A rectification purification system

Abstract

The application provides a rectification purification system, relates to the technical field of polysilicon, and comprises a main rectification tower, a side-line stripping tower with only a stripping section, a reaction rectification tower for DCS separation, a cooling assembly, and a reflux assembly for connecting the cooling assembly and the first reflux port and connecting the cooling assembly and the second reflux port. The second feed port is connected with the side-line sampling outlet. The main rectification tower is provided with a first feed port, a first overhead gas phase outlet, a first reflux port and a side-line sampling outlet. The side-line stripping tower is provided with a second feed port and a tower bottom TCS outlet. The upper portion of the reaction rectification tower is provided with a second overhead gas phase outlet and a second reflux port. The bottom portion of the reaction rectification tower is provided with a tower bottom liquid phase outlet. The side-line stripping tower has only the stripping section and does not have a rectification section, so that a tower overhead condensing device and a reflux device need not be independently arranged, and the number of devices is greatly reduced. The side-line stripping tower can directly sample material from the main tower by adopting a liquid phase self-flowing mode, and the devices and energy consumption for intermediate cooling, conveying and reheating are saved.

Description

Technical Field

[0001] This utility model relates to the field of polycrystalline silicon technology, and in particular to a distillation purification system. Background Technology

[0002] Polysilicon manufacturers currently employ numerous distillation columns in their purification systems to separate impurities from the raw materials (including dichlorosilane (DCS), trichlorosilane (TCS), silicon tetrachloride (STC), and boron (such as BCl3) and phosphorus (P) impurities). However, these distillation purification systems currently suffer from the following drawbacks:

[0003] 1. Current distillation purification systems require 2-3 complete distillation columns to form a production line. Each column is an independent "workstation," requiring its own column body, reboiler, condenser, reflux tank, pump, piping, and supports. This inevitably results in a large number of equipment, a large footprint, complex piping, and high initial investment.

[0004] 2. Most of the heat at the top of the distillation column is cooled to the required temperature by the condenser. The heat at the top of the column is not effectively utilized but is directly cooled and wasted.

[0005] 3. When the feed to the distillation column is cold, the amount of heat source (such as steam) required by the reboiler in the column bottom increases, which also increases the energy consumption of the unit.

[0006] 4. Condensers generally use circulating water coolers, and public works projects use a large amount of circulating water. Utility Model Content

[0007] In view of the above, the present invention provides a distillation and purification system, which aims to solve at least one of the defects pointed out in the background art.

[0008] To achieve the above objectives, this utility model provides the following technical solution:

[0009] This utility model provides a distillation purification system, comprising:

[0010] The main distillation column has a first feed inlet, a first overhead vapor outlet, a first reflux outlet, and a side stream outlet;

[0011] The side-stream stripping tower has a second feed inlet and a TCS outlet at the bottom of the tower; the second feed inlet is connected to the side-stream outlet.

[0012] A reactive distillation column is used for separation in a DCS (Distributed Control System). The upper part of the column has a second overhead vapor outlet and a second reflux port. The middle part of the column is a reaction section, which is equipped with a third feed inlet and a fourth feed inlet. The third feed inlet is connected to the first overhead vapor outlet. The fourth feed inlet is used to introduce a complexing agent. The bottom of the column has a bottom liquid outlet.

[0013] A cooling assembly for condensing the gas phase discharged from the first column top gas phase outlet, and for condensing the gas phase discharged from the second column top gas phase outlet;

[0014] A reflux assembly is used to connect the cooling assembly and the first reflux port, and to connect the cooling assembly and the second reflux port;

[0015] in:

[0016] The side-stream stripping tower has only a stripping section;

[0017] The complexing agent hardly reacts with DCS, but can undergo a rapid and reversible complexation reaction with BCl3 to generate a complex with a boiling point higher than that of DCS.

[0018] In some embodiments of this utility model, the cooling assembly includes:

[0019] The top air cooler is connected to the gas phase outlet of the first top column.

