An emergency supply control device for abnormal air separation nitrogen purity

Abstract

The application provides an air separation nitrogen purity abnormal emergency supply control device, and relates to the field of automatic control.The device comprises an air separation device, a trace oxygen analyzer, a DCS control system, a vent valve, a cut-off valve, a pressure transmitter, a buffer tank, a first regulating valve, a second regulating valve, a high-pressure nitrogen ball tank and a liquid nitrogen vaporizer.The trace oxygen analyzer detects the purity of nitrogen and transmits the purity to an analog input module.The pressure transmitter detects the pipeline pressure and transmits the pressure to another analog input module.The opening and closing of the vent valve and the cut-off valve are controlled by a digital output module according to the purity signal.The opening degree of the two regulating valves is controlled by an analog output module according to the pressure signal, so as to adjust the high-pressure nitrogen ball tank and the liquid nitrogen vaporizer to supplement high-purity nitrogen to the buffer tank or the pipeline.The application can quickly cut off unqualified nitrogen when the purity is abnormal, and maintain the stability of the production line gas supply purity and pressure by supplementing high-purity nitrogen.

Description

Technical Field

[0001] This application relates to the field of automatic control technology, and in particular to an emergency supply control device for abnormal purity of air separation nitrogen. Background Technology

[0002] An air separation nitrogen generation system is an industrial device used to produce high-purity nitrogen gas, which is widely used in electronics, chemicals, metallurgy, food packaging, and automobile manufacturing. In the production of automotive sheet metal, nitrogen is often used as a protective atmosphere, and its purity level directly affects the surface quality, weldability, and oxidation resistance of the sheet metal. Insufficient nitrogen purity can lead to quality problems such as oxidation and discoloration of the sheet metal, welding defects, and even cause the entire batch of products to be scrapped, resulting in serious economic losses for the company.

[0003] Currently, air separation nitrogen production systems generally employ cryogenic separation or pressure swing adsorption (PSA) processes, with product nitrogen directly transported to the production line via pipelines. Because the distillation conditions of air separation systems are highly sensitive, the stability of the pressure within the column is a critical prerequisite for ensuring nitrogen purity. In actual production, the product delivery pipeline is typically directly connected to the production line. Changes in the gas load on the production line side or fluctuations in pipeline pressure are quickly transmitted to the air separation column, causing pressure fluctuations within the column, which in turn disrupt the distillation equilibrium and lead to a decrease in product nitrogen purity. Therefore, interference from the gas load conditions on the production line is one of the direct causes of purity fluctuations in the air separation system.

[0004] Currently, nitrogen purity monitoring mainly relies on online sampling and analysis using a trace oxygen analyzer. Operators determine whether the purity is within acceptable limits based on the analyzer readings and manually perform venting or switching operations. However, this method has the following shortcomings: First, the analyzer's sampling pipeline is relatively long, resulting in a lag in sample gas transmission. The analyzer cannot reflect real-time purity changes within the air separation tower, making it difficult for operators to detect a decline in purity in a timely manner. Second, there is a long time window between the discovery of purity anomalies and manual intervention. During this window, a large amount of substandard nitrogen may have already entered the production line, causing actual losses. Third, once substandard nitrogen enters the pipeline, there is a lack of effective emergency handling measures to dilute or replace the substandard gas source; operators can only passively wait for the air separation system to re-establish acceptable operating conditions. Fourth, there is a lack of automated emergency switching and supplementary gas supply mechanisms, making it impossible to quickly remove substandard nitrogen and maintain a continuous and stable gas supply to the production line when purity anomalies occur.

[0005] Therefore, it is necessary to design an emergency supply control device that can automatically respond, quickly cut off substandard nitrogen and start a supplementary gas source when nitrogen purity is abnormal, so as to reduce or eliminate the impact of air separation system purity fluctuations on production line product quality and ensure production continuity and product quality stability. Summary of the Invention

[0006] This application provides an emergency supply control device for abnormal nitrogen purity in air separation systems. To enable the analyzer to reflect changes in purity within the air separation unit in real time, a manual vent valve is added, shortening the analyzer's sampling time. The analytical data is used as an interlock condition for automatic control. When the purity exceeds a set value, the DCS system outputs a signal to close the shut-off valve and open the vent valve, releasing the substandard nitrogen and preventing it from being output to the production line. A buffer tank is added between the air separation system and the production line. This ensures that when the shut-off valve is closed, the pressure in the buffer tank will maintain the pressure requirements of the production line for a certain period, diluting any substandard nitrogen input to the production line pipeline before the shut-off valve closes. Simultaneously, due to the reduced pipeline pressure, the pressure signal is used by the DCS system to regulate the regulating valve of the high-pressure nitrogen sphere system, delivering high-purity nitrogen from the high-pressure nitrogen sphere to the production pipeline. This further dilutes the substandard nitrogen, improving the nitrogen purity within the production pipeline. Because the high-purity nitrogen in the high-pressure nitrogen ball system is limited, the DCS system simultaneously activates the liquid nitrogen vaporization system to vaporize the liquid nitrogen in the liquid nitrogen storage tank into high-purity nitrogen through a vaporizer, which is then added to the buffer tank to further ensure the purity and pressure of the nitrogen supplied to the cold plate production line.

[0007] To achieve the above objectives, this application adopts the following technical solution: This application provides an emergency supply control device for abnormal nitrogen purity in air separation, including an air separation unit, a trace oxygen analyzer, a DCS control system, a vent valve, a shut-off valve, a pressure transmitter, a buffer tank, a first regulating valve, a second regulating valve, a high-pressure nitrogen balloon tank, and a liquid nitrogen vaporizer. The DCS control system is equipped with a first analog input module, a second analog input module, an analog output module, and a digital output module. The nitrogen outlet of the air separation unit is connected to the inlet of the shut-off valve through a first pipeline, the outlet of the shut-off valve is connected to the first inlet of the buffer tank through a second pipeline, and the outlet of the buffer tank is connected to the production line through a third pipeline. The vent valve is installed on the fourth pipe, one end of which is connected to a section of the first pipe, and the other end of the fourth pipe is used for venting. The air inlet of the trace oxygen analyzer is connected to a section of the first pipeline through a sampling pipeline, and the signal output terminal of the trace oxygen analyzer is connected to the first analog input module. The pressure transmitter is installed on the second pipeline, and the signal output terminal of the pressure transmitter is connected to the second analog input module. The outlet of the high-pressure nitrogen balloon tank is connected to the section of the third pipe through the fifth pipe, and the first regulating valve is installed on the fifth pipe. The outlet of the liquid nitrogen vaporizer is connected to the second inlet of the buffer tank through the sixth pipe, and the second regulating valve is installed on the sixth pipe; The digital output module is connected to the control terminal of the vent valve and the control terminal of the shut-off valve, respectively, and the analog output module is connected to the control terminal of the first regulating valve and the control terminal of the second regulating valve, respectively.

