Slags preparation

Properties of Pyrolytic Ash and Slag. Table IV shows the quantities of harmful substances contained in the ash removed from the pyrolysis furnace and also the quantities of harmful substances dissolved out of the slag prepared by melting the residues when immersed in fresh water. 

Silicon Reduction. The preparation of ferrovanadium by the reduction of vanadium concentrates with ferrosiUcon has been used but not extensively. It involves a two-stage process in which technical-grade vanadium pentoxide, ferrosiUcon, lime, and fluorspar are heated in an electric furnace to reduce the oxide an iron alloy containing ca 30 wt % vanadium but undesirable amounts of siUcon is produced. The siUcon content of the alloy is then decreased by the addition of more V2O5 and lime to effect the extraction of most of the siUcon into the slag phase. An alternative process involves the... 

Vanadium powder can be prepared by substituting V2O2 for the V20 as the vanadium source. The heat generated during the reduction of the trioxide is considerably less than for the pentoxide, so that only soHd products are obtained. The powder is recovered from the product by leaching the slag with dilute acid. 

Plutonium metal is prepared by two methods--direct reduction of the oxide by calcium (DOR)U,2J, and reduction of PuF by calcium in our metal preparation line (MPL)(3) (see Figure 1). In the DOR process, the plutonium contenF of the reduction slag is so low that the slag can be sent to retrievable storage without further processing. Metal buttons that are produced are no purer than the oxide feed and/or the calcium chloride salt. Los Alamos purifies the buttons by electrorefin-ing(4i,5 ), yielding metal rings that are > 99.96 percent plutonium. 

The preparation of ferrovanadium by this route is carried out batchwise in refractory-lined open reactors, with vanadium pentoxide, aluminum powder, iron scrap and lime or fluorspar constituting the charge. The reactions once initiated, proceed briskly to completion. The reaction heat is sufficient to melt the ferrovanadium and the alumina-lime/fluor-spar slag, which readily separate due to density difference. The aluminothermic ferroalloy product contains practically no carbon. 

Columbium (also known as niobium) and tantalum metals are produced from purified salts, which are prepared from ore concentrates and slags resulting from foreign tin production. The concentrates and slags are leached with hydrofluoric acid to dissolve the metal salts. Solvent extraction or ion exchange is used to purify the columbium and tantalum. The salts of these metals are then reduced by means of one of several techniques, including aluminothermic reduction, sodium reduction, carbon reduction, and electrolysis.19-21 Owing to the reactivity of these metals, special techniques are used to purify and work the metal produced. 

Farrand, B. and Emery, J., Recent Improvements in the Quality of Steel Slag Aggregate, paper prepared for presentation at 1995 annual meeting of the Transportation Research Board, Washington, DC, January 1995. 

Thermal cutting or fuel cutting for end preparation is acceptable if the surface is reasonably smooth, true, and free of slag. The thermal cutting shall be followed by mechanical preparation to achieve the final weld joint end detail. Discoloration (oxidation) remaining from the cutting method shall be removed. 

Databases, generally available for a fee, often together with software packages, have been prepared for several types of materials and systems. Typical examples are a database developed for Fe-rich alloys containing data for up to 15 components, and 55 types of phases or similar databases for Mg-rich, Al-rich, Ni-rich, Ti-rich alloys. Other databases are available for different types of materials semiconductors, solder alloys, ceramic systems, slag, molten salts, etc. 

Preparation. Indium is recovered by electrolysis or chemical reduction from residues, flues dusts, slags from zinc or lead or tin productions. 

Phosphorus is manufactured by the reduction of commercial-quality phosphate rock by coke in an electric furnace, with silica used as a flux. Slag, ferrophosphorus (from iron contained in the phosphate rock), and carbon monoxide are reaction byproducts. The standard process, as shown in Figure 2, consists of three basic parts phosphate rock preparation, smelting in an electric furnace, and recovery of the resulting phosphoms. Phosphate rock ores are first blended so that the furnace feed is of uniform composition and then pretreated by heat drying, sizing or agglomerating the particles, and heat treatment. 

In 1997, MBS technology was demonstrated for the U.S. Environmental Protection Agency s (EPA s) Superfund Innovative Technology Evaluation (SITE) program at the Midvale Slag Superfund site in Utah. For this demonstration, an estimate was prepared of the total costs to treat the approximately 2 million tons of waste at the site. This estimate was based on a full-scale facility capable of treating 10,000 tons per day. Based on a scale-up from the demonstration, and on information supplied by the vendor, costs were estimated to be 16 per ton (D176710, p. 2). 

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