High-density rapid fluidized bed reactor for hydrogenation reduction of silicon tetrachloride

Abstract

The utility model belongs to the technical field of new energy photovoltaic silicon material preparation, and discloses a high-density rapid fluidized bed reactor for hydrogenation reduction of silicon tetrachloride. The reactor consists of a high-density rapid fluidized bed, a cyclone separation system and a material returning system, wherein a turbulent fluidization section is connected with a rapid fluidization section through a reducing and reducing section; a first gas inlet, a distribution plate, a gas distributor, a particle feeding hole, a first material return inlet, a second gas inlet and a second material return inlet are sequentially arranged on the cone bottom, the turbulent flow fluidization section and the rapid fluidization section of the high-density rapid fluidized bed; particles separated by the first-stage cyclone separator of the reacted gas-solid mixture return to the turbulent flow fluidization section, and particles separated by the second-stage and above cyclone separators return to the rapid fluidization section. The high-density rapid fluidized bed reactor designed by the utility model has the advantages of full gas-solid contact, rapid heat transfer and mass transfer, higher hydrogenation reaction conversion rate, high operation flexibility and high volume utilization rate.

Description

Technical Field

[0001] The utility model belongs to the technical field of preparation of new energy photovoltaic silicon materials, and particularly relates to a high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride. Background Art

[0002] Polycrystalline silicon, the core raw material for photovoltaic cells, is primarily manufactured using a modified Siemens process. The hydrogenation reduction step is particularly critical in this method, successfully achieving a closed-loop recycling of the silicon tetrachloride byproduct. This significantly reduces the production cost of photovoltaic silicon materials and represents a significant breakthrough in the field of new energy photovoltaic technology in recent years.

[0003] Currently, silicon tetrachloride hydrogenation technologies can be divided into two types: hot hydrogenation and cold hydrogenation, depending on the feed method and reaction temperature. Cold hydrogenation technology, due to its advantages such as low reaction temperature, low energy consumption, and high conversion rate, has dominated hydrogenation processes both domestically and internationally. In the cold hydrogenation process, metallurgical-grade silicon powder, silicon tetrachloride, and hydrogen are used as the main raw materials. Trichlorosilane is produced through a gas-solid phase reaction in a fluidized bed reactor under specific temperature and pressure conditions, using a copper- or nickel-based catalyst.

[0004] However, the current design and application of silicon tetrachloride hydrogenation reactors, both domestically and internationally, mostly utilize bubbling fluidized beds. This type of reactor presents a series of issues, including low superficial gas velocity, low gas-solid contact efficiency, limited solids inventory, low reactor volume utilization, and significant carryover of silicon powder and catalyst. These issues result in actual conversion rates for hydrogenation reduction reactions far below theoretical values, leaving significant room for improvement.

[0005] In the prior art, Chinese Patent CN201210171854.7 discloses a method for hydrosilane tetrachloride using rapid cyclic fluidization. While this method rapidly fluidizes the particles within the reactor, it still suffers from low solids content, low reactor throughput, and low volume utilization, making it difficult to meet the requirements for reaction yield and thermal balance in actual production. Therefore, optimizing and improving hydrosilane tetrachloride reactors remains a key issue that needs to be addressed in the photovoltaic technology field. Utility Model Content

