A METHOD FOR PRODUCING HIGH-PURITY METALLURGICAL-GRADE SILICON METAL BY MEANS OF PURIFICATION WITH METALS AND OTHER COMPOUNDS, FOLLOWED BY LEACHING

摘要

The present invention relates to a novel method for producing high-purity metallurgical-grade silicon metal by leaching silicon metal and then purifying same in subsequent steps. Said method, which is the subject matter of the present patent, by utilizing the method of purifying silicon metal through introducing metals and/or other compounds into the bath, and other techniques, followed by leaching, washing and drying, improves the prior art by making the following advantages possible: 1. Significant reduction in the content of impurities and other metals in the silicon; 2. Economical viability for producing high-purity metallurgical-grade silicon metal in comparison to conventional methods; 3. Reduction in the number of process steps required for producing high-purity metallurgical-grade silicon; 4. Possibility of using low-cost products and/or substances for introducing and removing impurities or undesired components. The present invention consists of basically four steps for producing high-purity metallurgical-grade silicon metal with individual boron and phosphorus contents of less than 1 ppm: First step: - addition of alkali metals and/or alkaline earth metals and/or other components such as: fluorite, silica, silicates, synthetic slag, before, whilst or after melting the silicon metal. Second step: - simultaneous and/or consecutive injection of gas, such as argon, humidified argon, water vapour, oxygen, chlorine, hydrogen, hydroxides, etc., onto the bath, which is at a high temperature, said temperature being higher than the melting point of silicon metal. Gas injection onto the turbulent bath should be maintained long enough so that all of the volume/mass of metal is in contact with the mass of gas directed towards the bath. Third step: - optional purification of said product in a plasma refining furnace and/or induction furnace and/or electric furnace, resistance furnace, using various processes simultaneously and/or consecutively. Fourth step: - the silicon metal with individual boron and phosphorus contents of less than 0.5 ppm - produced using the aforedescribed method is submitted to the processes of remelting and directional solidification, in the presence or absence of thermal plasma and gas injection. These steps can be carried out simultaneously, or in the aforementioned order, or even with modifications or substitutions made to the aforementioned order, as well as to the frequency and number of repetitions of each step.