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Section 6. Technical sciences
Hoshimov Fozildzhon Abidovich, Doctor of Technical Sciences, Professor, Head of the Laboratory of the Institute of Energy and Automation, Academy of Sciences of
the Republic of Uzbekistan (Tashkent) Rakhmonov Ikromdzhon Usmonovich, assistant, Tashkent State Technical University (Uzbekistan)
E-mail: lider_1987@mail.ru
Analysis of the optimal energy indicators of electric arc furnace
Abstract: In this article, the role of electric arc furnace in the process of “Uzmetkombinat” is regarded, as well as an analysis of the mode of the unit integrated processing of steel, the continuous casting of steel.The actual value is the specific energy consumption by type of equipment shop EAFP for 2014.
Keywords: continuous, melting, oxidation, reduction, productivity, accuracy analysis.
In recent years, the consumption of electric energy of electric arc furnaces (EAF) increased sharply. With the continuous growth of the specific capacity and performance of electric furnaces the efficient uses of electric energy in smelting become great importance. In the article, the experience of operating EAF capacity of 100 tons of “Uzmetkombinat" is discussed.
Melt shop JSC “Uzmetkombinat” is a sophisticated technological complex of a number of interconnected units. The workshop is composed of the 100-tons electric arc furnaces each with transformer capacity of 95 MV • A. The shop is IME-unit complex processing of steel (ICCO), which allows you to heat the metal and implement a large number of fine-tuning operations to the required quality steel in the ladle. In addition, the shop is
equipped with varietal continuous casting machines (UNRS), each of which has four streams. The cross section blanks 250 х 320 mm.
Furnaces operate continuously. Prolonged shutdown occurs only when the furnace repair. Load of EAF is continuous-cyclic. Cyclical nature of the work is characterized by alternating heats with stops furnace drain metal filling the furnace and the filling mixture. There are three successive passing periods for melting steel: melting, oxidation, reduction.
Figure 1 shows a plot of the average power of the EAF-100 with transformer capacity of 95 MV • A for one smelting process cycle lasts about 60 minutes. The graph indicates the average load. In fact, the load has erratic dramatically alternating character, uneven in phases.
Fig.1. Schedule changes in the average power and voltage of arc furnace EAF for one technological cycle of melting
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Analysis of the optimal energy indicators of electric arc furnace
EAF load fluctuations, particularly reactive power fluctuations cause significant voltage fluctuations in the mains, which is the larger, the greater the power of the furnace transformer and a lower short-circuit power at the point of attachment of the arc furnace. Furthermore, EAF is the source of the higher harmonic components in the network and generates 3, 5, 7, 11 etc. harmonics.
Selection of the main electrical parameters of arc furnaces is complex and ambiguous. Furnaces operate in various conditions, and they conducted processes can also be different. Key performance indicators are production and specific energy consumption depend on many factors give
an analytical expression for optional values of these parameters, suitable for practical calculations and it isn’t represent possibility. Therefore, the definition of the main parameters of electric arc furnaces based on data from these operating systems and virtually experimental formulas derived on the basis ofstatistical data on existing furnaces.
In this workshop achieved an increase in productivity and reduction in specific energy consumption as well as reducing the time of melting by increasing the capacity of the furnace transformer with 45 MV • A up to 95 MV • A. Furnace, EAF -100 “Uzmetkombinat" has the following parameters.
Table 1. - Parameters furnace “Uzmetkombinat”
EAF-100 «Uzmetkombinat» Project characteristics Actual characteristics
Capacity, tons 100 120
The average weight of melting, tons 100 114
The total duration of melting, min. 90 60
Performance of work under the current, min. 60 46
Power transformer, MVA. 80 95
Limits secondary voltage, V. 250-600 250-750
Diameter, mm. 610 610
Nozzles of natural gas, MV. 2 х 20 4 х 3.5
Conversion of electrical energy into heat is carried out in these arc furnaces in electric arcs, burning in the furnace between the electrodes and metal covered with slag. In EAF electric arc burn on metal and represent the load, circuit is connected on Y to the location of the zero point or a strong charge, either liquid metal.
