Demonstrating Mercury Emissions Reduction Cost ... - Nalco

Demonstrating Mercury Emissions
Reduction Cost Management
By John Meier, Dr. Bruce Keiser*, Dr. Brian Higgins
Nalco Company, 1601 West Diehl Road, Naperville, IL 60563-1198
ABSTRACT
Meeting mercury emission regulations, whether state
or federal, is the primary goal of our work, while
simultaneously minimizing the impact on generated
electricity costs for a coal-fired power plant. 1–8
Determining the right solution for a combination of
boiler design, coal-type, and air quality control devices
(AQCD) can result in large reductions in mercury
compliance cost. An example of this is the cost savings
recently generated by the application of a holistic
Nalco engineered solution to mercury emission compliance
on a commercial boiler.
The commercial site consisted of a coal-fired 580 MWg
thermal electric supercritical boiler equipped with
low-NO x burners and selective catalytic reduction
(SCR) for NO x control, dry scrubbers (SDAs) for SO 2
control, and a pulse-jet fabric filter (FF) for particulate
control. The boiler burns subbituminous Powder
River Basin (PRB) coal. The site currently owns and
operates a Thermo Fischer continuous mercury monitor
(Thermo CMM) at the stack. The Thermo CMM is
used to control HPAC (halogenated powder activated
carbon) injection to maintain mercury emissions below
1.0 lb/TBtu, the targeted mercury emission rate. The
target represents approximately 90% mercury capture.
Historically, an HPAC injection rate averaging
1.65 lb/MMacf was required to meet this target.
Parametric testing and optimization of the engineered
mercury emission control solution were carried out
during the demonstration for HPAC alone and in
combination with Nalco MerControl 7895 technology.
The results showed that the mercury emission target
of less than 1.0 lb/TBtu could be maintained at lower
HPAC usage rates when combined with MerControl
7895. The HPAC usage rate was reduced 85% from
1.65 lb/MMacf to 0.25 lb/MMacf when MerControl
7895 was applied to the coal at a concentration of 25
ppmw. The optimized engineering solution reduced
the customer’s annual mercury compliance costs for
the 580 MWg electric generating unit (EGU) by over
$1.1 million per year.
Presented at Air Quality VIII, Arlington, VA, October 24-27, 2011
Reprint R-1031
We also will show recent work minimizing the cost of
mercury control through increasing the efficiency of
mercury capture by wet flue gas desulfurizer through
the application of MerControl 8034. Mercury emission
was reduced on a commercial unit from 10 µg/
dscm to less than 1 µg/dscm with no impact on EGU
operation. This work represents a simple low-capital
cost mercury strategy that enables EGUs to meet
regulations with existing AQCDs.
INTRODUCTION
An Ecolab Company
Hazardous air pollutants (HAPs) generated from the
use of fossil fuels to generate electricity continues to
be a topic of debate and subject for state and federal
regulatory bodies. 1–4 One HAP that continues to be
a focus of regulatory bodies is mercury emissions. It
is anticipated that the Clean Air Act will eventually
lead to federal mercury regulations on utility and
industrial boilers. While federal regulations remain
unclear, many states have established regulations
that apply to coal-fired power plants. 3–4 As the power
generating plants in these states and others move
to meet these regulations, it has become clear that
there are several control strategies. 5–8 The strategies
employed vary greatly based on existing unit
operations, coal type, and air quality control devices
(AQCDs) present at any given power generation plant.
The cost of air mercury emission compliance equally
varies greatly from one site to another. 7–8 Nalco has
been working in the field optimizing site specific
engineered solutions for customers. Holistic solutions
addressing both water and air mercury emissions
have been demonstrated for bituminous and subbituminous
coal-fired power plants with and without
selective catalytic reduction (SCRs) and wet flue gas
desulfurization (wFGD). 9–10 In all these cases, the goal
is always to meet air mercury emission regulations
while having the least impact on power generation
and electricity costs.
Recently, a demonstration was carried out applying
Nalco patented mercury control technology resulted
in a significant savings in meeting regulatory require-

ments. The demonstration site was a 580 MWg boiler
burning subbituminous Powder River Basin (PRB)
coal. The existing AQCDs included low NO x burners
and SCR to control NO x , a spray dryer absorber
(SDA) to control SO x , and a fabric filter to control
particulate emissions. The site utilized stack CMM
(i.e., continuous mercury measurement) to control
mercury emissions via injection of halogenated powder
activated carbon (HPAC) to a target of less than 1.0
lb/TBtu.
