Cutting off after sulfidation is completed in the converter
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Dear sea friends, after the catalytic conversion process is completed and it’s time to take the converter offline, the temperature of the converter bed is very high. Should we keep the system in a sulfur-rich state (that is, ensure a certain level of H2S in the system) when taking the converter offline, or should we wait until the H2S levels in the system are within the appropriate range before doing so? Which one is better?
It’s sufficient to maintain a sulfur-rich state and then cut it off; replacing it is also acceptable, but it’s just a waste of time.
It depends on the duration required to shut down the converter; if it takes a long time, it is better to shut down the converter after the system has been properly purged of H2S. If the time required is short, it is sufficient to maintain a sulfur-rich condition.
Agree with the third-floor view; the second-floor one is also okay. They are all details; from a manufacturing perspective, there’s nothing wrong with them, but factors such as equipment corrosion need to be taken into consideration as well.
Displacement isolation, with insulation and waiting patiently for the gas to be introduced, is a safer approach.
So what is the H2S level to maintain a high-sulfur condition? Are there specific figures? At what level does corrosion of the converter become a concern?
This post was last edited by 654262293 on 2016-5-24 05:33. Generally, high hydrogen sulfide levels occur in what you refer to as sulfur-rich conditions, that is, when the sulfur-resistant shift catalyst becomes sulfided. When sulfiding multiple shift reactors or multiple stages of shift catalysts, once the catalyst in one stage or the first shift reactor has been sulfided properly, that is, once catalyst activation is complete, the temperature is generally not reduced (the process of cooling involves a gradual reduction in the amount of carbon disulfide added, which in turn leads to a gradual decrease in the hydrogen sulfide concentration in the system). Instead, the cut-off method is used; at this point the hydrogen sulfide concentration can be as high as tens of grams per cubic meter or even hundreds of grams per cubic meter. Only after the catalysts in the subsequent stages have been sulfided is the temperature reduced, which helps save time. The sulfidation of sulfur-resistant shift catalysts used in the production of synthetic ammonia is carried out in this manner. Under anaerobic and anhydrous (no water vapor) conditions, the corrosion caused by hydrogen sulfide is minimal; moreover, the design of converters as well as the pipes and equipment in the system takes corrosion prevention into account. Cutting it for a short time of just over ten hours or for a longer period of several days is not a problem. Sulfur recovery can also take place in the presence of oxygen and water (water vapor), with hydrogen sulfide concentrations as high as 30–40 percent, and it operates without any problems over extended periods of time.