Polysilicon cold hydrogenation device and process method

Abstract

The present invention relates to the technical field of polysilicon production. Disclosed are a polysilicon cold hydrogenation device and a process method, which mainly aim to improve the production capacity of a single cold hydrogenation system. The main technical solution of the present invention involves a polysilicon cold hydrogenation device. The device comprises a vaporization column, a reaction section and a separation section. A feeding port of the vaporization column is connected to a tail gas pipe of a reduction furnace. The reaction section comprises two reaction units which are connected in parallel, wherein each reaction unit comprises a semi-ball valve, a mass flow meter, an electric heater and a fluidized bed which are connected in sequence, the middle of the fluidized bed is connected to a silicon powder replenishment pipe, and a control valve is installed on the silicon powder replenishment pipe; and inlet ends of the semi-ball valves of the two reaction units are connected to the upper end of the vaporization column. The separation section comprises a cooler and a fractionation column, wherein discharge ports at the upper ends of the fluidized beds, the cooler and the fractionation column are connected in sequence; and the upper end of the fractionation column is connected to a withdrawal pipe, and the lower end of the fractionation column is connected to the upper end side of the vaporization column.

Description

Polysilicon cold hydrogenation device and process method Technical Field

[0001] The present invention relates to the technical field of polysilicon production, and in particular to a polysilicon cold hydrogenation device and a process method. Background Art

[0002] During the polysilicon production process, large amounts of hydrogen (H2), silicon tetrachloride (SiCl4), and hydrogen chloride (HCl) are produced as byproducts. Silicon tetrachloride must be converted into trichlorosilane (TCS) through a hydrogenation process. Since 2010, domestic polysilicon companies have been implementing cold hydrogenation processes, gradually phasing out hot hydrogenation.

[0003] The existing cold hydrogenation technology operates as a single system with limited feed volume, which severely restricts the production capacity of polysilicon. In order to increase production capacity, the capacity is generally increased by repeatedly building a complete set of cold hydrogenation equipment, which results in large fixed investments and high costs. Summary of the Invention

[0004] In view of this, the present invention provides a polysilicon cold hydrogenation device and process method, the main purpose of which is to improve the production capacity of a single cold hydrogenation system.

[0005] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0006] In one aspect, the present invention provides a polysilicon cold hydrogenation device, the device comprising: a vaporization tower, a reaction part, and a separation part;

[0007] The feed port of the vaporization tower is connected to the tail gas pipe of the reduction furnace;

[0008] The reaction section includes two parallel-connected reaction units, each of which includes a semi-ball valve, a mass flow meter, an electric heater, and a fluidized bed connected in sequence. The middle of the fluidized bed is connected to a silicon powder feeding pipe, and the silicon powder feeding pipe is equipped with a control valve. The inlet ends of the semi-ball valves of the two reaction units are connected to the upper end of the vaporization tower.

[0009] The separation part includes a cooler and a distillation tower. The upper end discharge port of the fluidized bed, the cooler and the distillation tower are connected in sequence. The upper end of the distillation tower is connected to the production pipeline, and the lower end of the distillation tower is connected to the upper end side of the vaporization tower.

[0010] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0011] Optionally, a hydrogen feed pipe is further included, and the hydrogen feed pipe is connected to the vaporization tower reboiler.

[0012] Optionally, each of the reaction units further includes a global valve, and the upper end of the vaporization tower, the global valve and the hemispherical valve are connected in sequence.

[0013] Optionally, the control valve is a disc valve.

[0014] Optionally, the distance between two adjacent pressure measuring points of the fluidized bed is 2000 mm.

[0015] In another aspect, the present invention provides a polysilicon cold hydrogenation process, comprising the following steps:

[0016] (1) Silicon tetrachloride is introduced into the vaporization tower through the tail gas pipe of the reduction furnace, and steam is introduced into the reboiler tube side of the vaporization tower. The steam pressure is 1.2 MPa and the temperature is 195°C, thereby controlling the bottom temperature of the vaporization tower to be 175-185°C. At the same time, hydrogen is introduced into the shell side of the reboiler through the hydrogen feed pipe. The hydrogen pressure is 3.0 MPa and the flow rate is 43000-48000 Nm 3 / H, vaporizes silicon tetrachloride;

