Sulfate slag

Reverberator Furnace. Using a reverberatory furnace, a fine particle feed can be used, the antimony content can be controlled, and batch operations can be carried out when the supply of scrap material is limited. However, the antimony-rich slags formed must be reduced in a blast furnace to recover the contained antimony and lead. For treating battery scrap, the reverberatory furnace serves as a large melting faciUty where the metallic components are hquefted and the oxides and sulfate in the filler material are concurrently reduced to lead metal and the antimony is oxidized. The furnace products are antimony-rich (5 to 9%) slag and low antimony (less than 1%) lead. 

The oxidant preheater, positioned in the convective section and designed to preheat the oxygen-enriched air for the MHD combustor to 922 K, is located after the finishing superheat and reheat sections. Seed is removed from the stack gas by electrostatic precipitation before the gas is emitted to the atmosphere. The recovered seed is recycled by use of the formate process. Alkali carbonates ate separated from potassium sulfate before conversion of potassium sulfate to potassium formate. Sodium carbonate and potassium carbonate are further separated to avoid buildup of sodium in the system by recycling of seed. The slag and fly-ash removed from the HRSR system is assumed to contain 15—17% of potassium as K2O, dissolved in ash and not recoverable. 

Paints. Paints account for perhaps 3% of sulfur consumption (see Paint). The main sulfur use is for the production of titanium dioxide pigment by the sulfate process. Sulfuric acid reacts with ilmenite or titanium slag and the sulfur remains as a ferrous sulfate waste product. Difficulties with this process have led to the development of the chloride process (see Pigments, inorganic Titanium compounds). 

The resultant slag, a complex mixture of titanates, may contain 70—85% Ti02- The slag route is particularly useful when ilmenite is closely associated with haematite, from which it cannot economically be separated mechanically. Because the iron content of the slag is low, its use reduces the quantity of iron sulfate in the Hquid effluent of sulfate process plants. Slag used as a feedstock for TiCl production must be low in magnesium and calcium. A variety of other ilmenite beneficiation or synthetic mtile processes have been pursued, primarily to provide alternative chloride process feedstocks. Low grade ilmenite... 

Calcilox A process for converting calcium sulfate/sulfite wastes from flue-gas desulfurization into a disposable, earthy material, by use of a proprietary inorganic additive made from blast furnace slag. Developed by Dravo Corporation of Pittsburgh, PA. 

The significant increase in the use of supplementary cementing materials (such as fly ash and slag) in the last decade has dictated the need for an admixture that can offset the slowed hydration that results when such materials are incorporated in concrete. Strong basic salts such as sodium aluminate, alkali hydroxides, silicates, sulfates and thiosulfates have shown some promise. A number of proprietary admixtures which claim to catalyze the pozzalanic and thereby increase the rate of hydration are now marketed. 

Native 5b element is known, but it is too rare to be commercially important. It exists in nature in the form of several ores of which the most important is stibnite, which is sulfide, SbjSj. Commercial method for obtaining free Sb consists of fusing stibnite with icon turnings or shavings, followed by slagging off the resulting iron sulfide with NaCl or Na sulfate. Detailed descriptions of methods of Sb recovery from ores are given in Ref 5 pp 64-9... 

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