CN101585537A - Method and device for preparing solar-grade silicon - Google Patents
Method and device for preparing solar-grade silicon Download PDFInfo
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- CN101585537A CN101585537A CNA2009100121537A CN200910012153A CN101585537A CN 101585537 A CN101585537 A CN 101585537A CN A2009100121537 A CNA2009100121537 A CN A2009100121537A CN 200910012153 A CN200910012153 A CN 200910012153A CN 101585537 A CN101585537 A CN 101585537A
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Abstract
The invention provides a method for preparing solar-grade silicon. The method comprises an industrial silicon chlorination step, a silicon tetrachloride distillation-purification step, a silicon tetrachloride reduction step and a tail-gas separation step after silicon tetrachloride reduction. The method is characterized in that: (1) the silicon tetrachloride distillation-purification step is completed through a distillation tower of more than two levels, wherein the distillation temperature of a first level is 15 to 25 DEG C, and the distillation temperature after a second level is 60 to 70 DEG C; (2) a zinc vapor purification step consisting of three parts of which the working temperatures are 350 DEG C, 800 DEG C and 950 to 1,000 DEG C respectively is additionally added; (3) the silicon tetrachloride reduction step adopts zinc vapor as a reducing agent and is performed in a fluidized bed at a temperature between 950 and 1,000 DEG C; (4) the tail-gas separation step after silicon tetrachloride reduction is completed through two levels of condensation separator of which the working temperature are 650 to 700 DEG C and 350 to 400 DEG C respectively; and (5) a silicon tetrachloride circulation step is additionally added and is completed through a front segment of heating system and a rear segment of heating system of which the working temperatures are 650 to 700 DEG C and 950 to 1,000 DEG C respectively. The invention also puts forward a device for implementing the method. The invention has the advantages of saving cost and eliminating environmental pollution.
Description
Technical field
The invention belongs to the technical field of the purifying of silicon, specially refer to a kind of with zinc fume reduction silicon tetrachloride to produce the method and apparatus of solar energy level silicon.
Background technology
Solar energy level silicon means that content of impurities is lower than 1ppmw, and purity reaches the HIGH-PURITY SILICON of 6N (being 99.9999wt%), when making solar cell with it, can guarantee to reach needed photoelectric transformation efficiency; And tangible decay can not take place in the life-time service process.
For many years, the method that each major company of the world produces solar energy level silicon mainly is a Siemens Method, i.e. the chemical vapor deposition (CVD) method.The technical process of this method is: the first step generates trichlorosilane or silicon tetrachloride with hydrochloric acid or chlorine with the industrial silicon reaction; Second step was used distillation method purify trichlorosilane or silicon tetrachloride; The 3rd step obtained HIGH-PURITY SILICON at indoor hydrogen reducing trichlorosilane of reduction or silicon tetrachloride.For China, main problem just goes out on the 3rd step reduction reaction, and the one, recovery rate is only about 20%; The 2nd, the not remaining hypertoxic trichlorosilane of complete reaction, silicon tetrachloride and inflammable, the explosive not easily separated and processing of hydrogen.At present, the newly-built how tame large polycrystalline silicon factory of China is all because fail to grasp the core technology of Siemens Method, and consequently environmental pollution is serious and be forced to stop production, and exhausts the people and drains the treasury, and but can not get the benefit of expecting.In recent years, because the promotion of world energy sources crisis, various countries are to the equal pay attention to day by day of photovoltaic industry, thereby make the demand of solar energy level silicon increase sharply, and price is sharply soaring, and high always.The novel method of producing solar energy level silicon of seeking the photovoltaic industry development of more suitable China just seems very important under these circumstances!
