Device system for producing trichlorosilane by adopting cold hydrogenation reaction

Abstract

The utility model provides a device system for producing trichlorosilane by adopting a cold hydrogenation reaction, which adopts a cold hydrogenation reaction device in the form of a circulating fluidized bed, so that the contact area of a reactant and a catalyst is greatly increased, the reaction rate is increased, and the reaction energy consumption is reduced; the multi-stage heat exchange unit is arranged, so that the heat of the cold hydrogenation reaction tail gas is fully utilized, the utilization rate of the heat is increased, and the heat exchange cost is reduced; and the first gas-solid separation unit and the second gas-solid separation unit are arranged behind the cold hydrogenation reaction unit, so that pipeline blockage caused by the fact that large-particle silicon powder enters a subsequent system is avoided, and the device is suitable for large-scale popularization and application.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon production, in particular to a device system for producing trichlorosilane by cold hydrogenation reaction. Background Technique

[0002] At present, in the polysilicon production process, the improved Siemens method is widely used due to its mature process. This method uses trichlorosilane and hydrogen as raw materials to obtain polysilicon products through high-temperature reduction. This reaction will produce a large amount of by-products such as silicon tetrachloride. The mass ratio of product silicon to by-product silicon tetrachloride is about 1:14 to 1:20. These silicon tetrachlorides can react with silicon powder and hydrogen to regenerate trichlorosilane through cold hydrogenation reaction, which is used as the raw material for polysilicon. It not only realizes the recycling of silicon tetrachloride but also greatly reduces the production cost of enterprises.

[0003] The reaction equation in the cold hydrogenation process is: Si + 3SiCl4 + 2H2 = 4SiHCl3; the reaction temperature is 500 - 600 °C, and the pressure is 2MPaG - 3MPaG. The above reaction is carried out in a fluidized bed reactor. A fluidized bed reactor with a certain height of the bed layer is established. The heated silicon powder is added to the fluidized bed reactor to form a silicon powder bed layer. At the same time, silicon tetrachloride and hydrogen are mixed, and after heating, they are sent to the bottom of the cold hydrogenation reactor. Under the action of the gas distributor, the silicon powder in the fluidized bed reactor forms a fluidized state, and the raw material gas and silicon powder generate trichlorosilane under the action of a catalyst. However, the conversion rate of this process is not high, generally below 25%.

[0004] At present, when using this process, the following problems exist:

[0005] 1. In the existing cold hydrogenation process, the fluidized bed reactor is generally a bubbling bed, the gas velocity is about 0.05m / s - 0.3m / s, and the particle size of the silicon powder is relatively large, the fluidization degree is low, and the operation flexibility of the fluidized bed reactor is small, resulting in low utilization rate of the whole raw material, high raw material consumption and low overall conversion rate.

[0006] 2. Since large-particle silicon powder is likely to cause pipeline blockage when entering the subsequent system and the maintenance frequency is high, the production capacity of trichlorosilane is small.

[0007] CN102530958A discloses a device and method for producing trichlorosilane, including a silicon powder sending bin. The feed inlet of the silicon powder sending bin is connected with a silicon powder feed pipeline. The discharge port end of the silicon powder sending bin is provided with a silicon powder sending bin discharge valve. The outlet end of the silicon powder sending bin discharge valve is connected with a silicon powder conveying pipeline. The outlet end of the silicon powder conveying pipeline is connected with a high-level bin. The bottom outlet of the high-level bin is connected with a dryer. The silicon powder dryer is connected with a metering tank. The metering tank is connected with a synthesis furnace. The side outlet end of the high-level bin is also connected with a dust collector through a pipeline. A silicon powder recovery pipeline is provided between the dust collector and the dryer.

[0008] CN103101913A discloses a system and method for producing trichlorosilane by cold hydrogenation of silicon tetrachloride. The system includes a hydrogenation reaction device for subjecting raw materials including silicon tetrachloride, hydrogen and silicon powder to cold hydrogenation reaction to generate the required trichlorosilane; the hydrogenation reaction device includes a multi-stage hydrogenation reactor connected in series, and when working, the silicon tetrachloride passes through each stage of hydrogenation reactor in sequence and undergoes cold hydrogenation reaction therein respectively. By connecting at least two hydrogenation reactors in series, the one-time hydrogenation rate is much higher than the traditional cold hydrogenation process with catalyst added. Since no catalyst is used, on the one hand, a large amount of cost required for purchasing catalyst is saved; on the other hand, compared with the wear on pipelines and equipment caused by adding catalyst in the prior art, the cold hydrogenation system can operate stably for a long time, and the trichlorosilane product produced is of good quality.

