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• How to prevent gumming or carbon formation in prereformer catalyst aside from maintaning an inlet temperature? Is hydrogen recycle in the prereformer beneficial in preventing gum formation?

  Feb-2024

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Answers

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

  This is a common concern for operators of hydrogen generation units, especially for those applying naphtha as feed.

  Well, the available routes to control the carbon deposition of the pre reforming catalyst are listed below:
  1: Operating respecting the temperature ranges (considering the question, I understand that this is being respected);
  2: Increase the steam to carbon ratio;
  3: Improve the basicity of the catalyst through addition of promoters like potassium;
  4: Improve the partial pressure of hydrogen in the reactor;
  5: Maximize the gas flow rate in the reactor aiming to improve the heat flux and avoid hot points which tends to accelerate the carbon laydown over the catalyst.

  Considering the action 4, recycle hydrogen to the reactor can reduce the carbon laydown over the catalyst but it's necessary to study adequately this strategy aiming to avoid the contaminants concentration (mainly CO) in the reactor which will lead the side and deleterious effects like the Boudouard and Beggs reactions presented below:

  2CO = C + CO2 (Boudouard Reaction)
  CO + H2 = C + H2O (Beggs Reaction)

   

  Feb-2024