The Mineralogical Characteristics of the Ashes Derived from the Combustion of Lignite, Coal Washery Rejects, and Mustard Stalk

Abstract

With coal being the predominant and limited source of energy, extraction of energy from lignite, coal-washery rejects, and agro-wastes through combustion is being attempted globally. During combustion, minerals in the fuels undergo various transformations with corresponding impact on the process. Lignite fly ash, Jamadoba fly ash, and Kalptaru fly ash and corresponding fuels like lignite, coal-washery rejects, and mustard stalk from pulverized fuel, fluidized bed, and grate system of combustion at Neyveli, Jamadoba, Kalpataru, respectively, were characterized. Lignite has better fuel characteristics than washery rejects and mustard stalk. Of the major phases, SiO₂, Al₂O₃, and CaO are common, besides Fe₂O₃ in lignite fly ash and Jamadoba fly ash, and K₂O in Kalptaru fly ash. Among minor phases, MgO, Na₂O, SO₃, P₂O₅, and TiO₂ are common, despite K₂O in lignite fly ash and Jamadoba fly ash, and Fe₂O₃ in Kalptaru fly ash. Other minerals are mullite, silicates, sulphates, and carbonates of Ca in lignite fly ash; K-Al-Si species in Jamadoba fly ash; K/Ca-Al-Si species, and sulphates and carbonates of Ca in Kalptaru fly ash. These minerals are the product of mineralogical transformations, where source and composition of the fuels and operating conditions are crucial. Overall the combustion of lignite is more successful than that of washery rejects and mustard.

Keywords:

• ashes
• coal washery rejects
• combustion
• lignite
• minerals
• mustard stalk

Notes

^ad.b: Dried basis.