BASF Mercury Sorbent ZXTM for Control of Coal-fired

Power Plant Hg Emissions

Paper # 176

William J. Hizny

BASF Corporation, 2655 Route 22 West, Union, NJ 07083

Gary Magno

Xcel Energy, 1800 Larimer Street, Denver, CO 80202

Xiaolin Yang, PhD.

BASF Corporation, 25 Middlesex/Essex Turnpike, Iselin, NJ 08830

ABSTRACT

Electric utilities that operate coal-fired generating units continue to seek new, costeffective sorbents for controlling mercury emissions to meet regulatory requirements

while also preserving the value of salable fly ash for concrete applications as a partial

replacement for Portland cement.

The latest innovative BASF Mercury Sorbent platform technology - ZX - is a patentpending1,2 brominated mineral-based mercury adsorbent with an organic flow modifier

constituent. The flow modifier has been confirmed in third-party testing to be an

effective means to overcome sorbent agglomeration issues seen previously in other

mineral-based sorbents.

Full scale, parametric field trial results from Xcel Energy’s Pawnee Generating Station in

Brush, Colorado, a nominal 500MW PRB coal-fired generating unit equipped with a

fabric filter, demonstrated that BASF Mercury Sorbent ZX110TM controlled baghouse

outlet vapor-phase mercury emissions to the levels stated in the 2012 and 2018 Colorado

mercury control regulations for this plant of 0.0174 lb/GWh and 0.0087 lb/GWh

respectively. BASF Mercury Sorbent ZX110 also achieved greater than 90% vapor

phase mercury removal at the baghouse outlet at sorbent injection rates comparable to

those of a commercially available brominated powdered activated carbon, which was

tested parametrically at the site as a comparative reference.

Fly ash samples retrieved during extended full scale testing of BASF Mercury Sorbent

ZX110 were submitted for concrete property testing. Test results confirmed that the fly

ash retained salable properties for concrete applications, including satisfactory air

entrainment admixture dosing levels, concrete entrained air retention levels, and concrete

compressive strengths.
INTRODUCTION

Sorbent injection has emerged as the leading dedicated technology for mercury emissions

control from coal-fired electric generating units. It is well known that the predominant

operating cost associated with this technology is the cost of the sorbent material itself.

An additional significant cost may be incurred if the mercury sorbent renders the fly ash

unsalable into value applications such as a partial replacement for Portland cement in

ready-mix concrete applications. A revenue stream is lost and a new disposal expense is

incurred. Thus, electric utilities with coal-fired generating units continue to seek new,

cost-effective sorbents for controlling mercury emissions to meet regulatory requirements

while also preserving the value of salable fly ash.

Xcel Energy’s Pawnee Generating Station

Xcel Energy’s Pawnee Generating Station in Brush, Colorado is a nominal 500MW PRB

coal-fired generating unit equipped with a fabric filter. The Pawnee Generating Station is

subject to specific Colorado mercury regulations: 0.0174 lb/GWh (or 80% Hg capture) in

2012 and 0.0087 lb/GWh (or 90% Hg capture) in 2018.3 All of the fly ash is sold.

Facing the challenge of both impending regulatory compliance and jeopardized fly ash

sales, Xcel Energy and BASF Corporation conducted a full scale field demonstration test

program of BASF Mercury Sorbent ZX110—a specific ZX formulation customized for

fabric filter applications—at the Pawnee Generating Station in Brush, Colorado during

April 2010. The goals of the program were to demonstrate controlled outlet vapor-phase

mercury emissions consistent with those stated in the Colorado mercury control

regulation and to demonstrate that the fly ash with entrained ZX110 sorbent retained

salable properties for use in concrete applications.

BASF Mercury Sorbent ZX

BASF Mercury Sorbent ZX is the latest innovative technology platform from the

mineral-based mercury sorbent portfolio of BASF Corporation. The ZX platform is built

upon a patent-pending composition of a brominated zeolite and an organic flow modifier

constituent designed to mitigate agglomeration during injection. As a mineral-based

technology, ZX sorbents enable fly ash, with which it is entrained during use, to retain its

salable properties for use as a partial replacement for Portland cement in concrete

applications.
Typical properties of the BASF Mercury Sorbent ZX110 used in this full scale

demonstration test are given in Table 1.

