contents 

Page iii 

List of Tables 

Table E-1. Boiling Points and Temperatures for 10 Pa (0.075 mm Hg) Vapor Pressure of 

Mercury, Arsenic, selenium, and lead ......................................................................................viii
 

Table E-2. Typical Maximum Process Temperatures of Cement Clinker Kilns, Asphalt, and 

Wallboard Manufacturing and Laboratory Testing Temperatures ..........................................viii
 

Table 1-1. Fly Ash and FGD Gypsum Production and Use in the U.S.a

...................................................1-3
 

Table 2-1. Characteristics of air pollution control and for samples obtained from Brayton Point, 

Pleasant Prairie, Salem Harbor, and Facilities A, B, and E .....................................................2-4
 

Table 2-2. ADA Fly Ashes: Elemental Composition (by X-ray Fluorescence) and Other
 

Characteristics .........................................................................................................................2-10
 

Table 2-3. Facility A (SNCR, Facility B (SCR), Facility E (SCR) and Facility M CCRs: 

Elemental Composition (by X-ray Fluorescence) and Other Characteristics .......................2-11
 

Table 2-4. ADA Fly Ashes: Total Content of Mercury, Arsenic, Cadmium, Lead and Selenium1 .......2-12
 

Table 2-5. Facility A (SNCR, Facility B (SCR), Facility E (SCR) and Facility M (SCR) CCRs : 

Total Content of Mercury, Arsenic, Lead and Selenium .......................................................2-12
 

Table 2-6. USG FGD Gypsum Samples: Total Content of Mercury, Arsenic, Lead and 

Selenium1

.................................................................................................................................2-13
 

Table 2-7. Description of Asphalt, Wallboard and Cement Clinker Simulations to Test for Metal 

Thermal Stability.....................................................................................................................2-15
 

Table 3-1. Results of Cement Simulations for Arsenic, selenium, and lead (all values in μg/g 

unless noted)..............................................................................................................................3-1
 

Table 3-2. Asphalt Simulation Test results for Mercury on ADA Fly Ashes...........................................3-3
 

Table 3-3. Comparison of Mercury by Method 29 and Ontario Hydro for Brayton Point Fly
 

Ashes .........................................................................................................................................3-4
 

Table 3-4. Results for Asphalt Simulations of Brayton Point Fly Ashes for Arsenic, selenium,
 

and lead......................................................................................................................................3-5
 

Table 3-5. Mercury Results by Ontario Hydro Method for Non-ADA Fly Ashes...................................3-6
 

Table 3-6. Comparison of Mercury by Method 29 with Ontario Hydro for Facility B Fly Ashes ..........3-8
 

Table 3-8. Results for Asphalt Simulations of Facility M Fly Ash for Mercury, Arsenic, 

selenium, and lead.....................................................................................................................3-9
 

Table 3-9. Results of Wallboard Simulation Tests for Mercury .............................................................3-11
 

Table 3-10. Results of Wallboard Simulation Tests for Arsenic, selenium, and lead ..............................3-11
 

Table 3-11. Results of Additional Wallboard Simulation Tests for Mercury..............................................3-13
 
Table of Contents 

Page iv 

Table 3-12. Results for Wallboard Simulation Tests on Sample DaAW at Various Temperatures.............3-14
 

Table 5-1. Data Quality Indicator Goals ....................................................................................................5-1 

Table 5-2. Method 29 Matrix Spike Recoveries for Arsenic, Lead, and Selenium for the Cement 

Kiln Simulations........................................................................................................................5-3 

Table 5-3. Method 29 Matrix Spike Recoveries for Arsenic, Lead, and Selenium for the Asphalt 

Simulations................................................................................................................................5-4 

Table 5-4. Method 29 Matrix Spike Recoveries for Arsenic, Lead, and Selenium for the 

Gypsum Wallboard Simulations...............................................................................................5-4

Table C-1. Description of Facilities Providing Eight Gypsum Samples...........................................................1 

Table C-2. Detailed Results for Additional Wallboard Simulation Tests.........................................................2

Table C-3. Detailed Results for Wallboard Simulation Tests on Sample DaAW at Various 

Temperatures................................................................................................................................3

List of Figures 

Figure E-1. Fixed-Bed Reactor Design..........................................................................................................ix
 

Figure E-2. Results of High-Temperature Cement Kiln Simulations ............................................................x
 

Figure E-3. Normalized Results of Asphalt Simulations Tests for ADA Fly Ashes....................................xi
 

Figure E-4. Normalized Results of Asphalt Simulation Tests for Non-ADA Fly Ashes............................xii
 

Figure E-5. Results for Wallboard Simulation Tests on Gypsum Samples................................................xiii
 

1

The same gas mix was used for the simulation of cement clinker and asphalt production (a flow
 

rate of 400 cc/min of inlet flue gas consisting of 14% CO2, 3% O2, 5.6% H2O and 

100 ppm NOx,). The wall board similar used inlet gas of N2 since kettle calciners are 

indirectly fired and therefore the sample is not exposed to flue gas) ....................................2-14 

Figure 2-1. Schematic of the General Setup for Simulating the Production of Cement Clinker, 

Asphalt, and Wallboard...........................................................................................................2-14 

Figure 2-2. Asphalt and Wallboard Simulation Quartz Reactor and Furnace with Sample ....................2-14 

Figure 2-3. High Temperature Cement Simulation Furnace with Method 29 Mini-Impinger Train ......2-15 

Figure 3-1. Results of Cement Simulations for Arsenic, selenium, and lead.............................................3-2 

Figure 3-2. Asphalt Simulation Test results for Mercury by Ontario Hydro Method on ADA Fly 

Ashes .........................................................................................................................................3-4
 

Figure 3-3. Mercury Results by Ontario Hydro Method for Non-ADA Fly Ashes...................................3-7
 

Figure 3-4. Mercury Volatilization as a Function of Carbon Content......................................................3-10
 
Table of Contents 

Page v 

Figure 3-5. Results for Additional Wallboard Simulation Tests for Mercury .............................................3-14
 

Figure 3-6. Results for Wallboard Simulation Tests at Various Temperatures ...........................................3-15
 

Figure 5-1. Ontario Hydro spike recovery for multiple runs ......................................................................5-2
 

Figure 5-2. Method 29 Mercury spike recoveries for multiple runs...........................................................5-3
 
ACI Activated Carbon Injection 

ADA ADA Environmental Solutions 

ASTM ASTM International1 

BD Below Detection 

BML Below Method Limit 

CCR Coal Combustion Residues 

CVAA Cold Vapor Atomic Absorption 

DOE Department of Energy 

DRC Dynamic Reaction Chamber 

ELAN Emulated Local Area Network 

EPA U. S. Environmental Protection Agency 

EPRI Electric Power Research Institute 

ESP Electrostatic Precipitator 

FGD Flue Gas Desulfurization 

FIMS Flow Injection Mercury System 

HHV Higher Heating Value 

HMA Hot Mix Asphalt 

ICP-MS Inductively Coupled Plasma Mass Spectroscopy 

LOI Loss on Ignition 

MDL Method Detection Limit 

MLQ Minimum Level of Quantification 

NA Not Applicable 

NETL National Energy Technology Laboratory / DOE 

NR Not Recorded 

NRMRL National Risk Management Research Laboratory 

NT Not Tested 

OH Ontario Hydro 

PRB Powder River Basin 

QA/QC Quality Assurance/Quality Control 

QAPP Quality Assurance Project Plan 

SCA Specific Collection Area 

SCR Selective Catalytic Reduction 

SNCR Selective Non-Catalytic Reduction 

 

 

 

List of Acronyms 

Page vi 

List of Acronyms 

1

Previously ASTM was used as an acronym for American Society for Testing and Materials. The new name is ASTM 

International. 
STI 

STL 

Separation Technology Inc. 

Severn Trent Laboratories 

TBD To Be Determined 

TPD 

USG 

XRF 

Temperature Programmed Desorption 

United States Gypsum Company 

X-Ray Fluorescence 

List of Acronyms 

Page vii 
 

 

 

 

 

 

Executive Summary 

Page viii 

Executive Summary 

Research is underway by the U.S. Environmental Protection Agency (EPA) to document changes that 

may occur to coal combustion residues (CCRs) as a result of implementation of mercury and multipollutant control technology at coal-fired power plants. This work was cited as a priority in EPA’s 

Mercury Roadmap (http://www.epa.gov/mercury/roadmap.htm) to evaluate the potential for any crossmedia transfers from the management of coal combustion residues resulting from more stringent air 

pollution control at coal fired power plants. 

This report focuses on the potential for an increase in the volatilization of mercury and other metals from 

the utilization of CCRs in the production of cement clinker, asphalt, and wallboard. All three of these 

processes require heating during the production process. The four metals evaluated in this study are 

mercury (Hg), arsenic (As), selenium (Se), and lead (Pb) (Table E-1). Heating temperatures of the CCRs 

for this study were chosen to simulate actual conditions encountered in the cement, wallboard, and asphalt 

industries (Table E-2). 

Table E-1. Boiling points and temperatures for 10 Pa (0.075 mm Hg) vapor pressure of Mercury, 

Arsenic, selenium, and lead 

Element Boiling Point 

(°C) 

Temperature for Vapor 

Pressure of 10 Pa (°C) 

Mercury 357 76.6 

Arsenic 614 323 

Selenium 685 279 

Lead 1749 815 

Table E-2. Typical maximum process temperatures of cement clinker kilns, asphalt, and 

wallboard manufacturing and laboratory testing temperatures 

Process Maximum Manufacturing 

Plant Temperature (°C) 

Laboratory Testing 

Temperature (°C) 

Cement Clinker Kiln 1,450 1,450 

Asphalt Kettle 168 170 

Wallboard Calciner 

Kettle* 162 120, 140, 160 

*There are three processes in making wallboard that could result in Hg loss. However, the highest 

temperature that Hg is exposed to is during the calciner process. 

Fly ash and flue-gas desulfurization (FGD) gypsum was obtained from a range of facilities in an attempt 

to span differences in air pollution control configuration and coal types. The samples evaluated include: 

1.	 Fly ash from three different facilities evaluated by ADA-Environmental Solutions (ADA) under 

contract for the Department of Energy’s (DOE’s) National Energy Technology Laboratory (NETL) 

field evaluation program of sorbent to enhance mercury capture. At each of the three sites, the use of 
 

 

 

Executive Summary 

Page ix 

activated carbon injection (ACI) was evaluated by adding powdered activated carbon upstream of 

existing particulate control. Samples analyzed include fly ash from three facilities with and without 

the use of ACI for a total of six fly ashes; 

2.	 Fly ash from two facilities using selective catalytic reduction (SCR) for post-combustion control of 

NOx and one utilizing selective non-catalytic reduction (SNCR) (four with SCR and one with SNCR, 

total of five samples); and 

3.	 FGD gypsum kettle feedstock obtained from US Gypsum (two samples). 

4.	 FGD gypsum material obtained from eight different power plants (eight samples). 

A fixed-bed reactor design was used to simulate the thermal processes of concern in this study. Figure E-1 

provides a schematic of the general setup for simulating asphalt manufacturing, wallboard manufacturing, 

and cement clinker manufacturing. For all simulations, samples consisting of various mixes and matrices 

were loaded into shallow-bed containers and placed in the reactor. The fixed-bed reactor used for the 

asphalt and wallboard simulation assays consisted of a horizontal quartz tube in a thermally controlled 

unit (furnace). In the case of the high temperature cement clinker manufacturing (1450 °C), a Lindberg 

high temperature furnace was used. 

H2O Vapor 

Generation 

System 

High Temperature 

Furnace 

Method 29 

Train 

Low Temperature 

Furnace 

Method 29 

or 

OH Train 

To Vent 

Gas Mixing 

System 

= one-way valve 

= two-way valve 

Figure E-1. Fixed-bed reactor design 

In each simulation, the tests were performed in duplicate. Samples were exposed to a flow rate of 400 

cc/min of inlet flue gas consisting of 14% CO2, 3% O2, 5.6% H2O and 100 ppm NOx, except for the 

wallboard simulation of the kettle calciner, in which the inlet gas consisted solely of N2, because the 

kettle calciners are indirectly fired and therefore the sample is not exposed to flue gases. The time in the 

fixed-bed reactor for each simulation was one hour. The samples placed in the fixed-bed reactor, as well 

as the temperatures in the processes, varied for each simulation. For mercury, the effluent of the reactor 

was sampled using a mini-impinger Ontario Hydro train. For sampling the other metals, a Method 29 

mini-impinger train was used. 
 

 

Amount of metal volatilized

(average of two runs) 

Executive Summary 

Page x 

The making of cement involves the heating of various feedstocks in a cement kiln to make “clinker.” This 

clinker is ground with gypsum and transported to ready-mix concrete manufacturers. Various components 

are needed for feedstock including lime (CaO), iron oxide (Fe2O3), silica (SiO2) or alumina (Al2O3). Fly 

ash can replace a portion of these, representing a maximum of about 5% (by weight) of the typical raw 

mix to the kiln. Other inputs typically include limestone (90%), iron ore (3%), and sand (2%). Cement 

kiln residence time is typically one to three hours, and temperatures reach over 1427°C (2600°F) (EPA, 

2002). Cement simulation tests for arsenic, Se, and Pb desorption were performed in duplicate on the 

ADA fly ashes (baseline only). The tests show good reproducibility and indicate that virtually all of the 

metals tested are volatilized when exposed to high temperature as shown in Figure E-2. 

100% 

80% 

60% 

40% 

20% 

0%
 

Brayton Point Pleasant Prairie Salem Harbor
 

Arsenic Selenium Lead 

Figure E-2. Results of high-temperature cement kiln simulations 

Note: Se levels for Pleasant Prairie Baseline fly ash were below minimum detection levels; 

therefore, no volatility results are presented. 

Hot mix asphalt is a combination of 95% aggregate (e.g., stone, sand, or gravel) bound together by asphalt 

cement, a product of crude oil. Fly ash can make up approximately 5% of the total aggregate weight, 

replacing natural fillers such as hydrated lime or stone dust (EPA, 2002). Asphalt manufacturing consists 

of a very short residence time mixing process (about one minute), a long residence time storage process 

(several hours), and then application. The storage process occurs at temperatures of about 5 °C higher 

than the mixing process. Asphalt is delivered to the paving machine at approximately the same 

temperature as it is stored. Therefore, the most important step (in terms of thermal desorption) is the 

storage step. Storage temperatures typically range from 127 °C to 143 °C for binder grade PG46-28 and 

157 °C to 168 °C for binder grade PG82-22. 

Results for duplicate asphalt simulations tests at 170 °C using the ADA fly ashes are presented in 

Figure E-3. Results shown are normalized for mercury measured after completion of the simulation tests. 

In all cases, the majority of the mercury was retained in the solid after simulation, with minimal measured 

volatilization of mercury (<10% in all cases). Generally, the addition of ACI increased the tendency for 

mercury to be retained in the solids at the temperature tested. Total absolute mercury volatilized from 

samples with activated carbon injection was <1% for all samples tested. 
 

 

Executive Summary 

Page xi 

0% 

10% 

20% 

30% 

40% 

50% 

60% 

70% 

80% 

90% 

100% 

Normalized percentage of

mercury (average of two runs) 

Brayton 

Point 

Baseline 

Brayton Pleasant Pleasant Salem Salem 

Point w / 

ACI 

Prairie 

Baseline 

Prairie w / 

ACI 

Harbor 

Baseline 

Harbor w / 

ACI 

Retained in Solid Volatilized 

95.9% 100.0% 95.6% 99.6% 100.0% 99.9% 

Figure E-3. Normalized results of asphalt simulations tests for ADA fly ashes 

Asphalt simulations were run at 170 °C using fly ashes from six facilities (in addition to the ADA 

samples). Four of the fly ashes were obtained with and without post-NOx combustion control in use 

(Facility A and B). None of these samples had ACI in use. Except for Facility M with a mass balance of 

74%, the non-ADA fly ashes have a mercury mass balance ranging from 92.5 to 101%. Figure E-4 shows 

the results of these experiments that have been normalized by adjusting the mass balance to 100%. As 

was the case for the ADA fly ashes, Facility A and Facility E showed minimal mercury loss upon heating. 

Facility B, however, demonstrated high mercury volatility (~70-90% loss upon heating). 

There was no obvious reason for the higher loss of mercury seen for the Facility B fly ash. Perhaps the 

type of SCR catalyst in use at Facility B may have interacted with the fly ash making the mercury less 

tightly bound. Additional testing is needed to evaluate this using a wider range of samples 

Asphalt simulation tests at 170 °C for the Brayton Point and Facility B fly ashes showed no measurable 

volatilization of arsenic, Se, and Pb at the temperature tested during duplicate runs. 
 

