Passivation of hydrogenation reactor
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Hello everyone, I have a question regarding the passivation of the hydrogenation reactors in sulfur plants. We plan to carry out hydrogen passivation; currently, we use a circulating fan for cooling, with nitrogen being used in this process. After the temperature is reduced, air is introduced into the hydrogenation reactor. Is it necessary to stop the circulation fan during this process? Is nitrogen circulation still required? Thank you, looking forward to your participation
Air injection passivation is primarily used to control oxidation reactions; it is recommended to keep the circulation running during passivation, as this helps to reduce the oxygen content at the air injection point while cooling down, thereby preventing local overheating.
Nitrogen circulation is required; otherwise, overheating is likely to occur
The passivation process requires a gradual increase in oxygen content; nitrogen circulation is necessary, as introducing air directly will inevitably lead to overheating.
Hello, I have another question: for the pre-sulfurization of the hydrogenation reactor, we plan to use acidic gas for this purpose. Is it still necessary to use nitrogen for circulation?
The sulfur content in acidic gas is generally very high; only about 2% hydrogen sulfide is required for sulfidation. Therefore, when using acidic gas directly, there are two scenarios: 1) If the acidic gas is fed directly into the hydrogenation reactor, it still needs to be diluted with nitrogen before being introduced into the reactor. 2. If normal gas guidance is used, the exhaust gas coming from Claus can be utilized, thus eliminating the need for nitrogen.
On our end, nitrogen is used for cooling, and a circulation fan is activated to enable recycling.
Whether it is pre-vulcanization by injecting hydrogen sulfide during startup or passivation through gas flow during shutdown, a circulation fan is required for circulation. The passivation process releases a large amount of heat, requiring cooling with a cold medium. During pre-vulcanization, the circulating nitrogen can be considered a carrier for vulcanization, helping to distribute the sulfur attached to the catalyst more evenly. Since circulating nitrogen is a cold fluid, it needs to be heated, and its flow rate must be controlled appropriately.
An appropriate circulation rate, along with an adequate amount of incoming air, can control the rate of temperature rise, as well as the rates of passivation and sulfidation.
It is best to use nitrogen, being careful of bed fire.