Trichlorosilane multi-tower differential pressure coupling rectification system and rectification method

Abstract

The invention provides a trichlorosilane multi-tower differential pressure coupling rectification system and rectification method. The trichlorosilane multi-tower differential pressure coupling rectification system comprises a coarse separation tower, a light component removal tower and a heavy component removal tower, the light component removal tower comprises a crude distillation primary tower and a rectification primary tower, and the heavy component removal tower comprises a crude distillation secondary tower; the primary crude distillation tower is provided with a first reboiler, and the secondary crude distillation tower is provided with a second reboiler; a tower top outlet of the coarse separation tower is communicated with the second reboiler and then is communicated with a raw material inlet of the primary coarse distillation tower, and a tower top outlet of the primary rectification tower is communicated with the first reboiler. According to the trichlorosilane multi-tower differential pressure coupling rectification system provided by the invention, the reflux ratio of the light component removal tower can be reduced, the energy consumption in the trichlorosilane rectification process is effectively saved, and the equipment investment and operation cost are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rectification, and particularly relates to a multi-tower differential pressure coupled rectification system and method for trichlorosilane. BACKGROUND

[0002] In the production of high-purity polysilicon, the Siemens method has long been considered a standard process, which decomposes trichlorosilane into high-purity silicon through chemical vapor deposition (CVD) technology. However, with the rapid development of the global solar photovoltaic industry, the demand for high-purity polysilicon has increased dramatically, and the high energy consumption and high cost of the traditional Siemens method have gradually emerged, limiting its economic and sustainability in large-scale production.

[0003] A major challenge of the traditional Siemens method is the handling of silicon tetrachloride. In the process, silicon tetrachloride is generated in large quantities as a byproduct, and its handling and disposal not only increase production costs, but also pose an environmental burden. Therefore, how to efficiently utilize silicon tetrachloride has become an important issue for improving process economics.

[0004] The core of the improved Siemens method is to comprehensively utilize silicon tetrachloride through cold hydrogenation technology. Cold hydrogenation technology converts silicon tetrachloride into trichlorosilane by promoting the reaction of silicon powder, hydrogen, and silicon tetrachloride using a catalyst at high temperature. This process not only improves the utilization efficiency of silicon tetrachloride, reduces waste emissions, but also reduces production costs and improves resource utilization.

[0005] However, the synthesis gas produced in the cold hydrogenation process contains a variety of components, including the target product trichlorosilane, byproduct dichlorodisilane, and other heavy components (such as methyl dichlorosilane). Therefore, how to effectively separate and purify trichlorosilane from synthesis gas has become a key process.

[0006] Figure 1 A schematic diagram of a trichlorosilane rectification system in the prior art. As shown in FIG. 1, the rectification system includes a synthesis gas generator 1, a rectification tower 2, a condenser 3, a liquid separator 4, a trichlorosilane storage tank 5, and a trichlorosilane product tank 6. Figure 1As shown, the existing rectification system mainly includes a coarse separation column 1, a first-stage coarse distillation column 2, a second-stage coarse distillation column 3, a third-stage coarse distillation column 4, a first-stage rectification column 5, a second-stage rectification column 6, and a first-stage reduction column 7. The material to be separated (synthetic liquid) enters the coarse separation column 1 through the raw material inlet of the coarse separation column 1 for coarse separation treatment. The silicon tetrachloride obtained by side extraction of the coarse separation column 1 is returned to the cold hydrogenation reactor, and the high-boiling substances are discharged from the column bottom to obtain a first intermediate material (mainly including trichlorosilane and dichlorodisilane). The first intermediate material is extracted from the top of the coarse separation column 1 and enters the first-stage coarse distillation column 2 through the raw material inlet of the first-stage coarse distillation column 2 for first-stage coarse distillation treatment. The light components (mainly including dichlorodisilane) in the first intermediate material are extracted from the top of the first-stage coarse distillation column 2 to obtain a second intermediate material (mainly including trichlorosilane and heavy components). The second intermediate material is extracted from the column bottom of the first-stage coarse distillation column 2 and enters the second-stage coarse distillation column 3 through the raw material inlet of the second-stage coarse distillation column 3 for second-stage coarse distillation treatment. The heavy components with a boiling point higher than trichlorosilane in the second intermediate material are extracted from the column bottom of the second-stage coarse distillation column 3, and the light components (mainly including trichlorosilane) in the second intermediate material are extracted from the top of the second-stage coarse distillation column 3 to obtain a third intermediate material. The third intermediate material enters the column bottom reboiler of the third-stage coarse distillation column 4 to provide heat for the reboiler of the third-stage coarse distillation column 4. Part of the third intermediate material is returned, and the other part enters the third-stage coarse distillation column 4 through the raw material inlet of the third-stage coarse distillation column 4 for third-stage coarse distillation treatment to further separate the heavy components with a boiling point higher than trichlorosilane in the third intermediate material. The heavy components in the third intermediate material are extracted from the column bottom of the third-stage coarse distillation column 4, and the fourth intermediate material mainly including trichlorosilane in the third intermediate material is extracted from the top of the third-stage coarse distillation column 4. The fourth intermediate material enters the column bottom reboiler of the first-stage coarse distillation column 2 to provide heat for the column bottom reboiler of the first-stage coarse distillation column 2. Part of the fourth intermediate material is returned, and the other part enters the first-stage rectification column 5 for separation treatment. In the first-stage rectification column 5, the light components (mainly including boron and phosphorus compounds with a boiling point between dichlorodisilane and trichlorosilane) in the fourth intermediate material are extracted from the top of the first-stage rectification column 5, and the fifth intermediate material mainly including trichlorosilane is extracted from the column bottom of the first-stage rectification column 5. The fifth intermediate material enters the second-stage rectification column 6 through the raw material inlet of the second-stage rectification column 6 for separation treatment. In the second-stage rectification column 6, the heavy components in the fifth intermediate material are further separated to obtain high-purity trichlorosilane. The first-stage reduction column 7 in the reduction process provides heat for the column bottom reboiler of the second-stage rectification column 6. The heavy components in the fifth intermediate material are extracted from the column bottom of the second-stage rectification column 6 and enter the third-stage coarse distillation column 4 for further separation to further extract trichlorosilane in the fifth intermediate material. The high-purity trichlorosilane obtained from the second-stage rectification column 6 is extracted from the top of the second-stage rectification column 6, enters the column bottom reboiler of the first-stage rectification column 5 to provide heat for the first-stage rectification column 5, and part of the high-purity trichlorosilane is returned, and the other part is sent to the reduction process.

