Measurement of NH3 Transient Response in FTIR Sampling Systems

John  Hoard, University of Michigan

ORAL PRESENTATION: Experiments are reported using an MKS 2030HS FTIR with a variety of sampling line types, lengths, and temperatures in order to measure the effect on transient ammonia response.

It is widely known that ammonia interacts with walls and can be stored on them, slowing the transient response. Heated sample lines reduce this tendency. In addition various types of material can be used for the sample lines. In these experiments, the following parameters are varied:
Sample line and FTIR gas cell temperature 113 to 191°C
Sample line length  20  35 feet (6.1 – 10.7 meter)
Sample line diameter – ¼” – 3/8” (6.35 – 9.5 mm)
With and without water in the gas stream
Push and pull type sample system

Measurements were made by flowing a mixture of SF6 and NH3 in a synthetic gas reactor bench with solenoid switching to permit step changes in concentration. The instrument response time was recorded and the results tabulated for both components one that has a tendency to stick (NH3) and one that should present no changes with respect to temperature or material choice (SF6).

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