Polysilicon crushing method

Abstract

The present invention discloses a polysilicon crushing method, which comprises: (1) pre-cooling polysilicon to obtain pre-cooled polysilicon; (2) freezing the pre-cooled polysilicon to obtain frozen polysilicon; (3) heating the frozen polysilicon to obtain heated polysilicon; and (4) crushing the heated polysilicon to obtain crushed polysilicon. The polysilicon crushing method of the present invention can cause the polysilicon to obtain extremely large intercrystalline stress, thereby making the polysilicon easier to crush, improving the yield of the polysilicon crushing product, extending the service life of the crushing mechanism of the equipment, and reducing maintenance costs.

Description

Technical Field

[0001] The present invention relates to the field of polysilicon, and in particular to a polysilicon crushing method. Background Art

[0002] In the polysilicon industry, electronic-grade polysilicon produced by the vapor deposition method is a large rod-shaped material. It needs to be crushed into blocks before it can be used downstream. Because the purity requirements of electronic-grade polysilicon are extremely high, the control of impurity contamination is very important. Through years of polysilicon production experience, combined with literature surveys and statistics, this paper analyzes each process from the crushing mechanism to the crushing mode. Polysilicon crushing has long been done manually using a hammer embedded with carbide or tungsten carbide alloy bags. Even in some countries with more advanced polysilicon technology, this crushing method has been consistently used. As the basic material used in semiconductors, polysilicon is required to have a purity level of 9N. Therefore, in order to ensure the cleanliness of the silicon material, it is necessary to control the crushing process.

[0003] Currently, crushing methods on the market can be divided into three categories: manual crushing; mechanical crushing, which primarily includes cone crushing, roller crushing, and jaw crushing; and newer crushing methods, including pulse crushing and thermal crushing. Furthermore, under the same conditions, the same crusher can have different production capacities when crushing different materials, reflecting the varying brittleness of various materials. Density, structural uniformity, moisture content, viscosity, cracks, brittleness, as well as the material's strength and hardness, all influence its resistance to crushing. Therefore, the choice of crusher to use should be determined based on factors such as the material's physical and mechanical properties, particle size, and production volume. Generally, strong materials are difficult to crush, while hard materials are difficult to grind. Patent CN111921591A proposes a material crushing system and method to address the problems of large particle size distribution, high powder content, and material contamination associated with existing cold-explosion crushing methods for crushing strong crystalline materials. However, this method consumes a lot of energy, which, combined with the energy consumption of the reduction furnace itself, can lead to very high production costs, necessitating a breakthrough in the process. Patent CN208244812U proposes an integrated crusher that achieves automated crushing by crushing and screening silicon blocks through automatic transportation, crushing, and screening systems. However, these patents employ mechanical crushing methods. Due to the high hardness of the silicon material, the equipment's crushing mechanism has a short service life and increased maintenance costs.

[0004] Therefore, the polysilicon crushing process still needs to be improved. Summary of the Invention

[0005] The present invention aims to at least partially address one of the technical problems in the related art. To this end, one object of the present invention is to provide a method for crushing polycrystalline silicon that can impart significant intercrystalline stress to the polycrystalline silicon, thereby facilitating its crushing, improving the yield of the crushed polycrystalline silicon, extending the service life of the crushing mechanism of the equipment, and reducing maintenance costs.

[0006] In one aspect of the present invention, a method for crushing polysilicon is provided. According to an embodiment of the present invention, the method comprises:

[0007] (1) pre-cooling the polysilicon to obtain pre-cooled polysilicon;

[0008] (2) freezing the pre-cooled polycrystalline silicon to obtain frozen polycrystalline silicon;

[0009] (3) heating the frozen polycrystalline silicon to obtain heated polycrystalline silicon;

[0010] (4) Crushing the heated polycrystalline silicon to obtain crushed polycrystalline silicon.

[0011] According to the polysilicon crushing method of the above embodiment of the present invention, since the cooling process of polysilicon needs to be carried out gradually from the surface to the center, by pre-cooling the polysilicon, the polysilicon can be cooled to a lower temperature from the surface to the center in advance, thereby ensuring the effectiveness of the subsequent freezing and shortening the time required for the polysilicon to be completely frozen. After freezing the polysilicon and then heating it, the polysilicon deforms due to the temperature change, causing it to obtain extremely large intercrystalline stress. The destructive nature of the intercrystalline stress makes the polysilicon easy to crush, and can avoid the generation of a large amount of debris and fine powder, thereby improving the yield of the polysilicon crushing product. Therefore, the polysilicon crushing method of the present invention can obtain extremely large intercrystalline stress in the polysilicon, thereby making the polysilicon easy to crush and improving the yield of the polysilicon crushing product.

