Method for treating silane tail gas produced by chlorosilane disproportionation

Abstract

The application provides a treatment method of silane tail gas prepared by a chlorosilane disproportionation method, comprising the following steps: sending the silane safety valve discharge tail gas into a first leaching system to obtain leached lye A; sending the leached lye A into a recovery unit for recovery treatment to obtain recovered lye; sending the silane tail gas into a second leaching system to obtain leached lye B; performing first condensation treatment on the chlorosilane safety valve discharge tail gas to obtain first chlorosilane condensate and first condensed tail gas; performing second condensation treatment on the chlorosilane tail gas to obtain second chlorosilane condensate and second condensed tail gas; mixing the first condensed tail gas and the second condensed tail gas to obtain mixed chlorosilane tail gas; sending the mixed chlorosilane tail gas into a third leaching system to obtain leached lye C; and returning the leached lye B and the leached lye C to the recovery unit to perform recovery treatment together with the leached lye A. The technical scheme of the application simultaneously realizes harmless treatment of various silane tail gases prepared by a chlorosilane disproportionation method.

Description

Technical Field

[0001] This invention relates to the field of silane preparation and tail gas treatment, and more specifically, to a method for treating tail gas from silane production via chlorosilane disproportionation. Background Technology

[0002] In the process of producing silanes using the disproportionation method of chlorosilanes, the system will generate the following types of tail gases: (1) Chlorosilane tail gas: mainly the uncondensed chlorosilane tail gas discharged from the chlorosilane distillation tower and chlorosilane storage tank. These tail gases are common and have a relatively stable flow rate. The composition of this type of tail gas is relatively complex. In addition to chlorosilanes, there are also hydrogen, nitrogen and hydrogen chloride gases. However, after compression and condensation, most of the chlorosilanes can still be recovered and reused, thereby reducing the load on the tail gas scrubbing device. (2) Chlorosilane safety valve discharge tail gas: mainly the chlorosilane tail gas discharged from the safety valve of the chlorosilane distillation tower and chlorosilane storage tank. These tail gases are temporary, with a short duration but a large flow rate. There is no flow rate when not discharged. This type of tail gas is mainly composed of chlorosilanes. After cooling, most of the chlorosilanes can be condensed and separated. The remaining non-condensable gases need to be scrubbed. Under normal circumstances, the chlorosilane safety valve discharge tail gas after chlorosilane recovery can be combined with the chlorosilane tail gas for treatment. (3) Silane tail gas: This mainly refers to the silane tail gas discharged from silane distillation towers and silane storage tanks. These tail gases are common and have relatively stable flow rates. This type of tail gas is mainly composed of silane gas, along with components with very low boiling points such as hydrogen and methane gas. It is difficult to condense further and can be directly treated by scrubbing. (4) Silane safety valve discharge tail gas: This mainly refers to the chlorosilane tail gas discharged from the safety valves of chlorosilane distillation towers and chlorosilane storage tanks during accidents. This tail gas is temporary, with a large discharge flow rate from the safety valves, and no flow rate when not discharging. This type of tail gas is mainly composed of silane gas, which is difficult to condense further and can be directly treated by scrubbing.

[0003] For exhaust gases containing chlorosilanes, water washing can be used. The generated hydrogen gas can be directly released into the atmosphere. Hydrogen chloride dissolves in water to form hydrochloric acid, and silica floats on the surface of the hydrochloric acid. After treatment, it forms harmless solid waste. The relevant reaction formulas are as follows:

[0004] SiH n Cl 4-n +2*H2O→SiO2+(4-n)*HCl+n*H2 n=1,2,3,4

[0005] Additionally, some existing technologies use alkaline solutions to treat chlorosilanes, with the following reaction formula:

[0006] SiH n Cl 4-n +2*NaOH+H2O→Na2SiO3+4-n)*HCl+n*H2 n=1,2,3,4

[0007] However, for silane-containing exhaust gases, silanes have very low solubility in acidic water but high solubility in alkaline aqueous solutions (usually NaOH), and readily react violently with oxygen, potentially leading to combustion or explosion. Therefore, silane gases are generally treated by alkaline rinsing or combustion. The relevant reaction equations are as follows:

[0008] SiH4+2*NaOH+H2O→Na2SiO3+4*H2

[0009] SiH4 + 2O2 → SiO2 + 2H2O

[0010] The sodium metasilicate aqueous solution (pH < 9.5) generated during the above reaction process, known as water glass, has a low pH value and poor fluidity, which can cause blockages in related system pipelines. Furthermore, the water glass obtained from the exhaust gas contains a significant amount of impurities, resulting in low economic value, difficulty in selling, and unsuitability for direct landfill disposal. Therefore, the primary method for treating silane-containing exhaust gas is the combustion of silanes. To prevent deflagration, the silane content is diluted to a low level; however, if a large amount of silane exhaust gas is suddenly released through a safety valve, the silane content will severely exceed the safety limit, posing a safety risk. Using a continuous-burning flare would incur enormous operating costs and require specific site conditions.

