Baking system and using method thereof

Abstract

The invention relates to a baking system and a using method thereof, and belongs to the technical field of metallurgical baking. The system comprises a blast furnace gas supply pipeline, an ignition gas supply pipeline, an oxygen supply pipeline, a nitrogen supply pipeline and a compressed air supply pipeline, wherein each pipeline is provided with a stop valve, a regulating valve, a grouping control valve, a pressure reducing valve, a flowmeter, a check valve and a gas source treatment device. The using method comprises the steps that ignition coal gas and compressed air are introduced to ignite soft fire; starting a cooling fan; introducing blast furnace gas and oxygen to ignite the big fire; performing baking; and after completion, oxygen and blast furnace gas are closed in sequence, nitrogen purging is carried out, and finally the ignition pipeline and the cooling fan are closed. Through optimized hardware configuration and automatic control logic, the safety, reliability and energy efficiency of the system are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metallurgical baking, and relates to a baking system and a use method thereof. BACKGROUND

[0002] In the production of the metallurgical industry, baking is a crucial pretreatment process, which is widely used in the baking preheating of ladles, tundishes, hot metal ladles and other containers. The core purpose is to remove the moisture in the refractory lining through heating, to improve the temperature in the container, and to make full preparation for subsequent acceptance of high-temperature metal melt. The efficiency, stability and safety of the baking process are directly related to the smooth operation of smelting, energy consumption level and the final product quality.

[0003] At present, the baking system commonly used in the industry is usually based on gas combustion technology, and the energy medium is mainly industrial by-product gas such as blast furnace gas and coke oven gas, supplemented by combustion medium such as oxygen or air. However, through long-term production practice and application, the existing baking technology and system gradually expose many defects and limitations that need to be solved in the overall design and process flow. These problems seriously restrict the further improvement of production efficiency, and even bury the safety hazard.

[0004] Firstly, in terms of system configuration and integration, the layout of various medium pipelines (such as gas, oxygen, nitrogen, compressed air) of the existing baking system often lacks unified systematic planning and linkage control. The selection and configuration of key components such as pneumatic shut-off valves, regulating valves and detection instruments in each functional module cannot form an optimized collaborative scheme. This loose structure leads to slow system response, and when starting and stopping or switching conditions, the coordination timing between different media is prone to deviation, thereby affecting the success rate of ignition and the instantaneous stability of combustion. At the same time, the design of the pipeline purging circuit is often oversimplified or has blind spots, and incomplete purging can easily lead to the accumulation of flammable gas in the pipeline, forming a huge risk of combustion and explosion.

[0005] Secondly, in terms of reliability and safety of the ignition link, the existing technology has obvious shortcomings. Many systems use a single fire kindling mode, and the ignition gas pipeline control is rough, which cannot finely group manage the fire kindling of multiple burners. The connection between the ignition process and the main flame establishment process lacks stable and reliable flame signal monitoring and feedback mechanism as support. Often because of insufficient sensitivity of detection elements or unreasonable installation position, the system cannot accurately judge whether the ignition is truly successful, and then the dangerous situation of "mis-ignition" or "not igniting but passing in main combustion gas" appears. This not only causes waste of energy medium, but also constitutes a serious safety accident hazard.

[0006] Furthermore, the existing systems generally have the problem of insufficient logical rigor in the control logic and safety interlocking of the baking process. The system start-stop, especially the emergency shutdown or the process after normal end of baking, lacks a set of carefully designed, mandatory sequential shutdown and purging procedures. The operator may rely on experience to perform manual operation, which has the risk of misoperation, such as closing the combustion-supporting medium first and then closing the fuel, or failing to fully purge the pipeline before directly closing the system. This uncertainty in operation is extremely likely to cause incomplete combustion or backfire of the fuel in the burner or pipeline, as well as the presence of flammable gas, which poses a continuous threat to equipment and personnel safety.

