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电弧炉渣门机构设计【含全套12张CAD图纸】【答辩毕业资料】

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电弧炉渣门机构设计
摘要
本次设计，主要是针对电弧炉可升降的渣门的结构设计、冷却系统的设计、以及炉渣门的提升机构的设计。其中，炉渣门的结构设计包括：炉门材料的选择，炉门外形结构设计。冷却系统的设计包括：冷却方式的选择，材料的选择，以及设计炉门的计算。炉渣门的提升机构设计包括：提升的方式，传动方式，传动系统的布置，动力源装置，以及传动系统各部件的校核。电弧炉渣门提升机构在保证电弧炉安全稳定工作的情况下，炉门可以平稳提升降落，而且反应迅速。

关键词：电弧炉；电弧炉渣门；炉门提升

Electric arc furnace slag door mechanism design
Abstract
The design, design for the the slag door electric arc furnace can lift structural design, the design of the cooling system, and the slag door lifting mechanism. Among them, the structural design of the slag door comprising: a door the choice of materials, the door shape structural design. The design of the cooling system comprising: a cooling mode selection, material selection, as well as the design of the oven door calculation. The slag door lifting mechanism design includes: an elevated manner, the transmission mode, the arrangement of the transmission system, the power source means, and the transmission system of each member checked. Electric arc furnace slag door lifting mechanism in the case to ensure the security and stability of the electric arc furnace, the door can enhance the smooth landing and quick response.

Key Words: Electric arc furnace; slag door; Door upgrade

主要符号表
A 截面面积
K 安全系数
Dm 外径
d 内径
对无缝钢管系数取
C 管壁厚度附加值
[] 工作温度下管材许用应力
缸底材料抗拉强度（Pa）
S 为管壁厚度
P 为管内介质压力
Ps 缸内额定压强
V 体积
M 重量
α 齿距角
H 链轮中心至链窝底面垂直距离
Mv 垂直方向上弯矩
MH 水平方向上弯矩
P 液压缸的供油压力

目录
1 绪论 1
1.1题目背景 1
1.2 国内外发展的概况及研究意义 1
1.2.1国内外发展的概况 1
1.2.2研究意义 2
1.3论文的提出与本文的组织 3
1.3.1论文的提出及本人的主要工作 3
1.3.2方案设计 3
1.3.3论文主要内容 3
2 炉渣门冷却系统设计 4
2.1 冷却的方式 4
2.2 冷却系统的布置 5
2.3 管的材料的选择 6
2.4 冷却水量的计算 7
3 电弧炉渣门结构设计 8
3.1电炉渣门结构设计 8
3.2电炉渣门的材料选型及经济性分析 9
4 炉渣门提升机构设计 11
4.1 提升负载的计算 11
4.1.1炉门的质量计算及分析 11
4.1.2 冷却水重量的计算 11
4.1.3炉门总重量的计算 11
4.2炉渣门提升机构设计 12
4.2.1提升机构的基本要求 12
4.2.2提升方案比较及选择 12
4.2.3提升机构链轮设计 13
4.2.4提升机构链条设计 17
4.2.5 提升机构传动轴设计 17
4.2.6 提升机构液压系统设计 20
5 结论 27
参考文献 28
致谢 30
毕业设计（论文）知识产权声明 31
毕业设计（论文）独创性声明 32
附录1 33
附录2 34
附录3 36

1 绪论
1.1题目背景
众所周知，以电弧炉炼钢为核心的短流程炼钢工艺，在工程投资、占地面积、吨钢的资源消耗、能源消耗和二氧化碳等污染物排放量比长流程炼钢工艺大幅减少，同时以废钢为原料也直接体现了金属材料的循环利用，更符合钢铁行业可持续发展、科学发展和低碳经济发展的要求。全球电弧炉钢产量呈不断上升的趋势很大一部分也是得益于电弧炉炼钢技术和装备技术的不断创新和进步。现代工业化炼钢方法以高的生产率、优

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内容简介：: ISIJ International, Vol. 48 (2008), No. 9, pp. 119712051.IntroductionElectric arc furnace (EAF) production of steel has grownsignificantly in the past several decades. Much of this pro-duction is in state of the art plants producing higher valueadded products such as continuously cast flat rolled steels.These furnaces use large quantities of pig iron, injectedoxygen, and injected carbon for foamy slag1)and electricalenergy. Injected oxygen can react directly with iron to formiron oxide, carbon dissolved in iron or solid carbon to formCO, or with CO in the gas phase in the form of post com-bustion producing CO2. How the oxygen is distributedamong these reactions is critical to the furnace perform-ance.In the present study, a decarburization and slag formationmodel has been developed based on a mass balance, and thekinetic equations for decarburization, and the reduction re-action between carbonaceous materials and iron oxide inslag. Various melting patterns for scrap and pig iron wereexamined and the variations of carbon content in the metaland iron oxide content in slag were calculated. The modeldeveloped here can be used to optimize oxygen injection,flux additions, carbon injection, and yield as well as slagfoaming, which is the subject of a future paper.Several successful models have been developed for oxy-gen steelmaking (OSM).2)OSM is a true batch process inwhich all of the hot metal, scrap and fluxes are added be-fore the oxygen blow begins, and all of the metal and slagare tapped at the end of the process. The major part of anOSM vessel charge, liquid hot metal, is homogenous intemperature, physical properties and chemistry. Many mod-ern EAFs operate with a liquid heel of metal and slag fromthe previous heat, flux and carbon are injected continuouslyduring various stages of the process, and slag is flushed outof the furnace. Furthermore, injected carbon reduces FeOdissolved in the slag throughout the heat. In addition, theentire charge of an EAF is solid scrap, and extremely het-erogeneous with respect to chemistry, bulk density, andother