Method for avoiding abnormal feeding of polycrystalline silicon reduction furnace

Abstract

The present application relates to the technical field of polycrystalline silicon reduction furnace, and particularly relates to a feeding method for avoiding abnormality of polycrystalline silicon reduction furnace. The present application keeps the temperature of the gas inlet of the reduction furnace above 100 DEG C, and sets a pipeline valve with an opening degree of 1% on the gas inlet pipeline of trichlorosilane, so as to avoid the liquid deposited in the gas inlet pipeline from entering the reduction furnace, avoid the long hair of the atomized silicon core in the reduction furnace from affecting the quality of the polycrystalline silicon product, and also avoid the bottom plate of the reduction furnace from catching fire, so as to protect the equipment safety of the reduction furnace, save the shutdown time, and reduce the production cost. The present application solves the problem that the polycrystalline silicon reduction furnace is prone to abnormality in the prior art, and achieves the purposes of avoiding abnormality of the polycrystalline silicon reduction furnace, protecting the reduction furnace, and increasing the yield and quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polycrystalline silicon reduction furnace, in particular to a feeding method for avoiding abnormal polycrystalline silicon reduction furnace. BACKGROUND

[0002] In the production process of polycrystalline silicon, some problems of temperature and current fluctuation often occur, which are caused by many factors, and these factors greatly affect the production and reduction process of polycrystalline silicon. The reduction furnace is one of the core equipment for producing polycrystalline silicon. After the purified trichlorosilane and high-purity hydrogen are buffered, they are introduced into the reduction furnace at a temperature of 1150 DEG C for reaction, and the generated high-purity polycrystalline silicon is deposited on the polycrystalline silicon carrier to obtain a polycrystalline silicon rod. In the process of preparing polycrystalline silicon, hydrogen and trichlorosilane enter the reduction furnace through a static mixer.

[0003] In the existing polycrystalline silicon reduction process, high-purity polycrystalline silicon is generally produced by using a modified Siemens process. The principle is to reduce high-purity trichlorosilane with high-purity hydrogen on a high-purity silicon core at a temperature of about 1100 DEG C to generate polycrystalline silicon deposited on the silicon core. In the specific preparation, the current value at different times on the polycrystalline silicon rod is adjusted according to the temperature curve set in advance, or a PID adjustment method is used to gradually heat the polycrystalline silicon rod. However, the above-mentioned method has certain defects, and cannot control the temperature and circuit fluctuation caused by various uncertain factors, so it is impossible to ensure that the entire reduction reaction proceeds normally and stably. When feeding, the silicon core in the reduction furnace is prone to appear long hair-like burrs, and even the furnace may be stopped in the middle of the process. The final yield and quality are also unsatisfactory.

[0004] The abnormal reduction furnace appearing in the above-mentioned situation will affect the product quality and therefore the furnace needs to be stopped. The cost of a single reduction furnace is relatively high. Therefore, avoiding the occurrence of abnormal reduction furnace can save costs, save downtime, and improve the quality and yield of the product. SUMMARY

[0005] The present application provides a feeding method for avoiding abnormal polycrystalline silicon reduction furnace, which solves the problem of poor yield and quality caused by the easy occurrence of abnormal polycrystalline silicon reduction furnace in the prior art, and achieves the purpose of avoiding abnormal polycrystalline silicon reduction furnace, protecting the reduction furnace, and increasing the yield and quality.

[0006] The present application provides a feeding method for avoiding abnormal reduction furnace, which comprises the following steps:

[0007] S1, heating hydrogen and trichlorosilane respectively to obtain heated hydrogen and heated trichlorosilane;

[0008] S2, synchronously introducing the heated hydrogen and the heated trichlorosilane obtained in S1 into a static mixer to obtain a mixed feeding gas;

[0009] S3, keeping the temperature of the mixed feed gas obtained in S2 > 100℃;

[0010] S4, passing the mixed feed gas into a reduction furnace and reacting in the reduction furnace to obtain a polysilicon product.

[0011] According to the feeding method for avoiding abnormality of the polysilicon reduction furnace provided by the application, the trichlorosilane is passed into the static mixer through the trichlorosilane gas inlet pipe in S2, and the gas inlet end of the trichlorosilane gas inlet pipe is provided with a pipe valve, and the opening of the pipe valve is adjusted to 1%.

[0012] According to the feeding method for avoiding abnormality of the polysilicon reduction furnace provided by the application, the hydrogen and trichlorosilane are passed into the evaporator for heating in S1.

[0013] According to the feeding method for avoiding abnormality of the polysilicon reduction furnace provided by the application, the molar ratio of the hydrogen and trichlorosilane in S2 is (2.5-3):1.

[0014] According to the feeding method for avoiding abnormality of the polysilicon reduction furnace provided by the application, the gas outlet end of the static mixer is provided with a thermometer in S2, and the gas outlet end of the static mixer is communicated with the gas inlet end of the reduction furnace.

