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Measurement of NO y During SCOS97-NARSTO. Dennis R. Fitz University of California, Riverside College of Engineering Center for Environmental Research and Technology. ORGANIZATION. NO y BACKGROUND CONVERTER-BASED INTERFERENCES NITRIC ACID TYPICAL DATA CONCLUSIONS. NO y IMPORTANCE.

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measurement of no y during scos97 narsto

Measurement of NOy During SCOS97-NARSTO

Dennis R. Fitz

University of California, Riverside

College of Engineering

Center for Environmental Research and Technology

organization
ORGANIZATION
  • NOy BACKGROUND
  • CONVERTER-BASED INTERFERENCES
  • NITRIC ACID
  • TYPICAL DATA
  • CONCLUSIONS
no y importance
NOy IMPORTANCE
  • Mass Balance
    • Quality control
    • Missing species
  • Estimate Nitric Acid by Difference
    • Sum of other species
    • Scrub nitric acid and use a second converter and analyzer channel
definitions
DEFINITIONS
  • NOy = Reactive Oxidized Nitrogen (N2O not included)
  • NOy = NO + NO2 +HNO3 + PAcN + HONO+ 2N2O5 + HO2NO2 + Organic Nitrates + NO3 + NO3-
  • (NOy)i = Catalytically Reduced NOy
  • NOx = NO + NO2
  • NOz = NOy - NOx
no y i measurement
(NOy)i MEASUREMENT
  • Chemiluminescent NO Analyzer
  • (NOy)i Converter to NO Located Outside Without an Inlet Filter (to reduce HNO3 losses)
    • Heated Molybdenum (300°-350°C)
    • Heated Gold (400°C) + CO (or H2)
    • Heated Vitreous Carbon (350°C)
    • Ferrous Sulfate
interferences
INTERFERENCES
  • Chemiluminescent Analyzer
  • Converter
  • Both have become more noticeable with commercial analyzers as they have become more sensitive
interferences analyzer
INTERFERENCES - ANALYZER
  • Water Vapor- Quenching
    • Zero (sub ppb)
    • Span (can be 10 %)
  • Methods to Minimize
    • Zero and/or Calibrate with Ambient Air Scrubbed of NOy
    • Method of Standard Addition
interferences heated converters
INTERFERENCES - HEATED CONVERTERS
  • Variable Efficiency for Nitrogenous Species
  • Conversion of Ammonia and Amines
  • Conversion of Cyanides
molybdenum converter characteristics
MOLYBDENUM CONVERTER CHARACTERISTICS
  • Ammonia Conversion
  • “Memory Effect” (High NOy or Hydrocarbon Concentrations)
    • Long stabilization period
    • Elevated “zero” response
  • Compound Selective Degradation
  • Lowered Efficiencies at Atmospheric Pressure
nitric acid measurement
NITRIC ACID MEASUREMENT
  • Use dual converters and scrub nitric acid (NA) using a denuder from the inlet of one to obtain NA by difference
  • Problems
    • Difference between large numbers
    • Converter efficiencies must be exactly the same for all NOy species and interferences
    • NOy memory effect greater than NOy -NA
nitric acid measurement1

NO Analyzer

NOy Converter

3- Way Solenoid Valve

External Converter Housing

NaCl Coated Filter

NO Detector

NOy Converter

NITRIC ACID MEASUREMENT
conclusions
CONCLUSIONS
  • Present converters have significant biases and interferences
  • Frequent (hourly?) zero checks are needed to assess memory effect
  • Routine converter efficiency checks for major NOy species and ammonia are needed
  • Acid coated denuders should be tried to remove ammonia (but let all NA pass)
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