【作者】 何志强；

【导师】 田庆华； 朱刘；

【作者基本信息】 中南大学 ， 资源与环境（专业学位）， 2023， 硕士

【摘要】 碲属典型稀散金属,是我国战略性新兴产业发展不可或缺的关键材料,被誉为“现代工业、国防、尖端技术的维生素”。近年来,以5G通讯、半导体器件、热电材料等为代表的高新技术对碲、铟等原材料纯度要求愈加苛刻。针对目前区域熔炼制备高纯碲过程杂质脱除效率低、熔区宽度难以有效调控等问题,基于数值模拟分析方法,研究区域熔炼制备高纯碲过程中杂质元素的分布规律,明确区熔过程中熔区宽度的分布特征,为区域熔炼高效提纯碲提供理论依据和技术支持。论文取得的主要结果如下:（1）开展5N碲原料成分分析,确定了原料中主要杂质含量。5N碲原料中所含杂质种类较多,主要包括Se、Si、S、Cu、P、Zn、Cr、Ag等,其中含量较高的为杂质Se、Cu,在区域熔炼过程中较难脱除的杂质为Si和S。（2）开展了碲区域熔炼过程中杂质元素的理论分布研究。采用Stokes-Einstein方程及分配系数修正模型,计算获得了杂质Se、S、Si、Cu的有效分配系数。采用Spim模型计算了不同区熔次数、熔区移动速率条件下杂质的理论分布。结果表明,在最佳区熔次数9次条件下,碲棒中部杂质Se的含量可由186 ppb降低至106.6 ppb左右,杂质Si、S、Cu均可降低至1.0 ppb以下,碲纯度可达到7N。当区熔次数超过9次后,再次区熔对碲纯度的提升不明显。在无H₂气氛区熔体系中,当熔区移动速率从1.5 mm/min降低至0.25 mm/min时,杂质S、Si、Cu的含量可明显降低,杂质Se的含量降低不明显。（3）开展了区熔过程中熔区温度场的模拟研究,对熔区宽度进行了数值模拟解析。结果表明,区熔过程中的区熔温度场分布主要受加热器温度影响,加热器宽度及环境温度次之,空气流速对温度场影响较弱。在控制主加热器温度700-710℃、辅加热器温度630-650℃条件下,能形成理论熔区宽度50-70 mm。通过将实验中实际的熔区宽度与模拟的熔区宽度对比,验证实验结果与模型预测值较吻合。（4）系统研究了区域熔炼法提纯碲的工艺过程。在区熔次数9次、熔区移动速率0.5 mm/min、H₂流量0.5 L/min的最佳条件下,碲棒中部杂质Se、Si、S、Cu均可降低至15 ppb以下,脱除率可达到96.83%,碲棒首端的纯度可达到8N,中部纯度可达到7N8,满足7N碲标准。在还原气氛的区熔体系中,增加区熔次数能提高碲中杂质的脱除率,提升效果为Cu>Se>S>Si;降低熔区移动速率对碲中杂质脱除率的提升效果为Se>S>Si>Cu,且在区熔提纯碲的过程中,提高H₂流量可明显提升杂质Se的脱除率。（5）对比分析了杂质的实际分布与理论分布。结果表明,杂质S的实验值与理论值分布较一致,但杂质Se、Si、Cu的实验值与理论值仍存在差异。在实验过程中通入H₂,强化了杂质Se的脱除过程,且杂质Se属挥发性杂质,脱除过程同时受到挥发、H₂气氛和熔区移动的影响,使得杂质Se实验值均低于理论值。杂质Si、Cu的实验值均高于理论值,采用有效分配系数对杂质分布进行预测仍存在较大误差,杂质分配系数需进一步修正。本文共有图49幅,表17个,参考文献124篇更多还原