 

 

 

 

 

Executive Summary 

Page xii 

98.2% 94.7% 

10.7% 

23.5% 

90.8% 

64.3% 

0% 

10% 

20% 

30% 

40% 

50% 

60% 

70% 

80% 

90% 

100% 

Normalized percentage of mercury 

(average of two runs) 

Facility A 

SNCR on 

Facility A 

SNCR off 

Facility B SCR 

on 

Facility B SCR 

off 

Facility E SCR 

on 

Facility M 

SCR on 

Retained in Solid Volatilized 

Figure E-4. Normalized results of asphalt simulation tests for non-ADA fly ashes 

Wallboard is made using calcium sulfate which can be mined as natural rock or obtained from a coal-fired 

power plant using flue-gas desulfurization (FGD) gypsum. The first step in the process to make wall 

board is to dry the gypsum so that it contains no free moisture – only chemically bound waters of 

hydration. This material is referred to as “land plaster”. The next step is to calcine the land plaster in a 

kettle for about one hour to form calcium sulfate hemi hydrate (i.e., stucco or plaster of Paris) according 

to the following reaction: 

2 CaSO4•2H2O + heat ↔ 2 CaSO4•1⁄2H2O + 3 H2O 

The stucco is mixed with water and additives to form slurry that is extruded between two sheets of paper 

to form wallboard. The final step is to dry the wallboard prior to processing and stacking it as final 

product. Any potential loss is mercury is assumed to occur during the thermal processes with losses most 

likely to occur during the calcining step. The highest temperature that FGD gypsum is exposed to is 

128o

C. Loses could also occur in the gypsum dryer and the finished wallboard dryer. However, the 

maximum temperatures that FGD gypsum is exposed to in the dryers is less than calcining (77 to 110o

C). 

(Sanderson et al., 2008) 

Sanderson et al., (2008) provide the most extensive study to date on the fate of Hg when FGD gypsum is 

used as feedstock for wallboard production. This work was conducted by U.S. Gypsum Corporation 

(USG). Testing of full-scale production facilities is considered more reliable than laboratory testing to 

simulate wallboard production. However, the study did not include other metals. Therefore, laboratory 
 

 

 

 

 

 

Executive Summary 

Page xiii 

simulation of wallboard production was conducted as part of this study. Results from Sanderson et al., 

(2008) indicate that the process where Hg loss is more likely to occur is the kettle calciner. Therefore, 

laboratory simulation of wallboard production was conducted evaluating Hg and other metals with the 

focus on trying to simulate potential loss across the kettle calciner. Only FGD gypsum samples were 

used in this simulation since this is the material used in the production of wallboard (and not fly ash). 

This research was conducted in two phases. The first phase resulted in unacceptable mass balance for Hg. 

The results for the other metals are considered acceptable. Consequently, additional testing was 

conducting in a second phase using more recent FGD samples. 

The first phase of testing suggests that As and Se are more likely retained in the FGD gypsum and less 

likely to be volatilized during the kettle calcining process. The second phase of testing provided 

improved Hg mass balance results. The results (Figure E-5) indicate potential Hg loss of 9 to 48%. The 

USG results from wallboard manufacturing facilities indicate Hg loss across the kettle calciner (excluding 

the Texas lignite sample) of 2 to 50%. This is considered confirmation of the previous USG research and 

emphasizes the variability across samples that may be attributed to how the wet scrubber is operated. 

However, additional research is needed to better understand the parameters that might affect Hg loss 

across a production facility. 

79% 

23% 

81% 

21% 

49% 

44% 

72% 

35% 

51% 

48% 

68% 

26% 

92% 

9% 

79% 

21% 

0% 

20% 

40% 

60% 

80% 

100% 

120% 

Percentage of Mercury 

AaAW DaAW NAW OAW SAW TAW WAW XAW 

Sample ID 

Retained in Solid Volatilized 

Figure E-5. Results for wallboard simulation tests on gypsum samples. 

The results from this laboratory study demonstrate the varying degree of volatility for mercury, arsenic, 

Se and Pb in CCRs depending on the process temperature being used. A high temperature process such as 
 

 

Executive Summary 

Page xiv 

cement clinker production has the ability to release all four metals from fly ash when exposed to the high 

temperatures found in production. Laboratory simulation of the asphalt and wallboard production 

processes showed a significant release of mercury during heating, but the temperatures were too low to 

volatilize the arsenic, Se, or Pb. Whereas, the Hg loss for wallboard production suggest non-Hg metals 

being retained in wallboard with a potential Hg loss of 9 to 48%. However, the actual mass emission 

rates must be considered when determining potential concern to human health and the environment. 
 

 

 

Section 1 

Page 1-1 

Chapter 1 

Introduction 

More wide-spread implementation of multi-pollutant controls is occurring at U.S. coal-fired power plants. 

Research is underway by the U.S. Environmental Protection Agency (EPA) to document changes that 

may occur to coal combustion residues (CCRs) as a result of implementation of mercury and multipollutant control technology at coal-fired power plants. The Air Pollution Prevention and Control 

Division (APPCD) of EPA’s Office of Research and Development (ORD) is conducting research to 

evaluate cross media transfers of mercury and other constituents of potential concern (COPCs) resulting 

from the management of CCRs resulting from wider use of state-of-the art air pollution control 

technology. This research was cited as a priority in EPA’s Mercury Roadmap to ensure that one 

environmental problem is not being traded for another. (2006b) The objective is to understand the fate of 

mercury (Hg) and other COPCs in air pollution control residues and support EPA’s broader goal of 

ensuring that emissions being controlled in the flue gas at power plants are not later being released to 

other environmental media. The focus of this report is on the use of CCRs in high-temperature processes 

that are encountered during the production of cement clinker, asphalt, and wallboard. 

1.1 Coal Combustion Residues from Multi-Pollutant Control Technology 

Coal-fired power plants are the largest remaining source of anthropogenic mercury emissions in the U.S. 

Power plants are also a major source of nitrogen and sulfur oxides, particulate matter, and carbon dioxide. 

New environmental regulations in the U.S. will result in lower mercury air emissions. However, the 

mercury and other pollutants are transferred from the flue gas to fly ash and other air pollution control 

residues. The Clean Air Mercury Rule (CAMR) would have required the electric utility sector to remove 

at least 70% of the mercury released from power plant stack emissions by 2018. CAMR was vacated by 

the United States Court of Appeals for the District of Columbia Circuit in 2008. EPA is currently 

developing regulations under Section 112 of the Clean Air Act to reduce hazardous air pollutants 

(including mercury) from coal-fired power plants. Twenty states have implemented their own mercury 

regulations already, according to the National Association of Clean Air Agencies. (Senior et al., 2009) 

Other EPA regulations2 will necessitate the addition of new air pollution control devices for NOx and SO2 

at some power plants. This can also affect the fate of mercury and other COPCs. 

Figure 1 illustrates the types of air pollution control that coal-fired power plants are installing to reduce 

air emissions of concern. These control technologies include the addition of flue-gas desulfurization 

(FGD) systems to control sulfur dioxide, post-combustion NOx control [selective catalytic reduction 

(SCR) and selective non-catalytic reduction (SNCR)], and activated carbon injection to enhance mercury 

capture. These controls are typically added to particulate control devices which include the use of electric 

static precipitators (ESPs). Fabric filters are also in use for particulate control. The specific type and 

combination of control technology as well as the coal type being burned can impact the physical and 

2

On March 10, 2005, EPA announced the Clean Air Interstate Rule (CAIR) (FR 25612, May 2005) which is expected to increase 

the use of wet scrubbers and selective catalytic reduction (SCR) units to help reduce sulfur dioxide and nitrogen oxides emissions 

from coal-fired power plants. On July 11, 2008, United States Court of Appeals for the District of Columbia Circuit remanded 

CAIR back to EPA for further review and clarification. Thus the rule remains in effect; however, EPA is in the process of 

developing a replacement rule that will address the Court’s concerns. 
 

 

 

 

 

 

Section 1 

Page 1-2 

chemical characteristics of the CCRs. Use of air pollution control technologies will shift Hg and other 

pollutants from the stack gas to fly ash, FGD gypsum, and other air pollution control residues. 

Figure 1-1. Illustration of the types of air pollution control that can be used at a coal-fired power plant 

(U.S. Government Accountability Office, 2009) 

Annual statistics of CCR production and utilization is provided through the American Coal Ash 

Association. (www.acaa-usa.org) As of 2008, 136 million tons of CCRs were produced with ~61 million 

tons (or 45%) being used in commercial, engineering, and agricultural applications (ACAA, 2009). 

CCRs result from unburned carbon and inorganic materials in coals that do not burn, such as oxides of 

silicon, aluminum, iron, and calcium. Fly ash, representing 53% of CCRs, is the unburned material from 

coal combustion that is light enough to be entrained in the flue gas stream, carried out of the process, and 

collected as a dry material in the air pollution control equipment. Bottom ash is the unburned material that 

is too heavy to be entrained in the flue gas stream and drops out in the furnace. Boiler slag, unburned 

carbon or inorganic material in coal that does not burn, falls to the bottom of the furnace and melts. 

Bottom ash and boiler slag are not affected by air pollution control technology and, therefore, these 

materials are not being evaluated as part of this study. 

Both fly ash and FGD residues have been identified as CCRs with the potential to have increased mercury 

and/or other pollutant concentrations from the implementation of new air pollution technologies (EPA, 

2002; Srivastava et al., 2006; Thorneloe et al., 2008). The chemical and physical properties may also 

change as a result of sorbents and other additives being used to improve air pollution control. The 

samples used in this study have been evaluated for their chemical and physical composition and the 

potential for leaching of mercury and other COPCs. Companion reports are available providing 

additional data on the characterization of these samples. (EPA 2006b, 2008b, 2009) 

Table 1-1 provides the quantity of fly ash and FGD gypsum generated in 2008, the amount used in 

commercial applications, and the primary applications (ACAA, 2009). Three commercial applications of 
 

 

 

 

 

 

 

 

Section 1 

Page 1-3 

CCRs that involve exposure to high-temperature include production of cement clinker, asphalt, and 

wallboard. As shown in Table 1-1, fly ash and FGD gypsum are used in the production of cement 

clinker. According to the ACAA, 3.2 million tons of fly ash and 0.4 million tons of FGD gypsum are 

used in the production of cement clinker. For wallboard production, only FGD gypsum (and not fly ash) 

is used which avoids the need for mining natural gypsum. Of the 17.8 million tons of FGD gypsum 

produced in 2008, 8.5 million tons (or 48%) were used in the production of wallboard. Because of the 

wider use of wet scrubbers in response to CAIR regulations, this amount is expected to increase with a 

higher volume of FGD gypsum3

 being generated. Much less volume of CCRs is used in the production 

of asphalt. Review of the ACAA statistics indicate that only fly ash is used as mineral filler in the 

production of asphalt with a quantity of 17 thousand tons (ACAA, 2008). Therefore, of the three hightemperature processes, about 12 million tons of CCRs were used in the production of cement clinker, 

asphalt, and wallboard with asphalt representing less than 1% of this quantity. 

Table 1-1. Fly ash and FGD gypsum production and use in the U.S.a 

CCR Type Produced 

(million tons) 

Used in Commercial 

Applications (million tons) 

Percent 

Used Primary Applications 

Fly Ash 72.4 30.1 42% Concrete & grout, structural fill, waste 

stabilization/solidification, cement clinker 

FGD Gypsum 17.8 10.6 60% Wallboard, cement clinker, concrete 

a

Data from industry survey by ACAA, 2009 

Tracking the fate of Hg and other metals removed from the flue gas at a coal-fired power plant, requires 

an understanding of the air pollution control in use. Mercury can be found in the gaseous elemental 

(Hgo

), gaseous oxidized (Hg2+), and particulate bound (Hgp) forms. Air pollution control devices 

designed to capture SO2 and particulate matter (PM) can also remove Hg from flue gases in two ways: 

removal of Hgp in particulate control devices and removal of Hg2+ in FGD scrubbers. Thus, the Hg 

removed from the flue gas may be found in fly ash and in the scrubber solids and liquid effluent. (Senior 

et al., 2009) 

The Hg that is removed in the FGD scrubber can partition to the solid or liquid streams. Figure 1-2 

illustrates the measured partitioning of Hg in FGD outlet streams at five pulverized-coal fired power 

plants. (Withum, 2006) The plants fired bituminous coals and had cold-side ESPs for particulate control. 

Each of these plants had a selective catalytic reduction (SCR) system for NOx control and a wet FGD 

using calcium-containing slurry to control SO2. Gaseous Hg removal by the FGDs ranged from 77% to 

95%, and the Hg was found to be in the scrubber solids. (Senior et al., 2009) 

3

 If natural or inhibited oxidation occurs, then calcium sulfite and not calcium sulfate (i.e., gypsum) is produced. 
 

 

 

 

 

 

Section 1 

Page 1-4 

Fig. 1-2 Distribution of mercury in FGD scrubber outflows at five bituminous coal-fired power plants 

with SCR and FGD. (Senior et al., 2009; Withum, 2006) 

Mercury appears to be concentrated in fine particles of scrubber solids that are predominantly iron 

oxyhydroxides, and is not strongly associated with the solid calcium sulfate in the scrubber. (Senior et al., 

2009; Kaires et al., 2006; Schroeder, 2007). In some wet FGD systems, the fine solids are recycled back 

to the scrubber after dewatering of the byproduct solid, while in others, they are disposed of, as was the 

case for two FGDs noted in an EPRI study. (Richardson et al., 2003) Table 2 shows the distribution of 

mercury in the scrubber outlet streams for three limestone scrubbers in the EPRI study. For the two 

forced-oxidation scrubbers sampled, most of the Hg leaving the scrubber did so in the gypsum fines or 

fines liquor after the dewatering process. In forced oxidation scrubbers, this means that Hg can ultimately 

be in the gypsum fines as well as in the FGD byproduct. Therefore, it is important to understand how the 

FGD gypsum fines are managed in tracking the fate of Hg and other metals in the use of FGD gypsum in 

wall board production or other applications. 
 

 

 

 

 

Section 1 

Page 1-5 

Table 1-2. Distribution of mercury among scrubber outlet streams. (Richardson et al., 2007) 

Plant – Scrubber Type 

FGD 

Byproducta 

Gypsum 

Finesb 

Gypsum Fines 

Liquorc

 Stack Gas 

1 – Forced Oxidation 18.9% 

7.3% 

7.8% 

5.2% 

58.9% 

65.6% 

14.4% 

20.8% 

2 – Forced Oxidation 48.1% 48.1% 0.0% 3.7% 

3 – Inhibited Oxidation 65.7% 35.4% 

a

Calcium sulfate hemihydrate or gypsum produced by the FGD system. 

b

Solid phase from hydroclone overflow stream sent to disposal. 

c

Liquid phase from hydroclone overflow stream sent to disposal. 

1.1.1 CCR Use in Cement Clinker 

The making of cement involves the heating of various feedstocks in a cement kiln to make “clinker.” This 

clinker is ground with gypsum and transported to ready-mix concrete manufacturers. Various components 

are needed for feedstock including lime (CaO), iron oxide (Fe2O3), silica (SiO2) or alumina (Al2O3). Fly 

ash can replace a portion of these, representing a maximum of about 5% (by weight) of the typical raw 

mix to the kiln. Other inputs typically include limestone (90%), iron ore (3%), and sand (2%). Fly ash 

contains high amounts of calcium, iron, silicon, and aluminum, replacing or augmenting raw feed stocks 

used in cement production. Cement kiln residence time is typically one to three hours, and temperatures 

reach over 1427 °C (2600 °F) (EPA, 2002). Because of the high temperatures, virtually all mercury will 

be volatilized when CCRs are used as feedstock to cement kilns. 

Because of the concern for Hg and other hazardous air pollutants, EPA has proposed (74 FR 21136m May 

6, 2009) regulations to reduce Hg emissions from cement kilns, which may result in use of air pollution 

control technology similar to that used at coal-fired power plants (e.g, wet scrubbers and sorbents for 

enhanced Hg capture). The addition of air pollution control at cement kilns should not affect the ability to 

use fly ash or FGD gypsum in the production of clinker. However, to avoid installation of air pollution 

control, kiln inputs (such as fly ash) containing Hg may be avoided which could impact usage of some 

CCRs. 

1.1.2 CCR Use as Aggregate in Asphalt 

Hot mix asphalt is a combination of 95% aggregate (e.g., stone, sand, or gravel) bound together by asphalt 

cement, a product of crude oil. Fly ash can make up approximately 5% of the total aggregate weight, 

replacing natural fillers such as hydrated lime or stone dust (EPA, 2002). Asphalt manufacturing consists 

of a very short residence time mixing process (about one minute), a long residence time storage process 

(several hours), and then application. The storage process occurs at temperatures of about 5 °C higher 

than the mixing process. Asphalt is delivered to the paving machine at approximately the same 

temperature as it is stored. Therefore, the most important step (in terms of thermal desorption) is the 
 

 

 

 

 

 

Section 1 

Page 1-6 

storage step. Storage temperatures typically range from 127-143 °C for binder grade PG46-28 and 157­

168 °C for binder grade PG82-22.). 

1.1.3 FGD Gypsum Use in Wallboard 

In 2007, FGD gypsum (e.g., gypsum produced from use of wet scrubbers) accounted for 35% of the total 

domestic gypsum production (9.2 million tons of FGD gypsum used versus 26.4 million tons of domestic 

gypsum supply (ACAA, 2008; USGS, 2008). Almost 85% of the gypsum consumed in the U.S. 

(approximately 24 million tons) in 2008 was used in the manufacture of wallboard and plaster products 

with U.S. wallboard plant capacity at 27 billion square feet per year (USGS, 2009). As more coal 

combustion facilities add scrubbers, the production (and use) of FGD gypsum is projected to grow. 

