From: Chuck French/RTP/USEPA/US

To: "King, Heidi R." <Heidi_R._King@omb.eop.gov>

Cc: Amy Branning/DC/USEPA/US@EPA, Paula VanLare/DC/USEPA/US@EPA, Sharon Nizich/RTP/USEPA/US@EPA, Steve Fruh/RTP/USEPA/US@EPA

Date: 04/09/2010 04:39 PM

Subject: RE: Interagency comments under EO 12866 on the Gold Ore Processing

NESHAP Draft NPRM

Hi Heidi,

I recall you also wanted more information on the CEMs. Attached below is a draft chapter on Hg CEMs from a report that NESCAUM is developing. The report is still
draft and is currently undergoing a peer review. Nevertheless, NESCAUM gave us permission to share this draft with you. Please keep in mind that this is a preliminary draft report that is currently under review by EPA, and that the text
and conclusions are subject to change before the final report is released. They expect the final report to be completed by July 2010.Let me know if you have questions.

Thanks.

Chuck

(See attached file: Draft

‐ chapter

‐ by

‐ NESCAUM

‐ on

‐ CEMS

‐ April

‐ 2010.doc)Draft Under Development – Review Draft – by NESCAUM – April 2010

Preliminary DRAFT chapter on CE MS – by NESCAUM – for Review



## 3 Continuous Mercury Monitoring Technologies

There are two forms of continuous mercury m onitors (CMMs), devices that continuously sample mercury emissions and provide a measur ement of mercury emissions over time. They

are

• Analyzer-based mercury continuous em ission monitoring systems (CEMS); and

• Sorbent traps (STs).

Hg CEMS are analyzers that continuously sample the stack gases and provide an indication of mercury emissions concentration in the stack with in minutes of the gas being sampled. In this respect, the Hg CEMS provi de information to the operator about mercury emissions on a near real-time basis, or at least in a timely fashion that provides emissions data for a particular hour or day. The total mass emissions rate of mercury is determined by multiplying the measured concentration of mercury in the flue gas times the measured flue gas
flow rate.

Sorbent traps provide an indication of cumu lative mercury mass emissions over a period of time that could be hours, days, or even week s. Gas is pulled through a set of sorbent media traps filled with sorbent that captures mercury. The gas flow rate draw n through the sorbent is varied at a rate that is in propor tion to the flue gas flow rate, a nd must be isokinetic if there is significant particulate. After a period of time, the sorbent traps are removed and replaced. The used sorbent traps are analyzed for total merc ury captured by the ST. This can be used to estimate the average mercury emission rate over that period of time.

This chapter focuses on methods that are intended for permanent installation and continuous monitoring of mercury emissions. For continuous monitoring and reporting for the purpose of regulatory compliance there are requirem ents imposed that assure the reliability and accuracy of the measurement. The same technologies as discussed in this chapter have been used for short term test programs spanning hours, days, or even weeks. Many of the requirements that are discussed in this chapte r that are necessary for a method designed for compliance purposes would not be necessary fo r the same method when intended for a shortterm test.



### 1.1 Hg CEMS Technology Overview
There are currently two prin cipal suppliers of Hg CEMS technology, ThermoFisher
Scientific and Tekran Instruments. These two suppliers have supplied nearly every Hg CEMS ordered for utility power plants. This chapter, therefore, focu ses on the technologies offered by these two companies.

Each company has been working to addre ss the specific challenges associated with measuring mercury in flue gas. Some of these challenges include:

• The presence of mercury in small concen trations in power plant flue gas. Mercury is present in much smaller amounts than typical criteria pollutants, i.e., concentration measured in parts per tr illion versus parts per million. Although ambient monitors are capable of measuri ng mercury concentrations to much lower levels than what is experienced in power plant flue gases, some of the particularDraft Under Development – Review Draft – by NESCAUM – April 2010

characteristics of mercury and power plan t flue gas – such as interferences and reactivity - make the concentr ation of mercury in power plant flue gas especially
difficult to measure at such low levels.

• Ionic mercury is a reactive material that tends to react with or adhere to other materials, and thereby may be lost in sample handling without special precautions.

• Elemental mercury tends to form an amal gam with metals. So, to avoid loss of sample, metal surfaces in the sampling sy stem must be coated and temperature
maintained 180 0 C.

The challenge faced by the Hg CEMS suppliers has been to design a monitoring system
that is reliable while also a ddressing the above difficulties that are unique to mercury measurement in flue gas.



### 1.1.1 Hg CEMS Suppliers



### 1.1.1.1 ThermoFisher Scientific Hg CEMS

ThermoFisher Scientific has sh ipped more than 450 Hg CEMS. 28 Figure 3-1 shows how the ThermoFisher Hg CEMS is configured. Th e key components are th e Sample Extraction & Conversion system, the Probe Controller, th e Cold-Vapor Atomic Fluorescence (CVAF) Analyzer, and the Calibration System.

Sample Extraction and Converter Flue gas is sampled from the stack by the pr obe and is typically diluted at a 40:1 ratio with air (or in some cases with ni trogen). Within the probe is a converter that converts oxidized mercury, which is mostly in the form of HgCl 2 , to elemental mercury. Therefore, all of the mercury sent into the lines to the analyzer is in the form of elemental mercury. This makes the sample somewhat easier to trans port and also puts the mercury in a form that the analyzer is capable of measuring. The sample line from the probe to the analyzer must be heated to 120 0 C (248 0 F) in order to ensure that sample integrity is preserved. The probe also provides the means to convert elemental Hg gas from the calibrato r to oxidized mercury fo r the purpose of system integrity checks.

Probe Controller The Probe Controller sends signals to the probe that control the oxidi zed Hg to elemental Hg converter and the elemental Hg to oxidized Hg converter, nitrogen supply and other functions performed within the probe. It also contro ls probe and sample line temperature.Draft Under Development – Review Draft – by NESCAUM – April 2010

Figure 3-1. ThermoFisher Instru ments Mercury Freedom System. 28

CVAF Analyzer Within the analyzer the sample is conti nuously measured using CVAF. In the CVAF method, free mercury atoms (elemental mercury) in a carrier gas are ex cited by an ultraviolet light source. The excited mercury atoms re-ra diate their absorbed energy (fluoresce). The fluorescence intensity is related to the amount of mercury present. The technique is sensitive, selective, and linear over a wide range of concentrations; however, molecular gases (such as oxygen and nitrogen) present in the carrier gas quench the fluorescence signal, which reduces instrument sensitivity.

