A tail gas treatment system to prevent gas phase tempering

Abstract

The utility model discloses a kind of tail gas treatment systems to prevent gas phase tempering, it is related to the safety protection equipment technical field in the accident tail gas treatment in polysilicon production, including DCS, tail gas diffusion unit and nitrogen purging unit, tail gas diffusion unit includes tail gas main pipe, buffer tank and at least two levels of tail gas diffusion pipeline connected in turn;Nitrogen purging unit includes nitrogen main pipe, nitrogen main pipe is communicated with multiple nitrogen branch pipes, the number of nitrogen branch pipe is equal to the number of series of tail gas diffusion pipeline, each level tail gas diffusion pipeline is correspondingly connected with one nitrogen branch pipe;Pressure sensor I is equipped on buffer tank, valve is equipped on each tail gas diffusion pipeline, nitrogen branch pipe;DCS is respectively connected with pressure sensor I, and the valve control connection on tail gas diffusion pipeline and nitrogen branch pipe, solve the existing tail gas treatment system tempering problem in present polysilicon production.

Description

Technical Field

[0001] This utility model relates to the technical field of safety protection equipment for the treatment of accidental exhaust gases in polysilicon production, and specifically to an exhaust gas treatment system for preventing gas phase backfire. Background Technology

[0002] In the production process of silane gas manufacturing, the treatment of silane tail gas is a crucial step in ensuring production safety and meeting environmental compliance requirements. Currently, the industry commonly uses flare incineration to treat silane tail gas, converting the combustible components in the tail gas through combustion, thereby reducing its environmental harm and safety risks.

[0003] However, existing flare incineration methods pose a significant risk of backfire. This risk stems from fluctuations in the exhaust gas volume caused by changes in production conditions: as the exhaust gas volume gradually decreases, the exhaust gas velocity at the flare outlet also decreases. Once the exhaust gas velocity falls below the combustion velocity, the flame can easily propagate backward to the upstream system, triggering backfire. Backfire can cause a sharp increase in the temperature of the upstream system, which can then burn out sealing components such as flange gaskets. After the seals fail, hazardous materials such as silane may leak, potentially leading to explosions, poisoning, and other serious safety accidents, posing a significant threat to production equipment, personnel safety, and the surrounding environment.

[0004] To address the aforementioned backfire risk, the industry has developed two traditional backfire prevention technologies: one is to use flame arresters, but due to structural limitations, they have weak blocking capabilities against back-propagating flames, insufficient protection reliability, and difficulty in effectively cutting off the flame propagation path, leaving the upstream system still facing the risk of backfire; the other is to use backfire-proof liquid phase storage tanks, which, although having better flame-arresting capabilities than flame arresters, still have safety vulnerabilities, as the front end of the pipeline connected to the upstream system will continue to burn, failing to completely solve the problem of temperature rise in the upstream system, and the equipment manufacturing cost, installation cost, and subsequent maintenance cost are all high, which is not conducive to widespread application.

[0005] In summary, existing methods for preventing backfire in silane tail gas incineration systems either suffer from insufficient reliability leading to high safety risks or are too costly to be widely adopted, failing to achieve a balance between safety and economy. Therefore, optimization of existing processes or equipment is still necessary to address these technical issues. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of backfire in the tail gas treatment system in existing polysilicon production, and to propose a tail gas treatment system that prevents gas phase backfire.

[0007] This utility model is achieved through the following technical solution: An exhaust gas treatment system for preventing vapor phase backfire includes a DCS, an exhaust gas venting unit, and a nitrogen purging unit. The exhaust gas venting unit includes an exhaust gas main pipe, a buffer tank, and at least two stages of exhaust gas venting pipes connected in sequence. The nitrogen purging unit includes a main nitrogen pipe, which is connected to multiple nitrogen branch pipes. The number of nitrogen branch pipes is equal to the number of stages of the exhaust gas venting pipeline, and each stage of the exhaust gas venting pipeline is connected to a corresponding nitrogen branch pipe. Pressure sensor I is installed on the buffer tank. Each exhaust gas venting pipe and nitrogen distribution pipe is equipped with a valve; The DCS is connected to pressure sensor I, as well as the valves on the exhaust gas venting pipe and the nitrogen branch pipe.

