Polycrystalline silicon cold hydrogenation system

Abstract

The utility model provides a polycrystalline silicon cold hydrogenation system, aiming at solving the technical problems that the existing cold hydrogenation process equipment is high in cost and easy to block. According to the fluidized bed reactor disclosed by the invention, raw material mixed gas introduced into the fluidized bed reactor and silicon powder are subjected to chemical reaction. The cyclonic separation assembly has a plurality of cyclones and a first regulating valve. And the series / parallel connection adjustment of the plurality of cyclone separators is realized through the first adjusting valve. The input end of the cyclone separation assembly is connected with the fluidized bed reactor. The waste heat boiler tube pass input end is connected with the output end of the cyclone separation assembly. The waste heat boiler is provided with a first heat exchange part and a second heat exchange part. And shell passes between the two heat exchange parts are not communicated with each other and are used for two-stage cooling of silane gas introduced into the waste heat boiler. The input end of the washing tower is connected with the waste heat boiler tube pass output end. Through the cyclone separation assembly, serial-parallel connection and multi-stage washing of the washing tower can be switched, impurity particles in silane gas are reduced, meanwhile, equipment is not prone to being blocked, and the process operation stability is guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field related to polysilicon production, and in particular to a polysilicon cold hydrogenation system. Background Art

[0002] In the prior art, trichlorosilane is mainly synthesized by industrial silicon powder, silicon tetrachloride and hydrogen in a cold hydrogenation fluidized bed reactor, and the reaction equation is 3SiCl4+2H2+Si=4SiHCl3. Compared with the hot hydrogenation process, the cold hydrogenation process can avoid the problem of large amounts of silicon tetrachloride being difficult to handle. Although it is more advanced, the following problems need to be solved in the production process:

[0003] The silicon chloride gas discharged from the fluidized bed reactor often needs to pass through multiple condensing heat exchangers to cool the silane gas, and then be washed through a washing tower before being recovered, which results in a large footprint and high equipment cost;

[0004] (2) The silicon chloride gas discharged from the fluidized bed reactor is often accompanied by microparticles such as silicon powder and metal chloride. In order to avoid the influence of the above-mentioned impurity particles on the quality of silicon chloride products, the traditional cold hydrogenation process often uses a combination of dry and wet methods to treat the silicon chloride gas, that is, the silicon chloride gas from the hydrogenation furnace enters the cyclone separator to remove silicon powder of different particle sizes, and then enters the heat exchanger for heat exchange, and then passes to the wet dust removal system for cooling and washing to remove metal chlorides, high boiling points and a small amount of silicon powder. However, in actual operation, the ceramic filter element of the silicon powder filter of the cyclone separator is used under harsh conditions and is easily broken due to operating condition adjustments, thereby bringing microparticles such as silicon powder contained in the silicon chloride to the heat exchange system and the wet dust removal system. This not only easily causes the equipment used in the subsequent heat exchange and washing processes to become blocked, resulting in high maintenance costs, but also increases the operating energy consumption of the equipment, which is not conducive to sustainable development. Utility Model Content

[0005] The utility model aims to provide a polysilicon cold hydrogenation system to solve the problems raised in the above background technology.

[0006] A polysilicon cold hydrogenation system, comprising:

[0007] A fluidized bed reactor, which is used to chemically react the raw material mixed gas and silicon powder introduced therein;

[0008] A cyclone separation component has a plurality of cyclone separators; the cyclone separation component is provided with a first regulating valve for realizing the series / parallel connection of the plurality of cyclone separators; the input end of the cyclone separation component is connected to the fluidized bed reactor;

[0009] A waste heat boiler, whose tube side input end is connected to the cyclone separation component output end; the waste heat boiler has a first heat exchange part and a second heat exchange part; the shell side between the two heat exchange parts is not interconnected, and is used for two-stage cooling of the silane gas introduced into the waste heat boiler;

[0010] The washing tower has an input end connected to the output end of the waste heat boiler tube.

[0011] Furthermore, the cyclone separation assembly includes two cyclone separators; the input ends of the two cyclone separators are connected to the fluidized bed reactor, and a feed butterfly valve is arranged between one of the cyclone separators and the fluidized bed reactor; the two cyclone separators are connected to each other.

