Method for removing impurity ammonia in silane
By combining distillation, condensation, and solidification separators, and utilizing nitrogen to form micro ice crystals, the problem of equipment blockage caused by the removal of ammonia impurities in silanes was solved, achieving low-cost and high-efficiency silane purification.
Patent Information
- Application Number
- CN202411107565.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-13
- Publication Date
- 2026-02-13
AI Technical Summary
Existing technologies are prone to equipment blockage when removing ammonia impurities from silanes, and traditional adsorption processes are energy-intensive and costly, making it difficult to effectively reduce ammonia content.
By combining distillation, condensation, and solidification separator, gradient cooling condensation is achieved by controlling specific temperature and pressure conditions, and nitrogen is introduced into the solidification separator to form micro ice crystals, reducing the risk of equipment blockage and realizing continuous separation.
It significantly extends the equipment operating cycle, reduces the risk of equipment blockage, effectively removes impurities such as ammonia and hydrogen sulfide from silanes, obtains silanes with low ammonia content, and reduces process costs.
Smart Images
Figure CN121516871A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of silane purification technology, and more specifically to a method for removing ammonia, an impurity, from silanes. Background Technology
[0002] Silane products are widely used in the production processes of photovoltaics, panels, and semiconductors. Among them, the silane products used in the semiconductor field are electronic grade, so the requirements for the impurity content in silanes are strict.
[0003] In the production of silane gases, a common method is the magnesium-silicon process. This method produces silane and ethylsilane gases that contain a large amount of ammonia. During conventional condensation and liquefaction methods such as distillation and rectification, the purification process to obtain silane gases with low ammonia content often results in equipment blockage due to excessively low cooling, causing ammonia to solidify. To avoid frequent blockages, the separation temperature needs to be increased; however, this usually only reduces the ammonia content in the silane gases to ~1.0%, failing to completely remove it.
[0004] In existing technological applications, a common method is to further remove trace amounts of ammonia remaining in silane after distillation using pressure swing adsorption (PSA) technology, leveraging the selective adsorption properties of porous adsorbent materials at low temperatures. However, adsorption is a batch process, resulting in high energy consumption and equipment costs for regeneration. Reducing the ammonia content in the distillation process can significantly extend the regeneration cycle of ammonia adsorption equipment, thereby improving efficiency and reducing costs. Summary of the Invention
[0005] To address the problems existing in the prior art, the present invention provides a method for removing ammonia impurities from silanes. The method of the present invention can reduce the risk of equipment blockage, significantly extend the equipment operating cycle, and effectively remove ammonia and hydrogen sulfide impurities from silanes, thereby obtaining silanes with low ammonia content.
[0006] To achieve its objective, the present invention provides the following technical solution:
[0007] This invention provides a method for removing ammonia, an impurity, from silanes, comprising the following steps:
[0008] (1) The crude silane gas containing ammonia impurities is fed into a distillation column for distillation. The pressure of the distillation column is 0.12-2 MPa, the top temperature is ≤-10℃, preferably -10℃ to -75℃, and the bottom temperature is ≥10℃, preferably 10-35℃.
[0009] (2) The silane gas after distillation in step (1) is sent into a distillation condenser and condensed at a temperature of -40℃ to -90℃ and a pressure of 0.13-1.9Mpa.
[0010] (3) The silane gas processed in step (2) is sent into a solidification separator and condensed at a temperature of -80℃ to -160℃ and a pressure of 0.14-1.85 MPa; and nitrogen gas is introduced into the liquid phase obtained by condensation in the solidification separator during the condensation process.
[0011] The liquid phase in the coagulation separator is filtered to obtain purified silane.
[0012] Preferably, in step (3), the flow rate of nitrogen gas introduced into the solidification separator is 2-10% of the flow rate of silane gas introduced into the solidification separator, preferably 5-10%, and the unit of flow rate is m³ / s. 3 / h;
[0013] And / or, in step (3), the temperature difference between the nitrogen gas and the temperature of the solidification separator is ±10°C.
[0014] Preferably, in step (3), the uncondensed gas in the solidification separator is successively defoamed and filtered, and then sent to the cryogenic condenser for condensation. The liquid phase obtained in the cryogenic condenser is returned to the solidification separator, and the non-condensable gas containing nitrogen is pressurized and returned to the solidification separator and introduced into the liquid phase of the solidification separator.
