Device and method for removing impurities from trichlorosilane

Abstract

The present invention relates to the technical field of polycrystalline silicon production. Disclosed are a device and method for removing impurities from trichlorosilane, mainly aiming to improve the efficiency of removing impurities from trichlorosilane without increasing costs. The main technical solution of the present invention is: the device for removing impurities from trichlorosilane, comprising: an inlet of a first mixer is connected to one end of a first feeding pipe and a second feeding pipe, a plurality of baffle plates are arranged in a reaction tank in a staggered mode and used for forming a flow deflecting channel in the reaction tank, and one end of the flow deflecting channel is connected to an outlet of the first mixer; the other end of the flow deflecting channel, a filter and an inlet of a separation tower are sequentially connected, the inlet of the separation tower is further connected to a siloxane conveying pipe, a tower bottom of the separation tower is connected to the other end of the first feeding pipe and used for guiding siloxane to the first mixer, and an overhead draw-off pipe of the separation tower is connected to a rectification unit; and the second feeding pipe is used for guiding an impurity-containing trichlorosilane and dichlorosilane mixture to the first mixer.

Description

Device and method for removing impurities in trichlorosilane TECHNICAL FIELD

[0001] The present application relates to the technical field of polysilicon production, and in particular to a device and method for removing impurities in trichlorosilane. BACKGROUND

[0002] In the production of polysilicon by improved Siemens method, the purification of trichlorosilane relies on the rectifying tower of the rectifying process. Normal processing of cold hydrogenation synthesis material rectifying tower requires 5 towers or 6 towers, and multiple rectification purification is required to achieve qualified trichlorosilane product for polysilicon production in the reduction furnace.

[0003] In recent years, in order to reduce investment and operation cost and improve scale effect, the rectifying device is also becoming larger and larger. At present, the single-line rectifying device has been matched to the scale of 50,000 tons of polysilicon per year, and some devices have begun to try to match the single-line rectifying device of 70,000 to 100,000 tons.

[0004] In order to stabilize the quality, the common measures to strengthen rectification at present are 1, increasing the number of rectifying towers; 2, using some auxiliary rectification purification methods, such as adsorption of impurities by resin, activated carbon and other adsorbents.

[0005] Increasing the number of rectifying towers will increase the energy consumption of the device, increase the operation cost, and increase the equipment investment. The use of resin, activated carbon and other adsorbents has the disadvantages of high safety risk, easy occurrence of combustion and explosion accidents, short service life of adsorbents, inability to continuous operation, complex operation process, etc. SUMMARY

[0006] Therefore, the embodiments of the present application provide a device and method for removing impurities in trichlorosilane, mainly aiming to improve the removal efficiency of impurities in trichlorosilane without increasing the cost.

[0007] In order to achieve the above-mentioned purpose, the present application mainly provides the following technical solutions:

[0008] On the one hand, the embodiments of the present application provide a device for removing impurities in trichlorosilane, which comprises a reaction part and a filtering part.

[0009] The reaction part comprises a first mixer and a reaction tank, the inlet of the first mixer is connected to one end of a first feed pipe and a second feed pipe, a plurality of baffles are arranged alternately in the reaction tank to form a baffle channel in the reaction tank, and one end of the baffle channel is connected to the outlet of the first mixer.

[0010] The filtering part comprises a filter and a separation tower, the other end of the baffle channel, the filter and the inlet of the separation tower are sequentially connected, the inlet of the separation tower is further connected to a siloxane conveying pipe, the tower kettle of the separation tower is connected to the other end of the first feeding pipe for guiding siloxane to the first mixer, and the top pipe of the separation tower is connected to a rectification unit.

[0011] The second feeding pipe is used for guiding the mixture of trichlorosilane and dichlorodisilane containing impurities to the first mixer.

[0012] The purposes of the present application and the technical problems thereof can be further achieved by the following technical measures.

[0013] Optionally, the first mixer comprises a flow guide pipe shell and a spiral blade coaxially arranged in the flow guide pipe shell.

[0014] Optionally, the spiral blade comprises a plurality of branch spiral blades coaxially connected, and the end faces of adjacent two branch spiral blades are staggered.

