Abstract: A process for the granulation of precipitation products, formed from the reaction of ammonium compounds with alkaline-earth compounds, by introducing into the bottom of a reaction chamber an ammonium and alkaline-earth compound such that the alkaline-earth compound in aqueous solution is immediately and intimately mixed with the ammonium compound to form alkaline-earth compound precipitation products in the form of hard granules which are difficultly soluble in water. The alkaline-earth precipitation products are easily withdrawn from the bottom of the reaction chamber without forming a lime sludge which is difficult to remove.

Abstract: An apparatus for granulation of precipitation products, comprising a liquid-filled reaction chamber including a granulation chamber which receives aqueous streams of compounds which precipitate to form granules. The granulation chamber has an open upper edge connected to the narrow edge of a conical surface. The upper open edge of the conical surface merges with an apron which is spaced inwardly from the inner periphery of the reaction chamber. Conduit means conduct granules downwardly from the granulation chamber. Liquid and fine granules rise upwardly within the conical surface. Granules descend back into the granulating chamber. Clean liquid passes downwardly through the annular space between the apron and the reaction chamber for removal from the space between the conical surface and the apron.

Abstract: Industrial waste gases containing sulfur dioxide, hydrogen fluoride, hydrochloric acid and sulfur trioxide are treated within a reaction tank in a first stage with a solution containing ammonium ions to increase the dew point of the gases. The gases are then cooled below the elevated dew point in a second stage below which a deflector system directs the gases along the wall of the reaction tank into a third stage where the gases are cooled by a spray mist of an ammonia mixture to form ammonium salts. The gases are then treated in a fourth stage at the bottom of the reaction tank with the solution containing ammonium ions to precipitate ammonium salts into a reservoir below the reaction tank. Purified waste gases are discharged into a cooler where a stripper removes entrained droplets of liquid before discharge into the atmosphere. The droplet size of the solution sprayed into the second stage is larger than the droplet size of the solution sprayed into the first stage.