Nalco offers a method of controlling mercury in coal
combustion flue gas that increases the oxidized mercury
fraction in the gas and facilitates its capture.
Nalco is the exclusive licensee of MerControl 7895
technology. The oxidized form of mercury is more
readily collected in conventional air quality control
devices (AQCDs) such as electrostatic precipitators
(ESPs) and fabric filters (FFs). Oxidized mercury is
also more readily absorbed across acid gas scrubbers
like wet flue gas desulfurization (WFGD) and SDA
systems.
This paper provides a summary of the results of
this recent demonstration. Independent mercury
measurement was provided by Western Kentucky
University along with supplemental mercury speciation
measurements to aid performance analysis, additional
quality control, and determination of mercury
oxidation across existing air quality control devices
(AQCDs). WKU performed Ontario Hydro Method
2
(ASTM D6784-02/2008) and Method 30B (carbon trap
sampling), both considered reference methods for
measuring mercury. The study included injection of
halogenated powdered activated carbon (HPAC) only,
MerControl 7895 only, and both components together.
The performance of the mercury control solutions was
evaluated based on the ability to meet the mercury
air emission target and regulatory compliance cost.
Unit Description
EXPERIMENTAL
The test site has a 580 MWg, supercritical boiler
burning PRB coal, equipped with lox-NO x burners
and selective catalytic reduction (SCR) for NO x control,
spray dryer absorber (SDA) for SO 2 control, and
a pulse-jet fabric filter (FF) for particulate control
(Figure 1). A Thermo CMM (i.e., continuous mercury
monitor) is used to monitor mercury emissions and
to control HPAC injection rate. The HPAC is introduced
into the combustion gas after the air heater and
before the SDA. The HPAC injection rate is actively
controlled to maintain the target gas phase stack
mercury level of below 1.0 lb/TBtu as measured by the
Thermo CMM. Historical data shows that typically an
HPAC injection rate of 1.65 lb/MMacf was required to
maintain the target stack gas mercury concentration.
Figure 1 – Schematic of plant configuration and Hg measurements is provided. Note: M indicates mercury
measurement points within the unit while HPAC indicates injection points for halogenated powder activated carbon.

MerControl 7895 Temporary Supply System
The MerControl 7895 temporary supply system
(Figure 2) consists of three individual pumps, used
to supply chemical into three of the four coal feeders,
prior to the pulverizers. MerControl 7895 was stored
in a 260-gallon tote next to the temporary supply
system. MerControl 7895 supply levels were verified
by performing drawdown checks through individual
calibration columns on each pump. The temporary
supply system is equipped with flow metering and
data recording to insure that flow is not disrupted
during supply. The supply of MerControl 7895 was
maintained at a constant rate and did not change with
load or coal flow. Note that the load did not fluctuate
significantly during daily test periods. A permanent
MerControl 7895 installation includes a 4-20 mA
input signal to allow the flow rate to be varied with
load or coal flow. The flow rate of MerControl 7895 is
reported as part-per-million weight fraction (ppmw)
relative to the coal flow rate (e.g., mg 7895/kg of coal).
Validation of Gas Phase Mercury
Measurements
Mercury measurements were performed by Western
Kentucky University (WKU) after the air heaters and
at the stack. WKU performed Ontario Hydro Method
(ASTM D6784-02/2008) and Method 30B (carbon trap
sampling). A PSA Analytical CMM was also installed
by WKU at the outlet of one of two boiler air heaters
to monitor changing coal conditions. Ontario Hydro
measurements performed at the air heater outlet
was considered representative of the inlet mercury
concentration and used for calculation of mercury
removal performance. Ontario Hydro Method (OHM)
and Method 30B measurements made at the stack
by WKU were used to validate the Thermo CMM.
Table 1 – Comparison of Gas Phase Mercury Measurements.
3
Figure 2 – A typical temporary MerControl 7895
technology injection skid is shown.
Table 1 tabulates the OHM, Method 30B (abbreviated
as M30B in the table), and Thermo CMM gas phase
mercury concentrations at the stack.