[0008] Preferably, in the above-mentioned emergency supply control device for abnormal purity of air separation nitrogen, the sampling pipeline includes a seventh pipeline, an eighth pipeline, a ninth pipeline, a first flow meter, a second flow meter, and a manual vent valve; One end of the seventh pipe is connected to a section of the first pipe, and the other end of the seventh pipe is divided into two paths; the first path is connected to the air inlet of the trace oxygen analyzer through the eighth pipe, and the first flow meter is installed on the eighth pipe; the second path is connected to the inlet of the manual vent valve through the ninth pipe, and the outlet of the manual vent valve is vented to the outside through the tenth pipe, and the second flow meter is installed on the tenth pipe.

[0009] Preferably, in the above-mentioned emergency supply control device for abnormal purity of air separation nitrogen, the trace oxygen analyzer outputs a 4-20mA DC analog signal to the first analog input module, the pressure transmitter outputs an analog pressure signal to the second analog input module; the digital output module outputs a switch control signal, and the analog output module outputs a 4-20mA DC adjustment signal.

[0010] Preferably, in the above-mentioned emergency supply control device for abnormal purity of air separation nitrogen, both the vent valve and the shut-off valve are on / off type control valves. The control terminals of the vent valve and the shut-off valve are both connected to the output circuit of the digital output module. The digital output module outputs a switch signal to control the on / off state of the vent valve and the shut-off valve respectively.

[0011] Preferably, in the above-mentioned emergency supply control device for abnormal purity of air separation nitrogen, both the first regulating valve and the second regulating valve are flow regulating valves. The opening control terminal of the first regulating valve and the opening control terminal of the second regulating valve are both connected to the output circuit of the analog output module. The analog output module outputs analog signals to adjust the opening of the first regulating valve and the second regulating valve respectively.

[0012] Preferably, in the above-mentioned emergency supply control device for abnormal purity of air separation nitrogen, the buffer tank is provided with a first air inlet, a second air inlet and an air outlet; the first air inlet is connected to the outlet of the shut-off valve through a second pipeline, the second air inlet is connected to the outlet of the second regulating valve through a sixth pipeline, and the air outlet is connected to the production line and the fifth pipeline through a third pipeline.

[0013] Preferably, in the above-mentioned emergency supply control device for abnormal purity of air separation nitrogen, the high-pressure nitrogen balloon tank is normally maintained in a preset high-pressure reserve state, and the first regulating valve is normally kept closed.

[0014] Preferably, in the above-mentioned emergency supply control device for abnormal purity of air separation nitrogen, the liquid nitrogen vaporizer normally stops vaporization operation, and the second regulating valve normally remains closed.

[0015] Preferably, in the above-mentioned emergency supply control device for abnormal nitrogen purity in air separation, the manual vent valve is used to adjust the venting flow rate in the tenth pipeline to shorten the response time of the trace oxygen analyzer to changes in the purity of nitrogen output from the air separation unit.

[0016] Preferably, in the above-mentioned emergency supply control device for abnormal nitrogen purity in air separation, under normal nitrogen purity operating conditions, the shut-off valve remains open, the vent valve remains closed, and the nitrogen produced by the air separation unit enters the buffer tank through the first pipeline, the shut-off valve, and the second pipeline, and is then transported to the production line through the third pipeline; both the first regulating valve and the second regulating valve remain closed, and both the high-pressure nitrogen balloon tank and the liquid nitrogen vaporizer are in standby mode.

[0017] The emergency supply control device for abnormal purity of air separation nitrogen provided in this application has at least the following beneficial effects: This application utilizes a trace oxygen analyzer to monitor the purity of nitrogen gas produced by the air separation unit in real time and transmits the purity signal to the DCS control system. Simultaneously, a manual venting valve is used to shorten the sampling pipeline length, increasing the sample gas renewal rate and enabling the analyzer to quickly respond to purity changes within the air separation tower. This solves the problem of operators being unable to promptly detect a decreasing purity trend due to sampling delays. When the DCS control system determines that the purity exceeds the set value, it immediately outputs a switch signal through the digital output module to close the shut-off valve and open the venting valve, achieving automatic and rapid removal and venting of substandard nitrogen gas. This avoids the time delay of manual intervention and the problem of large amounts of substandard nitrogen gas entering the production line. Furthermore, a buffer tank prevents nitrogen gas from entering the pipeline before the shut-off valve is closed. A small amount of substandard nitrogen is mixed and diluted with the existing qualified nitrogen in the tank. In conjunction with a pressure transmitter to detect the pressure drop in the pipeline in real time, the DCS automatically adjusts the opening of the first regulating valve of the high-pressure nitrogen balloon tank and the second regulating valve of the liquid nitrogen vaporization system through the analog output module based on the pressure signal. As needed, the high-purity nitrogen in the high-pressure nitrogen balloon tank and the high-purity nitrogen generated by the liquid nitrogen vaporizer are simultaneously replenished to the buffer tank or pipeline. This not only solves the problem that the high-pressure nitrogen balloon tank has limited storage capacity and cannot supply gas continuously for a long time, but also realizes the secondary dilution of substandard nitrogen and the stable maintenance of pipeline pressure. Thus, it ensures that the production line has a continuous, stable and qualified nitrogen supply when the purity is abnormal, and eliminates the impact of the purity fluctuation of the air separation system on the product quality of the production line. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] Figure 1 A structural diagram of an emergency supply control device for abnormal nitrogen purity in air separation provided in this application embodiment; Figure 2 This is a schematic diagram of the electronic component connections of an emergency supply control device for abnormal nitrogen purity in air separation provided in an embodiment of this application.

[0020] Figure label: 1. Trace oxygen analyzer; 2. DCS control system; 3. First flow meter; 4. Second flow meter; 5. Manual vent valve; 6. Vent valve; 7. Shut-off valve; 8. Pressure transmitter; 9. Buffer tank; 10. First regulating valve; 11. Second regulating valve; 12. High-pressure nitrogen balloon tank; 13. Liquid nitrogen vaporizer; 14. Air separation unit; 15. First pipeline; 16. Second pipeline; 17. Third pipeline; 18. Fourth pipeline; 19. Fifth pipeline; 20. Sixth pipeline; 21. Seventh pipeline; 22. Eighth pipeline; 23. Ninth pipeline; 24. Tenth pipeline; AI1, First analog input module; AI2, Second analog input module; AO, Analog output module; DO, Digital output module.

