Device for removing impurities in trichlorosilane

Abstract

The utility model discloses a device for removing impurities in trichlorosilane, relates to the technical field of polycrystalline silicon production, and mainly aims to improve the removal efficiency of the impurities in the trichlorosilane on the basis of not increasing the cost. According to the main technical scheme, the device for removing the impurities in the trichlorosilane is characterized in that 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 baffle channel in the reaction tank, and one end of the baffle channel is connected to an outlet of the first mixer; the other end of the baffling channel, the filter and an inlet of the separating tower are sequentially connected, the inlet of the separating tower is further connected to a siloxane conveying pipe, a tower kettle of the separating tower is connected to the other end of the first feeding pipe and used for guiding siloxane to the first mixer, and a top collecting pipe of the separating tower is connected to the rectifying unit; wherein the second feeding pipe is used for guiding a trichlorosilane and dichlorosilane mixture containing impurities to the first mixer.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon production, in particular to a device for removing impurities in trichlorosilane. Background Art

[0002] In the process of producing polysilicon by the modified Siemens process, the purification of trichlorosilane depends on the distillation tower in the distillation process. Normally, 5 or 6 distillation towers are required to process cold hydrogenated synthetic materials. After multiple distillation and purification, qualified trichlorosilane products can be sent to the reduction furnace for polysilicon production.

[0003] In recent years, in order to reduce investment and operating costs and improve economies of scale, distillation units have become larger and larger. Currently, single-line distillation units have been matched to an annual production capacity of 50,000 tons of polysilicon, and some units have begun to try to match single-line distillation units with a scale of 70,000 to 100,000 tons. As the scale of the single line increases, the distillation tower becomes larger and the quality controllability becomes worse, which is accompanied by frequent fluctuations in the quality of polysilicon.

[0004] In order to stabilize the quality, the common measures to strengthen distillation are: 1. Increasing the number of distillation tower stages; 2. Adopting 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 will increase the energy consumption of the device, increase the operating cost, and increase the equipment investment. The use of adsorbents such as resins and activated carbon has the disadvantages of high safety risks, easy explosion accidents, short service life of adsorbents, inability to operate continuously, and complex operation procedures. Utility Model Content

[0006] In view of this, an embodiment of the utility model provides a device for removing impurities in trichlorosilane, the main purpose of which is to improve the removal efficiency of impurities in trichlorosilane without increasing the cost.

[0007] In order to achieve the above purpose, the utility model mainly provides the following technical solutions:

[0008] On the one hand, the embodiment of the utility model provides a device for removing impurities in trichlorosilane, the device comprising: a reaction part and a filtering part;

[0009] The reaction part comprises 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 arranged in a staggered manner 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, and is used to guide the siloxane to the first mixer, and the top collection 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 utility model and the solution to its technical problems can also 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 also 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 also included, one end of which is connected to the middle of the first feed pipe, and the other end of which is connected to the siloxane storage tank.

[0017] Optionally, the distillation unit includes a first distillation tower, a second distillation tower, a third distillation tower and a fourth distillation tower, the top sampling pipe of the separation tower is connected to the inlet of the first distillation tower, the top sampling pipe of the first distillation tower is connected to a deproportionator, the side sampling pipe of the first distillation tower is connected to the inlet of the second distillation tower, the top sampling pipe of the second distillation tower is connected to the inlet of the third distillation tower, the bottom of the second distillation tower is connected to an adsorption mechanism, the top sampling pipe of the third distillation tower is connected to the inlet of the first distillation tower, the bottom of the third distillation tower is connected to the inlet of the fourth distillation tower, the top sampling pipe of the fourth distillation tower is connected to a high purity tank, and the bottom of the fourth distillation tower is connected to the inlet of the second distillation tower.

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

[0019] On the other hand, the embodiment of the utility model also provides a method for removing impurities in trichlorosilane, using the above-mentioned device for removing impurities in 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, a reaction mass is formed, and 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 utility model 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, which prolongs 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 generate a high-boiling point complex, which is then filtered through a filter, with a high impurity removal rate and low silicon loss.

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

[0026] The siloxane delivery pipe first guides the siloxane to the separation tower, and then reaches the mixer through the bottom of the separation tower. Through the above design, during the period when the mixture stays in the reaction tank, it is inevitable that there are impurity ions that do not participate in the complex reaction. The impurities that do not participate in the reaction cannot be filtered by the filter. In the separation tower, the remaining impurity ions are captured by the siloxane again, and a complex reaction occurs. The high-boiling-point complex is deposited in the bottom of the separation tower, and then enters the first mixer and is finally filtered by the filter.

[0027] Because the complex reaction removes impurities first, the traditional five-stage or six-stage main tower distillation is reduced to a 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 utility model has a simple process flow, can reduce the number of subsequent distillation towers, 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 THE DRAWINGS

[0029] Figure 1A schematic diagram of the structure of a device for removing impurities from trichlorosilane provided in an embodiment of the utility model;

[0030] Figure 2 for Figure 1 A magnified 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, fourth distillation tower 16. DETAILED DESCRIPTION

[0034] In order to further explain the technical means and effects adopted by the utility model to achieve the predetermined utility model purpose, the specific implementation methods, structures, features and effects of the utility model application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0035] Before elaborating in detail the device and method for removing impurities from trichlorosilane of the utility model, it is necessary to further explain the complex reaction mentioned in the utility model to achieve better results.

