A method and control system for controlling element segregation in industrial silicon casting process

Abstract

The present invention belongs to the technical field of industrial silicon smelting. Aiming at the phenomenon of element segregation of products after silicon liquid casting, a method and control system for controlling element segregation in the process of industrial silicon casting are proposed. The steps include: collecting historical data of silicon liquid casting, screening it as a data source, establishing a linear regression relationship between multiple parameters according to the data in the data source, and calculating the average angular velocity reference value Ω1 of the silicon bag tilt by presetting the target element segregation degree, and the monitored pre-casting temperature, casting silicon liquid weight, and silicon bag tilt initial angle, and continuously casting silicon liquid on the chute, controlling the initial tilt angle of the silicon bag to be 5-11 degrees, the initial angular velocity of the silicon bag to be 8-9.99 degrees / minute, and the average angular velocity of the silicon bag to be Ω1 degrees / minute. The element segregation degree of the silicon plate cast by the control method of the present invention can be controlled to be about 0.001%, which is close to 0%, thereby ensuring the product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial silicon smelting, and in particular relates to a method and a control system for controlling element segregation in an industrial silicon casting process. Background Art

[0002] After industrial silicon refining is completed, a casting process is required: high-temperature silicon liquid is cast from a silicon bag onto the surface of the chute, and then flows into the ingot mold through the chute. After the silicon liquid in the ingot mold is cooled and shaped, a silicon plate is obtained. After sampling and testing, it is packaged and sold.

[0003] At present, due to the expansion of demand in the downstream market of industrial silicon, the capacity of industrial silicon furnaces has been increased, and the output of each furnace has increased from the original 1.5-1.7 tons per silicon plate to the current 1.7-2.4 tons. As the weight of the silicon plate increases, the amount of silicon liquid cooled by the ingot mold increases, and the cooling time is extended. This causes the phenomenon that there is a deviation between the elements of the cooled silicon plate and the composition of the liquid silicon liquid. The main reason is that the solute elements have enough time to migrate and redistribute, which increases the risk of element segregation. In actual production, it is easy for the impurity element content in the lower part of the silicon plate to exceed the liquid sample content, which is a quality accident in serious cases. However, if the cooling time is reduced blindly, it is easy to cause cracks, depressions or other surface defects on the surface of the silicon plate, affecting the appearance and surface quality of the finished product. The liquid sample is the state of silicon liquid after it is mixed after refining and flowing into the silicon bag. Measuring its composition is more accurate than measuring solid composition. Therefore, liquid samples are often used as the basis for judging the qualified composition. However, due to the occurrence of element segregation during the cooling process, the elements in some parts of the products delivered to downstream customers exceed the standard and become unqualified. Therefore, it is necessary to reduce and control the element segregation after silicon liquid casting so that the chemical composition content of each part of the finished product and the liquid sample can be kept as consistent as possible. Summary of the invention

[0004] The first purpose of the present invention is to provide a method for controlling element segregation in the casting process of industrial silicon in response to the above-mentioned problem. The method obtains the relevant parameters that should be maintained during casting by calculation, controls the casting process, reduces the element segregation phenomenon of silicon liquid during the casting process, and ensures product quality.

[0005] The second object of the present invention is to provide a casting control system that realizes a method for controlling element segregation in an industrial silicon casting process, and is used to control some parameters of the industrial silicon casting process so as to reduce the element segregation phenomenon.

[0006] A third object of the present invention is to provide a method for casting using a casting control system.

[0007] The first object of the present invention is implemented by the following technical solutions:

[0008] A method for controlling element segregation in an industrial silicon casting process, characterized in that it comprises the following steps:

[0009] S1. Obtaining a data source: collecting historical data of silicon liquid casting of several furnaces, and screening the historical data as a data source; the historical data includes the pre-casting temperature, the weight of the casting silicon liquid, the average casting speed, the liquid sample Fe mass fraction, the solid sample Fe mass fraction, the initial angle of inclination of the silicon bag, the initial angular velocity of inclination of the silicon bag, the average angular velocity of inclination of the silicon bag, and the calculated element segregation degree of each casting;

[0010] S2. Obtaining an average casting speed reference value: taking the pre-casting temperature, casting silicon liquid weight, and average casting speed in the data source as independent variables, and taking the element segregation degree as the dependent variable for regression analysis, determining the linear relationship between the element segregation degree and the pre-casting temperature, the casting silicon liquid weight, and the average casting speed, and obtaining formula (1); presetting an element segregation degree target value, and substituting the preset element segregation degree target value and the pre-casting temperature and casting silicon liquid weight in actual casting into PX, T, and G in formula (1), respectively, and recording the calculated average casting speed as the average casting speed reference value, V1 (tons / minute);

[0011] PX = a × T + b × G + c × v + d Formula (1);

[0012] Where, PX is the element segregation degree (%), T is the temperature before casting (thousands of degrees Celsius), G is the weight of the casting silicon liquid (tons), v is the average casting speed (tons / minute), a, b, c are the regression coefficients of T, G, v respectively, and d is a constant;

[0013] S3, obtaining a reference value of the average angular velocity of the silicon package tilt: using the average angular velocity of the silicon package tilt in the data source as an independent variable and the average casting speed as a dependent variable for regression analysis, determining the linear relationship between the average casting speed and the average angular velocity of the silicon package tilt, and obtaining formula (2); substituting the average casting speed reference value V1 obtained in step S2 into v in formula (2), and recording the calculated average angular velocity of the silicon package tilt as the reference value of the average angular velocity of the silicon package tilt, Ω1 (degrees / minute);

[0014] v = e × ω + f (2);

[0015] Where ω is the average angular velocity of the silicon package tilt (degrees / minute), e is the regression coefficient of ω, and f is a constant;

