Acoustic characteristics of electric arc furnaces

A mathematical model is constructed to describe the appearance and development of the noise characteristics of superpower electric arc furnaces. The noise formation is shown to be related to the pulsation of the axial plasma flows in arc discharges because of the electrodynamic pressure oscillations caused by the interaction of the self-magnetic field with the current passing in an arc. The pressure in the arc axis changes at a frequency of 100 Hz at the maximum operating pressure of 66 kPa for an arc current of 80 kA. The main ac arc sound frequencies are multiples of 100 Hz, which is supported in the practice of operation of electric arc furnaces. The sound intensity in the furnace laboratory reaches 160 dB and is decreased to 115–120 dB in the working furnace area due to shielding by the furnace jacket, the molten metal, and the molten slag. The appropriateness of increasing the hermetic sealing of electric furnaces and creating furnaces operating at low currents and high transformer voltages is corroborated.     

Heat losses and energy efficiency of arc steel-melting furnaces

The dependences of the heat loss power and the energy efficiency of arc steel-melting furnaces with a refractory lining on the arc current and length are analyzed. The influence of varying the heat loss power on the operating characteristics of an arc furnace is considered.     

Determination of the allowable graphite amount of a composite electrode for an electric arc furnace

Distribution of heat loads along the length and perimeter of electrodes in terms of the nominal power of transformer, optical characteristics of surfaces taking part in heat exchange and geometric dimensions of the furnace and electrodes has been obtained on the basis of mathematical simulation of processes of heat transfer in working volume of an electric arc furnace, the screening of radiation by electrodes being taken into account. The results obtained give an opportunity of determining the minimal permissible length of the composite electrode graphite part for furnaces with various nominal power transformers. The minimal permissible length of electrode-consumed graphite part is in the range of 80–100 cm for an 100-t electric arc furnace with the transformer of nominal power equal to 75 or 90 MVA. Decrease of the length of electrode graphite part will lead to damage of cooled metal part due to water burn-out.     

AC arc characteristics

The dynamic and static current-voltage characteristics of the arcs in steel-melting furnaces are considered. The influence of the operation conditions of furnaces (arc current and length) on the currentvoltage characteristics is studied. An attempt of generalizing the controlling characteristics of furnaces with various capacities is made.     

矿热炉变压器、短网和电极的选用与效果

介绍了矿热炉的变压器、短网、电极三个关键设备的选用,以及阐述合理选用后,产品质量、产量、功率因数、单耗等指标都有明显的改善和提高,取得较好的经济效益。     

直流埋弧炉的运行优势

目前已有的交流埋弧炉，由于载流导体存在着电感、集肤效应、干扰效应等诸多问题，造成功率因数非常低。若要向超大型化发展，受到了限制；若采用直流电源，这些问题便迎刃而解。本文论述了直流埋弧炉的运行优势及发展趋向。     

Electrical Conditions of Foundry Operation of DC and AC Arc Furnaces

The electrical conditions of operation of ac and dc 0.5- to 25-t furnaces, namely, the installed, active and net powers, the maximum electric arc voltage, the electric arc operating current, and the electrical efficiency, are considered and compared. The parameters of a dc twin furnace, where one power supply is used for two furnaces and the periods of melting and finishing of a liquid metal in these furnaces are separated in time, are analyzed.     

铸钢用50 t/32 MVA交流电弧炉炼钢过程电气运行特性

使用电气监测仪表对中信重工机械股份有限公司50t/32 MVA交流电弧炉炼钢过程中的电气参数进行了实测,得到52 310个有效数据。结果表明,有载条件下电抗器上端的功率因数均为0.800以上,供电回路中的电压、电流以及功率因数均处于三相平衡状态。以二次侧工作电流为自变量,建立非线性电抗模型,绘制电气运行特性曲线,确定现用各挡电压下的工作电流许用范围。研究表明,若将电抗器挡位由原来的3挡改设为4挡运行,则炉用变压器容量利用率将提高7.30%,功率因数将由原来的0.812提高为0.841。     

直流（DC）电弧炉技术的发展动态

大电流可控硅整流电源的发展和炉底电极这一难题的解决促使直流（ＤＣ）电弧炉的迅速发展，近几年大部分新建电弧炉为ＤＣ炉并将一些已有的交流（ＡＣ）电弧炉改成ＤＣ电弧冶炼。     

Symmetry of Arc Furnace Operation

The electrical asymmetry in the operation of arc furnace with an asymmetric triangular configuration of the electrodes is noted. Experimental data from the DSP-100 furnace permit analysis of how the electrical parameters affect the arc characteristics. Nonuniform power distribution over the phases of the electrofurnace decreases the component of the useful power consumed in heating the metal and slag. The power consumption by the furnace may potentially be reduced by 7.4% and the electrode consumption by 9%. The results confirm the need for research on phase-by-phase regulation of the power of ac arc furnaces.     

More efficient operation of arc furnaces with continuous scrap charging

The basic concepts of the Consteel process are analyzed. In that process, scrap is continuously charged in the liquid bath on a conveyer. The scrap is heated to 150?C250°C on the conveyer by the gases leaving the furnace. While continuous charging has clear benefits, the low efficiency of scrap heating means that Consteel furnaces cannot match the productivity and energy efficiency of modern arc furnaces. The melting rate of the scrap is 1.4 times greater in (100?C350)-t arc furnaces than in comparable Consteel furnaces, while the power consumption is 40 kW-h/t less. Unidirectional heating of the scrap on the Consteel conveyer by powerful gas-oxygen burners to a mean mass temperature of 800°C is proposed. The new 120-t TDSP fuel-arc smelting furnace, with equal power of the arc and the burners, reduces power consumption to 200 kW-h/t and reduces the smelting time to 32 min.     

