High-pressure measuring cell for Raman spectroscopic studies of natural gas

A system for obtaining Raman spectra of gases at high pressure has been con structed. In order to ensure that a natural gas sample is totally represent ative, a high-pressure gas-measuring cell has been developed, built up by s tainless steel fittings and a sapphire tube. The design and construction of this cell are described. A perfect pressure seal has been demonstrated up to 15.0 MPaA (MPa absolute). The cell has been successfully used to obtain Raman spectra of natural gas samples. Some of these spectra are presented a nd assigned. The most remarkable observation in the spectra is that it is p ossible to detect hydrogen sulfide at concentrations of 1-3 mg H2S/Nm(3). A n attempt to make a quantitative analysis of natural gas by the so-called " ratio method" is presented. In addition to this, the relative normalized di fferential Raman scattering cross sections for ethane and i-butane molecule s at 8.0 MPaA and 10.2 MPaA have been determined.