Reactivities of several carbons against a SO
2-CO
2-H
2O mixture gas were studied at the temperature range of 600-1000°C to collect the basic data for the design of reduction process of SO
2 to recover elementary sulfur.
The reactivities of carbons against SO
2 were generally much higher than those against H
2O and CO
2 except for Caribbean coke, which contained a significant amount of iron as the catalyst to the gasification by the latter gases. High reactivity of carbon against SO
2 may be ascribed to its exothermic reduction. Product distribution were determined by reactivities of gases against carbons (equations (1), (5), (6)) and consecutive reactions among reduced gases (equations (2)-(4), (7)-(10)).
At the lower temperature range, only SO
2 was reduced to give elementary sulfur. The higher temperature increased the yield until the reactions of sulfur with hydrogen or carbon monoxide, produced from H
2O and CO
2, took place, defining the optimum temperature for the highest sulfur yield. Such a temperature varied from a carbon to carbon, depending on its reactivity against the gases.
The reactivities of blast furnace cokes against SO
2 were discussed from their optical anisotropy, physical structure and catalytic contaminants, to suggest the second factor most influential under the experimental condition examined in the present study.
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