Analysis of the state of structure and the basic parameters and indices of the operation of the large EAFs operating in the metallurgical plants in Russia

16 mln t steel were melted in 24 large electric arc furnaces (EAFs) in the metallurgical plants in Russia furnaces in 2011 at an annual capacity of 22 mln t of these furnaces. Among them, 17 EAFs are equipped with eccentric bottom tapping and operate with a “bog.” Three EAFs use the heat of effluent gases for heating of a charged scrap: a shaft heater at the Cherepovets metallurgical works (CherMK) and conveyer heating in the Ashinsk metallurgical plant. The DSP-120 furnace in CherMK has the best indices in Russia for operation with cast iron: electric power consumption of 260 kWh/t and a heat time of 49 min. Nine EAFs operating in metallurgical works use 20–30% liquid iron in a charge, which decreases the electric power consumption by 80–100 kWh/t. The working space and the EAF dimensions are important. A groundless decrease in the electrode failure diameter (1200 mm or smaller) leads to problems in the EAF transformer operation at a transformer power higher than 100 MVA and a secondary voltage higher than 1000 V. The performance of EAFs and the reliability of equipment operation depend on the working space height, the electric holder stroke, the distance between the axes of chair segments, the distance from the furnace axis to the axis of electric holder supports, and so on. Engineers in OOO NTP Akont determined the optimum sizes and relations between them for 120- to 130-t EAFs.     

40 t电弧炉高效化生产实践

兴澄特钢3座40 t电弧炉(变压器容量每座15MVA)经过氧枪等改造和添加铁水等工艺措施优化后,使每炉冶炼时间由3 h降至60～70 min,电耗降至160 kWh/t,氧耗为50 m³/t,电极消耗2.0 kg/t,3座电弧炉年产能力达85万t。操作实践表明,每炉20～25 t的铁水加入量可使40 t电弧炉得到最佳的经济指标。     

粗银粉冶炼主要负载谐波治理实践

贵冶一车间主要从事从阳极泥中提纯金、银、铂钯等贵金属产品,其中提取的粗银粉需冶炼成银阳极板进行电解精炼进而浇铸出可出售的银锭,利用两台中频炉对粗银粉进行熔炼,两台设备是车间3#变压器主要负载,由于中频炉工作原理和负载特性,在运行中系统谐波大,电流畸变率很高。通过前期电能质量检测和分析,投入一台300A的APF对对应的3#变低压配电系统进行电能质量综合治理,取得了良好效果。     

Electrical optimization of superpowerful arc furnaces

Requirements on the systems controlling the electrical conditions of superpowerful arc furnaces in steel smelting are outlined. The basic principles for electrical optimization at different phases of smelting are considered. An improved mathematical model is proposed for analysis of the arc furnace’s electrical characteristics and the dynamics of the automatic control system governing electrode motion. A diagnostic system capable of identifying the phase of smelting on the basis of the harmonics of the arc currents shortens the furnace’s working cycle and reduces the power consumption.     

中小型三相交流硅锰炉电气特性不平衡分析

中小型三相交流矿热炉存在严重的电气参数不平衡问题,导致冶炼过程炉况不稳、功率因数低、电耗高,难以实现冶炼过程三相熔池功率和温度场的平衡控制.以容量为12.5 MVA的三相交流硅锰炉为对象,在对其关键电气参数进行检测与计算的基础上,分析了三相短网不平衡、现有人工操作机制以及炉内变化所致不平衡对三相交流矿热炉电气特性的影响...     

超高功率电弧炉变压器容量及技术参数的确定

除电弧炉容量外 ,原料、辅助能源、冶炼品种、冶炼工艺和生产流程等生产状况均影响电弧炉变压器额定容量的确定。经分析得出以废钢为原料的超高功率电弧炉变压器额定容量P_n/kVA与吨钢电耗W、变压器功率利用率C₂ 、总通电时间t_on、出钢量G之间的关系式为 :P_n=(W·G·60 )/(t_on·cosφ·C₂ ) ,同时给出了二次电压的确定方法。结合高阻抗技术 ,给出超高功率高阻抗电弧炉电抗容量与变压器技术参数的确定方法以及确定石墨电极二次导体截面积的思路     

现代超高功率电弧炉的技术特征

综述了现代超高功率电弧炉的技术特征和效果。指出目前超高功率电弧炉技术的发展主要体现在高变压器利用率、工艺和流程优化、改善环境等方面。     

对两种不同调压变压器的特点分析

分析了仿日三线圈补偿调压电炉变压器的构造原理、特点,并就引进俄罗斯双线圈电抗辅助调压变压器,分析其特点和相关点及运行情况。     

二次短网特性参数分析与计算及智能电极调节器参数计算

对于LF或EAF而言,二次短网特性参数(短路阻抗和短路感抗)具有至关重要的作用,它决定着冶炼时用电效率的高低、也决定着为获得最大有功功率和最大电弧功率所需的电流设定点。二次短网特性参数、变压器铭牌参数及冶炼时的操作设定决定了冶炼过程的用电效率和升温速度。本文简要分析二次短网特性参数对于冶炼特性的影响以及如何进行二次短网特性参数的计算,同时介绍由北京金自天正智能控制股份有限公司开发的智能电极调节器。