[0020] The top circulating water cooler is connected to the gas phase outlet of the second top of the tower.

[0021] In some embodiments of this utility model, the reflux assembly includes a first top reflux tank, a second top reflux tank, a first reflux pump, and a second reflux pump;

[0022] The first top gas phase outlet, the top air cooler, the first top reflux tank, the first reflux pump, and the first reflux port are connected in sequence.

[0023] The second top gas phase outlet, the top circulating water cooler, the second top reflux tank, the second reflux pump, and the second reflux port are connected in sequence.

[0024] In some embodiments of this invention, a high-purity DCS product is obtained in the second top reflux tank, and the high-purity DCS product is discharged from the outlet of the second top reflux tank by the second reflux pump.

[0025] In some embodiments of this utility model, a heat exchange component is also included, which is used to recover and utilize the heat at the bottom and top of the main distillation column.

[0026] In some embodiments of this utility model, the heat exchange assembly includes a tower top heat exchanger, a tower bottom high-boiling-point heat exchanger, and a feed heater;

[0027] The first column top gas phase outlet, the column top heat exchanger, and the column top air cooler are connected in sequence;

[0028] The main distillation column has a high-boiling point outlet at the bottom and near the bottom; the high-boiling point outlet passes sequentially through the high-boiling point heat exchanger at the bottom of the column and the feed heater; the feed heater is used to preheat the raw material entering the first feed inlet; the high-boiling point heat exchanger at the bottom of the column provides a reboiling heat source for the side-stream stripping column.

[0029] In some embodiments of this utility model, the outlet of the first top reflux tank is sequentially connected to the first reflux pump, the top heat exchanger, and the third feed inlet.

[0030] In some embodiments of this invention, the complexing agent includes dimethylformamide.

[0031] In some embodiments of this invention, the side-stream outlet is located above the first inlet and at the position where the TCS concentration is highest.

[0032] In some embodiments of this invention, the bottom liquid phase outlet of the tower is connected to the complexing agent recovery system.

[0033] The embodiments of this utility model have at least the following advantages or beneficial effects:

[0034] 1. A side-stream stripping column was added to the main distillation column, and a special reactive distillation process was adopted in the reactive distillation column to obtain electronic-grade TCS products and high-purity DCS products; that is, a variety of products can be obtained with a simple process flow and system.

[0035] 2. The side-stream stripper can be considered an auxiliary component of the main distillation column. The two are integrated to complete the separation work of two traditional distillation columns. The side-stream stripper only has a stripping section, not a rectification section, and therefore does not require a separate top condenser or reflux unit, significantly reducing the number of equipment. The side-stream stripper can directly extract material from the main column using gravity flow, eliminating the need for intermediate cooling, conveying, and reheating equipment and energy consumption.

[0036] Other features and advantages of this invention will be set forth in the following description. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of a distillation and purification system.

[0039] icon:

[0040] 1-Main distillation column, 11-First feed inlet, 12-First overhead vapor outlet, 13-First reflux inlet, 14-Side stream outlet.

[0041] 2-Side stripping tower, 21-Second feed inlet, 22-TCS outlet at the bottom of the tower.

[0042] 3-Reactive distillation column; 31-Second overhead vapor outlet; 32-Second reflux inlet; 33-Third feed inlet; 34-Fourth feed inlet; 35-Bottom liquid outlet.

[0043] 41-Top air cooler, 42-Top circulating water cooler

[0044] 51-First reflux tank at the top of the column, 52-Second reflux tank at the top of the column, 53-First reflux pump, 54-Second reflux pump.

[0045] 61-High boiling point heat exchanger at the bottom of the tower; 62-Heat exchanger at the top of the tower; 63-Feed heater. Detailed Implementation

[0046] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the present invention.

[0047] In the description of the embodiments of this utility model, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this utility model, "multiple" means two or more, unless otherwise explicitly specified.