[0015] Optionally, the second mixer comprises an outer sleeve and a conical pipe, the conical pipe is coaxially arranged in the outer sleeve, the tip of the conical pipe points to the outlet of the outer sleeve, the inlet of the outer sleeve is connected to the second feeding pipe, the outlet of the outer sleeve is connected to the inlet of the flow guide pipe shell, and the side wall of the outer sleeve between the conical pipe and the outlet of the outer sleeve is connected to one end of the first feeding pipe.

[0016] Optionally, a discharge pipe is further arranged, one end of the discharge pipe is connected to the middle part of the first feeding pipe, and the other end of the discharge pipe is connected to a siloxane storage tank.

[0017] Optionally, the rectification unit comprises a rectification first-stage tower, a rectification second-stage tower, a rectification third-stage tower and a rectification fourth-stage tower, the top pipe of the separation tower is connected to the inlet of the rectification first-stage tower, the top pipe of the rectification first-stage tower is connected to a reverse disproportionator, the side pipe of the rectification first-stage tower is connected to the inlet of the rectification second-stage tower, the top pipe of the rectification second-stage tower is connected to the inlet of the rectification third-stage tower, the tower kettle of the rectification second-stage tower is connected to an adsorption mechanism, the top pipe of the rectification third-stage tower is connected to the inlet of the rectification first-stage tower, the tower kettle of the rectification third-stage tower is connected to the inlet of the rectification fourth-stage tower, the top pipe of the rectification fourth-stage tower is connected to a high-purity tank, and the tower kettle of the rectification fourth-stage tower is connected to the inlet of the rectification second-stage tower.

[0018] Optionally, the tower kettle of the rectification first-stage tower is connected to the inlet of the first mixer.

[0019] In another aspect, the present application also provides a method for removing impurities from trichlorosilane, using the device for removing impurities from trichlorosilane as described above, comprising the following steps:

[0020] (1) the molar ratio of the siloxane to the mixture is greater than or equal to 1:1;

[0021] (2) after the siloxane and the mixture pass through the first mixer, a reaction material is formed, the flow rate of the reaction material is controlled so that the residence time of the reaction material in the reaction tank is greater than or equal to two hours, and the reaction temperature in the reaction tank is controlled to be 100℃ to 120℃;

[0022] (3) the pressure difference of the separation column is controlled to be 20KPa to 50KPa.

[0023] By the above technical solution, the present application has at least the following advantages:

[0024] The second feed pipe introduces the impurity-containing mixture of trichlorosilane and dichlorodisilane from the cold hydrogenation crude fraction column top to the first mixer, the mixture flows in a zigzag manner in the reaction tank, the residence time of the mixture in the reaction tank is prolonged, the impurities difficult to separate in the mixture react with the siloxane in the reaction tank to generate high-boiling complex, and the complex is filtered by the filter, so that the impurity removal rate is high and the silicon loss is small.

[0025] The impurities contained in the trichlorosilane and dichlorodisilane after complexation are greatly reduced, and the trichlorosilane and dichlorodisilane successively enter the separation column and the rectification unit for purification, so that high-quality liquid-phase trichlorosilane can be produced.

[0026] The siloxane delivery pipe first introduces the siloxane to the separation column, and then the siloxane reaches the mixer through the column bottom of the separation column. Through the above design, during the residence of the mixture in the reaction tank, impurity ions that do not participate in the complexation reaction are inevitable. The impurities that do not participate in the reaction cannot be filtered by the filter. In the separation column, the residual impurity ions are captured by the siloxane again to generate complexation reaction, the high-boiling complex is deposited to the column bottom of the separation column, and then enters the first mixer, and finally is filtered by the filter.

[0027] Because the complexation reaction removes impurities in advance, the traditional five-stage or six-stage main column rectification is reduced to four-stage main column rectification, which can ensure the purification degree of trichlorosilane, save equipment investment, and reduce the energy consumption of the rectification device.

[0028] The process flow of the present application is simple, which can reduce the number of subsequent rectification columns, reduce equipment investment, improve the removal efficiency of impurities in trichlorosilane, has strong operation continuity, high safety, and is convenient for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0029] Fig. 1 is a structural schematic view of a device for removing impurities from trichlorosilane according to an embodiment of the present application.

