How can a refrigeration system speed up ammonia discharge?
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A major overhaul is coming up, and I would like to ask everyone: how can the refrigeration system speed up the ammonia discharge process? Once the liquid ammonia has been almost completely drained into the ammonia tank and the pressures in each separation tank have also been reduced to acceptable levels, it is generally required to repeatedly purge the space with nitrogen until the conditions are satisfactory. But time is pressing; is it possible to directly pour water into the refrigeration system? How severe will the impact on the equipment be? This post was last edited by dujiangyun1234 on 2009-2-23 10:27.]
Mainly, a certain pressure is maintained after synthesis and shutdown to ensure delivery to the ammonia tank via residual pressure. Our ammonia discharge process involves connecting several ammonia coolers through bottom drains; the ammonia is first discharged into the first-stage ammonia cooler before being sent to the ammonia tank.
Our approach is as follows: 1. Lower the liquid level in the ammonia storage tank before shutting down the synthesis system. 2. Before shutting down the refrigeration system, increase the system pressure appropriately, and use the pressure difference to force the ammonia from the refrigeration system into the storage tank. 3. After pressurizing with liquid ammonia, the system is depressurized to begin replacement. Our replacement method involves using an ice machine to evacuate the air, which takes a long time. It is best not to add water to the system, as it is difficult to remove water completely while driving. A high water content in liquid ammonia can be corrosive to the equipment.
The consequences of pouring water into liquid ammonia are extremely serious! It’s easy to understand – if you want to increase the speed: 1. Don’t store too much ammonia; 2. Release the ammonia first and then relieve the pressure, as the release rate is faster when the pressure is high. It’s not too late to release the pressure after everything has been drained; on the other hand, if it’s not completely drained, the pressure won’t be fully released
For the evacuation of ammonia refrigeration systems, it is recommended to first create a vacuum and then break it with nitrogen, which is faster than purging directly with nitrogen. Water is not recommended for use for the following reasons: 1. When the system pressure is almost completely depleted, the interior is filled with ammonia. Considering the solubility of ammonia in water, the vacuum that occurs instantly upon the introduction of water can cause severe damage to the equipment; if air is drawn in, the consequences will be even worse ； 2. If water is introduced via spraying, it is slow, and the ammonia produced also faces issues related to discharge and replacement ； 3. It is difficult to clean the remaining water in the system when starting the machine after water is introduced; this exacerbates corrosion of the equipment and also delays the startup time of the refrigeration system.
Excuse me, someone upstairs: how exactly is vacuuming done? Is there any plan for it? I’ve never done this before and don’t know much about it; specialized vacuuming equipment must be needed! Thank you to the person above for their guidance!
Agree with the opinion from the third floor: 1. Lower the liquid level in the ammonia cooler as much as possible before shutting down the synthesis system. 2. Before shutting down the refrigeration system, increase the system pressure appropriately, and use the pressure difference to force the ammonia from the refrigeration system into the storage tank. 3. After pressurizing with liquid ammonia, replace it with medium-pressure nitrogen.
Simple problems have become complicated. Under conditions permitted by environmental regulations, the liquid ammonia can be drained away, and flushing is sufficient. It’s fine even if there is a small amount of liquid ammonia; just add some nitrogen. When driving, replace the air with nitrogen and drain the water at low points; this is sufficient, unless there are design flaws. As far as I know, that’s how ammonia synthesis plants operate.