CN103449448A

CN103449448A - Equipment for purifying trichlorosilane

Info

Publication number: CN103449448A
Application number: CN2013103737602A
Authority: CN
Inventors: 万烨; 张升学; 严大洲; 毋克力; 肖荣辉; 汤传斌; 杨永亮
Original assignee: China ENFI Engineering Corp
Current assignee: China ENFI Engineering Corp
Priority date: 2013-08-23
Filing date: 2013-08-23
Publication date: 2013-12-18
Anticipated expiration: 2033-08-23
Also published as: CN103449448B

Abstract

The invention discloses equipment for purifying trichlorosilane. The equipment is a first rectifying and purifying device and used for conducting first rectifying and purifying treatment on trichlorosilane so as to obtain purified trichlorosilane and first rectifying residual liquid, wherein the first rectifying and purifying device consists of a first rectifying tower, a second rectifying tower and a third rectifying tower which are connected in series, the rectifying of the first rectifying tower is conducted at the temperature of 60-100DEG C and the pressure of 0.2MPa according to the reflux ratio of (10-50):1; the rectifying of the second rectifying tower is conducted at the temperature of 100-140DEG C and the pressure of 0.5MPa according to the reflux ratio of (20-50):1; the rectifying of the third rectifying tower is conducted at the temperature of 60-80DEG C and the pressure of 0.2MPa according to the reflux ratio of (20-50):1. The equipment can be utilized for effectively purifying the trichlorosilane, and is simple, safe, energy-saving and environment-friendly and low-cost in technique, the purity of the purified trichlorosilane is high, the purified trichlorosilane can be effectively utilized for producing polycrystalline silicon, and the produced waste liquor can be recycled.

Description

Equipment for purifying trichlorosilane

Technical Field

The invention relates to the technical field of photovoltaic industry, in particular to equipment for preparing trichlorosilane for purification.

Background

Solar energy is regarded as a renewable clean energy source and a technology for generating electricity by utilizing solar energy resources is considered as a new energy technology with the most development prospect in the world at present. Thus, the photovoltaic industry, which is centered on solar power generation, has been rapidly developed in the beginning of the 21 st century. As the main raw material of the photovoltaic industry, the demand of polycrystalline silicon is greatly increased with the rapid development of the photovoltaic industry. Furthermore, the demand of trichlorosilane, a main raw material for producing polycrystalline silicon, is increased. However, in the existing process for preparing trichlorosilane, impurities in the product are more, and the purity of trichlorosilane is lower, so further purification is needed.

However, the existing process and equipment for purifying trichlorosilane still need to be improved.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention aims to provide low-cost, energy-saving and environment-friendly equipment for purifying trichlorosilane.

According to one aspect of the invention, the invention provides equipment for purifying trichlorosilane. According to the embodiment of the invention, the equipment is a first rectification purification device which is used for carrying out first rectification purification treatment on trichlorosilane so as to obtain purified trichlorosilane and first rectification residual liquid, wherein the trichlorosilane is provided in a form of a chlorohydrination synthesis reaction product, the first rectification purification device comprises a first rectification tower, a second rectification tower and a third rectification tower which are connected in series, each rectification tower is respectively provided with a feed inlet and a discharge outlet from bottom to top along the axial direction of the rectification tower, the rectification temperature of the first rectification tower is 60-100 ℃, the pressure is 0.2MPa, and the reflux ratio is 10-50: 1; the rectification temperature of the second rectification tower is 100-140 ℃, the pressure is 0.5MPa, and the reflux ratio is 20-50: 1; the rectification temperature of the third rectification tower is 60-80 ℃, the pressure is 0.2MPa, and the reflux ratio is 20-50: 1.

The inventor surprisingly finds that the equipment can be used for effectively purifying trichlorosilane, the related process of the equipment is simple, safe, energy-saving and environment-friendly, the cost is low, the purity of the purified trichlorosilane is high, the purified trichlorosilane can be effectively used for producing polycrystalline silicon, and the generated waste liquid can be continuously utilized.

In addition, the apparatus for purifying trichlorosilane according to the above embodiment of the present invention may further have the following additional technical features:

according to an embodiment of the present invention, further comprising: a hydrochlorination synthesis reaction device connected with the first rectification and purification device and used for carrying out hydrochlorination synthesis reaction on silicon powder, hydrogen and at least one of hydrogen chloride and silicon tetrachloride so as to obtain a hydrochlorination synthesis reaction product and supply the hydrochlorination synthesis reaction product to the first rectification and purification device.

According to an embodiment of the present invention, the chlorohydrination synthesis reaction apparatus is provided with a nickel-based catalyst or a copper-based catalyst, so that the chlorohydrination synthesis reaction occurs by contacting a gas mixture containing silicon tetrachloride and hydrogen with silicon powder in the presence of the nickel-based catalyst or the copper-based catalyst. Therefore, the efficiency of the hydrochlorination synthesis reaction can be effectively improved, and the subsequent steps can be favorably carried out.

According to the embodiment of the invention, in the gas mixture containing silicon tetrachloride and hydrogen, the molar ratio of the silicon tetrachloride to the hydrogen is 1: 2-5. Therefore, the efficiency of the hydrochlorination synthesis reaction is obviously improved, and the subsequent steps are facilitated.

According to the embodiment of the invention, the hydrochlorination synthesis reaction is carried out at the temperature of 500-550 ℃.

According to the embodiment of the invention, the hydrochlorination synthesis reaction is carried out at 500-550 ℃ and 1.5-3.5 MPa. Therefore, the efficiency of the hydrochlorination synthesis reaction is high, and the subsequent steps are facilitated.

According to an embodiment of the present invention, further comprising: the gas-liquid mixing device is used for mixing silicon tetrachloride liquid with hydrogen to obtain a gas-liquid mixture; the heat exchange device is respectively connected with the gas-liquid mixing device and the hydrochlorination synthesis reaction device and is used for carrying out heat exchange treatment on the gas-liquid mixture by using the hydrochlorination synthesis reaction product so as to obtain a preheated gas-liquid mixture and a cooled hydrochlorination synthesis reaction product; and the resistance heater is respectively connected with the heat exchange device and the hydrochlorination synthesis reaction device, and is used for heating the preheated gas-liquid mixture so as to obtain the gas mixture containing silicon tetrachloride and hydrogen, and supplying the gas mixture containing silicon tetrachloride and hydrogen to the hydrochlorination synthesis reaction device. Therefore, the cooling of the reaction product of the hydrochlorination synthesis and the preheating of the gas-liquid mixture can be realized simultaneously under the condition of least energy consumption, the gas mixture containing silicon tetrachloride and hydrogen can be effectively obtained, and the raw materials are provided for the circulating hydrochlorination synthesis reaction in the hydrochlorination synthesis reaction, so that the aims of saving energy, protecting environment and reducing cost can be effectively realized.

According to an embodiment of the present invention, further comprising: the dust removal device is connected with the heat exchange device so as to remove dust from the cooled chlorohydrination synthesis reaction product; and the first condensing device is respectively connected with the dust removal device and the first rectification purification device and is used for condensing the chlorine hydrogenation synthetic reaction product subjected to dust removal treatment so as to respectively recover hydrogen and chlorosilane liquid, the chlorosilane liquid contains trichlorosilane and silicon tetrachloride, and the chlorosilane liquid is supplied to the first rectification purification device to be used for the first rectification purification treatment. Therefore, after the cooled chlorohydrination synthesis reaction product is treated, chlorosilane liquid and hydrogen can be obtained, and the chlorosilane liquid and the hydrogen can be respectively supplied to corresponding devices of equipment for preparing polycrystalline silicon and recycled, so that the aims of saving energy, protecting environment and reducing cost can be effectively fulfilled.

According to an embodiment of the present invention, the first condensing means is connected to the hydrochlorination synthesis reaction means for supplying the hydrogen gas to the hydrochlorination synthesis reaction means. Therefore, the hydrogen can be reused, raw materials are provided for the hydrochlorination synthesis reaction in the hydrochlorination synthesis reaction device, energy is saved, the environment is protected, and the production cost can be reduced.

According to an embodiment of the invention, the apparatus of the invention further comprises: the disproportionation reaction device is connected with the first rectification and purification device and is used for carrying out disproportionation reaction on the purified trichlorosilane so as to obtain a disproportionation reaction product containing silicon tetrachloride and silane; the second rectification and purification device is connected with the disproportionation reaction device and is used for carrying out second rectification and purification treatment on the disproportionation reaction product so as to obtain silane gas and silicon tetrachloride; and the pyrolysis reaction device is connected with the second rectification and purification device and is used for carrying out pyrolysis reaction on the silane gas so as to obtain the polycrystalline silicon. Therefore, the purified high-purity trichlorosilane obtained by the method can be effectively used for producing electronic grade polycrystalline silicon, so that the equipment for purifying trichlorosilane and the devices can effectively form equipment for preparing electronic grade polycrystalline silicon based on the various connection relations, the equipment for preparing electronic grade polycrystalline silicon is low in production cost, low in energy consumption, energy-saving and environment-friendly, and the purity of the produced polycrystalline silicon is very high.