[0006] To address the problems existing in current cold hydrogenation fluidized bed reactors, the present invention provides a high-density fast fluidized bed reactor for the hydrogenation reduction of silicon tetrachloride. The high-density fast fluidized bed is designed with a fluidizing section divided into a turbulent fluidization section and a fast fluidization section, which are coupled via a tapered section. In the turbulent fluidization section, the superficial gas velocity is increased, thereby increasing the gas-solid contact, heat transfer, and mass transfer rates in the dense phase, while maintaining the high solids holdup and high inventory characteristics of the dense phase fluidized bed. In the fast fluidization section, the tapered section is used to increase the particle concentration and fine powder circulation volume in the dilute phase, prolonging the particle residence time and reducing fine powder carryover, thereby achieving high-load and high-efficiency operation of the high-density fast fluidized bed reactor.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions: a high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride, comprising a high-density fast fluidized bed and a cyclone separation system and a return system matched therewith, wherein the high-density fast fluidized bed comprises a fluidized bed body, and is divided into four parts from top to bottom, a fast fluidization section, a variable diameter tapering section, a turbulent fluidization section and a cone bottom, a reaction gas outlet is provided at the top of the fast fluidization section, a first gas inlet is provided on the cone bottom, a particle feeding port and a first return inlet are provided on the turbulent fluidization section from bottom to top, a second gas inlet and a second return inlet are provided on the fast fluidization section from bottom to top, a distribution plate is provided inside between the cone bottom and the turbulent fluidization section, a slag discharge port is provided at the bottom of the cone bottom, and a slag discharge valve is provided on it , a gas distributor connected to the first gas inlet is provided inside the cone bottom; the cyclone separation system includes a first-level cyclone separator and a second-level cyclone separator, the air inlet of the first-level cyclone separator is connected to the reaction gas outlet through a first pipe, and the air inlet of the second-level cyclone separator is connected to the exhaust port of the first-level cyclone separator through a second pipe; the return system includes a first return pipe and a second return pipe, the dust exhaust port of the first-level cyclone separator is connected to the first return inlet through the first return pipe, a flow sealing valve is provided on the first return pipe, and a flow gas inlet is provided on it with hydrogen as the conveying gas, the dust exhaust port of the second cyclone separator is connected to the second return inlet through the second return pipe, and a buffer tank, a cone top valve and a conveying gas inlet are provided on the second return pipe in sequence according to the return direction.

[0008] As a further explanation and limitation of the above technical solution, the height ratio of the turbulent fluidization section to the fast fluidization section is 0.1-0.5.

[0009] As a further explanation and limitation of the above technical solution, the diameter ratio of the turbulent fluidization section to the fast fluidization section is 0.2-0.75.

[0010] As a further explanation and limitation of the above technical solution, the diameter of the turbulent fluidization section is 100-400 mm and the height is 1.5-4 m.

[0011] As a further explanation and limitation of the above technical solution, the diameter of the fast fluidization section is 50-200 mm and the height is 8.5-20 m.

[0012] As a further explanation and limitation of the above technical solution, the opening rate of the distribution plate is 0.5%-4%.

[0013] As a further explanation and limitation of the above technical solution, the distance between the second gas inlet and the bottom of the fast fluidization section is 65-120 mm.

[0014] As a further supplementary explanation of the above technical solution, the second gas inlet includes at least one pair, and each pair of the second gas inlets is symmetrically arranged.

[0015] As a further explanation and limitation of the above technical solution, the diameter ratio of the variable diameter tapering section is 0.2-0.75.

[0016] Compared with the existing bubbling fluidized bed cold hydrogenation reactor, the high-density fast fluidized bed reactor designed in this utility model has the following advantages:

[0017] 1. Significantly improve the processing capacity and volume utilization of the reactor: The utility model introduces a variable diameter tapered section to couple the turbulent fluidization section and the rapid fluidization section, thereby designing a new type of high-density rapid fluidized bed. This design not only maintains the high solid content and high inventory characteristics of the traditional bubbling fluidized bed in the dense phase zone, but also significantly reduces the volume of the dilute phase zone, allowing the reaction particles to reach a higher concentration within a limited space. Therefore, the high-density rapid fluidized bed designed by the utility model greatly improves the production efficiency and volume utilization of the reactor, effectively reduces the overall equipment investment, and brings higher economic benefits to the enterprise.

[0018] 2. Significantly Improved Hydrogenation Conversion Rate: The high-density fast fluidized bed designed in this utility model utilizes turbulent fluidization and fast fluidization technologies, significantly enhancing gas-solid contact, heat transfer, and mass transfer efficiency compared to traditional bubbling fluidization. Furthermore, the riser design extends particle residence time, while the staged feeding of silicon tetrachloride and hydrogen further enhances the kinetics of the hydrogenation reaction. These innovative designs work together to significantly improve the single-pass conversion rate of silicon tetrachloride within the high-density fast fluidized bed, enhancing product quality and yield.