U.S. Pat 4,188,368 disclosed the method for preparing HIGH-PURITY SILICON with the sodium reduction silicon tetrachloride; 3310828 of German patent DE are produced HIGH-PURITY SILICON with the aluminium reducing silicon tetrachloride; U.S. Pat 2,773,745; US2,804,377; UA2,909,41 and US3,041,145 all disclosed and directly reduces silicon tetrachloride with zinc fume form the method for HIGH-PURITY SILICON in fluidized-bed reactor; And Chinese patent application case CN1962434A and CN101186299A also disclosed two kinds of methods of equally producing HIGH-PURITY SILICON with zinc fume reduction silicon tetrachloride, only the former using plasma reaction chamber; The latter adopts fluidized-bed.It seems, adopt zinc or other to come instead of hydrogen reduction silicon tetrachloride to prepare HIGH-PURITY SILICON than the more active metallic element of hydrogen, can be than Siemens Method more simple and easy to do and less investment, cost also low, this point has become common recognition.However, but the problem that exists also has a lot, for example: one. how does technical process dispose more reasonable? two. adopt the device of which kind of structure formation? three. choose which type of processing parameter such as temperature, pressure? in fact, these aspects all also have many deeply, careful research work need carry out.
Summary of the invention
The inventor has in depth studied the method for producing solar energy level silicon from theoretical and experiment two aspects, adopt zinc fume to make reductive agent, drawn best technical parameter, and a whole set of device energy-conservation, that solar energy level silicon is produced in zinc reduction that reduce discharging has been proposed on this basis, checking has obtained splendid technique effect by experiment.
The method of producing solar energy level silicon of the present invention comprises industrial silicon chlorinating step, silicon tetrachloride distillation purifying step, silicon tetrachloride reduction step, silicon tetrachloride reduction back tail gas separating step, it is characterized in that:
(1) silicon tetrachloride distillation purifying step is finished by the distillation tower more than the two-stage, and the distillation temperature of the first step is 15～25 ℃; The later distillation temperature in the second stage is 60～70 ℃;
(2) being added with by working temperature in addition is the zinc fume purification step that three parts of 350 ℃, 800 ℃ and 950～1000 ℃ constitute;
(3) adopt zinc fume to make reductive agent in the silicon tetrachloride reduction step, its reduction step is to carry out in 950～1000 ℃ of fluidized-beds in working temperature;
(4) silicon tetrachloride reduction back tail gas separating step is finished by the condensed in two stages separator, and first step condensation separator working temperature is 650～700 ℃, isolates silicon tetrachloride; Second stage condensation separator working temperature is 350～400 ℃, isolates zinc and zinc chloride;
(5) be added with the silicon tetrachloride circulation step in addition, it is finished by forward and backward two sections heating systems, and its leading portion working temperature is 650～700 ℃; The back segment working temperature is 950～1000 ℃.
Because will inevitably contain the muriate of a spot of other impurity element in the industrial silicon tetrachloride of the present invention, its physical properties is as shown in table 1:
Table 1
| Molecular formula | Density (g/cm 3) | Fusing point (℃) | Boiling point (℃) |
| BCl 3 | 1.43 | 107 | 12.5 |
| SiCl 4 | 1.48 | 67.7 | 57.6 |
| PCl 3 | 1.57 | 112 | 76 |
| PCl 5 | 140 | 168 | |
| AlCl 3 | 2.44 | 178 | |
| FeCl 3 | 3.80 | 282 | 375 |
As can be seen from Table 1: the muriate fusing point of these impurity is different with boiling point and silicon tetrachloride.Utilize this physical properties just, silicon tetrachloride distillation purifying of the present invention system adopts the method for low-temperature fractionation, with the first step distillation tower boron chloride evaporation is discharged earlier; With the second stage distillation tower silicon tetrachloride is separated with other muriate then, and further make silicon tetrachloride obtain purifying by later distillation tower.
Because contain impurity such as Pb, Cu, Fe, Sn and Cd in the commercial zinc, three parts of zinc fume purification step of the present invention are respectively:
(1) metallic zinc is heated to about 350 ℃, is incubated 1～2 hour, make low melting point impurity such as Qian, Cadmium carry out liquid-solid separation with zinc powder;
(2) solid zinc in the step (1) is heated to 800 ℃, is incubated 1～2 hour, vacuumize and get rid of residual De Cadmium steam, make cadmium carry out solution-air and separate with zinc liquid;
(3) liquid Zn in the step (2) is heated to 950～1000 ℃ and becomes zinc fume, and enter into silicon tetrachloride zinc reduction step.
