Summary of Ammonia Synthesis Accidents (everyone is encouraged to participate actively)
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Synthetic ammonia production is an old process, a complex one as well, and one in which accidents occur frequently. I hope that both you and I will share the accidents we have encountered, as well as the aspects we overlooked in our operations, so that we can all learn from them together and improve our skills. Let me start by mentioning a few cases: First: The steam pipeline at the inlet of the syngas compressor burst; the reason was the incorrect material used. Second: A blind end in the low-pressure steam pipeline was blown away; the reason was too rapid pressure increase. Third: During the nitrogen heating phase, the liquid level interlock in the inlet separator activated; the reason was that the steam valve for the second furnace wasn’t closed. Fourth: The steam control valve for the urea production process was closed, resulting in the shutdown of the urea production unit; the reason was that when the load was reduced, the settings for the steam pipeline were adjusted downward, but the settings for the urea production control valve weren’t adjusted accordingly, causing that valve to close and the urea compressor to stop working. Fifth: Over-temperature in the low-pressure transformer; the reason was that the on-site staff, not being familiar with the procedures, closed the water supply valve for the large steam drum. Sixth: Shutdown due to load adjustments; the reason could be either an issue with the keyboard, which caused the input value to become 0, or it could be due to human error by the operators, who entered the wrong values. I hope everyone will actively share the accidents they have encountered, so that we can all learn from them. The cases I mentioned are quite simple, but I hope they can serve as a starting point for further discussion
When a leak occurs at the square end at the bottom of the synthesis tower, high-temperature hydrogen can easily catch fire, leading to severe fire and explosion accidents
Reason for bubbling in the cold exchange unit at the synthesis station: excessive usage time and inadequate inspection
You mean the entire plant, right? As for accidents related to single synthesis units, I’m aware of a few typical cases: 1. Excessive temperature in the synthesis tower – a typical operational accident, and the causes are generally known； 2. Over-temperature in the synthesis tower is not likely to occur, but it does exist
3. Low or high level of waste boiler liquid, resulting in shutdown； 4. High-pressure ammonia split gas flow ； 5. The liquid level of high-pressure ammonia is too high, with liquid present ； 6. System overpressure caused by various reasons, etc
The exit temperature of the two-stage furnace has dropped significantly; this could be due to a tube failure in the waste heat boiler. The exit temperature of the syngas leaving the methanation furnace has also decreased, and the liquid level in the subsequent condensate separator has risen – this might be caused by a tube failure in the waste heat boiler for the methanation gas
Last edited by ZZJJAA70 on 2009-10-9 23:44: 1. Tube rupture due to overheating during the heating and reduction process in a furnace； It’s okay for beginners, but even experienced drivers drive in this way – how should I put it? 2. Bursting of the auxiliary boiler pipe ； Domestic products are really terrible to use! 3. Leakage at the bypass flange adjacent to the synthesis reactor ； When repairing and replacing flange gaskets, some people choose the wrong materials! 4. The soot blowing of the new catalyst in the first furnace was done carelessly, and the silicate content in the refractory materials of the second furnace was above the allowed limit leading to their detachment; once again, the maintenance work wasn’t done properly, from the selection and inspection of materials to the preparations for startup and beyond. Salt deposition on the heat exchange tube walls of the waste boiler at the outlet of the two-stage furnace, along with high variability and overheating ； 5. Co-precipitation of decarburized vanadium iron ； Process management is chaotic; no one is in charge. 6. Overtemperature in the methanation furnace ； Lack of staff and insufficient skills ； 7. Synthetic turbine reverse overspeed ； The post-parking handling was careless.
Start the compressor, reverse the valves, set the level to a low value, adjust the temperature across the reactor in the synthesis tower, and shut down the system
In May 2002, an explosion occurred at a synthesis station of a company; the explosion took place in the inlet pipeline of the water cooler. The cause was excessive service life – it is said to have been in use for 17 years – coupled with thinning due to internal and external corrosion, which led first to a physical explosion and then to a chemical one.
1. When the decarburization unit was started up, insufficient liquid discharge occurred in the process pipeline from the low-pressure stage to the decarburization stage, which caused the separation tank at the decarburization inlet to fill up with liquid when air was introduced. 2. The syngas compressor stopped operating, and the inlet pressure was not adjusted properly; as a result, the liquid level in the decarburization absorption tower dropped, high-pressure gas entered the regeneration tower, causing damage to the hydraulic turbine and the packing in the regeneration tower to be displaced
During the restart of the engine after parking, the natural gas heater was restarted, resulting in a deflagration in the furnace; flames erupted downward and burned two operators. Cause: The gas valve was not closed for long enough to allow the fuel gas to be expelled through the chimney effect. Action taken: The gas valve was closed, the air valves were opened, and ventilation was maintained for at least 10 minutes