RESULTS AND DISCUSSIONS
Validation of Stack Gas Phase Hg
Measurements
M30B = Method 30 B of 40 CFR Part 75.
a Relative Deviation or RD calculated following Appendix K of 40 CFR Part 75 section 11.7. 11
The Thermo CMM stack data for total mercury in
the gas phase was validated against that obtained
by WKU, see Table 1. The mercury concentrations are
shown in Table 1 in both gas concentrations (μg/dscm)
and relative to coal processed (lb/TBtu). The gas
concentrations were used in calculating the Relative
Deviation (RD) as percent between the correspond-

ing methods as shown in Table 1. 12 As can be seen,
the various methods compare well with RDs ranging
from 4 to 15%. One can also observe that for the first
two days, the RD between the Method 30B reference
method and CMM were high; i.e., ranging from 19 to
36%. The site CMM was calibrated during the second
day of testing resulting in the observed similar
results during the rest of the test. Indeed, using the
guidelines of Appendix K of 40 CFR Part 75, results
from the first day would be removed based on the high
RD values. A calculation of the Relative Accuracy
(RA) following Performance Specification 12A12 and
using data from only Day 3 through Day 5 of the test
yields a value of 18%. Analysis of the information in
Table 1 is shown in Figure 3 as well.
The comparison of either the site CMM or WKU OHM
results to the WKU Method 30B is shown in Figure
3. The red dotted line represents a theoretical exact
match between methods. Linear fits forced through
the origin were generated for both comparison methods;
i.e., site CMM and WKU OHM versus WKU
Method 30B. Please note that the highlighted data
points shown in Figure 3 were omitted from the linear
fit for the site CMM based on the discussion above. In
both cases, the R-squared values exceed 0.9 indicated
a good correlation between the respective methods.
Further, the slope of the fit for site CMM is 0.95 or
less than 5% from the theoretical value of 1.0. A plant
study comparing methods carried out by Sarunac, et
al., observed similar findings between Method 30B
and CMM indicated good agreement. 13 The data
shown in Table 1 and Figure 3 clearly indicate that
the site CMM after calibration provided reliable and
accurate gas phase mercury concentrations at the
stack and will be used through the remaining of this
paper.
Figure 3 –The comparison of mercury measurements is
made at the stack sampling point. Highlighted data
points were not used in construction of linear fit.
4
Parametric Tests
The plant load is shown in Figure 4 below during
the time of the demonstration. While load was
reduced overnight, the load was always near 580 MWg
during daylight testing. The MerControl 7895 was
supplied on a continual basis during the demonstration.
Plant data regarding load and coal usage were
used to calculate an “average” application concentration
of MerControl 7895.
Figure 4 – The plant load during the demonstration is
shown.
Table 2 contains a summary of the conditions, feed
rates, and stack total mercury levels measured during
the demonstration. The total mercury emission
rate reported in Table 2 is taken from the plant stack
CMM since, as shown above, these results were
essentially equivalent to independent OHM and
Method 30B. At the beginning of the trial HPAC
was being injected at a rate of 2.45 lb/MMacf to meet
the goal of less than 1.0 lb/TBtu mercury emission
rate. In fact this injection rate of HPAC resulted in
a mercury emission of 0.59 lb/TBtu. MerControl 7895
addition began on the second day at 46 ppmw based
on coal. Shortly after, the HPAC injection rate was
reduced from 2.45 to 0.22 lb/MMacf. As can be seen
in Table 2 and Figure 5, the stack mercury emission
rate remained less than 1.0 lb/TBtu. Indeed, at this
new condition of a 10-fold reduction of HPAC, a lower
mercury emission rate was observed. The combination
of MerControl 7895 and reduced HPAC injection
rate decreased mercury emissions by more than 50%
relative to only 0.3 lb/TBtu.
This demonstration condition was maintained to confirm
that the mercury emission levels were stable and
below 1.0 lb/TBtu. After about two hours, the HPAC
injection was turned off and remained off for the next

Table 2 – Summary of Supply Conditions and Performance.
*MerControl supply rate ppm is on weight basis, calculated from coal flow.
three days of the demonstration. MerControl 7895
(referred herein as BA or boiler additive) rates were
increased to maintain mercury emissions below the
targeted emission rate set point of 1.0 lb/TBtu.
