Simultaneous detection of K, KOH, and KCl in flames and released from biomass using photofragmentation TDLAS

Thorin, Emil; Zhang, Kun; Valiev, Damir; Schmidt, Florian M.

doi:10.1364/oe.446725

Cited by 16 publications

(13 citation statements)

References 34 publications

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“…This is reasonable as (i) the particle temperature during char conversion is higher, (ii) most of the K in the fuel is released after the devolatilization stage, and (iii) the gas temperature in the vicinity of the particle is closer to the flame temperature. ,, Beyond a height above the particle surface of about 5 mm (corresponding to HAP 8 mm), the LOS average concentration decreased to below 1 ppm (Figure ). This is in good agreement with previous measurements of K species above wheat straw particles in a CH 4 /air flame, the small differences in absolute values possibly explained by the different particle size used.…”

Section: Resultssupporting

confidence: 92%

“…As can be seen in Figure a, there are regions of high absorbance around the Pt plate edge, extending even below the plate, and the absorbance rapidly decreases as a function of HAP. The accumulation of atomic K near the plate edge has been observed in previous computational fluid dynamics (CFD) simulations and can be explained by recirculation due to the obstruction of the flow by the plate . Above approximately 4 mm HAP, the absorbance resembles a Gaussian shape as a function of horizontal position.…”

Section: Resultsmentioning

confidence: 52%

“…The Pt plate is indicated by the dotted line. (b) LOS atomic K concentrations at a horizontal position of 0 based on the radial atomic K concentration, as a function of HAP (line) compared to point measurements from previous work (markers) 26.…”

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confidence: 99%

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Quantitative Tomographic Laser Absorption Imaging of Atomic Potassium during Combustion of Potassium Chloride Salt and Biomass

2022

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Gaseous potassium (K) species play an important role in biomass combustion processes, and imaging techniques are powerful tools to investigate the related gas-phase chemistry. Here, laser absorption imaging of gaseous atomic K in flames is implemented using tunable diode laser absorption spectroscopy at 769.9 nm and a high-speed complementary metal oxide semiconductor (CMOS) camera recording at 30 kfps. Atomic K absorption spectra are acquired for each camera pixel in a field of view of 28 × 28 mm at a rate of 100 Hz. The technique is used to determine the spatial distribution of atomic K concentration during the conversion of potassium chloride (KCl) salt and wheat straw particles in a laminar premixed CH4/air flame with an image pixel resolution of up to 120 μm. Due to axisymmetry in setup geometry and, consequently, atomic K distributions, the radial atomic K concentration fields could be reconstructed by one-dimensional tomography. For the KCl sample, the K concentration field was in excellent agreement with previous point measurements. In the case of wheat straw, atomic K concentrations of around 3 ppm were observed in a cylindrical flame during devolatilization. In the char conversion phase, a spherical layer of atomic K, with concentrations reaching 25 ppm, was found within 5 mm of the particle surface, while the concentration rapidly decreased to sub-ppm levels along the vertical axis. In both cases, a thin (∼1 mm) layer without any atomic K was observed in close vicinity to the particle, suggesting that the potassium was initially not released in its atomic form.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 52%

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Quantitative Tomographic Laser Absorption Imaging of Atomic Potassium during Combustion of Potassium Chloride Salt and Biomass

2022

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“…The KCl release continued during the ash-cooking stage, but at a lower rate compared to the char combustion. More recently, Thorin et al 33 , 34 developed photofragmentation tunable diode laser absorption spectroscopy (PF-TDLAS) for simultaneous measurements of K, KOH, and KCl in both combustion and gasification, the latter usually characterized by optically thick conditions for K. The technique was applied for the detection of the three K species in a 140 kW EFG. 35 It was shown that the effects of small differences in fuel composition on the potassium release can be resolved by the PF-TDLAS method and that the obtained K species concentrations agreed reasonably well with the results from the thermodynamic equilibrium calculation.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study and Experimental Verification of Biomass Conversion and Potassium Release in a 140 kW Entrained Flow Gasifier

