CN109911902B - Silicon purification device and method - Google Patents

Abstract

The invention discloses a silicon purification device and a silicon purification method. When the equipment works, silicon-containing alloy or silicon melt is put into a smelting device, then an electrode and a coil are electrified, the electrode at the bottom of the smelting device generates a circular current at the bottom of the melt, the electrified coil generates a circular current at the middle and upper parts of the melt, and forced convection is formed in the whole melt, so that silicon elements at the middle and upper parts of the melt are transported to the bottom of the smelting device. Finally, the silicon-containing alloy or silicon melt starts directional solidification under the action of the pull rod and the cooling device, so that the silicon with higher purity is continuously precipitated and solidified. If the content of silicon element on the upper part of the melt in the smelting device is reduced, adding low-purity silicon into the smelting device, repeating the steps, and finally carrying out acid washing on the solidified silicon ingot to remove the metal element, thereby achieving the effect of purifying the silicon.

Description

A kind of silicon purification device and method

technical field

The invention belongs to the technical field of non-metal purification, and in particular relates to a silicon purification device and method.

Background technique

With the development of social civilization, human's demand for energy continues to increase, and energy issues have become one of the top priorities related to the national economy and people's livelihood. Traditional energy sources are gradually decreasing, and the research and development of renewable and clean energy has become the focus of various countries. As a renewable, non-polluting and inexhaustible new energy source, solar energy has developed rapidly in its research and application. New processes, new materials and new structures emerge in an endless stream in solar photovoltaic technology. More than 100 solar cells have been successfully developed, and the preparation process of solar cells has made great progress. So far, the solar photovoltaic industry is basically based on silicon materials, and most of the solar photovoltaic devices in the world are made of crystalline silicon. The rapid development of solar cells has created a large gap in the solar-grade silicon material market.

Among the many methods for preparing silicon materials, the ones that have been put into industrial production are mainly improved Siemens method, silane method and metallurgical method. Among them, the improved Siemens method has mature technology and good product quality, but this method has large investment, large pollution, high consumption and high cost. Compared with the improved Siemens method, the silane method has the advantages of low energy consumption and small investment, but the product quality is poor. Generally speaking, these two methods have problems such as large equipment investment, high cost, serious pollution and complex process, which are not conducive to The popular application of solar cells, and although the metallurgical method of preparing polysilicon has the advantages of short production cycle, low pollution and low cost, it is considered to be one of the most effective technologies to reduce the production cost of polysilicon, but there are also many problems with metallurgical methods, such as , the metallurgical method can only prepare solar-grade silicon, and it is not yet mature.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the above problems, the present invention proposes a high-efficiency, low-cost, pollution-free silicon purification device and method.

Technical solution: a silicon purification device according to the present invention, the purification device includes a temperature measuring device 1, an electrode 2, a thermal insulation heating device 3, an electrified coil 4, a smelting device 5, a tie rod 6, and a cooling device 7. The electrode 2 exists in pairs, the upper electrode 2 is located at the upper end of the smelting device 5, and is connected to the silicon-containing alloy 8, and the lower electrode 2 is the lower end of the heat preservation heating device 3, and is connected to the tie rod 6; The device 5; the silicon-containing alloy 8 is placed in the melting device 5; The inner wall is provided with an annular energized coil 4, and the annular energized coil 4 surrounds the smelting device 5 in the middle; the temperature measuring device 1 is used to monitor the temperature in the heat preservation and heating device 3, and can be placed on the upper part of the heat preservation and heating device 3 or lower.

Further, the shape of the heat preservation and heating device 3 may be a cylinder, or a cuboid or a cube, preferably a cylinder; the melting device 5 in the heat preservation and heating device 3 may be a crucible or an electric furnace for intermediate frequency melting, It is preferably a crucible, and the length and diameter of the smelting device 5 can be adjusted with the size of the production volume;

Further, the smelting device 5 and the thermal insulation heating device 3 are filled with thermal insulation material, and the thermal insulation material can be filled with thermal insulation bricks, thermal insulation cotton, graphite felt, or zirconia, preferably thermal insulation bricks;

Further, an electrode 2 is connected to the top of the smelting device 3 and the bottom of the tie rod. The electrode 2 can be a consumable electrode, a graphite electrode or a copper electrode or a copper-tungsten alloy electrode, preferably a consumable electrode.

Further, the lower end of the silicon purification device is connected to a cooling device 7. The cooling device 7 can be immersed in circulating cooling water for cooling or spray cooling, and the cooling device can be one or more. indivual.

