The spiral plate heat exchanger used for heat exchange between the raw materials in the ammonia vaporization tower and the high-temperature wastewater at the bottom of the tower often gets clogged – what should be done?

What type of ammonia filter does your company use?

The best approach is to install a shell-and-tube heat exchanger, and equip it with a steam cleaning device for regular cleaning. These modifications are very easy; our factory carries them out in this way, and the results are excellent. Additionally, removing oil from the remaining ammonia solution from the previous batch can also alleviate this situation.

An additional asphalt oil tank can be added; the waste ammonia water from the bottom of the ammonia vaporization tower first enters this asphalt oil tank for separation before going on to the heat exchanger.

Our factory faces the same problem; we use shell-and-tube heat exchangers, and a steam purge pipe has also been installed in the tube side. Yet blockages still occur, and the reason lies in the rough handling of the processes and equipment. The idea mentioned above of using a steam purge pipe isn’t feasible – only some of the tubes get blocked. How do you plan to clear those blockages? Is it installed on every pipe? As long as some of the pipes are blocked, you won’t be able to generate steam. Moreover, the wastewater heat exchanger is a pressure-free heat exchanger – do you really need to operate it under pressure? It’s not good to violate regulations. A solution could be to design or modify the heat exchangers used for raw ammonia by using thicker tubes in the tube side. Additionally, given your situation, it’s likely that your factory doesn’t recycle substances such as phenol and pyridine from the excess ammonia; in that case, modify the tank used to store the excess ammonia by regularly removing the tar at the bottom, or adjust the filters for the raw ammonia – you can replace the packing or add another filter column. The ammonia-vaporizing wastewater should first be filtered or sent to an asphalt oil tank, and more oil should be removed from the bottom of the tower. The temperature used for ammonia vaporization shouldn’t be too high, in order to prevent the formation of heavy oils. There are many solutions available, but they need to be adapted to your specific circumstances!

Let’s see if backwashing the heat exchanger works Or push the tower down a bit; maybe a solid foreign object is stuck there.

The section that is blocked should be on the side of the high-temperature wastewater. We draw out a stream of high-temperature wastewater from the bottom of the tower, through the slag discharge pipe at the bottom, into a slag removal tank; after solid-liquid separation, the wastewater flows into an underground wastewater tank. Make sure that the amount of wastewater drawn out isn’t too large, as this will ensure good results

This kind of situation has also occurred in my company; it involves substances similar to soft asphalt, but it’s not that serious. I’m not sure what kind of filters you use – we’ve been using air flotation for oil removal, and the results have been average. Now we’re switching to ceramic filters, and the results are quite good

The oil removal system consisting of the previous set of ceramic filters and a dissolved air flotation unit should be sufficient to handle this task.

1. Ammonia evaporation with ceramic filter； 2. It is recommended to use shell-and-tube heat exchangers as much as possible (multiple units can be used simultaneously) ； 3. Add a raw material ammonia tank, and install an overflow plate in front of the suction port at the bottom ； 4. Regularly discharge the tar from the raw material pipeline. The most crucial thing is to properly control the operation of the blow-down and condensation process in order to reduce the amount of tar present in the residual ammonia water and ammonia-rich water. This is the key point.