Open Access

ARTICLE

Scavenging Effects of Kaolin on Fine Ash Formation during Zhundong Coal Combustion

by Fangqi Liu¹, Xianpeng Zeng^1,2, Yimin Xia¹, Zihao Wang¹, Dunxi Yu^1,*

1 State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
2 WISDRI Engineering & Research Incorporation Limited, Wuhan, 430223, China

* Corresponding Author: Dunxi Yu. Email:

(This article belongs to the Special Issue: Advancement of Understanding of PM_2.5 and Hg Emissions and Their Control Technologies for Cleaner Combustion)

Energy Engineering 2021, 118(3), 459-471. https://doi.org/10.32604/EE.2021.014240

Received 12 September 2020; Accepted 18 November 2020; Issue published 22 March 2021

Abstract

The previous work found that the additive kaolin could scavenge not only sodium (Na) but also calcium (Ca) and magnesium (Mg), which is the important ash fluxing agents in low rank coal combustion. Such scavenging effects of kaolin on fine ash formation were studied in the present work. A typical Zhundong coal and its blends with kaolin at dosages of 1, 2 and 4 wt% were combusted in an electrically heated drop tube furnace (DTF) at 1300°C. The fine ashes generated were collected and size segregated by a low pressure impactor (LPI). The morphology and chemical composition of fine ash were analyzed by scanning electron microscopy equipped with an energy-dispersive spectrometer (SEM-EDS). In addition, char/ash particles were sampled at various positions of DTF to elucidate how kaolin additive affected the fine ash formation process. The results further showed that apart from the scavenging of volatile Na, kaolin additive could also strongly scavenge the refractory Ca, Mg and Fe in the fine ash during Zhundong coal combustion, which transformed the sintered particles with irregular shape into melted spherical particles, and finally resulted in the considerable decrease of these elements in both PM_0.4 and PM_0.4-10 by melting and agglomeration. The close contacts between kaolin particles and coal resulted from physically mixing were a key factor responsible for the reaction of kaolin with the refractory Ca, Mg and Fe.

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