Characterization of natural gas by Raman spectroscopy and its application for in-situ measurements

Gaseous hydrocarbons and nitrogen mixtures are characterized with an own designed portable Raman system equipped with a high pressure autoclave and fiber-optic probe. Backscattered radiation is collected through a sapphire window with a probe and transferred to the spectrometer. Samples are measured for a set of pressures in the range of 1–150 bar in ambient temperature. Measurement conditions are set to maintain an one-phase system. Spectra are collected in a wide range of wavenumber 350–3500 cm–1. Initial composition of measured samples is measured be means of gas chromatography. Design computer algorithms automatically detects and characterizes Raman bands for given species and their peak areas. The influence of both pressure and concentration of a given element on given band position and area are demonstrated.