[0021] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concepts of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0023] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0024] An air separation nitrogen production system is a device used to produce high-purity nitrogen, and the purity of the nitrogen directly affects the product quality of automotive sheet metal. The original production process involved directly transporting the nitrogen produced by air separation unit 14 to the production stage via pipeline. Because of the straight-through pipeline, changes in gas load or pressure fluctuations on the production line side would be rapidly transmitted to the interior of air separation unit 14, directly affecting the pressure stability within the tower. Maintaining stable pressure inside air separation unit 14 is a critical condition for ensuring nitrogen purity and stable operation of the air separation system; pressure fluctuations will lead to a decrease in nitrogen purity.

[0025] Therefore, this application provides an emergency supply control device for abnormal nitrogen purity in air separation systems, used to reduce or eliminate the impact of purity changes in air separation systems on the quality of user products. Specifically, as... Figure 1 and Figure 2 As shown, the emergency supply control device for abnormal nitrogen purity in air separation includes an air separation unit 14, a trace oxygen analyzer 1, a DCS control system 2, a vent valve 6, a shut-off valve 7, a pressure transmitter 8, a buffer tank 9, a first regulating valve 10, a second regulating valve 11, a high-pressure nitrogen balloon tank 12, and a liquid nitrogen vaporizer 13. The DCS control system 2 is equipped with a first analog input module AI1, a second analog input module AI2, an analog output module AO, and a digital output module DO. The nitrogen outlet of the air separation unit 14 is connected to the inlet of the shut-off valve 7 through a first pipeline 15, and the outlet of the shut-off valve 7 is connected to the first inlet of the buffer tank 9 through a second pipeline 16. The outlet of the buffer tank 9 is connected to the production line through a third pipeline 17. The vent valve 6 is installed on a fourth pipeline 18, one end of which is connected to a section of the first pipeline 15, and the other end of the fourth pipeline 18 is connected to the first pipeline 15. One end is vented to the outside; the air inlet of the trace oxygen analyzer 1 is connected to the section of the first pipe 15 through the sampling pipeline, and the signal output terminal of the trace oxygen analyzer 1 is connected to the first analog input module AI1; the pressure transmitter 8 is set on the second pipe 16, and the signal output terminal of the pressure transmitter 8 is connected to the second analog input module AI2; the air outlet of the high-pressure nitrogen balloon tank 12 is connected to the section of the third pipe 17 through the fifth pipe 19, and the first regulating valve 10 is set on the fifth pipe 19; the air outlet of the liquid nitrogen vaporizer 13 is connected to the second air inlet of the buffer tank 9 through the sixth pipe 20, and the second regulating valve 11 is set on the sixth pipe 20; the digital output module DO is connected to the control terminal of the vent valve 6 and the control terminal of the shut-off valve 7 respectively, and the analog output module AO is connected to the control terminal of the first regulating valve 10 and the control terminal of the second regulating valve 11 respectively.

[0026] like Figure 1As shown, nitrogen purity is detected and analyzed online by a trace oxygen analyzer 1. The analyzer's ability to quickly respond to purity changes within the air separation unit 14 directly affects the system's ability to quickly intervene in abnormal operating conditions. To enable the trace oxygen analyzer 1 to reflect purity changes within the air separation unit 14 in real time, a manual vent valve 5 is added to the sampling pipeline to shorten sampling time, increase sample gas renewal rate, and thus accelerate the analyzer's response speed.

[0027] The trace oxygen analyzer 1 operates based on electrochemical or zirconia sensing principles, indirectly reflecting nitrogen purity by detecting the residual oxygen content in the sample gas. The faster the sample gas refresh rate, the closer the value detected by the analyzer is to the real-time purity value at the air separation tower outlet, and the shorter the detection lag time. In this embodiment, by adding a vent branch containing the manual vent valve 5, the sample gas in the sampling pipeline is always in a flowing state rather than a static state, avoiding the passivation of the purity signal caused by diffusion and mixing of the sample gas in long-distance pipelines. This allows the trace oxygen analyzer 1 to more promptly capture the decreasing purity trend inside the air separation tower. The manual vent valve 5 maintains an appropriate opening during normal operation. Its opening degree can be manually set by the operator according to the pipeline length and analyzer response requirements. Once set, it remains fixed and is not used as an automatic adjustment element.

[0028] The detection data from the trace oxygen analyzer 1 is used as the interlocking condition for automatic control of the DCS control system 2. When the detected nitrogen purity exceeds the set value, the DCS control system 2 outputs a switch signal through the digital output module DO to close the shut-off valve 7 and open the vent valve 6, allowing the substandard nitrogen to be released through the fourth pipeline 18 and no longer output to the production line.

[0029] DCS control system 2 is short for Distributed Control System, whose core functions are data acquisition, logic operation, and automatic control. In this embodiment, the 4-20mA DC analog signal output by the trace oxygen analyzer 1 is acquired by the first analog input module AI1 and sent to the internal data processing unit of DCS control system 2. The internal data processing unit converts the current signal into the actual oxygen content percentage or nitrogen purity value and compares it with a purity threshold preset within DCS control system 2. This purity threshold is a process parameter determined according to the production line quality requirements, and is usually set slightly higher than the minimum allowable purity value of the production line to reserve a safety margin. The comparison operation uses numerical comparison logic. If the measured purity value is lower or higher than the set value, the logic operation result is reversed, triggering DCS control system 2 to output the corresponding control command.

[0030] The Digital Output Module (DO) is one of the output cards of the DCS control system 2. Each channel outputs only two states: on or off, open or closed, suitable for controlling on / off valves that only require fully open or fully closed states. In this embodiment, both the vent valve 6 and the shut-off valve 7 are air-to-open / air-to-close type on / off valves. After receiving the on / off signal from the DO, they control the pneumatic actuator through a solenoid valve to achieve rapid full opening or full closing of the valve. Once this interlock action is triggered, it can quickly complete the full stroke switching of the valve, with an execution speed faster than manual operation. The control logic of the vent valve 6 and the shut-off valve 7 is interlocked, meaning that the vent valve 6 and the shut-off valve 7 cannot be in the open state at the same time, ensuring that nitrogen is either normally delivered to the production line or completely vented, eliminating safety hazards caused by uncertain states.

