Spraying process method of silicon powder purification anti-sticking pan, crucible and ingot furnace

Abstract

The invention discloses a spraying process method of a silicon powder purification anti-sticking pan, a crucible and an ingot furnace. The spraying process method comprises the following steps: coating the inner wall of the crucible with a silicon nitride solution to construct a silicon nitride coating; the step of coating the silicon nitride coating with the silica sol comprises the substeps that the weight and the density of a molten silicon powder cake are obtained, and the silicon powder cake is a cake body formed by pressing silicon powder; the bottom area of the crucible is obtained, and according to the bottom area of the crucible, the weight of the molten silicon powder cake and the density of the molten silicon powder cake, the ingot height of the silicon ingot in the crucible after the silicon powder cake is hot-molten into a solution and solidified into the silicon ingot again is obtained; obtaining an ingot height line on the side wall of the crucible according to the ingot height; a painting area is obtained on the side wall of the crucible with the ingot height line as the reference, and the ingot height line is located in the painting area; and silica sol is coated on the brushing area. The silica sol is coated in the brushing area of the side wall of the crucible, so that the impurity content in a silicon ingot can be reduced, and the condition that the silicon ingot is stuck to the crucible can be effectively prevented.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal silicon ingot casting, and in particular to a spraying process method for a silicon powder purification anti-sticking pot, a crucible and an ingot casting furnace. Background Art

[0002] In the prior art, the inner wall of the crucible used in the ingot casting furnace must be coated. Most of the coatings use silicon nitride coatings to prevent the molten silicon crystals from reacting with the inner wall of the crucible during the silicon crystal purification process, resulting in more impurities in the purified silicon crystals. In addition, the silicon nitride coating can also prevent the pot from sticking.

[0003] Currently, ingot casting furnaces are mostly used to purify powder materials with smaller particle sizes. Since powder materials with smaller particle sizes have the characteristics of large specific surface area and strong adsorption capacity, they are easily contaminated by the thermal field atmosphere in the ingot casting furnace. Therefore, the silicon ingots produced after the traditional ingot casting process is used to purify powder materials with smaller particle sizes have a high impurity content, such as boron, phosphorus, oxygen, carbon and other impurities. Among them, due to the high content of impurity boron, when the amount of CZ single crystal exceeds a certain proportion, the efficiency attenuation ratio after string welding is high. Therefore, in order to reduce the impurity content in the silicon ingot, especially to reduce the content of impurity boron, and improve the purity of the silicon ingot, a low-pressure purification process is currently used to reduce the impurity content in the silicon ingot. The low-pressure purification process refers to a technical method in which the furnace pressure in the ingot casting furnace is reduced during the purification process to reduce the impurity content in the purified silicon ingot. However, the use of this technical method will expose the silicon nitride coating on the crucible surface at the solid-liquid boundary to a high-temperature, low-pressure thermal field atmosphere. Since silicon nitride has the characteristic of being easier to decompose as the ambient pressure is lower, this will lead to an increase in the impurity content in the produced silicon ingots. In addition, due to the decomposition of silicon nitride at the solid-liquid boundary, the coating disappears, and the molten silicon reacts with the inner wall of the crucible, thereby further increasing the impurity content in the produced silicon ingot. At the same time, the coating disappears, and sticking occurs at the solid-liquid boundary, resulting in cracks in the silicon ingot.

[0004] It can be seen from this that the existing coating treatment process cannot meet the requirements of the low-pressure purification process. The existing coating treatment process is prone to problems such as sticking to the pan, cracking of silicon ingots, and high impurity content in the produced silicon ingots. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a spraying process method for purifying silicon powder and preventing the crucible from sticking, which can solve the problem that the coating on the inner wall of the crucible is easy to decompose and become ineffective, solve the problem that the crucible is easy to stick to the crucible and the silicon ingot is cracked during the production process, and can effectively reduce the impurity content in the produced silicon ingot.

