From: "Barbanell, Melissa (Salt Lake City)" <mbarbanell@barrick.com>
To: Chuck French/RTP/USEPA/US@EPA
Date: 02/24/2010 08:40 PM Subject: CEMs White Paper

Chuck,
Attached you will find a copy of the memorandum we promised addressing continuous emissions monitors. We are having a call first thing tomorrow morning to discuss the status of the HCN report and I will be happy to follow up with you on that issue after that call concludes.
I will plan to call you around noon EST tomorrow. Thanks, Melissa(See attached file: cems white paper (6).pdf)4811

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CONTINUOUS EMISSION MONITORS ARE NOT FEASIBLE OR NECESSARY FOR GOLD MINING ROASTERS

Com pliance wi

th MACT standards under the gold mining NESHAP can be demonstrated reliably and efficient ly wi thout the f

easibilit y and reliabilit y concerns associ ated wi th cont inuous emissio n mo nit ors (CEMs) fo r mercury emissi ons. A s discussed below, it i s not feasible to install CEMs techno lo gy f or mercury

e missio ns generally, and especially not in th e unique emissio n condi

ti on s present in roasters used in th e gold mining industry . M oreover, established parametri c testing met hods current ly em ploy ed at these sources are proven and reliable met hods to confirm that mercury

emissi ons control s are func ti oning properly and consistent ly.
I. MERCURY CEMS TECHNOL OGY IS NOT FEASIBLE FOR GOLD MINING ROASTERS Despite several years of sustained efforts to develop mercury CEMs technology f or l arge source categori es such as coal

- fi red electri c generating uni ts, this techno lo gy mu st continue to improve before it c an be reliably used fo r demonstrating cont inuous co mp liance wi th m ercur y emissio n standards. T he fe asibili ty o f applying mercury CEMs techno lo gy t o gold mining roasters is even farther down th e road. M ost o f th e challenges to co nt inuously measuring mercury f rom p oint s ources (stacks) fa ll int o on e of th ree general categori es: (1) mercury CEMs calibrat io n; (2) sample transport; and (3) system o perabilit y and reliabilit y. T he unique characterist ic s of

roaster s used in th e gold mining industry and the fact that mercury CEMs have not been designed to meet these specific characteristics further com plicate the resol

ut io n of each of these ty pes of challenges. A. Mercury CEMs Calibration A principal concern of a pplying mercury CEMs to gold mining roasters is th e unavailabilit y of

a m eans to calibrate th e CEMs for this applicat io n, resul ting in data of

l imited and suspect value. C ontinuous mo nit oring of m ercury, even from

a b est

- con trolled gold mining roaster presents a twof

old calibrat io n challenge for exist ing mercury CEMs technology . First, all vendors would have to mo dify th eir exist ing head

- space c alibrator unit s. An important com ponent of am ercury

C EMs is th e mercury calibrator (or gas generator) unit. I n simpl est terms, mercury

c alibrators are head

- space devices th at wo rk on th e principal th at mercury vapor has well defined pressure and tem perature characterist ic s. T hus, passing a known vo lu me of carri er gas over a pool

o f liquid mercury at a carefully control led tem perature and pressure produces a known mercury concentration, ty pically expressed in th e uni ts of m icrograms of mercury p er cubic meter of

c arri er gas (μg/m 3 ). E xisting calibrator designs are simply not capable of generating mercury c oncentrations high enough to provide meaningful upscale calibrat io n points that correspond to gold mining source characterist ics. Second, and much mo re problematic, is th e unavailabilit y of N at io nal In st it ute of Standards and Technology (NIST) traceable calibration ga s. N IST certifies methods and gases used fo r calibrat ing mo nit ors, an important and necessary p rocedure fo r ensuring th at measured data is accurate and reliable. A s EPA acknowledged at our meet ing on February 1 7, NIST traceable mercury gases and methods fo r generating such gases are not currently available and4811

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are not expected to be available wi th in the time fr ame th at EPA ant ic ipates prom ulgating a final MACT standard for the gold mining industry