[0031] A buffer tank 9 is installed between the air separation unit 14 and the production line. Its purpose is to maintain the pressure supply requirements of the production line for a short time by relying on the pressure gas stored in the buffer tank 9 when the shut-off valve 7 is closed. At the same time, the qualified nitrogen gas originally in the buffer tank 9 is used to mix and dilute the small amount of unqualified nitrogen gas that has entered the second pipeline 16 before the shut-off valve 7 is closed, so as to reduce the risk of unqualified nitrogen gas entering the production line.

[0032] The buffer tank 9 operates on the principle of pressure equalization and mixing. Nitrogen gases of different purities naturally mix within the tank due to pressure and concentration differences, eventually reaching a homogeneous composition. Since the volume of the buffer tank 9 is much larger than that of the second pipeline 16, the total mass of substandard nitrogen remaining in the second pipeline 16 before the shut-off valve 7 closes is much smaller than the total mass of qualified nitrogen originally present in the buffer tank 9. After mixing, the substandard nitrogen is significantly diluted, resulting in a limited decrease in nitrogen purity, which may still remain within the production line's acceptable range. Even if the purity after mixing is slightly below the acceptable level, the mixed gas provides a buffer time for subsequent high-purity nitrogen replenishment to the high-pressure nitrogen balloon tank 12 and the liquid nitrogen vaporizer 13. This allows the system to connect to the replenishment gas source before the nitrogen purity in the production line drops to an unacceptable level, thus achieving seamless switching. The volume design of the buffer tank 9 needs to comprehensively consider the instantaneous gas flow rate of the production line, the volume of the second pipeline 16, and the duration of purity abnormalities. For example, when the gas flow rate of the production line is 500 standard cubic meters per hour, a buffer tank 9 with a volume of 5 cubic meters can be installed. This volume is sufficient to accommodate and effectively dilute the residual substandard nitrogen in the second pipeline 16 after the shut-off valve 7 is closed, while maintaining the gas supply pressure of the production line for several seconds to tens of seconds after the shut-off valve 7 is closed. It should be understood that the above volume and flow rate data are only an exemplary configuration of this application. In practical applications, those skilled in the art can calculate and select buffer tanks of different specifications according to the actual gas consumption of the production line and the pipeline size, all of which can achieve the same technical effect.

[0033] As the shut-off valve 7 closes, the outlet pressure of the second pipeline 16 and the buffer tank 9 gradually decreases. The pressure transmitter 8 detects this pressure change in real time and transmits the pressure signal to the second analog input module AI2 of the DCS control system 2.

[0034] The pressure transmitter 8 is a sensing device that converts physical pressure signals into standard industrial electrical signals. Its internal sensing element converts pressure into an electrical signal, which is then amplified and linearized by a signal conditioning circuit before outputting a 4-20mA DC analog signal. The 4-20mA signal is a standard analog signal format widely used in industrial automation. 4mA corresponds to the lower limit of the measurement range, and 20mA corresponds to the upper limit. The current value and pressure value have a linear relationship. This signal is insensitive to changes in line resistance and is suitable for long-distance transmission.

[0035] When the pipeline pressure drops below the preset start-up threshold, the DCS control system 2 outputs an analog signal through the analog output module AO based on the pressure signal, adjusts the opening of the first regulating valve 10, and transports the high-purity nitrogen gas in the high-pressure nitrogen balloon tank 12 to the third pipeline 17 through the fifth pipeline 19, further diluting the unqualified nitrogen gas in the pipeline and improving the purity of the nitrogen gas delivered to the production line.

[0036] The analog output module AO is one of the output cards of the DCS control system 2. Its output signal is a 4-20mA DC current signal, and the magnitude of the output current is determined by the control algorithm inside the DCS control system 2. The control algorithm usually adopts proportional-integral-derivative control, i.e., PID control. This algorithm calculates the output value based on the deviation between the pressure setpoint and the measured value of the pressure transmitter 8, using a weighted sum of proportional, integral, and derivative actions, thereby driving the regulating valve to the corresponding opening position. Using PID control can make the pipeline pressure smoothly approach the setpoint, avoiding pressure oscillations caused by large jumps in valve opening. The first regulating valve 10 is a pneumatic diaphragm regulating valve or an electric regulating valve. Its valve core position is controlled by the received analog signal. The change in the valve core position changes the flow cross-sectional area of ​​the valve, thereby regulating the nitrogen flow rate through the valve. This regulation process is a continuous stepless adjustment, which can dynamically adjust the gas supply flow rate according to the change in pressure deviation until the pipeline pressure returns to the setpoint.

[0037] For example, when the pressure drops to 90% of the set value, the DCS control system 2 controls the first regulating valve 10 to quickly replenish the gas volume with a large opening. When the pressure rises back to above 95% of the set value, the opening is gradually reduced to avoid overshoot. The high-pressure nitrogen spherical tank 12 maintains a preset high-pressure reserve state under normal conditions. The pressure of the high-purity nitrogen stored inside is typically maintained between 2.0 MPa and 3.0 MPa, with the specific pressure value depending on the output pressure of the air separation unit 14 and the design pressure rating of the pipeline system. The first regulating valve 10 remains closed under normal conditions to prevent unnecessary consumption of high-purity nitrogen under normal operating conditions. The nitrogen purity in the high-pressure nitrogen spherical tank 12 is typically above 99.999%, which is superior to the product purity under normal operating conditions of the air separation unit 14. Therefore, when mixed with the substandard nitrogen remaining in the pipeline, it can effectively improve the overall purity of the mixed gas.

[0038] Since the high-pressure nitrogen spherical tank 12 has a limited high-purity nitrogen storage capacity, the DCS control system 2 simultaneously outputs an analog signal through the analog output module AO to adjust the opening of the second regulating valve 11 and start the liquid nitrogen vaporizer 13 to vaporize the liquid nitrogen in the liquid nitrogen storage tank into high-purity nitrogen, which is then replenished into the buffer tank 9 through the sixth pipeline 20, thereby further ensuring the continuous stability of the purity and pressure of nitrogen in the production line.

