The Electric Arc Process

The furnace consists of a shallow cylindrical bath with a roof that can be lifted and swivelled, and through which three carbon electrodes ean be inserted (Fig. 27.5). At the start of the process, the electrodes are withdrawn and the roof swung clear. The scrap is then charged into the furnace. When charging is complete, the roof is swung back into position and the electrodes are lowered to make contact with the scrap. 

A powerful electric current is then passed through the charge, an arc is struck, and the heat produced melts the scrap. Quicklime (typically 35 to 40kg/t steel), calcined dolomite (about lOkg/t) and fluorspar (about 7kg/t) are added [27.2, 27.5]. A recent trend has been the use of pre-mixed blends containing 80 % of quicklime and 20 % of dolomite. The fluxing agents combine with the impurities 

Samples of the steel are taken periodically to check its composition. When the required composition has been achieved, the temperature of the steel is measured and, if necessary adjusted to the level required for casting (about 1,600 °C). 

The slag is removed by tilting the furnace so that it pours through the slag hole at the back of the furnace. The steel is then discharged through the tap hole at the front into a teeming ladle. 

Cycle times are generally slow relative to the BOS process. When operating in the traditional manner with an oxidising slag, followed by a reducing slag, cycle times of 4 hours are common. When the process is used primarily to melt scrap steel, cycle times of 1.5 hours are more typical [27.18]. 

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The vision of the late W E Ballard ensured that this chapter is still very relevant but there have been some changes in emphasis. Of the spraying techniques, the electric arc process is now generally more economical in operation than oxy-fuel gas processes. The rate of spraying is proportional to the current used and several types of equipment are available ranging from 200 to 1 000 A capacity. For manual operation, pistols using currents up to... 

James, D. H., Thermal Spraying by the Electric Arc Process , Metallurgist and Materials Technologist, IS, 85-90 (1983)... 

A technical exploitation of these experiments appeared unattractive, until 1909. Other methods of the chemical fixation of nitrogen, particularly the electric arc process for the formation of nitrous oxides (18) and the calcium cyanamide process (19) appeared far superior at that time. 

Table 5.4 shows the influence of electricity expenditures on the cost price of acetylene for the five main ocesses examined above. Among them, the electric arc processes and techniques based on calcium carbide are those that benefit most from the advantages of electricity, and guarantee some tsd ndence of the acetylene price from that of petroleuin products. 

A vast amount of research in all three directions led to commercial processes for each of them the electric arc process, the cyanamid process, and ammonia synthesis, which finally displaced the other two and rendered them obsolete. 

Derivation Oxidation of ammonia above 500C, decomposition of nitrous acid (aqueous solution). Also from atmospheric oxygen and nitrogen in the electric-arc process for fixation of nitrogen. 

Karrer, S. Phenomena in the Electric Arc Process of Nitrogen Fixation, Trans. Am. Electrochem. Soc. 48, 223-32... 

An alternate process named after Frank and Caro was based on the reaction of calcium carbide with nitrogen. The production of calcium carbide from calcium oxide and carbon needed temperatures above 2000 K, but the overall energy requirement was considerably smaller than that required in the electric arc process. Nevertheless, this route to nitrogen fixation was also soon replaced by the Haber-Bosch process. 

In the electric arc process for fullerene production, carbon material is heated using an electric arc between two electrodes to form carbon vapor. Fullerene molecules are condensed later and collected as soot. Fullerenes are later purified by extraction of soot using a suitable solvent, followed by evaporation of the solvent to yield the solid fullerene molecules. 

Feynman s vision of miniaturization and the Drexler-versus-Smalley debate on feasibility of mechanosynthetic reactions using molecular assemblers were discussed. Fullerenes are the third allotropic form of carbon. Soccer-ball-structured Cgo with a surface filled with hexagons and pentagons satisfies Euler s law. Howard patented the first generation combustion synthesis method for fullerene production. The projected price of the fullerenes has decreased from 165,000 per kg to 200 per kg in the second-generation process. Fullerenes can also be synthesized using chemical methods, a supercritical extraction method, and the electric arc process. Applications of fullerenes include high temperature superconductors, bucky onion catalysts, advanced composites and electromechanical systems, synthetic diamonds. 

Acetylene black must not be confused with the carbon black produced as a by-product during the production of acetylene in the electric arc process. 

As BASF also decided that it should not miss the opportunity to participate in the commercial development of the electric arc process getting under way in Norway, it concluded a cooperative agreement with Norsk Hydro, proprietors of the Birkeland-Eyde design, in December 1906. In the fall of 1907 the company set up an experimental plant at Kristianssand in southern Norway where it tested electric arc furnaces with power requirements of up to 450 kW. Any patentable increase... 

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