Abstract: A compact lime slaker has an inner vessel forming an initial slaking chamber disposed in an outer vessel forming a final slaking chamber, with agitators provided In both chambers. Slaked lime from the final slaking chamber is pumped to a collection trough where slaked lime and grit are removed therefrom, while a major portion of slaked lime, with grit removed is returned to the final slaking chamber. The slaked lime in the final slaking chamber, at an elevated temperature due to the slaking exotherm, insulates the lime being slaked in the initial slaking chamber and provides heat thereto to aid in the initial slaking. Removal of grit from the portion of slaked lime recycled to the final slaking chamber prevents clogging or attrition of components of the slaker.

Abstract: A process for removing sulfur dioxide from flue gases where calcium sulfate and magnesium hydroxide are produced, with the magnesium hydroxide separated in an impure state and purified by addition of water thereto to dissolve contaminant calcium sulfate. The calcium sulfate preferentially dissolves to form an aqueous solution and purified magnesium hydroxide is separated therefrom. At least a portion of the resultant aqueous solution of calcium sulfate is returned to the wet scrubbing system as make-up water to replenish water lost from the aqueous medium during scrubbing of the flue gases.

Abstract: Sulfur dioxide is removed from a gaseous stream by contact with a lime slurry which contains sulfur to produce thiosulfate ions and 2,000-10,000 ppm of effective sodium ions to effect removal of the sulfur dioxide A bleed stream, removed from the scrubbing loop has calcium sulfite solids removed therefrom while separated liquor is returned to the scrubbing loop.

Abstract: A process for removing sulfur dioxide and nitrogen oxide from flue gases in a wet scrubbing system using lime to remove the sulfur dioxide and ferrous-EDTA to remove the nitrogen oxides, where an initial reducing agent, such as sodium sulfide, and an antioxidant, such as hydrazine, are added to the scrubbing system, with oxidation of the ferrous-EDTA to ferric-EDTA curtailed while removal of nitrogen oxides is increased.

Abstract: A wet scrubbing process for removing sulfur dioxide from combustion gases uses an aqueous slurry containing calcium components resulting from the slaking of lime, with the slaked lime formed by mixing lime with water containing a calcium sulfur-oxide salt. The presence of the calcium sulfur oxide salt in the slaking water results in a more easily dewatered sludge that is subsequently removed from the wet scrubbing system.

Abstract: A process for desulfurizing sulfur dioxide-containing gases wherein the sulfur-containing gases are contacted with an aqueous solution of magnesium hydroxide in a wet scrubber, wherein magnesium sulfite and magnesium bisulfite are formed, a portion of spent scrubbing medium is subjected to oxidation to convert the magnesium sulfite and the magnesium bisulfite therein to magnesium sulfate, the oxidized product is contacted with a magnesium-containing lime slurry to obtain magnesium hydroxide and calcium sulfate, calcium sulfate is separated from the resulting product and the magnesium hydroxide is recycled to the scrubber.

Abstract: A process for removing sulfur dioxide from a flue gas in a wet scrubber with an aqueous slurry formed from calcium hydroxide and magnesium hydroxide with magnesium hydroxide or magnesium oxide recovered therefrom. A thickened sludge from a thickener containing calcium sulfite solids is separated and an aqueous sulfite solution removed, with a first portion of the solution returned to the thickener while a second portion thereof is oxidized to form a sulfate solution. Lime is added to the sulfate solution to precipitate calcium sulfate and form an aqueous magnesium hydroxide suspension, with the precipitated calcium sulfate separated from the magnesium hydroxide suspension which may be dewatered to form a magnesium hydroxide product or calcined to produce magnesium oxide.

Abstract: A method for removing sulfur dioxide from flue gases in a wet scrubbing system where calcium thiosulfate and calcium polysulfides are formed by the reaction of lime and emulsified sulfur and the mixture added to a recycle tank of the wet scrubber where it reacts with sulfites and bisulfites in the scrubbing slurry to produce thiosulfates from the calcium polysulfides, with the slurry then returned to the scrubber. The mixture of calcium thiosulfate and calcium polysulfides may be formed in the lime slaking tank or lime storage tank of a lime scrubbing system or formed in a mixing tank and added to a lime or limestone scrubbing system.

Abstract: A method for removing sulfur dioxide from flue gases, with oxidation of calcium sulfite in the discharge from a liquid scrubbing system to produce gypsum, oxidizes the sulfite in a thickener overflow at a pH of between 4.0 and 6.5. The calcium sulfite is oxidized to a calcium sulfate which precipitates from the aqueous media and is separated, while the acidic aqueous media is recycled to an acidification step preceding the oxidation. A further minor portion of scrubber slurry may be discharged from the liquid scrubber unit at a pH of 4.5 to 6.0 and also treated with acid, oxidized, and the resultant gypsum separated.