[0011] In summary, the treatment of tail gas from the disproportionation process of chlorosilanes to produce silanes generally involves water scrubbing of the chlorosilane tail gas. For silane-containing tail gas, if alkaline scrubbing is also used, a batch production method with multiple parallel towers and scrubbing each tower sequentially is typically employed. However, this generates a large amount of waste alkaline solution that needs to be treated, and improper operation can lead to the formation of water glass that clogs equipment and pipelines. Treating different types of tail gas separately requires building multiple tail gas treatment and wastewater treatment systems, resulting in low material utilization efficiency and huge investment. Furthermore, the methods currently used either primarily treat single, small-volume silane tail gases or have extremely high operating costs and demanding site requirements, making implementation difficult.

[0012] Therefore, how to provide a treatment method for the tail gas generated by the disproportionation process of chlorosilane to produce silane, so as to simultaneously achieve efficient treatment of both chlorosilane-containing tail gas and silane-containing tail gas, is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0013] The main objective of this invention is to provide a method for treating the tail gas from the silane production process via chlorosilane disproportionation, thereby solving the problem that existing technologies cannot efficiently and harmlessly treat the various tail gases generated during the silane production process via chlorosilane disproportionation, namely, the tail gas released by the silane safety valve, the silane tail gas, the tail gas released by the chlorosilane safety valve, and the chlorosilane tail gas simultaneously.

[0014] To achieve the above objectives, the present invention provides a method for treating tail gas from the silane production process via chlorosilane disproportionation, comprising: step S1, providing tail gas from the silane production process via chlorosilane disproportionation, the tail gas including silane safety valve venting tail gas, silane tail gas, chlorosilane safety valve venting tail gas, and chlorosilane tail gas; step S2, the silane safety valve venting tail gas enters a first scrubbing system, undergoes a first scrubbing with a sodium hydroxide aqueous solution of 10%–25% by mass, yielding scrubbing alkaline solution A and scrubbing tail gas A; the scrubbing alkaline solution A is sent to a recovery unit for recovery treatment, yielding recovered alkaline solution; the silane tail gas enters a second scrubbing system, undergoes a second scrubbing with the recovered alkaline solution, yielding scrubbing alkaline solution B and scrubbing tail gas B; step S3, chlorosilane safety valve venting tail gas... The valve-vented tail gas undergoes a first condensation treatment to obtain a first chlorosilane condensate and a first condensed tail gas; the chlorosilane tail gas undergoes a second condensation treatment to obtain a second chlorosilane condensate and a second condensed tail gas; the first condensed tail gas and the second condensed tail gas are mixed to obtain a mixed chlorosilane tail gas; the mixed chlorosilane tail gas enters a third rinsing system, and after being rinsed with recovered alkali, it obtains rinsed alkali solution C and rinsed tail gas C; in step S4, the rinsed alkali solution B and rinsed alkali solution C are returned to the recovery unit and recycled together with the rinsed alkali solution A; wherein, the recovery unit includes a sedimentation reaction tank and a filter press connected in sequence, quicklime is added to the sedimentation reaction tank to carry out a sedimentation reaction to obtain a sediment slurry, and the filter press is used to filter the sediment slurry to obtain solid precipitate and recovered alkali solution.

[0015] Furthermore, the mass concentration of sodium hydroxide in the recovered alkaline solution is 2% to 5%.

[0016] Furthermore, the first rinsing system includes two sets connected in parallel. Each set of the first rinsing system includes a rinsing tower and an alkaline circulation pump configured outside the rinsing tower. The alkaline circulation pump is used to circulate sodium hydroxide aqueous solution to the rinsing tower to complete the first rinsing.

