太阳能级回收硅料清洗效果研究

通过对光伏领域回收硅料表面处理一般方法的研究,使用ICP-MS对比分析了光伏产业使用不同类型硅料经混酸腐蚀处理前后,表面金属杂质种类、含量及清洗效果的变化,并使用SEM对硅料清洗前后的形貌进行了微观分析。结果表明HF/HNO3混酸体系对于过渡族金属杂质Cu、Zn、Mn去除效果较好,对于Ti、Cr金属杂质特别是Fe的去除效果较差;硅料表面微观结构越光滑,杂质去除效果越好。

采用HF酸浸蚀沉降的方法从单晶硅切割废浆料中回收硅粉

采用HF酸浸蚀沉降的方法回收单晶硅切割废浆料中的硅粉。系统地研究了在回收硅粉过程中,HF酸的浓度,HF酸处理的时间,以及在HF酸浸蚀沉降处理前的超声震荡时间等实验条件对回收率和纯度等性能的影响因素。研究表明,在HF酸浓度为2%,HF酸处理时间24h,超声震荡时间60min的条件下,回收得到的粉体中硅的纯度可以达到82%(质量分数),且回收率可以达到62%的水平。通过此方法可以实现从切割废浆料中回收硅粉。

金刚线切割硅片废料制备高模数硅酸钾的研究

近年来,我国光伏能源飞速发展,对晶体硅片的需求量逐年大幅增加。但在生产太阳能硅片过程中,会产生大量的切割废料,有效地回收利用该废料已成为亟待解决的问题。本研究以金刚线切割硅片废料为原料,考察不同反应条件对制备4.8模数硅酸钾的影响。试验确定最佳的反应条件为:采用分批缓慢将前处理后的回收硅粉加入到预热好的碱液中反应的加料方式,控制反应温度为50~60℃,反应时间为4~5 h。区别于传统的硅酸钾生产方法,本方法在常压下,即可生产出模数高达4.8、稳定性良好的无色透明硅酸钾,为金刚线切割硅片废料的回收利用,提供了一个新的处理方法。

用动态膜技术回收半导体加工中的含硅废水

应用动态膜技术回收半导体厂晶片切割废水,研究了动态膜的形成条件及其水处理效果.通过恒压过滤形成动态膜：恒压过滤压差5 kPa,曝气强度10 L/min,过滤高浓度（TS=1 800 mg/L）含硅废水,形成了均匀而阻力较小的动态膜;之后在一定的过滤运行条件下,研究膜过滤低浓度晶片切割废水的运行周期和水处理效果：要处理的废水TS（总固形物）=40mg/L,恒速过滤滤速为0.6 m/d,曝气量为15 L/min.结果表明：该动态膜可保护基膜不被污染,维持较长的过滤周期,稳定运行时间达260-360 h.膜过滤单元中的TS（总固形物）可被浓缩达到1 200 mg/L.动态膜对原水浊度、TS的去除效果很好,产水水质稳定,浊度为0.14NTU,TS几乎为0,SDI15为0.5,电导率为12μS/cm,满足反渗透深度处理的进水要求.当压力上升至14 kPa时,排出浓缩液、用产水冲刷清洗基膜表面的滤饼层,以回收高纯硅,同时基膜经过擦洗后通量可以完全恢复.

浅谈工业硅厂电炉烟尘治理及微硅粉回收工程设计

本文结合工程设计实例,从设计主要内容,主要设备,技术经济指标等方面论述了工业硅电炉烟尘治理及微硅粉回收。

工业硅生产过程的配碳率与硅回收率关系的理论分析

根据工业硅炉熔池的结构,确立了高硅合金生产中的内、外反应区,简化并确定了工业硅生产过程的化学反应及传质与内、外反应区的特征,分析了在原料理想条件下的理论配碳率与硅回收率的对应关系。

基于大气等离子体烧结技术的硅晶圆加工废料回收工艺研究

目前的硅晶圆加工过程中通常会对直拉法制成的单晶硅棒进行线切割操作,从而得到单晶硅圆薄片,但该过程会造成较大的单晶硅材料浪费.因此,寻求各种方法回收晶体硅切割废料成为一个重要课题.本文根据加工样本与加工仪器的特性,探究了利用放电等离子体烧结技术加工回收单晶硅粉末技术的可能性,并基于这些成果调节工艺参数进行了烧结实验.通过表征观察烧结成品的表面形貌与元素组成后,可观察到其含有氧化膜与其他杂质,且该成品具有在经过优化实验步骤与进一步处理后可回收的潜力.