The invention allows for a whole set of for implementing the above-mentioned custom-designed device of method of producing solar energy level silicon, it comprises industrial silicon chloridizing unit, silicon tetrachloride distillation tower, silicon tetrachloride zinc reduction reaction chamber, reaction chamber tail gas condensation separator, storage zinc can, it is characterized in that:
(1) silicon tetrachloride distillation tower shell adopts bilayer structure, and its internal layer adopts Monel metal to make, and pressure is 1～2 normal atmosphere in the distillation tower;
(2) have additional the zinc fume purification devices, be made up of with the forward and backward two sections heating tubes that are connected with its top a cylindrical tank, back segment heating tube afterbody is connected to the zinc reduction reaction chamber;
(3) silicon tetrachloride zinc reduction reaction chamber adopts cylindrical fluidisation bed formula structure, except that being mounted with silicon tetrachloride inlet mouth, zinc fume inlet mouth, the import of HIGH-PURITY SILICON grain and tail gas relief outlet respectively, the bottom is mounted with the HIGH-PURITY SILICON relief outlet in addition, the fluidized-bed shell is a bilayer structure, be equipped with heating unit in its interlayer, inwall adopts the Monel metal manufacturing;
(4) reaction chamber tail gas tripping device is made up of the condensed in two stages separator, and its first step condensation separator is designed to cylindrical tank, has three interfaces, and they are connected respectively to zinc reduction chamber, silicon tetrachloride circulation line and second stage condensation separator; Second stage condensation separator also is designed to cylindrical tank, also is mounted with three interfaces, and they are connected respectively to first step condensation separator, storage zinc can and zinc chloride drainer;
(5) storage is mounted with well heater in the zinc can, and tank deck is equipped with in addition sends the zinc fume after the heating into water back in the zinc fume purification devices;
(6) in above-mentioned each device, temperature is made heat-transfer medium at dried nitrogen of the employing below 400 ℃ or thermal oil; Temperature is higher than 600 ℃ employing electrically heated or fused salt heating.
Because the chemical property of zinc is more than more active than hydrogen, can see from the metal activity command table to draw:
K Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H Cu Hg Ag Pt Au event is produced HIGH-PURITY SILICON with zinc instead of hydrogen reduction silicon tetrachloride should be more favourable; And, also prove through contriver's test of many times: as long as temperature is higher than ZnCl
2The following chemical reaction of fusing point (283 ℃) just can finish:
SiCl
4+2Zn＝Si+2ZnCl
2
At this moment, theoretically, its recovery rate can reach 100%; And actual recovery rate also really can be more than 95%.The HIGH-PURITY SILICON that present method is produced is easy to reach the technological standard of solar energy level silicon, and its purity can also surpass and reach higher level more than the 6N, but wants to realize such target, to equipment and peopleware higher requirement will be arranged.
Adopt system of the present invention and device to possess following advantage:
(1) owing to do not need to adopt high-purity hydrogen to make reductive agent, increases the security of operation, also improved the recovery rate of polysilicon;
(2) owing to reduced by 150～200 ℃, conserve energy consumption in a large number than the temperature of hydrogen reduction reaction with the temperature of zinc reduction reaction;
(3) because reaction back tail gas is reclaimed well, make each component that participates in reaction be able to closed cycle, both eliminated environmental pollution, saved production cost again;
(4) traditional Siemens Method then must can be realized with temperature from 1050～1150 ℃ of boiling points (57.6 ℃) that drop to silicon tetrachloride if the silicon tetrachloride that will react in the tail gas of back separates with hydrogen; And the present invention only needs temperature get final product from 950～1050 ℃ of boiling points (732 ℃) that drop to zinc chloride, and both contrast, and calorific loss significantly reduces, so tail gas recycle of the present invention is simple and easy to do, and save energy greatly;
(5) present domestic many producers are from the equipment of external introduction Siemens Method, owing to the core technology that Siemens Method abroad is not provided, so can't solve problem of environmental pollution! Adopt method of the present invention, only need the equipment of Siemens Method is transformed slightly, suitably increase zinc fume purification devices and tail gas tripping device those idle equipment of can vitalizing them, and also can reduce production costs after going into operation; Eliminate environmental pollution.See on this point that the present invention has great application value.
