To highlight the research and achievements of Australian researchers, the Global CCS Institute together with ANLEC R&D will hold a series of webinars throughout 2017. Each webinar will highlight a specific ANLEC R&D research project and the relevant report found on the Institute’s website. This is the seventh webinar of the series and presented the results of a test program on the retrofitted Callide A power plant in Central Queensland. The behaviour of trace metals and the related characteristics of the formation of fine particles may have important implications for process options, gas cleaning, environmental risk and resultant cost in oxy-fuel combustion. Environmental and operational risk will be determined by a range of inter-related factors including: The concentrations of trace metals in the gas produced from the overall process; Capture efficiencies of the trace species in the various air pollution control devices used in the process; including gas and particulate control devices, and specialised systems for the removal of specific species such as mercury; Gas quality required to avoid operational issues such as corrosion, and to enable sequestration in a variety of storage media without creating unacceptable environmental risks; the required quality for CO2 transport will be defined by (future and awaited) regulation but may be at the standards currently required of food or beverage grade CO2; and Speciation of some trace elements Macquarie University was engaged by the Australian National Low Emissions Coal Research and Development Ltd (ANLEC R&D) to investigate the behaviour of trace elements during oxy-firing and CO2 capture and processing in a test program on the retrofitted Callide A power plant, with capability for both oxy and air-firing. Gaseous and particulate sampling was undertaken in the process exhaust gas stream after fabric filtration at the stack and at various stages of the CO2 compression and purification process. These measurements have provided detailed information on trace components of oxy-fired combustion gases and comparative measurements under air fired conditions. The field trials were supported by laboratory work where combustion took place in a drop tube furnace and modelling of mercury partitioning using the iPOG model. The results obtained suggest that oxy-firing does not pose significantly higher environmental or operational risks than conventional air-firing. The levels of trace metals in the “purified” CO2 gas stream should not pose operational issues within the CO2 Processing Unit (CPU). This webinar was presented by Peter Nelson, Professor of Environmental Studies, and Anthony Morrison, Senior Research Fellow, from the Department of Environmental Sciences, Macquarie University.

1. Mercury and other trace metals in the gas from an oxy-
combustion demonstration plant
Webinar – Tuesday, 21 February 2017

2.  Peter Nelson was appointed Professor of Environmental Studies, Macquarie
University 2001, and is currently Pro Vice Chancellor (Research Performance
and Innovation). He was previously Senior Principal Research Scientist
in CSIRO Energy Technology, where he managed projects on energy and the
environment, air pollutant measurement, mechanism of formation and control.
Professor Nelson has had more than 30 years experience in research on the
assessment and control of air pollution and on environmental issues
associated with energy use.
 Professor Nelson’s research expertise is in the assessment and control of
pollution and on environmental issues associated with energy use, with
emphasis on toxic organics from industrial and vehicular sources, trace
elements and waste management. The outputs of this research have been
published in the scientific literature (> 200 peer-reviewed journal and
conference papers), and in major commissioned reports for government and
industry. Much of this work was done in close co-operation either directly with
industry (e.g., ARC-Linkage projects with RioTinto; CRC program; Australian
Coal Association Research Program, NSW Power Generators) or government
(e.g., with the Australian Greenhouse Office; Department of Environment
Water Heritage & the Arts, New South Wales Department of Environment
Climate Change & Water).
Professor of Environmental Studies, Department of Environmental
Sciences
Peter Nelson

3.  Tony Morrison is currently a Senior Research Fellow in the Department of
Environmental Sciences, Macquarie University working on projects
across a diverse range of air pollution and environmental land
contaminant issues. He previously worked for the CSIRO Division of
Minerals as a project developer, manager and researcher in
environmental and metallurgical projects across a range of commodities
and processes. Several of his recent publications have particular
relevance where he has examined atmospheric mercury concentrations,
mercury emissions from power plants using fabric filtration and
electrostatic precipitators and characterisation of particulates in Broken
Hill (ceiling dusts), the Hunter Valley (silica) and North Lake Macquarie
(smelter slags). He is the author of 32 publications in the open literature
and 90 client reports to sponsors of industry projects as project manager
or as a senior team member.
Senior Research Fellow, Department of Environmental Sciences
Tony Morrison