. B. Sample Transport Current designs of

m ercury C EMs fo r co al

- fir ed electri c generat ing uni ts requi re high

tem perature umbilical lines to transport the sample from th e stack to the analyzer. T he mercury sample transport lines must be ma int ained at a higher tem perature th an convent io nal (i .e., SO 2 /NO X /CO 2 ) sample lines because mercury is a “ st icky” mo lecule, especially th e oxidized fo rm ( e.g., HgCl

2 ). A s th ese systems have been installed on coal

- fired electri c generat ing uni ts, an inordinate number of u mbilical failures appear to be occurring. T he umbilical failures represent another challenge to having CEMs functio n consistent ly fo r the continuous mo nit oring of mercury f rom industri al

sources. C. System Operability and Reliability Mercury C EMs are mu ch mo re com plex systems th an are convent io nal SO 2 /NO X /CO 2 mo nit oring systems. Mercury CEMs must contain some ty pe of converter f

or reducing oxidized Hg (Hg +2 ) to elemental Hg (Hg 0 ). T his is because only Hg 0 can be “seen” or detected by ei th er atomic absorpti on or atomic fluorescence. I n th e early stages of m ercury

C EMs commercializat io n (circa 1997

– 2003), th e prevalent technique fo r mercury conversio n used chemical processes. T his approach was doomed to fa ilure as various flue gas consti tuents qui ckly proved to be poi sonous to th e chemical catalysts. M ost mercury CE Ms suppliers have changed to a th ermal cataly ti c process fo r mercury conversio n, and this approach has proven to be generally sat is factory . Premature cataly ti c failures peri odically occur in these uni ts; however, and this often results in periods of missing data of several days.
In init ial phases of

implement ing this techno lo gy by th e electric utilit y industry, users have reported mercury CEMs to be unavailable as much as 30 to 40 percent of the uni t operating time. B ased on th e co mp lexit ie s of a pplying this techno lo gy

t o a new source category s uch as gold mining roasters which have gas stream d ifferences fro m electri c ut ilit y generat ing uni ts (where mercury

C EMs remain probl emat ic), th e amo unt of d owntime to b e expected fro m th ese systems would likely b e even higher. These breakdown events, combined wit h the other ty pes o f failures discussed herein, resul t in data availability

t hat is substant ia lly inferior to parametric mo nit oring and therefore cannot j ust ify the significant cost and resource investmen t n ecessary to install, operate and maintain these devices.
D. Mercury CEMs Face Prohibitive Uncertainties Associated with Cost, Reliability and Accuracy In summary, there are no viable prospects fo r a successful implementation of m ercur y CEMs at gold mining roasters at th e present or any time in the near future. A ft er years of development fo r coal

- fired electri c generat ing unit s, a much larger market fo r CEMs technology th an gold mining roasters, significant progress still needs to be made before CEMs will w ork reliably f or th at source category

. B ased on th e com plexi ti es associ ated wi

th a dapting th at techno lo gy to effectively mo nit or mercury emissi ons fro m unique sources such as roasters, availabilit y of

m ercury C EMs is even farther off fo r th e gold mining s ource categories, especially when th e very small number of r oasting unit s nat io nwide is considered (a total of six4811

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units, emitt ing th

rough only

f our stacks, and lit tle likelihood th at any mo re unit s will be constructed). As noted above, th e challenges facing mercury CEMs are not ju st based on cost and reliabilit y, but al so include undeveloped calibrat io n standards. E ven assuming th e devices were online and operating, wi

thout adequate calibrat io n met hods and protocol s, th ere is no assurance th at th e results obtained fro m mercury C EMs would be accurate and representative of a ctual stack emissio ns. T hus, even if th e mercury C EMs were used only to provide assurances th at emissio n control s were fu nct io ning properly, and were not used to determine co mp liance wi t h th e NESHAP, such data would not be verifiable wi thout proper calibrat io n of t he equipment. This probl em could resul t in both fa lse alarms that emissio n control s are not working, when in fact th ey are, and vice versa. T o rely on CEMs fo r th e limited pur pose of v erifying proper emissio n control