[0007] In the prior art rectification system, the crude distillation secondary tower 3 provides heat for the crude distillation tertiary tower 4, the crude distillation tertiary tower 4 provides heat for the crude distillation primary tower 2, the reduction primary tower 7 provides heat for the rectification secondary tower 6, and the rectification secondary tower 6 provides heat for the rectification primary tower 5. However, the reflux ratio of the crude distillation secondary tower 3, the crude distillation tertiary tower 4 and the rectification secondary tower 6 is 3-5, and the gas phase flow at the top of the crude distillation secondary tower 3, the crude distillation tertiary tower 4 and the rectification secondary tower 6 is large, and the material amount of the crude distillation primary tower 2 is small. In order to enable the crude distillation primary tower 2 to utilize the heat of the crude distillation secondary tower 3 and the crude distillation tertiary tower 4, and enable the rectification primary tower 5 to utilize the heat of the rectification secondary tower 6, the reflux ratio of the crude distillation primary tower 2 and the rectification primary tower 5 is usually increased to 50-150, which is much larger than the actual reflux ratio required by the crude distillation primary tower 2 and the rectification primary tower 5, thereby increasing the equipment investment and operation cost of the crude distillation primary tower 2 and the rectification primary tower 5. SUMMARY

[0008] The main purpose of the present application is to provide a trichlorosilane multi-tower differential pressure coupled rectification system, which can reduce the reflux ratio of the light removal tower, effectively save the energy consumption in the trichlorosilane rectification process, and reduce the equipment investment and operation cost.

[0009] The present application also provides a trichlorosilane multi-tower differential pressure coupled rectification method, which uses the above-mentioned rectification system, so that the method can reduce the reflux ratio of the light removal tower and reduce the energy consumption.

[0010] In the first aspect, the present application provides a trichlorosilane multi-tower differential pressure coupled rectification system, which comprises a crude separation tower, a light removal tower and a heavy removal tower; the light removal tower comprises a crude distillation primary tower and a rectification primary tower, and the heavy removal tower comprises a crude distillation secondary tower;

[0011] The crude distillation primary tower has a first reboiler, and the crude distillation secondary tower has a second reboiler;

[0012] The top outlet of the crude separation tower is communicated with the second reboiler, and then communicated with the raw material inlet of the crude distillation primary tower, and the top outlet of the rectification primary tower is communicated with the first reboiler.

