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idx?SID=16c0a0b368e352351c8a30361c36c4e4&node=40:8.0.1.1.1&rgn=div5#40:8.0.1.1.1.0.1 .1.9

P ERFORMANCE S PECIFICATION 12A

— S PECIFICATIONS AND T EST P ROCEDURES FOR T OTAL V APOR
P HASE M ERCURY C ONTINUOUS E MISSION M ONITORING S YSTEMS IN S TATIONARY S OURCES

1.0 Scope and Application

1.1 Analyte. The analyte measured by these procedures and specif ications is total vapor phase mercury (Hg) in the flue gas, which represents the sum of elemental Hg (Hg°, CAS

Number 7439

- 97

- 6) and oxidized forms of gaseous Hg (Hg +2 ), in concentration units of micrograms per cubic meter (μg/m 3 ).

1.2 Applicability.

1.2.1 This specification is for evaluating the acceptability of total vapor phase Hg continuous emission monitoring systems (CEMS) installed at stationary sources at the time of or soon after installation and whenever specified in the regulations. The Hg CEMS must be capable of measuring the total concentration in μg/m 3 of vapor phase Hg, regardless of speciation, and recording that concentration at standard conditions on a wet or dry basis. These specifications do not address measurement of particle boun d Hg.

1.2.2 This specification is not designed to evaluate an installed CEMS's performance over an extended period of time nor does it identify specific calibration techniques and auxiliary procedures to assess the CEMS's performance. The source owner or operator, however, is responsible to calibrate, maintain, and operate the CEMS properly. The Administrator may require, under section 114 of the Clean Air Act, the operator to conduct CEMS performance evaluations at other times besides the initial perform ance evaluation test. See §§60.13(c) and 63.8(e)(1).

1.2.3 Mercury monitoring approaches not entirely suited to these specifications may be approvable under the alternative monitoring or alternative test method provisions of §60.13(i) and §63.8(f) or §60 .8(b)(3) and §63.7(f), respectively.

2.0 Summary of Performance Specification

Procedures for determining CEMS relative accuracy, linearity, and calibration drift are outlined. CEMS installation and measurement location specifications, data reduction proc edures, and performance criteria are included.

3.0 Definitions

3.1 Continuous Emission Monitoring System (CEMS) means the total equipment required to measure a pollutant concentration. The system generally consists of the following three major subsyste ms:3.2 Sample Interface means that portion of the CEMS used for one or more of the

following: sample acquisition, sample transport, sample conditioning, and protection of the

monitor from the effects of the stack effluent.

3.3 Hg Analyzer means that p ortion of the Hg CEMS that measures the total vapor phase Hg mass concentration and generates a proportional output.

3.4 Data Recorder means that portion of the CEMS that provides a permanent electronic record of the analyzer output. The data recorder ma y provide automatic data reduction and CEMS control capabilities.

3.5 Span Value means the measurement range as specified in the applicable regulation or other requirement. If the span is not specified in the applicable regulation or other requirement,

t hen it must be a value approximately equivalent to two times the emission standard. Unless otherwise specified, the span value may be rounded up to the nearest multiple of 10.

3.6 Measurement Error Test means a test procedure in which the accuracy of the concentrations measured by a CEMS at three or more points over its measurement range is evaluated using reference gases. For Hg CEMS, elemental and oxidized Hg (Hg 0 and mercuric chloride, HgCl 2 ) gas standards of known concentration are used for this proce dure.

3.7 Measurement Error (ME) means the absolute value of the difference between the concentration indicated by the CEMS and the known concentration of a reference gas, expressed as a percentage of the span value, when the entire CEMS, including the s ampling interface, is challenged.

3.8 Calibration Drift (CD) means the absolute value of the difference between the CEMS output response and either an upscale Hg reference gas or a zero

- level Hg reference gas, expressed as a percentage of the span value, when the entire CEMS, including the sampling interface, is challenged after a stated period of operation during which no unscheduled maintenance or repair took place.

3.9 Relative Accuracy Test Procedure means a test procedure consisting of at least nin e test runs, in which the accuracy of the concentrations measured by a CEMS is evaluated by comparison against concurrent measurements made with a reference method (RM). Relative accuracy tests repeated on a regular, on

- going basis are referred to as relat ive accuracy test audits

or RATAs.

