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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 CONVERTER

  • 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 CONVERTER

NOy Converter

3- Way Solenoid Valve

External Converter Housing

NaCl Coated Filter

NO Detector

NOy Converter

NITRIC ACID MEASUREMENT


Typical response lag due to memory effect
TYPICAL RESPONSE LAG DUE TO MEMORY EFFECT CONVERTER

To Zero Air 1005




Hno 3 comparison vs tdlas
HNO CONVERTER3 Comparison vs TDLAS



Smog chamber no y na
SMOG CHAMBER NO CONVERTERy -NA


No y response to filtered air with nitric acid removed
NO CONVERTERy RESPONSE TO FILTERED AIR WITH NITRIC ACID REMOVED


Conclusions
CONCLUSIONS CONVERTER

  • 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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