合金精炼—造渣法提纯冶金硅的研究

发布时间：2018-02-12 18:39

本文关键词： 冶金硅合金精炼造渣法硼杂质　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：能源危机带来的诸多问题导致依赖传统能源的能源结构必须进行改革,应运而生的新能源因为具有可循环无污染绿色环保等优点有望取代传统能源。太阳能因为储量大、开采方便、无地域限制、清洁无污染等优点使其能超越风能、水能、地热能等成为极具潜质且未来可广泛高效应用的清洁能源。太阳能电池是实现光电转化的主要装置,硅料因为储量大、光电转化效率高、性能稳定等优点占据太阳电池原材料的绝大部分市场,硅太阳能电池的原料以多晶硅为主。初期硅的提纯主要依赖以西门子法为代表的化学法,其能耗高,设备复杂,且产品纯度不适用于太阳能电池,冶金法可以解决这些问题,此方法能耗低,提纯温度低,设备构造简单且成本低,有利于工业化生产。本文研究利用合金精炼-造渣法提纯冶金硅,通过结合合金精炼提纯法和造渣提纯法来研究低温条件下硼的去除,以改变传统造渣法在高温条件下的高能耗问题,从而真正实现低能耗、低成本去除冶金硅中硼杂质。本文通过对M-Si合金体系结合造渣法进行实验,通过改变合金组成、渣剂种类、熔炼时间、渣金比以及碱度,研究不同实验条件对除硼效果的影响,主要得到以下结论：(1)采用Si-Sn合金以及Na2SiO3-CaO-SiO2渣剂进行精炼提纯,随着Sn添加量的增大,渣金比的增大,熔炼时间的增加,硅中硼杂质含量逐渐降低,硼的去除率逐渐增大,Sn添加量为50at%时,经过一次造渣,硅中的硼含量由初始值12.92ppmw降至0.786ppmw,去除率为93.92%；在渣金比达到1.75：1之后硅中的硼含量基本达到稳定状态；(2)采用Si-Sn合金以及Na2CO3-SiO2渣剂进行精炼提纯,随着熔炼时间的增加,Sn添加量的增大,渣金比的增大,硅中硼含量表现出逐渐降低的趋势；当Sn添加量为50at%时,经过一次造渣,硅中的硼含量降至0.9ppmw,去除率为93.03%；在渣金比达到1.25：1之后硅中的硼含量基本达到稳定状态；随着碱度的增加,硅中的硼含量先降低后增加,这主要是因为硼的去除受渣剂碱度以及氧分压的双重影响,当渣剂碱度较小时,碱度是制约反应的主要因素,当碱度较大时,氧分压成为制约反应的主要因素。(3)采用Al-Si合金以及Na3AlF6-Al2O3渣进行精炼提纯,渣剂的引入对Al-Si合金精炼除硼的效果有一定的强化作用,与同时间的合金精炼效果相比,引入造渣过程后,除硼效率能够提高15.7%。杂质硼含量降低至2.85ppmw。同时,熔炼时间对除硼效果也有较大影响,随着熔炼时间的增加,初晶硅中杂质硼含量逐渐降低,去除率逐渐增加。分析合金精炼-造渣法对Al-Si合金除B过程的影响,硼原子在渣剂及金属中的溶解度不同所引起的分配系数及渣剂挥发过程可能是强化杂质硼去除的主要原因。
[Abstract]:Many problems brought about by the energy crisis have led to the reform of the energy structure that depends on traditional energy sources. The new energy, which has the advantages of recycling, pollution-free, green and environmental protection, is expected to replace traditional energy sources. The advantages of easy exploitation, no geographical restriction, clean and pollution-free make it possible to surpass wind, water and geothermal energy to become a potential clean energy source which can be widely and efficiently used in the future. Solar cells are the main devices to realize photovoltaic conversion. Because of its large reserves, high photoelectric conversion efficiency and stable performance, silicon occupies the vast majority of the market of raw materials for solar cells. Polysilicon is the main raw material for silicon solar cells. In the initial stage, the purification of silicon mainly depends on the chemical method represented by Siemens method. Its energy consumption is high, the equipment is complex, and the product purity is not suitable for solar cells. Metallurgical method can solve these problems. This method has the advantages of low energy consumption, low purification temperature, simple structure and low cost. Boron removal under low temperature is studied by combining alloy refining and slag purification to change the problem of high energy consumption in the traditional slag making process at high temperature so as to realize the real low energy consumption. Removal of boron impurities from metallurgical silicon at low cost. In this paper, the effects of different experimental conditions on the effect of boron removal were studied by changing the composition of the alloy, the type of slag, the melting time, the ratio of slag to gold and the alkalinity through the experiments on M-Si alloy system combined with slagging method. The main conclusions are as follows: (1) Si-Sn alloy and Na2SiO3-CaO-SiO2 slag are used for refining and purification. With the increase of Sn content, the ratio of slag to gold, the melting time, the boron impurity content in silicon decreases gradually. When the removal rate of boron is increasing gradually, the content of tin is 50 at%, and after primary slagging, The boron content in silicon decreases from 12.92 ppmw to 0.786ppmw, the removal rate is 93.92pmw, and the boron content in silicon reaches stable state after the ratio of slag to gold reaches 1.75: 1. The boron content in silicon is refined and purified by Si-Sn alloy and Na2CO3-SiO2 slag agent. With the increase of smelting time, the content of Sn is increased. With the increase of slag / gold ratio, the content of boron in silicon decreases gradually, when the content of Sn is 50 at%, the content of boron in silicon decreases to 0.9ppmwand the removal rate is 93.030.When the ratio of slag to gold reaches 1.25: 1, the content of boron in silicon basically reaches a stable state. With the increase of alkalinity, the content of boron in silicon decreases first and then increases. This is mainly because the removal of boron is affected by the alkalinity of slag agent and the partial pressure of oxygen. When the alkalinity of slag agent is small, alkalinity is the main factor restricting the reaction, and when the alkalinity is large, Oxygen partial pressure is the main factor restricting the reaction. (3) Al-Si alloy and Na3AlF6-Al2O3 slag are used to refine and purify. The introduction of slag agent can strengthen the refining effect of Al-Si alloy, compared with the refining effect of the alloy at the same time. The boron removal efficiency can be increased by 15.7ppmw. the boron content of impurity decreases to 2.85ppmw. at the same time, the boron content in primary silicon decreases with the increase of smelting time. The effect of alloy refining and slag making on the process of removing B from Al-Si alloy was analyzed. The distribution coefficient and volatilization process of boron atoms in slag and metal due to the different solubility of boron atoms may be the main reasons for enhancing the removal of impurity boron.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304.12

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