The analyzer provides a measure of total mercury and cannot speciate mercury on its own. In order to measure mercury speciation, it is necessary to take two measurements – one with the converter in the probe operating (for total mercury) and anot her with the converter bypassed and with HgCl 2 removed from the gas (to arrive at elemental Hg). The difference between the amount of total mercury and the amount of elemental mercury equals the amount of oxidized mercury. When used for regulatory pur poses, CEMS are not typically operated in speciating mode, but rather used to measure total mercury only.

The gas in the analyzer is maintained at a vacuum to suppress quenching and improve sensitivity. Sensitivity of the analyzer’s CVAF measurement can be improved roughly five-fold by using nitrogen as the dilution gas in the probe rather than air beca use oxygen has a greater tendency to quench the atomic fluorescence than nitrogen. 28 Therefore, for low concentration measurements (less than 2 μg/m 3 ), nitrogen dilution gas is re commended by the manufacturer.Draft Under Development – Review Draft – by NESCAUM – April 2010

The analyzer has digital outputs for various data protocols. The advantage of digital output is that, with the high de gree of linearity expected fr om the CVAF analysis method combined with digital output, good linearity over a broad dynamic range is expected.

Calibration Gases and Standards It is periodically necessary to verify the accu racy of the Hg CEMS using calibration gases
that have known concentrations of both elementa l and oxidized mercury. As an alternative to commercial, bottled calibration gases, the Hg CEMS manufacturers have been working with EPA and NIST on traceable methods for the instruments to produce elemental mercury calibration gases utilizing known relati onships for mercury vapor pressure. 62 The elemental mercury calibration gas generators for both supplie rs operate by carefully controlling a sample o Hg and dilution gas to a specific temperature an d pressure that is determined by the desire vapor pressure. In this manner, the mercury concentr ation of the gas exi ting the calibration gas generator is determined by the mercury vapor pr essure relationship. The calibrator output is
NIST-traceable. f
d

It is important that the Hg CEMS measure all forms of mercury accurately. A system integrity check is performed to verify the accurate measurement of oxidized mercury. For system integrity checks it is necessary to have oxidized mercury calibration gas provided to the probe tip where it is drawn through the probe and through the converter and to the analyzer. To do this, the ThermoFisher Hg CEMS adds chlori ne to the elemental Hg calibration gas at the probe in order to convert the elemental mercur y from the elemental mercury gas generator to oxidized mercury. It is necessary to have a bottl e of chlorine gas at th e probe for this system integrity check. The probe has a converter that converts the oxidized mercury back to elemental mercury, which is then transported to the analy zer for measurement. So, for system integrity checks on ThermoFisher’s Hg CEMS, elemental mercury calibration gas is oxidized with chlorine, sent through the probe tip, and then the oxidized mercury is converted back to elemental mercury before leaving the probe.



### 1.1.1.2 Tekran Instruments Hg CEMS

Tekran instruments has sold roughly 175 Hg CEMS to electric utilities plus additional systems sold for the purpose of mercury monito ring for control technology test programs, for research or for other purposes. The Tekran Instruments Hg CEMS, shown schematically in Figure 3-2 , has some similarities and some significant differences with the ThermoFisher Hg CEMS; these will be discussed below.

Sample Extraction The Tekran probe extracts sample from the st ack and dilutes it with air at roughly a 30:1 ratio. The probe is heated. The portion of the probe that is in the gas stream is made of Hasteloy (a corrosion-resistant metal) coat ed with a thin quartz layer. Th e probe body is made of coated
stainless steel. The filter is titanium. Unlike the Thermo Fisher analyzer, which conditions the sample at the probe, the sample is sent in its sampled form to the sample conditioner, which is near the analyzer. The sample line from the pr obe to the sample conditioner is maintained at
about 180 o C (356 o F) to avoid loss of ionic or elemental mercury or pl ating out of selenium. If selenium were allowed to build up in the sample line, the elemental mercury would be lost in the line because elemental mercury reac ts with condensed selenium. An unheated line is also used in some cases to carry air for the probe. The unheated line does not carry sample or calibration

gas.Draft Under Development – Review Draft – by NESCAUM – April 2010

Figure 3-2. Schematic of Tekran Hg CEMS. 63

Sample Conditioner The sample conditioner converts the oxidized mercury to elemental mercury using a pyritic converter. Also, acid gases, which could induce mercur y recombination reactions and could adversely affect analyzer reliability, are scrubbed out using deionized water. The conditioner therefore provides an acid-gas free stream with elemental mercury and other gases to the analyzer. The sample conditioner facilitate s speciation by providing one of two gas streams to the analyzer: 1) 100 % of the flue gas mercury after ha ving converted any ionic mercury to elemental mercury; and 2) a sample with the i onic mercury removed so that only the elemental mercury from the flue gas remains. Similarly to the ThermoFisher analyzer, ionic mercury is determined in the Tekran analyzer by subtrac ting the elemental mercury concentration from the total mercury concentration.Draft Under Development – Review Draft – by NESCAUM – April 2010

Analyzer
Both the ThermoFisher instrument and the Te kran instrument use CVAF for analysis. However, Tekran’s analyzer uses a gold amalgam to collect and concentrat e the mercury prior to analysis. This also permits the mercury to be re -released into an inert gas (argon) atmosphere. The argon gas ensures that fluores cence is not quenched by molecu lar gases that are present in the boiler flue gas. The gold amalgam concentr ation method and the use of inert gas help the analyzer to provide high sens itivity. The analyzer consumes argon gas; one tank of argon is expected to last roughly 6 weeks. Like the Th ermoFisher analyzer, the Tekran analyzer produces an output concentration of total mercury. Speciat ion is performed in concert with the sample
conditioner.

The analyzer has digital outputs for various da ta protocols. The high degree of linearity expected from the CVAF analysis method combined with digital output provides good linearity over a broad dynamic range.

Calibrators The Tekran Hg CEMS has two calibrators – one for elemental mercury and another for ionic mercury. The calibrator produces a gas st ream with a known concen tration of elemental mercury in a similar manner as the ThermoFi sher analyzer – by carefully controlling the temperature and pressure of a sa mple of mercury and dilution gases to provide a gas with a wellcontrolled elemental mercury vapor pressure.