[0015] According to the feeding method for avoiding abnormality of the polysilicon reduction furnace provided by the application, the detection temperature of the mixed feed gas is always kept > 100℃ when the reduction furnace is reacted in S4.

[0016] According to the feeding method for avoiding abnormality of the polysilicon reduction furnace provided by the application, a high-purity silicon core is arranged in the reduction furnace in S4, and the temperature in the reduction furnace is kept at 1080-1150℃.

[0017] According to the feeding method for avoiding abnormality of the polysilicon reduction furnace provided by the application, tail gas is also generated when the reduction furnace is reacted in S4, and the tail gas is passed into a tail gas treatment device.

[0018] The beneficial effects of the application are as follows:

[0019] According to the application, when the temperature of the mixed feed gas is detected by the thermometer arranged at the outlet end of the static mixer and is > 100℃, it is ensured that the trichlorosilane in the mixed feed gas all enters the reduction furnace in the form of gas, and the long hair of the atomized silicon core in the reduction furnace is avoided to affect the quality of the polysilicon product.

[0020] The gas inlet end of the trichlorosilane gas inlet pipe is provided with a pipeline valve, the opening of the pipeline valve is adjusted to 1%, liquid in the trichlorosilane gas inlet pipe enters the reduction furnace, polycrystalline silicon product is atomized and long hair is generated, and the reduction furnace bottom is on fire, the quality and yield of the polycrystalline silicon product are improved, the reduction furnace is protected, abnormality of the reduction furnace is avoided, the shutdown time is saved, and the production cost is reduced.

[0021] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0023] Figure 1 is a flow chart of the feeding method of the present application;

[0024] Figure 2 is a schematic diagram of the feeding method of the present application. DETAILED DESCRIPTION

[0025] In order to make the objects, technical solutions and advantages of the present application clearer, the following will combine the drawings in the present application to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the protection scope of the present application.

[0026] In the description of the embodiments of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application. In addition, the terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0027] In the description of the embodiments of the present application, it should be noted that unless specifically defined and limited otherwise, the terms "connected", "connected to", "connection" should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integral connection, can be mechanical connection, can also be electrical connection, can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0028] In the embodiments of the present application, unless specifically defined and limited otherwise, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be "above", "over" and "on" the second feature, which can be that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature can be "below", "under" and "under" the second feature, which can be that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0029] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms is not directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0030] The technical solutions of the present application will be described below in conjunction with the embodiments shown in Figure 1 and Figure 2

[0031] The present application provides a feeding method for avoiding abnormality of a reduction furnace, comprising the following steps:

[0032] S1, hydrogen and trichlorosilane are introduced into an evaporator for heating to obtain heated hydrogen and heated trichlorosilane;

[0033] Because hydrogen is easy to purify and has very low solubility in silicon, the purity of polysilicon prepared by selecting hydrogen as a reducing agent is much higher;

[0034] ​Since SiHCl3 liquid needs to be evaporated into gas to provide raw material for the reduction furnace, the SiHCl3 liquid needs to be heated by hot water to maintain the temperature of the SiHCl3 liquid;

[0035] S2, the heated hydrogen and the heated trichlorosilane obtained in S1 are synchronously introduced into the static mixer at a molar ratio of (2.5-3):1 to obtain a mixed feed gas;

[0036] The heated trichlorosilane obtained in S1 is introduced into the static mixer through the trichlorosilane gas inlet pipe, and a pipe valve is arranged on the trichlorosilane gas inlet pipe, and the opening degree of the pipe valve is adjusted to 1%;

[0037] Because the temperature of trichlorosilane is relatively low when the feeding starts, the reduction furnace is generally stopped for 4-5 hours, and the pipe valve of the trichlorosilane gas inlet pipe is kept closed during the shutdown. The gas in the pipe of the trichlorosilane gas inlet pipe becomes liquid state, and there is liquid accumulation in the pipe of the trichlorosilane gas inlet pipe before the reduction furnace is started. Adjusting the opening degree of the pipe valve of the trichlorosilane gas inlet pipe to 1% can make the liquid accumulation vaporize. If the opening degree of the pipe valve is not controlled, the trichlorosilane liquid accumulation in the pipe cannot be vaporized, which will cause the silicon core in the reduction furnace to be easily atomized and grow into a long hair, affecting the quality of the reduction product;

[0038] S3, detecting and keeping the temperature of the mixed feed gas obtained in S2 > 100℃; a thermometer is arranged at the gas outlet end of the static mixer, and the gas outlet end of the static mixer is communicated with the gas inlet end of the reduction furnace;

[0039] If the mixed feed gas entering the reduction furnace is mixed with trichlorosilane liquid accumulation, the bottom plate of the reduction furnace is easy to fire, and the bottom plate is easy to burn the electrode and the bottom plate, which will cause a certain degree of damage to the reduction furnace, increase the maintenance cost of the reduction furnace and waste the working time of the reduction furnace, thereby reducing the yield, quality and working efficiency of the reduction furnace;

