A kind of method and apparatus of directional freeze tailing quick collection purifying polycrystalline silicon
Technical field
The invention belongs to the metallurgy purification technical field, particularly a kind of method and apparatus of tailing taking-out type directional solidification purified polysilicon.
Background technology
The purification of silicon raw material is the important step of photovoltaic industrial chain, and the fast development of photovoltaic industry depends on high-level efficiency, method of purification cheaply.Directional solidification technique has been widely used in the numerous areas of purification of metals, has obtained significant effect.In the process that the silicon raw material is purified, segregation coefficient can to enrichment in the liquid phase, finally be removed in the directional freeze process much smaller than 1 metallic impurity.This method is that present metallurgy method prepares one of key link of solar-grade polysilicon, is the effective means of removing metallic impurity in the polysilicon.The principle of directional freeze is to adopt compulsory means to form the thermograde of specific direction in melt, the position that temperature is lower in the silicon melt becomes at first crystallization nucleation of forming core source, become the starting point of melt solidifying and begin growth, because the existence of unidirectional thermograde, melt is constantly grown along the direction opposite with hot-fluid, the final column crystal with specific orientation that forms.It is to utilize the different solubility of impurity element in melt and solid that directional freeze is purified, the impurity element that segregation coefficient is less in process of setting is discharged from forward position, solid-liquid interface place and enters in the liquid phase, and constantly enrichment in melt, afterbody at ingot casting solidifies at last, the zone excision that ingot casting afterbody impurity concentration is higher, can obtain the ingot casting of low-metal content, and then reach the purpose of purification.
Yet, solidifying latter stage, along with the continuous enrichment of impurity and constantly reducing of melt volume, the concentration of impurity can be more and more higher, and the impurity of high density is retained in the zone of final set.In slow cooling process subsequently, the impurity of area with high mercury can spread to low concentration region, so that silicon purity reduces on the contrary gradually along with the prolongation of soaking time, this has affected refining effect, and in this case, need cut afterbody waste material up to 25% ~ 35%, yield rate only is 65-75%.Simultaneously, because the hardness ratio of silicon is larger, need high-power cutting facility silicon ingot and the high ingot casting tailing of afterbody foreign matter content of purifying could be separated, the method of at present normal operation line cutting and the cutting of diamond saw band is cut, but the cutting facility cost is high, and saw band consumption is large, is unfavorable for the reduction of industrial production cost, at present, domestic rarely seen fruitful method makes things convenient for the removal of tailing.
Summary of the invention
The present invention seeks to as overcoming above deficiency, a kind of method of directional freeze tailing quick collection purifying polycrystalline silicon has been proposed, solidifying latter stage, the graphite bend pipe is stretched among the higher silicon melt of the not solidified foreign matter content in upper strata, the other end extracting vacuum at the graphite bend pipe, the silicon melt that the not solidified foreign matter content in upper strata is high enters in the graphite bend pipe under the effect of pressure difference, entering under the guiding of graphite guide tube among the water-cooled collection box, realize directly separating of impurity enriched district and the HIGH-PURITY SILICON ingot casting that has solidified solidifying ending phase, suppressed the back diffusion of impurity, improve the purity of polysilicon and the yield of ingot casting, reduced process procedure, also proposed in addition the equipment that the method adopts, this equipment is simple, easy and simple to handle, cost is lower, and is beneficial to the high tailing of foreign matter content and is removed quickly and easily.
The technical scheme that adopts for achieving the above object is: a kind of method of directional freeze tailing quick collection purifying polycrystalline silicon is characterized in that: in the protection of inert gas environment, being heated to the silicon material of cleaning fully, fusing is incubated after forming silicon melt; Lower the temperature afterwards, draw ingot vertically downward, carry out directional freeze; Wait to solidify when finishing 85 ~ 90%, stop to draw ingot, the graphite bend pipe is stretched in the not solidified excess silicon melt in upper strata, afterwards with vacuum unit to graphite bend pipe the other end extracting vacuum, the not solidified excess silicon melt in upper strata enters in the graphite bend pipe under the pressure difference effect, and is entering under the guiding of graphite guide tube among the water-cooled collection box; After the not solidified excess silicon melt in upper strata all imports the water-cooled collection box, to cut off the electricity supply, stopped heating solidifies the tailing that is that obtains in the water-cooled collection box, solidify the ingot casting that obtains in the crucible and be the HIGH-PURITY SILICON ingot casting.