[0007] In addition, the existing systems also perform poorly in terms of energy utilization efficiency and temperature control accuracy. Since the flow regulation of fuel gas and combustion-supporting medium (such as oxygen) often lacks precise follow-up matching function, it is unable to optimize the air-fuel ratio in real time according to different stages of baking (such as heating and holding), often leading to incomplete combustion or excessive combustion-supporting medium taking away a large amount of heat. This not only causes waste of energy, but also makes the temperature field in the baking container uneven, with frequent local overheating or overcooling, making it difficult to achieve the ideal preheating effect required by the process, ultimately affecting the service life of the turnover container and the temperature drop control of the smelting process.

[0008] Finally, the automation and intelligence level of the system is low. The entire baking process, including ignition, flame monitoring, flow regulation, purging, cooling, etc., has not achieved highly integrated one-key automatic control, and there is also a lack of real-time monitoring and data recording of key parameters, which is not conducive to process optimization and fault tracing.

[0009] In summary, the existing baking system has significant technical defects in system integration design, ignition reliability, safety interlocking protection, energy efficiency, and automation control. The existence of these problems has been a bottleneck restricting the development of metallurgical baking process to be more efficient, safer, and more energy-saving. Therefore, there is an urgent need for a new technical solution to systematically solve the above-mentioned problems. SUMMARY

[0010] Therefore, the purpose of the present application is to provide a baking system and a method for using the same to solve the above-mentioned problems.

[0011] To achieve the above object, the present application provides the following technical scheme: a baking system, comprising a blast furnace gas supply pipeline, an ignition gas supply pipeline, an oxygen supply pipeline, a nitrogen supply pipeline and a compressed air supply pipeline; the blast furnace gas supply pipeline is provided with a first pneumatic cut-off valve and a first pneumatic regulating valve; the ignition gas supply pipeline is provided with a second pneumatic cut-off valve and a third pneumatic cut-off valve, which are respectively used for controlling different groups of burner ignition pipelines; the oxygen supply pipeline is provided with a pressure reducing device, a flow detection device, a fourth pneumatic cut-off valve and a second pneumatic regulating valve; the nitrogen supply pipeline comprises a purging pipeline, which is provided with a fifth pneumatic cut-off valve and a check device; the compressed air supply pipeline is provided with a gas source treatment device and a sixth pneumatic cut-off valve; wherein each supply pipeline is connected to a burner device, and each control valve is connected to a system control device.

[0012] Optionally, the first pneumatic cut-off valve and the first pneumatic regulating valve in the blast furnace gas supply pipeline are sequentially arranged along the airflow direction.

[0013] Optionally, the second pneumatic cut-off valve and the third pneumatic cut-off valve in the ignition gas supply pipeline independently control different groups of burner ignition pipelines.

[0014] Optionally, the pressure reducing device in the oxygen supply pipeline is arranged close to the gas source, and the flow detection device is arranged upstream of the second pneumatic regulating valve.

[0015] Optionally, the purging pipeline is connected downstream of the blast furnace gas supply pipeline, and is used for purging the pipeline after the baking is completed.

[0016] Optionally, the gas source treatment device comprises a filter, a pressure regulator and a lubricator.

[0017] A method using the above baking system, comprising the following steps:

[0018] S1, ignition preparation stage: opening the cut-off valves of the ignition gas supply pipeline and the compressed air supply pipeline, igniting the gas by the ignition device, and confirming the ignition state by the flame detection device;

[0019] S2, system cooling stage: starting the cooling device to deliver the cooling medium to the burner;

[0020] S3, main flame ignition stage: opening the cut-off valve of the blast furnace gas supply pipeline and adjusting the opening degree of the regulating valve thereof, and opening the cut-off valve of the oxygen supply pipeline and adjusting the opening degree of the regulating valve thereof;

[0021] S4, baking operation stage: controlling the baking cover to descend to the working position to perform the baking operation;

[0022] S5, system shutdown stage: according to the predetermined sequence, the shut-off valves of the oxygen supply pipeline and the blast furnace gas supply pipeline are closed in turn, the nitrogen gas purging pipeline is opened for pipeline purging, and finally all auxiliary pipelines are closed and the cooling device is closed after a time delay.

[0023] 8. The roasting system use method according to claim 7, characterized in that, in the ignition preparation stage, the ignition device is stopped after working for a predetermined time, and the flame signal is confirmed by the ion detection device.