[0017] Furthermore, in the two sets of first shower systems, one set is in continuous operation and the other is on standby; at the same time, the spray volume of the continuously operating set is less than that of the standby set, and the opening and closing state of the standby set changes with the air intake pressure of the continuously operating set. When the air intake pressure exceeds the threshold, the standby set changes from the closed state to the open state.

[0018] Furthermore, the threshold is 0.075 MPa to 0.15 MPa.

[0019] Furthermore, the threshold is 0.1 ± 0.02 MPa.

[0020] Furthermore, the precipitation reaction was carried out at room temperature and pressure.

[0021] Furthermore, the temperatures of the first condensation treatment and the second condensation treatment are each independently -10℃ to -40℃.

[0022] Furthermore, the temperatures for the first and second condensation treatments are each independently -20±2℃.

[0023] Furthermore, the recovered alkaline solution is divided into a first part, a second part, and a third part, wherein the first part is used for the second rinsing and the second part is used for the third rinsing; the treatment method for the tail gas of silane production by the chlorosilane disproportionation method also includes: step S5, discharging the third part of the recovered alkaline solution into a neutralization reaction tank, and adding hydrochloric acid into the neutralization reaction tank, and obtaining a sodium chloride solution after neutralization reaction; the sodium chloride solution is evaporated and crystallized to obtain sodium chloride crystals and condensate, and the condensate is returned to step S4 for pressure filtration treatment.

[0024] Applying the technical solution of this invention, a new method for treating the tail gas of silane production by the disproportionation method of chlorosilane is proposed. This method can simultaneously treat different types of tail gas. By using sodium hydroxide solution rinsing and quicklime precipitation reaction, harmful substances in the tail gas released by the silane safety valve, the silane tail gas, the tail gas released by the chlorosilane safety valve, and the chlorosilane tail gas are effectively removed, that is, the harmless treatment of multiple tail gases is achieved simultaneously. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 A schematic flowchart of a method for treating tail gas from the production of silane via chlorosilane disproportionation in one embodiment of the present invention is shown. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0028] As described in the background section, existing technologies struggle to efficiently and effectively treat the various tail gases generated during the disproportionation process of silane production from chlorosilanes, including silane safety valve venting tail gas, silane tail gas, chlorosilane safety valve venting tail gas, and chlorosilane tail gas. To address these technical problems, this invention provides a method for treating tail gases from the chlorosilane disproportionation process of silane production, such as... Figure 1As shown, the treatment method includes: Step S1, providing silane tail gas produced by the chlorosilane disproportionation method, the silane tail gas produced by the chlorosilane disproportionation method including silane safety valve venting tail gas, silane tail gas, chlorosilane safety valve venting tail gas, and chlorosilane tail gas; Step S2, the silane safety valve venting tail gas enters the first scrubbing system, and after being scrubbed with a sodium hydroxide aqueous solution with a mass concentration of 10% to 25%, a scrubbing alkaline solution A and a scrubbing tail gas A are obtained; the scrubbing alkaline solution A is sent to the recovery unit for recovery treatment to obtain a recovered alkaline solution; the silane tail gas enters the second scrubbing system, and after being scrubbed with the recovered alkaline solution, a second scrubbing is performed to obtain a scrubbing alkaline solution B and a scrubbing tail gas B; Step S3, the chlorosilane safety valve venting tail gas undergoes a first condensation treatment. The process involves obtaining a first chlorosilane condensate and a first condensed tail gas; the chlorosilane tail gas undergoes a second condensation treatment to obtain a second chlorosilane condensate and a second condensed tail gas; the first condensed tail gas and the second condensed tail gas are mixed to obtain a mixed chlorosilane tail gas; the mixed chlorosilane tail gas enters a third rinsing system, and after being rinsed with recovered alkali, rinsed alkali solution C and rinsed tail gas C are obtained; in step S4, rinsed alkali solution B and rinsed alkali solution C are returned to the recovery unit for recovery treatment together with rinsed alkali solution A; wherein, the recovery unit includes a sedimentation reaction tank and a filter press connected in sequence, quicklime is added to the sedimentation reaction tank to carry out a sedimentation reaction to obtain a sediment slurry, and the filter press is used to filter the sediment slurry to obtain solid precipitate and recovered alkali solution.

