A method and system for heating up a trichlorosilane synthesis furnace

Abstract

The invention discloses a method for heating a trichlorosilane synthesis furnace, belonging to the technical field of trichlorosilane synthesis in polysilicon production. The method adopts heated chlorosilane or a mixed gas of hydrogen and chlorosilane to heat the trichlorosilane synthesis furnace. The discharge port at the top of the trichlorosilane synthesis furnace is connected to a gas recovery subsystem at the rear end. The method solves the problem of a large amount of nitrogen and hydrogen chloride being wasted in a process of heating the trichlorosilane synthesis furnace by using nitrogen in the prior art, or the problem of slow heating and affected production efficiency in heating the trichlorosilane synthesis furnace by using heated hydrogen. At the same time, the invention proposes a heating system matching the process. The arrangement of devices and pipelines is reasonable, which is convenient for control and significantly reduces production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of trichlorosilane synthesis in polysilicon production, and particularly relates to a heating method and system for a trichlorosilane synthesis furnace. Background Art

[0002] At present, in the trichlorosilane synthesis section of polysilicon production, the trichlorosilane synthesis furnace is generally heated with nitrogen before startup (nitrogen is first heated to 350~380℃ with an electric heater, and then the heated nitrogen is introduced from the bottom of the synthesis furnace to heat the synthesis furnace, and the gas after heat exchange is vented from the vent pipeline at the top of the synthesis furnace). When the temperature of the synthesis furnace rises to >280℃, silicon powder is added, and then the nitrogen is gradually withdrawn and hydrogen chloride is introduced. After all the nitrogen is withdrawn, the valve on the vent pipeline at the top of the synthesis furnace is closed, and at the same time, the valve on the pipeline from the top to the back-end processing system is opened to send the synthesis gas to the back-end processing system for processing. The synthesis furnace is then incorporated into the production system and the startup is successful.

[0003] Currently, considering factors such as production efficiency and production costs, the trichlorosilane synthesis process generally uses multiple trichlorosilane synthesis furnaces, each with a corresponding dust removal and back-end condensation system. When only a single synthesis furnace needs to be started up while the others are operating normally, the nitrogen heating scheme requires opening the top vent line of this synthesis furnace and preventing it from being directly integrated into the system (because the hydrogen by-product from the other normally operating synthesis furnaces needs to be recycled, and the introduction of nitrogen will contaminate the hydrogen and affect the quality of the recovered hydrogen). Only after the heating is completed and silicon powder and hydrogen chloride are introduced can the nitrogen be gradually withdrawn and the synthesis furnace can be integrated into the system. This heating process is complex, and a large amount of nitrogen and hydrogen chloride is wasted, which also increases the load on the tail gas leaching system.

[0004] In order to simplify the complexity of starting up a single synthesis furnace and directly integrate the gas from the top of the synthesis furnace during the heating stage into the system to solve the aforementioned problems, R&D personnel in the industry are also constantly exploring and experimenting, trying to find new process solutions to improve the above-mentioned technical difficulties and achieve the goals of energy conservation, consumption reduction and emission reduction.

[0005] In the prior art, for example, the application number "201811076256.5" published on November 30, 2018, entitled "An Energy-Saving Synthesis System for Trichlorosilane", uses heated hydrogen to heat the synthesis furnace. Hydrogen, as a product of the trichlorosilane synthesis reaction, can be used to heat the synthesis furnace and other equipment, and the gas discharged from the top of the synthesis furnace during the heating stage can be directly incorporated into the gas recovery system. However, hydrogen has a small molecular weight, carries less heat, and has a slow heating rate, which affects production efficiency. Summary of the Invention

[0006] To solve the aforementioned problems, the present invention provides a trichlorosilane synthesis furnace heating method and system, which can directly incorporate the gas discharged from the top of the synthesis furnace during the heating stage into the gas recovery system. At the same time, the heating speed is relatively fast, thereby improving production efficiency and reducing production costs.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for heating a trichlorosilane synthesis furnace comprises heating chlorosilane or a mixture of hydrogen and chlorosilane to heat the trichlorosilane synthesis furnace, wherein a discharge port at the top of the trichlorosilane synthesis furnace is connected to a gas recovery subsystem at the rear end.