[0019] 3. The operational flexibility of the reactor is greatly enhanced: The high-density fast fluidized bed designed in the present invention is able to operate stably within a wide range of gas velocities, thanks to the flexibility of turbulent fluidization and fast fluidization technologies. According to the reaction kinetics of the particles and the required conversion rate, the air intake of the turbulent fluidization section and the fast fluidization section can be flexibly adjusted to achieve the optimal reaction conditions. In addition, by adjusting the fluidizing gas volume of the flow sealing valve, the particle circulation volume can be effectively controlled, further expanding the operating range of the reactor. This highly flexible operating mode enables the reactor to adapt to a variety of different process requirements and improves the adaptability and reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a process structure diagram of a high-density fast fluidized bed reactor in the utility model;

[0021] Figure 2 This is a structural diagram of a high-density fast fluidized bed in an embodiment of the present utility model.

[0022] In the figure: the high-density fast fluidized bed is 100, the cyclone separation system is 200, and the return system is 300.

[0023] The high-density fast fluidized bed comprises: a fluidized bed body 1, a fast fluidizing section 101, a diameter-reducing and tapering section 102, a turbulent fluidizing section 103, a conical bottom 104, a reaction gas outlet 105, a first gas inlet 2, a particle feeding port 3, a second gas inlet 4, a slag discharge port 5, a slag discharge valve 6, a first return material inlet 7, a second return material inlet 8, a gas distributor 9, and a distribution plate 10;

[0024] The cyclone separation system includes: a first-stage cyclone separator 11, a second-stage cyclone separator 12, a first pipeline 13, and a second pipeline 14;

[0025] The return system includes: a first return pipe 15 , a flow sealing valve 16 , a second return pipe 17 , a buffer tank 18 , a cone top valve 19 , a conveying gas inlet 20 , and a flow gas inlet 21 . DETAILED DESCRIPTION

[0026] In order to further illustrate the technical solution of the present invention, Figure 1 and 2 According to the design scheme and implementation process, we select the optimal embodiment to further illustrate the utility model.

[0027] As attached Figure 1 and 2As shown, a high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride includes a high-density fast fluidized bed 100 and a cyclone separation system 200 and a return system 300 matched therewith. The high-density fast fluidized bed 100 includes a fluidized bed body 1, and is divided into four parts from top to bottom: a fast fluidizing section 101, a variable diameter tapered section 102, a turbulent fluidizing section 103 and a conical bottom 104. A reaction gas outlet 105 is provided at the top of the fast fluidizing section 101. The cone bottom 104 is provided with a first gas inlet 2, the turbulent fluidization section 103 is provided with a particle feeding port 3 and a first return material inlet 7 in sequence from bottom to top, the fast fluidization section 101 is provided with a second gas inlet 4 and a second return material inlet 8 in sequence from bottom to top, a distribution plate 10 is provided inside between the cone bottom 104 and the turbulent fluidization section 103, a slag discharge port 5 is provided at the bottom of the cone bottom 104, and a slag discharge valve 6 is provided thereon, and a gas distributor 9 connected to the first gas inlet 2 is provided inside the cone bottom 104; the cyclone separation system 200 includes a first-level cyclone separator 11 and a second-level cyclone separator 12, the air inlet of the first-level cyclone separator 11 is connected to the reaction gas outlet 105 through a first pipe 13, and the air inlet of the second-level cyclone separator 12 is connected to the exhaust port of the first-level cyclone separator 11 through a second pipe 14; the return material system 300 includes a first return pipe 15 and a second return pipe 16. The material pipe 17, the dust exhaust port of the first-level cyclone separator 11 is connected to the first return material inlet 7 through the first return material pipe 15, and a flow sealing valve 16 is provided on the first return material pipe 15, and a flow gas inlet 21 is provided thereon to use hydrogen as the conveying gas, the dust exhaust port of the second-level cyclone separator 12 is connected to the second return material inlet 8 through the second return material pipe 17, and a buffer tank 18, a cone top valve 19, and a conveying gas inlet 20 are provided on the second return material pipe 17 in sequence according to the return direction.

