A method for selecting silicon powder particles suitable for cold hydrogenation fluidized bed

Abstract

The present invention discloses a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed. The key points of the technical solution are to assume that the potential energy of the silicon powder in the bed is offset by the kinetic energy of the gas phase material, calculate the gas flow rate μ of the gas phase on the surface of the silicon powder in the fluidized bed; select the mesh size of the silicon powder particles according to the real-time rising gas flow rate, and maintain the bulk density in the fluidized bed at 200-2500 kg / m 3 The mesh ratio of all silicon powder particles fed into the fluidized bed is calculated. The present invention provides a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed based on the amount of silicon tetrachloride vaporized and the rising gas velocity within the fluidized bed. The method is simple to calculate and easy to operate, making it suitable for use in cold hydrogenated fluidized bed production operations. It reduces the amount of metallic silicon powder particles carried out of the fluidized bed, prevents damage to the distributor, and achieves a high conversion rate.

Description

Technical Field

[0001] The present invention relates to the technical field of polysilicon production, and more particularly to a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed. Background Art

[0002] Silicon powder is one of the main raw materials for the reaction in the cold hydrogenation fluidized bed reactor and is the reactant that directly participates in the conversion reaction in the fluidized bed. The metal silicon powder particles and the catalyst pass through the silicon powder drying tank and the high-pressure silo, and the moisture and oxygen contained in the metal silicon powder and the catalyst are dried and replaced. After passing the replacement, they are directly added to the fluidized bed to measure the bed stacking density. A suitable proportion of hydrogen and silicon tetrachloride mixed gas is introduced through the feed port at the bottom of the fluidized bed to react. The existing problem is that the particle size of the metal silicon powder is too small. After being added to the fluidized bed, the bed is not stacked and fluidized before being carried out by the airflow. This results in a lower fluidized bed conversion rate, high silicon powder consumption, and excessive discharge to the post-processing system, which increases the difficulty of post-processing in the post-processing system. The particle size of the metal silicon powder is too large, and the airflow cannot lift the metal silicon powder particles for fluidization. The metal silicon powder particle bed accumulates at the distributor at the bottom of the fluidized bed, damaging the distributor nozzle and posing a risk of bed collapse. Therefore, it is necessary to regulate the selection of the particle size of the metal silicon powder particles added to the fluidized bed to ensure that the metal granular silicon powder forms an effective bed accumulation in the fluidized bed, thereby improving the fluidized bed conversion rate, reducing the amount of metal silicon powder particles being carried out of the fluidized bed, and preventing damage to the distributor.

[0003] Chinese patent CN104634708A discloses a method for predicting particle density and size distribution within a fluidized bed based on computational fluid dynamics. The method includes steps 1: establishing a basic flow reaction model within the fluidized bed; 2: establishing a mathematical model describing the variation patterns of particle phase density and particle size; and 3: predicting the density and particle size distribution within the fluidized bed. This method uses computational fluid dynamics to simulate the fluidized bed and, in conjunction with the mathematical model describing the variation patterns of particle phase density and particle size, makes real-time corrections to the particle density and particle size. This method accurately predicts the particle density and particle size distribution within the fluidized bed, providing a theoretical basis for fluidized bed performance prediction, optimization control, and scale-up design.

[0004] However, when it comes to selecting silicon powder particles for cold hydrogenation fluidized bed reactors, the above method is too theoretical and the calculation process is quite complicated, making it unsuitable for practical applications. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed. The method provides a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed based on different silicon tetrachloride vaporization amounts and different rising gas flow rates in the fluidized bed. The method is simple to calculate and easy to operate, and is suitable for production operations in a cold hydrogenated fluidized bed. It reduces the amount of metallic silicon powder particles carried out of the fluidized bed, prevents damage to the distributor, and can also achieve a higher conversion rate.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solution: a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed, the specific steps of which are as follows:

[0007] S1. Obtain the rising gas velocity in the fluidized bed in real time, select the mesh size of silicon powder according to the real-time rising gas velocity, and maintain the bulk density in the fluidized bed at 200-2500 kg / m 3 Inside.

[0008] The critical fluidization velocity μmf and entrainment velocity μt of each mesh size silicon powder are obtained through experiments, and μmf~μt is the gas flow rate range of the silicon powder of that mesh size; if the real-time rising gas flow rate is within the gas flow rate range of the silicon powder of a certain mesh size, the silicon powder of that mesh size is selected and put into the fluidized bed.

[0009] S2. Calculate the mesh ratio of all silicon powder particles added, and use this mesh ratio for subsequent silicon powder addition.

[0010] The calculation steps for the real-time ascending gas velocity in S1 are as follows:

[0011] S11. Calculate bed density ρ b .

[0012]

[0013] Where g is the acceleration due to gravity, Δp is the pressure difference in the fluidized bed, and Δh is the bed height.