[0009] Preferably, when the trichlorosilane synthesis furnace is heated by using a mixture of hydrogen and chlorosilane, hydrogen and chlorosilane are introduced into the trichlorosilane synthesis furnace simultaneously to heat it.

[0010] Preferably, when a mixture of hydrogen and chlorosilane is used to heat the trichlorosilane synthesis furnace, the hydrogen and chlorosilane are first mixed, vaporized, and heated, and then used to heat the trichlorosilane synthesis furnace.

[0011] Preferably, the mixed gas temperature at the outlet of the heating device is 350-380°C.

[0012] Preferably, the molar ratio of the introduced chlorosilane to hydrogen is 1.5:1 to 5:1.

[0013] A system for a trichlorosilane synthesis furnace heating method includes a trichlorosilane synthesis furnace connected to a chlorosilane pipeline or a mixed gas pipeline of hydrogen and chlorosilane for heating the trichlorosilane synthesis furnace, the chlorosilane pipeline or the mixed gas pipeline being provided with a heating device, the chlorosilane pipeline or the mixed gas pipeline being further provided with a vaporizer disposed on a front end pipeline of the heating device, and a discharge port at the top of the trichlorosilane synthesis furnace being connected to a gas recovery subsystem.

[0014] Preferably, the gas inlet end of the vaporizer on the mixed gas pipeline is connected to a hydrogen inlet pipe and a chlorosilane inlet pipe, and a regulating valve I and a regulating valve II are respectively provided on the hydrogen inlet pipe and the chlorosilane inlet pipe.

[0015] Preferably, the gas recovery subsystem includes a silicon powder filter, a washing tower and a condenser connected in sequence, the gas phase outlet of the condenser is connected to the hydrogen recovery pipeline, and the liquid phase outlet of the condenser is connected to the chlorosilane recovery pipeline. The silicon powder filter removes large particles of silicon powder in the gas phase flow, the washing tower separates the slag of metal chloride and fine silicon powder and the mixed gas of hydrogen and chlorosilane, and the condenser processes and separates chlorosilane and hydrogen.

[0016] Preferably, the hydrogen recovery pipeline is connected to the hydrogen inlet pipe, and the chlorosilane recovery pipeline is connected to the chlorosilane inlet pipe.

[0017] The beneficial effects of this technical solution are as follows:

[0018] 1. In the present invention, chlorosilane or a mixture of hydrogen and chlorosilane is used to heat the trichlorosilane synthesis furnace. Compared with the technical solution of using nitrogen to heat the trichlorosilane synthesis furnace in the prior art, no external discharge is required, the utilization rate of raw materials is improved, energy loss is reduced, emissions are reduced, pollution to the environment is reduced, production energy consumption is effectively reduced, and production costs are reduced. Compared with the technical solution of using hydrogen to heat the trichlorosilane synthesis furnace, the heating rate is fast, the heating time is shortened, the production efficiency is improved, and the production cost is reduced.

[0019] 2. In the present invention, one of the preferred methods is to use a mixture of hydrogen and chlorosilane to heat the trichlorosilane synthesis furnace. Preferably, chlorosilane and hydrogen are simultaneously introduced into a vaporizer at a certain molar ratio (chlorosilane to hydrogen molar ratio of 1.5:1 to 5:1) for vaporization, and then heated by an electric heater. The heated mixture (controlled within the range of 350 to 380°C) is then used to heat the trichlorosilane synthesis furnace, thereby achieving the purpose of convenient control and adjustment, energy saving, and reduced production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Figure 2 It is a structural diagram of another implementation method.

[0022] Figure 3 The diagram is a schematic structural diagram of one embodiment.

[0023] Figure 4 It is a structural diagram of another preferred embodiment.

[0024] Figure 5 It is a structural diagram of another preferred embodiment.

[0025] Figure 6 It is a structural diagram of Example 7.

[0026] In the figure, 1. trichlorosilane synthesis furnace; 2. chlorosilane pipeline; 3. mixed gas pipeline; 4. heating device; 5. vaporizer; 6. gas recovery subsystem; 7. hydrogen inlet pipe; 8. chlorosilane inlet pipe; 9. regulating valve I; 10. regulating valve II; 11. silicon powder filter; 12. elution tower; 13. condenser; 14. hydrogen recovery pipeline; 15. chlorosilane recovery pipeline; 16. hydrogen chloride pipeline; 13.1. gas phase outlet; 13.2. liquid phase outlet. DETAILED DESCRIPTION

[0027] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0028] The following examples take a trichlorosilane production section with an annual output of 20,000 tons as an example to further illustrate this solution.

