Steel industry slag

Uses. The sinter oxide form is used as charge nickel in the manufacture of alloy steels and stainless steels (see Steel). The oxide furnishes oxygen to the melt for decarburization and slagging. In 1993, >100, 000 metric tons of nickel contained in sinter oxide was shipped to the world s steel industry. Nickel oxide sinter is charged as a granular material to an electric furnace with steel scrap and ferrochrome the mixture is melted and blown with air to remove carbon as CO2. The melt is slagged, pouted into a ladle, the composition is adjusted, and the melt is cast into appropriate shapes. A modification of the use of sinter oxide is its injection directiy into the molten metal (33). 

Ferrovanadium. The steel industry accounts for the majority of the world s consumption of vanadium as an additive to steel. It is added in the steelmaking process as a ferrovanadium alloy [12604-58-9] which is produced commercially by the reduction of vanadium ore, slag, or technical-grade oxide with carbon, ferrosiHcon, or aluminum. The product grades, which may contain 35—80 wt % vanadium, are classified according to their vanadium content. The consumer use and grade desired dictate the choice of reductant. 

The marketable slag makes up about 10 to 15% of the steel output, or 210 to 300 lb/t of steel.1 BOF dust and sludge generated during the cleaning of gases emitted from the BOF represent two of the three largest-volume wastes typically land disposed by the iron and steel industry. 

The last part of ionic electrochemistry, ionics, is about pure electrolytes. A few decades back this electrochemistry would have been all about high-temperature liquids (liquid common salt at 850 °C was the role model). However, this has changed, and the temperatures for eliminating the solvent have deaeased considerably. Some molten salts are now room temperature liquids. At the other end of the temperature scale are the molten silicates, where large polyanions predominate. These are important not only in the steel industry, where molten silicate mixtures form blast furnace slags, but also in the corresponding frozen liquids, the glasses. 

Alumina-containing refractory linings are widely utilized in the steel industry. Bricks with high alumina contents are, due to their resistance to alkali slags, also used in the cement and glass industries. 

One common misconception of the steel industry is that it produces steel products, together with a number of waste streams including slag, dust and millscale, which require disposal. But the truth is very different. Environmental awareness and economic necessity have prompted the steel industry to seek alternative solutions to disposal. 

Vanadium has an abundance in the earth s crust of about 0.2% (Clark, 1975). It is quite eveniy distributed in minerais. A few commerciai deposits contain more than 3% vanadium pentoxide, but normai concentrations are 0.1 - 1% (NAS. 1974). The main sources of vanadium are vanadium suiphide (patronite), carnotite and titanomagnetite ores. Many crude oiis contain considerabie amounts (even about 0.1%) of vanadium, notably those from Venezuela. The ash obtained from burning vanadium-containing oils may have many tens of per cent vanadium. Vanadium can be extracted from fuel ashes. A considerable amount of vanadium production is based on the extraction of converter slag in the steel industry, which can contain 2-10% (Michels, 1973) or even 25% (NAS 1974) vanadium pentoxide. Vanadium is usually manufactured by converting the vanadium minerals to a water- soluble form (Levanto, 1969). 

A somewhat similar product, Roechling phosphate, uses a soda slag that is a byproduct from the steel industry as the source of sodium. Also, the naturally occurring minerals, trona (sodium sesquicarbonate) or natron (sodium carbonate), may be used. Experiments have shown that a similar product can be made by sintering potassium carbonate with phosphate rock and silica to produce a product grade of 0-25-25. The phosphate compound in this product is presumed to be CaKP04. 

Large quantities of lime are used in the steel industry to hne furnaces and as a component of molten slags, which take an active part in the refining of steel. For production of this type of lime, rocks can be used that contain at least 80% of the car-... 

The recovery of vanadium from these slags is of commercial interest because of the depletion of easily accessible ores and the comparatively low concentrations (ranging from less than 100 ppm to 500 ppm) of vanadium in natural deposits (147,148). In the LILCO appHcations the total ash contained up to 36% 20 (147). Vanadium is of value in the manufacture of high strength steels and specialized titanium alloys used in the aerospace industry (148,149). Magnesium vanadates allow the recovery of vanadium as a significant by-product of fuel use by electric utiUties (see Recycling, nonferrous LffiTALS). 

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