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

Abstract

This work studied the effect of potassium chloride (KCl) on soot formation during the combustion of municipal solid waste (MSW). The nanostructural and oxidative properties of soot particles were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) spectroscopy, Raman spectroscopy (RS), and thermogravimetric analysis (TGA). HRTEM images showed that, under the same combustion environment, the KCl-loaded fuel samples generated soot particles with smaller particle sizes and more compact morphologies. Quantification of the nanostructure further indicated that, with increasing potassium concentrations from 1 to 5%, the fringe separation distance and fringe tortuosity of soot particles slightly increased, yet no clear trend was observed in the fringe length. Raman spectral analysis verified the fringe analysis, suggesting that the addition of KCl made the soot nanostructure more disordered with a larger separation distance and higher fringe tortuosity. In addition, oxidation profiles determined that the reactivity of K-doped soot was enhanced because of a decrease in the apparent activation energy (E a) from 167 to 124 kJ/mol. Moreover, E a showed strong linearity with the fringe tortuosity and fringe separation distance, with R 2 values of 0.91 and 0.97, respectively. On the basis of the experimental data, a schematic of four K–soot interaction routes is proposed to better understand the soot formation during the combustion of solid wastes.

Effect of Alkaline Salts on Pyrolyzed Solid Wastes in Used Edible Oils: An Attenuated Total Reflectance Analysis of Surface Compounds as a Function of the Temperature

“…The presence of bands around 3000 cm −1 , due to aliphatic hydrocarbons in the biochars obtained from the water-washed samples (not detected in the unwashed sample), evidences the incomplete decomposition of the initial material. Given that in similar conditions of pyrolysis, the degree of decomposition is lower when inorganic salts are eliminated, we can think that this is a catalytic effect of these salts, as previously reported in the literature [35,36].…”

“…The observed trend suggests that the cracking reaction (1) occurs at T > 500 • C, but the condensation reactions seem to be limited. As the initial biomass composition is similar to that of a conventional biomass, the unexpected evolution of the DOC with the temperature should be caused by the presence of inorganic salts, such as NaCl (and KCl), in the initial material [35,36].…”