[0029] Example 1

[0030] A method for heating a trichlorosilane synthesis furnace 1 belongs to the technical field of trichlorosilane synthesis in polysilicon production. The method uses vaporized and heated chlorosilane to heat the trichlorosilane synthesis furnace 1. The discharge port at the top of the trichlorosilane synthesis furnace 1 is connected to a gas recovery subsystem 6 at the rear end.

[0031] To adopt Figure 1 Taking the trichlorosilane synthesis heating system shown as an example, it includes a trichlorosilane synthesis furnace 1, which is connected to a chlorosilane pipeline 2 for heating the trichlorosilane synthesis furnace 1. The chlorosilane pipeline 2 is provided with a heating device 4. The chlorosilane pipeline 2 is also provided with a vaporizer 5. The vaporizer 5 is placed on the front pipeline of the heating device 4. The discharge port at the top of the trichlorosilane synthesis furnace 1 is connected to a gas recovery subsystem 6.

[0032] The heating device 4 in this embodiment uses an electric heater to heat the gas phase.

[0033] In this embodiment, four trichlorosilane synthesis furnaces 1 correspond to one set of gas recovery subsystem 6 , and one of the trichlorosilane synthesis furnaces 1 is used as the monitoring object, and relevant data are recorded as shown in Table 1 below.

[0034] Table 1

[0035]

[0036] In this implementation, since the mass of chlorosilane is six times that of nitrogen and its specific heat capacity is 3.3 times that of nitrogen at the same molar mass, using chlorosilane to heat the trichlorosilane synthesis furnace 1 significantly increases the heating rate from a heat transfer perspective. However, due to inherent equipment requirements, the heating rate is typically controlled to no more than 50°C / h. Therefore, in actual production, the chlorosilane flow rate is reduced to accommodate equipment requirements. As shown in Table 1, using chlorosilane to heat the trichlorosilane synthesis furnace 1 takes approximately 6-7 hours, a relatively short heating time and low power consumption.

[0037] Example 2

[0038] This embodiment is a further optimization of the embodiment 1. The difference is that the gas recovery subsystem 6 includes a silicon powder filter 11, a washing tower 12 and a condenser 13 connected in sequence. Figure 2 The gas phase outlet 13.1 of the condenser 13 is connected to the hydrogen recovery pipeline 14, and the liquid phase outlet 13.2 of the condenser 13 is connected to the chlorosilane recovery pipeline 15. The silicon powder filter 11 removes large particles of silicon powder in the gas phase flow, and the elution tower 12 separates the slag of metal chloride and fine silicon powder and the mixed gas of hydrogen and chlorosilane. The condenser 13 processes and separates the chlorosilane and hydrogen to realize the recycling of the chlorosilane and hydrogen generated in the system.

[0039] Example 3

[0040] The difference between this embodiment and embodiment 2 is that the chlorosilane recovery pipeline 15 is connected to the chlorosilane inlet pipe 8. Figure 3 , which can be used again to heat up the trichlorosilane synthesis furnace 1.

[0041] Example 4

[0042] A method for heating a trichlorosilane synthesis furnace belongs to the technical field of trichlorosilane synthesis in polysilicon production. A mixture of vaporized and heated hydrogen and chlorosilane is used to heat a trichlorosilane synthesis furnace 1. The discharge port at the top of the trichlorosilane synthesis furnace 1 is connected to a gas recovery subsystem 6 at the rear end.

[0043] To adopt Figure 4 Taking the trichlorosilane synthesis heating system shown as an example, it includes a trichlorosilane synthesis furnace 1, which is connected to a mixed gas pipeline 3 of hydrogen and chlorosilane for heating the trichlorosilane synthesis furnace 1. A heating device 4 is provided on the mixed gas pipeline 3, and a vaporizer 5 is also provided on the mixed gas pipeline 3. The vaporizer 5 is placed on the front pipeline of the heating device 4. The discharge port at the top of the trichlorosilane synthesis furnace 1 is connected to a gas recovery subsystem 6.

[0044] The heating device 4 in this embodiment uses an electric heater to heat the gas phase.

