Quantitative Hydrogen Chloride Detection in Combustion Environments Using Tunable Diode Laser Absorption Spectroscopy with Comprehensive Investigation of Hot Water Interference

Abstract

Hydrogen chloride (HCl) monitoring during combustion/gasification of biomass fuels and municipal solid waste, such as polyvinyl chloride (PVC) and food residues, is demanded to avoid the adverse effect of HCl to furnace operation and to improve the quality of the gas products. Infrared tunable diode laser absorption spectroscopy (IR-TDLAS) is a feasible nonintrusive in-situ method for HCl measurements in harsh environments. In the present work, the measurement was performed using the R(3) line of the ν2 vibrational band of HCl at 5739.25 cm–1 (1742.4 nm). Water vapor is ubiquitous in combustion/gasification environments, and its spectral interference is one of the most common challenges for IR-TDLAS. Spectral analysis based on the current well-known databases was found to be insufficient to achieve an accurate measurement. The lack of accurate temperature-dependent water spectra can introduce thousands parts per million (ppm) HCl overestimation. For the first time, accurate spectroscopic data of temperature-dependent water spectra near 5739.3 cm–1 were obtained based on a systematic experimental investigation of the hot water lines in a well-controlled, hot flue gas with a temperature varying from 1100 to 1950 K. With the accurate knowledge of hot water interference, the HCl TDLAS system can achieve a detection limit of about 100 ppm⋅m at around 1500 K, and simultaneously the gas temperature can be derived. The technique was applied to measure the temporally resolved HCl release and local temperature over burning PVC particles in hot flue gas at 1790 K.

Research and Innovation Needs for the Waste-To-Energy Sector towards a Net-Zero Circular Economy

“…Measurements further upstream inside WtE boilers are made challenging by the high temperature and high dust concentration at which probes and sensors would be exposed [37]. Methods based on sampling might be affected by substantial uncertainties associated with the need to cool down and dehydrate the gas sample, especially for highly reactive components, such as HCl below the dew point [38]. Therefore, recent research has focused on the development of robust and reliable in situ measurements of the chemical species released by waste combustion.…”

“…Therefore, recent research has focused on the development of robust and reliable in situ measurements of the chemical species released by waste combustion. For example, tunable diode laser absorption spectroscopy (TDLAS) has been explored as a sampling-free sensing option for the measurement of HCl [38,39], while the release of alkali metals from combustion has been tested at grate incinerators by means of flame emission spectroscopy (FES, [40,41]). At the same time, the sampling of particulate matter in high-temperature flue gas, which is useful to characterize the role of the particulate phase in corrosion is still a technical challenge [42], and novel approaches have been tested in recent years [43].…”

An Interactive Spectral Analysis Tool for Chemical Identification and Quantification of Gas-Phase Species in Complex Spectra

“…Quantitative spectroscopy has a wide range of applications in a variety of research domains. Notable applications of Fourier transform infrared (FT-IR) gas-phase spectroscopy include atmospheric and environmental monitoring, as well as in remediation processes [1][2][3][4][5] where the ability to reliably detect and quantify gas-phase species at the parts per million (ppm), or even parts per billion (ppb) level, is critical. This capability is often implemented in the longwave infrared region (i.e., the fingerprint region) where nearly all molecular species, including environmental contaminants, exhibit unique spectral absorption features that can be used for rapid signature identification.…”

Optimized CT-TDLAS reconstruction performance evaluation of least squares with the polynomial-fitting method

“…Tunable diode laser absorption spectroscopy (TDLAS) is one of the spectral analysis technologies which can measure the temperature and gas concentration parameters. TDLAS has several advantages including high sensitivity, high noise immunity, high repetition rate, and easy compatibility with communication fiber optic components [10][11][12]. It means the TDLAS system is easy to be integrated, and the cost is lower than that of other spectral analysis technologies [13,14].…”