Diode laser spectrometry for monitoring acetylene on-line in a liquefaction plant

A diode laser source spectrometer has been acquired for use as an on-line monitor for acetylene in the rich (oxygen-enriched) liquid stream of the Oak Ridge Gaseous Diffusion Plant (ORGDP) liquefaction plant. The liquefaction plant produces high purity liquid nitrogen for use in the gaseous diffusion plant and for development activities on the ORGDP site. The facility is of a design that runs continuously with considerable automation, but in addition to the built-in hydrocarbon analyzer in the final stage, a special instrument is required to monitor acetylene to ensure that concentration does not exceed the specification limit--0.5 ppm in the product reflux condenser shell. The instrument chosen for this application, a research-grade infrared spectrometer, requires somewhat special handling in order to be useful in this context but affords selectivity substantially in excess of that available with conventional ''on-stream'' monitors