[0015] Preferably, the temperature of the cryogenic condenser is 10-20°C lower than the temperature of the solidification separator.
[0016] Preferably, the coagulation separator includes a tank, which is provided with a nitrogen inlet, a silane gas inlet, a gas outlet, a baffle, a second filter, a liquid phase outlet, a demister, and a first filter.
[0017] The partition is disposed in the inner cavity of the tank and divides the inner cavity into an air inlet area and an air outlet area. The lower part of the air inlet area and the lower part of the air outlet area are interconnected. The nitrogen inlet and the silane gas inlet are disposed on the wall surface of the tank corresponding to the air inlet area. The air outlet is disposed on the wall surface of the tank corresponding to the air outlet area. In the air outlet area, along the gas flow direction of the air outlet, the demister and the second filter are sequentially disposed at the bottom of the air outlet.
[0018] The first filter is located in the inner cavity of the tank and is used to filter the liquid phase inside the tank. The liquid phase outlet is used to output the liquid phase filtered by the first filter. Preferably, the liquid phase outlet is connected to the product output pipeline, and the product output pipeline is equipped with a liquid filter and a valve.
[0019] In some embodiments, the pore size of the demister is no greater than 5 μm, and the pore sizes of the second filter and the first filter are each no greater than 0.01 μm.
[0020] Preferably, the first filter is a filter plate, which is disposed above the liquid phase outlet and arranged at an angle;
[0021] More preferably, the coagulation separator has a crystallization precipitate outlet at the bottom, and the filter plate is arranged at an angle so that the crystallization precipitate trapped on the filter plate tends to flow towards the area at the bottom of the coagulation separator where the crystallization precipitate outlet is located.
[0022] More preferably, the crystallized precipitate outlet is connected to the distillation condenser via a crystallized precipitate output pipeline, and a valve is provided on the crystallized precipitate output pipeline to send the crystallized precipitate deposited in the solidification separator into the distillation condenser via the crystallized precipitate output pipeline.
[0023] Preferably, the nitrogen inlet is connected to a nitrogen inlet pipe, and the outlet end of the nitrogen inlet pipe extends into the inner cavity of the solidification separator and is configured to contact or be immersed in the liquid phase condensed inside the solidification separator.
[0024] The gas inlet of the cryogenic condenser is connected to the gas outlet of the solidification separator via a pipeline. The non-condensable gas outlet of the cryogenic condenser is connected to the nitrogen inlet pipe via a non-condensable gas outlet pipeline, and a compressor is installed on the nitrogen inlet pipe. The liquid phase outlet of the cryogenic condenser is connected to the solidification separator via a pipeline.
[0025] Preferably, the vapor outlet at the top of the distillation column is connected to a distillation condenser via a pipeline, the distillation condenser is connected to the distillation condenser tank via a pipeline, and a reboiler is provided at the bottom of the distillation column.
[0026] The silane gas, after being distilled in the distillation column, is output from the gas phase outlet at the top of the distillation column, flows through the distillation condenser, and then enters the distillation condenser tank.
[0027] More preferably, the temperature of the distillation condenser is -20 to -50°C.
[0028] In some embodiments, at least a portion of the condensate from the distillation condenser is refluxed back into the distillation column, preferably at a reflux ratio of 2-15.
[0029] In some embodiments, the silane includes one or more of methylsilane, disilane, and propane;
[0030] In some implementations, the crude silane gas also contains hydrogen sulfide impurities.
[0031] In some embodiments, the crude silane gas contains 10-50% ammonia by volume and 1-2% H2S by volume.
[0032] The technical solution provided by this invention has the following beneficial effects:
[0033] The method of the present invention for purifying crude silane gas can reduce the risk of equipment and pipeline blockage, significantly extend the operating cycle of the process system, and obtain silane with low ammonia content. The method of the present invention can also remove any small amount of hydrogen sulfide gas that may be present.
[0034] The method of this invention can reduce the ammonia content in silanes, thereby increasing efficiency and reducing costs, and thus better solving the problem of impurity removal in some key technologies in the silane industry. Attached Figure Description
[0035] Figure 1 This is a schematic diagram of a silane impurity removal system in one embodiment.
