The behaviour of mineral matter during combustion of Spanish subbituminous and brown coals

Abstract

The concept of force of crystallization is combined with that of depression of dissolution to explain diagenetic volume-for-volume replacement in both cases, either when the pressure is increased in early sedimentary settings, or when it is diminished in a late exposure. Also, a new textural criterion is added to the three classical ones in order to recognize diagenetic volume-for-volume replacement, and calculations are carried out to estimate the speed of the replacement.

Comparative mineralogical study of thermally-altered coal-dump waste, natural rocks and the products of laboratory heating experiments

“…Silicon spinel is, with quartz and an amorphous aluminosilicate phase, a thermal-transformation product of meta-illite and metakaolinite at 900°C (Nel, 2009;Querol et al, 1994;Wang et al, 2004). Starting from 86°C and up to 1100°C, silicon spinel reacting with CaO may give anorthite and pseudomullite.…”

“…Silicon spinel is regarded as a solid solution of γ-Al 2 O 3 and SiO 2 (McHale et al, 1997). Its composition is sometimes given as 3Al 2 O 3 ·2SiO 2 (Querol et al, 1994). Chemical analysis of hercynite, silicon-spinel and titanomagnetite was impossible due to the extreme finess of the minerals and their dispersed occurrence.…”

“…Later, cooling melts give silicate and oxide minerals, and glass (Sokol et al, 2002). The final product of clay-mineral decomposition is mullite, usually given as Al 6 Si 2 O 13 (Querol et al, 1994).…”

Variations in fly ash composition with sampling location: Case study from a Portuguese power plant

“…The ash from each location has different proportions of the various mineral and amorphous components; for example the ash from the upstream sampling locations (Economizer and Air-heater) have higher proportions of quartz, possibly derived from quartz in the feed coal preserved due to the high melting temperature of this mineral (Hower et al, 1997;Querol et al, 1994) combined with the lower combustion temperatures associated with low-NO x burners (Robl et al, 1995). SEM/EDS observations indicate that the quartz typically occurs as very large grains, probably originally of detrital origin, especially at the locations closest to the furnace, or inside small glassy fly ash spheres.…”

Fine-grained pyrite in some Chinese coals

“…The behavior of pyrite during the preparation, combustion, and coking of coal has gotten particular attention (Atesok et al, 1999;Jassim et al, 2011;Querol et al, 1994;Shen et al, 2012;Wang et al, 2013;Yani and Zhang, 2010;Zhao et al, 2015). On the basis of spectroscopic analysis, some Chinese researchers thought that pyrite in coal contains some carbon (Shao et al, 1992(Shao et al, , 1994Wang, 1996;Wu and Zhu, 2010;Xu et al, 2007).…”