CO Precursor Gas Monitoring Training Overview Solomon Ricks

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CO Precursor Gas Monitoring Training Overview Solomon Ricks, U. S. EPA Office of Air

CO Precursor Gas Monitoring Training Overview Solomon Ricks, U. S. EPA Office of Air Quality Planning and Standards Ambient Air Monitoring Group EPA Precursor Gas Training Workshop

Outline • • Introduction Methodology Burdens Creek Operation Cautions Instrument Operation Interferences and Operational

Outline • • Introduction Methodology Burdens Creek Operation Cautions Instrument Operation Interferences and Operational Issues Summary EPA Precursor Gas Training Workshop

Introduction Why analyze for Carbon Monoxide (CO) as a precursor gas? • CO is

Introduction Why analyze for Carbon Monoxide (CO) as a precursor gas? • CO is formed from incomplete combustion • Values across the nation are falling below the sensitivity of current CO methods • Characterize typical urban/rural concentrations for long-term trends analysis. EPA Precursor Gas Training Workshop

Methodology Measurement Principles – Non-Dispersive Infrared (NDIR) based on Beers Law T = I/Io

Methodology Measurement Principles – Non-Dispersive Infrared (NDIR) based on Beers Law T = I/Io = e(-ax. C) where: T I Io a x C = Transmittance of light through the gas to the detector = light intensity after absorption by CO = light intensity at zero CO concentration = specific CO molar absorption coefficient = path length, and = CO concentration EPA Precursor Gas Training Workshop

Methodology Measurement Principles – Non-Dispersive Infrared (NDIR) based on Beers Law I/Io = e(-ax.

Methodology Measurement Principles – Non-Dispersive Infrared (NDIR) based on Beers Law I/Io = e(-ax. C) Rearranging this equation: ln I/Io = ax. C Rearranging this equation: C = (ln I/Io)/(a*x) I and Io are measured by detector (i. e. The M/R or S/R ratios of the instruments readout) “a” is a constant CO molar absorption coefficient at a wavelength of 4. 6 micrometers “x” is the path length of the detection cell EPA Precursor Gas Training Workshop

Methodology What makes a precursor gas CO instrument? The Precursor CO instrument is identical

Methodology What makes a precursor gas CO instrument? The Precursor CO instrument is identical to a non-precursor CO analyzer with the following exceptions: • Required sample stream dried using permeation or Nafion™ Dryer • Analyzer baseline determined and corrected using heated or other catalytic converter • Frequent auto-zero • The instrument has an ultra-sensitive or “hot” detector EPA Precursor Gas Training Workshop

Methodology Diagram of a Precursor Gas CO instrument EPA Precursor Gas Training Workshop

Methodology Diagram of a Precursor Gas CO instrument EPA Precursor Gas Training Workshop

Burdens Creek Operations T-API 300 EU TEI 48 C-TLE EPA Precursor Gas Training Workshop

Burdens Creek Operations T-API 300 EU TEI 48 C-TLE EPA Precursor Gas Training Workshop

Responses to Daily Checks 10 -25 -2006 thru 05 -22 -2007 Point Source Value

Responses to Daily Checks 10 -25 -2006 thru 05 -22 -2007 Point Source Value TEI Avg T_API Avg TEI Std Dev. T_API Std Dev. Span 4500 ppb 4614 ppb 4612 ppb 81 ppb 155 ppb Precision 500 ppb 514 ppb 550 ppb 17 ppb 30 ppb Zero 0 ppb 1 ppb -8 ppb 17 ppb 33 ppb EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

EPA Precursor Gas Training Workshop

Cautions • Bench Cleaning • Inspections • Cylinders, handling, shipping, storage • CO is

Cautions • Bench Cleaning • Inspections • Cylinders, handling, shipping, storage • CO is poisonous!!! • The Catalytic Converter and Bench are operated at 48 – 50 o C. It is Hot! EPA Precursor Gas Training Workshop