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5. ANLEC R&D is a not-for-profit agency, funded by the Australian Government Department Industry, Innovation and Science through the
National Low Emissions Coal Initiative, and by the ACA Low Emissions Technologies Ltd (ACALET) through the COAL21 Fund.
Enabling research to reduce greenhouse emissions from coal technologies
Australian National Low Emissions Coal Research & Development
ANLEC R&D is an Australian National Research
Initiative to support Carbon Capture and Storage
(CCS) deployment in Australia.
$100M+ Invested
In one of the largest partnerships, the Australian
Coal Industry and the Australian Government has
deployed a research effort in over 25 institutions
nationwide since 2010.
Our present focus supports CO2 storage across
3 Australian geological basins:
Surat Basin, Gippsland Basin, S Perth Basin
This Presentation;
Mercury and other trace metals in the gas from an oxy-combustion demonstration plant
For more information please visit www.anlecrd.com.au

6. Mercury and other trace metals in the gas
from an oxy-combustion demonstration
plant.
Peter Nelsona*, Anthony Morrisona, P. Sargent Braya, Hugh
Malfroyb, Rohan Stangerc, Chris Sperod
a Department of Environmental Sciences, Macquarie University, NSW, Australia, 2109
bMalfroy Environmental Strategies, 18/37 Nicholson Street, East Balmain, NSW, Australia, 2041
cFaculty of Engineering and Built Environment,,Newcastle University, University Drive, Callaghan,
NSW, Australia, 2308
dCS Energy/Callide Oxyfuel Services Pty Ltd, Level 2 540 Wickham Street, Fortitude Valley
Queensland Australia 4006

7. Project Parameters
• Examination of trace metal fate and concentration
• Four coal feeds (Coal C, Blend 1, Blend 2, Coal M)
• Combination of sampling:
– solids inputs and outputs (coal and ash)
– at the stack exhaust (under both air and oxyfired
conditions)
– at various points of the CO2 Processing Unit (CPU)
• Sampling targets:
– Mercury (using both sorbent traps and continuous
analysis)
– Other trace metals (As, B, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb,
Sb, Se, Zn)
– Halides (HBr, HCl, HF, Br, Cl, F)
– Particulates

8. Stack, Ash and CPU Sampling

9. Stack Sampling Methods
• Sampling probes and collection trains
complied to the following standards where
practicable:
– Metals : USEPA Method 29
– Halides : USEPA Method 26/26a
– Particulates: Australian Standard 4323.2
– Mercury : USEPA Method 30b ( sorbent
trap modified for measurement of Hg++)

10. CPU Sampling Methods
• Pressurised process stream
- no sampling probes used
- collection trains identical to
those on the exhaust stack
• Continuous Tekran mercury
analyser:
– deployed at several locations within
the CPU
– parallel determinations of mercury
using sorbent tubes

11. CPU Sampling Locations
Blower
Outlet
Compressor
Outlet
Dryer Outlet
Coldbox
Outlet

12. OutcomesHalides:
Location
Air Oxy
HBr 0.06-0.61 <0.10
HCl 10 - 67 9 - 18
HF 9 - 36 4 - 12
Br
Cl
F
STACK
<MDL
<MDL
<MDL
(mg/Nm³)
CPU
<MDL
<MDL
<MDL
<MDL
<MDL
<MDL
(mg/Nm³)
*MDL Minimum Detection Limit
for Method

13. 0.0
1.0
2.0
3.0
B Cr Mn Ni Zn
mg/Nm³
0.00
0.05
0.10
0.15
0.20
Cd Co Cu Pb Se
mg/Nm³
Airfiring Oxyfiring
The elements Sb, As, Be were
below MDL under both air and
oxyfiring conditions, Cd was below
the MDL under airfiring conditions.
Outcomes
All elements were at or around MDL
values in the CPU beyond the first
low pressure scrubber.
Metals:

14. Summary of Outcomes
• Halides and Metals – variations in stack gas
concentrations appear influenced by both firing
method (oxy or air) and coal type;
• Halides – detectable in stack gases; all species
below method detection limits beyond blower
outlet (i.e following initial low pressure gas
scrubbers)
• Metals - elemental concentrations at very low
levels in the CPU at the blower outlet and
beyond; often below method detection limits