[0012] Furthermore, the scrubbing tower is provided with a demister, a leaching pipe connected to a leaching feed pipe, a venturi scrubber and a barrel cover in sequence from the top to the bottom of the tower;

[0013] The input end of the venturi scrubber is connected to the output end of the waste heat boiler tube; an annular spray pipe is provided at the top of the barrel cover; a thorn portion is provided at the bottom of the barrel cover and a water bath space is left with the bottom end of the washing tower.

[0014] Furthermore, a liquid outlet pipe is provided at the bottom end of the washing tower; and a shut-off valve is provided on the liquid outlet pipe.

[0015] Furthermore, the polysilicon cold hydrogenation system also includes a collecting tank; the collecting tank is connected between the cyclone separation assembly and the fluidized bed reactor.

[0016] Furthermore, the first heat exchange section is divided into a preheating section and a heating section by a partition; hydrogen gas is introduced into the shell side of the preheating section; the heating section is arranged above the preheating section; and the shell side outlet of the heating section is connected to the fluidized bed reactor.

[0017] Furthermore, the shell side between the preheating section and the heating section is interconnected through a connecting pipe; the connecting pipe is provided with a second regulating valve.

[0018] Furthermore, the second heat exchange part is matched and connected with the gas-liquid separation tank through an ascending pipe and a descending pipe, so as to realize gas-liquid separation in the gas-liquid separation tank; the gas-liquid separation tank is provided with a steam outlet;

[0019] Among them, boiler water is introduced into the gas-liquid separation tank and passed to the shell side of the second heat exchange part through the downcomer to exchange heat with the silane gas in the tube side. The steam drum generated by the heat exchange is discharged from the riser through the gas-liquid separation tank.

[0020] Further, one end of the riser is connected to the shell side of the second heat exchange part; the other end of the riser is arranged in the gas-liquid separation tank at a height exceeding the boiler water inlet height of the gas-liquid separation tank;

[0021] The downcomer has one end connected to the shell side of the second heat exchange part, and the other end connected to the bottom end of the gas-liquid separation tank.

[0022] Furthermore, the gas discharged from the steam outlet is used to heat the chlorosilane raw material required before the reaction in the fluidized bed reactor.

[0023] Compared with the prior art, the beneficial effects of the utility model are:

[0024] (1) When the silane gas of the polysilicon cold hydrogenation system of the present application passes through the first heat exchange part and the second heat exchange part in turn for secondary heat exchange and cooling, not only the waste heat of the silane gas is fully utilized, but also the waste heat is used to supply the heat energy required by the raw materials for the hydrogenation reaction, thereby realizing the recycling of energy. The silane gas entering the preheating boiler is separated by the cyclone separation component. The multiple cyclone separators of the cyclone separation component can be adjusted in series and parallel to achieve efficient separation of silicon powder and silane gas, greatly reducing the silicon powder content in the silane gas entering the waste heat boiler, so that when the waste heat of the silane gas is subsequently utilized, the pipe process of the waste heat boiler is not easily blocked due to the large amount of silicon powder contained in the silane gas, thereby ensuring the stability of the process operation and at the same time helping to improve the waste heat utilization rate of the silane gas in the waste heat boiler.

[0025] (2) Through the coordinated effect of the switchable series-parallel connection of the cyclone separation components and the multi-stage washing of the silane gas washing tower, microparticles such as silicon powder can be efficiently removed while not causing equipment clogging, greatly improving the purity and purification efficiency of the recovered silane gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a schematic diagram of a process connection of a polysilicon cold hydrogenation system according to Example 1 of the present application;

[0028] Figure 2 This is a schematic diagram of the process connection of a polysilicon cold hydrogenation system according to Example 2 of the present application.

[0029] Reference numerals:

[0030] 1. Fluidized bed reactor;

[0031] 20. Cyclone separator; 21. Feed butterfly valve;

[0032] 3. Waste heat boiler; 30. Preheating section; 31. Second heat exchange section; 32. Heating section; 33. Baffle; 34. Connecting pipe; 35. Second regulating valve; 36. Rising pipe; 37. Downcoming pipe; 38. Feed channel;

[0033] 40. Gas-liquid separation tank; 41. Steam outlet pipe; 42. Pressure regulating valve; 43. Remote pressure gauge; 44. Remote liquid level gauge; 45. Boiler water inlet;

[0034] 5. Scrubber; 50. Defoamer; 51. Leaching pipe; 52. Venturi scrubber; 53. Annular elution pipe; 54. Cylinder cover; 55. Thorn part; 56. Shut-off valve; 57. Leaching feed pipe; 58. Remote thermometer;

[0035] 6. Electric heater; 7. Collection tank. DETAILED DESCRIPTION

[0036] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0037] In the description of the present invention, it should be understood that the terms "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships conventionally placed when the product of the present invention is used, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do 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 should not be understood as a limitation on the present invention.

