WO2014026588A1 - 高球形度籽晶和流化床颗粒硅的制备方法 - Google Patents

高球形度籽晶和流化床颗粒硅的制备方法 Download PDF

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WO2014026588A1
WO2014026588A1 PCT/CN2013/081356 CN2013081356W WO2014026588A1 WO 2014026588 A1 WO2014026588 A1 WO 2014026588A1 CN 2013081356 W CN2013081356 W CN 2013081356W WO 2014026588 A1 WO2014026588 A1 WO 2014026588A1
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silicon
seed crystal
fluidized bed
preparing
granular silicon
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PCT/CN2013/081356
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English (en)
French (fr)
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米克森·大卫
尼兰·克里斯托弗
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江苏中能硅业科技发展有限公司
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Priority to US14/418,790 priority Critical patent/US20150290650A1/en
Priority to KR1020157003480A priority patent/KR101658178B1/ko
Priority to CN201380041563.9A priority patent/CN104540590B/zh
Priority to EP13829331.1A priority patent/EP2883613B1/en
Publication of WO2014026588A1 publication Critical patent/WO2014026588A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C4/00—Crushing or disintegrating by roller mills
    • B02C4/28—Details
    • B02C4/32—Adjusting, applying pressure to, or controlling the distance between, milling members
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C4/00—Crushing or disintegrating by roller mills
    • B02C4/28—Details
    • B02C4/30—Shape or construction of rollers
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
    • B02C23/08—Separating or sorting of material, associated with crushing or disintegrating
    • B02C23/16—Separating or sorting of material, associated with crushing or disintegrating with separator defining termination of crushing or disintegrating zone, e.g. screen denying egress of oversize material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
    • B02C23/18—Adding fluid, other than for crushing or disintegrating by fluid energy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
    • B02C23/18—Adding fluid, other than for crushing or disintegrating by fluid energy
    • B02C23/24—Passing gas through crushing or disintegrating zone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C4/00—Crushing or disintegrating by roller mills
    • B02C4/02—Crushing or disintegrating by roller mills with two or more rollers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C4/00—Crushing or disintegrating by roller mills
    • B02C4/28—Details
    • B02C4/286—Feeding devices

Definitions

  • the invention relates to the technical field of polycrystalline silicon preparation, in particular to a preparation method of a high sphericity seed crystal and a method for continuously producing granular silicon in a fluidized bed reactor by using the foregoing seed crystal.
  • Polysilicon is a key raw material for the photovoltaic power generation industry and the electronic information industry, and is an important product for realizing the national new energy strategy. Since 2005, with the rise and prosperity of the photovoltaic industry, China's polysilicon industry has also experienced leapfrog development. However, in recent years, in the face of the shrinking of the major PV markets in Europe and the launch of the “double-reverse” investigation in Europe and the United States, how to achieve the PV-level price online is the key measure to ensure the continued development of the industry. It is important.
  • methods for preparing polycrystalline silicon include improved Siemens method, metallurgy method, fluidized bed method and the like.
  • the fluidized bed method is a polysilicon preparation process technology developed by United Carbon Chemical Corporation in the early years.
  • the method uses silicon tetrachloride (SiCl 4 ), H 2 , HC1 and industrial silicon as raw materials to form trichlorosilane (SiHCl 3 or TCS) in a high temperature and high pressure fluidized bed (boiling bed), and then SiHCl 3 is further Further disproportionation hydrogenation reaction to form dichlorodihydrosilane (SiH 2 Cl 2 ), followed by disproportionation to form silane, silane or chlorosilane into the addition of granular silicon seed crystal (also known as "silicon seed crystal”), 500 ° C ⁇ 1200
  • a continuous thermal decomposition reaction is carried out in a fluidized bed reactor at a reaction temperature of ° C to produce a granular polycrystalline silicon product.
  • the type of silicon-containing gas introduced into the fluidized bed reactor it is generally classified into a fluidized bed of silane and a fluidized bed of chlorosilane (for example, a fluidized bed of trichlorosilane). Since the surface area of the particulate silicon participating in the reaction in the fluidized bed reactor is large, the method has high production efficiency, low power consumption, and low cost.
  • Another advantage of the fluidized bed process is that during the downstream crystal growth process, the granular silicon can be directly loaded into the crystal growth crucible, but the conventional modified Siemens method produces a rod-shaped polysilicon product that needs to be crushed before being loaded into the crucible.
  • the sorting process also requires a series of processes such as etching with high-purity inorganic acid, washing with ultrapure water, drying, and treatment in a clean environment. Therefore, compared with the modified Siemens method, the fluidized bed process has extremely low energy consumption, high deposition efficiency, and continuous operation. At the same time, the granular silicon product is beneficial for downstream use, which can reduce the manufacturing cost of the silicon wafer, thereby greatly reducing the current photovoltaic cell production. cost.
  • Granular silicon seed crystals are usually prepared by methods such as sieving, grinding, and crushing. For example by using a fluidized bed The prepared granular silicon is screened according to the particle size, the qualified granular silicon is packaged as a product, and the unqualified granular silicon is recycled as a seed crystal into the fluidized bed reactor.
  • the seed crystal is prepared by the screening method. Generally, the large-sized particles are first screened, and the small-sized particles are screened. The utilization rate of the raw materials is low, the raw material processing amount and the seed crystal yield are limited. However, the conventional grinding method is easy to generate dust, which is inconvenient for the separation and subsequent use of the seed crystal.
  • the seed crystal can also be prepared by referring to the method of breaking the silicon rod, but only the seed crystal having a low sphericity can be prepared, that is, the prepared seed crystal is mostly irregular.
  • Such seed crystals are very disadvantageous for fluidized beds because of their irregular fluidization characteristics and reduced minimum fluidization velocity and slug flow velocity. This will result in more spouted particles in the fluidized bed and will also increase bed porosity.
  • the instability of the fluidization and the increased boiling phase will result in a gas phase decomposition of the silicon-containing feed gas (eg, SiHCl 3 , SiH 2 Cl 2 , SiHBr 3 , SiH 2 Br 2 or SiH 4 ) in a free space or homogeneous nucleation mechanism.
  • the silicon-containing feed gas eg, SiHCl 3 , SiH 2 Cl 2 , SiHBr 3 , SiH 2 Br 2 or SiH 4
  • silicon micropowders will clog downstream equipment and piping if not properly removed by filtration.
  • these silicon micropowders are prone to surface contamination due to their large specific surface area, and are easily adsorbed and occluded by the grown silicon particles in the subsequent growth process, resulting in a decrease in the purity of the granular silicon product.
  • the more non-spherical particles will result in a lower minimum fluidization rate during continuous operation than with mostly spherical particles.
  • a dense bed formed of non-spherical particles it is necessary to increase the intake air velocity to initially fluidize.
  • the entire bed is subjected to an irregular high pressure drop until the irregularly shaped particles become "unlocked" and fully fluidized.
  • the porosity of the bed having more non-spherical particles is significantly larger. As mentioned earlier, this will result in the formation of undesirable silicon micropowder.
  • irregular particles have a sharp edge and are more susceptible to formation of unwanted dust by abrasion or friction mechanisms.
  • It is an object of the present invention to provide a method for preparing a high sphericity seed crystal comprising the step of subjecting a granular silicon product prepared by a fluidized bed process as a raw material to roll crushing by a roll device, according to the preparation of the present invention.
  • the seed crystal product prepared has a high sphericity and a narrow particle size distribution.
