Morphology and elemental analysis of freshly emitted particles from packed-bed domestic coal combustion

Masilu Daniel Masekameni,Tebogo Isaac Rampedi,Tafadzwa Makonese,Goitsemang Salvation Keretetse

doi:10.17159/caj/2020/30/2.8582

Masilu Daniel Masekameni, Tebogo Isaac Rampedi + Show 2 more

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https://doi.org/10.17159/caj/2020/30/2.8582

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Abstract

This study was conducted in a laboratory-controlled environment to analyse the physical properties and elemental composition of coal combustion particles in a brazier. Particles were sampled ~1 m above the stove, using a partector. Particles were collected on gold transmission electron microscopy (TEM) grids, and polycarbonate filters for TEM and inductively coupled plasma mass spectrometry (ICP-MS) analysis, respectively. Particles for elemental analysis were collected on a 37 µm polycarbonate filter, and the exhaust was drawn in using a GilAir Plus pump. During sampling, a 2.5 µm cyclone was attached to the sampling cassette to isolate larger particles. Combustion particles emitted during the early stage of combustion were single organic spherical particles with similar characteristics to tarballs. As the combustion progressed, the particle diameter gradually decreased (from 109 nm), and the morphology changed to smaller particles (to 34.3 nm). The particles formed accretion chain structures, showing evidence of agglomeration. Furthermore, a fluffy microstructure, resembling the formation of soot, was formed in the post flaming phase. In the char-burning phase, an irregular structure of semi-spherical particles was formed, showing evidence of mineral particles infused with small carbonaceous particles. Similarly, with the findings of previous studies, the present research also observed organic spherical particles similar to tarballs. Given that during the ignition phase there was a simultaneous burning of wood as kindling and coal, the provenance of these particle emissions can be attributed to both coal and wood.

Highlights

The Despite efforts to reduce dependence on solid fuel, more than 3 billion people continue to burn coal and wood for cooking and space heating (Naeher et al, 2007; Gordon et al, 2014)
Morphology of smoke particles emitted during the ignition phase The morphology of particles observed using a transmission electron microscopy (TEM) for the ignition phase shows giant single spherical particles
Emission of spherical organic particles is synonymous with smouldering combustion conditions

Summary

Introduction

The Despite efforts to reduce dependence on solid fuel, more than 3 billion people continue to burn coal and wood for cooking and space heating (Naeher et al, 2007; Gordon et al, 2014). Suspension of fine particles has been associated with household emissions from wood and coal burning (Mc Donald and Biswas, 2004; Chafe et al, 2015). Several epidemiological studies have shown that particles below PM2.5 are strongly associated with infection of the lower respiratory tract, cardiovascular system disruption, and morbidity (Lim et al, 2012, 2013). The source to exposure mechanisms from domestic coal and wood-burning has not yet been established. The correct determination of the physicochemical properties of coal/ wood emissions particles is essential for source identification and characterisation. Very few studies have been conducted on the physicochemical properties of particles emitted from small scale coal combustion technologies, even though significant associated health risks have been reported in countries such as China, India and Finland (Niemi et al, 2006; Wilkinson et al, 2009; Zhang and Tao, 2009)

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