Efficiency of power consumption EAF is provided with optimal electric mode, ie, when the electric arc furnace operates with the highest performance at the lowest power consumption. Both of these conditions do not coincide with the same operating current. However,
there is a relatively small range of operating currents, within which one can get close to the optimum values for both the main indicators.
For determining the energy saving mode, the optimal active power is set in furnace installation.
Changing the active power is achieved by changing the operating voltage and the alternation of continuous operation at different voltages.
The following Table 2 shows the actual value of specific energy consumption by type of equipment shop EAFP for 2014.
Table 2. - The actual value of specific energy consumption by type of equipment EAF shop in 2014.
№ N 2013 The specific energy consumption, kW • h/t
EAF (ICCO) UNRS Total EAFP
1 January 363.4 35.8 27.2 426.4
2 February 354.9 28.5 26.6 410.0
3 March 358.0 31.8 26.0 415.8
4 April 361.3 28.6 25.7 415.6
5 May 360.1 28.3 23.0 411.4
6 June 357.4 27.5 24.6 409.5
7 July 355.8 30.4 23.6 409.8
8 August 360.0 29.5 24.9 414.4
9 September 358.5 28.6 25.1 412.2
10 October 351.6 28.5 26.9 407.0
11 November 352.2 25.6 25.8 403.6
12 December 369.2 22.3 27.8 419.3
Average Months 359.0 28.8 25.6 412.9
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Section 6. Technical sciences
The table shows that 87 % of electricity consumption is used in the furnace EAF, 7 % in the ICCO, and 6 % in the continuous caster.
Based on the above data on the energy indicators of main equipment of ESMS by using empirical equations are mathematical methods to determine the flow rate and specific energy consumption during operation of technological equipment under normal conditions.
Equipment — EAF:
WEAF = 0,335 • nEAF +1844, kW • h / month;
1844
eEAF = 0,335 +--- ,kW • h / t.
П
x± EAF
Equipment — ICCO:
WlCCO = 0,019 • П1СС0 + 619 , kW • h / month; 619
eiCCO = °,°19 +
П
kW • h / t.
Equipment — UNRS:
WUNRS = 0,019 ■ nuNRS + 371,45 , kW • h / month; 371 45
euNRs = 0,019 + ——1 ,kW ■ h / t.
П UNRS
For lime-burning site — YOW:
WYOW = 0,0208 • nYOW + 55,457, kW • h / month;
eYOW = 0,0208 + , kW • h / t.
nYOW
The resulting mathematical models of flow and the specific energy consumption for production equipment EAFP shop allow a sufficient accuracy for practical purpose to analyze and predict the energy performance and evaluate the efficiency of their work.
Thus, analysis, optimum energy performance of electric arc furnaces leads to the following conclusions:
1. Maintain at each stage of steelmaking optimal modes EAF-100 minimizes the duration of melting and power consumption.
2. Standards of electricity consumption in the smelting of various steel grades obtained during the examination EAF -100.
3. Statistics by sampling the energy performance EAF -100 include information about melting, corresponding to the normal conditions of their conduct.
References:
1. Hoshimov F. A., Allan K. Energy conservation in industry. - Tashkent: Publishing House of the «Fan», 2011. - 209 p.
2. Hoshimov F. A., Rahmonov I. U. Rationing of electricity productation in the rolling of ferrous metallurgy.// European Science review Scientific journal - № 11-12. - 2014 (November-December). - Austria, Vienna.
3. Hoshimov F. A., Rasulov A. N., Rahmonov I. U. Forecasting electricity consumption by improving the efficiency of the compressor stations. “INNOVATION-2014” International scientific conference. - Tashkent, 2014, 23-24 October. - Collected articles - 144 p.
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