Description of drawings
Fig. 1 is a system flow block diagram of the present invention; Fig. 2 is a zinc reduction fluidized-bed structure synoptic diagram of the present invention; Fig. 3 is tail gas condenser and silicon tetrachloride, zinc circulation line flow process configuration schematic diagram.In above-mentioned each figure, 1 fluidized-bed; 2 shells; 3 inner casings; 4 silicon tetrachloride inlet mouths; 5 zinc fume imports; 6 HIGH-PURITY SILICON grain imports; The outlet of 7 tail gas; 8 heating elements; 9 HIGH-PURITY SILICON discharge gates; 10 HIGH-PURITY SILICON grains; 11 fluidized-bed dividing plates; 12 first step condensation separators; 13 silicon tetrachloride vapor outlet port; 14 second stage condensation separators; 15 storage zinc cans; 16 zinc chloride drainers; 17 silicon tetrachloride circulation lines; 18 zinc fume purification devices.
Embodiment
The present invention is further illustrated and replenish below in conjunction with Figure of description and embodiment.
Elder generation arranges appropriate by Fig. 1 each step just of the present invention (being each technical process) devices needed, and with flange or valve each parts is connected.Usually, the silicon tetrachloride raw material can outsourcing, if there is not source of goods, we also can produce voluntarily, and method is to make industrial silicon and chlorine 300～450 ℃ of reactions.This reaction is thermopositive reaction, and it is low excessively, too high to control speed of reaction, otherwise can generate SiCl
6(low excessively); Si
2Cl
6Si
3Cl
8(too high); In addition, chlorine will dewater, purifying treatment, otherwise, SiCl
4Can decompose after meeting water! Silicon tetrachloride distillation tower more than the two-stage is connected in series with pipeline, and the output tube of last step distillation tower connects reduction chamber (fluidized-bed), and the pressure in the distillation tower is 1～2 normal atmosphere, can regulate by the equational requirement of model moral gas gaseous state.In addition, will store zinc can 15, zinc fume purification devices 18 is connected in series, the output tube of zinc fume purification devices also is connected to the reduction chamber.The reduction chamber has outlet to connect the tail gas tripping device in addition.As shown in Figure 3, the tail gas tripping device is made up of the condensed in two stages separator, two-stage separator serial connection, and wherein, 12 first step condensation separators also have 13 silicon tetrachloride vapor outlet port, and it is connected with the reduction chamber by 17 silicon tetrachloride circulation lines; 14 second stage condensation separators have two outlets, are connected respectively to storage zinc can and 16 zinc chloride (ZnCl by two valves
2) drainer.Storage zinc can bottom is provided with the heating unit that can make the zinc evaporation, and the top also has the output tube that communicates with the zinc fume purification devices except that the input tube that communicates with second stage condensation separator is arranged.
Main device of the present invention is a zinc reduction fluidized-bed, and its structural profile illustrates in Fig. 2.Fluidized-bed main body 1 adopts cylindrical structural, and shell 2 usefulness carbon steels are welded, and inner casing 3 adopts Monel metals to make, and it is upper and lower respectively to be provided with 4 silicon tetrachloride inlet mouths and 5 zinc fume imports; Sidepiece is provided with 6 HIGH-PURITY SILICON grain imports and the outlet of 7 tail gas.What settle between the inside and outside two-layer housing is 8 heating elements, and the top is mounted with 9 HIGH-PURITY SILICON discharge gates, is provided with dividing plate 11, the 10 HIGH-PURITY SILICON grains that load in order to bear in the bed.Be evacuated to 1 * 10 earlier in the fluidized-bed
-2～1 * 10
-3Vacuum valve is closed in holder then, and the zinc fume that feeds silicon tetrachloride again and bring into drying nitrogen is regulated silicon tetrachloride and zinc fume pressure and can be made HIGH-PURITY SILICON grain " boiling " in fluidized-bed, and the HIGH-PURITY SILICON after the reduction is deposited on the surface of silicon grain.Temperature is made heat-transfer medium at dried nitrogen of the employing below 400 ℃ or thermal oil in above-mentioned each device; Temperature is higher than 600 ℃ employing electrically heated or fused salt heating.Consider that each embodiment of the present invention all adopts above-mentioned identical device,, then no longer repeated about the details of above device so when enumerating following each embodiment, only every processing parameter is narrated.
