Pilot-Plant Performance Testing to Support 

Development of an EPA HCl CEMS 

Performance Specification

Office of Research and Development

National Risk Management Research Laboratory. 

The 22nd Utility Continuous Emissions Monitoring User Group Meeting

May 9th, 2013 - Raleigh, North Carolina

Jeff Ryan

US EPA – Office of Research and Development
Background

• OAQPS is developing a new Performance 

Specification (PS-18) for HCl CEMS to support 

emissions monitoring in the Portland Cement MACT 

and Electric Utility MATS rules

• Data regarding CEMs measurement performance and 

quality to inform decision making is a component of 

the development process

• ORD is conducting research to support data needs

• Independent, industry-driven research/demonstration 

testing also taking place

1
Many Things to Consider ...

• HCl emissions monitoring is a new requirement with its 

own challenges

–Multiple technologies are available with many fundamental 

differences and technical issues

–Movement towards a performance based Performance Specification 

that is inclusive of these technologies

–Low level regulatory emission limits present technical challenges

• HCl CEMS

• Reference Methods (RMs)

–Quality and availability of Reference Gas Standards

–Practicality of associated procedures

2
EPA Research and Support Objectives

• Establish data supporting finalization of PS

• Evaluate commercial HCl CEMS (extractive only) as per 

Draft PS under controlled and representative emission 

environments

–Stack gas composition

–HCl emission levels

• Demonstrate suitability of candidate RMs

• Demonstrate status and quality of available Gas Standards

• Provide environment for vendors to optimize their CEMS

3
Participating HCl CEMS

• 4 Commercially-available, extractive technologies in 

Test Program

–2 Gas Filter Correlation (GFC)

–1 FTIR

–1 Cavity Ring-Down (CRD)

–No TDLAS cross stack system

• Targeted span ranges:

–0-5 ppm

–0-10 ppm?

–<5 ppm?

4 –Over span measurement capabilities (≤100 ppm)
PS-18 Elements and ORD Testing Focus

• Interference Tests

• Limit of Detection (LOD) Tests

• 7-Day Drift

• Linearity

• RATAs

• Dynamic Spiking

• Reference Methods

5
Test Facility

• ORD’s Multi-Pollutant Combustion 

Research Facility

–4M Btu/h down-fired combustor firing coal 

and/or NG

–Multiple pollution control configurations 

possible

• SCR,ESP,FF,Wet Scrubber

–Duct injection of gases to control 

emission profiles and combinations

• HCl, SO2, NOx, CH4, CO, NH3, H2O, CH2O

–All CEMS and RM measurements from 

same basic location

6
Reference Methods

• Method 26A (MATS only)

–Paired trains

–Focus on QLs/DLs, measurement quality and RM performance 

at very low HCl levels

• Methods 320/321 (ASTM D6348-12 too)

–Looking at 3 different high resolution FTIR analyzers

–Focus on QLDLs, measurement quality and RM performance 

at very low HCl levels

–Point of reference for HCl Gas Standards

7
Testing Status

• Still in early stages of testing due to extended facility 

maintenance

• All HCl CEMSs and RM FTIRs installed

–Vendors recently returned for final optimization

• Testing to date has focused on:

–FTIR RM measurement capabilities and performance

–Evaluating HCl Gas Standards

–Preliminary interference tests

–Preliminary LOD tests

–Reference Method performance

–All while firing on NG with HCl injection

• Target HCl stack concentrations 0.2 – 2 ppm

8
Testing ...

• We’re only now just getting started

–Mostly proof-of-concept at this time

–“Learning and practicing”

• Working primarily with NG and pure gas injections

–Some coals, but HCl concentrations too high

• We’ve still managed to try a few things ...

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HCl Concentration (ppm)

~80 ppm SO2

~700 ppm SO2

~800 ppm 

~750 ppm CH4

~20 ppm Formaldehyde

Interference Testing ...

• What gases and concentrations to test?

• How practical is performing the test?