[0013] The rectification system as described above further comprises a crude distillation tertiary tower and a rectification secondary tower, and further comprises a reduction primary tower;

[0014] The crude distillation tertiary tower has a third reboiler, and the rectification secondary tower has a fourth reboiler;

[0015] The tower bottom outlet of the crude distillation first-stage tower is communicated with the raw material inlet of the crude distillation second-stage tower, the tower top outlet of the crude distillation second-stage tower is communicated with the raw material inlet of the crude distillation third-stage tower, the tower top outlet of the crude distillation third-stage tower is communicated with the raw material inlet of the rectification first-stage tower, the tower bottom outlet of the rectification first-stage tower is communicated with the raw material inlet of the rectification second-stage tower, the tower bottom outlet of the rectification second-stage tower is communicated with the raw material inlet of the crude distillation third-stage tower, the tower top outlet of the reduction first-stage tower is communicated with the fourth reboiler, and the tower top outlet of the rectification second-stage tower is communicated with the third reboiler, and then the reduction process is performed.

[0016] The rectification system as described above, wherein the crude distillation tower has a tower pressure of 0.40-0.47 MPaG, a tower temperature of 87-122℃, a reflux ratio of 3.2-4.2, and a tower diameter of 3700-4300 mm.

[0017] The rectification system as described above, wherein the crude distillation first-stage tower has a tower pressure of 0.23-0.25 MPaG, a tower temperature of 58-72℃, a reflux ratio of 13-23, and a tower diameter of 3300-3900 mm.

[0018] The rectification system as described above, wherein the crude distillation second-stage tower has a tower pressure of 0.15-0.19 MPaG, a tower temperature of 61-65℃, a reflux ratio of 2.5-3.5, and a tower diameter of 6000-6600 mm.

[0019] The rectification system as described above, wherein the crude distillation third-stage tower has a tower pressure of 0.15-0.18 MPaG, a tower temperature of 61-65℃, a reflux ratio of 2.3-3.3, and a tower diameter of 5400-6000 mm.

[0020] The rectification system as described above, wherein the rectification first-stage tower has a tower pressure of 0.40-0.41 MPaG, a tower temperature of 87-88℃, a reflux ratio of 30-50, and a tower diameter of 3100-3700 mm.

[0021] The rectification system as described above, wherein the rectification second-stage tower has a tower pressure of 0.28-0.30 MPaG, a tower temperature of 76-78℃, a reflux ratio of 2.7-3.7, and a tower diameter of 4900-5500 mm.

[0022] The rectification system as described above, wherein the reduction first-stage tower has a tower pressure of 0.50-0.52 MPaG, a tower temperature of 93-127℃, a reflux ratio of 2.0-3.0, and a tower diameter of 5700-6800 mm.

[0023] In a second aspect, the present application provides a method for rectifying trichlorosilane by using a multi-tower differential pressure coupled rectification system as described above.

[0024] The three-chlorosilane multi-tower differential pressure coupled rectification system provided by the application can reduce the reflux ratio of the light-removing tower, effectively save the energy consumption in the three-chlorosilane rectification process, and reduce the equipment investment and operation cost. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the accompanying drawings needed to be used in the description of the embodiments of the present application or the related art are briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and other accompanying drawings can be obtained by those skilled in the art without any creative effort on the basis of these accompanying drawings.

[0026] Figure 1 It is a schematic diagram of the three-chlorosilane rectification system in the prior art;

[0027] Figure 2 It is a schematic diagram of the three-chlorosilane multi-tower differential pressure coupled rectification system provided by the application.

[0028] Explanation of reference signs:

[0029] 1 - coarse separation tower; 2 - coarse distillation first-stage tower; 3 - coarse distillation second-stage tower; 4 - coarse distillation third-stage tower; 5 - rectification first-stage tower; 6 - rectification second-stage tower; 7 - reduction first-stage tower; 8 - first reboiler; 9 - second reboiler; 10 - third reboiler; 11 - fourth reboiler. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope of the present application.

[0031] In a first aspect, the present application provides a three-chlorosilane multi-tower differential pressure coupled rectification system, as shown in Figure 2 which comprises a coarse separation tower 1, a light-removing tower and a heavy-removing tower; the light-removing tower comprises a coarse distillation first-stage tower 2 and a rectification first-stage tower 5, and the heavy-removing tower comprises a coarse distillation second-stage tower 3; the coarse distillation first-stage tower 2 is provided with a first reboiler 8, and the coarse distillation second-stage tower 3 is provided with a second reboiler 9; the tower top outlet of the coarse separation tower 1 is communicated with the second reboiler 9, and then communicated with the raw material inlet of the coarse distillation first-stage tower 2, and the tower top outlet of the rectification first-stage tower 5 is communicated with the first reboiler 8.

[0032] The material to be separated in the present application is from a condensing system, mainly including trichlorosilane, silicon tetrachloride, dichlorodisilane and other impurity components.

