The Absorption of SO2 by Solids

The abatement of sulfur dioxide emissions is a major problem in most industrialized nations that use fossil fuel for power generation. It has been shown that over 35 million tons of SO2 were emitted into the atmosphere in 1970 in the United States [73]. Electric power generation using fossil fuel was the single largest contributor (55 %), while copper and lead smelters processing sulfide ores accounted for about 10% of the total emission. 

Due to recent research efforts numerous methods have been proposed for reducing the SO2 content of stack gases. Good reviews of the available and proposed technologies may be found in Slack [73] Mills and Perry [74], Raben [75], and Burchard et al. [76]. A list of operating and planned full-size lime/limestone desulfurization systems in the United States is given in Table 8.6. 

The techniques actually available for SO2 removal from flue gases may be broadly classified into wet and dry systems. The wet methods employ a slurry or solution of some absorbent for SO2, whereas the dry systems use dry particles of absorbent in such gas-solid contacting devices as fluidized beds, packed beds, and entrainment reactors. It is with these latter methods that we are concerned here, although wet methods appear to be at least as satisfactory as the dry systems. 

A further classification can be made on the basis of whether the absorbent is regenerated or thrown away. The former methods employ a separate step(s) to convert the spent absorbent back into a usable form, at the same time generating a salable sulfur species (sulfuric acid, elemental sulfur, etc.) or one that can readily be converted into a useful product (H2S, a gas stream containing high levels of SO2, etc.). In contrast the throw away processes aim to produce a sulfur-containing compound (e.g., calcium sulfate) that can be 

Operating and Planned Full-Size Lime/Limestone Desulfurization Facilities in the U.S. 

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