[0029] It should be explained beforehand that in the process of producing silanes via the disproportionation of chlorosilanes, both the silane safety valve venting gas and the chlorosilane safety valve venting gas are exhaust gases that may be generated to ensure the safe operation of the production process. That is, when the system pressure exceeds the set safety value, the valve automatically opens to release the excess pressure, preventing damage to equipment or pipelines due to overpressure, thereby releasing the safety valve venting gas. In particular, both the chlorosilane safety valve venting gas and the chlorosilane exhaust gas are byproducts or unreacted raw materials in the silane preparation process, but the volume of the chlorosilane safety valve venting gas is larger, and therefore their treatment methods and the conditions involved differ.

[0030] The above-mentioned method for treating the tail gas of silane production by chlorosilane disproportionation provided by the present invention effectively removes harmful substances from the tail gas released by the silane safety valve, the silane tail gas, the chlorosilane safety valve tail gas, and the chlorosilane tail gas by using sodium hydroxide solution rinsing and quicklime precipitation reaction, and simultaneously achieves the harmless treatment of various tail gases generated in the process of silane production by chlorosilane disproportionation.

[0031] Specifically, step S2 involves passing the silane safety valve venting exhaust gas and the silane exhaust gas separately through a rinsing system using sodium hydroxide as the rinsing solution. This effectively removes harmful substances such as silane from both exhaust gases, ensuring the safety and efficiency of subsequent treatment steps. This method is suitable for treating exhaust gases containing high concentrations of silane. Step S3 first condenses the chlorosilane safety valve venting exhaust gas and the chlorosilane exhaust gas, recovering the chlorosilane from both. The first and second condensed exhaust gases, separated from the chlorosilane condensate, are then mixed and rinsed with sodium hydroxide alkaline solution to remove any residual chlorosilane. The rinsing exhaust gases produced during the above rinsing process are all high-purity hydrogen that can be directly vented. In step S4, the rinsing solutions generated during rinsing, namely sodium metasilicate solutions, react with quicklime to produce calcium metasilicate insolubles and sodium hydroxide. The solid sodium metasilicate can be directly landfilled, while the resulting sodium hydroxide solution is used as a recovered alkaline solution in the second and third rinsing processes. In other words, step S4, through a precipitation reaction, converts water glass, which is difficult to recover and treat under conventional conditions, into insoluble substances, avoiding potential blockages in the corresponding system equipment and pipelines. It further removes other harmful substances from the alkaline solutions A, B, and C after rinsing that were not completely removed by rinsing, ensuring that the treated filtrate meets discharge and recovery standards. More importantly, by incorporating this step, the entire system's alkaline solution is recycled and reused, thus making more rational use of the concentrated alkali introduced and used in the first rinsing process. This significantly improves the economic and environmental friendliness of the method and more efficiently achieves the harmless treatment of various tail gases generated during the disproportionation process of silane production from chlorosilanes. Furthermore, the sodium hydroxide concentration in the recovered alkaline solution is 2%–5%. Based on the exhaust gas released by the silane safety valve, the preferred first scrubbing solution is a sodium hydroxide solution with a mass concentration of 10% to 25%. This allows the silane in the exhaust gas to react more thoroughly with the NaOH in the alkaline solution and be removed. This method is suitable for treating exhaust gas from silane safety valves containing high concentrations of silane, improving the thoroughness and safety of the treatment. It also allows for more efficient recovery of the alkaline solution, facilitating subsequent treatment processes.

[0032] In several typical implementations, to make the rinsing processes in the first, second, and third rinsing systems more efficient, and thus more thoroughly remove chlorosilanes and silanes, achieving a more significant harmless treatment effect, it is preferable that the flow rate of the silane safety valve releasing tail gas into the first rinsing system is 800 Nm³. 3 / h~1200Nm 3 / h, more preferably 1000±50Nm 3 / h; The flow rate of silane tail gas entering the second scrubbing system is 200 Nm³ / h. 3 / h~400Nm 3 / h, more preferably 300±50Nm 3 / h; the spray volume of the recovered alkaline solution entering the second rinsing system is 8m³ / h. 3 / h~12m 3 / h, more preferably 10±0.5m 3 / h; The flow rate of the mixed chlorosilane tail gas entering the third scrubbing system is 300 Nm³ / h. 3 / h~500Nm 3 / h, more preferably 400±50Nm 3 / h; the spray rate of the recovered alkaline solution entering the third rinsing system is 20m³ / h. 3 / h~40m 3 / h, more preferably 30±2m 3 / h.