[0016] S4. Control parameters for casting: continuously cast the silicon liquid on the chute, control the average casting speed to be V1 ton / minute, control the initial angular velocity of the silicon package tilt to be 8~9.99 degrees / minute, and control the average angular velocity of the silicon package tilt to be Ω1 degree / minute. Since silicon bags with different amounts of silicon liquid and different times of use will flow out silicon liquid after tilting at different tilt angles, if the initial tilting angular velocity is too slow, the silicon liquid will cool down quickly and silicon slag will easily stick to the silicon bag and the chute. If the initial tilting angular velocity is too fast, the silicon liquid will splash. Therefore, it is necessary to preset a suitable initial tilting angular velocity of the silicon bag. The maximum amount of silicon liquid loaded in a new silicon bag is 2.24 tons. When the silicon bag is rotated to 5° at a tilting angular velocity of 9.99° / min, the silicon liquid begins to flow out from the bag mouth without splashing. Because the maximum loading amount of the silicon bag is required to be 2.24 tons, in actual use, generally less than 2.24t of silicon liquid is loaded. Moreover, as the number of times the silicon bag is used increases, the degree of erosion of the inner wall of the silicon bag increases. In both cases, the liquid level will be lower than the liquid level when the new silicon bag is 2.24 tons. Tilt the silicon bag at a tilting angular velocity of 9.99° / min and no splashing will occur. Therefore, 8~9.99° / min is used as the control parameter of the initial tilting angular velocity of the silicon bag (the faster the better without splashing, 9.99° / min is the optimal control parameter).

[0017] Furthermore, the element segregation degree is calculated according to formula (3);

[0018] PX = Fe1-Fe2 formula (3);

[0019] In the formula, Fe1 is the mass fraction of Fe in the solid sample (%), and Fe2 is the mass fraction of Fe in the liquid sample (%). At present, the smelting industry of the industrial silicon industry is mainly based on polysilicon and silicone products. The two types of products have strict requirements on impurity elements such as Fe, Ti, Al, Ca, and C. In actual production, the remaining impurity elements (Ti, Al, Ca, C, etc.) except Fe can be mixed and matched by finding the corresponding raw materials with low impurity elements, and the price of the corresponding raw materials with low impurity elements will not be very high, so that the content of other impurities in the blended smelting raw materials is relatively low; however, due to the high content of impurity element Fe in the raw material end and the high cost of low-Fe raw materials, not too much low-Fe raw materials will be purchased for cost considerations. Therefore, in order to reduce costs, it is generally sufficient to control the impurity Fe content in the product composition to be lower than the impurity Fe required by downstream customers ≤0.49%. Therefore, the degree of element segregation is calculated based on the degree of deviation of the Fe element.

[0020] Furthermore, in step S1, the screening is specifically as follows: select data in historical data that simultaneously satisfies the pre-casting temperature of 1480~1560℃ and the average casting speed of 0.130~0.315 tons / minute as the data source to remove abnormal data and interference. During the casting process, the temperature of the silicon liquid is low, which will cause a large amount of slag to accumulate in the silicon bag after the casting is completed. The silicon bag is difficult to clean. If the temperature is higher than 1560℃, it is high-temperature silicon discharge, and the life of the refractory material is reduced, causing the silicon liquid in the silicon bag to leak out. Therefore, a pre-casting temperature of 1480~1560℃ is selected; in actual production, the weight of the casting silicon liquid is generally above 1700kg. At the same time, according to the general internal dimensions of the ingot mold (length×width×height=2260×1960×220 mm) and the silicon liquid density of 2.3t / m 3 According to calculation, the maximum weight of silicon liquid in the ingot mold is 2301kg. In actual application, considering the thermal expansion and contraction of silicon plate filled with silicon liquid, the weight of casting silicon liquid is generally below 2240kg. For silicon plates weighing 1700~2240kg, the casting time is generally required to be 7.1min~12.47min. If the time is less than 7.1min, the casting time is short and the speed is fast, which may cause splashing of silicon liquid during casting, resulting in pitting on the surface of silicon plate and poor quality of silicon plate. If the time exceeds 12.47min, the temperature of silicon liquid will decrease, the heat loss will be large, and slag will easily stick to the silicon bag. Therefore, historical data with an average casting speed range of 0.130~0.315 t / min is selected as the data source.

[0021] Furthermore, in the formula (1) of step S2, a = 0.440, b = 0.053, c = 1.104, and d = –1.003.

[0022] Further, in the step S3, the data in the data source are divided into three categories according to the initial angle θ (degrees) of the silicon package tilt being 5≤θ<7, 7≤θ<9, and 9≤θ<11, and regression analysis is performed with the average angular velocity of the silicon package tilt as the independent variable and the average casting speed as the dependent variable to determine the linear relationship between the average casting speed and the average angular velocity of the silicon package tilt under different initial angles of the silicon package tilt, and obtain formula (4)-formula (6); when the initial angle θ of the silicon package tilt is 5≤θ<7, the average casting speed reference value V1 is substituted into v in formula (4); when the initial angle θ of the silicon package tilt is 7≤θ<9, the average casting speed reference value V1 is substituted into v in formula (5); when the initial angle θ of the silicon package tilt is 9≤θ<11, the average casting speed reference value V1 is substituted into v in formula (6); the calculated average angular velocity of the silicon package tilt is recorded as the average angular velocity reference value Ω1 of the silicon package tilt;

[0023] v = 0.026 × ω + 0.0716 (4);

[0024] v = 0.023 × ω + 0.0027 (5);

[0025] v = 0.021 × ω + 0.0020 (6);

[0026] In step S4, the initial tilt angle of the silicon package is controlled to be 5-11 degrees.