FGD gypsum is typically dewatered at the utility plant before shipment to a wallboard manufacturing 

facility (EPA, 2002). The mercury in the FGD sludge has been reported to be associated with the fines 

(i.e., fine solid particles) and not the FGD liquors (DOE; 2005; Schroeder and Kairies, 2005). There are 

several ways FGD solids can be prepared for use at a wallboard manufacturing plant. If the FGD sludge 

does not meet the wallboard manufacturer’s specifications (as-is), then the fine solid particles are 

typically removed. This removal process is often completed with hydrocyclones and the fines are either 

disposed or sold for other uses (DOE, 2005). Other facilities have to “blow down gypsum fines” as a part 

of the chlorine purge, limiting chlorine buildup in the FGD liquor (DOE, 2005). As wall deposits 

buildup, the scrubber efficiency will be reduced until scrubber water rich in solids or salts is wasted or 

“blown down” and replaced with low solids water. Since Hg is associated with the fine particles of the 

FGD sludge (DOE, 2005), both of these processes result in a gypsum product which typically contains 

less mercury than the wet FGD sludge itself. If the FGD sludge is used as-is, the mercury content is 

typically greater than those processes that remove the fines. 

The first process in making wall board is to dry the gypsum so that it contains no free moisture – only 

chemically bound waters of hydration. This material is referred to as “land plaster”. The next step is to 

calcine the land plaster to form calcium sulfate hemi hydrate (i.e., stucco or plaster of Paris) according to 

the following reaction: 

2 CaSO4•2H2O + heat ↔ 2 CaSO4•1⁄2H2O + 3 H2O 

The stucco is mixed with water and additives to form slurry that is extruded between two sheets of paper 

to form wallboard. The final step is to dry the wallboard prior to processing and stacking it as final 

product. The drying step is not likely a release point for mercury since the wallboard is between two 

sheets of paper at this point and typically does not reach temperatures of more than 100 oC. Meischen 

(2004) conducted a study on laboratory-produced FGD containing Hg and concluded that Hg 

volatilization would not be likely where only the edges of the wallboard were exposed. Mercury release 

diminished as the weight of the wallboard increased. 

Any potential loss in Hg is considered more likely to occur during the calcining step. The highest 

temperature that FGD gypsum is exposed to is 128o

C. However, possible loses could also occur in the 

gypsum dryer and the finished wallboard dryer. However, the maximum temperature to which the 

gypsum is exposed in the dryers is less than during calcining (77 to 110o

C). (Sanderson et al., 2008) 

The drying step is not likely a release point for mercury since the wallboard is between two sheets of 

paper at this point and typically does not reach temperatures of more than 100 oC. Meischen (2004) 

conducted a study on laboratory-produced FGD containing mercury and concluded that mercury 
 

 

 

 

 

 

 

Section 1 

Page 1-7 

volatilization would not be likely where only the edges of the wallboard were exposed. Mercury release 

diminished as the weight of the wallboard increased. 

Sanderson et al., 2008, provide data evaluating the fate of Hg in FGD gypsum across wallboard 

production plants. This work was conducted by U.S. Gypsum through funding by DOE and the Electric 

Power Research Institute (EPRI). Table 1-3 provides a summary of the results from measurements of the 

Hg content in FGD gypsum and across the gypsum dryer, calciner, and wallboard dryer. The results show 

a wide-range of Hg losses ranging from 2 to 55% loss of mercury in the feedstock and using Ontario 

Hydro method at the process stacks. Most of the loss was found to occur at the gypsum calciner when the 

total Hg loss was greater than 10%. There was less of a difference across the gypsum dryer, calciner, and 

wall board dryer when the mercury loss was below 10%. (Sanderson et al., 2008) 

The authors caution drawing conclusions from this research because only seven sets of wallboard plant 

measurements were made and it is difficult to identify what factors impact mercury loss percentages. One 

finding is that the operation of the wet scrubber can affect the fate of Hg. The effectiveness of the 

scrubbing solution in removal of COPCs depends on the concentration of the scrubbing chemical which is 

continuously being depleted during the process. COPCs transferred to the liquid phase are removed from 

the scrubber by continuous or periodic overflow of blow down. For those facilities using higher blow 

down rates of chlorides and fine solid particles at wet FGD systems led to higher percentage of Hg loss at 

the wallboard plant. However, higher purge rates also led to FGD gypsum with lower Hg concentrations. 

The authors conclude that improved understanding the physical and chemical association of the Hg in 

gypsum might clarify the conditions that lead to the higher Hg loss. 

The US Gypsum study did not include analysis of metals other than mercury. Therefore, wallboard 

simulation study was included as part of this research. However, testing of full scale production facilities 

is considered preferable over conducting smaller-scale laboratory simulations. US Gypsum provide two 

samples from their earlier testing to use in this study. 

1.2 Objective 

With the increasing metals content of CCRs as a result of changes in air pollution control at coal-fired 

power plants, there is interest in evaluating the fate of mercury and other metals. The objective of this 

research is to conduct laboratory simulations of three high temperatures processes that use CCRs in the 

production of cement clinker, asphalt and wallboard to determine the likelihood of metals being 

volatilized during the production process. The metals that were analyzed for this study include Hg, 

arsenic (As), selenium, and lead (Pb). The study support EPA’s broader goal of ensuring that emissions 

being controlled in the flue gas at power plants are not later being released to other environmental media 

Table 1-3. Sanderson et al., 2008 study to evaluate of Hg loss across wallboard production 

facilities 

Test # 1 2 3 4 5 

Test Date (2 day test) July 2004 Dec 20004 Sept 2004 Feb 2005 March 2006 Sep

Power Plant A A B C E 

Coal Type High-Sulfur 

Bituminous 

High-Sulfur 

Bituminous 

High-Sulfur 

Bituminous 

Texas 

Lignite 

High-Sulfur 

Bituminous 

High

Bitum

SCR in use Yes By-passed Yes No By-passed Y

FGD Fines Blow Downa Low rate Low rate High rate None High rate Hig

Wallboard plant 1 1 2 3 4 

Hg content, FGD gypsum (μg/g)d 

0.96 ± 0.03 1.10 ± 0.04 0.21 ± 0.02 0.53 ± 0.01 0.20 ± 0.04 0.13 

Moisture content, wt% 11.9 11.1 11.3 12.6 10.9 6Hg Loss at Wallboardd - % of inlet Hg to each process step 

 -Across Dryer Mill (%) 1.1 ± 0.9 0.3 ± 0.1 1.0 ± 0.3 0.8 ± 0.1 1.8 ± 0.4 4.1 

 -Across Kettle Calciner (%) 2.3 ± 1.0 2.6 ± 0.0 41 ± 2 0.8e 50 ± 6 45 

 -Across Board Dryer Kiln (%) 1.9 ± 0.6 5.5 ± 2.4 14 ± 6 0.3e 1.4 ± 1.2 5.8 

 Overall Loss 5.1 ± 1.7 8.3 ± 2.0 46 ± 16 1.8e 51 ± 5 55 

Hg Loss Based on Raw Gypsum & Wallboard

 Product Hg Conc d, % 

2.0 ± 5.0 16 ± 8 66 ± 2 8.7e 40 ± 21 32 

Hg Loss from Process Stacks, g/hr 

4.1 ± 1.7 2.7 ±0.1 8.2 ± 0.5 0.26e 2.0 ± 0.2 1.4 

Hg Loss Rate, lb/MM ft2 of 

wallboard 

0.1 0.1 0.2 0.01e 0.2 0

Hg Loss Rate, g/ton of dry FGD gypsum 

0.05 0.08 0.09 0.01e 0.09 0

Hg Loss Rate, g/ton of dry FGD gypsum 

0.05 0.08 0.09 0.01e 0.09 0

aMore qualitative than quantitative as reported by Sanderson et al, 2008.bWastewater treatment plant for FGD system uses filter press for removing fine particles from hydrocyclone overflow liquor, so fine a

down” independently.
 

cDuring this test, soluble tri-sodium salt (or TMT) was used to precipitate dissolved Hg (by chemically binding to heavy metals via su

separated from the FGD liquor by filtration). 

dMean value for three runs 5 ± 95% confidence interval of mean, unless noted otherwise; loss percentages across dryer mill, kettle cal

are based on feed material to each step, so percentages cannot be summed to the wallboard product overall loss percentage show.
 

eMean value for two runs
 

 

 

 

 

 

 

 

 

 

 

Section 1 

Page 2-1 

Chapter 2 

Materials and Methods 

2.1 CCR Materials for Evaluation 

Twenty-one CCR samples were used to evaluate the thermal stability of mercury and other metals during 

the production of cement clinker, asphalt, and wallboard. This work has been conducted in stages with 

initial work using samples collected as part of a DOE-funded program to evaluate sorbent technology for 

enhanced mercury capture. Samples were also obtained through CCR characterization study evaluating 

changes in CCR composition and constituent release by leaching that may occur to fly ash and FGD 

gypsum in response to changes in air pollution control technology at coal-fired power plants (EPA 2006, 

2008b, 2009). Because samples were obtained on a voluntary basis and represent a minor fraction (<1%) 

of U.S. boilers, these results are not considered to provide a statistically representative sample. 

Regardless, care was taken to obtain samples that are considered typical of the CCRs resulting from 

improvements in air pollution control. 

The samples analyzed include: 

1.	 Fly ash from three different facilities evaluated by ADA-Environmental Solutions (ADA) under 

contract for the Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). 

Powdered activated carbon was injected upstream of particulate control to improve the capture 

efficiency of mercury. Samples were collected from Brayton Point, Pleasant Prairie, and Salem 

Harbor with and without the use of activated carbon injection (ACI) for a total of six samples as 

shown in Table 2-4.4 

2.	 Fly ash from two facilities with and without the use of post-NOx combustion control [Facility A 

using selective non-catalytic reduction (SNCR) and facility B using selective catalytic reduction 

(SCR). Fly ash from two additional facilities (Facility E and M) both with SCR in use. This 

represents a total of five samples as shown in Table 2-5; and 

3.	 FGD gypsum kettle feedstock obtained from U.S. Gypsum (two samples) as part of the research 

documented in Sanderson et al., 2008. Only a small sample size was provided which did not allow 

detail characterization as done for the other CCRs. 

4 These samples were collected during early test programs to evaluate use of ACI for enhancing mercury 

capture. Samples were obtained prior to and after ACI in use. Industry has found that less carbon is needed 

to obtain the same level of mercury capture obtained during the early test programs. Therefore more recent 

samples are suspected to contain less carbon than that used in this evaluation. However, this is not 

suspected to impact the thermal evaluation. 
 

 

 

 

 

 

Section 1 

Page 2-2 

4.	 FGD gypsum material obtained directly from eight power plants with web scrubbers in use (eight 

samples). 

The fly ash samples from the NETL field evaluation program represent the first time that sorbent was 

used to enhance mercury capture over a test program of several weeks. All three of the facilities in the 

NETL program (Brayton Point, Salem Harbor and Pleasant Prairie) have particulate control devices and 

do not use scrubbers (at the time the samples were collected). The same commercial sorbent, Norit 

Americas Flue Gas Desulfurization (FGD) Carbon, was used for each test. This sorbent has a surface area 

of 600 m2

/g and a mass-mean diameter of 18 μm. The ACI was injected at a rate of 10 lb/Macf during the 

sorbent testing phase of these tests. 

All of the facilities mentioned above are further described in subsequent sections. Tables 2-1 and 2-3 

provide the elemental characteristics of the coal combusted at Brayton point, Pleasant Prairie, and 

Facilities A, B, and E. Table 2-2 provides the elemental analysis [by x-ray fluorescence (XRF) 

spectroscopy] of the fly ashes from the ADA samples and Facility A, B, E, and M. Except for the 

samples from U.S. Gypsum (the sample size was too small), for each of the CCRs used in this study, 

more detailed information is available on the air pollution control configurations, coal burned, and the 

CCR composition and leaching characteristics. (EPA 2006, 2008b, 2009). 

2.1.1 Brayton Point 

Brayton Point Station, located in Somerset, Massachusetts, is operated by PG&E National Energy Group. 

Unit 1 of this facility was selected for evaluation. Emissions from this facility are controlled through the 

use of low-sulfur coal and cold-side ESP which is typical of coal-fired power plants in the eastern U.S. 

The unit has a tangentially fired boiler rated at 245 MW, fires low-sulfur coal, and uses a cold-side ESP 

for particulate control (Senior et al., 2003a). 

The primary particulate control equipment consists of two cold-side ESPs in series, with an EPRICON 

flue gas conditioning system provides SO3 for fly ash resistivity control and is used on an as-needed basis. 

The first ESP in this particular configuration was designed and manufactured by Koppers with a weighted 

wire design and a specific collection area of 0.512 m2

/ am3/min (156 ft2/1000 acfm). The second ESP in 

the series configuration was designed and manufactured by Research-Cottrell with a rigid electrode 

design and a specific collection area of 1.3 m2

/ am3/min (403 ft2/1000 acfm). The precipitator inlet gas 

temperature is nominally 138 °C (280 °F) at full load (Senior et al., 2003b). The facility uses ACI to 

increase mercury capture. The ACI control system injects the carbon between the ESPs to capture the 

mercury with the fly ash. The baseline and post-control ashes used for this study were collected as 

composite samples from the third row of ash hoppers of the second ESP. The baseline ash was collected 

on June 6, 2002. The post-control fly ash was collected on July 21, 2002. Both fly ashes were stored in 

five-gallon buckets in the onsite ADA-ES trailer at ambient temperatures. The buckets were filled to 

approximately three-fourths capacity. 

Elemental composition by XRF and additional characteristics of the fly ashes from baseline and enhanced 

mercury control testing are provided in Table 2-2. Results for total content analyses for mercury, arsenic, 

Pb, and Se are provided in Table 2-4. 
Section 1 

Page 2-3 

2.1.2 Salem Harbor 

PG&E National Energy Group owns and operates Salem Harbor Station located in Salem, Massachusetts. 

There are four fossil fuel fired units at the facility designated as Units 1, 2, 3, and 4. Units 1-3 fire a low 

sulfur, bituminous coal and use oil for startup. Unit 1 was selected for the control technology evaluation 

because of its combination of firing low-sulfur bituminous coal with urea-based selective non-catalytic 

reduction (SNCR) for nitrogen oxide reduction, a cold-side ESP, and high loss-on ignition (LOI). This 

configuration provided an opportunity to quantify the impact of SNCR on mercury removal and sorbent 

effectiveness. In addition, test results from prior mercury tests have indicated 87 to 94% mercury 

removal efficiency on this unit. Unit 1 is a B&W single-wall-fired unit with twelve DB Riley CCV-90 

burners and is rated at 88 gross MW (Senior et al., 2003b). 
Section 1 

Page 2-4 Table 2-1.	 Characteristics of air pollution control and for samples obtained from Brayton Point, Pleasant Prairie

Facilities A, B, and E 

Parameter Measured Brayton Point Pleasant Prairie Salem Harbor Facility A 

Coal Type Low sulfur bituminous Powder River Basin (PRB) sub-bituminous Low sulfur bituminous Medium sulfur bituminous 

Sulfur, wt% 0.7 0.3 0.67 1.05 

Ash, wt % 10.8 5.1 6.48 10.29 

Moisture, wt: 4.7 30.7 9.05 6.0 

HHV, Btu/lb 12,780 8,385 12,420 12,790 

Hg, μg/g 0.044 0.109 0.0617 0.086 

Cl, μg/g 1475 8.1 64.3 166 

As, μg/g 5.68 NT 2.4 NT 

Pb, μg/g 8.9 NT 3.8 NT 

Se, μg/g 3 NT 4.8 NT 

Particulate Control 

Device 

Two Cold-Side ESPs 

in Series Cold-Side ESP Cold-Side ESP Fabric Filter C

Sorbent Injection Point Between Two ESPs Before ESP Before ESP NA 

Sampling Location Ash Hopper Row C ESP Hopper 1 and 2 Composite ESP Hopper A Pug Mill A

NT = Not tested, NA = Not applicable, HHV = Higher Heating Value (Heat of Combustion) 
 

 

 

 

Section 2 

Page 2-5 

The particulate control equipment consists of a two-chamber, cold-side ESP (chambers designated 1-1 

and 1-2), which provides two separate gas flow paths from the outlet of the tubular air heaters to the 

inducted draft (ID) fan inlets. This Environmental Elements ESP has a rigid electrode design and a 

specific collection area of 1.56 m2

/ am3/min (474 ft2/1000 acfm). The precipitator inlet gas temperature is 

nominally 124 °C (255 oF) at full load. Typical LOI of the Unit 1 ash is about 25%. This ash is landfilled 

(Senior et al., 2003b). 

The baseline and post-control ashes used for this study were collected as grab samples from the first ash 

hopper (hopper A) of row 1-1 of the ESP. The baseline ash was collected on June 6, 2002. The postcontrol fly ash was collected on July 7, 2002. Both fly ashes were stored in five gallon buckets in the 

onsite ADA-ES trailer at ambient temperatures. The buckets were filled to approximately three-fourths 

capacity. Elemental composition by XRF and additional characteristics of the fly ashes from baseline and 

enhanced mercury control testing are provided in Table 2-2. Results for total content analyses for 

mercury, arsenic, Pb, and Se are provided in Table 2-4. 

2.1.3 Pleasant Prairie 

Wisconsin Electric Power Company, a subsidiary of Wisconsin Energy, owns and operates Pleasant 

Prairie Power Plant located near Kenosha, Wisconsin. The plant has two 600 MW balanced-draft coalfired boilers designated units 1 and 2. Unit 2 was selected for inclusion in the NETL program because it 

burns a variety of Powder River Basin low sulfur, sub-bituminous coals. (Starns et al., 2002). 