Table 1. BASF Mercury Sorbent ZX110 typical properties.

Typical Property Value

U.S. Sieve Series (by weight)

 Through 325 mesh (45 mm), % 95% min

Bulk density, tamped, g/cc 0.6 – 0.8

Surface area, m2/g 400 min

Flow Modifier Technology

Particle agglomeration is characterized by a shift in particle size distribution towards

fewer but larger particles. A mercury sorbent agglomerating during use would

experience a consequential loss of performance as fewer, larger particles spaced apart

farther than intended in the exhaust stream would slow the effective mass transfer rate of

vapor phase mercury from the bulk flow to the outer surface of the sorbent particles.

Agglomeration has been suggested as a possible influence in those full scale

demonstration trials4,5 in which a mercury sorbent exhibited a flat parametric injection

response curve, as increased sorbent addition rates did not yield the expected increase in

mercury removal.

BASF has developed flow modifier technology to mitigate a sorbent’s agglomeration

potential.6 To supplement internal development and testing efforts and further

characterize quantitatively the range of effects that flow modifiers may have, BASF

funded an experimental test program with a leading researcher in sorbent particle flow

properties, Prof. Herek Clack of the Illinois Institute of Technology.

Prof. Clack’s research group has exploited the well-defined light scattering characteristics

of particulate laden air streams to infer in situ particle size distributions.7 In their

experiment, a fixed mass of sorbent is fluidized and expelled from an acoustic powder

feeder in a batch process and directed across the path of a He/Ne laser beam directed onto

an associated photodiode. A light intensity metric, I/Io, is recorded by the photodiode as

a function of time. In some trials, the expelled sorbent travels through a tube modeling

the sorbent delivery system used in full scale trials before it crosses the laser’s path.

Experimental results have shown the efficacy of flow modifier technology by the

significant differences in the characteristics of interrogated particle streams across the

range of flow modifiers tested and in the presence or absence of the tube modeling the

full scale sorbent delivery system.8
EXPERIMENTAL METHOD

Pawnee Generating Station Characteristics

Xcel Energy’s Pawnee Generating Station may be described by the general

characteristics summarized in Table 2.

Table 2. Xcel Energy’s Pawnee Generating Station Unit 1 characteristics.

Parameter Value

Boiler type Conventional pulverized coal

Turbine-generator nameplate 508 MW

Exhaust gas flow rate (typical, full load) 77 MSCFH

Coal type Powder River Basin

Coal source Eagle Butte Mine

Coal properties (typical, as received)

Mercury 0.09 ppm (dry basis)

Chlorine 50 ppm (dry basis)

Sulfur 0.37%

Moisture 30%

Ash 4.8%

Baghouse type Reverse Air

Air-to-cloth ratio 1.63 acfm/ft2

NOX controls Low NOX burner with

overfire air

SO2 controls None

Fly ash LOI ~ 0.3%

Ash use/sale 100%

Test Methodology

Apogee Scientific, Inc. was contracted by BASF to conduct the field demonstration test

program, including the supply and installation of the portable sorbent injection system,

the sorbent delivery system including multi-hole injection lances, and the continuous

mercury monitors (CMM).

The portable sorbent injection system, which had been proven in previous full scale

demonstration trials, accommodated sorbent supplied in supersacks, which were

suspended over and fed into a conical hopper. A volumetric screw feeder metered

sorbent from the hopper into an eductor, which was driven by a blower drawing ambient

air into the system as a means of conveying the sorbent through the delivery lines and

into the duct. Load cells integrated into the injection system structure supplied a

gravimetric feedback signal tracking the net loss of weight due to sorbent consumption

over time. The signal helped to trim the sorbent injection rate as it tracked a nominal

targeted value. The main sorbent delivery line was a single three inch diameter rubber

hose that was routed up the side and onto the top of the exhaust aftertreatment ductwork.

At this elevation, the main sorbent line connected to a T-fitting, whose outlets were
themselves connected to T-fittings, such that four individual sorbent delivery lines of 2

inch diameter each fed a multi-hole injection lance designed and supplied by Apogee.