[0040] If the temperature at the outlet end of the static mixer is controlled below 100℃, it cannot be guaranteed that all the trichlorosilane in the mixed feed gas is in gaseous state. If the mixed feed gas entering the reduction furnace is mixed with trichlorosilane liquid accumulation, the silicon core in the reduction furnace is easy to be atomized and grow into a long hair, so the temperature at the outlet end of the static mixer must be controlled above 100℃, and the detection temperature of the mixed feed gas needs to be kept > 100℃ during the reaction of the reduction furnace;

[0041] S4, introducing the mixed feed gas into the reduction furnace, keeping the temperature in the reduction furnace at 1080-1150℃, and arranging high-purity silicon core in the reduction furnace. The mixed feed gas is reduced in the reduction furnace to obtain high-purity polycrystalline silicon product deposited on the silicon core, and corresponding reduction tail gas is generated;

[0042] The main control of the production process of the reduction furnace is the reaction temperature and the gas flow of the mixed feed gas. After the mixed feed gas enters the reduction furnace, it reacts on the surface of the hot silicon core to generate polycrystalline silicon and deposit on the silicon core, increasing the diameter of the silicon core and forming a polycrystalline silicon rod. At the same time, by-products such as HCl gas and SiCl4 gas are generated. The by-product gas and the unreacted H2 and SiCl4 gas are discharged from the tail gas pipeline of the reduction furnace and enter the tail gas recovery system along the pipeline.

[0043] The tail gas generated by the reduction furnace is cooled and separated. The condensed SiCl4 is sent to the separation and purification system for separation and purification. The separated chloride gas is used to synthesize SiHCl3, which is then returned to the polycrystalline silicon production process. The separated hydrogen gas is returned to the hydrogen gas inlet pipe for recycling.

[0044] The reduction tail gas generated by the reduction furnace is introduced into the tail gas treatment device to recover all components in the reduction tail gas. The reduction tail gas is effectively recovered, reducing the consumption of raw materials, ensuring the full use of raw materials, and reducing waste discharge and pollution, protecting the environment.

[0045] When the polycrystalline silicon rod in the reduction furnace grows to the required diameter, the reaction in the reduction furnace is stopped, and the polycrystalline silicon rod is removed from the reduction furnace. Since the temperature of the polycrystalline silicon rod in the reduction furnace is as high as thousands of degrees, the reduction furnace needs to be cooled by cooling water, and the power supply part of the reduction furnace also needs to be cooled.

[0046] The reduction reaction equation involved in the reduction furnace is:

[0047] 4SiHCl3=Si+3SiCl4+2H2

[0048] SiCl4+2H2=Si+4HCl

[0049] The silicon core misting long bristles in the reduction furnace mean that the reduction furnace is abnormal. The abnormality of the reduction furnace will affect the quality of the final reduction product, polycrystalline silicon rod. Therefore, the reduction furnace needs to be stopped when it is abnormal. The cost of each reduction furnace is 50,000 yuan. Avoiding the abnormality of the reduction furnace can improve the quality and yield of the polycrystalline silicon rod, save non-stop time, improve the production efficiency of the polycrystalline silicon rod, reduce the workload of the staff, and protect the reduction furnace equipment.

[0050] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of feeding a polysilicon reduction furnace to avoid an abnormality, characterized by, The method comprises the following steps: S1, heating hydrogen and trichlorosilane respectively to obtain heated hydrogen and heated trichlorosilane; S2, synchronously feeding the heated hydrogen and the heated trichlorosilane obtained in S1 into a static mixer to obtain mixed feed gas, wherein the trichlorosilane is fed into the static mixer through a trichlorosilane feeding pipe, and a pipe valve is arranged at the gas inlet end of the trichlorosilane feeding pipe, and the opening of the pipe valve is adjusted to 1%; S3, maintaining the temperature of the mixed feed gas obtained in S2 at more than 100℃; S4, feeding the mixed feed gas into a reduction furnace to obtain polysilicon product.

2. The method of claim 1, wherein the method is characterized by: The hydrogen and the trichlorosilane in S1 are heated in an evaporator.

3. The method of claim 1, wherein the method further comprises: The molar ratio of the hydrogen to the trichlorosilane in S2 is (2.5-3):

1.

4. The method of claim 1, wherein the method further comprises: A thermometer is arranged at the gas outlet end of the static mixer in S2, and the gas outlet end of the static mixer is communicated with the gas inlet end of the reduction furnace.

5. The method of claim 1, wherein the method further comprises: In S4, the detection temperature of the mixed feed gas is always maintained at more than 100℃ during the reaction of the reduction furnace.

6. The method of claim 1, wherein the method further comprises: A high-purity silicon core is arranged in the reduction furnace in S4, and the temperature in the reduction furnace is maintained at 1080-1150℃. ​ 7. The method of claim 1, wherein the method further comprises: determining whether the polycrystalline silicon reduction furnace is abnormal based on the first and second data. Tail gas is also generated in the reaction of the reduction furnace in S4, and the tail gas is fed into a tail gas treatment device.

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