o perati on ignores th e very real concern th at is presented by cont inuous data reports of

m ercury emissio ns to th e at mo sphere th at are not accurate, reliable or credible. Further, we are concerned th at, notwi th stand ing EPA’s representati ons that it d oes not int end to utilize the CEMs data fo r di rect com pliance purposes, the uncertifiable data that resul ts fro m th e mo nit oring might nonetheless be offered as “credible evidence” to assert a vio lation. T his is parti cularly troubling where, in Nevada, there are separate mercury limi ts established pursuant to state law. II. PARAMETRIC MONITORIN G IS AN ACCURATE AND COST EFFECTIVE ALTERNATIVE FOR DEMO NSTRATING COMPLIANCE Fortunately, th e lack of

f easible CEMs techno lo gy fo r merc ury emi ssi on s at gold mining operati ons is of

fset by th e availabilit y of e stablished, com

prehensive parametri c mo nit oring programs th at can be used to co nfirm th at emission control s are fu nct io ning properly

. T wo examples of

s uccessful parametri c mo nit oring programs fo r demonstrating co mp liance at ore roasting facilit ies are di scussed in the fo llo wing secti ons. A. The Goldstrike Roaster 1. The Goldstrike Roaster is Able to Demonstrate Compliance with Mercury Emission Limitations By Use of Parametric Monitoring Th e Goldstri

ke Mine operates a roaster facili ty which consists of two roasters that share a commo n of

f

- gas cleaning system and a commo n quenching, neutralizat io n and leaching circui t. The roasting process oxidizes th e carbon and sulfide co mpounds in th e ore to facilitate gold recovery
. O xygen, supplied by th e oxygen plant, is added to each of t he roasters to create an oxidizing envi

ronment. Each of the roasters is a two stage, fluidized bed roaster that is permitted to process up to 500 tons per hour. T he fir st stage bed of th e roasters operates at about 1030°F and th e second stage bed operates at about 980°F. T he roasters were designed to operate autogenously and ore is blended for the optimum fuel value of sulfides and carbonates. Coal and fuel oil c an be added to the roaster to provi de additi onal fu el value fo r roasting. Due to the high tem peratures at which th e roasters operate, th e naturally

- occurring mercury f ound in th e ore is vaporized int o gaseous, elemental m ercury . Af

ter roasting, the ore i s quenched, neutralized wi th slaked lime and pumped to th e carbon in leach (CIL) ci rcui t. S ee figure 1 below. T he exhaust fro m each roaster is cycloned, th en treated in th e off

- gas cleaning system before being released to the atmosphere.4811

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- 3877.3 4 Figure 1

– Roaster Ore Circuit

The off

- gas cleaning system

on the roaster consi sts of two gas quenchers, two venturi wet scrubbers, two co ndensers, tw o mist eliminators, a wet electrostati c preci pi tator (WESP), a Boliden Norzinc mercury s crubber, an SO 2 scrubber, a CO thermal oxidizer and a NO X select ive catalyt ic reducti on (SCR) system

. F igure 2 shows the roaster off

- gas system

. E ach roaster has it s own gas quencher, venturi wet scrubber, condenser and mist eliminator. The WESP, mercur y scrubber, SO 2 scrubber, CO oxidizer and NO X SCR are common to both roasters. Figure 2

– Roaster Off

- Gas System

DUST SCRUBBERS (2) OFF-GAS FROM ROASTERS

GAS

QUENCHERS (2)

CONDENSERS (2)

SO2 SCRUBBER WET ESP

MERCURY SCRUBBER CYCLONES

MERCURY TAP COOLING TOWER

CHILLED WATER TANK

CONDENSATE COLLECTION TANK MIST ELIMINATORS (2)

WET ESP DRAIN TANK
CALOMEL AND REAGENT REAGENTREAGENT MIST ELIMINATOR BOOSTER FANS (2)