[0036] Explanation of some figure labels:
[0037] T101: Distillation column; E101: Distillation condenser; V101: Distillation condenser; V102: Solidification separator; E102: Cryogenic condenser; E103: Reboiler; C101: Compressor; Defoamer 1; Second filter 2; First filter 3; Liquid filter 4; Nitrogen valve 5; Valves 6 and 7; Nitrogen inlet pipe 8. Detailed Implementation
[0038] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.
[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.
[0040] The directional terms such as "upper," "lower," "top," and "bottom" mentioned or potentially used in this specification are defined relative to the structures shown in the accompanying drawings. These are relative concepts and may therefore vary depending on their location and usage. The terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.
[0041] This invention provides a method for removing ammonia, an impurity, from silanes. The following is a description of the method. Figure 1The method of the present invention will be described. The method includes the following steps:
[0042] (1) The crude silane gas containing ammonia impurities is fed into the distillation column T101 for distillation. The pressure of the distillation column T101 is 0.12-2 MPa, the top temperature is ≤-10℃, preferably -10℃ to -75℃, and the bottom temperature is ≥10℃, preferably 10-35℃.
[0043] (2) The silane gas after distillation in step (1) is sent into the distillation condenser V101 and condensed under the conditions of -40℃ to -90℃ and pressure of 0.13-1.9Mpa.
[0044] (3) The silane gas processed in step (2) is sent into the solidification separator V102 and condensed at a temperature of -80℃ to -160℃ and a pressure of 0.14-1.85 MPa; and nitrogen gas is introduced into the liquid phase obtained by condensation in the solidification separator V102 during the condensation process; the liquid phase in the solidification separator is filtered to obtain purified silane.
[0045] The method provided by this invention processes crude silane containing ammonia impurities sequentially in a distillation column T101, a distillation condenser V101, and a solidification separator V102, and performs gradient cooling and condensation treatments sequentially under specific temperature and pressure conditions. Simultaneously, nitrogen gas is introduced into the condensed liquid phase during the solidification separator treatment. Using this method to purify crude silane gas reduces the risk of equipment and pipeline blockage, significantly extends the process system's operating cycle, and yields silane with low ammonia impurity content. Furthermore, this method can simultaneously remove any small amounts of hydrogen sulfide gas that may be present.
[0046] In this invention, ammonia at a constant level in silane is separated by distillation in step (1), and the remaining trace ammonia is separated by condensation in step (2). Then, deep condensation continues in step (3), where the entrained trace ammonia condenses into ice crystals. Simultaneously, nitrogen gas is introduced into the condensed liquid phase, which reduces the ice crystal size during the ammonia condensation process, forming micro-ice crystals. This further reduces the risk of equipment blockage, ultimately reducing the ammonia content in the silane to trace levels. The process flow of this invention has the advantages of being continuous, rapid, and stable.
[0047] In the solidification separator V102, nitrogen gas is introduced into the liquid phase. The nitrogen gas provides a large number of microbubbles as condensation nuclei for the trace ammonia in the liquid. Under the action of the condensation nuclei, the trace ammonia in the liquid silane environment forms micro ice crystals and precipitates to the bottom. At the same time, the nitrogen gas introduced into the solidification separator V102 can also prevent ice crystals from depositing on the pipe wall and the inner wall of the container, and it is also beneficial to obtain smaller-sized micro ice crystals, reducing the risk of blockage. Preferably, in step (3), the flow rate of the nitrogen gas introduced into the solidification separator V102 is 2-10% of the flow rate of the silane gas introduced into the solidification separator V102, preferably 5-10%, and the unit of flow rate is m³ / s. 3 / h. Using a preferred nitrogen flow rate is beneficial for obtaining better results; preferably, in step (3), the temperature difference between the nitrogen and the temperature of the solidification separator is ±10℃.
[0048] Preferably, in step (3), the uncondensed gas in the condensation separator V102 is sequentially defoamed and filtered before being sent to the cryogenic condenser E102 for condensation. The liquid phase obtained in the cryogenic condenser E102 is refluxed back to the condensation separator V102, and the non-condensable gas containing nitrogen is pressurized and refluxed back to the condensation separator V102 and introduced into the liquid phase of the condensation separator V102.
[0049] Preferably, the temperature of the cryogenic condenser E102 is 10-20°C lower than the temperature of the solidification separator.