[0009] However, the above-mentioned device for producing trichlorosilane fails to realize the rational utilization of heat in each part and still has the problem of high heat exchange cost. Utility Model Content

[0010] In view of the problems existing in the prior art, the utility model provides a device system for producing trichlorosilane by cold hydrogenation reaction. The cold hydrogenation reaction device in the form of a circulating fluidized bed is adopted to greatly improve the turbulence degree of reactants and catalysts, thereby increasing the trichlorosilane production capacity. In addition, a multi-stage heat exchange unit is arranged to realize cascade heat extraction, fully utilizing the heat of the cold hydrogenation reaction tail gas, increasing the heat utilization rate, and reducing the heat exchange cost.

[0011] To achieve this purpose, the utility model adopts the following technical solutions:

[0012] The utility model provides a device system for producing trichlorosilane by cold hydrogenation reaction, the device system comprises a raw gas delivery unit, a first heat exchange unit, a cold hydrogenation reaction unit, a first gas-solid separation unit, a second gas-solid separation unit, a washing unit, a second heat exchange unit, a refrigeration unit and a trichlorosilane storage unit;

[0013] The raw gas delivery unit, the first heat exchange unit, the cold hydrogenation reaction unit and the first gas-solid separation unit are connected in sequence;

[0014] The first gas-solid separation unit is connected to the second gas-solid separation unit and the washing unit in sequence via the first heat exchange unit;

[0015] The raw gas delivery unit comprises a hydrogen storage device, a hydrogen preheating device, a silicon tetrachloride storage device, a silicon tetrachloride preheating device, a mixing device and a gasification device; the hydrogen storage device, the hydrogen preheating device and the mixing device are connected in sequence; the silicon tetrachloride storage device, the silicon tetrachloride preheating device and the mixing device are connected in sequence; the mixing device and the gasification device are connected in sequence;

[0016] The washing unit is successively connected to a silicon tetrachloride preheating device, a hydrogen preheating device, a second heat exchange unit, a refrigeration unit, and a trichlorosilane storage unit;

[0017] The cold hydrogenation reaction unit includes a cold hydrogenation reaction device in the form of a circulating fluidized bed.

[0018] The device system for producing trichlorosilane by cold hydrogenation reaction described in the present utility model has a reasonable design. By adopting a cold hydrogenation reaction device in the form of a circulating fluidized bed, the gas flow rate in the reaction device is increased, enabling the reactants and the catalyst to circulate in the bed, thereby increasing the contact area between the reactants and the catalyst, accelerating the reaction rate, significantly improving the reaction speed, reducing the reaction energy consumption, and shortening the production cycle. In addition, a first gas-solid separation unit and a second gas-solid separation unit are arranged after the cold hydrogenation reaction unit to prevent large-particle silicon powder from entering the subsequent system and causing pipeline blockage; a first heat exchange unit, a second heat exchange unit, and a refrigeration unit are provided to achieve multi-stage heat exchange, making full use of the heat of the cold hydrogenation reaction tail gas, increasing the heat utilization rate, and being suitable for large-scale popularization and application.

[0019] Preferably, the cold hydrogenation reaction device is respectively connected to a catalyst conveying device and a silicon powder conveying device.

[0020] Preferably, the first gas-solid separation unit includes a cyclone separator or at least two serially connected cyclone separators.

[0021] Preferably, at least two serially connected cyclone separators share a dipleg. After separation, the silicon powder flows into the cold hydrogenation reaction device along the shared dipleg to form a cycle, reducing the silicon powder consumption and at the same time preventing large-particle silicon powder from entering the subsequent device unit and causing pipeline blockage.

[0022] Preferably, the bottom of the first gas-solid separation unit is connected to the cold hydrogenation reaction device.

[0023] Preferably, the top of the first gas-solid separation unit is connected to the first heat exchange unit.

[0024] Preferably, the first heat exchange unit includes 1 to 4 heat exchangers, for example, it can be 1 stage, 2 stages, 3 stages, or 4 stages.

[0025] Preferably, the inner wall of the first gas-solid separation unit is provided with a wear-resistant lining.

[0026] Preferably, the second heat exchange unit includes an air-cooled heat exchange device, a water-cooled heat exchange device, and a first heat exchange device connected in sequence.

[0027] Preferably, the washing unit includes a washing tower.

[0028] Preferably, the refrigeration unit includes an ice machine.

