Laser-induced fluorescence for studying the influence of potassium and sodium salts on PAH formation in sooting premixed flames

Abstract

Previous studies have shown that alkali salts influence combustion processes and soot formation, although the effects seem to vary across systems. Moreover, fundamental studies on the effect of potassium and sodium salts on formation of polycyclic aromatic hydrocarbons (PAH), which are precursors in soot formation, are scarce. Here, we report a study in which the effects on PAH formation due to the addition of alkali metal salts (KCl, KOH, K2CO3, NaCl and NaOH) to premixed ethylene–air flames were investigated. Different size classes of PAHs were probed using both spectral and 2D measurements of laser-induced fluorescence (PAH-LIF) using the excitation wavelengths 266 nm and 532 nm, while detecting the fluorescence emission at selected wavelength ranges. Elastic light scattering (ELS) measurements were also used to complement the fluorescence data. It was found that potassium and sodium salts do not significantly influence the formation of small PAHs (2–3 rings), while decreasing the concentration of larger PAHs at higher heights above burner (HAB). Another important result was that the anion in the salt (Cl−, OH−, CO32−) negligibly influences the PAH and soot formation processes after dissociation of the salts.

Single-pulse real-time billion-frames-per-second planar imaging of ultrafast nanoparticle-laser dynamics and temperature in flames

“…The transmission bandwidth of the band-pass filter for detecting ELS is only 0.15 nm, therefore the fluorescence signal from PAHs is negligible. The scattering from PAH molecules has been reported to be negligible as well in previous studies 59 . The normalized total intensity of ELS reaches the minimum at 12 ns.…”

Ex Vivo Glucose Detection in Human Blood Serums with Carbon Quantum Dot-Doped Oleic Acid-Treated Chitosan Nanocomposites

“…The fluorescence intensity remained almost constant at all acidic conditions of pH; however, the gradual decrease in fluorescence intensity in basic pH conditions is ascribed to the formation of sodium salt of OL. The influence of potassium and sodium salts on the fluorescence intensity of polycyclic aromatic hydrocarbon formation has previously been studied by Mannazhi et al with quite similar observations. The common reaction of OL with both NaOH and NaCl is shown in Figure e.…”

Effect of Potassium Chloride on the Nanostructure and Reactivity of Soot Particles from Combustion of Municipal Solid Waste

“…This is because the relatively low ionization potential of KCl can result in a larger K concentration in the flame, making the soot particles harder to coagulate. The ionic mechanism is introduced afterward to explain the phenomenon, and more similar results could also be seen in recent studies. ,− These investigations are most focused on the particle size distribution (PSD) and volume concentration of soot particles using in situ optical measurements, yet minimal information is available on their nanostructural and oxidative characteristics. It is widely accepted that the nanostructure of soot particles has a significant impact on oxidative reactivity, which essentially determines their toxicity. , In our previous work, the effect of typical components of MSW on soot formation during open burning has been investigated .…”