CN101555013A

CN101555013A - Refining method of industrial silicon

Info

Publication number: CN101555013A
Application number: CNA2009101025683A
Authority: CN
Inventors: 吴展平
Original assignee: GUIYANG BAOYUAN YANGGUANG SILICON CO Ltd
Current assignee: GUIYANG BAOYUAN YANGGUANG SILICON CO Ltd
Priority date: 2009-05-18
Filing date: 2009-05-18
Publication date: 2009-10-14

Abstract

The invention relates to a refining method of industrial silicon, in particular to a refining method of industrial silicon used for preparing solar battery silicon materials. Industrial silicon water flowing out from a submerged arc furnace is poured into a silicon water container in a 'tower type' refining furnace containing liquated and specially prepared slag; inert gases, purified gases and processed gases are introduced into the container in sequence under the heating condition; the purified gases and the processed gases are introduced to the bottom part of the silicon water container; after gas introduction and heating are stopped, the cooling speed for refined silicon is controlled and a silicon ingot is taken out after cooling; and a slag layer and the part with high content of metal impurities are cut off and washed by acidic washing water to obtain the industrial silicon. The refining method has the advantages of short production period, low energy consumption, high gas utilization rate and low cost. The product obtained by the refining method can meet the requirements of the solar battery with low cost to the silicon materials.

Description

A kind of refining method of purification of industrial silicon

Technical field:

The present invention relates to a kind of industrial silicon refining method of purification, relate to a kind of industrial silicon method of purification that is used to prepare the solar cell silicon material especially.

Background technology:

In recent years, owing to, make the silicon that can be used as solar cell material to increase sharply to the energy/environmental problem.Purity is the 98-99% industrial silicon, industrial general employing carbon reduction silicon-dioxide is made in large quantities, use for solar cell, the silicon purity of Zhi Zaoing is too low in this way, because of existing plurality of impurities in the industrial silicon, these impurity have a strong impact on its performance and use, need to increase the purification process of removing impurity.

" purification " is meant according to the physicochemical property that form matrix element or impurity element, by the impurity element in the suitable physical chemistry technology removal matrix.Recently a kind of method that has been concerned about be by utilize redox reaction or solidify/metallurgical process of segregation comes the technology of purifying industrial silicon materials.In metallurgical industry, during finishing metal silicon, utilize the segregation coefficient of metallic element to be significantly less than 1 character, can remove metallic impurity by directional freeze.But in the contained impurity of the silicon that is used for solar cell, element, the particularly phosphorus of decision silicon conduction type and the content of boron must strictly be controlled, but, known these elements have the very large segregation coefficient of about 0.35-0.8 respectively, and the solidifying of unidirectional solidification/segregation is purified and come down to not have effect.Therefore, the removal of phosphorus, boron impurity element must be in conjunction with other method.

For the removal of phosphorus, because its saturation vapour pressure at high temperature is far longer than silicon, therefore, under certain high vacuum, the phosphorus volatilization is entered in the gas phase by the method for vacuum melting, can obtain fine phosphor-removing effect.But the high temperature high vacuum needs high energy consumption, thereby has increased cost.

For boron impurity, its boiling point is up to 2550 ℃, and therefore the way by vacuum does not have obvious removal effect yet, but discovers that the oxide compound ratio of boron, phosphorus is easier to enter in the basic slag.Therefore at present the slag of the main method of removing boron by oxidizing gas or oxidisability is oxidized to their oxide compound with boron, or by under comparatively high temps with gas evolution, or with the slag complexing of alkalescence, thereby reach the purpose of purified silicon.

Domestic and international in recent years many researchists are devoted to the research with physical metallurgy method purified silicon.Introducing the main method that the said firm's preparation is used for the solar energy level silicon of photovoltaic production as the people such as Hiroyuki Baba of Japanese Nippon Steel (JFE steel corporation) is: raw material is the Pure Silicon Metal of 99.5% purity, remove boron with the argon plasma oxidation, the vacuum electron beam dephosphorization, remove metallic impurity with the method for directional freeze again, Pure Silicon Metal is purified is the solar energy level silicon of 6N.

The people such as (raghar tronstad) of Norway Elkem company adds liquid oxide compound mixing deslagging agent earlier and removes boron in the silicon liquid of fusing, be ground into particle after solidifying and remove metallic impurity with the pickling wet processing, impurity is removed in fractional condensation in specially designed apparatus for directional solidification again.