Tekran also has an oxidized mercury calib rator, the Model 3315, which generates a defined mixture of air and water vapor and mercur ic chloride by evaporating a controlled amount of aqueous mercury chloride solution of known concentration into a carefully controlled gas volume, as shown in Figure 3-3 . Since this approach starts with oxidized mercury in a NISTtraceable aqueous solution, there is assurance that only oxidize d mercury is produced. Also,
since the solution and the hardwa re can be NIST-traceable, a NI ST-traceable amount of oxidized mercury can result. This method of generating oxidized mercury does re quire transporting the oxidized Hg from the generator, up a heated um bilical to the probe ti p, through the probe, and back through a heated umbilical to the sample conditioner for the system integrity check.Draft Under Development – Review Draft – by NESCAUM – April 2010



### Mixing Chamber DI Water 1.0 μ g/ml HgCl 2



### Dry Air Misting Device Precision

MicroPumps

Mass Flow

Meter 

### Hg 2+



### Calibration Gas

Figure 3-3. Simplified diagram of the Tekr an Model 3315 Ionic Mercury Calibrator.



### 1.1.1.3 Other suppliers of Hg CEMS
Three other suppliers of Hg CEMS have b een identified: PS An alytical, Cemtrex and Ohio Lumex. These systems have primarily b een used for temporary testing rather than permanent Hg CEMS. PS Analytical’s Sir Ga lahad mercury CEMS uses an amalgamation method combined with CVAF, the same general method as the Tekran CEMS. The Cemtrex and Ohio Lumex CEMS analyze the gas using the met hod of atomic absorption spectroscopy (AAS). In AAS, a light source is scanned at a wavelength where elemental mercury vapor is expected to absorb light. The amount of light that is absorbed is related to the amount of mercury in the light path.

These analyzers may see greater use in the future. However, because of the limited operating experience in coal-fired boilers with these products, this chapter focuses on the results achieved so far with the more widely us ed ThermoFisher and Tekran analyzers.



### 1.1.2 Approximate Costs of Hg CEMS

Both ThermoFisher and Tekran confirmed that the initial cost of a Hg CEMS is typically on the order of $500,000. 28,64 These costs include

• Approximately $200K for system including startup and training;

• Another $200-$300K for site preparation.
Costs will vary somewhat from this $500,000 figure. The heated umbilical alone is a significant cost item that might cost anywhe re from about $10,000 for a short stack to over $100,000 for a very tall stack. Other factors that impact cost in clude the Hg CEMS located at the site, site conditions, and local climate.Draft Under Development – Review Draft – by NESCAUM – April 2010

Typical annual operating costs are more diffi cult to estimate, because there has been limited experience with the learning curve associ ated with the use of Hg CEMS and the actual quality assurance (QA) and reporting require ments are not certain. Midwest Generation estimates that it takes three times as many labor hours to support the Hg CEMS as traditional
NOx and SO 2 CEMS. 65 Using US EPA’s CEMS cost estimating tool, there is roughly $20,000 in annual plant labor charges for a typical utility CEMS with NOx, SO 2 , opacity, and flow, and
total annual costs incl uding Relative Accuracy Test Audits (RATAs), reporting, parts and consumables, and other costs of about $65,000. The EPA CEMS cost model 66 would sugge that Midwest Generation’s annual labor charges ha ve been in the range of about $60,000 for the Hg CEMS. Due to the learning curve with thes e instruments, experience to date should not represent long-term requirements. st

er



### 1.1.3 Approximate number of units installed/in operation
n shipped to date. Of these, m

e

n’t

n

s

usage of Hg
CMMS and these data are summarized in Table 3-1 . In these states, 116 CEMS and 44 ST system n of According to ThermoFisher, long term, th e operator requirements are expected to approach those of the dilution CEMS that most utilities currently have installed for NOx and
SO 2

. 67 This is consistent with information from Tekran that labor co sts should ultimately approach those of th e existing NOx and SO 2 CEMS; but that total annual costs will be somewhat higher when including RATAs, reporting, parts and consumables, NIST traceability and oth costs for a total of about $100,000 or more. 68 These estimates are based upon the vacated Part 75 requirements of the Clean Air Mercury Rule (CAMR). The actual costs of monitoring will depend upon the requirements of any future monitoring rule.

Accor ding to ThermoFisher, over 450 Hg CEMS systems have bee

ore than 160 systems were installed dire ctly by Thermo Fisher, and the balance of the Hg CEMS were installed by CE MS system integration companies – other companies that purchase the analyzer from ThermoFisher and in stall it on the customer’s site. Because th manufacturers, ThermoFisher and Tekran, sell sp are parts, provide service, and in many cases monitor instruments remotely, they can estimate the number of Hg CEMS in operation. Of the total 450 Hg CEMS, ThermoFisher estimates that about 375 are actively in operation in the US. 28 About 75 of the ThermoFisher systems are not activ e at least in part because some owners do currently have a need to mon itor mercury emissions and are c hoosing to avoid the cost of operating the systems. According to Tekran, of the 175 systems sold, approximately 140 are i operation, 100 have completed RATA testing. The balance of the systems represent later order that are still in the proces s of installation and startup. 68

In 2009, NECAUM surveyed nine states and one city as to the purchase and

s had been purchased. Most of the CEMS (73%) were installed and operating, but only a third of the ST systems were inst alled and operating. Half of the states required the collectio Hg emissions data and information on the availability of the CMMs.Draft Under Development – Review Draft – by NESCAUM – April 2010

Table 3-1. NESCAUM 2009 survey of Hg CMMs in nine states and one city.

Data Summary
Number of States Surveyed 9

Number of Cities Surveyed 1
States/city collecting Hg data 5

States collecting monitoring

reliability/availability data 4

Hg CEM Prevalence

CEMs Purchased 116

CEMs Installed 99 CEMs Operating 85

ST Prevalence

STs Purchased 44

STs Installed 20 STs Operating 14 Number of units sold per vendor:

Thermo Fisher 34+

Tekran 9+

Apex 5

Frontier Geosciences 1 Monitors' First Year of Use

2006 3

2007 1

2008 41+

2009 28+

A CMM being active does not mean that th e company is reporting data. The reason many companies operate Hg CMM systems (even w ithout a current requirement to operate them or to report data) is because of the anticipated need to do so in the future and the benefit gained from the experience of operating them prior to facing the requirement.

With few exceptions, RATA tests and other tests such as system integrity tests have been performed for the purpose of verifying that the systems met their contractual performance requirement rather than under an emissions reporting requirement imposed by a regulation. Therefore, the results of these tests are not pub licly available unless th ey were published in a paper or other forum. Some of these published results will be shown later in this chapter.



