Experimental investigations of potassium chemistry in premixed flames

Leffler, Tomas; Brackmann, Christian; Weng, Wubin; Gao, Qiang; Aldén, Marcus; Li, Zhongshan

doi:10.1016/j.fuel.2017.05.013

Cited by 20 publications

(9 citation statements)

References 31 publications

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“…Obtaining accurate spectrally resolved absorption cross-sections for alkali hydroxides is thus crucial in UV absorption measurements. 28 Compared with alkali chlorides, alkali hydroxides melt at a lower temperature and the vapor pressures for solid–gas equilibrium are lower than for chlorides. The typical temperatures needed for calibration in the previously mentioned cell are therefore much higher than the melting points: 591 K for NaOH and 679 K for KOH, 21 which presents a challenge for the quartz cell, since the hydroxides are very reactive in the liquid phase.…”

Section: Introductionmentioning

confidence: 99%

Spectrally Resolved Ultraviolet (UV) Absorption Cross-Sections of Alkali Hydroxides and Chlorides Measured in Hot Flue Gases

et al. 2018

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Spectrally resolved ultraviolet (UV) absorption cross-sections of gas-phase sodium chloride (NaCl), potassium hydroxide (KOH), and sodium hydroxide (NaOH) were measured, for the first time, in hot flue gases at different temperatures. Homogenous gas-phase NaCl, KCl (potassium chloride), NaOH, and KOH at temperatures 1200 K, 1400 K, 1600 K, and 1850 K were prepared in the post-flame zone of laminar flames by seeding nebulized droplets out of aqueous solution of corresponding alkali species. The amount of droplets seeded into the flame was kept constant, so the relative concentration of different alkali species can be derived. The broadband UV absorption cross-section of KCl vapor reported by Leffler et al. was adopted to derive the absorption cross-section curves of NaCl, NaOH, and KOH with the corresponding measured spectrally resolved absorbance spectra. No significant changes in the spectral structures in the absorption cross-sections were found as the temperature varied between 1200 K and 1850 K, except for NaOH at around 320 nm. The difference between the absorption spectral curves of alkali chlorides and hydroxides is significant at wavelengths above 300 nm, which thus can be used to distinguish and obtain the concentrations of alkali chlorides and hydroxides in the broadband UV absorption measurements.

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Section: Introductionmentioning

confidence: 99%

Spectrally Resolved Ultraviolet (UV) Absorption Cross-Sections of Alkali Hydroxides and Chlorides Measured in Hot Flue Gases

et al. 2018

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“…In the present work, a new method is developed to directly evaluate the UV absorption cross sections of KOH and KCl in environments with temperatures of ∼1300 and 1800 K. Using the obtained cross sections, quantitative measurements of potassium species were made in flames seeded with a constant amount of KCl, but with equivalence ratios varied from 0.67 to 1.32 and a post-flame temperature of ∼1800 K. Comprehensive experimental data were obtained as a substantial improvement in the study of the potassium chemistry, compared to the previous research based on the measurement of K atoms 25,26 or the total amount of KCl and KOH. 15 The concentration variation with equivalence ratios is discussed. The chemical balance between potassium species in different flame environments is presented.…”

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confidence: 99%

“…To obtain reliable quantitative results, the application of absorption spectroscopic techniques is essential. Broadband UV absorption spectroscopy is a powerful tool for measurement of KCl and KOH, − and tunable diode laser absorption spectroscopy (TDLAS) has been applied to measure K atoms. , Collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) was developed by Sorvajärvi et al for simultaneous detection of KCl, KOH, and atomic K.…”

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Ultraviolet Absorption Cross Sections of KOH and KCl for Nonintrusive Species-Specific Quantitative Detection in Hot Flue Gases

et al. 2019

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An understanding of potassium chemistry in energy conversion processes supports the development of complex biomass utilization with high efficiency and low pollutant emissions. Potassium exists mainly as potassium hydroxide (KOH), potassium chloride (KCl), and atomic potassium (K) in combustion and related thermochemical processes. We report, for the first time, the measurement of the ultraviolet (UV) absorption cross sections of KOH and KCl at temperatures between 1300 K and 1800 K, using a newly developed method. Using the spectrally resolved UV absorption cross sections, the concentrations of KOH and KCl were measured simultaneously. In addition, we measured the concentrations of atomic K using tunable diode laser absorption spectroscopy, both at 404.4 and 769.9 nm. The 404.4 nm line was utilized to expand the measurement dynamic range to higher concentrations. A constant amount of KCl was seeded into premixed CH4/air flames with equivalence ratios varied from 0.67 to 1.32, and the concentrations of KOH, KCl, and atomic K in the hot flue gas were measured nonintrusively. The results indicate that these techniques can provide comprehensive data for quantitative understanding of the potassium chemistry in biomass combustion/gasification.

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“…This method allows sensitive detection and imaging of alkali species; however, it is incapable of distinguishing between, for example, KCl and KOH, but relies on equilibrium calculations when concentrations of individual molecules are given. Differential optical absorption spectroscopy (DOAS) is capable of providing sensitive online monitoring of alkali species . As it, similar to PF‐LIF, relies on alkali molecule absorption in ultraviolet (UV) region of the electromagnetic spectrum, DOAS suffers from spectral overlapping of alkali species’ absorption bands, causing interference in the collected signal .…”

Section: Introductionmentioning

confidence: 99%

Detection of gaseous species during KCl‐induced high‐temperature corrosion by the means of CPFAAS and CI‐APi‐TOF

Lehmusto

Olin

Viljanen

et al. 2019

Materials & Corrosion

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Two different analytical approaches—collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) and chemical ionization atmospheric pressure interface time‐of‐flight mass spectrometer (CI‐APi‐TOF)—were applied to detect and identify the online gaseous KOH and HCl formed in the addressed high‐temperature reactions. Samples of pure KCl, KCl+Cr, KCl+Fe, and KCl+316 L were studied at 550°C under dry and humid conditions with varying oxygen concentrations. The goal was to shed more light on the gas‐phase chemistry during KCl‐induced corrosion under conditions relevant to biomass combustion. CI‐APi‐TOF proved to be a valuable tool for high‐temperature corrosion studies: HCl was identified to have formed during the reactions under humid conditions. On the contrary, despite the known sensitivity of CPFAAS, the formation of KOH could not be verified in any of the performed measurements.

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Experimental investigations of potassium chemistry in premixed flames

Cited by 20 publications

References 31 publications

Spectrally Resolved Ultraviolet (UV) Absorption Cross-Sections of Alkali Hydroxides and Chlorides Measured in Hot Flue Gases

Spectrally Resolved Ultraviolet (UV) Absorption Cross-Sections of Alkali Hydroxides and Chlorides Measured in Hot Flue Gases

Ultraviolet Absorption Cross Sections of KOH and KCl for Nonintrusive Species-Specific Quantitative Detection in Hot Flue Gases

Detection of gaseous species during KCl‐induced high‐temperature corrosion by the means of CPFAAS and CI‐APi‐TOF

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