[0027] The second object of the present invention is implemented by the following technical solutions:

[0028] A casting control system for realizing a method for controlling element segregation in an industrial silicon casting process, the casting control system comprising a silicon bag, a bag turning machine for controlling the inclination of the silicon bag, a chute, an ingot mold, and a DCS control device;

[0029] A temperature measuring coupler is installed in the silicon bag to monitor the temperature before casting; a first weight sensor is installed at the bottom of the silicon bag to monitor the weight of the casting silicon liquid; a second weight sensor is installed at the bottom of the chute to monitor the weight of the chute; the signal input end of the DCS control device is respectively connected to the signal output end of the temperature measuring coupler, the signal output end of the first weight sensor, and the signal output end of the second weight sensor, and the signal output end of the DCS control device is connected to the motor signal of the bag turning machine.

[0030] Furthermore, a tilt sensor is provided on one side of the silicon package to monitor the tilt angle of the silicon package; and the signal input end of the DCS control device is signal-connected to the signal output end of the tilt sensor.

[0031] The third object of the present invention is implemented by the following technical solutions:

[0032] The method for casting using a casting control system is characterized in that it comprises the following steps:

[0033] P1, firstly, a target value of element segregation is preset, the temperature measuring head transmits the monitored pre-casting temperature signal to the DCS control device, the first weight sensor transmits the monitored casting silicon liquid weight signal to the DCS control device, the DCS control device substitutes the target value of element segregation, the pre-casting temperature, and the casting silicon liquid weight into PX, T, and G in the formula (1) set in advance for calculation, and records the obtained average casting speed as the average casting speed reference value V1 (tons / minute);

[0034] P2, the DCS control device controls the motor of the bag turning machine to start running, so that the silicon bag starts to tilt at an initial angular velocity of 8-9.99 degrees / minute;

[0035] P3, the second weight sensor transmits the monitored chute weight signal to the DCS control device. When the monitored chute weight continues to increase in a short period of time, it indicates that the silicon liquid has fallen from the silicon bag onto the chute; the DCS control device substitutes the average casting speed reference value V1 in step P1 into the v in the formula (2) set in advance for calculation, and records the obtained average angular velocity of the silicon bag tilt as the average angular velocity reference value Ω1 (degrees / minute) of the silicon bag tilt;

[0036] P4. The DCS control device controls the bag turning machine motor to continue running at an average angular velocity of silicon bag tilting of Ω1 degree / minute until the casting is completed.

[0037] Further, in step P3, the inclination sensor transmits the monitored silicon bag inclination angle signal to the DCS control device, and the second weight sensor transmits the monitored chute weight signal to the DCS control device. When it is monitored that the weight of the chute continues to increase in a short period of time, it means that the silicon liquid has fallen from the silicon bag onto the chute. The inclination angle of the silicon bag monitored by the inclination sensor at this time is used as the initial inclination angle θ (degrees) of the silicon bag, and it is determined whether it belongs to the category of 5≤θ<7 or 7≤θ<9 or 9≤θ<11. The average casting speed reference value V1 is substituted into v in formula (4) or formula (5) or formula (6) for calculation, and the obtained average angular velocity of the silicon bag inclination is recorded as the average angular velocity reference value Ω1.

[0038] Glossary:

[0039] Pre-casting temperature: After the industrial silicon refining is completed, the high-temperature silicon liquid flows into the silicon bag and is cast into the chute. The temperature of the silicon liquid in the silicon bag before it is poured out is the pre-casting temperature;

[0040] Casting silicon liquid weight: After the industrial silicon refining is completed, the high-temperature silicon liquid flows into the silicon bag. The weight of the silicon liquid in the silicon bag is the casting silicon liquid weight;

[0041] Average casting speed: the average speed of the silicon liquid in the silicon bag being cast into the chute, calculated as the weight change of the silicon bag / time;

[0042] Fe mass fraction of liquid sample: The liquid sample is the state of the silicon liquid after it is mixed after flowing into the silicon bag after refining. The Fe mass fraction of the liquid sample is detected to obtain the Fe mass fraction of the liquid sample;

[0043] Fe mass fraction of solid sample: The solid sample is a sample randomly sampled from the silicon plate formed after the silicon liquid is cooled and shaped in the ingot mold. The Fe mass fraction of the solid sample is detected, that is, the Fe mass fraction of the solid sample is obtained;

[0044] Initial angle of silicon bag tilt: When preparing for casting, the silicon bag needs to be gradually tilted to allow the silicon liquid in the silicon bag to flow out; due to different amounts of silicon liquid in the silicon bag (when there is more silicon liquid, the silicon liquid can also flow out when the silicon bag is tilted at a smaller angle) and different times the silicon bag is used (if it is used many times, its inner wall will be eroded), in order to make the silicon liquid in the silicon bag flow out, the silicon bag needs to be tilted at different angles; when the silicon bag is gradually tilted from a flat state to a certain angle, the silicon liquid begins to flow out, and this tilt angle is the initial tilt angle of the silicon bag;

[0045] Initial angular velocity of silicon package tilt: angular velocity is the tilt angle / time of silicon package. If the tilt angular velocity of silicon package is too fast, liquid flow will splash. If the tilt angular velocity of silicon package is too slow, the temperature of silicon liquid will drop too fast. Therefore, the tilt angular velocity of silicon package needs to be controlled. The initial tilt angle / time of silicon package is the initial angular velocity of silicon package tilt.

[0046] The average angular velocity of silicon bag tilting: from the time when the silicon bag tilts and the silicon liquid starts to flow out, to the time when all the silicon liquid in the silicon bag flows out, the average value of the silicon bag tilting angle / the time used in this process is the average angular velocity of the silicon bag tilting.

[0047] Beneficial effects:

[0048] The present invention provides a method and control system for controlling element segregation in the process of industrial silicon casting, and obtains the average angular velocity of the silicon bag tilt that should be maintained during casting by presetting the target element segregation degree, and the casting silicon liquid weight, pre-casting temperature, silicon bag state and other conditions measured in actual production, and provides a corresponding casting control system and control method. The element segregation degree of the silicon plate cast by the control method of the present invention can be controlled to be about 0.001%, which is close to 0%, ensuring the product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 This is a signal connection diagram for the DCS control device.