The primary particulate control equipment consists of cold-side ESPs of weighted wire design with a 

Wahlco gas conditioning system that provides SO3 for fly ash resistivity control. The precipitators were 

designed and built by Research-Cottrell. The design flue gas flow was 61,164 am3

/min (2,610,000 acfm). 

The precipitator inlet gas temperature is nominally 138 °C (280 oF) at full load (Starns et al., 2002). 

Precipitator #2 is comprised of four electrostatic precipitators that are arranged piggyback style and 

designated 2-1, 2-2, 2-3, and 2-4. Each of the four precipitators is two chambers wide and four 

mechanical fields deep with eight electrical fields in the direction of gas flow. The specific collection area 

is 1.54 m2

/ am3/min (468 ft2/1000 acfm) (Starns et al., 2002). 

Hopper ash is combined from all four precipitators in the dry ash-pull system. The ash is sold as a “Class 

C” fly ash to be used as a base for concrete (Senior et al., 2004). The baseline ash was collected as a 

composite sample from ash hoppers 7-1 and 7-2 of ESP 2-4. The post-control ash was collected as a grab 

sample from ash hopper 7-2 of ESP 2-4. The baseline ash was collected on September 11, 2001. The postcontrol fly ash was collected on November 13, 2001. Elemental composition by XRF and additional 

characteristics of the fly ashes from baseline and enhanced mercury control testing are provided in 

Table 2-2. Results for total content analyses for mercury, arsenic, Pb, and Se are provided in Table 2-4. 

2.1.4 Facility A5 

The test site was a 440-MW coal-fired power plant with a reverse-air fabric filter followed by a wet flue 

gas desulfurization system. The unit burns ~1 percent sulfur eastern bituminous coal. The unit operated at 

nominally full load for the duration of the test program. A schematic diagram of the power plant is shown 

in Appendix A. The unit is equipped with a pulverized-coal boiler and in-furnace selective non-catalytic 

reduction (SNCR); urea was injected into the boiler during the course of operations within the duration of 

5

 EPA was requested not to disclose the identity of the other sites. Therefore, the remaining sites are coded as letters. 
 

Section 2 

Page 2-6 

the initial part of this test program. However, urea was not injected into the boiler for the final comparison 

test (“SNCR off”). Gas exiting the furnace is split between two flues equipped with comparable control 

equipment. Particulate is removed with a reverse-air fabric filter. Flue gas is then scrubbed through a 

multiple tower wet FGD unit; FGD is a limestone forced-oxidation design. The two flues are joined prior 

to exhausting to a common stack. The annular stack rises 93.9 meters (308 feet) above the top of the 

incoming flue. The stack is operated in a saturated condition with no reheat. The fly ash and FGD waste 

are combined and then dewatered before landfill disposal. Elemental composition by XRF and additional 

characteristics of the fly ashes from baseline and enhanced mercury control testing are provided in 

Table 2-3. Results for total content analyses for mercury, arsenic, Pb, and Se are provided in Table 2-5. 

2.1.5 Facility B 

The test site was a 640 MW coal fired power plant with cold side ESP followed by a wet flue gas 

desulfurization system with inhibited Mag-lime (CaO + MgO). The unit burns medium- to high-sulfur 

eastern bituminous coal. The plant is equipped with a pulverized coal boiler and an in-furnace selective 

catalytic reduction (SCR) system composed of vanadium pentoxide (V2O5), tungsten trioxide (WO3), and 

titanium dioxide (TiO2) mixture. One set of samples was collected during a season of elevated ambient 

ozone while ammonia was injected into the catalyst box at a concentration of 320 ppm (“SCR on”) to 

control NOx. A second set of samples was collected during the winter when ammonia was not being 

injected (“SCR off”). Particulate is removed with a cold-side ESP. Flue gas is then scrubbed through a 

wet FGD unit; the FGD unit is an inhibited Mag-lime design. The fly ash and FGD waste are combined 

and then dewatered before landfill disposal in a clay-lined site. Elemental composition by XRF and 

additional characteristics of the fly ashes from baseline and enhanced mercury control testing are 

provided in Table 2-3. Results for total content analyses for mercury, arsenic, Pb, and Se are provided in 

Table 2-5. 

2.1.6 Facility E 

The test site was a 390 MW coal fired boiler with cold side ESP. The unit burns low-sulfur eastern 

bituminous coals. The unit is equipped with a pulverized coal boiler and selective catalytic reduction 

(SCR) system using a titanium dioxide/tungsten trioxide/silicon dioxide/vanadium pentoxide catalyst. 

Particulate is removed with a cold-side ESP. The fly ash is transported by a dry handling system to a silo 

where it is combined with fly ash from three additional boilers and wetted with water prior to being 

transported to a clay-lined landfill. Elemental composition by XRF and additional characteristics of the 

fly ash are provided in Table 2-3. Results of total content analyses for mercury, arsenic, Pb, and Se are 

provided in Table 2-5. 

2.1.7 Facility M 

This test site was a 1,000 + megawatt (MW) power plant. The plant burns high-sulfur bituminous coal in 

a dry-bottom pulverized coal boiler. Electrostatic precipitators (ESPs) are used on all units for particulate 

control, and wet FGD systems are used to reduce SO2 emissions on two units. The wet FGD systems 

utilize limestone slurry and an inhibited oxidation process. The FGD sludge, consisting primarily of 

calcium sulfite, is pumped from the absorber to a thickener. Liquid overflow from the thickener is 

recycled back into the FGD system, and the thickened sludge is pumped to a series of drum vacuum filter 

for further dewatering. Water removed by the drum vacuum filters is recycled back into the FGD system, 

and the filter cake is taken by conveyor belt to a pug mill, where it is mixed with dry fly ash and dry 

quicklime for stabilization. The resulting stabilized FGD solids are taken by conveyor to a temporary 

outdoor stockpile, and then transported by truck either to a utilization site or to an on-site landfill. The 

active portion of the landfill is lined and leachate is collected. An older inactive portion of the landfill is 

clay-lined but does not have leachate collection. 
 

 

 

 

 

 

 

 

 

Section 2 

Page 2-7 

2.1.8 Facility N 

Facility N is a wall fired 715 MW coal-fired power plant with cold side ESP followed by a wet FGD 

system using wet limestone in a forced oxidation process. The unit burns medium to high sulfur eastern 

bituminous coals with approximately 3% sulfur. The gypsum is washed, dried and then sold to the 

wallboard industry. 

One 5 gallon bucket of un-washed gypsum (NAU) and one 5 gallon bucket of washed gypsum (NAW) 

were collected from this site. Facility N was sampled on June 1, 2006. The samples were collected by 

RMB Consulting & Research, Inc. (Raleigh, NC) personnel. The washed gypsum sample (NAW) was 

used in the laboratory wallboard simulation. 

2.1.9 Facility O 

Facility O is a tangentially fired 500 MW coal-fired plant with cold side ESP followed by a wet FGD 

system with wet limestone forced oxidation. The unit is equipped with a pulverized coal boiler and 

ammonia based SCR. This unit burns high sulfur eastern bituminous coals. Slurry from the absorber goes 

to a primary hydrocyclone for initial dewatering. The gypsum (hydrocyclone underflow) is dried on a 

vacuum belt and washed to remove chlorides, before use in wallboard. 

Two samples were collected from the FGD gypsum drying facility by compositing samples collected on 

June 10, 11, and 12, 2006 when the SCR was operating. On each day, two gallon pails of unwashed 

gypsum and washed/dried gypsum were collected. The unwashed gypsum was collected from the vacuum 

belt prior to the chloride spray wash. The washed/dried gypsum was collected from the end of the vacuum 

belt. The three daily samples were sent to Arcadis for compositing to form sample OAU (unwashed 

gypsum) and sample OAW (washed gypsum). All samples were collected by plant personnel. The 

washed gypsum sample (OAW) was used in the laboratory wallboard simulation. 

2.1.10 Facility S 

This test site is a 600 megawatt (MW) per unit power plant. The plant burns eastern high sulfur 

bituminous coal in a dry-bottom pulverizer boiler. Cold-side electrostatic precipitators (ESPs) are used 

on all units for particulate control, and wet FGD systems are used to reduce SO2 emissions on two units. 

The wet FGD systems utilize limestone slurry sorbents and an forced oxidation process 

Samples of washed (SAW) and unwashed (SAU) gypsum were collected at this site in July, 2007. One 

five-gallon bucket of each was collected by plant personnel. The washed gypsum sample (SAW) was 

used in the laboratory wallboard simulation. 

2.1.11 Facility T 

This power plant test site has three boilers producing a total of a 2,000+ megawatts (MW). The plant 

burns medium sulfur eastern bituminous coal in a dry-bottom pulverizer boiler. Units 1 and 2 have coal 

cleaning equipment to reduce ash ad SOx emissions. All three of these units have low NOx burners and 

selective catalytic reduction systems for NOx control. Ammonia was injected upstream of the SCR 
 

 

 

 

 

 

 

 

 

 

Section 2 

Page 2-8 

catalysts. Cold-side electrostatic precipitators (ESPs) are used on all three units for particulate control. A 

wet FGD systems using limestone in a forced oxidation mode are used to reduce SO2 emissions on Unit 3. 

Four samples were collected by plant personnel on September 17, 2007: one 5 gallon bucket of fly ash 

from Unit 2 (TFA), one 5 gallon bucket of un-washed gypsum from Unit 3 (TAU), one 5 gallon bucket of 

washed gypsum from Unit 3 (TAW), and one 5 gallon bucket of FGD waste water treatment plant filter 

cake from Unit 3 (TFC). The washed gypsum sample (TAW) was used in the laboratory wallboard 

simulation. 

2.1.12 Facility W 

This site is operated by American Electric Power (AEP) and has two 800 MW coal-fired boilers for a 

plant total of 1,600 MW. The plant burns eastern bituminous coal in a dry-bottom pulverizer boiler. 

Cold-side electrostatic precipitators (ESPs) are used on both units for particulate control, and wet FGD 

systems are used to reduce SO2 emissions on two units. The wet FGD systems utilize limestone slurry 

sorbents and a forced oxidation process. SO2 concentrations of the inlet FGD are approximately 1990 

ppm with removal efficiencies of 98%. The plant has a Trona injection system for SO3 control, but this 

system was not operating at the time of sampling. 

Samples were collected as follows: dry FGD gypsum after water wash (WAW), moist FGD gypsum 

before the water wash (WAU), wastewater treatment system filter cake (WFC), and dry fly ash (WFA). 

Five gallon buckets of each of the samples were collected by plant personnel on 11/20/08. Samples were 

delivered to ARCADIS on 11/28/07. The washed gypsum sample (WAW) was used in the laboratory 

wallboard simulation. 

2.1.13 Facility X 

Wisconsin Electric Power Company, a subsidiary of Wisconsin Energy, owns and operates Pleasant 

Prairie Power Plant located near Kenosha, Wisconsin. The plant has two 600 MW balanced-draft coalfired boilers designated units 1 and 2. Unit 2 was selected for inclusion in the NETL program because it 

burns a variety of Powder River Basin low sulfur, sub-bituminous coals. In addition, this facility has the 

ability to isolate one ESP chamber (1/4 of the unit) (Starns et al., 2002). 

The primary pollution control equipment consists of SCR, cold-side ESPs, and a wet-FGD system. NOx 

is controlled in the SCR by injecting ammonia in the presence of a catalyst. The forced oxidation FDG 

system uses wet-limestone as a sorbent for SO2 control. This site also contains an additional mercury 

oxidation catalyst. 

Samples were collected as follows: dry FGD gypsum after water wash (XAW), moist FGD gypsum 

before the water wash (XAU), FGD wastewater treatment system filter cake (XFC), and dry fly ash 

(XFA). Five gallon buckets of each of the samples were collected by plant personnel and delivered to 

ARCADIS on 6/16//08. The washed gypsum sample (XAW) was used in the laboratory wallboard 

simulation. 

2.1.14 Facility Aa 

This test site has four boilers producing a total of 2,424 megawatt (MW) of power. The plant burns 

eastern-bituminous coal in a dry-bottom pulverizer boiler. Cold-side electrostatic precipitators (ESPs) are 

used on three units and hot-side ESP on one unit for particulate control. Unit 1 at this plant was burning 
 

 

 

 

 

Section 2 

Page 2-9 

medium sulfur coal and the SCR was operating. Unit 2 burns medium sulfur coal and has an SCR, but 

this unit was not operating during the time of sampling. Unit 3 was burning high sulfur coal and the SCR 

was operating. Unit 4 was burning low sulfur coal; the SCR was operating, and uses a hot-side ESP to 

control particulate. A dry handling system is used to collect the fly ash from the ESPs. 

Units 3 and 4 were connected to a single FGD system. The wet FGD systems utilize limestone slurry 

sorbents and a forced oxidation process. Samples of the washed (AaAW) and un-washed (AaAU) FGD 

gypsum were collected. Fly ash was collected from units 1 (AaFA), 3 (AaAB), and 4 (AaFC). Unit 2 

was not operating at the time of sampling. The washed gypsum sample (AaAW) was used in the 

laboratory wallboard simulation. 

2.1.15 Facility Da 

This test site has two supercritical boilers producing 2,240 megawatts (MW) of power. The plant burns 

eastern-bituminous coal in a dry-bottom pulverizer boiler. The primary pollution control equipment 

consists of low NOx burners, SCR, cold-side ESPs, and a wet-FGD system. NOx is controlled in the SCR 

by injecting ammonia in the presence of a catalyst. The forced oxidation FDG system uses wet-limestone 

as a sorbent for SO2 control. A dry handling system is used to collect the fly ash from the ESPs. 

One five gallon bucket each of fly ash (DaFA), washed gypsum (DaAW), and FGD waste water treatment 

plant filter cake (DaFC) were collected by plant personnel. Samples were received by ARCADIS on 

12/12/2008. The washed gypsum sample (DaAW) was used in the laboratory wallboard simulation. 
Section 2 

Page 2-10 

Table 2-2. ADA fly ashes: elemental composition (by X-ray Fluorescence) and other 

characteristics 

Element 

Reference 

Fly Ash 

Pleasant Prairie Brayton Point Salem Harbor 

Baseline w/ACI Baseline w/ACI Baseline w/ACI 

Average % Average 

% 

Average 

% 

Average 

% 

Average 

% 

Average 

% 

Average 

% 

Al 14.7 10.0 10.2 13.4 12.4 9.52 7.62 

As 0.010 BML BML BML BML BML BML 

Ba 0.110 0.695 0.647 0.010 0.095 0.091 0.099 

Br BML BML BML 0.005 0.065 BML BML 

Ca 0.860 18.4 16.6 6.08 2.03 1.30 0.803 

Cl 0.026 BML 0.045 0.030 0.440 0.101 0.203 

Cr 0.017 0.016 0.013 0.022 0.018 0.011 0.012 

Cu 0.018 0.022 0.022 0.022 0.020 0.007 0.008 

Fe 5.11 4.31 4.28 4.650 2.50 4.87 3.63 

I BML BML BML BML 0.014 BML BML 

K 2.46 0.371 0.455 1.85 1.50 1.250 0.977 

Mg 0.637 2.81 2.46 0.800 0.641 0.785 0.420 

Mn 0.015 0.057 0.020 0.041 0.020 0.045 0.021 

Na 0.346 1.66 1.31 0.511 0.242 0.270 0.293 

Ni 0.011 0.006 0.006 0.015 0.016 0.009 0.009 

Pb 0.008 BML BML BML 0.010 0.005 BML 

Px1 0.087 0.560 0.508 0.161 0.042 0.086 0.057 

Se BML BML BML 0.005 0.020 0.005 0.005 

Si 26.4 16.6 16.2 23.1 23.2 21.9 23.5 

Sr 0.089 0.369 0.341 0.124 0.083 0.042 0.032 

Sx2 0.174 0.635 0.971 0.351 0.582 0.335 0.761 

Ti 0.897 0.964 0.943 1.015 0.100 0.453 0.407 

V 0.031 0.030 0.033 0.043 0.032 0.029 0.030 

Zn 0.023 0.009 0.010 0.021 0.011 0.013 0.013 

Zr 0.050 0.035 0.035 0.031 0.031 0.019 0.019 

Total Carbon (%) 0.76 0.25 3.6 2.3 13 7.8 11 

Surface Area (m2

/g) 1.36 1.8 23 6.5 92 28 36 

LOI (wt %) 0.85 0.60 3.5 5.5 12 21 25 

Notes: BML=below method limit (As<0.009%, Cl<0.006%, I<0.006%, Pb<0.003%, Se<0.003%); 1

