Analysis of an Electric Arc Furnace Used for Casting of Steel: An Exergy Approach
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ANALYSIS OF AN ELECTRIC ARC FURNACE USED FOR CASTING OF STEEL: AN EXERGY APPROACH U. Camdali,1 M. Tunc,2 and G. Arasil 3 An electric arc furnace with a liquid steel capacity of 30 t was analyzed using the second law of thermodynamics. To carry out the exergy analysis, materials and energies entering and exiting the electric arc furnace were determined. The materials included several types of scrap, cokes, fluxes, oxygen, liquid steel, stack gases, and dust. Electrical and exothermic chemical energies of these materials were considered. Energies of the materials leaving the furnace, including liquid steel, slag, stack gases, and dust, were determined, as were the chemical reactions and exergies entering and leaving the electric arc furnace. Exergy efficiency and lost exergy were calculated. It was found that 42.6% of exergy is lost because of the chemical reactions, heat transfer, and other reasons. The overall exergy efficiency of the entire system was found to be 46%. Keywords: steel, electric arc furnace, exergy analysis, exergy.
Nomenclature
CP g gE h m n Q T V W Z
Ξe ΞI
Ξ Ξ Ξ
in/ex
phy Q
specific heat at constant pressure (kJ/kg K) specific Gibbs function (kJ/kg) gravitational acceleration ( m/sec 2 ) specific enthalpy (kJ/kg, kJ/kmole) mass (kg) number of moles (kmole) heat (kJ)
temperature (K) velocity (m/sec) work (kJ) height of flow (m)
exergy of electric energy (kJ, MJ)
loss exergy due to irreversibilities (kJ, MJ) inlet/exit exergy of the system (kJ, MJ) physical exergy (kJ, MJ)
heat exergy (kJ, MJ)
1
Ankara Yildirim Beyazit University, Faculty of Engineering and Natural Sciences, Mechanical Engineering Department, 06100 Etlik, Ankara, Turkey; e-mail: [email protected]. 2 Istanbul Bilgi University, Engineering and Natural Sciences Faculty, Energy Systems Engineering, 34060 Eyup, Istanbul, Turkey; e-mail: [email protected]. 3 Istanbul Technical University, Control and Automation Engineering, 34469 Maslak, Istanbul, Turkey; e-mail: gorkemarasil@ gmail.com. 0026-0894/20/0506-0483
© 2020
Springer Science+Business Media, LLC
483
U. CAMDALI, M. TUNC,
484
Ξs
che
Ξ ψ
ε µ i0
µ i00
AND
G. ARASIL
exergy of system (kJ, MJ)
exergy of chemical reaction (kJ, MJ) exergy efficiency (kJ/kJ)
specific exergy (kJ/kg) chemical exergy potential per kg at ambient condition (kJ/kg) chemical exergy potential per kg at dead state (kJ/kg)
Subscripts che cv cw deoxmat dst ex elctr exc flx i in j kin ls oxy phy pot rev s scr sg st-slg tot 0 00 0/1
chemical control volume cooling water deoxidizing material dust exit electrode excess of carbon fluxes component i inlet component j
kinetic liquid steel oxygen physical potential reversible system scrap stack gases steel in slag total property at environmental conditions dead state inlet/exit condition
Introduction Owing to an increasing global population, steel production is continuously increasing. From 1950 to 2017, steel production increased from 189 million tons to 1689 million tons [1]. In 2017, approximately 473 million tons of liquid steel (28%
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