[0024] Optionally, in the main flame ignition stage, the opening degrees of the blast furnace gas regulating valve and the oxygen regulating valve are adjusted within the range of 0-100% according to process requirements.

[0025] Optionally, in the system shutdown stage, the duration of nitrogen gas purging is determined according to the pipeline volume and process requirements.

[0026] The beneficial effects of the present application are:

[0027] 1. The intrinsic safety level of the system is greatly improved: by setting multiple pneumatic shut-off valves (such as FSV101, FSV501 / 502, FSV201, etc.) and supplemented by strict sequence start-stop control logic, it is ensured that various dangerous media (such as blast furnace gas, oxygen) are in an absolute isolation state in the non-working state. In particular, the independent nitrogen purging pipeline and its interlocking control can automatically and thoroughly remove the residual combustible gas in the pipeline after the roasting is completed, fundamentally eliminating the risk of combustion and explosion caused by the accumulation of combustible gas, and providing strong hardware and program protection for safe production.

[0028] 2. The reliability and success rate of the ignition operation are significantly improved: the hierarchical and grouped ignition gas control strategy (FSV601 controls the central burner, and FSV602 controls the surrounding burners) is adopted, which realizes the fine management of small fire ignition and adapts to the characteristics of different burners. Combined with the real-time detection of flame signals by the ion flame detection relay, accurate and error-free ignition success feedback is provided to the control system, avoiding the risk of "mistaken gas injection" or explosion caused by misjudgment, and ensuring the safety of the ignition process.

[0029] 3. The precise and stable control of the roasting process is realized: by setting high-precision pneumatic regulating valves (FCV101, FCV501) and flow meters (FT501) on the blast furnace gas pipeline and the oxygen pipeline respectively, the system can accurately set and real-time adjust the flow ratio (air-fuel ratio) of the fuel gas and the combustion-supporting medium according to the process requirements, ensuring that the combustion is always in the best state. This not only makes the roasting temperature (which can be raised to 700℃) more uniform and stable, meeting the process requirements of high-temperature roasting, but also provides crucial thermal protection for the stable production of the converter.

[0030] 4. Optimized system energy consumption, energy saving and consumption reduction: precise air-fuel ratio control avoids excess supply of combustion-supporting medium or incomplete combustion of fuel, greatly improving fuel utilization efficiency. At the same time, automated process control avoids energy waste due to human operation errors or delays. Precise duration control of the purging process also avoids excessive consumption of purging medium, effectively reducing the overall energy consumption of the system from multiple aspects.

[0031] 5. High automation reduces operation difficulty and human error: the whole process from lighting small fire to lighting large fire to purging shutdown is realized by automatic program control. The operator only needs to issue a start command, and the subsequent complex and time-accurate process is automatically completed by the system, greatly reducing the labor intensity and psychological burden of the operator, and minimizing various faults and safety accidents caused by human errors.

[0032] 6. Enhance the durability and reliability of the system: the interlocking start and delay shutdown mechanism of the cooling fan ensures sufficient cooling of the burner before and after baking, effectively preventing the burner from being damaged due to overheating, and prolonging the service life of the core equipment. The application of pneumatic three-piece gas source treatment device also ensures the stable and reliable operation of the pneumatic components.

[0033] In summary, the present application brings breakthrough benefits in safety, reliability, economy and automation level through systematic hardware configuration innovation and intelligent process control method innovation, and the comprehensive performance is significantly better than that of traditional baking systems.

[0034] Other advantages, objects and features of the present application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by the methods and instrumentalities particularly pointed out in the description. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to make the purpose, technical scheme and advantages of the present application clearer, the preferred detailed description of the present application will be made below in combination with the drawings, in which:

[0036] Figure 1 The overall schematic diagram of the baking system of the present application. DETAILED DESCRIPTION

[0037] Following make clear the advantages and effects of the present application to those skilled in the art by specific, concrete examples. The present application can also be implemented or applied by other different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the following examples and features in the examples can be combined with each other without conflict.

