Device and method for removing impurities from trichlorosilane

Abstract

The present invention discloses a device and method for removing impurities from trichlorosilane, which relates to the technical field of polysilicon production. The main purpose is to improve the efficiency of removing impurities from trichlorosilane without increasing costs. The main technical solution of the present invention is: a device for removing impurities from trichlorosilane, comprising: an inlet of a first mixer connected to one end of a first feed pipe and a second feed pipe, a plurality of baffles arranged alternately in a reaction tank to form a baffle channel in the reaction tank, one end of the baffle channel connected to the outlet of the first mixer; the other end of the baffle channel, a filter, and the inlet of a separation tower are connected in sequence, the inlet of the separation tower is also 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 sampling pipe of the separation tower is connected to a distillation unit; wherein the second feed pipe is used to drain the mixture of trichlorosilane and dichlorosilane containing impurities to the first mixer.

Description

Technical Field

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

[0002] During the modified Siemens process for polysilicon production, trichlorosilane is purified by distillation towers. Normally, five or six distillation towers are required to process cold hydrogenated synthetic material. After multiple distillation steps, qualified trichlorosilane product is produced and sent to the reduction furnace for polysilicon production.

[0003] In recent years, to reduce investment and operating costs and maximize economies of scale, distillation units have become increasingly larger. Currently, single-line distillation units are capable of producing 50,000 tons of polysilicon annually, and some plants are beginning to experiment with single-line distillation units with 70,000 to 100,000 tons. This increase in single-line capacity also increases the size of the distillation tower, compromising quality controllability and leading to frequent fluctuations in polysilicon quality.

[0004] In order to stabilize the quality, the common measures to strengthen distillation are: 1. Increasing the number of distillation tower stages; 2. Using some auxiliary distillation and purification methods, such as resin, activated carbon and other adsorbents to remove impurities.

[0005] Increasing the number of distillation tower stages increases energy consumption, operating costs, and equipment investment. The use of adsorbents such as resins and activated carbon carries significant safety risks, including the risk of explosions, short service lives, inability to operate continuously, and complex operational procedures. Summary of the Invention

[0006] In view of this, embodiments of the present invention provide a device and method for removing impurities from trichlorosilane, the main purpose of which is to improve the efficiency of removing impurities from trichlorosilane without increasing the cost.

[0007] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0008] In one aspect, an embodiment of the present invention provides a device for removing impurities from trichlorosilane, the device comprising: a reaction part and a filtering part;

[0009] The reaction part includes 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;

[0010] The filtration unit includes a filter and a separation tower. The other end of the baffle channel, the filter, and the inlet of the separation tower are connected in sequence. The inlet of the separation tower is also connected to the siloxane delivery pipe. The bottom of the separation tower is connected to the other end of the first feed pipe for draining the siloxane to the first mixer. The top sampling pipe of the separation tower is connected to the distillation unit.

[0011] The second feed pipe is used to guide the mixture of trichlorosilane and dichlorosilane containing impurities to the first mixer.

[0012] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

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

[0014] Optionally, the spiral blade includes a plurality of coaxially connected branch spiral blades, and end surfaces of two adjacent branch spiral blades are staggered with each other.

[0015] Optionally, a second mixer is further included, 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.

[0016] Optionally, a discharge pipe is further included, 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.

[0017] Optionally, 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 an 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.

[0018] Optionally, the bottom of the first distillation tower is connected to the inlet of the first mixer.

[0019] On the other hand, an embodiment of the present invention further provides a method for removing impurities from trichlorosilane, using the above-mentioned device for removing impurities from trichlorosilane, 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 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.;

[0022] (3) The tower pressure difference of the separation tower is controlled to be 20 kPa to 50 kPa.

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

[0024] The second feed pipe guides the impurity-containing mixture of trichlorosilane and dichlorosilane collected from the top of the cold hydrogenation crude fraction tower to the first mixer. The mixture flows in a zigzag shape in the reaction tank, extending the residence time of the mixture in the reaction tank. The impurities that are difficult to separate in the mixture react with siloxane in the reaction tank to form a high-boiling point complex. The complex is then filtered through a filter, resulting in a high impurity removal rate and low silicon loss.

