Semidry removal of SO2 in circulating reactor

Abstract

A semi-dry process for removing SO2, from a waste gas involves the introduction of a water-bearing particulate solid alkaline absorbent, as a free-flowing powder, into an absorption zone. The waste gas is passed through the absorption zone to entrain the powder, forming a moving bed, while the SO2 is first dissolved in the aqueous phase to form an acid and the acid then reacts with the alkaline absorbent. The moving bed is continuously transported toward a gas/solids separator wherein solids, including a water-insoluble reaction product of the SO2, are removed from the gas stream and recovered. The recovered particulate solids are reconditioned for return to the absorption zone by admixing with a particulate alkaline material, e.g., Ca(OH)2, and water to form a coating of an aqueous slurry of the alkaline material on the recycled solids as the water-bearing particulate solid alkaline absorbent. The reconditioned, recycled solids are returned to the absorption zone containing 5-40 wt. % water. By eliminating the slurry spray of the prior art from the absorption zone and providing a large surface area for drying and absorption, the drying and reaction times are reduced to less than 5 seconds, and nozzle plugging, nozzle abrasive wear and external deposits on the nozzle are eliminated. The large surface area and short drying time also help to avoid agglomeration of solids within the absorption zone.

Dependencies are inferred from the claim text.