CO THERMAL REDUCTION SCR NOx REDUCTION TO ATMOSPHERE

SCRUBBER FAN CARB ONIN -LEACH TANKS DRY GRINDING CI RC UI T FROM CRUSHING CI RCUIT

NE UTRALIZATION TANKS CA LC INE QUENCH TANKS ROASTER4811

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- 3877.3 5 a. Mercury

Remov al Mercury v aporized during th e roasting process is captured in the roaster off

- gas system by both physical (condensat io n) and chemical (scrubbing) processes. P hysical capture of mercury i s achieved by lo wering th e tem perature of

t he gas stream

t o less th an 90°F at th e condenser outlet. The gas quenchers, venturi scrubbers and condensers are all cooling processes in th e gas stream

. A s t he tem perature of

t he gas decreases, th e concentration of m ercury in th e gas phase decreases and mercury c ondenses out of

t he gas stream

. T he elemental m ercury i s collected and poured into mercury flasks. The chemical removal process for mercury is comple ted in the Boliden

- Norzinc scrubber. The scrubber uses a mercuric chloride sol ut io n to scrub mercury

f rom th e gas stream , fo rming a mercurous chloride, or calomel, preci pi tate. The calomel is co llected and poured int o d rums fo r subsequent recovery

of the mercury. b. Moni

toring and Mercury

Remov al Effect iveness Goldstri ke mo nit ors a number of parameters wi thin th e off

- gas system

t o ensure th at all mercury c ontrol s are operating and fu ncti oning wi thin manufacturers’ specified ranges. T he mo nit ored parameters indicate how well th e system i s operating. E ach of

t he parameters and specified operating ranges listed in this sect io n are current ly mo nit ored and recorded and are al ready requi

red by Go ldstrike’s Phase I Nevada Mercury C ontrol P rogram (NMCP) permit. Th e current ly mo nit ored parameters that affect mercury are listed below:

● Water flow rate to gas quenchers ● Venturi

scrubbers’ different ia l pressure ● Venturi

scrubbers’ water flow rate ● Gas stream

tem perature at condenser outlets ● Mercury

scrubber inlet gas tem

perature ● Mercury

scrubber head pressure ● Mercury

scrubber mercuric chloride (HgCl 2 ) concentrati on The water flo w rate to th e gas quencher, th e venturi s crubber differential pressure and water flo w rate, and th e condenser outlet tem perature are mo nit ored co nt inuously. T he water flow rate to each of

t he gas quenchers averages approximately 375 to 400 gallo ns per minute, and must be maintained above 60 gallon s per minute. T he different ia l pressure fo r each of t he venturi scrubbers is required to be ma int ained above 35 inches of H 2 O and the water flo w rate is kept above 300 gallo ns per minute. T he condenser gas stream o ut let tem

perature must be maintained below 90°F. The venturi scrubbers remov e part icu late mercury and aid in gas stream cooling a nd th e quenchers and condensers further cool t he gas stream

t o aid in mercury condensat io n. T he cont inuous mo nit oring of th ese devices shows that they are operating wi thin specified ranges, and providing maximum scrubbing, cooling and mercury c ondensat io n . Th ese parameters are th e same as operati ng ranges during stack testing, ensuring th at th e system is operating in the same manner as during annual testing. If any of these parameters fall outside the specified ranges, ore feed to the roasters is suspend ed until the situat io n is corrected. After physical condensati on of mercury, a chemical s crubbing process takes place. T he gas stream

e nt ers th e Bo liden Norzinc s crubber. T he scrubber is a packed co lu mn th at4811

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continuously circulates a mercuric chloride so lut ion which reacts wit h th e elemental mercury i n th e gas stream . The mercuri c chlori de reacts wi th elemental

m ercury to form

m ercurous chloride (calomel). T he important parameters fo r efficient operati on of t he mercury scrubber are the mercuric chlori de concentration in the effluent soluti on, the inlet gas stream tem perature and the head pressure of

t he scrubber. T he gas inlet tem perature is mo nit ored con tinuously a nd maintained below 134°F to ensure th at th e scrubber is operating at th e optimum tem pe rature. The so lut io n exi

ting th e scrubber is tested twi ce daily f or mercuric chlori de concentration to ensure that the mercury scrubber has enough mercuri c chloride in the feed so lut io n to efficiently scrub th e mercury from th e gas stream

