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• The Hydrogen Production Unit (SMR) is designed for both natural gas and naphtha. The sulfur in naphtha feed is in limit. My queries are:
  1) What will be effect of PONA of naphtha on hydrogen production and methane production?

  2) What will happen if naphtha feed contains more amount of naphthenes (more then permissible)?

  3) What is possiblity of conversion of naphthenes into methane?

  Mar-2024

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Answers

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

  I believe the question is considering that the operating conditions of the SMR unit is considered constant and only the feed characteristics is changed (from natural gas to naphtha), in this case we have the following scenarios:

  1: With high content of heavier hydrocarbons (aromatics and naphthenes) the production of methane tends to be high and the hydrogen falls in the syngas produced;

  2: Keeping the same operating conditions (temperature, pressure and steam/carbon ratio, the methane concentration will be high and the hydrogen production will fall;

  3: To improve the conversion for heavier feeds it's necessary to improve the steam/carbon ratio as well as maximise the temperature and reduce the operating pressure as low as possible. Despite these alternatives, maximising temperature and reducing operating pressure can be difficult to carry out in practice, the best way to improve the conversion in this case is to maximise the steam/carbon ratio. Here, it's fundamental to taking into account that operating with heavier feeds (naphthenic naphtha) will raise significantly the carbon deposition issues over the catalyst once the side reactions like hydrocarbons pyrolysis tends to take place and you can face severe troubles with operating lifecycle of SMR unit. It' important to carry out a sensibility study to determine which is economically attractive to install a naphtha splitter upstream the SMR unit and operate the unit with lighter feed.

   

  Mar-2024