[0008] Furthermore, the exhaust gas venting unit includes a three-stage exhaust gas venting pipeline, which includes a primary venting pipeline, a secondary venting pipeline, and a tertiary venting pipeline. The nitrogen purging unit includes nitrogen branch pipe I, nitrogen branch pipe II, and nitrogen branch pipe III. The primary, secondary, and tertiary venting pipelines are respectively connected to nitrogen branch pipe I, nitrogen branch pipe II, and nitrogen branch pipe III. Nitrogen branch pipe I, nitrogen branch pipe II, and nitrogen branch pipe III are respectively equipped with valve I, valve II, and valve III.

[0009] Furthermore, valve I, valve II, and valve III are one type of on / off valve or solenoid valve.

[0010] Furthermore, it also includes a flame detection device at the outlet of the primary venting pipe for monitoring the flame status. The flame detection device is connected to the DCS signal and includes an ultraviolet flame detection device or a sheathed thermocouple.

[0011] Furthermore, the fire detection equipment is fixedly installed on the upper side of the outlet end of the primary venting pipe using a bracket.

[0012] Furthermore, it also includes an industrial television for visual monitoring of the exit conditions. The image acquisition lens connected to the industrial television signal is made of high-temperature resistant quartz glass, the industrial television housing is an explosion-proof housing, and the industrial television is connected to the DCS signal.

[0013] Furthermore, a pressure sensor II is installed on the nitrogen main pipe.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: I. This utility model proposes a tail gas treatment system to prevent vapor-phase backfire. Through the coordinated design of DCS, tail gas venting unit, and nitrogen purging unit, automated and precise control of silane tail gas treatment is achieved. A buffer tank stabilizes tail gas pressure, preventing sudden changes in flow rate caused by gas volume fluctuations and reducing the risk of backfire. At least two parallel tail gas venting pipelines can adapt to tail gas emission volumes under different operating conditions, ensuring that the tail gas velocity is always maintained within a safe range. Nitrogen branch pipes correspond one-to-one with the venting pipelines, allowing for rapid intervention and purging when a risk is triggered, effectively blocking the flame propagation path. The linkage control between pressure sensors and DCS allows the system to respond to changes in operating conditions in real time, automatically adjusting valve states, significantly improving the timeliness and reliability of backfire prevention, while simplifying manual operation and balancing safety protection and operational efficiency.

[0015] II. In this utility model, a preferred design employs a three-stage parallel exhaust gas venting pipeline and three nitrogen branch pipes, further refining the adaptability range for different operating conditions. This allows for precise matching of exhaust gas treatment needs at high, medium, and low volumes, avoiding the problem of excessively low flow rates in a single pipeline when gas volume fluctuates. Each nitrogen branch pipe corresponds to a primary venting pipeline and is equipped with an independent valve, enabling nitrogen purging to target pipelines at risk of backfire, ensuring purging effectiveness while avoiding nitrogen resource waste. The tiered control design makes system operation more flexible, allowing selective opening of corresponding pipelines and purging branches based on actual exhaust gas emissions, improving the system's operational economy and enhancing the accuracy of backfire protection.

[0016] Third, in this utility model, the valves selected are either on / off valves or solenoid valves, which meet the core requirements of the system's automated control. On / off valves offer advantages such as stable structure and reliable sealing performance, effectively preventing exhaust gas or nitrogen leakage and ensuring the system's sealing and safety. Solenoid valves, on the other hand, have a fast response speed, facilitating valve opening adjustment and ensuring timely nitrogen purging to quickly block backfire propagation. The optional design of these two valve types allows users to flexibly adapt to actual production conditions and cost budgets, improving the system's versatility and practicality while meeting the backfire prevention response efficiency requirements in different scenarios.

[0017] IV. In this utility model, a flame detection device is installed at the outlet of the primary venting pipeline and connected to the DCS signal, realizing real-time monitoring and rapid early warning of the flame status. The ultraviolet flame detection device can accurately capture the ultraviolet spectrum of the flame, and the armored thermocouple can promptly detect sudden temperature changes. Both devices can quickly identify signs of backfire and feed them back to the DCS, making up for the limitations of single pressure monitoring. Through the linkage control of the DCS, protective actions such as nitrogen purging and valve adjustment can be triggered the instant a backfire risk is detected, significantly shortening the risk response time, further improving the reliability of the system's backfire prevention, and preventing the flame from spreading backward to the upstream system.