[0033] For the scrubbing process of silane safety valve exhaust gas, to balance the silane removal efficiency and equipment operating costs, it is preferable that the first scrubbing system comprises two sets connected in parallel. Each first scrubbing system includes a scrubbing tower and an alkaline solution circulation pump located outside the scrubbing tower. The alkaline solution circulation pump circulates sodium hydroxide aqueous solution to the scrubbing tower to complete the first scrubbing. Furthermore, to better adapt to different flow rates of silane safety valve exhaust gas and thus achieve more efficient silane removal, it is further preferable that one set of the two first scrubbing systems is continuously operating, while the other is on standby. Simultaneously, the spray volume of the continuously operating system is less than that of the standby system, and the opening / closing state of the standby system varies with the inlet pressure of the continuously operating system. When the inlet pressure exceeds a threshold, the standby system changes from a closed state to an open state. The preferred threshold is 0.075 MPa to 0.15 MPa, more preferably 0.1 ± 0.02 MPa, thereby achieving a more efficient first scrubbing process.

[0034] Furthermore, in order to achieve better precipitation results and improve the efficiency of harmless treatment, it is further optimized to carry out the precipitation reaction under normal temperature and pressure conditions.

[0035] Regarding the composition of the chlorosilane safety valve vent gas and the chlorosilane tail gas, it is further preferred that the temperatures of the first and second condensation treatments are each independently -10℃ to -40℃, and more preferably -20±2℃. By optimizing and further optimizing the condensation treatment temperatures, the chlorosilane components can be recovered more effectively, reducing resource waste. Simultaneously, a mixed chlorosilane tail gas with a lower chlorosilane content is obtained, laying the groundwork for subsequent rinsing treatment and ultimately improving the removal rate of chlorosilanes in the entire treatment process.

[0036] In several typical implementations, the recovered alkali solution is divided into a first part, a second part, and a third part, wherein the first part is used for the second rinsing, and the second part is used for the third rinsing. The treatment method for the tail gas from the silane production process via chlorosilane disproportionation further includes: step S5, discharging the third part of the recovered alkali solution into a neutralization reaction tank, adding hydrochloric acid to the neutralization reaction tank, and obtaining a sodium chloride solution after neutralization; the sodium chloride solution is evaporated and crystallized to obtain sodium chloride crystals and condensate, and the condensate is returned to step S4 for pressure filtration to further realize resource reuse. In addition, excess sodium hydroxide filtrate can be concentrated and sold directly, thereby further reducing the cost of the above treatment method.

[0037] The aforementioned exhaust gases originate from existing chlorosilane disproportionation process production systems for silane. In several typical embodiments, by weight, the silane safety valve venting exhaust gas includes 40-45 parts of silane and 50-55 parts of chlorosilane; and / or, by weight, the silane exhaust gas includes 55-60 parts of silane, 2-4 parts of chlorosilane, and 40-45 parts of nitrogen; and / or, by weight, the chlorosilane safety valve venting exhaust gas and the chlorosilane exhaust gas each independently include 3-5 parts of chlorosilane, 37-40 parts of hydrogen, 55-60 parts of nitrogen, and 1-2 parts of hydrogen chloride.

[0038] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0039] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0040] It should be noted in advance that the silane tail gas produced by the chlorosilane disproportionation method of the present invention is the silane safety valve venting tail gas, silane tail gas, chlorosilane safety valve venting tail gas and chlorosilane tail gas obtained in the process of producing silane by the chlorosilane disproportionation method. The main component contents are shown in Table 1 below (a small amount of impurity gases are not listed).

[0041] Table 1

[0042] Silane safety valve releases exhaust gas 44 55 \ \ \ Silane tail gas 55 2 \ 43 \ Chlorosilane safety valve releases tail gas and chlorosilane tail gas \ 3 37 59 1

[0043] Example 1

[0044] A method for treating tail gas from silane production via chlorosilane disproportionation, employing... Figure 1 The system shown proceeds as follows:

[0045] (1) A 25% sodium hydroxide aqueous solution is used as the first rinsing solution and introduced into the first rinsing system. The system contains two spray towers, each equipped with a separate rinsing system and alkali circulation pump. Tower A is normally open but has a small spray volume (10m³ / s). 3 / h), B-set spray volume is large (30m³ / h), 3 / h) However, it is interlocked with the pressure at the inlet of the silane safety valve's exhaust gas vent; the alkaline circulation pump in Set B will only start when this pressure exceeds (0.1MPa, gauge pressure). The silane safety valve exhaust gas is released at 1000Nm 3 A flow rate of / h enters the first rinsing system, and after the first rinsing, rinsing alkaline solution A and rinsing tail gas A are obtained. The obtained rinsing alkaline solution A is discharged into the sedimentation reaction tank, and the rinsing tail gas A can be directly vented.