[0033] The rectification system of the present application specifically comprises: the material to be separated is introduced into the crude separation tower 1 from the raw material inlet of the crude separation tower 1 for crude separation treatment, the silicon tetrachloride is returned to the cold hydrogenation reactor from the lower side of the crude separation tower 1, the high-boiling substances are discharged from the tower kettle, i.e. the heavy components are separated, and the first intermediate material (mainly including trichlorosilane and dichlorodisilane) is obtained. The first intermediate material is output from the overhead outlet of the crude separation tower 1 and introduced into the second reboiler 9 of the crude distillation secondary tower 3 to provide heat for the crude distillation secondary tower 3, forming a liquid phase, part of which is introduced into the crude distillation primary tower 2 from the raw material inlet of the crude distillation primary tower 2 for the first crude distillation treatment, so that the light components (mainly including dichlorodisilane) in the first intermediate material are taken out from the overhead of the crude distillation primary tower 2, and the second intermediate material (mainly including trichlorosilane and heavy components) is obtained. The crude distillation secondary tower 3 can fully utilize the heat of the overhead gas phase of the crude separation tower 1, thereby reducing the total steam consumption.

[0034] Meanwhile, the light components (mainly including boron and phosphorus compounds with boiling points between dichlorodisilane and trichlorosilane) in the fourth intermediate material in the rectification primary tower 5 are output from the overhead outlet of the rectification primary tower 5 and introduced into the first reboiler 8 of the crude distillation primary tower 2 to provide heat for the crude distillation primary tower 2, and the light components (mainly including dichlorodisilane) are output, which can reduce the reflux ratio of the crude distillation primary tower 2 and the rectification primary tower 5. The heat of the rectification primary tower 5 is provided by steam. The crude distillation primary tower 2 can fully utilize the heat of the overhead gas phase of the rectification primary tower 5, thereby reducing the total steam consumption.

[0035] The rectification system of the present application can reduce the reflux ratio of the light component removal tower, effectively save the energy consumption in the trichlorosilane rectification process, and reduce the equipment investment and operating cost.

[0036] In some embodiments of the present application, the heavy component removal tower further comprises a crude distillation tertiary tower 4 and a rectification secondary tower 6, and the rectification system further comprises a reduction primary tower 7; the crude distillation tertiary tower 4 has a third reboiler 10, and the rectification secondary tower 6 has a fourth reboiler 11; the tower kettle outlet of the crude distillation primary tower 2 is in communication with the raw material inlet of the crude distillation secondary tower 3, the overhead outlet of the crude distillation secondary tower 3 is in communication with the raw material inlet of the crude distillation tertiary tower 4, the overhead outlet of the crude distillation tertiary tower 4 is in communication with the raw material inlet of the rectification primary tower 5, the tower kettle outlet of the rectification primary tower 5 is in communication with the raw material inlet of the rectification secondary tower 6, the tower kettle outlet of the rectification secondary tower 6 is in communication with the raw material inlet of the crude distillation tertiary tower 4, the overhead outlet of the reduction primary tower 7 is in communication with the fourth reboiler 11, and the overhead outlet of the rectification secondary tower 6 is in communication with the third reboiler 10, and then the reduction process.

[0037] In the present application, the second intermediate material (mainly including trichlorosilane and heavy components) is taken out from the bottom of the first crude distillation column 2, and is introduced into the second crude distillation column 3 through the raw material inlet of the second crude distillation column 3 for the second crude distillation treatment, so that the heavy components with a higher boiling point than trichlorosilane in the second intermediate material are taken out from the bottom of the second crude distillation column 3, and the third intermediate material (mainly including trichlorosilane) is obtained;

[0038] The third intermediate material is taken out from the top of the second crude distillation column 3, and is introduced into the third crude distillation column 4 through the raw material inlet of the third crude distillation column 4 for the third crude distillation treatment, so as to further separate the heavy components with a higher boiling point than trichlorosilane in the third intermediate material, and the heavy components in the third intermediate material are taken out from the bottom of the third crude distillation column 4, and the fourth intermediate material (mainly including trichlorosilane) remaining in the third intermediate material is taken out from the top of the third crude distillation column 4, and is introduced into the first rectification column 5 through the raw material inlet of the first rectification column 5 for the first rectification treatment, in the first rectification column 5, the light components (mainly including boron and phosphorus compounds with a boiling point between dichlorosilane and trichlorosilane) in the fourth intermediate material are taken out from the top of the first rectification column 5, and the fifth intermediate material (mainly including trichlorosilane) remaining is taken out from the bottom of the first rectification column 5; the fifth intermediate material is introduced into the second rectification column 6 through the raw material inlet of the second rectification column 6 for the second rectification treatment, in the second rectification column 6, the heavy components in the fifth intermediate material are further separated, and high-purity trichlorosilane is obtained. After the first reduction column 7 in the reduction process provides heat for the fourth reboiler 11 of the second rectification column 6, part of the reflux is returned, and the other part is introduced into the third crude distillation column 4 through the raw material inlet of the third crude distillation column 4 for further separation, so as to further extract trichlorosilane in the fifth intermediate material, and the high-purity trichlorosilane obtained from the second rectification column 6 is taken out from the top of the second rectification column 6, and is introduced into the third reboiler 10 of the third crude distillation column 4 to provide heat for the third crude distillation column 4, and the high-purity trichlorosilane after using the heat is taken to the reduction process.