[0050] More preferably, see Figure 1The solidification separator V102 includes a tank 16, which is provided with a nitrogen inlet, a silane gas inlet, a gas outlet, a baffle 14, a second filter 2, a liquid phase outlet, a demister 1, and a first filter 3. The baffle 14 is disposed in the inner cavity of the tank 16 and divides the inner cavity into an inlet area 12 and an outlet area 13. The lower part of the inlet area 12 and the lower part of the outlet area 13 are interconnected. The nitrogen inlet and the silane gas inlet are disposed on the wall surface of the tank 16 corresponding to the inlet area 12, and the gas outlet is disposed on the wall surface of the tank 16 corresponding to the outlet area 13. In the outlet area 13, along the gas flow direction of the outlet, the demister 1 and the second filter 2 are sequentially disposed at the bottom of the outlet. The first filter 3 is located in the inner cavity of the tank 16 and is used to filter the liquid phase in the tank. The liquid phase outlet is used to output the liquid phase after being filtered by the first filter 3. Specifically, the first filter 3 is located in the lower part of the inner cavity of the tank 16 and corresponds to the position of the liquid phase outlet, so that the liquid phase in the tank 16 first flows through the first filter 3 and then flows into the liquid phase outlet. That is, in the solidification separator V102, the condensed liquid phase is first filtered by the first filter 3 to intercept the crystal precipitates entrained therein, and then it is collected from the liquid phase outlet.
[0051] Furthermore, the liquid phase outlet of the coagulation separator V102 is connected to the product output pipeline 11, which is equipped with a liquid filter 4 and a valve 7, through which purified silane is output.
[0052] Uncondensed gas in the condenser V102 passes through the demister 1 and the second filter 2 in the outlet zone 13, where droplets are trapped, before entering the cryogenic condenser E102. Preferably, the pore size of the demister 1 is no greater than 5 μm, and the pore sizes of the second filter 2 and the first filter 3 are each no greater than 0.01 μm. The filters are, for example, made of sintered ceramic.
[0053] Better, such as Figure 1As shown, the first filter 3 is a filter plate, which is inclinedly arranged above the liquid phase outlet of the solidification separator V102. Preferably, the solidification separator V102 has a crystallization precipitate outlet at its bottom, and the filter plate is inclined and arranged so that the crystallization precipitate trapped on the filter plate tends to flow towards the area at the bottom of the solidification separator V102 where the crystallization precipitate outlet is located, so that the crystallization precipitate can be easily collected and discharged. Preferably, the crystallization precipitate outlet is connected to the distillation condenser V101 through the crystallization precipitate output pipeline 10. The crystallization precipitate output pipeline 10 is equipped with a valve 6, which can be used to send the crystallization precipitate deposited in the solidification separator V102 into the distillation condenser V101 through the crystallization precipitate output pipeline 10 for heating and liquefaction.
[0054] Preferably, the nitrogen inlet is connected to a nitrogen inlet pipe 8, the outlet of which extends into the inner cavity of the condenser V102 and is configured to contact or be immersed in the liquid phase condensed within the condenser V102. The nitrogen inlet pipe 8 is connected to a nitrogen source via a pipeline, which is equipped with a nitrogen valve 5. The gas inlet of the cryogenic condenser E102 is connected to the outlet of the condenser V102 via a pipeline, and the non-condensable gas outlet of the cryogenic condenser E102 is connected to the nitrogen inlet pipe 8 via a non-condensable gas outlet pipeline 15. A compressor C101, such as a diaphragm compressor, is installed on the nitrogen inlet pipe 8. The liquid phase outlet of the cryogenic condenser E102 is connected to the condenser V102 via a pipeline.
[0055] In the process, silane gas, after being condensed in the distillation condenser V101, enters the solidification separator V102 through pipeline 9 via the silane gas inlet and is condensed. A liquid phase is obtained at the bottom of the solidification separator V102. Nitrogen gas is simultaneously introduced into the liquid phase during condensation. Crystalline precipitates formed in the liquid phase settle at the bottom of the solidification separator V102. The remaining gas, which is not condensed during condensation, is demisted by a demister in the outlet area 13 and filtered by the second filter 2 before entering the cryogenic condenser E102 for condensation. Non-condensable gas flows through the non-condensable gas outlet and non-condensable gas output pipeline 15 into the nitrogen inlet pipe 8. After being compressed and heated by compressor C101, it is returned to the solidification separator V102 and introduced into the liquid phase, thus allowing for the recycling of nitrogen. The liquid phase obtained from condensation in the cryogenic condenser E102 flows back to the solidification separator V102 through a pipeline.