[0017] (2) hydrogen and silicon tetrachloride sequentially pass through the hemispherical valve, the mass flow meter, and the electric heater and enter the fluidized bed;

[0018] (3) Adjust the opening of the hemispherical valve to control the gas phase flow rate of the mass flow meter to 38000-42000Nm 3 / H, which is conducive to the even distribution of the gas phase flow rate in the reactor, and avoids the gas phase feed amount of a single fluidized bed exceeding the design capacity, causing a large amount of silicon powder in the fluidized bed to be carried out of the reaction system;

[0019] (4) adjusting the opening of the control valve and controlling the amount of silicon powder added so that the bed pressure difference of the fluidized bed is 120-180 kPa and the operating pressure of the fluidized bed is 2.6-2.9 MPa;

[0020] (5) The material flowing out of the fluidized bed passes through the cooler and the distillation tower in sequence, and the heavy component silicon tetrachloride obtained by distillation enters the vaporization tower again.

[0021] Optionally, in step (1), the bottom temperature of the vaporization tower is 183±1°C, and the hydrogen flow rate is 45000±200Nm 3 / H.

[0022] Optionally, in step (3), the gas phase flow rate is 40000±200Nm 3 / H.

[0023] Optionally, in step (4), the bed pressure difference of the fluidized bed is 150±5 KPa.

[0024] Optionally, in step (4), the fluidized bed operating pressure is 2.8 MPa.

[0025] By means of the above technical solution, the present invention has at least the following advantages:

[0026] During the operation of the polysilicon cold hydrogenation device, the tail gas material of the reduction furnace enters the vaporization tower. Due to the heating effect of the reboiler of the vaporization tower, the silicon tetrachloride in the tail gas material of the reduction furnace is vaporized and enters two parallel reaction units from the upper end of the vaporization tower. By adjusting the opening of the two hemispherical valves, the feed amount of the two fluidized beds is controlled. At the same time, the opening of the control valves of the silicon powder feeding pipes of the two fluidized beds is adjusted to control the silicon powder feeding amount of the fluidized beds. In the fluidized bed, the silicon tetrachloride is partially converted into trichlorosilane. After the fluidized bed reaction, the material first enters the cooler for cooling and liquefaction, and then enters the distillation tower for rectification. The trichlorosilane flows out from the extraction pipe at the upper end of the distillation tower as a light component, and the silicon tetrachloride flows back to the vaporization tower from the lower end of the distillation tower as a heavy component and enters the fluidized bed reaction again.

[0027] The electric heater heats the material before it enters the fluidized bed. Simultaneously, the operator can monitor the material flow rate in the pipeline using a mass flow meter. The outlet temperature of the electric heater is 550°C. The amount of material entering the heater can be calculated using the formula Q = CmΔt (where Q is the heater power, C is the material specific heat capacity, Δt is the temperature difference between the heater inlet and outlet, and m is the amount of material entering the heater). This calculated value and the flow rate displayed by the mass flow meter are then mutually corrected. By adjusting the opening of the hemispherical valves at the inlets of the two heaters, the amount of material entering the heaters is kept essentially the same, thereby ensuring a consistent feed rate to the fluidized bed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic structural diagram of a polysilicon cold hydrogenation device provided in an embodiment of the present invention.

[0029] The figure marks in the drawings of the specification include: vaporization tower 1, reduction furnace tail gas pipe 2, hemispherical valve 3, mass flow meter 4, electric heater 5, fluidized bed 6, silicon powder feeding pipe 7, control valve 8, cooler 9, distillation tower 10, production pipeline 11, hydrogen feed pipe 12, vaporization tower reboiler 13, global valve 14. DETAILED DESCRIPTION

[0030] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] As shown in FIG1 , on the one hand, an embodiment of the present invention provides a polysilicon cold hydrogenation device, which includes: a vaporization tower 1, a reaction part and a separation part;

[0033] The feed port of the vaporization tower 1 is connected to the tail gas pipe 2 of the reduction furnace;

[0034] The reaction section includes two parallel reaction units, each of which includes a semi-ball valve 3, a mass flow meter 4, an electric heater 5, and a fluidized bed 6 connected in sequence. The middle of the fluidized bed 6 is connected to a silicon powder feeding pipe 7, and the silicon powder feeding pipe 7 is equipped with a control valve 8. The inlet ends of the semi-ball valves 3 of the two reaction units are connected to the upper end of the vaporization tower 1.