[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection" and the like 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; it can be a direct connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention may repeat reference numerals in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments discussed.

[0041] The embodiments of the present utility model are described in detail below with reference to the accompanying drawings.

[0042] Example 1

[0043] The present invention provides a polysilicon cold hydrogenation system. Figure 1 The polysilicon cold hydrogenation system comprises a fluidized bed reactor 1 , a cyclone separation component, a waste heat boiler 3 and a washing tower 5 .

[0044] The fluidized bed reactor 1 is used to carry out hydrogenation reaction between the raw material mixed gas and silicon powder introduced therein.

[0045] The cyclone separation assembly includes two cyclone separators 20. The input ends of the two cyclone separators 20 are connected to the top of the fluidized bed reactor 1. A feed butterfly valve 21 is provided between one of the cyclone separators 20 and the fluidized bed reactor 1. The two cyclone separators 20 are connected to each other through a pipeline.

[0046] When the feed butterfly valve 21 is closed, the two cyclone separators 20 operate in series; when the feed butterfly valve 21 is opened, the two cyclone separators 20 operate in parallel. Therefore, the feed butterfly valve 21 can be adjusted according to the silicon powder particles contained in the silane gas discharged from the fluidized bed reactor 1, so as to achieve efficient separation of silane gas and silicon powder, and greatly reduce the silicon powder content in the silane gas. Even if one of the cyclone separators 20 works abnormally, the feed butterfly valve 21 can be adjusted to maintain the normal separation of silicon powder in the silane gas by the cyclone separation component, thereby ensuring the stability of the process operation.

[0047] A collecting tank 7 is connected between the cyclone separation assembly and the fluidized bed reactor 1 to collect the silicon powder after cyclone separation.

[0048] The waste heat boiler 3 has a tube side input end connected to the cyclone separation component output end. The waste heat boiler 3 has a first heat exchange part and a second heat exchange part 31. The shell side between the two heat exchange parts is not interconnected, and is used for two-stage cooling of the silane gas introduced into the waste heat boiler 3.

[0049] The first heat exchange part is divided into a preheating section 30 and a heating section 32 by a partition plate 33. The heating section 32 is arranged above the preheating section 30.

[0050] The preheating section 30 has a feed channel 38 in its shell side for the introduction of hydrogen gas. The shell side outlet of the heating section 32 is connected to the fluidized bed reactor 1. The silane gas treated by the cyclone separation component is introduced into the first heat exchange section tube side, which can avoid the problem that a large amount of silicon powder contained in the silane gas enters the first heat exchange section tube side and causes the tube side to be easily blocked. At the same time, the silane gas exchanges heat with the hydrogen gas in the shell side of the first heat exchange section, making full use of the waste heat of the silane gas to heat the hydrogen gas raw material to meet the process requirements, realizing the recovery of waste heat while saving energy. In addition, an electric heater 6 can be provided between the shell side outlet of the heating section 32 and the fluidized bed reactor 1 to further ensure that the temperature of the hydrogen gas raw material leading to the fluidized bed reactor 1 meets the reaction requirements.

[0051] The shell side between the heating section 32 and the preheating section 30 is interconnected through a connecting pipe 34. The connecting pipe 34 is provided with a second regulating valve 35. The second regulating valve 35 is controlled to control the flow rate of hydrogen gas entering the heating section 32 from the preheating section 30, so as to adjust the temperature of the hydrogen gas after heat exchange in the first heat exchange part.

[0052] The second heat exchange part 31 is matched and connected with the gas-liquid separation tank 40 through the riser 36 and the downcomer 37, so as to realize the gas-liquid separation of the gas-liquid separation tank 40. That is, one end of the riser 36 is connected to the shell side of the second heat exchange part 31, and the other end is arranged in the gas-liquid separation tank 40 at a height exceeding the height of the boiler water inlet 45 of the gas-liquid separation tank 40. One end of the downcomer 37 is connected to the shell side of the second heat exchange part 31, and the other end is connected to the bottom of the gas-liquid separation tank 40. In order to facilitate the control of the liquid level of the gas-liquid separation tank 40, a remote liquid level gauge 44 is provided on the side wall of the gas-liquid separation tank 40. A steam outlet pipe 41 is provided at the top of the gas-liquid separation tank 40. The steam outlet pipe 41 can be connected to the four silicon preheater and the four silicon vaporizer, and is used for heating and raising the temperature of the chlorosilane raw materials required before the reaction of the fluidized bed reactor 1. In order to facilitate the control of the gas pressure of the steam outlet pipeline 41 , a remote pressure gauge 43 is provided on the top wall of the gas-liquid separation tank 40 , and a pressure regulating valve 42 is provided on the steam outlet pipeline 41 .