The concrete steps of the method that adopts are as follows:
The first step pre-treatment: in crucible, add the silicon material that crucible volume 90 ~ 95% is cleaned, close vent line, open the vacuum pump group, first the vacuum tightness in the vacuum chamber is extracted into 0.01-10Pa, close afterwards the vacuum pump group, open vent line, in vacuum chamber, be filled with rare gas element, reach 500 ~ 10000Pa to pressure, close vent line;
The second step melting, solidify: power-on, utilize ruhmkorff coil and graphite heater that the silicon material in the crucible is heated to 1450 ~ 1650 ℃ to being fused into silicon melt fully, and under this temperature, be incubated 30 ~ 60min, spur vertically downward aqueous cold plate, make silicon melt in the crucible with the speed of 0.1-2mm/min uniform motion vertically downward, draw ingot, silicon melt carries out directional freeze by crucible bottom to the top, when silicon melt is solidified to 85 ~ 90%, stop to draw ingot, the graphite bend pipe is moved down, its lower end extend in the not solidified excess silicon melt in upper strata, open valve, open vacuum unit, the vacuum tightness in graphite bend pipe and the graphite guide tube is evacuated to 1-500Pa, mineralization pressure is poor between graphite bend pipe and graphite guide tube and the vacuum chamber, the not solidified excess silicon melt in upper strata enters the graphite bend pipe under the pressure difference effect, and enters in the cold-crucible under the guiding of graphite guide tube;
The 3rd step aftertreatment: treat that the not solidified excess silicon melt in upper strata all enters cold-crucible, cut off the electricity supply, stopped heating, the tailing that is rich in impurity has just been collected among the cold-crucible, after melting finishes, opens the collection case lid, reclaim tailing, solidifying the ingot casting that obtains in the crucible is the HIGH-PURITY SILICON ingot casting, and its purity will reach 99.99%-99.999%, and yield rate reaches 85-95%.
Described silicon material is industrial silicon, and its purity is 99.0% ~ 99.9%.
Described rare gas element is high-purity argon gas or high-purity helium, and its purity is more than 99.9%.
The equipment that a kind of method of directional freeze tailing quick collection purifying polycrystalline silicon adopts, consist of outer wall by vacuum chamber, vacuum-lines is installed on the outer wall, vacuum-lines one end links to each other with the vacuum pump group, it is characterized in that: be installed with vent line on the outer wall, aqueous cold plate is movably installed in chamber bottom, graphite cake places the aqueous cold plate top, have the hole on the graphite cake, graphite pillar one end is connected by hole and graphite cake are nested, the other end is connected with the graphite pallet is nested, crucible places on the graphite pallet, graphite heater is placed in the crucible periphery and is fixed in the vacuum chamber sidewall, carbon felt insulated tank is placed in outside the graphite heater and is fixed in the vacuum chamber sidewall, have the hole on the carbon felt insulation cover, place carbon felt insulated tank top, ruhmkorff coil is placed in outside the carbon felt insulated tank, and be fixed on the vacuum chamber sidewall, graphite bend pipe upper end is fixedly installed on the expansion link, and its lower end is passed carbon felt insulation cover and is placed central position directly over the crucible, graphite bend pipe upper end open place is tightly connected by junctor and graphite guide tube intermediate openings, graphite guide tube upper end air-tight movable is installed on the vacuum chamber top, its upper end open is tightly connected by valve and vacuum withdraw device, the sealing of water-cooled collection box is fixedly installed on the vacuum chamber sidewall, and graphite bend pipe lower ending opening is connected with water-cooled collection box air-tight movable.
At least 3 in hole on the described graphite cake has draw-in groove on the graphite pallet.
Described graphite bend pipe is sharp mouth graphite bend pipe, and its lower end mouth of pipe is sharp mouth taper.
Described graphite guide tube middle part is installed with expansion link.
On the described water-cooled collection box outer side wall collection case lid is installed
Described vacuum withdraw device adopts the bleed line air-tight movable to be installed on the graphite guide tube upper end open, and vacuum unit is fixedly installed in the other end of bleed line, and vacuumometer is installed on the bleed line.
The unusual effect of the inventive method is: when melt solidifying to impurity phase during to the silicon ingot top of concentrating, utilize the pressure difference tailing that foreign matter content is high to collect in the water-cooled collection box, so just reduced the back diffusion of impurity, improved the yield of ingot casting, yield reaches 85%-95%, reduce the consumption of line cutting and the cutting of diamond saw band, reduced process procedure, reduced energy consumption.
Equipment of the present invention is to increase breather line, graphite bend pipe, graphite guide tube and water-cooled collection box on the basis of original apparatus for directional solidification, scrap build is easy for installation, simple to operate, can effectively remove the impurity of ingot casting afterbody enrichment, the not only recursive use of this tailing collection device, and the tailing amount that can collect is larger, and equipment safety is reliable, save production cycle and cost, be applicable to large-scale industrialization production.