[0056] Specifically, the vapor outlet at the top of distillation column T101 is connected to distillation condenser E101 via a pipeline, and distillation condenser E101 is connected to distillation condenser V101 via a pipeline. The silane gas, after distillation treatment in the distillation column, exits from the vapor outlet at the top of the column, flows through distillation condenser E101, and then enters distillation condenser V101. Preferably, the temperature of distillation condenser E101 is -20 to -50°C. A reboiler is installed at the bottom of distillation column T101 for heating and evaporation. The reboiler may be a tubular design, and the heating method may be circulating hot water. The packing material inside distillation column T101 can be conventional packing material in the art, and the packing material can be one or more combinations of packing materials, including but not limited to perforated metal plates, porous ceramic materials, and metal wire mesh packing. Temperature control at the top of the distillation column can be achieved using a refrigeration unit.
[0057] For example, the gaseous component taken from the top of the distillation column is mainly silane, with an ammonia content of no more than 1%; the purified silane taken from the liquid phase outlet of the solidification separator V102 has an ammonia content of no more than 0.01% (the volume percentage obtained by detection after heating and converting to gaseous state).
[0058] Preferably, at least a portion of the condensate from the distillation condenser V101 is refluxed to the distillation column T101, with a reflux ratio preferably between 2 and 15. Inside the distillation condenser V101, ammonia-containing silanes are cooled and liquefied. Due to the lower boiling point and higher vapor pressure of silanes, they are fed into the solidification separator V102 via a gas path; the liquid phase contains a higher proportion of ammonia and is returned to the distillation column T101 via a liquid path.
[0059] In some embodiments, the silane includes one or more of methylsilane, disilane, and propane.
[0060] In some embodiments, the crude silane also contains hydrogen sulfide impurities.
[0061] In some examples, the crude silane gas contains 10-50% ammonia by volume and 1-2% H2S by volume.
[0062] The method of this invention can be carried out continuously, providing a continuous separation method that can further reduce the ammonia content in silanes separated by distillation. This method balances reducing the risk of clogging with obtaining silanes with lower ammonia content, avoiding or reducing the need for large-scale adsorption towers to treat ammonia in silanes, thus reducing process costs. For silanes prepared using crude ammonia as a reaction feedstock, the reaction gas will contain a small amount of H2S gas; this method can remove hydrogen sulfide gas along with the ammonia.
[0063] The present invention will be further illustrated by the following examples.
[0064] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0065] Examples 1-4 below all employ Figure 1 The system shown is used to purify crude silane. Figure 1 The system shown includes a distillation column T101, a distillation condenser E101, a distillation condenser V101, a solid-solid separator V102, and a cryogenic condenser E102. A reboiler E103 is installed at the bottom of the distillation column T101. The crude silane gas containing ammonia impurities is first fed into distillation column T101 for distillation. The silane gas output from the top of distillation column T101 first flows through distillation condenser E101, and then enters distillation condenser V101 for condensation. At least a portion of the liquid phase obtained from condensation is returned to distillation column T101. The silane gas processed in distillation condenser V101 enters the inlet gas area 12 from the silane gas inlet of solidification separator V102 for further condensation. During the condensation process, pressurized nitrogen is introduced into the liquid phase obtained from condensation through nitrogen inlet pipe 8. The remaining gas that has not condensed is filtered in the outlet gas area 13 by demister 1 and second filter 2, and then enters cryogenic condenser E102. The non-condensable gas in cryogenic condenser E102 flows into nitrogen inlet pipe 8 through non-condensable gas outlet pipeline 15, and is then pressurized by compressor C101 and circulated back to solidification separator V102. The liquid phase in the cryogenic condenser E102 is refluxed to the solidification separator V102. The liquid phase in the solidification separator V102, after being filtered by the first filter 3 to remove crystalline precipitates, enters the product output line 11 through the liquid phase outlet. After filtration by the liquid filter 4, it is collected as purified silane. The demister 1 has a pore size of 5 μm, and the pore sizes of the second filter 2 and the first filter 3 are 0.01 μm each. (Regarding...) Figure 1 Unless otherwise explained, all other aspects of the system shown are described above and will not be repeated here.