3.10 Relative Accuracy (RA) means the absolute mean difference between the pollutant concentrations determined by the CEMS and the values determined by the RM plus the 2.5 percent error confidence coefficient of a serie s of tests divided by the mean of the RM tests. Alternatively, for sources with an average RM concentration less than 5.0 micrograms per standard cubic meter (μg/scm), the RA may be expressed as the absolute value of the difference

between the mean CEMS an d RM values.

4.0 Interferences [Reserved]5.0 Safety

The procedures required under this performance specification may involve hazardous materials, operations, and equipment. This performance specification may not address all of the safety problems associated with these procedures. It is the responsibility of the user to establish appropriate safety and health practices and determine the applicable regulatory limitations prior to performing these procedures. The CEMS user's manual and materials recom mended by the RM should be consulted for specific precautions to be taken.

6.0 Equipment and Supplies

6.1 CEMS Equipment Specifications.

6.1.1 Data Recorder Scale. The Hg CEMS data recorder output range must include the full range of expected Hg conc entration values in the gas stream to be sampled including zero and the span value.

6.1.2 The Hg CEMS design should also provide for the determination of CD and ME at a zero value (zero to 20 percent of the span value) and at upscale values (between 50 a nd 100 percent of the span value). The Hg CEMS must be constructed to permit the introduction of known concentrations of Hg and HgCl 2 separately into the sampling system of the CEMS immediately preceding the sample extraction filtration system such that th e entire CEMS can be challenged.

6.2 Reference Gas Delivery System. The reference gas delivery system must be designed so that the flowrate exceeds the sampling system flow requirements of the CEMS and that the gas is delivered to the CEMS at atmospheric pressure.

6.3 Other equipment and supplies, as needed by the reference method used for the Relative Accuracy Test Procedure. See Section 8.6.2.

7.0 Reagents and Standards

7.1 Reference Gases. Reference gas standards are required for both elemental and oxidized Hg (Hg and mercuric chloride, HgCl 2 ). The use of National Institute of Standards and Technology (NIST)

- traceable standards and reagents is required. The following gas concentrations are required.

7.1.1 Zero

- level. 0 to 20 percent of the span value.

7.1.2 Mid

- level. 50 to 60 percent of the span value.

7.1.3 High

- level. 80 to 100 percent of the span value.

7.2 Reference gas standards may also be required for the reference methods. See Section

8.6.2.8.0 Performance Specification Test Pr ocedure

8.1 Installation and Measurement Location Specifications.

8.1.1 CEMS Installation. Install the CEMS at an accessible location downstream of all pollution control equipment. Place the probe outlet or other sampling interface at a point or

locati on in the stack (or vent) representative of the stack gas concentration of Hg. Since the Hg CEMS sample system normally extracts gas from a single point in the stack, a location that has been shown to be free of stratification for Hg or, alternatively, SO 2 is recommended. If the cause of failure to meet the RA test requirement is determined to be the measurement location and a satisfactory correction technique cannot be established, the Administrator may require the CEMS

to be relocated. Measurement locatio ns and points or paths that are most likely to provide data that will meet the RA requirements are described in Sections 8.1.2 and 8.1.3 below.

8.1.2 Measurement Location. The measurement location should be (1) at least two equivalent diameters downstrea m of the nearest control device, point of pollutant generation or other point at which a change of pollutant concentration may occur, and (2) at least half an equivalent diameter upstream from the effluent exhaust. The equivalent duct diameter is

calculate d according to Method 1 in appendix A

- 1 to this part.

8.1.3 Hg CEMS Sample Extraction Point. Use a sample extraction point either (1) no less than 1.0 meter from the stack or duct wall, or (2) within the centroidal velocity traverse area of

the stack or duct cross section. This does not apply to cross

- stack, in

- situ measurement systems.