【Abstract】 Tellurium is a typical rare metal and a key material indispensable for the development of strategic emerging industries in China,and is known as"the vitamin of modern industry,national defense and cutting-edge technology".In recent years,the purity of tellurium and indium has become more and more demanding for high technology such as 5G communication,semiconductor devices and thermoelectric materials.To address the problems of low impurity removal efficiency and difficult to effectively regulate the melt zone width in the process of preparing high-purity tellurium by zone refining,we study the distribution law of impurity elements in the process of preparing high-purity tellurium by regional melting based on numerical simulation analysis,and clarify the distribution characteristics of melt zone width in the process of zone refining,so as to provide theoretical basis and technical support for efficient purification of tellurium by zone refining.The main results obtained in the thesis are as follows:（1）The analysis of 5N tellurium raw material composition was carried out to determine the content of main impurities in the raw material.5N tellurium contains many kinds of impurities,mainly including Se,Si,S,Cu,P,Zn,Cr,Ag,etc.The impurities with high content are Se and Cu,and the impurities that are difficult to be removed in the zone melting process are Si and S.Therefore,the impurities Se,S,Si and Cu were taken as the object of study to investigate their distribution pattern in the zone melting process.（2）A study on the theoretical distribution of impurity elements in the tellurium zone refining process was carried out.The effective distribution coefficients of impurities Se,S,Si and Cu were obtained by using Stokes-Einstein equation and distribution coefficient correction model.The Spim model was used to calculate the theoretical distribution of impurities under the conditions of different pass of zone refining and melt zone movement rate.The results show that under the condition of optimal pass of zone refining 9 times,the content of impurity Se in the middle of tellurium rod can be reduced from 186 ppb to about 106.6 ppb,and impurities Si,S and Cu can be reduced to less than 1.0 ppb,and the purity of tellurium can reach 7 N.When the pass of zone refining exceeds 9 passes,the improvement of tellurium purity by re-zone refining is not obvious.In the zone refining system without H₂ atmosphere,the content of impurities S,Si and Cu can be significantly reduced when the melt zone movement rate is reduced from 1.5 mm/min to 0.25 mm/min,and the content of impurities Se is not significantly reduced.（3）A simulation study of the melt zone temperature field in the zone refining process was carried out,and the width of the melt zone was analyzed by numerical simulation.The results show that the distribution of the zone melt temperature field in the zone refining process is mainly influenced by the heater temperature,followed by the heater width and ambient temperature,and the air flow rate has a weak influence on the temperature field.The theoretical melt zone width of 50-70 mm was achieved by controlling the main heater temperature of 700-710°C and the auxiliary heater temperature of 630-650°C.By comparing the actual melt zone width with the simulated melt zone width,the experimental results were verified to be in good agreement with the predicted values of the model.（4）The process of tellurium purification by zone refining was systematically studied.Under the optimal conditions of 9 passes of zone refining,0.5 mm/min of melt zone movement rate and 0.5 L/min of H₂ flow rate,the impurities Se,Si,S and Cu in the middle of the tellurium rod can be reduced to below 15 ppb,and the removal rate can reach 96.83%.The purity of the first end of the tellurium rod can reach 8N,and the purity of the middle can reach 7N8,meeting the standard of 7N tellurium.In the zone refining system with reducing atmosphere,increasing the pass of zone melting can improve the removal rate of major impurities in tellurium,and the improvement effect is Cu>Se>S>Si>Si;decreasing the moving rate of refining zone can improve the removal rate of major impurities in tellurium,and the improvement effect is Se>S>Si>Cu,and in the process of purifying tellurium by zone refining,increasing the H₂ flow rate can obviously improve the removal rate of impurity Se.（5）The actual distribution of impurities was compared and analyzed with the theoretical distribution.The results showed that the distribution of impurity S was consistent with the theoretical values,but the experimental values of impurities Se,Si and Cu were still different from the theoretical values.The experimental values of impurity Se were lower than the theoretical values because the process of impurity Se removal was strengthened by the introduction of H₂ during the experiment,and the impurity Se was a volatile impurity,and the removal process was affected by volatilization,H₂ atmosphere and the movement of the refining zone at the same time.The experimental values of impurities Si and Cu are higher than the theoretical values,and there is still a large error in the prediction of impurity distribution using the effective distribution coefficient,and the impurity distribution coefficient needs to be further revised.更多还原