[0051] The accompanying drawings are described as follows: 1. DCS control device; 2. Temperature measuring coupler; 3. First weight sensor; 4. Inclination sensor; 5. Second weight sensor; 6. Bag turning machine motor. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Example 1

[0054] A method for controlling element segregation in an industrial silicon casting process comprises steps S1-S4.

[0055] S1. Obtaining data source: collecting historical data of several silicon liquid castings, including the pre-casting temperature, casting silicon liquid weight, average casting speed, liquid sample Fe mass fraction, solid sample Fe mass fraction, silicon package tilting initial angle, silicon package tilting initial angular velocity, silicon package tilting average angular velocity, and calculating the element segregation degree of each casting by formula (3); screening the historical data, selecting the data that simultaneously meets the pre-casting temperature of 1480~1560℃ and the average casting speed of 0.130~0.315 t / min as the data source, so as to remove abnormal data and interference;

[0056] PX = Fe1-Fe2 formula (3);

[0057] Wherein, PX is the element segregation degree (%), Fe1 is the mass fraction of Fe in the solid sample (%), and Fe2 is the mass fraction of Fe in the liquid sample (%).

[0058] S2. Obtaining the average casting speed reference value: taking the pre-casting temperature, casting silicon liquid weight, and average casting speed in the data source as independent variables, and taking the element segregation degree as the dependent variable for regression analysis, determining the linear relationship between the element segregation degree and the pre-casting temperature, casting silicon liquid weight, and average casting speed, and obtaining formula (1); presetting the element segregation degree target value, and substituting the preset element segregation degree target value, the pre-casting temperature, and the casting silicon liquid weight into PX, T, and G in formula (1), respectively, and recording the calculated average casting speed as the average casting speed reference value, V1 (t / min);

[0059] PX = a × T + b × G + c × v + d Formula (1);

[0060] Wherein, T is the temperature before casting (thousands of degrees Celsius), G is the weight of the casting silicon liquid (t), v is the average casting speed (t / min), a, b, c are the regression coefficients of T, G, v respectively, and d is a constant; the temperature before casting and the average casting speed are factors that affect the cooling of the silicon liquid. The weight of the casting silicon liquid can reflect the amount of silicon liquid in the ingot mold, which is also the main factor affecting the solidification of the silicon liquid. The impurity content in the silicon liquid is a factor that affects the melting point of the silicon liquid. According to the Handbook of Thermodynamics, the melting point of pure silicon liquid is 1412℃. The Si content of the products currently produced by our factory is more than 99.5%, and the other impurity elements are less than 0.05%. Therefore, the effect on the melting point can be ignored.

[0061] S3. Obtaining a reference value of the average angular velocity of the silicon package tilt: taking the average angular velocity of the silicon package tilt in the data source as the independent variable and the average casting speed as the dependent variable for regression analysis, determining the linear relationship between the average casting speed and the average angular velocity of the silicon package tilt, and obtaining formula (2); substituting the average casting speed reference value V1 into v in formula (2), and recording the calculated average angular velocity of the silicon package tilt as the reference value of the average angular velocity of the silicon package tilt, Ω1 (° / min);

[0062] v = e × ω + f (2);

[0063] Where ω is the average angular velocity of the silicon package tilt (° / min), e is the regression coefficient of ω, and f is a constant.

[0064] S4. Control parameters for casting: continuously cast the silicon liquid on the chute, control the average casting speed to be V1 ton / minute, control the initial angular velocity of the silicon package tilt to be 8~9.99 degrees / minute, and control the average angular velocity of the silicon package tilt to be Ω1 degree / minute.

[0065] Example 2

[0066] A method for controlling element segregation in an industrial silicon casting process is the same as Example 1 in its entirety, except that:

[0067] In step S2, the pre-casting temperature, casting silicon liquid weight, and average casting speed in the data source are used as independent variables, and the element segregation degree is used as the dependent variable for regression analysis. The fitting results are shown in Table 1-3. The linear relationship between the element segregation degree and the pre-casting temperature, casting silicon liquid weight, and average casting speed is determined to obtain formula (1-1); the element segregation degree target value is preset, and the preset element segregation degree target value, the pre-casting temperature, and the casting silicon liquid weight are substituted into PX, T, and G in formula (1-1) respectively. The calculated average casting speed is recorded as the average casting speed reference value, V1 (t / min);

[0068] PX = 0.440×T + 0.053×G + 1.104×v - 1.003 (1-1);

[0069] The temperature before casting and the average casting speed are factors that affect the cooling of the silicon liquid. The weight of the cast silicon liquid can reflect the amount of silicon liquid in the ingot mold, which is also the main factor affecting the solidification of the silicon liquid. The impurity content in the silicon liquid is a factor that affects the melting point of the silicon liquid. According to the "Handbook of Thermodynamics", the melting point of pure silicon liquid is 1412℃. The Si content of the products currently produced by our factory is above 99.5%, and the remaining impurity elements are <0.05%. Therefore, the impact on the melting point can be ignored.

[0070] Table 1 Model summary

[0071]

[0072] Table 2 Analysis of variance

[0073]

[0074] Table 3 Regression coefficients

[0075]

[0076] It can be seen from Tables 1-3 that the Sig of pre-casting temperature, casting silicon liquid weight, and average casting speed all show a significance level of <0.005. The hypothesis test is valid and the regression equation is significant; and the corresponding regression coefficients of the three are all positive, indicating that these three factors are positively correlated with the element segregation degree. When any value of these three factors increases, the element segregation degree will increase.

