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Precursor Gas Monitoring NO y Monitoring Training Overview. Kevin A Cavender EPA-Office of Air Quality, Planning and Standards. Outline. Methodology Interferences and operational issues Commercially available NOy Monitors Calibration Current work in progress Summary. Methodology.

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Presentation Transcript
outline
Outline
  • Methodology
  • Interferences and operational issues
  • Commercially available NOy Monitors
  • Calibration
  • Current work in progress
  • Summary
methodology
Methodology

What is NOy?

NOy consists of the sum of all reactive nitrogen oxides. including NO, and NO2, and other nitrogen oxides referred to as NOz.

NO + NO2 + NOz = NOy

The major components of NOz include nitrous acids [nitric acid (HNO3), and nitrous acid (HONO)], organic nitrates [peroxyl acetyl nitrate (PAN), methyl peroxyl acetyl nitrate (MPAN), and peroxyl propionyl nitrate, (PPN)], and particulate nitrates.

methodology1
Methodology
  • Why Measure NOy?
  • NOy is a precursor to both ozone and PM2.5 formation
  • Conventional NOx boxes “accidentally” measure some NOz species, but not all.
methodology2
Methodology

Measurement Principles

NO is measured based on its chemiluminescent reaction with O3

NO + 03 -> NO2 + hv

The amount of light generated is linearly proportional to the concentration of NO.

NOy is measured by first passing the sample through a converter that converts NO2 and NOz species to NO and then measuring for NO as above.

methodology3
Methodology

Diagram of a High Sensitivity NOy instrument

methodology4
Methodology
  • What makes a high sensitivity NOy monitor different than a conventional (low sensitivity) NOx monitor?
  • A high sensitivity NOy monitor is very similar to conventional NOx monitors with the following exceptions:
    • Remote converter is located at sample inlet, not inside monitor
    • Pre-reactor to reduce non-NOy interferences
    • Increased sample flow rate
    • Reduced reaction chamber temperature and pressure
installation remote converter
InstallationRemote Converter

Remote Converter on 10 meter tower

interferences and operational issues
Interferences and Operational Issues
  • Reaction of NO with ambient O3
    • Ambient ozone will react with NO in sample lines creating negative NO interference
    • Residence in sample line should be kept to less than 2 seconds
  • Ammonia
    • Converter may convert a small amount of ammonia to NO creating positive NO interference
    • Avoid locating near ammonia sources (e.g., feed lots)
  • Converter height above ground level and “fetch”
commercially available noy monitors
Commercially Available NOy Monitors

TAPI 200EU/501 NOy TEI 42CY

EC9841A-NOy

histogram of noy data collected at burden s creek site 5 1 05 1 29 06
Histogram of NOy Data Collected at Burden\'s Creek Site5/1/05-1/29/06

NO

NOy

NO2 +

NOz

Percent

0

0-1

1-5

5-10

10-50

50-100

100-200

200+

Concentration (ppb)

instrument operation initial calibration
Instrument OperationInitial Calibration
  • Note: Supply sufficient calibration gas to ensure excess flow through converter inlet (supply > 5 liters per minute)
  • Supply zero air until stable readings are obtained (approximately 20-30 minutes)
  • Adjust monitor to read zero response for NO and NOy.
  • Supply NO calibration gas at approximately 90% of scale
  • Adjust monitor after stable NO and NOy readings are obtained
  • Add ozone to calibration gas to produce NO2 at approximately 70% of scale
  • Amount NO decreases equals the amount of NO2 created
  • Calculate conversion efficiency as (NOy-NO)/(NO2 created)
  • Conversion efficiency should be greater > 96%.
  • Adjust NO2 + NOz reading to amount of NO2 created
instrument operation converter efficiency test
Instrument OperationConverter Efficiency Test
  • Converter efficiency test designed to challenge converter with more difficult to convert NOy species
    • N-propyl nitrate, isopropyl nitrate
  • Supply sufficient calibration gas to ensure excess flow at converter inlet (> 5 liters per minute)
  • Supply calibration gas at approximately 90% of scale
  • Allow sufficient time for readings to stabilize
  • Calculate converter efficiency as –
  • (NOy reading/Concentration Suppliedx100%)
  • If converter efficiency is less than 96% the converter should be repaired/replaced
current work in progress
Current Work In Progress
  • Evaluation of inlet materials for API
    • Testing HNO3 loss on stainless steel, silico steel, and FTP teflon.
  • Evaluation of “proof of concept” NO/true NO2/NOy monitor
    • Two converters
      • Moly for NOy
      • High intensity LED for NO2
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