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

[0037] The utility model is further described in detail below in conjunction with the accompanying drawings and embodiments.

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

[0039] The reaction part includes a first mixer and a reaction tank 1, wherein the inlet of the first mixer is connected to one end of a first feed pipe 2 and a second feed pipe 3, and a plurality of baffles 4 are arranged in a staggered manner 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 filtering part 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 the siloxane delivery pipe 7, the bottom of the separation tower 6 is connected to the other end of the first feed pipe 2, for guiding the siloxane to the first mixer, and the top collection 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, thereby prolonging 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 generate a high-boiling point complex, which is then filtered through the filter 5, with a high impurity removal rate and low silicon loss.

[0044] After the complexation, the impurities contained in trichlorosilane and dichlorodihydrosilane are greatly reduced, and they enter the separation tower 6 and the distillation unit for purification in turn, so as to produce high-quality liquid trichlorosilane.

[0045] The siloxane delivery pipe 7 first guides the siloxane to the separation tower 6, and then reaches the mixer through the bottom of the separation tower 6. With the above design, it is inevitable that there are impurity ions that do not participate in the complex reaction during the mixture stays in the reaction tank 1. The impurities that do not participate in the reaction cannot be filtered by the filter 5. In the separation tower 6, the remaining impurity ions are captured by the siloxane again, and a complex reaction occurs. The high-boiling-point complex is deposited in the bottom of the separation tower 6, and then enters the first mixer, and is finally filtered by the filter 5.

[0046] Because the complex reaction removes impurities first, the traditional five-stage or six-stage main tower distillation is reduced to a 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 utility model, the utility model has a simple process flow, can reduce the number of subsequent distillation towers, reduce equipment investment, improve the removal efficiency of impurities in trichlorosilane, has strong operation continuity, high safety, and is convenient for industrial production.

[0048] Specifically, the filter 5 adopts a sintered filter, the mesh number of the sintered filter is ≤1μm, the number of units is ≥2, one is in use and the other is in standby. When the flux is less than the normal flow rate, the standby 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 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 tube shell 8 and a spiral blade 9 coaxially arranged in the flow guide tube shell 8.

[0052] In this embodiment, specifically, the spiral blades 9 divide the inner space of the flow guide 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 flow guide 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, two adjacent branch spiral blades are respectively a first branch spiral blade 901 and a 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 speed of the material is blocked by the second branch spiral blade 902, and the original flow trajectory of the material is disrupted, the flow speed 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 speed 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 complex reaction.

[0056] like Figure 2 As shown, in a specific embodiment, it also includes a second mixer, which includes an outer sleeve 10 and a tapered tube 11, the tapered tube 11 is coaxially arranged in the outer sleeve 10, 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, the outlet of the outer sleeve 10 is connected to the inlet of the guide tube shell 8, and 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, so that siloxane is accelerated 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 also included, one end of which 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 guide 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 the 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 tower bottom, and the impurity-removed mixture of trichlorosilane and dichlorosilane enters the primary distillation tower 13 through the top sampling pipe of the separation tower 6;

[0062] In the primary distillation tower 13, dichlorosilane enters the anti-disproportionator through the top sampling pipe to participate in the anti-disproportionation reaction, and trichlorosilane containing a small amount of impurities enters the secondary 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 the heavy component 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 third-stage distillation tower 15, the light component impurities therein flow back to the first-stage distillation tower 13 from the top sampling pipe, 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 gathered 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-stage distillation tower 16 and the top material of the third-stage distillation tower 15 are refluxed respectively and distilled repeatedly, 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 of 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 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 the liquid chromatography detection, the contents of boron and phosphorus impurities in the top fraction of the separation tower 6 can be controlled to be 0.001 ug / mL.

[0073] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the utility model, which should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A device for removing impurities from trichlorosilane, characterized in that: include: A reaction part, the reaction part comprises a first mixer and a reaction tank, the inlet of the first mixer is connected to one end of the first feed pipe and the second feed pipe, a plurality of baffles are staggeredly arranged in the reaction tank to form a baffle channel in the reaction tank, one end of the baffle channel is connected to the outlet of the first mixer; A filtering section, wherein the filtering section comprises 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 a siloxane delivery pipe, the bottom of the separation tower is connected to the other end of the first feed pipe for guiding the siloxane to the first mixer, and the top collection 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 tube shell and a spiral blade coaxially arranged in the flow guide tube 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, wherein 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 of which 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 comprises a primary distillation tower, a secondary distillation tower, a tertiary distillation tower and a quaternary distillation tower, the top sampling pipe of the separation tower is connected to the inlet of the primary distillation tower, the top sampling pipe of the primary distillation tower is connected to an anti-disproportionator, the side sampling pipe of the primary distillation tower is connected to the inlet of the secondary distillation tower, the top sampling pipe of the secondary distillation tower is connected to the inlet of the tertiary distillation tower, the bottom of the secondary distillation tower is connected to an adsorption mechanism, the top sampling pipe of the tertiary distillation tower is connected to the inlet of the primary distillation tower, the bottom of the tertiary distillation tower is connected to the inlet of the quaternary distillation tower, the top sampling pipe of the quaternary distillation tower is connected to a high purity tank, and the bottom of the quaternary distillation tower is connected to the inlet of the secondary distillation tower.

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

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