EAF slag

The chemical composition of EAF slags are given in Table 3.11. The reported values were based on the analyses of 3 samples. 

Dust emission levels and PM distribution from a German IF foimdry are given in Table 3.12. 

Flue-gas eleaning Volume Total dust PMio PMjs 

As for the chemical composition of the particulate matter, there is no published data regarding the melting of steel, but there is reason to believe that it is close to that of the composition of the dust emitted during the melting of cast iron as shown in Table 3.13. The presence of Zn, Pb or Cd will lead to metallic fumes during the meltdown of the charge. 

The melting of iron and steel in induction furnaces results in low emissions compared to the cupola furnace. Emissions due to the combustion of fossil fuel are especially prevented. An exhaust capture efficiency of up to 95 % is possible using special capture systems, such as side-draughts, movable hoods and partial covering of the furnace. Filtration of the off-gases is mainly performed using dry systems. Dust emission levels below 5 mg/Nm can be obtained [225, TWG, 2003]. Typical emission data are given in Table 3.14. 

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Table 3.11 Chemical composation of EAF slag [171, The Castings Development Centre, 1999]...

EAF slag Crushing - generation of glassy dust - handling requirements due to glassy nature - tittle data available on leachates... 

In this study, C. kessleri was cultured with CA medium (pH 7.2) [6] cmitaining an eluate from each EAF slag under natural white fluorescent light at 23 2 °C. After treatment of algae with each eluate for 1 week, the number and physiological features of algae were quantified respectively using hemocytometry and flow cytometry. 

Other methods for removing scale include salt pickling, electrolytic pickling, and blasting blasting is environmentally desirable, where feasible. EAFs produce metal dusts, slag, and gaseous emissions. 

Cooled and solidified slag is crushed and screened to recover metafiles for recycle or reuse and the lower metallic aggregate is used in construction applications. The slag produced in EAFs is either reused or landfilled. EAF dust is conveyed into a gas cleaning system.1... 

In this process EAF dust, other zinc-bearing wastes, recycled materials, coke or coal, lime, and silica are mixed and fed to a rotary furnace. The zinc and other volatile nonferrous metals in the feed are entrained in the furnace off-gas and are carried from the furnace to an external dust collection system. The resulting oxide (zinc calcine) is a crude zinc-bearing product that is further refined at zinc smelters. A byproduct of the process is a nonhazardous, iron-rich slag that can be used in road construction. Solidification technologies change the physical form of the waste to produce a solid structure in which the contaminant is mechanically trapped. 

For the most part, the zinc materials recovered from secondary materials such as slab zinc, alloys, dusts, and compounds are comparable in quality to primary products. Zinc in brass is the principal form of secondary recovery, although secondary slab zinc has risen substantially over the last few years because it has been the principal zinc product of electric arc furnace (EAF) dust recycling. Impure zinc oxide products and zinc-bearing slags are sometimes used as trace element additives in fertilizers and animal feeds. About 10% of the domestic requirement for zinc is satisfied by old scrap. 

Electric furnaces, 12 286-318 76 144, 145. See also Electric arc furnace (EAF) Fuel-fired furnaces applications for, 12 315-316 arc furnaces, 12 297-306 classification of, 12 286 economic aspects of, 12 313-314 health and safety factors related to, 12 314 induction furnaces, 12 307-313 in phosphorus manufacture, 19 8-11 resistance furnaces, 12 287-297 for secondary slags, 14 759-760 Electric furnace steelmaking processes,... 

As an indication of the flexibility of the EAF, it is used in some developing countries for the direct reduction of iron ore by carbon [27.18]. The furnace is charged with iron ore intimately mixed with ground carbon. Quicklime, calcined dolomite and fluorspar are added and an oxygen lance is used to oxidise the impurities much as in the BOS process. The slag is removed and the chemical... 

Steel slag (EAF) modified asphalt mix Steel slag (BOF) modified asphalt mix Hot mix asphalt control Methacrylate sealer (MMA)... 

Table 4.12 Energy and temperature data for EAF furnace melting with normal slag and foamy slag...

The main benefit of the technique is a decrease in the net amount of dust sent out by the foimdry, for disposal or recovery. The produced dust contains a higher load of metals. This allows the recovery of Zn from the EAF dusts. The technique results in an enrichment of the Zn in die cupola dust, while for Pb a larger share ends up in the iron. If the Zn is effectively recuperated from the dust, the technique decreases the heavy metal load of the final dust for disposal, as well as its amount. On the other hand, the amount of slag produced, increases. 

The overall reduction of noise levels involves developing a noise reduction plan. Here each of the sources needs to be checked and evaluated. Alternative techniques with lower noise levels may be applied and/or point sources may be enclosed. Examples for alternative techniques have been given in Section 4.2A.2 (oxybumer in RF) and 4.2.2.2 (foamy slag for EAF). Some examples of the enclosiue of sources have been given for furnaces (Section 4.5.3.1) and shakeout (4.5.9.3). 

Residues produced by EAF melting include dust and slags. 

Table 1 Chemical compositions of EAF steel slags used for this study [mass%] [6]...

Origin of slag Eluate of EAF stainless steel oxidation slag (Slag A) Eluate of EAF normal steel oxidation slag (Slag B) Environmental quality standards ... 

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