What exactly potash fixation means for reformer catalyst and does over steaming have some impact on catalyst performance? What factors will lead to leaching of potash from reformer catalyst?
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30/04/2014
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Rajesh Nandanwar, Bharat Oman Refineries Limited, Bina, rajesh.nandanwar@borl.co.in
Like to add more on the subject- Potash is provided in the top section catalyst where the potential of coke formation is higher due to naphtha feed. Almost all the higher HCs are getting converted to methane and H2 in top 50% and remaining catalyst in bottom tube provides necessary heat for conversion of methane to H2. Fixation of potash is done during catalyst reduction. Normally initial reduction of catalyst is done at relatively lower temperature of say 725-750 deg C with steam/H2 ratio of 6:1 to 8:1 for 6 hours. THis allows binding of potash in catalyst pores. Further reduction is continued at higher temperature of 825-850 depending on tube skin temp design. Once this fixation is done, potash is released slowly from catalyst thus providing protection from coke formation. Fresh reformer catalyst is having potash content of 6-8% which gets depleted during operation. Depletion below 2.5-3% is considered as potency to coke formation. Potash release can be faster by steaming of catalyst without H2 or HC present in feed. Condensate carry over would leach the catalyst of potash within few hours and thus it has to be avoided under any circumstances.
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05/12/2012
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Gene Yeh, Saudi Aramco, gene.yeh@aramco.com
Potash in the steam reforming catalyst can promote coke gasification and prevent coke formation with heavy feedstocks. Potash is designed to release gradually in normal operation during the catalyst life. However steaming at high temperature will accelerate potash release. Over-steaming at high temperature might deplete potash from the steam reforming catalyst faster resulting in coke formation in the reformer.
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