[0048] In this embodiment of the invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment of the invention according to the specific circumstances.

[0049] The embodiments of this utility model will be described in detail below.

[0050] Example

[0051] See Figure 1This embodiment provides a distillation and purification system, including a main distillation column 1, a side-stream stripping column 2, a reactive distillation column 3, a cooling assembly, a reflux assembly, and a heat exchange assembly.

[0052] Main distillation column 1 is used for the preliminary separation of feedstocks (containing dichlorosilane (DCS), trichlorosilane (TCS), silicon tetrachloride (STC), boron (such as BCl3), and phosphorus (P)). Main distillation column 1 has a first feed inlet 11, a first overhead vapor outlet 12, a first reflux inlet 13, a side stream outlet 14, and a high-boiling-point outlet. The side stream outlet 14 is located above the first feed inlet 11 of the main distillation column 1 and at the position where the TCS concentration is highest. The high-boiling-point outlet is located at the bottom of the main distillation column 1 and near the bottom.

[0053] The side-stream stripping column 2 has only a stripping section (generally including a rectification section and a stripping section) for TCS separation; the side-stream stripping column 2 has a second feed inlet 21, a bottom TCS outlet 22, and a vapor return inlet; the second feed inlet 21 is connected to the side-stream outlet 14, the bottom TCS outlet 22 is used to export high-purity TCS products, and the vapor return inlet is connected to the upper part of the main rectification column 1.

[0054] The reactive distillation column 3 is used for separation in the DCS. The upper part of the reactive distillation column 3 is the rectification section, which has a second top vapor outlet 31 and a second reflux port 32. The middle part of the reactive distillation column 3 is the reaction section, which is equipped with a third feed port 33 and a fourth feed port 34. The third feed port 33 is connected to the first top vapor outlet 12. The fourth feed port 34 is used to introduce complexing agents such as dimethylformamide (DMF). The lower part of the reactive distillation column 3 is the stripping section, which has a bottom liquid outlet 35 at the bottom. The bottom liquid outlet 35 is connected to the complexing agent recovery system, which is used to recover complexing agents such as dimethylformamide (DMF).

[0055] The cooling assembly includes an overhead air cooler 41 and an overhead circulating water cooler 42. The overhead air cooler 41 is connected to the first overhead gas outlet 12 and is used to condense the gas phase discharged from the first overhead gas outlet 12 of the main distillation column 1. The overhead circulating water cooler 42 is connected to the second overhead gas outlet 31 and is used to condense the gas phase discharged from the second overhead gas outlet 31 of the reactive distillation column 3.

[0056] The reflux assembly is used to connect the cooling assembly and the first reflux port 13, and to connect the cooling assembly and the second reflux port 32, so as to reflux a portion of the condensate obtained from the cooling assembly back to the main distillation column 1 and the reactive distillation column 3. The reflux assembly includes a first top reflux tank 51, a second top reflux tank 52, a first reflux pump 53, and a second reflux pump 54; the first top vapor outlet 12, the top heat exchanger 62, the top air cooler 41, the first top reflux tank 51, the first reflux pump 53, and the first reflux port 13 are connected in sequence; the second top vapor outlet 31, the top circulating water cooler 42, the second top reflux tank 52, the second reflux pump 54, and the second reflux port 32 are connected in sequence. The outlet of the first top reflux tank 51 is connected in sequence to the first reflux pump 53, the top heat exchanger 62, and the third feed port 33. High-purity DCS product is obtained in the second top reflux tank 52, and the high-purity DCS product is discharged from the outlet of the second top reflux tank 52 through the second reflux pump 54.