[0035] The separation section includes a cooler 9 and a distillation tower 10. The upper discharge port of the fluidized bed 6, the cooler 9 and the distillation tower 10 are connected in sequence. The upper end of the distillation tower 10 is connected to the production pipeline 11, and the lower end of the distillation tower is connected to the upper end side of the vaporization tower 1.

[0036] A polysilicon cold hydrogenation device works as follows:

[0037] During the operation of the polysilicon cold hydrogenation device, the tail gas material of the reduction furnace enters the vaporization tower 1. Due to the heating effect of the reboiler 13 of the vaporization tower 1, the silicon tetrachloride in the tail gas material of the reduction furnace is vaporized and enters the two parallel reaction units from the upper end of the vaporization tower 1. By adjusting the opening of the two hemispherical valves 3, the feed amount of the two fluidized beds 6 is controlled. At the same time, the opening of the control valve 8 of the silicon powder feeding pipe 7 of the two fluidized beds 6 is adjusted to control the silicon powder feeding amount of the fluidized bed 6. In the fluidized bed 6, the silicon tetrachloride is partially converted into trichlorosilane. After the reaction in the fluidized bed 6, the material first enters the cooler 9 for cooling and liquefaction, and then enters the fractionation tower 10 for rectification. The trichlorosilane therein flows out from the extraction pipe 11 at the upper end of the fractionation tower 10 as a light component, and the silicon tetrachloride therein flows back to the vaporization tower 1 from the lower end of the fractionation tower 10 as a heavy component and enters the fluidized bed 6 again for reaction.

[0038] The electric heater 5 heats the material before it enters the fluidized bed 6. Simultaneously, the operator can monitor the material flow rate in the pipeline via the mass flowmeter 4. The outlet temperature of the electric heater 5 is 550°C. The amount of material entering the electric heater 5 can be calculated using the formula Q = CmΔt (where Q is the power of the electric heater 5, C is the specific heat capacity of the material, Δt is the temperature difference between the inlet and outlet of the electric heater 5, and m is the amount of material entering the electric heater 5). (This calculated value and the flow rate displayed by the mass flowmeter 4 are mutually corrected.) By adjusting the opening of the hemispherical valves 3 at the inlets of the two electric heaters 5, the amount of material entering the electric heaters 5 is controlled to be essentially the same, thereby ensuring that the feed rate to the fluidized bed 6 is essentially the same.

[0039] In the technical solution of the present invention, the silicon tetrachloride that does not participate in the reaction in the fluidized bed 6 is re-gasified and enters the fluidized bed 6 after distillation separation, thereby increasing the percentage of silicon tetrachloride participating in the reaction and improving the production capacity of a single cold hydrogenation system. At the same time, the device uses two fluidized beds 6 in parallel, and measures the feed amount of the fluidized beds 6 by mutual correction, so that the feed amount of the two fluidized beds 6 is the same, so that the two fluidized beds 6 use the same control indicators, which facilitates standardized control of the device and further improves the production capacity of the single cold hydrogenation system.

[0040] In a specific embodiment, a hydrogen feed pipe 12 is further included, and the hydrogen feed pipe 12 is connected to the reboiler 13 of the vaporization tower 1 .

[0041] In this embodiment, specifically, steam is introduced into the tube side of the reboiler 13 of the vaporization tower 1, the shell side of the reboiler 13 of the vaporization tower 1 is connected to the bottom of the vaporization tower 1, and the hydrogen feed pipe 12 is connected to the shell side of the reboiler 13 of the vaporization tower 1, thereby changing the partial pressure of silicon tetrachloride in the reboiler, lowering the boiling point of silicon tetrachloride, thereby making the silicon tetrachloride in the vaporization tower 1 easier to vaporize, improving the efficiency of silicon tetrachloride flowing to the fluidized bed 6, and the mixed gas of vaporized silicon tetrachloride and hydrogen enters the electric heater 5 and the fluidized bed 6 in sequence.

[0042] In a specific embodiment, each of the reaction units further includes a global valve 14 , and the upper end of the vaporization tower 1 , the global valve 14 and the semi-spherical valve 3 are connected in sequence.