[0006] According to the spraying process method for purifying a silicon powder anti-stick pan according to an embodiment of the present invention, the method includes coating a silicon nitride solution on the inner wall of a crucible to construct a silicon nitride coating; and then coating a silica sol on the silicon nitride coating, wherein the coating of the silica sol on the silicon nitride coating includes: obtaining the weight and density of a melted silicon powder cake, wherein the silicon powder cake is a cake body pressed from silicon powder; obtaining the bottom area of ​​the crucible, and obtaining the ingot height of the silicon ingot in the crucible after the silicon powder cake is hot-melted into a solution and solidified into a silicon ingot again according to the bottom area of ​​the crucible, the weight of the melted silicon powder cake, and the density of the melted silicon powder cake; obtaining an ingot height line on the side wall of the crucible according to the ingot height; obtaining a brushing area on the side wall of the crucible based on the ingot height line, wherein the ingot height line is located in the brushing area; and coating the silica sol in the brushing area.

[0007] According to the spraying process method for purifying silicon powder and preventing sticking to the pan according to the embodiment of the present invention, by coating silica sol in the brushing area of ​​the side wall of the crucible, it is not only possible to effectively reduce the impurity content in the produced silicon ingots, but also possible to effectively prevent the silicon ingots from sticking to the pan.

[0008] In addition, the spraying process method for purifying anti-stick pan with silicon powder according to the present invention may also have the following additional technical features:

[0009] In some embodiments, coating the inner wall of the crucible with a silicon nitride solution to form a silicon nitride coating includes: coating a first layer of silicon nitride coating on the coating area; and then coating a second layer of silicon nitride coating on the first layer of silicon nitride coating, wherein the second layer of silicon nitride coating covers the inner wall of the crucible.

[0010] In some embodiments, the side wall of the crucible also includes a first spraying area, which is located at the lower side of the brushing area, and the bottom wall of the crucible has a second spraying area connected to the first spraying area, and a second layer of silicon nitride coating is coated on the brushing area, the first spraying area and the second spraying area.

[0011] In some embodiments, in the height direction of the crucible, the coating area has an upper edge line and a lower edge line, and coating silicon nitride on the inner wall of the crucible to construct a silicon nitride coating includes: setting a baffle on the upper side of the coating area to reveal the upper edge line after silicon nitride is coated on the inner wall of the crucible.

[0012] In some embodiments, the upper edge line and the lower edge line are symmetrical along the ingot height line.

[0013] In some embodiments, coating the first layer of silicon nitride coating in the brushing area includes: coating the first layer of silicon nitride coating in the brushing area by brushing.

[0014] In some embodiments, the solution of the first layer of silicon nitride coating includes silicon nitride, silica sol, water and a binder, wherein the weight proportion of the silicon nitride is 25%-48%, the weight proportion of the silica sol is 18%-28%, the weight proportion of the water is 24%-56%, and the weight proportion of the binder is 0%-1%.

[0015] In some embodiments, the solution of the second layer of silicon nitride coating includes silicon nitride, silica sol and water, wherein the weight proportion of the silicon nitride is 25%-35%, the weight proportion of the silica sol is 12%-21%, and the weight proportion of the water is 44%-63%.

[0016] In some embodiments, before the silica sol is coated on the coating area, the method includes: adding silicon powder or a binder into the silica sol solution and stirring the solution evenly.

[0017] In some embodiments, in the height direction of the crucible, the width H1 of the coating area satisfies: 60 mm ≤ H1 ≤ 140 mm.

[0018] The present invention also provides a crucible having the above embodiment.

[0019] According to the crucible of the embodiment of the present invention, the silicon ingot can be effectively prevented from sticking to the pan by coating a silicon nitride coating and a silica sol in the crucible using the above-mentioned spraying process method for purifying silicon powder to prevent sticking to the pan.

[0020] The present invention also provides an ingot casting furnace having the above embodiment.

[0021] According to the ingot casting furnace of the embodiment of the present invention, the production efficiency of the ingot casting furnace can be improved by providing the above-mentioned crucible.

[0022] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a method for spraying a silicon powder-purified anti-stick pan according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, 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 should not be construed as limiting the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0026] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] The following describes a spraying process method for purifying silicon powder and preventing sticking of a pan according to an embodiment of the present invention.

