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This study presented new field measurement data on the particle size distributions, morphological characteristics, and elemental composition of particulate matter (PM)2.5 (particle diameter less than 2.5 mm) from 12 industrial boilers, including eight circulating fluidized bed boilers (CFB) and four bubbling fluidized bed boilers (BFB). Measurement in situ was taken with an electrical low-pressure impactor equipped with a two-stage dilution sampling system. Morphological characteristics were determinded by electron microscope (SEM), and elemental compositions of the samples were determinded by X-ray fluorescence (XRF) and inductively coupled plasma (ICP). The results show that before and after the dust removal, the number concentration distributions of PM2.5 display bimodal distributions, one peak is between 0.07 and 0.12 μm, and the other peak is between 0.32 and 0.48 μm. And the particle concentrations of PM2.5 depended mainly on submicron particles (less than 1 µm in diameter), formed by gasification-condensation mechanisms. The mass concentration distributions of PM2.5 showing no peak distribution and increase with the particle size. Compared to electrostatic precipitators (ESPs) and fabric filters (FFs) , the ESPs has a lower removal efficiency of PM2.5. The morphological characteristics of PM2.5 before and after dust removal contain irregular particles and spherical particles. The mass percentages of Na, K, and Fe in PM2.5 after the dust removal are nearly the same as those before the dust removal, but Si, Ca, and Al in PM2.5 decreased after dust removal and S in PM2.5 increased after dust removal. Although the hazardous elements Cr, V, Mn, and Ni in PM2.5 after dust removal did not change significantly, the Pb, Cd, As, Se, and Hg increased after dust removal. These data clearly show that the composition of PM2.5 changes as dust are removed by air pollution control devices. [ABSTRACT FROM AUTHOR]

Particle size distributions, concentrations, morphological characteristics, and elemental compositions of PM 2.5 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 PM 2.5 were monitored and sampled using an electrostatic low pressure impactor. We found that before and after dust removal, the number concentration distributions of PM 2.5 displayed obvious unimodal distributions, with peaks in the range 0.07–0.38 μm. In both instances, the particle concentrations of PM 2.5 depended mainly on submicron particles (less than 1 μm in diameter), formed by gasification-condensation mechanisms. The concentration of the particles larger than 0.38 μm reflected aggregation of carbon black particles; this fraction tended to gradually decrease in concentration with increasing size. Total number and mass removal efficiencies of PM 2.5 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 PM 2.5 generated by industrial layer-burning boilers mainly comprised soot aggregates. However, the mass percentages of S, Si, K, and Al in PM 2.5 decreased after dust removal but increased after the desulfurization. In contrast, the mass percentage of Na in PM 2.5 increased after both dust removal and desulfurization processes, while the mass percentages of Ca and Fe in PM 2.5 decreased after dust removal but remained constant after desulfurization. These data clearly show that the composition of PM 2.5 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 PM 2.5 emitted by industrial layer-burning boilers of various sizes. • The first study on field measurements of the generation and emission characteristics of PM2.5 generated by industrial layer burning boilers in china. • The limestone-gypsum WFGDs and the double-alkali WFGDs have different mechanism on PM2.5 emission characteristics. • The removal efficiency of bag filter for the PM2.5 in the industrialized layer-fired boiler is much higher than that of the mechanical or wet precipitator. • PM2.5 produced by the layer-burning boiler contains spherical particles, irregular particles and soot aggregates, the majority are soot aggregates. [ABSTRACT FROM AUTHOR]