Page 413 - Instrumentation Reference Book 3E

396 Chemical analysis: gas analysis

Table 18.2 Properties and applications of gas detectors
Detector Applicubility Selectivity Carrier or Lower linirt Linear Tvpical
bulk gas of detection range applications
(grams)
Thermal Universal non-selective 10-6-10-7 104 Analysis of
conductivity binary or
pseudo-binary
mixtures; gas
chromatogaphy
Flame Organic compounds non-selective lo-" 106 Gas
ionization chromatography;
hydrocarbon
analyzers
Photo- Organic compounds limited N2 1o-II-10-1? 107 Gas
ionization except low molecular chromatography
weight hydrocarbons
Helium Trace levels of non-selective He lo-" 104 Gas
ionization permanent gases chromatography
Electron Halogenated and response is highly Ar, Nz, 10-"-10-'3 I 03 Gas
capture oxygenated compound- N2 + IO'%, CH4 chromatography,
compounds dependent tracer gas
detectors,
explosive
detectors
Flame Sulphur and selective to Nz, He 10-1' 5 x 102(S) Gas
photometric phosphorus compounds of lo3 (P) chromatography,
compounds S or P sulphur analyzers
Ultrasonic Universal non-selective Hz.He.Ar, 10-9--10-10 io6 Gas
detector mainly low N2. CO? chromatography
molecular weight
Catalytic Flammable gases selective to Air Flammable gas
(pellistor) flammable gases detectors
Seniiconductor Flammable gases, limited Air * Low-cost flammable
other gases gas detectors

* The performance of these detectors depends on the individual design and application
Sample to
disposal Constant temperature
* enclosure
-7

I
.-J
I I
I I
FI

I
I ProGammer

Bypass return
to plant or disposal display

Figure 18.17 Functional diagram of process gas chromatograph.