[0012] In addition, the polysilicon crushing method according to the above embodiment of the present invention may also have the following additional technical features:

[0013] In some embodiments of the present invention, the heating is performed by microwave heating, thereby maximizing the intercrystalline stress of the polycrystalline silicon and making the polycrystalline silicon easier to break.

[0014] In some embodiments of the present invention, the heating temperature is 300° C. to 350° C., and the heating time is 3 minutes to 7 minutes. This can facilitate the crushing of polycrystalline silicon and improve the yield of the crushed polycrystalline silicon product.

[0015] In some embodiments of the present invention, the pre-cooling temperature is -3°C to -7°C, and the pre-cooling time is 18 minutes to 22 minutes. This ensures the effect of subsequent freezing and shortens the time required for complete freezing of the polysilicon.

[0016] In some embodiments of the present invention, the freezing temperature is -150°C to -170°C, and the freezing time is 28 minutes to 32 minutes. This makes it easier to break the polysilicon and improves the yield of the broken polysilicon product.

[0017] In some embodiments of the present invention, the freezing is performed by liquid nitrogen refrigeration or ethanol refrigeration.

[0018] In some embodiments of the present invention, the interval between the freezing end time and the heating start time is no more than 20 seconds. This makes it easier to break the polysilicon and improves the yield of the broken polysilicon product.

[0019] In some embodiments of the present invention, the polysilicon is in a rod shape, the length of the polysilicon is 300 mm to 400 mm, and the diameter of the polysilicon is 120 mm to 200 mm.

[0020] In some embodiments of the present invention, the crushing is performed by jaw crushing.

[0021] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0023] Figure 1 1 is a flow chart of a polysilicon crushing method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0025] In one aspect of the present invention, the present invention provides a method for crushing polysilicon. Figure 1 The polysilicon crushing method of the present invention comprises:

[0026] S100: Pre-cooling the polysilicon

[0027] In this step, the polysilicon is pre-cooled to obtain pre-cooled polysilicon. Since the cooling process of polysilicon needs to be carried out gradually from the surface to the center, by pre-cooling the polysilicon, the polysilicon can be cooled to a lower temperature in advance from the surface to the center, thereby ensuring the effectiveness of the subsequent freezing and shortening the time required for the polysilicon to be completely frozen.

[0028] According to some embodiments of the present invention, the pre-cooling temperature can be -3°C to -7°C, for example, -3°C, -3.5°C, -4°C, -4.5°C, -5°C, -5.5°C, 6°C, -6.5°C, -7°C, etc., and the pre-cooling time can be 18 minutes to 22 minutes, for example, 18 minutes, 18.5 minutes, 19 minutes, 19.5 minutes, 20 minutes, 20.5 minutes, 21 minutes, 21.5 minutes, 22 minutes, etc. The inventors have found through a large number of experiments that if the pre-cooling temperature is too high or the time is too short, it will affect the subsequent freezing effect, thereby reducing the product yield of polysilicon fragmentation. If the pre-cooling temperature is too low or the time is too long, it will cause a waste of energy. Therefore, the present invention controls the pre-cooling temperature to -3°C to -7°C and the pre-cooling time to 18 minutes to 22 minutes, which can not only ensure the effect of subsequent freezing but also save energy. It should be noted that the specific method of pre-cooling is not particularly limited and can be selected by those skilled in the art based on actual needs. As a specific example, the polysilicon can be placed in a clean environment maintained at a temperature of -3°C to -7°C for 18 to 22 minutes to pre-cool the polysilicon. This ensures that the polysilicon is not contaminated during the pre-cooling process, while also allowing the polysilicon to be cooled to a lower temperature from the surface to the center in advance, thereby ensuring the effectiveness of subsequent freezing and shortening the time required for complete freezing of the polysilicon. Furthermore, the shape and size of the polysilicon are not particularly limited. For example, the polysilicon can be rod-shaped, and the length of the polysilicon can be 300 mm to 400 mm, such as 300 mm, 310 mm, 320 mm, 330 mm, 340 mm, 350 mm, 360 mm, 370 mm, 380 mm, 390 mm, 400 mm, etc. The diameter of the polysilicon can be 120 mm to 200 mm, such as 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, etc. This can further help ensure the effect of subsequent freezing and shorten the time required for complete freezing of the polysilicon.

[0029] S200: Freezing the pre-cooled polysilicon

[0030] In this step, the pre-cooled polysilicon is frozen to obtain frozen polysilicon. By freezing the pre-cooled polysilicon, the polysilicon is cooled to a lower temperature from the surface to the center, thereby ensuring that the intercrystalline stress effect is achieved during subsequent heating, making the polysilicon easier to break and improving the yield of the broken polysilicon product.

