Fig 1 - uploaded by Anatoliy Makarov
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Triangle connection of the primary and secondary windings of an EAF transformer and the short circuit of a highhpower EAF: (1) primary winding of the transformer; (2) voltage step switch; (3) secondary winding of the transs former; (4) busbar bridge; (5) fixed shoes; (6) flexible cables; (7) movable shoes; (8) tube bus; (9) electrodes of phases a, b, and c; (10) lined part of the roof; (11) waterr cooled roof panels; (12) waterrcooled wall panels; (13) injection equipment for blowing powdered carbon; (14) gas-oxygen burner (GOB); (15) burner torch; (16) electric arc moved by an electromagnetic force from the electrode axis to the periphery of the end of the elecc trode and to the metal bath surface; (17) lined part of the walls and banks; (18) bottom tapping channel; (19) hearth; (20) liquid metal bath coated with a slag layer; (21) electric arc glowing along the electrode axis at the beginning of an electric current halffcycle.
Source publication
The effect of electromagnetic blowing and the slag layer height on the arc efficiency is analytically studied. An arc is blown from under an electrode toward the furnace walls under an electromagnetic force. The arc efficiency of a 100-t high-power electric arc furnace changes from 0.47 to 0.76 when the slag height increases from 0 to 550 mm.
Contexts in source publication
Context 1
... (EAFs), we consider the electromagnetic phenomena occurring in arcs and the section of the electric power circuit of EAF from a furnace transs former to the load represented by electric arcs. The powerrsupply circuit from the highhvoltage terminal of the threeephase transformer to arcs is a secondary powerrsupply circuit, or a short circuit (Fig. 1). Figure 1 shows the triangle connection of the prii mary winding of a transformer with switchable voltage steps; the connection of the secondary winding of the transformer according to the "busbar bridge triangle" scheme; and the short circuit containing a busbar bridge, immovable shoes, flexible cables, movable shoes, tube buses, and ...
Context 2
... powerrsupply circuit from the highhvoltage terminal of the threeephase transformer to arcs is a secondary powerrsupply circuit, or a short circuit (Fig. 1). Figure 1 shows the triangle connection of the prii mary winding of a transformer with switchable voltage steps; the connection of the secondary winding of the transformer according to the "busbar bridge triangle" scheme; and the short circuit containing a busbar bridge, immovable shoes, flexible cables, movable shoes, tube buses, and electrodes. The central part of the lining and the peripheral part of the roof of superr power EAFs consist of waterrcooled panels, and the walls are made of copper (in the bottom part) and steel (in the top part) waterrcooled panels. ...
Context 3
... the beginning of a current halffcycle τ 1 (Fig. 2a), an arc glows along the electrode axis, moves over the electrode as a cathode spot and over a metal bath depression as an anode spot in the halffperiod, and occupies position 16 by the middle of the cycle τ 2 (Fig. 1). The arc current changes at a frequency of 50 Hz. Figure 2a shows one arc cycle in glowing onto a liquid metal bath. When an instantaneous arc curr rent vanishes (τ < τ 1 ), the arc temperature decreases to 4500°C rather than to the metal bath temperature because of significant thermal inertia and reaches 6000°C at the maximum ...
Context 4
... an arc fully hidden in a metal and slag, 35% of the arc power is radiated to the free space, absorbed by furnace gases and the water of the wall and roof panels, and is removed from the furnace as losses because of electromagnetic blowing. It was shown (Fig. 1) that the bottom arc semicylinder (16) radiates to the metal and the top semicylinder radiates to the metal, walls, and roof. The calculations demonstrate that the arc efficiency increases with the slag height ...
Citations
... . Electromagnetic forces [16][17][18][19][20] . Heat distribution and refractory material influences [5,[21][22][23][24]] -Electrode geometry optimization [18,25] -Scrap management [26][27][28]. ...
Štore Steel Ltd. makes more than 1400 steel grades. The highest costs in steel production from scrap stems from the electric arc furnace electric energy consumption. Electrical energy is used to produce heat energy generated by the burning arc between the graphite electrodes and steel scrap. In general, the balanced heat input of all electrodes is essential. Based on the input of thermal energy from all electrodes, also the possibility of occurrence of hot and cold spots in the electric arc furnace can be determined. Perception and elimination of the unequal heat load of electrodes have a major impact on reducing operating costs and increasing the efficiency of the electric arc furnace production. Most authors have modeled the arc furnace as an electrical equivalent circuit, where the electric arc is modeled using the macroscopic approach. In the paper the microscopic approach to the electric arc model is described, where a set of equations (electrical neutrality, Dalton law, Saha-Eggert) was solved using the differential evolution algorithm. The results of modeling were practically confirmed by measuring electric parameters (voltage, current, active power) during the electric arc furnace operation. In November 2016 the investment in a new electrode controller using implemented logic will be carried out.
... In Equation (3) angles α, β, distances l arc , l open , r are determined from geometrical constructions, thereof calculation presents no difficulty. Heat transfer theory was acknowledged by the international scientific community of metallurgists and electrochemists and is presently in use in training the students [2], in developing new arc and plasma-arc steel melting furnaces [11]- [13]. ...
It is proven that the law of radiation from solid bodies, Stefan-Boltzmann law shall not be used to calculate heat radiation from gas volumes which are formed in fuel flaring. The determining influence on heat fluxes density of the torch to the heating surfaces has not only a temperature, but power, dimensions, geometrical position of radiative gas volumes. The laws of radiation from gas volumes disclosed in 2001 and the method for calculating heating fluxes from gas volumes, developed on its basis, which takes into account the radiation from full set of particles in gas volume are stated. The torch model in the form of radiative gas volume is used to calculate heat transfer in torch heating furnaces, steam boiler boxes, turbogas unit combustors. The disclosure has enabled us to create new furnaces, fire boxes, combustion chambers, enhance unit performance, and decrease fuel rate, pollutant emissions.
Knowledge of the nature and behavior of forces acting on an arc is important when designing furnaces, controlling and automating their work. The effect of electromagnetic arc blowing has a negative effect on technical and economic indicators of the furnace, since the arc is removed from dimples in metal and slag. Radiation of the arc on walls and arch increases. And the effective power absorbed by the metal decreases. For this and a number of other tasks, it is necessary to know the dynamic behavior of the arc, which is largely determined by the instantaneous values and directions of the individual forces and the resultant force. The paper discusses the behavior of an electromagnetic force acting on an arc column from currents flowing through a liquid metal and currents flowing through other parallel arcs and graphitized electrodes in a three-phase AC arc furnace. It was assumed that the arcs burn perpendicular to the surface of the metal bath (their axes coincide with the axes of the electrodes) and effective value of the linear currents in different phases is the same. A mathematical model is proposed for calculating the instantaneous values and directions of the main electromagnetic forces acting on arcs in a three-phase arc furnace, allowing to reveal the nature of arcs dynamic behavior. A computer program has been created that makes it possible to visualize the behavior of a hodograph of forces acting on an arc. Hodographs of forces acting on the arc from the currents flowing through the melt are shown; they are ellipses lying in a horizontal plane. The resulting force deflecting an arc is also an even harmonic function with a frequency twice as high as the industrial frequency of the current. Its hodograph is an ellipse lying in a horizontal plane, the big semi-axis of which makes an angle of 20 – 80° with a line connecting the center of decay of the electrodes and the electrode axis.
