HCL CEMS For MATS Compliance

Mechanical Systems, Inc. Apr 25, 2017

MSI/Mechanical Systems, Inc.

VendorHub Training

Evansville, Indiana

April 12, 2017

Topics

MATS Compliance Requirements For HCl
Ways To Measure HCl
Review of HCl Project
PS-18 Certification Tests/Results
Factors Affecting TDL Measurement of HCl
Summary

MATS Compliance Rules For HCl

Three ways to demonstrate MATS compliance for HCl:

SO2 emission rate < 0.200 lbs/mmbtu (scrubbed units only)
- Relatively easy for units firing low sulfur western coals with spray dryer absorber (SDA) or wet scrubber (FGD)
- Not easy for units firing high sulfur Illinois basin coal or high sulfur Appalachian coals
- High sulfur units need 97% removal across SDA or FGD
HCl Quarterly Testing
- Three hourly runs with HCl below emission limit – 0.002 lbs/mmbtu
- Failure of any run is notice of violation and fine
HCl Continuous Emission Monitoring System
- Thirty day rolling average below emission limit 0.002 lbs/mmbtu

Ways To Measure HCl

FTIR (Fourier Transform Infrared Spectroscopy)
- Complicated analyzer (Gasmet, ABB, CAI, MKS)
- Measures lots more than just HCl
- Straight extractive with limitation on sample line length
- Real effort being made by some utilities, but results not known
TDL (Tunable Diode Laser)
- Less complicated than FTIR (Unisearch, Siemens, Yokogawa, Opsis)
- Measures only HCl
- Cross stack like opacity (EPA calls this IP – Integrated Path)
- Calibration are easy to run, but hard to pass if background concentration of HCl in stack is changing.
Sorbent Trap
- In development, little information available on compliance units
- Much more potential for RATA testing

HCl TDL CEMS - Site Information

Unit A Main stack and Bypass stack
- Main: ESP, FGD, SBS, CI, CaBr, Brick/Diameter 22’, 1995 scrubber
- Bypass: ESP, SBS, CI, CaBr, Steel/2” Block/Diameter 20’
Unit B Main stack and Bypass stack
- Main: FF, FGD, SBS, CI, CaBr, Brick/Diameter 29’-6”, 1995 scrubber
- Bypass: FF, SBS, CI, CaBr, Brick/Diameter 22’-2”
Unit C with FGD Bypass
- ESP, FF, FGD, SBS, CI, CaBr, Steel/C-276/Diameter 22’-0”, 1977 scrubber
Unit D with FGD Bypass
- ESP, FGD, SBS, CI, CaBr, Brick/Diameter 26’-7”, 1986 scrubber

Additional Site Information

Expected normal HCL concentrations:
- FGD stacks: Less than 1 ppm
- Bypass stacks: 10-100 ppm
Redundant HCl monitors on all stacks (12 units total)
- Unisearch LAS-RR101-FC-HCL, SPSO-18-F2 Optics Dual range
  - Low range 0-10 ppm
  - High range 0-100 ppm
Customer’s Instructions: We want to be in compliance, and we want to run our scrubbers the way we have always run our scrubbers.

Unisearch Tunable Diode Laser

Model LAS-RR101-FC-HCL

Infra red (invisible, 1810 nm) laser Cross stack measurement (Integrated path) Single or dual pass design Beam diameter controls signal strength Minimal electronics on stack Calibration cell in analyzer on ground

Test/calibration tools

Red laser alignment tool Infra red power meter Permeation audit module/cell

Installation

Alignment is critical

Beam is very narrow. Can be as small as 0.5” diameter. Like an opacity monitor but more difficult.

Path length is critical

Need path length to get good level of detection (0.1 ppm).

Single pass system if path length > 5 meters (17 feet).

Double pass system if path length < 5 meters (17 feet).

All installation were single pass at this site.

Need purge system to keep optics clean.
Need pressure and temperature signals for EPA reporting.
Need to give much more thought to the calibration system.

Purge System

Dual blowers, one for launcher/transmitter, one for receiver.
Blowers and other equipment panel mounted.
Alarm for plugged filter.
Alarm for blower failure.
Remote operation of shutters for weekly testing.
Used same purge components including controllers and shutters as opacity systems.

