SCRAP REDUCTION

Blending also benefits the manufacturer by offering (i) Improved processability, product uniformity, and scrap reduction, (ii) Quick formulation changes, (iii) Plant flexibility and high productivity, (iv) Reduction of the number of grades that need to be manufactured and stored, (v) Inherent recyclability, etc. 

Blending improves product uniformity (scrap reduction) and plant economy. 

Rework/Scrap Costs. Scrap and rework can consume significant amounts of labor in trying to recover the material. Scrap recovery savings are always less than the cost of the original material. This is a good candidate for continuous improvement, and I have seen a lot of low-hanging fruit to be picked in the area of scrap reduction. 

TiH2 is prepared on an industrial scale by dkect combination of hydrogen and the metal (sponge, ingot, scrap, etc) at 200—650°C, followed by cooling in an H2 atmosphere. An alternative method is the reduction of the oxide using calcium hydride under hydrogen ... 

Direct Reduction. Direct reduction processes are distinguished from other ironmaking processes in that iron oxide is converted to metallic iron without melting. Because this product, called direct reduced iron (DRI), is soHd, it is most suitable for melting in an electric arc furnace (EAF) as a substitute for scrap (see Furnaces, electric). The briquetted form of DRI, hot briquetted iron (HBI) is used when the product is to be transported. Briquetting increases density and chemical stabiUty. The predominant direct reduction processes (MIDREX and HyL III) are based on natural gas as a fuel and reductant source. They are economically attractive in regions where natural gas is cheap and abundant, especially if iron ore is available nearby (see Iron BY DIRECT reduction). ... 

As can be seen in Figure 8, the proportion of world pig iron produced in the United States has decreased dramatically since 1950. Also notable is the widening gap between pig iron and steel production, indicating the increasing use of recycled iron or scrap (see Recycling, ferrous metals) and alternative iron sources such as DRI and HBI. The increased demand for scrap is reflected in scrap iron prices (Fig. 9), which in turn have spurred growth in direct reduction processes. 

Some of this material is reclaimed by ketde melting and refining. However, most scrap is a combination of metallic lead and its aUoying constituents mixed with compounds of these metals, usuaUy oxides and sulfates. Therefore, recovery as metals requires reduction and refining procedures. 

Under normal conditions about 95—97% of TiOg from ilmenite is solubilized. Most of the iron in the solution is in the Fe " oxidation state. Any Fe " present must be reduced to Fe " because iron can only be removed by crystallization in its divalent form. The reduction is usually done by adding some scrap iron during the digestion step. 

Blast furnaces are charged through the top with coke, flux (usually iron metal and siUca), and scrap while air is iajected through tuyeres continuously at the bottom just above the black copper. The coke (100 kg/1 slag) bums to maintain furnace temperatures of 1200°C, provides the reductant, and maintains an open border. A charge of 10 t/h is typical. The furnace produces a molten black copper that contains about 80% copper. The 2iac, lead, and... 

E. Goodrich have burned a 10% tire chip mixture with coal (11—13). Tire grinding size reduction problems and deflvery costs have stymied projects based on combined tire and coal fuel. Transportation of tire scrap can cost 0.05 /kg, exclusive of grinding costs, thus tire-fired boilers are limited to areas with sample scrap tire suppHes, eg, large cities or tire manufacturers. The cost of burning one metric ton of tires per hour in an incinerator was ca 0.20—0.40 per tire in 1974, which increased to 0.35—0.70 per tire in 1987 (14). 

The United States generates ca 250 x 10 scrap tines per year. In 1977, ca 52 t of reclaimed mbber and 14,400 t of cmmb mbber were produced from these tires (40). In 1980, ca 4050 t of reclaimed and cmmb mbber were used in asphalt—mbber compounds, which is less than 5% of the recycled mbber. Except for a reduction in reclaimed mbber, the 1986 production rates were higher an estimated 25,200 t of mbber were used in asphalt. 

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