Wettability of Fly Ashes from Four Coal-Fired Power Plants in China

Abstract

Wet flue gas desulfurization, heterogeneous condensation, and chemical agglomeration have been reported to be promising methods for controlling fine particulate matter (PM) from coal combustion flue gas. The effectiveness of these processes is affected by the wettability of the fly ash particles. A novel method based on the flotation mechanism using a laser particle size analyzer was used to measure the wettability of fly ash particles in water, sodium dodecylbenzene sulfonate (SDBS), and Triton X-100 (TX100) solutions. Fly ash samples were collected from four coal-fired power plants in China [Xuanwei (XW), Jungar (JG), Xiaolongtan (XLT), and Yangzonghai (YZH)], representing high-silicon, high-aluminum, high-calcium, and high-iron fly ashes, respectively. The particle size distributions, surface areas, zeta (ζ) potentials, densities, chemical compositions, mineral compositions, and morphologies of the fly ash samples were investigated as well. PM0.1 and PM10+ were readily wetted in water, but most particles within the 1–10-μm range exhibited lower wettabilities. The wettability of fly ashes in water is related to other physical or chemical characteristics and follows the trend YZH > XLT > XW > JG. For YZH fly ash, PM0.1 and PM1+ can be completely wetted in water. For XW, JG, and XLT fly ashes, only PM0.1 and PM10+ can be wetted completely in water. Addition of SDBS or TX100 promoted most wetting processes, and the promotional effect is also related to other characteristics of fly ash particles such as surface roughness, surface area, and ζ potential.