Production of metallurgical-grade silicon from Egyptian quartz

Abstract

Metallurgical-grade silicon (MG-Si) is an important metal which has a range of diverse industrial applications such as a deoxidizer in steelmaking industry, alloying element in the aluminum industry, the preparation of organosilanes, and the production of hyperpure 'electronic grade' silicon (>99.99% Si), which is used in the electronics industry as well as solar cells (PV Education. 2013; Aasly, 2008). MG-silicon is produced by the carbothermic reduction-smelting process, in which silica is reduced by carbon in a submerged arc furnace at temperatures between 1300 and 2000°C under atmospheric pressure. The charge materials include a silicon source (quartz, sand, or quartzite) and a typical reductant blend comprising coke, coal, charcoal, and wood chips. The reduction process occurs according to the following reaction: SiO 2 (s) + 2C (s) → Si (s,l) + 2CO (g) [1] ΔH 2000°C = 687 kJ/mol This overall reaction is the sum of different reactions inside the furnace, which can be specified according to the temperature range. The furnace environment is divided into two zones; high temperature (approx. 2000°C) and low temperature (< 1811°C) zones, in which different reactions dominate. In the hightemperature zone around the electrode tip, the following reactions occur:

Pilot-Plant Production of High-Performance Silicon Nanowires by Molten Salt Electrolysis of Silica

“…It was reported that a current efficiency of about 87% and an energy consumption of 10 kW h/kg-Si were obtained when 1.0 mm depth of quartz was reduced. 42 In comparison with the energy consumption of the Siemens process (about 120−200 kW h/kg-Si) 53 and metallurgicalgrade silicon (>20 kW h/kg-Si), 7,54 this molten salt electrolysis technology shows a bright prospect for future industrialization and application in LIBs because of its much lower energy consumption.…”

Thermodynamic analysis of interaction of components in the SIO2-C system: improvement of technical silicon production technological process

“…It is known that the production of technical silicon is carried out in single-or three-phase furnaces with two or three graphite electrodes, where melting is carried out mainly on high-quality quartzite (SiO2 > 98 %) using charcoal, petroleum coke and coal as a reducing agent [13]. For loosening the сcharge in large furnaces (> 6 MVA), wood chips are usually applied.…”

Preparation of Polycrystalline Silicon from Rice Husk by Thermal Decomposition and Aluminothermic Reduction

“…The exothermic nature of calcium-silica reaction, which has potential explosion, made it impractical for calciothermic process (Houli et al, 2018). Recently, Ali, El-Sadek, Morsi, El-Barawy, & Abou-Shahba (2018) reported the carbothermic reduction process of Egyptian quartz using the high power of electrical furnace to recover about 75% polysilicon with about 97% purity. Several researchers carried out a magnesiothermic reduction of silica at a temperature between 600-950 o C. A maximum Si yield more than 99.9% was achieved (Barati, Sarder, McLean, & Roy, 2011;Won, Nersisyan, & Won, 2011;Larbi, Barati, & McLean, 2013;Swatsitang & Krochai, 2009;Houli et al, 2018).…”