[0045] In practical applications, feed regulating valves can be installed on both the hydrogen inlet pipe 7 and the chlorosilane inlet pipe 8 to adjust their respective flow rates, depending on the production line conditions. After the chlorosilane feed rate is set, the regulating valve on the hydrogen line automatically adjusts its opening according to the set molar ratio. Simultaneously, a regulating valve is installed on the steam line used for heating the vaporizer 5 to regulate the liquid level in the vaporizer 5 and ensure its stability. The hydrogen and chlorosilane mixture, vaporized by the vaporizer 5, enters the electric heater for further heating and temperature increase. The temperature at the electric heater outlet is set, and the electric heater automatically adjusts its power based on the set outlet temperature to ensure a stable outlet temperature. The hydrogen and chlorosilane mixture, at a predetermined temperature, exits the electric heater and enters the system through the bottom of the trichlorosilane synthesis furnace 1, heating the furnace. The mixture then exits the system through the top outlet pipeline of the trichlorosilane synthesis furnace 1. During the operation of the equipment, the feed amounts of hydrogen and silicon tetrachloride can be adjusted according to the heating speed of the trichlorosilane synthesis furnace 1 to ensure that the heating speed of the trichlorosilane synthesis furnace 1 does not exceed 50°C / h.

[0046] In this embodiment, four trichlorosilane synthesis furnaces 1 correspond to one set of gas recovery subsystem 6, and one of the trichlorosilane synthesis furnaces 1 is used as the monitoring object, and relevant data are recorded as shown in Table 2 below.

[0047] Table 2

[0048]

[0049] As shown in Table 2, using the method of this embodiment to heat the trichlorosilane synthesis furnace 1, the heating time can be controlled to within 18.5 hours. Compared with the prior art technical solution of using hydrogen to heat the trichlorosilane synthesis furnace 1, the heating time can be shortened by 5.8 to 18.4 hours. In addition, using this embodiment, the heat-exchanged mixed gas discharged from the top discharge port of the trichlorosilane synthesis furnace 1 can be directly incorporated into the original gas recovery subsystem 6 for centralized processing and recovery of hydrogen, chlorosilane, and other materials therein, thereby reducing waste gas emissions, alleviating the processing pressure of the post-processing system, and lowering production costs.

[0050] In a preferred embodiment, hydrogen and chlorosilane are simultaneously introduced into the vaporizer 5 , mixed, vaporized, and heated, and then the temperature in the trichlorosilane synthesis furnace 1 is increased.

[0051] Example 5

[0052] This embodiment is a further optimization of the embodiment 1. The difference is that the gas inlet end of the vaporizer 5 on the mixed gas pipeline 3 is connected to the hydrogen inlet pipe 7 and the chlorosilane inlet pipe 8, and the hydrogen inlet pipe 7 and the chlorosilane inlet pipe 8 are respectively provided with a regulating valve I9 and a regulating valve II10. Figure 5By adopting this system, the opening of regulating valve I9 and regulating valve II10 can be controlled to control the feed ratio of hydrogen and chlorosilane, thereby facilitating the control of the temperature at the outlet of the electric heater within the expected range (generally 350~380℃).

[0053] In this embodiment, this method is used to heat trichlorosilane synthesis furnace 1. By controlling the openings of regulating valves I9 and II10, the feed ratio of hydrogen to chlorosilane is controlled, thereby regulating the outlet temperature of vaporizer 5. Compared with the scheme in Examples 1-3, which only uses chlorosilane to heat trichlorosilane synthesis furnace 1, this scheme has the advantages of a lower chlorosilane vaporization temperature, lower steam consumption in vaporizer 5, and easily controllable heating rate of trichlorosilane synthesis furnace 1.

[0054] Example 6

[0055] The difference between this embodiment and embodiment 4-5 is that the gas recovery subsystem 6 includes a silicon powder filter 11, a washing tower 12 and a condenser 13 connected in sequence. Figure 5 The gas phase outlet 13.1 of the condenser 13 is connected to the hydrogen recovery pipeline 14, and the liquid phase outlet 13.2 of the condenser 13 is connected to the chlorosilane recovery pipeline 15. The silicon powder filter 11 removes large particles of silicon powder in the gas phase flow, and the elution tower 12 separates the slag of metal chloride and fine silicon powder and the mixed gas of hydrogen and chlorosilane. The condenser 13 processes and separates chlorosilane and hydrogen.