[0039] The liquid nitrogen vaporizer 13 is a device that heats liquid nitrogen into gaseous nitrogen. Its working principle involves using the heat of ambient air or an electric heater to cause the liquid nitrogen to absorb latent heat and vaporize. The vaporization capacity of the liquid nitrogen vaporizer 13 is determined by its heat exchange area and heat source temperature. The amount of nitrogen produced by vaporization can be controlled by adjusting the flow rate of liquid nitrogen entering the vaporizer or by adjusting the heating power. In this embodiment, a second regulating valve 11 is installed on the outlet pipe of the liquid nitrogen vaporizer 13. The flow rate of high-purity nitrogen entering the buffer tank 9 is controlled by adjusting the opening of this valve. The purity of the nitrogen produced by the liquid nitrogen vaporizer 13 is consistent with the purity of the liquid nitrogen raw material, typically reaching over 99.999%, classifying it as high-purity nitrogen. The high-pressure nitrogen spherical tank 12 and the liquid nitrogen vaporizer 13 form a complementary relationship in terms of time: the high-pressure nitrogen spherical tank 12 responds quickly and can start supplying gas within seconds of the DCS control system 2 issuing a command to make up for short-term shortages, but its storage capacity is limited and can generally only maintain gas supply for a few minutes to tens of minutes; the liquid nitrogen vaporizer 13 starts up a little slower, but its gas source comes from the liquid nitrogen storage tank, and as long as the liquid nitrogen storage is sufficient, it can continuously supply gas for several hours or even several days. The coordinated work of the two ensures that the gas supply can be effectively guaranteed from the initial short-term emergency when a purity abnormality occurs to the continuous gas supply for a longer period of time thereafter. For example, when the air separation unit 14 needs to be shut down for maintenance due to a malfunction, the high-pressure nitrogen spherical tank 12 first provides high-purity nitrogen for the first 5 to 10 minutes, and then the liquid nitrogen vaporizer 13 gradually starts up and takes over the gas supply, ensuring that the production line can still continuously obtain qualified nitrogen during the maintenance period of several hours. The vaporization rate of the liquid nitrogen vaporizer 13 can be steplessly adjusted by adjusting the opening of the second regulating valve 11 to meet the gas replenishment requirements under different gas flow conditions.

[0040] In some embodiments, such as Figure 1 As shown, the sampling pipeline includes a seventh pipeline 21, an eighth pipeline 22, a ninth pipeline 23, a first flow meter 3, a second flow meter 4, and a manual vent valve 5. One end of the seventh pipeline 21 is connected to a section of the first pipeline 15, and the other end of the seventh pipeline 21 is divided into two paths. The first path is connected to the air inlet of the micro oxygen analyzer 1 through the eighth pipeline 22, and the first flow meter 3 is installed on the eighth pipeline 22. The second path is connected to the inlet of the manual vent valve 5 through the ninth pipeline 23, and the outlet of the manual vent valve 5 is vented to the outside through the tenth pipeline 24, and the second flow meter 4 is installed on the tenth pipeline 24.

[0041] This embodiment provides an exemplary construction of a sampling pipeline. A first flow meter 3 and a second flow meter 4 are used to observe the gas flow rates in the inlet branch of the trace oxygen analyzer 1 and the vent branch of the manual vent valve 5, respectively. The second flow meter 4 allows the operator to observe the vent flow rate in the vent branch in real time, thereby assisting in manually adjusting the opening of the vent valve 5 to a suitable venting amount. The principle of this embodiment is as follows: by continuously drawing and discharging a portion of the sample gas from the sampling pipeline through the manual vent valve 5, the sample gas is kept flowing within the sampling pipeline, preventing the sample gas from stagnating in the pipeline and causing the detection value to lag behind the actual purity value. According to fluid mechanics principles, when the gas in the pipeline is in a flowing state, changes in the gas composition upstream can be transmitted to the downstream analyzer detection end at a speed close to the gas flow velocity. The transmission time is equal to the pipeline length divided by the gas flow velocity; therefore, increasing the flow velocity can shorten the transmission time. The first flow meter 3 and the second flow meter 4 are preferably rotor flow meters or thermal mass flow meters, which provide intuitive readings, have low cost, and are suitable for on-site observation. For example, when the total length of the sampling pipeline is 20 meters, without venting, the sample gas relies on diffusion to reach the analyzer, and the response time may be as long as tens of seconds to several minutes. When the venting flow rate is established at 2 standard liters per minute through the manual vent valve 5, the average flow velocity of the sample gas can reach several meters per second, and the response time can be shortened to within a few seconds. The reading of the second flow meter 4 can be used to calibrate and confirm whether the venting flow rate has reached the predetermined value. It should be understood that the specific values ​​of the above pipeline length and venting flow rate are only an exemplary configuration of this application. In practical applications, those skilled in the art can obtain different venting flow rates by adjusting the opening degree of the manual vent valve 5 according to the actual length of the on-site sampling pipeline and the analyzer response time requirements, all of which can achieve the technical effect of improving the analyzer response speed.

[0042] In some embodiments, such as Figure 2 As shown, the trace oxygen analyzer 1 outputs a 4-20mA DC analog signal to the first analog input module AI1, and the pressure transmitter 8 outputs an analog pressure signal to the second analog input module AI2; the digital output module DO outputs a switch control signal, and the analog output module AO outputs a 4-20mA DC adjustment signal.

[0043] This embodiment defines the specific types and transmission directions of each signal. The 4-20mA DC analog signal is a standardized industrial signal. Its lower limit of 4mA can be used to detect line breakage faults. When the signal is below 4mA, the DCS control system 2 can determine that there is a line fault and issue an alarm, enhancing the system's fault diagnosis capability. The analog signal is sampled by analog input modules AI1 and AI2 and converted into a digital signal for internal calculation by the DCS control system 2. The switch control signal is the on / off signal output by the digital output module DO. Its voltage level is usually 24V DC or 220V AC, determined according to the solenoid valve drive voltage of the connected valve. The 4-20mA DC regulation signal output by the analog output module AO corresponds to the opening command of the first regulating valve 10 and the second regulating valve 11. 4mA corresponds to the fully closed position of the valve, and 20mA corresponds to the fully open position of the valve. The intermediate current value has a linear relationship with the opening percentage, thereby realizing continuous valve opening regulation. Shielded cables are used for signal transmission to reduce the impact of electromagnetic interference in the industrial environment on signal accuracy.

[0044] In some embodiments, such as Figure 2 As shown, both the vent valve 6 and the shut-off valve 7 are on / off control valves. The control terminals of the vent valve 6 and the shut-off valve 7 are connected to the output circuit of the digital output module DO. The digital output module DO outputs a switch signal to control the on / off state of the vent valve 6 and the shut-off valve 7 respectively.