[0029] According to the spraying process method for purifying silicon powder and preventing sticking in a pan according to an embodiment of the present invention, the method includes coating a silicon nitride solution on the inner wall of a crucible to construct a silicon nitride coating; and then coating a silica sol on the silicon nitride coating. In this embodiment, a silicon nitride coating is coated on the inner wall of the crucible to prevent the silicon melt after the silicon powder is melted from reacting with the inner wall of the crucible, thereby preventing impurities generated by the reaction from entering the silicon melt, resulting in a high impurity content in the produced silicon ingot. Coating the silicon sol on the surface of the silicon nitride coating can effectively improve the overall wettability of the silicon nitride coating, making the silicon nitride coating and silicon more wettable. In this way, the silicon melt can form a dense silicon protective film on the surface of the silicon nitride coating, which can effectively prevent the decomposition of the silicon nitride coating, so that the silicon melt cannot contact and react with the inner wall of the crucible, thereby effectively reducing the impurity content in the produced silicon ingot and preventing sticking cracks.

[0030] Furthermore, coating the silicon nitride coating with silica sol includes: obtaining the weight and density of the silicon powder cake after melting, wherein the silicon powder cake is a cake body pressed from silicon powder; obtaining the bottom area of ​​the crucible, and obtaining the ingot height of the silicon ingot in the crucible after the silicon powder cake is melted into a solution and solidified into a silicon ingot again according to the bottom area of ​​the crucible, the weight of the silicon powder cake after melting, and the density of the silicon powder cake after melting; obtaining an ingot height line on the side wall of the crucible according to the ingot height; obtaining a brushing area on the side wall of the crucible based on the ingot height line, wherein the ingot height line is located in the brushing area; and coating the silica sol in the brushing area. The ingot height of the produced silicon ingot can be calculated based on the bottom area of ​​the crucible, the weight and density of the silicon powder cake after melting, and the ingot height of the silicon ingot is used as a reference. The position of the side wall of the crucible relative to the ingot height of the silicon ingot is the ingot height line, and a brushing area is divided on the side wall of the crucible based on the ingot height line, and silica sol is coated in the brushing area.

[0031] Furthermore, when the silicon powder is purified, the silicon powder is first placed in a crucible in the form of a silicon powder cake. Secondly, after heating, the silicon powder cake in the crucible melts into silicon melt. Finally, the silicon melt re-solidifies into a silicon ingot, wherein the liquid level of the silicon melt is lower than the ingot height of the silicon ingot. Therefore, there is a height difference between the liquid level of the silicon melt and the ingot height of the silicon ingot. The area of ​​the side wall of the crucible relative to the height difference is the solid-liquid boundary area of ​​the silicon powder. After the silicon powder cake is heated and melted into silicon melt, the silicon nitride coating located at the solid-liquid boundary area is not covered and protected by the silicon melt. Completely exposed to the hot field atmosphere in the ingot casting furnace, the silicon nitride coating is prone to decomposition at this time. At the same time, since the silicon powder purification adopts a low-pressure purification process, that is, during the purification process, the furnace pressure in the ingot casting furnace is reduced to reduce the impurity content in the purified silicon ingot. Silicon nitride has the characteristic that the lower the ambient pressure, the easier it is to decompose. Therefore, the silicon nitride coating located in the solid-liquid boundary area is in a high-temperature and low-pressure hot field atmosphere, and is more prone to decomposition, which can easily lead to a higher impurity content in the produced silicon ingots and easy sticking to the pot and cracking of the ingots.

[0032] Finally, in order to prevent the decomposition of the silicon nitride coating located at the solid-liquid boundary area, a coating area is divided on the side wall of the crucible based on the ingot height line, wherein the solid-liquid boundary area is located in the coating area. In this way, coating the coating area with silica sol can make the molten silicon climb onto the silicon nitride coating in the coating area, and form a dense silicon protective film on the surface of the silicon nitride coating in the coating area, so that the silicon nitride coating in the coating area will not decompose. This not only avoids the decomposition of silicon nitride and the impurities generated after the decomposition from entering the molten silicon, but also avoids the contact and reaction between the molten silicon and the inner wall of the crucible. On the one hand, it further reduces the impurity content in the molten silicon, so that the impurity content in the solidified silicon ingot is less and the purity is better. On the other hand, it prevents the silicon ingot from sticking to the pot.

[0033] In some embodiments, the coating area is determined with the ingot height line as the center line, which facilitates the coating of the silica sol and can improve production efficiency.

[0034] In some embodiments, after the ingot height line is determined, it can be calibrated later by a measuring tool or by other methods, which are not specifically limited here.

[0035] According to the spraying process method for purifying silicon powder and preventing sticking to the pan according to the embodiment of the present invention, by coating silica sol in the brushing area of ​​the side wall of the crucible, it is not only possible to effectively reduce the impurity content in the produced silicon ingots, but also possible to effectively prevent the silicon ingots from sticking to the pan.