氟化钠提纯工艺研究

经过处理后的氟化钠原料中含有较多的硅酸钠杂质。为了去除其中的杂质,提高氟化钠的纯度,获得更高的工业价值。利用溶出硅胶与蒸发结晶操作过程相结合,设计了溶出硅胶-蒸发结晶提纯氟化钠工艺,提高了氟化钠的纯度,降低了硅的含量,并且改善了氟化钠产品的外观。在溶出硅胶实验中,考察了硫酸用量比、温度、时间、搅拌速率对脱硅过程的影响,并进行了正交试验。结果表明,在溶出硅胶实验中,综合效果最好的脱硅条件为硫酸的用量比(硫酸与氟化钠原料的质量比)为0.04、反应温度为25℃、反应时间为30 min、搅拌速率为300 r/min。在蒸发结晶实验中,当蒸发时间为60 min时,蒸发结晶提纯氟化钠的综合效果最好。在最佳的实验条件下,能得到纯度>98%,二氧化硅质量分数<0.5%的氟化钠产品。研究表明,硫酸与硅酸钠反应能溶出硅胶,再过滤分离能达到除硅的效果,而通过蒸发结晶,能进一步提高氟化钠的纯度。该研究可为提纯氟化钠、回收氟硅资源提供新思路。

磨矿方式对回收工业硅精炼渣中单质硅的影响

工业硅精炼渣(MGSRS,简称硅渣)中单质硅被渣紧紧包裹,且硅颗粒粒度分布不均,存在很多细小颗粒,在浮选过程中硅渣分离困难,导致单质硅的回收率较低。提出首先需要解决的是单质硅与渣的解离,研究了磨矿方式对硅渣解离的影响,进而研究了磨矿方式对浮选回收硅渣中单质硅的影响。结果表明,硅渣湿磨后进行浮选,单质硅的回收率为17.28%,远高于干磨的2.10%,这主要是由于湿法磨矿得到的硅渣颗粒平均粒度为21.07μm,且较干磨的颗粒均匀。微观形貌结果可见明显解离的单质硅颗粒,硅与渣分离的效果优于干磨。此外,由X射线光电子能谱(XPS)结果可知,湿磨中伴随着硅酸盐的水解过程,进一步提高了硅酸盐的亲水性。傅里叶变换红外光谱(FTIR)分析表明,湿磨后硅表面形成了悬挂的Si-H键,表面更加疏水,利于浮选。

Recovery of high purity silicon from SoG crystalline silicon cutting slurry waste

The composition and size distribution of cutting waste were characterized. The Si-rich powders were obtained from the cutting waste using a physical sedimentation process, and then further purified by removing impurity using acid leaching. The effects of process parameters such as acid leaching time, temperature and the ratio of solid to liquid on the purification efficiency were investigated, and the parameters were optimized. Afterwards, the high-purity Si ingot was obtained by melting the Si-rich powders in vacuum furnace. Finally, the high purity Si with 99.96%Si, 1.1×10^-6 boron （B）, and 4.0×10^-6 phosphorus （P） were obtained. The results indicate that it is feasible to extract high-purity Si, and further produce SoG-Si from the cutting slurry waste.