According to the embodiment of the invention, in the disproportionation reaction device, the disproportionation reaction is carried out at 50-80 ℃ and under the condition of 0.2-0.6 MPa. Therefore, the method has the advantages of safe production, low energy consumption, low production cost, high disproportionation reaction efficiency and good effect, and is beneficial to the implementation of subsequent steps.

According to an embodiment of the present invention, the disproportionation reaction apparatus is a disproportionation reactor, the disproportionation reactor further comprising: the disproportionation reactor comprises a disproportionation reactor body, wherein a disproportionation reaction space is defined in the disproportionation reactor body, and a catalyst layer is arranged in the disproportionation reaction space; the trichlorosilane feed inlet is arranged below the catalyst layer and used for supplying purified trichlorosilane to the disproportionation reaction space; and a disproportionation reaction product discharge port arranged above the catalyst layer for discharging the formed disproportionation reaction product containing silicon tetrachloride and silane out of the disproportionation reactor. Therefore, the disproportionation reaction has high efficiency, good effect, safe production, low energy consumption and low cost, and is beneficial to the subsequent steps.

According to an embodiment of the invention, at least a portion of the silicon tetrachloride in the gas mixture comprising silicon tetrachloride and hydrogen originates from the disproportionation reaction unit. Therefore, silicon tetrachloride in the disproportionation reaction product is recycled, so that the purposes of energy conservation, environmental protection and cost reduction can be achieved.

According to the embodiment of the invention, the second rectification and purification device is connected with the hydrochlorination synthesis device, so that the silicon tetrachloride obtained in the second rectification and purification device is used for the hydrochlorination synthesis reaction. Therefore, the silicon tetrachloride in the product of the second rectification and purification device is recycled, so that the purposes of energy conservation, environmental protection and cost reduction can be achieved.

According to the embodiment of the invention, the second rectification and purification device is a low-temperature rectification tower, wherein the temperature in the low-temperature rectification tower is-60 to-80 ℃, the pressure in the low-temperature rectification tower is 0.6 to 1.0MPa, and the reflux ratio is 5 to 20: 1. Therefore, the method has the advantages of safe production, low energy consumption, low production cost, high rectification and purification efficiency and good effect, and is beneficial to the implementation of subsequent steps.

According to the embodiment of the invention, the device further comprises a vaporization treatment device which is respectively connected with the second rectification purification device and the pyrolysis reaction device and is used for carrying out vaporization treatment on the silane gas stored in the form of liquid in advance before the pyrolysis reaction. Therefore, the method is beneficial to the pyrolysis reaction in the pyrolysis reaction device, so that the polycrystalline silicon can be effectively prepared, and the method has the advantages of low cost, less energy consumption, energy conservation, environmental protection and high pyrolysis reaction efficiency.

According to the embodiment of the invention, the pyrolysis reaction device is a reduction furnace, and a silicon core is arranged in the reduction furnace and used as a carrier for crystal deposition. Therefore, the pyrolysis reaction efficiency is high, the effect is good, and the purity of the prepared electronic grade polycrystalline silicon is high.

According to the embodiment of the invention, the reduction furnace is a bell jar type reduction furnace. Therefore, the pyrolysis reaction efficiency is high, and the effect is good.

According to the embodiment of the invention, 12, 24 or 36 pairs of silicon rods are arranged in the reduction furnace. Thus, a silicon core is used as a carrier. Further, according to the embodiment of the invention, a cooling jacket which is consistent with the number of silicon cores is arranged in the reduction furnace. Therefore, the method is beneficial to silane gas cracking deposition and the preparation of the high-purity electronic grade polysilicon.

According to the embodiment of the invention, the temperature in the reduction furnace is 750-900 ℃ and the pressure in the reduction furnace is 0.15-0.30 MPa. Therefore, the pyrolysis reaction efficiency is high, the effect is good, the reaction is safe, and the purity of the prepared electronic grade polycrystalline silicon is high.

According to an embodiment of the present invention, further comprising: the flash evaporation treatment device is connected with the first rectification and purification device and is used for carrying out flash evaporation treatment on the first rectification residual liquid so as to obtain silicon tetrachloride gas and solid residues; the second condensing device is respectively connected with the flash evaporation treatment device and the gas-liquid mixing device, and is used for condensing the silicon tetrachloride gas so as to obtain silicon tetrachloride liquid, and supplying the silicon tetrachloride liquid to the gas-liquid mixing device for the hydrochlorination synthesis reaction; and the residue treatment device is connected with the flash evaporation treatment device and is used for sequentially carrying out alkali liquor hydrolysis neutralization treatment and filter pressing treatment on the solid residues. Therefore, the first rectification residual liquid can be effectively recycled, and the purposes of energy conservation, environmental protection and cost reduction are achieved.

According to an embodiment of the present invention, further comprising: the first compression device is connected with the pyrolysis reaction device and is used for compressing the reduction tail gas of the pyrolysis reaction to the pressure of 6.0-10.0 MPa; and the third condensing device is connected with the first compressing device, the gas-liquid mixing device and the vaporization treatment device and is used for condensing the compressed reduction tail gas to the temperature of-100 to-120 ℃ so as to condense silane gas into silane liquid and obtain hydrogen, supplying the silane liquid to the vaporization treatment device, and supplying the hydrogen to the gas-liquid mixing device for the chlorine hydrogenation synthesis reaction. From this, can effectively handle the reduction tail gas that produces in the pyrolytic reaction device, realize pollution-free emission, guarantee clean production to realize the circulation recycle of reduction tail gas, thereby reach energy-concerving and environment-protective, reduce cost's purpose.

According to an embodiment of the present invention, further comprising: the second compression device is used for compressing tail gas which contains chlorosilane and does not contain silane and is generated in each device to the pressure of 0.25-0.50 MPa; the fourth condensing device is respectively connected with the second compressing device and the first rectifying and purifying device and is used for cooling the compressed tail gas containing chlorosilane and not containing silane to the temperature of-15 to-30 ℃ so as to obtain chlorosilane liquid and residual gas, and supplying the chlorosilane liquid to the first rectifying and purifying device for the first rectifying and purifying treatment; the leaching device is connected with the fourth condensing device and is used for leaching the residual gas so as to obtain leached gas and leaching water; and the leaching water treatment device is connected with the leaching device and is used for neutralizing the leaching water by using alkali liquor and performing filter pressing on the neutralized liquid so as to obtain neutralized water and filter residues. Therefore, the tail gas which contains chlorosilane and does not contain silane and is generated in each device can be effectively treated, pollution-free emission is realized, clean production is guaranteed, and the tail gas is recycled, so that the aims of saving energy, protecting environment and reducing cost are fulfilled.

According to an embodiment of the invention, the neutralizing water is supplied to the rinsing device for rinsing the surplus gas. Therefore, the neutralization water can be recycled, so that the production cost is reduced, pollution-free discharge is realized, and clean production is guaranteed.

It should be noted that, compared with the prior art, the apparatus for purifying trichlorosilane of the present invention has the following advantages:

1. the whole process system is safe and stable, the process is simple and can be realized.

2. The trichlorosilane obtained by purification has high purity, low cost and energy-saving and environment-friendly process.

3. The equipment for purifying trichlorosilane can be effectively combined with the chlorine hydrogenation synthesis reaction device, the disproportionation reaction device, the second rectification purification device, the pyrolysis reaction device and the like, so that new equipment for preparing electronic-grade polycrystalline silicon is formed, and the equipment for preparing electronic-grade polycrystalline silicon can effectively realize the one-step disproportionation of trichlorosilane into silane gas; silane gas and chlorosilane are easy to separate, and the purity after purification is high and can reach more than 9N; the obtained silane gas has lower cracking temperature and lower energy consumption, so that the cost for producing the polycrystalline silicon is lower; the prepared polysilicon is electronic grade polysilicon, and has high purity which can reach 9N-11N; the discharged tail gas and waste residue meet the environmental protection requirement, and the device is a polysilicon clean production device.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 shows a schematic flow diagram of a method for preparing polycrystalline silicon according to one embodiment of the present invention;

FIG. 2 shows a schematic flow diagram of a method for preparing polycrystalline silicon according to one embodiment of the invention;

fig. 3 shows a schematic structural view of an apparatus for preparing polycrystalline silicon according to an embodiment of the present invention;

fig. 4 to 11 respectively show partial structural views of an apparatus for preparing polycrystalline silicon according to an embodiment of the present invention,

fig. 5 shows a schematic structural diagram of a first rectification and purification device, namely the equipment for purifying trichlorosilane according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, the terms "axial," "upper," "lower," "top," "bottom," and the like refer to orientations or positional relationships based on those shown in the drawings, which are for convenience only and do not require that the present invention be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "fixed," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

It should be noted that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

According to one aspect of the invention, the invention provides equipment for purifying trichlorosilane. According to the embodiment of the invention, the equipment for purifying trichlorosilane is a first rectification purification device, and is used for performing first rectification purification treatment on trichlorosilane so as to obtain purified trichlorosilane and first rectification residual liquid. Wherein the trichlorosilane is provided in the form of a hydrochlorination synthesis reaction product. According to some specific examples of the present invention, referring to fig. 5, the first rectification and purification apparatus 2 comprises a first rectification tower 21, a second rectification tower 22 and a third rectification tower 23 connected in series, wherein each rectification tower is provided with a feed inlet and a discharge outlet from bottom to top along the axial direction of the rectification tower, the rectification temperature of the first rectification tower 21 is 60-100 ℃, the pressure is 0.2MPa, and the reflux ratio is 10-50: 1; the rectification temperature of the second rectification tower 22 is 100-140 ℃, the pressure is 0.5MPa, and the reflux ratio is 20-50: 1; the rectification temperature of the third rectification tower 23 is 60-80 ℃, the pressure is 0.2MPa, and the reflux ratio is 20-50: 1.