8.2 Measurement Error (ME) Test Procedure. Sequentially inject each of at least three elemental Hg reference gases (zero, mid

- level, and high level, as defined in Sectio n 7.1), three times each for a total of nine injections. Inject the gases in such a manner that the entire CEMS is challenged. Do not inject the same gas concentration twice in succession. At each reference gas concentration, determine the average of the t hree CEMS responses and subtract the average response from the reference gas value. Calculate the measurement error (ME) using Equation 12

- 1 by expressing the absolute value of the difference between the average CEMS response (A) and the reference gas valu e (R) as a percentage of the span ( see example data sheet in Figure

12A

- 1). For each elemental Hg reference gas, the absolute value of the difference between the CEMS response and the reference value must not exceed 5 percent of the span value. If this

spe cification is not met, identify and correct the problem before proceeding. Repeat the measurement error test procedure using oxidized Hg reference gases. For each oxidized Hg reference gas, the absolute value of the difference between the CEMS response and the reference value shall not exceed 10 percent of the span value. If this specification is not met, identify and correct the problem before proceeding.

8.3 Seven

- Day Calibration Drift (CD) Test Procedure.8.3.1 CD Test Period. While the affected fa cility is operating normally, or as specified in

an applicable regulation, determine the magnitude of the CD once each day (at 24

- hour intervals, to the extent practicable) for 7 consecutive unit operating days according to the procedures in

Sections 8.3.2 and 8.3.3. The 7 consecutive unit operating days need not be 7 consecutive calendar days. Use either Hg 0 or HgCl 2 standards for this test.

8.3.2 The purpose of the CD measurement is to verify the ability of the CEMS to conform

to the established CEMS re sponse used for determining emission concentrations or emission rates. Therefore, if periodic automatic or manual adjustments are made to the CEMS zero and upscale response settings, conduct the CD test immediately before these adjustments, or conduct

it i n such a way that the CD can be determined.

8.3.3 Conduct the CD test using the zero gas specified and either the mid

- level or high

level gas as specified in Section 7.1. Sequentially introduce the reference gases to the CEMS at the sampling system of the CEMS immediately preceding the sample extraction filtration system. Record the CEMS response (A) for each reference gas and, using Equation 12A

- 2, subtract the corresponding reference value (R) from the CEMS value, and express the absolute value of the difference as a percentage of the span value ( see also example data sheet in Figure 12A

- 2). For each reference gas, the absolute value of the difference between the CEMS response and the reference value must not exceed 5 percent of the span value. If thes e specifications are not met, identify and correct the problem before proceeding.

8.4 Relative Accuracy (RA) Test Procedure.

8.4.1 RA Test Period. Conduct the RA test according to the procedure given in Sections 8.4.2 through 8.4.6 while the affected facility is operating normally, or as specified in an applicable subpart. The RA test may be conducted during the CD test period.

8.4.2 Reference Methods (RM). Unless otherwise specified in an applicable subpart of the regulations, use Method 29, Method 30A, or Method 30B in appendix A

- 8 to this part or American Society of Testing and Materials (ASTM) Method D6784

- 02 (incorporated by reference, see §60.17) as the RM for Hg concentration. For Method 29 and ASTM Method

D6784

- 02 only, the filterable portion of the sample need not be included when making comparisons to the CEMS results. When Method 29, Method 30B, or ASTM D6784

- 02 is used, conduct the RM test runs with paired or duplicate sampling systems and use the average of the vapor phase Hg concentratio ns measured by the two trains. When Method 30A is used, paired sampling systems are not required. If the RM and CEMS measure on a different moisture basis, data derived with Method 4 in appendix A

- 3 to this part must also be obtained during the RA

test.

8. 4.3 Sampling Strategy for RM Tests. Conduct the RM tests in such a way that they will yield results representative of the emissions from the source and can be compared to the CEMS data. The RM and CEMS locations need not be immediately adjacent. Locate t he RMmeasurement points in accordance with section 8.1.3 of Performance Specification 2 (PS 2) in

this appendix. It is preferable to conduct moisture measurements (if needed) and Hg measurements simultaneously, although moisture measurements that are take n within an hour of the Hg measurements may be used to adjust the Hg concentrations to a consistent moisture basis. In order to correlate the CEMS and RM data properly, note the beginning and end of each RM test period for each paired RM run (including the exact time of day) on the CEMS chart recordings or other permanent record of output.