[0028] In this embodiment, the design parameters of the high-density fast fluidized bed are as follows: (1) the height ratio of the turbulent fluidization section 103 to the fast fluidization section 101 is 0.1-0.5; (2) the diameter ratio of the turbulent fluidization section 103 to the fast fluidization section 101 is 0.2-0.75; (3) the distance between the second gas inlet 4 and the bottom of the fast fluidization section 101 is 65-120 mm; (3) the diameter ratio of the tapered section 102 is 0.2-0.75; (5) the porosity of the distribution plate 10 is 0.5%-4%, preferably a concave sieve plate.

[0029] As a further feature of this embodiment, the diameter of the turbulent fluidization section 103 is 100-400 mm, and the height is 1.5-4 m. The diameter of the fast fluidization section 101 is 50-200 mm, and the height is 8.5-20 m.

[0030] In addition, the second gas inlet 4 includes at least one pair, and each pair of the second gas inlet 4 is symmetrically arranged.

[0031] The process flow is as follows: Step 1. Pretreated silicon powder and catalyst particles are added to the turbulent fluidization section 103 through the particle feeding port 3. Step 2. Silicon tetrachloride and hydrogen are pressurized, heated, and vaporized to a temperature of 450-650°C and a pressure of 1-5 MPa, respectively. They then enter the gas distributor 9 through the first gas inlet 2, and then enter the turbulent fluidization section 103 after being evenly distributed through the distribution plate 10. Step 3. The temperature of the turbulent fluidization section 103 is controlled to 400-600°C, the pressure to 1-5 MPa, and the superficial gas velocity to 0.5-4 m / s, so that the particles in the turbulent fluidization section 103 are turbulently fluidized, improving the backmixing of silicon powder and catalyst while reducing the backmixing of hydrogen and chlorosilane, thereby achieving high gas-solid contact efficiency, heat transfer, and mass transfer rates, and improving the reaction conversion rate. Step 4. Under the influence of the gas, a large number of particles in the dilute phase region of the turbulent fluidization section 103 enter the rapid fluidization section 101 through the variable diameter tapered section 102. Step 5. The temperature of the rapid fluidization section 101 is controlled to be 450-650°C, the pressure is 1-5 MPa, and the superficial gas velocity is 1-10 m / s. The particles in the rapid fluidization section 101 are rapidly fluidized. The particles maintain rapid fluidization, increase the fine powder concentration and gas-solid contact efficiency, extend the particle residence time, and further improve the hydrogenation reaction conversion rate. Step 6. Silicon tetrachloride and hydrogen are continuously introduced into the bottom of the rapid fluidization section 101 to increase the reaction temperature and ensure good reaction kinetics, so that the particles further react, thereby achieving a high conversion rate of the hydrogenation reaction and solving the problem of large amounts of fine powder being carried out. Step 7. The gas-solid mixture after the reaction enters the cyclone separation system 200, where the large-sized particles separated by the first cyclone separator 11 are returned to the turbulent fluidization section via the first return pipe 15 and the flow seal valve 16. The small-sized fine powder separated by the second cyclone separator 12 is returned to the rapid fluidization section 101 via the buffer tank 18 and the second return pipe 17. In the cyclone separation system 200, the particle circulation rate is flexibly controlled by adjusting the flow seal valve 16 and the cone-top valve 19, thereby achieving high-load and high-efficiency operation of the hydrogenation reaction in the new high-density rapid fluidized bed reactor. Step 8. The crude product gas at the outlet of the cyclone separator is sequentially passed through the waste heat recovery system to recover heat and the condensation system to separate hydrogen from chlorosilane. The separated hydrogen is returned to the fluidized bed to continue the hydrogenation reaction; the separated liquid chlorosilane enters the fractionation tower, and the obtained light component trichlorosilane is used for reduction to prepare polysilicon, while the heavy component silicon tetrachloride is returned to the storage tank again, and after pressurization and heating, it is returned to the fluidized bed for hydrogenation reaction.

