Field measurements on the generation and emission characteristics of PM2.5 generated by industrial layer burning boilers

Particle size distributions, concentrations, morphological characteristics, and elemental compositions of PM2.5 from 15 industrial layer-burning boilers were determined experimentally in air, before and after dust removal and after desulfurization processes. The morphological characteristics and elemental compositions were analyzed using scanning electron microscopy and X-ray fluorescence, respectively. The concentrations and particle size distributions of PM2.5 were monitored and sampled using an electrostatic low pressure impactor. We found that before and after dust removal, the number concentration distributions of PM2.5 displayed obvious unimodal distributions, with peaks in the range 0.07 0.38 mu m. In both instances, the particle concentrations of PM2.5 depended mainly on submicron particles (less than 1 gm in diameter), formed by gasification-condensation mechanisms. The concentration of the particles larger than 0.38 gm reflected aggregation of carbon black particles; this fraction tended to gradually decrease in concentration with increasing size. Total number and mass removal efficiencies of PM2.5 indicate that fabric filters were superior to mechanical precipitators, although mechanical precipitators were superior to integrated dust removal and desulfurization devices. Typically, the number concentration increased after desulfurization, suggesting that better demisters need to be implemented in these systems. The PM2.5 generated by industrial layer-burning boilers mainly comprised soot aggregates. However, the mass percentages of S, Si, K, and Al in PM2.5 decreased after dust removal but increased after the desulfurization. In contrast, the mass percentage of Na in PM2.5 increased after both dust removal and desulfurization processes, while the mass percentages of Ca and Fe in PM2.5 decreased after dust removal but remained constant after desulfurization. These data clearly show that the composition of PM2.5 changes as dust and sulfur are removed by air pollution control devices. Data generated in this study are useful for selecting the most effective strategy for reducing PM2.5 emitted by industrial layer-burning boilers of various sizes. (C) 2018 Energy Institute. Published by Elsevier Ltd. All rights reserved.