[0077] In step S3, the data in the data source are divided into three categories according to the initial angle θ (°) of the silicon package tilt of 5≤θ<7, 7≤θ<9, and 9≤θ<11, and the average angular velocity of the silicon package tilt in the data source is used as the independent variable, and the average casting speed is used as the dependent variable for regression analysis to determine the linear relationship between the average casting speed and the average angular velocity of the silicon package tilt under different initial angles of the silicon package tilt, and obtain formula (4)-formula (6); according to the initial angle of the silicon package tilt, the average casting speed reference value V1 is selected and substituted into v in formula (4) or formula (5) or formula (6), and the calculated average angular velocity of the silicon package tilt is recorded as the reference value of the average angular velocity of the silicon package tilt, Ω1;

[0078] When the initial tilt angle θ of the silicon package is: 5≤θ<7, then substitute into formula (4):

[0079] v = 0.026 × ω + 0.0716 (4);

[0080] When the initial tilt angle θ of the silicon package is: 7≤θ<9, then substitute into formula (5):

[0081] v = 0.023 × ω + 0.0027 (5);

[0082] When the initial tilt angle θ of the silicon package is: 9≤θ<11, then substitute into formula (6):

[0083] v = 0.021 × ω + 0.0020 (6);

[0084] In the process of preliminary experiments and fitting, it was found that if the initial tilt angle of the silicon package is not limited to three categories, the fitting result is v = 0.0169×ω + 0.0716, and the fitting R 2 is 0.116, while R of the above formulas (1), (2), and (3) 2 They are 0.713, 0.689 and 0.697 respectively, indicating that the method for calculating the reference value of the average angular velocity of the silicon package tilt in step S3 of this embodiment is relatively accurate and practical.

[0085] In step S4, it is also necessary to control the initial tilt angle of the silicon package to be 5 to 11 degrees.

[0086] Example 3

[0087] A method for controlling element segregation in the process of industrial silicon casting, firstly calculating an average casting speed reference value V1 and an average angular velocity reference value Ω1 of the silicon package tilt according to the actual casting situation. Wherein:

[0088] The calculation steps of the average casting speed reference value V1 include: presetting the target element segregation degree (PX) to 0%, and substituting the actually measured pre-casting temperature (T) of 1.493 kilodegrees Celsius and the actually measured weight of the silicon liquid cast in the silicon ladle (G) of 1.75t into formula (1-1), that is, 0 = 0.440×1.493 + 0.053×1.75 + 1.104×v - 1.003, and the calculated average casting speed (v) is recorded as the average casting speed reference value V1, V1=0.229 t / min;

[0089] PX = 0.440×T + 0.053×G + 1.104×v - 1.003 (1-1);

[0090] The calculation steps of the average angular velocity reference value Ω1 of the silicon package inclination include: the initial inclination angle (θ) of the silicon package during this casting is 6°, the average casting speed reference value V1=0.229 t / min is substituted into formula (4), that is, 0.229 = 0.026×ω +0.0716, and the calculated average angular velocity (ω) of the silicon package inclination is recorded as the average angular velocity reference value Ω1 of the silicon package inclination, Ω1=6.05° / min;

[0091] v = 0.026 × ω + 0.0716 Formula (4).

[0092] After the calculation is completed, the silicon liquid is continuously cast on the chute, the average casting speed is controlled to be 0.229 t / min, the initial angular velocity of the silicon bag tilting is controlled to be 9.99° / min, and the average angular velocity of the silicon bag tilting is controlled to be 6.05° / min.

[0093] Silicon liquid casting is performed in the above manner. After the silicon liquid flows into the silicon bag, the silicon liquid is sampled (i.e., liquid sample) to detect its Fe mass fraction, and the Fe mass fraction of the liquid sample is Fe2=0.442%; after the silicon liquid is cooled and shaped in the ingot mold, a random sample (i.e., solid sample) is taken from the bottom of the silicon plate to detect its Fe mass fraction, and the Fe mass fraction of the solid sample is Fe1=0.443%, and the element segregation degree PX=Fe1-Fe2=0.001% is calculated, which is close to 0, indicating that the casting according to the method of this embodiment can achieve the purpose of controlling the element segregation in the industrial silicon casting process.

[0094] Example 4

[0095] A method for controlling element segregation in the process of industrial silicon casting, firstly calculating an average casting speed reference value V1 and an average angular velocity reference value Ω1 of the silicon package tilt according to the actual casting situation. Wherein:

[0096] The calculation steps of the average casting speed reference value V1 include: presetting the target element segregation degree (PX) to 0%, and substituting the actually measured pre-casting temperature (T) of 1.512 kilodegrees Celsius and the actually measured weight of the silicon liquid cast in the silicon bag (G) of 1.91 t into formula (1-1), that is, 0 = 0.440×1.512 + 0.053×1.91 + 1.104×v - 1.003, and the calculated average casting speed (v) is recorded as the average casting speed reference value V1, V1=0.214 t / min;

[0097] PX = 0.440×T + 0.053×G + 1.104×v - 1.003 (1-1);

[0098] The calculation steps of the average angular velocity reference value Ω1 of the silicon package inclination include: the initial inclination angle (θ) of the silicon package during this casting is 8°, the average casting speed reference value V1=0.214 t / min is substituted into formula (5), that is, 0.214 = 0.023×ω +0.0027, and the calculated average angular velocity (ω) of the silicon package inclination is recorded as the average angular velocity reference value Ω1 of the silicon package inclination, Ω1=9.19° / min;

[0099] v = 0.023 × ω + 0.0027 (5).

[0100] After the calculation is completed, the silicon liquid is continuously cast on the chute, the average casting speed is controlled to be 0.214 t / min, the initial angular velocity of the silicon bag tilting is controlled to be 9.99° / min, and the average angular velocity of the silicon bag tilting is controlled to be 9.19° / min.

