Regarding the issue of hydrogen ignition
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Hello everyone: Recently, a problem arose during the trial production of a new project – there was a slight external leakage at the large flange located at the bottom of the converter used for hydrogen production via methanol cracking. The external insulation had already been applied at that time, so the leak wasn’t detected in time. The leaking gas accumulated inside the insulation layer; once it emerged from the connection points, it caused a fire. Although the amount of leakage was small and the fire wasn’t intense, it was extinguished using dry powder. Yet, after a few dozen minutes, the fire started up again. After extinguishing it two or three times, the insulation was removed to prevent the accumulation of hydrogen gas. The auto-ignition temperature of hydrogen should be around 560°C, but the maximum temperature in the equipment pipelines is only 250°C – so how could a fire start? It was confirmed that there was no one at the scene, and there were no electrical switches near the converter either. There was no thunder or lightning, so it’s unclear where static electricity could have come from. The cause of the fire is truly puzzling; is there anyone who can explain it? Thank you!
Hydrogen catches fire and burns because its minimum ignition energy is only 20 microjoules; when its concentration exceeds the upper explosive limit, combustion can occur due to friction under high pressure. There is only a slight popping sound at the moment of ignition, and the blue flame is not easily visible during the day.
You’re just starting to work with hydrogen, right? As the brother above mentioned, the minimum ignition energy is extremely low; as long as there is a leak and the flow rate is high, ignition can occur very easily. Once, while sitting on a pipe to scald my bottom, I realized that the flange was on fire. Therefore, the hydrogen system requires inspection in a dark environment; hydrogen detectors should be worn at all times, and fixed hydrogen detectors should also be available on site.
The ignition point is related to the composition. The auto-ignition temperature is indeed 560°, but that is in pure, dry air. Even a small amount of gaseous impurities can lower the auto-ignition point.
It is very important for the device to operate safely. As for the reasons behind combustion in the event of a leak, I don’t think it’s necessary to delve into them; the focus should be on handling accidents and preventing them. 1. The method of extinguishing a fire that occurs due to a device leak is not recommended. A fire resulting from a device leak is a safety accident related to the operation of the device; it is not possible to continue operating the device after the fire has been extinguished – the device must be stopped immediately for handling. To prevent the accident from escalating into a major incident. In the event of a fire caused by a leak at the converter flange, it is necessary to immediately stop the flow of vaporized methanol steam into the converter. Nitrogen should be used to purge the converter, allowing the fire to extinguish itself; under no circumstances should fire extinguishers be used to put out the fire. In the event of a large fire, even using a whole trainload of fire extinguishers won’t be enough to put it out (the method of extinguishing the fire is incorrect), and there is also a risk to the safety of the people on site during such operations (doesn’t your factory provide any safety training?) 2. After maintenance (or after catalyst replacement), the converter must undergo a cold pressure test; moreover, before feeding material after starting up and raising the temperature, the flange bolts of the equipment must be tightened under heat. (These are all required by the factory’s maintenance procedures.) Remember! Safe operation is of the utmost importance; most major safety accidents in chemical plants occur due to neglecting minor issues.
Most of those involved in hydrogen production know that hydrogen is highly flammable; the static electricity generated by the leaked hydrogen can ignite it. Although the internal temperature is very low.
Your factory is really bold – with leaks and fires occurring, you still don’t stop to fix them. :Funk: Hydrogen gas will behave naturally at high flow rates; it is generally not recommended to extinguish it directly – the source of the gas must be cut off first.
Hydrogen has an extremely low ignition energy; it can catch fire due to friction from leaks. A clamp can be used to seal it off, and if it’s necessary to extinguish the fire, steam can be used to cover it continuously. However, the surrounding environment must facilitate dispersion to prevent the gas from accumulating. If it is a toxic gas, then fire cannot be extinguished
Their courage should be on par with ours
Static discharge caused by flow velocity can lead to fires; it’s not visible during the day but can be seen at night, which is quite dangerous.