【Ethylene Question Bank】The main factors affecting the shutdown of ethylene plants are

Based on years of experience in ethylene production, the main factors that cause shutdowns of ethylene plants are: 1. Nozzle failures； 2、Severe coking and burn-through of the furnace tubes ； 3. Severe TLE coking ； 4. Failure of the pyrolysis gas compressor ； 5. Failures in the ethylene plant and propylene plant ； 6. Failures in the quenching system, etc. 2

1. Pyrolysis furnace area: The pyrolysis furnace is a key focus of daily operation management in an ethylene plant, and its performance directly reflects the load of the plant. This includes cracking furnaces, fuel supply systems, waste heat recovery equipment, exhaust fans, startup boilers, etc. The cracking furnace is a key equipment in an ethylene plant. Whether this equipment operates properly has a direct impact on the material and energy consumption of the ethylene plant, as well as on its ability to operate in a safe, stable manner over extended periods of time. This area is a zone with open flames, presenting hazards such as high temperature and pressure, as well as flammability and explosiveness. If issues such as tube blockage or rupture occur, they may not cause the plant to stop operating, but they do affect the plant’s load. 2. Compression zone: The compressor is the heart of the unit; it is responsible for compressing the cracked gas or providing cooling for the separation system. Therefore, any failure in the compressor itself, or its associated oil system, steam system, or sealing system, will directly result in a complete shutdown of the equipment. Furthermore, if a failure in the compressor’s components occurs and it is necessary to empty it, replace parts, open it for maintenance, the process takes a long time and has a significant impact. 3. Separation system (1) Quenching zone: In the gasoline distillation tower, the viscosity of the quench oil can be high, leading to poor system circulation and difficulties in shutting down the system for emptying it. This is especially true in winter; if shutdown is necessary when the viscosity is high, it takes a lot of time, and restarting the system becomes difficult. (2) Cold zone, hot zone: The distillation tower is the core of the separation system and directly affects product quality. In the hot zones where carbon tetra exists, polymer buildup can occur on the trays of various towers; in severe cases, partial shutdown is required for treatment. Cold zone systems have strict requirements regarding water content; exceeding these limits can lead to hydration and freezing blockages. Should any of the above situations occur or if the valves in the pipelines leak, it will lead to a shutdown; in severe cases, fires and explosions may happen, causing damage to equipment, cables, etc. (3) Waste alkali treatment system: This system operates intermittently and can be shut down at any time, so it generally does not affect the operation of the facility. However, the system contains large amounts of toxic substances such as H2S; in the event of a leak, this could have significant safety and social consequences. Moreover, alkalis are highly corrosive, so the pipelines and components in this area are prone to corrosion and leakage, and proper precautions must be taken. (4) Ethylene sphere tank area: The ethylene sphere tanks are areas that require special attention in ethylene plants. There is not much daily operation in these areas, but since each tank stores large amounts of ethylene, and the valves and pipelines connecting them to the system cannot be maintained over time, any leakage or other fire/explosion incident could pose a threat to the other tanks, with serious consequences. (5) Torch system: During the normal operation of the ethylene plant and other facilities, the torch system releases combustible materials resulting from uncontrolled combustion leaks, ensuring compliant emissions. In the event of a system failure, a large amount of material needs to be discharged and burned promptly; otherwise, it will cause overpressure and leakage into the plant area, leading to more serious accidents. The constant-flame line of the torch must remain in a burning state at all times, or the automatic ignition system must be under control; otherwise, problems may arise that cannot be controlled. The torch system is a low-pressure system and cannot hold pressure. The discharge of materials should be done slowly, and care should be taken to prevent large amounts of C5 from entering the flare header, in order to avoid a \"fire rain\" beneath the flare. The liquid level in the collection tank on the flare header should be checked regularly, and the oil that has condensed in the water seal tank must be recovered promptly to prevent pressure buildup in the header and a \"fire rain\" at the base of the flare”

1. Pyrolysis furnace area: The pyrolysis furnace is a key focus of daily operation management in an ethylene plant, and its performance directly reflects the load of the plant. This includes cracking furnaces, fuel supply systems, waste heat recovery equipment, exhaust fans, startup boilers, etc. The cracking furnace is a key equipment in an ethylene plant. Whether this equipment operates properly has a direct impact on the material and energy consumption of the ethylene plant, as well as on its ability to operate in a safe, stable manner over extended periods of time. This area is a zone with open flames, presenting hazards such as high temperature and pressure, as well as flammability and explosiveness. If issues such as tube blockage or rupture occur, they may not cause the plant to stop operating, but they do affect the plant’s load. 2. Compression zone: The compressor is the heart of the unit; it is responsible for compressing the cracked gas or providing cooling for the separation system. Therefore, any failure in the compressor itself, or its associated oil system, steam system, or sealing system, will directly result in a complete shutdown of the equipment. Furthermore, if a failure in the compressor’s components occurs and it is necessary to empty it, replace parts, open it for maintenance, the process takes a long time and has a significant impact. 3. Separation system (1) Quenching zone: In the gasoline distillation tower, the viscosity of the quench oil can be high, leading to poor system circulation and difficulties in shutting down the system for emptying it. This is especially true in winter; if shutdown is necessary when the viscosity is high, it takes a lot of time, and restarting the system becomes difficult. (2) Cold zone, hot zone: The distillation tower is the core of the separation system and directly affects product quality. In the hot zones where carbon tetra exists, polymer buildup can occur on the trays of various towers; in severe cases, partial shutdown is required for treatment. Cold zone systems have strict requirements regarding water content; exceeding these limits can lead to hydration and freezing blockages. Should any of the above situations occur or if the valves in the pipelines leak, it will lead to a shutdown; in severe cases, fires and explosions may happen, causing damage to equipment, cables, etc. (3) Waste alkali treatment system: This system operates intermittently and can be shut down at any time, so it generally does not affect the operation of the facility. However, the system contains large amounts of toxic substances such as H2S; in the event of a leak, this could have significant safety and social consequences. Moreover, alkalis are highly corrosive, so the pipelines and components in this area are prone to corrosion and leakage, and proper precautions must be taken. (4) Ethylene sphere tank area: The ethylene sphere tanks are areas that require special attention in ethylene plants. There is not much daily operation in these areas, but since each tank stores large amounts of ethylene, and the valves and pipelines connecting them to the system cannot be maintained over time, any leakage or other fire/explosion incident could pose a threat to the other tanks, with serious consequences. (5) Torch system: During the normal operation of the ethylene plant and other facilities, the torch system releases combustible materials resulting from uncontrolled combustion leaks, ensuring compliant emissions. In the event of a system failure, a large amount of material needs to be discharged and burned promptly; otherwise, it will cause overpressure and leakage into the plant area, leading to more serious accidents. The constant-flame line of the torch must remain in a burning state at all times, or the automatic ignition system must be under control; otherwise, problems may arise that cannot be controlled. The torch system is a low-pressure system and cannot hold pressure. The discharge of materials should be done slowly, and care should be taken to prevent large amounts of C5 from entering the flare header, in order to avoid a \"fire rain\" beneath the flare. The liquid level in the collection tank on the flare header should be checked regularly, and the oil that has condensed in the water seal tank must be recovered promptly to prevent pressure buildup in the header and a \"fire rain\" at the base of the flare”

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