[0018] V. In this utility model, the flame detection equipment is installed on the upper side of the outlet end of the primary venting pipe via a bracket. This installation position effectively avoids direct impact of exhaust gas on the equipment, reduces the corrosion of the flame detection element by high-temperature exhaust gas and impurities, and extends the service life of the equipment. At the same time, the upper side installation angle ensures that the detection field of view covers the entire cross-section of the pipe outlet, avoids blind spots in monitoring, and improves the accuracy and comprehensiveness of flame status identification.

[0019] VI. In this utility model, the addition of an industrial television enables visualized monitoring of the exhaust gas emission outlet conditions, forming a dual guarantee with the signal monitoring of the flame detection equipment. This allows operators to intuitively observe the flame status, promptly detect abnormalities, and assist in judgment. The high-temperature resistant quartz glass lens can withstand the high temperatures generated by exhaust gas combustion, and the explosion-proof housing is suitable for the hazardous environment of silane exhaust gas, ensuring stable operation of the industrial television under harsh conditions without safety hazards. The signal connection with the DCS allows the visualized image to be synchronized to the control terminal in real time, improving the convenience and safety of system operation and maintenance, and avoiding the risk omission due to the failure of a single monitoring method.

[0020] VII. In this utility model, a pressure sensor II is installed on the nitrogen main pipe to monitor the nitrogen source pressure in real time, ensuring sufficient and stable pressure support during nitrogen purging. When the nitrogen pressure is lower than the preset threshold, the DCS can promptly issue an early warning signal to remind the operator to replenish the gas source or troubleshoot the fault, avoiding problems such as insufficient purging force and inability to effectively block the flame due to insufficient nitrogen pressure. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the exhaust gas treatment system to prevent vapor phase backfire. Figure 1 .

[0022] Figure 2 This is a schematic diagram of the exhaust gas treatment system to prevent vapor phase backfire. Figure 2 .

[0023] Figure 3 This is a schematic diagram of the exhaust gas treatment system to prevent vapor phase backfire. Figure 3 .

[0024] Figure 4 This is a schematic diagram of the exhaust gas treatment system to prevent vapor phase backfire. Figure 4 .

[0025] The components are as follows: 1. DCS; 2. Exhaust gas main pipe; 3. Buffer tank; 4. Primary vent pipe; 5. Secondary vent pipe; 6. Tertiary vent pipe; 7. Nitrogen main pipe; 8. Pressure sensor I; 9. Nitrogen branch pipe I; 10. Nitrogen branch pipe II; 11. Nitrogen branch pipe III; 12. Valve I; 13. Valve II; 14. Valve III; 15. Flame detection equipment; 16. Industrial television; 17. Pressure sensor II; 18. Combustion furnace; 19. Valve IV; 20. Valve V; 21. Valve VI. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0027] Example 1 This embodiment is a basic implementation method, a tail gas treatment system for preventing gas phase backfire, including DCS1, tail gas venting unit and nitrogen purging unit.

[0028] The exhaust gas venting unit includes an exhaust gas main pipe 2, a buffer tank 3, and at least two parallel exhaust gas venting pipes connected in sequence; the nitrogen purging unit includes a nitrogen main pipe 7, which is connected to multiple nitrogen branch pipes. The number of nitrogen branch pipes is equal to the number of stages of the exhaust gas venting pipes, and each stage of the exhaust gas venting pipe is connected to a corresponding nitrogen branch pipe; the buffer tank 3 is equipped with a pressure sensor I8, and each exhaust gas venting pipe and nitrogen branch pipe is equipped with a valve; the DCS1 is connected to the pressure sensor I8 and the valves on the exhaust gas venting pipes and nitrogen branch pipes for control.