[0057] The heat exchange assembly includes a high-boiling-point heat exchanger 61 at the bottom of the column, a heat exchanger 62 at the top of the column, and a feed heater 63. The high-boiling-point heat exchanger 61 at the bottom of the column is used to heat the liquid phase at the bottom of the side-stream stripping column 2 using the heat from the bottom of the main distillation column 1. The high-boiling-point substances in the high-boiling-point outlet pass sequentially through the high-boiling-point heat exchanger 61 at the bottom of the column and the feed heater 63 to recover the heat from the bottom of the main distillation column 1. The high-boiling-point heat exchanger 61 at the bottom of the column uses the heat from the bottom of the main distillation column 1 as the reboiling heat source for the side-stream stripping column 2. The feed heater 63 uses the heat from the bottom of the main distillation column 1 to heat the feedstock. The heat exchanger 62 at the top of the column is connected to the first top vapor phase outlet 12 and is used to recover the heat from the top of the main distillation column 1 to preheat the material entering the second top vapor phase outlet 31.

[0058] The method of using the above-mentioned distillation purification system includes the following steps:

[0059] Step 1: After the raw material is preheated by the feed heater 63, it enters the main distillation column 1 for separation. The raw material comes from the tank area and contains dichlorosilane (DCS), trichlorosilane (TCS), silicon tetrachloride (STC), and impurities such as boron (B, such as BCl3) and phosphorus (P).

[0060] Step 2: After condensing the vapor at the top of the main distillation column 1, it is divided into a first part of the material and a second part of the material. The second part of the material contains impurities such as DCS and BCl3. The first part of the material is refluxed back to the main distillation column 1, and the second part of the material enters the reactive distillation column 3.

[0061] The liquid side stream at the top of the main distillation column 1 is collected and flows by gravity into the side stream stripping column 2, which has only a stripping section, for stripping. Electronic-grade TCS product is obtained at the bottom of the stripping column. Light substances (such as BCl3) in the stripping column are returned to the main distillation column 1 from the top of the stripping column.

[0062] Step 3: The complexing agent undergoes a rapid and reversible complexing reaction with the second batch of material from the main distillation column 1 in the reactive distillation column 3 to generate a complex with a boiling point much higher than that of DCS. The complexing agent hardly reacts with DCS, but can undergo a rapid and reversible complexing reaction with BCl3 to generate a complex with a boiling point much higher than that of DCS.

[0063] High-purity DCS gas was separated by distillation and purification in reactive distillation column 3.

[0064] After being cooled, part of the high-purity DCS gas is returned to the reactive distillation column 3, and the other part is sent out as a high-purity DCS product.

[0065] Step 4: Recover the complexing agent from the heavy components (bottom liquid phase) in the bottom of the reactive distillation column 3.

[0066] In the above scheme, a side-stream stripping tower 2 is added to the main distillation tower 1, and a special reactive distillation process is used in the reactive distillation tower 3 to obtain electronic-grade TCS products and high-purity DCS products; that is, multiple products are obtained with a simple process flow. The side-stream stripping tower 2 can be regarded as an auxiliary component of the main distillation tower 1. The two are integrated to complete the separation work of two traditional distillation towers. The side-stream stripping tower 2 only has a stripping section and no rectification section, so it does not require a separate top condenser or reflux device, which greatly reduces the number of equipment. The side-stream stripping tower 2 uses liquid phase gravity flow to directly collect the material from the main tower, eliminating the need for intermediate cooling, transportation, and reheating equipment and energy consumption.

[0067] In step two, the overhead vapor of the main distillation column 1 is condensed and divided into a first part and a second part. The second part contains impurities such as DCS and BCl3. The first part is refluxed back to the main distillation column 1, and the second part enters the reactive distillation column 3, including:

[0068] The gas phase in the first top gas outlet 12 of the main distillation column 1 recovers the top heat of the main distillation column 1 after passing through the top heat exchanger 62, and is condensed by the top air cooler 41 and enters the first top reflux tank 51. Then, a portion of the material is refluxed back to the main distillation column 1 through the first reflux port 13 by the first reflux pump 53, and the other portion of the material (containing DCS and boron impurities such as BCl3) is preheated by the top heat exchanger 62 and enters the reactive distillation column 3 through the third feed port 33 for further separation.