The lances were inserted into the duct at 4 of 5 access points spanning the cross-section

of the duct (see Figure 1). Although this arrangement did not uniformly cover the duct

cross-section with sorbent at the point of injection, it was believed that an immediate 90-

degree turn in the duct just downstream of the injection point would promote strong

mixing and mitigate this issue. The main duct subsequently split into two ducts that each

turned 90-degrees prior to entering two separate baghouses, whose individual exit ducts,

stacked upon the inlet ducts, were rejoined to feed a single, common stack. The sorbent

injection design was considered sufficient for the goals of the test plan.

Figure 1. Pawnee Generating Station aftertreatment duct schematic.

Apogee utilized two QSIS sample extraction probes with continuously refreshed wet

chemical, impinger based sample conditioning systems at the point of sample extraction

to maximize sample integrity. One probe was installed upstream of the sorbent injection

system just after the air preheater to measure the inlet mercury concentration; the other

was installed in a duct leading from one of the two baghouses to the stack to measure the

outlet mercury concentration.

A continuous mercury monitor was dedicated to each probe enabling total and elemental

vapor phase mercury measurements to be made across the sorbent injection and

collection points. The CMM were of Apogee’s own design and construction based on a

cold vapor atomic absorption spectrometer coupled with a gold amalgamation mercury

trapping media. The CMM had been proven extensively in previous full scale testing.
As part of their standard QA/QC protocol, Apogee personnel conducted a daily CMM

calibration check at the start of each test day and a mercury spike evaluation at the end of

each test day.

During parametric testing, mercury sorbent injection rates were held at/near a nominal

target rate for at least 100 minutes or until a stable outlet mercury signal was readily

apparent. The 100 minutes threshold corresponded to the nominal, continuous cleaning

frequency of the fabric filter elements during full load operation.

Test Plan

The results that are the subject of this paper were obtained as part of a larger test

program, which evaluated several mercury control technology options including chemical

addition and experimental sorbent formulations.

The parametric test of BASF Mercury Sorbent ZX110 on day 6 of the test program

constructed an experimental curve describing total vapor phase mercury removal as a

function of sorbent injection concentration. A comparative parametric test of Norit

Darco® Hg-LH was conducted on day 13 of the test program subsequent to a system

recovery day. Norit Darco® Hg-LH is a brominated, powdered activated carbon that

served as a comparative reference in this trial due to its pervasive use as such in previous

industry test programs documented in the technical literature. Darco® is a registered

trademark of Atlas Powder Company; Norit Americas, Inc. last listed owner.

To facilitate the evaluation of the Pawnee Generating Station fly ash concrete properties

with BASF Mercury Sorbent ZX110 entrained under actual operating conditions, the

sorbent was continuously injected for an extended period to maintain a nominal 90%

vapor-phase mercury removal rate at the baghouse outlet during days 11 and 12 of the

test program. The fly ash silo, from which samples were pulled, was emptied prior to

extended testing. Two sets of ash samples were retrieved, one after about 12 hours of

continuous injection during a period of sustained plant low-load operation (“6:00

Sample”) and another after about 15 hours of continuous injection during the onset of

plant full load operation. (“9:30 Sample”).

The Pawnee Generating Station maintained their normal operating procedures during the

test program, including load shedding as warranted by economics or consumer demand.

Efforts were made to burn coal from the same source during normal daytime testing

hours.
RESULTS & DISCUSSION

Mercury Removal

Baseline Results

Baseline monitoring prior to the commencement of the test program showed negligible

native vapor-phase mercury removal, which was consistent with expectations due to the

known minimal carbon content of the fly ash. Consequently, the inlet and outlet CMM

showed good agreement.