8.4.4 Number and Length of RM Test Runs. Conduct a minimum of nine RM test runs. When Method 29, Method 30B, or ASTM D6784

- 02 is used, only test runs for which the pair ed RM trains meet the relative deviation criteria (RD) of this PS must be used in the RA calculations. In addition, for Method 29 and ASTM D6784

- 02, use a minimum sample time of 2 hours and for Methods 30A and 30B use a minimum sample time of 30 minutes.

N OTE : More than nine sets of RM test runs may be performed. If this option is chosen, RM test run results may be excluded so long as the total number of RM test run results used to determine the CEMS RA is greater than or equal to nine. However, all data mu st be reported including the excluded test run data.

8.4.5 Correlation of RM and CEMS Data. Correlate the CEMS and the RM test data as to the time and duration by first determining from the CEMS final output (the one used for reporting) the integrated av erage pollutant concentration for each RM test period. Consider system response time, if important, and confirm that the results are on a consistent moisture basis with the RM test. Then, compare each integrated CEMS value against the corresponding RM

valu e. When Method 29, Method 30B, or ASTM D6784

- 02 is used, compare each CEMS value against the corresponding average of the paired RM values.

8.4.6 Paired RM Outliers.

8.4.6.1 When Method 29, Method 30B, or ASTM D6784

- 02 is used, outliers are identified through the determination of relative deviation (RD) of the paired RM tests. Data that do not meet the RD criteria must be flagged as a data quality problem and may not be used in the calculation of RA. The primary reason for performing paired RM sampling is to ensure the quality of the RM data. The percent RD of paired data is the parameter used to quantify data quality. Determine RD for paired data points as follows:

Where:

C

a and C b are the Hg concentration values determined from the paired samples.

8. 4.6.2 The minimum performance criteria for RM Hg data is that RD for any data pair must be ≤ 10 percent as long as the mean Hg concentration is greater than 1.0 μg/m 3 . If the mean Hg concentration is less than or equal to 1.0 μg/m 3 , the RD must be ≤ 20 p ercent or ≤ 0.2 μg/m 3absolute difference. Pairs of RM data exceeding these RD criteria should be eliminated from the

data set used to develop a Hg CEMS correlation or to assess CEMS RA.

8.4.7 Calculate the mean difference between the RM and CEMS values in the units of micrograms per cubic meter (μg/m 3 ), the standard deviation, the confidence coefficient, and the RA according to the procedures in Section 12.0.

8.5 Reporting. At a minimum (check with the appropriate EPA Regional Office, State or local Ag ency for additional requirements, if any), summarize in tabular form the results of the CD tests, the linearity tests, and the RA test or alternative RA procedure, as appropriate. Include all data sheets, calculations, charts (records of CEMS responses), r eference gas concentration certifications, and any other information necessary to confirm that the CEMS meets the performance criteria.

9.0 Quality Control [Reserved]

10.0 Calibration and Standardization [Reserved]

11.0 Analytical Procedure

For Method 30A, sample collection and analysis are concurrent. For the other RM, post

- run sample analyses are performed. Refer to the RM employed for specific analytical procedures.

12.0 Calculations and Data Analysis

Calculate and summarize the RA test resu lts on a data sheet similar to Figure 12A

- 3.

12.1 Consistent Basis. All data from the RM and CEMS must be compared in units of micrograms per standard cubic meter (μg/scm), on a consistent and identified moisture basis.

The values must be standardized to 20 °C, 760 mm Hg.

12.1.1 Moisture Correction (as applicable). If the RM and CEMS measure Hg on a different moisture basis, they will need to be corrected to a consistent basis. Use Equation 12A

4a to correct data from a wet basis to a dry basis.

Use E quation 12A

- 4b to correct data from a dry basis to a wet basis.

Where:

B
ws is the moisture content of the flue gas from Method 4, expressed as a decimal fraction (e.g.,

for 8.0 percent H 2 O, B

ws = 0.08).12.2 Arithmetic Mean. Calculate d, the arithmetic mean of the differences (d i ) of a data set

as follows:

Where:

n = Number of data points.