[0030] Fig. 2 is an enlarged view of part A in Fig. 1;

[0031] Fig. 3 is a top view of the reaction tank;

[0032] Fig. 4 is a perspective view of the first mixer.

[0033] The reference signs in the drawing of the specification include: reaction tank 1, first feed pipe 2, second feed pipe 3, baffle plate 4, filter 5, separation column 6, silicone delivery pipe 7, draft tube shell 8, helical blade 9, outer sleeve 10, conical pipe 11, discharge pipe 12, rectification primary column 13, rectification secondary column 14, rectification tertiary column 15, rectification quaternary column 16. DETAILED DESCRIPTION

[0034] To further clarify the technical means and effects taken by the present application to achieve the predetermined object of the application, the specific embodiments, structures, features and effects thereof according to the present application are described in detail below in combination with the drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0035] Before the device and method for removing impurities in trichlorosilane are described in detail, it is necessary to further explain the complexation reaction mentioned in the present application to achieve better results.

[0036] Trichlorosilane is contacted with a small amount of oxygen, and the temperature is controlled at 170-300℃. Oxygen will react with Si-H bond to form a compound containing Si-OH, which can complex with boron chloride, phosphorus chloride and other impurities to form a high-boiling compound.

[0037] The present application will be further described in detail below in combination with the drawings and embodiments.

[0038] As shown in Figs. 1, 2 and 3, on the one hand, one embodiment of the present application provides a device for removing impurities in trichlorosilane, which comprises a reaction part and a filtering part;

[0039] The reaction part comprises a first mixer and a reaction tank 1, the inlet of the first mixer is connected to one end of the first feed pipe 2 and the second feed pipe 3, and a plurality of baffle plates 4 are staggered arranged in the reaction tank 1 to form a baffle passage in the reaction tank 1, one end of the baffle passage is connected to the outlet of the first mixer;

[0040] The filtering part comprises a filter 5 and a separation tower 6, the other end of the baffle channel, the inlet of the filter 5 and the inlet of the separation tower 6 are sequentially connected, the inlet of the separation tower 6 is further connected to a siloxane conveying pipe 7, the tower kettle of the separation tower 6 is connected to the other end of the first feeding pipe 2 for guiding the siloxane to the first mixer, and the top pipe of the separation tower 6 is connected to a rectification unit;

[0041] The second feeding pipe 3 is used for guiding the trichlorosilane and dichlorodisilane mixture containing impurities to the first mixer.

[0042] The working process of the device for removing impurities in trichlorosilane is as follows:

[0043] The second feeding pipe 3 guides the trichlorosilane and dichlorodisilane mixture containing impurities from the top of the crude separation tower to the first mixer, the mixture flows in the reaction tank 1 in a zigzag shape, the residence time of the mixture in the reaction tank 1 is prolonged, the impurities which are difficult to separate in the mixture are complexed with siloxane in the reaction tank 1 to generate high-boiling complex, and then the complex is filtered through the filter 5, so that the impurity removal rate is high and the silicon loss is small.

[0044] After the complexation, the impurities contained in the trichlorosilane and dichlorodisilane are greatly reduced, and then enter the separation tower 6 and the rectification unit in sequence for purification, so that high-quality liquid-phase trichlorosilane can be produced.

[0045] The siloxane conveying pipe 7 first guides the siloxane to the separation tower 6, and then to the mixer through the tower kettle of the separation tower 6. Through the above design, during the residence of the mixture in the reaction tank 1, there are inevitably some impurity ions which do not participate in the complexation reaction. The impurities which do not participate in the reaction cannot be filtered by the filter 5, and in the separation tower 6, the residual impurity ions are captured by the siloxane again to generate complexation reaction, the high-boiling complex is deposited to the tower kettle of the separation tower 6, and then enters the first mixer, and finally is filtered by the filter 5.

[0046] Because the complexation reaction removes the impurities in advance, the traditional five-stage or six-stage main tower rectification is reduced to four-stage main tower rectification, which can ensure the purification degree of trichlorosilane, save the equipment investment, and reduce the energy consumption of the rectification device.