  • Another object of the present invention is to provide a process for preparing particulate silicon by using the high sphericity seed crystal cycle prepared as described above to enter a fluidized bed reactor.
  • a method for preparing a high sphericity seed crystal comprising the step of subjecting a granular silicon product having a certain particle size distribution range as a raw material to roll crushing by a roll device, characterized in that the roll device comprises at least one set For the roller, by adjusting the gap between the rollers of the pair of rollers, the granular silicon having a size larger than the gap of the roller is broken The fine particles having a size smaller than the gap of the roller pass directly through the gap, thereby preparing a seed crystal having a high degree of sphericity.
  • the granular silicon product may be a granular silicon product prepared by a fluidized bed method, and may be used as a raw material feed for preparing a seed crystal without performing any pretreatment such as sieving, and those skilled in the art can understand that it is from a fluidized bed.
  • the produced granular silicon has a certain particle size distribution range.
  • the raw material for preparing the seed crystal of the present invention may also be prepared by other methods, preferably by a fluidized bed method.
  • the roll gap size X is equal to the median diameter d 5Q of the raw material particle silicon and the median particle diameter D 5 Q of the target seed crystal: 10 ( m ⁇ D 5 Q ⁇ d 5 Q ⁇ X ⁇ 240 ( m , wherein the particle silicon size distribution d p ranges from 100 ⁇ m to 2400 ⁇ m ⁇ .
  • the roll device comprises two sets of counter rolls, the two sets of rolls are placed one above the other, and the granular silicon product as a raw material passes through the upper and lower sets of counter rolls in sequence. More preferably, the gap size X1 of the upper and lower sets of the pair of roll rolls satisfies the relationship X1 ⁇ , where X1 is the gap size between the two rolls located above the roll, and is the two of the rolls located below The size of the gap between the rollers.
  • a method of preparing fluidized bed granular silicon comprising the steps of:
  • the silicon-containing raw material gas and the fluidized gas are continuously thermally decomposed in a fluidized bed reactor with a seed crystal at a reaction temperature of 500 ° C to 1200 ° C, and silicon is deposited on the surface of the seed crystal. Preparation of granular silicon products;
  • the produced granular silicon product is prepared, and a part of the high sphericity seed crystal according to any one of claims 1 to 5 is prepared to obtain a high sphericity granular silicon seed crystal, and is circulated into the fluidized Inside the bed reactor, the number of seed crystals in the fluidized bed is kept stable.
  • the silicon-containing source gas is a silane.
  • the silicon-containing source gas is chlorosilane.
  • the silicon-containing raw material gas is trichlorosilane.
  • a granular silicon product having a certain particle size distribution is used as a raw material, and roll milling and crushing are performed by a roll device, and the roller between the rollers of the roller is adjusted by adjusting the roller device.
  • the void size satisfies ⁇ ⁇ D 50 ⁇ d 50 ⁇ x ⁇ 2400 ⁇ , so that the granular silicon having a size larger than the gap of the roller is broken, and most of the granular silicon having a size smaller than the gap of the roller passes directly and remains intact.
  • the spherical morphology makes most of the seed crystals spherical, resulting in a highly spherical seed crystal.
  • the present invention can also adjust the pore size of the roll device to the roll of the roll according to the particle size distribution of the granular silicon product as a raw material to obtain a seed crystal having a high sphericity of a certain size and a narrow particle size distribution range.
  • a high spherical shape can be obtained by one-time treatment of the roller device
  • the seed crystal is simpler than the screening method. It does not require grading and screening, saving time.
  • the large-size particles can be broken by one-time roll grinding, while the small particles are directly sieved through.
  • the method has a large amount of processing. All are converted into seed crystals, and the utilization rate of raw materials is high. Compared with the grinding method, no fine silicon powder is produced, and the prepared seed crystal has high sphericity and narrow particle size distribution.
  • a seed crystal having a high sphericity and a narrow particle size distribution is prepared and circulated into a fluidized bed reactor, and the seed crystal is favorable for maintaining fluidization.
  • the smooth operation of the bed extends the operating cycle of the fluidized bed.
  • the porosity of the bed is small, which avoids the problems of free space or homogeneous nucleation to form a silt of silicon micropowder to block downstream pipelines or contaminate products.
  • FIG. 1 is a schematic view showing the apparatus for preparing a high sphericity seed crystal of the present invention.
  • FIG. 2 is a schematic view of another preparation apparatus of the high sphericity seed crystal of the present invention.
  • FIG. 3 is a schematic flow chart of a method for preparing a fluidized bed granular silicon and seed crystal of the present invention.
  • Figure 4 is a plot of sphericity versus minimum fluidization velocity.
  • Fig. 5 is a view showing the particle size distribution of the raw material particle silicon of Example 1.
  • Fig. 6 is a schematic view showing the columnar distribution of the particle size distribution of the raw material particles of silicon and seed crystal before and after the roll milling of Example 1.
  • Fig. 7 is a graph showing the particle size distribution curve of the raw material particles of silicon and seed crystal before and after the roll milling of Example 1.
  • Figure 8 is a physical diagram of the silicon of the raw material particles of Example 1.
  • Fig. 9 is a view showing the seed crystal of the raw material particle silicon after the roll crushing in Example 1.
  • Fig. 10 is a schematic view showing the particle size distribution of the raw material particles of silicon and seed crystal before and after the roll milling of Comparative Example 1.
  • Figure 11 is a graph showing the particle size distribution curves of the raw material particles of silicon and seed crystal before and after the roll milling of Comparative Example 1.
  • Figure 12 is a physical diagram of the raw material particle silicon of Comparative Example 1.
  • Fig. 13 is a view showing the seed crystal of the raw material particle silicon after being subjected to roll crushing in Comparative Example 1.
  • Fig. 14 is a view showing the particle size distribution of the seed crystals prepared in Example 1 and Comparative Example 1.
  • 1 is a fluidized bed reactor, 2 granular silicon products, 3 packages, 4 roll type devices, 5 granular silicon finished products, 6 seed crystals, 7, 7' counter rolls.
  • a method for preparing a high sphericity seed crystal wherein the granular silicon product 2 having a certain particle size distribution range is used as a raw material, and the roller device is subjected to roll grinding and crushing, and the roller device comprises at least one pair of rollers, as shown in FIG.
  • the roller device comprises a pair of counter rollers 7, each set of rollers 7 comprising two rollers that rotate in opposite directions.
  • the gap size x between the rolls the granular silicon having a size larger than the roll gap X is ground, and most of the granular silicon having a size smaller than the roll gap is directly passed, due to the prepared seed.
  • the crystal is a mixture of particles which are directly passed through the unbroken particles and the particles after the crushing, wherein the unbroken particles account for a large portion, so that the prepared seed crystal has a high degree of sphericity.
  • the seed crystal can have a relatively narrow particle size distribution range.
  • the sphericity is the ratio of the number of seed crystals having a spherical shape to the total number of seed crystals in the prepared seed crystal, and the larger the proportion of the spherical seed crystals, the larger the sphericity.
  • the roller device can be referred to the prior art, for example, the roller device disclosed in the U.S. Patent No. US20090114748A1, which is composed of at least one pair of oppositely rotating rollers having a hard metal coating such as tungsten carbide. Etc., but not limited to this.
  • the difference is that the patented roller device is used to completely break the silicon rods to obtain small silicon blocks of small difference in size.
