7 November, 2018
Electric Arc Furnace: What is it and how does it work?
Approximately one-quarter of global steel production utilises an electric arc furnace for electrode handling, which primarily uses high-voltage electrified arcs to melt scrap steel for conversion into liquid steel without altering the electrochemical properties of the specific metal.
For three to four decades now, industrial electric arc furnaces have been running for more extended hours, faster and harder as steel-making facilities have made it a priority to increase production. Besides ramped up production and intensive operating schedules, more electric arc furnaces have been outfitted with larger electrodes, more oxygen lances and in some cases, secondary chemical sources to generate more power and boosting furnace rating.
While electric arc furnaces are increasingly stretched and pushed to the limits, the aim of ensuring safe and dependable processes has never been more critical. With rising production demands, electric arc furnace accidents are escalating. But, with the correct prevention and safety measures and by using automated lifting solutions, industries can avoid work-related accidents, enhancing safety whilst increasing productivity.
How does an Electric Arc Furnace for Electrode Handling work?
The Electric Arc Furnace is a thick, cylindrical boiler made of reinforced steel plates. It consists of a refractory-lined vessel covered with a retractable roof, and through which one or more graphite electrodes enter the furnace. The furnace is normally divided into three sections:
· the shell, 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 can be shaped as a section of a sphere, or as a frustum (conical section).
Separate from the furnace structure is the electrode support and electrical system, and the tilting platform on which the furnace rests.
A typical EAF is powered by a three-phase electrical supply and therefore has three electrodes. Electrodes are round in section, and typically in segments with threaded couplings, so that as the electrodes wear, new segments can be added. The arc forms between the charged material and the electrode, the charge is heated both by current passing through the charge and by the radiant energy evolved by the arc. The furnace is built on a tilting platform so that the liquid steel can be poured into another vessel for transport.
The scrap is loaded into baskets. Heavy melt is placed on top of a light layer of protective shred, on top of which is placed more shred. The scrap basket is then taken to the melt shop, the roof is swung off the furnace, 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. To speed up the process, metal charging, burnt lime, slag formation and spar are added to the basket.
Once heated, the meltdown processes begin. Electrodes are lowered down into the scrap to produce the arc in a low voltage condition. Once the arc is formed, the voltage is increased to speed up the melting process while simultaneously oxidising manganese, silicon and carbon. As melting continues, the refining process begins.
Advantages of the Electric Arc Furnace for Electrodes
- – Energy Efficient
The method is mostly adopted by steelmaking companies all over the world, which means there is massive consumption of graphite electrodes which significantly reduces the amount of energy needed to make steel. Unlike traditional steelmaking from ores, electric arc furnace makes steel from 100% metal scrap feedstock; therefore, it’s more energy efficient.
- – Flexibility
An EAFs process can be rapidly scaled up or down as needed, unlike blast furnaces which cannot easily be adjusted according to production demand. While the primary feedstock for electric arc furnaces is scrap steel, direct-reduced iron or hot metal from blast furnaces can also be used to feed the electric arc furnace.
From Safety to Productivity
The unfavourable and highly dangerous working conditions in a steel mill means that companies must take preventive measures to prevent both minor and severe incidents. Minor incidents like small explosions may not cause injuries but often cause property damage. To mitigate such events in a production facility, automating processes results in minimising human risks, reducing errors and improving safety in the work environment.
- – The ability to control the lifting hook with the use of a remote control eliminates the risk of having operators or personnel get too close to the furnace and operate the manoeuvring process from a safe distance.
- – Better health and wellness due to automated processes, non-exposure to toxic radiation materials, etc.
- – The use of the remote control simplifies engaging and releasing the electrodes’ lifting point to the automatic lifting hook.
- – Minimal risks of injury or fatality thanks to the automatic engage and release features. Accidents are avoided, the fabrication process isn’t affected and production times are decreased.
Get a clearer view of the lifting and transporting process of electrodes and the added benefits of the patented automatic lifting hook in the below video.