In addition, according to an embodiment of the present invention, referring to fig. 3, the apparatus 2 for purifying trichlorosilane of the present invention may further include: a hydrochlorination synthesis reaction device 1, wherein the hydrochlorination synthesis reaction device 1 is connected with the first rectification and purification device 2 and is used for performing a hydrochlorination synthesis reaction on silicon powder, hydrogen and at least one of hydrogen chloride and silicon tetrachloride so as to obtain a hydrochlorination synthesis reaction product and supply the hydrochlorination synthesis reaction product to the first rectification and purification device 2.

According to other embodiments of the present invention, referring to fig. 3, the apparatus 2 for purifying trichlorosilane of the present invention may further include: a disproportionation reaction device 3, a second rectification and purification device 4 and a pyrolysis reaction device 5. According to an embodiment of the invention, a disproportionation reaction device 3 is connected with the first rectification and purification device 2, and is used for carrying out disproportionation reaction on the purified trichlorosilane so as to obtain a disproportionation reaction product containing silicon tetrachloride and silane; the second rectification and purification device 4 is connected with the disproportionation reaction device 3 and is used for carrying out second rectification and purification treatment on the disproportionation reaction product so as to obtain silane gas and silicon tetrachloride; the pyrolysis reaction device 5 is connected with the second rectification and purification device 4 and is used for carrying out pyrolysis reaction on the silane gas so as to obtain polycrystalline silicon.

Therefore, the purified high-purity trichlorosilane obtained by the method can be effectively used for producing electronic grade polysilicon, and further based on the various connection relations, the equipment (namely, the first rectification purification device) for purifying trichlorosilane can be effectively combined with the chlorine hydrogenation synthesis reaction device, the disproportionation reaction device, the second rectification purification device, the pyrolysis reaction device and the like, so that a novel equipment for preparing electronic grade polysilicon is formed, the equipment for preparing electronic grade polysilicon has the advantages of low production cost, low energy consumption, energy conservation and environmental protection, and the purity of the produced polysilicon is very high.

Thus, according to another aspect of the present invention, there is also provided an apparatus for preparing polycrystalline silicon. According to an embodiment of the present invention, referring to fig. 3, the apparatus for preparing polycrystalline silicon of the present invention includes: a hydrochlorination synthesis reaction device 1, a first rectification and purification device 2, a disproportionation reaction device 3, a second rectification and purification device 4 and a pyrolysis reaction device 5. According to some embodiments of the present invention, the chlorohydrination synthesis reaction apparatus 1 is used for performing a chlorohydrination synthesis reaction on silicon powder, hydrogen and at least one selected from hydrogen chloride and silicon tetrachloride so as to obtain a chlorohydrination synthesis reaction product containing trichlorosilane; the first rectification and purification device 2 is connected with the hydrochlorination synthesis reaction device 1 and is used for carrying out first rectification and purification treatment on the hydrochlorination synthesis reaction product containing trichlorosilane so as to obtain purified trichlorosilane and first rectification residual liquid; the disproportionation reaction device 3 is connected with the first rectification and purification device 2 and is used for carrying out disproportionation reaction on the purified trichlorosilane so as to obtain a disproportionation reaction product containing silicon tetrachloride and silane; the second rectification and purification device 4 is connected with the disproportionation reaction device 3 and is used for carrying out second rectification and purification treatment on the disproportionation reaction product so as to obtain silane gas and silicon tetrachloride; the pyrolysis reaction device 5 is connected with the second rectification and purification device 4 and is used for carrying out pyrolysis reaction on the silane gas so as to obtain polycrystalline silicon. The inventor surprisingly finds that the electronic grade polycrystalline silicon can be effectively prepared and obtained by utilizing the equipment, the process related to the equipment is simple, safe, energy-saving and environment-friendly, the cost is low, the purity of the produced polycrystalline silicon is high, and the produced tail gas and waste residues can meet the environment-friendly requirement, so that the equipment is a clean production process of the electronic grade polycrystalline silicon.

In order to make the method for preparing polycrystalline silicon and the apparatus for preparing polycrystalline silicon to which the method of the present invention is applied more easily understood by those skilled in the art, the whole apparatus for preparing polycrystalline silicon and its partial structure and function will be described in detail with reference to fig. 3 to 11.

It should be noted that "STC" in the drawings and herein refers to silicon tetrachloride, "TCS" refers to trichlorosilane.

According to the embodiment of the present invention, the conditions of the hydrochlorination synthesis reaction in the hydrochlorination synthesis reaction apparatus 1 shown in fig. 3 are not particularly limited. According to some specific examples of the present invention, the chlorohydrination synthesis reaction apparatus 1 is provided with a nickel-based catalyst or a copper-based catalyst so that the chlorohydrination synthesis reaction occurs by contacting a gas mixture containing silicon tetrachloride and hydrogen with silicon powder in the presence of the nickel-based catalyst or the copper-based catalyst. Wherein, the chemical reaction mainly involved is: 3SiCl₄+2H₂+Si——4SiHCl₃. Therefore, the efficiency of the hydrochlorination synthesis reaction can be effectively improved, and the subsequent steps can be favorably carried out. Wherein the ratio of silicon tetrachloride and hydrogen in the gas mixture comprising silicon tetrachloride and hydrogen is not particularly limited. According to the embodiment of the invention, in the gas mixture containing silicon tetrachloride and hydrogen, the molar ratio of the silicon tetrachloride to the hydrogen is 1: 2-5. Therefore, the efficiency of the hydrochlorination synthesis reaction is obviously improved, and the subsequent steps are facilitated.

According to the embodiment of the present invention, the temperature and pressure at which the chlorohydrination synthesis reaction is carried out in the chlorohydrination synthesis reaction apparatus 1 are not particularly limited as long as the reaction can be efficiently carried out to obtain a chlorohydrination synthesis reaction product containing trichlorosilane. According to some embodiments of the invention, the hydrochlorination synthesis reaction is carried out at a temperature of 500 to 550 degrees celsius. According to other embodiments of the present invention, the hydrochlorination synthesis reaction is performed at 500-550 ℃ and 1.5-3.5 MPa. Therefore, the efficiency of the hydrochlorination synthesis reaction is high, and the subsequent steps are facilitated.

In addition, the source of the silicon tetrachloride used in the chlorohydrination synthesis reaction apparatus 1 is not particularly limited, and may be supplied directly or may be separated from a reaction product or a waste liquid in the subsequent step. According to an embodiment of the present invention, at least a portion of the silicon tetrachloride originates from the disproportionation reaction apparatus 3. Therefore, silicon tetrachloride in the disproportionation reaction product is recycled, so that the purposes of energy conservation, environmental protection and cost reduction can be achieved.

According to an embodiment of the present invention, the second rectification and purification device 4 is connected to the hydrochlorination synthesis device 1 (not shown in the figure), so that the silicon tetrachloride obtained in the second rectification and purification device is used for the hydrochlorination synthesis reaction. Therefore, the silicon tetrachloride generated in the second rectification and purification device can be recycled, so that the purposes of energy conservation, environmental protection and cost reduction can be achieved.

According to an embodiment of the present invention, referring to fig. 4, the apparatus for preparing polycrystalline silicon of the present invention may further include: a gas-liquid mixing device 6, a heat exchange device 7 and an electric resistance heater 8. According to the embodiment of the invention, the gas-liquid mixing device 6 is used for mixing silicon tetrachloride liquid with hydrogen to obtain a gas-liquid mixture; the heat exchange device 7 is respectively connected with the gas-liquid mixing device 6 and the hydrochlorination synthesis reaction device 1, and is used for performing heat exchange treatment on the gas-liquid mixture by using the hydrochlorination synthesis reaction product so as to obtain a preheated gas-liquid mixture and a cooled hydrochlorination synthesis reaction product; the resistance heater 8 is connected to the heat exchange device 7 and the hydrochlorination synthesis reaction device 1, respectively, and is configured to heat the preheated gas-liquid mixture to obtain the gas mixture containing silicon tetrachloride and hydrogen, and supply the gas mixture containing silicon tetrachloride and hydrogen to the hydrochlorination synthesis reaction device 1. Therefore, the cooling of the reaction product of the hydrochlorination synthesis and the preheating of the gas-liquid mixture can be realized simultaneously under the condition of least energy consumption, the gas mixture containing silicon tetrachloride and hydrogen can be effectively obtained, the raw material is provided for the hydrochlorination synthesis reaction in the subsequent circulation, and the purposes of energy conservation, environmental protection and cost reduction can be effectively realized.

