Non-ferrous metal melting

For non-ferrous metals, this document (only) considers the melting of ingots and internal scrap, since this is standard practice in non-ferrous foundries. 

For the melting of copper, lead and zinc and their alloys, induction or crucible furnaces are used. For copper alloys, hearth type furnaces are used as well. The selection depends on technical criteria. 

For magnesium melting, only crucible furnaces are used. A cover gas is used to prevent 

Induction furnace melting of aluminium, copper, lead and zinc 

Hearth type furnace melting of aluminium and copper 

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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 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.. 

The silicate slag systems are involved in most pyro-metallurgical processes which result in the formation of a number of ferrous and non-ferrous metals (Cu, Ag, Zn, Cd Sn, Pb, Sb, Bi). These systems are oxide- and sulfide-oxide melts, and, therefore, the processes of their interaction with raw materials are dependent on the melt properties (oxidation ability, solubility of metals), and on their oxoacidic properties. Any metallurgical slag contains MgO, CaO, FeO and Si02 as one of main components. The oxidation ability of the slags increases with a rise of their basicity (increase of equilibrium O2-concentration), caused by the following electrochemical process ... 

Foundries melt ferrous and non-ferrous metals and alloys and reshape them into products at or near their finished shape through the pouring and solidification of the molten metal or alloy into a mould. The foundry industry is a differentiated and diverse industry. It consists of a wide range of installations, from small to very large each with a combination of technologies and unit operations selected to suit the input, size of series and types of product produced in the specific installation. The organisation within the sector is based on the type of metal input, with the main distinction being made between ferrous and non-ferrous foundries. 

Aluminium melting in foundries generally uses alloyed ingots as a starting material, although in some cases the metal is delivered already as a liquid. The secondary melting of aluminium scrap is usually not performed in foundries and falls outside the scope of this document. It is discussed in the BAT reference document for the non-ferrous metals industries. 

These techniques are applied in other industrial sectors, such as steel and non-ferrous metal production and waste incineration. Judging on a technical basis, they may be transposed to foundry furnace types that show a risk of dioxin formation cupola, rotary and electric arc furnaces melting iron and steel (Section 3.8.2). For new and existing installations primary dioxin reduction measmes, such as efficient combustion, furnace design modifications and scrap quality control have to be taken into consideration on a case-by-case basis, before turning to secondary measures. 

Emission data for non-ferrous metals are mainly based on single installations. For the melting of copper and zinc, only emission factors (given in kg/tonne of metal or kg/tonne of casting) were supplied. For the melting of magnesium and lead, no consumption and emission levels were provided. For the melting of aluminium, no emission data were provided for induction, rotary or... 

Smitheries were excluded from this document s scope since no European smitheries were reported which met the conditions stated in Annex I 2.3.(b). This document therefore only discusses foundry processes. Cadmium, titanium and precious metals foundries, as well as bell casting and art casting foundries were also excluded on capacity grounds. Continuous casting (into sheets and slabs) has already been covered in the BREF documents related to iron and steel production and non-ferrous metal industries, and therefore, it is not dealt with in this document. In covering non-ferrous metals in this document, the process is considered to start with the melting of ingots and internal scrap or with liquid metal. 

Dust is generated in each of the process steps, albeit with different levels of mineral oxides, metals and metal oxides. Dust levels for metal melting range from below detection limit, for certain non-ferrous metals, to above 10 kg/tonne, for the cupola melting of cast iron. The high... 

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