[0045] This embodiment further defines the valve types of the vent valve 6 and the shut-off valve 7, and their connection method with the control module. The on / off control valve, also known as a two-position control valve, differs from a regulating valve in that it only has two working positions: fully open and fully closed, and cannot remain in the middle opening position. This type of valve has a simple structure and fast action speed, suitable for operating conditions where only rapid switching between two states is required. In this embodiment, the vent valve 6 and the shut-off valve 7 preferably employ a pneumatic diaphragm actuator in conjunction with a spring reset device. When the digital output module DO outputs a signal to energize the solenoid valve, compressed air enters the actuator cylinder, pushing the valve core to move and open or close the valve. When the output signal disappears and the solenoid valve is de-energized, the spring force pushes the valve core to reset, returning the valve to its initial safe position. In this embodiment, the on / off control circuit can adopt a relay-isolated output method, that is, each output channel of the digital output module DO is connected to an intermediate relay, and the relay contacts control the on / off state of the solenoid valve, thereby achieving electrical isolation between the low-pressure control signal of the DCS control system 2 and the high-voltage drive circuit of the field valve, improving the system's safety and anti-interference capability. The digital output module DO outputs switch signals to control the on / off states of vent valve 6 and shut-off valve 7, respectively. These two valves employ interlocking logic, meaning that the two output channels of the DO module cannot be open simultaneously, ensuring that shut-off valve 7 and vent valve 6 will not open at the same time. This interlocking logic can be implemented either through the control program within the DCS control system 2 or through an external hard-wired interlocking circuit; both methods guarantee safety.

[0046] In some embodiments, such as Figure 2 As shown, both the first regulating valve 10 and the second regulating valve 11 are flow regulating valves. The opening control terminals of the first regulating valve 10 and the second regulating valve 11 are connected to the output circuit of the analog output module AO. The analog output module AO outputs analog signals to adjust the opening of the first regulating valve 10 and the second regulating valve 11 respectively.

[0047] This embodiment further defines the valve types of the first regulating valve 10 and the second regulating valve 11 and their connection method with the analog output module AO. A flow regulating valve is a control valve that can continuously change the valve opening to regulate fluid flow. Its core components are the valve core and valve seat, and the flow rate is adjusted by changing the flow cross-sectional area between the valve core and the valve seat. The valve opening control terminal is usually an electrical converter or positioner, which receives a 4-20mA DC analog signal and converts the electrical signal into a corresponding pneumatic pressure signal or mechanical displacement, driving the valve stem to move to the target position. The positioner has valve position feedback and closed-loop control functions, ensuring that the actual position of the valve core corresponds to the input signal value and eliminating position deviations caused by nonlinear factors such as valve stem friction. The positioner is usually an intelligent positioner, which can have built-in valve characteristic correction functions to make the valve's flow characteristics closer to equal percentage or linear characteristics, adapting to the requirements of different control systems. The output channels of the analog output module AO are independent of each other, allowing the DCS control system 2 to independently adjust the opening of the first regulating valve 10 and the second regulating valve 11 without interference, making the control strategy more flexible.

[0048] In some embodiments, such as Figure 1 As shown, the buffer tank 9 has a first air inlet, a second air inlet, and an air outlet. The first air inlet is connected to the outlet of the shut-off valve 7 through the second pipe 16, the second air inlet is connected to the outlet of the second regulating valve 11 through the sixth pipe 20, and the air outlet is connected to the production line and the fifth pipe 19 through the third pipe 17.

[0049] This embodiment further defines the specific interface layout and pipeline connection relationship of the buffer tank 9. The buffer tank 9 is a horizontal or vertical pressure vessel with multiple process pipes on its body. The specific positions of each interface on the tank body can be flexibly arranged according to the manufacturing process and installation space. In this embodiment, the first and second air inlets are located at the top and bottom of the tank body, and the air outlet is located in the middle of the tank body. The third pipeline 17 connects the production line and the fifth pipeline 19, which means that the air outlet pipeline of the buffer tank 9 merges with the fifth pipeline 19 from the high-pressure nitrogen balloon tank 12 downstream of the buffer tank 9. That is, the high-purity nitrogen from the high-pressure nitrogen balloon tank 12 does not pass through the buffer tank 9 but directly flows into the main pipeline transported to the production line. This connection method allows the high-purity nitrogen from the high-pressure nitrogen balloon tank 12 to reach the production line via the shortest path, avoiding the pressure loss and response delay that may be caused by passing through the buffer tank 9, and further accelerating the response speed of high-purity nitrogen replenishment. The nitrogen gas generated by the liquid nitrogen vaporizer 13 enters the buffer tank 9 through the second inlet, mixes thoroughly with the gas inside, and is then output through the outlet. This facilitates heat exchange and component mixing between the low-temperature nitrogen gas generated by the liquid nitrogen vaporizer 13 and the existing gas in the buffer tank 9, preventing the direct delivery of low-temperature nitrogen gas into the production line and avoiding pipeline thermal stress problems. It should be understood that the above-mentioned interface positions and connection methods are only one exemplary arrangement of this application. In practical applications, those skilled in the art can make adaptive adjustments according to the on-site pipeline routing and equipment layout to achieve the same technical effect.

[0050] In some embodiments, the high-pressure nitrogen balloon tank 12 is normally maintained in a preset high-pressure reserve state, and the first regulating valve 10 is normally kept closed.

[0051] This embodiment defines the normal operating state of the high-pressure nitrogen spherical tank 12 and the first regulating valve 10. "Normal" refers to the normal operating condition, meaning the nitrogen output from the air separation unit 14 is of acceptable purity and the production line is operating normally. The high-pressure nitrogen spherical tank 12 is a spherical or cylindrical pressure vessel, widely used for gas storage due to the uniform stress distribution and material savings of spherical containers. The preset high-pressure reserve state means that the nitrogen pressure stored in the high-pressure nitrogen spherical tank 12 is higher than the normal operating pressure of the pipeline system. Therefore, when it is necessary to replenish the pipeline system, nitrogen can be supplied to the pipeline using its own pressure without the need for additional pressurization equipment. This preset high pressure is typically 1.2 to 1.5 times the pipeline operating pressure, with the specific value determined by the design pressure of the high-pressure nitrogen spherical tank 12 and the safety valve setting pressure. The fact that the first regulating valve 10 remains closed under normal conditions means that the high-pressure nitrogen spherical tank 12 is isolated from the third pipeline 17, preventing nitrogen leakage into the pipeline system and thus conserving high-purity nitrogen resources. In abnormal operating conditions requiring nitrogen replenishment, the DCS control system 2 outputs a signal via the analog output module AO to open the first regulating valve 10, thereby releasing nitrogen from the high-pressure nitrogen bladder 12. The closed state of the first regulating valve 10 has a fail-safe characteristic, meaning that when the control system loses power or the gas supply is interrupted, the valve automatically returns to a preset safe position under the action of spring force. This safe position is usually the fully closed position, ensuring that the nitrogen in the high-pressure nitrogen bladder 12 will not leak accidentally due to a control system malfunction.

