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Melting furnaces
This document discusses different types of melting furnaces used in industry. It describes four main types: electric arc furnaces, basic oxygen furnaces, blast furnaces, and induction furnaces. Electric arc furnaces use electric arcs to melt scrap metal up to temperatures of 1800°C. Basic oxygen furnaces lower the carbon content of molten pig iron by blowing oxygen through it to produce steel. Blast furnaces reduce and convert iron oxides into liquid iron through the combustion of coke and air blown into the bottom of a tall refractory furnace. Induction furnaces use powerful alternating currents to induce eddy currents in metal to be melted, heating it through resistance without touching the metal.
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Melting furnaces
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- 3. Introduction • Amelting furnace is an appliance capable of heating materials to such a high temperature that they melt, which from a chemical perspective basically means that they reach the critical threshold temperature at which they convert from a solid to a liquid. • Not all materials will melt, and those that do
- 4. Types of furnaces: 1. Electric arc furnace 2. Basic oxygen furnace 3. Blast furnace 4. Induction furnace
- 5. 1. Electric arcfurnace An Electric Arc Furnace (EAF) is a furnace that heats charged material by means of an electric arc. Industrial arc furnaces range in size from small units of approximately one ton capacity up to about 400 ton units Industrial electric arc furnace temperatures can be up to 1,800 °C
- 6. Construction • theshell, which consists of the sidewalls and lower steel "bowl"; • the hearth, which consists of the refractory that lines the lower bowl; • the roof, which may be refractory-lined or water-cooled, and ca
- 7. Operation • Scrapmetal is delivered to a scrap bay, located next to the melt shop. • The scrap is loaded into large buckets called baskets, and the furnace is charged with scrap from the basket. • After charging, the roof is swung back over the furnace and meltdown commences. • The electrodes are lowered onto the scrap, an arc is struck and the electrodes are then set to bore into the layer of shred at the top of the furnace. • Oxygen is blown into the scrap, combusting or cutting the steel, and extra chemical heat is provided by wall-mounted oxygen-fuel burners. Both processes accelerate scrap meltdown
- 8. 2.Basic Oxygen furnace • Basic Oxygen Steelmaking (BOS, BOP, BOF, and OSM), also known as Linz–Donawitz-steelmaking or the oxygen converter process. • It is a method of primary steelmaking in which carbon-rich molten pig iron is made into steel. • Blowing oxygen through molten pig iron lowers the carbon content of the alloy and changes it into low carbon steel. • The process is known as basic because fluxes of burnt lime or dolomite, which are chemical bases, are added to promote the removal of impurities and protect the lining of the converter
- 9. Process • Moltenpig iron from a blast furnace is poured into a large refractory-lined container called a ladle. • Pre-treatment stage • Filling the furnace with the ingredients(cold metal) is called charging. • copper tipped lance with 3-7 nozzles is lowered down into it and high purity oxygen is d
- 10. 3.BLAST FURNACE •Thepurpose of a blast furnace is to reduce and convert iron oxides into liquid iron called "hot metal”. • The blast furnace is a huge, steel stack lined with refractory brick. • Iron ore, coke and limestone are put into the top, and preheated air is blown into the bottom.
- 11. Method Three substancesare needed to enable to extraction of iron from its ore. The combined mixture is called the Charge: • Iron ore, haematite - often contains sand with iron oxide, Fe 2 O 3 . • Limestone (calcium carbonate). • Coke - mainly carbon • The charge is placed a giant chimney called a blast furnace. The blast furnace is around 30 metres high and lined with fireproof bricks. Hot air is blasted through the bottom.
- 12. 4.INDUCTION FURNACE •AnInduction Furnace is an electrical furnace in which the heat is applied by induction heating of metal. Induction furnace capacities range from less than one kilogram to one hundred tonnes, and are used to melt iron, steel, copper, aluminium, and precious metals. •The advantage of the induction furnace is a clean, energy-efficient and well-controllable melting process compared to most other means of metal melting. •Most modern foundries use this type of furnace, and now also more iron foundries are replacing cupolas with induction furnaces to melt cast iron, as the former emit lots of dust and other pollutants.
- 13. Operation •An inductionfurnace consists of a nonconductive crucible holding the charge of metal to be melted, surrounded by a coil of copper wire. •A powerful alternating current flows through the wire. The coil creates a rapidly reversing magnetic field that penetrates the metal. •The magnetic field induces eddy currents, circular electric currents, inside the metal, by electromagnetic induction. • The eddy currents, flowing through the Electrical resistance of the bulk metal, heat it byJoule heating. Once melted, the eddy currents cause vigorous stirring of the melt, assuring good mixing. • An operating induction furnace usually emits a hum or whine (due to fluctuating magnetic forces), the pitch of which can be used by operators to identify whether the furnace is operating correctly or no.
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