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Misc electric arc furnace
eafh.com
Environmental issues
Although the modern electric arc furnace is a highly efficient recycler of steel
scrap, operation of an arc furnace shop can have adverse environmental effects.
Much of the capital cost of a new installation will be devoted to systems
intended to reduce these effects, which include:
High sound levels
Dust and off-gas production
Slag production
Cooling water demand
Heavy truck traffic for scrap, materials handling, and products
Environmental effects of electricity generation
Because of the very dynamic quality of the arc furnace load, power systems may
require technical measures to maintain the quality of power for other customers;
flicker and harmonic distortion are common side-effects of arc furnace operation
on a power system.
Other electric arc furnaces
For steelmaking, direct current (DC) arc furnaces are used, with a single
electrode in the roof and the current return through a conductive bottom lining
or conductive pins in the base. The advantage of DC is lower electrode
consumption per ton of steel produced, since only one electrode is used, as well
as less electrical harmonics and other similar problems. However, the size of DC
arc furnaces is limited by the available electrodes and maximum allowable
voltage. Maintenance of the conductive furnace hearth is a bottleneck in
extended operation of a DC arc furnace.
In a steel plant, a ladle furnace can be used to maintain the temperature of
liquid steel during processing after tapping from the scrap-melting furnace.
This also allows the molten steel to be kept ready for use in the event of a
delay later in the steelmaking process. The ladle furnace consists of only the
refractory roof and electrode system of a scrap-melting furnace, but it has no
need for a tilting mechanism or scrap charging.
Electric arc furnaces are also used for production of non-ferrous alloys, and
for production of phosphorus. Furnaces for these services are physically
different from steel-making furnaces and may operate on a continuous, rather
than batch, basis. Continuous process furnaces may also use paste-type (Soderberg)
electrodes to prevent interruptions due to electrode changes. Such furnaces are
usually known as submerged arc furnaces, because the electrode tips are buried
in the slag/charge, and arcing occurs through the slag, between the matte and
the electrode. A steelmaking arc furnace, by comparison, arcs in the open. The
key is the electrical resistance, which is what generates the heat required: the
resistance in a steelmaking furnace is the atmosphere, while in a submerged arc
furnace, the slag or charge forms the resistance. The liquid metal formed in
either furnace is too conductive to form an effective heat-generating
resistance.
Amateurs have constructed a variety of arc furnaces, often based on electric arc
welding kits contained by silical blocks or flower pots. Though crude, these
simple furnaces are capable of melting a wide range of materials and creating
calcium carbide etc.
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