Parametric Testing

Vestigial Impact of Preceding Tests

The ZX110 sorbent parametric test day followed two days of testing that included nonBASF technologies for mercury emissions control. One unanticipated consequence of

this testing was an overnight system recovery curve of continuously increasing outlet

vapor-phase mercury emissions whose peak value exceeded a stable inlet CMM reading

by as much as 60%. Both the probe sampling train and the continuous mercury monitor

instrumentation were rechecked and recalibrated by Apogee personnel. No measurement

issues were identified that would invalidate the outlet CMM reading as an accurate

assessment of the mercury emissions from the baghouse. Qualitative trending data from

the Pawnee Generating Station’s stack CMM, which was operated simultaneously but

independently of the test program, matched the trend shown in the outlet CMM. In light

of these issues and the prohibitive amount of time suggested by the data trends to allow

realignment of the inlet and outlet mercury emission measurements, it was decided that

the daily baseline outlet mercury emission value, which was recorded after morning

calibration but before sorbent injection, would serve as the reference value for

comparative mercury emission percent reduction calculations.

Impact of Plant Operating Conditions

Due to fluctuating load demands experienced by the plant during its normal course of

operation, the operating temperature of the aftertreatment ductwork and baghouse varied

significantly during the parametric testing of Norit Darco® Hg-LH relative to the

parametric testing of BASF Mercury Sorbent ZX110. Table 3 shows the average

baghouse temperature at each of the parametric data points for the 2 sorbents.
Table 3. Parametric data temperature.

ZX110 Sorbent Darco® Hg-LH

Sorbent

Injection Rate

lb/MMacf

Average

Baghouse

Temperature

°F

Sorbent

Injection Rate

lb/MMacf

Average

Baghouse

Temperature

°F

0.4 308.2 0.4 277.8

1.0 312.9 0.9 279.3

1.8 316.0 1.1 296.8

2.7 307.4 1.5 307.5

It is recognized in the technical literature that the adsorption characteristics of a mercury

sorbent, carbon or natural zeolite based, improves as its operating temperature

decreases.9,10 To facilitate a direct comparison, the parametric test results presented in

the next section were segmented by nominal plant operating condition as a surrogate for

the nominal operating temperature.

Parametric Results

The parametric test results at nominal full load were summarized in Figure 2.

FIGURE 2: PARAMETRIC INJECTION SUMMARY at FULL LOAD

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5

SORBENT INJECTION CONCENTRATION, LB/MMACF

VAPOR-PHASE MERCURY REMOVAL, %

ZX110 Sorbent - Parametric Test

ZX110 Sorbent - Extended Test

Darco Hg-LH - Parametric Test
The filled blue squares represented the parametric vapor-phase mercury removal

performance of BASF Mercury Sorbent ZX110 at plant full load conditions. A best-fit

dashed line was drawn through the data. BASF Mercury Sorbent ZX110 achieved 90%

vapor-phase mercury removal at nominally 1.8 lb/MMacf. At a comparable plant load,

Norit Darco® Hg-LH achieved 90% vapor-phase mercury removal at nominally 1.5

lb/MMacf. This was shown in Figure 2 as the filled black triangle.

The performance of BASF Mercury Sorbent ZX110 during its extended test day, when

under plant full load conditions, also was shown in Figure 2 for reference purposes. It

was in good agreement with the parametric data trend. The extended testing occurred

much later in the test program, by which time the pretest baseline values reported on the

inlet and outlet CMM had returned to nominal agreement indicative of negligible native

vapor-phase mercury removal and the significantly diminished vestigial impact of

previously tested non-BASF mercury control technologies.

During its extended test day, BASF Mercury Sorbent ZX110 demonstrated a controlled

baghouse outlet vapor-phase mercury emission of 0.0057 lb/GWh on a 100 minute

rolling average basis.

For the sake of completeness, the part-load, low temperature performance of Norit

Darco® Hg-LH was shown as the open black triangles in Figure 3.

FIGURE 3: PARAMETRIC INJECTION SUMMARY at PART LOAD

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5

SORBENT INJECTION CONCENTRATION, LB/MMACF

VAPOR-PHASE MERCURY REMOVAL, %

Darco Hg-LH - Parametric Test
Concrete Properties

Two sets of fly ash samples were retrieved from the Pawnee Generating Station baghouse

ash hoppers during extended testing of BASF Mercury Sorbent ZX110: “6:00 Sample”

and “9:30 Sample”. These samples and a pre-test baseline fly ash reference sample were

submitted for concrete property testing to the labs of a reputable fly ash marketer and

BASF Corporation Admixture Systems. Concrete properties tested included air

entrainment admixture dosing levels, concrete entrained air retention levels, and concrete

compressive strengths.

