CN1313368C - Production equipment and method of silicon used for solar battery - Google Patents

Abstract

The invention belongs to the technical field of smelting, and in particular relates to equipment and technology for preparing solar photovoltaic materials, that is, equipment and technology for preparing silicon for solar cells. The uniqueness of the present invention lies in making full use of the advantages of the plasma furnace and the intermediate frequency induction furnace. An induction coil connected to an intermediate frequency power supply is set between the inner wall of the furnace shell of the plasma furnace and the outer wall of the crucible, and the plasma gun is used to supplement energy for the induction coil. , using argon as the working gas of the plasma, and the partial pressure of _O2 and CO in the atmosphere of the pole paper, achieved a vacuum smelting. Since plasma is a heat source with high energy density, the high temperature zone can reach several thousand degrees, and the atmosphere is controllable. Under the action of high temperature and medium frequency induction coil, the molten silicon melt is fully melted with the refining slag, so that the impurities flow to the The slag is transferred, thereby speeding up the reaction and simplifying the process. The invention has the characteristics of simple equipment structure and process, easy processing and operation, large-scale equipment, large-scale industrial production, high product quality, less investment, and low production cost.

Description

A kind of production equipment and method of silicon for solar cells

Technical field: The present invention belongs to the field of smelting technology, and in particular relates to equipment and technology for producing solar photovoltaic materials—that is, equipment and technology for producing silicon for solar cells.

Background technology: With the rapid development of the world economy, the demand for energy is also increasing, and the use of a large amount of coal, gas, and oil has caused serious pressure on the ecological environment. Therefore, the utilization and development of renewable solar energy resources have become the focus of energy strategies of countries all over the world. Using the photovoltaic effect of silicon to directly convert solar radiation energy into electrical energy, this technology has been used in many fields by various countries. However, due to the difficult production technology, complex process, low pass rate and high production cost of the existing silicon used in solar cells, solar cells cannot be widely used in large-scale economic construction, social development and people's daily life. . In the production of solar cells, silicon materials account for more than 50% of the cost of solar cells, and reducing the cost of silicon materials is the key to the rapid development of the solar cell industry. Therefore, exploring cheap production equipment and methods of silicon for solar cells, so that it can not only meet the quality requirements of silicon for solar cells, but also enable large-scale industrial production, and achieve a substantial reduction in product costs, has become a must for all countries in the world. A must for professionals in the technical field.

At present, the production methods of silicon for solar cells at home and abroad mainly adopt SiHCl ₃ hydrogen reduction method and silane pyrolysis method. Traditional craft route:

Metal Si→gasification→rectification→Si precipitation→high-purity Si→Si melting→solidification and refining→cutting and cleaning

↑ ↑ ↑

HCl H ₂

From the above process route, it can be seen that this process technology is difficult, complex process, large infrastructure investment, and high production cost. The polysilicon produced by this process has low output and high purity, and is suitable for the semiconductor industry. If it is used for solar cells, it must be tempered. In order to develop and utilize solar energy resources on a large scale, people have done a lot of work in exploring production methods that can greatly reduce product costs and produce silicon for solar cells on a large scale. The technology of producing polysilicon by smelting ultra-high-purity quartz material (or quartz product waste) as raw material with electric arc furnace has appeared in China. However, the production of polysilicon by electric arc furnace is restricted by technical problems in terms of refining effect, product quality and production cost.

SUMMARY OF THE INVENTION: The object of the present invention is to provide a silicon production equipment and method for solar cells with simple process and high yield.

