Research and modeling on thermal conductivity of high temperature heat storage material based on vanadium tailings
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摘要: 利用提钒尾渣为主要原料,高硅粘土为辅料,石墨材料为改性剂,通过碳热还原-粉末冶金方法进行了高温显热蓄热材料的制备研究,分析石墨含量对显热蓄热材料的物相演变、比热容变化及导热变化规律。XRD物相分析表明,材料的主要物相包括石英、含高硅组分的钠长石、钛铁矿以及碳酸盐等物相,随着石墨含量的增加,石英相比率随之减少。比热容测试结果表明,比热容随石墨含量的增加先增大后减小,当石墨含量为3%时,比热容最高,在 500~700 ℃下的比热容值为820~3 180 J/(kg·K)。导热系数测试结果表明,当石墨含量小于5%时,蓄热材料导热系数变化不大,基本保持在0.75 W/(m·K)左右;当石墨含量大于5%时,导热系数呈现明显的上升趋势。为了进一步探索石墨对蓄热材料导热性能的影响,进行了模拟计算,利用非线性修正项代替分散体体积分数项,修正后的Maxwell模型可很好地预测试验结果。Abstract: Using vanadium tailings as the base material, high silicon containing clay as auxiliary material and graphite material as modifier, the preparation of the high temperature sensible heat storage materials was carried out by means of carbon thermal reduction followed by powder metallurgy. The effects of graphite content on phase evolution, specific heat capacity and heat conduction of sensible heat storage material were studied. XRD phase analysis result shows that the main phases of the material include quartz, albite, ilmenite and carbonate. With the increase of graphite content, the ratio of quartz decreases. The specific heat capacity test results show that the specific heat capacity firstly increases and then decreases with the increase of graphite content. When the graphite content is 3%, the specific heat capacity is the highest, and the specific heat capacity at 500~700 ℃ is 820~3 180 J/(kg·K). The thermal conductivity test results show that when the graphite content is less than 5%, the thermal conductivity of the heat storage material changes slightly, basically remains at about 0.75 W/(m·K); when the graphite content is more than 5%, the thermal conductivity presents an upward trend. In order to further explore the effect of graphite on thermal conductivity of heat storage materials, the modeling calculation is carried out, and by replacing the volume fraction term of dispersion with the nonlinear correction term, the modified Maxwell model could well predict the experimental data.
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表 1 提钒尾渣化学成分
Table 1. Chemical components of vanadium tailings
% Na2O Fe2O3 SiO2 TiO2 MnO Al2O3 MgO CaO V2O5 Cr2O3 其他 9.6 40.1 17.0 11.0 6.5 5.4 3.1 2.4 1.6 1.1 2.2 表 2 提铁尾渣化学成分
Table 2. Chemical components of iron tailings
% Fe2O3 SiO2 TiO2 MgO Al2O3 CaO Cr2O3 MnO 2.22 15.94 16.94 2.98 3.9 4.0 1.5 11.23 表 3 粘土的化学成分
Table 3. Chemical components of clay
% Fe SiO2 TiO2 MgO Al2O3 CaO Mn 2.65 32.16 0.12 4.61 9.6 0.38 0.17 表 4 制备钒钛蓄热材料的材料配比
Table 4. Material proportioning in the preparation of vanadium-titanium heat storage material
试验号 提铁尾渣/g 粘土/g 石墨/g 石墨含量/% S1 3 3 0 0 S2 2.91 2.91 0.18 3 S3 2.85 2.85 0.3 5 S4 2.79 2.79 0.42 7 S5 2.7 2.7 0.6 10 S6 2.55 2.55 0.9 15 表 5 修正Maxwell模型中的A和B值
Table 5. A and B values in modified Maxwell model
类别 A B 前期研究系列[13]:尾渣+石墨基蓄热材料 −0.044 95 4.139 32 本研究系列:尾渣+粘土+石墨基蓄热材料 0.130 188 −2.642 8 -
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