Method for preparing acicular high-purity silicon aggregates and equipment thereof

Abstract

The invention relates to a method for preparing acicular high-purity silicon aggregates and equipment thereof. The preparation method is characterized in that silicon particles and aluminum are added into a crucible and are heated to a temperature higher than the eutectic point, and molten-state unsaturated silicon aluminum alloy solution is formed; titanium and calcium are added, and the temperature is maintained for 2 to 8 hours for removing boron and phosphorus impurities in the alloy solution; and a heater arranged at the upper part of a furnace barrel is switched off, or a cooling bar is inserted into the upper part of the crucible, so the temperature gradient with lower temperature at the upper part and higher temperature at the lower part is formed inside the crucible, the power of the heater arranged at the lower part of the furnace barrel is controlled so that the hearth temperature is reduced at the velocity of 1 to 10 DEG C per hour, a rotating tray is started, the crucible and paddles arranged at the bottom of the crucible are driven to rotate, the melt bodies at the bottom and upper part of the crucible are driven to realize the convection, and the acicular high-purity silicon aggregates are formed at the upper part of the crucible. The method has the advantages that large-block acicular high-purity silicon aggregates are prepared in a single region and can be directly taken out from the solution without filtering, the energy is saved, the environment is protected, and the economic benefit is high.

Description

technical field [0001] The invention relates to a production process and professional equipment for removing impurities and purifying industrial silicon into solar-grade silicon. Background technique [0002] Solar-grade polysilicon requires a very low content of impurity elements, among which the content of boron is required to be less than 0.4ppmw, and the content of phosphorus is less than 0.7ppmw. The mainstream manufacturing process is the Siemens method. The process includes: reacting metallurgical-grade silicon with hydrogen chloride to generate three Chlorosilane, distillation and purification of trichlorosilane, and reduction of purified trichlorosilane with high-purity hydrogen at a high temperature of 1100°C to obtain high-purity polysilicon. Due to serious pollution and high energy consumption, this method was listed as a prohibited construction project by the Chinese government in 2009. (For details, see the "Notice of the State Council Approving the Developmen...

AI Technical Summary

Problems solved by technology

However, since the temperature of the water-cooled graphite head is lower than the eutectic temperature of Al-Si, only a large amount of α-phase aluminum and a small amount of β-phase acicular silicon are attached to the graphite head.

[0014] U.S. Patent US 7883680 removes impurity phosphorus by blowing oxidizing gas into the aluminum-silicon solution, which directly leads to the loss of aluminum

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