[0069] In the above scheme, the heat at the top of the main distillation column 1 is recovered through the top heat exchanger 62 to preheat the second batch of material about to enter the reactive distillation column 3, effectively recovering heat and reducing system energy consumption. The use of the top air cooler 41 reduces the amount of circulating water used in public utilities.

[0070] In step two, the liquid side stream of the main distillation column 1 is collected and flows by gravity into the side stream stripping column 2, which has only a stripping section, for stripping. At the bottom of the stripping column, electronic-grade TCS products are obtained, including:

[0071] The liquid phase side stream is collected from the position with the highest TCS concentration above the first feed inlet 11 of the main distillation column 1. The liquid phase of the main distillation column 1 flows by gravity into the side stream stripping column 2 through the second feed inlet 21 for stripping. The stripping column only has a stripping section.

[0072] The high-boiling-point material collected from the bottom and near the bottom of the main distillation column 1 is used as the reboiling heat source for the side-stream stripping column 2. After the liquid portion at the bottom of the side-stream stripping column 2 is vaporized, it flows upward and comes into countercurrent contact with the liquid flowing down from the top of the column to transfer heat and mass, thereby achieving TCS separation. The purified product TCS (with light impurities removed) flows out from the bottom TCS outlet 22 at the bottom of the stripping column, thus obtaining a high-purity electronic-grade TCS product.

[0073] In the above scheme, the side-stream stripper 2 can be regarded as an auxiliary component of the main distillation column 1. The two are integrated to complete the separation work of two traditional distillation columns. The side-stream stripper 2 only has a stripping section and no rectification section, so it does not require a separate top condenser or reflux device, which significantly reduces the number of equipment. The side-stream stripper 2 directly draws material from the main column by liquid-phase gravity flow, eliminating the need for intermediate cooling, conveying, and reheating equipment and energy consumption. Using the high-boiling-point material drawn from the bottom and near the bottom of the main distillation column 1 as the reboiling heat source for the side-stream stripper 2 further reduces the system energy consumption.

[0074] Step two also includes:

[0075] The high-boiling-point substances collected from the high-boiling-point outlet (located at the bottom and near the bottom of the main distillation column 1) are sent to the tank area after recovering the heat from the bottom of the main distillation column 1 through the high-boiling-point heat exchanger 61 and the feed heater 63.

[0076] In the above scheme, the high heat of the high boiling point in the main distillation column 1 is recovered by using the high boiling point heat exchanger 61 and the feed heater 63 to serve as the reboiling heat source for the side stripping column 2 and the preheating heat source for the raw materials, thereby further reducing the system energy consumption.

[0077] Step 3 includes: introducing a complexing agent such as dimethylformamide (DMF) into the reaction section of the reactive distillation column 3 through the fourth feed inlet 34. This complexing agent hardly reacts with DCS, but can undergo a rapid and reversible complexation reaction with BCl3 to generate a complex. The boiling point of this complex is much higher than that of DCS. After further purification by distillation in the reactive distillation column 3, high-purity DCS gas can be separated.

[0078] The vapor phase at the top of the reactive distillation column 3 is highly volatile, high-purity DCS. After being cooled by the top cooler, it enters the top reflux tank. Part of it is refluxed back to the reactive distillation column 3 via the second reflux pump 54, while the other part is sent to the tank area as high-purity DCS product.

[0079] In the above scheme, the light component at the top of the main distillation column 1 (the gas phase in the first top gas phase outlet 12 of the main distillation column 1) contains DCS and boron impurities such as BCl3. Since DCS and boron impurities, especially BCl3, are extremely similar (relative volatility close to 1), it is almost economically infeasible to distill to the ppb level using conventional processes (it requires extremely high column height and extremely high reflux ratio). Therefore, the above-mentioned special reactive distillation process is adopted.