[0025] After complexation, the impurities in trichlorosilane and dichlorosilane are greatly reduced, and they enter the separation tower and distillation unit for purification in sequence, and can produce high-quality liquid trichlorosilane.

[0026] The siloxane delivery pipe first directs the siloxane to the separation tower, then through the bottom of the separation tower to the mixer. This design allows the mixture to retain impurity ions that do not participate in the complexation reaction during its stay in the reaction tank. These impurities cannot be filtered out by the filter. Within the separation tower, the remaining impurity ions are captured again by the siloxane, causing a complexation reaction. The high-boiling-point complex is deposited in the bottom of the separation tower, then enters the first mixer and is ultimately filtered out by the filter.

[0027] Because the complexation reaction removes impurities first, the traditional five-stage and six-stage main tower distillation is reduced to four-stage main tower distillation, which can also ensure the purity of trichlorosilane, save equipment investment, and reduce the energy consumption of the distillation device.

[0028] The process flow of the present invention is simple, the number of subsequent distillation towers can be reduced, equipment investment can be reduced, the removal efficiency of impurities in trichlorosilane can be improved, the operation continuity is strong, the safety is high, and industrial production is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1A schematic structural diagram of a device for removing impurities from trichlorosilane provided in an embodiment of the present invention;

[0030] Figure 2 for Figure 1 Enlarged view of part A;

[0031] Figure 3 It is a top view of the reaction tank;

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

[0033] The figure marks in the drawings of the specification include: reaction tank 1, first feed pipe 2, second feed pipe 3, baffle 4, filter 5, separation tower 6, siloxane delivery pipe 7, guide pipe shell 8, spiral blade 9, outer sleeve 10, tapered pipe 11, discharge pipe 12, first distillation tower 13, second distillation tower 14, third distillation tower 15, and fourth distillation tower 16. DETAILED DESCRIPTION

[0034] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0035] Before elaborating in detail the device and method for removing impurities from trichlorosilane according to the present invention, it is necessary to further explain the complexation reaction mentioned in the present invention in order to achieve better results.

[0036] When trichlorosilane comes into contact with a small amount of oxygen and the temperature is controlled at 170-300°C, the oxygen will react with the Si-H bond to generate a compound containing Si-OH, which can complex with impurities such as boron chloride and phosphorus chloride to generate a high-boiling point compound.

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] like Figure 1 、 Figure 2 、 Figure 3 As shown, on the one hand, an embodiment of the present invention provides a device for removing impurities from trichlorosilane, which includes: a reaction part and a filtering part;

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

[0040] The filtration unit includes a filter 5 and a separation tower 6. The other end of the baffle channel, the filter 5, and the inlet of the separation tower 6 are connected in sequence. The inlet of the separation tower 6 is also connected to a siloxane delivery pipe 7. The bottom of the separation tower 6 is connected to the other end of the first feed pipe 2 for draining siloxane to the first mixer. The top sampling pipe of the separation tower 6 is connected to the distillation unit.

[0041] The second feed pipe 3 is used to guide the mixture of trichlorosilane and dichlorosilane containing impurities to the first mixer.

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

[0043] The second feed pipe 3 guides the impurity-containing mixture of trichlorosilane and dichlorosilane collected from the top of the cold hydrogenation crude fraction tower to the first mixer. The mixture flows in a zigzag shape in the reaction tank 1, extending the residence time of the mixture in the reaction tank 1. The impurities that are difficult to separate in the mixture react with siloxane in the reaction tank 1 to form a high-boiling point complex. The complex is then filtered through the filter 5, resulting in a high impurity removal rate and low silicon loss.

[0044] After the complexation, the impurities in trichlorosilane and dichlorosilane are greatly reduced, and they enter the separation tower 6 and the distillation unit for purification in sequence, thereby producing high-quality liquid trichlorosilane.

[0045] Siloxane delivery pipe 7 first directs siloxane to separation tower 6, then through the bottom of separation tower 6 to the mixer. With this design, while the mixture remains in reaction tank 1, impurity ions inevitably remain unaffected by the complexation reaction. These impurities cannot be filtered out by filter 5. Within separation tower 6, the remaining impurity ions are captured by siloxane again, causing a complexation reaction. High-boiling-point complexes are deposited in the bottom of separation tower 6, then enter the first mixer and are ultimately filtered out by filter 5.

