冶金法制备太阳能硅过程的湿法提纯研究

湿法提纯作为冶金法路线制备太阳能级硅的前处理工序,可以去除大部分金属杂质,提高最终产品收率。考察了硅粉粒径、浸出剂浓度、温度、时间、搅拌等因素的影响,采用ICP、SEM等对产品进行了表征。当工艺条件为:硅粉平均粒径44μm、w(HCl)=5%、温度80℃、时间6h,处理后产品中杂质w(Fe)=2.4×10-5,去除率为99.2%,杂质w(Al)=6.4×10-5,去除率为80%。描述了酸浸过程在前后不同阶段分别为受反应速度和内扩散控制历程。为太阳能级硅制备工业化开发,大幅度降低成本提供了参考。     

湿法提纯制备太阳能级硅过程的研究

采用盐酸和氢氟酸两步法湿法提纯制备太阳能级多晶硅,当工艺条件为w(HCl)=8%,w(HF)=6%,可使铁中杂质质量分数降到26×10-6,去除率达到99.1%;铝中杂质质量分数降低到60×10-6,去除率为82.3%。分析和讨论了酸浸过程中硅晶体的形貌和结构的变化。FESEM图像表明杂质在硅的表面呈现集中链状分布,晶粒沿着高应力和缺陷区直线式分裂;XRD数据显示,在反应过程中,杂质的析出对硅晶格结构的影响有限,晶格因温度增加、应力不平衡等因素反而呈现膨胀的趋势。研究和分析湿法冶金中硅晶体结构和形貌的变化,对于了解酸浸过程反应机理,提高湿法提纯的除杂效率,优化太阳能级硅生产工艺具有重要意义。     

湿法冶金去除太阳能级硅中硼的研究

湿法提纯作为冶金法制备太阳能级硅的前处理工序,可以去除大部分金属和硼杂质。研究了以氢氟酸-硫酸混合酸为浸出剂,有机溶剂甲醇作为后处理剂,去除硅粉中硼杂质的方法。采用电感耦合等离子体发射光谱仪（ICP）等对产品进行表征。酸浸过程优化工艺条件：硫酸质量分数为55%,氢氟酸质量分数为7%,酸浸温度为70 ℃、酸浸时间为4 h、液固质量比为8∶1。酸浸后可使硅粉中的硼杂质质量分数由6.893×10^-6降至3.867×10^-6,去除率为41.9%。在酸浸基础上采用有机溶剂甲醇作为后处理剂,杂质硼质量分数降至3.84×10^-6,去除率为44.29%。从硼酸浸后形成的产物入手探索提高硼去除率的方法,实验验证了该方法的可行性,为研究湿法冶金预处理太阳能级硅提供了新的参考。     

太阳能硅制备过程湿法提纯SiO2的工艺优化

考察了HF质量分数、H2C2O4质量分数、HNO3质量分数、酸浸时间、粒径、液体质量与固体质量的比值(简称液固比,下同)等因素对混酸法提纯SiO2工艺过程的影响,利用电感耦合等离子体发射光谱仪(ICP-OES)、场发射扫描电子显微镜(SEM)进行表征。结果表明,最佳工艺条件为:w(HF)=2%、w(H2C2O4)=3%、w(HNO3)=30%、酸浸时间4 h、粒径100～120目、液固比4∶1、酸浸温度30℃。Fe、Al、Ca、P杂质的去除率分别达到99.99%、14.02%、73.27%、60.00%,经混酸法处理后SiO2中杂质总量的质量分数降至1.465×10-4。     

湿法提纯冶金硅中的废酸回收

介绍湿法提纯冶金级硅废酸回收的方法,经实验和生产表明该方法能有效回收废酸,控制网收酸中的颗粒杂质和离子浓度在一个合理的范尉,并能利用于下一次湿法提纯中。     

高硼硅玻璃太阳能管环切显微结构分析

介绍了玻璃环切显微结构分析的方法,并对高硼硅玻璃太阳能管的显微结构进行了定性分析,总结了同检测高硼硅玻璃内热应力、结构应力和条纹的方法,以便评价玻璃质量,改进产品质量。     

湿法生产碳酸锶过程中除钙工艺的研究

湿法加工天青石制备碳酸锶时，采用新的硫酸－助剂－硫铵除钙工艺，既达到了传统工艺的除钙效果，又回收了天青石中的碳酸锶，不仅降低了产品成本，而且所得碳酸锶产品质量还优于彩管坡壳质量标准。     

中国3.3高硼硅玻璃管发展历程

近20年来中国的太阳能利用量始终保持世界第一。介绍我国膨胀系数3.3的硼硅玻璃发展过程,全玻璃真空太阳能集热管的产能变化和技术革新情况,同时总结了太阳能热利用过程中的经验和教训。     

卤水除硼工艺研究

根据硼酸的物性特征,采用酸化—冷冻—溶液固硼工艺提取卤水中的硼,并对各影响因素进行考察,在最优工艺条件下,卤水中硼的去除率可达到96.59％,除硼后卤水中硼酸浓度为0.045％,折合B2O30.025％,即250×10^-6,氢氧化镁产品中B2O3含量达到0.15％.     