According to an embodiment of the present invention, referring to fig. 4, the apparatus for preparing polycrystalline silicon of the present invention may further include: a dust removal device 9 and a first condensation device 10. According to an embodiment of the invention, a dust removal device 9 is connected to the heat exchange device 7 for removing dust from the cooled chlorohydrination synthesis reaction product; the first condensing device 10 is respectively connected with the dust removal device 9 and the first rectification purification device 2 and is used for condensing the chlorine hydrogenation synthesis reaction product subjected to dust removal treatment so as to respectively recover hydrogen and chlorosilane liquid, wherein the chlorosilane liquid contains trichlorosilane and silicon tetrachloride and is supplied to the first rectification purification device 2 for first rectification purification treatment. Therefore, after the cooled chlorohydrination synthesis reaction product is treated, chlorosilane liquid and hydrogen can be obtained, and the chlorosilane liquid and the hydrogen can be respectively supplied to corresponding devices of the equipment for recycling, so that the aims of saving energy, protecting environment and reducing cost can be effectively fulfilled.

According to an embodiment of the present invention, the first condensing means 10 is connected to the hydrochlorination synthesis reaction apparatus 1 for supplying the hydrogen gas to the hydrochlorination synthesis reaction apparatus 1. Therefore, the hydrogen can be reused, raw materials are provided for the hydrochlorination synthesis reaction in the hydrochlorination synthesis reaction device, energy is saved, the environment is protected, and the production cost can be reduced.

According to some specific examples of the present invention, referring to fig. 5, the first rectification and purification device 2 comprises a first rectification tower 21, a second rectification tower 22 and a third rectification tower 23 connected in series, wherein each rectification tower is provided with a feed inlet and a discharge outlet from bottom to top along the axial direction of the rectification tower. Therefore, the method can simultaneously ensure the proper production cost and higher rectification and purification efficiency, and is beneficial to the implementation of the subsequent steps. The conditions for performing the first rectification and purification treatment in the first rectification and purification device 2, that is, the reaction conditions in each rectification column, are not particularly limited, as long as trichlorosilane can be efficiently purified and obtained from a chlorohydrination synthesis reaction product containing trichlorosilane. According to the embodiment of the invention, the rectification temperature of the first rectification tower 21 is 60-100 ℃, the pressure is 0.2MPa, and the reflux ratio is 10-50: 1; the rectification temperature of the second rectification tower 22 is 100-140 ℃, the pressure is 0.5MPa, and the reflux ratio is 20-50: 1; the rectification temperature of the third rectification tower 23 is 60-80 ℃, the pressure is 0.2MPa, and the reflux ratio is 20-50: 1. Therefore, the method can ensure safe production, has low energy consumption, low production cost, high rectification and purification efficiency and good effect, and is beneficial to the implementation of subsequent steps.

Wherein, the chemical reaction involved in the disproportionation reaction device 3 is mainly as follows: 4SiHCl₃——SiH₄+3SiCl₄. However, according to the embodiment of the present invention, the conditions for performing the disproportionation reaction in the disproportionation reaction apparatus 3 are not particularly limited as long as the disproportionation reaction of trichlorosilane can be safely performed and the disproportionation reaction product can be effectively obtained. According to some specific examples of the present invention, in the disproportionation reaction device 3, the disproportionation reaction is performed at 50-80 ℃ and 0.2-0.6 MPa. Therefore, the method has the advantages of safe production, low energy consumption, low production cost, high disproportionation reaction efficiency and good effect, and is beneficial to the implementation of subsequent steps.

According to an embodiment of the present invention, the disproportionation reaction apparatus 3 is a disproportionation reactor, and referring to fig. 6, the disproportionation reactor further includes: a disproportionation reactor body 31, a trichlorosilane feeding port 34 and a disproportionation reaction product discharging port 35. Wherein, according to the embodiment of the present invention, a disproportionation reaction space 32 is defined in the disproportionation reactor body 31, and a catalyst layer 33 is provided in the disproportionation reaction space 32; the trichlorosilane feed inlet 34 is arranged below the catalyst layer 33 and used for feeding trichlorosilane into the disproportionation reaction space 32; the disproportionation reaction product discharge port 35 is provided above the catalyst layer 33, and is used for discharging the formed disproportionation reaction product containing silicon tetrachloride and silane out of the disproportionation reactor. Therefore, the disproportionation reaction has high efficiency, good effect, safe production, low energy consumption and low cost, and is beneficial to the subsequent steps.

According to the embodiment of the present invention, the type of the second rectification purification apparatus 4 and the conditions in which the treatment is performed are not particularly limited. According to some specific examples of the present invention, referring to fig. 7, the second distillation and purification device 4 is a cryogenic distillation tower, wherein the temperature in the cryogenic distillation tower is-60 to-80 ℃, the pressure in the cryogenic distillation tower is 0.6 to 1.0MPa, and the reflux ratio is 5 to 20: 1. Therefore, the method has the advantages of safe production, low energy consumption, low production cost, high rectification and purification efficiency and good effect, and is beneficial to the implementation of subsequent steps.

According to an embodiment of the present invention, referring to fig. 8, the apparatus for preparing polycrystalline silicon according to the present invention may further include a vaporization treatment device 11, the vaporization treatment device 11 being connected to the second rectification purification device 4 and the pyrolysis reaction device 5, respectively, for previously vaporizing the silane gas stored in a liquid form before the pyrolysis reaction. Therefore, the method is beneficial to the pyrolysis reaction in the pyrolysis reaction device, so that the polycrystalline silicon can be effectively prepared, and the method has the advantages of low cost, less energy consumption, energy conservation, environmental protection and high pyrolysis reaction efficiency.

According to an embodiment of the present invention, the type of the pyrolysis reaction apparatus is not particularly limited. According to some specific examples of the present invention, the pyrolysis reaction apparatus 5 is a reduction furnace in which a silicon core is disposed as a carrier for crystal deposition. Therefore, the pyrolysis reaction efficiency is high, the effect is good, and the purity of the prepared electronic grade polycrystalline silicon is high. According to other embodiments of the present invention, referring to fig. 8, the reduction furnace is a bell jar type reduction furnace. Therefore, the pyrolysis reaction efficiency is high, and the effect is good. In addition, the number of silicon rods in the reduction furnace and the temperature and pressure conditions in the reduction furnace are not particularly limited as long as the pyrolysis reaction is facilitated. According to the embodiment of the invention, 12, 24 or 36 pairs of silicon rods are arranged in the reduction furnace. Thus, a silicon core can be used as a carrier. Further, according to the embodiment of the invention, a cooling jacket which is consistent with the number of silicon cores is arranged in the reduction furnace. Therefore, the method is beneficial to silane gas cracking deposition and the preparation of the high-purity electronic grade polysilicon. According to other embodiments of the invention, the temperature in the reduction furnace is 750-900 ℃ and the pressure in the reduction furnace is 0.15-0.30 MPa. Therefore, the pyrolysis reaction efficiency is high, the effect is good, the reaction is safe, and the purity of the prepared electronic grade polycrystalline silicon is high.

According to an embodiment of the present invention, referring to fig. 9, the apparatus for preparing polycrystalline silicon of the present invention may further include: a flash processing device 12, a second condensing device 13 and a residue processing device 14. According to the embodiment of the invention, as shown in fig. 9, the flash evaporation treatment device 12 is connected with the first rectification and purification device 2 and is used for performing flash evaporation treatment on the first rectification residual liquid so as to obtain silicon tetrachloride gas and solid residue; the second condensing device 13 is connected to the flash evaporation processing device 12 and the gas-liquid mixing device 6, and is configured to condense the silicon tetrachloride gas to obtain silicon tetrachloride liquid, and supply the silicon tetrachloride liquid to the gas-liquid mixing device 6 for the hydrochlorination synthesis reaction; the residue treatment device 14 is connected with the flash evaporation treatment device 12 and is used for sequentially carrying out alkali liquor hydrolysis neutralization treatment and filter pressing treatment on the solid residues. Therefore, the first rectification residual liquid can be effectively recycled, and the purposes of energy conservation, environmental protection and cost reduction are achieved. It should be noted that, when the first rectification and purification device 2 is a first rectification tower, a second rectification tower and a third rectification tower which are connected in series as shown in fig. 5, the first rectification residual liquid is the residual liquid discharged from the bottom of the second rectification tower.

According to an embodiment of the present invention, referring to fig. 10, the apparatus for preparing polycrystalline silicon of the present invention may further include: the first compression device 15 and the third condensation device 16 are connected with the pyrolysis reaction device 5 according to an embodiment of the invention, and are used for compressing the reduction tail gas of the pyrolysis reaction to a pressure of 6.0-10.0 MPa; the third condensing device 16 is connected to the first compressing device 15, the gas-liquid mixing device 6 and the vaporization processing device 11, and is configured to condense the compressed reduction tail gas to a temperature of-100 to-120 degrees celsius, so as to condense silane gas into silane liquid and obtain hydrogen gas, and supply the silane liquid to the vaporization processing device 11 and the hydrogen gas to the gas-liquid mixing device 6 for the chlorine hydride synthesis reaction. From this, can effectively handle the reduction tail gas that produces in the pyrolytic reaction device, realize pollution-free emission, guarantee clean production to realize the circulation recycle of reduction tail gas, thereby reach energy-concerving and environment-protective, reduce cost's purpose.