physical parameters. In the EAF, decarburization iscontrolled by liquid phase mass transfer at low carbon con-tent, which this paper will demonstrate is true for much ofthe EAF melting cycle. These considerations make a modelfor the EAF much more complicated than for the OSMprocess. Several previous models have been developed,such as energy and materials balances for charge controland for FeO formation.2)However, no comprehensivemodel exists, which takes into account the many dynamiceffects and reaction rates.2.Model DevelopmentThe present decarburization and slag formation model isbased a mass balance for each component in metal and slagphases, and the rate equations for decarburization and theDevelopment of a Decarburization and Slag Formation Model forthe Electric Arc FurnaceHiroyuki MATSUURA,1)Christopher P. MANNING,2)Raimundo A. F. O. FORTES3)and Richard J. FRUEHAN4)1) Formerly Center for Iron and Steelmaking Research, Department of Materials Science and Engineering, Carnegie MellonUniversity. Now at Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University ofTokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 Japan.2) Materials Processing Solutions, Inc., PO Box 1203,Easton, MA 02334 U.S.A.3) Department of Technology and Industrial Process, Gerdau Aos Longos Brasil S.A., Av.Joao XXIII, 6777-Distrito Industrial Santa Cruz, Rio de Janeiro RJ 23560-900 Brazil.4) Center for Iron and Steelmaking Research, Department of Materials Science and Engineering, Carnegie Mellon University,5000 Forbes Avenue, Pittsburgh, PA 15213 U.S.A.(Received on March 6, 2008; accepted on June 9, 2008)A decarburization and slag formation model for the electric arc furnace was developed, which includesthe rate phenomena for decarburization and the reaction between carbonaceous materials and iron oxide inslag, mass balance for each species in the metal, slag and gas phases, and the melting behavior of pig iron,scrap and fluxes. The model was applied to a two bucket charge operation electric arc furnace and the dy-namic metal and slag compositions were calculated as a function of time. The effects of melting patternsfor raw materials, carbonFeO reaction rate, and the post combustion ratio were examined. The critical pa-rameters, which most strongly influence chemistry development, were identified. These parameters werefitted to an industrial case, such that the model could accurately predict slag and metal chemistry develop-ment. This model could be utilized to optimize the operation in order to improve yield, energy efficiency, andincrease consistency of metal and slag chemistries from heat to heat.KEY WORDS: electric arc furnace; decarburization; slag formation; mass balance; model development.11972008 ISIJreduction of iron oxide in slag by injected carbonaceousmaterials. Figure 1 shows the model calculation algorithmchart. The calculation algorithm is mainly composed of (A)melting of scrap and pig iron, and dissolution of impuritiesassociated with scrap, such as dirt, and flux, (B) oxidationof carbon and other elements including iron by injectedoxygen, (C) reduction of iron oxide by injected carbona-ceous materials, (D) slag discharge or flushing, and (E)mass balance calculations. Steps (A) to (E) were repeateduntil the end of the refining by the time step of Dt.(A)Scrap and Pig Iron Melting, and Impurity and FluxDissolutionScrap, pig iron and the accompanying impurities aremelted or dissolved into slag, and included in metal andslag phases based on the defined (assumed) melting or dis-solution rate. If flux is injected during refining, this also istaken into consideration. Metal and slag phases are as-sumed to be homogeneous, and then compositions of eachelement in metal and slag phases are calculated.(B)Oxidation of Carbon and Other Elements by OxygenInjected oxygen first oxidizes elements more easily oxi-dized than carbon and iron. In the present model, as thescrap melts the silicon, aluminum and manganese are oxi-dized until their compositions reach the set points of eachelement. In the present calculation, it was assumed that sili-con and aluminum in melt are completely oxidized, andmanganese is oxidized until manganese content reaches0.05mass%.Si?O2(g)?(SiO2).(1)Al?3/4O2(g)?1/2(Al2O3).(2)Mn?1/2O2(g)?(MnO) .