[0046] (2) The silane tail gas is discharged at 300 Nm 3 The second scrubbing system for the silane tail gas enters at a flow rate of / h. The second scrubbing solution used in this system, namely the recovered sodium hydroxide alkaline solution, has a mass concentration of 5% and is applied at a flow rate of 10m³ / h. 3 After a second rinsing process, a spray rate of / h yields rinsed alkaline solution B and rinsed tail gas B. The resulting rinsed alkaline solution B is also discharged into the sedimentation reaction tank, while the rinsed tail gas B can be directly vented.

[0047] (3) The chlorosilane safety valve exhaust gas undergoes a first condensation treatment at -20℃ to obtain a first condensed exhaust gas and chlorosilane condensate; the chlorosilane exhaust gas undergoes a second condensation treatment at -20℃ to obtain a second condensed exhaust gas and chlorosilane condensate. The two chlorosilane condensates are recycled, and the first and second condensed exhaust gases are mixed to obtain a mixed chlorosilane exhaust gas; then, the obtained mixed chlorosilane exhaust gas is discharged at 400 Nm³ / h. 3 The gas enters the third scrubbing system at a flow rate of / h, using a 2% (w / h) recovered sodium hydroxide aqueous solution as the third scrubbing liquid. The mixed chlorosilane tail gas is then discharged at a flow rate of 30m³ / h. 3 After the third rinsing, the spraying rate of / h yields rinsing alkaline solution C and rinsing tail gas C. The rinsing alkaline solution C is discharged into the sedimentation reaction tank, and the rinsing tail gas C can be directly vented.

[0048] (4) After rinsing, alkaline solutions A, B, and C were all placed in a precipitation reaction tank. Quicklime (CaO) was added to the tank, and a precipitation reaction was carried out under normal temperature and pressure conditions. The amount added was 2934 kg, until the silicon element in the reaction tank was completely precipitated. During the precipitation process, Na2SiO3 in the three rinsing solutions reacted with CaO and water to form insoluble solid precipitates CaSiO3 and NaOH, resulting in a slurry. The slurry was then filtered to obtain CaSiO3 solid precipitate and NaOH filtrate.

[0049] (5) The obtained NaOH filtrate is reused as the second and third rinsing solutions to continue participating in the second and third rinsing processes. Excess NaOH filtrate is sent to a neutralization reaction tank to react with hydrochloric acid to produce NaCl and water. The NaCl aqueous solution is sent to an evaporation crystallization system (multi-effect evaporation or MVR) to separate NaCl. The resulting condensate is preferentially returned to the pressure filter for rinsing and dilution, and excess condensate is discharged from the system.

[0050] In the above treatment method, the vented tail gas A, tail gas B, and tail gas C after rinsing are all hydrogen-nitrogen mixtures with purities of 100%, 28%, and 60%, respectively, and do not contain any polluting or harmful components. The resulting solid precipitate, namely sodium metasilicate, has a purity of 100% and can be directly landfilled. The sodium hydroxide filtrate solution can be recycled in the manner described above.

[0051] That is, the processing method provided in this embodiment achieves the harmless treatment of tail gas from the silane production process by the disproportionation of chlorosilane.

[0052] As can be seen from the above description, the embodiments of the present invention achieve efficient and harmless treatment of four types of tail gases generated during the disproportionation process of silanes using sodium hydroxide alkaline solutions of different concentrations: silane safety valve venting tail gas, silane tail gas, chlorosilane safety valve venting tail gas, and chlorosilane tail gas. The tail gases generated after rinsing in the first, second, and third rinsing systems are all high-purity hydrogen gases that can be directly vented. The sodium metasilicate solution generated during rinsing reacts with quicklime in the subsequent precipitation reaction tank to produce calcium metasilicate and sodium hydroxide. The solid sodium metasilicate can be directly landfilled, while the sodium hydroxide solution can be recycled.