According to an embodiment of the present invention, referring to fig. 11, the apparatus for preparing polycrystalline silicon of the present invention may further include: a second compression device 17, a fourth condensation device 18, a leaching device 19 and a leaching water treatment device (not shown in the figure). According to the embodiment of the invention, the second compression device 17 is used for compressing the tail gas which contains chlorosilane and does not contain silane and is generated in each device to the pressure of 0.25-0.50 MPa; the fourth condensing device 18 is respectively connected with the second compressing device 17 and the first rectifying and purifying device 2, and is used for cooling the compressed tail gas containing chlorosilane but not containing silane to a temperature of-15 to-30 ℃ so as to obtain chlorosilane liquid and residual gas, and supplying the chlorosilane liquid to the first rectifying and purifying device 2 for the first rectifying and purifying treatment; the leaching device 19 is connected with the fourth condensing device 18 and is used for leaching the residual gas so as to obtain leached gas and leaching water; the leaching water treatment device is connected with the leaching device 19 and is used for neutralizing the leaching water by using alkali liquor and carrying out filter pressing on the neutralized liquid so as to obtain neutralized water and filter residues. Therefore, the tail gas which contains chlorosilane and does not contain silane and is generated in each device can be effectively treated, pollution-free emission is realized, clean production is guaranteed, and the tail gas is recycled, so that the aims of saving energy, protecting environment and reducing cost are fulfilled.

According to an embodiment of the present invention, the neutralizing water may also be supplied to the rinsing device 19 through a pipe for rinsing the surplus gas. Therefore, the neutralization water can be recycled, so that the production cost is reduced, pollution-free discharge is realized, and clean production is guaranteed.

The apparatus for preparing polycrystalline silicon according to the present invention has been described in detail in the above section, and in order to better understand the apparatus, a method to which the apparatus is applied will be described in detail. According to one aspect of the present invention, a method of preparing polycrystalline silicon is presented. According to an embodiment of the invention, referring to fig. 1 and 2, the method comprises the steps of:

s100: hydrochlorination synthesis reaction

Firstly, silicon powder, hydrogen and at least one selected from hydrogen chloride and silicon tetrachloride are subjected to a hydrochlorination synthesis reaction to obtain a hydrochlorination synthesis reaction product containing trichlorosilane. Wherein, the chemical reaction mainly involved in the step is as follows:

3SiCl₄+2H₂+Si——4SiHCl₃。

according to the embodiment of the present invention, the conditions of the chlorohydrination synthesis reaction are not particularly limited. According to some specific examples of the present invention, a gas mixture comprising silicon tetrachloride and hydrogen may be contacted with silicon powder in the presence of a nickel-based catalyst or a copper-based catalyst in order for the chlorohydrination synthesis reaction to occur. Therefore, the efficiency of the hydrochlorination synthesis reaction can be effectively improved, and the trichlorosilane generation and the subsequent purification steps are facilitated. Wherein the ratio of silicon tetrachloride and hydrogen in the gas mixture comprising silicon tetrachloride and hydrogen is not particularly limited. According to the embodiment of the invention, in the gas mixture containing silicon tetrachloride and hydrogen, the molar ratio of the silicon tetrachloride to the hydrogen is 1: 2-5. Therefore, the efficiency of the hydrochlorination synthesis reaction is obviously improved, and the method is favorable for the generation of trichlorosilane and the subsequent purification steps.

According to an embodiment of the present invention, the method for obtaining the gas mixture comprising silicon tetrachloride and hydrogen is not particularly limited. According to some embodiments of the invention, the gas mixture comprising silicon tetrachloride and hydrogen may be obtained by: mixing silicon tetrachloride liquid with hydrogen to obtain a gas-liquid mixture; performing heat exchange treatment on the gas-liquid mixture by using the chlorohydrination synthesis reaction product so as to obtain a preheated gas-liquid mixture and a cooled chlorohydrination synthesis reaction product; and heating the preheated gas-liquid mixture by using a resistance heater so as to obtain the gas mixture containing silicon tetrachloride and hydrogen. Therefore, the cooling of the reaction product of the hydrochlorination synthesis and the preheating of the gas-liquid mixture can be realized simultaneously under the condition of least energy consumption, the gas mixture containing silicon tetrachloride and hydrogen can be effectively obtained, the raw material is provided for the hydrochlorination synthesis reaction in the subsequent circulation, and the purposes of energy conservation, environmental protection and cost reduction can be effectively realized.

In addition, the cooled hydrochlorination synthesis reaction product may be further treated. According to an embodiment of the present invention, the method of the present invention described above may further include: carrying out dust removal treatment on the cooled chlorohydrination synthesis reaction product; condensing the chlorine hydrogenation synthetic reaction product subjected to dust removal treatment so as to respectively recover hydrogen and chlorosilane liquid, wherein the chlorosilane liquid comprises trichlorosilane and silicon tetrachloride; and using the chlorosilane liquid for the first rectification purification treatment. Therefore, after the cooled chlorohydrination synthesis reaction product is treated, chlorosilane liquid and hydrogen can be obtained, and the chlorosilane liquid and the hydrogen can be respectively supplied to subsequent corresponding steps in the polysilicon preparation process and recycled again, so that the aims of saving energy, protecting environment and reducing cost can be effectively fulfilled. While with respect to recovering the obtained hydrogen, according to an embodiment of the present invention, the hydrogen may be returned for performing the chlorohydrination synthesis reaction. Therefore, the hydrogen can be recycled, raw materials are provided for the hydrochlorination synthesis reaction, energy is saved, the environment is protected, and the production cost can be reduced.

According to the embodiment of the present invention, the temperature and pressure of the hydrochlorination synthesis reaction are not particularly limited as long as the reaction can be efficiently performed to obtain a hydrochlorination synthesis reaction product containing trichlorosilane. According to some embodiments of the invention, the hydrochlorination synthesis reaction is carried out at a temperature of 500 to 550 degrees celsius. Therefore, the efficiency of the hydrochlorination synthesis reaction is high, and the method is favorable for the generation of trichlorosilane and the subsequent purification steps. According to the embodiment of the invention, the hydrochlorination synthesis reaction is carried out at 500-550 ℃ and 1.5-3.5 MPa. Therefore, the hydrochlorination synthesis reaction is safe and high in efficiency, and is beneficial to the generation of trichlorosilane and the subsequent purification steps.

In addition, the source of the silicon tetrachloride used in the hydrochlorination synthesis reaction is not particularly limited, and the silicon tetrachloride may be directly supplied or may be separated from the reaction product or waste liquid in the subsequent step. According to an embodiment of the invention, at least a portion of the silicon tetrachloride is obtained by disproportionation of trichlorosilane. Therefore, the silicon tetrachloride in the disproportionation reaction product in the subsequent step of the polysilicon preparation process is recycled, so that the purposes of energy conservation, environmental protection and cost reduction can be realized. According to other embodiments of the invention, the silicon tetrachloride-containing first rectification residual liquid produced in the subsequent first rectification purification treatment step can be separated. Therefore, the recycling of the production waste liquid can be effectively realized, and the aims of energy conservation, environmental protection and cost reduction are fulfilled.

S200: first rectification purification treatment

Secondly, performing first rectification purification treatment on the obtained chlorine hydrogenation synthetic reaction product containing trichlorosilane so as to obtain purified trichlorosilane and first rectification residual liquid.

According to the embodiment of the present invention, the apparatus used for the first rectification purification treatment is not particularly limited as long as the purification treatment of the chlorohydrination synthesis reaction product containing trichlorosilane can be effectively achieved. According to some embodiments of the invention, the first rectification purification treatment is performed by using a plurality of rectification towers connected in series, wherein in each rectification tower, the material for rectification treatment moves from bottom to top along the axial direction of the rectification tower. Therefore, the efficiency of rectification and purification treatment can be effectively improved, high-purity trichlorosilane can be obtained, and the subsequent steps can be favorably carried out. According to some preferred embodiments of the present invention, the first rectification purification treatment is performed by using a first rectification column, a second rectification column and a third rectification column connected in series. Therefore, the method can simultaneously ensure the proper production cost and higher rectification and purification efficiency, thereby obtaining the high-purity trichlorosilane and being beneficial to the implementation of the subsequent steps. The conditions of the first distillation purification treatment, that is, the reaction conditions in each of the distillation columns are not particularly limited, as long as trichlorosilane can be efficiently purified from a chlorohydrination synthesis reaction product containing trichlorosilane. According to the embodiment of the invention, the rectification temperature of the first rectification tower is 60-100 ℃, the pressure is 0.2MPa, and the reflux ratio is 10-50: 1; the rectification temperature of the second rectification tower is 100-140 ℃, the pressure is 0.5MPa, and the reflux ratio is 20-50: 1; the rectification temperature of the third rectification tower is 60-80 ℃, the pressure is 0.2MPa, and the reflux ratio is 20-50: 1. Therefore, the method can ensure safe production, has low energy consumption, low production cost, high rectification and purification efficiency and good effect, and can purify and obtain the trichlorosilane with the purity of more than 99 percent.

