Apparatus and method for producing silicon by carboreduction

A method for producing silicon from quartz using an apparatus for producing silicon from quartz, the apparatus comprising:

• a sealed enclosure defining an enclosed space, the enclosure being connected to at least one suction pump to generate a pressure difference between the interior and the exterior of the enclosed space, the pressure inside the enclosed space being lower than the pressure outside the enclosed space when the suction pump is activated,
• an electric arc furnace housed inside the sealed enclosure, the arc furnace including:
• a tank for containing a mixture of raw materials for the production of silicon,
• a set of electrodes configured to form an electric arc for heating the mixture,
• a movable lid housed in the enclosure, the lid being adapted to cover an upper opening of the tank,
• wherein the method comprises the following phases:
• a pre-treatment phase including the steps consisting of:
• reducing the pressure inside the enclosed space to a value below atmospheric pressure,
• implementing resistive heating of the mixture of raw materials,
• separating the lid from the edges of the upper opening,
• a carboreduction phase including:
• an initiation step composed of sub-steps consisting of:
• increasing the pressure inside the enclosed space to a value substantially equal to atmospheric pressure,
• implementing electric arc heating of the mixture of raw materials,
• contacting the lid with the edges of the upper opening,
• then when the temperature of the mixture is greater than 1500° C., a treatment step composed of sub-steps consisting of:
• maintaining the pressure inside the enclosed space at the value substantially equal to atmospheric pressure,
• maintaining electric arc heating of the mixture of raw materials,
• half opening the lid,
• a post-treatment phase including the steps consisting of:
• reducing the pressure inside the enclosed space,
• separating the lid from the edges of the upper opening.