[0043] In this embodiment, specifically, the global valve 14 is a hard-sealed ball valve, which is closed when the system is isolated for maintenance and can provide a better sealing effect than the semi-ball valve 3.

[0044] In a specific embodiment, the control valve 8 is a disk valve.

[0045] In this embodiment, the disc valve has a longer service life, which is beneficial to the equipment maintenance and operation adjustment of the fluidized bed 6.

[0046] In a specific embodiment, the distance between two adjacent pressure measuring points of the fluidized bed 6 is 2000 mm.

[0047] In this embodiment, specifically, 2000 mm is the distance between the pressure-inducing points, and the pressure difference between the pressure-inducing points is the pressure difference of the six layers of the fluidized bed.

[0048] On the other hand, embodiments of the present invention also provide a polysilicon cold hydrogenation process method, and the embodiments are as follows:

[0049] Example 1

[0050] (1) Silicon tetrachloride is introduced into the vaporization tower through the tail gas pipe of the reduction furnace, and steam is introduced into the reboiler tube side of the vaporization tower. The steam pressure is 1.2 MPa and the temperature is 195°C, thereby controlling the bottom temperature of the vaporization tower to be 185°C. At the same time, hydrogen is introduced into the shell side of the reboiler through the hydrogen feed pipe. The hydrogen pressure is 3.0 MPa and the flow rate is 43000 Nm 3 / H, vaporizes silicon tetrachloride;

[0051] (2) hydrogen and silicon tetrachloride sequentially pass through the hemispherical valve, the mass flow meter, and the electric heater and enter the fluidized bed;

[0052] (3) Adjust the opening of the hemispherical valve to control the gas phase flow rate of the mass flow meter to 38000Nm 3 / H;

[0053] (4) adjusting the opening of the control valve and controlling the amount of silicon powder added so that the bed pressure difference of the fluidized bed is 120 kPa and the operating pressure of the fluidized bed is 2.6 MPa;

[0054] (5) The material flowing out of the fluidized bed passes through the cooler and the distillation tower in sequence, and the heavy component silicon tetrachloride obtained by distillation enters the vaporization tower again.

[0055] After material balance, the conversion rates of the two fluidized beds were both about 25%, and there was no fluidized bed deviation.

[0056] Example 2

[0057] (1) Silicon tetrachloride is introduced into the vaporization tower through the tail gas pipe of the reduction furnace, and steam is introduced into the reboiler tube side of the vaporization tower. The steam pressure is 1.2 MPa and the temperature is 195°C, thereby controlling the bottom temperature of the vaporization tower to be 183°C. At the same time, hydrogen is introduced into the shell side of the reboiler through the hydrogen feed pipe. The hydrogen pressure is 3.0 MPa and the flow rate is 45000 Nm 3 / H, vaporizes silicon tetrachloride;

[0058] (2) hydrogen and silicon tetrachloride sequentially pass through the hemispherical valve, the mass flow meter, and the electric heater and enter the fluidized bed;

[0059] (3) Adjust the opening of the hemispherical valve to control the gas phase flow rate of the mass flow meter to 40000Nm 3 / H;

[0060] (4) adjusting the opening of the control valve and controlling the amount of silicon powder added so that the bed pressure difference of the fluidized bed is 150 kPa and the operating pressure of the fluidized bed is 2.8 MPa;

[0061] (5) The material flowing out of the fluidized bed passes through the cooler and the distillation tower in sequence, and the heavy component silicon tetrachloride obtained by distillation enters the vaporization tower again.

[0062] After material balance, the conversion rates of the two fluidized beds were both about 26%, and there was no fluidized bed deviation.