[0053] Boiler water is introduced into the gas-liquid separator 40 through the boiler water inlet 45, and is introduced into the shell side of the second heat exchange part 31 through the downcomer 37 to exchange heat with the silane gas in the tube side of the second heat exchange part 31. The steam drum after heat exchange is discharged from the riser 36 through the gas-liquid separator 40, and can be used to heat the chlorosilane raw material required before the reaction of the fluidized bed reactor 1.

[0054] When the silane gas passes through the first heat exchange part and the second heat exchange part 31 in turn for secondary heat exchange and cooling, not only the waste heat of the silane gas is fully utilized, but also the waste heat is used to supply the heat energy required by the raw materials for the hydrogenation reaction, thereby realizing the recycling of energy.

[0055] The input end of the washing tower 5 is connected to the output end of the tube side of the waste heat boiler 3. The output end of the tube side of the waste heat boiler 3 discharges the silane gas and leads to the washing tower 5 for washing to remove metal chlorides, high boiling products and a small amount of silicon powder contained in the silane gas.

[0056] The working principle of this embodiment is:

[0057] The silane gas produced by the hydrogenation reaction in the fluidized bed reactor 1 is passed to the cyclone separation assembly, and the silicon powder is separated from the silane gas by cyclone separation. Among them, the multiple cyclone separators 20 of the cyclone separation assembly can be adjusted in series and parallel to achieve efficient separation of silicon powder and silane gas. For example: when a cyclone separator 20 operates abnormally, the cyclone separators 20 can be adjusted in series and parallel to maintain the normal operation of the cyclone separation. Therefore, the silane gas after passing through the above-mentioned cyclone separation assembly is then passed to the waste heat boiler 3 pipe side, and the waste heat boiler 3 pipe side is not prone to blockage.

[0058] Subsequently, the silane gas is passed into the pipe of the waste heat boiler 3 and exchanges heat with the hydrogen gas and boiler water respectively, realizing the secondary utilization of waste heat while supplying the heat energy utilized for heat exchange to the heat energy required by the raw materials for the hydrogenation reaction, thus realizing the recycling of energy. Moreover, the pipe of the waste heat boiler 3 is not easily blocked by the large amount of silicon powder contained in the silane gas, which not only ensures the stability of the process operation, but also helps to improve the waste heat utilization rate of the silane gas in the waste heat boiler 3.

[0059] The silane gas finally discharged from the waste heat boiler 3 is passed to the washing tower 5 for washing and recovery.

[0060] Example 2

[0061] Based on Example 1, please refer to Figure 2. In order to further improve the purity of the recovered silane gas and reduce the temperature of the silane gas, the washing tower 5 of the present application is equipped with a demister 50 and a leaching pipe 51 connected to the leaching feed pipe 57, a venturi scrubber 52 and a barrel cover 54 in sequence from the top to the bottom of the tower. Among them, the input end of the venturi scrubber 52 is connected to the output end of the pipe side of the waste heat boiler 3. An annular spray pipe 53 is provided at the top of the barrel cover 54. A thorn portion 55 is provided at the bottom end of the barrel cover 54, and a water bath space is left at the bottom end of the washing tower 5. A gas outlet pipeline with a remote thermometer 58 is connected to the top of the washing tower 5. A liquid outlet pipeline with a shut-off valve 56 is connected to the bottom end of the washing tower 5. By adjusting the shut-off valve 56, the leaching liquid that converges in the water bath space is discharged.