[0036] In one embodiment of the present invention, coating the inner wall of the crucible with a silicon nitride solution to form a silicon nitride coating includes: coating a first layer of silicon nitride coating on the coating area; and then coating a second layer of silicon nitride coating on the first layer of silicon nitride coating, wherein the second layer of silicon nitride coating covers the inner wall of the crucible. In this embodiment, the first layer of silicon nitride coating and the second layer of silicon nitride coating are coated on the coating area, respectively, so that if the second layer of silicon nitride coating on the coating area decomposes under a high-temperature, low-pressure hot field atmosphere, the first layer of silicon nitride coating can still protect the side wall of the crucible on the coating area, and can effectively prevent the silicon melt from directly contacting and reacting with the side wall of the crucible to produce impurities, thereby ensuring the purity of the silicon ingot produced.

[0037] Furthermore, in order to avoid direct contact between the inner wall of the crucible outside the coating area and the molten silicon, the inner wall of the crucible outside the coating area is coated with a second layer of silicon nitride coating. Since the inner wall of the crucible outside the coating area is below the liquid level of the molten silicon, the molten silicon can prevent the second layer of silicon nitride coating below the liquid level from being exposed to the high temperature and low pressure thermal field atmosphere, thereby preventing the second layer of silicon nitride coating from decomposing. Therefore, there is no need to coat the first layer of silicon nitride coating on the inner wall of the crucible outside the coating area. Only spraying the second layer of silicon nitride coating can meet the process requirements.

[0038] In some embodiments, both the first layer of silicon nitride coating and the second layer of silicon nitride coating can be coated on the inner wall of the crucible. In this way, the corrosion resistance of the crucible can be further improved and the silicon melt can be prevented from reacting with the inner wall of the crucible to produce impurities. Furthermore, the inner wall of the crucible can also be coated with a third layer of silicon nitride coating, a fourth layer of silicon nitride coating, a fifth layer of silicon nitride coating, and so on. The number of layers of silicon nitride coating can be adjusted according to actual needs and is not specifically limited here.

[0039] In a specific embodiment of the present invention, the side wall of the crucible also includes a first spraying area, the first spraying area is located at the lower side of the brushing area, the bottom wall of the crucible has a second spraying area connected to the first spraying area, and the second layer of silicon nitride coating is coated on the brushing area, the first spraying area and the second spraying area. In this specific embodiment, the first spraying area and the second spraying area refer to the inner wall of the crucible below the brushing area. Since the upper boundary of the brushing area is not lower than the ingot height of the silicon ingot, the inner wall of the crucible outside the brushing area, the first spraying area and the second spraying area does not need to be coated with the second layer of silicon nitride coating, so that the production cost can be reduced, the production time can be shortened, and the production efficiency can be improved.

[0040] In a specific embodiment of the present invention, in the height direction of the crucible, the brushing area has an upper edge line and a lower edge line, and coating the inner wall of the crucible with silicon nitride to construct a silicon nitride coating includes: arranging a baffle on the upper side of the brushing area to show the upper edge line after the inner wall of the crucible is coated with silicon nitride. In this specific embodiment, arranging a baffle on the upper side of the brushing area can prevent the first layer of silicon nitride coating or the second layer of silicon nitride coating from being coated on the inner wall of the crucible above the brushing area when the first layer of silicon nitride coating and the second layer of silicon nitride coating are coated. On the one hand, the coated silicon nitride coating can be made more regular and beautiful, and on the other hand, the clear upper edge line can provide a reference, facilitate silica gel coating, and also reduce the shedding of silicon nitride and the introduction of impurities.

[0041] Furthermore, the upper edge line and the lower edge line are symmetrical along the ingot height line. Such a design not only facilitates the determination of the coating area, but also facilitates the coating of the silica sol, and can effectively improve production efficiency.

[0042] In a specific embodiment of the present invention, coating the first silicon nitride coating in the brushing area includes: coating the first silicon nitride coating in the brushing area by brushing. In this specific embodiment, the first silicon nitride coating is coated by brushing, which can prevent the first silicon nitride coating from exceeding the brushing area during coating. At the same time, the brushing method has good controllability, is easy to operate, and can save material costs and reduce waste.