[0038] The drawings are only used for illustrative description, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation of the present application. In order to better illustrate the embodiments of the present application, some components in the drawings can be omitted, enlarged or reduced, and do not represent the actual size of the product. It is understandable for those skilled in the art that some well-known structures and their descriptions in the drawings can be omitted.

[0039] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore the terms describing the positional relationship in the drawings are only used for illustrative description, and cannot be understood as a limitation of the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0040] Embodiment 1

[0041] The present embodiment provides a roasting system for roasting large steel ladles and a specific use method thereof. Please refer to Figure 1 , the roasting system mainly includes the following components:

[0042] Blast furnace gas supply pipeline: this pipeline is used to transport blast furnace gas as the main fuel. In the direction of the gas flow, a first pneumatic shut-off valve (corresponding to FSV101 in the document) and a first pneumatic regulating valve (corresponding to FCV101 in the document) are arranged in sequence on the pipeline. The first pneumatic shut-off valve is used to quickly and safely shut off or connect the main gas supply, and the first pneumatic regulating valve is used to accurately regulate the gas flow in the range of 0-100% according to the heat load required for roasting.

[0043] Ignition gas supply pipeline: this pipeline is used to transport the coke oven gas for ignition. Two pneumatic shut-off valves are provided on the pipeline, namely the second pneumatic shut-off valve (corresponding to FSV601 in the document) and the third pneumatic shut-off valve (corresponding to FSV602 in the document). Among them, the second pneumatic shut-off valve is specially used to control the on-off of the ignition pipeline of the middle burner, and the third pneumatic shut-off valve is used to control the on-off of the ignition pipeline of the surrounding three burners. This grouping control strategy allows more refined management of the ignition process.

[0044] Oxygen supply pipeline: this pipeline is used to provide combustion-supporting oxygen to the main flame. Near the oxygen source, two pressure reducing valves (PCV501 and PCV502 in the document, collectively constituting a pressure reducing device) are first provided to stabilize the oxygen pressure at the required working pressure. Subsequently, a flow meter (FT501 as a flow detection device), two fourth pneumatic shut-off valves (FSV501 and FSV502), and a second pneumatic regulating valve (FCV501) are sequentially provided on the pipeline. The flow meter is used to monitor the oxygen flow in real time, and the second pneumatic regulating valve is used to accurately adjust the oxygen flow to match the blast furnace gas flow at the optimal air-fuel ratio.

[0045] Nitrogen supply pipeline: this pipeline is divided into two parts, one part provides nitrogen gas for the pneumatic actuator of the valve, and the other part is a purge pipeline. The purge pipeline is a safety-critical part of this embodiment, which is connected downstream of the blast furnace gas supply pipeline and mainly consists of a fifth pneumatic shut-off valve (FSV201) and a check valve (as a check device), used to inject nitrogen into the blast furnace gas pipeline after shutdown to disperse and replace the residual combustible gas, preventing deflagration.

[0046] Compressed air supply pipeline: this pipeline mainly provides combustion-supporting air for the ignition gun. A set of pneumatic triplets (as a gas source treatment device, including a filter, a pressure regulator, and an oil mist separator (lubricator)) is provided on the pipeline to purify, pressure regulate, and lubricate the compressed air to ensure reliable operation of the ignition system. Subsequently, a sixth pneumatic shut-off valve (FSV401) is provided to control the on-off of the compressed air to the ignition gun.

[0047] Cooling fan: this device is independent of the above-mentioned pipeline system and is used to supply cooling air to the burners during the baking process to prevent overheating and damage to the burners.

[0048] All the above-mentioned pneumatic shut-off valves, pneumatic regulating valves, ignition devices, flame detection devices, and cooling fans are connected to a system control device (such as a PLC or DCS control system), accept its instructions and feedback status signals, thereby realizing the automatic program control of the entire baking process.