A kind of method is also disclosed, wherein melting the silicon and the main component that contain boron is the slag of calcium oxide, when stirring this melted silicon by rotating driving device, oxidizing gas is blown in the melted silicon, thereby by oxidation removal boron (the open NO2003-213345 of Japanese Patent);

As removing the method for low boron by making boron become boron oxide and from melted silicon, volatilizing, also has a kind of method at this, wherein shine the surface of melted silicon with the plasma body of mixed gas, thereby promote the oxidation of boron, this mixed gas is argon gas or the argon gas that adds hydrogen, it contains water vapor, also contains SiO 2 powder (day disclosure NO.4-228414)

All there is certain limitation in main processing method at present, " from Pure Silicon Metal, remove the method and apparatus of boron " and equal using plasma air blowing of Chinese patent CN20061004652 () and electromagnetic induction heating vacuum melting furnace purified silicon as the patent No. 98105942.2, but because the action of plasma scope is little, it is low to be blown into the oxidizing gas utilization ratio, current consumption is big, handle several kilograms of polysilicons and need more than 1 hour, be not suitable for large-scale production.

And the method for passing through metallurgical scheme purifying industrial silicon of suitable scale operation, just like Japanese publication NO.4-228414 and Japanese Patent 3205352, to Japanese publication NO.4-228414, this method is with the surface of the plasma irradiating melted silicon of oxidizing gas, with in the molten silicon impurity duration of contact short, may exist the plasma jet with oxidizing gas have little time with silicon in impurity reaction, the silicon face of just overflowing, thereby in order to reach the purpose of removing impurity, need the long period to feed a large amount of waiting and flow daughter, thereby the manufacturing cost height, the commercialization difficulty.

3205352 disclosed powder silicon-dioxide are joined oxidation in the molten silicon as the oxidisability slag remove impurity in the silicon, still, because the wettability of SiO 2 powder and molten silicon is relatively poor, the viscosity height, so refining effect is limited.

Summary of the invention:

In method by metallurgical scheme purifying industrial silicon, as mentioned above, thereby exist with the surperficial method that makes that boron oxide volatilizees and removed from bath surface of the plasma irradiating melted silicon that contains oxidizing gas, the objective of the invention is to overcome the shortcoming of aforesaid method, overcome the Japanese publication NO.4-228414 surperficial manufacturing cost height that exists of plasma irradiating melted silicon of oxidizing gas, the shortcoming of commercialization difficulty; Overcome Japanese Patent 3205352 usefulness powder silicon-dioxide and make the limited shortcoming of the existing refining effect of slag, a kind of method of effective purified silicon is provided, thereby provides a kind of low cost, high efficiency production to be used for the method for the raw material silicon of solar cell.

The present invention achieves the above object by following measures: (1) the present invention adopts tower purification furnace, on the basis of physical metallurgy method, effectively introduce tower principle of absorption and equipment, with the ratio of the pool depth H of prior art and molten bath inside diameter D is that " silicon water bag " formula external refining equipment of about 1 changes " tower " refining furnace into, by increasing the ratio of pool depth H and molten bath inside diameter D, thereby increase gas, contact between the silicon liquid, lengthening gas-liquid contact time and gas-to-liquid contact course, more abundant effective reaction that has promoted impurity and purified gases in the molten silicon, more effectively purifying industrial silicon.Help fully carrying out of chemical reaction, improve the decreasing ratio of impurity and the quality of silicon, can reduce power consumption, thereby reduce cost; (2) adopt and the diverse special slag of prior art, be used for metallurgical slag ratio with routine, slag of the present invention is not only the alkaline residue of oxidisability, it has the particularly effect of boron, phosphorous oxides of oxide impurity in the strong complexing industrial silicon simultaneously, and can reduce the fusing point and the viscosity of silicon melt, effectively improve impurity reacting dynamics condition in slag and the silicon system, more effectively reduce the content of B in the silicon, P, As; (3) in silicon water, feed rare gas element, purified gases and processing gas successively; (4) stop ventilation heating after, control refined silicon speed of cooling is cooled off.

The refining of taking above-mentioned measure to finish industrial silicon together in conjunction with existing technology is purified, and is met the polysilicon in solar cell.

In sum, characteristics of the present invention are equipped with the impouring of the effusive industrial silicon water of the hot stove in ore deposit in the Sheng silicon water receptacle in the special slag of fused " tower " refining furnace in advance, under heating state, feed rare gas element, purified gases and processing gas successively, purified gases and processing gas feed contains silicon water receptacle bottom, after stopping ventilation and heating, control refined silicon speed of cooling, treat refined silicon cooling back taking-up silicon ingot, cut the high part of molten slag layer and metallic impurity according to a conventional method, with washing the clear product with water behind the high purity acid processing silico briquette.