[0029] Preferably, the refrigeration unit is connected to the hydrogen preheating device.

[0030] The operation method of the device system for producing trichlorosilane by cold hydrogenation reaction according to the present utility model includes the following steps:

[0031] The hydrogen in the hydrogen storage device is preheated by a hydrogen preheating device with a designed temperature of 100 - 150°C and then enters the mixing device, where it is mixed with the silicon tetrachloride preheated by a silicon tetrachloride preheating device with a designed temperature of 100 - 150°C from the silicon tetrachloride storage device. The mixed gas passes through the gasification device and is introduced into the tube side of the first heat exchange unit, where it is heated from 100 - 150°C to 540 - 570°C and exchanges heat with the tail gas from the outlet of the first gas-solid separation unit, further heating the mixed gas, and finally forming the inlet gas of the cold hydrogenation reaction unit. The inlet gas of the cold hydrogenation reaction unit, the catalyst in the catalyst delivery device, and the silicon powder in the silicon powder delivery device are introduced into the cold hydrogenation reaction unit, and the gas flow rate is controlled at 0.4 m / s - 2 m / s. The catalyst includes any one or at least two combinations of nickel-based, copper-based, or aluminum-based. A cold hydrogenation reaction occurs under the conditions of a reaction pressure of 2 MPa - 3 MPa and a reaction temperature of 540 - 570°C. The formed outlet separates silicon powder through the first gas-solid separation unit and returns it to the cold hydrogenation reaction unit to form a cycle. The tail gas separated by the first gas-solid separation unit is cooled through the shell side of the first heat exchange unit, cooled from 540 - 570°C to 180 - 220°C, and then passes through the second gas-solid separation unit to remove fine silicon powder, and is sent to the washing unit for washing. The washed gas passes through the silicon tetrachloride preheating device and the hydrogen preheating device in sequence, exchanges heat with silicon tetrachloride gas and silicon powder respectively, cools down the washing gas, and then passes through an air-cooled heat exchange device, a water-cooled heat exchange device, a first heat exchange device, and a refrigeration unit for liquefaction, and enters the trichlorosilane storage unit. The uncondensed gas returns to the hydrogen preheating device and continues to participate in the cycle. All the condensed liquids in the hydrogen preheating device are drained into the trichlorosilane storage unit.

[0032] Compared with the prior art, the present utility model has at least the following beneficial effects:

[0033] (1) In the device system for producing trichlorosilane by cold hydrogenation reaction provided by the present utility model, a cold hydrogenation reaction device in the form of a circulating fluidized bed is adopted, realizing the circulating flow of reactants and catalysts in the bed, increasing the contact area between reactants and catalysts, significantly improving the cold hydrogenation reaction rate, and reducing the reaction energy consumption;

[0034] (2) The device system for producing trichlorosilane by cold hydrogenation reaction provided by the present utility model arranges a first gas-solid separation unit outside the cold hydrogenation reaction unit. The collected silicon powder is returned to the cold hydrogenation reaction unit, reducing the consumption of silicon powder and avoiding the problem of pipeline blockage caused by large particle silicon powder entering the subsequent device units.

[0035] (3) The device system for producing trichlorosilane by cold hydrogenation reaction provided by the present utility model sets up a multi-stage heat exchange unit, making full use of the heat of the tail gas at the outlet of the cold hydrogenation reaction, improving the utilization rate of heat, and having broad prospects for large-scale application. Description of the Drawings

[0036] Figure 1 is a schematic structural diagram of the device system for producing trichlorosilane by cold hydrogenation reaction in the specific embodiment of the present utility model.

[0037] In the figure: 1 - hydrogen storage device; 2 - silicon tetrachloride storage device; 3 - hydrogen preheating device; 4 - silicon tetrachloride preheating device; 5 - mixing device; 6 - first heat exchange unit; 7 - cold hydrogenation reaction unit; 8 - catalyst conveying device; 9 - silicon powder conveying device; 10 - first gas-solid separation unit; 11 - second gas-solid separation unit; 12 - washing unit; 13 - air-cooled heat exchange device; 14 - water-cooled heat exchange device; 15 - trichlorosilane storage unit; 16 - gasification device; 17 - first heat exchange device; 18 - refrigeration unit. Specific Embodiments

[0038] The technical solution of the present utility model will be further described below in conjunction with the drawings and through specific embodiments.

[0039] The present utility model will be further described in detail below. However, the following examples are merely simple examples of the present utility model and do not represent or limit the scope of the protection of the present utility model. The scope of protection of the present utility model shall be subject to the claims.