[0080] Step four includes sending the heavy components in the bottom of the reactive distillation column 3 to the complexing agent recovery system to recover complexing agents such as dimethylformamide (DMF).

[0081] In the above scheme, since complexing agents such as dimethylformamide (DMF) can undergo rapid and reversible complexation reactions with BCl3, the complexing agents can be recycled to reduce the consumption of complexing agents.

[0082] Finally, it should be noted that the above are merely preferred embodiments of this application and are not intended to limit this application. For those skilled in the art, this application can have various modifications and variations. Without conflict, the embodiments and features described in the embodiments of this application can be arbitrarily combined with each other. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A distillation purification system, characterized in that, include: The main distillation column has a first feed inlet, a first overhead vapor outlet, a first reflux outlet, and a side stream outlet; A side-stream stripping tower with only a stripping section has a second feed inlet and a TCS outlet at the bottom of the tower; the second feed inlet is connected to the side-stream outlet. A reactive distillation column is used for separation in a DCS (Distributed Control System). The upper part of the reactive distillation column has a second top gas outlet and a second reflux outlet; the bottom of the reactive distillation column has a bottom liquid outlet. A cooling assembly for condensing the gas phase discharged from the first column top gas phase outlet, and for condensing the gas phase discharged from the second column top gas phase outlet; A reflux assembly is used to connect the cooling assembly and the first reflux port, and to connect the cooling assembly and the second reflux port.

2. The distillation and purification system according to claim 1, characterized in that, The middle section of the reactive distillation column is the reaction section, which is equipped with a third feed inlet and a fourth feed inlet; the third feed inlet is connected to the vapor outlet at the top of the first column; the fourth feed inlet is used to introduce a complexing agent. The complexing agent hardly reacts with DCS, but can undergo a rapid and reversible complexation reaction with BCl3 to generate a complex with a boiling point higher than that of DCS.

3. The distillation and purification system according to claim 2, characterized in that, The cooling assembly includes: The top air cooler is connected to the gas phase outlet of the first top column. The top circulating water cooler is connected to the gas phase outlet of the second top of the tower.

4. The distillation and purification system according to claim 3, characterized in that, The reflux assembly includes a first top reflux tank, a second top reflux tank, a first reflux pump, and a second reflux pump; The first top gas phase outlet, the top air cooler, the first top reflux tank, the first reflux pump, and the first reflux port are connected in sequence. The second top gas phase outlet, the top circulating water cooler, the second top reflux tank, the second reflux pump, and the second reflux port are connected in sequence.

5. The distillation and purification system according to claim 4, characterized in that, A high-purity DCS product is obtained in the second top reflux tank, and the high-purity DCS product is discharged from the outlet of the second top reflux tank by the second reflux pump.

6. The distillation and purification system according to claim 4, characterized in that, It also includes a heat exchange component for recovering and utilizing the heat at the bottom and top of the main distillation column.

7. The distillation and purification system according to claim 6, characterized in that, The heat exchange components include a top heat exchanger, a bottom high-boiling-point heat exchanger, and a feed heater; The first column top gas phase outlet, the column top heat exchanger, and the column top air cooler are connected in sequence; The main distillation column has a high-boiling point outlet at the bottom and near the bottom; the high-boiling point outlet passes sequentially through the high-boiling point heat exchanger at the bottom of the column and the feed heater; the feed heater is used to preheat the raw material entering the first feed inlet; the high-boiling point heat exchanger at the bottom of the column provides a reboiling heat source for the side-stream stripping column.

8. The distillation and purification system according to claim 7, characterized in that, The outlet of the first top reflux tank is connected in sequence to the first reflux pump, the top heat exchanger, and the third feed inlet.

9. The distillation and purification system according to claim 1, characterized in that, The side sampling outlet is located above the first inlet and at the position where the TCS concentration is highest.

10. The distillation and purification system according to claim 2, characterized in that, The bottom liquid phase outlet of the tower is connected to the complexing agent recovery system.

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