湿法冶金过程除铁净化技术的应用研究进展

主要综述了湿法冶金过程除铁净化技术应用研究进展,并对主要的除铁技术进行了优缺点分析。目前冶金过程除铁工艺技术各有利弊,但是树脂法和萃取法由于其独特性,因此具有广阔的应用前景。     

Boron removal from silicon by slag refining using Na2O-SiO2 in industrial applications

Boron (B) removal by slag refining using Na₂O-SiO₂ was investigated in industrial applications. The experimental results showed that the reasonable ratio range of slag to silicon is about 0.7–0.8; the suitable holding time is about 30 min; the concentration of B is reduced from 1.90 ppmw to 0.17 ppmw by three times slag re?ning; and the removal efficiency of B reaches 91.1%. Moreover, it is discussed that B in silicon is more inclined to be oxidized by Na₂O than SiO₂ according to thermodynamic analysis and then volatilized to the atmosphere in the form of Na₂B₂O₄ according to kinetic analysis.     

氢氧化镁中微量元素硼硅铝的测定

以盐湖高镁卤水为原料生产的氢氧化镁产品纯度不高,含有部分无机杂质离子,为提高产品质量,改进产品性能,通过实验确定了氢氧化镁中微量元素硼、硅、铝的分光光度测定方法。此方法准确度与精密度较高,测定样品中的硼、硅、铝加标回收率分别为98.3%-101.5%,96.0%-99.3%,96.5%-97.3%,相对标准偏差（n=6）分别为2.06%,2.27%,2.39%,快速、简便、成本低,可作为企业生产的常规检测方法使用。     

Enhanced boron removal from metallurgical grade silicon by the slag refining method with the addition of tin

An effective boron removal method was developed through a process of combining Si–Sn alloy with slag treatment. Boron content in refined silicon and boron removal fraction by slag containing 5 wt% CaO, 25 wt% SiO₂ and 70 wt% Na₂SiO₃ and was investigated under varied Si–Sn alloy composition, slag/Si–Sn alloy mass ratio and refining time. Boron was effectively removed by adding tin to metallurgical grade silicon. In particular, the boron content in metallurgical grade silicon decreased from 12.92 ppmw to 0.79 ppmw by adding 50 at% tin under a mass ratio of 2:1 (slag:alloy) at 1723 K. The amount of boron removed increased with increasing amount of tin added, mass ratio and refining time.     

The effect of the third invariant on the strength and failure of boron carbide and silicon carbide

This article presents new test data to assess the effect the third invariant has on the strength and failure of two ceramic materials: boron carbide and silicon carbide. Two experimental techniques are used: the Brazilian test that produces a biaxial state of stress, and a new technique that uses a high-pressure confinement vessel to load a specially designed dumbbell specimen in triaxial extension. The dumbbell geometry provides two important advantages over the typically used cylindrical specimen: no adhesive is required to bond the specimen to the load cell because the dumbbell geometry naturally takes the specimen into tension, and any loading asymmetries are essentially eliminated due to the axisymmetric geometry. The results show that when the stress state is on the tensile meridian the equivalent stress at failure is constant, independent of the hydrostatic pressure. The average equivalent stress at failure is for boron carbide and for silicon carbide. The Brazilian test was only performed on boron carbide and failed at , much higher than when on the tensile meridian () indicating that the effect of the third invariant is significant (because of the difference in the failure strength) and must be accounted for to accurately predict when failure will occur.     

Electrical,thermal, and mechanical properties of porous silicon carbide ceramics with a boron carbide additive

The effects of the boron carbide (B₄C) content and sintering atmosphere on the electrical, thermal, and mechanical properties of porous silicon carbide (SiC) ceramics were investigated in the porosity range of 58.3%–70.3%. The electrical resistivities of the nitrogen-sintered porous SiC ceramics (∼10^–1 Ω·cm) were two orders of magnitude lower than those of argon-sintered porous SiC ceramics (∼10¹ Ω·cm). Both the thermal conductivities (3.3–19.8 W·m^–1·K^–1) and flexural strengths (8.1–32.9 MPa) of the argon- and nitrogen-sintered porous SiC ceramics increased as the B₄C content increased, owing to the decreased porosity and increased necking area between SiC grains. The electrical resistivity of the porous SiC ceramics was primarily controlled by the sintering atmosphere owing to the N-doping from the nitrogen atmosphere, and secondarily by the B₄C content, owing to the B-doping from the B₄C. In contrast, the thermal conductivity and flexural strength were dependent on both the porosity and necking area, as influenced by both the sintering atmosphere and B₄C content. These results suggest that it is possible to decouple the electrical resistivity from the thermal conductivity by judicious selection of the B₄C content and sintering atmosphere.     

Optimization of the process parameters for the removal of boron from drinking water by electrocoagulation—a clean technology

BACKGROUND: There are a number of articles related to removal of boron by electrocoagulation using aluminium electrodes, but there are fewer articles describing the use of magnesium as the anode material. The main disadvantage of aluminium electrodes is the residual aluminium present in the treated water due to cathodic dissolution, which can create health problems. In the case of magnesium electrodes, there is no such disadvantage. This paper presents the results of studies on the removal of boron using magnesium and stainless steel as anode and cathode, respectively. RESULTS: Results show that a maximum removal efficiency of 86.32% was achieved at a current density of 0.2 A dm^?2 and pH of 7 using magnesium as the anode and stainless steel as the cathode. The adsorption of boron fitted the Langmuir adsorption isotherm, suggesting monolayer coverage of adsorbed molecules. The adsorption process follows second‐order kinetics. Temperature studies showed that adsorption was endothermic and spontaneous in nature. CONCLUSIONS: The magnesium hydroxide generated in the cell remove the boron present in the water and reduced to a permissible level and making it drinkable. The process scale up results was consistent with the results obtained from the laboratory scale, showing the robustness of the process. Copyright © 2010 Society of Chemical Industry