[0040] It should be understood that, in the description of the present utility model, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0041] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0042] Those skilled in the art should understand that the utility model must include necessary pipelines, conventional valves and general pump equipment for realizing a complete process, but the above content does not belong to the main utility model points of the utility model. Those skilled in the art can add layouts on their own based on the process flow and equipment structure selection, and the utility model does not make special requirements and specific limitations on this.

[0043] As a specific embodiment of the present invention, a device system for producing trichlorosilane by cold hydrogenation reaction is provided, and its structural schematic diagram is as follows: Figure 1 shown.

[0044] The device system includes a raw gas delivery unit, a first heat exchange unit 6, a cold hydrogenation reaction unit 7, a first gas-solid separation unit 10, a second gas-solid separation unit 11, a washing unit 12, a second heat exchange unit, a refrigeration unit 18 and a trichlorosilane storage unit 15;

[0045] The raw gas delivery unit, the first heat exchange unit 6, the cold hydrogenation reaction unit 7 and the first gas-solid separation unit 10 are connected in sequence;

[0046] The first gas-solid separation unit 10 is connected to the second gas-solid separation unit 11 and the washing unit 12 in sequence via the first heat exchange unit 6;

[0047] The raw material gas transportation unit includes a hydrogen storage device 1, a hydrogen preheating device 3, a silicon tetrachloride storage device 2, a silicon tetrachloride preheating device 4, a mixing device 5 and a gasification device 16; the hydrogen storage device 1, the hydrogen preheating device 3 and the mixing device 5 are connected in sequence; the silicon tetrachloride storage device 2, the silicon tetrachloride preheating device 4 and the mixing device 5 are connected in sequence; the mixing device 5 and the gasification device 16 are connected in sequence;

[0048] The washing unit 12 is connected to the silicon tetrachloride preheating device 4, the hydrogen preheating device 3, the second heat exchange unit, the refrigeration unit and the trichlorosilane storage unit 15 in sequence;

[0049] The cold hydrogenation reaction unit 7 includes a cold hydrogenation reaction device in the form of a circulating fluidized bed.

[0050] The cold hydrogenation reaction device is respectively connected to a catalyst delivery device 8 and a silicon powder delivery device 9.

[0051] The first gas-solid separation unit 10 includes a cyclone separator or at least two serially connected cyclone separators;

[0052] At least two serially connected cyclone separators share a dipleg.

[0053] The bottom of the first gas-solid separation unit 10 is connected to the cold hydrogenation reaction device;

[0054] The top of the first gas-solid separation unit 10 is connected to the first heat exchange unit.

[0055] The first heat exchange unit includes a two-stage heat exchanger.

[0056] The inner wall of the first gas-solid separation unit 10 is provided with a wear-resistant lining.

[0057] The second heat exchange unit includes an air-cooled heat exchange device 13, a water-cooled heat exchange device 14 and a first heat exchange device 17 connected in sequence.

[0058] The washing unit 12 includes a washing tower.

[0059] The refrigeration unit 18 includes an ice machine.

[0060] The refrigeration unit 18 is connected to the hydrogen preheating device 3.

[0061] As a specific embodiment of the present invention, there is also provided an operation method of the above device system for producing trichlorosilane by cold hydrogenation reaction, including the following steps:

[0062] The hydrogen gas in the hydrogen storage device 1 enters the mixing device 5 after being preheated by the hydrogen preheating device 3 with a designed temperature of 150°C, and is mixed with the silicon tetrachloride that has been preheated by the silicon tetrachloride preheating device 4 with a designed temperature of 150°C from the silicon tetrachloride storage device 2. The mixed gas passes through the vaporization device 16 and is introduced into the tube side of the first heat exchange unit 6, where it is heated from 150°C to 570°C and exchanges heat with the tail gas at the outlet of the first gas-solid separation unit 10, further heating the mixed gas, and finally forming the inlet gas of the cold hydrogenation reaction unit 7. The inlet gas of the cold hydrogenation reaction unit 7, the catalyst nickel powder in the catalyst delivery device 8, and the silicon powder in the silicon powder delivery device 9 are introduced into the cold hydrogenation reaction unit 7, with the gas flow rate controlled at 2 m / s. A cold hydrogenation reaction occurs under the conditions of a reaction pressure of 3 MPa and a reaction temperature of 570°C. The formed outlet separates out silicon powder through the first gas-solid separation unit 10 and returns to the cold hydrogenation reaction unit 7 to form a cycle. The tail gas separated by the first gas-solid separation unit 10 is cooled through the shell side of the first heat exchange unit 6, from 570°C to 180°C, and then passes through the second gas-solid separation unit 11 to remove fine silicon powder, and is sent to the washing unit 12 for washing. The washed gas successively passes through the silicon tetrachloride preheating device 4 and the hydrogen preheating device 3, exchanges heat with silicon tetrachloride gas and silicon powder respectively, the washing gas is cooled, and then passes through the air-cooled heat exchange device 13, the water-cooled heat exchange device 14, the first heat exchange device 17 and the refrigeration unit 18 for liquefaction, and enters the trichlorosilane storage unit 15. The uncondensed gas returns to the hydrogen preheating device 3 and continues to participate in the cycle. All the condensed liquids in the hydrogen preheating device 3 are discharged into the trichlorosilane storage unit 15.