[0039] By optimizing the coupling relationship among the first crude distillation column 2, the second crude distillation column 3, the third crude distillation column 4, the first rectification column 5, the second rectification column 6 and the first reduction column 7, the present application can reduce the reflux ratio of the first crude distillation column 2 and the first rectification column 5, effectively save the energy consumption in the trichlorosilane rectification process, reduce the equipment investment and operating cost, and has a wide application prospect.

[0040] The rectification system of the present application can reduce the reflux ratio, column diameter, steam consumption, volume of reflux tank and flow of reflux pump of the first crude distillation column 2 and the first rectification column 5, and can reduce the column pressure of the second crude distillation column 3 and the third crude distillation column 4, so as to obtain high-purity trichlorosilane under the conditions of saving energy consumption, equipment investment and operating cost.

[0041] In the present application, an example is exemplarily illustrated by taking 5wt polysilicon production capacity per year as an example.

[0042] In some embodiments of the present application, the column pressure of the rough fractionating tower 1 is 0.40-0.47 MPaG, for example, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47 MPaG or a range between any two of them; the column temperature is 87-122℃, for example, 87, 90, 92, 95, 100, 110, 120, 122℃ or a range between any two of them; the reflux ratio is 3.2-4.2, for example, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2 or a range between any two of them; and the column diameter is 3700-4300 mm, for example, 3700, 3800, 3900, 4000, 4100, 4200, 4300 mm or a range between any two of them.

[0043] Figure 1 In the shown rectifying system, the column pressure of the rough fractionating tower 1 is 0.15-0.22 MPaG, the column temperature is 60-97℃, the reflux ratio is 3.7, and the column diameter is 4600 mm. It can be seen that the rectifying system of the present application can reduce the column diameter of the rough fractionating tower 1, and the column pressure and column temperature of the rough fractionating tower 1 of the present application are higher, which can provide heat for the rough distillation secondary tower 3 and reduce the steam consumption.

[0044] In some embodiments of the present application, the column pressure of the rough distillation primary tower 2 is 0.23-0.25 MPaG, for example, 0.23, 0.235, 0.24, 0.245, 0.25 MPaG or a range between any two of them; the column temperature is 58-72℃, for example, 58, 60, 62, 65, 68, 70, 72℃ or a range between any two of them; the reflux ratio is 13-23, for example, 13, 15, 17, 19, 20, 23 or a range between any two of them; and the column diameter is 3300-3900 mm, for example, 3300, 3400, 3500, 3600, 3700, 3800, 3900 mm or a range between any two of them.

[0045] Figure 1In the shown rectification system, the tower pressure of the primary tower 2 for crude distillation is 0.23-0.25 MPaG, the tower temperature is 58-72℃, the reflux ratio is 66.4, and the tower diameter is 6400 mm. It can be seen that the rectification system of the present application can reduce the reflux ratio and the tower diameter of the primary tower 2 for crude distillation, and can effectively save the energy consumption in the rectification process of trichlorosilane.

[0046] In some embodiments of the present application, the tower pressure of the secondary tower 3 for crude distillation is 0.15-0.19 MPaG, for example, it can be 0.15 MPaG, 0.16 MPaG, 0.17 MPaG, 0.18 MPaG, 0.19 MPaG, or a range consisting of any two of them; the tower temperature is 61-65℃, for example, it can be 61℃, 62℃, 63℃, 64℃, 65℃, or a range consisting of any two of them; the reflux ratio is 2.5-3.5, for example, it can be 2.5, 2.7, 2.9, 3.0, 3.3, 3.5, or a range consisting of any two of them; and the tower diameter is 6000-6600 mm, for example, it can be 6000 mm, 6100 mm, 6200 mm, 6300 mm, 6400 mm, 6500 mm, 6600 mm, or a range consisting of any two of them.