[0047] In the technical scheme of the present application, the process flow of the present application is simple, the number of subsequent rectification towers can be reduced, the equipment investment is reduced, the removal efficiency of impurities in trichlorosilane is improved, the operation continuity is strong, the safety is high, and the industrial production is facilitated.

[0048] Specifically, the filter 5 adopts a sintered filter, the mesh number of the sintered filter is ≤1 μm, the number of the sintered filter is ≥2, one is used and the other is standby, when the flux is less than the normal flux, the standby filter is switched to use, and the clogged filter is backwashed or replaced and cleaned.

[0049] As shown in Fig. 1 and Fig. 3, specifically, the reaction tank 1 adopts a horizontal tank, the outlet of the first mixer is connected to one end of the discharge pipe, the other end of the discharge pipe penetrates the upper side wall of the other end of the reaction tank 1 and extends to the bottom of the reaction tank 1; the upper side wall of the other end of the reaction tank 1 is connected to one end of the delivery pipe, the other end of the delivery pipe is connected to the inlet of the filter 5, so that the reaction mixture of the reaction tank 1 flows to the full liquid level.

[0050] Specifically, the siloxane is from a high boiling recovery section or purchased, and the content of the siloxane is greater than 99%.

[0051] As shown in Fig. 1 and Fig. 4, in the specific embodiment, the first mixer comprises a flow guide pipe shell 8 and a spiral blade 9 coaxially arranged in the flow guide pipe shell 8.

[0052] In the embodiment, specifically, the spiral blade 9 divides the internal space of the flow guide pipe shell 8 into a spiral flow channel, when the siloxane transported by the first feeding pipe 2 and the impurity-containing mixture transported by the second feeding pipe 3 enter the flow guide pipe shell 8, they flow along the spiral flow channel to mix.

[0053] As shown in Fig. 4, in the specific embodiment, the spiral blade 9 comprises a plurality of branch spiral blades coaxially connected, and the end faces of adjacent two branch spiral blades are staggered.

[0054] In the embodiment, the adjacent two branch spiral blades are respectively a first branch spiral blade 901 and a second branch spiral blade 902, the end face of the first branch spiral blade 901 and the end face of the second branch spiral blade 902 are perpendicular to each other, when the material flows through the first branch spiral blade 901 and the second branch spiral blade 902 in sequence, the flow speed of the material is blocked by the second branch spiral blade 902 when the material flows out of the first branch spiral blade 901, the original flow track of the material is disturbed, the flow speed is slowed down, and the material flows forward again along the shape formed by the second branch spiral blade 902 and the flow guide pipe shell 8, and the flow speed is accelerated again.

[0055] Through the above process, the flow speed of the material is periodically changed, and the different components in the mixture are fully mixed, which prepares for the complexation reaction.

[0056] As shown in Fig. 2, in the specific embodiment, a second mixer is further included, the second mixer comprises an outer sleeve 10 and a conical pipe 11, the conical pipe 11 is coaxially arranged in the outer sleeve 10, the tip of the conical pipe 11 points to the outlet of the outer sleeve 10, the inlet of the outer sleeve 10 is connected to the second feeding pipe 3, the outlet of the outer sleeve 10 is connected to the inlet of the flow guide pipe shell 8, and the side wall of the outer sleeve 10 between the conical pipe 11 and the outlet of the outer sleeve 10 is connected to one end of the first feeding pipe 2.

[0057] In the embodiment, when the trichlorosilane and dichlorodisilane mixture containing impurities in the second feeding pipe 3 enters the outer sleeve pipe 10 and flows through the tip port of the tapered pipe 11, the flow rate increases and the static pressure decreases, forming a Venturi effect, so that a pressure difference is formed between the two ends of the first feeding pipe 2, causing the siloxane to accelerate along the first feeding pipe 2 into the outer sleeve pipe 10.

[0058] As shown in FIG. 1, in the specific embodiment, a discharge pipe 12 is further included, one end of the discharge pipe 12 being connected to the middle of the first feeding pipe 2 and the other end being connected to a siloxane storage tank.

