Real-time in situ multi-parameter TDLAS sensing in the reactor core of an entrained-flow biomass gasifier

Abstract

Real-time in situ multi-parameter TDLAS sensing in the reactor core of an entrained-flow biomass gasifier. Proceedings of the Combustion AbstractTunable diode laser absorption spectroscopy (TDLAS) was used to measure several important process parameters at two different locations inside the reactor of an atmospheric, air-blown 0.1 MWth biomass gasifier. Direct TDLAS at 2298 nm was employed for carbon monoxide (CO) and water vapor (H2O), calibration-free scanned wavelength modulation spectroscopy at 1398 nm for H2O and gas temperature, and direct TDLAS at 770 nm for gaseous elemental potassium, K(g), under optically thick conditions.These constitute the first in situ measurements of K(g) and temperature in a reactor core and in biomass gasification, respectively. In addition, soot volume fractions were determined at all TDLAS wavelengths, and employing fixed-wavelength laser extinction at 639 nm. Issues concerning the determination of the actual optical path length, as well as temperature and species non-uniformities along the line-of-sight are addressed. During a 2-day measurement campaign, peat and stem wood powder were first combusted at an air equivalence ratio (lambda) of 1.2 and then gasified at lambdas of 0.7, 0.6, 0.5, 0.4 and 0.35.Compared to uncorrected thermocouple measurements in the gas stream, actual average temperatures in the reactor core were significantly higher. The CO concentrations at the lower optical access port were comparable to those obtained by gas chromatography at the exhaust. In gasification mode, similar H2O values were obtained by the two different TDLAS instruments. The measured K(g) concentrations were compared to equilibrium calculations. Overall, the reaction time was found to be faster for peat than for stem wood. All sensors showed good performance even in the presence of high soot concentrations, and real-time detection was useful in resolving fast, transient behaviors, such as changes in stoichiometry.Practical implications of in-situ TDLAS monitoring on the understanding and control of gasification processes are discussed.

Distribution of temperature, H2O and atomic potassium during entrained flow biomass combustion – Coupling in situ TDLAS with modeling approaches and ash chemistry

“…Laser absorption spectroscopy enables fast, selective and accurate quantitative measurements without calibration procedures. Robust TDLAS setups have been applied in larger plants for analysis of temperature and major species in syngas and flue gas [23,24], and are suitable for measurements in the harsh and sooty environments of EFR reactor cores [24][25][26][27]. The technique has also been used for detection of atomic potassium in entrained flow coal combustion [28] and biomass gasification [27].…”

“…Simultaneous real-time detection of H2O, temperature and K(g) in one beam path was achieved by combining two existing TDLAS instruments previously applied and validated in flat-flames [35], single pellet conversion experiments [19,36] and pilot-scale entrained flow biomass gasification [27]. Calibration-free scanned wavelength modulation spectroscopy (CF-WMS) at 1398 nm provided path-averaged H2O concentrations and H2O density-weighted, path-averaged gas temperature [35,36],…”

Towards a dTDLAS-Based Spectrometer for Absolute HCl Measurements in Combustion Flue Gases and a Better Evaluation of Thermal Boundary Layer Effects

“…Fundamentally, the dTDLAS evaluation requires spatial homogeneity in gas temperature and matrix gas composition Sepman et al 2017;Bürkle et al 2018). If the homogeneity requirement is not fulfilled, which is typically the case in industrial applications, the question needs to be answered, what systematic deviation arises and how can those be quantified and minimized (Ouyang and Varghese 1989;Goldenstein et al 2013).…”

In-situ measurement of pyrolysis and combustion gases from biomass burning using swept wavelength external cavity quantum cascade lasers

“…and temperatures in flames [17,18], but is limited to detection of small molecules with resolved ro-vibrational lines due to limitations in laser tuning range. In biomass burning applications, TDLAS has been used to measure molecular species from combustion of wood fuel pellets [4,19] and biomass gasification [20].…”