In Situ Measurement Technique for Simultaneous Detection of K, KCl, and KOH Vapors Released during Combustion of Solid Biomass Fuel in a Single Particle Reactor

Abstract

A quantitative and simultaneous measurement of K, KCl, and KOH vapors from a burning fuel sample combusted in a single particle reactor was performed using collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) with a time resolution of 0.2 s. The previously presented CPFAAS technique was extended in this work to cover two consecutive fragmentation pulses for the photofragmentation of KCl and KOH. The spectral overlapping of the fragmentation spectra of KCl and KOH is discussed, and a linear equation system for the correction of the spectral interference is introduced. The detection limits for KCl, KOH, and K with the presented measurement arrangement and with 1 cm sample length were 0.5, 0.1, and 0.001 parts per million, respectively. The experimental setup was applied to analyze K, KCl, and KOH release from 10 mg spruce bark samples combusted at the temperatures of 850, 950, and 1050 °C with 10% of O2. The combustion experiments provided data on the form of K vapors and their release during different combustion phases and at different temperatures. The measured release histories agreed with earlier studies of K release. The simultaneous direct measurement of atomic K, KCl, and KOH will help in the impact of both the form of K in the biomass and fuel variables, such as particle size, on the release of K from biomass fuels.

Development of an alkali chloride vapour-generating apparatus for calibration of ultraviolet absorption measurements

“…There is also a need for calibration data for sodium hydroxide (NaOH) and for potassium hydroxide (KOH). 5 Previous studies indicate that hydroxides exhibit lower absorption cross sections than chlorides. 32 Moreover, since vapour pressures for solid-gas equilibrium for these compounds are rather low, 14 the cell needs to be operated above the melting points, 318 • C for NaOH and 406 • C for KOH, to achieve sufficient vapour pressures in the cell.…”

“…While quantitative species concentrations in principle can be achieved by evaluation of measurements using the literature data for necessary physical quantities, e.g., absorption cross sections, for many cases, calibration under well-defined experimental conditions is necessary. For example, there might be insufficient data for relevant species such as an absorption cross section for potassium hydroxide as reported by Sorvajärvi et al 5 New techniques developed for flue gas measurements, such as the LIDAR concept for KCl detection, 6 also require calibration for a) Electronic mail: tomas.leffler@forbrf.lth.se accurate quantitative measurements. Moreover, extension of instruments based on broadband absorption such as the in situ alkali chloride monitor (IACM) 7,8 to incorporate additional alkali species also call for the possibility to measure well-defined reference spectra.…”

In situ H2O and temperature detection close to burning biomass pellets using calibration-free wavelength modulation spectroscopy

“…Strategies to tackle the above mentioned research questions include thermochemical conversion of single biofuel particles in well controlled and characterized laboratory flames or reactors [4][5][6][7][8]. In such experiments, the combustion process (drying, devolatilization, char combustion) occurs on the order of seconds or minutes (depending on the particle size and oxidizing conditions), during which the particle itself and the surrounding atmosphere will undergo large and fast changes in temperature and composition.…”

Characteristics of alkali species release from a burning coal/biomass blend

“…Among these techniques are collinear photo-fragmentation atomic absorption spectroscopy (CPFAAS) [26], laser induced fragmentation fluorescence (ELIF) [27], tunable diode laser 5 absorption spectroscopy (TDLAS) [28], planar laser-induced fluorescence (PLIF) [29] and laser-induced breakdown spectroscopy (LIBS) [30]. Application of these techniques to co-firing biomass and coal will provide valuable information about temporal release of alkali during combustion.…”