  • the present invention is useful for preparing a seed crystal having a high degree of sphericity, and it is necessary to adjust the void size of the roll to the roll according to the particle size distribution range of the raw material, and the raw material particle silicon is crushed by a roll by a roll type device.
  • the particle size distribution of the raw material particles of the roll type device is in the range of ⁇ 2 to 2400 ⁇ m, and the gap size between the two rolls of the roll can be adjusted according to the particle size distribution.
  • the large particles include, but are not limited to, more than 1500 ⁇ m
  • the roll gap can be adjusted to 1500 ⁇ m or less, and the particles of ⁇ to 1500 ⁇ m or less pass through the gap directly, and are not broken, maintaining the original sphericity.
  • the large particles include, but are not limited to, greater than 1250 ⁇ m
  • the roll gap can be adjusted to 1250 ⁇ m or less, and the particles of ⁇ 1250 ⁇ m or smaller are not broken, maintaining the original sphericity.
  • the roll gap X can be adjusted to ⁇ or less, and the particles of 100 ⁇ m to 1000 ⁇ m or less are not broken, maintaining the original sphericity.
  • the roll gap X can be adjusted to 750 ⁇ m or less, and at this time, the particles of ⁇ to 750 ⁇ or less are not broken, and the original sphericity is maintained.
  • the roll gap can be adjusted to 1750 ⁇ m or less, and the particles of 100 ⁇ m to 1750 ⁇ m or less are not broken, and the original sphericity is maintained.
  • the roll gap can be adjusted to 2000 ⁇ m or less, and the particles of ⁇ to 2000 ⁇ m or less are not broken and the original sphericity is maintained.
  • the roll gap X can be adjusted to 2250 ⁇ m or less, and the particles of ⁇ 2250 ⁇ m or less are not broken, maintaining the original sphericity.
  • the roll gap X can be adjusted to 2400 ⁇ m or less, and the particles of ⁇ 2400 ⁇ m or less are not broken, maintaining the original spherical shape.
  • the median diameter of the raw material silicon and the target seed crystal can also be used.
  • D 5Q to adjust the roll gap size x.
  • D 5Q refers to the particle size corresponding to a cumulative particle size distribution percentage of a sample of 50%. Its physical meaning is that the particle size is larger than 50% of its particles, and its particle is also 50%, so generally D 5Q is also called the median diameter or median particle size.
  • the median diameter of the granular silicon having a certain particle size distribution as a raw material is denoted by d 5Q
  • the median diameter of the target seed crystal prepared by roll milling is recorded as D 5Q . .
  • the particle size distribution range and the median diameter of the granular silicon raw material can be determined by detection calculation.
  • the roller gap X and the particle size distribution d p , the median diameter d 5Q of the particulate silicon as a raw material, and the prepared target seed crystal median diameter D 5Q satisfy the following relationship: ⁇ ⁇ D 50 ⁇ d 50 ⁇ x ⁇ 2400 ⁇ , wherein the particle size distribution d p is in the range of ⁇ 2400 ⁇ m, but is not limited thereto, and may be, for example, 50 ⁇ m to 3000 ⁇ m.
  • the particle size distribution range of the granular silicon product collected in the fluidized bed reactor can be calculated by an on-line particle size analyzer, and the median diameter can be calculated, so that the pair can be purposefully adjusted.
  • Roll gap size X Roll gap size X.
  • the adjustment roller gap ⁇ is greater than 1500 ⁇ m, and the particles having a size larger than 1500 ⁇ m are all broken, and the broken silicon is broken.
  • the proportion of particles is less than 50%.
  • most of the silicon particles are not broken directly by the roll device and maintain the original sphericity.
  • the seed crystal prepared at this time is a mixture of unbroken particles and broken particles, but the unbroken particles account for the majority, and thus the prepared seed crystal has a high degree of sphericity.
  • the adjustment roller gap X is larger than the corresponding median diameter, and most of the particles The silicon is directly broken by the roll device, thereby increasing the sphericity of the seed crystal.
  • the roller device comprises two sets of counter rolls 7 and 7', the two sets of counter rolls are placed one above the other, and the granular silicon as a raw material passes through the upper and lower two pairs of rolls in sequence.
  • the upper and lower sets of rollers of the roller gap Xl satisfy the relationship Xl ⁇ , which is positioned on two rollers roll gap, a pair of rollers located two rolls above the gap below.
  • the counter roller located below can be used to finely adjust the particle size range and sphericity of the target seed crystal.
  • the pair of rolls may be further finely adjusted according to the seed target diameter to be prepared, preferably D 5Q ⁇ x 2 ⁇ Xl , but is not limited thereto.
  • the first X needs to be adjusted to 1500 ⁇ ⁇ ⁇ ⁇ 2400 ⁇ , further fine adjustment, if it needs to be adjusted to 800 ⁇ ⁇ ⁇ 2 ⁇ 1500 ⁇ , it can be finely adjusted by the underlying roller roll gap to obtain a seed particle with a narrower particle size distribution range and high sphericity.
  • the roller device may further include more pairs of rollers, such as three groups, four groups, five groups or six groups, but is not limited thereto. This allows the corresponding roller gap to be set and adjusted according to the requirements of the target seed crystal. It is also possible to use several sets of roller devices in series or in parallel to improve the preparation efficiency of the seed crystal.
  • a granular silicon seed crystal for a fluidized bed method is prepared by a roll milling method, which is decomposed by a silicon-containing raw material gas in a fluidized bed reactor 1, and continuously on a silicon seed crystal. Deposition of silicon yields a high purity granular silicon product 2 .
  • a portion of the granular silicon product 2 is obtained through package 3 to obtain a final finished silicon wafer 5.
  • the granular silicon product 2 obtained in the fluidized bed reactor is crushed by a roll device 4 having a set of cylindrical rolls to obtain a seed crystal 6, which reduces the particle size distribution (PSD).
  • PSD particle size distribution
  • the seed crystal 6 particles enter the silicon deposition fluidized bed 1 (FBR) as a recycled material, which produces a granular silicon product by continuous or semi-continuous operation.
  • FBR silicon deposition fluidized bed 1
  • This seeding cycle is important to maintain a constant amount of particles and a constant PSD within the bed, which in turn extends the operating cycle of continuous or semi-continuous operation.
  • the cycle rate (the percentage of the product that circulates into the fluidized bed as a percentage of the product that is ground into the seed crystal), the sphericity of the PSD and the circulating seed crystal, the PSD and sphericity of the initial bed and the deposition rate determine the steady state PSD and The main factor of particle sphericity in fluidized bed. Therefore, it is extremely important to prepare a seed crystal having a narrow particle size distribution and a high sphericity and to circulate into the fluidized bed in a smooth amount to maintain fluidized bed performance and smooth operation. In comparison, existing methods such as sorting and grinding cannot meet this requirement.
  • the above cycle rate is controlled, and a seed crystal having a narrow particle size distribution and a high sphericity is prepared, and the above technical effects can be achieved, thereby realizing long-term stable operation of the fluidized bed reactor.
  • Fig. 4 is a graph showing the relationship between the sphericity of the particles and the minimum fluidization velocity when the seed grain size distribution d 5Q is 850 ⁇ . Among them, the minimum fluidization velocity is calculated by the following equation:
  • the silicon-containing source gas is silane or chlorosilane, more preferably trichlorosilane, but is not limited thereto.