Px = phosphorus in 

oxidized form such as phosphate; 2

Sx = sulfur in oxidized form such as sulfate 
Section 2 

Page 2-11 

Table 2-3. Facility A (SNCR, facility B (SCR), facility E (SCR) and facility M CCRs: elemental 

composition (by X-ray Fluorescence) and other characteristics 

Element 

Fly Ash 

Facility A 

Fly Ash 

Facility B 

Fly Ash 

Facility E 

FGD Fly Ash 

Mix Facility M 

With 

SNCR % 

Without 

SNCR % 

With SCR 

% 

Without 

SCR % With SCR % With SCR % 

Al 11.4 12.8 10.8 11.0 15.7 6.44 

As 0.013 0.014 0.014 BML 0.010 BML 

Ba 0.096 0.124 0.128 0.122 0.116 0.021 

Br 0.009 0.008 BML BML BML BML 

Ca 3.53 3.60 3.40 3.11 1.21 32.3 

Cl 0.542 0.610 0.044 0.030 0.010 0.096 

Co 0.007 0.006 0.005 BML 0.014 0.004 

Cr 0.018 0.017 0.024 0.022 0.020 0.009 

Cu 0.019 0.018 0.005 0.006 0.023 0.013 

Fe 4.68 5.20 10.782 11.1 4.17 7.63 

Ga 0.005 0.005 0.004 BML 0.011 0.003 

Ge BML BML 0.003 BML 0.003 0.006 

K 1.67 2.10 1.960 1.87 2.50 0.972 

La 0.012 BML BML BML 0.011 0.009 

Mg 0.835 0.931 0.869 0.774 0.714 0.797 

Mn 0.030 0.052 0.025 0.024 0.021 0.018 

Mo BML BML BML BML BML 0.005 

Na 0.375 0.362 0.724 0.663 0.350 0.884 

Nb BML 0.004 0.003 BML 0.004 BML 

Ni 0.012 0.010 0.007 0.005 0.021 0.044 

Pb 0.007 0.007 0.004 BML 0.013 0.007 

Px1 0.122 0.137 0.235 0.170 0.060 0.056 

Rb 0.011 0.013 0.013 0.011 0.016 0.006 

Sc 0.003 0.002 0.002 0.002 0.003 0.008 

Se 0.003 0.003 BML BML BML BML 

Si 19.5 23.1 21.2 21.2 25.2 11.6 

Sr 0.092 0.116 0.111 0.099 0.100 0.038 

Sx2 0.364 0.394 0.711 0.512 0.162 37.7 

Ti 0.767 0.931 0.596 0.570 1.03 0.399 

V 0.033 0.029 0.019 0.019 0.041 0.024 

Y 0.009 0.009 0.003 0.005 0.012 0.003 

Zn 0.013 0.013 0.014 0.013 0.022 0.021 

Zr 0.026 0.031 0.021 0.020 0.030 0.016 

Total Carbon (%) 9.15 3.69 5.74 2.37 1.12 0.75 

Surface Area (m2

/g) 13.9 2.57 5.30 6.20 4.48 7.36 

LOI (wt %) 17.6 5.30 10.8 11.0 5.62 4.01 

Notes: BML=below method limit (As<0.009%, Cl<0.006%, I<0.006%, Pb<0.003%, Se<0.003%); 1

Px = phosphorus in 

oxidized form such as phosphate; 2

Sx = sulfur in oxidized form such as sulfate 
 

 

 

 

 

 

 

Section 2 

Page 2-12 

Table 2-4. ADA fly ashes: total content of mercury, arsenic, lead and selenium1 

Sample ID Mercury 

(ng/g) 

Arsenic 

(μg/g) 

Lead 

(μg/g) 

Selenium 

(μg/g) 

Brayton Point Baseline 651 ± 6.8 80.5 ± 1.9 117 ± 4.9 51.4 ± 1.7 

Brayton Point (w/ACI) 1530 ± 1.1 27.9 ± 2.1 82.9 ± 2.3 152 ± 6.2 

Pleasant Prairie Baseline 158 ± 0.2 21.3 ± 0.3 41.5 ± 0.8 BML 

Pleasant Prairie (w/ACI) 1180 ± 1.2 24.0 ± 0.8 47.0 ± 0.3 BML 

Salem Harbor Baseline 528 ± 5.2 25.9 ± 0.04 24.9 ± 1.4 41.9 ± 0.06 

Salem Harbor (w/ACI) 412 ± 13 26.0 ± 0.03 24.0 ± 0.02 44.0 ± 0.04 

1

All analyses according to EPA Method 3052. Mercury analysis performed by ARCADIS, arsenic, Pb, and Se analysis 

performed by STL Savannah. All samples tested in duplicate. 

BML = below method limit (4.0 μg/g) 

ACI = Activated Carbon injection (sorbent for enhancing mercury capture) 

Table 2-5. Facility A (SNCR, facility B (SCR), facility E (SCR) and facility M (SCR) CCRs : 

total content of mercury, arsenic, lead and selenium 

All analyses were conducted according to EPA Method 3052. Mercury analysis performed by ARCADIS, arsenic, Pb, 

and Se analysis performed by STL Savannah. 

Sample ID Mercury 

(ng/g) 

Arsenic 

(μg/g) 

Lead 

(μg/g) 

Selenium 

(μg/g) 

Facility A Fly Ash (SNCR on) 602 ± 5.2 70.8 ± 1.4 80.5 ± 2.1 25.6 ± 0.2 

Facility A Fly Ash (SNCR off) 380 ± 7.0 88.2 ± 0.3 68.6 ± 0.3 21.9 ± 0.6 

Facility B Fly Ash (SCR on) 88.3 ± 27.4 82.3 ± 12.6 47.4 ± 8.1 2.5 ± 0.4 

Facility B Fly Ash (SCR off) 114 ± 9.6 90.0 ± 3.4 36.0 ± 0.1 2.9 ± 0.0 

Facility E Fly Ash (SCR on) 396 ± 57.4 50.1 ± 0.1 34.1 ± 0.1 24.0 ± 2.9 

Facility M Fly Ash (SCR on) 121 ± 0.2 106 ± 6.8 5.2 ± 0.4 91.0 ± 6.5 

Note: All samples tested in duplicate. 

2.1.16 FGD Gypsum Sample from U.S. Gypsum 

As discussed in Section 1.1.3, U.S. Gypsum (USG) performed an evaluation of mercury release from 

FGD gypsum use in the production of wallboard. This evaluation was completed at five wallboard 

manufacturing plants (Marshall et al., April 2005). The USG study was limited to mercury and did not 

evaluate other metals. Therefore, samples of the FGD gypsum from the USG study were obtained for a 

simulation test in the U.S. EPA laboratory. The first USG sample, corresponding to Task #1 of the 

USG/DOE study, obtained for this study was from a power plant that burned high-sulfur bituminous coal, 

used limestone as the FGD reagent, had in situ forced oxidation, online SCR, and did not practice fines 

blow down (no fines removed) (Marshall et al., April 2008). The sub-sample consisted of the FGD 

gypsum fed to the kettle calciner (the most likely point of release as discussed in Section 1.1.3). For 
 

 

 

 

 

 

Section 2 

Page 2-13 

further details on the characteristics of this sample see Marshall et al., April 2005. The second USG 

sample obtained for this study was from the same plant during recent testing performed by DOE. This 

plant was sampled during a time period during which the SCR was bypassed. Results for total content 

analyses for mercury, arsenic, Pb, and Se are provided in Table 2-6. 

Table 2-6. USG FGD gypsum samples: total content of mercury, arsenic, lead and selenium1 

Sample ID Mercury 

(ng/g) 

Arsenic 

(μg/g) 

Lead 

(μg/g) 

Selenium 

(μg/g) 

USG Sample #1 

(Corresponds to DOE Task #1) 674 ± 0.4 5.88 ± 0.4 2.31 ± 0.03 5.4 ± 0.7 

USG Sample #2 

(Corresponds to DOE Task #2) 468 ± 21 5.74 ± 0.26 2.08 ± 0.09 5.26 ± 0.98 

1

All analyses according to EPA Method 3052. Mercury analysis performed by ARCADIS, arsenic, Pb, and Se analysis 

performed by STL Savannah. All samples tested in duplicate. 

2.2 Thermal Stability Protocols 

A fixed-bed reactor design was used to simulate the thermal processes of concern in this study. Figure 2-1 

provides a schematic of the general setup for simulating asphalt manufacturing, wallboard manufacturing, 

and cement clinker manufacturing. For all simulations, samples consisting of various mixes and matrices 

were loaded into shallow-bed containers and placed in the reactor. The fixed-bed reactor used for the 

asphalt and wallboard simulation assays consisted of a horizontal quartz tube in a thermally controlled 

furnace. The low temperature furnace was manufactured by Lindberg/Blue M (Model 55035) and had a 

reactor size of 12” by 1” and a maximum temperature of 1200 °C (Figure 2-2). In the case of the high 

temperature cement clinker manufacturing (1450 °C), a high temperature furnace was utilized. This high 

temperature furnace was manufactured by Lindberg/Blue M (Model STF54233C) and had a reactor size 

of 12” by 2” and a maximum temperature of 1500 °C (Figure 2-3). 

In each simulation the tests were performed in duplicate. Samples were exposed to a flow rate of 400 

cc/min of inlet flue gas consisting of 14% CO2, 3% O2, 5.6% H2O and 100 ppm NOx, except for the 

wallboard simulation of the kettle calciner, in which the inlet gas consisted of N2. Kettle calciners are 

indirectly fired and therefore the sample is not exposed to flue gases. The time in the fixed-bed reactor for 

each simulation was one hour. The samples placed in the fixed-bed reactor, as well as the temperatures in 

the processes varied for each simulation. For mercury, the effluent of the reactor was sampled using a 

mini-impinger Ontario Hydro train (ASTM, 2002). For sampling the other metals, a Method 29 (EPA, 

1996b) mini-impinger train was utilized. Table 2-7 outlines the differentiations in the various simulations. 

Some simulations involved the addition of sand, limestone (CaCO3) or iron powder. All added materials 

were certified reagent grade from Fisher Scientific. 
 

 

 

Section 2 

Page 2-14 

H2O Vapor 

Generation 

System 

High Temperature 

Furnace 

Method 29 

Train 

Low Temperature 

Furnace 

Method 29 

or 

OH Train 

To Vent 

Gas Mixing 

System1 

= one-way valve 

= two-way valve 

1

The same gas mix was used for the simulation of cement clinker and asphalt production (a flow rate of 400 cc/min of 

inlet flue gas consisting of 14% CO2, 3% O2, 5.6% H2O and 100 ppm NOx,). The wall board similar used inlet gas of N2 

since kettle calciners are indirectly fired and therefore the sample is not exposed to flue gas) 

Figure 2-1.	 Schematic of the setup for simulating the production of cement clinker, asphalt, and 

wallboard 

Figure 2-2. Asphalt and wallboard simulation quartz reactor and furnace with sample 
 

Section 2 

Page 2-15 

Figure 2-3. High temperature cement simulation furnace with Method 29 mini-impinger train 

Although the percentage of fly ash in asphalt is typically 5%, a mix containing 50% fly ash was tested for 

the ADA fly ashes. During the initial phase of these studies a 50% mix was used as a conservative 

approach to optimize the chances of detecting any volatilized mercury. The fly ashes from Facilities A, B 

and E were tested using a mix containing 10% fly ash. 

Table 2-7.	 Description of asphalt, wallboard and cement clinker simulations to test for metal 

thermal stability 

Simulation Sample Inlet Gas Temperature 

Asphalt (ADA-ES samples) – Hg 5 g of fly ash and 5 g of quartz sand Flue gases 170 °C 

Asphalt (Facilities A and B 

samples) – Hg 1 g of fly ash and 9 g of quartz sand Flue gases 170 °C 

Asphalt – As, Se, Pb 1 g of fly ash and 9 g of quartz sand Flue gases 170 °C 

Wallboard 10 g of FGD gypsum kettle feed Nitrogen 160 °C 

Cement clinker (high temp) 1 g of fly ash, 8.55 g CaCO3, 0.3 g iron 

powder and 0.2 g sand Flue gases 1450 °C 

Notes: all samples were tested in duplicate, exposed to gases/temperatures for one hour. 
 

 

 

 

 

 

 

Section 2 

Page 2-16 

2.3 Analytical Methods 

2.3.1 Mercury (CVAA Method 7471A, Method 3052, Method 7473, Method 30B) 

Gas phase mercury emissions from the simulation studies for the production of cement clinker, asphalt, 

and USG gypsum testing were analyzed according to ASTM Method D6784-02, Ontario Hydro (OH), 

with the following modifications. Due to spacing constraints, mini-impingers were used for sampling 

instead of the large impingers described in the OH method. The method states that flow will be pulled 

through the impingers using negative pressure; however, for these experiments the flow had to be pushed 

through the impingers using positive pressure in order to not change the flow through the reactor. The 

method also requires a dry gas meter to continuously measure flow, but instead a Gilian Gilibrator 2 

(Sensidyne, Inc.) bubble flow meter was used and measurements were recorded every five minutes 

throughout the entire sampling period. A silica gel trap was not used in this study, so the measurements 

obtained were wet gas flow rates. Because the flue gas was not particle-laden, the filter apparatus setup 

prior to the impingers (i.e., Method 5 filter) was not required. Analysis of the samples was performed as 

outlined in Method D6784-02, Ontario Hydro. 

Sample preparation for the cement clinker, asphalt, and USG gypsum solids was carried out by HF/HNO3 

microwave digestion according to Method 3052 (EPA, 1996a). Mercury analysis of each digest was 

carried out by Cold Vapor Atomic Absorption Spectrometry (CVAA) according to EPA SW-846 Method 

7470A “Mercury in Liquid Waste (Manual Cold Vapor Technique)”, (EPA, 1998a). A Perkin Elmer 

FIMS 100 Flow Injection Mercury System was used for the analyses. The instrument was calibrated with 

known standards ranging from 0.025 to 1 μg/L Hg. The method detection limit for Hg in aqueous samples 

is 0.01 μg/L. 

Gas phase Hg sampling for the repeated gypsum testing was performed using an EPA Method 30B (EPA 

2008a) system. This technique used an iodated activated carbon tube to capture the Hg in the gas stream. 

A Lumex RA-915+ Zeeman effect atomic adsorption Hg analyzer with a RA-91C combustion furnace 

attachment to analyze the carbon tubes. The Hg analyzer was calibrated with known standards ranging 

from 50 to 1000 ng of Hg. The method detection limit for Hg in the carbon tube is 0.2 ng. Blank samples 

measured by the analyzer resulted in an average of 0.5 ng detectable concentration by the software. 

Thermal Hg analysis was conducted of the FGD solids that were retested. This analysis used a modified 

Method 7473 “Mercury in Solids and Solutions by Thermal Decomposition, Amalgamation, and Atomic 

Absorption Spectrophotometry” (EPA, 1998b). The instrument used was a Lumex RA-915+ Zeeman 

effect atomic adsorption Hg analyzer with a RA-91C combustion furnace attachment for solids analysis. 

The instrument was calibrated with known standards ranging from 50 to 1000 ng of Hg. The method 

detection limit for Hg in solids is 0.145 ng/g. Blank samples measured by the analyzer resulted in a 0.0 

ng/g. 

2.3.2 Arsenic, Selenium and Lead (ICP-MS, Method 3052, Method 6020) 

Inductively coupled plasma-mass spectroscopy (ICP-MS) analysis for other elements of interest were 

carried out by Oxford and STL laboratories. 

Liquid samples were analyzed by ICP-MS as recovered from the Method 29 trains. Solid samples were 

digested by EPA Method 3052 prior to ICP-MS analysis. 
 

Section 2 

Page 2-17 

2.3.2.1 Severn Trent Laboratories, Inc. (STL) 

STL (Savannah, Georgia) was selected to carry out the solid digest ICP-MS analyses for this project. 

Analysis for As, Se, and Pb was performed on an Agilent ICP-MS with octopole reaction system (ORS). 

Mixed calibration standards were prepared for each metal at five levels ranging from 0.5 μg/L to 100 

μg/L. 

2.3.2.2 Oxford Laboratories 

Oxford Laboratories (Wilmington, North Carolina) was selected to carry out the ICP-MS analyses for this 

project on the Method 29 impinger samples. Analysis for As, Se, and Pb was performed on an Agilent 

ICP-MS with octopole reaction system (ORS). Mixed calibration standards were prepared for each metal 

at five levels ranging from 0.5 μg/L to 100 μg/L. 

 

 

 

 

Section 3 

Page 3-1 

Chapter 3 

Results and Discussions 

3.1 Cement Simulations 

Cement simulation tests for As, Se, and Pb desorption were performed in duplicate on the ADA fly ashes 

without the use of ACI. Because of its inherently high volatility, Hg was assumed to volatilize at the 

1450o

C and therefore recovery was not analyzed in the samples. Table 3-1 and Figure 3-1 present the 

results of these tests. Therefore the focus was on the other metals (i.e., As, Se, and Pb). 

The tests show excellent reproducibility and indicate that virtually all of the metals tested were volatilized 

when exposed to a temperature of 1450o

C. 

Table 3-1. Results of cement simulations for arsenic, selenium, and lead (all values in μg/g unless 

noted) 

Metal Run Brayton Point 

(μg/g) 

Pleasant Prairie 

 (μg/g) 

Salem Harbor 

(μg/g) 

As received 80.5 ± 1.9 21.3 ± 0.3 25.9 ± 0.04 

Arsenic Run 1 82.6 103% 20.6 96.8% 27.5 106% 

Run 2 81.8 102% 20.6 96.6% 25.2 97.5% 

As received 51.4 ± 1.7 BML 41.9 ± 0.8 

Selenium Run 1 53.6 104% BML NA 39.8 94.9% 

Run 2 52.6 102% BML NA 43.6 104% 

As received 117 ± 4.9 41.5 ± 0.8 24.9 ± 1.4 

Lead Run 1 118.6 101% 40.6 97.9% 21.5 86.3% 

Run 2 106.0 90.4% 38.8 93.5% 23.4 94.1% 

BML – Below method limit (4.0 μg/g) 

NA = not applicable 
 

 

 

 

Amount of metal volatilized

(average of two runs) 

Section 3 

Page 3-2 

100% 

80% 

60% 

40% 

20% 

0% 

Brayton Point Pleasant Prairie Salem Harbor 

Arsenic Selenium Lead 

Note: Se was not tested for Pleasant Prairie fly ash; the amount in the baseline 

fly ash was below minimum detection levels. 