[0014] S12. Calculate the total mass mtotal of the fluid and particles in the bed.

[0015] mtotal=ρ b *V

[0016] Where V is the bed volume, which is calculated based on the cross section and bed height of the fluidized bed.

[0017] S13. Assuming that the potential energy of the silicon powder in the bed is offset by the kinetic energy of the gas phase, calculate the gas flow rate μ of the gas phase on the surface of the silicon powder in the fluidized bed. The formula is as follows:

[0018]

[0019] E P = mtotal*g*Δh

[0020] Among them, m p is the total mass of particles in the bed, and is the measured value.

[0021] The present invention is further configured as follows: S1 also needs to limit the height of the dense phase zone, and the bulk density of the dense phase zone is greater than 600 kg / m 3 , the height of the dense phase zone in the fluidized bed is maintained in the range of 1 to 10m.

[0022] The present invention is further configured as follows: silicon powder particles are divided into four groups according to mesh number, namely 0-20 mesh silicon powder particles, 20-30 mesh silicon powder particles, 30-40 mesh silicon powder particles, and silicon powder particles above 40 mesh.

[0023] The present invention is further configured to include: step S3, performing S1 and S2 respectively with different vaporized amounts of silicon tetrachloride to obtain silicon powder particle ratios of different mesh sizes corresponding to different vaporized amounts of silicon tetrachloride.

[0024] The present invention is further configured such that the vaporization rate of silicon tetrachloride in the experiment in S3 ranges from 60 to 140 t / h.

[0025] The present invention is further configured as follows: the silicon powder particle ratio in S3 is as follows: when the silicon tetrachloride vaporization rate is 60t / h, the silicon powder particle ratio of the four mesh groups is 0-5:10-20:10-35:20-40; when the silicon tetrachloride vaporization rate is 70t / h, the silicon powder particle ratio of the four mesh groups is 0-5:15-25:10-30:20-40; when the silicon tetrachloride vaporization rate is 80t / h, the silicon powder particle ratio of the four mesh groups is 5-10:15-25:10-40:10-25; when the silicon tetrachloride vaporization rate is 90t / h, the silicon powder particle ratio of the four mesh groups is 5-15:15-45:10-20:10-20; when the silicon tetrachloride vaporization rate is 100t / h When the vaporization rate of silicon tetrachloride is 110t / h, the ratio of silicon powder particles of the four mesh groups is 20-35:30-45:0-10:5-10; when the vaporization rate of silicon tetrachloride is 120t / h, the ratio of silicon powder particles of the four mesh groups is 25-35:35-45:5-15:0-5; when the vaporization rate of silicon tetrachloride is 130t / h, the ratio of silicon powder particles of the four mesh groups is 30-35:40-45:10-15:0-5; when the vaporization rate of silicon tetrachloride is 140t / h, the ratio of silicon powder particles of the four mesh groups is 30-40:30-40:10-15:0-5.

[0026] The present invention is further configured such that the rising gas velocity in S1 is maintained at 0.5 to 10 m / s.

[0027] The present invention is further configured as follows: the ratio of the silicon powder particles of the four mesh groups in S2 is 24-37:34-49:9-24:10-17.

[0028] In summary, the present invention has the following beneficial effects compared to the prior art: the present invention provides a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed based on different silicon tetrachloride vaporization amounts and different rising gas flow rates in the fluidized bed. The method is simple to calculate and easy to operate, and is suitable for production operations in a cold hydrogenated fluidized bed. It reduces the amount of metallic silicon powder particles carried out of the fluidized bed, prevents damage to the distributor, and can also achieve a higher conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of an embodiment;

[0030] Figure 2 The fluidized bed structure applicable to this embodiment;

[0031] Figure 3 Schematic diagram of the silicon powder particle ratio results in S1;

[0032] Figure 4 The corresponding diagram of conversion rate in fluidized bed under different silicon tetrachloride vaporization amounts;

[0033] Figure 5 This is the distribution diagram of silicon powder particle size when the rising gas flow rate is 0.5m / s to 10m / s;

[0034] In the figure: 1. Feed pipe; 2. Distributor; 3. Guide trough; 4. Cyclone separator; 5. Silicon powder feed port; 6. Exhaust gas outlet pipe. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the invention.

[0036] Example 1

[0037] like Figure 1 As shown, this is a flow chart of Example 1 of the present invention; Figure 2 As shown, the fluidized bed structure applicable to this embodiment includes a feed pipe 1, a distributor 2, a guide trough 3, a cyclone separator 4, a silicon powder feed port 5, an exhaust gas outlet pipe 6 and pressure measuring ports P1 to P5.

