Update on Hg CEMSUpdate on Hg CEMS

Jeffrey V. Ryanryan.jeff@epa.gov

(919) 541-1437

U.S. Environmental Protection AgencyOffice of Research and Development

Air Pollution Prevention and Control DivisionResearch Triangle Park, NC 27711, U.S.A.

OAQPS Measurement Technology Workshop 2010December 6, 2010

They’re here to stay …

Overview

• Regulatory Update• Hg CEMS• Sorbent trap monitoring• Hg Emissions monitoring performance and related issues• NIST Traceability • Take home messages …• Questions

Regulatory Update

• EPA Part 60 compliance monitoring procedures promulgated as part of Portland Cement MACT amendments(75 FR 54970 9/9/2010) PS12A

http://www.epa.gov/ttn/emc/perfspec/ps-12A.pdf Appendix F Procedure 5 (Hg CEMS continued QA/QC)

http://www.epa.gov/ttn/emc/perfspec/AppFProc5.pdf PS12B (Sorbent traps initial certification and continued QA/QC)

http://www.epa.gov/ttn/emc/perfspec/ps-12B.pdf

• Hg CEMS and sorbent trap monitoring procedures now formally exist

Monitoring Requirements

• PS12A: Hg CEMS - Performance specifications for initial certification Measurement Error Test (linearity) with Hg0 and HgCl2 7-Day Calibration Drift Test with zero and mid-level Hg0

Relative Accuracy Test

• Appendix F Procedure 5: Continued QC/QA requirements Daily Calibration Drift Assessment Weekly System Integrity Check Data Accuracy Assessment

• Relative Accuracy Test Audit• Quarterly Gas Audit• Relative Accuracy Audit (alternative)

• PS12B: Sorbent Traps – Performance specifications for initial certification and continued QC/QA requirements

Hg Emissions Monitoring

• Hg CEMS

• Sorbent Traps

Tekran

• 50 lpm sample extraction• Inertial filter• Dilution-based• Thermal-catalytic converter

located in the rack• Pre-concentration CVAFS• 0.001 ug/wm3 resolution• 150 second cycle time• Fully automated

Thermo-Scientific

• 50 lpm sample extraction• Inertial filter• Dilution-based• Thermal converter located in the

probe• Real-time CVAFS• 0.01 ug/wm3 resolution• Fully automated

CEMTREX

• 10 lpm sample extraction• Standard filter• Dilution-based• Thermal converter located in

the probe• Pre-concentration CVAAS• 0.01 ug/wm3 resolution• 180–360 second cycle time• Fully automated

Hg CEMS: Where we’re at …

• ~600 sold to utilities At least half installed/certified

(see NESCAUM Report for breakdown)http://www.nescaum.org/documents/hg-control-and-measurement-techs-at-us-pps_201007.pdf

How many implementing NIST traceability program?

• Trend towards low level measurements (< 1µg/m3) • Hg CEMS now considered for other source categories

Sorbent Trap Hg Emission Monitoring Systems

• Multiple providers and systems Manual and automated

• >200 sold to utilities Many installed/certified Many as “backups” to Hg CEMS

• Suitable for low and high level Hg measurements

• More vulnerable to data loss(due to length of monitoring)

Hg CEMS Emission Monitoring Issues …

• Reliability• Low Hg concentrations• Other source categories

Measurement environment Dynamic range of emissions

• Status of NIST traceability• Range of available Hg

calibration gas concentrations

Percent Monitor Availability for HgCEMSFull Year Results 2009

PMA (%) for Ten HgCEMSMidwest UtilityAVG PMA = 91.64

Jan 1, 2009 - Dec. 31, 2009

85

90

95

100

B1 C1 C2 D3 D4 S5 K2 L4 S1 OS

Site Designation

Per

cent

Mon

itor

A

vaila

bilit

y

PMA (%)

Source: Tekran

Low Level Hg Accuracy Check With M&C Probe - Wet Stack

0.173 0.154

0.562

1.024

0.453

1.059

0

0.25

0.5

0.75

1

1.25

1.5

1.75

Run #1 Run #2 Run #3

Run Number

HgT

(ug/

m3)

Sorbent Traps (HgT)

Tekran HgT

Source: Tekran

Power Plant - Hg CEMS RATA Results Low-Level Emissions Tests

Cement Plant - Hg CEMS RATA Results Low-Level Emissions Tests

RATA TEST RESULTS MW CEMENT PLANTLow-Level Emissions Example

-1.000

-0.500

0.000

0.500

1.000

1.500

1 2 3 4 5

Run Number

Hg

Co

nce

ntr

atio

n -

ug

/m3

REF METH

TEK CEM

DIFF

Source: Tekran

Cement Plant - Hg CEMS RATA Results Low-Level Emissions Tests

RATA TEST RESULTS PLANT BHigher Level Emissions Example

-20

0

20

40

60

80

100

120

140

6 7 8 9

Run Number

Hg

Co

nc

en

tra

tio

n (

ug

/m3

)

REF METH

TEK CEM

DIFF

Source: Tekran

(a)

(b) Source: NESCAUM 2010

Hg Emissions DataHg CEMS vs. Sorbent Traps

• See what you’re missing … Process characterization Data variability

NIST Traceability

• Certified “NIST Traceable” gas standards are needed to support regulatory applications

• EPA defines NIST Traceability• Where possible, the certified concentration is derived from

an unbroken chain of direct comparisons linked to a primary reference originating from NIST

• With collaboration from the utility industry, Hg CEM vendors and NIST, EPA has developed Interim Protocols to establish certification and continuing QA procedures for Hg0 and HgCl2 gas standards

How NIST Traceability Works

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

Hg Calibration Gases

• NIST-traceable Hg0 and Hg+2 calibration gases now available• Hg0 and Hg+2 Interim Protocols used to establish traceability

http://www.epa.gov/ttn/emc/metals/ElemHgProtocol.pdf

http://www.epa.gov/ttn/emc/metals/OxHgProtocol.pdf • Final NIST traceability protocols expected in the next 12-18

months• Nominal NIST-traceable Hg0 concentrations of 0.5 µg/m3 to

300 µg/m3 now available(NIST recently extended upper end from 45 µg/m3)

• Fundamental bias (7-10%) exists between Hg0 and evaporative Hg+2 standards Reason unknown (but we’re still working on it) Does not limit NIST traceability or regulatory use of Hg CEMs

Take Home Messages …

• Hg CEMS are indeed ready for “prime time”• Now being used on multiple source categories

Cement plants, HWIs, steel plants, power plants

• Promulgated monitoring procedures for Hg CEMS and sorbent traps now available

• NIST traceability available and functional for Hg0 and Hg+2 calibration gases

• NIST traceable Hg0 gases available from ~0.5 µg/m3 to 300 µg/m3

• Don’t underestimate the benefit of using Hg CEMS for process characterization.

Questions?