Figure 3-1. Results of cement simulations for arsenic, selenium, and lead 

3.2 Asphalt Simulations 

3.2.1 Asphalt Simulation Tests for Mercury Thermal Stability on ADA Fly Ashes 

Results for duplicate asphalt simulation tests using the ADA fly ashes are presented in Table 3-2. In all 

cases, the majority of the Hg was retained in the solid after simulation, with minimal measured 

volatilization of Hg (<10% in all cases). Generally, the addition of carbon increased the tendency for Hg 

to be retained in the solids at the temperature tested. Total Hg volatilized from samples with activated 

carbon injection was <1% for all samples tested. Figure 3-2 shows the results of these experiments that 

have been normalized by adjusting the mass balance to 100%. Mass balances were approximately 90% 

for all tests except for the Pleasant Prairie Baseline tests (~67%). No reason for the lack of closure for Hg 

for this sample was found, though it is noted that the as-prepared sample had the lowest initial Hg value 

of these fly ashes. 

For confirmatory purposes, measurements of volatilized Hg were taken from Method 29 total metals 

analyses for comparison to the Ontario Hydro values for the Brayton Point fly ashes. Table 3-3 shows the 

comparison. The Method 29 runs agree well with the total Hg values obtained from the Ontario Hydro 

tests, indicating minimal volatilization of Hg. 
 

Section 3 

Page 3-3 

Table 3-2. Asphalt simulation test results for mercury on ADA fly ashes 

As Prepared 

ng/g) 

After 

Simulation 

(Solid) ng/g 

Hg2+ gas 

ng/g 

Hg0 

gas 

ng/g 

Total Percent 

Volatilized Hg 

Mass 

Balance 

Brayton Point Run 1 

650.6 ± 6.8 

526 31.7 8.0 6.1% 86.9% 

Baseline Run 2 606 5.3 1.8 1.1% 94.7% 

Brayton Point Run 1 

1529.6 ± 1.1 

1,340 BML BML 0.0% 87.3% 

ACI Run 2 1,420 BML BML 0.0% 93.2% 

Pleasant Prairie Run 1 

157.7 ± 0.2 

105 BML 1.9 1.2% 67.8% 

Baseline Run 2 95.5 BML 7.3 4.7% 65.2% 

Pleasant Prairie Run 1 

1180.1 ± 1.2 

1,110 1.3 2.3 0.3% 94.6% 

ACI Run 2 1,100 2.2 3.3 0.5% 93.9% 

Salem Harbor Run 1 

528.5 ± 5.2 

488 0.1 BML 0.0% 92.4% 

Baseline Run 2 486 BML BML 0.0% 91.9% 

Salem Harbor Run 1 

411.5 ± 12.6 

388 BML 0.5 0.1% 94.4% 

ACI Run 2 387 BML BML 0.0% 94.0% 

BML=below method limit (Hg<0.05 ng/g) 

3.2.2	 Asphalt Simulation Tests for Non-Mercury Metals Thermal Stability on ADA 

Fly Ashes 

Since significant amounts of Hg were not significantly released from the ADA fly ash samples (and Hg is 

the most volatile of the metals being investigated), only one of the three ADA facility sites was chosen to 

evaluate the release of other metals. The Brayton Point facility samples were chosen because they 

contained the highest amount of As and Se. Asphalt simulation tests for As, Se, and Pb volatilization were 

performed on the Brayton Point fly ashes. Table 3-4 summarizes the results. The tests showed no non-Hg 

metals in the gas phase, indicating that all the As, Se, and Pb were retained in the solid. While the mass 

balances between the solids after simulation and the as-prepared sample prior to testing are not ideal 

(varying between 50 and 150%), they generally agree and support that the metals are retained in the solids 

for the asphalt simulation. 
 

Section 3 

Page 3-4 

95.9% 100.0% 95.6% 99.6% 100.0% 99.9% 

0% 

10% 

20% 

30% 

40% 

50% 

60% 

70% 

80% 

90% 

100% 

Normalized percentage of

mercury (average of two runs) 

Brayton 

Point 

Baseline 

Brayton 

Point w / 

ACI 

Pleasant 

Prairie 

Baseline 

Pleasant 

Prairie w / 

ACI 

Salem 

Harbor 

Baseline 

Salem 

Harbor w / 

ACI 

Retained in Solid Volatilized 

Figure 3-2. Asphalt simulation test results for mercury by Ontario Hydro Method on ADA fly ashes 

Table 3-3. Comparison of mercury by Method 29 and Ontario Hydro for Brayton Point fly ashes 

Sample Run As Prepared 

ng/g 

Gas-Phase 

Mercury 

ng/g 

Percent 

Volatilized 

Method 29 

Average OH Average 

Brayton 

Point 

Baseline 

Run 1 

651 ± 6.8 

72.0 11.1% 

7.3% ± 5.3% 3.6% ± 3.5% 

Run 2 23.0 3.5% 

Brayton Run 1 

1530 ± 1.1 

20.0 1.3% 

1.4% ± 0.1% 0.0% ± 0% Point w/ACI Run 2 23.0 1.5% 
Section 3 

Page 3-5 

Table 3-4. Results for asphalt simulations of Brayton Point fly ashes for arsenic, selenium, and 

lead 

Metal Run As Received 

μg/g 

As Prepared 

μg/g 

After 

Simulation 

(solid) μg/g 

Volatilized 

Metal (gas 

phase) μg/g 

Mass 

Balance 

Baseline Test 1 

80.5 ± 1.9 90.5 ± 6.6 

85.5 ± 2.0 BML 94.5% 

Baseline Test 2 95.5 ± 22 BML 106% 

Arsenic 

ACI Test 1 26.0 ± 0.07 BML 62.1% 

27.9 ± 2.1 41.9 ± 0.15 

ACI Test 2 50.1 ± 8.6 BML 120% 

Baseline Test 1 

51.4 ± 1.7 47.7 ± 2.6 

45.7 ± 8.0 BML 95.8% 

Baseline Test 2 53.7 ± 13 BML 113% 

Selenium 

ACI Test 1 83.1 ± 7.3 BML 53.1% 

152 ± 6.2 156.7 ± 9.3 

ACI Test 2 208 ± 47 BML 132% 

Baseline Test 1 

117 ± 4.9 245 ± 71 

318 ± 25 BML 128% 

Baseline Test 2 279 ± 55 BML 113% 

Lead 

ACI Test 1 227 ± 74 BML 117% 

82.9 ± 2.3 194 ± 0.68 

ACI Test 2 291 ± 14 BML 150% 

BML=below method limit (As<4.0 μg/g, Pb<0.6 μg/g, Se<4.0 μg/g) 

3.2.3 Asphalt Simulation Tests for Mercury Thermal Stability on Non-ADA Fly Ashes 

Asphalt simulations were run using the non-ADA fly ashes. These samples were from utilities not using 

ACI; rather, the samples were taken from utilities using SNCR (Facility A) and SCR (Facilities B and E) 

for NOX control, or none (Facility M). Table 3-5 shows the results of these experiments. Mass balances 

for all runs were excellent (92.5 to 101%). Figure 3-3 shows the results of these experiments that have 

been normalized by adjusting the mass balance to 100%. As was the case for the ADA fly ashes, minimal 

Hg loss upon heating was found for the fly ashes from Facilities A and E. Facility B, however, 

demonstrated high Hg volatility (~70-90% loss upon heating). Facility M showed moderate amounts of 

the Hg being volatilized. 

As with the Brayton Point fly ash, Method 29 sampling for Hg was conducted to confirm the results 

obtained using the Ontario Hydro methodology. These comparisons are shown in Table 3-6. While 

differing slightly from the Ontario Hydro results, the Method 29 experiments confirm that the Facility B 

samples showed significantly greater loss of Hg on heating than the other fly ashes tested. 
 

 

Section 3 

Page 3-6 

Table 3-5. Mercury results by Ontario Hydro Method for non-ADA fly ashes 

Sample Run 

As 

Prepared 

ng/g 

After 

Simulation 

(Solid) ng/g 

Hg2+ gas 

ng/g 

Hgo 

gas 

ng/g 

Total Percent 

Volatilized Hg 

Mass 

Balance 

Facility A Run 1 

602 

576 5.2 6.0 1.9% 97.5% 

SNCR On Run 2 583 4.6 5.8 1.7% 98.6% 

Facility A Run 1 

380 

366 9.8 8.8 4.9% 101% 

SNCR Off Run 2 358 8.5 13.5 5.8% 100% 

Facility B Run 1 

88.3 

9.2 36.5 41.3 88.1% 98.5% 

SCR On Run 2 9.3 37.6 38.5 86.2% 98.6% 

Facility B Run 1 

114 

27.0 37.5 42.8 70.4% 94.1% 

SCR Off Run 2 23.1 40.4 42.2 72.4% 92.7% 

Facility E Run 1 

396 

365 15.0 14.7 7.5% 99.6% 

SCR On Run 2 326 22.6 17.6 10.1% 92.5% 

Facility M 121 57.5 NA NA 26.6% 74.2% 

Facility M was sampled by Method 29 under Asphalt Simulation Conditions. 

Gas phase total Hg emissions for Facility M were 32.1 ng/g. 

NA = not applicable / no gas phase speciation
 
Section 3 

Page 3-7 

98.2% 94.7% 

10.7% 

23.5% 

90.8% 

64.3% 

0% 

10% 

20% 

30% 

40% 

50% 

60% 

70% 

80% 

90% 

100% 

Normalized percentage of mercury 

(average of two runs) 

Facility A 

SNCR on 

Facility A 

SNCR off 

Facility B SCR 

on 

Facility B SCR 

off 

Facility E SCR 

on 

Facility M 

SCR on 

Retained in Solid Volatilized 

Figure 3-3. Mercury results by Ontario Hydro Method for non-ADA fly ashes 

Facility M was sampled by Method 29. Series 1 = Retained in Solid, Series 2 = Gas Phase under Asphalt simulation 

Conditions. 
 

 

 

Section 3 

Page 3-8 

Table 3-6. Comparison of mercury by Method 29 with Ontario Hydro for facility B fly ashes 

As Prepared, 

ng/g 

Method 

29Gas-Phase 

Mercury, ng/g 

Method 29 

Percent 

Volatilized 

Ontario Hydro 

Gas-Phase 

Mercury, ng/g 

Ontario Hydro 

Percent 

Volatilized 

Facility B Run 1 

88.3 ± 27.4 

44.2 50.1% 77.8 89.4% 

SCR on Run 2 37.8 42.8% 76.1 89.1% 

Facility B Run 1 

114.0 ± 9.6 

75.2 65.9% 80.3 74.8% 

SCR off Run 2 57.5 50.5% 82.6 78.1% 

No clear-cut reason for the higher loss of Hg seen for the Facility B sample can be demonstrated. The 

SCR design is of the in-furnace variety, contact between fly ash and SCR catalyst occurred even during 

tests when SCR was not in use. Speculation is that contact between fly ash and SCR catalyst occurred 

even when no ammonia injected. However, too little information is available to make a more definitive 

statement. In addition, a similar effect was not found for the sample from Facility E (which is also has 

SCR in use). Therefore, these results suggest that additional research may be warranted on a wider range 

of samples to evaluate potential Hg loss from use of CCR in asphalt applications. 

3.2.4	 Asphalt Simulation Tests for Non-Mercury Metals Thermal Stability on 

Non-ADA Fly Ashes 

Because of the high volatility seen for Hg in the Ontario Hydro analyses for the Facility B fly ash, the 

Facility B fly ash was selected for testing of volatility of As, Se, and Pb. Results from Method 29 tests 

are shown in Table 3-7. As was the case for the Brayton Point fly ash, mass balances from the tests show 

a high degree of variability (41-300%). However, once again no metals were detected in the gas phase, 

indicating that As, Se, and Pb were retained in the solid after heating. The Pb results likely indicate some 

degree of contamination of the solid sample prior to analysis. However, As, Se, and Pb were not detected 

in the gas phase for the Facility B sample. 
Section 3 

Page 3-9 

Table 3-7. 

lead 

Results for Asphalt Simulations of Facility B Fly Ashes for arsenic, selenium, and 

Metal Run As Prepared 

μg/g 

After 

Simulation 

(solid) μg/g 

Volatilized 

Metal (gas 

phase) μg/g 

Mass 

Balance 

SCR on Test 1 95.8 85.4 BML 89.1% 

Arsenic 

SCR on Test 2 96.0 89.6 BML 93.3% 

SCR off Test 1 75.6 88.2 BML 117% 

SCR off Test 2 75.8 104 BML 137% 

SCR on Test 1 5.4 5.6 BML 104% 

Selenium 

SCR on Test 2 5.4 5.7 BML 105% 

SCR off Test 1 13.5 6.6 BML 48.8% 

SCR off Test 2 13.5 5.6 BML 41.4% 

SCR on Test 1 236 292 BML 124% 

Lead 

SCR on Test 2 237 180 BML 76.0% 

SCR off Test 1 81.2 239 BML 295% 

SCR off Test 2 81.4 215 BML 264% 

BML=below method limit (As<4.0 μg/g, Pb<0.6 μg/g, Se<4.0 μg/g) 

Table 3-8. Results for asphalt simulations of facility M fly ash for mercury, arsenic, selenium, 

and lead 

Metal Run As Prepared 

After 

Simulation 

(solid) 

Volatilized 

Metal 

(gas phase) 

Amount 

Volatilized Mass 

Balance 

Arsenic SCR on Test 1 101 106 BML 0 105 

μg/g SCR on Test 2 110 108 BML 0 97.5% 

Selenium SCR on Test 1 5.5 6.0 BML 0 111 

μg/g SCR on Test 2 4.9 5.5 BML 0 113 

Lead μg/g 

SCR on Test 1 86.4 91.2 BML 0 106 

SCR on Test 2 95.6 90.6 BML 0 94.8% 

Mercury SCR on Test 1 121 57.8 31.6 26 74% 

ng/g SCR on Test 2 120 57.2 32.5 27 74% 

Note: As, Se, and Pb concentrations in μg/g, Hg concentration in ng/g 

BML = below method limit (As<4.0 μg/g, Pb<0.6 μg/g, Se<4.0 μg/g) 
 

 

 

 

 

 

 

Section 3 

Page 3-10 

3.2.5 Correlation of Carbon Content and Mercury Volatilization 

In general, Hg volatilization appears to decrease with increasing carbon content. This was the case for 18 

of the 22 samples evaluated. The four facilities that did not fit this trend are from the facility that has the 

in-furnace SCR system. The mercury results were normalized using the ratio of the amount volatilized to 

the total Hg remaining in the solids plus the amount of mercury volatilized. Figure 3-4 provides these 

results along with the equation that was derived. The significant figures are not considered more than 1 

given the uncertainties. Recommendations for future work include using a larger sample size to evaluate 

potential Hg loss during asphalt production and to evaluate if the correlation for carbon content and Hg 

loss is confirmed. 

 Percent of Hg Volatilized 

12.0% 

10.0% 

8.0% 

6.0% 

4.0% 

2.0% 

0.0% 

0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 

Percent of Carbon in Fly Ash 

14.0% 

y = 0.1e-61.7x 

R2 = 0.6 

Note – The % Hg volatilized is “normalized” by dividing by the total amount of mercury in the solid and 

gas phase. Significant figures are not greater than one. 

Figure 3-4. Mercury volatilization as a function of carbon content 

3.3 Wallboard Simulations 

Sanderson et al., (2008) provide the most extensive study to date on the fate of Hg when FGD gypsum is 

used as feedstock for wallboard production. Testing of full-scale production facilities is considered more 

reliable than laboratory testing to simulate wallboard production. However, the study did not include 

other metals. Therefore, laboratory simulation of wallboard production was conducted. Results from 

Sanderson et al., (2008) indicate that the process where Hg loss is more likely to occur is the kettle 

calciner. Therefore, laboratory simulation of wallboard production was conducted evaluating Hg and 

other metals with the focus on trying to simulate potential loss across the kettle calciner. Only FGD 

gypsum samples were used in this simulation since this is the material used in the production of wallboard 

(and not fly ash). This research was conducted in two phases. The first phase resulted in unacceptable 
 

 

Section 3 

Page 3-11 

mass balance for Hg. The results for the other metals are considered acceptable. Consequently, 

additional testing was conducting in a second phase using more recent FGD samples. The results from 

this work are reported along with the results from phase 1. Please note, only the results from non-Hg 

metals for phase 1 are considered reliable. However, we have not excluded the Hg results from phase 1. 

3.3.1	 Wallboard Simulation Tests for Mercury Thermal Stability on USG FGD 

Gypsum 

Results for multiple wallboard simulations using the two samples received from U.S. Gypsum are shown 

in Table 3-9. As noted, the results for the first USG sample had poor mass balance. The amount of Hg 

remaining in the solids ranged between 90 to 99% which agrees fairly well with the results reported by 

USG (~98.6%). The results for the second USG sample had a better mass balance than the first sample; 

however, the mass balances were still less than ideal. The gas-phase results, however, indicate that the 

samples lost between 75 and 105% of the Hg compared to a USG-reported value of ~2.3%. The gas 

phase results are not considered reliable as indicated by the poor Hg mass balance results. Therefore, and 

additional testing was conducted. 