[0059] In the embodiment, specifically, when the amount of siloxane supplied by the first feeding pipe 2 is greater than the amount of siloxane required for treating the impurities in the trichlorosilane and dichlorodisilane mixture, the valve of the discharge pipe 12 is opened, and the excess siloxane is guided to the siloxane storage tank.

[0060] As shown in FIG. 1, in the specific embodiment, the rectification unit includes a rectification first-stage tower 13, a rectification second-stage tower 14, a rectification third-stage tower 15, and a rectification fourth-stage tower 16, the top sampling pipe of the separation tower 6 being connected to the inlet of the rectification first-stage tower 13, the top sampling pipe of the rectification first-stage tower 13 being connected to a disproportionation device, the side sampling pipe of the rectification first-stage tower 13 being connected to the inlet of the rectification second-stage tower 14, the top sampling pipe of the rectification second-stage tower 14 being connected to the inlet of the rectification third-stage tower 15, the tower kettle of the rectification second-stage tower 14 being connected to an adsorption mechanism, the top sampling pipe of the rectification third-stage tower 15 being connected to the inlet of the rectification first-stage tower 13, the tower kettle of the rectification third-stage tower 15 being connected to the inlet of the rectification fourth-stage tower 16, the top sampling pipe of the rectification fourth-stage tower 16 being connected to a high-purity tank, and the tower kettle of the rectification fourth-stage tower 16 being connected to the inlet of the rectification second-stage tower 14.

[0061] In the embodiment, specifically, in the separation tower 6, siloxane accumulates in the tower kettle, and the trichlorosilane and dichlorodisilane mixture after impurity removal enters the rectification first-stage tower 13 through the top sampling pipe of the separation tower 6;

[0062] In the rectification first-stage tower 13, dichlorodisilane enters the disproportionation device through the top sampling pipe to participate in the disproportionation reaction, and trichlorosilane containing a small amount of impurities enters the rectification second-stage tower 14 through the side sampling pipe;

[0063] In the rectification second-stage tower 14, trichlorosilane enters the rectification third-stage tower 15 through the top sampling pipe, in which heavy component impurities accumulate in the tower kettle and finally enter the adsorption mechanism (activated carbon is used as the adsorbent in the adsorption mechanism) for further impurity removal;

[0064] In the rectification third-stage tower 15, light component impurities therein return to the rectification first-stage tower 13 through the top sampling pipe, and trichlorosilane concentrates in the tower kettle and finally enters the rectification fourth-stage tower 16;

[0065] In the rectification fourth-stage column 16, trichlorosilane is introduced from the top into a high-purity tank, in which residual heavy component impurities are collected in the tank bottom and refluxed into the rectification second-stage column 14.

[0066] In the rectification unit, the tank bottom material of the rectification fourth-stage column 16 and the top material of the rectification third-stage column 15 are refluxed respectively, and repeated rectification can reduce the amount of residual liquid flowing out of the rectification unit and reduce silicon loss.

[0067] As shown in FIG. 1, in the specific embodiment, the tank bottom of the rectification first-stage column 13 is connected to the inlet of the first mixer.

[0068] In this embodiment, specifically, because the material introduced into the rectification first-stage column 13 from the top of the separation column 6 still contains a certain proportion of impurities, the impurities are deposited in the tank bottom of the rectification first-stage column 13 after rectification, and the impurities are refluxed again into the first mixer to participate in the complexation reaction again.

[0069] On the other hand, another embodiment of the present application provides a method for removing impurities from trichlorosilane, which uses the above-described device for removing impurities from trichlorosilane and includes the following steps:

[0070] (1) A pneumatic control valve is installed on each of the first feed pipe 2 and the discharge pipe 12, and a flow meter is installed on each of the first feed pipe 2 and the second feed pipe 3, so that the molar ratio of the siloxane and the mixture introduced into the mixer is greater than or equal to 1:1, thereby ensuring sufficient complexation reaction;

[0071] (2) After the siloxane and the mixture pass through the first mixer, the reaction material is formed, the flow rate of the reaction material is controlled (because the reaction mixture flows at full level in the reaction tank 1, the sum of the flow rates of the siloxane and the impurity-containing mixture per hour is set to half the volume of the reaction tank 1), the residence time of the reaction material in the reaction tank 1 is greater than or equal to two hours, and the reaction temperature in the reaction tank 1 is controlled to be 100-120°C;

[0072] (3) The pressure difference of the separation column 6 is controlled to be 20-50 KPa, and the contents of boron and phosphorus impurities in the top fraction of the separation column 6 are controlled to be 0.001 ug / mL by liquid chromatography detection.