[0066] Example 1
[0067] Crude silane gas containing ammonia impurities (ammonia volume percentage 20%) is fed into distillation column T101 for distillation. Column T101 operates at a pressure of 0.6 MPa, a top temperature of -40°C, and a bottom temperature of 25°C. Raschig ring packing is used in column T101. The vapor phase from the top of column T101 flows through distillation condenser E101 (temperature -43°C) and then enters distillation condenser V101, which operates at a temperature of -58°C and a pressure of 0.55 MPa. The silane gas, after condensation in the distillation condenser, is then fed into solidification separator V102, which operates at a temperature of -80°C and a pressure of 0.5 MPa. Nitrogen gas (flow rate in m³ / s) at a temperature of -90°C is introduced through nitrogen inlet pipe 8 at a flow rate of 5% of the silane gas flow rate. 3 / h). The gas output from the outlet of the condenser enters the cryogenic condenser E102 for condensation. The temperature of the cryogenic condenser E102 is 15°C lower than that of the condenser. The non-condensable gas in the cryogenic condenser E102 flows into the nitrogen inlet pipe 8. The liquid phase obtained from the condensation in the cryogenic condenser E102 flows back to the condenser.
[0068] In the above process, the condensate obtained in the distillation condenser is refluxed into the upper part of the distillation column T101, with a reflux ratio of 5.
[0069] Purified silane was extracted from pipeline 11, heated to a gaseous state, and then the impurity content was tested. The volume content of ammonia was found to be <0.01%.
[0070] In this embodiment, the process system has been running for a total of 2160 hours, during which no cleaning or maintenance was required due to blockage.
[0071] Example 2
[0072] Referring to Example 1, the following mainly describes the differences from Example 1, while the similarities will not be repeated:
[0073] Crude silane gas containing ammonia impurities (ammonia accounting for 30% by volume) is fed into distillation column T101 for distillation. Column T101 has a pressure of 0.6 MPa, a top temperature of -43°C, and a bottom temperature of 20°C. The packing material in column T101 is corrugated metal plate packing. The vapor phase from the top of column T101 flows through distillation condenser E101 (temperature -48°C) and then enters distillation condenser V101, which has a temperature of -63°C and a pressure of 0.58 MPa. The silane gas after condensation in the distillation condenser is then fed into solidification separator V102, which has a temperature of -100°C and a pressure of 0.55 MPa. Nitrogen gas at a temperature of -95°C and a flow rate of 5% of the silane gas flow rate is introduced through nitrogen inlet pipe 8.
[0074] Purified silane was extracted from pipeline 11, heated to a gaseous state, and then the impurity content was tested. The volume content of ammonia was found to be <0.01%.
[0075] In this embodiment, the process system operated for a total of 2400 hours without any need for cleaning or maintenance due to blockage.
[0076] Example 3
[0077] Referring to Example 1, the following mainly describes the differences from Example 1, while the similarities will not be repeated:
[0078] A crude silane gas containing impurities of ammonia and H2S (ammonia accounting for 20% by volume and H2S accounting for 2% by volume) is fed into distillation column T101 for distillation. The pressure in distillation column T101 is 1.8 MPa, the top temperature is -30°C, and the bottom temperature is 28°C. Raschig ring packing is used in distillation column T101. The vapor phase from the top of distillation column T101 flows through distillation condenser E101 (temperature -40°C) and then enters distillation condenser V101. The temperature in the distillation condenser is -50°C, and the pressure is 1.75 MPa. The silane gas after condensation in the distillation condenser is sent to solidification separator V102. The temperature in the solidification separator is -80°C, and the pressure is 1.7 MPa. Nitrogen gas at a temperature of -80°C and a flow rate of 5% of the silane gas flow rate is introduced through nitrogen inlet pipe 8.
[0079] In the above process, the condensate obtained in the distillation condenser V101 is refluxed into the upper part of the distillation column T101, with a reflux ratio of 12.