A production equipment of silicon for solar cells consists of a furnace shell 1, a graphite crucible 2, a hollow furnace cover 7 connected to a water inlet pipe 8 and a water outlet pipe 12, an observation hole 9, and a graphite hollow cathode 10 through which argon gas can pass through. , feeding hole 11, molten silicon outlet hole 13, insulation layer 15 and graphite anode 16. The furnace shell 1 is in the shape of a barrel, and the opening of the cone-shaped graphite crucible 2 is placed upwards inside the furnace shell 1. And its bottom is close to the bottom of furnace shell 1, and the space between graphite crucible 2 and furnace shell 1 is insulation layer 15; One end is sealed and inserted into the cavity of the hollow furnace cover 7 and communicated with the cavity; one end of the graphite hollow cathode 10 passes through the middle part of the hollow furnace cover 7 and extends into the furnace shell 1; one end of the observation hole 9 and the charging hole 11 Respectively seal through the hollow furnace cover 7 and communicate with the upper part of the furnace shell 1; the tubular molten silicon outlet hole 13 is obliquely inserted and sealed and fixed in the opening of the upper part of the furnace shell 1, and the tubular molten silicon outlet hole 13 axis and furnace The circular holes for letting the molten silicon flow out on the insulation layer 15 in the shell 1 are on the same axis, and the high-purity quartz sand insulation layer is evenly bonded to the inner wall of the tube. The lower port of the round hole where the molten silicon flows out is on the edge of the upper opening of the graphite crucible 2, the upper port of the molten silicon outlet hole 13 is higher than the lower port, and the upper port is sealed with a flange plate; one end of the graphite anode 16 passes through the furnace shell The middle of the bottom of 1 and the bottom of the furnace shell 1 are connected to the bottom of the graphite crucible 2 with the insulation layer 15 in the middle of the bottom of the graphite crucible 2; the raw material silicon 14 is in the inside of the graphite crucible 2 during the production process, and after the molten pool is formed (raw material The surface of silicon 14 is melted) and the refining slag 5 prepared by CaO and SiO is added from the feeding hole ₁ , and the argon gas enters the furnace through the graphite hollow cathode 10, and then the power is turned on, and the plasma arc is formed after the graphite hollow cathode 10 and the graphite anode 16 are powered. 6 is located at the bottom of one end of the graphite hollow cathode 10 extending toward the interior of the furnace shell 1 . It is characterized in that: an induction coil 3 connected to an intermediate frequency power supply 4 is installed between the inner wall of the furnace shell 1 and the outer wall of the graphite crucible 2 .

A method for producing silicon for solar cells, wherein raw material silicon 14 is added to a furnace shell 1, a graphite crucible 2, a hollow furnace cover 7 fixedly communicated with a water inlet pipe 8 and an outlet pipe 12, an observation hole 9, In the graphite crucible 2 in the furnace shell 1 of the production equipment that can make the graphite hollow cathode 10 that argon passes through, the molten silicon outlet 13, the insulation layer 15 and the graphite anode 16 form, open the water inlet pipe 8 and the water outlet pipe 12, Adjust the argon gas to the working pressure and send it into the space inside the furnace shell 1 through the graphite hollow cathode 10 under an atmospheric pressure state, turn on the power supply to send electricity to the graphite hollow cathode 10 and the graphite anode 16, and adjust the height of the graphite hollow cathode 10 so that The plasma arc 6 is in normal working condition and reaches the set smelting temperature above 1600°C. After 30 minutes, when the upper part of the raw material silicon 14 in the graphite crucible 2 is melted to form a molten pool, the refining slag 5 prepared by CaO and SiO ₂ is fed from the The hole 11 is added to the upper part of the graphite crucible 2, wherein the content of one of CaO and _SiO2 is 40%-60%, and the amount of refining slag 5 added is 10%-15% of the amount of raw silicon added. After 2 hours of refining After purification, open the flange seal of the molten silicon outlet hole 13, tilt the smelting furnace, inject the silicon melt from the molten silicon outlet hole 13 into the mold kept at 1410°C-1544°C, and separate the silicon slag during the gradual cooling process , the polycrystalline silicon ingot is generated, and the silicon ingot block for the solar cell is obtained by cutting and cleaning, which is characterized in that: after the raw material silicon 14 is added to the graphite clamp pot 2, when the water inlet pipe 8 and the water outlet pipe 12 are opened, the induction coil is opened 3 is connected to the water inlet and outlet control device, and the intermediate frequency power supply 4 connected to the induction coil 3 is opened.

Description of the drawings: the accompanying drawing is a schematic diagram of the structure of the production equipment in the production equipment and method of silicon for solar cells of the present invention, wherein:

1——Furnace shell 2——Graphite crucible

3——Induction coil 4——Intermediate frequency power supply

5——Refining slag 6——Plasma furnace

7——Hollow furnace cover 8——Water inlet pipe

9——Observation hole 10——Graphite hollow cathode

11—feeding hole 12—outlet pipe

13——Molten silicon hole 14——Raw silicon

15——Insulation layer 16——Graphite anode

Specific embodiments: In conjunction with the accompanying drawings, the implementation process of a silicon production equipment and method for solar cells of the present invention will be described. The present invention consists of two parts, equipment and production process. The production equipment is described first: the main body of the production equipment is a plasma intermediate frequency induction furnace, which consists of a furnace shell 1, a graphite crucible 2, and a hollow furnace cover connected to the water inlet pipe 8 and the water outlet pipe 12. 7. Observation hole 9, graphite hollow cathode 10 through which argon gas can pass through, feeding hole 11, molten silicon outlet hole 13, insulation layer 15 and graphite anode 16; furnace shell 1 is processed by steel plate, barrel-shaped, There is a through hole at the center of the bottom that allows the graphite anode 16 to pass through. The opening of the cone-shaped graphite crucible 2 is placed upwards inside the furnace shell 1 and its bottom is close to the bottom of the furnace shell 1. The crucible is made of high-purity graphite. formed; the gap between the graphite crucible 2 and the furnace shell 1 is an insulating layer 15, and the insulating layer 15 is high-purity quartz sand, which is fixed with a high-strength adhesive; the hollow furnace cover 7 is sealed on the upper part of the furnace shell 1 One end of the water inlet pipe 8 and the water outlet pipe 12 is sealed and inserted into the cavity of the hollow furnace cover 7, and the lower part of the hollow furnace cover 7 (the side facing the inside of the furnace shell 1) is a heat-resistant and erosion-resistant insulation layer; the graphite hollow cathode One end of 10 extends into the furnace shell 1 through the middle part of the hollow furnace cover 7, and one end of the observation hole 9 and the feeding hole 11 are respectively sealed through the hollow furnace cover 7 and communicated with the upper part of the furnace shell 1; Hole 13 is a short tube, one end of which is obliquely inserted and sealed and fixed in the upper opening of furnace shell 1. The circular hole through which the silicon body flows out has the same axis, and the inner wall of the tube is glued with a high-purity quartz sand insulation layer with uniform thickness. The edge of the graphite crucible 2 upper mouth, the upper port of the molten silicon outlet 13 is higher than its lower port, and the upper port is sealed with a flange; one end of the graphite anode 16 passes through the middle of the bottom of the furnace shell 1 and in the bottom of the furnace shell 1. The insulation layer 15 between the bottoms of the graphite crucible 2 is in contact with the bottom of the graphite crucible 2; the difference between this production equipment and the general plasma furnace is that an intermediate frequency is installed between the inside of the furnace shell 1 and the outer wall of the graphite crucible 2. The induction coil 3 connected to the power supply 4; the induction coil 3 is sheathed on the outside of the graphite crucible 2 in a spiral shape and is made of copper tubes. During the process, water is passed through the copper pipes for cooling.

The power supply of 100Hz and 100KW required by the induction coil 3 is supplied by a thyristor intermediate frequency power supply; the graphite crucible 2 is made of high-purity graphite, and the inside of the hollow furnace cover 7 is a heat-resistant and erosion-resistant insulation material. Circulating water cooling; the hollow furnace cover 7 is equipped with an observation hole 9 and a feeding hole 11. The observation hole 9 is mainly used to observe the conditions in the furnace during operation. The raw material silicon 14 and the pre-prepared refining slag 5 are added from the feeding hole 11; Both the hollow cathode 10 and the graphite anode 16 are made of high-purity graphite, and the 80-100V, 400-500A power supply is powered by a plasma arc power supply; the graphite hollow cathode 10 is hollow, and argon gas is introduced at the beginning of production, and the working pressure is Atmospheric pressure, the surface of the melt is protected by an argon atmosphere; when the graphite hollow cathode 10 and the graphite anode 16 work, a plasma arc 6 is generated as an energy supplement for the induction coil 3; Transfer; the polysilicon is refined and purified in the molten pool for 2 hours, and then the furnace body is tilted, and the polysilicon melt is poured into the mold from the molten silicon outlet hole 13; the temperature of the mold is set at 1410°C-1544°C, and the refining slag 5 precipitates at this temperature Solidify to achieve the separation of silicon slag, and after cooling by heat exchange, polycrystalline silicon ingots are generated; the silicon ingots are taken out and trimmed and sliced to produce solar cells; the molten silicon outlet hole 13 is sealed with a flange during the smelting process.

Production method: feed raw silicon 14 with suitable particle size and silicon content into the graphite crucible 2 in the furnace shell 1 through the feeding hole 11 until it is full. Open the water inlet pipe 8 and the water outlet pipe 12, open the water inlet and outlet control device communicated with the induction coil 3; argon is sent into the inside of the furnace shell 1 through the graphite hollow cathode 10; the intermediate frequency power supply 4 and the graphite anode 16 are respectively opened And the power supply of graphite hollow cathode 10 power supply, adjust the height of graphite hollow cathode 10 to make the plasma arc in normal working condition; Add a certain amount of refining slag 5 prepared in proportion to the upper part of the graphite crucible 2 in the furnace shell 1 from the feeding hole 11; after 2 hours of refining and purification, open the flange seal of the molten silicon outlet hole 13, and tilt the smelting furnace The silicon melt is poured from the molten silicon outlet hole 13 into a mold kept at 1410°C-1544°C, the silicon slag is separated during the gradual cooling process, and polycrystalline silicon ingots are formed, and silicon ingots for solar cells are obtained by cutting and cleaning.