Description of drawings
The equipment synoptic diagram that the method for a kind of directional freeze tailing of Fig. 1 quick collection purifying polycrystalline silicon adopts
Among the figure: (1) graphite bend pipe, (2) vacuum chamber, (3) carbon felt insulation cover, (4) carbon felt insulated tank, (5) ruhmkorff coil, (6) graphite heater, (7) crucible, (8) solidify silicon ingot, (9) graphite pallet, (10) graphite pillar, (11) graphite cake, (12) aqueous cold plate, (13) vent line, (14) vacuum pump group, (15) vacuum-lines, (16) collect case lid, (17) water-cooled collection box, (18) graphite guide tube, (19) junctor, (20) valve, (21) bleed line, (22) expansion link, (23) vacuumometer, (24) vacuum unit
Embodiment
Describe the present invention in detail below in conjunction with specific embodiments and the drawings, but the present invention is not limited to specific embodiment.
Embodiment 1
The equipment that a kind of directional freeze tailing quick collection purifying polycrystalline silicon as shown in Figure 1 adopts, consist of outer wall by vacuum chamber 2, vacuum-lines 15 is installed on the outer wall, and vacuum-lines 15 1 ends link to each other with vacuum pump group 14, and the vacuum pump group is used for the vacuum chamber extracting vacuum.
Be installed with vent line 13 on the outer wall, vent line is used for vacuum chamber is filled with gas, such as rare gas element etc., aqueous cold plate 12 is movably installed in vacuum chamber 2 bottoms, aqueous cold plate can be according to speed rising or the decline set under the effect of leading screw and motor, graphite cake 11 places the aqueous cold plate top, have 4 holes on the graphite cake 11, graphite pillar 10 1 ends are by hole and 11 nested connections of graphite cake, the other end and 9 nested connections of graphite pallet, have draw-in groove on the graphite pallet, be beneficial to the graphite pillar and be connected with the nested of its.
Crucible 7 places on the graphite pallet 9, graphite heater 6 is placed in the crucible periphery and is fixed in vacuum chamber 2 sidewalls, carbon felt insulated tank 4 is placed in outside the graphite heater 6 and is fixed in vacuum chamber 2 sidewalls, have the hole on the carbon felt insulation cover 3, place carbon felt insulated tank 4 tops, ruhmkorff coil 5 is placed in outside the carbon felt insulated tank 4, and is fixed on vacuum chamber 2 sidewalls.
Graphite bend pipe 1 upper end is fixedly installed on the expansion link 22, and its lower end is passed carbon felt insulation cover 3 and is placed central position directly over the crucible, graphite bend pipe 1 upper end open place is tightly connected by junctor 19 and graphite guide tube 18 intermediate openings, graphite guide tube upper end air-tight movable is installed on vacuum chamber 2 tops, its upper end open is tightly connected by valve 20 and vacuum withdraw device, 17 sealings of water-cooled collection box are fixedly installed on vacuum chamber 2 sidewalls, and graphite bend pipe 1 lower ending opening is connected with water-cooled collection box 17 air-tight movables.
Graphite bend pipe 1 is sharp mouth graphite bend pipe, and its lower end mouth of pipe is sharp mouth taper, is beneficial to upper strata not solidified afterbody silicon material is collected among the water-cooled collection box
Graphite guide tube 18 middle parts are installed with expansion link 22, are tightly connected by junctor between graphite bend pipe and the graphite guide tube, and rise under the effect of expansion link 22 together and descend.
Be equipped with on water-cooled collection box 17 outer side walls and collect case lid 16, after collecting full tailing in the water-cooled collection box, can open and take out and reclaim tailing after collecting case lid.
Vacuum withdraw device adopts bleed line 21 air-tight movables to be installed on the graphite guide tube upper end open, vacuum unit 24 is fixedly installed in the other end of bleed line, vacuumometer 23 is installed on the bleed line, and this device is used for graphite guide tube and graphite bend pipe extracting vacuum.
Embodiment 2
Adopt embodiment 1 described equipment to get tailing and carry out directional solidification purified polysilicon, at first adding the purity that crucible volume 90% cleans in the crucible 7 is 99.0% silicon material, close vent line 13, open vacuum pump group 15, the vacuum tightness in the vacuum chamber 2 is extracted into 10Pa, close vacuum pump group 14, open vent line, in vacuum chamber 2, be filled with 99.91% argon gas, reach 500Pa to pressure, close vent line;
The second step melting, solidify: power-on, utilize ruhmkorff coil 5 and graphite heater 6 that the silicon material in the crucible 7 is heated to 1450 ℃ to being fused into silicon melt fully, and under this temperature, be incubated 30min, spur vertically downward aqueous cold plate 12, make silicon melt in the crucible 7 with the speed of 2.0mm/min uniform motion vertically downward, draw ingot, silicon melt carries out directional freeze by crucible 7 bottoms to the top, when silicon melt is solidified to 85%, stop to draw ingot, graphite bend pipe 1 is moved down, its lower end extend in the not solidified excess silicon melt in upper strata, open valve 20, open vacuum unit 24, the vacuum tightness in graphite bend pipe and the graphite guide tube 18 is evacuated to 1Pa, mineralization pressure is poor between graphite bend pipe and graphite guide tube and the vacuum chamber 2, the not solidified excess silicon melt in upper strata enters the graphite bend pipe under the pressure difference effect, and enters in the cold-crucible under the guiding of graphite guide tube 18;
The 3rd step aftertreatment: treat that the not solidified excess silicon melt in upper strata all enters cold-crucible, cut off the electricity supply, stopped heating, the tailing that is rich in impurity has just been collected among the cold-crucible, after melting finishes, opens the collection case lid, reclaim tailing, solidifying the ingot casting that obtains in the crucible is the HIGH-PURITY SILICON ingot casting, and its purity will reach 99.99%, and yield rate reaches 85%.