[0101] Silicon liquid casting is performed in the above manner. After the silicon liquid flows into the silicon bag, the silicon liquid is sampled (i.e., liquid sample) to detect its Fe mass fraction, and the Fe mass fraction of the liquid sample Fe2= 0.458% is obtained; after the silicon liquid is cooled and shaped in the ingot mold, a random sample (i.e., solid sample) is taken at the bottom of the silicon plate to detect its Fe mass fraction, and the Fe mass fraction of the solid sample Fe1= 0.460% is obtained, and the calculated element segregation degree PX= Fe1- Fe2= 0.002%, which is close to 0, indicating that casting according to the method of this embodiment can achieve the purpose of controlling element segregation in the industrial silicon casting process.

[0102] Example 5

[0103] A method for controlling element segregation in the process of industrial silicon casting, firstly calculating an average casting speed reference value V1 and an average angular velocity reference value Ω1 of the silicon package tilt according to the actual casting situation. Wherein:

[0104] The calculation steps of the average casting speed reference value V1 include: presetting the target element segregation degree (PX) to 0%, and substituting the actually measured pre-casting temperature (T) of 1.492 kilodegrees Celsius and the actually measured weight of the silicon liquid cast in the silicon ladle (G) of 1.87 t into formula (1-1), that is, 0 = 0.440×1.492 + 0.053×1.87 + 1.104×v - 1.003, and the calculated average casting speed (v) is recorded as the average casting speed reference value V1, V1=0.224 t / min;

[0105] PX = 0.440×T + 0.053×G + 1.104×v - 1.003 (1-1);

[0106] The calculation steps of the average angular velocity reference value Ω1 of the silicon package inclination include: the initial inclination angle (θ) of the silicon package during this casting is 10°, the average casting speed reference value V1=0.224 t / min is substituted into formula (6), that is, 0.224 = 0.021×ω +0.0020, and the calculated average angular velocity (ω) of the silicon package inclination is recorded as the average angular velocity reference value Ω1 of the silicon package inclination, Ω1=10.57° / min;

[0107] v = 0.021 × ω + 0.0020 (6).

[0108] After the calculation is completed, the silicon liquid is continuously cast on the chute, the average casting speed is controlled to be 0.224 t / min, the initial angular velocity of the silicon bag tilting is controlled to be 9.99° / min, and the average angular velocity of the silicon bag tilting is controlled to be 10.57° / min.

[0109] Silicon liquid casting is performed in the above manner. After the silicon liquid flows into the silicon bag, the silicon liquid is sampled (i.e., liquid sample) to detect its Fe mass fraction, and the Fe mass fraction of the liquid sample is Fe2 = 0.475%; after the silicon liquid is cooled and shaped in the ingot mold, a random sample (i.e., solid sample) is taken at the bottom of the silicon plate to detect its Fe mass fraction, and the Fe mass fraction of the solid sample is Fe1 = 0.476%, and the calculated element segregation degree PX = Fe1- Fe2 = 0.001%, which is close to 0, indicating that casting according to the method of this embodiment can achieve the purpose of controlling element segregation in the industrial silicon casting process.

[0110] Example 6

[0111] A casting control system for realizing a method for controlling element segregation in an industrial silicon casting process, the casting control system comprises a silicon bag, a bag turning machine for controlling the inclination of the silicon bag, a chute, an ingot mold, and a DCS control device 1. A temperature measuring probe 2 is arranged in the silicon bag for monitoring the temperature before casting, a first weight sensor 3 is arranged at the bottom of the silicon bag for monitoring the weight of the casting silicon liquid; a second weight sensor 5 is arranged at the bottom of the chute for monitoring the weight of the chute.

[0112] The signal input end of the DCS control device 1 is respectively connected to the signal output end of the temperature measuring head 2, the signal output end of the first weight sensor 3, and the signal output end of the second weight sensor 5, and the signal output end of the DCS control device 1 is connected to the bag turning machine motor 6.

[0113] Example 7

[0114] A casting control system for realizing a method for controlling element segregation in an industrial silicon casting process, which is the same as Example 6 as a whole, except that, Figure 1 As shown, a tilt sensor 4 is provided on one side of the silicon package for monitoring the tilt angle of the silicon package; the signal input end of the DCS control device 1 is signal-connected to the signal output end of the tilt sensor 4 .

[0115] Example 8

[0116] The method for casting using the casting control system of Example 7 comprises the following steps:

[0117] P1, firstly, a target value of element segregation is preset, the temperature measuring head 2 transmits the monitored pre-casting temperature signal to the DCS control device 1, the first weight sensor 3 transmits the monitored casting silicon liquid weight signal to the DCS control device 1, the DCS control device 1 substitutes the target value of element segregation, the pre-casting temperature, and the casting silicon liquid weight into the PX, T, and G in the formula (1) set in advance for calculation, and records the obtained average casting speed as the average casting speed reference value V1 (t / min);

[0118] PX = a × T + b × G + c × v + d Formula (1);

[0119] P2, the DCS control device 1 controls the motor 6 of the bag turning machine to start running, so that the silicon bag starts to tilt at an initial angular velocity of 8-9.99° / min;

[0120] P3, the second weight sensor 5 transmits the monitored chute weight signal to the DCS control device 1. When the monitored chute weight continues to increase in a short period of time, it means that the silicon liquid has fallen from the silicon bag onto the chute. At this time, the DCS control device 1 substitutes the average casting speed reference value V1 into the v in the formula (2) set in advance for calculation, and obtains the average angular velocity reference value Ω1 (° / min);

[0121] v = e × ω + f (2);

[0122] P4. The DCS control device 1 controls the bag turning machine motor 6 to continue running at an average angular velocity of the silicon bag tilting of Ω1° / min until the casting is completed.