15. Mercury Mass Balance
Mercury analysis at the following stages of the
process:
• Coal Input
• Ash Outputs (fly ash, bottom ash, rear pass and
air heater ash)
• Flue gas concentration at stack
• Process gas concentration in CPU
– Blower outlet
– Compressor Outlet
– Dryer Outlet
– Coldbox outlet

16. Coal
feed
stockpile
Hg in coal feed
22.9 -39.4 (ng/g)
5-13%
87-95%
Slag &
Ash100%
Mercury Distribution
Airfiring
Total mercury
concentration in
flue gas
0.1- 0.8 µg/m³

17. UBC in Flyash (%)a
Location
Air Oxy
Coal C 4.4 1.0-2.6
Blend 1 10.6 4.0
Blend 2 6.0 3.5
Coal Mb
11.0 12.5
STACK
a Weighted averaged from 8 hoppers
b Results likely to be sub-optimal due to failure of
coal swirler during testing period

18. Coal
feed
stockpile
Total mercury
concentration in
flue gas
2.7-4.9 µg/m³
Hg in coal feed
22.9 -39.4 (ng/g)
23-33%
64-74%
Slag &
Ash100%
Approx 80%
of flue gas Hg
to CPU
removed at
scrubber
Total mercury
concentration in
process gas
0.4-0.9 µg/m³
Total mercury
concentration in
process gas
<0.1 - 2 ng/m³
Mercury Distribution
Oxyfiring(%)
2.0-2.9%
Approx
10% of
total
flue
gas
flow

19. Mercury loss from CPU process
gas
0%
20%
40%
60%
80%
100%
FlueGasIN
LP
Scrubber
Blower
Compressor
HP
Scrubber
Dryers
Coldbox
CPU Process Operation
ApproximateMercuryLossfrom
ProcessGas
Total mercury concentration
in process gas
<0.1 - 2 ng/m³
Total mercury concentration
in flue gas input
2.7 - 4.9 µg/m³
Total mercury concentration
in process gas
0.4 - 0.9 µg/m³

20. Gas Phase Mercury Speciation
• Estimations of Hg++ using KCl segments in sorbent traps;
• Imperfect technique for Hg++ as some breakthrough in
the KCl occurred even at low sampling flow rates;
• Will result in small underestimation of Hg++ ;
• Total mercury estimation unaffected, negligible
breakthrough to second activated carbon segment ;
• Total of 115 sorbent tubes analysed (71 stack, 34 CPU).
KCl segments (Hg++)
Activated carbon segments
FLUE GAS FLOW

21. Averaged Ratio Hg++/Hgtotal
Location
Air Oxy Blower Outlet
Coal C 0.52 0.68
Blend 1 0.65 n.a.
Blend 2 0.47 0.68
Coal Ma
0.63 0.72
STACK CPU
0.08
n.a.
0.11
0.06
a Results likely to be sub-optimal due to failure of
coal swirler during testing period
n.a not available

22. Hg increases* following CPU
depressurisation
TEKRAN LOG 12th Dec
0
10
20
30
40
50
60
70
80
00 02 04 07 09 12 14 16 19
TIME (HRS)
HgConcentration(ng/m³)
Compressor
Trip
Compressor
Restored
* Sampling location CPU compressor outlet

23. Summary Hg outcomes
• Hg was more likely to report to slag and ash under
air firing conditions, most likely a result of generally
higher UBC (%) in flyash when air firing;
• Ratios of Hg++/Hgtotal seem relatively unaffected by
firing condition (air or oxy);
• Approximately 80% of Hg in CPU process gas was
removed by the initial low pressure scrubber;
• Following depressurisation of the CPU, evidence of
significant Hg concentration increases was
observed using the Tekran continuous Hg analyser;
• Final CPU process gas Hg approached the levels
measured in ambient air (<2 ng/m³).

24. Predicting Hg capture using iPOG
• United Nations Environment Program (UNEP)
Coal Mercury Partnership Process Optimization
Guidance document, or POG, to predict the
effects of coal properties, power station design
and operating conditions on mercury emissions;
• iPOG provides quantitative estimates of Hg
based on a few coal properties, the gas cleaning
configuration, selected firing and gas cleaning
conditions, and Hg control technologies;
• Hg emission estimates are based primarily on
regression equations developed from emission
data gained from an extensive campaign in the
USA.