Table 3-9. Results of wallboard simulation tests for mercury 

Pre test 

(solid), ng/g 

After 

Simulation 

(solid), ng/g 

Volatilized 

Mercury (gas 

phase), ng/g 

Percent 

Volatilizeda 

Percent 

Remaining 

in Solid 

Mass 

Balance 

Run 1 664 518 77% 99% 175% 

USG-1 

Run 2 

674.0 ± 0.4 

626 602 89% 93% 182% 

Run 3 627 606 90% 93% 183% 

Run 4 606 705 105% 90% 195% 

USG-2 

Run 1 

467.9 ± 21.3 

98.4 478.7 102% 21.0% 123% 

Run 2 81.9 334.9 71.6% 17.5% 89.1% 

a

These results are not considered reliable as indicated by the Hg mass balance. Therefore, additional 

testing was conducted. 

3.3.2	 Wallboard Simulation Tests for Non-Mercury Metals Thermal Stability on USG 

FGD Gypsum 

Results for duplicate wallboard simulations using samples received from U.S. Gypsum are shown in 

Table 3-10. In general, the results for the first USG sample showed that the non-Hg metals including As, 

Se and Pb did not volatilize from the sample during the wallboard simulation test. While the mass 

balances between the solids after simulation and the as-prepared sample prior to testing are not ideal 

(varying between 116 and 128%). However, the results tend to suggest that As and Se are more likely 

retained in the FGD gypsum and less likely to be volatilized during the kettle calcining process. 

Table 3-10. Results of wallboard simulation tests for arsenic, selenium, and lead 

Metal Run As Prepared After Volatilized Mass 
 

 

 

 

Section 3 

Page 3-12 

μg/g Simulation 

(solid) μg/g 

Metal (gas 

phase) μg/g 

Balance 

Arsenic 

USG-1 

Run 1 

5.88 

7.02 BML 119% 

Run 2 7.34 BML 125% 

USG-2 

Run 1 

5.74 

5.89 BML 102% 

Run 2 5.79 BML 100% 

USG-1 

Run 1 

5.39 

6.27 BML 116% 

Selenium 

Run 2 6.62 BML 123% 

USG-2 

Run 1 

5.26 

5.17 BML 98.2% 

Run 2 5.30 BML 101% 

USG-1 

Run 1 

2.31 

2.95 BML 128% 

Lead 

Run 2 2.82 BML 122% 

USG-2 

Run 1 

2.08 

2.04 BML 98.2% 

Run 2 1.97 BML 94.7% 

BML=below method limit (As<0.4 μg/g, Pb<0.06 μg/g, Se<0.4 μg/g) 

3.3.3	 Additional Wallboard Simulation Tests for Mercury Thermal Stability on 

Gypsum Samples 

Because of the unacceptable Hg mass balance in the previous wallboard simulation, additional testing was 

conducted using FGD samples from eight different facilities. Sufficient quantity of the USG FGD 

gypsum was not available to be used in the repeated wallboard simulation tests. The experimental 

method was modified to include additional quality assurance. Vapor phase Hg was collected with iodated 

carbon sorbent tubes using Method 30B, at a constant temperature of 160 °C. Method 7473 was used to 

analyze the Hg content of the solid gypsum. For each sample, three replicates were conducted. The 

amount of volatilized Hg was calculated using the Hg trapped on the carbon tubes and the solid gypsum 

before heating. The amount remaining in solid was calculated using the solid gypsum before and after 

heating. Table 3-11 shows the averages and standard deviation for each sample. Figure 3-6 shows the 

amount of Hg retained in solid and Hg volatilized. Appendix C has more detailed results. 

This series of tests gave improved mass balance results compared to the earlier testing to loss of Hg 

across the kettle calciner. The results (Figure 3-5) indicate potential Hg loss of 9 to 48%. The USG 

results from wallboard manufacturing facilities indicate Hg loss across the kettle calciner (excluding the 

Texas lignite sample) of 2 to 50% (found in Table 1-3). This is considered confirmation of the previous 

USG research with emphasis on the degree of variability across samples. 
Section 3 

Page 3-13 

Table 3-11. Results of additional wallboard simulation tests for mercury 

Sample 

ID 

Pre-test 

(solid), 

ng/g 

After 

Simulation 

(solid), ng/g 

Volatilized 

Mercury 

(gas phase), 

ng/g 

Percent 

Volatilized 

Percent 

Remaining in 

Solid 

Mass 

Balance 

AaAW Average 538 426 122 23% 79% 102% 

St Dev 20.9 24.3 24.5 5% 5% 4% 

DaAW Average 653 529 134 21% 81% 102% 

St Dev 15.0 6.86 3.86 1% 3% 4% 

NAW Average 466 228 204 44% 49% 93% 

St Dev 9.27 17.8 7.51 2% 3% 3% 

OAW Average 44.3 32.0 15.5 35% 72% 108% 

St Dev 2.12 1.29 0.68 2% 6% 7% 

SAW Average 312 159 151 48% 51% 99% 

St Dev 6.75 27.8 17.3 6% 8% 3% 

TAW Average 765 519 198 26% 68% 94% 

St Dev 58.3 17.5 64.6 8% 6% 4% 

WAW Average 938 865 87.5 9% 92% 101% 

St Dev 18.6 26.1 44.4 5% 3% 5% 

XAW Average 1,030 815 212 21% 79% 100% 

St Dev 6.24 14.0 16.8 2% 2% 2% 
 

 

 

 

Section 3 

Page 3-14 

79% 

23% 

81% 

21% 

49% 

44% 

72% 

35% 

51% 

48% 

68% 

26% 

92% 

9% 

79% 

21% 

0% 

20% 

40% 

60% 

80% 

100% 

120% 

Percentage of Mercury 

AaAW DaAW NAW OAW SAW TAW WAW XAW 

Sample ID 

Retained in Solid Volatilized 

Figure 3-5. Results for additional wallboard simulation tests for mercury 

3.3.4	 Wallboard Simulation Tests for Mercury Thermal Stability at Various 

Temperatures 

Gypsum sample DaAW was tested at three temperatures (120°C, 140 °C, 160 °C) to compare the amount 

of volatilized Hg versus temperature during the simulation test. Method 30B and Method 7473 were 

used. Table 3-12 and Figure 3-7 display a summary of the results and show that the amount of volatilized 

Hg increases as temperature increases. The linear trend line in Figure 3-7 shows an R-squared value of 

0.9269. Detailed results are included in Appendix C. Therefore, the operating temperature of the kettle 

calciner is important to consider in predicting potential loss at a production facility. 

Table 3-12. Results for wallboard simulation tests on sample DaAW at various temperatures 

Furnace 

Temperature, 

°C 

Pre-test 

(solid), 

ng/g 

After 

Simulation 

(solid), 

ng/g 

Volatilized 

Mercury 

(gas 

phase), 

ng/g 

Percent 

Volatilized 

Percent 

Remaining 

in Solid 

Mass 

Balance 

120 Average 551 532 10.8 2% 97% 99% 

St Dev 8.85 5.13 2.64 0% 1% 2% 

140 Average 621 588 42.1 7% 95% 102% 

St Dev 34.7 23.3 1.80 1% 2% 2% 

160 Average 653 529 134 21% 81% 102% 

St Dev 15.0 6.86 3.86 1% 3% 4% 
 

Section 3 

Page 3-15 

Sample DaAW 

R2 = 0.9269 

0% 

5% 

10% 

15% 

20% 

25% 

100 110 120 130 140 150 160 170 

Furnace Temperature (degrees C) 

Percentage of Mercury 

Volatilized Linear (Volatilized) 

Figure 3-6. Results for wallboard simulation tests at various temperatures 

 

 

 

 

 

 

 

Section 4 

Page 4-1 

Chapter 4 

Conclusions and Future Considerations 

Approximately 40% of the 126 million tons of CCRs produced in the U.S. as of 2006 were utilized in 

agricultural, commercial, and engineering applications. The remainder (i.e., 75 million tons) was managed 

in either landfills or impoundments. The physical and chemical characteristics of CCRs make them 

potentially suitable as replacements for materials used in a wide range of products including cement, 

concrete, road base, and wallboard. Use of CCRs as an alternative to virgin materials helps conserve 

natural resources and energy, as well as decrease the amount of CCRs being land disposed. 

This study evaluated the potential loss of Hg and other metals for the production of cement clinker, 

asphalt, and wallboard. When this study was originally started, there were no controls for Hg from the 

production of cement. Subsequent to this research, EPA has proposed (74 FR 21136m May 6, 2009) 

regulations to reduce mercury emissions from cement kilns, which may result in use of air pollution 

control technology similar to that used at coal-fired power plants (e.g, wet scrubbers and sorbents for 

enhanced Hg capture). The addition of air pollution control at cement kilns should not affect the ability to 

use fly ash or FGD gypsum in the production of clinker. However, to avoid installation of air pollution 

control, kiln inputs (such as fly ash) containing Hg may be avoided which could impact usage of some 

CCRs. 

The focus of the laboratory simulation of cement clinker production using a high-temperature Lindberg 

was on non-Hg metals (i.e., As, Se, and Pb). The results indicate that all of the As, Se and Pb are 

volatilized as a result of the high temperatures (1450 °C) the samples are exposed to during this process. 

With potential changes in air pollution control at cement plants, there will be less Hg and other metals 

being emitted. However, these metals will be retained in the cement kiln dust and the air pollution control 

residues. Ensuring that these metals are not later released based on how the air pollution control residues 

(FGD gypsum and cement kiln dust) are managed, requires additional research to evaluate the potential 

leaching of Hg and other metals for the conditions that the residues are managed. Currently there are no 

federal requirements for lining of landfills used for cement kiln dust disposal. In addition, some sites are 

using cement kiln dust in engineering and commercial applications. 

The asphalt manufacturing simulation results presented indicate that all of the non-Hg metals including 

As, Se and Pb are retained in the samples after exposure. Mercury showed minimal volatilization from the 

ADA samples as well as the samples from Facilities A and E. The Facility B results, however, showed 

significant loss of Hg into the gas-phase as a result of exposure to the asphalt manufacturing conditions. 

Facility B is the only facility included in this study that has an in-furnace SCR design. This design type 

necessitates that the fly ash come in contact with the SCR catalyst surface regardless of whether ammonia 

is being injected or not. Further investigation of fly ashes from facilities with an in-furnace SCR design is 

probably warranted. 

Sanderson et al., (2008) provide the most extensive study to date on the fate of Hg when FGD gypsum is 

used as feedstock for wallboard production. Testing of full-scale production facilities is considered more 

reliable than laboratory testing to simulate wallboard production. However, the study did not include 

other metals. Therefore, laboratory simulation of wallboard production was conducted as part of this 
 

 

 

 

 

 

 

 

 

Section 4 

Page 4-2 

study. Results from Sanderson et al., (2008) indicate that the process where Hg loss is more likely to 

occur is the kettle calciner. Therefore, laboratory simulation of wallboard production was conducted 

evaluating Hg and other metals with the focus on trying to simulate potential loss across the kettle 

calciner. Only FGD gypsum samples were used in this simulation since this is the material used in the 

production of wallboard (and not fly ash). This research was conducted in two phases. The first phase 

resulted in unacceptable mass balance for Hg. The results for the other metals are considered acceptable. 

Consequently, additional testing was conducting in a second phase using more recent FGD samples. 

The first phase of testing suggests that As and Se are more likely retained in the FGD gypsum and less 

likely to be volatilized during the kettle calcining process. The second phase of testing provided 

improved Hg mass balance results. The results (Figure 3-5) indicate potential Hg loss of 9 to 48%. The 

USG results from wallboard manufacturing facilities indicate Hg loss across the kettle calciner (excluding 

the Texas lignite sample) of 2 to 50% (found in Table 1-3). This is considered confirmation of the 

previous USG research with emphasis on the degree of variability across samples. Additional testing 

was conducted at three different temperatures that the kettle calciner can be operated. The linear trend 

line in Figure 3-7 shows an R-squared value of 0.9269. Therefore, the operating temperature of the kettle 

calciner is important to consider in predicting potential loss at a production facility. 

In interpreting the results from this study, please note that the samples are not considered to be a 

representative sample. Samples were obtained on a voluntary basis and represent a minor fraction (<1%) 

of U.S. boilers at coal-fired power plants. However, every effort was made to obtain samples that are 

considered typical of the air pollution control configurations to be more widely used as the result to 

changes in U.S. EPA and state regulations. 

The results from this laboratory study demonstrate the varying degree of volatility for mercury, arsenic, 

Se and Pb in CCRs depending on the process temperature being used. A high temperature process such as 

cement clinker production has the ability to release all four metals from fly ash when exposed to the high 

temperatures found in production. Laboratory simulation of the asphalt and wallboard production 

processes showed a significant release of mercury during heating, but the temperatures were too low to 

volatilize the arsenic, Se, or Pb. Whereas, the Hg loss for wallboard production suggest non-Hg metals 

being retained in wallboard with a potential Hg loss of 9 to 48%. However, the actual mass emission 

rates must be considered when determining potential concern to human health and the environment. 
Section 4 

Page 4-3 

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Section 5 

Page 5-1 

Chapter 5 

Quality Assurance / Quality Control 

5.1 Quality Indicator Goals 

Data quality indicator goals for critical measurements in terms of accuracy, precision and completeness 

are shown in Table 5-1. 

Table 5-1. Data Quality Indicator Goals 

Measurement Method Accuracy Precision Completeness 

As, Se, and Pb Concentration ICP/6010B 90 – 110 % 10% >90% 

Hg Concentration CVAA/7470A 80 – 120 % 10% >90% 

Accuracy was determined by calculating the percent bias from a known standard. Precision was 

calculated as relative percent difference (RPD) between duplicate values and relative standard deviation 

(RSD) for parameters that have more than two replicates. Completeness is defined as the percentage of 

measurements that meet DQI goals of the total number measurements taken. Types of QC samples used 

in this project included blanks, instrument calibration samples, replicates, and matrix spikes 

5.2 Ontario Hydro and Method 29 Mercury Analyses 

Accuracy and precision for the Ontario Hydro samples for Hg concentration in the process gas 

determinations were made using replicates and matrix spike analyses. The Figure 5-1 shows the spike 

recoveries obtained during the analysis of the recovered fractions. Figure 5-2 shows the spike recoveries 

for Hg obtained during the Method 29 sampling. The Ontario Hydro samples had a completeness of 98% 

and the Method 29 samples had a completeness of 94%. 

Required QC samples for metals and Hg sampling trains are detailed in EPA Method 29 and the Ontario 

Hydro Method. QC samples required for CVAA analysis are detailed in 7470A. The Hg analyzer 

software has been programmed with the acceptance criteria for Method 7470A. All calibrations and 

samples analysis parameters have passed the QA/QC criteria and may be considered valid samples. The 

Ontario Hydro samples had a completeness of 98% and the Method 29 samples had a completeness of 

94%. 

5-1 
140% 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

KMNO4 fraction KCl fraction H2O2 fraction Acceptance criteria 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 

Recovery 

Figure 5-1. Ontario Hydro spike recovery for multiple runs 

Section 5 

Page 5-2 
 

 

Section 5 

Page 5-3 

0% 

20% 

40% 

60% 

80% 

100% 

120% 

140% 

1 2 3 4 5 6 7 8 9 10 

H2O2/HNO3 fraction KMNO4 fraction Acceptance Criteria 

Figure 5-2.	 Method 29 mercury spike recoveries for multiple runs 

5.3 Method 29 Analyses for Arsenic, Lead, and Selenium 

QA/QC samples for the determination of As, Pb, and Se included blanks, replicates, and matrix spikes. 

Table 5-2 presents accuracy of the matrix spike recovery data for the Method 29 cement kiln simulation 

metals analyses. Table 5-3 presents the accuracy of the matrix spike recovery data for the asphalt 

simulation testing. Table 5-4 presents the accuracy of the matrix spike recovery data for the gypsum 

wallboard simulation testing. 

Table 5-2. Method 29 Matrix Spike Recoveries for Arsenic, Lead, and Selenium for the Cement 

Kiln Simulations 

Facility Name As Se Pb 

Brayton Point BL 111% 104% 108% 

Pleasant Prairie BL 104% 102% 109% 

Salem Harbor BL 92% 90% 89% 

5-3 
 

Section 5 

Page 5-4 

Table 5-3. Method 29 Matrix Spike Recoveries for Arsenic, Lead, and Selenium for the Asphalt 

Simulations 

Facility Name As Se Pb 

Brayton Point BL 109% 111% 101% 

Brayton Point ACI 109% 103% 111% 

Facility B (SCR on) 91% 92% 91% 

Facility B (SCR off) 93% 97% 110% 

USG-1 106% 107% 108% 

USG-2 101% 103% 100% 

Table 5-4. Method 29 Matrix Spike Recoveries for Arsenic, Lead, and Selenium for the Gypsum 

Wallboard Simulations 

Facility Name As Se Pb 

USG-1 106% 107% 108% 

USG-2 101% 103% 100% 

Overall completeness for the Method 29 non-Hg metals matrix spike samples was 30 valid out of 33 total 

matrix spikes or 91%. 
 

