Raman Analysis for Gas Turbine Fuel Gas Characterization

Abstract Fuel flexibility in GTs is one of the main challenges in GT operability today, as fuel gas composition is becoming increasingly complex and varied. Fast and reliable fuel gas property monitoring is a key requirement for managing fuel flexibility and ensuring proper GT combustion control—especially in DLE machines. At the same time, the growing focus on emission reduction imposes constraints on traditional extractive gas analyzers, where venting to flare can significantly impact both accuracy and response time. A new approach to fast, reliable, and zero-emission fuel gas analysis, based on Raman spectroscopy, has been tested in both laboratory and field applications. The results of these tests will be presented. Raman spectroscopy is a well-established technique in which a laser induces changes in the vibrational state of a molecule, resulting in the emission of a photon with an intensity and frequency characteristic of the molecule. While Raman spectroscopy is widely used for liquid analysis, its fast response time makes it a valuable option for fuel gas monitoring in GT applications. Therefore, we have investigated the performance of a Raman-based analyzer for fuel gas characterization, traditionally carried out using GCs or gas calorimeters. Additionally, the ability to monitor homonuclear molecules such as H2 is a significant advantage, considering the rapid and widespread adoption of hydrogen blending in fuel gas to reduce emissions. To further minimize the environmental impact of sample release—typical of extractive analyzers—a specially designed probe was developed to reinject the analyzed sample back into the fuel gas pipeline. This study demonstrates that a Raman spectroscopy-based analyzer is a viable alternative to gas calorimeters that measure residual O2, achieving an accuracy of ±1% on mass-based LHV with an overall response time below 30 seconds—significantly faster than conventional process GCs typically used for GT control.