Temperature/Pressure Inputs

Used existing flow monitors.
Converted the ultrasonic flow monitors from internal to external pressure and temperature inputs during the annual RATAs.
Temperature measurements are Platinum RTDs.
Pressure measurement is barometric pressure on the stack.
Using flow monitors avoids a competing set of temperature and pressure measurements.

Calibration Considerations

Tunable diode lasers use calibration cells.
Calibration gas values are based on the geometric ratio of the path length in the stack to the path length of the sample cell.
- nside diameter of the stack = 240”
- Length of calibration cell = 6”
- Calibration ratio = 240/6 = 40.0
Order calibration gases based on calibration ratio.
- Need calibration results at 1.25 ppm, 2.75 ppm, 4.5 ppm
- Order cylinders at 50 ppm, 110 ppm, 180 ppm

Initial Operation

MSI technicians were able to align launcher and receiver and optimize performance with the wet stacks on line.
Had much more beam strength than we anticipated on the wet stacks.
No problem with alignment even during startup and shutdown of stacks. Brick stacks moved as much as 4”.
Panel mounted purge blowers did not cause any vibration or effect instrument operation.
Calibration cell had to be purged continuously with air when not flowing span gas. Without purging residual desorbing effects could be seen for an hour after end of calibrations.

Certification Tests

Interference
Level of detection (LOD)
Beam intensity test
Temperature verification
Pressure verification
Measurement error (linearity)
Response time
Seven day drift
Relative accuracy

Interference Test

Measure response of HCl tunable diode laser to mixtures of:
- Carbon Dioxide, CO2 - 15 Percent
- Carbon Monoxide, CO -100 ppm
- Formaldehyde, CH2O - 20 ppm
- Methane, CH4 -100 ppm
- Nitrogen Dioxide, NO2 - 250 ppm
- Oxygen, O2 - 3 percent
- Sulfur Dioxide, SO2 - 200 ppm
- Water Vapor, H2O - 10 percent
- Water Vapor, H2O - 5 percent (MSI Option)
- Water Vapor, H2O - 15 percent (MSI Option)
- Nitric Oxide, NO - 250 ppm (MSI Option)

Interference Test Continued

Option to do test onsite or offsite with check in field.
Test cannot be done in the field or checked in the field.
One time test.
Very expensive.
For MATS units there are four criteria for success:
- Percent of span
- Percent of baseline concentration
- Six times level of detection
- Absolute sum of errors (total combined interference) < 0.5 ppm

Interference Test Results

Interference Test:
- Single pass and double pass.
- Three different temperatures 77 °F, 284 °F, 374 °F.
- Three different moisture levels 5%, 10%, 15%.
- 28 sequences, 15 test runs per sequence, 420 test runs.
- Interesting results NO2 and H2O.
- Test took four months, three modifications to test equipment, and patience.
- Passed using absolute sum of errors (total combined interference) < 0.5 ppm HCl.
- Test conducted by University of California
- Riverside Center for Environmental Research and Technology.

Level of Detection (LOD) Test

Must determine the minimum amount HCl that can be detected above background.
Run seven low range calibrations, calculate standard deviation of the measured values, and define the LOD as three times the standard deviation of the measurements.
One time test for all similar instruments.
Must be done in a lab and checked in the field.
Typically done in conjunction with interference test.
Instrument must have LOD < 20% of emission limit ppm equivalent concentration, typically between 0.2 and 0.3 ppm.

Level of Detection (LOD) Test Results

Level of detection varied with temperature.
- 0.58 ppm-meter at 25 Celsius (77 Fahrenheit)
- 0.69 ppm-meter at 100 Celsius (212 Fahrenheit)
- 0.79 ppm-meter at 160 Celsius (320 Fahrenheit)
- 0.82 ppm-meter at 185 Celsius (365 Fahrenheit)
Results for a path length of 20 feet (6.09 meters).
- 0.58/6.09 = 0.095 ppm at 25 Celsius (77 Fahrenheit)
- 0.69/6.09 = 0.113 ppm at 100 Celsius (212 Fahrenheit)
- 0.79/6.09 = 0.130 ppm at 160 Celsius (320 Fahrenheit)
- 0.82/6.09 = 0.135 ppm at 185 Celsius (365 Fahrenheit)
All twelve systems passed.