[0047] Figure 1 In the shown rectification system, the tower pressure of the secondary tower 3 for crude distillation is 0.75-0.79 MPaG, the tower temperature is 111-113℃, the reflux ratio is 4.1, and the tower diameter is 6700 mm. It can be seen that the rectification system of the present application can reduce the tower pressure, the tower temperature, the reflux ratio, and the tower diameter of the secondary tower 3 for crude distillation, which is beneficial to the removal of heavy components in the secondary tower 3 for crude distillation, effectively saves the energy consumption in the rectification process of trichlorosilane, and reduces the equipment investment and the operating cost.

[0048] In some embodiments of the present application, the tower pressure of the tertiary tower 4 for crude distillation is 0.15-0.18 MPaG, for example, it can be 0.15 MPaG, 0.16 MPaG, 0.165 MPaG, 0.17 MPaG, 0.18 MPaG, or a range consisting of any two of them; the tower temperature is 61-65℃, for example, it can be 61℃, 62℃, 63℃, 64℃, 65℃, or a range consisting of any two of them; the reflux ratio is 2.3-3.3, for example, it can be 2.3, 2.5, 2.8, 3.0, 3.1, 3.3, or a range consisting of any two of them; and the tower diameter is 5400-6000 mm, for example, it can be 5400 mm, 5500 mm, 5600 mm, 5700 mm, 5800 mm, 5900 mm, 6000 mm, or a range consisting of any two of them.

[0049] Figure 1In the shown rectification system, the tower pressure of the crude distillation third-stage tower 4 is 0.41-0.44 MPaG, the tower temperature is 88-90℃, the reflux ratio is 3.8, and the tower diameter is 6100 mm. It can be seen that the rectification system of the present application can reduce the tower pressure, tower temperature, reflux ratio and tower diameter of the crude distillation third-stage tower 4, effectively saving the energy consumption in the trichlorosilane rectification process, and reducing the equipment investment and operating cost.

[0050] In the present application, the crude distillation third-stage tower 4 is used as the coupling last-stage tower, which can reduce the tower pressure, tower temperature, reflux ratio and tower diameter of the crude distillation third-stage tower 4, and is beneficial to the removal of heavy components in the crude distillation third-stage tower 4.

[0051] In some embodiments of the present application, the tower pressure of the rectification first-stage tower 5 is 0.40-0.41 MPaG, for example, it can be 0.40 MPaG, 0.402 MPaG, 0.404 MPaG, 0.406 MPaG, 0.408 MPaG, 0.41 MPaG or a range consisting of any two of them; the tower temperature is 87-88℃, for example, it can be 87℃, 87.2℃, 87.4℃, 87.6℃, 87.8℃, 88℃ or a range consisting of any two of them; the reflux ratio is 30-50, for example, it can be 30, 32, 35, 38, 40, 42, 45, 48, 50 or a range consisting of any two of them; and the tower diameter is 3100-3700 mm, for example, it can be 3100 mm, 3200 mm, 3300 mm, 3400 mm, 3500 mm, 3600 mm, 3700 mm or a range consisting of any two of them.

[0052] Figure 1 In the shown rectification system, the tower pressure of the rectification first-stage tower 5 is 0.15-0.16 MPaG, the tower temperature is 61-62℃, the reflux ratio is 123.1, and the tower diameter is 5700 mm. It can be seen that the rectification system of the present application can reduce the reflux ratio and tower diameter of the rectification first-stage tower 5, which can effectively save the energy consumption in the trichlorosilane rectification process. Moreover, the tower pressure and tower temperature of the rectification first-stage tower 5 of the present application are relatively high, which can provide heat for the crude distillation first-stage tower 2 and reduce the steam consumption.

[0053] In some embodiments of the present application, the tower pressure of the rectification secondary tower 6 is 0.28-0.30 MPaG, for example, it can be 0.28 MPaG, 0.285 MPaG, 0.29 MPaG, 0.295 MPaG, 0.30 MPaG or a range consisting of any two of them; the tower temperature is 76-78℃, for example, it can be 76℃, 76.5℃, 77℃, 77.5℃, 78℃ or a range consisting of any two of them; the reflux ratio is 2.7-3.7, for example, it can be 2.7, 3.0, 3.2, 3.5, 3.6, 3.7 or a range consisting of any two of them; the tower diameter is 4900-5500 mm, for example, it can be 4900 mm, 5000 mm, 5100 mm, 5200 mm, 5300 mm, 5400 mm, 5500 mm or a range consisting of any two of them.

