The characterization of weathered discard coals and their behaviour during combustion

• Published in: Fuel (Guildford) Vol. 87; no. 8; pp. 1687 - 1697
• Main Author: Wagner, N.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.07.2008; Elsevier
• Subjects: Applied sciences; Chars; Coal; Combustion of solid fuels; Combustion. Flame; Drop tube furnace; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Petrography; Theoretical studies. Data and constants. Metering; South Africa; Africa; Petrography; Chars; Drop tube furnace; Coal; Characterization; Storage; Ash; Weathering; Combustion; Performance
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2007.09.009

With a finite amount of economically viable coal reserves in South Africa, it is becoming increasingly important to consider coal discards as vital energy resources. The energy content of discard coal is generally low and high in ash, but can be effectively utilised in power stations. However, coals weather during storage, and weathered coals behave differently to their fresh counterparts. During this investigation, discard coals from four stockpiles varying in age from 5 to 40 years were characterised chemically and petrographically, with a specific focus on the petrographic-based abnormal condition analysis to determine the degree of secondary weathering. Drop tube furnace tests were conducted to determine the combustibility of the weathered stockpiled or dumped coals relative to typical Eskom coals, and the resultant char forms were characterised. A direct correlation with the extent of weathering and combustion performance was determined, with the more weathered coals reporting enhanced combustion reactions at lower temperatures.