A TUNABLE FILTER OPTICAL SYSTEM FOR ON-LINE AND REAL-TIME HYDROCARBON GAS COMPOSITION ANALYSIS

摘要

An all-optical sensor platform has been developed for hydrocarbon gas composition analysis enabling speciation and quantification of the individual hydrocarbon components in multi-component matrices of alkanes, alkynes, alkenes and/or alcohols. It performs such speciation without requiring physical separation of the compounds as performed in chromatography. The flow-through optical sensor provides unattended, real-time and consumable-free analysis suitable for on-line fuel gas analysis, combustion control, pipeline gas quality monitoring, BTU/heating value measurement and various hydrocarbon processing applications. The system consists of a light spectrometer, a flow-through sample cell, a single-element photo-detector and electronics. The spectrometer uses a unique tunable Fabry-Perot assembly that provides wavelength scanning with high Etendue. An advanced spectral processing and chemometric algorithm provides highly accurate and robust speciation performance compensating for various spectral nonlinearities due to pressure, flow and temperature variations. Challenges due to inherent spectral overlaps and nonlinearities will be presented, including methods of calibration and verification demonstrating the system performance in resolving interfering hydrocarbon spectra. Various test results using standard mixtures consisting of methane, ethane, propane, n-butane, iso-butane, propylene and ethylene compounds, as well as natural gas samples will be presented.