[0054] Figure 1 In the rectification system shown, the tower pressure of the rectification secondary tower 6 is 0.28-0.30 MPaG, the tower temperature is 76-78℃, the reflux ratio is 3.2 and the tower diameter is 5500 mm. It can be seen that the tower pressure, tower temperature, reflux ratio and tower diameter of the rectification secondary tower 6 in the rectification system of the present application are basically equivalent to those of the rectification secondary tower 6 in the rectification system of the prior art. Figure 1

[0055] In some embodiments of the present application, the tower pressure of the reduction primary tower 7 is 0.50-0.52 MPaG, for example, it can be 0.50 MPaG, 0.505 MPaG, 0.51 MPaG, 0.515 MPaG, 0.52 MPaG or a range consisting of any two of them; the tower temperature is 93-127℃, for example, it can be 93℃, 95℃, 98℃, 100℃, 110℃, 120℃, 125℃, 127℃ or a range consisting of any two of them; the reflux ratio is 2.0-3.0, for example, it can be 2.0, 2.2, 2.4, 2.5, 2.7, 3.0 or a range consisting of any two of them; the tower diameter is 5700-6800 mm, for example, it can be 5700 mm, 5900 mm, 6000 mm, 6100 mm, 6300 mm, 6500 mm, 6800 mm or a range consisting of any two of them.

[0056] Figure 1 In the rectification system shown, the tower pressure of the reduction primary tower 7 is 0.50-0.52 MPaG, the tower temperature is 93-127℃, the reflux ratio is 2.5 and the tower diameter is 5700-6800 mm. It can be seen that the tower pressure, tower temperature, reflux ratio and tower diameter of the reduction primary tower 7 in the rectification system of the present application are basically equivalent to those of the reduction primary tower 7 in the rectification system of the prior art. Figure 1 ​The tower pressure, tower temperature, reflux ratio and tower diameter of the reducing primary tower 7 are substantially equivalent, and the distillation secondary tower 6 and the crude distillation tertiary tower 4 can be provided with heat, and the steam consumption is reduced.

[0057] The present application can improve the separation efficiency of the coarse separation tower 1, the crude distillation primary tower 2, the crude distillation secondary tower 3, the crude distillation tertiary tower 4, the distillation primary tower 5 and the distillation secondary tower 6 respectively, and high-purity trichlorosilane is obtained.

[0058] It can be understood that the tower pressure of the present application is the whole tower pressure, and in each tower, the tower kettle pressure is greater than the tower top pressure, and the pressure of the lower stage tower coupled is less than the pressure of the upper stage tower coupled.

[0059] The tower temperature of the present application is the whole tower temperature.

[0060] As shown in Figure 2 Compared with the prior art distillation system as shown in Figure 1 The present application reduces the tower pressure and the tower temperature of the crude distillation secondary tower 3 and the crude distillation tertiary tower 4 respectively, reduces the reflux ratio of the crude distillation primary tower 2, the crude distillation secondary tower 3, the crude distillation tertiary tower 4 and the distillation primary tower 5 respectively, and reduces the tower diameter of the coarse separation tower 1, the crude distillation primary tower 2, the crude distillation secondary tower 3, the crude distillation tertiary tower 4 and the distillation primary tower 5 respectively, which not only can improve the separation efficiency, but also can effectively reduce the equipment investment and the operation cost.

[0061] Further, Figure 1 The total steam consumption of the distillation system as shown in Figure 2 The total steam consumption of the distillation system of the present application is 144.4t / h, and it can be concluded that compared with the prior art distillation system as shown in Figure 1 Compared with the prior art distillation system as shown in

[0062] In a second aspect, the present application provides a method for rectifying trichlorosilane by using a multi-tower differential pressure coupled rectification system as described above.

[0063] The method for rectifying trichlorosilane by using a multi-tower differential pressure coupled rectification system as described above can reduce the reflux ratio of the light-removing tower, i.e. the primary tower 2 for rough distillation and the primary tower 5 for rectification, and has the advantage of low energy consumption, and is suitable for wide application.

[0064] The technical solutions of the present application will be further described below in combination with specific examples.

[0065] Example 1

[0066] The multi-tower differential pressure coupled rectification system for trichlorosilane in this example is shown in FIG. 1, and includes: Figure 2

[0067] The primary tower 1, the primary tower 2 for rough distillation, the secondary tower 3 for rough distillation, the tertiary tower 4 for rough distillation, the primary tower 5 for rectification, the secondary tower 6 for rectification, and the primary tower 7 for reduction.

[0068] The primary tower 2 for rough distillation has a first reboiler 8, the secondary tower 3 for rough distillation has a second reboiler 9, the tertiary tower 4 for rough distillation has a third reboiler 10, and the secondary tower 6 for rectification has a fourth reboiler 11.

[0069] The overhead outlet of the primary tower 1 is communicated with the second reboiler 9, and then communicated with the raw material inlet of the primary tower 2 for rough distillation, and the overhead outlet of the primary tower 5 for rectification is communicated with the first reboiler 8.