[0080] Purified silane was extracted from pipeline 11, heated to a gaseous state, and then the impurity content was tested. The volume content of ammonia was found to be <0.01%, and the volume content of H2S was <1%.
[0081] In this embodiment, the process system has been running for a total of 2200 hours, during which no cleaning or maintenance was required due to blockage.
[0082] Example 4
[0083] The procedure is the same as in Example 1, except that:
[0084] In the solidification separator V102, the flow rate of nitrogen introduced through the nitrogen inlet pipe 8 is 2% of the flow rate of silane gas introduced into the solidification separator.
[0085] Purified silane was extracted from pipeline 11, heated to a gaseous state, and the impurity content was tested. The volume content of ammonia was found to be 4%.
[0086] In this embodiment, after the process system has accumulated 1900 hours of operation, blockage cleaning and maintenance are carried out.
[0087] Comparative Example 1 (compared to Example 1)
[0088] The impurity removal treatment of crude silane gas was carried out according to Example 1, with the following differences: the pressure of distillation column T101 was 0.6 MPa, the top temperature was 0°C, and the bottom temperature was 25°C. The temperature of the distillation condenser was -30°C and the pressure was 0.55 MPa. The temperature of the solidification separator was -50°C and the pressure was 0.5 MPa. All other process conditions remained the same as in Example 1.
[0089] Purified silane was extracted from pipeline 11, heated to a gaseous state, and its impurity content was tested. The volume content of ammonia was found to be 7%. After the system has accumulated 900 hours of operation, blockage cleaning and maintenance are required.
[0090] Comparative Example 2 (compared to Example 3)
[0091] The crude silane gas was purified according to Example 3, with the following differences: the pressure of distillation column T101 was 0.1 MPa, the top temperature was -30°C, and the bottom temperature was 10°C. The temperature of the distillation condenser was -50°C, and the pressure was 0.1 MPa. The temperature of the solidification separator was -70°C, and the pressure was 0.1 MPa. All other process conditions remained the same as in Example 3.
[0092] Purified silane was extracted from pipeline 11, heated to a gaseous state, and then tested for impurities. The volume content of ammonia was found to be 8%, and the volume content of H2S was 1.8%. After the system has accumulated 930 hours of operation, blockage cleaning and maintenance are required.
[0093] Comparative Example 3
[0094] The procedure was carried out in accordance with Example 2, except that the distillation condenser was omitted and the silane gas output from the distillation condenser E101 was directly sent to the solidification separator for processing by the distillation column T101.
[0095] The purified silane was heated to a gaseous state and the impurity content was tested. The volume content of ammonia was found to be 10%. After the system had been running for a total of 520 hours, it was necessary to clean the blockage and carry out maintenance.
[0096] Comparative Example 4
[0097] The same procedure was followed as in Example 1, except that the temperature of the solidification separator was -70°C.
[0098] The purified silane was heated to a gaseous state and the impurity content was tested. The volume content of ammonia was found to be 12%. After the system had been running for a total of 490 hours, it was necessary to clean the blockage and carry out maintenance.
[0099] Comparative Example 5
[0100] The procedure was carried out in accordance with Example 1 above, except that nitrogen was not introduced into the solidification separator.
[0101] The purified silane was heated to a gaseous state and the impurity content was tested. The volume content of ammonia was found to be 8%. After the system had been running for a total of 480 hours, it was necessary to clean the blockage and carry out maintenance.
[0102] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for removing ammonia, an impurity, from silane, characterized in that, Includes the following steps: (1) The crude silane gas containing ammonia impurities is fed into a distillation column for distillation. The pressure of the distillation column is 0.12-2 MPa, the top temperature is ≤-10℃, preferably -10℃ to -75℃, and the bottom temperature is ≥10℃, preferably 10-35℃. (2) The silane gas after distillation in step (1) is sent into a distillation condenser and condensed at a temperature of -40℃ to -90℃ and a pressure of 0.13-1.9Mpa. (3) The silane gas processed in step (2) is sent into a solidification separator and condensed at a temperature of -80℃ to -160℃ and a pressure of 0.14-1.85 MPa; and nitrogen gas is introduced into the liquid phase obtained by condensation in the solidification separator during the condensation process. The liquid phase in the coagulation separator is filtered to obtain purified silane.