[0056] Example 7

[0057] The difference between this embodiment and embodiment 6 is that the hydrogen recovery pipeline 14 is connected to the hydrogen inlet pipe 7, and the chlorosilane recovery pipeline 15 is connected to the chlorosilane inlet pipe 8. Figure 6 The chlorosilane and hydrogen obtained after treatment by the gas recovery subsystem 6 are recycled into the trichlorosilane synthesis heating system to reduce heat loss and reduce the external emission of waste gas.

[0058] Comparative Example 1

[0059] In this scheme, taking the production of the same amount of trichlorosilane as an example, using the same type of trichlorosilane synthesis furnace, and using heated nitrogen to heat the trichlorosilane synthesis furnace, an additional 624,000 Nm3 of nitrogen will be emitted annually. 3 The waste gas will increase the waste gas treatment capacity of the waste gas washing system. Compared with this technical solution, the cost of treating this part of the mixed waste gas will increase by about 1.25 million yuan / year.

[0060] Comparative Example 2

[0061] In this solution, taking the production of the same amount of trichlorosilane as an example, the same type of trichlorosilane synthesis furnace is used, and the heated hydrogen is used to heat the trichlorosilane synthesis furnace, which generally takes about 28 hours. Compared with this technical solution, each heating of the trichlorosilane synthesis furnace takes 9.8 to 22.4 hours longer.

Claims

1. A method for heating a trichlorosilane synthesis furnace, characterized in that: The trichlorosilane synthesis furnace (1) is heated by using chlorosilane heated to an outlet temperature of 350°C or 380°C by an electric heater; or a mixture of hydrogen and chlorosilane heated to an outlet temperature of 350-380°C by using an electric heater. The discharge port at the top of the trichlorosilane synthesis furnace (1) is connected to a gas recovery subsystem (6) at the rear end. When a mixture of hydrogen and chlorosilane is used to heat the trichlorosilane synthesis furnace (1), the hydrogen and chlorosilane are first mixed, vaporized, and heated, and then used to heat the trichlorosilane synthesis furnace (1).

2. A trichlorosilane synthesis furnace heating method according to claim 1, characterized in that: The molar ratio of the introduced chlorosilane to hydrogen is 1.5:1 to 5:

1.

3. The system for the trichlorosilane synthesis furnace heating method according to claim 1, wherein: The invention comprises a trichlorosilane synthesis furnace (1), wherein the trichlorosilane synthesis furnace (1) is connected to a chlorosilane pipeline (2) or a mixed gas pipeline (3) of hydrogen and chlorosilane for heating the trichlorosilane synthesis furnace (1), a heating device (4) is provided on the chlorosilane pipeline (2) or the mixed gas pipeline (3), and a vaporizer (5) is further provided on the chlorosilane pipeline (2) or the mixed gas pipeline (3), and the vaporizer (5) is placed on the front end pipeline of the heating device (4). The discharge port at the top of the trichlorosilane synthesis furnace (1) is connected to a gas recovery subsystem (6); The gas inlet end of the vaporizer (5) on the mixed gas pipeline (3) is connected to a hydrogen inlet pipe (7) and a chlorosilane inlet pipe (8), and the hydrogen inlet pipe (7) and the chlorosilane inlet pipe (8) are respectively provided with a regulating valve I (9) and a regulating valve II (10); The gas recovery subsystem (6) includes a silicon powder filter (11), a washing tower (12) and a condenser (13) connected in sequence. The gas phase outlet (13.1) of the condenser (13) is connected to a hydrogen recovery pipeline (14), and the liquid phase outlet (13.2) of the condenser (13) is connected to a chlorosilane recovery pipeline (15). The silicon powder filter (11) removes large particles of silicon powder in the gas phase flow, the washing tower (12) separates metal chloride and fine silicon powder slag and a mixed gas of hydrogen and chlorosilane, and the condenser (13) processes and separates chlorosilane and hydrogen.

4. The system for the trichlorosilane synthesis furnace heating method according to claim 3, characterized in that: The hydrogen recovery pipeline (14) is connected to the hydrogen inlet pipe (7), and the chlorosilane recovery pipeline (15) is connected to the chlorosilane inlet pipe (8).

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