• How do individual vs. combined gases compare?
11 -20

0

20

40

60

80

100

120

140

160

0 50 100 150 200 250 300

Concentration (ppmv)

Time (minutes)

Reference FTIR with HCl and Formaldehyde

HCl

Formaldehyde

HCL at 3.9 ppmv
12 -20

0

20

40

60

80

100

120

10:04:48 AM 11:16:48 AM 12:28:48 PM 1:40:48 PM 2:52:48 PM 4:04:48 PM HCl Concentration (ppmv)

Time (HH:MM:SS)

HCl CEMS Response to Formaldehyde
13

System 

Config

ASTM MDC 1 ASTM MDC 2 ASTM MDC 3 EPA M320 MAU EPA M320 

FMU*R

EPA OCU

LN2 -16 0.14 0.14 0.15 0.25 0.27 0.27

LOD Testing

Reference FTIR HCl CEMS "A" HCl CEMS "B" HCl CEMS "C"

0.5 ppm Point avg 0.61 0.57 0.78 0.70

std 0.03 0.02 0.01 0.07

LOD 0.08 0.05 0.04 0.22

2 ppm Point avg 2.00 1.99 2.61 1.95

std 0.04 0.01 0.04 0.05

LOD 0.12 0.04 0.12 0.16

0.2 ppm Point avg 0.19 0.19 0.41 0.35

std 0.02 0.01 0.04 0.07

LOD 0.06 0.04 0.13 0.21

• How well does the approach work?

• What concentration(s) should be used?

• How does this approach compare to others?
14

Cal Points Area Calculated Agreement y = mx+b

ug/mL Counts ug/mL % m = 35.41747

0.20 6.81088 0.19 -3.74% b = -7.8701E-03

1.00 36.57592 1.03 3.29% y = area

5.00 178.89946 5.05 1.03% x = amount

10.00 353.41158 9.98 -0.21% MDL = 0.03 ug/mL

15.00 529.28789 14.94 -0.37%

Liquid Total Total Total

Target Functional Sample Sample Sample Sample Sample Sample Sample Sample 

Conc. Dilution Conc. Volume Mass Rate Time Volume Volume Conc Conc

ug/ml Factor ug/ml mL mg cfm min ft3 m3 mg/m3 ppm

0.20 1 0.2 275.0 0.06 0.75 30 22.5 0.637 0.086 0.06

Method 26A - How low can you go?

• Analytical

• In-stack Example
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-0.5

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0.5

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1.5

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2.5

11:30:49 AM11:36:50 AM11:42:50 AM11:48:52 AM11:54:52 AM

12:00:53 PM12:06:54 PM12:12:54 PM12:18:55 PM12:24:56 PM12:30:56 PM12:36:57 PM12:42:58 PM12:48:59 PM12:55:00 PM

1:01:00 PM1:07:01 PM1:13:02 PM1:19:03 PM1:25:03 PM1:31:04 PM1:37:05 PM1:43:06 PM1:49:06 PM1:55:07 PM2:01:08 PM2:07:08 PM2:13:09 PM2:19:10 PM2:25:11 PM2:31:12 PM2:37:12 PM2:43:13 PM2:49:14 PM2:55:15 PM3:01:15 PM3:07:16 PM3:13:17 PM3:19:17 PM3:25:18 PM3:31:19 PM

Concentration

Dynamic Spiking on Natural Gas

HCl (ppm)

SF6 (ppm)

FTIR- How low can you go?

Spike Amount Recovery

ppm HCl %

0.5 93.1%

0.4 89.0%

0.2 67.1%
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M321/AST

M M-26A Absolute

Target FTIR HCl HCl Avg Difference

ppm ppmv / wet ppmv / wet ppmv / wet

0.2 0.19 0.27 0.08

0.5 0.59 0.58 0.01

2.0 1.98 2.01 0.02

Reference Method Agreement
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0.5

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1.5

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2.5

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9:00:099:07:399:15:189:22:579:30:279:38:099:45:369:53:10

10:00:4510:08:2410:15:5410:23:3310:31:1410:38:4210:46:2110:54:0011:01:3011:09:0911:15:4711:23:2411:30:5411:38:3311:46:0311:53:4212:01:2112:08:5812:16:3012:24:0912:31:3912:39:1812:46:4812:54:1813:02:0513:09:3613:17:1513:24:4513:32:2413:39:5413:47:3313:55:1414:02:4214:10:2114:17:5114:25:3014:33:0914:40:39

HCl Concentration (ppm)

Time

Let’s Put it All Together ...