[0029] refer to Figure 1 , Figure 1 The diagram illustrates the structure of an exhaust gas venting unit connected to two parallel exhaust gas venting pipes, including a primary venting pipe 4 and a secondary venting pipe 5. The nitrogen purging unit includes nitrogen branch pipes I 9 and II 10, which are respectively connected to the primary venting pipe 4 and the secondary venting pipe 5. Valves I 12 and II 13 are respectively installed on nitrogen branch pipes I 9 and II 10.

[0030] This tail gas treatment system for preventing vapor phase backfire is applied to the tail gas treatment during the silane gas manufacturing process. The tail gas venting unit is used to transport the silane tail gas to be treated. When tail gas needs to be treated, valve IV19 on the primary venting pipeline 4 is opened according to the pressure of the gas in the buffer tank 3, or valves IV19 and V20 on both the primary venting pipeline 4 and the secondary venting pipeline 5 are opened simultaneously. The tail gas is then introduced into the combustion furnace 18 for combustion through the venting pipeline. When the tail gas volume is small and the pressure of the gas in the buffer tank 3 is low, only valve IV19 needs to be opened. When the pressure in the buffer tank 3 continues to rise and reaches the preset value, valve V20 is then opened to connect the secondary venting pipeline 5.

[0031] Backfire prevention is achieved through nitrogen-controlled purging, the steps of which include: The system presets multiple decreasing pressure thresholds, monitors the system pressure in real time (the pressure value in buffer tank 3 monitored by pressure sensor I8) and compares it with the thresholds; When the pressure is lower than the corresponding threshold, the interlock opens the valve on the nitrogen branch pipe connected to the corresponding level of venting pipeline to purge nitrogen continuously. As the pressure decreases, the pipelines at each level are opened in sequence for purging. The pressure and flame status are continuously monitored. When the pressure is lower than the minimum threshold and the flame is confirmed to be completely extinguished, the interlock closes the valve on all nitrogen branch pipes.

[0032] Example 2 This embodiment is a further optimization of embodiment 1, the difference being that, as referenced... Figure 3 The exhaust gas venting unit includes a three-stage exhaust gas venting pipeline, which includes a primary venting pipeline 4, a secondary venting pipeline 5, and a tertiary venting pipeline 6. The nitrogen purging unit includes a nitrogen branch pipe I 9, a nitrogen branch pipe II 10, and a nitrogen branch pipe III 11. The primary venting pipeline 4, the secondary venting pipeline 5, and the tertiary venting pipeline 6 are respectively connected to the nitrogen branch pipes I 9, II 10, and III 11. Valves I 12, II 13, and III 14 are respectively installed on the nitrogen branch pipes I 9, II 10, and III 11.

[0033] Preferably, valve I12, valve II13 and valve III14 are one of the following: a switching valve and a solenoid valve.

[0034] Example 3 The difference between this embodiment and embodiments 1-2 is that, in reference to... Figure 4 It also includes a flame detection device 15 at the outlet of the primary venting pipe 4 for monitoring the flame status. The flame detection device 15 is connected to the DCS1 signal and includes an ultraviolet flame detection device or a sheathed thermocouple.

[0035] Preferably, the flame detection device 15 is fixedly installed on the side above the outlet end of the primary venting pipe 4 by a bracket.

[0036] Example 4 The difference between this embodiment and embodiments 1-3 is that, in reference... Figure 4 It also includes an industrial television 16 for visual monitoring of the exit conditions. The camera lens of the industrial television 16 is made of high-temperature resistant quartz glass, and the housing of the industrial television 16 is an explosion-proof housing. The industrial television 16 is connected to the DCS1 signal.

[0037] Example 5 The difference between this embodiment and embodiments 1-4 is that a pressure sensor II17 is provided on the nitrogen main pipe 7. Figure 2 .

[0038] Example 6 To facilitate public understanding of this utility model, this embodiment uses a preferred tail gas treatment system for preventing vapor phase backfire as an example to further illustrate the solution. (Reference) Figure 4 The system includes DCS1, exhaust gas venting unit and nitrogen purging unit.

[0039] In this embodiment, the exhaust gas venting unit includes an exhaust gas main pipe 2, a buffer tank 3, and three parallel exhaust gas venting pipes connected in sequence. The three-stage exhaust gas venting pipes include a primary venting pipe 4, a secondary venting pipe 5, and a tertiary venting pipe 6.