(3)The SiO2, Al2O3and MnO produced enter into the slagphase.Second, decarburization proceeds by Eq. (4) as in OSM.3)It is well accepted that the reaction proceeds by oxygen firstreacting with iron to form FeO in slag. Then carbon dif-fuses in the metal reducing the FeO to metallic iron andproducing CO as indicated by the following reactions.C?1/2O2(g)?CO(g).(4)Fe?1/2O2(g)?(FeO).(5)(FeO)?C?Fe?CO(g) .(6)The CO can be further oxidized to CO2by post combustion.If the carbon content is high, the driving force for masstransfer of carbon is sufficient to reduce all of the FeOformed. As a result, the rate of decarburization is limited bythe oxygen mass flow rate. At low carbon contents, themass transfer rate decreases and not all of the FeO is re-duced, thus the FeO content of the slag increases. There-fore, the decarburization rate is controlled by liquid phasemass transfer of carbon at lower carbon content as ex-pressed by Eq. (7), or by oxygen gas flow rate at higher car-bon content described by Eq. (8).(7).(8)where, m is the liquid phase mass transfer coefficient ofcarbon, A is the interfacial area where the decarburizationoccurs, ris the density of melt, WtMeltis the weight of metalphase at time is t, VtOxyis the oxygen gas injection rate attime is t, and RPCis the post combustion ratio. Since theequilibrium carbon content %Ceis negligibly small com-pared to carbon content in melt, %Cewas assumed to bezero. The point where the rate mechanism changes is calledthe critical carbon content %CC.The value of “mA” is normally obtained by measuringthe rate of decarburization in the furnace and back calculat-ing the parameter using Eq. (7). However, due to the hetero-geneous distribution of solid and liquid in an EAF duringmelting, it is nearly impossible to get a representative liquidmetal sample during the first half of the oxygen injectionperiod. As a result, no measurements are available for anEAF. In the present work, the value of “mA” was extrapo-lated from OSM operations assuming the parameter is pro-portional to the oxygen flow rate. This assumption is validin OSM, as the stirring energy in the bath is typically pro-portional to the oxygen injection rate. Since the value ofmA/VOxydepends on many factors such as the furnace size,shape, O2injection method and so on, the intrinsic valueshould be known to calculate the decarburization rate in theparticular furnace accurately. In the present calculation, thevalue of mA/VOxyused in this study was 0.050 which valueis reported for 300t vessel4)based on the above assumptionand the critical carbon content was calculated by equatingEqs. (7) and (8), and is approximately 0.3mass%.3,4)When the carbon content decreases below the criticalvalue, the oxidation reaction of iron becomes dominant,and iron oxide is produced, which is absorbed by the slagphase. The reactions between decarburization and iron oxi-dation are competitive, and the proportion between thesetwo reactions is determined by the carbon content as de-ddtVRWttt%COxyPCMelt?1000 22 420 012100/.().ddtmAWtttt%C%C%CMelte?()ISIJ International, Vol. 48 (2008), No. 911982008 ISIJFig. 1.Calculation algorithm in the present model.scribed by Eqs. (7) and (8). The amount of FeO in the slagis determined from the oxygen injected minus any oxygenused for carbon burning, post combustion and the oxidationof alloying elements (Al,Si,Mn) in the scrap. In the EAF,part of oxygen reacts directly with the solid scrap produc-ing FeO, and as the scrap melts, the FeO on the scrap re-ports to the slag phase. However, the calculated FeOformed in the model is based on a mass balance in whichthe oxygen not used for carbon, CO, or elements in themetal oxidizes iron. Therefore, the formation of FeO by thereaction of oxygen with scrap is accounted for, though notexplicitly calculated.(C)Reduction of Iron Oxide by Injected CarbonaceousMaterialsDuring EAF steelmaking, carbonaceous materials suchas coke and coal are injected into the slag to reduce ironoxide in slag phase and make the slag foam. Slag foamingis critical for the protection of refractories and the watercooled roof and sidewalls from the arc, as well as, to mini-mize the heat loss. However, it is frequently observed thatthe some injected carbon remains in slag and is dischargedas unreacted particles. It was assumed that the reductionrate of iron oxide by carbon particles is expressed as Eq.