Physical and chemical characterization of fugitive particulate matter emissions of the iron and steel industry

Abstract

The iron and steel industry is a notable particulate matter emitter. In source apportionment of particulate matter, it is important to identify the characteristics of particulate matter originating from steel sites. However, previous studies mostly focus on stack emission sources, while few reports on fugitive emission sources are available. Aiming to fill this gap, the physical and chemical characteristics of fugitive emission sources in the whole iron and steel production process were explored. The emission factor, particle size distribution (PSD), and morphological and chemical profiles of fugitive particulate matter (FPM) originating from fugitive emission sources at the observed site were analyzed through on-site sampling and in-lab testing. The emission factors in descending sequence are those of steelmaking plants, sinter plants, ironmaking plants and coking plants. The particle size of FPM mainly ranges from 0.1 to 716 μm, while distribution forms with both unimodal and bimodal peaks occur. The microscopic morphology of FPM is mainly divided into: irregular Fe-, Si-, Ca- and Mg-rich mineral particles formed by physical means, layered carbonaceous particles formed by mechanical crushing and combustion cracking, spherical Si-, Al- and Fe-rich particles in a high-temperature molten state, and chain and agglomerate particles formed by the polymerization of high-temperature flue gas and volatile minerals. The mass fraction of Fe ranks first in the sintering, ironmaking, and steelmaking processes, with values ranging from 1.40% to 57.79%. C attains the highest mass fraction, 69.80%, in the PFM originating from crushing mills.