 

 

 

 

Section 6 

Page 6-1 

Chapter 6 

References 

ACAA (American Coal Ash Association), 2004. 2003 Coal Combustion Product (CCP) Production and 

Use Survey, http://acaa.affiniscape.com/associations/8003/files/2003_CCP_Survey (10-1-04).pdf 

Accessed July 2008. 

ASTM. Standard test method for elemental, oxidized, particle-bound, and total mercury in flue gas 

generated from coal-fired stationary sources (Ontario-Hydro method), Method D 6784-02, 

American Society for Testing and Materials, 2002. 

Garrabrants, A. C., F. Sanchez, and D. S. Kosson. Changes in constituent equilibrium leaching and pore 

water characteristics of a Portland cement mortar as a result of carbonation, Waste Management 

24: 19-36 (2004). 

Gervais, C., A. C. Garrabrants, F. Sanchez, R. Barna, P, Moszkowicz, and D. S. Kosson. The effects of 

carbonation and drying during intermittent leaching on the release of inorganic constituents form 

a cement-based matrix. Cement and Concrete Research 34:119-131, (2004). 

Kilgroe, J., C. Sedman, R. Srivastava, J. Ryan, C. W. Lee, and S. Thorneloe. Control of mercury 

emissions from coal-fired electric utility boilers: interim report. EPA-600/R-01-109, U.S. 

Environmental Protection Agency, December 2001. 

Marshall, Jessica, Gary Blythe and Mandi Richardson. Fate of mercury in synthetic gypsum used for 

wallboard production, topical report, task 1 wallboard plant test results. U.S. Department of 

Energy, Pittsburgh, PA, Cooperative Agreement Number DE-FC26-04NT42080, April, 2005. 

Marshall, Jessica, Gary Blythe and Mandi Richardson. Fate of mercury in synthetic gypsum used for 

wallboard production, topical report, task 2 wallboard plant test results. U.S. Department of 

Energy, Pittsburgh, PA, Cooperative Agreement Number DE-FC26-04NT42080, August, 2005. 

Marshall, Jessica, Gary Blythe and Mandi Richardson. Fate of mercury in synthetic gypsum used for 

wallboard production, topical report, task 3 wallboard plant test results. U.S. Department of 

Energy, Pittsburgh, PA, Cooperative Agreement Number DE-FC26-04NT42080, August, 2005. 

Meischen, S. The effect of mercury controls on wallboard manufacture. ECM-01-CBRC-M12, 

Combustion Byproducts Recycling Consortium, Tennessee Valley Authority, Final Report, July, 

2004. 

Sanderson, J., Blythe, G.M., and Richardson, M. 2008. Fate of Mercury in Synthetic Gypsum Used for 

Wallboard Production. Final Report. 

http://www.netl.doe.gov/technologies/coalpower/ewr/coal_utilization_byproducts/pdf/42080Final 

Rpt20080624.pdf. Retrieved: March 10, 2009. 

6-1 
 

 

Section 6 

Page 6-2 

Schroeder, K. and C. Kairies. Distribution of mercury in FGD byproducts. U.S. Department of Energy, 

National Energy Technology Laboratory, 2005. 

Senior, C., S. Thorneloe, B. Khan, and D. Goss (2009). "Fate of Mercury Collected from Air Pollution 

Control Devices." Environmental Management, Journal of the Air & Waste Management Association 

(A&WMA): 15-21. 

Senior, C., C. J. Bustard, K. Baldrey, T. Starns, and M. Durham. “Characterization of Fly Ash From FullScale Demonstration of Sorbent Injection for Mercury Control on Coal-Fired Power Plants,” 

presented at the Combined Power Plant Air Pollutant Control Mega Symposium, Washington 

D.C., May 19-22, 2003. 

Senior, C., C. J. Bustard, M. Durham, T. Starns, and K. Baldrey. “Characterization of Fly Ash From FullScale Demonstration of Sorbent Injection for Mercury Control on Coal-Fired Power Plants,” 

presented at the Air Quality IV Conference and Exhibition, Washington D.C, September 22-27, 

2003. 

Senior, C., C. J. Bustard, M. Durham, K. Baldrey, and D. Michaud. Characterization of fly ash from fullscale demonstration of sorbent injection for mercury control on coal-fired power plants. Fuel 

Processing Technology 85: 601-612, 2004. 

Srivastava, R.K., and W. Jozewicz. Flue gas desulfurization: the state of the art. Journal of Air and Waste 

Management 51, 1676-1688, 2001. 

Srivastava, R.K., N. Hutson, B. Martin, F. Princiotta, and J. Staudt. Control of mercury emissions from 

coal-fired electric utility boilers. Environ. Sci. & Technol. A-Pages, 40(5): 1385-1393, 2006. 

Starns, T., J. Bustard, M. Durham, C. Lindsey, C. Martin, R. Schlager, B. Donnelly,S. Sjostrom, P. 

Harrington, S. Haythornthwaite, R. Johnson, E. Morris, R. Change, and S. Renninger. “Full-Scale 

Test of Mercury Control with Sorbent Injection and an ESP at Wisconsin Electric’s Pleasant 

Prairie Power Plant,” presented at the Air & Waste Management Association 95th Annual 

Conference and Exhibition, Baltimore, MD, June 23-27 2002. 

Thorneloe, S., D. Kosson, F. Sanchez, B. Khan, and P. Kariher. ”Improved leach testing for evaluating 

the fate of mercury and other metals from management of coal combustion residues,” In 

Proceedings for the Global Waste Management Symposium, Copper Mountain Conference 

Center, Colorado, USA, September 7-10, 2008. 

U.S. Geological Survey, 2009. Gypsum, Mineral Commodity Summaries, Prepared by Alan Founie, 

http://minerals.usgs.gov/minerals/pubs/commodity/gypsum/mcs-2009-gypsu.pdf; Accessed on 

11/10/09. 

U.S. Environmental Protection Agency, 1996a. Microwave assisted acid digestion of siliceous and 

organically based matrices, SW-846, Method 3052, Test Methods for Evaluating Solid Waste, 

Physical/Chemical Methods, U.S. Environmental Protection Agency, 1996. 

U.S. Environmental Protection Agency, 1996b. “Method 29, Determination of Metals Emissions from 

Stationary Sources.” In Code of Federal Regulations, Title 40, Part 60, Appendix A, U.S. 

Environmental Protection Agency, April 1996. 
 

 

 

Section 6 

Page 6-3 

U.S. Environmental Protection Agency, 1998a. Mercury in liquid waste (manual cold-vapor technique). 

SW-846, Method 7470A, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, 

U.S. Environmental Protection Agency, 1998. 

U.S. Environmental Protection Agency, 1998b. Study of hazardous air pollutant emissions from electric 

utility steam generating units-final report to congress, Volume I, EPA-453/R-98-004a. U.S. 

Environmental Protection Agency/Office of Air Quality and Standards, Research Triangle Park, 

NC, 1998. 

U.S. Environmental Protection Agency, 1998c. Test methods for evaluating solid waste, 

physical/chemical methods, SW-846, U.S. Environmental Protection Agency, 1998. 

U.S. Environmental Protection Agency, 1998d. Method 7473, “Mercury in Solids and Solutions by 

Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry.” Test 

Methods for Evaluating Solid Waste, Physical/Chemical Methods (SW-846). U.S. Environmental 

Protection Agency, 1998. 

U.S. Environmental Protection Agency, 1999. Report to congress-wastes from the combustion of fossil 

fuels: Volume 2-methods, findings and recommendations, EPA 530-R-99-010, Washington, DC, 

U.S. Environmental Protection Agency/Office of Solid Waste and Emergency Response, 1999. 

U.S. Environmental Protection Agency, 2002. Characterization and management of residues from coalfired power plants, interim report. EPA-600/R-02-083, U.S. Environmental Protection Agency, 

2002. 

U.S. Environmental Protection Agency, 2003. Revised Assessment of Detection and Quantitation 

Approaches, EPA-821-B-04-005, U.S. Environmental Protection Agency, October 2004. 

U.S. Environmental Protection Agency, 2006a. Characterization of Mercury-Enriched Coal 

Combustion Residues from Electric Utilities Using Enhanced Sorbents for Mercury 

Control"(EPA-600/R-06/008) Feb 2006, Office of Research and Development (ORD), 

National Risk Management Research Laboratory (NRMRL), Air Pollution Prevention and 

Control Division (APPCD), Research Triangle Park, NC, 2006. Available at: 

http://www.epa.gov/nrmrl/pubs/600r06008/600r06008.pdf 

U.S. EPA, 2006b. EPA’s Roadmap for Mercury, EPA-HQ-OPPT-2005-0013. Available at: 

http://www.epa.gov/mercury/pdfs/FINAL-Mercury-Roadmap-6-29.pdf. 

U.S. Environmental Protection Agency, 2008a. Method 30B, “Determination of Total Vapor Phase 

Mercury from Coal-Fired Combustion Sources Using Carbon Sorbent Traps.” Code of Federal 

Regulations, 40 CFR Part 60; January, 2008. 

U.S. Environmental Protection Agency, 2008b.	 Characterization of Coal Combustion Residues from 

Electric Utilities Using Wet Scrubbers for Multi-Pollutant Control (EPA/600/R-08/077) 

 July 2008, ORD/NRMRL/APPCD, Research Triangle Park, NC, 2008. Available at: 

http://www.epa.gov/nrmrl/pubs/600r08077/600r08077.htm. 

6-3 
 

Section 6 

Page 6-4 

U.S. Environmental Protection Agency, 2009.	 Characterization of Coal Combustion Residues from 

Electric Utilities-Leaching and Characterization Data. Anticipated publication date is 

December 2009. 
Section 6 

Page 6-5 

This page intentionally left blank. 

6-5 

Appendix A 

Page A-1 

Appendix A 

DOE NETL Full-Scale Test Site Flow Diagrams 

A.1 Brayton Point Unit 1 

 Carbon injected upstream of second ESP (Research Cottrell). Only 1⁄2 of the unit was treated, or 

carbon was injected into one of the two new ESPs (Research Cottrell ESPs). 

 Hopper ID’s also shown. Samples from C-row are from the first row of hoppers in the second ESP. 

Gas Flow 

Figure A-1. Brayton Point Unit 1 

1 
Appendix A 

Page A-2 

Figure A-2. Brayton Point Unit 1 Hopper Identification 
Appendix A 

Page A-3 

ESP 2-4 

A.2 Pleasant Prairie Unit 2 

 Carbon injected upstream of cold-side ESP. Only 1/4 of the unit was treated. Test ESP was ESP 2-4. 

Spray Cooling

Carbon Injection

SCEM Inlet

SCEM Outlet

on vertical drop

ESP 2-4 

Spray Cooling 

Carbon Injection 

SCEM Inlet 

SCEM Outlet 

on vertical drop 

Figure A-3. Pleasant Prairie Unit 2 

3 
I.D. 

Fan

F.D. 

Fan

ESP

I.D. 

Fan

F.D. 

Fan

ESP

Appendix A 

Page A-4 

A.3 Salem Harbor Unit 1 

 Carbon injected upstream of cold-side ESP. Row-A hoppers were the front hoppers. 

Long Air

Heater

Short Air

Heater

Steam Coils

Boiler

Long Air

Heater

Short Air

Heater

Steam Coils

Boiler

Long Air 

Heater 

Short Air 

Heater I.D. 

Fan 

F.D. 

Steam Coils Fan

ESP 

Boiler 

Figure A-4. Salem Harbor Unit 1 
Appendix B 

Page B-1 

Appendix B 

Non-DOE NETL Full-Scale Test Site Flow Diagrams 

B.1 Facility A 

Figure B-1. Facility A 

1 
Appendix B 

Page B-2 

This page intentionally left blank. 
Appendix B 

Page B-3 

3 

 

Appendix C 

Page C-1 

Appendix C 

Detailed Results for Additional Wallboard Simulation Tests 

Table C-1. Description of Facilities Providing Eight Gypsum Samples. 

 FGD Scrubber Type 

Sample ID Coal Rank NOx Control Particulate 

Control 

Lime Type Oxidation Date Received 

AaAW EasternBituminous SCR ESP Limestone Forced 10/14/08 

DaAW EasternBituminous SCR ESP Limestone Forced 12/12/08 

NAW Bituminous None CS-ESP Limestone Forced 6/1/06 

OAW Bituminous SCR CS-ESP Limestone Forced 6/10-6/12/06 

SAW High 

Sulfur 

Bituminous 

SCR CS-ESP Limestone Forced 7/19/07 

TAW EasternBituminous SCR CS-ESP Lime Forced 9/18/07 

WAW EasternBituminous SCR off ESP Limestone 

Trona 

Forced 11/28/07 

XAW SubBituminous 

Powder 

River 

Basin 

SCR ESP Limestone Forced 6/16/08 

SCR = selective catalytic reduction 

ESP = electro static precipitator 

CS-ESP = cold-side electro static precipitator 

1 
 

 

 

 

 

 

 

Appendix C 

Page C-2 

Table C-2. Detailed Results for Additional Wallboard Simulation Tests 

Sample ID Pre-test 

(solid), ng/g 

After 

Simulation 

(solid), ng/g 

Volatilized 

Mercury 

(gas phase), 

ng/g 

Percent 

Volatilized 

Percent 

Remaining 

in Solid 

Mass 

Balance 

AaAW 

Run 1 571 428 107 19% 75% 94% 

Run 2 554 467 112 20% 84% 104% 

Run 3 515 440 97.2 19% 85% 104% 

Run 4 522 412 111 21% 79% 100% 

Run 5 536 414 149 28% 77% 105% 

Run 6 531 398 157 30% 75% 105% 

Average 538 426 122 23% 79% 102% 

St Dev 20.9 24.3 24.5 5% 5% 4% 

DaAW 

Run 1 647 528 132 20% 82% 102% 

Run 2 670 523 132 20% 78% 98% 

Run 3 641 536 139 22% 84% 105% 

Average 653 529 134 21% 81% 102% 

St Dev 15.0 6.86 3.86 1% 3% 4% 

NAW 

Run 1 473 240 196 41% 51% 92% 

Run 2 455 207 206 45% 46% 91% 

Run 3 469 237 211 45% 51% 96% 

Average 466 228 204 44% 49% 93% 

St Dev 9.27 17.8 7.51 2% 3% 3% 

OAW 

Run 1 46.7 30.7 15.5 33% 66% 99% 

Run 2 42.8 32.0 16.2 38% 75% 113% 

Run 3 43.3 33.3 14.8 34% 77% 111% 

Average 44.3 32.0 15.5 35% 72% 108% 

St Dev 2.12 1.29 0.68 2% 6% 7% 

SAW 

Run 1 307 127 167 54% 41% 96% 

Run 2 320 172 153 48% 54% 101% 

Run 3 309 178 133 43% 58% 100% 

Average 312 159 151 48% 51% 99% 

St Dev 6.75 27.8 17.3 6% 8% 3% 

TAW 

Run 1 831 521 240 29% 63% 92% 

Run 2 723 536 123 17% 74% 91% 

Run 3 739 501 230 31% 68% 99% 

Average 765 519 198 26% 68% 94% 

St Dev 58.3 17.5 64.6 8% 6% 4% 

WAW Run 1 910 843 97.3 11% 93% 103% 

Run 2 929 836 24.0 3% 90% 93% 

Run 3 928 870 33.7 4% 94% 97% 

Run 4 960 866 128 13% 90% 104% 

Run 5 933 890 103 11% 95% 107% 

Run 6 955 906 84.1 9% 95% 104% 

Run 7 954 843 141 15% 88% 103% 

Average 938 865 87 9% 92% 101% 
 

 

 

 

 

Appendix C 

Page C-3 

St Dev 18.6 26.1 44.4 5% 3% 5% 

XAW 

Run 1 1033 799 222 21% 77% 99% 

Run 2 1023 823 193 19% 80% 99% 

Run 3 1021 823 222 22% 81% 102% 

Average 1026 815 212 21% 79% 100% 

St Dev 6.24 14.0 16.8 2% 2% 2% 

Table C-3. Detailed Results for Wallboard Simulation Tests on Sample DaAW at Various 

Temperatures 

Furnace 

Temperature 

( ̊C) 

Pre-test 

(solid), 

ng/g 

After 

Simulation 

(solid), 

ng/g 

Volatilized 

Mercury 

(gas 

phase), 

ng/g 

Percent 

Volatilized 

Percent 

Retained in 

Solid 

Mass 

Balance 

Run 1 547 525 8.87 2% 96% 98% 

Run 2 546 531 14.6 3% 97% 100% 

120 Run 3 546 536 9.08 2% 98% 100% 

Run 4 564 536 10.6 2% 95% 97% 

Average 551 532 10.8 2% 97% 99% 

St Dev 8.85 5.13 2.64 0% 1% 2% 

Run 1 640 601 40.4 6% 94% 100% 

Run 2 642 603 41.8 7% 94% 100% 

140 Run 3 581 561 44.0 8% 97% 104% 

Average 621 588 42.1 7% 95% 102% 

St Dev 34.7 23.3 1.80 1% 2% 2% 

Run 1 647 528 132 20% 82% 102% 

Run 2 670 523 132 20% 78% 98% 

160 Run 3 641 536 139 22% 84% 105% 

Average 653 529 134 21% 81% 102% 

St Dev 15.0 6.86 3.86 1% 3% 4% 

3