Further, the temperature measuring device 1 can select a thermocouple to monitor the temperature in real time, or a temperature control instrument can be used, preferably a thermocouple, wherein the thermocouple is placed along the vertical direction of the smelting device, or can be placed above the heat preservation and heating device. It is placed under the heat preservation and heating device to measure the temperature field state and alloy solidification during the solidification process.

The present invention adopts the method for purifying silicon by the above-mentioned device, and the above-mentioned device is used to carry out the molding operation. And the power switch of the pulse current, the electrode at the bottom of the smelting device generates a circulating current at the bottom of the silicon-containing alloy, and the energized coil will generate a circulating current in the same direction in the middle and upper parts of the silicon-containing alloy, thereby forming forced convection in the entire melt, and then The silicon element in the middle and upper part of the silicon-containing alloy is transported to the bottom of the silicon-containing alloy, and at the same time, the pull rod is pulled at a certain speed to make the silicon-containing alloy move downward into the cooling device. The silicon-containing alloy begins to solidify slowly at the bottom of the melting device and gradually High-purity silicon is precipitated. When the silicon content of the upper part of the silicon-containing alloy in the smelting device decreases, low-purity silicon or silicon alloy is added to the smelting device, and so on. Finally, the lower half of the solidified silicon ingot is pickled to remove a small amount. metal elements to obtain high-purity silicon, which has the effect of purifying silicon. Using the method of the present invention, high-purity silicon with a purity greater than 99.99% can be extracted.

Beneficial effects: compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

The above-mentioned high-purity silicon extraction device proposed by the present invention is simple, and the silicon purification method is simple and easy to implement, not only has a wide source of raw materials, but also has the characteristics of low cost, high efficiency, low energy consumption, no pollution, etc., and is convenient for large-scale implementation in factories.

Description of drawings

Fig. 1 is the simple schematic diagram of the device for purifying silicon of the present invention, wherein the pull rod is not pulled down;

Fig. 2 is a simple schematic diagram of the device of the present invention, wherein the pull rod has been pulled down, and there is one cooling device, and the cooling method is immersion cooling through circulating cooling water, and the temperature measuring device is above the heat preservation heating device;

Fig. 3 is a simple schematic diagram of the device of the present invention, wherein the pull rod has been pulled downward, wherein there are multiple cooling devices, the cooling method is immersion cooling through circulating cooling water, and the temperature measuring device is below the thermal insulation heating device;

4 is a simple schematic diagram of the device of the present invention, wherein the pull rod has been pulled down, there are multiple cooling devices, the cooling method is spray cooling, and the temperature measuring device is below the heat preservation heating device.

Detailed ways

The technical solutions of the present invention will be further described in detail below with reference to specific accompanying drawings 2 , 3 and 4 .

Description of the accompanying drawing numbers: temperature measuring device (1), electrode (2), thermal insulation heating device (3), energizing coil (4), smelting device (5), tie rod device (6), cooling device (7), silicon alloy (8).

The present invention adopts a silicon purification device, as shown in FIG. 1 , and the adopted thermal insulation heating device can be cylindrical, rectangular, square and other shapes.

When the device of the present invention combines the melt holding device and the cooling device to purify silicon, as shown in Figures 1 to 4, the temperature measuring device can be placed above the silicon purification device, as shown in Figure 2, or it can be placed below , as shown in Figure 3; only one cooling device can be placed in the silicon purification device, or multiple smelting, pulling rods, and cooling devices can be placed in the thermal insulation heating device to perform purification work at the same time, as shown in Figure 3, to speed up the purification rate; The cooling method can be immersed in circulating cooling water, as shown in Figure 2 and Figure 3, or spray cooling, as shown in Figure 4.

Example 1

Adopt the device shown in Figure 2 to purify silicon in Al-20.5%wt.Si hypercoalloy

(1) First, the raw materials are pure aluminum (99.9wt%) and Si (99.9wt%) into a furnace for smelting to obtain an Al-20.5%Si hypereutectic alloy, which is kept at a temperature of 1000K in a resistance furnace. The resistance furnace at the place is the thermal insulation heating device of the present invention;

(2) Start the switch of electrode current and coil pulse current, and pull the rod at the speed of 1mm/s at the same time;

(3) After the directional solidification of the sample is realized, the sample is taken out for pickling to obtain high-purity silicon.