25. 0
20
40
60
80
100
120
0 5 10 15 20
Overall Combined Ash (LOI%)
Mercuryretainedinash(%)
Oxy-fired values fieldtrial
Air-fired values fieldtrial
iPOG estimate oxy-fired
iPOG estimate air-fired
Measurements and predictions using iPOG
for Callide air and oxy-fired conditions
Mercury retained in ash (%) as a function carbon in ash (LOI, %)

26. Implications of iPOG modelling for
Callide Oxy-fuel process
• Measured data show >5% C in Ash results in
>90% Hg capture in FF;
• Implies Hg management through the ash
stream rather than CPU;
• Capture reduces with C in ash;
• At higher combustion efficiencies (with lower C
in ash) increasing amounts of Hg are likely to
be transported to the CPU.

27. Environmentally available chromium
and chromium speciation
• Typically chromium is found as Cr(III) or Cr(VI);
• Cr(III) is an essential nutrient whereas Cr(VI) is highly
toxic to plants, animals and humans;
• Acid digestible chromium (CrAD) and hexavalent
chromium (Cr(VI)) were determined in samples from fly
ash hoppers, furnace (bottom) ash and ash samples
from the rear pass and air heater collection points
(n=193)
• Total chromium (Crtotal ) was also determined on a series
of composited ash samples (n=13).

28. 0
10
20
30
40
50
60
70
80
4 5 6 7 8 9
Acid Digestible Chromium (mg/kg)
TotalChromium(mg/kg)
Comparison of Crtotal and CrAD
• Levels of environmentally available chromium (CrAD) in the ash
are low (4.4 – 8.4 mg/kg);
• 85-90% of Crtotal is isolated within the siliceous glass matrix of
the ash and is not environmentally available, even in
aggressive acid environments;
• Environmentally available chromium is very low compared to
soil health investigation levels of 100 mg/kg.

29. Cr(VI) determination
• Cr(VI) was below the Limit of Reporting (LOR = 0.5 mg/kg) of
the analysis method for all samples;
• Qualitative evaluation (with high errors of determination) at a
LOR of 0.05 mg/kg detected Cr(VI) in 33 of 193 samples;
• Cr(VI) was not detected in any of the coal, bottom ash, rear
pass or air heater ash samples;
• Levels determined in flyash ranged from revised LOR (0.05
mg/kg) – 0.3 mg/kg;
• CR(VI) was detected predominantly in flyash samples from the
later hoppers in the collection train;
• No apparent differences between oxy and air-fired results.

30. Assessment of trace component
concentrations in product CO2
• Assess the suitability of the CO2 for various uses:
pipeline quality for transport and storage,
food grade;
• Whether the product CO2 would require additional cleaning
required to meet food grade standards.

31. Element
Drinking
Water
Guideline
value
1
(mg/L)
Calculated
maximum
allowable
concentration
in CO2
(mg/Nm
3
)
Measured
concentration
in CPU at
Drier Outlet
(mg/Nm
3
)
Antimony 0.003 0.7 <0.00082
Arsenic 0.007 1.7 <0.0021
Beryllium 0.5
2
123 <0.00082
Boron 4 983 <0.0021
Cadmium 0.002 0.5 0.0019
Chromium 0.05 12.3 <0.00082
Cobalt ng
3
ng <0.00082
Copper 2 491 0.0014
Lead 0.01 2.5 <0.00082
Manganese 0.5 123 0.012
Mercury 0.001 0.2 <0.000002
Nickel 0.02 4.9 <0.00082
Selenium 0.01 2.5 <0.0021
Zinc 3 737 0.0076
Chlorine 0.6 147.4 <0.16
Sulfur
4
0.6 <0.5
Calculated maximum acceptable concentrations of elements in
produced CO2 for food use based on NHMRC water guidelines
(greyed areas based on MDL)
1 all values NHMRC (2004) unless otherwise noted
2 WHO (2008) 3 ng no guidance value provided 4 EIGA (2008)

32. Implications of CO2 quality for
the Callide Oxy-fuel process
• Produced CO2 assessed against food quality guidance for a wide
range of elements;
• Standard is much more stringent than for pipeline quality for use in
enhanced oil recovery;
• All concentration values in the produced CO2 orders of magnitude
lower than the levels which might be required for use in the beverage
industry, except for potentially sulfur for which the MDL is close to the
allowable limit of 0.6 mg/Nm3;
• Food quality specifications include a number of elements and
compounds (eg, hydrocarbons, oxides of nitrogen and water) which
require further testing and their presence or concentration may
preclude this use.