Characterization of Field Samples

The field retrieved samples of fly ash with entrained ZX110 sorbent, and the pre-test

baseline fly ash reference sample, were submitted for physical characterization with

respect to compositional markers unique to the sorbent over and above those levels found

in the baseline fly ash. A review of the physical characterization data determined that the

6:00 Sample and the 9:30 Sample were distinctly different with respect to the amount of

ZX110 sorbent entrained with the fly ash. The 6:00 Sample was consistent with a sorbent

content of about 0.67% - 0.75%-wt, which corresponded to a nominal sorbent injection

rate of 2.3 - 2.6 lb/MMacf, and the 9:30 Sample was consistent with a sorbent content of

about 0.27% - 0.28%-wt, which corresponded to a nominal sorbent injection rate of 0.95

– 1.0 lb/MMacf. A review of the plant operating data suggested an increase in plant load

from around 60% capacity at about 6:00 to 100% capacity at about 9:30, which may have

contributed to an increase in ash generation and thus dilution of the 9:30 sample relative

to the entrained sorbent content.

Concrete Property: Air Entrainment Admixture Dosing

Two different air entrainment admixtures (AEA) were utilized to evaluate the concrete

properties of the fly ash samples over a range of concrete admixture chemistries. A

reputable fly ash marketer used Grace Construction Products Daravair® AT60, which

had a manufacturer recommended typical dosing range of 1⁄4 to 3 fl oz/100 lbs of cement

(oz/cwt) and combined natural and synthetic constituents in its formulation. Daravair® is

a registered trademark of W. R. Grace & Co.; W. R. Grace & Co.-Conn last listed owner.

BASF Corporation Admixture Systems used MB-AETM 90, which had a manufacturer

recommended typical dosing range of 1⁄4 to 4 oz/cwt and is formulated from only natural

constituents. Tables 4 and 5 describe the concrete samples prepared by each test lab.
Table 4. Concrete samples prepared by a reputable fly ash marketer.

Property Value

Cement type Capitol Type I Capitol Type I Capitol Type I

Cement, lb/yd3388 388 388

Fly ash source Baseline 6:00 Sample 9:30 Sample

Fly ash, lb/yd3129 129 129

Replacement % 25% 25% 25%

Fine aggregate 1280 1280 1280

Coarse aggregate 1650 1650 1650

Water 344 280 320

Admixture type AT60 AT60 AT60

Admixture dose, oz/cwt 1.25 1.25 1.25

Fresh concrete properties

Slump, in. 6.0 6.0 5.75

Unit weight, lb/ft3134.0 139.4 135.8

Concrete air, % 8.0 7.6 8.0

Table 5. Concrete samples prepared by BASF Corporation Admixture Systems.

Property Value

Cement type Lehigh Mitchell

Type I/II

Lehigh Mitchell

Type I/II

Lehigh Mitchell

Type I/II

Lehigh Mitchell

Type I/II

Cement, lb/yd3571 452 452 454

Fly ash source n/a Baseline 6:00 Sample 9:30 Sample

Fly ash, lb/yd30 113 113 114

Replacement % 0% 20% 20% 20%

Fine aggregate 1206 1185 1185 1190

Coarse aggregate 1851 1819 1819 1827

Water 271 266 266 267

Admixture type MB-AE 90 MB-AE 90 MB-AE 90 MB-AE 90

Admixture dose, oz/cwt 1.5 2.0 3.0 2.85

Fresh concrete properties

Slump, in. 6.75 6.50 7.00 7.00

Unit weight, lb/ft3145.3 144.4 142.8 143.5

Concrete air, % 6.4 7.4 7.4 7.0

The AEA dosing levels required to achieve a stable mixture for the field returned samples

were within the manufacturers’ recommended typical dosing ranges for both the

Daravair® AT60 product and the MB-AETM 90 product.