[0063] Example 3

[0064] (1) Silicon tetrachloride is introduced into the vaporization tower through the tail gas pipe of the reduction furnace, and steam is introduced into the reboiler tube side of the vaporization tower. The steam pressure is 1.2 MPa and the temperature is 195°C, thereby controlling the bottom temperature of the vaporization tower to be 178°C. At the same time, hydrogen is introduced into the shell side of the reboiler through the hydrogen feed pipe. The hydrogen pressure is 3.0 MPa and the flow rate is 48000 Nm 3 / H, vaporizes silicon tetrachloride;

[0065] (2) hydrogen and silicon tetrachloride sequentially pass through the hemispherical valve, the mass flow meter, and the electric heater and enter the fluidized bed;

[0066] (3) Adjust the opening of the hemispherical valve to control the gas phase flow rate of the mass flow meter to 42000Nm 3 / H;

[0067] (4) adjusting the opening of the control valve and controlling the amount of silicon powder added so that the bed pressure difference of the fluidized bed is 180 kPa and the operating pressure of the fluidized bed is 2.9 MPa;

[0068] (5) The material flowing out of the fluidized bed passes through the cooler and the distillation tower in sequence, and the heavy component silicon tetrachloride obtained by distillation enters the vaporization tower again.

[0069] After material balance, the conversion rates of the two fluidized beds were both about 26%, and there was no fluidized bed deviation.

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A polysilicon cold hydrogenation device, characterized in that: include: A vaporization tower, wherein the feed port of the vaporization tower is connected to the tail gas pipe of the reduction furnace; A reaction section comprising two parallel-connected reaction units, each of which comprises a semi-ball valve, a mass flow meter, an electric heater, and a fluidized bed connected in sequence. The middle portion of the fluidized bed is connected to a silicon powder feeding pipe equipped with a control valve. The inlet ends of the semi-ball valves of the two reaction units are connected to the upper end of the vaporization tower. The separation part includes a cooler and a distillation tower. The upper end discharge port of the fluidized bed, the cooler and the distillation tower are connected in sequence. The upper end of the distillation tower is connected to the production pipeline, and the lower end of the distillation tower is connected to the upper end side of the vaporization tower.

2. The polysilicon cold hydrogenation device according to claim 1, characterized in that: It also includes a hydrogen feed pipe, which is connected to the vaporization tower reboiler.

3. The polysilicon cold hydrogenation device according to claim 1, characterized in that: Each of the reaction units further includes a global valve, and the upper end of the vaporization tower, the global valve and the semi-spherical valve are connected in sequence.

4. The polysilicon cold hydrogenation device according to claim 1, characterized in that: The control valve is a disc valve.

5. The polysilicon cold hydrogenation device according to claim 1, characterized in that: The distance between two adjacent pressure measuring points of the fluidized bed is 2000 mm.

6. A polysilicon cold hydrogenation process, characterized in that: Using the polysilicon cold hydrogenation device according to claim 2, the steps are as follows: (1) Silicon tetrachloride is introduced into the vaporization tower through the tail gas pipe of the reduction furnace, and steam is introduced into the reboiler tube side of the vaporization tower. The steam pressure is 1.2 MPa and the temperature is 195°C, thereby controlling the bottom temperature of the vaporization tower to be 175-185°C. At the same time, hydrogen is introduced into the shell side of the reboiler through the hydrogen feed pipe. The hydrogen pressure is 3.0 MPa and the flow rate is 43000-48000 Nm 3 / H, vaporizes silicon tetrachloride; (2) hydrogen and silicon tetrachloride sequentially pass through the hemispherical valve, the mass flow meter, and the electric heater and enter the fluidized bed; (3) Adjust the opening of the hemispherical valve to control the gas phase flow rate of the mass flow meter to 38000-42000Nm 3 / H; (4) adjusting the opening of the control valve and controlling the amount of silicon powder added so that the bed pressure difference of the fluidized bed is 120-180 kPa and the operating pressure of the fluidized bed is 2.6-2.9 MPa; (5) The material flowing out of the fluidized bed passes through the cooler and the distillation tower in sequence, and the heavy component silicon tetrachloride obtained by distillation enters the vaporization tower again.

7. The polysilicon cold hydrogenation process according to claim 6, characterized in that: In step (1), the temperature of the bottom of the vaporization tower is 183±1°C, and the hydrogen flow rate is 45000±200Nm 3 / H.

8. The polysilicon cold hydrogenation process according to claim 6, characterized in that: In step (3), the gas phase flow rate is 40000±200Nm 3 / H.

9. The polysilicon cold hydrogenation process according to claim 6, characterized in that: In step (4), the bed pressure difference of the fluidized bed is 150±5 KPa.

10. The polysilicon cold hydrogenation process according to claim 6, characterized in that: In step (4), the fluidized bed operating pressure is 2.8 MPa.

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