### 1.1.4 Operating Issues of Hg CEMS
Although ambient mercury analyzers have b een available and operating well for many years, Hg CEMS for power plant or other co mbustion exhaust gases are new. There are numerous challenges in accurately and reliably measuring mercury emissions from power plants that do not exist for ambient analyzers. These include:

• Transporting the sample from the stack to the analyzer while preserving sample integrity;Draft Under Development – Review Draft – by NESCAUM – April 2010

• Measuring small amounts of mercury in the presence of large amounts of combustion gases that may inte rfere with the measurement;

• Measuring mercury that may exist in multiple chemical forms;

• Having the means to verify the accuracy of the measurement for the purpose of assuring that the instrument is pr oviding reliable measure of emissions compliance; and

• Doing all of this while having a system that is not unduly expensive or difficult for a power plant to use under the harsh industrial conditions at a power plant.

The suppliers of mercury analyzers have made great progress in addressing these issues. The following paragraphs examine the key issues relating to operation of Hg CEMS, including:

• Reliability;

• Calibration and NIST traceability;

• Measurement bias and bias adjustment factor;

• Accuracy/precision at low concentrations; and

• Availability/data substitution.



### 1.1.4.1 Reliability
Because Hg CEMS are fairly new devices, there is reasonable concern regarding the reliability of the devices for power plant applic ations. In some cases product development has been occurring concurrently with implementation of Hg CEMS at power plants, as challenges associated with these applications have been encountered and design changes implemented to address these challenges. Rec ognizing that these systems have been under development and that some of the problems encountered a few years a go have been addressed, the focus here will be on issues that may continue to have an impact on reliability.

Umbilical Failure The umbilical is the heated sample line(s) from the probe to the analyzer or sample conditioner. It is often several hundred feet long. Failure of the umbilicals has been a problem. Dominion Generation stated that 5 of 13 umbilicals on their Tekran systems installed in Illinois
and Massachusetts had failed. 69 These failures are mostly due to overheating. Midwest Generation noted similar experiences with the umbilicals to their ThermoFisher analyzers
installed on boilers in Illinoi s and Pennsylvania, with 6 of 13 umbilicals failing. Midwest Generation also noted that there were appr oximately 50 umbilical failures industry-wide. 65 T is roughly consistent with other sources. Tekran stated that about 10% of umbilicals have failed which has led to new designs for umb ilicals with better temperature control. 64 This is consistent with information from Dekoron/Unitherm, the pr imary manufacturer of these umbilicals for bo Hg CEMS suppliers, who reported a failure rate of 8.4% . 70

The causes of umbilical failur his

,

th

es have vari ed. According to Dekoron/Unitherm, about
half of

o the failures were field repaired, the balance required repl acement. In some cases there was an installation error, as installers were not accustomed to in stallations of se veral hundred t a thousand feet of this type of heated and insulated sample line. Failure modes varied from leads being pulled apart during in stallation, to short circ uit of heaters, and in a small number of cases,Draft Under Development – Review Draft – by NESCAUM – April 2010

fires. Every one of the cases in which there were fires was the result of faulty installation (i.e., no ground fault protection despite recommendation by the manufacturer and requirements of the National Electric Code). The other causes of the failures ranged from improper installation to incomplete information at the time of design, to defective heater elements (that were ultimately replaced by the manufacturer), to lack of individual and high lim it temperature control (a heater controller design issue). To address these causes, there have been design changes to eliminate the failure modes, education of installers to re duce risk of damage duri ng installation or failure upon start up, and education of all parties i nvolved to improve specification, design and
installation to reduce risk of failure. 70 In addition, many facilities have installed redunda umbilicals to provide a backup in the event of an umbilical failure.

As a result of the improvements made by the various companies involved in the nt

manufa ures

ercise the en tire sampling, conditioning, analysis, and
calibrat nts will

y

80-

ure

h

h

explored more fully in th following section.

t emissions monitors provide measurements , NIST standards. This is done through regular
calibrat

erformed using a ST. EPA has established interim
traceab
bined cture, supply and installati on of the umbilicals, it is antic ipated that umbilical fail
should be less troublesome in the future.

System Integrity Tests System Integrity Tests ex ion gas generating system. A shortcoming in any one of the associated compone result in a failed System Integr ity Test. According to Dominion, 69 this was the most frequently failed QA test. Also, unlike the calibration tests, the system integrity test requires use of oxidized mercury calibration gases, which are more difficult to assure because oxidized mercur is so reactive that it can be lost easily in sample streams after leaving the calibration gas generator (such as in the Tekran instrument), or the conversion rate of elemental to oxidized Hg in the probe (in the case of ThermoFisher) may be difficult to verify. Dominion recorded 150 hours of down time per Hg CEMS in 2008 as a result of failed System Integrity Tests. 69

Dominion has found that it is benefi cial to perform the system inte grity test manually to ens that a technician can observe the physical proc ess and identify problems during the test, whic has proven to be helpful in avoi ding false failures of the test. 71 This is consistent with the experience of Midwest Generating, who reported th at their Hg CEMS do not have a good record at passing System Integrity Checks. 65 At this point, it appears that the equipment associated wit the system integrity checks may not yet be to th e point where the test can be performed in an automated fashion with high reliability. This af fects how the tests can be scheduled so that a
technician will be available to monitor the test. 71

The difficulty of system integrity tests ar e closely related to development of NIST traceable oxidized Hg standards, which will be e



### 1.1.4.2 Calibration and NIST Traceability

For com pliance purposes it is important tha with accuracy that can be traced back to verifiab le ion checks of the Hg CEMS against gases of a known mercury concentration.

Elemental Mercury Calibration Standards Traceability of the elemental mercury measurem ent of each Hg CEMS is to be p calibration gas generator that is certi fied by NI ility protocols for elementa l gas generators, which provide procedures to: “(1) establish the quantitative output of elemental Hg genera tors; and (2) determine the expanded, com uncertainty values of the gas standards produced by the elemental Hg generators.” 62 TheDraft Under Development – Review Draft – by NESCAUM – April 2010

protocol also specifies the maxi mum allowable uncertainty for the elemental Hg gas standards. Elemental mercury is also available as a bottled gas, but EPA has not yet established traceabilit protocols for gas cylinders.