[0040] The nitrogen purging unit includes a main nitrogen pipe 7, which is connected to three nitrogen branch pipes. The three nitrogen branch pipes are nitrogen branch pipe I 9, nitrogen branch pipe II 10 and nitrogen branch pipe III 11 connected in parallel.

[0041] The primary venting pipe 4, secondary venting pipe 5, and tertiary venting pipe 6 are respectively connected to nitrogen branch pipes I 9, II 10, and III 11. Valves I 12, II 13, and III 14 are respectively installed on nitrogen branch pipes I 9, II 10, and III 11. Pressure sensor I 8 is installed on buffer tank 3, and pressure sensor II 17 is installed on main nitrogen pipe 7. In this embodiment, primary venting pipe 4, secondary venting pipe 5, and tertiary venting pipe 6 are respectively connected to valves IV 19, V 20, and VI 21. DCS1 is controlled by pressure sensors I 8, II 17, I 12, II 13, III 14, IV 19, V 20, and VI 21.

[0042] In this embodiment, valves I12, II13, III14, IV19, V20, and VI21 ​​are on / off valves.

[0043] In this embodiment, a flame detection device 15 for monitoring the flame status at the outlet of the primary venting pipe 4 is also included. The flame detection device 15 is connected to the DCS1 signal and is an ultraviolet flame detection device. The flame detection device 15 is fixedly installed on the upper side of the outlet end of the primary venting pipe 4 by a bracket.

[0044] In this embodiment, an industrial television 16 is also included for visual monitoring of the outlet operating conditions. The industrial television 16 collects the flame status at the window of the combustion furnace 18 through its camera. The camera lens of the industrial television 16 is made of high-temperature resistant quartz glass, and the housing of the industrial television 16 is an explosion-proof housing. The industrial television 16 is connected to the DCS1 signal.

[0045] This tail gas treatment system for preventing vapor phase backfire is applied to the tail gas treatment process in silane gas manufacturing. The tail gas venting unit is used to transport the silane tail gas to be treated. When the tail gas volume is small, the primary venting pipe 4 is opened to send the tail gas to the combustion furnace 18 for combustion treatment. As the amount of tail gas released increases (as can be seen by monitoring the gas pressure in the buffer tank 3 through pressure sensor I8), the valves on the secondary venting pipe 5 and the tertiary venting pipe 6 are opened sequentially. When the tertiary tail gas venting pipe is opened simultaneously, the system's tail gas treatment capacity is maximized.

[0046] The nitrogen main pipe 7 of the nitrogen purging unit is connected to the nitrogen source, and the other end outlet is connected to the three-stage nitrogen branch pipes, namely nitrogen branch pipe I 9, nitrogen branch pipe II 10 and nitrogen branch pipe III 11. Nitrogen branch pipe I 9, nitrogen branch pipe II 10 and nitrogen branch pipe III 11 are respectively connected to the primary venting pipe 4, the secondary venting pipe 5 and the tertiary venting pipe 6.

[0047] Based on the above system, the method for preventing vapor phase flashback includes the following steps: S1. A preset exhaust gas emission system has multiple pressure thresholds, including a first pressure threshold P1 of 10 kPa, a second pressure threshold P2 of 5 kPa, a third pressure threshold P3 of 3 kPa, and a fourth pressure threshold P4 of 1 kPa arranged in descending order. S2. The pressure in the buffer tank 3, i.e. the system pressure of the exhaust gas venting system, is monitored in real time by pressure sensor I8, and the real-time monitored pressure is compared with the preset pressure thresholds. S3. Based on the pressure comparison results, the valve on the nitrogen branch pipe connected to the corresponding level exhaust gas venting pipeline is opened and closed by interlock control to introduce nitrogen into the corresponding exhaust gas venting pipeline for purging. When P2 < P 实 When ≤P1, open valve Ⅲ14 on nitrogen branch pipe Ⅲ11 and purge nitrogen into the third-stage venting pipe 6 for continuous blowing; When P3 < P 实 When P2 is ≤, open valve II13 on nitrogen branch pipe II10 and purge nitrogen into secondary vent pipe 5 for continuous blowing; When P4 < P 实 When P3 is ≤, open valve I12 on nitrogen manifold I9; When P 实 When the pressure is ≤P4, hold valve I12 on nitrogen pipe I9 open or gradually reduce the opening of valve I12 until the flame is confirmed to be completely extinguished, then close valve I12. S4. Continuously monitor the system pressure and the flame status of the exhaust gas venting system. When the system pressure is lower than the fourth pressure threshold and it is confirmed that the flame is completely extinguished, interlock and close all valves on the nitrogen branch pipes to stop nitrogen purging.

