Optimal Design of a Multi-Product Polycrystalline Silicon Facility

Abstract

The silicon industry is a source of different types of products, including materials for the implementation of renewable energy systems, with a comparatively lower environmental impact than conventional fossil energy sources, and high added value byproducts. In this context, the exploitation of the different by-products generated in the production of polycrystalline silicon (polysilicon) offers opportunities to increase the economic efficiency of the polycrystalline silicon production processes. In this work, a silicon based refinery is conceptually designed, estimating the optimal operating conditions by using surrogate models for the major units involved. Although the main product is polysilicon, there are different products that could be generated in the process increasing its profitability, such as tetraethoxysilane (at different purities). Likewise, series of chlorosilanes with high added value, including SiH4, SiH2Cl2, and SiH3Cl, can also be produced. Additionally, an economic evaluation of the facility is carried out to determine its economic feasibility. The results show that the refinery produces tetraethoxysilane and chlorosilanes in addition to the production of polysilicon. The proposed design reduces the cost for polycrystalline silicon to 6.86 $/kg, below the commercial price estimated at 10 $/kg. Therefore, the refinery is not only capable to meet the market share requirements but that the generation of different high added value by-products increases the plant profit compared with the net income earned by a traditional polysilicon mono-product plants.