Embodiment 3
Adopt embodiment 1 described equipment to get tailing and carry out directional solidification purified polysilicon, at first adding the purity that crucible volume 92% cleans in the crucible 7 is 99.3% silicon material, close vent line 13, open vacuum pump group 15, the vacuum tightness in the vacuum chamber 2 is extracted into 2Pa, close vacuum pump group 14, open vent line, being filled with purity in the vacuum chamber 2 is 99.96% argon gas, reaches 5000Pa to pressure, closes vent line;
The second step melting, solidify: power-on, utilize ruhmkorff coil 5 and graphite heater 6 that the silicon material in the crucible 7 is heated to 1550 ℃ to being fused into silicon melt fully, and under this temperature, be incubated 45min, spur vertically downward aqueous cold plate 12, make silicon melt in the crucible 7 with the speed of 1.0mm/min uniform motion vertically downward, draw ingot, silicon melt carries out directional freeze by crucible 7 bottoms to the top, when silicon melt is solidified to 86%, stop to draw ingot, graphite bend pipe 1 is moved down, its lower end extend in the not solidified excess silicon melt in upper strata, open valve 20, open vacuum unit 24, the vacuum tightness in graphite bend pipe and the graphite guide tube 18 is evacuated to 200Pa, mineralization pressure is poor between graphite bend pipe and graphite guide tube and the vacuum chamber 2, the not solidified excess silicon melt in upper strata enters the graphite bend pipe under the pressure difference effect, and enters in the cold-crucible under the guiding of graphite guide tube 18;
The 3rd step aftertreatment: treat that the not solidified excess silicon melt in upper strata all enters cold-crucible, cut off the electricity supply, stopped heating, the tailing that is rich in impurity has just been collected among the cold-crucible, after melting finishes, opens the collection case lid, reclaim tailing, solidifying the ingot casting that obtains in the crucible is the HIGH-PURITY SILICON ingot casting, and its purity will reach 99.996%, and yield rate reaches 91%.
Embodiment 4
Adopt embodiment 1 described equipment to get tailing and carry out directional solidification purified polysilicon, at first adding the purity that crucible volume 95% cleans in the crucible 7 is 99.9% silicon material, close vent line 13, open vacuum pump group 14, the vacuum tightness in the vacuum chamber 2 is extracted into 0.01Pa, close vacuum pump group 14, open vent line, be filled with purity in the vacuum chamber 2 and be 99.95% helium, reach 10000Pa to pressure, close vent line;
The second step melting, solidify: power-on, utilize ruhmkorff coil 5 and graphite heater 6 that the silicon material in the crucible 7 is heated to 1650 ℃ to being fused into silicon melt fully, and under this temperature, be incubated 60min, spur vertically downward aqueous cold plate 12, make silicon melt in the crucible 7 with the speed of 0.1mm/min uniform motion vertically downward, draw ingot, silicon melt carries out directional freeze by crucible 7 bottoms to the top, when silicon melt is solidified to 90%, stop to draw ingot, graphite bend pipe 1 is moved down, its lower end extend in the not solidified excess silicon melt in upper strata, open valve 20, open vacuum unit 24, the vacuum tightness in graphite bend pipe and the graphite guide tube 18 is evacuated to 500Pa, mineralization pressure is poor between graphite bend pipe and graphite guide tube and the vacuum chamber 2, the not solidified excess silicon melt in upper strata enters the graphite bend pipe under the pressure difference effect, and enters in the cold-crucible under the guiding of graphite guide tube 18;
The 3rd step aftertreatment: treat that the not solidified excess silicon melt in upper strata all enters cold-crucible, cut off the electricity supply, stopped heating, the tailing that is rich in impurity has just been collected among the cold-crucible, after melting finishes, opens the collection case lid, reclaim tailing, solidifying the ingot casting that obtains in the crucible is the HIGH-PURITY SILICON ingot casting, and its purity will reach 99.999%, and yield rate reaches 95%.