[0031] According to some embodiments of the present invention, the freezing temperature may be -150°C to -170°C, for example, -150°C, -152°C, -154°C, -156°C, -158°C, -160°C, -162°C, -164°C, -166°C, -168°C, -170°C, etc., and the freezing time may be 28 minutes to 32 minutes, for example, 28 minutes, 28.5 minutes, 29 minutes, 29.5 minutes, 30 minutes, 30.5 minutes, 31 minutes, 31.5 minutes, 32 minutes, etc. The inventors have found through extensive experiments that if the freezing temperature is too high or the freezing time is too short, it will affect the effect of obtaining intercrystalline stress when the polysilicon is subsequently heated, thereby reducing the yield of the broken polysilicon product. If the freezing temperature is too low or the freezing time is too long, it will cause excessive crushing effect, thereby increasing powder and reducing the yield of the broken polysilicon product. Therefore, the present invention controls the freezing temperature to -150°C to -170°C and the freezing time to 28 minutes to 32 minutes, which not only ensures that the intercrystalline stress effect is obtained during subsequent heating, but also avoids excessive crushing effect and reduces powder, thereby facilitating the reasonable control of crushing size distribution and improving the product yield of polysilicon crushing.

[0032] It should be noted that the specific freezing method is not particularly limited and can be selected by those skilled in the art based on actual needs. As a specific example, the polycrystalline silicon can be placed in a relatively closed clean environment maintained at a temperature of -150°C to -170°C using liquid nitrogen or ethanol refrigeration for 28 to 32 minutes to freeze the polycrystalline silicon. This ensures that the polycrystalline silicon is not contaminated during the freezing process and that the temperature of the polycrystalline silicon is lowered from the surface to the center, thereby ensuring that the intercrystalline stress effect is achieved during subsequent heating.

[0033] S300: Heating the frozen polysilicon

[0034] In this step, the frozen polysilicon is heated to obtain heated polysilicon. After the rapid transition between freezing and heating, the polysilicon deforms due to temperature changes, generating internal forces between the various parts of the polysilicon to resist the effects of this external factor and strive to restore the various parts of the polysilicon from their deformed positions to their pre-deformation positions, resulting in extremely high intercrystalline stress. The destructive nature of the intercrystalline stress makes the polysilicon easier to break, avoids the generation of large amounts of debris and fine powder, and improves the yield of broken polysilicon products.

[0035] According to some embodiments of the present invention, the heating temperature may be 300° C. to 350° C., for example, 300° C., 305° C., 310° C., 315° C., 320° C., 325° C., 330° C., 335° C., 340° C., 345° C., 350° C., etc., and the heating time may be 3 min to 7 min., for example, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, etc. The inventors have found through extensive experiments that if the heating temperature is too high or the heating time is too long, the crushing effect will be excessive, thereby increasing the powder and reducing the yield of the broken polysilicon product. If the heating temperature is too low or the heating time is too short, the effect of the polysilicon obtaining intercrystalline stress will be affected, thereby reducing the yield of the broken polysilicon product. Therefore, the present invention controls the heating temperature to 300°C to 350°C and the heating time to 3 minutes to 7 minutes, which not only ensures that the intercrystalline stress effect is obtained when the polysilicon is heated, but also avoids excessive crushing effect and reduces powder, which is conducive to reasonably controlling the crushing size distribution and improving the product yield of polysilicon crushing.

[0036] According to some embodiments of the present invention, the specific method of heating is not particularly limited, and those skilled in the art can select it according to actual needs. As a preferred solution, microwave heating can be used. Polycrystalline silicon has good thermal conductivity (mostly exceeding 200W / (m·K)), and microwave heating is completely different from traditional heating methods. During microwave heating, the heated material itself becomes a heating element and does not require a heat conduction process. Therefore, even if the material has relatively poor thermal conductivity, it can reach the preset heating temperature in a very short time. Therefore, the heating speed of polycrystalline silicon heated by microwaves will be faster and the heating is very uniform. After the polycrystalline silicon is frozen and then microwave heated, the polycrystalline silicon quickly heats up and deforms from the surface to the center, so that it maximizes the intercrystalline stress. The destructiveness of the intercrystalline stress makes the polycrystalline silicon more easily broken. At the same time, it can further ensure the cleanliness of the processing process, guarantee the quality of the polycrystalline silicon, and reduce production safety risks. Furthermore, the interval between the freezing end time and the heating start time is no more than 20 seconds, and can be, for example, 1 second, 3 seconds, 5 seconds, 8 seconds, 10 seconds, 11 seconds, 13 seconds, 15 seconds, 18 seconds, 20 seconds, etc. This ensures that intercrystalline stress is achieved when the polycrystalline silicon is heated, making the polycrystalline silicon easier to break, thereby improving the yield of the broken polycrystalline silicon product.