Reference FTIR

HCl CEMS "A"

HCl CEMS "B"

HCl CEMS "C"

17

M321/ASTM M-26A

Target FTIR HCl HCl Avg HCl CEMS "A" HCl CEMS "B" HCl CEMS "C"

ppm ppmv / wet ppmv / wet ppmv / wet ppmv / wet ppmv / wet

0.2 0.19 0.27 0.19 0.41 0.35

0.5 0.59 0.58 0.57 0.78 0.70

2.0 1.98 2.01 1.99 2.61 1.95
Gas Standards

• Gas Standards are needed as part of PS and on-going 

Quality Assurance operations

• Conventional compressed gases (dry), evaporative 

(wet), and humidification of dry gases being considered

• NIST traceable gas standards do not yet exist

(but are in the works – really!)

• Reference Gas quality at low concentrations and 

practicality of use a focus of our efforts

18
Gas Standard Testing

• Compressed Gases:

–Ordered ~20 HCl cylinders (concentrations 

ranging from ~2-100 ppm) from Airgas and 

Linde last Summer 

–Initial measurements 10-50% low, most ~20%

–After 6 months - some stable, some not

–Good news ...

19

Airgas FTIR

Tag Value Measured Agreement

ppm ppm %

1.84 1.88 1.98%

4.60 4.67 1.42%

9.28 9.11 -1.82%

47.55 46.37 -2.49%

100.7 96.37 -4.30%

• Hovacal:

–We have many years experience with 

the Hovacal

–Much faster response and equilibration

–We believe it to be accurate, but ...

• Bottom line is that it is critical to our research 

that we have a reliable reference gas

Target Hovacal FTIR 

Concentration Calculated Measured Agreement

HCl ppm HCl ppm HCl ppm %

0.5 0.45 0.37 -17.78%

1.0 0.86 0.79 -8.14%

2.0 1.72 1.66 -3.49%

5.0 4.60 4.51 -1.96%

10.0 9.00 8.78 -2.44%
NIST Status

• Actively developing their capabilities to provide traceability

–Prepared multiple ref gas cylinders (8-12ppm)

–Cylinders concentrations established and confirmed

• Electrochemical titration (U= 0.5%)

• IC confirmation

–Now establishing their RGM naming system (Tiger Optics CRDS)

–Expect to be able to provide RGMs with U ≤ 2%

• Future plans

–Expect to be able to name RGM cylinders for gas vendors in the next 

several months

–Prepare and study low level (~2 ppm) ref gas cylinders

–Inter-laboratory comparison study with VSL this Summer

20
Gas Vendor Status

• Multiple gas vendors now providing low level (<10 ppm) HCl

gas standards

–Targeting 1-2 ppm gases

• Very aware of recent discrepancies and are working to resolve 

those issues

• Improving/establishing their certification system instrumentation

• Examining stability

• Discussing guidance for cylinder use

• Ready to send cylinders to NIST to be named as RGMs

21
What We’ve Learned So Far ...

• Interferences are an important consideration

–Spectral and chemical

• Candidate Reference Methods are suitable for low levels

• HCl Gas Standards are a challenge

–Need accurate and reliable point of reference/traceability – soon!

–Dry gases have transport concerns

–Practicality of the wet, evaporative systems

• There’s much work left to do ...

22
Future Plans ...

• Expect to be testing through end of CY13

• Fully implement PS-18 (multiple times)

–Conduct more comprehensive Interference Tests

–Conduct more comprehensive LOD Tests

–RATAs on spiked NG and low HCl coal

–Consider practical alternatives

• Work on HCl CEMS Dynamic Spiking

–levels, techniques, during RM measurements

• Continue to facilitate the establishment of NIST Traceability

• Support regulatory data needs

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Questions ...

24