Embodiment 1
Earlier silicon tetrachloride liquid is injected first step distillation tower, temperature is controlled at 15 ℃ in the tower, and the boron chloride volatilization is discharged; And then with the silicon tetrachloride extracting to the distillation tower of the second stage, temperature is controlled at 60 ℃, silicon tetrachloride is converted into gas, in this steam suction third stage distillation tower, continues the silicon tetrachloride of purified gas attitude, stay infusible impurity discharge bottom distillation tower in the distillation tower of the second stage.
Gasiform silicon tetrachloride gas is sent in the fluidized-bed that is filled with the HIGH-PURITY SILICON grain from fluidized-bed top silicon tetrachloride inlet mouth, and zinc fume is then brought in the fluidized-bed by the zinc fume import from bottom to up by nitrogen.Calculate by molar weight, the ratio of silicon tetrachloride and zinc fume is 1: 2.The working temperature of fluidized-bed is 950 ℃, and the HIGH-PURITY SILICON that is generated after both react just can deposit on HIGH-PURITY SILICON grain (as the seed crystal) surface of fluidized-bed.The silicon grain just can increase thereupon, and when the silicon grain increased to a certain degree, the fluidized-bed dividing plate just can regularly overturn; Opening the HIGH-PURITY SILICON discharge gate discharges it; Meanwhile, the HIGH-PURITY SILICON grain that adds some amount by the import of HIGH-PURITY SILICON grain again in the fluidized-bed.The HIGH-PURITY SILICON grain itself is 6N, and also meets the polysilicon technological standard of the relevant 6N level of country fully through test from the HIGH-PURITY SILICON material that discharge gate is discharged.
Method of the present invention can guarantee the recovery rate of reduction reaction basically more than 95%, but time one is long, and fluidized-bed is raised difficult questions and exempted from tail gas and accumulate.Advance tail gas the tail gas condensation separating unit from tail gas outlet row this moment.
Tail gas enters in the tripping device, at first enter first step condensation separator, temperature is dropped to 650 ℃ from 950 ℃, at this moment, zinc (907 ℃ of boiling points) and zinc chloride (732 ℃ of boiling points) all are condensed into liquid, having only silicon tetrachloride is gas, just it can be sent in the fluidized-bed by the silicon tetrachloride circulation line.Circulation line is divided into forward and backward two sections, and front-end temperature is that 650 ℃, back segment temperature are 950 ℃.Remaining zinc and zinc chloride liquid enter in the condensation separator of the second stage, further temperature is reduced to 350 ℃, this moment, zinc was frozen into solid-state (fusing point is 419.4 ℃), and zinc chloride remains liquid (fusing point is 283 ℃), zinc chloride can leach, and solid zinc is sent in the storage zinc can.By being input to again in the reduction chamber after the heating of storage zinc can.Remaining liquid zinc chloride is let alone to flow in the zinc chloride drainer, is cooled to can be used as byproduct behind the solid and sell.
Needed high purity zinc steam among the present invention is by a cover purification system supply of other design.The zinc fume purification devices of this system is made up of with the forward and backward two sections heating tubes that are connected with its top a cylindrical tank, and back segment heating tube afterbody is connected to the zinc reduction reaction chamber.It is divided into three steps in the process of producing: (1) is heated to metallic zinc about 350 ℃, is incubated 1 hour, makes low melting point impurity such as Qian, Cadmium carry out liquid-solid separation with zinc powder; (2) solid zinc in the step (1) is heated to 800 ℃, is incubated 2 hours, vacuumize and get rid of residual De Cadmium steam, make cadmium carry out solution-air and separate with zinc liquid; (3) liquid Zn in the step (2) is heated to 950 ℃ and becomes zinc fume, and pass through the device of zinc fume circulation step, enter into silicon tetrachloride zinc reduction step again.
Processing step is identical with embodiment 1, earlier silicon tetrachloride liquid is injected first step distillation tower, and temperature is controlled at 25 ℃ in the tower, and the boron chloride volatilization is discharged; And then with the silicon tetrachloride extracting to the distillation tower of the second stage, temperature is controlled at 70 ℃, silicon tetrachloride is converted into gas, in this steam suction third stage distillation tower, continues the silicon tetrachloride of purified gas attitude, stay infusible impurity discharge bottom distillation tower in the distillation tower of the second stage.