  • it may be silane (SiH4), dichlorosilane (SiH2C12), trichlorosilane (SiHC13), silicon tetrachloride (SiC14), dibromosilane (SiH2Br2), tribromosilane (SiHBr3), silicon tetrabromide (SiBr4). ), diiodosilane (SiH 2 I 2 ), triiodosilane (SiHI 3 ), silicon tetraiodide (SiI 4 ), and mixtures thereof.
  • the silicon-containing source gas may also be disilane (Si2H6), higher silane (SinH2n+2), or the like.
  • the silicon-containing source gas may also be mixed with one or more fluidizing gases, including hydrogen or one or more inert gases selected from the group consisting of nitrogen (N2), hydrazine. (He), argon (Ar), and neon (Ne), etc., can be used to fluidize the bed. Anything not specifically mentioned in the present invention can be referred to the prior art, which is also well known to those skilled in the art.
  • the fluidization rate of the fluidized bed reactor is generally slightly larger than the minimum fluidization velocity Urf, and preferably the fluidization bed has a fluidization velocity of 1.1 Umf ⁇ .OUrf, preferably 1.2 U mf to 2.0 U mf .
  • the particle diameter of the silicon seed particles typically 50 ⁇ 1000 ⁇ , preferably 100 ⁇ 500 ⁇ ; produced a granular polycrystalline silicon product dimensions generally 100 ⁇ 3000 ⁇ , preferably 800 ⁇ 2000 ⁇ .
  • the granular silicon product prepared by the fluidized bed reactor was prepared by a roll apparatus, and its parameter settings are shown in Table 1 below.
  • the roll gap of the upper pair of rolls is 2000 ⁇
  • the roll gap of the lower pair of rolls is 1500 ⁇
  • the granular silicon products with a particle size distribution range of 100 - 2400 ⁇ and a median diameter of 1135 ⁇ are used.
  • a seed crystal having a median diameter of 857 ⁇ m was prepared by roll mill crushing.
  • Fig. 5 is a schematic view showing the particle size distribution of the raw material particle silicon of this embodiment.
  • Fig. 5 shows the particle size distribution of silicon particles and seed crystals before and after roll milling. It can be seen that the large-sized silicon particles are broken into small-sized granular silicon, and the particle size distribution range of the seed crystal is narrowed.
  • a more intuitive response from the percentage curve calculated in Figure 7 shows that the particle size becomes smaller and the proportion of particles of the same size increases.
  • Figures 8 and 9 show physical photographs of granular silicon and seed crystals magnified 13.4 times before and after roll milling.
  • the sphericity of the raw materials before the roller mill is better, but the granular silicon has different sizes and a wide particle size distribution.
  • the obtained seed crystals include most of the unbroken granular silicon and a small portion of the broken granular silicon, and the overall sphericity is relatively high, and the particle size is relatively uniform, as shown in FIG.
  • Example 2 For comparative studies, the silicon particles were all broken by alternate grinding to obtain a similar particle size as in Example 1. The seed crystals in the cloth range are shown in Table 2.
  • Figure 10 is a bar graph showing the particle size distribution of granular silicon and seed crystals before and after grinding. It can be seen that the large particles are all ground to small particles.
  • Figure 1 1 shows the corresponding calculation curve. It is more intuitive to see that the particles above 2400 ⁇ are all ground to below 2000 ⁇ .