[0032] In the above reaction, the deactivated silicon powder, catalyst and impurities are discharged through the slag discharge port 5 of the cone bottom 104 .

[0033] The above shows and describes the main features and advantages of the present invention. For those skilled in the art, it is obvious that the specific implementation of the present invention is not limited to the details of the above exemplary embodiments. In addition, without departing from the spirit or basic characteristics of the present invention, the creative ideas and design concepts of the present invention can be realized in other specific forms, which should be equivalent to the scope of protection disclosed in the technical solution of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0034] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride, comprising a high-density fast fluidized bed (100) and a cyclone separation system (200) and a material return system (300) matched therewith, characterized in that: The high-density fast fluidized bed (100) comprises a fluidized bed body (1), which is divided into four parts from top to bottom: a fast fluidizing section (101), a diameter-reducing and tapering section (102), a turbulent fluidizing section (103) and a conical bottom (104). A reaction gas outlet (105) is arranged at the top of the fast fluidizing section (101), a first gas inlet (2) is arranged on the conical bottom (104), and a particle feeding port (3) and a first gas inlet (2) are arranged on the turbulent fluidizing section (103) from bottom to top. a first recycle inlet (7), a second gas inlet (4) and a second recycle inlet (8) are sequentially arranged on the fast fluidization section (101) from bottom to top, a distribution plate (10) is arranged inside between the cone bottom (104) and the turbulent fluidization section (103), a slag discharge port (5) is arranged at the bottom of the cone bottom (104), and a slag discharge valve (6) is arranged on the slag discharge port, and a gas distributor (9) connected to the first gas inlet (2) is arranged inside the cone bottom (104); The cyclone separation system (200) comprises a primary cyclone separator (11) and a secondary cyclone separator (12), wherein the air inlet of the primary cyclone separator (11) is connected to the reaction gas outlet (105) via a first pipeline (13), and the air inlet of the secondary cyclone separator (12) is connected to the exhaust port of the primary cyclone separator (11) via a second pipeline (14); The return material system (300) comprises a first return material pipe (15) and a second return material pipe (17); the dust discharge port of the first-stage cyclone separator (11) is connected to the first return material inlet (7) via the first return material pipe (15); a flow sealing valve (16) is provided on the first return material pipe (15), and a flow gas inlet (21) is provided on the first return material pipe; the dust discharge port of the second-stage cyclone separator (12) is connected to the second return material inlet (8) via the second return material pipe (17); a buffer tank (18), a cone-top valve (19), and a conveying gas inlet (20) are provided on the second return material pipe (17) in sequence according to the return material direction.

2. A high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride according to claim 1, characterized in that: The height ratio of the turbulent fluidization section (103) to the fast fluidization section (101) is 0.1-0.

5.

3. A high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride according to claim 2, characterized in that: The diameter ratio of the turbulent fluidization section (103) to the fast fluidization section (101) is 0.2-0.

75.

4. A high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride according to claim 3, characterized in that: The turbulent fluidization section (103) has a diameter of 100-400 mm and a height of 1.5-4 m.

5. A high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride according to claim 3 or 4, characterized in that: The fast fluidization section (101) has a diameter of 50-200 mm and a height of 8.5-20 m.

6. A high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride according to claim 5, characterized in that: The distribution plate (10) has an opening rate of 0.5%-4%.

7. A high-density fast fluidized bed reactor for hydroreduction of silicon tetrachloride according to any one of claims 1 to 4 or 6, characterized in that: The distance between the second gas inlet (4) and the bottom of the fast fluidization section (101) is 65-120 mm.

8. A high-density fast fluidized bed reactor for hydrogenation reduction of silicon tetrachloride according to claim 7, characterized in that: The second gas inlet (4) comprises at least one pair, and each pair of the second gas inlet (4) is symmetrically arranged.

9. A high-density fast fluidized bed reactor for hydroreduction of silicon tetrachloride according to any one of claims 1 to 4 or 6 or 8, characterized in that: The diameter reduction ratio of the diameter-reducing tapered section (102) is 0.2-0.75.

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