(9). This equation assumes that the rate is controlled bymass transfer of FeO in the slag or chemical kinetics andthe surface area of carbon is proportional to its weight inthe slag.(9)where, kredis the reaction rate constant between carbon andiron oxide in slag, and WtCMis the weight of carbon existingin slag at time is t. In this model, the reduced iron returns tothe metal phase. In the present calculations, kredis consid-ered as a constant value throughout the refining time. Onthe other hand, kredis obviously a function of temperatureand temperature profile of the metal and slag during the op-eration should be considered to determine kredmore exactly.However, change of temperature is not calculated in thismodel and other calculation (estimation) model should beutilized to estimate temperature in the future step. In addi-tion, the optimized kredcalculated in the present applicationis 0.57min?1as discussed in the following section. Thoughan increased kredof 1.5min?1(corresponding to the activa-tion energy of 282kJ/mol in the case of temperature changefrom 1823 to 1923K) was examined in the case study, car-bon content profile in metal did not change and the differ-ence in FeO content profile by the use of two kredvalues wasonly within 2.5mass%. Therefore, the effect of temperaturechange in the present calculation is limited.(D)Slag DischargeDuring EAF steelmaking, slag is discharged or flushedduring the process. Assuming that the slag phase is homo-geneous, part of the slag is discharged according to a de-fined slag discharge rate. Unreacted carbon remaining inslag is also discharged with the slag.(E)Mass Balance CalculationsThe mass balance calculations in metal and slag phasesare expressed by following equations. In the present model,the refractory dissolution has not been included for the slagmass balance calculation. It will be incorporated in the fur-ther model development. The refractory consumption indifferent EAF operations varies greatly, and can be between0.22.0kg/t-metal.5)At present, the model assumes the in-crease of MgO content in the slag is expected to be minor.Metal phase.(10).(11).(12).(13).(14).(15)Slag phase.(16).(17).(18).(19).(20).(21).(22).(23).(24)A number of other factors are important and primarilydepend on the specific operation. For example dust lossesare not considered. As discussed latter up to 10kg/t-scrapof iron or more leaves the furnace as dust. Post combustiondepends on the actual operation. In this model it is an inputand usually assumed to be 10%. As mentioned above, re-fractory dissolution will also affect the chemistry andamount of slag.3.Application of the ModelIn the present study, the model developed was applied toa two bucket charge operation furnace. Table 1 shows typi-cal operational conditions and raw materials for this fur-WWrtCttttttnn?MeOSlagDisMeO()CWWttttnn?MeOMeOSlagWWttnSlagMeO?WWWttt?MnOMnOMn-Oxi7155WWrCtWtttt?Al OAl ODirtDirtAl OAl-Oxi2323235127WWrCrCttttt?MgOMgOFluxFluxMgODirtDirtMgO()WWrCrCtWttttt?SiOSiODirtDirtSiOCMCMSiOSi-Oxi2222()6028WWrCrCttttt?CaOCaOFluxFluxCaODirtDirtCaO()WWWWtttt?FeOFeOFe-OxiFe-Red()7256WWrCtWttttt?AlAlScrapScrapAlAl-OxiWWrCrCtWtttttt?SiSiPigPigSiScrapScrapSiSi-Oxi()WWrCrCtWtttttt?MnMnPigPigMnScrapScrapMnMn-Oxi()WWrCrCtWtttttt?CCPigPigCScrapScrapCC-Oxi()WWrCrCtWWttttttt?FeFePigPigFeScrapScrapFeFe-OxiFe-Red()WWWWWWttttttMeltFeCMnSiAl?rkWtttredredCM(%FeO)?100ISIJ International, Vol. 48 (2008), No. 911992008 ISIJnace. In this model, the calculated results are obtained byintegrating calculated values with a time interval of Dt. Ef-fect of Dt on the calculation results was preliminary exam-ined and sufficiently small value of Dt?1/60min (1.0s)was selected as a calculation condition.The furnace is a 120t capacity with a 105t tap weight.Scrap and pig iron are charged in two buckets. Dolomiteand lime are charged with the scrap and pig iron in the firstbucket. In the latter stage of the refining, coke is injectedfor foaming and FeO reduction, and slag is discharged fromthe furnace.3.1.Effect of Materials Melting PatternThe effect of the pig iron and scrap melting rates wereexamined for the furnace. The oxygen injection rate varieswith time, reflecting oxygen injection in the actual process.Since the furnace is operated with a two bucket charge,there is an idle time between 5 and 13min after the start ofthe operation for the second bucket charge. During the idletime the oxygen flow rate is very low. There are two