Over the next 67+ hours of the demonstration, mercury
emission rates were maintained below 1.0 lb/TBtu
without addition of HPAC. During this period of the
demonstration, MerControl 7895 addition rate was
varied. In the initial 48 hours, it was observed that
lower rates of BA addition were required to maintain
mercury emission rates. It was hypothesized that the
cessation of activated carbon injection was leading to
the disappearance of residual HPAC from the boiler
surfaces, the fabric filter and the SDA system. During
previous HPAC parametric testing by the client,
they found that the activated carbon memory effect
on mercury removal lasted approximately 2.5 days. It
was observed that after 2.5 days the “memory effect”
of HPAC injection was reduced. Before the 2.5 days
elapsed, MerControl 7895 injection resulted in lower
mercury emissions due to residual carbon. After 2.5
days elapsed, it appeared that this effect had dissipated
and that the demonstration ran long enough
to minimize or eliminate the effect.
On the fourth day of the demonstration, 58 ppmw of
MerControl 7895 controlled mercury emission rates
to between 0.77 and 0.89 lb/TBtu. The average was
0.83 lb/TBtu with a standard deviation of 0.083 lb/
TBtu or 10% relative standard deviation. Further, as
can be seen in Table 2 and Figure 5, increasing the
BA application rate further decreased the mercury
emission rate to less than 0.71 lb/TBtu on Day 5 of
the demonstration.
Therefore, during the demonstration, it was shown
that HPAC injection could be reduced from 2.45 lb/
MMacf to less than 0.22 lb/MMacf while maintaining
the mercury emission rate below the 1.0 lb/TBtu limit
through the application of MerControl 7895.
5
Figure 5 – The stack total mercury emissions are
shown for conditions during the demonstration. Note:
ΔT represents the elapse time in hours after HPAC was
stopped. See Table 2 above for label codes. The optimal
condition was found to be 0.22 lb/MMacf HPAC and
25 ppmw MerControl 7895 technology.
Optimized Solution
After the Nalco demonstration period was complete,
the site performed further optimization using
the stack Thermo CMM. Various combinations of
MerControl 7895 and HPAC injection were investigated
to further reduce the cost of mercury compliance. They
concluded that by adding a small amount of HPAC, the
MerControl 7895 dosage could be decreased by 67%.
The most cost effective solution was between 25 to
50 ppmw of MerControl 7895 and 0.25 lb/MMacf of
HPAC. They also noted that MerControl 7895 application
provided a simple and easy means to respond
to variations in mercury emission rates.

Economic Analysis
Variations in mercury content of the fuel and anticipated
changes in mercury emission regulations, the
solution demonstrated above provides the necessary
flexibility to provide a long term operational solution.
To further highlight this, two economic analyses are
provided for the reader’s consideration. The first case
considered is an analysis of the cost required to reach
83% mercury emission reduction or a target of less
than 1.0 lb/TBtu. The second case to consider is the
cost associated with reaching 90% mercury reduction
or an emission rate of less than 0.71 lb/TBtu.
To determine the yearly solution costs for meeting
mercury emission regulations, the cost of consumables
for the “mercury emissions solution” on an hourly basis
was determined. Plant operations were assumed
to consist of 8760 hours per year with a capacity factor
of 90%. The cost for HPAC was taken as $0.98/lb.
Case 1: Mercury emission control below
1.0 lb/TBtu (or 83% Mercury Reduction):
As can be seen in Table 3, the control strategy provided
reduces the cost of consumables to meet this plant’s
mercury emissions regulation by over $1.1 million
per year.
Case 2: Mercury emission control below
0.7 lb/TBtu (or 90% Mercury Reduction):
Here also, the demonstrated mercury emission control
strategy maintains stack emissions below 0.7 lb/TBtu
at a savings of over $1.7 million per year.
The additional capital equipment required to
apply MerControl 7895 technology is recovered in savings
in less than 2 months. For this particular unit,
the injection system EPC cost was less than $200,000;
however, actual system costs can vary greatly due to
scope and system requirements.
Table 3 – Comparative cost to meet 83% total mercury reduction is
presented.
Condition
HPAC
(lb/MMacf)
MerControl 7895
(ppmw)
$/yr
HPAC only 1.65 $1,450,000
HPAC+MerControl 7895 0.25 28 $ 360,000
Savings $1,090,000
Table 4 – Comparative cost to meet 90% total mercury reduction is
presented.