[0049] The method for using the baking system is performed according to a predetermined safety logic sequence, specifically including the following steps:

[0050] S1, Ignition Preparation Stage (Ignite Small Fire): The system control device first issues an instruction, while opening the second pneumatic shut-off valve (FSV601), the third pneumatic shut-off valve (FSV602), and the sixth pneumatic shut-off valve (FSV401), coke oven gas and compressed air enter the ignition gun. At the same time, the ignition transformer works, and the end of the ignition gun discharges. After about 15 seconds, the discharge stops. At this time, the ion fire detection relay detects a stable flame signal, indicating that the small fire is successfully ignited. If no flame is detected, the system will alarm and lock, and will not proceed to the next step, ensuring safety.

[0051] S2, System Cooling Stage: After the small fire is ignited, the system control device immediately starts the cooling fan to deliver cooling air to the burner for pre-cooling, preparing for the high temperature of the main flame.

[0052] S3, Main Flame Ignition Stage (Ignite Large Fire): After confirming the stability of the small fire and the operation of the cooling fan, the system control device opens the first pneumatic shut-off valve (FSV101), and the blast furnace gas enters the main pipeline. At the same time, the first pneumatic regulating valve (FCV101) opens to the corresponding opening degree (e.g., 40%) according to the preset flow value. Almost simultaneously, two fourth pneumatic shut-off valves (FSV501, FSV502) are opened, and the second pneumatic regulating valve (FCV501) is also opened to the corresponding opening degree (e.g., 30%) according to the calculated air-fuel ratio. After the blast furnace gas mixes with oxygen, it is ignited by the small fire to form a stable main flame.

[0053] S4, Roasting Operation Stage: After the main flame is stable, the system control device controls the roasting cover to descend, covering the flame in the ladle opening, and starts to roast the ladle. During this stage, the system can adjust the gas and oxygen flow through the first pneumatic regulating valve (FCV101) and the second pneumatic regulating valve (FCV501) according to temperature feedback, to stabilize the roasting temperature at the target value of about 700°C.

[0054] S5, System Shutdown Stage: When the preset roasting time ends, the system shuts down in strict order.

[0055] First, the system control device closes the two fourth pneumatic shut-off valves (FSV501, FSV502) to cut off the oxygen supply.

[0056] Next, the first pneumatic shut-off valve (FSV101) is closed to cut off the blast furnace gas supply.

[0057] Then, the fifth pneumatic shut-off valve (FSV201) is immediately opened, and the nitrogen purge pipeline is opened to continuously purge the blast furnace gas pipeline (e.g., for 60 seconds), completely removing the residual gas.

[0058] After purging is completed, the fifth pneumatic shut-off valve (FSV201) is closed.

[0059] Subsequently, the second pneumatic shut-off valve (FSV601), the third pneumatic shut-off valve (FSV602), and the sixth pneumatic shut-off valve (FSV401) are closed, and all ignition media are shut off.

[0060] Finally, the cooling fan is automatically turned off after continuing to run for a certain period of time (e.g., a delay of 120 seconds), ensuring that the burner is fully cooled.

[0061] Example 2

[0062] This example has the same main system configuration as Example 1, but its design and application focus on situations with higher requirements for safety and reliability, such as rapid baking of large tundishes.

[0063] This example is based on Example 1 and adds the following redundancy and safety design:

[0064] 1. On the oxygen supply pipeline, two pressure reducing valves (PCV501 and PCV502) are used in a one active and one standby configuration, and are switched through a three-way valve. When the online pressure reducing valve fails, it can be quickly switched to the standby pressure reducing valve to ensure uninterrupted baking operations.

[0065] 2. At key positions of the blast furnace gas and oxygen pipelines, additional manual shut-off valves and pressure gauges are added to facilitate physical isolation and state confirmation during equipment maintenance, increasing the safety of maintenance.

[0066] 3. The purging time of the purging nitrogen pipeline is no longer fixed at 60 seconds, but is calculated by the system control device according to the actual volume of the blast furnace gas pipeline, the pressure and flow rate of the purging nitrogen, and is dynamically adjusted to ensure complete purging under any operating conditions.