2. The method according to claim 1, characterized in that, In step (3), the flow rate of nitrogen gas introduced into the solidification separator is 2-10% of the flow rate of silane gas introduced into the solidification separator, preferably 5-10%, and the unit of flow rate is m³ / s. 3 / h; And / or, in step (3), the temperature difference between the nitrogen gas and the temperature of the solidification separator is ±10°C.
3. The method according to any one of claims 1-2, characterized in that, In step (3), the uncondensed gas in the solidification separator is successively defoamed and filtered, and then sent to the cryogenic condenser for condensation. The liquid phase obtained in the cryogenic condenser is returned to the solidification separator. The non-condensable gas containing nitrogen is pressurized and returned to the solidification separator and introduced into the liquid phase of the solidification separator. Preferably, the temperature of the cryogenic condenser is 10-20°C lower than the temperature of the solidification separator.
4. The method according to claim 3, characterized in that, The solidification separator includes a tank, which is equipped with a nitrogen inlet, a silane gas inlet, a gas outlet, a baffle, a first filter, a liquid phase outlet, a demister, and a second filter. The partition is disposed in the inner cavity of the tank and divides the inner cavity into an air inlet area and an air outlet area. The lower part of the air inlet area and the lower part of the air outlet area are interconnected. The nitrogen inlet and the silane gas inlet are disposed on the wall surface of the tank corresponding to the air inlet area. The air outlet is disposed on the wall surface of the tank corresponding to the air outlet area. In the air outlet area, along the gas flow direction of the air outlet, the demister and the second filter are sequentially disposed at the bottom of the air outlet. The first filter is disposed in the inner cavity of the tank and is used to filter the liquid phase inside the tank. The liquid phase outlet is used to output the liquid phase filtered by the first filter. Preferably, the liquid phase outlet is connected to the product output pipeline, and the product output pipeline is equipped with a liquid filter and a valve.
5. The method according to claim 4, characterized in that, The demister mesh has a pore size of no more than 5 μm, and the pore sizes of the second filter and the first filter are each no more than 0.01 μm.
6. The method according to claim 4, characterized in that, The first filter is a filter plate, which is disposed above the liquid phase outlet and is arranged at an angle; Preferably, the coagulation separator has a crystallization precipitate outlet at the bottom, and the filter plate is arranged at an angle so that the crystallization precipitate trapped on the filter plate tends to flow towards the area at the bottom of the coagulation separator where the crystallization precipitate outlet is located. Preferably, the crystallized precipitate outlet is connected to the distillation condenser via a crystallized precipitate output pipeline, and a valve is provided on the crystallized precipitate output pipeline to send the crystallized precipitate deposited in the solidification separator into the distillation condenser via the crystallized precipitate output pipeline.
7. The method according to claim 4, characterized in that, The nitrogen inlet is connected to a nitrogen inlet pipe, and the outlet end of the nitrogen inlet pipe extends into the inner cavity of the solidification separator and is configured to contact or be immersed in the liquid phase condensed inside the solidification separator. The gas inlet of the cryogenic condenser is connected to the gas outlet of the condensation separator via a pipeline. The non-condensable gas outlet of the cryogenic condenser is connected to the nitrogen inlet pipe via a non-condensable gas outlet pipeline, and a compressor is provided on the nitrogen inlet pipe. The liquid phase outlet of the cryogenic condenser is connected to the solidification separator via a pipeline.
8. The method according to any one of claims 1-7, characterized in that, The vapor outlet at the top of the distillation column is connected to the distillation condenser via a pipeline, and the distillation condenser is connected to the distillation condenser tank via a pipeline. A reboiler is installed at the bottom of the distillation column. The silane gas, after being distilled in the distillation column, is output from the gas phase outlet at the top of the distillation column, flows through the distillation condenser, and then enters the distillation condenser tank. Preferably, the temperature of the distillation condenser is -20°C to -50°C.
9. The method according to any one of claims 1-8, characterized in that, At least a portion of the condensate from the distillation condenser is refluxed back into the distillation column, preferably at a reflux ratio of 2-15.
10. The method according to any one of claims 1-9, characterized in that, The silane includes one or more of methylsilane, disilane, and propane; And / or, the crude silane gas also contains hydrogen sulfide impurities; And / or, in the crude silane gas, the volume content of ammonia is 10-50%, and the volume content of H2S is 1-2%.