In method of purification according to industrial silicon of the present invention, described " tower " refining furnace, it comprises body of heater and bell, and heating unit is equipped with the bell cover above bell, be provided with vapor pipe in the bell cover, and vapor pipe links to each other with recovery system with vent gas treatment.The furnace depth of body of heater is 2.5-10 with the diameter of burner hearth ratio; Corresponding consistent with " tower " stove with the aspect ratio that places the container that is used to contain industrial silicon and slag in the body of heater, its ratio is so that equipment should be processed is as the criterion.

In the method for purification according to industrial silicon of the present invention, described heating unit can be the resistive heating mode, also can be the Frequency Induction Heating mode;

In the method for purification according to industrial silicon of the present invention, described rare gas element can be argon gas or nitrogen;

In the method for purification according to industrial silicon of the present invention, described purified gases can comprise water vapour;

Described purified gases is the gas that contains with the composition of assorted element reaction in the melted silicon, and impurity element is iron, aluminium, calcium, comprises boron, carbon, phosphorus etc., can use oxidizing reaction to remove from melted silicon especially.Preferably, this purified gases comprises oxygen, then is the water vapour that wherein contains argon gas.Introduce gaseous tension greater than 0.1MPa, preferably between 0.1-0.3MPa, like this, the bubble that is blown into the processed gas in the molten silicon becomes very thin, fully contact with melted silicon, homodisperse, and, prolonged the residence time of feeding gas in molten silicon by increasing the aspect ratio of containing the silicon container, the more abundant reaction that has promoted impurity and purified gases in the molten silicon effectively, the product of reaction or with the gas mode silicon face of overflowing, or enter in the slag of the purified silicon that adds in advance, purified silicon effectively.

Because purified gases may generate silicon-dioxide with pasc reaction, the generation of silicon-dioxide will increase the viscosity of molten silicon, and speed of response is slowed down, therefore, feeding has the processing gas of reductibility, preferably hydrogen is added to and handles in the gas, thereby improve the effect that reduces melt viscosity.

In the method for purification according to industrial silicon of the present invention, described processing gas comprises argon gas or nitrogen;

In the method for purification according to industrial silicon of the present invention, described processing gas comprises hydrogen;

In the method for purification according to industrial silicon of the present invention, the material of described ventpipe is aluminum oxide, silicon carbide, silicon nitride, graphite;

In method of purification according to industrial silicon of the present invention, silicate and carbonate that described refining slag mainly is basic metal and alkaline-earth metal, its quality is than calcium oxide: sodium oxide: silicon-dioxide=48: 11: 41; In the method for purification according to industrial silicon of the present invention, the refined silicon speed of cooling is 10～20 ℃/h.Method of refining step of the present invention: industrial silicon liquid that (1) comes the hot stove in ore deposit is poured in the Sheng silicon container in the tower refining furnace that molten slag is housed in advance, by heating unit, industrial silicon and slag is remained under the molten state.Wherein type of heating can adopt electromagnetic induction heating, also resistance wire heating; Heating temperature is at 1450-1600 ℃.The industrial silicon water that hot stove comes from the ore deposit contains a large amount of waste heats, when with after tower refining furnace is contained slag in the silicon container and mixed, transmits a part of heat by heating unit, silicon and slag can be remained under the molten state; (2) then,, will rotate ventpipe and drop to the silicon face preheating, feed rare gas element simultaneously, the displacement furnace air by promoting and reducing device.Prevent silicon oxidation; (3) then deployed in advance purified gases is passed into the ventpipe ingress, ventpipe is immersed in the crucible,, ventilate while rotate by rotating driving device; (4) after purified gases feeds certain hour, change processings gas is blown into and melt in the silicon; (5) treat that ventilation is finished after, close the rotation knob, rise the rotation breather, and close source of the gas; (6) controlled chilling speed is treated but back taking-up silicon ingot of silicon liquid cooling, cuts the high part of molten slag layer and metals content impurity; (7) handle the silico briquette of gained with high purity acid, remove the metallic impurity that may have silicon face and the oxide compound of boron, high purity water cleans repeatedly, and silicon is further purified, and is met the polysilicon in solar cell.

