Optimal Portfolio of Products in a Polycrystalline Silicon Refinery

Abstract

The silicon industry is a source of various 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 byproducts generated in the production of polycrystalline silicon (polysilicon) offers opportunities to increase the economics of the polycrystalline silicon production process. In this work, a silicon based refinery is conceptually designed using surrogate models for the major units to evaluate the portfolio of products. Although the main product is polysilicon, there are a number of products that might be obtained in the process to improve its profitability, such as tetraethoxysilane (at different purities) as well as chlorosilanes, including SiH 4 , SiH 2 Cl 2 , and SiH 3 Cl. Next, 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, compared to a cost of 8.93 $/kg of polycrystalline silicon if the plant does not generate high value-added byproducts, both values below the commercial price of polycrystalline silicon, which is estimated at 10 $/kg. Therefore, the refinery is not only capable of meeting the market share requirements, but in a way that the generation of different high added value byproducts increases the plant profit compared to that of the net income earned by traditional polysilicon monoproduct plants.