Significantly, regardless of the AEA product used, the field returned samples

demonstrated minimal difference between their AEA dosing levels even though their

relative ZX110 sorbent content varied by a factor between 2x - 3x. This feature

represented a highly valued concrete property intrinsic to the mineral-based BASF

Mercury Sorbent ZX110 product. Stable AEA dosing rates translate into stable and

reliable use of the fly ash in ready-mix concrete applications. In comparison, powdered

activated carbon sorbents have shown in published trials an AEA dosing variability that

may challenge the practical use in concrete applications of the fly ash with which they are

entrained.11
Concrete Property: Entrained Air Retention

Entrained air testing of the concrete samples—baseline fly ash (no entrained sorbent),

6:30 Sample, and 9:30 Sample—prepared with various air entrainment admixtures was

conducted upon initial preparation and in regular intervals thereafter during continuous

sample agitation to simulate the transit mixing speed of a ready-mix concrete truck. The

test results, using the Daravair® AT60 product, were presented in Figure 4. The test

results, using the MB-AETM 90 product, were presented in Figure 5.

FIGURE 4. CONCRETE ENTRAINED AIR RETENTION SAMPLES

PREPARED WITH DARAVAIR AT60

0.0

2.0

4.0

6.0

8.0

10.0

0 10 20 30 40 50 60 70

ELAPSED SAMPLE AGITATION TIME, MIN

CONCRETE ENTRAINED AIR, %

Baseline Sample

6:00 Sample

9:30 Sample
The concrete samples prepared with fly ash entrained with ZX110 sorbent (6:00 Sample

and 9:30 Sample) and Daravair® AT60 showed no appreciable change in their concrete

entrained air content even after 60 minutes of agitation. The baseline fly ash (no sorbent)

sample showed a marked increase in concrete entrained air over time. Stable concrete

entrained air content was more desirable than varying concrete entrained air content, even

one that increased with time and agitation, because it contributed significantly to a

consistent and stable concrete end-product. An increase in concrete entrained air over

time may contribute to a premature loss of concrete strength and thereby decrease the

long term durability of the concrete.

The impact of air entrainment admixture chemistry is shown via relative comparison of

the concrete samples prepared with MB-AETM 90. Although all samples showed a loss of

concrete entrained air after 60 minutes, those samples containing fly ash with entrained

ZX110 sorbent (6:00 Sample & 9:30 Sample) had the highest initial and final air content

and the lowest rate of concrete entrained air loss.

Concrete Property: Compressive Strength

The samples prepared with the MB-AETM 90 product were submitted to BASF

Corporation Admixture Systems for compressive strength testing on concrete samples

over a 28 day period. Test results for those samples were shown in Figure 6.

Compressive strength testing was not performed on those samples prepared with the

Daravair® AT60 product.

FIGURE 5. CONCRETE ENTRAINED AIR RETENTION SAMPLES

PREPARED WITH MB-AE 90

0.0

2.0

4.0

6.0

8.0

10.0

0 10 20 30 40 50 60 70

ELAPSED SAMPLE AGITATION TIME, MIN

CONCRETE ENTRAINED AIR, %

Cement Only

Baseline Sample

6:00 Sample

9:30 Sample
A comparison among the concrete samples showed that the compressive strengths of the

6:00 Sample and the 9:30 Sample were slightly less than that of the baseline fly ash

sample, although the difference lessened over time. This general trend demonstrated by

the concrete samples was not unexpected, since the reduction in compressive strength

was nominally consistent with the demonstrated increase in concrete entrained air

content.

Economics of Preserved Fly Ash Salability

In May 2007, U.S. Department of Energy / National Energy Technology Laboratory

released an updated economic analysis of activated carbon injection for mercury

emissions control.12 The analysis identified two main drivers of O&M costs: the cost of

the mercury sorbent material consumed and, where applicable, the costs associated with

lost sales revenue and incurred disposal expenses for fly ash entrained with sorbent that

precluded the continued sale of the fly ash into applications such as ready-mix concrete.

The following example illustrates the relative magnitude of these two drivers by

computing a total cost of use for a hypothetical sorbent that rendered the fly ash

unsalable.