In addition, the waste liquid generated by the first rectification purification treatment, namely the first rectification residual liquid, can be further treated. According to an embodiment of the present invention, further comprising: carrying out flash evaporation treatment on the first rectification residual liquid so as to obtain silicon tetrachloride gas and solid residues; condensing the silicon tetrachloride gas to obtain silicon tetrachloride liquid; the silicon tetrachloride liquid is used for the hydrochlorination synthesis reaction; and sequentially carrying out alkali liquor hydrolysis neutralization treatment and filter pressing treatment on the solid residues. Therefore, the first rectification residual liquid can be effectively recycled, and the purposes of energy conservation, environmental protection and cost reduction are achieved. When the first rectification purification treatment is carried out by using the first rectification tower, the second rectification tower and the third rectification tower which are connected in series, the first rectification residual liquid is the residual liquid discharged from the bottom of the second rectification tower.

S300: disproportionation reaction

Then, the purified trichlorosilane is subjected to disproportionation reaction so as to obtain the trichlorosilane containing tetrachloroDisproportionation reaction products of silicon and silane. Wherein, the chemical reaction mainly involved in the step is as follows: 4SiHCl₃——SiH₄+3SiCl₄。

According to the embodiment of the present invention, the disproportionation reaction conditions are not particularly limited as long as the disproportionation reaction of trichlorosilane can be safely performed and the above-mentioned disproportionation reaction product can be efficiently obtained. According to some embodiments of the invention, the disproportionation is performed at 50-80 ℃ and 0.2-0.6 MPa. Therefore, the method has the advantages of safe production, low energy consumption, low production cost, high disproportionation reaction efficiency and good effect, and is beneficial to the implementation of subsequent steps.

In addition, the apparatus for carrying out the disproportionation reaction is not particularly limited as long as it can be carried out safely and efficiently. According to an embodiment of the present invention, the disproportionation reaction is carried out in a disproportionation reactor, which may further include: the device comprises a disproportionation reactor body, a trichlorosilane feeding hole and a disproportionation reaction product discharging hole. According to some specific examples of the present invention, the disproportionation reactor body defines a disproportionation reaction space therein, and the disproportionation reaction space is provided with a catalyst layer therein; the trichlorosilane feed inlet is arranged below the catalyst layer and used for supplying trichlorosilane to the disproportionation reaction space; the disproportionation reaction product discharge port is arranged above the catalyst layer and is used for discharging the formed disproportionation reaction product containing silicon tetrachloride and silane out of the disproportionation reactor. Therefore, the disproportionation reaction has high efficiency, good effect, safe production, low energy consumption and low cost, and is beneficial to the subsequent steps.

S400: second rectification purification treatment

Next, the disproportionation reaction product is subjected to a second rectification purification treatment to obtain silane gas and silicon tetrachloride.

According to the embodiment of the present invention, the apparatus for performing the second rectification purification treatment and the required conditions are not particularly limited. According to some specific examples of the invention, the second rectification purification treatment is performed in a low-temperature rectification tower, wherein the temperature in the low-temperature rectification tower is-60 to-80 ℃, the pressure in the low-temperature rectification tower is 0.6 to 1.0MPa, and the reflux ratio is 5 to 20: 1. Therefore, the production safety can be ensured, the energy consumption is low, the production cost is low, the rectification and purification efficiency is high, the effect is good, and the subsequent steps can be favorably carried out.

Wherein, the silicon tetrachloride residual liquid produced in the second rectification and purification treatment step can be further treated. According to the embodiment of the invention, the silicon tetrachloride residual liquid is treated, and the obtained silicon tetrachloride is used for the hydrochlorination synthesis reaction. Therefore, the cyclic utilization of the silicon tetrachloride residual liquid is effectively realized, and the allocation of the raw materials for the hydrochlorination synthesis reaction is reduced, so that the purposes of energy conservation, environmental protection and cost reduction can be realized.

S500: pyrolysis reaction

Then, the silane gas obtained above is subjected to a pyrolysis reaction in a reduction furnace in which a silicon core is provided as a carrier for crystal deposition, so as to obtain polycrystalline silicon. Wherein, the chemical reaction mainly involved in the step is as follows: SiH₄——Si+2H₂。

According to an embodiment of the present invention, the silane gas obtained in the last step is collected and stored in a liquid form, and the silane in the liquid form is subjected to vaporization treatment in a vaporizer in advance before entering a reduction furnace for pyrolysis reaction. Therefore, the transportation of silane gas is facilitated, the pyrolysis reaction is facilitated, the polycrystalline silicon can be effectively prepared, the cost is low, the energy consumption is low, the energy is saved, the environment is protected, and the pyrolysis reaction efficiency is high.

According to an embodiment of the present invention, the type of the reduction furnace that the pyrolysis reaction may employ is not particularly limited. According to some specific examples of the present invention, the reduction furnace is a bell jar type reduction furnace. Therefore, the pyrolysis reaction efficiency is high, the effect is good, and the purity of the prepared electronic grade polycrystalline silicon is high.

In addition, the number of silicon rods in the reduction furnace and the temperature and pressure conditions in the reduction furnace are not particularly limited as long as the pyrolysis reaction is facilitated. According to the embodiment of the invention, 12, 24 or 36 pairs of silicon rods are arranged in the reduction furnace. Thus, a silicon core can be used as a carrier. Further, according to the embodiment of the invention, a cooling jacket which is consistent with the number of silicon cores is arranged in the reduction furnace. Therefore, the method is beneficial to silane gas cracking deposition and the preparation of the high-purity electronic grade polysilicon. According to other embodiments of the invention, the temperature in the reduction furnace is 750-900 ℃ and the pressure in the reduction furnace is 0.15-0.30 MPa. Therefore, the pyrolysis reaction efficiency is high, the effect is good, the reaction is safe, and the purity of the prepared electronic grade polycrystalline silicon is high.

Wherein, the reduction tail gas generated in the pyrolysis reaction can be further processed for recycling, wherein, the method for processing the reduction tail gas is not particularly limited. According to an embodiment of the present invention, it may further include: compressing the reduction tail gas of the pyrolysis reaction to the pressure of 6.0-10.0 MPa; condensing the compressed reduction tail gas to the temperature of-100 to-120 ℃ so as to condense the silane gas into silane liquid and obtain hydrogen; and using the hydrogen in the hydrochlorination synthesis reaction. Therefore, the reduction tail gas can be effectively treated, pollution-free emission is realized, clean production is guaranteed, and the reduction tail gas is recycled, so that the aims of saving energy, protecting environment and reducing cost are fulfilled.

In addition, the tail gas containing chlorosilane but not containing silane, which is generated in each step, can be further treated for recycling, wherein the treatment method is not particularly limited. According to an embodiment of the present invention, it may further include: compressing the tail gas which contains chlorosilane and does not contain silane and is generated in each step to the pressure of 0.25-0.50 MPa, and further cooling to the temperature of-15-30 ℃ so as to obtain chlorosilane liquid and residual gas; performing the first rectification purification treatment on the chlorosilane liquid; leaching the residual gas to obtain leached gas and leaching water; and neutralizing the leaching water by using an alkali liquor, and performing filter pressing on the neutralized liquid so as to obtain neutralized water and filter residues. Therefore, the tail gas which contains chlorosilane and does not contain silane and is generated in each step can be effectively treated, pollution-free emission is realized, clean production is guaranteed, and the tail gas is recycled, so that the aims of saving energy, protecting environment and reducing cost are fulfilled. Wherein the above neutralized water can also be reused, and according to an embodiment of the present invention, the neutralized water is used for rinsing the residual gas. Therefore, the neutralization water can be recycled, so that the production cost is reduced, pollution-free discharge is realized, and clean production is guaranteed.

According to other embodiments of the present invention, the method for preparing polycrystalline silicon of the present invention may further comprise: and returning the silicon tetrachloride separated in the intermediate step to S100 (hydrochlorination synthesis reaction) to participate in the hydrochlorination synthesis reaction, and further entering the process steps of the method for preparing the polycrystalline silicon for sequential circulation. Therefore, the production aim of economy and environmental protection can be achieved.

The inventor surprisingly finds that the method for preparing the polycrystalline silicon can effectively prepare and obtain the electronic grade polycrystalline silicon, the method is simple and safe in process, energy-saving and environment-friendly, low in cost, the produced polycrystalline silicon is high in purity, and the produced tail gas and waste residues can meet the environment-friendly requirement, so that the method is a clean production process of the electronic grade polycrystalline silicon.