NIST certification is achieved through an unbroken chain of comparison of one eleme mercury calibration gas generator to another and ev entually to a NIST verified standard. An y

ntal

interim

a

or).

gas

as

as he NIST Prim e gas generator needs to be periodi rime

bility protocol was promulgated July 1, 2009. 73

The int rovides procedures for: “(1) establishing the
NIST t

oxidize
l 2 he

d traceability protocol has been developed to provide for this and was promulgated by US EPA on July 1, 2009. 72 In this protocol, NIST uses isot ope dilution inductively coupled plasm mass spectrometry (ICP-MS) as the fundamental measurement to certify the NIST Prime elemental mercury calibration ga s generator (a Tekran Model 3310 Calibration Gas Generat This NIST Prime calibration gas generator is used to certify Vendor Prime calibration gas generators. The Vendor Prime calibration gas genera tors are used to certify User calibration generators that are sent in to the vendors for certification. In cases where a user cannot send in their calibration gas gene rator to the vendor for certification, a Field Re ference calibration g generator, which is certified against the Vendor Pr ime calibration gas generator, can be used at the user’s site to certify the Us er calibration gas generator. Figure 3-4 shows how this approach produces an unbroken chain of measurement comp arisons for certification back to a NISTverified standard.

Certification of gas generators is valid fo r a period of time, and each calibration g generator needs to be periodica lly recertified. T cally recertified agains t ICP-MS (or another method determined by NIST), Vendor P gas generators are periodically sent to NIST for recertification agai nst the NIST Prime gas generator and User and Field Refere nce gas generators need to be periodically recertified against the Vendor Prime gas generators. As a result, this will become a regular requirement for all companies involved in mercury monitoring.

Oxidized Hg Calibration Gas Standards The interim oxidized Hg NIST tracea erim oxidized Hg gas traceability protocol p raceability and quantitative pe rformance of key components of HgCl 2 generators; (2) determining the uncertainty contributed by each of these components; and (3) calculating certified output concentrations and expanded, combined uncertainty values for the gas standards produced by the generators.” 62 Oxidized mercury must be used for system integrity checks. There are no gas cylinders for oxidized me rcury, so the two CEMS manufacturers have developed different generators for oxidized Hg calibration gas.

The ThermoFisher Hg CEMS starts with el emental mercury, transports it to the probe, oxidizes it to HgCl 2 in the probe using chlorine that is added at that location, and sends the d Hg sample to the probe tip. Certif ication of the ThermoFisher oxidized mercury generator is related to the elemental gas generator. 74 The combined uncertainty of the HgC
calibration standards is calculated based on the un certainty of the elemental Hg generator, t water vapor dilution (if applicab le), and the chlorine dilution. In the interim oxidized Hg protocol, the oxidation efficiency of Thermo sy stems is not included in the overall combine uncertainty calculation. However th e apparent percent conversion of elemental Hg to mercuric chloride is calculated as part of the periodic QA (data quality) assessments. 75

For the Tekran Model 3315 oxidized mercury calibrator that uses an evaporative gas generator, NIST traceability may be achieved in a different manner because NIST-traceableDraft Under Development – Review Draft – by NESCAUM – April 2010

solution ed

g actual s are available and it is possible to verify the precision of the metering pumps, etc., us in the device. For a reason that is not clear, comparisons of this type of oxidized Hg gas generator (Tekran 3315 or any othe r evaporative type) against elemental gas generators have shown a fairly consistent difference of about 8% to 9%, with the ionic calibrator always producing a lower level. Because of the consistency of this difference, this type of oxidized H calibration gas generator can be certified by NIST. 76 This approach does not involve an measurement to verify the output concentration, but relies on the calibrated, theore tical value.

NIST ID -ICP Mass Spec

NIST Prime gas
generator

Vendor 1 Prime gas
generator Vendor 2 Prime
gas generator

User F gas
generator User C gas
generator User A gas
generator User D gas
generator Vendor 1

Field Reference gas

generator Vendor 2

Field Reference gas

generator NIST

User B gas
generator User E gas
generator

Figure 3-4. General approach for elemental mercu ry calibration gas generator certification.



### 1.1.4.3 Measurement Bias and Bias Adjustment Factor

M),

ents (up or down) may be
made.

ances in the market, bias adjustments are made up, but not
down. up so

t

nces or to When a measurement device indicates a diffe rent value than a reference method (R
and that difference is consistent, the difference is regarded as bias . To correct for this difference and make the reported values consistent with the RM, bias adjustm 40 CFR Part 75 monitoring requirements require such adjustments, but Part 60 monitoring requirements do not.

When compliance is achieved under a trad ing mechanism, where the measurement provides the “currency” used in the allowance ma rket and where an excess in emissions can be made up through purchase of allow That is to say, if the RM shows a higher valu e than the monitor, the bias is adjusted that the reported emissions are higher than would otherwise be indicated by the monitor. But, on the other hand, if the RM shows lo wer emissions than the monitor, a downward bias adjustmen is not made. This is how the bias adjustment was made under the Part 75 monitoring requirements of the CAMR, which have been vacated. However, under a compliance mechanism where trading is not an option there may be an argument to make bias adjustments both ways rather than one way. This is because th ere is no ability to sell excess allowaDraft Under Development – Review Draft – by NESCAUM – April 2010

purchase allowances that are needed. The potenti al problem if there is no requirement for low bias is that it could potentially open an opportunity for sources to deliberately adjust the Hg CEMS to read below the reference method, while staying marginally within the percent relative accuracy requirements wh en performing a RATA. This could result in under-reporting
of emissions. 77

The issue of bias adjustment was raised in testimony before the Illinois Pollution Control Board by representatives of electric utilities. 69 The Illinois EPA subsequently agreed to remove bias adjustme 78 to adjust
ir

nts from their rule. However, for the most part th e Illinois utilities are complying with a p
is is a
in
ents is

w ry concentrations because some air pollu tion control systems (or combinations of air removal of mercury that can thermore, some states have required
90% re
oth

ire system – probe, samp le line, sample conditioning, etc., in the presence
of flue

, and an accuracy that ha s a relatively steady offset that is generally
under 0 ws ercent reduction requirement or altern atively with a technol ogy-based standard and therefore have been given the opti on of quarterly stack tests rather than Hg CEMS. So, th
different situation than would exist with an annual mass emission limit where the argument favor of bias adjustments is stronger. As a resu lt, the argument in favor of bias adjustm not as great under Illinois’ rule.



### 1.1.4.4 Accuracy/Precision at Low Concentrations
Accurate and precise mercury measurements are becoming increasingl y important at lo

mercu polluti on control systems) are cap able of producing high percent result in emissions concentrations well below 1.0 μg/m 3 . Fur moval of mercury from flue gases. Accur acy relates to how close the measurement is to the actual number. Precision relates to how repeat able a measurement is at a given level. B qualities are desirable.