typesof oxygen injectors; the main lances for refining of melt,and secondary injectors for the post combustion. In thepresent calculation, post combustion occurring above themelt and slag phases are not taken into account, becausethis does not affect the melt and slag chemistries. There-fore, it was assumed that 100% of main lance oxygen and20% of post combustion oxygen reacts with the melt andslag based on discussions with furnace operators. It wasalso assumed that the scrap impurities and charged flux inthe first bucket dissolve in slag with a constant dissolutionrate in the first 30min. The reaction rate constant betweenFeO and carbon particles in slag kredand the post combus-tion ratio RPCwere fixed to be 1.0min?1and 0.1, respec-tively. Four pig iron melting patterns and three scrap melt-ing patterns were defined (assumed) as shown in Fig. 2based on discussions with the furnace operators and thefundamental considerations. In the calculations, the finalmetal and slag chemistries were used as the initial conditionof the metal and slag heel for the next calculation, and thisprocedure was repeated several times until the steady stateresults were obtained.Figure 3 shows the change of carbon content in melt as afunction of time for each melting pattern, together with theanalytical results of collected melt samples. The furnacehas only 15000kg of initial heel compared to 115600 kg ofcharged materials. Therefore, the carbon content in the meltchanges considerably with different melting patterns of pigiron and scrap. Assuming a fast melting rate for pig iron atthe early stage of operation, the carbon content goes up to0.7mass%. For all melting patterns, stable carbon contentprofiles were seen after about 30min. However, those wereapproximately 0.10.25mass%, which is higher than theobserved carbon content in the furnace of about0.06mass%.Figure 4 shows the change of FeO content in slag as afunction of time for each melting pattern with the analyticalISIJ International, Vol. 48 (2008), No. 912002008 ISIJFig. 2.Defined melting patterns for (a) pig iron and (b) scrap.Table 1.Operational conditions, the raw materials and calcu-lation conditions.results of collected slag samples. The minimum FeO con-tent was calculated to occur between 10 and 20min. Thenthe FeO content increased again or remained almost con-stant. Faster melting of pig iron in the early stage, such aspatterns W and X for pig iron melting, leads to a large de-crease in FeO content. This is because the carbon content inthe melt increases, and all oxygen injected is consumed bythe decarburization reaction and no FeO is produced, whilethe scrap impurities and fluxes dissolve continuously caus-ing the FeO to be diluted. In the early stage of the opera-tion, some FeO should be produced and supplied to the slagphase to enhance the flux dissolution and maintain FeOlevel. On the other hand, in the case of patterns Y and Z forpig iron melting, the FeO content was almost constant dur-ISIJ International, Vol. 48 (2008), No. 912012008 ISIJFig. 3.Change of carbon content in the melt calculated with various pig iron and scrap melting patterns.Fig. 4.Change of FeO content in slag calculated with various pig iron and scrap melting patterns.ing the operation. Considering the change of carbon andFeO contents with time, slower melting of pig iron in theearly stage, for example patterns Y and Z, would be realis-tic for this furnace. However, the calculated FeO contentwas higher compared to the analyzed results by about510mass% as shown in Fig. 4. The overestimated FeOcontent would be due to (i) the overestimation of the contri-bution of the injected oxygen from the post combustion in-jectors to the reaction and (ii) the underestimated post com-bustion ratio.The calculated FeO and carbon loss by slag discharge areshown in Table 2 for each melting pattern of pig iron andscrap. The FeO and carbon loss changes with pig iron melt-ing pattern, while the effect of scrap melting pattern issmall. The carbon loss with the slag discharge is 0.6%.Considering effect of melting patterns for pig iron on theprofile of carbon content in metal and FeO content in slag,pig iron melting pattern Z seems most realistic one. The op-timization of pig iron melting pattern should be conductedtogether with other operational variables to reproduce theoperational results. In the following