[0052] In some embodiments, the liquid nitrogen vaporizer 13 normally stops vaporization, and the second regulating valve 11 normally remains closed.

[0053] This embodiment defines the normal operating state of the liquid nitrogen vaporizer 13 and the second regulating valve 11. The liquid nitrogen vaporizer 13 is a heat exchange device that uses ambient heat or an external heat source to convert liquid nitrogen into gaseous nitrogen. Specifically, it can be an air-bath vaporizer, which uses natural convection of ambient air to heat the liquid nitrogen in the coil, causing it to vaporize; or it can be a water-bath vaporizer or an electrically heated vaporizer, which uses hot water or an electric heating element to provide the heat required for vaporization. Stopping vaporization under normal conditions means that under normal operating conditions, liquid nitrogen does not enter or the heating system is not working, and the liquid nitrogen vaporizer 13 is in a standby state, consuming neither liquid nitrogen nor heating energy. The fact that the second regulating valve 11 remains closed under normal conditions means that the second air inlet of the buffer tank 9 is sealed under normal operating conditions, preventing the nitrogen generated by the liquid nitrogen vaporizer 13 from entering the buffer tank 9. When the DCS control system 2 detects an abnormal purity and requires continuous nitrogen replenishment, it opens the second regulating valve 11 and starts the vaporization operation of the liquid nitrogen vaporizer 13 via an analog output signal from the AO module. The liquid nitrogen vaporizer 13 begins to produce high-purity nitrogen, which is then sent to the buffer tank 9 through the second regulating valve 11. Under normal conditions, the second regulating valve 11 is also fault-safe, ensuring that it will not be accidentally opened and waste liquid nitrogen resources in the event of a power failure in the control system. The liquid nitrogen vaporizer 13 can be started either by opening the liquid nitrogen inlet valve to allow liquid nitrogen to enter the vaporizer coil for spontaneous vaporization, or by starting an electric heater or circulating hot water pump to provide heat for vaporization. The specific starting method depends on the type and configuration of the liquid nitrogen vaporizer 13. For example, the start-up time of the air-bath type liquid nitrogen vaporizer 13 mainly depends on the ambient temperature and the heat exchange efficiency of the finned tube. Under an ambient temperature of 20 degrees Celsius, it usually takes several minutes to tens of minutes to reach the rated vaporization capacity. Therefore, in the initial stage after the purity abnormality occurs, the high-pressure nitrogen balloon tank 12 provides a short-term supply of high-purity nitrogen. After the liquid nitrogen vaporizer 13 reaches the normal working state, it takes over the gas supply, forming a time-series connection.

[0054] In some embodiments, the manual vent valve 5 is used to adjust the venting flow rate in the tenth pipeline 24 to shorten the response time of the trace oxygen analyzer 1 to changes in the purity of nitrogen output from the air separation unit 14.

[0055] This embodiment further defines the function and role of the manual vent valve 5 in the entire device. The manual vent valve 5 is a shut-off valve or ball valve whose opening is changed by manually rotating a handwheel or handle. Once set, its opening remains constant and it is not an actuator of the automatic control system. The vent flow rate refers to the sample gas flow rate discharged to the atmosphere through the tenth pipe 24. The existence of this vent flow rate ensures continuous flow of sample gas within the sampling pipeline, with new sample gas constantly being drawn to the analyzer's detection end, thereby shortening the detection lag time. According to Taylor's dispersion theory in fluid mechanics, in laminar or turbulent flow conditions, the axial diffusion coefficient of gas components decreases with increasing flow velocity. Therefore, increasing the sample gas flow rate helps maintain a steep concentration front, making the concentration change detected by the analyzer closer to the actual step change. By manually adjusting the opening of the manual vent valve 5, the vent flow rate within the tenth pipe 24 can be changed. The larger the vent flow rate, the higher the sample gas renewal rate, and the faster the analyzer's response. However, the venting flow rate should not be too large to avoid wasting excessive product nitrogen. Furthermore, an excessively large venting flow rate may create a significant negative pressure within the sampling pipeline, affecting the detection accuracy and stability of the trace oxygen analyzer 1. Therefore, the opening degree of the manual vent valve 5 should be adjusted comprehensively based on the length and diameter of the sampling pipeline and the analyzer's minimum operating pressure. Generally, a venting flow rate of 10% to 20% of the total sampling flow rate is suitable. This adjustment process should be completed once by the on-site operator during the device commissioning phase and does not require repeated adjustments during daily operation.

[0056] In some embodiments, under normal nitrogen purity conditions, the shut-off valve 7 remains open, the vent valve 6 remains closed, and the nitrogen produced by the air separation unit 14 enters the buffer tank 9 through the first pipeline 15, the shut-off valve 7, and the second pipeline 16, and is then transported to the production line through the third pipeline 17; the first regulating valve 10 and the second regulating valve 11 both remain closed, and the high-pressure nitrogen balloon tank 12 and the liquid nitrogen vaporizer 13 are both in standby mode.

[0057] This embodiment describes the complete airflow path and valve on / off states of the device under normal operating conditions, serving as a reference for understanding the device's operational logic under abnormal conditions. Under normal operating conditions, the airflow path of the entire device is as follows: High-purity nitrogen produced by the air separation unit 14 flows out from its nitrogen outlet, enters the first pipeline 15, passes through the open shut-off valve 7, enters the second pipeline 16, then enters the buffer tank 9 through its first inlet, flows out from the buffer tank 9's outlet, and enters the third pipeline 17, ultimately being delivered to the production line for user use. The vent valve 6 is closed, so the nitrogen in the first pipeline 15 will not leak through the fourth pipeline 18. The manual vent valve 5 is slightly open, used only to maintain the continuous flow of sample gas in the sampling pipeline; its discharge is extremely small relative to the total product gas flow rate and can be ignored. The first regulating valve 10 and the second regulating valve 11 are both fully closed, so the high-pressure nitrogen balloon tank 12 and the liquid nitrogen vaporizer 13 are isolated from the main gas supply system and do not participate in gas supply. Although the high-pressure nitrogen spherical tank 12 stores high-pressure, high-purity nitrogen, it is in a sealed, standby state due to its closed outlet valve. The liquid nitrogen vaporizer 13 is not in operation, and its outlet pipeline is isolated from the buffer tank 9 due to the closure of the second regulating valve 11, also placing it in a standby state. Under this condition, the nitrogen required by the production line is entirely supplied by the air separation unit 14. The entire system operates in the same manner as the traditional direct-supply method without this emergency control device; that is, under normal operating conditions, this emergency control device does not interfere with or affect the original production process.

