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Research Article
ScienceAsia 15 (1989): 017-037 |doi: 10.2306/scienceasia1513-1874.1989.15.017
IN-SITU DESULFURIZATION OF COAL BRIQUETTES BY LIME
SOMCHAI OSUWAN, KUNCHANA BUNYAKIAT
AND DUANGPORN THEERAPABPISIT
ABSTRACT: The combustion of coal briquettes causes corrosion and air pollution, which is due to sulfur in the coal. Coal briquette desulfurization by addition. of lime was studied. Calcium oxide reacts with sulfur dioxide, evolved from combustion, according to the equation:
CaO + S02 + 1/2O2  CaSO4
The resulting calcium sulfate remains in the ash after combustion.
Variables that affected sulfur oxides capture by lime during combustion of
coal briquettes at true operating conditions in bucket-type cooking stoves were found to be: amount of lime added in terms of mole ratio of CaOIS (from 0 to 4), percentage of clay used as binder (from 0 to 40), and types of coal fines used.
Lime was found to be highly effective in desulfurization, as the percentage
of calcium sulfate in coal ash increased sharply with increasing CaO/S mole ratio
from 0-2, and levelled off at higher ratios. The maximum in-situ sulfur capture was 90-95%, based on the total sulfur present initially, leaving only 5-10% emitted as sulfur oxides. Clay produced a similar (but less pronounced) effect to that of lime.
In conclusion, it is demonstrqted that coal briquettes made from coal fines
from various sources in Thailand can be well desulfurized by lime. The recommended value of CaO/S mole ratio is in the range of 2.0-2.5, together with a 20% addition of clay
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The Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10500, Thailand
Received 31 October 1988
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