  • Figures 12 and 13 show physical pictures of 13.4 times magnification of granular silicon and seed crystals before and after crushing. The raw material particles have a high sphericity and a uniform size. After grinding, the granular silicon is completely broken and the sphericity is low.
  • Figure 14 shows a comparison of Example 1 and Comparative Example 1, from which it can be seen that the seed grain size distribution prepared by the two methods is similar, but the seed crystal morphology prepared by the two methods is extremely different, and the method of the present invention The seed crystal sphericity prepared was much higher than that of Comparative Example 1.
  • the present invention further investigates the porosity of the prepared seed crystals in a fluidized bed reactor.
  • Table 3 shows the fluidized bed of the granular silicon product prepared in the fluidized bed reactor, the seed crystal prepared in Example 1, the seed crystal prepared in Comparative Example 1 in the compact bed and the minimum fluidization rate.
  • Porosity ie the ratio of the void volume between the granular silicon in the bed to the total volume. It can be seen that the seed crystal forming bed prepared by the two methods of the examples and the comparative examples has a higher porosity than the fluidized bed granular silicon product.
  • the porosity of Comparative Example 1 was 19.4% higher than that of the seed crystal prepared in Example 1, but the seed crystal prepared in Example 1 was less different from the granular silicon product, and the porosity was only It is 10.4% higher than the granular silicon product as a seed crystal. Therefore, the seed crystal prepared by the present invention has a lower porosity than the conventional grinding method, and it is easier to avoid the negative influence caused by the formation of the silicon fine powder.

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Abstract

本发明公开了一种高球形度籽晶和流化床颗粒硅的制备方法，其步骤包含，通过辊式装置将流化床法制备的颗粒硅作为原料进行破碎，所述辊式装置包括至少一组对辊，通过调节辊轮之间的空隙，使得大于空隙尺寸的颗粒硅被破碎，小于空隙尺寸的颗粒硅不被破碎，制备得到籽晶产品，并循环进入流化床中参与反应，沉积生成颗粒硅。本发明制备的籽晶具有较窄的粒度分布、高球形度，与低球形度的籽晶相比，其流化床床层具有较小的孔隙率，减少了均相成核生成硅微粉的几率。

Description

高球形度籽晶和流化床颗粒硅的制备方法
技术领域
本发明涉及多晶硅制备技术领域， 具体涉及一种高球形度籽晶的制备方法以及采 用前述籽晶在流化床反应器中连续生产颗粒硅的方法。
背景技术
多晶硅是光伏发电行业和电子信息行业的关键原材料， 是实现国家新能源战 略的重要产品。 自 2005年以来， 随着光伏行业的兴起与繁荣， 中国多晶硅行业也 经历了跨越式的发展。 但近年来， 面对欧洲主要光伏市场的不断萎縮、 欧美相继 发起 "双反" 调查的局面， 如何实现光伏发电平价上网才是保障行业继续发展的 关键举措， 这其中基础原料多晶硅的成本下降至关重要。
目前， 制备多晶硅的方法有改良西门子法、 冶金法、 流化床法等。 流化床法 是美国联合碳化学公司早年研发的多晶硅制备工艺技术。 该方法是以四氯化硅 ( SiCl4)、 H2、 HC1和工业硅为原料， 在高温高压流化床内 （沸腾床） 生成三氯氢 硅（SiHCl3或 TCS ) ,将 SiHCl3再进一步歧化加氢反应生成二氯二氢硅（SiH2Cl2)， 继而歧化生成硅烷，硅烷或氯硅烷通入加有颗粒硅籽晶（也叫做"硅籽晶"）、 500 °C 〜1200 °C的反应温度的流化床反应器内进行连续热分解反应， 生成粒状多晶硅产 品。 按照通入流化床反应器内的含硅气体的种类， 通常分为硅烷流化床和氯硅烷 流化床（例如三氯氢硅流化床）。 由于在流化床反应器内参与反应的颗粒硅表面积 大， 故该方法生产效率高、 电耗低、 成本低。 流化床法的另一优点是： 在下游的 晶体生长过程中， 颗粒硅可以直接装入晶体生长的坩埚中， 但传统的改良西门子 法生产的棒状多晶硅产品在装入坩埚之前需要进行破碎和分选处理， 另外还需要 例如用高纯度无机酸刻蚀、 用超纯水清洗、 干燥以及在干净的环境下处理等一系 列的工艺过程。 因此， 与改良西门子法相比， 流化床法生产过程能耗极低、 沉积 效率高、 能够连续运行， 同时颗粒硅产品利于下游使用， 能够降低硅片制造成本， 从而大幅降低现在的光伏电池生产成本。
对于流化床而言， 维持流化床床层内颗粒的稳态和高球形度对于确保平稳、 连续的 FBR操作和流态化气体固定的进气速度至关重要。 与使用低球形度的颗粒 相比， 高球形度的流态化颗粒有利于增加流化床的最小流态化速度， 同时在需要 采用固定流态化气体进气速度和固定 Ug/U^ft况下， 对于减小反应器直径具有显著 效果。 其中， Ug是流态化气体的超临界速度， 是最小流态化速度。 因此， 制备 出高球形度的籽晶对流化床的性能与长周期稳定运行十分关键。
