A multi-laser hybrid absorption sensor for simultaneous measurement of NH3, NO, and temperature in denitrification flue gas.

• A multi-laser hybrid sensor is designed based on tunable diode laser absorption spectroscopy (TDLAS) for simultaneous measurement of NH 3 , NO, and flue gas temperature. • In calibration-free wavelength modulation spectroscopy (CF-WMS) measurements, we used a method to obtain the laser wavelength response by a simple fit to the S 2f/1f line pattern of a standard gas with a standard deviation of less than 5 × 10-3 cm-1. • Under static conditions, the relative accuracy of NH 3 and NO detected by the sensor is 4.2% and 2%, respectively, and the maximum relative standard deviation of temperature is 1.3%. • When tested under flowing conditions, the sensor can accurately capture NH 3 , NO, and temperature changes. The relative accuracy of NH 3 and NO is 4.7% and 2.2%, and the relative standard deviation of temperature is 0.9%. The real-time monitoring of NH 3 , NO, and flue gas temperatures is critical to controlling NO x emissions from coal-fired power plants, reducing ammonia slip, and realizing accurate ammonia injection. However, few previous studies have utilized laser absorption sensors to measure these three indicators simultaneously. In this paper, a multi-laser hybrid sensor is designed based on tunable diode laser absorption spectroscopy (TDLAS) for simultaneous measurement of NH 3 , NO, and flue gas temperature. The sensor uses a distributed feedback (DFB) laser to target the NH 3 and the H 2 O lines, and a quantum cascade laser (QCL) is used to target the NO line. In the measurements of NH 3 and NO using calibration-free wavelength-modulated spectroscopy (CF-WMS), we employ a method to obtain the laser wavelength response by fitting the demodulated signal of a standard gas. Additionally, temperature measurements are obtained using the time-division multiplexing (TDM) strategy and direct absorption spectroscopy (DAS) techniques with the help of the absorption spectrum of H 2 O. Under static conditions, the relative accuracy of NH 3 and NO detected by the sensor is 4.2% and 2%, respectively, and the maximum relative standard deviation of temperature is 1.3%. When tested under flowing conditions, the sensor can accurately capture NH 3 , NO, and temperature changes. The relative accuracy of NH 3 and NO is 4.7% and 2.2%, and the relative standard deviation of temperature is 0.9%. The sensor has great potential in optimizing denitrification processes in thermal power plants. [ABSTRACT FROM AUTHOR]