Effect of mineral matter particle size on ash particle size distribution during pilot-scale combustion of pulverized coal and coal-water slurry fuels

Abstract

The objective of this work was to investigate the effect of the particle size distribution (PSD) of mineral matter in coal on the particle size distribution of ash produced during firing of two coals in pulverized coal and coal-water slurry forms. The coals used in this work were Beulah (North Dakota) lignite and Elk Creek (West Virginia) high volatile A bituminous coal. Combustion experiments were performed in a pilot-scale 316 MJ/h down-fired unit with 20% excess air. The dominant mechanism of ash formation in the Beulah pulverized coal was fragmentation of mineral particles, specifically pyrite, resulting in a finer ash particle size distribution than that of the origiml ' mineral matter (62% reduction in dw of mineral matter). By contrast, the main mechanism for determining the ash particle size in the Beulah coal-water slurry fuel (CWSF) was coalescence and agglomeration of the inorganic portion of the fuel (225% increase in dm of mineral matter). The size distribution and occurrence of inorganic matter in the fuels were the most important factors in determining ash size. Differences in pyrite PSD and occurrence between the two fuels were significant in determining the dominant mechanism for aiilh formation. The CWSF preparation process resulted in a significant reduction in the pyrite PSD and removal of organically bound sodium from the CWSF. The reduction in sodium in the CWSF did not significantly reduce the coalescence of ash particles during combustion. The PSDs of ashes from both pulverized and slurried Elk Creek coal are coarser than the original mineral matter, due to coalescence of inherent aluminosilicates and silicates during combustion. The particle size of the Elk Creek coal-water slurry fuel ash is slightly coarser than that from pulverized coal, due to the larger agglomerate formed upon atomization of the Elk Creek slurry. Atomization quality was the most important factor in determining the particle size of the ash. Subsequent papers will discuss the chemical interactions among the inorganic components during combustion of these fuels.

Emission of inorganic PM10 from included mineral matter during the combustion of pulverized coals of various ranks

“…The emission/formation of PM 10 is thus governed by two key aspects: coal mineral properties and local combustion conditions experienced by coal/char particles [3,13], both being often related to coal rank. For example, our review of some published papers [11,[14][15][16][17][18][19][20][21][22][23][24] shows that the kaolinite content in coal broadly correlates with coal rank (see Fig. S1 of the Supplementary Material).…”

Investigation on Inorganic Constituents in Indian Coal and Emission Characteristics of the Particulates (PM2.5 and PM10)

“…More than 50% of the minerals are found with sizes <10 µm. The size distribution of minerals in the coals is one of the most significant factors in determining ash size (Vassilev and Vassilevam, 1996;Miller and Schobert, 1993). Minerals with a finer size distribution will produce finer ash particles.…”

“…In addition, CCSEM analysis can also supply information on the particle-size distribution (PSD) of mineral species as well as their association with carbonaceous matter, which are also significant for keeping in mind before going to implement the clean coal technology. Because of these advantages, CCSEM has been widely used in fuel science since its inception (Gupta et al, 1998;Wells et al, 2005;Kim et al, 1989;Ghosal et al, 1995;Chen et al, 2004;Zygarlicke and Steadman, 1990;Vassilev and Vassileva, 1996;Miller and Schobert, 1993;Miller and Schobert, 1994). Such PSD information has relevance to our understanding and modelling of the behaviour of mineral matter during pulverised coal combustion and the formation of ash and slag deposits as well as other clean coal technology related problems.…”

Recruitment strategies and challenges: Lessons learned from a coal ash and children's health study

“…Fly ash is a fine gray to tan silt, consisting of spherical particulate matter with diameters ≤10 µm. The geochemical properties of the coal used and the burning process determine the toxicity of fly ash (Brown, Jones, & BéruBé, ; el‐Mogazi, Lisk, & Weinstein, ; Liu, Niu, Van Niekerk, Xue, & Zheng, ; Miller & Schobert, ; Spencer & Drake, ). Fly ash is composed mainly of silica, aluminum, iron, calcium, and oxygen, but particles also contain trace elements including heavy metals such as mercury, lead, cadmium, and arsenic (Bednar et al, ; Brown et al, ; Liberda & Chen, ; Patra, Rautray, Tripathy, & Nayak, ).…”