Effect of the present invention: technological process of the present invention is simple, make full use of the waste heat of the next industrial silicon of the hot stove in ore deposit, effectively utilize the external refining stove of industrial silicon, after traditional industry silicon purification furnace is made improvements, can carry out the refining of industrial silicon and purify, industrial silicon is purified is polycrystalline silicon used for solar battery.Compared with the prior art: the gas effciency height of feeding, speed of response is accelerated, and shorten reaction time, and reduced melting unit power consumption, cost reduction.The quality product that obtains can satisfy the requirement of low-cost solar battery to the silicon raw material.

Embodiment:

Embodiment 1: the industrial silicon water that the hot stove in 100kg ore deposit is come is poured in the Sheng silicon container in the tower refining furnace that the 20kg molten slag is housed in advance, wherein slag mainly is Calucium Silicate powder powder, water glass powder and calcium carbonate powders, convert it into calcium oxide: sodium oxide: silicon-dioxide=48: 11: 41 (mass ratio), and will add in the plumbago crucible in advance after it mixing.Described tower refining furnace, it comprises body of heater bell and heating unit, and the bell cover is housed above bell, is provided with vapor pipe in the bell cover, vapor pipe links to each other with recovery system with vent gas treatment.The furnace depth of body of heater is 2.5～10 with the diameter of burner hearth ratio; Containing the silicon container is plumbago crucible, and the aspect ratio of plumbago crucible is consistent with tower refining furnace, and it is 6 that present embodiment is selected the aspect ratio of refining furnace for use, and the aspect ratio of plumbago crucible also is 6.Then,, will rotate ventpipe and drop to silicon face, feed argon gas simultaneously, the displacement furnace air by promoting and reducing device.By induction heating, industrial silicon and slag are remained under 1550 ℃.

Then purified gases is passed into the ventpipe ingress, ventpipe is immersed in the crucible, by rotating driving device, while the flow velocity that rotates with 200L/min feeds purified gases, purified gases at first is an oxygen, is the water vapour that wherein contains argon gas then.Introduce gaseous tension and be located at 0.15MPa.Behind the aerating oxygen 40 minutes, change and feed the water vapour 40 minutes contain argon gas, argon gas that then will hydrogeneous 20% (volume ratio) is blown into and melted in the silicon 30 minutes.

After treating that ventilation is finished, close the rotation knob, rise the rotation breather.10～20 ℃/hour of controlled chilling speed are treated but back taking-up silicon ingot of silicon liquid cooling, cut the high part of molten slag layer and metals content impurity; With the silico briquette of high purity hydrochloric acid, hydrofluoric acid elder generation aftertreatment gained, remove the metallic impurity that may have silicon face and the oxide compound of boron, clean repeatedly with high purity water at last, silicon is further purified.

Embodiment 2

Directly compare the effect of feeding gas in order to illustrate tower refining tower height, make with extra care in the mode of similar first example, the aspect ratio 4 of tower refining furnace,, the aspect ratio of plumbago crucible also is 4, and other condition is with embodiment 1, and experimental result sees attached list 1.By experimental result as can be known, the aspect ratio of tower refining furnace is big more, and is good more to the effect of purified silicon.

Embodiment 3

In the present embodiment, change among the embodiment 1 time that feeds purified gases, handles gas, the feeding gas time is long more, and the purity of silicon is high more.Feed purified gases oxygen after 60 minutes, change and feed the water vapour 60 minutes that contains argon gas, argon gas that then will hydrogeneous 20% (volume ratio) is blown into and melted in the silicon 50 minutes.Experimental result sees attached list 1.Experimental result shows that the time that feeds purified gases is long more, and the purity of silicon is high more.

Embodiment 4

In the present embodiment, except changing the amount that adds slag, make with extra care purification in the mode of similar first embodiment, being about to industrial silicon water that the hot stove in 100kg ore deposit comes is poured in the Sheng silicon container in the tower refining furnace that the 10kg melting slag is housed in advance, wherein slag mainly is Calucium Silicate powder powder, water glass powder, calcium carbonate powders, converts it into calcium oxide: sodium oxide: silicon-dioxide=48: 11: 41 (mass ratio).Result of implementation sees attached list 1.From result of implementation as can be seen, the amount that adds the slag of molten silicon also can influence the purity of purified silicon, because the impurity element in the silicon particularly boron phosphorus has a partition ratio in molten silicon and slag, to specific slag, its coefficient is constant in theory, therefore by increasing the quantity of slag, can more effectively remove impurity in the silicon.

Below in conjunction with the embodiments the present invention detailed explanation and explanation have been carried out, but those skilled in the art understand, do not breaking away from the spirit and scope of the invention, any change of the embodiment of the invention, improvement, variant and equivalent are all in the scope of the invention of claims definition.