Example 2

The device shown in Figure 3 was used to purify silicon with a boron content of 14.83 ppm

(1) First, place the boron content of 14.83ppm silicon and aluminum raw materials in the calculated mass ratio in a crucible (smelting device), heat at a temperature of 1200K in a resistance furnace, and smelt to obtain Al-40%Si Eutectic alloy melt; the resistance furnace here is the heat preservation heating device of the present invention, and the crucible is the smelting device of the present invention;

(2) Start the electrode current switch and the coil pulse current switch, and pull the rod at a speed of 2mm/s at the same time to start the directional solidification of the alloy;

(3) In the directional solidification process, industrial silicon with the grade of 1101 can be added to supplement the silicon element with reduced melt content;

(4) After the directional solidification of the sample is realized, the sample is taken out for pickling to obtain high-purity silicon.

Example 3

Take the device shown in Figure 4 to purify 1101 industrial silicon

(1) First, 184.7kg of silicon material is placed in a crucible, and remelted in an induction melting furnace to make the silicon material a silicon-containing melt; the crucible here is the melting device of the present invention, and the induction melting furnace is the present invention thermal insulation heating device;

(2) Start the electrode current switch and the coil pulse current switch, and at the same time pull the tie rod at a certain speed to make the silicon-containing melt leave the induction heating zone, and open the cooling spray device to start directional solidification;

(3) In the process of directional solidification, industrial silicon with the grade of 1101 can be added to supplement the melt;

(4) After the whole process is finished, high-purity silicon is obtained.

Claims (4)

1. a method for purifying silicon using a silicon purifying device, is characterized in that, the method comprises the steps: (1) put the silicon-containing alloy (8) into the smelting device (5), then heat up and melt the silicon-containing alloy and keep warm by the heat preservation heating device (3); (2) The upper and lower electrodes (2) and the energizing coil (4) are energized. After the electrode (2) at the bottom of the pull rod (6) is energized, the current flows through the pull rod (6) into the silicon-containing alloy of the melting device (5). A circulating current is generated at the bottom of the melt, and the magnetic field induced by the energized coil (4) generates a circulating current in the same direction in the middle and upper parts of the silicon-containing alloy, forming forced convection in the entire melt; (3) Pull down the tie rod (6), so that the silicon-containing alloy (8) enters the cooling device (7), and under the cooling action of the cooling device (7), it solidifies at the bottom of the smelting device (5) and gradually precipitates high purity At the same time, the pull rod (6) continues to pull down, and the current introduced by the electrode and the flow of the magnetic field induced by the coil in the melt transports the silicon element continuously to the solid-liquid interface and continuously precipitates high-purity silicon; when smelting When the content of silicon element in the silicon-containing alloy (8) in the device (5) decreases, the silicon-containing alloy or low-purity silicon is directly added to the smelting device (5) to dissolve it in the silicon-containing alloy melt, and under the action of flowing High-purity silicon is continuously precipitated at the solidification interface, and finally the solidified silicon ingot is pickled to remove metal elements, leaving silicon elements to obtain high-purity silicon; The silicon purification device includes a temperature measuring device (1), an electrode (2), a thermal insulation heating device (3), an electrified coil (4), a smelting device (5), a tie rod (6), and a cooling device (7). The electrodes (2) exist in pairs, the upper electrode (2) passes through the upper end of the heat preservation and heating device (3) and is connected with the silicon-containing alloy (8), and the lower electrode (2) is located at the lower end of the heat preservation and heating device (3), and is connected to the tie rod. The lower ends of (6) are connected; one or more melting devices (5) are placed in the heat preservation and heating device (3); the silicon-containing alloy (8) is placed in the melting device (5); the bottom of the melting device (5) is connected to the tie rod ( 6) Through connection, cooling devices (7) are provided on both sides of the outside of the tie rod (6) for directional solidification of the silicon-containing alloy (8). There is an energizing coil (4) with a bracket, and the energizing coil (4) surrounds the smelting device (5) in the middle; the temperature measuring device (1) is used to monitor the temperature in the heat preservation heating device (3), and is placed in the heat preservation device (3). The upper or lower part of the heating device (3). 2 . The method for purifying silicon using a silicon purification device according to claim 1 , wherein the shape of the thermal insulation heating device ( 3 ) is any one of a cylinder, a rectangular parallelepiped, and a cube. 3 . 3 . The method for purifying silicon using a silicon purifying device according to claim 1 or 2 , wherein the cooling device ( 7 ) is one or more. 4 . 4. a kind of method that adopts silicon purification device to carry out the purification method of silicon according to claim 1 and 2, is characterized in that, the described electrode of electrode (2) is consumable electrode, graphite electrode, red copper electrode, copper-tungsten alloy electrode , Any kind of steel electrode.

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