Condition
HPAC
(lb/MMacf)
MerControl 7895
(ppmw)
$/yr
HPAC only 2.50 $2,200,000
HPAC+MerControl 7895 0.25 53 $ 500,000
Savings $1,700,000
6
The reduced cost of mercury emission compliance
can translate into reductions in the cost of electricity
for the consumer as can be seen in Figure 6. Figure
6 shows the cost of meeting mercury emission
regulations on a $/MWhr basis over about a year of
operation. The initial 140 days of operation shows
the cost of meeting mercury emission regulations
utilizing a control strategy of HPAC alone. During
HPAC application alone, the average cost of mercury
emission compliance is about $0.30/MWhr. During
the MerControl 7895 technology demonstration,
mercury emission compliance cost was reduced to
about $0.11/MWhr. After about 170 days, a mercury
emission compliance strategy based on the results of
this demonstration was implemented consisting of
combining HPAC and MerControl 7895 technology.
With optimization of this control strategy, mercury
compliance costs from about 221 days on have been
further reduced to about $0.07/MWhr and continues
to provide the flexibility to responds to fuel and
operational variations.
Figure 6 –The cost of control mercury emission is
presented for solutions as practiced. The (*) indicates
periods during which the temporary equipment was
used to control the program resulting in higher costs.

The reduced cost of mercury emission compliance
can translate into reductions in the cost of electricity
for the consumer as can be seen in Figure 6. Figure 6
shows the cost of meeting mercury emission regulations
on a $/MWhr basis over about a year of operation.
The initial 140 days of operation shows the cost
of meeting mercury emission regulations utilizing
a control strategy of HPAC alone. During HPAC
application alone, the average cost of mercury emission
compliance is about $0.30/MWhr. During the
MerControl 7895 demonstration, mercury emission
compliance cost was reduced to about $0.11/MWhr.
After about 170 days, a mercury emission compliance
strategy based on the results of this demonstration
was implemented consisting of combining HPAC
and MerControl 7895. With optimization of this control
strategy, mercury compliance costs from about
221 days on have been further reduced to about $0.07/
MWhr and continues to provide the flexibility to responds
to fuel and operational variations.
CONCLUSIONS
A demonstration of Nalco MerControl 7895 technology
was performed on a 580 MWg boiler to reduce mercury
emission compliance costs relative to a HPAC injection
alone strategy. Mercury was controlled to as low
as 0.7 lb/TBtu, below the target control limit of 1.0 lb/
TBtu, utilizing only MerControl 7895. Lower levels
of mercury emissions were recorded when combining
low rates of MerControl 7895 and lower rates HPAC.
It was found that about 2.5 days are required to completely
remove “memory effects” of HPAC injection
from the unit based on the response of stack mercury
emission to the feed rate of MerControl 7895. Specifically,
it was found that MerControl 7895 results
in further utilization of residual carbon to produce
mercury capture. It is clear from the results that
7
the demonstration ran long enough to minimize or
eliminate the effect.
At a MerControl 7895 rate of 70 ppmw, the site
was able to maintain mercury emissions below the
targeted rate of 1.0 lb/TBtu. Further optimization
resulted in an economical mercury control strategy
that provided operational flexibility while meeting
mercury emission regulations with 25 ppmw of
MerControl 7895 and 0.25 lb/MMacf of HPAC
injection. Historically the previous control strategy
required about 1.65 lb/MMacf of HPAC injection to
maintain the mercury emissions below 1.0 lb/TBtu.
Due to the addition of Nalco MerControl 7895 technology,
the client reduced mercury emission compliance costs by
$1.1 million per year. In the future, this mercury control
strategy provides a means to meet 90% mercury
reduction at a mercury compliance cost reduction of
$1.7 million per year compared to HPAC alone.
MERCURY REEMISSION CONTROL FROM
WFGD (RECENT DEVELOPMENTS)
Recently, Nalco MerControl 8034 technology for control
of mercury re-emission in wet flue gas desulfurizers
was performed on a combined 140 MWe EGU
(Figure 7) fueled by high chlorine bituminous coal,
i.e., 1200 ppm as chlorine. The EGU consisted of a
SCR, selective catalytic reduction for NO x control,
cold-side ESP to control particulate emissions, and
limestone forced-oxidation wet flue gas desulfurizer
to control SO x emissions. At the time of the request,
total mercury capture was less than 50%. The reason
for low mercury with a wFGD was not well understood.
The goal of the demonstration was to improve
the mercury capture efficiency of existing air quality
control devices (AQCDs) while minimizing capital
cost and operational complexity.
Figure 7 –Schematic of commercial EGU (electricity generating unit) where Nalco successfully
demonstrated wFGD mercury reemission reduction was shown. Mercury gas-phase measurements
were made at the indicated “Monitoring Points” for the demonstration.