[0046] Because the complexation reaction removes impurities first, the traditional five-stage and six-stage main tower distillation is reduced to four-stage main tower distillation, which can also ensure the purity of trichlorosilane, save equipment investment, and reduce the energy consumption of the distillation device.

[0047] In the technical solution of the present invention, the process flow is simple, the number of subsequent distillation towers can be reduced, equipment investment can be reduced, the removal efficiency of impurities in trichlorosilane can be improved, the operation continuity is strong, the safety is high, and it is convenient for industrial production.

[0048] Specifically, the filter 5 is a sintered filter with a mesh size of ≤1μm and a number of ≥2 units, one in use and one in reserve. When the flux is less than the normal flow, the reserve filter is switched to use, and the clogged filter is backwashed or the filter element is replaced and removed for cleaning.

[0049] like Figure 1 and Figure 3 As shown, 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 passes through the upper side wall of one 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 feed pipe, and the other end of the feed pipe is connected to the inlet of the filter 5, so that the reaction mixture in the reaction tank 1 flows at the full liquid level.

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

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

[0052] In this embodiment, specifically, the spiral blades 9 divide the internal space of the guide tube shell 8 into a spiral flow channel. When the siloxane delivered by the first feed pipe 2 and the impurity-containing mixture delivered by the second feed pipe 3 enter the guide tube shell 8, they flow along the spiral flow channel and mix.

[0053] like Figure 4 As shown, in a specific embodiment, the spiral blade 9 includes a plurality of coaxially connected branch spiral blades, and the end surfaces of two adjacent branch spiral blades are staggered with each other.

[0054] In this embodiment, the two adjacent branch spiral blades are the first branch spiral blade 901 and the second branch spiral blade 902, and the end faces of the first branch spiral blade 901 and 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, when the flowing material leaves the first branch spiral blade 901, the flow rate of the material is blocked by the second branch spiral blade 902, the original flow trajectory of the material is disrupted, the flow rate slows down, and the material flows forward again along the shape constrained by the second branch spiral blade 902 and the guide tube shell 8, and the flow rate is accelerated again.

[0055] Through the above process, the flow rate of the material changes periodically, and the different components in the mixture are fully mixed to prepare for the complexation reaction.

[0056] like Figure 2 As shown, in a specific embodiment, a second mixer is further included, which includes an outer sleeve 10 and a tapered tube 11. The tapered tube 11 is coaxially arranged in the outer sleeve 10, and the tip end of the tapered tube 11 points to the outlet of the outer sleeve 10. The inlet of the outer sleeve 10 is connected to the second feed pipe 3, and the outlet of the outer sleeve 10 is connected to the inlet of the guide tube shell 8. The side wall of the outer sleeve 10 between the tapered tube 11 and the outlet of the outer sleeve 10 is connected to one end of the first feed pipe 2.

[0057] In this embodiment, when the mixture of trichlorosilane and dichlorosilane containing impurities in the second feed pipe 3 enters the outer sleeve 10 and flows through the pointed end of the tapered tube 11, the flow velocity increases and the static pressure decreases, forming a Venturi effect, so that a pressure difference is formed at both ends of the first feed pipe 2, causing the siloxane to accelerate along the first feed pipe 2 into the outer sleeve 10.

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

[0059] In this embodiment, specifically, when the amount of siloxane supplied by the first feed pipe 2 is greater than the amount of siloxane required to treat impurities in the mixture of trichlorosilane and dichlorosilane, the valve of the discharge pipe 12 is opened to divert the excess siloxane to the siloxane storage tank.