颗粒硅籽晶通常采用筛分、 研磨、 破碎等方法制备而来。 例如通过将流化床 制备的颗粒硅按照颗粒尺寸筛选， 合格的颗粒硅作为产品包装， 不合格的颗粒硅 作为籽晶循环进入流化床反应器。 利用筛分的方法制备籽晶一般先筛选大尺寸颗 粒， 再筛选小尺寸颗粒， 制备工艺原料利用率低， 原料处理量以及籽晶的产量有 限。 而利用常规的研磨方法则容易产生粉尘， 为籽晶的分离和后续使用造成不便。 还可参考破碎硅棒的方法制备籽晶， 但只能制备出低球形度的籽晶， 即制备的籽 晶大部分为不规则形状。 这种籽晶对于流化床非常不利， 因为其不规则的流态化 特性和减小的最小流态化速度以及段塞流速度。 这将导致流化床层的喷动颗粒更 多， 也会增加床层孔隙率。 流态化的不稳定和增加的沸腾相将导致含硅原料气体 (例如 SiHCl3、 SiH2Cl2、 SiHBr3、 SiH2Br2或 SiH4 )发生自由空间或均相成核机制的 气相分解， 促使副产的亚微米级硅微粉形成。 这些硅微粉如果不被合理地过滤除 去， 将堵塞下游设备和管道。 同时， 这些硅微粉由于具有较大的比表面积， 容易 发生表面污染， 在后续的生长过程中容易被长大的硅颗粒吸附包藏， 造成颗粒硅 产品的纯度降低。
此外， 在连续操作过程中， 与使用多数为球形的颗粒相比， 非球形颗粒越多 将导致最小流态化速度越低。 对于非球形颗粒形成的致密床层， 需要提高进气速 度来初始流态化。 同时， 整个床层遭受不规则的高压降直到不规则形貌的颗粒变 成 "解锁" 状态， 实现完全流态化。 与较多球形颗粒构成的床层相较， 一旦达到 流态化状态， 具有较多非球形颗粒构成床层的孔隙率明显偏大。 如前所述， 这将 导致形成不希望看到的硅微粉。 通常， 不规则的颗粒因为具有尖锐的边缘， 更容 易通过磨蚀或摩擦机制形成不想要的粉尘。 因此， 为避免前述负面因素， 仍旧需 要一种能够制备出高球形度籽晶的方法， 工艺简单， 能满足工业化大批量生产， 又不产生粉尘， 得到的籽晶具有较窄的粒度分布范围。
发明内容
本发明的目的是提供一种制备高球形度籽晶的方法， 包括将流化床法制备得到 的颗粒硅产品作为原料， 通过辊式装置对其进行辊式破碎的步骤， 根据本发明的制备 方法， 所制备的籽晶产品球形度高、 粒度分布窄。
本发明的另一目的是提供一种利用前述制备的高球形度籽晶循环进入流化床 反应器制备颗粒硅的方法。
为了实现上述目的和技术效果， 本发明采用如下的技术方案：
一种高球形度籽晶的制备方法， 包括将具有一定粒度分布范围的颗粒硅产品作为 原料， 通过辊式装置对其进行辊式破碎的步骤， 其特征在于所述辊式装置包括至少一 组对辊， 通过调节对辊的辊轮之间的空隙， 使得尺寸大于所述辊轮空隙的颗粒硅被破 碎， 尺寸小于所述辊轮空隙的颗粒硅直接通过空隙， 从而制备出高球形度的籽晶。 所 述颗粒硅产品可以是流化床法制备的颗粒硅产品， 无需进行任何筛分等预处理即可作 为制备籽晶的原料进料， 本领域技术人员可以理解的是， 从流化床中采出的颗粒硅具 有一定粒度分布范围。 当然本发明制备籽晶的原料也可以是其他方法制备的， 优选流 化床法制备的。
在一个优选的实施方案中，所述辊轮空隙尺寸 X与原料颗粒硅的中位粒径 d5Q以及 目标籽晶的中位粒径 D5Q满足以下关系： 10( m < D5Q< d5Q< X < 240( m， 其中颗粒硅尺 寸分布 dp的范围为 100μιη〜2400μιη。
在一个优选的实施方案中， 所述辊式装置包括两组对辊， 所述两组对辊上下放置， 作为原料的颗粒硅产品依次通过上下两组对辊。 更为优选地， 所述上下两组对辊辊轮 的空隙尺寸 Xl、 满足关系式 Xl≥ ， 其中 Xl为位于上方对辊的两个辊轮间的空隙尺 寸， 为位于下方对辊的两个辊轮间的空隙尺寸。
本发明的另一方面， 一种流化床颗粒硅的制备方法， 包括以下步骤：
1 )含硅原料气体和流态化气体在加有籽晶的流化床反应器内，于 500°C〜1200°C 的反应温度下进行连续的热分解反应， 并在籽晶表面沉积硅制备颗粒硅产品；
2) 所述制备的颗粒硅产品采出后一部分包装作为最终产品；
3 )所述采出的颗粒硅产品采出后一部分经权利要求 1-5任一项所述的高球形度籽 晶的制备方法制备得到高球形度的颗粒硅籽晶， 并循环进入流化床反应器内部， 维持 流化床床层籽晶数量稳定。
其中， 所述含硅原料气体选自 SiHaXb， 其中， X=F、 Cl、 Br、 I， a、 b各自独立 选自 a =0〜4、 b=0〜4， 且 a+b=4。
在一个优选的实施方案中， 所述含硅原料气体为硅烷。
在另一个优选的实施方案中， 所述含硅原料气体为氯硅烷。 优选地， 所述含硅原 料气体为三氯氢硅。
根据本发明的高球形度籽晶的制备方法， 以具有一定粒度分布的颗粒硅产品作 为原料， 通过辊式装置进行辊磨、 破碎， 通过调节所述辊式装置对辊的辊轮之间的空 隙尺寸满足 ΙΟΟμιη < D50<d50< x <2400μιη,使得尺寸大于所述辊轮空隙的颗粒硅被破碎， 而绝大部分尺寸小于所述辊轮空隙的颗粒硅直接通过并保持原有的球形形貌， 从而使 得大多数籽晶均为球形， 得到高球形度的籽晶。 本发明还可以根据作为原料的颗粒硅 产品的粒度分布来调节辊式装置对辊辊轮的孔隙尺寸， 以得到一定尺寸和较窄粒度分 布范围的高球形度的籽晶。
根据本发明的高球形度籽晶的制备方法， 通过辊式装置一次处理即可得到高球形 度的籽晶， 与筛分的方法相比， 工艺较为简单， 无需分级筛选， 节约时间， 一次性辊 磨即可将大颗粒破碎， 而小颗粒直接筛分通过， 该方法处理量大， 原料全部转化为籽 晶， 原料利用率高。 与研磨的方法相比， 不产生细硅粉， 制备的籽晶球形度高、 粒度 分布窄。
根据本发明的高球形度籽晶和流化床颗粒硅的制备方法， 制备的高球形度、 粒度 分布窄的籽晶， 循环进入流化床反应器中， 这种籽晶有利于维持流化床平稳操作， 延 长了流化床的运行周期。 同时， 床层的孔隙率较小， 避免了自由空间或均相成核形成 硅微粉带来的堵塞下游管道或污染产品等问题。
附图说明
图 1是本发明的高球形度籽晶的制备装置示意图。
图 2是本发明的高球形度籽晶的另一制备装置示意图。
图 3是本发明的流化床颗粒硅及籽晶的制备方法流程示意图。
图 4是球形度与最小流态化速度的关系曲线。
图 5是实施例 1的原料颗粒硅的粒度分布示意图。
图 6是实施例 1辊磨前后原料颗粒硅与籽晶的粒度分布柱形示意图。
图 7是实施例 1辊磨前后原料颗粒硅与籽晶的粒度分布曲线示意图。
图 8是实施例 1原料颗粒硅的实物图。
图 9是实施例 1原料颗粒硅经辊式破碎后的籽晶实物图。
图 10是对比例 1辊磨前后原料颗粒硅与籽晶的粒度分布柱形示意图。
图 11是对比例 1辊磨前后原料颗粒硅与籽晶的粒度分布曲线示意图。
图 12是对比例 1原料颗粒硅的实物图。
图 13是对比例 1原料颗粒硅经辊式破碎后的籽晶实物图。
图 14是实施例 1与对比例 1制备籽晶的粒度分布示意图。
其中， 1为流化床反应器、 2颗粒硅产品、 3包装、 4辊式装置、 5颗粒硅成品、 6 籽晶、 7、 7' 对辊。
具体实施方式：
下面结合附图对本发明的具体实施方式进行详细说明， 但是， 必需说明的是， 本 发明的保护范围并不受这些具体实施方式的限制， 具体实施方式中所涉及的具体装置 装配及参数设置是为说明本发明而列举在本具体实施方式中， 并不是对本发明的任何 限制。 本发明所保护的范围， 由权利要求书确定。
一种高球形度籽晶的制备方法， 将具有一定粒度分布范围的颗粒硅产品 2作为原 料， 通过辊式装置 4进行辊磨破碎， 所述辊式装置包括至少一组对辊， 如图 1所示， 所述辊式装置包括一组对辊 7，每组对辊 7包括两个相向转动的辊轮。通过调节所述辊 轮之间的空隙尺寸 x，使得尺寸大于所述辊轮空隙 X的颗粒硅被磨碎，而大部分尺寸小 于所述辊轮空隙的颗粒硅则直接通过， 由于制备的籽晶是直接通过而未被破碎的颗粒 与破碎后颗粒的混合物， 其中， 未被破碎的颗粒占大部分， 从而制备出的籽晶具有较 高的球形度。
通常，流化床中采出的颗粒硅产品的颗粒尺寸范围 dp从 100μηι〜2400μηι不等，但 不限于此， 具有较宽的粒度分布范围。而通过调节所述辊轮空隙 χ， 就可以实现籽晶具 有比较窄的粒度分布范围。 在本发明中， 球形度即所制备籽晶中形貌为球形的籽晶数 量占总籽晶数量的比例， 球形籽晶数量占比越多， 球形度越大。