氯化铵浸出镁还原渣提钙工艺

皮江法炼镁过程产生大量的镁还原渣,堆存过程中易造成土壤碱化和板结等环境问题,在消纳方面主要用于制备水泥、建筑砖和脱硫剂,综合利用价值低。基于此,提出氯化铵浸出镁还原渣工艺路线,该工艺可以提取和分离镁还原渣中的钙、硅等元素,使镁还原渣成为钙源和硅源,实现镁还原渣的零排放和高值化利用。现针对工艺中的浸出过程,研究在各单因素条件下钙的浸出率及浸出渣物相,得出以下结论:氯化铵能对镁还原渣中钙进行选择性浸出,其浸出率与反应温度、氯化铵浓度、液固体积质量比等密切相关;浸出率随氯化铵浓度、液固体积质量比的增大而增大,随温度的升高先增加后减小;较佳浸出工艺条件为反应温度25℃、氯化铵浓度15%、液固体积质量比40∶1,该条件下,钙的浸出率达到88.7%;浸出渣物相主要为氧化镁、碳酸钙、二氧化硅等物质,通过洗涤工序可以获得较为纯净的含硅原料。

硅铁炉烟气净化及微硅粉回收系统研究

本项目研究的硅铁炉烟气净化系统,不仅可以解决烟气净化问题,更重要的是可以高效回收微硅粉,使其成为一种变废为宝,能为企业创造高利润的新型系统。

Process of aluminum dross recycling and life cycle assessment for Al-Si alloys and brown fused alumina

In 2008,around 596 000 t of aluminum dross was generated from secondary aluminum industry in China;however,it was not sufficiently recycled yet.Approximately 95% of the Al dross was land filled without innocent treatment.The purpose of this work is to investigate Al dross recycling by environmentally efficient and friendly methods.Two methods of Al dross recycling which could utilize Al dross efficiently were presented.High-quality aluminum-silicon alloys and brown fused alumina(BFA) were produced successfully by recycling Al dross.Then,life cycle assessment(LCA) was performed to evaluate environmental impact of two methods of Al dross recycling process.The results show that the two methods are reasonable and the average recovery rate of Al dross is up to 98%.As the LCA results indicate,they have some advantages such as less natural resource consumption and pollutant emissions,which efficiently relieves the burden on the environment in electrolytic aluminum and secondary aluminum industry.

Recycling waste crystalline-silicon solar cells: Application as high performance Si-based anode materials for lithium-ion batteries

Recycling useful materials such as Ag, Al, Sn, Cu and Si from waste silicon solar cell chips is a sustainable project to slow down the ever-growing amount of waste crystalline-silicon photovoltaic panels. However, the recovery cost of the above-mentioned materials from silicon chips via acid-alkaline treatments outweights the gain economically.Herein, we propose a new proof-of-concept to fabricate Si-based anodes with waste silicon chips as raw materials.Nanoparticles from waste silicon chips were prepared with the high-energy ball milling followed by introducing carbon nanotubes and N-doped carbon into the nanoparticles, which amplifies the electrochemical properties. It is explored that Al and Ag elements influenced electrochemical performance respectively. The results showed that the Al metal in the composite possesses an adverse impact on the electrochemical performance. After removing Al, the composite was confirmed to possess a pronounced durable cycling property due to the presence of Ag, resulting in significantly more superior property than the composite having both Al and Ag removed.

Recovery of Gold from Aqueous Solution Containing Au（Ⅲ） by Silicon Organic Polymer

The silicon organic polymer containing PSOT-3 （dioxothiocarbamide groups） has been synthesized and characterized, and the adsorption of Au（III） on PSOT-3 was investigated. The results showed that PSOT-3 had good adsorption capacity for Au（III）, and the adsorption of Au（III） was found to be the most effective in 0.1-0.3 mol/dm^3 hydrochloric acid solution. The adsorption is physical and the process is endothermic, and Freundlich isotherm fits the data better than the Langmuir isotherm. The adsorption can be generally described by electrostatic interaction （Coulomb＇s force） between the adsorbent and the adsorbate. The high adsorption capacity of this sorbent has significant potential for gold recovery from aqueous solutions.