[0123] Example 9

[0124] The method for casting using the casting control system of Example 7 comprises the following steps:

[0125] P1. First, a target value of element segregation is preset. The temperature measuring head 2 transmits the monitored pre-casting temperature signal to the DCS control device 1. The first weight sensor 3 transmits the monitored casting silicon liquid weight signal to the DCS control device 1. The DCS control device 1 substitutes the target value of element segregation, the pre-casting temperature, and the casting silicon liquid weight into PX, T, and G in the formula (1-1) set in advance for calculation, and records the obtained average casting speed as the average casting speed reference value V1 (t / min);

[0126] PX = 0.440×T + 0.053×G + 1.104×v - 1.003 (1-1);

[0127] P2, the DCS control device 1 controls the motor 6 of the bag turning machine to start running, so that the silicon bag starts to tilt at an initial angular velocity of 8-9.99° / min;

[0128] P3, the inclination sensor 4 transmits the monitored silicon bag inclination angle signal to the DCS control device 1, and the second weight sensor 5 transmits the monitored chute weight signal to the DCS control device 1. When the weight of the chute is monitored to increase continuously in a short period of time, it means that the silicon liquid has fallen from the silicon bag to the chute. The inclination angle of the silicon bag monitored by the inclination sensor 4 at this time is used as the initial inclination angle θ of the silicon bag, and it is determined whether it belongs to the range of 5≤θ<7, 7≤θ<9, 9≤θ<11. Based on this, the average casting speed reference value V1 is selected to be substituted into the v in the pre-set formula (4) or formula (5) or formula (6) for calculation to obtain the average angular speed reference value Ω1 (° / min);

[0129] When the initial tilt angle θ of the silicon package is: 5≤θ<7, then substitute into formula (4):

[0130] v = 0.026 × ω + 0.0716 (4);

[0131] When the initial tilt angle θ of the silicon package is: 7≤θ<9, then substitute into formula (5):

[0132] v = 0.023 × ω + 0.0027 (5);

[0133] When the initial tilt angle θ of the silicon package is: 9≤θ<11, then substitute into formula (6):

[0134] v = 0.021 × ω + 0.0020 (6);

[0135] P4. The DCS control device 1 controls the bag turning machine motor 6 to continue running at an average angular velocity of the silicon bag tilting of Ω1° / min until the casting is completed.

[0136] Example 10

[0137] The method for casting using the casting control system of Example 7 comprises the following steps: firstly, the target value of element segregation is preset to 0%, the temperature measuring head 2 transmits the monitored pre-casting temperature (1.493 kilo degrees Celsius) to the DCS control device 1, the first weight sensor 3 transmits the monitored casting silicon liquid weight (1.75 t) to the DCS control device 1, and the DCS control device 1 calculates according to the formula (1-1) set in advance to obtain the average casting speed reference value V1=0.229 t / min; the DCS control device 1 controls the motor 6 of the bag flipping machine to start running, so that the silicon bag starts to tilt at an initial angular velocity of 9.99° / min. The tilt sensor 4 transmits the detected tilt angle of the silicon bag to the DCS control device 1, and the second weight sensor 5 transmits the detected weight of the chute to the DCS control device 1. When the weight of the chute is detected to increase continuously within 3s, it indicates that the silicon liquid has flowed out of the silicon bag and fallen on the chute. The tilt angle of the silicon bag detected by the tilt sensor 4 at this time is used as the initial tilt angle θ (6°) of the silicon bag. The DCS control device 1 determines that it belongs to the range of 5≤θ<7, and accordingly selects to substitute the average casting speed reference value V1 into formula (4), and obtains the average angular velocity reference value Ω1=6.05° / min; the DCS control device 1 controls the motor 6 of the bag flipping machine to continue running at an average angular velocity of 6.05° / min until the casting is completed;

[0138] v = 0.026 × ω + 0.0716 Formula (4).

[0139] The present invention is not limited to the technical field of industrial silicon casting, and the principles contained therein can also be applied to other melt casting industries.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling element segregation in an industrial silicon casting process, characterized in that: It includes the following steps: S1. Obtaining a data source: collecting historical data of silicon liquid casting of several furnaces, and screening the historical data as a data source; the historical data includes the pre-casting temperature, the weight of the casting silicon liquid, the average casting speed, the liquid sample Fe mass fraction, the solid sample Fe mass fraction, the initial angle of inclination of the silicon bag, the initial angular velocity of inclination of the silicon bag, the average angular velocity of inclination of the silicon bag, and the calculated element segregation degree of each casting; S2. Obtaining an average casting speed reference value: taking the pre-casting temperature, casting silicon liquid weight, and average casting speed in the data source as independent variables, and taking the element segregation degree as the dependent variable for regression analysis, determining the linear relationship between the element segregation degree and the pre-casting temperature, the casting silicon liquid weight, and the average casting speed, and obtaining formula (1); presetting an element segregation degree target value, and substituting the preset element segregation degree target value and the pre-casting temperature and casting silicon liquid weight in actual casting into PX, T, and G in formula (1), respectively, and recording the calculated average casting speed as the average casting speed reference value, V1 (tons / minute); PX = a × T + b × G + c × v + d Formula (1); Where, PX is the element segregation degree (%), T is the temperature before casting (thousands of degrees Celsius), G is the weight of the casting silicon liquid (tons), v is the average casting speed (tons / minute), a, b, c are the regression coefficients of T, G, v respectively, and d is a constant; S3, obtaining a reference value of the average angular velocity of the silicon package tilt: using the average angular velocity of the silicon package tilt in the data source as an independent variable and the average casting speed as a dependent variable for regression analysis, determining the linear relationship between the average casting speed and the average angular velocity of the silicon package tilt, and obtaining formula (2); substituting the average casting speed reference value V1 obtained in step S2 into v in formula (2), and recording the calculated average angular velocity of the silicon package tilt as the reference value of the average angular velocity of the silicon package tilt, Ω1 (degrees / minute); v = e × ω + f (2); Where ω is the average angular velocity of the silicon package tilt (degrees / minute), e is the regression coefficient of ω, and f is a constant; S4. Control parameters for casting: continuously cast the silicon liquid on the chute, control the average casting speed to be V1 ton / minute, control the initial angular velocity of the silicon package tilt to be 8~9.99 degrees / minute, and control the average angular velocity of the silicon package tilt to be Ω1 degree / minute.