[0043] In some embodiments, when applying the first layer of silicon nitride coating, manual brushing can be used. The advantage of manual brushing is that workers can ensure that they are brushing within the brushing area, and during the brushing process, they can also observe the overall brushing situation in real time, and can make timely adjustments when encountering problems such as uneven brushing and omissions. Machines can also be used to apply the first layer of silicon nitride coating. This brushing method is efficient, but the brushing accuracy is poor. In addition to the above-mentioned brushing methods, other brushing methods can also be used to apply the first layer of silicon nitride coating, which are not specifically limited here.

[0044] In a specific embodiment of the present invention, a second silicon nitride coating is applied on the first silicon nitride coating, comprising: spraying the second silicon nitride coating on the first silicon nitride coating with predetermined parameters, wherein the predetermined parameters include: atomization pressure, spray width pressure, flow rate and spray width. In this specific embodiment, the second silicon nitride coating is applied by spraying, and the predetermined parameters of the spraying machine need to be adjusted before spraying, wherein the predetermined parameters involve atomization pressure, spray width pressure, flow rate and spray width, and the predetermined parameters can be adjusted according to the actual conditions of factors such as weather environment, viscosity of coating solution, spray object, etc., to ensure that the sprayed second silicon nitride coating meets the process requirements.

[0045] Furthermore, the atomization pressure P1 is: 0.18Mpa; the spray width pressure P2 is: 0.06Mpa; the flow rate Q satisfies: 70ml / 20s≤Q≤85ml / 20s; the spray width amp satisfies: 16cm≤amp≤20cm. Adjusting the predetermined parameters to the above values ​​or value ranges can ensure that the sprayed second layer of silicon nitride coating meets the process requirements.

[0046] In a specific embodiment of the present invention, the solution of the first layer of silicon nitride coating includes silicon nitride, silica sol, water and a binder, wherein the weight proportion of silicon nitride is 25%-48%, the weight proportion of silica sol is 18%-28%, the weight proportion of water is 24%-56%, and the weight proportion of the binder is 0%-1%. The solution of the first layer of silicon nitride coating prepared according to the corresponding proportions can meet the requirements of the process and is easy to apply.

[0047] In a specific embodiment of the present invention, the solution of the second layer of silicon nitride coating includes silicon nitride, silica sol and water, wherein the weight proportion of silicon nitride is 25%-35%, the weight proportion of silica sol is 12%-21%, and the weight proportion of water is 44%-63%. The solution of the second layer of silicon nitride coating prepared according to the corresponding proportions can meet the requirements of the process and is easy to apply.

[0048] In one embodiment of the present invention, before the silica sol is applied to the brushing area, the process includes: adding silicon powder or a binder to the silica sol solution and stirring it evenly. In this embodiment, adding silicon powder to the silica sol solution can make the carbon powder in the silica sol applied to the brushing area melt into silicon liquid earlier when the ingot furnace is heated, and form a dense and hard silicon protective film on the surface of the silicon nitride coating in the brushing area, so as to protect the first silicon nitride coating and the second silicon nitride coating on the brushing area earlier and prevent the first silicon nitride coating and the second silicon nitride coating from decomposing.

[0049] Furthermore, adding a binder to the silica sol solution can further improve the wettability of the silica sol solution, so that the molten silicon in the crucible can climb up to the coating area faster and cover the entire coating area, thereby faster forming a dense and hard silicon protective film on the surface of the silicon nitride coating in the coating area, thereby protecting the first layer of silicon nitride coating and the second layer of silicon nitride coating on the coating area to prevent them from decomposition.

[0050] In a specific embodiment of the present invention, in the height direction of the crucible, the width H1 of the brushing area satisfies: 60mm≤H1≤140mm. In this specific embodiment, the brushing area is determined with the ingot height line as the center line, wherein the minimum width of the brushing area is 60mm and the maximum width of the brushing area is 140mm. When the width of the brushing area is within this range, it can not only meet the process requirements, but also produce silicon ingots with higher purity.

[0051] The present invention also provides a crucible having the above embodiment.

[0052] According to the crucible of the embodiment of the present invention, the silicon ingot can be effectively prevented from sticking to the pan by coating a silicon nitride coating and a silica sol in the crucible using the above-mentioned spraying process method for purifying silicon powder to prevent sticking to the pan.

[0053] The present invention also provides an ingot casting furnace having the above embodiment.

