Combustion properties and desulfurization of high sulfur containing Indian and Nepali coals using lime-based products

Many brick industries and industrial boilers in South Asia use high sulfur containing coal as the major fuel. The combustion of these coals leads to serious environmental pollution and health problems. The SO2 emissions from the combustion of coal can be captured by adding lime-based desulfurizing agents (DSA) to the coal briquettes. The physical and combustion characteristics of some Indian (Bihar, Assam) and Nepali (Dang, Abidhara, Lignite) coal have been studied. The process of desulfurization of these coals was investigated using calcium hydroxide and calcium carbonate as DSA. Calcium carbonate is more efficient in char combustion than volatile combustion, whereas calcium hydroxide and sodium hydroxides are efficient as DSA in both char and volatile combustion. For most of the coals the desulfurization efficiencies are over 80% in case of Ca(OH)2 and NaOH for molar ratios of DSA to sulfur (Ca/S) of 2 and 3. For the same Ca/S ratios the desulfurization efficiency is about 75% when calcium carbonate is used. Use of calcium carbonate and calcium hydroxide as DSA in coal briquettes could be an efficient and economical way to control the pollution from the use of high sulfur containing coals used in brick industries in Nepal and South Asia.