Instrument Operation Item Schedule Replace particle filter Bi-weekly Diagnostics Checks Bi-weekly Perform Level I

Instrument Operation Item Schedule Replace particle filter Bi-weekly Diagnostics Checks Bi-weekly Perform Level I check Daily Replace IR source As needed Leak Check and Pump Check Out Annually Inspect Pneumatic Lines Semi-annually Clean inside of Chassis As needed Rebuild or replace pump As needed Clean optic bench As needed Replace wheel motor As needed EPA Precursor Gas Training Workshop

Interferences and Operational Issues • Water Vapor • Water absorbs strongly in many IR

Interferences and Operational Issues • Water Vapor • Water absorbs strongly in many IR spectra • Water must be removed using permeation or Nafion dryer • Carbon Dioxide • CO 2 absorbs in several of the same regions as CO • Baseline adjustment via Auto-zero (Azero) or Autoreference (Aref) Cycle EPA Precursor Gas Training Workshop

Interferences and Operational Issues • Why auto-reference or auto-zero? – Continuous measurements at low

Interferences and Operational Issues • Why auto-reference or auto-zero? – Continuous measurements at low concentrations may be limited by gradual changes in baseline • What cause the changes? – Environmental changes, i. e. , temperature – Drift related to the age of optical bench components – Interferents, such as CO 2 EPA Precursor Gas Training Workshop

Interferences and Operational Issues Auto-reference or auto-zero cycle TEI 48 C-TLE • Performs an

Interferences and Operational Issues Auto-reference or auto-zero cycle TEI 48 C-TLE • Performs an auto-zero, or “Azero”, cycle - 10 minutes through the Carolite scrubber. • Length of test not adjustable • Frequency is adjustable • Adjusts the baseline of the instrument T-API 300 EU • Performs an auto-reference, or “Aref”, cycle - <15 minutes through the heated palladium catalytic converter • Length of test not adjustable • Frequency is adjustable • Adjusts the measurement/reference (M/R) ratio EPA Precursor Gas Training Workshop

Interferences and Operational Issues Auto-Reference Cycle API 300 EU 1. 2. 3. 4. 5.

Interferences and Operational Issues Auto-Reference Cycle API 300 EU 1. 2. 3. 4. 5. 6. Instrument goes into “Aref” cycle (<15 minutes) • 3 -minute dwell period before and after auto-ref measurements • Auto-ref measurement lasts 9 minutes Sample air re-routed to pass through converter - all CO is converted to CO 2 Analyzer examines the M/R Ratio Since CO is scrubbed out, any change in this ratio from last Aref cycle must mean that CO 2 or H 20 are interfering Analyzer CPU adjusts the M/R ratio to compensate and the offset is changed Note: API recommends that you set this to once every 24 hours for ambient conditions. For process control, more often. We have set it to once every 12 hours EPA Precursor Gas Training Workshop

Interferences and Operational Issues Auto-Zero Cycle, TEI 48 C-TLE 1. 2. 3. 4. 5.

Interferences and Operational Issues Auto-Zero Cycle, TEI 48 C-TLE 1. 2. 3. 4. 5. Sample stream re-routed through internal scrubber 10 -minute duration Adjusts the zero background Not intended to replace routine calibration Front panel display does not freeze EPA Precursor Gas Training Workshop

Summary • Carbon Monoxide in rural and suburban settings can be an indicator for

Summary • Carbon Monoxide in rural and suburban settings can be an indicator for VOCs • OAQPS continues operating instruments at its on-site monitoring station, Burdens Creek: TEI 48 C-TLE and T-API 300 EU • Other instrument(s) are available: Ecotech • Auto-reference or auto-zero sequence is an operational issue • Water vapor and CO 2 can cause interference. The dryer and CO scrubber must be plumbed and working properly or baseline shifts occur EPA Precursor Gas Training Workshop