Transient Temperature Analysis of Slab in Erdemir

Available online at www.sciencedirect.com“ScienceDirectJOURNAL OF IRON AND STEEL RESEARCH, INTERNATIONAL. 2008, 15(2); 43-45Transient Temperature Analysis of Slab in ErdemirUnal Camdali'，Murat Tunc2' ，Sedat Sisbot2(1. Faculty of Engineering and Architecture, Abant Izet Baysal University, Bolu 14280, Turkey;2. Engineering Faculty, Yeditepe University, Istanbul 81120, Turkey)Abstract: A transient thermal model was developed for slab furnaces in Eregli lron and Steel Works (Erdemir) inTurkey and the model was solved using the FlexPDE computer program. This program uses the finite element meth-od. Program codes were written to solve the temperature distribution of slabs that are put into furnaceat25 c andremoved at about 1 250 C. To obtain the optimum slab exit temperature variation, the necessry air temperature in-side the furnace was calculated to be 1390 C. The slab temperature versus time and the temperature variation insidethe slab were depicted,Key words; Erdemir; finite element method; industrial system; slab; slab furnace; temperature analysisEnergy demand has been rising with the in-steel production capacity of 3 Mt, it is the largest ironcreased degree of industrialization and populationnd steel factory and the sole producer of steel in theand with the increased use of iron and steel in thecountry. Erdemir produces hot and cold rolled coils,world.zinc, tin, and chromium plated steels-r. The pro-The iron and steel industry is one of the most，duction amounts in Erdemir, between 1999 andimportant industries in the development of any coun-2004, are given in Table 1.try because it is the basis of all development strate-The slabs are generated by continuous castinggieslt]. Prior to 1950 or thereabout, steel was madefacilities and are also imported. They are reheated to .in furnaces, such as open hearths, converters, andthe slab furnaces to bring them to a rolling tempera-eletric furnaces. Currently, there are two steel pro-ture. There are two slab heating furnaces in Er-duction routes: the integrated route with blast fur-demir. They aid the hot- rlling mill. These arenace and basic oxygen furnace and the electric arcpush-type furnaces and have a capacity of 320 t/h. .furnace route[)]. Slabs are heated or reheated in slabSlabs are charged into the furnaces by slab pushers.furnaces to bring them to a rlling temperature in ironThey are tempered up to 1 250 C in the slab fur-and steel facilities. There are many studies relatingnaces, following which, they are placed on the roll-to heat and temperature analysis in the iron and steeling line by slab carriers.industry, as mentioned in Ref. [3- -6].2 Slab Thermal ModellingIn the present study, the transient thermal analysisfor the slab is carried out and applied to the slab fur-There are three slab inlet temperatures in thenace in Eregli Iron and Steel Works (Erdemir) inslab furnaces. Slabs enter the slab furnaces at theTurkey.surrounding temperature, or at 150- 500 C or 1150一1250 C. In this study, transient temperature anal-1 Erdemir Incysis is carried out for the first type of slabs.Erdemir began its activities on May 15, 1965,These slabs are loaded into the slab furnace atwith an annual production capacity of 450 kt, and25 C (Fig. 1). Then, they should leave the furnacehas made important contributions to Turkey s econ-atarig.2. The thermalomy ever since. Today, with a total amount of crudemode中国煤化工(1). Their nmerCNMHGBiogrophy,Onal Canmdali(1964-), Male, Doctor, Associate Profesors E-mail: candal ulb edutr; Kevnea uate: December1, 2006Journal of Iron and Steel Research, InternationalVol. 15Table 1 Production capacity in Erdemir in recent years199920002001200220032004Hot metal2386533 2193532 2726 0062664142 2821 4452 786 340Liquid steel2695185 2478694. 3075048 2991 2853 1893393 129 138Crude steel (slab)2 160 7342 388 0122 962 2552 887 7233 087 9783 031 338Tinplate77 726137 46095 516124 424192 963219 438Galvanized steel40 959207 465233 916305 967Cold rlld steel931 5561 062 489818 510689 289989 5481127 192Hot rlled seel1812153 1878436 1944931 2074987 2069866 1 909 956Plates4081851 57155 59648 03248 22753 612Total products2 862 2533 129 9562955 5123144 1973 534 5203616 165From Erdemir slab289441 2164677. 2570142 2696057 2836279 2 730 829From imported slab and hot rolled coil572 812965 279385 370448 140698 241885 335material, (J●kg~'●C-1); andk is the thermal con-ductivity of slab material, (W.m~'. C-1).