The SO2 emission is less than the theoretical value without additional limestone put in a circulating fluidized bed (CFB) combustor because of the self-desulfurization ability of calcium-based minerals in coal ash. The modeling and experiment on limestone sulfur retention should consider the self-desulfurization of coal ash. The self-desulfurization performance of some coal (18 kinds of coal) are researched and analyzed by the 1MWth CFB combustor in order to evaluate the limestone desulfurization performance. The experimental results show that the self-desulfurization efficiency decreases with the temperature increasing. The self-desulfurization difference exits between different types of coal and has effect on the sulfur retention with additional limestone. Through the experimental result of 18 coals, simple equations of the self-desulfurization efficiency based on the total sulfur and the combustible sulfur are proposed. The self-desulfurization efficiency based on the combustible sulfur is between 40–40%. For high incombustible sulfur fraction in coal, the self-desulfurization efficiency and the sulfur retention of limestone is very high.

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