[0038] A method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed, comprising the following steps:

[0039] S1. Obtain the rising gas velocity in the fluidized bed in real time, select the mesh size of silicon powder according to the real-time rising gas velocity, and maintain the bulk density in the fluidized bed at 200-2500 kg / m 3 In this embodiment, the bulk density is further limited to 1000-2000 kg / m 3 Inside.

[0040] The critical fluidization velocity μmf and entrainment velocity μt of each mesh size silicon powder are obtained through experiments, and μmf~μt is the gas flow rate range of the silicon powder of that mesh size; if the real-time rising gas flow rate is within the gas flow rate range of the silicon powder of a certain mesh size, the silicon powder of that mesh size is selected and put into the fluidized bed.

[0041] Specifically, silicon powder can be selected according to the rising gas velocity of each bed layer in the fluidized bed.

[0042] S2. Calculate the mesh ratio of all silicon powder particles added, and use this mesh ratio for subsequent silicon powder addition.

[0043] The calculation steps for the real-time ascending gas velocity in S1 are as follows:

[0044] S11. Calculate bed density ρ b .

[0045]

[0046] Where g is the acceleration due to gravity, Δp is the pressure difference in the fluidized bed, and Δh is the bed height. Δp is calculated based on the test data from pressure gauges P1 to P5, and Δh is calculated based on the heights of the pressure gauges P1 to P5.

[0047] S12. Calculate the total mass mtotal of the fluid and particles in the bed.

[0048] mtotal=ρ b *V

[0049] Where V is the bed volume, which is calculated based on the cross section and bed height of the fluidized bed.

[0050] S13. Assuming that the potential energy of the silicon powder in the bed is offset by the kinetic energy of the gas phase, calculate the gas flow rate μ of the gas phase on the surface of the silicon powder in the fluidized bed. The formula is as follows:

[0051]

[0052] E P = mtotal*g*Δh

[0053] Among them, mp is the total mass of particles in the bed, and is the measured value.

[0054] In S1, the height of the dense phase zone must be limited. The bulk density of the dense phase zone is greater than 600 kg / m 3 , the height of the dense phase zone in the fluidized bed is maintained in the range of 1 to 10 m. In this embodiment, the height of the dense phase zone in the fluidized bed is further limited to the range of 5 to 8 m.

[0055] Silica powder particles are divided into four groups according to the mesh number, namely 0-20 mesh silica powder particles, 20-30 mesh silica powder particles, 30-40 mesh silica powder particles, and silica powder particles above 40 mesh.

[0056] This embodiment further includes step S3, performing steps S1 and S2 respectively with different vaporized silicon tetrachloride amounts to obtain silicon powder particle ratios of different mesh sizes corresponding to different vaporized silicon tetrachloride amounts.

[0057] Specifically, the vaporization rate of silicon tetrachloride in the experiment in S3 ranges from 60 to 140 t / h.

[0058] like Figure 3 As shown, the silicon powder particle ratio results in S3 are as follows: when the silicon tetrachloride vaporization rate is 60t / h, the silicon powder particle ratio of the four mesh groups is 0-5:10-20:10-35:20-40; when the silicon tetrachloride vaporization rate is 70t / h, the silicon powder particle ratio of the four mesh groups is 0-5:15-25:10-30:20-40; when the silicon tetrachloride vaporization rate is 80t / h, the silicon powder particle ratio of the four mesh groups is 5-10:15-25:10-40:10-25; when the silicon tetrachloride vaporization rate is 90t / h, the silicon powder particle ratio of the four mesh groups is 5-15:15-45:10-20:10-20; when the silicon tetrachloride vaporization rate is 100t / h, the silicon powder particle ratio of the four mesh groups is 0-5:15-25:10-30:20-40 The ratio of silicon powder particles in each mesh group is 10-30:20-45:5-20:0-5; when the vaporization rate of silicon tetrachloride is 110t / h, the ratio of silicon powder particles in four mesh groups is 20-35:30-45:0-10:5-10; when the vaporization rate of silicon tetrachloride is 120t / h, the ratio of silicon powder particles in four mesh groups is 25-35:35-45:5-15:0-5; when the vaporization rate of silicon tetrachloride is 130t / h, the ratio of silicon powder particles in four mesh groups is 30-35:40-45:10-15:0-5; when the vaporization rate of silicon tetrachloride is 140t / h, the ratio of silicon powder particles in four mesh groups is 30-40:30-40:10-15:0-5.

[0059] like Figure 4As shown, the conversion rate in the fluidized bed corresponding to different silicon tetrachloride vaporization amounts. It can be seen that this embodiment can not only reduce the metal silicon powder particles being carried out of the fluidized bed and prevent damage to the distributor, but also ensure that the metal particle silicon powder forms an effective bed accumulation in the fluidized bed, thereby improving the fluidized bed conversion rate to more than 25%.

