Ferrous metal melting

Steel is melted in both electric arc furnaces (EAF) and induction furnaces (IF). The choice between furnace types is based on technical criteria (e.g. capacity, steel grade). Due to its refining ability, the EAF allows the melting of lower grade scrap. This is an advantage in terms of the recycling of metals, but requires an appropriate flue-gas capture and cleaning system, as will be presented below. 

For cast iron melting cupola, electric arc, induction and rotary furnaces are applicable. The selection will be based on technical and economic criteria. 

For the operation of any selected furnaces type, elements of BAT are given below. 

Residues produced by cupola melting include dust, slags and coke breeze. 

Electric arc furnace melting of steel and cast iron 

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Air Quality Criteria forTead Supplement to the 1986 Addendum, U.S. EPA, Environmental Criteria and Assessment Office, Washington, D.C., 1990. Technical Support Document to Proposed Airborne Toxic Control Measure for Emissions of Toxic Metalsfrom Non-Ferrous Metal Melting, State of California Air Resources Board, Stationary Source Division, Sacramento, Calif., 1992. 

Stationary sources Waste incineration Steel industry Recycling plants Energy production Municipal solid waste, clinical waste, hazardous waste, sewage sludge Steel mills, sintering plants, hot-strip mills Non-ferrous metals (melting, foundry Al, Cu, Ptx, Zn, Sn) Fossil fuel power plants, wood combustion, landfill gas... 

The hearth type furnace is also known as a reverberatory or bale-out furnace. It is a static furnace with direct heating. Hot air and combustion gases from oil or gas burners are blown over the metal (melt) and exhausted out of the furnace. The hearth t5q)e furnace finds its main application in non-ferrous metal melting. A typical furnace design is given in Figure 2.18. 

This furnace t5q)e is only used for non-ferrous metal melting, mainly for aluminiiun. Due to the complex construction and difficult renewal of the refractory, the furnace is only used for metals with low melting points. Therefore, the maintenance requirements of the furnace lining are rather limited. Typical refractory lifetimes are 4 to 8 years. 

This furnace type is only used for non-ferrous metal melting. Due to the indirect heating (through the crucible wall) no bum-off or gas take-up can take place. These furnaces are used for the production of small amounts of molten metal (less than 500 kg per batch) and for low production capacities. Example furnaces are displayed in Figure 2.20. 

The dioxin emission data for the various ferrous metal melting furnaces are discussed below. 

Table 5.1 Emission to air associated with the use of BAT for ferrous metal melting and treatment...

The BAT AEL for dust for non-ferrous metal melting and treatment is 1 - 20 mg/Nm . Additional values for the melting of aluminium are given in Table 5.5. 

The main issues of diseussion at the final meeting concerned the techniques for the collection and treatment of off-gas, the minimisation of fugitive emissions, noise reduction, the role of enviromnental considerations in teehnieal ehoiees and the BAT associated emission levels. For some proeesses, mainly in the field of non-ferrous metal melting, the information was ineomplete and therefore no BAT AEL eould be agreed. During the meeting, there was little diseussion on the teehniques that are speeifie for non-ferrous foundries, partially due to the absenee of industry experts in this field. 

Melting of non-ferrous metals Emission data for non-ferrous foundries are presented in this doeument only for some specific installations. There is a need for more complete information on both guided and fugitive emissions from non-ferrous metal melting in foundries. This should be based on operational practice and expressed both as emission levels and mass flows.. 

Refractoriness (Melting Temperature). Instantaneous grinding temperatures may exceed 3500°C at the interface between an abrasive and the workpiece being ground (14). Hence melting temperature is an important property. Additionady, for alumina, sdicon carbide, B C, and many other materials, hardness decreases rapidly with increasing temperature (7). Fortunately, ferrous metals also soften with increasing temperatures and do so even more rapidly than abrasives (15). 

The successful conversion of graphite to diamond involves crystallizing the diamond from a liquid melt. The solvent most often used is nickel metal, or alloys of nickel with other ferrous metals. The reason for this success can be seen by referring to Figure 15.7, the binary (solid + liquid) phase diagram for (nickel + carbon).u8 We note from the figure that (Ni + C) forms a simple... 

Naidich and Taranets (1995) reported contact angles of ferrous metals on AIN for temperatures in the range 1500-1600°C. The values were 95° and 105° for Ni and Pd much lower than those in Table 7.7 for low or moderate melting point metals. Since the reactivity barriers existing at low temperatures (i.e., oxide films on AIN) are unlikely to be present at temperatures as high as 1500°C, a strong reactivity... 

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