争(1) Initial and final conditions for slabInlet temperature Tm=25 C att=0s;EntranceExitOutlet temperature Tom=1 250 C att=3 600 s.Heat transfer is carried out by convection andFig 1 Slab furnace in Erdemirradiation. Therefore, the total heat transfer coeffi-cient, h, is defined by the following formula:h=he +h,(2)h; =ae(T+ T)(T+ T)(3)where, h, is the heat transfer coefficient for convec-tion; h, is the heat transfer coefficient for radiation;σ is the Stefan Boltzmann constant, which is 5. 66XFig2 Slab and coordinate system10-8 w.m-●K~';ε is emissivity cofficient; T. iscal values are given in Table 2. Slab temperature distri-air temperature inside the furnace.(2) Boundary conditionsbution as a function of x (m) and time t (s) is obtainedFor top surface of the slabfor the given initial and boundary conditions.- T=h(T,-T)(4)p dT=kT(1)pe dFor the other surfaces of the slabwhere T is the slab temperature, C; p is the densitydT_of slab material, (kg. m^”); c is specific heat of slabq=0(5)Table 2 Properties of slabp/(kg.m-3) e/(J.kg-1.C-1) k/(W.m-1●C-1) he/(W.m72.C-1)LiXL2XLs7 87044916 mX1.3 mX0.2 m3 Solution of Problem.3厂Partial diferential equation given in Eqn. (1) issolved using the FlexPDE 4. 2.12 computer pro-gram. This program is convenient for solving par-中国煤化工0912tial differential equations. It uses finite elementmethods. Mesh analysis for the slab is given inMYHCNMHGFig. 3.Fig. 3 Mesh analysis for slabIssue 2.Transient Temperature Analysis of Slab in Erdemir4 Results14:47:42 1227107Transient conducdonFlexPDE4.2.12in slap furmaceFig. 4 shows the temperature increase inside theTemperatureslabs during the period of stay in the furnace. It is1.2516x102from (0, Ly/2)observed from this figure that the actual slab tempera-如, Ly/2)gaTemperatureture reaches1 250 C in1 h at the exit, It is importantto note that the slab internal temperature has reached upto milling temperature with the present casting speed.The temperature distribution along the xaxis of theslab is shown in Fig.5. It is evident that the tem-1.2515x 10perature is homogeneous around 1 251.5土0.4 C.Homogeneous temperature distribution inside theslab is very critical for the hot milling process and0.3.60.1x/mhas a direct impact on the steel quality. Hot steelmilling relies heavily on homogeneous temperatureSlab; Cycle=4l, Time=3 600.0, dt=532. 53 P2distribution.Nodes= : 219, Cells= 92 RMS, Err=5. 5X10-*Integral=1 626. 9865 ConclusionFig.5 Variation of temperature of heated slab with xThe developed model can be used to observe theprocess. Finally, it is apparent from the results thattemperature distribution inside the slabs for differ-when slabs are preheated prior to the furnace entry, :ent pusher furnace setups. Furthermore, it allowsthe duration of stay in the furnace can be shortenedoperators to feed the furnace faster or slower toand more heat energy is saved.change the thermal quality dynamics during the millingReferences:[1] Camndali U, Tunc M, Dikee F. A Thermodynamic Analysis of1200 Transient conductionin slap furnacea Seel Production Step Crried Out in a Ladle Furnace U].Appl Thermal Eng, 2001, 21(6); 643.[2] Cayir E Optimization of Energy Consunption in Iron and14:39:18 72105900Steelmaking Process by Use Second Law of ThermodynamicsHistory[D]. lstanbul, Turkey: Istanbul Technical University Insti1. Temperaturetute of Science and Technology. 1996.[3] Camdali U, Tunc M. Transient Temperature Analysis for In600 |dustrial ac Are Fumace Bottom [J]. J lIron snd Steel Res, Int,2004, 11(6); 1.[4] Camndali U, Tunc M. Heat Transfer Analysis for Industrial AC300abedeAre Furnace []. J Iron and Steel Res, Int, 2005, 12(4); 9.[5] Camdali U, Tunc M. Steady State Heat Transfer Analysis ofthe Ladle Furnace During Steel Production Process [UJ]. J lronand Steel Res, Int, 2006, 13(3); 18.[6] Bisio G, Rubatto G, Martini R. Heat Transfer, Energy Sav-15002 5003500ings and Pllution Control in UHP Electric Are Furnaces [J].Time/sEnergy, 2000, 25(11); 1047.Slab 1, Cydle= 100, Time=3 600.0, dt= 385.72 Pz[7] Ertem M E, Ordabok A. Energy Balance Aplication for ErNodes= 395, Cells 178 RMS, Err=7. 3X10-4demir Coke Plant With Thermal Camera Measurements [J].Fig4 Variation of tempernture of slab with timeApplied Thermnal Engineering, 2005, 25(2-3); 423.中国煤化工MYHCNMHG