Refining slag 5 plays the role of absorbing impurities and refining and purifying in the smelting process. There are multiple options for refining slag 5. In the present invention, refining slag 5 is a mixture of CaO and SiO ₂ . between. During the entire smelting period, the temperature of the two cooling water inlets shall not exceed 25°C, and the temperature of the outlet water shall not exceed 50°C.

Example of production method: Taking a 0.5-ton plasma intermediate frequency induction furnace as an example, weigh 160 kg of particles with a particle size of 10-25 mm, a Si content of not less than 99.0%, and a sum of impurities of not more than 1.0% (wherein Fe≤0.6%, Al≤0.4 , Ca≤0.4) Industrial silicon is raw material silicon 14, which is added to the graphite crucible 2 in the furnace shell 1 through the feeding hole 11; the valves of the water inlet pipe 8 and the water outlet pipe 12 are opened, and the copper pipe internally connected with the induction coil 3 is opened. Water inlet and outlet control valves; send argon gas into the interior of the furnace shell 1 through the graphite hollow cathode 10: turn on the intermediate frequency power supply to supply power to the induction coil 3, turn on the power supply to the graphite anode 16 and the graphite hollow cathode 10, and adjust the graphite hollow cathode. The height of the cathode 10 is such that the plasma arc 6 at the lower port in the furnace shell 1 is in normal working condition. After 45 minutes, when the raw material silicon 14 in the upper part of the graphite crucible 2 is seen from the observation hole 9 and begins to melt, add 20 kg of granule ≤ 5 mm from the feed hole 11 to the graphite crucible 2, which is made of CaO and _SiO2 . Slag 5, of which CaO accounts for 45%: After refining and purifying at a temperature above 1600°C for 2 hours, open the flange seal of the molten silicon outlet 13, tilt the furnace body, and inject the silicon melt from the molten silicon outlet 13 into the insulation In the casting mold at 1410°C-1544°C, impurities in the silicon melt precipitate and solidify, and the silicon slag is separated. Polycrystalline silicon ingots are formed during the heat exchange cooling process. The silicon ingots are taken out, cut and cleaned, and weighed as 140kg. The ingredients are as follows:

After trimming and slicing, it can be used for solar cells.

Effects and advantages: A production equipment of silicon for solar cells in the present invention—plasma intermediate frequency ingredients Si Al Ca Ti C Fe mn P B content% ≥99.999 0.0002 0.00005 0.00005 0.0001 0.0002 0.0002 0.0001 0.0001

The induction furnace combines the advantages of the plasma furnace and the intermediate frequency induction furnace. _The plasma arc is used to supplement the energy of the induction coil 3, and argon is used as the working gas of the plasma. The partial pressure of O2 and CO in the atmosphere is extremely low, reaching the level of vacuum smelting .

Plasma is a heat source with high energy density, and the temperature in the high-temperature zone can reach thousands or even tens of thousands of degrees, and the atmosphere is controllable. The plasma itself is in an ionized state and has a strong ability to activate surrounding reactants. Therefore, it is not only a clean and ideal high-temperature heat source, but also a direct participant or protector of various physical and chemical reaction processes. These characteristics of high-temperature plasma are of great significance to the polysilicon smelting and refining process, which can accelerate the reaction speed and simplify or shorten the production process.

The refining and purification of silicon used in the production of solar cells by the plasma intermediate frequency induction furnace is completed once in the furnace, so the process is simple. Technology of the present invention is:

  Refining slag

        ↓Metallic silicon → plasma medium frequency induction furnace → directional solidification ingot casting → cutting and cleaning → silicon ingots for solar cells

From the process diagram, we can see the advantages of this process technology: the process is simple, easy to master and operate, so the production equipment can be large-scale, large-scale industrial production can be produced, the product quality is high, the infrastructure investment is small, and the production cost is low.

In terms of process technology, the use of plasma intermediate frequency induction furnace as refining equipment is to give full play to the role of plasma technology in the field of refining and purification. The plasma intermediate frequency induction furnace not only exerts the advantages of high temperature, high heat flux density, energy concentration, and controllable atmosphere of the plasma arc, but also exerts the characteristics of the intermediate frequency induction furnace, such as temperature raising, good heat preservation effect, and good stirring of the molten pool, so that the refining effect be significantly improved.