[0037] S400: Crushing the heated polysilicon

[0038] In this step, the heated polycrystalline silicon is crushed to obtain crushed polycrystalline silicon. It should be noted that the specific method for crushing the heated polycrystalline silicon is not particularly limited and can be selected by those skilled in the art based on actual needs. As a specific example, the heated polycrystalline silicon can be crushed using a jaw crusher. Since the intercrystalline stresses obtained by the heated polycrystalline silicon make it easy to break, crushing the heated polycrystalline silicon can extend the service life of the equipment's crushing mechanism and reduce maintenance costs.

[0039] Therefore, the polysilicon crushing method of the present invention can enable polysilicon to obtain extremely large intercrystalline stress, thereby making polysilicon easy to crush, improving the product yield of polysilicon crushing, extending the service life of the equipment crushing mechanism, and reducing maintenance costs.

[0040] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way.

[0041] Example 1

[0042] Polycrystalline silicon rods with a length of 300-400mm and a diameter of 120-200mm were placed in a -5°C environment for 20 minutes for pre-cooling (cooling) to obtain pre-cooled polycrystalline silicon rods; the pre-cooled polycrystalline silicon rods were placed in a -150°C freezing chamber for 30 minutes for freezing to obtain frozen polycrystalline silicon rods; the frozen polycrystalline silicon rods were transferred to a heating chamber within 20 seconds for microwave heating, with the heating time set to 5 minutes and the heating temperature reaching 300°C; the heated polycrystalline silicon rods were crushed using a jaw crusher to obtain crushed polycrystalline silicon. The particle size distribution of the crushed polycrystalline silicon was measured by screening, and the product yield of particles with a size between 10mm and 100mm was calculated. The results are shown in Table 1.

[0043] The process steps for crushing polycrystalline silicon rods in Examples 2-6 and Comparative Examples 1-9 are the same as those in Example 1, and the differences are shown in Table 1.

[0044] Table 1

[0045]

[0046] As can be seen from Examples 1-6, the yield of products with a particle size between 10 mm and 100 mm obtained by the polysilicon crushing method of the present invention is above 82%. As can be seen from Comparative Examples 1-2, when the pre-cooling temperature is too high or the time is too short, the product yield is lower than that of Examples 1-6. In Comparative Example 3, the pre-cooling temperature is -8°C and the time is 25 minutes. Its product yield is not significantly improved compared with Example 1, but because the pre-cooling temperature is low and the time is long, the energy consumption is higher. As can be seen from Comparative Examples 4-5, when the freezing temperature is too high, or the freezing temperature is too low and the time is too long, the product yield is lower than that of Examples 1-6. As can be seen from Comparative Examples 6-7, when the heating temperature is too low or the time is too short, the product yield is lower than that of Examples 1-6. As can be seen from Comparative Example 8, when the heating temperature is too high and the time is too long, the product yield is lower than that of Examples 1-6. As can be seen from Comparative Example 9, when the freezing time is too short, the product yield is lower than that of Examples 1-6. It can be seen that the polysilicon crushing method of the present invention can enable the polysilicon to obtain extremely large intercrystalline stress, thereby making the polysilicon easy to crush and improving the product yield of the polysilicon crushing.

[0047] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0048] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A polysilicon crushing method, characterized in that: include: (1) pre-cooling the polysilicon to obtain pre-cooled polysilicon, wherein the pre-cooling temperature is -3°C to -7°C, and the pre-cooling time is 18 minutes to 22 minutes; (2) freezing the pre-cooled polysilicon to obtain frozen polysilicon, wherein the freezing temperature is -150°C to -170°C and the freezing time is 28 minutes to 32 minutes; (3) heating the frozen polycrystalline silicon to obtain heated polycrystalline silicon, wherein the heating temperature is 300° C. to 350° C. and the heating time is 3 min to 7 min; (4) Crushing the heated polycrystalline silicon to obtain crushed polycrystalline silicon.

2. The polysilicon crushing method according to claim 1, characterized in that: The heating is carried out by microwave heating.

3. The polysilicon crushing method according to claim 1 or 2, characterized in that: The freezing is carried out by adopting liquid nitrogen refrigeration or ethanol refrigeration.

4. The polysilicon crushing method according to claim 1 or 2, characterized in that: The interval between the freezing end time and the heating start time is no more than 20s.

5. The polysilicon crushing method according to claim 1 or 2, characterized in that: The polysilicon is in a rod shape, the length of the polysilicon is 300 mm to 400 mm, and the diameter of the polysilicon is 120 mm to 200 mm.

6. The polysilicon crushing method according to claim 1 or 2, characterized in that: The crushing is carried out by jaw crushing.

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