Infrared analysers for measuring the composition of simple
flowing gas streams on chemical plant have been available for more
than 40 years. For almost as long, infrared spectrometers have been
used in research laboratories to measure the composition of complex
liquid and solid samples.
Instrument performance has been improved, new sampling methods
have been devised and mathematical procedures developed whereby
measurements can now be made in plant laboratories by plant operators
on complex gas and condensed phase products with sufficient precision
zor specification testing and sufficient speed to permit composition
trends to be followed.
Recently, IR probes have been developed which permit remote
measurements on liquids inside chemical plant vessels, and these
sensors may well produce information of sufficient quality to permit
real plant control.
It is the object of this paper to follow these developments and
assess the present position.