12.3 Standard Deviation. Calculate the standard deviation, S d , as follows:

12.3 Confidence Coefficient (CC). Calculate the 2.5 percent error confidence coeffic ient (one

- tailed), CC, as follows:

12.4 Relative Accuracy. Calculate the RA of a set of data as follows:

Where:

= Absolute value of the mean of the differences (from Equation 12A

- 5)

| CC | = Absolute value of the confidence coefficient (from Equation 12A

- 7)

= Average reference method value13.0 Method Performance

13.1 Measurement Error (ME). For Hg 0 , the ME must not exceed 5 percent of the span

value at the zero

- , mid

- , and high

- level reference gas concentrations. For HgCl 2 , the ME must not exceed 10 percent of the span value at the zero

- , mid

- , and high

- level reference gas

concentrations.

13.2 Calibration Drift (CD). The CD must not exceed 5 percent of the span value on any of the 7 days of the CD test.

13.3 Relative Accuracy (RA). The RA of the CEMS must be no greater than 20 percent of the mean value of the RM test data in terms of units of μg/scm. Alternatively, if the mean RM is less than 5.0 μg/scm, the results are acceptable if the absolute value of the difference between the

m ean RM and CEMS values does not exceed 1.0 μg/scm.

14.0 Pollution Prevention [Reserved]

15.0 Waste Management [Reserved]

16.0 Alternative Procedures [Reserved]

17.0 Bibliography

17.1 40 CFR part 60, appendix B, “Performance Specification 2

— Specif ications and Test

Procedures for SO 2 and NO X Continuous Emission Monitoring Systems in Stationary Sources.”

17.2 40 CFR part 60, appendix A, “Method 29

— Determination of Metals Emissions from Stationary Sources.”

17.3 40 CFR part 60, appendix A, “Method 30A

— Determination of Total Vapor Phase Mercury Emissions From Stationary Sources (Instrumental Analyzer Procedure).

17.4 40 CFR part 60, appendix A, “Method 30B

— Determination of Total Vapor Phase Mercury Emissio ns From Coal

- Fired Combustion Sources Using Carbon Sorbent Traps.”

17.5 ASTM Method D6784

- 02, “Standard Test Method for Elemental, Oxidized, Particle

Bound and Total Mercury in Flue Gas Generated from Coal

- Fired Stationary Sources (Ontario Hydro Method). ”18.0 Tables and Figures

T ABLE 12A

- 1

— T

- V ALUES

n a t 0.975 n a t 0.975 n a t 0.975

2 12.706 7 2.447 12 2.201

3 4.303 8 2.365 13 2.179

4 3.182 9 2.306 14 2.160

5 2.776 10 2.262 15 2.145

6 2.571 11 2.228 16 2.131

a The values in this table are already corrected for n

- 1 degrees of freedom. Use n equal to the number of

individual values.

F IGURE 12A

- 1

— ME D ETERMINATION

Date Time Reference

gas value (μg/m 3 ) CEMS

measured value (μg/m 3 ) Absolute

difference (μg/m 3 ) ME

(% of span value)

Zero level

Average

Mid level

Average

High level

AverageF IGURE 12A

- 2

— 7

- D AY C ALIBRATION D RIFT D ETERMINATION

Date Time Reference

gas value (μg/m 3 ) CEMS

measured value (μg/m 3 ) Absolute

difference (μg/m 3 ) CD

(% of span value)

Zero level

Upscale (Mid or High)F IGURE 12A

- 3

— R ELATIVE A CCURACY T EST D ATA

Run

No. Date Begin

time End

time RM value

(μg/m 3 ) CEMS value

(μg/m 3 ) Difference

(μg/m 3 ) Run used?

(Yes/No) RD 1

1

2

3

4

5

6

7

8

9

10

11

12

Average Values

Arithmetic Mean Difference:

Standard Deviation:

Confidence Coefficient:

T

- Value:

% Relative Accuracy:

| (RM) avg − (CEMS) avg | :

1 Calculate the RD only if paired samples are taken using RM 30B, RM 29, or ASTM 6784

- 08. Express RD as a percentage or, for very low RM concentrations (≤ 1.0 μg/m 3 ), as the absolute difference between C
a and C b

.