[0073] The above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A device for removing impurities from trichlorosilane, characterized in that: include: A reaction section comprising a first mixer and a reaction tank, wherein the inlet of the first mixer is connected to one end of the first feed pipe and the second feed pipe, and a plurality of baffles are staggeredly arranged in the reaction tank to form a baffle channel in the reaction tank, and one end of the baffle channel is connected to the outlet of the first mixer; a filtration section comprising a filter and a separation tower, wherein the other end of the baffle channel, the filter, and the inlet of the separation tower are sequentially connected, the inlet of the separation tower is further connected to a siloxane delivery pipe, the bottom of the separation tower is connected to the other end of the first feed pipe for draining siloxane to the first mixer, and the top extraction pipe of the separation tower is connected to a distillation unit; The second feed pipe is used to guide the mixture of trichlorosilane and dichlorosilane containing impurities to the first mixer.

2. The device for removing impurities from trichlorosilane according to claim 1, characterized in that: The first mixer includes a flow guide shell and a spiral blade coaxially arranged in the flow guide shell.

3. The device for removing impurities from trichlorosilane according to claim 2, characterized in that: The spiral blades include a plurality of coaxially connected branch spiral blades, and the end surfaces of two adjacent branch spiral blades are staggered with each other.

4. The device for removing impurities from trichlorosilane according to claim 2 or 3, characterized in that: It also includes a second mixer, which includes an outer sleeve and a tapered tube. The tapered tube is coaxially arranged in the outer sleeve, the tip end of the tapered tube points to the outlet of the outer sleeve, the inlet of the outer sleeve is connected to the second feed pipe, the outlet of the outer sleeve is connected to the inlet of the guide tube shell, and the side wall of the outer sleeve between the tapered tube and the outer sleeve outlet is connected to one end of the first feed pipe.

5. The device for removing impurities from trichlorosilane according to any one of claims 1 to 3, characterized in that: It also includes a discharge pipe, one end of which is connected to the middle of the first feed pipe, and the other end is connected to the siloxane storage tank.

6. The device for removing impurities from trichlorosilane according to any one of claims 1 to 3, characterized in that: The distillation unit includes a first-stage distillation tower, a second-stage distillation tower, a third-stage distillation tower and a fourth-stage distillation tower. The top sampling pipe of the separation tower is connected to the inlet of the first-stage distillation tower, the top sampling pipe of the first-stage distillation tower is connected to the anti-disproportionator, the side sampling pipe of the first-stage distillation tower is connected to the inlet of the second-stage distillation tower, the top sampling pipe of the second-stage distillation tower is connected to the inlet of the third-stage distillation tower, the bottom of the second-stage distillation tower is connected to the adsorption mechanism, the top sampling pipe of the third-stage distillation tower is connected to the inlet of the first-stage distillation tower, the bottom of the third-stage distillation tower is connected to the inlet of the fourth-stage distillation tower, the top sampling pipe of the fourth-stage distillation tower is connected to a high-purity tank, and the bottom of the fourth-stage distillation tower is connected to the inlet of the second-stage distillation tower.

7. The device for removing impurities from trichlorosilane according to claim 6, characterized in that: The bottom of the first distillation tower is connected to the inlet of the first mixer.

8. A method for removing impurities from trichlorosilane, using the device for removing impurities from trichlorosilane according to any one of claims 1 to 7, characterized in that: The steps include: (1) The molar ratio of the siloxane to the mixture is greater than or equal to 1:1; (2) After the siloxane and the mixture pass through the first mixer to form a reaction mass, the flow rate of the reaction mass is controlled so that the residence time of the reaction mass in the reaction tank is greater than or equal to two hours, and the reaction temperature in the reaction tank is controlled to be 100° C. to 120° C.; (3) The tower pressure difference of the separation tower is controlled to be 20 kPa to 50 kPa.

Images