[0070] The outlet of the kettle of the primary tower 2 for rough distillation is communicated with the raw material inlet of the secondary tower 3 for rough distillation, the overhead outlet of the secondary tower 3 for rough distillation is communicated with the raw material inlet of the tertiary tower 4 for rough distillation, the overhead outlet of the tertiary tower 4 for rough distillation is communicated with the raw material inlet of the primary tower 5 for rectification, the outlet of the kettle of the primary tower 5 for rectification is communicated with the raw material inlet of the secondary tower 6 for rectification, the outlet of the kettle of the secondary tower 6 for rectification is communicated with the raw material inlet of the tertiary tower 4 for rough distillation, the overhead outlet of the primary tower 7 for reduction is communicated with the fourth reboiler 11, and the overhead outlet of the secondary tower 6 for rectification is communicated with the third reboiler 10, and then goes to the reduction process.

[0071] Finally, it should be noted that other embodiments of the present application will be readily apparent to those skilled in the art upon considering the description herein and the disclosure of the application made herein. The present application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such variations, uses, or adaptations of the present application as come within the general scope of the application, other than those expressly set forth herein, and including those that are not presently, or are inherently, disclosed and directed to that which is inherently combinable with or reducible to the known art in this field of technology, without departing from the scope of the present application as defined by the appended claims. The scope of the present application is limited only by the claims that follow.​

Claims

1. A rectification system of trichlorosilane with multi-tower differential pressure coupling, characterized in that, The crude separation column, the light removal column and the heavy removal column; the light removal column comprises a first crude distillation column and a first rectification column, and the heavy removal column comprises a second crude distillation column; The first crude distillation column has a first reboiler, and the second crude distillation column has a second reboiler; The overhead outlet of the crude separation column is communicated with the second reboiler, and then communicated with the raw material inlet of the first crude distillation column, and the overhead outlet of the first rectification column is communicated with the first reboiler.

2. The rectification system of claim 1, wherein, The heavy removal column further comprises a third crude distillation column and a second rectification column, and the rectification system further comprises a first reduction column; The third crude distillation column has a third reboiler, and the second rectification column has a fourth reboiler; The bottom outlet of the first crude distillation column is communicated with the raw material inlet of the second crude distillation column, the overhead outlet of the second crude distillation column is communicated with the raw material inlet of the third crude distillation column, the overhead outlet of the third crude distillation column is communicated with the raw material inlet of the first rectification column, the bottom outlet of the first rectification column is communicated with the raw material inlet of the second rectification column, the bottom outlet of the second rectification column is communicated with the raw material inlet of the third crude distillation column, the overhead outlet of the first reduction column is communicated with the fourth reboiler, the overhead outlet of the second rectification column is communicated with the third reboiler, and then goes to the reduction process.

3. Distillation system according to claim 1 or 2, characterized in that The column pressure of the crude separation column is 0.40-0.47 MPaG, the column temperature is 87-122℃, the reflux ratio is 3.2-4.2, and the column diameter is 3700-4300 mm.

4. Distillation system according to any one of claims 1-3, characterized in that The column pressure of the first crude distillation column is 0.23-0.25 MPaG, the column temperature is 58-72℃, the reflux ratio is 13-23, and the column diameter is 3300-3900 mm.

5. Distillation system according to any of the claims 1-4, characterized in that The column pressure of the second crude distillation column is 0.15-0.19 MPaG, the column temperature is 61-65℃, the reflux ratio is 2.5-3.5, and the column diameter is 6000-6600 mm.

6. The rectification system of claim 2, wherein, The column pressure of the third crude distillation column is 0.15-0.18 MPaG, the column temperature is 61-65℃, the reflux ratio is 2.3-3.3, and the column diameter is 5400-6000 mm.

7. Distillation system according to any of the claims 1-6, characterized in that The column pressure of the first rectification column is 0.40-0.41 MPaG, the column temperature is 87-88℃, the reflux ratio is 30-50, and the column diameter is 3100-3700 mm.

8. The rectification system according to claim 2 or 6, characterized in that The column pressure of the second rectification column is 0.28-0.30 MPaG, the column temperature is 76-78℃, the reflux ratio is 2.7-3.7, and the column diameter is 4900-5500 mm.

9. Distillation system according to claim 2 or 6 or 8, characterized in that The column pressure of the first reduction column is 0.50-0.52 MPaG, the column temperature is 93-127℃, the reflux ratio is 2.0-3.0, and the column diameter is 5700-6800 mm.

10. A method for rectifying trichlorosilane by multi-column differential pressure coupling, characterized in that, The rectification system of any one of claims 1-9 is used.

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