Has the catalyst temperature hotspot in the synthesis tower shifted downward?
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Our company underwent a shutdown for major repairs in early June (mainly to install new gasifiers and related piping). The ammonia synthesis towers are of the double-layer parallel type; during the repairs, no work was done on these synthesis towers. However, since restart at the end of June, the temperature at the hot spots has dropped to the lower frame, whereas before the shutdown it was at the fourth point on the upper frame. In my opinion, the reasons could be: 1) issues with the internal components, 2) catalyst aging. Please share your thoughts so that we at Xin Hai can gain more knowledge. Thank you
Personally, I think it is caused by chronic poisoning of the catalyst； I’m wondering if there have been any changes in the production conditions after the major repairs – for example, has the production load increased, or have there been any changes in the composition of the refined gas? ； A slight increase over a long period at trace levels occurs very easily when the synthesis system does not thoroughly wash away these trace amounts ； There is a chance to increase the catalyst temperature and operate for a few hours at a low volume, and to treat it using the method of mild poisoning to see if there is any improvement.
Catalyst aging and increased load are the primary causes.
Catalyst poisoning leads to reduced activity
Under normal circumstances, if the hot spot moves downward slowly, it indicates that the catalyst’s activity is gradually decreasing; in such cases, the temperature can be increased temporarily. If the hot spot moves upward after the temperature is raised, it is due to a decline in the catalyst’s activity. No change after heating indicates a possible poisoning in the upper part. For the parallel process, one can refer to the situation of another tower and make a comprehensive judgment.
Under normal conditions, as the catalyst is used for an extended period of time, impurities present in the gas such as oil, water, sulfur, carbon monoxide, carbon dioxide, and other such substances will reduce the catalyst’s activity, leading to catalyst aging. The shift of hot spots downward is one manifestation of this phenomenon； upstairs just mentioned some other possible causes; you can take that into consideration ； To truly explain it in detail and accurately, does it also require a specific analysis of your relevant circumstances?
I also think it’s catalytic aging or poisoning; check what the ammonia level is and examine the gas composition； Treatment: Reduce the load; avoid increasing the amount of input in a hasty manner. Once the temperature improves, maintain production for a while before gradually increasing the amount.
The amount of gasification has been increased, resulting in higher loads on conversion and purification. It is necessary to ensure that the parameters of the refined gas meet the required standards; an increase in the levels of harmful gases such as CO, CO2, and H2S can lead to catalyst poisoning and a shift in the hot spots!
It was 4 o’clock before parking, and just over twenty days after parking the operating temperature dropped to 6 o’clock; it is certain that this is not simply a problem caused by catalyst aging. It is likely related to parking and the operations during driving, such as any mistakes in operation – like poisoning, the presence of oil or water, too rapid cooling, or too sudden heating, etc. The original poster should think carefully to prevent similar problems from occurring again.
If, after shutdown for maintenance, the start-up temperature of the synthesis tower decreases, catalyst oxidation should be suspected as the cause – factors such as moisture and oxygen may be responsible. Take advantage of the shutdown period to raise the temperature at zero meter to 450°C and maintain it at that level for 2–4 hours.
I think the replacement wasn’t done properly, resulting in a high oxygen content inside