合金法提纯硅过程中氢对杂质硼的捕获去除行为及机制

Al–Si solvent refining is considered as a low–cost process to fabricate the solar–grade silicon, which is the research hotspots currently. The difficulty of this process is how to separate the B impurity phase and the Si phase efficiently and economically. In this project, it is proposed that a combination of hydrogen blowing and electromagnetic directional solidification can realize the separation of multiphase. By using the characteristics that the hydrogen can absorb the B, and that the method of electromagnetic enhanced crystallization, the B impurities can be removed (upper melt) and the primary Si can agglomerate together (lower melt) simultaneously. Based on these, this project will focus on the separation mechanism and the model theory. First, the reaction and adsorption behaviors of B phase and H will be studied systematically, and thus the interaction relationship of components and selective adsorption mechanism can be clarified. Second, we will establish the kinetics models of the reaction and the mass transport, which can reveal the migration characteristics and separation law of the different components. Finally, by analyzing the effect of process parameters on the efficiency of B removal, and optimizing the data, it can obtain the regulating mechanism of deep B removal under the combination effect of the migration characteristics and the process parameters. The achievements of this study will be beneficial to forming the theoretical foundation on the purification technology of metallurgical silicon. On the other hand, it will provide a new way and a new idea for the preparation of the other high purity materials.

采用铝硅合金提纯硅是目前低成本制备太阳能级硅的研究热点，如何实现杂质硼相与硅相的绿色高效分离是该技术亟待解决的难题。本项目提出采用高温熔体吹氢–电磁定向凝固进行多相分离的方法，利用氢对硼选择性吸附的特点，同时通过电磁强化结晶，一并实现杂质硼的清洁分离去除(熔体上部)和硅的高效结晶富集(熔体下部)。基于此，本项目拟围绕多相分离机制的理论和模型实验展开研究。首先，系统研究合金熔体中氢与硼及金属硼化物的反应和吸附行为，探索各组元之间的相互作用关系及其选择性吸附机理；其次，构建氢气除硼的反应和传质动力学模型，考察杂质组分在多相分离过程中的迁移、分离规律与净化效率；最后，分析工艺参数对杂质硼去除效率的影响，通过拟合数据并优化，探明多因素共同作用下的深度除硼调控机制。通过本项目研究，为形成低成本、高效短流程的冶金硅提纯新技术奠定基础，并为同类型高纯材料的制备提供新的技术思路和理论借鉴。

采用Al-Si合金法提纯冶金级硅是当前硅精炼领域的研究热点，如何低成本实现硅中杂质硼的去除是当前该领域的研究难点。本项目采用高温熔体吹氢-电磁定向凝固进行多相分离的方法，利用氢与硅中杂质硼选择性反应的特点，通过开展氢对硼的捕获行为及氢与硼的相互作用关系研究，探究了杂质硼清洁分离去除和硅高效结晶富集的机理。采用基于量子化学的密度泛函理论，研究了Al-Si熔体内[H]与[Si]、[B]、[Al]之间和[B]与[Si]、[Al]、[Ti]之间的多组元多相反应作用机制，通过氢化物和硼化物的态密度、能带结构和Mulliken布居值等探讨了其相互作用的机理，研究了可能的反应途径，结果表明B2H6是熔体中[H]与[B]的主要化学反应产物；根据[B]和[H]在熔体中可能的反应途径建立了氢与硼的反应动力学模型，确立了[H]与[B]反应的速率方程和反应速率常数，构建了杂质硼的传质动力学模型，获得了硼去除的动力学限制环节，结果表明B2H6的扩散环节是该过程的限制性步骤；研究了工艺参数对除硼的影响规律，建立了深度除硼的过程调控机制；开展了电磁强化结晶富集硅的研究，明确了影响硅结晶富集的关键技术参数，获得了电磁强化结晶富集硅的调控机制。在本实验设置的优化条件下，杂质硼的去除率可达96.3%，取得了较为满意的项目实施效果。通过本项目研究，为冶金法多晶硅除硼提供了新思路和技术理论支撑。