Assessment and Study on the Impact on Environment by Multi-crystalline Silicon Preparation by Metallurgical Route

Abstract

The process of the production of multi-crystalline silicon is also that of incessant purification of metallurgical grade silicon, during which high energy consumption and environmental pollutants are inevitable. The paper, which is based on life cycle assessment (LCA), presents calculation and analysis on resource input, energy consumption, emissions into and comprehensive impact on environment generated from the whole process in which 1 kg of solar grade multi-crystalline silicon (SoG-Si) is produced with metallurgical route. The program is based on its research on four representative processes in metallurgical route, namely slag refining, wet purification, directional solidification and electron beam melting. Key factors determining environmental load are sought out through contribution analysis and improvement evaluation. Measures and suggestions on how to improve are proposed. For the first time, the LCA model of comparison of metallurgical route and modified Siemens process to SoG-Si environmental impact is constructed. The environmental impacts of SoG-Si production via metallurgical route is compared with purification via modified Siemens process. Results show that the comprehensive environmental impact of metallurgical route SoG-Si is only 49.57% of modified Siemens process SoG-Si. The metallurgical route enjoys obvious environmental advantage. The improvement should be focused on the reduction of electric power consumption in production processes.