[0053] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating tail gas from the disproportionation process of chlorosilane to produce silane, characterized in that, include: Step S1, providing the tail gas from the silane production process by the chlorosilane disproportionation method, wherein the tail gas from the silane production process by the chlorosilane disproportionation method includes tail gas released by a silane safety valve, silane tail gas, tail gas released by a chlorosilane safety valve, and chlorosilane tail gas. In step S2, the silane safety valve releases tail gas into the first scrubbing system, where it undergoes a first scrubbing with a sodium hydroxide aqueous solution of 10%–25% by mass, yielding scrubbing alkaline solution A and scrubbing tail gas A. The scrubbing alkaline solution A is then sent to a recovery unit for recycling, yielding recovered alkaline solution. The silane tail gas then enters the second scrubbing system, undergoes a second scrubbing with the recovered alkaline solution, yielding scrubbing alkaline solution B and scrubbing tail gas B. Step S3: The chlorosilane safety valve releases tail gas through a first condensation treatment to obtain a first chlorosilane condensate and a first condensed tail gas; the chlorosilane tail gas undergoes a second condensation treatment to obtain a second chlorosilane condensate and a second condensed tail gas; the first condensed tail gas and the second condensed tail gas are mixed to obtain a mixed chlorosilane tail gas; the mixed chlorosilane tail gas enters a third rinsing system, and after being rinsed with the recovered alkaline solution, rinsing alkaline solution C and rinsing tail gas C are obtained. Step S4: The leached alkaline solution B and the leached alkaline solution C are returned to the recovery unit and recycled together with the leached alkaline solution A. The recovery unit includes a sedimentation reaction tank and a filter press connected in sequence. Quicklime is added to the sedimentation reaction tank to carry out a sedimentation reaction to obtain a sediment slurry. The filter press is used to filter the sediment slurry to obtain solid precipitate and the recycled alkaline solution.

2. The method for treating tail gas from the silane production process via chlorosilane disproportionation according to claim 1, characterized in that, The sodium hydroxide concentration in the recovered alkaline solution is 2% to 5% by mass.

3. The method for treating tail gas from the silane production process via chlorosilane disproportionation according to claim 1, characterized in that, The first rinsing system includes two sets connected in parallel. Each set of the first rinsing system includes a rinsing tower and an alkaline circulation pump disposed outside the rinsing tower. The alkaline circulation pump is used to circulate the sodium hydroxide aqueous solution to the rinsing tower to complete the first rinsing.

4. The method for treating tail gas from the silane production process via chlorosilane disproportionation according to claim 3, characterized in that, In the two sets of the first shower system, one set is in continuous operation and the other set is on standby. At the same time, the spray volume of the continuously operating set is less than that of the standby set, and the opening and closing state of the standby set changes with the air intake pressure of the continuously operating set. When the air intake pressure exceeds a threshold, the standby set changes from the closed state to the open state.

5. The method for treating tail gas from the silane production process via chlorosilane disproportionation according to claim 4, characterized in that, The threshold is 0.075MPa to 0.15MPa.

6. The method for treating tail gas from the silane production process via chlorosilane disproportionation according to claim 5, characterized in that, The threshold is 0.1 ± 0.02 MPa.

7. The method for treating tail gas from the silane production process via chlorosilane disproportionation according to claim 6, characterized in that, The precipitation reaction is carried out at room temperature and pressure.

8. The method for treating tail gas from the chlorosilane disproportionation process for producing silane according to any one of claims 1 to 7, characterized in that, The temperatures of the first condensation treatment and the second condensation treatment are each independently -10℃ to -40℃.

9. The method for treating tail gas from the silane production process via chlorosilane disproportionation according to claim 8, characterized in that, The temperatures of the first condensation treatment and the second condensation treatment are each independently -20±2℃.

10. The method for treating tail gas from the chlorosilane disproportionation process for producing silane according to any one of claims 1 to 9, characterized in that, The recovered alkali solution is divided into a first part, a second part, and a third part, wherein the first part is used for the second rinsing. The second part is used for the third rinse; The method for treating the tail gas from the silane production process via chlorosilane disproportionation also includes: Step S5: The recovered alkaline solution from the third part is discharged into the neutralization reaction tank, and hydrochloric acid is added to the neutralization reaction tank. After neutralization reaction, a sodium chloride solution is obtained. The sodium chloride solution is evaporated and crystallized to obtain sodium chloride crystals and condensate. The condensate is returned to step S4 for the pressure filtration process.

Images