Comparative study on arc characteristics of hollow and solid electrode electric furnace melting titanium slag
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摘要: 为了深入探究中空电极技术在钛渣电炉冶炼工艺中的优势所在，以25.5 MW钛渣电炉实际电极尺寸为基础，分别建立了中空和实心电极电弧的数学模型，模拟得到中空、实心电极电弧的电磁场、温度场和流场分布特性，研究了电流大小和电弧长度对熔池表面温度分布的影响规律。结果表明，电弧内电流密度、焦耳热值、速度和温度的较大值位于阴极斑点附近，中空电极是内外径中心线下方区域，实心电极是中心轴线附近区域。采用中空电极时，周围的电弧会向中轴线汇聚，该现象有利于提高电弧加热物料的效率。当电流值由34 kA增大到54 kA，两种情形下的熔池表面平均温度分别提升了708 K和109 K。当电弧长度由0.3 m缩短到0.1 m，两种情形下的熔池表面平均温度分别提升了2500 K和46 K。相比于实心电极，中空电极更适合采用大电流和短弧长的运行方式，且合理控制弧长对提高中空电极电弧加热效率的效果更显著。Abstract: In order to further explore the advantages of hollow electrode technology in titanium slag electric furnace smelting process, based on the actual electrode size of 25.5 MW titanium slag electric furnace, the mathematical models of hollow and solid electrode arc were established, and the distribution characteristics of electromagnetic field, temperature field and flow field of hollow and solid electrode arc were simulated. The effects of current magnitude and arc length on the surface temperature distribution of molten pool were studied. The results show that the larger values of current density, joule heating value, velocity, and temperature in the arc are located near the cathode spot. In the situation of hollow electrode, the area is below the centerline of the inner and outer diameters. And in the situation of solid electrode, the area is near the central axis. When using hollow electrode, the surrounding arc will converge towards the central axis, which is beneficial for improving the efficiency of arc heating materials. When the current value increases from 34 kA to 54 kA, the average surface temperature of the molten pool in both cases increases by 708 K and 109 K, respectively. When the arc length was reduced from 0.3 m to 0.1 m, the average surface temperature of the molten pool in both cases increased by 2500 K and 46 K, respectively. Compared to solid electrode, the hollow electrode is more suitable for using the operation mode of high current and short arc length, and the reasonable control of arc length has a more significant effect on improving the heating efficiency of hollow electrode arc.
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图 2 不同电流下中心轴线上各点模拟值与测量值对比
Figure 2. Comparison of simulated and measured values at various points on the central axis under different currents
图 3 不同中心压力下模拟值与测量值对比
Figure 3. Comparison of simulated and measured values under different central pressures
图 4 垂直截面上电磁场分布对比
Figure 4. Comparison of electromagnetic field distribution on vertical cross sections
图 5 水平截面上电磁场分布对比
Figure 5. Comparison of electromagnetic field distribution on horizontal cross section
图 6 垂直截面上流场和温度场分布对比
Figure 6. Comparison of flow field and temperature field distribution on a vertical cross section
图 7 水平截面上流场和温度场分布对比
Figure 7. Comparison of flow field and temperature field distribution on a horizontal cross section
图 9 不同电流下中空电极电弧温度场分布
Figure 9. Temperature field distribution of hollow electrode arc under different currents
图 10 不同电流下实心电极电弧温度场分布
Figure 10. Temperature field distribution of solid electrode arc under different currents
图 11 不同电流下熔池上表面平均温度对比
Figure 11. Comparison of average surface temperature on the molten pool under different currents
图 12 不同电弧长度下中空电极电弧温度场分布
Figure 12. Temperature field distribution of hollow electrode arc under different arc lengths
图 13 不同电弧长度下实心电极电弧温度场分布
Figure 13. Temperature field distribution of solid electrode arc under different arc lengths
图 14 不同电弧长度下熔池上表面平均温度对比
Figure 14. Comparison of average surface temperature of the molten pool under different arc lengths
表 1 中空电极电弧模拟边界条件
Table 1. Boundary conditions of the hollow electrode arc simulation
边界 温度/K 压力/Pa $ \varphi $ $ \vec{A} $ $ {A}{{A}}' $ 1000 101325 $ \dfrac{\partial \varphi }{\partial z}=0 $ $ \dfrac{\partial \vec{A}}{\partial n}=0 $ $ {A}{B}/{{A}}'{{B}}' $ 2000 $ \dfrac{\partial P}{\partial z}=0 $ $ \dfrac{\partial \varphi }{\partial z}=0 $ $ \dfrac{\partial \vec{A}}{\partial n}=0 $ $ {B}{C}/{{B}}'{{C}}' $ 4130 $ \dfrac{\partial P}{\partial z}=0 $ $ \dfrac{\partial \varphi }{\partial z}=-\dfrac{{J}_{\mathrm{h}\mathrm{o}\mathrm{l}\mathrm{l}\mathrm{o}\mathrm{w}}}{\sigma } $ $ \dfrac{\partial \vec{A}}{\partial n}=0 $ $ {C}{D}/{{C}}'{{D}}' $ 2000 $ \dfrac{\partial P}{\partial z}=0 $ $ \dfrac{\partial \varphi }{\partial z}=0 $ $ \dfrac{\partial \vec{A}}{\partial n}=0 $ $ {D}{E}/{{D}}'{{E}}' $ 1000 101325 $ \dfrac{\partial \varphi }{\partial z}=0 $ $ \dfrac{\partial \vec{A}}{\partial n}=0 $ $ {E}{F}/{{E}}'{{F}}' $ 1000 101325 $ \dfrac{\partial \varphi }{\partial x}=\dfrac{\partial \varphi }{\partial y}=0 $ 0 $ {F}{{F}}' $ 1800 $ \dfrac{\partial P}{\partial z}=0 $ 0 $ \dfrac{\partial \vec{A}}{\partial n}=0 $ 
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