Gasiform silicon tetrachloride gas is sent in the fluidized-bed that is filled with the HIGH-PURITY SILICON grain from fluidized-bed top silicon tetrachloride inlet mouth, and zinc fume is then brought in the fluidized-bed by the zinc fume import from bottom to up by nitrogen.Calculate by molar weight, the ratio of silicon tetrachloride and zinc fume is 1: 2.The working temperature of fluidized-bed is 1000 ℃, and the HIGH-PURITY SILICON that is generated after both react just can deposit on HIGH-PURITY SILICON grain (as the seed crystal) surface of fluidized-bed.The silicon grain just can increase thereupon, and when the silicon grain increased to a certain degree, the dividing plate that just can regularly overturn was opened the HIGH-PURITY SILICON discharge gate it is discharged; Meanwhile, the HIGH-PURITY SILICON grain that adds some amount by the import of HIGH-PURITY SILICON grain again in the fluidized-bed.The HIGH-PURITY SILICON of being discharged meets national relevant technologies standard.
Method of the present invention can guarantee the recovery rate of reduction reaction basically more than 95%, but time one is long, and fluidized-bed is raised difficult questions and exempted from tail gas and accumulate.Advance tail gas the tail gas tripping device from tail gas outlet row this moment.
Tail gas enters in the tripping device, at first enter first step condensation separator, temperature is dropped to 700 ℃ from 1000 ℃, at this moment, zinc (907 ℃ of boiling points) and zinc chloride (732 ℃ of boiling points) all are condensed into liquid, and having only silicon tetrachloride is gas, just it can be turned back in the fluidized-bed by the silicon tetrachloride circulation line, circulation line is divided into forward and backward two sections, and front-end temperature is that 700 ℃ of back segments are 1000 ℃.Remaining zinc and zinc chloride liquid enter in the condensation separator of the second stage, further temperature is reduced to 400 ℃, this moment, zinc was frozen into solid-state (fusing point is 419.4 ℃), and zinc chloride remains liquid (fusing point is 283 ℃), zinc chloride can leach, and solid zinc is sent in the storage zinc can.By being input in the fluidized-bed again after the heating of storage zinc can.Remaining liquid zinc chloride is let alone to flow in the drainer, is cooled to can be used as byproduct behind the solid and sell.
Needed high purity zinc steam among the present invention is by a cover purification system supply of other design.The zinc fume purification devices of this system is made up of with the forward and backward two sections heating tubes that are connected with its top a cylindrical tank, and back segment heating tube afterbody is connected to the zinc reduction reaction chamber.It is divided into three steps in the process of producing: (1) is heated to metallic zinc about 350 ℃, is incubated 2 hours, makes low melting point impurity such as Qian, Cadmium carry out liquid-solid separation with zinc powder; (2) solid zinc in the step (1) is heated to 800 ℃, is incubated 2 hours, vacuumize and get rid of residual De Cadmium steam, make cadmium carry out solution-air and separate with zinc liquid; (3) liquid Zn in the step (2) is heated to 1000 ℃ and becomes zinc fume, and pass through the device of zinc fume circulation step, enter into silicon tetrachloride zinc reduction step again.
Embodiment 3
Processing step is identical with embodiment 1,2, earlier silicon tetrachloride liquid is injected first step distillation tower, and temperature is controlled at 20 ℃ in the tower, and the boron chloride volatilization is discharged; And then with the silicon tetrachloride extracting to the distillation tower of the second stage, temperature is controlled at 65 ℃, silicon tetrachloride is converted into gas, in this steam suction third stage distillation tower, continues the silicon tetrachloride of purified gas attitude, stay infusible impurity discharge bottom distillation tower in the distillation tower of the second stage.
