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• Q1. In Hydrotreating units(Diesel and VGO), why is that Feed introduction is not allowed above 200degC?

  Q2. During Normal startup post maintanence work, having H2S in HP loop above 1000ppm, why feed introduction is done at 180degC only, what would be the issue if feed introduction is done at 230 or 240degC and why it is not generally not recommended?

  Oct-2024

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Answers

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• Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

  According to the literature review, below is presented some responses to these questions: Q1 - The feed temperature is controlled in the range of 180 oC to 200 oC in order to avoid coke deposition or undesired reactions over the catalyst which can lead to temperature runaway in the reactor. Another reason is that during the first stage of the sulfiding process, the temperature should be controlled between 180 to 230 oC (approximately) in order to ensure the decomposition of the sulfiding agent (DMDS is commonly applied as sulfiding agent). Q2 - As previously mentioned, the feed temperature is controlled under this range in order to keep under control the sulfiding reactions of the catalyst allowing the adequate conversion of the sulfiding agent to the active phases capable to promote the reactions which will led the active metals over the catalyst from the oxide phase to the reduced phase. The feed temperature over 200 oC in the initial phase of the sulfiding process can lead to a poor performance of the process considering that the sulfiding agent will not be decomposed in the adequate phase to promote the desired catalyst sulfiding reactions leading to higher consumption of sulfiding agent, another effect is the risk of coking deposition over the catalyst and temperature runaway in the catalyst bed.

   

  Oct-2024