A Remote Sensor System Based on TDLAS Technique for Ammonia Leakage Monitoring

Abstract

The development of an efficient, portable, real-time, and high-precision ammonia (NH3) remote sensor system is of great significance for environmental protection and citizens’ health. We developed a NH3 remote sensor system based on tunable diode laser absorption spectroscopy (TDLAS) technique to measure the NH3 leakage. In order to eliminate the interference of water vapor on NH3 detection, the wavelength-locked wavelength modulation spectroscopy technique was adopted to stabilize the output wavelength of the laser at 6612.7 cm−1, which significantly increased the sampling frequency of the sensor system. To solve the problem in that the light intensity received by the detector keeps changing, the 2f/1f signal processing technique was adopted. The practical application results proved that the 2f/1f signal processing technique had a satisfactory suppression effect on the signal fluctuation caused by distance changing. Using Allan deviation analysis, we determined the stability and limit of detection (LoD). The system could reach a LoD of 16.6 ppm·m at an average time of 2.8 s, and a LoD of 0.5 ppm·m at an optimum averaging time of 778.4 s. Finally, the measurement result of simulated ammonia leakage verified that the ammonia remote sensor system could meet the need for ammonia leakage detection in the industrial production process.

Improvement of the Detection Sensitivity for Tunable Diode Laser Absorption Spectroscopy: A Review

“…Figure 2 shows the linestrength of various infrared absorption transitions for a few common species in the range of 400-10,000 cm −1 at 296 K. Therefore, it is important to select an appropriate absorption line for trace gas detection. Firstly, the absorption lines should be sufficiently independent to avoid interference from other gases that are abundant in the atmosphere, such as H 2 O and CO 2 [12]. Furthermore, the line strength should be appropriate to improve the detection sensitivity of the TDLAS system [13,14].…”

Application and algorithm research of TDLAS

“…Finally, the Monte Carlo method was used to simulate the proposed error allocation scheme [16]. Hongbin Lu et al developed a remote sensing monitoring system for NH3 gas leakage based on TDLAS by using 2f/1f signal processing technology with the detection limit of 16.6 ppm• m after Allan deviation analysis and verified the system feasibility by simulating ammonia leakage [17]. Ping Gong et al established a onefold humidness indicator for H2O gas and heavy-oxygen water vapor measurement based on TDLAS [18].…”

Interference fringe suppression in tunable diode laser absorption spectroscopy based on CEEMDAN-WTD

“…Figure 12 shows the relationship between the Allan deviation and averaging time τ. From these, the lower limit of detection (LOD) of the system can be obtained [37]; when the averaging time was 1 s, the LOD was 7.82 ppm, and when the averaging time was 148 s, the LOD reached a minimum of 3.08 ppm.…”