[0062] The working principle of this embodiment is:

[0063] The silane gas discharged from the waste heat boiler 3 enters the venturi scrubber 52 for washing, and then flows to the barrel cover 54 for washing. During this period, the eluent mixed with silane gas is guided by the barrel cover 54 to the water bath space for purification. The eluent water bath converged by the water bath space is bubbled and broken in turn to make the silane gas break the bubble out, and then flows back to the eluent pipe 51 along the gap between the outer wall of the barrel cover 54 and the inner wall of the washing tower 5 for washing, and then after the defoamer 50 removes the foam, it is discharged from the gas outlet pipe for recovery. This avoids the problem that the impurity particles mixed in the silane gas diffuse arbitrarily in the washing tower 5 and easily block the tower plate. In summary, this embodiment achieves the efficient removal of microparticles such as silicon powder and is not easy to cause the equipment to be blocked through the switchable series-parallel connection of the cyclone separation component and the coordinated effect of the multi-stage washing of the silane gas washing tower 5, which greatly improves the purification efficiency and the purity of the recovered silane gas.

Claims

1. A polysilicon cold hydrogenation system, characterized in that: The polysilicon cold hydrogenation system comprises: A fluidized bed reactor, which is used to chemically react the raw material mixed gas and silicon powder introduced therein; A cyclone separation component has a plurality of cyclone separators; the cyclone separation component is provided with a first regulating valve for realizing the series / parallel connection of the plurality of cyclone separators; the input end of the cyclone separation component is connected to the fluidized bed reactor; A waste heat boiler, whose tube side input end is connected to the cyclone separation component output end; the waste heat boiler has a first heat exchange part and a second heat exchange part; the shell side between the two heat exchange parts is not interconnected, and is used for two-stage cooling of the silane gas introduced into the waste heat boiler; The washing tower has an input end connected to the output end of the waste heat boiler tube.

2. The polysilicon cold hydrogenation system according to claim 1, characterized in that: The cyclone separation assembly includes two cyclone separators; the input ends of the two cyclone separators are both connected to the fluidized bed reactor, and a feed butterfly valve is arranged between one of the cyclone separators and the fluidized bed reactor; the two cyclone separators are connected to each other.

3. The polysilicon cold hydrogenation system according to any one of claims 1 or 2, characterized in that: The scrubbing tower is provided with a defoamer, a leaching pipe connected to the leaching feed pipe, a venturi scrubber and a barrel cover in sequence from the top to the bottom of the tower; Among them, the input end of the venturi scrubber is connected to the output end of the waste heat boiler tube; the top of the barrel cover is provided with an annular spray pipe; the bottom end of the barrel cover is provided with a thorn part and a water bath space is left with the bottom end of the washing tower.

4. The polysilicon cold hydrogenation system according to claim 3, characterized in that: A liquid outlet pipe is provided at the bottom end of the washing tower; a cut-off valve is provided on the liquid outlet pipe.

5. The polysilicon cold hydrogenation system according to claim 1, characterized in that: The polysilicon cold hydrogenation system further includes a collecting tank; the collecting tank is connected between the cyclone separation component and the fluidized bed reactor.

6. The polysilicon cold hydrogenation system according to claim 1, characterized in that: The first heat exchange part is divided into a preheating section and a heating section by a partition; hydrogen gas is introduced into the shell side of the preheating section; the heating section is arranged above the preheating section; and the shell side outlet of the heating section is connected to the fluidized bed reactor.

7. The polysilicon cold hydrogenation system according to claim 6, characterized in that: The shell side between the preheating section and the heating section is interconnected through a connecting pipe; the connecting pipe is provided with a second regulating valve.

8. The polysilicon cold hydrogenation system according to claim 1, characterized in that: The second heat exchange part is matched and connected with the gas-liquid separation tank through the ascending pipe and the descending pipe, so as to realize the gas-liquid separation of the gas-liquid separation tank; the gas-liquid separation tank is provided with a steam outlet; Among them, boiler water is introduced into the gas-liquid separation tank and passed to the shell side of the second heat exchange part through the downcomer to exchange heat with the silane gas in the tube side. The steam drum generated by the heat exchange is discharged from the riser through the gas-liquid separation tank.

9. The polysilicon cold hydrogenation system according to claim 8, characterized in that: One end of the riser is connected to the shell side of the second heat exchange part; the other end of the riser is arranged in the gas-liquid separation tank at a height exceeding the boiler water inlet height of the gas-liquid separation tank; The downcomer has one end connected to the shell side of the second heat exchange part, and the other end connected to the bottom end of the gas-liquid separation tank.

10. The polysilicon cold hydrogenation system according to claim 8, characterized in that: The gas discharged from the steam outlet is used to heat the chlorosilane raw material required before the reaction in the fluidized bed reactor.

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