. T he mercuric c hloride so lut io n must be above 1.0 gram /Li ter. In a ddi ti on , th e mercury scrubber head pressure, which is an indicat io n of s crubber sol ut io n flow rate, is mo nit ored con tinuously and must be maintained between 1.0 and 9.0 psi. Moni toring th ese parameters e nsures th at th e mercury s crubber is operating efficiently. T hese parameters are wi

thin operating ranges during stack testing and ensure th at th e scrubber is operating at the same efficiency as during annual testing. In summary, th e operating parameters th at Goldstrike mo nit ors on a regular basis are key parameters fo r measuring th e efficiency and operati on of t he mercury

c ontrol s in th e off

- gas cleaning system . Operating each of th ese uni ts within th e optimum ranges ensures th at mercury emissio ns are bein g effect ively controlled. B ecause th ese parameters are mo nit ored regularly and controlled to certain specificat io ns consistent with annual test ing condit io ns, the operati on of th e system

i s known to be reliable and consistent. The annual testing values are representative of day to day operati ons, as shown by the records of the moni tored parameters. Though installing a CEMs fo r mercury would provide addi ti onal data (albeit of

questi onable accuracy and reliabilit y), addi

ti onal mo nit oring is not necessary b ecause th e current ly mo nit ored parameters provi de daily reassurance that the system i s operating properly

. 2. Periodic Testing of Mercury Emissions Using Method 30B would

—if Necessary

—Provide a Superior Basis for Monitoring Mercury Emissions than would CEMs. As discussed in th e preceding sect io n, robust parametric mo nit oring is currently being conducted fo r th e Goldstri ke roaster providing a sound basis fo r ensuring cont inuous mercur y removal and control

p erf ormance. T his peri odic mo nit oring is established, r eliable and proven. For the reasons noted above, mercury CEMs are unproven for application to gold mining roasters and are, in fact, unavailable fro m a regulatory /compliance perspect ive in th at th ere is simply no means current ly available to conduct calibrat io n checks, rendering th e data immediately suspect and unreliable. D ata generated from th e use of CEMs would raise mo re questions th an it w ould provi de useful informat io n. Notwi th standing th e fo regoing, to th e extent th at EPA ma int ains th at something more th an th e parametri c mo nit oring described above and annual stack testing is necessary fo r th e Goldstri ke roaster, a much superi or opti on to CEMs would be quarterly testing using Method 30B. Method 30B does not suffer from the same infi rmi ti es identifie d f

or CEMs; i

t will produce a reliable estimate of emissions using EPA

- approved methods. We hasten to add that we do not believe that such testing is necessary; however, quarterly M ethod 30B testing would clearly be a better alternat ive than mercury CEMs.4811

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B. The Newmont Gold Quarry Roaster Ensures Proper Mercury Control Operation with Parametric Monitoring Newmont’s Refractory

O re Treat me nt P lant (ROTP) also consists of t wo ident ical roasting trains wi

th a unique series of

a irp ollut io n control

d evices. A ft e r th e roasting process, th e effluent gas streams pass th rough Waste Heat Bo ilers, Hot Gas Electrostati c Precipi tators, and th en merge and pass th rough th e fo llo wing seri es of G as Cleaning/Cooling controls: ( 1) a Wash Tower (cooling sprays); (2) Heat Excha ngers (two st ar coolers); (3) Wet Electrostati c Preci pi tators (two units); (4) a Fluorine Remov al Tower; and (5) a Bo liden/Norzinc Mercur y Removal Tower (calomel

scrubber).