et al. 2023

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In this study, a Eulerian−Lagrangian model is used to study biomass gasification and release of potassium species in a 140 kW atmospheric entrained flow gasifier (EFG). Experimental measurements of water concentration and temperature inside the reactor, together with the gas composition at the gasifier outlet, are used to validate the model. For the first time, a detailed K-release model is used to predict the concentrations of gas-phase K species inside the gasifier, and the results are compared with experimental measurements from an optical port in the EFG. The prediction errors for atomic potassium (K), potassium chloride (KCl), potassium hydroxide (KOH), and total potassium are 1.4%, 9.8%, 5.5%, and 5.7%, respectively, which are within the uncertainty limits of the measurements. The numerical model is used to identify and study the main phenomena that occur in different zones of the gasifier. Five zones are identified in which drying, pyrolysis, combustion, recirculation, and gasification are active. The model was then used to study the transformation and release of different K species from biomass particles. It was found that, for the forest residue fuel that was used in the present study, the organic part of K is released at the shortest residence time, followed by the release of inorganic K at higher residence times. The release of inorganic salts starts by evaporation of KCl and continues by dissociation of K 2 CO 3 and K 2 SO 4 , which forms gas-phase KOH. The major fraction of K is released around the combustion zone (around 0.7−1.3 m downstream of the inlet) due to the high H 2 O concentration and temperature. These conditions lead to rapid dissociation of K 2 CO 3 and K 2 SO 4 , which increases the total K concentration from 336 to 510 ppm in the combustion zone. The dissociation of the inorganic salts and KOH formation continues in the gasification zone at a lower rate; hence, the total K concentration slowly increases from 510 ppm at 1.3 m to 561 ppm at the outlet.

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“…Many semiconducting materials are used for conductometric H 2 sensing, including graphene-based materials, transition metal dichalcogenides, and metal oxides [ 5 , 6 ]. Many different sensing technologies have been developed for H 2 sensing [ 7 , 8 , 9 ] and semiconductor-based H 2 sensors mainly present high sensitivity, quick response, and good stability based on their physical and electrochemical characteristics [ 10 , 11 , 12 , 13 , 14 ]. Commonly, the exceptional physical, optical, and electrical properties of 2D semiconductors, such as high surface to volume ratios and numerous active sites, lead to promising gas sensing performance (i.e., gas selectivity, excellent response, durability, and quick response and recovery) because of a change in charge density concentration near or on the sensing layer [ 15 , 16 , 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

Ultra-Sensitive Photo-Induced Hydrogen Gas Sensor Based on Two-Dimensional CeO2-Pd-PDA/rGO Heterojunction Nanocomposite

Hashtroudi

Juodkazis

et al. 2022

Nanomaterials

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A two-dimensional (2D) CeO2-Pd-PDA/rGO heterojunction nanocomposite has been synthesised via an environmentally friendly, energy efficient, and facile wet chemical procedure and examined for hydrogen (H2) gas sensing application for the first time. The H2 gas sensing performance of the developed conductometric sensor has been extensively investigated under different operational conditions, including working temperature up to 200 °C, UV illumination, H2 concentrations from 50–6000 ppm, and relative humidity up to 30% RH. The developed ceria-based nanocomposite sensor was functional at a relatively low working temperature (100 °C), and its sensing properties were improved under UV illumination (365 nm). The sensor’s response towards 6000 ppm H2 was drastically enhanced in a humid environment (15% RH), from 172% to 416%. Under optimised conditions, this highly sensitive and selective H2 sensor enabled the detection of H2 molecules down to 50 ppm experimentally. The sensing enhancement mechanisms of the developed sensor were explained in detail. The available 4f electrons and oxygen vacancies on the ceria surface make it a promising material for H2 sensing applications. Moreover, based on the material characterisation results, highly reactive oxidant species on the sensor surface formed the electron–hole pairs, facilitated oxygen mobility, and enhanced the H2 sensing performance.

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Simultaneous detection of K, KOH, and KCl in flames and released from biomass using photofragmentation TDLAS

Cited by 16 publications

References 34 publications

Quantitative Tomographic Laser Absorption Imaging of Atomic Potassium during Combustion of Potassium Chloride Salt and Biomass

Quantitative Tomographic Laser Absorption Imaging of Atomic Potassium during Combustion of Potassium Chloride Salt and Biomass

Numerical Study and Experimental Verification of Biomass Conversion and Potassium Release in a 140 kW Entrained Flow Gasifier

Ultra-Sensitive Photo-Induced Hydrogen Gas Sensor Based on Two-Dimensional CeO2-Pd-PDA/rGO Heterojunction Nanocomposite

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