[0054] According to the ingot casting furnace of the embodiment of the present invention, the production efficiency of the ingot casting furnace can be improved by providing the above-mentioned crucible.

[0055] The spraying process method of the anti-stick pan for purifying silicon powder according to the embodiment of the present invention, other structures and operations of the crucible and the ingot casting furnace are well known to those skilled in the art and will not be described in detail here.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0057] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A spraying process for purifying silicon powder to prevent sticking pans, characterized in that: include: coating the inner wall of the crucible with a silicon nitride solution to form a silicon nitride coating; Then, coating silica sol on the silicon nitride coating, wherein coating silica sol on the silicon nitride coating comprises: Obtaining the weight and density of the melted silicon powder cake, wherein the silicon powder cake is a cake body pressed from silicon powder; Obtaining the bottom area of ​​the crucible, and obtaining the ingot height of the silicon ingot in the crucible after the silicon powder cake is hot-melted into a solution and solidified again into a silicon ingot according to the bottom area of ​​the crucible, the weight of the silicon powder cake after melting, and the density of the silicon powder cake after melting; Obtaining an ingot height line on the side wall of the crucible according to the ingot height; Obtaining a coating area on the side wall of the crucible based on the ingot height line, wherein the ingot height line is located in the coating area; The silica sol is coated on the coating area.

2. The spraying process for purifying silicon powder and preventing sticking of pans according to claim 1, characterized in that: The coating of the silicon nitride solution on the inner wall of the crucible to form a silicon nitride coating comprises: Applying a first layer of silicon nitride coating on the coating area; A second layer of silicon nitride coating is sprayed on the first layer of silicon nitride coating, and the second layer of silicon nitride coating covers the inner wall of the crucible.

3. The spraying process for purifying silicon powder and preventing sticking of pans according to claim 2, characterized in that: The side wall of the crucible further comprises a first spraying area, the first spraying area is located below the painting area, and the bottom wall of the crucible comprises a second spraying area connected to the first spraying area. A second layer of silicon nitride coating is sprayed in the painting area, the first spraying area and the second spraying area.

4. The spraying process for purifying silicon powder and preventing sticking of a pan according to claim 2 or 3, characterized in that: In the height direction of the crucible, the coating area has an upper edge line and a lower edge line, The coating of silicon nitride on the inner wall of the crucible to form a silicon nitride coating comprises: A baffle is disposed on the upper side of the coating area to reveal the upper edge line after the inner wall of the crucible is coated with silicon nitride.

5. The spraying process for purifying silicon powder and preventing sticking of pans according to claim 4, characterized in that: The upper edge line and the lower edge line are symmetrical along the ingot height line.

6. The spraying process for purifying silicon powder and preventing sticking of pans according to claim 3, characterized in that: The step of coating the first layer of silicon nitride coating in the coating area comprises: The first silicon nitride coating is applied in the brushing area by brushing.

7. The spraying process for purifying silicon powder and preventing sticking of pans according to claim 3, characterized in that: The solution of the first layer of silicon nitride coating includes silicon nitride, silica sol, water and a binder, wherein the weight proportion of the silicon nitride is 25%-48%, the weight proportion of the silica sol is 18%-28%, the weight proportion of the water is 24%-56%, and the weight proportion of the binder is 0%-1%.

8. The method for spraying silicon powder to purify an anti-stick pan according to claim 3, characterized in that: The solution of the second layer of silicon nitride coating includes silicon nitride, silica sol and water, wherein the weight proportion of the silicon nitride is 25%-35%, the weight proportion of the silica sol is 12%-21%, and the weight proportion of the water is 44%-63%.

9. The spraying process for purifying silicon powder and preventing sticking of pans according to claim 1, characterized in that: Before the silica sol is applied to the coating area, the method comprises: Add silicon powder or binder to the silica sol solution and stir evenly.

10. The spraying process for purifying silicon powder and preventing sticking of pans according to claim 5, characterized in that: In the height direction of the crucible, the width H1 of the coating area satisfies: 60 mm ≤ H1 ≤ 140 mm.

11. A crucible, characterized in that: A silicon nitride coating and silica sol are coated in the crucible using the spraying process method for purifying an anti-stick pan with silicon powder as described in any one of claims 1 to 10.

12. An ingot casting furnace, characterized in that: Comprising the crucible according to claim 11.

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