The gas-phase mercury measurements were carried
out by an independent company using continuous
mercury monitors (CMMs). The CMMs results were
verified via Method 30B carbon traps. The complete
study will be presented subsequently and is only
briefly summarized here. A segment of the demonstration
results is presented in Figure 8. This segment
includes periods related to baseline measurement,
control strategy application and demonstration that
the control strategy is actively controlling mercury
re-emission from the wFGD (Figure 8).
Reduction of mercury from oxidized to elemental
across wFGDs, i.e. mercury re-emission, has previously
been the subject of laboratory and commercial
studies with limited success in the latter case. 14–15 The
results shown in Figure 8 document the successful
application of a simple mercury re-emission control
program. The inlet mercury gas-phase measurements
are shown in blue diamonds with the elemental fraction
shown in blue open diamonds. Not surprisingly,
the high coal chlorine, in combination with the SCR,
results in high mercury oxidized speciation, i.e., about
85%. If the wFGD were 100% efficient at capturing
oxidized mercury, there would be 85% mercury capture
relative to the inlet mercury concentration. As
is seen in Figure 8, under baseline conditions, the
stack total mercury concentration equals that of the
total inlet mercury concentration representing near
0% capture across the wFGD. Note that the stack
mercury emissions are represented by the red squares
with the elemental fraction represented by the open
symbols. Indeed, the elemental fraction of the stack
mercury concentration is greater than 70% of the
total. The percent re-emission, calculated from the
inlet oxidized fraction and the increase across the
wFGD of the elemental fraction was observed to be
greater than 77%. This was consistently observed over
the course of several weeks. Therefore, the focus of
this demonstration, i.e. the reduction of total mercury
emission from the EGU, became the elimination of
mercury re-emission across the wFGD.
Nalco has developed the patented application of a
proprietary liquid scrubber additive for the purpose
of controlling mercury reduction across a wFGD.
The product, MerControl 8034, is simple to apply,
requiring minimal application equipment and with no
impact on scrubber or EGU operations. As can be seen
Table 5 – Summary of key performance parameters during demonstration.
8
Figure 8 – Mercury results are shown from the
demonstration showing periods of mercury re-emission
from the wFGD and the reduction by MerControl 8034
addition. Feed rate is shown on the left y-axis. Elemental
mercury concentrations are shown by open symbols.
in Figure 8, this EGU responded to the application
of MerControl 8034 within one hour of application.
Within 2 hours of application, the stack total mercury
concentration was the same as the mercury inlet
elemental concentration. Re-emissions was reduced
to zero and controlled throughout the remainder of
the application period. Typically, initial high application
rates are used to quickly eliminate re-emissions,
with lower rates needed for “maintenance” of control.
During application, the stack emissions are nearly
100% elemental mercury. As a result of Nalco control
technology the percent mercury capture reached
greater than 85%.
After demonstrating control for several hours, the
application of MerControl 8034 was stopped. As
expected, control continues after cessation of product
application and in this case lasted for about 2
hours. After MerControl 8034 is depleted, mercury
re-emission returns resulting in an observed increase
in stack total mercury concentrations.
Table 5 contains a summary of measured parameters
from the three stages of the demonstration. First, it
is clear that throughout the demonstration the flue
gas mercury speciation did not change. The percent
mercury oxidation ranged from 87 to 95% during
the course of the test. In contrast, the amount of reemission,
capture and the relative efficiency of the
WFGD to capture ionic mercury changed significantly

esulting from the application of MerControl 8034.
Table 5 shows that before application, re-emission
was averaging over 100% with mercury capture at
zero. The application of MerControl 8034 decreased
re-emission to near zero percent while increasing
the scrubber mercury capture efficiency to 100% resulting
in mercury capture increase to nearly 97%.
With the cessation of application of MerControl 8034,
re-emission increased again to baseline as did the
mercury capture, i.e. near zero percent. Similarly, the
scrubber efficiency related to ionic mercury capture
from the flue gas decreased to zero percent.
This demonstration shows the ability of Nalco to design
and apply a mercury control strategy that works
while managing costs. Our low-capital-equipment
solution minimizes modifications of existing plant
equipment and operating procedures. This and
other successful demonstrations have proven the
viability of Nalco 8034 in solving mercury reemission
across wFGDs.
ACKNOWLEDGMENTS
The authors would like to acknowledge the contributions
made to this paper by Jianwei Yuan and Gerald
Hunt.
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