In addition, according to some embodiments of the present invention, referring to fig. 2, the method for preparing polycrystalline silicon of the present invention may further include the steps of:

(a) a hydrochlorination synthesis step: silicon powder, hydrogen, supplemented silicon tetrachloride (or hydrogen chloride) and silicon tetrachloride from the subsequent steps (b) and (c) are used as raw materials, the temperature is controlled to be 500-550 ℃, the pressure is 1.5-3.5 MPa, the ratio of the silicon tetrachloride to the hydrogen is 1: 2-1: 5, the silicon tetrachloride is converted into trichlorosilane in a fixed bed (or fluidized bed) hydrogenation reactor under the action of a nickel-based or copper-based catalyst, and the trichlorosilane raw material is provided for the step (c). The main reaction is as follows: 3SiCl₄+2H₂+Si——4SiHCl₃。

(b) The trichlorosilane rectification purification step: enabling the chlorosilane mixed liquid from the step (a) to enter three rectifying towers connected in series, and controlling the temperature of the first rectifying tower to be 60-100 ℃, the pressure to be 0.2MPa and the reflux ratio to be 10: 1-50: 1; controlling the temperature of the second rectifying tower to be 100-140 ℃, the pressure to be 0.5MPa and the reflux ratio to be 20: 1-50: 1; controlling the temperature of the third rectifying tower to be 60-80 ℃, the pressure to be 0.2MPa and the reflux ratio to be 20: 1-50: 1. And (4) obtaining trichlorosilane with the purity of more than 99 percent, and returning the silicon tetrachloride to the step (a).

(c) A trichlorosilane disproportionation step: and (c) introducing the trichlorosilane from the step (b) into a disproportionation reactor, and under the action of a catalyst, controlling the temperature in the reactor to be 50-80 ℃ and the pressure to be 0.2-0.6 MPa, so that the trichlorosilane is converted into silane gas. The main reaction equation is: 4SiHCl₃——SiH₄+3SiCl₄。

(d) Low-temperature rectification of silane gas: and (c) feeding the silane gas containing the impurities from the step (c) into a low-temperature rectifying tower, and controlling the temperature in the tower to be-60 to-80 ℃, the pressure to be 0.60 to 1.0MPa and the reflux ratio to be 5:1 to 20: 1. Therefore, the purity of the silane extracted from the tower top can reach 9N-11N, and impurity compounds such as B, P, Al, C and the like are mainly removed. This portion of the silane gas is withdrawn as a liquid and stored.

(e) Preparing polysilicon by high-temperature cracking of silane gas: and (d) introducing the silane gas from the step (d) into a bell-type reduction furnace, controlling the internal temperature to be 750-900 ℃ and 0.15-0.30 MPa, cracking and depositing the silane gas on a silicon core, and returning the generated hydrogen to the step (a) for recycling. The conversion efficiency of the silane gas by one-time cracking can reach more than 90 percent. The main reaction equation is: SiH₄——Si+2H₂。

(f) And (3) residual liquid recovery: and (c) recovering silicon tetrachloride after the first rectification residual liquid generated in the step (b), namely the residual liquid discharged from the bottom of the second rectification tower, is mainly rich in silicon tetrachloride and a small amount of solid residues and is subjected to flash evaporation, dust removal, condensation and other treatment, and discharging the solid residues to the step (h) for treatment.

(g) Tail gas recovery: mainly treating two parts of tail gas, wherein one part of tail gas which is discharged in the steps (a), (b), (c) and (f) and is rich in chlorosilane is compressed, deep-frozen, most of chlorosilane is separated and recycled in the step (b), a small amount of tail gas containing chlorosilane is discharged into the atmosphere after being hydrolyzed and qualified in a tail gas leaching tower, and hydrolysis residues are treated in the step (h); the other part is the reduction tail gas from the step (e), the part of the tail gas contains hydrogen and silane gas, after compression and deep cooling, the hydrogen is separated and supplied to the step (a) for recycling, and the silane gas is condensed into liquid and is vaporized to be recycled to the step (e).

(h) Residue neutralization: and (3) adding a neutralizing agent (calcium hydroxide alkali liquor) into the solid residue from the step (f) and the hydrolysis residue from the step (g) for neutralization and filter pressing treatment, discharging qualified solid residue in an environment-friendly manner, and returning the wastewater to the tail gas leaching tower in the step (g) for recycling.

The present invention is illustrated by the following specific examples, which are intended to be illustrative only and should not be construed as limiting the invention in any way. In addition, in the following examples, if not specifically mentioned, all the equipment and materials used are commercially available.

Example 1

With the apparatus shown in fig. 3 to 11 and with reference to the flow charts shown in fig. 1 and 2, according to the method for preparing polycrystalline silicon of the present invention, trichlorosilane is prepared and purified according to the following process steps, and polycrystalline silicon is further prepared:

(1) a hydrochlorination synthesis step: mixing the silicon tetrachloride and the hydrogen obtained in the following steps (2) and (3) in a gas-liquid mixer, performing heat exchange with gas at the outlet of a hydrogenation reactor, heating the gas to a certain temperature in a resistance heater, directly feeding the mixed gas into the hydrogenation reactor, controlling the temperature to be 500-550 ℃ and the pressure to be 1.5-3.5 MPa, mixing the silicon tetrachloride and the hydrogen in a ratio of 1: 2-1: 5, and reacting the mixed gas with silicon powder under the action of a nickel-based or copper-based catalyst. The reacted gas passes through a high-efficiency gas-solid dust remover and then exchanges heat with gas from a gas-liquid mixer in a gas-gas heat exchanger, the cooled reaction gas enters a bubbling dust removal tower, solid dust is further removed, the dust enters an integrated condenser, chlorosilane is condensed and enters a liquid collecting tank, and hydrogen is separated out and enters the gas-liquid mixer through a compressor for recycling.

(2) Chlorosilane purification step: the trichlorosilane is purified by three towers (namely rectifying towers) by utilizing the principle that the trichlorosilane and the silicon tetrachloride have different volatilities at the same temperature by utilizing the difference of the boiling points. And (3) discharging residual liquid from the second rectifying tower, extracting purified TCS from the top of the third rectifying tower, and discharging the recovered STC from the bottom of the third rectifying tower and returning the recovered STC to the gas-liquid mixer in the step (1). The trichlorosilane with the purity of more than 99 percent is obtained.

(3) A trichlorosilane disproportionation step: and controlling the temperature of the disproportionation reactor to be 50-80 ℃ and the pressure to be 0.2-0.6 MPa, and introducing TCS extracted from the top of the third rectifying tower into the reactor under the action of a catalyst to perform disproportionation reaction to generate silane gas.

(4) Low-temperature rectification of silane gas: the silane gas is purified by a low-temperature rectifying tower by utilizing the principle that B, P, C and other impurities, chlorosilane and silane gas have different volatilities at the same temperature and the difference of boiling points. And (4) feeding the silane gas from the step (3) into a low-temperature rectifying tower, and controlling the temperature in the tower to be-60 to-80 ℃, the pressure to be 0.60 to 1.0MPa and the reflux ratio to be 5:1 to 20: 1. The purity of the silane extracted from the tower top can reach 9N-11N, and impurity compounds such as B, P, Al, C and the like are mainly removed. The high purity silane gas extracted from the top of the column is sent to the step (5), and impurities and the like are discharged from the bottom of the column.

(5) Silane gas high-temperature pyrolysis step: and (3) introducing the high-purity silane gas from the step (4) into a vaporizer, vaporizing the high-purity silane gas into gas, introducing the gas into a bell-type reduction furnace, and arranging a silicon core as a carrier for crystal deposition in the furnace, wherein the silicon core can be 12 pairs of rods, 24 pairs of rods or 36 pairs of rod reduction furnaces. Controlling the internal temperature to be 750-900 ℃ and 0.15-0.30 MPa, and cracking and depositing silane gas on a silicon core to generate the rod-shaped electronic grade polysilicon. And (4) recovering the generated reduction tail gas and returning the reduction tail gas to the step (7) for treatment. Wherein, the one-time cracking conversion efficiency of the silane gas can reach more than 90 percent.

(6) And (3) residual liquid recovery: and (3) evaporating residual liquid, which is discharged from the bottom of the third rectifying tower in the step (2) and is rich in silicon tetrachloride and a small amount of solid residues, by using a flash tank, wherein the flash tank is provided with a stirring device, a shaft and a body are mechanically sealed, and the outside of the flash tank is provided with a steam jacket and is heated by adopting steam. And (3) condensing the silicon tetrachloride gas evaporated from the flash tank in a subsequent water cooler, and returning the silicon tetrachloride liquid to the gas-liquid mixer in the step (1). And (3) hydrolyzing and neutralizing the solid residues with alkali liquor, and then performing filter pressing to obtain harmless neutralized residues, and discharging the harmless neutralized residues.