2. A method for controlling element segregation in an industrial silicon casting process according to claim 1, characterized in that: The element segregation degree is calculated according to formula (3); PX = Fe1 - Fe2 (3); Wherein, Fe1 is the mass fraction of Fe in solid sample (%), and Fe2 is the mass fraction of Fe in liquid sample (%).

3. The method for controlling element segregation in an industrial silicon casting process according to claim 1, characterized in that: In the step S1, the screening is specifically: selecting data in the historical data that simultaneously satisfies the pre-casting temperature of 1480-1560° C. and the average casting speed of 0.130-0.315 t / min as the data source, so as to remove abnormal data and interference.

4. A method for controlling element segregation in an industrial silicon casting process according to claim 3, characterized in that: In the formula (1) of step S2, a = 0.440, b = 0.053, c = 1.104, and d = -1.

003.

5. The method for controlling element segregation in an industrial silicon casting process according to claim 3, characterized in that: In the step S3, the data in the data source are divided into three categories according to the initial angle θ (degrees) of the silicon package tilt: 5≤θ<7, 7≤θ<9, and 9≤θ<11, and a regression analysis is performed with the average angular velocity of the silicon package tilt as the independent variable and the average casting speed as the dependent variable to determine the linear relationship between the average casting speed and the average angular velocity of the silicon package tilt at different initial angles of the silicon package tilt, and obtain equations (4) to (6); When the initial inclination angle θ of the silicon bag is 5≤θ<7, the average casting speed reference value V1 is substituted into v in formula (4); when the initial inclination angle θ of the silicon bag is 7≤θ<9, the average casting speed reference value V1 is substituted into v in formula (5); when the initial inclination angle θ of the silicon bag is 9≤θ<11, the average casting speed reference value V1 is substituted into v in formula (6); the calculated average angular velocity of the silicon bag inclination is recorded as the average angular velocity reference value Ω1 of the silicon bag inclination; v = 0.026 × ω + 0.0716 (4); v = 0.023 × ω + 0.0027 (5); v = 0.021 × ω + 0.0020 (6); In step S4, the initial tilt angle of the silicon package is controlled to be 5 to 11 degrees.

6. A casting control system for realizing a method for controlling element segregation in an industrial silicon casting process as described in any one of claims 1 to 5, characterized in that: The casting control system includes a silicon bag, a bag turning machine for controlling the inclination of the silicon bag, a chute, an ingot mold, and a DCS control device; A temperature measuring coupler is arranged in the silicon bag to monitor the temperature before casting; a first weight sensor is arranged at the bottom of the silicon bag to monitor the weight of the casting silicon liquid; a second weight sensor is arranged at the bottom of the chute to monitor the weight of the chute; the signal input end of the DCS control device is respectively connected to the signal output end of the temperature measuring coupler, the signal output end of the first weight sensor, and the signal output end of the second weight sensor, and the signal output end of the DCS control device is connected to the motor signal of the bag turning machine.

7. The casting control system according to claim 6, characterized in that: A tilt sensor is arranged on one side of the silicon package to monitor the tilt angle of the silicon package; and a signal input end of the DCS control device is signal-connected to a signal output end of the tilt sensor.

8. A method for casting using the casting control system according to claim 7, characterized in that: It includes the following steps: P1, firstly, a target value of element segregation is preset, the temperature measuring head transmits the monitored pre-casting temperature signal to the DCS control device, the first weight sensor transmits the monitored casting silicon liquid weight signal to the DCS control device, the DCS control device substitutes the target value of element segregation, the pre-casting temperature, and the casting silicon liquid weight into PX, T, and G in the formula (1) set in advance for calculation, and records the obtained average casting speed as the average casting speed reference value V1 (tons / minute); P2, the DCS control device controls the motor of the bag turning machine to start running, so that the silicon bag starts to tilt at an initial angular velocity of 8-9.99 degrees / minute; P3, the second weight sensor transmits the monitored chute weight signal to the DCS control device. When the monitored chute weight continues to increase in a short period of time, it indicates that the silicon liquid has fallen from the silicon bag onto the chute; the DCS control device substitutes the average casting speed reference value V1 in step P1 into the v in the formula (2) set in advance for calculation, and records the obtained average angular velocity of the silicon bag tilt as the average angular velocity reference value Ω1 (degrees / minute) of the silicon bag tilt; P4. The DCS control device controls the bag turning machine motor to continue running at an average angular velocity of silicon bag tilting of Ω1 degree / minute until the casting is completed.

9. The method for casting using a casting control system according to claim 8, characterized in that: In step P3, the inclination sensor transmits the monitored silicon bag inclination angle signal to the DCS control device, and the second weight sensor transmits the monitored chute weight signal to the DCS control device. When it is monitored that the weight of the chute continues to increase in a short period of time, it means that the silicon liquid has fallen from the silicon bag to the chute. The inclination angle of the silicon bag monitored by the inclination sensor at this time is used as the initial inclination angle θ (degrees) of the silicon bag, and it is determined whether it belongs to the category of 5≤θ<7 or 7≤θ<9 or 9≤θ<11. The average casting speed reference value V1 is substituted into v in formula (4) or formula (5) or formula (6) for calculation, and the obtained average angular velocity of the silicon bag inclination is recorded as the average angular velocity reference value Ω1.

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