6.3 Can the combination of the Maoming Petrochemical fire and Flarenet address the potential hazards in the flare system?
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“During the fire at Maoming Petrochemical Plant on June 3, a lightning strike caused the plant’s units to shut down, resulting in a large amount of flare gas being discharged into the flare network at the same time. Meanwhile, the detachment of the molecular seal dome led to blockages in the flare column, causing pressure buildup in the flare system and poor exhaust flow. This ultimately led to the cracking furnace pipelines leaking and catching fire due to exceeding their set pressure. I would like to ask: Are such accidents caused by blockages in the flare pipeline network, which lead to overpressure inside the network? Is there any interlock system that can prevent such accidents from occurring? The Aspen Flare System Analyzer simulates the backpressure by working backwards from the flare tip, in order to determine the pressure in each section of the pipeline. Can this software be used to simulate the problem of overpressure in the flare piping system itself at Maoming Petrochemical?
Sure, the Aspen Flare System Analyzer models the pipeline layout and performs precise calculations to determine the pressure at various points. It allows for analysis under different operating conditions, helping to identify bottlenecks.
Do you know whether the real cause of the Maoming Petrochemical accident was pressure buildup and leakage in the containers, or overpressure leakage in the pipelines?
You can take a look at this; I don’t quite understand it. Excerpt: This accident occurred on June 3, 2008. Due to lightning strikes on the overhead lines of the Outer Grid Xieyene North Line at that time, a ground short circuit in phase A occurred, resulting in a power outage for one of the power supplies at the Ethylene North Substation. After a brief power outage (within 2 seconds), the automatic power switching devices managed to restore power supply successfully. However, the short-term power outage caused 12 units to shut down, and approximately 150 t/h of gas was released into the D flare tower, whose designed capacity is 910 t/h. Due to defects in the manufacturing quality of the D-flare molecular seal, the bell inside the molecular seal came off and blocked the flare tube, resulting in poor flare discharge and pressure buildup. At 18:46, the pressure in the flare system reached 0.22 MPa, which triggered an interlock shutdown due to high exhaust pressure in the dry gas seal of compressor CB301, which is used for the pyrolysis gas from Unit 2. As a result, approximately 250 t/h of pyrolysis gas was sent to the flare system, causing the pressure there to rise to 0.591 MPa – exceeding the design pressure of the pyrolysis gas pipeline at the outlet of the pyrolyzer (the design pressure being 0.35 MPa). At 18:57, the expansion joint in the pyrolysis gas pipeline at the outlet of Unit 2 failed, resulting in leakage and a fire, thus leading to an accident. “What does “At 18:46, the pressure in the flare system reached 0.22 MPa, which triggered an interlock shutdown due to high exhaust pressure in the dry gas seal of the intermediate-pressure cylinder of compressor CB301 in Unit 2# cracking; as a result, approximately 250 t/h of cracking gas was sent to the flare system, causing the pressure in that system to rise to 0.591 MPa, exceeding the design pressure of the cracking gas pipeline at the outlet of the cracking furnace (design pressure: 0.35 MPa)” mean? Is the pyrolysis gas compressor for 2# pyrolysis a device? Why is it parked high up in a chain? Where exactly is the pyrolysis gas pipeline at the outlet of the pyrolyzer? Is it inside the torch piping network or in the equipment area in front of the discharge valve?
The Aspen Flare System Analyzer is used to design or verify pipeline networks, and it can also be used to identify bottlenecks. It can be used to calculate the size of the flare network required under various operating conditions, or to determine whether it meets the requirements. To find a control logic suitable for various operating conditions, dynamic simulation may be required.
1. The pressure in the torch system increased to 0.591 Mpa, exceeding the design pressure of the cracking gas pipeline at the outlet of the cracking furnace (design pressure: 0.35 Mpa). This could lead to pipe rupture, as the wall thickness is insufficient to withstand such high pressures. 2. The outlet of the pyrolysis gas compressor in the pyrolysis unit is designed to trigger an emergency shutdown when pressure rises to high levels; this is done primarily to protect downstream equipment and pipelines from overpressure. In general, oil and gas systems require high-level interlock shutdown at the outlets of pumps and compressors, primarily to prevent overpressure from causing damage to pipeline equipment and resulting in oil and gas leaks that could pose a danger. This is also required by the standards; API 14C can be referred to.
Can the torch seal be replaced with a water seal?
Due to defects in the manufacturing quality of the D-flare molecular seal, the bell inside the molecular seal came off and blocked the flare tube, resulting in poor flare discharge and pressure buildup. At 18:46, the pressure in the flare system reached 0.22 MPa, which triggered an interlock shutdown due to high exhaust pressure in the dry gas seal of compressor CB301, which is used for the pyrolysis gas from Unit 2. As a result, approximately 250 t/h of pyrolysis gas was sent to the flare system, causing the pressure there to rise to 0.591 MPa – exceeding the design pressure of the pyrolysis gas pipeline at the outlet of the pyrolyzer (the design pressure being 0.35 MPa). At 18:57, the expansion joint in the pyrolysis gas pipeline at the outlet of Unit 2 failed, resulting in leakage and a fire, thus leading to an accident.