Gas stream tem

peratures are mo nit ored continuously to ensure th e proper cooling op eration o f th e Spray Tower and Heat Exchangers. Vol tages of the Wet ESPs are moni tored on a continuous basis to ensure proper operati on of these control

devices. The fe ed to the roaster i s shut off if both of

t hese devices are not in proper operati on. T he mercuric io n concentration of th e calomel scrubber so lut io n is mo nit ored on a daily basis to ensure proper operati on of t he Mercury R emov al Tower. B ased on th e NMCP Phase 1 permit th e mo nt hly average must be maintained between 2.0 and 4.0 g/L. In addi ti on , Newmont’s Phase 2 application proposed to (i) maintain th e chloride io n concentration between 2.0 and 5.0 g/L; (i i) maintain th e tower le vel at 20% to 65% of

c apacit y; and (i ii) bleed calomel f rom t he tower each shift as needed fo r chlorinat io n and e lectrowinning. M oni toring th ese parameters ensures th at th e contro l equi pment is operating properly and consistently wi th t he operati on th at was me asured fo r th e mercury e missio n test, ensuring ongoing stack emissio ns wi th in th e range of

t he annual test r esul ts. The gas stream

i s further dri ed and sent to th e acid plant, where SO 2 is converted to sulfuric acid. T his product acid is sampled on a daily basis fo r mercury concentration. While thi s mercury

i s actually

r emov ed fro m th e gas stream a nd not emit t ed to th e atmosphere, it i s indicat ive of

t he amount of

m ercury t hat makes it p ast th e Mercury Remov al Tower and is another reliable daily indicator of whether the upstream m ercury control s are properly operating. Newmont’s goal

i s to maintain a concentrati on of ≤ 1 mg/L Hg in the sulfuric acid and this level Roa ster

Calc

ine

Cal cine C

ooler Wa ste H eat Bo iler Ho

t E lec tro sta tic P reci pi ta tor Gas Clean in g cooli ng wetESP ( 2 ) fluo rine removal Boli den

- Norzinc Me

rcury Rem ov al

Acid P la nt dr ying tower SO 2 converter tw o stage adsorpti on SO 2 str ip ping to wer

RTO

– CO c onversi on Qu en ch Tank Duco n Sc rub ber

Quen ch W at er At mosphe re

Sl urry to CIL At mo sphe re Preh eat ed Ore

SO 2

SO

2 CO Recir c Burn er Recirc to roaster

Oxyge n Burne r Co mb us tion G as to a tmosphere H 2 O 2 Scru bb er 94% Su lfu ric Ac id Hg , Fe , SO 24811

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- 3877.3 8

is contained in Gold Quarry’s NMCP Ph ase I permit. I f sample resul ts indicate higher concentrations, corrective act io ns are taken to ensure th e proper operati on of t he calom el scrubber and any upstre am devices, and to ensure that the operation of such controls is optimized to reduce mercury emissi ons. I n addi ti on to en suring proper operati on of th e control

e quipment and co mp liance wi

th i ts permit requi

rements, Newmont has an independent business reas on to mo nit or mercury fro m th e acid and maintain mercury l evels at or below th e 1 mg/L target

– it s sales contracts wi

th purchasers of the acid specify that the acid will contain no m ore than 1 mg/L of mercury
. After the acid plant, approximately 50% of th e gas stream i s recycled back to the roasting process. T he remaining gas stream p asses th

rough another Peroxide Scrubber and a Regenerat ive Thermal Oxidizer (RTO) pri or to exit ing th e exhaust stack. D ue to th e numerous and diverse control s and th eir int e rdependency and cri ti cal int eract io ns, along wi th t he diligent continuous and ri gorous mo nit oring th at al ready occurs, it d oes not appear th at an addi ti onal CEMs fo r mercury

w ould improve th e operati on of th ese control s. N or is it l ikely th at mercury emis si on s would be significant ly improved, given th e testing history o f this exhaust stack th at consistent ly shows less th an 5 lbs of m ercury emissi on s per year. An addi ti onal concern would be th e rel iabilit y of

m ercury CEMs in this exhaust gas stream whi ch i s heated up to 1600 deg F pri or to di scharge fro m th e RTO. I t is also quite likely that design mo dificat io ns would be requi red to CEMs th at are currently used in oth er industries to account fo r th e unique chemical com posi ti on of this gas stream

. C. Jerritt C anyon Roaster Periodic Monitoring We understand that NDEP is providing informat io n relevant to moni toring conducted fo r th e Jerritt Canyon roaster.