Sulfur Form in Coal and SO2 Emission Behavior at AFBC Plant
Ichiro SAITO, Munehide KAWAMURA, Hideki GOTO
pp. 48-56
DOI:
10.3775/jie.82.48Abstract
This paper reports the results of an investigation on SO2 formation from sulfur in fuel (Fuel-S) and SO2 capture by limestone in a bench-scale bubbling fluidized bed combustor. Conversion of fuel-S to S in ash (ash-S), S in char (Char-S) and S in volatile matter (Volatile-S) during pyrolysis and combustion was experimentally evaluated under fluidized bed combustion condition. The formation of SO2 from fuel-S in a fluidized bed consisted of sand, which was inert for SO2 capture, indicated that SO2 was formed from char-S and volatile-S and the contribution of ash-S played only minor role in SO2 formation.
Under limestone feed conditions, the emission of SO2 was strongly dependent on conversion of fuel-S to char-S during pyrolysis, whereas conversion to volatile-S had little influence on SO2 emission. This implies that the sulfur in the volatile matter is oxidized at the bottom of the bed and most part of SO2 from volatile-S is captured in the dense bed. In contrast, char-S is considered to be oxidized to SO2 throughout the bed, thus the SO2 from char formed in the vicinity of the bed surface is considered to escape from the bed without being captured by limestone since the contact time is short. These results suggest that the conversion of combustible sulfur (char-S+volatile-S) to char-S is very important to predict the SO2 emission from bubbling fluidized bed combustors under limestone feed conditions.
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