Catalyst deactivation
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Why is it necessary to use more catalysts for passivation when the sulfur recovery unit is shut down?
To prevent oxygen from mixing in and causing combustion when driving again
During system shutdown for maintenance, the catalyst’s temperature is first reduced using steam or nitrogen. At the same time, a small amount of air is introduced to allow the catalyst to oxidize gradually; an oxide film forms on its surface before it can come into contact with air. This process is known as catalyst passivation.
The so-called passivation process involves causing the ferrous sulfide accumulated on the surface of the catalyst to burn when in contact with air, thereby forming stable iron sulfide; this way, once the catalyst is released, it will not react spontaneously upon encountering air
The catalyst is passivated when the sulfur recovery unit is shut down, in order to prevent the catalyst or equipment from being damaged as a result of ferrous sulfide self-igniting upon contact with air during maintenance work
When the unit is put into operation, catalyst pre-sulfidization is required for the catalyst to function; when it is shut down, the sulfided catalyst can catch fire in contact with oxygen, so passivation treatment is necessary
Catalysts containing ferrous sulfide can catch fire when exposed to oxygen, so passivation treatment is required
Passivating the hydrogenation catalyst means oxidizing the sulfided state to the oxidized state, thereby preventing the catalyst from catching fire upon contact with air during maintenance