[0067] The usage method and process are basically the same as in Example 1, with the main difference being in the system shutdown phase of step S5:

[0068] During the purging step, the system control device will first calculate the required purging time T (in seconds). For example, if the system has a pre-set pipeline volume of V (cubic meters) and a working flow rate of purging nitrogen of Q (cubic meters / second), then the purging time T = (V * safety factor) / Q. The safety factor is usually taken as 2.0 to 3.0 to ensure complete purging. After calculation, the nitrogen purging will continue for the dynamically calculated time T, rather than a fixed value. This method further optimizes the purging effect and avoids the problems of incomplete purging or waste of medium that may occur when the pipeline volume changes or the nitrogen pressure fluctuates.

[0069] Although the embodiments of the present application have been shown and described above, it should be understood by those having ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

[0070] Finally, it is to be understood that the above-described embodiments are merely exemplary of the application and that a person skilled in the art can make various modifications or equivalent replacements to the technical solutions of the application without departing from the purpose and scope of the technical solutions, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A baking system, characterized in that: This includes blast furnace gas supply pipelines, ignition gas supply pipelines, oxygen supply pipelines, nitrogen supply pipelines, and compressed air supply pipelines; The blast furnace gas supply pipeline is equipped with a first pneumatic shut-off valve and a first pneumatic regulating valve; the ignition gas supply pipeline is equipped with a second pneumatic shut-off valve and a third pneumatic shut-off valve, which are used to control the ignition pipelines of different groups of burners respectively; the oxygen supply pipeline is equipped with a pressure reducing device, a flow detection device, a fourth pneumatic shut-off valve and a second pneumatic regulating valve; the nitrogen supply pipeline includes a purging pipeline, which is equipped with a fifth pneumatic shut-off valve and a check valve; the compressed air supply pipeline is equipped with a gas source treatment device and a sixth pneumatic shut-off valve; Each supply line is connected to the burner unit, and each control valve is connected to the system control device.

2. The baking system according to claim 1, characterized in that: The first pneumatic shut-off valve and the first pneumatic regulating valve in the blast furnace gas supply pipeline are arranged sequentially along the airflow direction.

3. The baking system according to claim 1, characterized in that: The second and third pneumatic shut-off valves in the ignition gas supply pipeline independently control the burner ignition pipelines of different groups.

4. The baking system according to claim 1, characterized in that: The pressure reducing device in the oxygen supply pipeline is located near the gas source, and the flow detection device is located upstream of the second pneumatic regulating valve.

5. A baking system according to claim 1, characterized in that: The purging pipeline is connected downstream of the blast furnace gas supply pipeline and is used for purging the pipeline after baking.

6. A baking system according to claim 1, characterized in that: The gas source treatment device includes a filter, a pressure regulator, and a lubricator.

7. A method using the baking system as described in any one of claims 1-6, characterized in that, Includes the following steps: S1, Ignition preparation stage: Open the shut-off valve of the ignition gas supply pipeline and the shut-off valve of the compressed air supply pipeline, ignite the gas through the ignition device, and confirm the ignition status through the flame detection device. S2, System Cooling Stage: Start the cooling device and deliver cooling medium to the burner; S3, Main flame ignition stage: Open the shut-off valve of the blast furnace gas supply pipeline and adjust its regulating valve opening; at the same time, open the shut-off valve of the oxygen supply pipeline and adjust its regulating valve opening. S4, Baking Operation Stage: Control the baking lid to descend to the working position to perform the baking operation; S5, System shutdown phase: Close the shut-off valves of the oxygen supply pipeline and the blast furnace gas supply pipeline in a predetermined sequence, open the nitrogen purging pipeline for pipeline purging, and finally close all auxiliary pipelines and shut down the cooling device after a delay.

8. The method of using the baking system according to claim 7, characterized in that, During the ignition preparation phase, the ignition device stops operating after a predetermined time, and the flame signal is confirmed by the ion detection device.

9. The method of using the baking system according to claim 7, characterized in that, During the main flame ignition stage, the opening degree of both the blast furnace gas regulating valve and the oxygen regulating valve is adjusted within the range of 0-100% according to process requirements.

10. The method of using the baking system according to claim 7, characterized in that, During the system shutdown phase, the duration of nitrogen purging is determined based on the pipeline volume and process requirements.

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