Gasiform silicon tetrachloride gas is sent in the fluidized-bed that is filled with the HIGH-PURITY SILICON grain from fluidized-bed top silicon tetrachloride inlet mouth, and zinc fume is then brought in the fluidized-bed by the zinc fume import from bottom to up by nitrogen.Calculate by molar weight, the ratio of silicon tetrachloride and zinc fume is 1: 2.The working temperature of fluidized-bed is 975 ℃, and the HIGH-PURITY SILICON that is generated after both react just can deposit on HIGH-PURITY SILICON grain (as the seed crystal) surface of fluidized-bed.The silicon grain just can increase thereupon, and when the silicon grain increased to a certain degree, the dividing plate that just can regularly overturn was opened the HIGH-PURITY SILICON discharge gate it is discharged; Meanwhile, the HIGH-PURITY SILICON grain that adds some amount by the import of HIGH-PURITY SILICON grain again in the fluidized-bed.The HIGH-PURITY SILICON purity of being discharged meets the relevant technological standard of country.
Method of the present invention can guarantee the recovery rate of reduction reaction basically more than 95%, but the time one is long, has a certain amount of tail gas to accumulate in the fluidized-bed unavoidably.Can advance tail gas the tail gas tripping device from tail gas outlet row this moment.
Tail gas enters in the tripping device, at first enter first step condensation separator, temperature is dropped to 670 ℃ from 975 ℃, at this moment, zinc (907 ℃ of boiling points) and zinc chloride (732 ℃ of boiling points) all are condensed into liquid, and having only silicon tetrachloride is gas, just it can be turned back in the fluidized-bed by the silicon tetrachloride circulation line, the silicon tetrachloride circulation line is divided into forward and backward two sections, and front-end temperature is that 670 ℃, back segment are 975 ℃.Remaining zinc and zinc chloride liquid enter in the condensation separator of the second stage, further temperature is reduced to 370 ℃, this moment, zinc was frozen into solid-state (fusing point is 419.4 ℃), and zinc chloride remains liquid (fusing point is 283 ℃), zinc chloride can leach, and solid zinc is sent in the storage zinc can.By being input to again in the zinc fume purification devices after the heating of storage zinc can.Remaining liquid zinc chloride is let alone to flow in the zinc chloride drainer, can be used as byproduct and sell after being cooled to solid.
Needed high purity zinc steam among the present invention is by a cover purification system supply of other design.The zinc fume purification devices of this system is made up of with the forward and backward two sections heating tubes that are connected with its top a cylindrical tank, and back segment heating tube afterbody is connected to the zinc reduction reaction chamber.It is divided into three steps in the process of producing: (1) is heated to metallic zinc about 350 ℃, is incubated 2 hours, makes low melting point impurity such as Qian, Cadmium carry out liquid-solid separation with zinc powder; (2) solid zinc in the step (1) is heated to 800 ℃, is incubated 1 hour, vacuumize and get rid of residual De Cadmium steam, make cadmium carry out solution-air and separate with zinc liquid; (3) liquid Zn in the step (2) is heated to 975 ℃ and becomes zinc fume, and pass through the device of zinc fume circulation step, enter into silicon tetrachloride zinc reduction step again.
Zinc chloride (ZnCl must be replenished a bit
2) itself be a kind of industrial chemicals of having many uses, so in production process of the present invention, sell as byproduct, if but Market Situation when bad, can be with its fusion electrolysis, needed high purity zinc of production technology of the present invention and chlorine, chlorine can be used for producing silicon tetrachloride; Zinc can be made reductive agent and use.So just, can realize the production of " totally-enclosed circulation " formula, though need increase several equipment again, its economic benefit also is expected to improve.
Claims (3)
1. a method of producing solar energy level silicon comprises industrial silicon chlorinating step, silicon tetrachloride distillation purifying step, silicon tetrachloride reduction step, silicon tetrachloride reduction back tail gas separating step, it is characterized in that:
(1) silicon tetrachloride distillation purifying step is finished by the distillation tower more than the two-stage, and the distillation temperature of the first step is 15～25 ℃; The later distillation temperature in the second stage is 60～70 ℃;
(2) being added with by working temperature in addition is the zinc fume purification step that three parts of 350 ℃, 800 ℃ and 950～1000 ℃ constitute;
(3) adopt zinc fume to make reductive agent in the silicon tetrachloride reduction step, its reduction step is to carry out in 950～1000 ℃ of fluidized-beds in working temperature;
(4) silicon tetrachloride reduction back tail gas separating step is finished by the condensed in two stages separator, and first step condensation separator working temperature is 650～700 ℃, isolates silicon tetrachloride; Second stage condensation separator working temperature is 350～400 ℃, isolates zinc and zinc chloride;
(5) be added with the silicon tetrachloride circulation step in addition, it is finished by forward and backward two sections heating systems, and its leading portion working temperature is 650～700 ℃; The back segment working temperature is 950～1000 ℃.