(7) Tail gas recovery: the whole system is divided into two tail gases. The tail gas 1 is a tail gas containing chlorosilane and does not contain silane gas. Compressing the part of tail gas to 0.25-0.50 MPa by a compressor, entering a deep cooler, controlling the cryogenic temperature to be-15 to-30 ℃, condensing chlorosilane, returning to the step (2), feeding uncondensed gas into a tail gas leaching tower, discharging the qualified gas after leaching, neutralizing leaching water and alkali liquor, then performing filter pressing, discharging filter residues, and returning the neutralizing water to the leaching tower for recycling; the tail gas 2 is a gas rich in hydrogen and a small amount of silane gas, namely a reduction tail gas from the bell-type reduction furnace, the gas is compressed to 6.0-10.0 MPa by a compressor, the gas enters a deep cooler to be condensed to-100 to-120 ℃, the silane gas is condensed into liquid and enters a vaporizer, and the hydrogen is separated and enters a chlorine hydrogenation synthesis reaction device.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A device for purifying trichlorosilane is characterized in that,

the equipment is a first rectification purification device and is used for carrying out first rectification purification treatment on trichlorosilane so as to obtain purified trichlorosilane and first rectification residual liquid,

wherein,

the trichlorosilane is provided in the form of a hydrochlorination synthesis reaction product,

the first rectification and purification device comprises a first rectification tower, a second rectification tower and a third rectification tower which are connected in series,

wherein, each rectifying tower is respectively provided with a feed inlet and a discharge outlet from bottom to top along the axial direction of the rectifying tower.

2. The apparatus of claim 1, further comprising: a hydrochlorination synthesis reaction device connected with the first rectification and purification device and used for carrying out hydrochlorination synthesis reaction on silicon powder, hydrogen and at least one of hydrogen chloride and silicon tetrachloride so as to obtain a hydrochlorination synthesis reaction product and supply the hydrochlorination synthesis reaction product to the first rectification and purification device.

3. The apparatus of claim 2, wherein the hydrochlorination synthesis reaction device is provided with a nickel-based catalyst or a copper-based catalyst, so that the hydrochlorination synthesis reaction occurs by contacting a gas mixture comprising silicon tetrachloride and hydrogen with silicon powder in the presence of the nickel-based catalyst or the copper-based catalyst.

4. The apparatus according to claim 3, wherein the molar ratio of silicon tetrachloride to hydrogen in the gas mixture comprising silicon tetrachloride and hydrogen is 1: 2-5.

5. The apparatus of claim 3, wherein the hydrochlorination synthesis reaction is carried out at a temperature of 500 to 550 degrees Celsius.

6. The apparatus of claim 5, wherein the hydrochlorination synthesis reaction is performed at 500-550 ℃ and 1.5-3.5 MPa.

7. The apparatus of claim 3, further comprising:

the gas-liquid mixing device is used for mixing silicon tetrachloride liquid with hydrogen to obtain a gas-liquid mixture;

the heat exchange device is respectively connected with the gas-liquid mixing device and the hydrochlorination synthesis reaction device and is used for carrying out heat exchange treatment on the gas-liquid mixture by using the hydrochlorination synthesis reaction product so as to obtain a preheated gas-liquid mixture and a cooled hydrochlorination synthesis reaction product; and

and the resistance heater is respectively connected with the heat exchange device and the hydrochlorination synthesis reaction device and is used for heating the preheated gas-liquid mixture so as to obtain the gas mixture containing silicon tetrachloride and hydrogen, and supplying the gas mixture containing silicon tetrachloride and hydrogen to the hydrochlorination synthesis reaction device.

8. The apparatus of claim 7, further comprising:

the dust removal device is connected with the heat exchange device so as to remove dust from the cooled chlorohydrination synthesis reaction product; and

and the first condensing device is respectively connected with the dust removal device and the first rectification and purification device and is used for condensing the chlorine hydrogenation synthetic reaction product subjected to dust removal treatment so as to respectively recover hydrogen and chlorosilane liquid, the chlorosilane liquid contains trichlorosilane and silicon tetrachloride, and the chlorosilane liquid is supplied to the first rectification and purification device to be used for the first rectification and purification treatment.

9. The apparatus according to claim 8, wherein said first condensing means is connected to said hydrochlorination synthesis reaction means for supplying said hydrogen gas to said hydrochlorination synthesis reaction means.

10. The apparatus of claim 7, further comprising:

the disproportionation reaction device is connected with the first rectification and purification device and is used for carrying out disproportionation reaction on the purified trichlorosilane so as to obtain a disproportionation reaction product containing silicon tetrachloride and silane;

the second rectification and purification device is connected with the disproportionation reaction device and is used for carrying out second rectification and purification treatment on the disproportionation reaction product so as to obtain silane gas and silicon tetrachloride; and

and the pyrolysis reaction device is connected with the second rectification and purification device and is used for carrying out pyrolysis reaction on the silane gas so as to obtain the polycrystalline silicon.

11. The apparatus of claim 10, wherein the disproportionation reaction in the disproportionation reaction device is carried out at 50-80 ℃ and 0.2-0.6 MPa.

12. The apparatus of claim 10, wherein the disproportionation reactor is a disproportionation reactor, the disproportionation reactor further comprising:

the disproportionation reactor comprises a disproportionation reactor body, wherein a disproportionation reaction space is defined in the disproportionation reactor body, and a catalyst layer is arranged in the disproportionation reaction space;

the trichlorosilane feed inlet is arranged below the catalyst layer and used for supplying the purified trichlorosilane to the disproportionation reaction space; and

a disproportionation reaction product discharge port arranged above the catalyst layer for discharging the formed disproportionation reaction product containing silicon tetrachloride and silane out of the disproportionation reactor.

13. The apparatus of claim 10, wherein at least a portion of the silicon tetrachloride in the gaseous mixture comprising silicon tetrachloride and hydrogen originates from the disproportionation reaction unit.

14. The apparatus according to claim 10, characterized in that the second rectification and purification unit is connected to the hydrochlorination synthesis unit in order to use the silicon tetrachloride obtained in the second rectification and purification unit for the hydrochlorination synthesis reaction.

15. The apparatus according to claim 10, wherein the second rectification and purification device is a low-temperature rectification tower, wherein the temperature in the low-temperature rectification tower is-60 to-80 ℃, the pressure in the low-temperature rectification tower is 0.6 to 1.0MPa, and the reflux ratio is 5 to 20: 1.

16. The apparatus as claimed in claim 10, further comprising a vaporization treatment device connected to the second distillation purification device and the pyrolysis reaction device, respectively, for vaporizing the silane gas stored in liquid form in advance before the pyrolysis reaction.

17. The apparatus of claim 10, wherein the pyrolysis reaction device is a reduction furnace in which a silicon core is disposed as a carrier for crystal deposition.

18. The apparatus of claim 17, wherein the reduction furnace is a bell jar reduction furnace.

19. The apparatus of claim 18, wherein 12, 24 or 36 pairs of silicon rods are provided in the reduction furnace.

20. The apparatus according to claim 18, wherein the temperature in the reduction furnace is 750 to 900 ℃ and the pressure is 0.15 to 0.30 MPa.

21. The apparatus of claim 7, further comprising:

the flash evaporation treatment device is connected with the first rectification and purification device and is used for carrying out flash evaporation treatment on the first rectification residual liquid so as to obtain silicon tetrachloride gas and solid residues;

the second condensing device is respectively connected with the flash evaporation treatment device and the gas-liquid mixing device, and is used for condensing the silicon tetrachloride gas so as to obtain silicon tetrachloride liquid, and supplying the silicon tetrachloride liquid to the gas-liquid mixing device for the hydrochlorination synthesis reaction; and

and the residue treatment device is connected with the flash evaporation treatment device and is used for sequentially carrying out alkali liquor hydrolysis neutralization treatment and filter pressing treatment on the solid residues.

22. The apparatus of claim 16, further comprising:

the first compression device is connected with the pyrolysis reaction device and is used for compressing the reduction tail gas of the pyrolysis reaction to the pressure of 6.0-10.0 MPa; and

and the third condensing device is connected with the first compressing device, the gas-liquid mixing device and the vaporization treatment device and is used for condensing the compressed reduction tail gas to the temperature of-100 to-120 ℃ so as to condense silane gas into silane liquid and obtain hydrogen, supplying the silane liquid to the vaporization treatment device, and supplying the hydrogen to the gas-liquid mixing device for the chlorine hydrogenation synthesis reaction.

23. The apparatus of claim 10, further comprising:

the second compression device is used for compressing tail gas which contains chlorosilane and does not contain silane and is generated in each device to the pressure of 0.25-0.50 MPa;

the fourth condensing device is respectively connected with the second compressing device and the first rectifying and purifying device and is used for cooling the compressed tail gas containing chlorosilane and not containing silane to the temperature of-15 to-30 ℃ so as to obtain chlorosilane liquid and residual gas, and supplying the chlorosilane liquid to the first rectifying and purifying device for the first rectifying and purifying treatment;

the leaching device is connected with the fourth condensing device and is used for leaching the residual gas so as to obtain leached gas and leaching water; and

and the leaching water treatment device is connected with the leaching device and is used for neutralizing the leaching water by using alkali liquor and performing filter pressing on the neutralized liquid so as to obtain neutralized water and filter residues.

24. The apparatus according to claim 23, wherein the neutralizing water is supplied to the rinsing device for rinsing the surplus gas.