所述辊式装置可参考现有技术， 例如瓦克公司专利 US20090114748A1中公开的辊 式装置， 由相向转动的至少一组对辊构成， 所述对辊表面具有硬质金属涂层， 例如碳 化钨等， 但不限于此。 不同的是该专利的辊式装置用于将硅棒全部破碎， 得到大小差 不多的小硅块。 但本发明用于制备高球形度的籽晶， 需要根据原料的粒度分布范围调 节对辊辊轮的空隙尺寸， 所述原料颗粒硅通过辊式装置， 被辊式破碎。
在具体的实施方式中， 所述辊式装置的原料颗粒硅粒度分布范围为 ΙΟΟμηι 〜2400μηι， 可根据颗粒尺寸分布调节对辊的两个辊轮间的空隙尺寸。 当大颗粒包括但 不限于大于 1500μηι时，可通过调节辊轮空隙 χ为 1500μηι或更小，此时 ΙΟΟμηι〜1500μηι 或更小的颗粒直接通过空隙， 不被破碎， 保持原有的球形度。 当大颗粒包括但不限于 大于 1250μηι时， 可通过调节辊轮空隙 χ为 1250μηι或更小， 此时 ΙΟΟμηι 〜1250μηι或 更小的颗粒不被破碎， 保持原有的球形度。 当大颗粒包括但不限于大于 ΙΟΟΟμηι 时， 可通过调节辊轮空隙 X为 ΙΟΟΟμηι或更小， 此时 100μηι〜1000μηι或更小的颗粒不被破 碎， 保持原有的球形度。 当大颗粒包括但不限于大于 750μηι时， 可通过调节辊轮空隙 X为 750μηι或更小， 此时 ΙΟΟμηι〜750μηι或更小的颗粒不被破碎， 保持原有的球形度。 当大颗粒包括但不限于大于 1750μηι时， 可通过调节辊轮空隙 χ为 1750μηι或更小，此 时 100μηι〜1750μηι或更小的颗粒不被破碎， 保持原有的球形度。 当大颗粒包括但不限 于大于 2000μηι时， 可通过调节辊轮空隙 χ为 2000μηι或更小， 此时 ΙΟΟμηι 〜2000μηι 或更小的颗粒不被破碎， 保持原有的球形度。 当大颗粒包括但不限于大于 2250μηι时， 可通过调节辊轮空隙 X为 2250μηι或更小， 此时 ΙΟΟμηι〜2250μηι或更小的颗粒不被破 碎， 保持原有的球形度。 当大颗粒包括但不限于大于 2400μηι 时， 可通过调节辊轮空 隙 X为 2400μηι或更小， 此时 ΙΟΟμηι〜2400μηι或更小的颗粒不被破碎， 保持原有的球 形度。
为进一步提高所制籽晶的球形度， 还可以根据原料颗粒硅和目标籽晶的中位粒径 D5Q来调节对辊空隙尺寸 x。 通常， D5Q是指一个样品的累计粒度分布百分数达到 50% 时所对应的粒径。它的物理意义是粒径大于它的颗粒占 50%， 小于它的颗粒也占 50%， 因此一般 D5Q也叫中位径或中值粒径。而在本发明中， 为便于区分， 作为原料的具有一 定颗粒尺寸分布的颗粒硅的中位粒径记为 d5Q， 而通过辊磨破碎制备的目标籽晶的中位 粒径记为 D5Q。 当制备籽晶的原料确定时， 该颗粒硅原料的粒度分布范围及中位粒径即 可通过检测计算确定。 在本发明中， 优选地， 所述辊轮空隙 X与作为原料的颗粒硅的 颗粒尺寸分布 dp、中位粒径 d5Q以及制备的目标籽晶中位粒径 D5Q满足以下关系： ΙΟΟμηι < D50<d50< x <2400μηι, 其中颗粒尺寸分布 dp的范围为 ΙΟΟμηι〜2400μηι， 但不限于此， 例如还可以为 50μηι〜3000μηι。本领域技术人员熟知的是，可通过在线的粒度分析仪分 析计算出流化床反应器中采出的颗粒硅产品的粒度分布范围， 并计算出中位粒径， 如 此可以有目的地调节对辊空隙尺寸 X。
在具体的实施方式中， 粒度分布范围为 100μηι〜2400μηι的原料颗粒硅的中位粒径 为 1500μηι时， 调节辊轮空隙 χ大于 1500μηι， 则尺寸大于 1500μηι的颗粒全被破碎， 且被破碎的硅颗粒占比小于 50%。 此时大部分硅颗粒直接通过辊式装置未被破碎且保 持原有的球形度。 此时制备的籽晶为未被破碎的颗粒与破碎颗粒的混合物， 但未被破 碎的颗粒占大多数， 因此所制备的籽晶具有较高的球形度。 以此类推， 当所述颗粒硅 的中位粒径还可以为 1250μηι、 750μηι、 1750μηι、 2000μηι、 2250μηι等， 但不限于此， 调节辊轮空隙 X大于相应的中位粒径， 则大部分颗粒硅直接通过辊式装置而未被破碎， 从而提高所制籽晶的球形度。
在一个优选的实施方案中， 如图 2所示， 所述辊式装置包括两组对辊 7和 7'， 所 述两组对辊上下放置， 作为原料的颗粒硅依次通过上下两组对辊。 更为优选地， 所述 上下两组对辊的辊轮空隙 Xl、 满足关系式 Xl≥ ，其中 为位于上方的对辊两个辊轮 空隙， 为位于下方的对辊的两个辊轮空隙。 位于下方的对辊可用于精细调节目标籽 晶的粒度范围和球形度。 例如可以根据需要制备的籽晶目标直径进一步细调所述对辊 尺寸 ， 优选为 D5Q< x2 < Xl， 但不限于此。 例如当作为制备籽晶的原料硅颗粒的中位 粒径 d5Q为 1500μηι， 所需制备籽晶的目标中位粒径 D5G为 800μηι时， 按照上述描述首 先 X 需调节至 1500μηι < Χι<2400μηι, 进一步细调 ， 则 需调节至 800μηι < χ2 <1500μηι, 则可以通过下方的对辊辊轮空隙精细化调节， 得到更窄粒度分布范围且具 有高球形度的籽晶颗粒。 可以理解的是， 在籽晶制备过程中， 所述辊式装置还可以包 括更多的对辊， 比如三组、 四组、 五组或六组， 但不限于此。 这可根据目标籽晶的要 求进行设置和调节相应的辊轮空隙。 还可以几组辊式装置串联或并列使用， 提高籽晶 的制备效率。 另一方面， 如图 3所示， 采用辊磨的方法制备用于流化床法的颗粒硅籽晶， 在流 化床反应器 1 中通过含硅原料气体分解、 并在硅籽晶上不断沉积硅得到高纯颗粒硅产 品 2。 一部分颗粒硅产品 2通过包装 3得到最终颗粒硅成品 5。 为了制备籽晶， 流化床 反应器得到的颗粒硅产品 2被具有一组圆柱形辊的辊式装置 4破碎，得到籽晶 6，减小 了颗粒尺寸分布 （PSD)。 籽晶 6颗粒作为循环物料进入硅沉积流化床 1 (FBR), 其通 过连续或半连续操作采出颗粒硅产品。 这一籽晶循环过程对于维持床层内部颗粒数量 和 PSD恒定非常重要， 进而可延长连续或半连续操作的运行周期。 因为当反应器内的 颗粒硅表面发生硅沉积不断长大时， 颗粒的直径和球形度不断增加。 而循环率 （循环 进入流化床的籽晶占被辊磨成籽晶的产品百分比）、 PSD和循环籽晶的球形度， 初始床 层的 PSD和球形度和沉积速率是决定稳态 PSD和流化床床层颗粒球形度的主要因素。 因此， 制备得到窄粒度分布且高球形度的籽晶并以平稳的数量循环进入流化床对于维 持流化床性能和平稳操作极为重要。 相比较而言， 现有的分选、 研磨等方法均无法满 足该要求。 只有通过本发明辊磨的方法， 控制上述循环率、 制备得到窄粒度分布、 高 球形度的籽晶， 即可实现上述技术效果， 从而实现流化床反应器的长周期稳定运行。
此外， 籽晶的球形度越高， 则流化床反应器的最小流态化速度越大。 图 4是籽晶 粒度分布 d5Q为 850μηι时颗粒球形度与最小流态化速度的关系曲线。 其中， 最小流态 化速度 通过下面的方程计算而来：
Figure imgf000009_0001
从图 4可以看出， 随着籽晶颗粒球形度的增大， 其作为流化床床层的最小流态化 速度 也逐渐增大。 在需要采用固定流态化气体进气速度和固定 Ug/Umf情况下， 对 于减小流化床反应器直径具有显著效果。