2. by the described method of producing solar energy level silicon of claim 1, it is characterized in that three parts of said zinc fume purification step are respectively:
(1) metallic zinc is heated to about 350 ℃, is incubated 1～2 hour, make low melting point impurity such as Qian, Cadmium carry out liquid-solid separation with zinc powder;
(2) solid zinc in the step (1) is heated to 800 ℃, is incubated 1～2 hour, vacuumize the residual De Cadmium steam ， Shi Cadmium of eliminating and carry out the solution-air separation with zinc liquid;
(3) liquid Zn in the step (2) is heated to 950～1000 ℃ and becomes zinc fume, and enter into silicon tetrachloride zinc reduction step.
3. one kind is the described designed device of method of producing solar energy level silicon of enforcement claim 1 specially, it comprises industrial silicon chloridizing unit, silicon tetrachloride distillation tower, silicon tetrachloride zinc reduction reaction chamber, reaction chamber tail gas tripping device, storage zinc can, it is characterized in that:
(1) silicon tetrachloride distillation tower shell adopts bilayer structure, and its internal layer adopts Monel metal to make, and pressure is 1～2 normal atmosphere in the distillation tower;
(2) have additional the zinc fume purification devices and be made up of with the forward and backward two sections heating tubes that are connected with its top a cylindrical tank, back segment heating tube afterbody is connected to the zinc reduction reaction chamber;
(3) silicon tetrachloride zinc reduction reaction chamber adopts cylindrical fluidisation bed formula structure, except that being mounted with silicon tetrachloride inlet mouth, zinc fume inlet mouth, high-purity zinc granule import and tail gas relief outlet respectively, the bottom is mounted with the HIGH-PURITY SILICON relief outlet in addition, the fluidized-bed shell is a bilayer structure, be equipped with heating unit in its interlayer, inwall adopts the Monel metal manufacturing;
(4) reaction chamber tail gas tripping device is made up of the condensed in two stages separator, and its first step condensation separator is designed to cylindrical tank, has three interfaces, and they are connected respectively to zinc reduction chamber, silicon tetrachloride circulation line and second stage condensation separator; Second stage condensation separator also is designed to cylindrical tank, also is mounted with three interfaces, and they are connected respectively to first step condensation separator, storage zinc can and zinc chloride drainer;
(5) storage is mounted with well heater in the zinc can, and the tank top is equipped with in addition sends the zinc fume after the heating into water back in the zinc fume purification devices;
(6) in above-mentioned each device, temperature is made heat-transfer medium at dried nitrogen of the employing below 400 ℃ or thermal oil; Temperature is higher than 600 ℃ employing electrically heated or fused salt heating.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102616785A (en) * | 2011-10-27 | 2012-08-01 | 内蒙古神舟硅业有限责任公司 | Method for preparing nano-silicon powder particles by reducing silicon tetrachloride with zinc |
| CN102774838A (en) * | 2011-05-12 | 2012-11-14 | 潘凯 | Method for manufacturing high-purity crystalline silicon through zinc reduction process |
| CN108101065A (en) * | 2017-11-29 | 2018-06-01 | 天津中科拓新科技有限公司 | A kind of method for preparing industrial grade silicon tetrachloride |
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2009
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102774838A (en) * | 2011-05-12 | 2012-11-14 | 潘凯 | Method for manufacturing high-purity crystalline silicon through zinc reduction process |
| CN102616785A (en) * | 2011-10-27 | 2012-08-01 | 内蒙古神舟硅业有限责任公司 | Method for preparing nano-silicon powder particles by reducing silicon tetrachloride with zinc |
| CN108101065A (en) * | 2017-11-29 | 2018-06-01 | 天津中科拓新科技有限公司 | A kind of method for preparing industrial grade silicon tetrachloride |
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