33. Conclusions
• Successful sampling campaign;
• Minimal transfer of trace elements beyond
the first scrubber in the CPU;
• Hg levels in CPU produced process gas
approach those measured in ambient air;
• iPOG modelling suggests higher
combustion efficiencies may result in
increased amounts of Hg being
transported to the CPU

34. Conclusions (cont)
• Trace element concentrations in produced
CO2 are below food quality guidance;
• 85-90% of Crtotal is isolated in the ash
matrix environmentally available;
• Available chromium is very low compared
to soil health investigation levels of 100
mg/kg.

35. Acknowledgements
• The authors acknowledge the significant input to the
success of the project made by the sampling team from
ECS Pty Ltd, Simon Newbigin, Michelle Yu, Henry Diona
and Dante Mude.
• The authors wish to also acknowledge financial
assistance provided through Australian National Low
Emissions Coal Research and Development (ANLEC
R&D). ANLEC R&D is supported by Australian Coal
Association Low Emissions Technology Limited and the
Australian Government through the Clean Energy
Initiative.

36. OutcomesMetals:
Location
Air Oxy Blower Outlet Compressor Outlet
Antimony <MDL <MDL
Arsenic <MDL <MDL
Beryllium <MDL <MDL
Boron 0.60 - 1.11 1.22 - 2.03 0.004 - 0.011
Cadmium <MDL <0.006
Chromium 0.34 - 0.98 0.01 - 1.22
Cobalt 0.005-0.019 0.003-0.013
Copper 0.041-0.110 0.024-0.065
Lead 0.008-0.021 0.009-0.017
Manganese 0.085-0.390 0.097-0.375
Nickel 0.205-1.700 0.009-0.649
Selenium <0.015 <0.043
Zinc 0.073-0.410 0.047-0.172
<MDL <MDL
<0.0013 <0.005
<0.006
<MDL<0.001
<MDL <0.002
<MDL
<MDL
0.002-0.008
<MDL
<MDL
<MDL
<MDL
0.003-0.010
CPU
(mg/Nm³)
<MDL
<MDL
<MDL
<0.0008
0.001-0.019
<0.0008
0.001-0.039
<0.001
STACK CPU
(mg/Nm³) (mg/Nm³)
*MDL Minimum Detection Limit
for Method

37. Method Detection Limits
Stack CPU
MDL (mg/dsm³) MDL (mg/dsm³)
Halides
HBr 0.038 - 0.077 0.016 - 0.033
HCl 0.19 - 0.39 0.082 - 0.17
HF 0.19 - 0.39 0.082 - 0.17
Br 0.031 - 0.077 0.016 - 0.033
Cl 0.15 - 0.39 0.082 - 0.17
F 0.031 - 0.077 0.016 - 0.13
Metals
Antimony 0.0017 -0.0043 0.00055 - 0.00082
Arsenic 0.0042 - 0.0110 0.0014 - 0.0021
Beryllium 0.0017 -0.0043 0.00055 - 0.00082
Boron 0.0042 - 0.0110 0.0014 - 0.0024
Cadmium 0.0017 -0.0043 0.00055 - 0.00082
Chromium 0.0017 -0.0043 0.00055 - 0.00082
Cobalt 0.0017 -0.0043 0.00055 - 0.00082
Copper 0.0017 -0.0043 0.00055 - 0.00082
Lead 0.0017 -0.0043 0.00055 - 0.00082
Manganese 0.0017 -0.0043 0.00055 - 0.00082
Nickel 0.0017 -0.0043 0.00055 - 0.00082
Selenium 0.0043 - 0.0110 0.0014 - 0.0021
Zinc 0.0042 - 0.0110 0.0014 - 0.0021

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