Recovery of Sillimanite from Beach Sands--An Operator＇s Nightmare？

Sillimanite, chemically named aluminum silicate, 3Al2O3SiO2 is one of the three forms of alumino silicate polymorphs and commonly encountered in aluminous metamorphic, plutonic and volcanic rocks and their weathering products. Traditionally in India, sillimanite is upgraded by froth floatation technique using oleic acid as a collector cum frother, sodium silicate as depressant and soda ash as pH regulator. At TSPL （Trimex Sands Pvt Ltd）, conventional mechanical float cells are installed to float sillimanite. In addition to the usual problems associated with conventional cells, poor flow ability of the sillimanite concentrate is experienced in dry circuit due to the presence of sodium oleate. Fine garnet in the sillimanite concentrate contributes to high iron content in the final product, making sillimanite separation a nightmare for operators （lower recoveries coupled with inferior grades）. Various efforts were made to improve the performance of the circuit such as introduction of additional frother like MIBC （methyl ISO butyl carbinol）, optimizing the operating parameters such as pulp density, collector dosage, depressant dosage, air flow rate, pH etc., use of collector aids, stage wise addition of reagents etc.. The challenges faced to produce a sillimanite product with stringent quality norms and the efforts made to improve the grade and recovery are described in this paper.

PVDMS-Al2O3 Composite Hollow Fibre Membranes for Chloroform Recovery from Gas Streams

Sorption isotherm of chloroform in polyvinyl dimethylsiloxane (PVDMS) polymer film was measured via the gravimetric method, and this film was confirmed experimentally to be good membrane material to recover chloroform from gas stream with high sorption capacity. A new PVDMS-Al2O3 composite hollow fibre membrane was further prepared by coating a PVDMS film on the outer surface of Al2O3 hollow fibre porpous substrate prepared by a dry/wet phase inversion method. Microstructure of the composite membranes was examined by scanning electron microscopy (SEM), indicating the PVDMS coating layer was uniform, free of defects, and around 15μm thick. Performance of the PVDMS-Al2O3 composite hollow fibre membranes for chloroform recovery was investigated. By comparing the experimental data that derived from a mathematical model, the permeabilities of chloroform and nitrogen in the PVDMS polymer membrane were obtained. The effects of temperature and feed flow rate on the chloroform recovery and permeate concentration were investigated both experimentally and theoretically.

Flotation tree analysis for recovery of sillimanite from red sediments

In this paper an attempt is made to recover sillimanite by flotation tree analysis process and conventional flotation process from non magnetic fraction of red sediments.The experimental results of both the processes are presented.The data reveal that the deslimed sample contains 33.2%(by weight) total heavy minerals and out of which the sillimanite mineral content is 3.6%(by weight).It is observed that flotation tree analysis needs 10 cells to get five output products and where as conventional flotation process needs 15 cells to recover similar grade of five output products.Thus,flotation tree analysis is not only economic process but also efficient process(to say efficient process,the tree analysis product should be higher grade).

Solvent Recovery from Soybean Oil/Hexane Miscella by PDMS Composite Membrane

Traditional solvent recovery in the extraction step of edible oil processing is distillation,which consumes large amounts of energy.If the distillation is replaced by membrane process,the energy consumption can be reduced greatly.In this work,two kinds of membrane,PDMS(polydimethylsiloxane) composite membrane and Zeolite filled PDMS membrane were prepared,in which asymmetric microporous PVDF(polyvinylidenefluoride) membrane prepared with phase inversion method was functioned as the microporous supporting layer in the flat-plate composite membrane.The different function compositions of the PDMS/PVDF composite membranes were characterized by reflection Fourier transform infrared(FTIR) spectroscopy.The surface and section of PDMS/PVDF composite membranes were investigated by scanning electron microscope(SEM).The PDMS NF(nanofiltration) membranes were then applied in the recovery of hexane from soybean oil/hexane miscellas(1:3,mass ratio).The effects of pressure(0.5-1.5 MPa),cross-linking temperature and PDMS layer thickness on membrane performances were investigated.The results indicated that both two kinds of NF membranes were promising for solvent recovery,and zeolite filled in PDMS NF membrane could enhance the separation performance.