Subordinate list 1

Title	Si％	Fe(ppm)	Al(ppm)	Ca(ppm)	B(ppm)	P(ppm)
Title	Si％	Fe(ppm)	Al(ppm)	Ca(ppm)	B(ppm)	P(ppm)	Raw silicon	98.6	5000	5000	3000	30	50
Embodiment 1		10	3	3	5	3	Raw silicon	98.6	5000	5000	3000	30	50
Embodiment 1		10	3	3	5	3	Embodiment 2		20	15	10	7	5
Embodiment 3		8	3	2	3	3	Embodiment 2		20	15	10	7	5
Embodiment 3		8	3	2	3	3	Embodiment 4		25	18	12	8	10

Industrial applicibility

According to the present invention, can from industrial silicon, effectively remove impurity, and can be provided for the cheap silicon material of solar cell.

Claims

1. the refining method of purification of an industrial silicon, comprise the pickling and the washing of refined silicon, it is characterized in that the impouring of the effusive industrial silicon water of the hot stove in ore deposit is equipped with in the Sheng silicon water receptacle in " tower " refining furnace of the special slag of fused in advance, under heating state, feed rare gas element, purified gases and processing gas successively, after stopping ventilation and heating, control refined silicon speed of cooling, treat refined silicon cooling back taking-up silicon ingot, cut the high part of molten slag layer and metallic impurity according to a conventional method, with washing the clear product with water behind the high purity acid processing silico briquette.

2. the refining method of purification of a kind of industrial silicon according to claim 1, it is characterized in that the refining purification step is successively: (1) is poured into the industrial silicon water that the hot stove in ore deposit comes in the Sheng silicon container of the tower refining furnace that melting slag is housed in advance, pass through heating unit, industrial silicon and slag are remained under the molten state, promptly remain on 1450-1600 ℃; (2) then, by promoting and reducing device, will rotate ventpipe and drop to the silicon face preheating, and feed rare gas element simultaneously, the displacement furnace air prevents silicon oxidation; (3) then deployed in advance purified gases is passed into the ventpipe ingress, ventpipe is immersed in the crucible,, ventilate while rotate by rotating driving device; (4) after purified gases feeds certain hour, change processings gas is blown in the molten silicon with the slag contact, reduction viscosity is convenient to that oxidative impurities fully contacts in slag and the silicon; (5) treat that ventilation is finished after, close the rotation knob, rise the rotation breather, and close source of the gas; (6) controlled chilling speed is treated but back taking-up silicon ingot of silicon liquid cooling, cuts the high part of molten slag layer and metals content impurity; (7) handle the silico briquette of gained with high purity acid, remove the metallic impurity that may have silicon face and the oxide compound of boron, high purity water cleans repeatedly, and silicon is further purified, and is met the polysilicon in solar cell.

3. the method for refining of a kind of industrial silicon according to claim 1 and 2, wherein: described tower refining furnace, it comprises body of heater and bell, heating unit, the bell cover is housed above bell, is provided with vapor pipe in the bell cover, vapor pipe links to each other with recovery system with vent gas treatment.The furnace depth of body of heater is 2.5～10 with the diameter of burner hearth ratio; Corresponding consistent with " tower " stove with the aspect ratio that places the crucible that is used to contain industrial silicon and slag in the body of heater, its ratio is so that equipment should be processed is as the criterion.

4. the method for refining of a kind of industrial silicon according to claim 1 and 2, wherein: heating unit can be the resistive heating mode, also can be the Frequency Induction Heating mode.

5. the method for refining of a kind of industrial silicon according to claim 1 and 2, wherein: described rare gas element is argon gas or nitrogen.

6. the method for refining of a kind of industrial silicon according to claim 1 and 2, wherein: described purified gases comprises oxidizing gas, preferably oxygen and water vapour.

7. the method for refining of a kind of industrial silicon according to claim 1 and 2, wherein: described processing gas comprises rare gas element, preferred argon gas and nitrogen.

8. the method for refining of a kind of industrial silicon according to claim 1 and 2, wherein: described processing gas comprises reducing gas, and is preferred as hydrogen.

9. the method for refining of a kind of industrial silicon according to claim 1 and 2, the material of its Center Vent tube is aluminum oxide, silicon carbide, silicon nitride, graphite.

10. the method for refining of a kind of industrial silicon according to claim 1 and 2 is characterized in that the refining slag that adds mainly is silicate, the carbonate of basic metal and alkaline-earth metal.Wherein: described refining slag quality proportioning CaO: Na ₂O: SiO ₂=48: 11: 41.