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A gas detection system includes a light detector, a pump laser with spectral emission between UV and IR wavelengths and structured to generate a laser beam, a hollow waveguide structured to receive a sample gas, the hollow waveguide having a bandwidth sufficient to transmit the laser beam and Stokes Raman photons scattered by the sample gas, and an optical system. The optical system is structured to: (i) direct the laser beam into the hollow waveguide such that it propagates in the hollow waveguide in one or more low-order low-loss waveguide modes, and (ii) direct Raman signals generated within the hollow waveguide in response to the laser beam interacting with the sample gas toward the light detector, the Raman signal including the Stokes Raman photons.
Industries that utilize natural gas, gasifier syngas, biogas, landfill gas, or any type of fuel gas can benefit from knowing the composition of a fuel gas mixture in real-time. Natural gas, the most common fuel, can have significant variation in hydrocarbon composition in areas supplied by multiple sources. The “opportunity fuels” such as biogas and landfill gases, also have significant variation in quality, and operators often use natural gas as a backup fuel. There is a need for a sensing system that is able to quickly and reliably identify, characterize, and determine the concentration of the various gases in a gas mixture. The current invention meets this need by providing a gas sensor system capable of accurate and continuous readout of the relative mole percent of all major fuel-gas components including H2, CO, CO2, CH4, C2H6, and C3H8, along with O2, N2, and water vapor. The sensor system is based on Raman spectroscopy, and has been developed to utilize low laser powers and low-resolution spectrometers and detectors to reduce cost while giving readouts in 1 second or less. This sensor system will greatly benefit the power industry, as well as other industries utilizing gaseous input or output streams by enabling faster, smarter control to increase process efficiency and reduce emissions. Currently, NETL is testing field prototype sensor systems to demonstrate use in applications and long-term operation.
Reports concentrations of all majority gases to better than 0.1% in 1 second or less, and can be used for real-time gas analysis and system control. -Real-time capability enables turbine operators to switch from one fuel to another with continuous adjustment of the fuel/air ratio for optimum operation efficiency and flameout prevention. -Current field-unit prototypes are rated for pressures between 10 psi and 800 psi and gas temperatures up to 200oC for regulated or direct pipeline measurement.


Patent Number: 
Patent Issue Date: 
November 4, 2012
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