calculations, pig ironmelting pattern Z was used as a most conceivable patternfor the time being to examine other parameters. On theother hand, “the ideal melting pattern” of pig iron for a par-ticular furnace to operate the furnace at the best conditioncan be obtained from this model with other tuned parame-ters.3.2.Effect of CarbonFeO Reaction Rate ConstantThe effect of the reaction rate constant kredwas examinedwith fixed pig iron and scrap melting patterns (Z and 3, re-spectively). The post combustion ratio was assumed to be0.1. Change of the reaction rate constant kreddoes not affectcarbon content in metal considerably (within 0.008mass%),though FeO content changes. Figure 5 shows the FeO con-tent profiles in slag with various carbonFeO reaction rateconstants at steady state. Decreasing the rate constant in-creases FeO content in slag and, as a result, FeO and carbonloss also increase. The loss of FeO and unreacted carbonwith various reaction rate constants are shown in Table 3.The value of the reaction rate constant is between 0.1 and0.5min?1to reach 10% of carbon loss. In the case of0.5min?1, the calculated FeO level was approximately10mass% above the analyzed slag composition.3.3.Effect of Post Combustion RatioThe effect of post combustion ratio on FeO content wasexamined with fixed pig iron and scrap melting patterns (Zand 3, respectively) and carbonFeO reaction rate constant(0.5min?1). Figure 6 shows the FeO content profiles in theslag with three post combustion ratios at steady state. Whenthe post combustion ratio is increased to RPC?0.3, the FeOcontent in the slag decreases or remains constant reproduc-ing the analyzed slag chemistry after 30min. The large in-crease of FeO content after 45min is due to the terminationof pig iron melting, resulting in an FeO content in slag atthe end of the heat of 4045mass%.The post combustion ratio just above the melt is around0.16)and the computed optimized post combustion ratio of0.3 is considered to be overestimated. As mentioned before,it was assumed that 20% of the injected oxygen through thepost combustion injectors participates in the decarburiza-tion and oxidation reactions occurring in the melt and slag.When the contribution of the post combustion injector oxy-gen is decreased, the amount of FeO is also decreased re-sulting a decrease of the FeO in the slag.ISIJ International, Vol. 48 (2008), No. 912022008 ISIJTable 2.Calculated FeO and carbon loss for each melting pattern (unit: kg).Fig. 5.Change of FeO content in slag with changing carbonFeO reaction rate constant kred.Fig. 6.Change of FeO content in slag with changing post com-bustion ratio.Table 3.Calculated FeO and carbon loss with various car-bonFeO reaction rate constants with fixed pig ironand scrap melting patterns.4.DiscussionThe model developed depends on a number of inputs in-cluding melting rates and reduction rate constants. The op-timized set of parameters, which closely match the opera-tional results are given in Table 4. The pig iron melting pat-tern is an important factor, while scrap melting is less im-portant. Parameters in this table were obtained from abovediscussion, where one parameter was optimized with fixedother parameters. The complete optimization of parametersneeds many heat data together with the proper optimizationtool such as a sequential quadratic programming (SQP) al-gorithm. For instance, the SQP optimization is conductedwith the objective function expressed as Eq. (25) to mini-mize the differences between the predicted values by themodel and the operational results.(25)where, (P)iis %Cmetalor (%MeOn)slag(Me?Fe, Ca, Si,Mg, etc.). Superscripts “model” and “data” represent thepredicted value by the model and the operational result, re-spectively. riis the weight for species i resulting in differ-ent priority for the parameter optimization.In general, the model over predicted the carbon contentcompared to the measured by about 0.1 %. The assumeddecarburization rate constant may be larger than extrapo-lated from OSM. It was assumed that the rate decreased dueto the lower oxygen flow rates. The effect of decarburiza-tion rate on the carbon content in the metal is shown in Fig.7. The final carbon content in the melt and the final FeOcontent in the slag decreases from 0.037 to 0.018mass%and from 47.5 to 48.0mass%. The proper decarburizationrate constant for each furnace can