本发明中， 所述含硅原料气体选自 SiHaXb， 其中， X=F、 Cl、 Br、 I， a、 b各自 独立选自 a =0〜4、 b=0〜4， 且 a+b=4。 优选为， 所述含硅原料气体为硅烷或氯硅烷， 更 优选为三氯氢硅， 但不限于此。 例如可以为硅烷 （SiH4)、 二氯硅烷 （SiH2C12)、 三氯 硅烷 （SiHC13 )、 四氯化硅 （SiC14)、 二溴硅烷 （SiH2Br2)、 三溴硅烷 （SiHBr3 )、 四 溴化硅（SiBr4)、 二碘硅烷（SiH2I2)、 三碘硅烷（SiHI3 )、 四碘化硅（SiI4)及其混合 物。 本领域技术人员可以理解的是， 所述含硅原料气体还可以是乙硅烷 （Si2H6)、 高 级硅烷 （SinH2n+2) 等等。 所述含硅原料气体也可以与一种或多种流态化气体混合， 所述流态化气体包括氢气或选自如下气体中的一种或多种惰性气体， 如氮 （N2)、 氦 (He)、 氩 （Ar)、 以及氖 （Ne) 等， 可用于使床层流态化。 在本发明中没有特别述及之处均可参考现有技术， 这也是本领域技术人员所熟知 的。 例如籽晶循环进入流化床的操作、 流化床采出颗粒硅产品、 产品分选包装等， 这 都不是本发明的创新所在。 此外， 所述流化床反应器的流态化速度一般略大于最小流 态化速度 Urf, 优选流化床的流态化速为 1.1 Umf ^.OUrf, 优选 1.2 Umf〜2.0Umf。 所述 颗粒硅籽晶的粒径通常在 50〜1000μηι， 优选 100〜500μηι; 而生产出的粒状多晶硅 产品的尺寸通常 100〜3000μηι， 优选 800〜2000μηι。
下面通过几个具体的实施例进一步说明本发明的技术效果， 但对本发明并不构成 任何限制， 仅仅用于解释本发明。
实施例 1
采用流化床反应器制备的颗粒硅产品通过辊式装置制备籽晶，其参数设置如下表 1 所示。 通过采用上下两组对辊， 其中上方对辊的辊轮空隙为 2000 μηι， 下方对辊的辊 轮空隙为 1500 μηι， 将粒度分布范围为 100 - 2400μηι、 中位粒径为 1135μηι的颗粒硅产 品通过辊磨破碎制备出中位粒径为 857μηι的籽晶。
表 1 实施例 1实验数据
进料速度 250 lb/h
上方对辊空隙尺寸， Χ1 2000 μηι
下方对辊空隙尺寸， 1500 μηι
进料原料粒度分布范围 dp 100 - 2400μηι 进料原料中位粒径 d50 1135μηι
制备的籽晶中位粒径 D5Q 857μηι
图 5为该实施例原料颗粒硅的粒度分布示意图。 从图中可以看出， 78%的颗粒硅 直接通过了辊式装置辊轮的空隙而未被破碎， 只有 22%的硅颗粒被辊磨破碎。 图 6示 出了辊磨前后硅颗粒及籽晶的粒度分布。 从中可以看出， 大尺寸的硅颗粒被破碎变成 小尺寸的颗粒硅， 且籽晶的粒度分布范围变窄。 从图 7计算的百分比曲线中更能直观 的反应看出颗粒尺寸变小， 同一尺寸颗粒比例增加。 图 8和图 9分别给出了辊磨前后 放大 13.4倍的颗粒硅及籽晶的实物照片。 从图 8中可以看出辊磨之前的原料球形度较 好， 但颗粒硅大小不一， 粒度分布较宽。 但经过辊磨破碎后， 得到的籽晶包括大部分 未被破碎的颗粒硅和小部分经破碎的颗粒硅， 总体球形度较高， 颗粒尺寸比较均一， 如图 9所示。
对比例 1
为比较研究， 通过交替研磨的方法将硅颗粒全部破碎得到与实施例 1类似粒度分 布范围的籽晶， 如表 2所示。
表 2 对比例 1实验数据
进料速度 250 lb/h
进料原料中位粒径 d5Q > 2400 μηι
制备的籽晶中位粒径 D5Q 858μηι
图 10示出了研磨前后颗粒硅及籽晶的粒度分布柱状图。 可以看出， 大颗粒全 部被磨碎变成小颗粒。 图 1 1给出了相应的计算曲线， 更加直观地看出 2400μηι以上 的颗粒全部被磨碎至 2000μηι以下。 图 12和 13给出了破碎前后颗粒硅及籽晶放大 13.4倍的实物照片。 原料颗粒硅球形度高、 尺寸均一， 通过研磨后颗粒硅全部被 破碎， 球形度较低。 图 14给出了实施例 1和对比例 1的比较图， 从中可以看出两种 方法制备的籽晶粒度分布类似， 但两种方法制备的籽晶形貌差异极大， 本发明的 方法制备的籽晶球形度远远高于对比例 1的方法。
本发明进一步研究了所制备的籽晶在流化床反应器中的孔隙率。 表 3给出了 流化床反应器制备的颗粒硅产品、 实施例 1制备的籽晶、 对比例 1制备的籽晶在致 密床层和最小流态化速度两种状况下的流化床层孔隙率 （即床层中颗粒硅之间的 空隙体积占总体积的比例） 。 可以看出， 实施例与对比例两种方法制备的籽晶形 成床层的孔隙率均比流化床颗粒硅产品要高。 在最小流态化速度情况下， 对比例 1的孔隙率比实施例 1制备的籽晶要高 19.4%， 但实施例 1制备的籽晶与颗粒硅产品 相比差异较小， 其孔隙率仅比颗粒硅产品作为籽晶时高 10.4%。 因此， 与常规的 研磨方法相比， 本发明制备的籽晶孔隙率更低， 更易于避免硅微粉的形成而造成 的负面影响。
表 3 几种不同籽晶形成床层孔隙率比较 致密床层孔隙率 最小流态化时孔隙率
% %
流化床颗粒硅产品 33.5 35.3
实施例 1制备籽晶 35.7 45.7
对比例 1制备籽晶 43.4 54.7
尽管上文对本发明的具体实施方式给予了详细描述和说明， 但是应该指明的 是， 本领域技术人员可以依据本发明的构想对上述实施方式进行各种等效改变和 修改， 其所产生的功能作用仍未超出说明书所涵盖的精神时， 均应在本发明的保 护范围之内。

Claims

权 利 要 求 书
1. 一种高球形度籽晶的制备方法，包括将具有一定粒度分布范围的颗粒硅产品作为原 料， 通过辊式装置对其进行辊式破碎的步骤， 其特征在于所述辊式装置包括至少一组 对辊， 通过调节所述对辊的辊轮之间的空隙， 使得尺寸大于所述辊轮空隙的颗粒硅被 破碎， 尺寸小于所述辊轮空隙的颗粒硅直接通过空隙， 从而制备出高球形度的籽晶。
2. 根据权利要求 1所述的高球形度籽晶的制备方法，其特征在于所述辊轮空隙尺寸 X 与原料颗粒硅的中位粒径 d5C以及目标籽晶的中位粒径 D5。满足以下关系： ΙΟΟμιη < D50< d50< x < 2400μηι, 其中颗粒硅尺寸分布 dp的范围为 100μηι ~2400μηι。
3. 根据权利要求 2所述的高球形度籽晶的制备方法，其特征在于所述辊式装置包括两 组对辊， 所述两组对辊上下放置， 作为原料的颗粒硅产品依次通过上下两组对辊。
4. 根据权利要求 3所述的高球形度籽晶的制备方法，其特征在于所述上下两组对辊辊 轮的空隙尺寸 Xl、 ¾满足关系式 Xl≥ , 其中 ^为位于上方对辊的两个辊轮间的空隙 尺寸， 为位于下方对辊的两个辊轮间的空隙尺寸。
5. 一种流化床颗粒硅的制备方法， 包括以下步骤：
1 )含硅原料气体和流态化气体在加有籽晶的流化床反应器内，于 500°C ~1200°C 的反应温度下进行连续的热分解反应， 并在籽晶表面沉积硅制备颗粒硅产品；
2)所述制备的颗粒硅产品采出后一部分包装作为最终产品；
3 )所述采出的颗粒硅产品采出后一部分经权利要求 1-5任一项所述的高球形度籽 晶的制备方法制备得到高球形度的颗粒硅籽晶， 并循环进入流化床反应器内部， 维持 流化床床层籽晶数量稳定。
6. 根据权利要求 5所述的流化床颗粒硅的制备方法，其特征在于所述含硅原料气体选 自 SiHaXb， 其中， X=F、 CK Br、 I， a、 b各自独立选自 a =0~4、 b=0~4, 且 a+b=4。
7. 根据权利要求 6所述的流化床颗粒硅的制备方法，其特征在于所述含硅原料气体为 娃院。
8. 根据权利要求 6所述的流化床颗粒硅的制备方法，其特征在于所述含硅原料气体为 氣娃焼。
9. 根据权利要求 8所述的流化床颗粒硅的制备方法，其特征在于所述含硅原料气体为 三氯氢硅。
PCT/CN2013/081356 2012-08-13 2013-08-13 高球形度籽晶和流化床颗粒硅的制备方法 WO2014026588A1 (zh)

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CN201380041563.9A CN104540590B (zh) 2012-08-13 2013-08-13 高球形度籽晶和流化床颗粒硅的制备方法
EP13829331.1A EP2883613B1 (en) 2012-08-13 2013-08-13 Method for preparing high sphericity seed crystal and fluidized bed particle silicon

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