## 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 patentpending 1,2brominated 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 trials 4,5 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. 6To 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. 7In 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 n ameplate 508 MW Exhaust gas flow rate (typical, full load) 77 MSCFH Coal type Powder River Basin Coal s ource Eagle Butte Mine C oal 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
NO X controls Low NO X burner with overfire air SO 2 c ontrols None Fly a sh LOI ~ 0.3% Ash use/s ale 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 werethemselves 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. 9,10To 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/MMACFVAPOR-PHASE MERCURY REMOVAL, %

ZX110 Sorbent - Parametric Test
ZX110 Sorbent - Extended Test Darco Hg-LH - Parametric TestThe 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/MMACFVAPOR-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/yd 3 388 388 388 Fly ash s ource Baseline 6:00 S amp le 9:30 S ample Fly a sh, lb/yd3 129 129 129 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/ft 3 134.0 139.4 135.8 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/yd 3 571 452 452 454 Fly ash s ource n/a Baseline 6:00 S ample 9:30 S ample Fly a sh, lb/yd3 0 113 113 114 Replacement % 0% 20% 20% 20% Fine aggregate 1206 1185 1185 1190 Coarse aggregate 185 1 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/ft 3 145.3 144.4 142.8 143.5 Concr ete 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. 11Concrete 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, MINCONCRETE ENTRAINED AIR, %

Baseline Sample 6:00 Sample 9:30 SampleThe 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, MINCONCRETE ENTRAINED AIR, %

Cement Only Baseline Sample 6:00 Sample 9:30 SampleA 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. 12The 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 SAMPLECOMPRESSIVE STRENGTH (PSI)

8 DAY 28 DAYA 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