Because the CVAF method is capable of measur ing mercury concentrations to levels far lower than what is experienced in the flue gas, as demonstrated in its use in ambient monitoring, the concern regarding accuracy and precision at low concentrati ons is driven by concern about the reliability of the ent gas. Also, there is con cern about the ability to verify these against a RM, such as Ontario Hydro or Method 30B (STs), which also is likel y to have poorer relativ e accuracy and precision
at lower concentrations.

As demonstrated in Figure 3-5 , Hg CEMS have demonstrated the ability to measure mercury concentrations well below 1.0 μg/m 3 and to agree with the Ontario Hydro Method (the RM) measurements within about 0.09 μg/m 3 . The trend shown indicates good precision when compared against the RM .10 μg/m 3

. Figure 3-6 , which shows data taken from a stack with a wet scrubber, sho that good agreement between Hg CEMS and STs ha s also been achieved at levels well under 1.0 μg/m 3

.Draft Under Development – Review Draft – by NESCAUM – April 2010

Figure 3-5. RATA results at low mercury concentrations. 64

Figure 3-6. Low level Hg CEMS accuracy check against sorbent traps on a stack that follows a wet scrubber,
or wet stack. 64

Because the absolute difference between the RM and the Hg CEMS at low concentrations may be a significant percenta ge of the measurement due to low absolute values of the measurement, this can be a significant issue when making bias adju stments. In the absence of bias adjustments, the concern may be less critical. However, with regard to certifying accuracy under a RATA, if measurements are expected to be well under 1.0 μg/m 3 , as shown in Figure 3-5 and Figure 3-6

, then accuracy requirements (expressed as within X% or Y μg/m 3 ) will need to be considered, so
that the allowed error band at these low levels is sufficiently large that well-running instruments will pass their QA requirements, yet not so gr eat as to make the reported measurement meaningless. In the original requirements under CAMR, the re lative accuracy requirements did
take this into consideration and had different provisions under 1 μg/m 3

.



### 1.1.4.5 Availability and Data Substitution
For Hg CEMS used for compliance under a trad ing system, there are strict requirements for both availability and data subs titution. Availability is a m easurement of the number of hours in an operating period the device is providing reliable data. Data substitution is sometimes required for periods in which a monitored facil ity is operating, but the emissions monitoringDraft Under Development – Review Draft – by NESCAUM – April 2010

device is not providing reliable data (not available). Data substitution introduces assumed emissions data for the period of time when the monitoring device is not available. The monitoring requirements under the Clean Air Merc ury Rule required 75% data availability. Even absent trading, due to the variability in mercury emissions, there is an argument for having high data availability. Mercury emissions are sensitive to many fa ctors that can vary routinely for a power plant, such as furnace oxygen (thr ough its impact on fly ash carbon), soot blowing, coal mercury levels and other factors. Figure 3-7 shows results of a RATA at Nebraska Public Power’s Sheldon Unit 2. Measured mercury concentr ations varied by more than a factor of two over the period of the RATA using Hg CEMS (show n in figure as HgT) versus sorbent traps as the reference method (shown as 30B). As a re sult, data substitution can be inaccurate and periods of lost data should be minimized.

There are several factors th at affect Hg CEMS availa bility, including the following.

• Stringency of Regulation – If QA testing re quirements are stringent, then there is likely to be more down time since failure of a QA test will require troubleshooting.

• Technician Skill Level – This will vary from plant to plant. The higher the skill level of the technicians, the faster they will be able to restore an instrument to
service in the event of a failure.

• Priority of Preventive Maintenance (PM) Program – Is the PM program at the plant a management priority that ha s adequate resources? If not, then maintenance in general for all equipment will be poor and uptime will suffer.

• Spare Parts Stocking – If spares are on ha nd, the instrument can be restored to
service faster than if parts must be ordered.

According to ThermoFisher, customers that are conscienti ously operating and maintaining the equipment, even with no current reporting requirement, have been able to keep the instruments operational about 90-98% of the time. 28Draft Under Development – Review Draft – by NESCAUM – April 2010 HgT = Total Mercury from Hg CEMS CEM Ave = average Hg CEMS reading during sorbent trap sample period

30B = Sorbent Trap measurment run diff = the difference between CEM Ave and Sorbent Trap

allowed = allowed difference for RATA 9 run mean difference = average difference for nine RATA runs

Figure 3-7. Nebraska Public Power Sheldon 2 RATA results. 79

Availability is a concern for new technol ogy. Although few states require reporting of availability, Massachusetts did reque st that the coal plants in Massachusetts report availability of their Hg CEMS. As shown inDraft Under Development – Review Draft – by NESCAUM – April 2010

Table 3-2 , the Hg CEMS at the Brayton Point stati on reported availability ranging from 88% to
94%. 80 Mount Tom generating stati on reported 98% availability. 81

Strictly speaking, the reported availability statistics inDraft Under Development – Review Draft – by NESCAUM – April 2010

Table 3-2 for Hg CEMS in Massachusetts are not subj ect to the Part 75 requirements of CAMR because those requirements were vacated when the CAMR was vacated. Also, there are some aspects of the original Part 75 CAMR rule that have since evol ved out of technical necessity, particularly with regard to the move to on-site calibration gas generato rs that will be NISTtraceable rather than use of NI ST-traceable compressed gas cylinders. The reported data are not QA-tested by the Massachusetts Department of Environmental Protection (DEP) in exactly the same manner as US EPA would have done under a Part 75 requirement because US EPA – who has the capability to perform Part 75 data QA - lost the authority to perform data QA when CAMR was vacated. According to the Mass achusetts Department of Environmental Protection, 82 the Massachusetts requirements under 310 CMR 7.00 et al. are otherwise identical to those of the now-vacated Part 75 CAMR requi rements. The units in Massachusetts must undergo the same daily calibration checks, weekly system integrity checks, quarterly linearity checks, RATAs and other requirements of the now vacated Part 75, and these availability statistics and the good quality emissions data being generated are a stro ng indication of the industry’s efforts and ability to operate Hg CEMS.Draft Under Development – Review Draft – by NESCAUM – April 2010

Table 3-2. Availability of Hg CEMS at Dominion Brayton Point power plant in 2008. 79