[0060] In summary, this embodiment provides a method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed based on different silicon tetrachloride vaporization amounts and different rising gas flow rates in the fluidized bed. The method is simple to calculate and easy to operate, and is suitable for production operations in a cold hydrogenated fluidized bed. It reduces the amount of metallic silicon powder particles carried out of the fluidized bed, prevents damage to the distributor, and can also achieve a high conversion rate.

[0061] Example 2

[0062] like Figure 5 As shown, this embodiment differs from Example 1 in that S3 is omitted and the ascending gas velocity in S1 is limited to 0.5-10 m / s. The optimal silicon powder particle ratios for the four mesh sizes in S2 obtained through testing are 24-37:34-49:9-24:10-17, resulting in a final conversion rate of 23-28%.

[0063] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed, characterized in that: The specific steps are as follows: S1. Obtain the rising gas velocity in the fluidized bed in real time, select the mesh size of silicon powder according to the real-time rising gas velocity, and maintain the bulk density in the fluidized bed at 200-2500 kg / m 3 Inside; The critical fluidization velocity μmf and carry-out velocity μt of each mesh size silicon powder are obtained through experiments. μmf~μt is the gas flow rate range of the mesh size silicon powder. If the real-time rising gas flow rate is within the gas flow rate range of a certain mesh size silicon powder, the mesh size silicon powder is selected and fed into the fluidized bed. The bulk density in the dense phase is greater than 600kg / m 3 , the height of the dense phase zone in the fluidized bed is maintained within the range of 1 to 10 m; S2. Calculate the mesh ratio of all silicon powder particles added, and use this mesh ratio for subsequent silicon powder addition; S3, performing S1 and S2 respectively with different amounts of vaporized silicon tetrachloride to obtain silicon powder particle ratios of different mesh sizes corresponding to different amounts of vaporized silicon tetrachloride; The calculation steps for the real-time ascending gas velocity in S1 are as follows: S11. Calculate bed density ρ b ; Where g is the acceleration of gravity, Δp is the pressure difference in the fluidized bed, and Δh is the bed height; S12, calculate the total mass mtotal of the fluid and particles in the bed; mtotal=ρ b *V Where V is the bed volume, which is calculated based on the cross section and bed height of the fluidized bed; S13. Assuming that the potential energy of the silicon powder in the bed is offset by the kinetic energy of the gas phase, calculate the gas flow rate μ of the gas phase on the surface of the silicon powder in the fluidized bed. The formula is as follows: E P = m_total * g * Δh Among them, m p is the total mass of particles in the bed, and is the measured value.

2. The method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed according to claim 1, characterized in that: Silica powder particles are divided into four groups according to the mesh number, namely 0-20 mesh silica powder particles, 20-30 mesh silica powder particles, 30-40 mesh silica powder particles, and silica powder particles above 40 mesh.

3. The method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed according to claim 1, characterized in that: The vaporization rate of silicon tetrachloride in the experiment S3 ranged from 60 to 140 t / h.

4. The method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed according to claim 3, characterized in that: The results of the silicon powder particle ratio in S3 are as follows: when the silicon tetrachloride vaporization rate is 60t / h, the silicon powder particle ratio of the four mesh groups is 0-5:10-20:10-35:20-40; when the silicon tetrachloride vaporization rate is 70t / h, the silicon powder particle ratio of the four mesh groups is 0-5:15-25:10-30:20-40; when the silicon tetrachloride vaporization rate is 80t / h, the silicon powder particle ratio of the four mesh groups is 5-10:15-25:10-40:10-25; when the silicon tetrachloride vaporization rate is 90t / h, the silicon powder particle ratio of the four mesh groups is 5-15:15-45:10-20:10-20; when the silicon tetrachloride vaporization rate is 100t / h, the silicon powder particle ratio of the four mesh groups is 0-5:15-25:10-30:20-40 The ratio of silicon powder particles in each group is 10-30:20-45:5-20:0-5; when the vaporization rate of silicon tetrachloride is 110t / h, the ratio of silicon powder particles in four mesh groups is 20-35:30-45:0-10:5-10; when the vaporization rate of silicon tetrachloride is 120t / h, the ratio of silicon powder particles in four mesh groups is 25-35:35-45:5-15:0-5; when the vaporization rate of silicon tetrachloride is 130t / h, the ratio of silicon powder particles in four mesh groups is 30-35:40-45:10-15:0-5; when the vaporization rate of silicon tetrachloride is 140t / h, the ratio of silicon powder particles in four mesh groups is 30-40:30-40:10-15:0-5.

5. The method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed according to claim 1, characterized in that: The rising gas velocity in S1 is maintained at 0.5-10 m / s.

6. The method for selecting silicon powder particles suitable for a cold hydrogenated fluidized bed according to claim 5, characterized in that: The ratio of silicon powder particles in the four mesh groups in S2 is 24~37:34~49:9~24:10~17.

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