Beam Intensity Test

Establish beam intensity attenuation tolerance of your system and demonstrate that the HCl response is independent of the beam intensity.
- Calibrate, reduce intensity, recalibrate
- Less than 3% difference in cals is a pass.
Results:
- Calibration errors ranged between 0.34% and 2.53%.
- Beam intensity reductions ranged between 94% and 96%.
- All twelve systems passed.
In the future you may not operate at a beam intensity lower than that established during the test.
Procedure 6 QA: check and record beam intensity (laser power) on a daily basis.

Temperature Test

Temperature measuring device must be within 1% or 5° of approved standard temperature measurement
Field or bench testing allowed
No instructions on exactly how to run this test
MSI did three ten minute runs in the field during RATA and averaged ten one minute data points for each run
Compared our results to reference method temperature results
Results
- Temperature differences ranged between 0.3 °F and 3.7 °F
- All twelve systems

PASSED Pressure Test

You must be within 5% or 0.5 inwc of approved standard.
Field or bench testing allowed.
No instructions on exactly how to run this test.
MSI did three ten minute runs in the field during RATA and averaged ten one minute data points for each run.
Compared our results to reference method temperature results.
Results
- Pressure difference ranged between 0.01% and 4.61%.
- All twelve systems passed.

Measurement (Calibration) Error Test

Standard linearity test except the results are based on 5% of span not a percentage of cylinder value.
All MATS units have a 5 ppm span and a limit of 0.25 ppm.
For a TDL measurement error test is much more cumbersome and time consuming than normal calibration error testing.
- Measure background, low, purge, measure background, mid, purge, measure background, high, purge, measure background
Results:
- Error ranged between 0.4 and 4.4%.
- All twelve systems passed.

Response Time Test

Same procedure as in 40CFR75 but final PS-18 rule surprising did not list a performance specification criteria.
MSI used standard 15 minute response time.
Results
- Response time ranged between 1 and 4 minutes.
- All twelve systems passed.

Seven Day Drift Test

Standard seven day drift test with limit of 5% of span for seven of seven operating days.
All MATS units have a 5 ppm span and a limit of 0.25 ppm.
Results
- Highest drift values ranged between 2.8% to 4.96%.
- Difficult because of background capture during calibrations.
- All twelve systems passed.

Relative Accuracy Test Audit

Standard RATA.
Choice of Method 26A, 320, 321.
Recommend using Method 320 (FTIR) because you want instantaneous measurements to set up and verify analyzer operation and to know system passed RATA.
Results:
- Wet stacks used < 0.2 ppmvw absolute mean difference.
- Results ranged between 0.072 and 0.115 ppmvw difference
- Two dry systems used < 20% of mean reference method.
  - 19.54 and 19.90%
- Two dry systems used < 15% of emission limit equivalent.
  - 1.55 and 11.95%

Factors Affecting TDL Measurements

All tunable diode lasers do not measure in the same manner.
We call these the area versus the peak measurement methods.
You must know how your analyzer works.
EPA requires measurement of and correction for the following factors:
- Line Strength Multiplier
- Temperature
- Pressure
- Water Vapor

Factors Affecting TDL Measurement

For measurements on a dry stack burning Illinois basin coal at 350 °F, we have the following corrections:
- Line strength multiplier = 0.96
- Temperature = 1.52
- Pressure = 0.985
- Water = 1.31
We have one stack where the moisture level varies from 8 to 12 percent depending on process operation – the water correction factor varies from 1.31 to 1.47.
How an instrument handles corrections, particularly water and temperature, is the key to the quality of the HCl measurement.

Summary

Operation of TDL analyzers have exceeded expectations:
- Had more than enough power to do wet stacks.
- Alignment was not an issue.
- Calibration standards are available (50/110/180 ppm instead of 1.25/2.75/4.5 ppm)
- Minimal maintenance and service.
Unexpected benefits for plants with wet scrubbers that cannot maintain 97%+ removal rate. Surprisingly wet scrubbers end up to be relatively easy to monitor.
- Stable background with very low and often zero ppm
- Stable temperature
- Stable moisture