title: In situ measurements of nitric oxide in coal-combustion exhaust using a sensor based on a widely tunable external-cavity GaN diode laser.
abstract: A diode-laser-based sensor has been developed to measure nitric oxide mole fractions using absorption spectroscopy. The sensor is based on sum-frequency mixing of a 395 nm external-cavity diode laser (ECDL) and a 532 nm laser in a beta-barium-borate crystal. Using a new tuning scheme, the GaN ECDL wavelength was modulated over 90 GHz without mode hops. The sensor was applied for measurements of the NO mole fraction in the exhaust of a laboratory-scale, 30 kW(t) coal-fired boiler burner. Absorption measurements were successfully performed despite severe attenuation by scattering from ash particles in the exhaust stream and on the exhaust-section windows. A detection limit (1sigma) of 4.5 ppm m/(square root)Hz at 700 K was demonstrated in coal- combustion exhaust at a maximum detection rate of 5 Hz.
authors.affiliation: School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907-2088, USA.
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Anderson
authors.forename: Robert P
authors.initials: RP
authors.lastname: Lucht
authors.forename: Soyuz
authors.initials: S
authors.lastname: Priyadarsan
authors.forename: Kalyan
authors.initials: K
authors.lastname: Annamalai
authors.forename: Jerald A
authors.initials: JA
authors.lastname: Caton
mesh_terms: D000042:Absorption; D000393:Air Pollutants / Q000032:analysis; D001881:Borates / Q000737:chemistry; D003031:Coal; D003460:Crystallization; D004784:Environmental Monitoring / Q000379:methods*; D007834:Lasers; D009569:Nitric Oxide / Q000737:chemistry*; D055095:Optics and Photonics; D009991:Oscillometry; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D001881:Borates; D003031:Coal; D009569:Nitric Oxide; C021755:tetraborate