[0063] In this specific embodiment, the average mass conversion rate of the device system for producing trichlorosilane by cold hydrogenation reaction can reach over 31%. The energy of the entire device system is fully utilized, and by performing multi-stage gas-solid separation treatment on the silicon powder, the blockage of the subsequent system by the silicon powder is avoided.

[0064] The applicant declares that the present utility model uses the above embodiments to illustrate the detailed structural features of the present utility model, but the present utility model is not limited to the above detailed structural features, that is, it does not mean that the present utility model must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present utility model, the equivalent replacement of the components selected by the present utility model, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present utility model.

[0065] The preferred embodiments of the present utility model have been described in detail above. However, the present utility model is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present utility model, various simple modifications can be made to the technical solution of the present utility model, and these simple modifications all fall within the protection scope of the present utility model.

[0066] In addition, it should be noted that, for each of the specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present utility model will not separately describe various possible combination manners.

[0067] In addition, any combinations can be made among various different embodiments of the present utility model, as long as they do not violate the idea of the present utility model, and they should also be regarded as the content disclosed by the present utility model.

Claims

1. A device system for producing trichlorosilane by cold hydrogenation reaction, characterized in that: The device system includes a raw gas delivery unit, a first heat exchange unit, a cold hydrogenation reaction unit, a first gas-solid separation unit, a second gas-solid separation unit, a washing unit, a second heat exchange unit, a refrigeration unit and a trichlorosilane storage unit; The raw gas delivery unit, the first heat exchange unit, the cold hydrogenation reaction unit and the first gas-solid separation unit are connected in sequence; The first gas-solid separation unit is connected to the second gas-solid separation unit and the washing unit in sequence via the first heat exchange unit; The raw gas delivery unit comprises a hydrogen storage device, a hydrogen preheating device, a silicon tetrachloride storage device, a silicon tetrachloride preheating device, a mixing device and a gasification device; the hydrogen storage device, the hydrogen preheating device and the mixing device are connected in sequence; the silicon tetrachloride storage device, the silicon tetrachloride preheating device and the mixing device are connected in sequence; the mixing device and the gasification device are connected in sequence; The washing unit is sequentially connected to the silicon tetrachloride preheating device, the hydrogen preheating device, the second heat exchange unit, the refrigeration unit and the trichlorosilane storage unit; The cold hydrogenation reaction unit comprises a cold hydrogenation reaction device in the form of a circulating fluidized bed.

2. The device system according to claim 1, characterized in that: The cold hydrogenation reaction device is connected to the catalyst conveying device and the silicon powder conveying device respectively.

3. The device system according to claim 1, characterized in that: The first gas-solid separation unit comprises a cyclone separator or at least two cyclone separators connected in series; At least two cyclone separators connected in series share one dipleg.

4. The device system according to claim 3, characterized in that: The bottom of the first gas-solid separation unit is connected to a cold hydrogenation reaction device; The top of the first gas-solid separation unit is connected to the first heat exchange unit.

5. The device system according to claim 1, characterized in that: The first heat exchange unit includes 1 to 4 stages of heat exchangers.

6. The device system according to claim 1, characterized in that: The inner wall of the first gas-solid separation unit is arranged with a wear-resistant lining.

7. The device system according to claim 1, characterized in that: The second heat exchange unit includes an air-cooling heat exchange device, a water-cooling heat exchange device and a first heat exchange device which are connected in sequence.

8. The device system according to claim 1, characterized in that: The washing unit includes a washing tower.

9. The device system according to claim 1, characterized in that: The refrigeration unit includes an ice machine.

10. The device system according to claim 9, characterized in that: The refrigeration unit is connected to the hydrogen preheating device.

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