Synthetic Ammonia Process Technology Exchange Area [Daily Question 2009-03-05]

Take a look at this link: http://bbs.hcbbs.com/thread-384260-1-1.html to see if it’s helpful to you. This post was last edited by snowdfr on 2009-3-5 at 11:43.]

During major overhauls, pressure must be released in a timely manner to prevent the catalyst bed temperature from dropping below the dew point of water vapor, which would cause water to condense and reduce the strength of the catalyst. The pressure relief rate should not be too fast and should be less than 0.2 MPa/min, in order to avoid hazards such as catalyst particle pulverization, bed loosening, gas channeling, and reduced activity.

If the converter is not maintained, nitrogen is introduced under positive pressure for protection after pressure release. If the reformer is to be overhauled, it is necessary to passivate the catalyst: air is mixed with nitrogen, starting with an oxygen content of 0.1%; after the bed temperature stabilizes each time, the oxygen content is increased by 0.1% increments. Once the bed temperature stops rising and the oxygen contents at the inlet and outlet remain unchanged, the amount of air is increased while the amount of nitrogen is reduced. Finally, the system is switched to air purging to cool the temperature below 60 degrees, marking the end of the passivation process. (0.6 MPa superheated steam can also be used in place of nitrogen)

After shutting down the highly variable catalyst, it is first purged with steam for displacement, followed by displacement with nitrogen. Once this process is complete, the outlet valve of the converter is closed, and nitrogen is introduced into the furnace to maintain a positive pressure and prevent oxygen from entering. If the equipment needs to be opened for a short period of time, it is necessary to isolate the converter from the outside environment, either by blocking the connections or by filling each section of the furnace with nitrogen to maintain a slight positive pressure. When shutting down a low-temperature transformer, it is necessary to purge it with nitrogen; it is advisable to lower the temperature below 100 degrees, which is more beneficial for protection

What the user above said is more or less the same. I just watched a maintenance inspection of the transformation section a few days ago. It’s more or less the same as what the sailors said. . . .

How to protect the converter catalyst when parking

How did you protect the catalyst in the medium-pressure converter during the major repair?

How to protect the catalyst in the converter when parking the vehicle. Last edited by *aoye613 on 2009-3-24 11:48]

1. Drain the liquid from the catalyst bed (as the temperature of the catalyst bed decreases and the pressure drops, water present in the process gas will condense; it is necessary to drain this water continuously to prevent the catalyst from being soaked). 2. Reduce the pressure to a slight positive level, in order to avoid too low a pressure that could allow air to enter and cause the bed temperature to rise sharply. 3. Use nitrogen for protection – since nitrogen has a lower temperature, using it not only helps maintain a certain pressure but also reduces the temperature of the catalyst bed. Of course, during short-term shutdowns, the shift reactor can be kept at its current temperature and pressure without the need for gas replacement. If the vehicle is parked for a long time and the temperature drops below the dew point, it is not allowed. Attention should be paid. At this point, replacement should be carried out, or the pressure should be reduced, which can also decrease the chances of condensation.