[0048] In this step, the industrial television 16 is used to observe and confirm whether the flame has been completely extinguished. The monitoring screen of the industrial television 16 is transmitted to the control terminal in real time. The control terminal determines the flame extinguishing status, or the operator makes a manual determination based on the monitoring screen. The determination result triggers the valve of the nitrogen branch pipe to close.

[0049] In this embodiment, the nitrogen purging pressure needs to be higher than the operating pressure of the exhaust gas venting system to ensure a stable flow of nitrogen into the exhaust gas venting pipe. The above description is merely a preferred embodiment of this utility model and is not intended to limit the invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of this utility model shall fall within the protection scope of this utility model.

Claims

1. A tail gas treatment system for preventing vapor phase backfire, characterized in that: Includes DCS (1), exhaust gas venting unit and nitrogen purging unit, The exhaust gas venting unit includes an exhaust gas main pipe (2), a buffer tank (3), and at least two stages of exhaust gas venting pipes connected in sequence. The nitrogen purging unit includes a nitrogen main pipe (7), which is connected to multiple nitrogen branch pipes. The number of nitrogen branch pipes is equal to the number of stages of the tail gas venting pipeline, and each stage of the tail gas venting pipeline is connected to a nitrogen branch pipe. Pressure sensor I (8) is installed on the buffer tank (3). Each exhaust gas venting pipe and nitrogen distribution pipe is equipped with a valve; The DCS (1) is connected to the pressure sensor I (8) and the valves on the exhaust gas venting pipe and the nitrogen branch pipe, respectively.

2. The exhaust gas treatment system for preventing vapor phase backfire according to claim 1, characterized in that: The exhaust gas venting unit includes a three-stage exhaust gas venting pipeline, which includes a first-stage venting pipeline (4), a second-stage venting pipeline (5) and a third-stage venting pipeline (6). The nitrogen purging unit includes a nitrogen branch pipe I (9), a nitrogen branch pipe II (10) and a nitrogen branch pipe III (11). The first-stage venting pipeline (4), the second-stage venting pipeline (5) and the third-stage venting pipeline (6) are respectively connected to the nitrogen branch pipe I (9), the nitrogen branch pipe II (10) and the nitrogen branch pipe III (11). The nitrogen branch pipe I (9), the nitrogen branch pipe II (10) and the nitrogen branch pipe III (11) are respectively equipped with valve I (12), valve II (13) and valve III (14).

3. The exhaust gas treatment system for preventing vapor phase backfire according to claim 2, characterized in that: The valves I (12), II (13) and III (14) are one type of switch valve or solenoid valve.

4. The exhaust gas treatment system for preventing vapor phase backfire according to claim 2, characterized in that: It also includes a flame detector (15) at the outlet of the primary vent pipe (4) for monitoring the flame status. The flame detector (15) is connected to the DCS (1) signal and includes an ultraviolet flame detector or a sheathed thermocouple.

5. The exhaust gas treatment system for preventing vapor phase backfire according to claim 4, characterized in that: The fire detection equipment (15) is fixedly installed on the side above the outlet end of the primary venting pipe (4) by a bracket.

6. The exhaust gas treatment system for preventing vapor phase backfire according to claim 2, characterized in that: It also includes an industrial television (16) for visual monitoring of the exit conditions. The industrial television (16) has an explosion-proof housing and is connected to the DCS (1) for signal transmission.

7. The exhaust gas treatment system for preventing vapor phase backfire according to claim 1, characterized in that: Pressure sensor II (17) is installed on the nitrogen main pipe (7).

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