Under the high temperature and inert atmosphere of the plasma arc, some impurities with low melting point can be volatilized rapidly, thereby improving the refining and purification effect. Compared with ordinary electric arc furnaces and vacuum consumable remelting furnaces, the content of harmful residual elements such as Pb, Ca, Zn, etc. in plasma smelting is less. Plasma intermediate frequency induction furnace is refined and purified with refining slag, which has a remarkable effect of removing O, and can remove S and P at the same time. During the smelting process, the refining slag can transfer B, Fe, Al, etc. in silicon to the slag, which saves the process of removing P and B in vacuum.

Claims (2)

1. A production equipment for silicon used in solar cells, consisting of a furnace shell [1], a graphite crucible [2], a hollow furnace cover [7] connected to a water inlet pipe [8] and a water outlet pipe [12], and an observation hole [9 ], a graphite hollow cathode [10] that allows argon to pass through it, a feeding hole [11], a molten silicon outlet [13], an insulating layer [15] and a graphite anode [16], the furnace shell [1 ] is barrel-shaped, and the opening of the conical graphite crucible [2] is placed upwards inside the furnace shell [1] and its bottom is close to the bottom of the furnace shell [1]. The graphite crucible [2] and the furnace shell The gap between the body [1] is the insulation layer [15]; the hollow furnace cover [7] is sealed on the upper part of the furnace shell [1], and one end of the water inlet pipe [8] and the water outlet pipe [12] is sealed and inserted into the hollow furnace In the cavity of the cover [7] and connected with the cavity, one end of the graphite hollow cathode [10] passes through the middle part of the hollow furnace cover [7] and extends into the furnace shell [1], the observation hole [9] and One end of the feeding hole [11] is respectively sealed through the hollow furnace cover [7] and communicates with the upper part of the furnace shell [1]; the tubular molten silicon outlet hole [13] is obliquely inserted and sealed and fixed on the upper part of the furnace shell [1] In the opening of the furnace, the axial center of the tubular molten silicon outlet hole [13] is the same axis as the round hole that is set on the insulation layer [15] in the furnace shell [1] to allow the molten silicon to flow out, and the inner wall of the tube is evenly bonded. High-purity quartz sand insulation layer, the lower port of the round hole that allows the molten silicon to flow out of the thermal insulation layer [15] in the furnace shell [1] is located on the edge of the upper opening of the graphite crucible [2], and the molten silicon exits the hole The upper port of [13] is higher than its lower port, and the upper port is sealed with a flange plate; one end of the graphite anode [16] passes through the middle of the bottom of the furnace shell [1] and the insulation layer between the bottom of the furnace shell [1] [15] is connected to the bottom of the graphite crucible [2]; it is characterized in that: an induction coil [3] connected to an intermediate frequency power supply [4] is arranged between the inner wall of the furnace shell [1] and the outer wall of the graphite crucible [2]. ]. 2. A method for producing silicon for solar cells. The raw material silicon [14] is added to the furnace shell [1], graphite crucible [2], water inlet pipe [8] and water outlet pipe [14] through the feeding hole [11]. 12] Fixed and connected hollow furnace cover [7], observation hole [9], graphite hollow cathode [10] through which argon gas can pass, molten silicon outlet hole [13], insulation layer [15] and graphite anode [16] ] in the graphite crucible [2] in the furnace shell [1] of the production equipment, open the water inlet pipe [8] and the water outlet pipe [12], adjust the argon to the working pressure and pass through the graphite hollow cathode in an atmospheric pressure state [10] into the space inside the furnace shell [1], turn on the power supply to the graphite hollow cathode [10] and graphite anode [16], adjust the height of the graphite hollow cathode [10] to make the plasma arc [6] in In normal working condition, when the set temperature is above 1600°C, after 30 minutes, when the raw silicon [14] in the graphite crucible [2] starts to melt from the upper part and forms a molten pool, a certain amount of refining compound made of CaO and _SiO2 The slag [5] is added to the upper part of the graphite crucible [2] from the feeding hole [11], wherein the content of one of CaO and _SiO2 is 40%-60%, and the amount of refining slag [5] is the amount of raw silicon added After refining and purifying for 2 hours, open the seal of the molten silicon exit hole [13], tilt the smelting furnace, and inject the silicon melt from the molten silicon exit hole [13] into the heat preservation at 1410°C-1544°C In the casting mold at ℃, the silicon slag is separated during the gradual cooling process, and polycrystalline silicon ingots are formed. After cutting and cleaning, the silicon ingots for solar cells are obtained. , when opening the water inlet pipe [8] and the water outlet pipe [12], open the inlet and outlet water valves communicated with the induction coil [3], and then open the intermediate frequency power supply [4] connected with the induction coil [3].

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