Quarter 1 Quarter 2 Quarter 3 Quarter 4 Overall Operating Hours 1,536 2,076 2,102 2,159 7,873
Out of Service Hours 96 223 87 52 458
Unit 1 Availability, % 93.7 89.3 95.9 97.6 94.2 Year-to-date Availability, % 93.7 91.17 92.89 94.2 Operating Hours 2,184 2,116 1,994 2,208 8,501
Out of Service Hours 140 123 415 346 1,024
Unit 2 Availability, % 93.6 94.2 79.2 84.3 88.0 Year-to-date Availability, % 93.6 93.88 89.23 88.0 Operating Hours 2,170 1,422 1,929 2,072 7,593
Out of Service Hours 359 253 55 104 771
Unit 3 Availability, % 83.5 82.2 97.1 95.0 89.8 Year-to-date Availability, % 83.5 82.96 87.92 89.8

Missing data are normally substituted under a Part 75 system because of the ability to
trade mass emissions allowances. Under a rule wh ere a percent reduction or implementation of a specific control technology is re quired, it could be argued that data substitution may not be necessary. On the other hand, in the case wher e there is a mass emissions limit, it could be argued that data substi tution should be performed to ensure that mass emissions are not underreported. Also, data substitution for missing data provides motivation for maintaining a high availability of the instrument.



### 1.2 Sorbent Trap Method (EPA Method 30B)

1.2.1 Sorbent Trap Method Description
The sorbent trap (ST) method is an approach to measuring total mercury emissions over a period of time. The continuous measurement me thod was addressed by Appendix K of the Part 75 requirements of the now vacated CAMR. EP A Method 30B has replaced Appendix K and is
a reference method that can be used for RATAs as well as for monitoring. The ST method is pictured in Figure 3-8 . Gas is drawn through two separate traps concurrently. Two traps are necessary for the purpose of quality assurance, a nd agreement must be within prescribed levels or the sample fails QA. The two traps can be in stalled within the same probe or in separate probes. The mercury traps must also be installed in the probe such that gas is pulled directly into the traps. The method assumes that there is not a significant concentration of particulate matter in the flue gas. A common trap sorbent material is activated carbon impre gnated with iodine or another halogen like bromine. For continuous monitoring each trap must have the sorbent configured into three sections that can be tested independently. The first section is for primary mercury collection. The second section is to pr ovide an indication of mercury breakthrough. If there is too much breakthrough, the sample fails QA. The third section is for spike recovery testing using a spiked mercury sample gas. Analysis of the third section must show good recovery of the spiked sample for acceptable results. After a period of sampling, the traps are removed and analyzed to measure the total amount of mercury in the tr aps. The mercury found in the traps divided by the tota l gas flow over the period of the sampling indicates mercury concentration in the gas.

The balance of the sampling system includes a moisture removal system, and dry gas flow pump and dry gas flow meter (or other equivalent mass flow equipment) and relatedDraft Under Development – Review Draft – by NESCAUM – April 2010

instrumentation. The flow meter and associated instrumentation (barom eter and temperature indication) must be regularly calibrated to ensure that they are reporti ng the correct volume of gas. The flow meter must also have a variable flow control to maintain sample flow rate in proportion with load.

Figure 3-8. Method 30B sorbent trap equipment. 84

Because of the QA requirements that could cau se a sample to be rejected, most users replace traps every 4-7 days. This assures that if a sample is rejected for QA reasons, that only 4-7 days of data are lost. 83

The two most widely used approaches to an alyzing the traps for me rcury are: 1) a wet digestion method using atomic ab sorption or fluorescence analysis ; and 2) thermal release with atomic absorption analysis. The latter approach can be done on site with the proper equipment. However, it has the disadvantage that the sample is destroyed, so that if there is a problem with the analysis it cannot be checked again.

Sorbent traps can be used as a reference me thod against a CMM or as a CMM. Sorbent trap requirements as CMMs were defined under the CAMR as Appendix K. As a reference method, STs are EPA Method 30B. Since it is used as a reference method, Method 30B has different QA requirements than Appendix K in term s of spike recovery, et c., and is somewhat different in procedure.



### 1.2.2 Sorbent Trap Accuracy/Precision
The ST method for measuring mercury gene rally has good measurement accuracy down to relatively low mercury c oncentrations well under 1 μg/m 3 . This can be influenced by sample time, trap size and other parameters that the user can control dependi ng upon their needs. Figure
3-9 (presented in Ref. 85) and Figure 3-10 (presented in Ref. 86) show results from six different RATA’s from six different power plants, in each case a, b and c showing results for low concentrations (under 1 μg/m 3 ), moderate concentr ations (about 1 μg/m 3 ), and higherDraft Under Development – Review Draft – by NESCAUM – April 2010

concentrations (over 1 μg/m 3 ), respectively. Relative accuracy can be more difficult at the
lower concentrations because ther e appears to be more variation in concentration on a percent of value basis at these low levels of mercury. Th e sorbent trap CMM in the figure being compared to a sorbent trap reference method (Met hod 30B) is either MET-80 (sold by CleanAir Engineering) or Appendix K. In these cases bo th sorbent trap methods (either Appendix K o Method 30B) were being drawn at the same time. So, in each case there was a comparison of total mercury collected in the traps over the same period. rDraft Under Development – Review Draft – by NESCAUM – April 2010



### (a)

(b)

(c)

Figure 3-9. RATA results reported by Wright and Schmid 85 with (a) concentrations under 1 μg/m 3 ; (b) concentrations near 1 μg/m 3 ; (c) concentrations over 1 μg/m 3

.Draft Under Development – Review Draft – by NESCAUM – April 2010



### (a)

(b)

(c)

Figure 3-10. RATA results reported by Wright 86 with (a) concentrations under 1 μg/m 3 ; (b) concentrations near 1 μg/m 3 ; (c) concentrations over 1 μg/m 3

.Draft Under Development – Review Draft – by NESCAUM – April 2010



### 1.2.3 Approximate Costs of Sorbent Trap Systems
The initial installed cost of a sorbent trap system is on the order of $150,000. Operating costs entail roughly $500 to $700 per week fo r traps and analysis ($26,000 to $36,000 per year). 61,68 The cost of labor for operating the traps corresponds to about two people for half a day per stack every 4 to 7 days. 86 At $50/hr for labor, that is roughly another $21,000 to $36,00

per year. 0



### 1.2.4 Advantages/Disadvantages of STs When Compared to Hg CEMS
The advantages of STs versus Hg CEMS are:

• Significantly lower capital cost - The pr incipal advantage of STs over Hg CEMS is much lower capital cost – about $150,000 versus about $500,000.