be obtained from the op-eration results of many heats.The model can be used to optimize several aspects of theprocess. As will be presented in the next part of this paper,slag foaming can be optimized by controlling the FeO con-tent, slag basicity and CO generation. Also nitrogen re-moval can be improved by changing the operation.The model can be used to optimize yield. Yield can beimproved by reducing the amount of FeO in the slag. Thiscan be done by using carbon injection more effectively.Using more reactive forms of carbon will lower the FeO inthe slag. The FeO content can also be lowered by reducingthe oxygen flow rate at appropriate times during the meltingcycle. Simulated case studies have been conducted, whichindicate potential yield increases by changing these opera-tional parameters. A 5% decrease of the oxygen flow rate(Case 1), 5% increase of the amount of carbon injected(Case 2), or an increase of the carbonFeO reaction rateconstant to 1.5min?1, simulating a more reactive form ofcarbon (Case 3), were applied while other operational pa-rameters were fixed. Table 5 shows the parameters appliedand the summary of calculated results. In this paper, yieldis calculated based on the iron (Fe) input into a furnace notthe total scrap and pig iron. Figure 8 shows the change ofthe carbon content in the metal and the FeO content in theslag with time for each case. The final carbon content in themetal increases by 0.005mass% with the decreased oxygenflow rate (Case 1), while the carbon content does notchange much in other cases. On the other hand, the finalFeO content in the slag and the FeO loss with slag dis-charge decreases greatly, thus improving the yield by 0.12to 0.76%.In this model, the iron loss as dust is neglected. The dustproduced is between 9 and 18kg/t-scrap and containsaround 50mass% of iron oxide.5,7)Therefore, the iron lossis considered to be more than that calculated in the presentmodel, though the difference is small. Therefore, the actualyield would be slightly lower (0.20.5%) than calculated.Yield is one aspect of the operation that should be con-sidered together with the proper physical and chemical slagproperties required for refining of the metal to remove im-|( )( )|PPiiiimodeldata?ISIJ International, Vol. 48 (2008), No. 912032008 ISIJTable 4.The optimized set of parameters and the calculatedresults.Table 5.Case study for yield improvement and the calculated result.Fig. 7.Change of carbon content in metal with changing decar-burization rate constant.purities and for effective slag foaming behavior. These ad-ditional points of consideration will be the subject of a fu-ture paper. The heat balance in the furnace should also beconsidered. For instance, the FeO loss and the yield are im-proved much in Case 1. However, the heat generated fromthe oxidation of iron must be compensated for with addi-tional electrical input or a loss in overall productivity willresult. The model developed in the present work will be uti-lized to optimize these inputs and outputs including theyield and the overall production cost.5.ConclusionsIn the present study, a decarburization and slag formationmodel for the electric arc furnace was developed. Themodel considers the rate phenomena for the decarburizationand the carbonFeO reaction in the slag, mass balance foreach element in the metal, slag and gas phases, as well asthe melting behavior of pig iron, scrap and fluxes. Themodel developed was applied to a two bucket charge opera-tion furnace and the change of melt and slag compositionswas calculated based on the operating conditions and com-pared to the operational results. The model can be used topredict iron yield and carbon loss with the discharged slag.It was determined that the pig iron melting pattern is veryimportant in determining the carbon content in the melt.The change of FeO content in slag is affected by pig ironmelting pattern, as well as the carbonFeO reaction rateconstant and post combustion ratio. The accurate input ofoperating parameters, such as the amount and compositionsof charged raw materials and the initial heel, are required tosimulate the operation. In addition, the optimization ofmelting patterns for pig iron, scrap and fluxes, carbonFeOreaction rate constant and the post combustion ratio shouldbe conducted through the c

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