[0058] The air separation nitrogen purity abnormality emergency supply control device provided in this application can automatically adjust each production link according to the purity change of the air separation system. When the purity is abnormal, it can quickly cut off the unqualified nitrogen and eliminate the impact of the air separation system purity change on the production line product quality through the coordinated replenishment of the high-pressure nitrogen balloon tank 12 and liquid nitrogen vaporizer 13. It can improve the production process, ensure the continuity and stability of nitrogen supply, and achieve the purpose of ensuring the quality of user products.

[0059] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An emergency supply control device for abnormal purity of air separation nitrogen, characterized in that, It includes an air separation unit (14), a trace oxygen analyzer (1), a DCS control system (2), a vent valve (6), a shut-off valve (7), a pressure transmitter (8), a buffer tank (9), a first regulating valve (10), a second regulating valve (11), a high-pressure nitrogen balloon tank (12), and a liquid nitrogen vaporizer (13). The DCS control system (2) is equipped with a first analog input module (AI1), a second analog input module (AI2), an analog output module (AO), and a digital output module (DO). The nitrogen outlet of the air separation unit (14) is connected to the inlet of the shut-off valve (7) through the first pipe (15), the outlet of the shut-off valve (7) is connected to the first air inlet of the buffer tank (9) through the second pipe (16), and the air outlet of the buffer tank (9) is connected to the production line through the third pipe (17). The vent valve (6) is installed on the fourth pipe (18), one end of the fourth pipe (18) is connected to the pipe section of the first pipe (15), and the other end of the fourth pipe (18) is vented to the outside; The air inlet of the micro oxygen analyzer (1) is connected to a section of the first pipe (15) through a sampling pipeline, and the signal output terminal of the micro oxygen analyzer (1) is connected to the first analog input module (AI1). The pressure transmitter (8) is installed on the second pipeline (16), and the signal output terminal of the pressure transmitter (8) is connected to the second analog input module (AI2). The outlet of the high-pressure nitrogen balloon tank (12) is connected to the section of the third pipe (17) through the fifth pipe (19), and the first regulating valve (10) is installed on the fifth pipe (19); the outlet of the liquid nitrogen vaporizer (13) is connected to the second air inlet of the buffer tank (9) through the sixth pipe (20), and the second regulating valve (11) is installed on the sixth pipe (20); The digital output module (DO) is connected to the control terminal of the vent valve (6) and the control terminal of the shut-off valve (7) respectively, and the analog output module (AO) is connected to the control terminal of the first regulating valve (10) and the control terminal of the second regulating valve (11) respectively.

2. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, The sampling pipeline includes a seventh pipeline (21), an eighth pipeline (22), a ninth pipeline (23), a first flow meter (3), a second flow meter (4), and a manual vent valve (5). One end of the seventh pipe (21) is connected to the pipe section of the first pipe (15), and the other end of the seventh pipe (21) is divided into two paths; the first path is connected to the air inlet of the micro oxygen analyzer (1) through the eighth pipe (22), and the first flow meter (3) is installed on the eighth pipe (22); the second path is connected to the inlet of the manual vent valve (5) through the ninth pipe (23), and the outlet of the manual vent valve (5) is vented to the outside through the tenth pipe (24), and the second flow meter (4) is installed on the tenth pipe (24).

3. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, The trace oxygen analyzer (1) outputs a 4-20mA DC analog signal to the first analog input module (AI1), and the pressure transmitter (8) outputs an analog pressure signal to the second analog input module (AI2); the digital output module (DO) outputs a switch control signal, and the analog output module (AO) outputs a 4-20mA DC adjustment signal.

4. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, Both the vent valve (6) and the shut-off valve (7) are on / off control valves. The control terminals of the vent valve (6) and the shut-off valve (7) are connected to the output circuit of the digital output module (DO). The digital output module (DO) outputs a switch signal to control the on / off state of the vent valve (6) and the shut-off valve (7) respectively.

5. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, Both the first regulating valve (10) and the second regulating valve (11) are flow regulating valves. The opening control terminal of the first regulating valve (10) and the opening control terminal of the second regulating valve (11) are connected to the output circuit of the analog output module (AO). The analog output module (AO) outputs analog signals to adjust the opening of the first regulating valve (10) and the second regulating valve (11) respectively.

6. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, The buffer tank (9) is provided with a first air inlet, a second air inlet and an air outlet. The first air inlet is connected to the outlet of the shut-off valve (7) through the second pipe (16), the second air inlet is connected to the outlet of the second regulating valve (11) through the sixth pipe (20), and the air outlet is connected to the production line and the fifth pipe (19) through the third pipe (17).

7. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, The high-pressure nitrogen balloon tank (12) is normally maintained in a preset high-pressure reserve state, and the first regulating valve (10) is normally kept closed.

8. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, The liquid nitrogen vaporizer (13) normally stops vaporization, and the second regulating valve (11) normally remains closed.

9. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 2, characterized in that, The manual vent valve (5) is used to adjust the vent flow rate in the tenth pipeline (24) to shorten the response time of the trace oxygen analyzer (1) to the change in the purity of nitrogen output from the air separation unit (14).

10. The emergency supply control device for abnormal purity of air separation nitrogen as described in claim 1, characterized in that, Under normal operating conditions, the shut-off valve (7) remains open and the vent valve (6) remains closed. The nitrogen produced by the air separation unit (14) enters the buffer tank (9) through the first pipeline (15), the shut-off valve (7), and the second pipeline (16), and is then transported to the production line through the third pipeline (17). The first regulating valve (10) and the second regulating valve (11) remain closed, and the high-pressure nitrogen balloon tank (12) and the liquid nitrogen vaporizer (13) are both in standby mode.

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