• Simpler system to operate and maintain – Sorbent trap systems are less complex than Hg CEMS and don’t require as sophist icated a technical staff to support. However, the personnel involved in STs do need training on how to properly handle the traps to avoid contamination and other problems that could introduce

errors.

• Lower concentrations - In principal, STs may be able to measure to lower concentrations than Hg CEMS, but this is very methodology dependent. Furthermore, Hg CEMS are improving their ability to measure to low levels such that any advantage in this respect may be small.

Disadvantages of STs versus Hg CEMS are:

• No real-time, or near real-time data – Th is is the principal t echnical advantage of Hg CEMS over STs. The information is available in minutes, which enables the performance of Hg emission control processe s to be monitored in near real time and can thereby offer advantages in Hg control. Figure 3-11 shows how Hg CEMS data and ST data compare at one facility equipped with a wet scrubber over a period of 5 days and 30 days, resp ectively. As shown, there was a wide variation in Hg emissions that is not captured by the STs.

• Higher Labor Costs - This may not have been realized yet since Hg CEMS have been coming down a fairly steep learning curve, which means that owners have
had to dedicate more hours to service and support than they ultimately should have to. Sorbent traps, on the other hand, will always require regular trap replacement and testing (typi cally every 4-7 days) and th e labor associated with replacing and testing the traps is not likely to drop very much.

• Loss of Data – If there is a problem with a ST sample, it may not be discovered until after the sample is completed, and when ST samples fail the quality control tests, the data are lost for the full samp ling period. For this reason, ST systems have quality control procedur es in place to minimize this risk, and in practice samples are limited to about 4-7 days. Fo r Hg CEMS the existence of a problem that would cause lost data is generally apparent right away, so that corrective action can be immediately taken to restor e the instrument to a fully functioning

state.Draft Under Development – Review Draft – by NESCAUM – April 2010

• Personnel Safety – STs require that personnel regularly go up to the sampling point to remove and replace sorbent traps. This creates an added concern for personnel safety.

• Speciation – Although only total Hg emi ssions would have been reported under the vacated Part 75 CAMR requirement s, oxidized Hg and elemental Hg do behave differently in terms of capture and in terms of how they behave once released to the environment. So, there is a benefit with respect to emissions control and with respect to understand ing environmental impact in having speciated Hg emissions information. Although approaches do exist for speciated Hg measurements with STs, due to the reactivity of oxidized mercury, this is difficult. And, there is limited experi ence with taking speciated measurements
with STs.

• Process Steps - There can be many people and steps necessary to assure a good measurement; a mistake at any point in the process could introduce error.

• Hazardous Wastes - Hazardous wastes can be generated from the analysis methods that need to be disposed of in accordance with procedures for handling and disposing of hazardous materials.

• Trap Analysis - The analysis of the trap (thermal desorption or wet chemical analysis) destroys the sample, so that it can’t be checked in the event of an analysis error.Draft Under Development – Review Draft – by NESCAUM – April 2010



### (a)

(b)

Figure 3-11. Hg CEMS performanc e compared with Sorbent Traps. 87



### 1.2.5 Availability of STs used as CMMs
Because Hg monitoring data have not been required to be reported by many states, there are limited data on reported availability of the method. However, information on short-term experience (under 6 months) using Part 75 availability requirements has shown availability generally over 90%. Figure 3-12 shows availability data over se veral months for eight different STs. Also, as shown in Table 3-3 , year-long data from Dominion reported to the Commonwealth
of Massachusetts on their Salem Harbor Units 1 through 3 CMMs show availability of 89% to
96%. 87Draft Under Development – Review Draft – by NESCAUM – April 2010

Figure 3-12. Sorbent Trap availabilit y reported by Wright and Schmid. 89

Table 3-3. Availability information for Dominion Salem Harbor Units 1, 2, 3 CMMs. 87

Unit 1 Unit 2 Unit 3
O nline Operating Hours 5,922 6,209 3,620
Monitored Hours 5,263 5,587 3,480 Total Operating H ours of Downtime 659 622 140 Availability 89% 90% 96% Missing data caused by: Monitor not operated* 269 82 0
Monitor Malfunction/M aintenance 1 ** 12 74 29 Trap QA/QC*** 360 429 0 Trap Change Out 5 17 3
Monitor Calibratio n 13 12 8

Notes:

* E arly on in the monitoring program the monitor operating parameters (e.g., vacuum, trap flow) were not well

ved.
**
r. In

.
The importance of availa bility is illustrated by Figure 3-13 , which shows variation of

mercur

s enough understood to use as predictiv e information to change out traps in a timely manner to avoid the monitor shutting down on its own. Automated alerts were not sufficient. The issue has since been resol One recurring maintenance issue caused the bulk of this downtime. The issue has since been resolved. *** Initially the sorbent traps were not able to sample for longer than three days due to a loss of spike recove June 2008 the design of the traps was improved, which allowed the duration of the run to increase. Subsequently, data loss due to trap quality assura nce/quality control (QA/QC) has been greatly reduced

y concentration over a several month peri od for three different boilers: bituminous and
unscrubbed in the case of Figure 3-13 a, bituminous and scrubbed in the case of Figure 3-13 b,
and PRB and unscrubbed in the case of Figure 3-13 c. In each of these three cases – which are very different situations from th e perspective of coal types or i nherent mercury capture - there iDraft Under Development – Review Draft – by NESCAUM – April 2010

significant variation of mercury concentration over the period. Because of this variability in emission rate for each boiler, the lack of hi gh CMM availability would result in much less confidence that the measured mercury emissions were a reliable indicator of actual mercury emissions over the period.

Strictly speaking, the reported availability statistics in Table 3-3 for the STs in Massachusetts are not subject to the Part 75 requirements of the CAMR because those requirements were vacated when the CAMR was v acated. And as discussed previously, some changes from the original Part 75 CAMR protocol have been made out of technical necessity. In other words, these changes would have occurred ev en if CAMR were still in place. According to the Massachusetts DEP, 82 the Massachusetts requiremen ts under 310 CMR 7.00 et al. are
otherwise identical to those of the now vacated Part 75 CA MR requirements, and these availability statistics and the good quality emissi ons data being generated are a strong indication of the industry’s efforts and ability to use STs for the continuous monitoring of mercury
emissions.Draft Under Development – ReviewDraft – by NESCAUM – April 2010(a)(b)(c)Figure 3-13. Sorbent Trap data from Wright89for (a) bituminous, unscrubbed; (b) bituminous, scrubbed; (c) PRB, unscrubbed.