[0060] like Figure 1 As shown, in a specific embodiment, the distillation unit includes a first-stage distillation tower 13, a second-stage distillation tower 14, a third-stage distillation tower 15 and a fourth-stage distillation tower 16, the top sampling pipe of the separation tower 6 is connected to the inlet of the first-stage distillation tower 13, the top sampling pipe of the first-stage distillation tower 13 is connected to the anti-disproportionator, the side sampling pipe of the first-stage distillation tower 13 is connected to the inlet of the second-stage distillation tower 14, the top sampling pipe of the second-stage distillation tower 14 is connected to the inlet of the third-stage distillation tower 15, the bottom of the second-stage distillation tower 14 is connected to the adsorption mechanism, the top sampling pipe of the third-stage distillation tower 15 is connected to the inlet of the first-stage distillation tower 13, the bottom of the third-stage distillation tower 15 is connected to the inlet of the fourth-stage distillation tower 16, the top sampling pipe of the fourth-stage distillation tower 16 is connected to a high-purity tank, and the bottom of the fourth-stage distillation tower 16 is connected to the inlet of the second-stage distillation tower 14.

[0061] In this embodiment, specifically, in the separation tower 6, siloxane accumulates in the bottom of the tower, and the mixture of trichlorosilane and dichlorosilane after impurities removal enters the first distillation tower 13 through the top sampling pipe of the separation tower 6;

[0062] In the first distillation tower 13, dichlorosilane enters the deproportionator through the top sampling pipe and participates in the deproportionation reaction. Trichlorosilane containing a small amount of impurities enters the second distillation tower 14 through the side sampling pipe.

[0063] In the secondary distillation tower 14, trichlorosilane enters the tertiary distillation tower 15 through the top sampling pipe, where heavy impurities accumulate in the tower bottom and eventually enter the adsorption mechanism (activated carbon is used as the adsorbent in the adsorption mechanism) for further impurity removal;

[0064] In the three-stage distillation tower 15, the light component impurities are refluxed from the top sampling pipe to the first-stage distillation tower 13, and trichlorosilane is concentrated in the tower bottom and finally enters the fourth-stage distillation tower 16;

[0065] In the fourth-stage distillation tower 16 , trichlorosilane enters the high-purity tank from the top sampling pipe, and the remaining heavy component impurities are collected in the tower bottom and refluxed to the second-stage distillation tower 14 .

[0066] In the above distillation unit, the bottom material of the fourth distillation tower 16 and the top material of the third distillation tower 15 are refluxed separately and repeatedly distilled, which can reduce the outflow of residual liquid from the distillation unit and reduce silicon loss.

[0067] like Figure 1 As shown, in a specific embodiment, the bottom of the first distillation tower 13 is connected to the inlet of the first mixer.

[0068] In this embodiment, specifically, because impurities still account for a certain proportion in the material entering the first distillation tower 13 from the top sampling pipe of the separation tower 6, the impurities are deposited in the bottom of the first distillation tower 13 after distillation, and this part of the impurities flows back to the first mixer again to participate in the complex reaction again.

[0069] On the other hand, another embodiment of the present invention provides a method for removing impurities from trichlorosilane, using the above-mentioned device for removing impurities from trichlorosilane, comprising the following steps:

[0070] (1) pneumatic control valves are installed on the first feed pipe 2 and the discharge pipe 12, respectively, and flow meters are installed on the first feed pipe 2 and the second feed pipe 3 to control the molar ratio of the siloxane and the mixture entering the mixer to be greater than or equal to 1:1, thereby ensuring that the complexation reaction is fully carried out;

[0071] (2) After the siloxane and the mixture pass through the first mixer, a reaction mass is formed, and the flow rate of the reaction mass is controlled (because the reaction mixture flows at the full liquid level in the reaction tank 1, the sum of the hourly flow rates of the siloxane and the impurity-containing mixture is set to half the volume of the reaction tank 1) so that the residence time of the reaction mass 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° C. to 120° C.;

[0072] (3) The tower pressure difference of the separation tower 6 is controlled to be 20 kPa to 50 kPa. According to liquid chromatography detection, the boron and phosphorus impurity contents in the top fraction of the separation tower 6 can be controlled to be 0.001 ug / mL.

[0073] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for removing impurities from trichlorosilane, characterized in that: The devices used to remove impurities from trichlorosilane 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; Wherein, the second feeding pipe is used to guide the mixture of trichlorosilane and dichlorosilane containing impurities to the first mixer; 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; The method comprises the following steps: (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.

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

3. The method for removing impurities from trichlorosilane according to claim 2, wherein: 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 method 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 method 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 method for removing impurities from trichlorosilane according to claim 1, characterized in that: The bottom of the first distillation tower is connected to the inlet of the first mixer.

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