FIGURE 6. CONCRETE COMPRESSIVE STRENGTH SAMPLES

PREPARED WITH MB-AE 90

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

CEMENT-ONLY BASELINE 6:00 SAMPLE 9:30 SAMPLE

SAMPLE

COMPRESSIVE STRENGTH (PSI)

8 DAY 28 DAY
A hypothetical sorbent with the performance described in Table 6 is assumed for the sake

of the calculation.

Table 6. Hypothetical sorbent properties.

Parameter Metric

Price $1.00/lb

Injection rate 1.5 lb/MMacf

Performance 90% Hg removal

% sorbent entrained in fly ash 0.5 %-wt

One ton (2,000 lbs) of fly ash would be expected to entrain 10 lbs (0.5%-wt) of the

hypothetical mercury sorbent at an injection rate of 1.5 lb/MMacf. Assuming the

economic values used in the DOE/NETL analysis of $18/ton fly ash lost sales revenue

and $17/ton fly ash incurred disposal expenses, the total negative economic impact of fly

ash rendered unsalable by the mercury sorbent is $35/ton of fly ash, or $3.50/lb mercury

sorbent entrained in the ash. This number is significantly greater than the hypothetical

price, $1.00/lb, of the mercury sorbent itself.

Thus, in this hypothetical example, the total cost of use for the sorbent product would be

much more sensitive to the retention or loss of fly ash salability than to nominal

perturbations in the sorbent price and/or sorbent injection rate to achieve a fixed

performance level.

Leaching

To confirm the ability of BASF Mercury Sorbent ZX110 to retain adsorbed mercury, the

baseline fly ash, 6:00 Sample, and 9:30 Sample were submitted for testing per TCLP

(Toxicity Characteristic Leaching Procedure; EPA Method 1311) and SPLP (Synthetic

Precipitation Leaching Procedure; EPA Method 1312) by San Antonio Testing

Laboratory, Inc. A summary of the test results is presented in Table 7.

Table 7. TCLP & SPLP test results.

Sample TCLP (Hg, mg/L) SPLP (Hg, mg/L)

Baseline fly ash <0.0002 0.0006

6:00 Sample 0.0004 0.001

9:30 Sample 0.002 <0.0002

US EPA limit 0.2 n/a

TCLP testing of field returned fly ash samples with entrained ZX110 sorbent satisfied the

EPA limit for mercury of 0.2 mg/L being nominally 100 times less than this value.
SUMMARY

BASF Mercury Sorbent ZX110 successfully demonstrated in full scale testing at Xcel

Energy’s Pawnee Generating Station controlled baghouse outlet vapor-phase mercury

emissions to the levels stated in the 2012 and 2018 Colorado mercury control regulations

for this plant of 0.0174 lb/GWh and 0.0087 lb/GWh respectively. BASF Mercury

Sorbent ZX110 also achieved greater than 90% vapor-phase mercury removal at the

baghouse outlet at sorbent injection rates comparable to those of a commercially

available brominated powdered activated carbon, which was tested parametrically at the

site as a comparative reference.

Test results demonstrated that the fly ash entrained with ZX110 sorbent retained salable

properties for concrete applications, including satisfactory air entrainment admixture

dosing levels, concrete entrained air retention levels, and concrete compressive strengths.

BASF remains committed to the continued innovation of its portfolio of mineral-based

mercury control technologies towards greater product performance efficiency and

expanded applicability in high temperature applications and bituminous coal-fired

applications. To this end, BASF welcomes opportunities to demonstrate its latest

technology in full scale test programs.

ACKNOWLEDGEMENTS

The authors would like to acknowledge the significant contributions of the following

individuals, and the organizations they represent, in making this field demonstration test

program a success: Barry Andrews (Xcel Energy’s Pawnee Generating Station), Trevor

Ley and Rick Slye (Apogee Scientific, Inc.), Brad Violetta and Steve Farrington (BASF

Corporation Admixture Systems), Dr. Herek Clack and Eric Lee (Illinois Institute of

Technology).

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KEYWORDS

BASF Mercury Sorbent ZXTM

Mercury

Mercury control

Sorbent

Sorbent injection

PRB coal

Coal

Fabric filter

FF

Baghouse

Concrete

Cement

Fly ash

Agglomeration